WO2016072778A1

WO2016072778A1 - Method and apparatus of contending for channel resources in long-term evolution system

Info

Publication number: WO2016072778A1
Application number: PCT/KR2015/011884
Authority: WO
Inventors: Yingyang Li; Chengjun Sun
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2014-11-07
Filing date: 2015-11-06
Publication date: 2016-05-12
Anticipated expiration: 2017-05-07
Also published as: CN105592467A

Abstract

The present disclosure relates to a pre-5th-Generation (5G) or 5G communication system to be provided for supporting higher data rates beyond 4th-Generation (4G) communication system such as a Long Term Evolution (LTE). A long-term evolution (LTE) device may perform clear channel assessment (CCA) within channel bandwidth of a channel in an unlicensed band, and determine whether to perform data transmission according to a channel state obtained in the bandwidth. The above mechanism enables channel state assessment in an unlicensed band, distinguishes signal power of LTE systems from signal power of other wireless systems, thus improves performances of the LTE system.

Description

METHOD AND APPARATUS OF CONTENDING FOR CHANNEL RESOURCES IN LONG-TERM EVOLUTION SYSTEM

The present disclosure relates to wireless communication systems, and particularly to a method and an apparatus of contending for channel resources in a long term evolution (LTE) system.

To meet the demand for wireless data traffic, which has increased since deployment of 4th-generation (4G) communication systems, efforts have been made to develop an improved 5th-generation (5G) or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a 'beyond 4G network' or a 'post long-term evolution (LTE) system'.

It is considered that the 5G communication system will be implemented in millimeter wave (mmWave) bands, e.g., 60GHz bands, so as to accomplish higher data rates. To reduce propagation loss of radio waves and increase a transmission distance, a beam forming technique, a massive multiple-input multiple-output (MIMO) technique, a full dimensional MIMO (FD-MIMO) technique, an array antenna technique, an analog beam forming technique, and a large scale antenna technique are discussed in 5G communication systems.

In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud radio access networks (RANs), ultra-dense networks, a device-to-device (D2D) communication, a wireless backhaul, a moving network, a cooperative communication, coordinated multi-points (CoMP), reception-end interference cancellation, and the like.

In the 5G system, a hybrid frequency shift keying (FSK) and quadrature amplitude modulation (QAM) modulation (FQAM) and a sliding window superposition coding (SWSC) as an advanced coding modulation (ACM) scheme, and a filter bank multi carrier (FBMC) scheme, a non-orthogonal multiple Access (NOMA) scheme, and a sparse code multiple access (SCMA) scheme as an advanced access technology have been developed.

3GPP LTE systems support both frequency division duplexing (FDD) and time division duplexing (TDD). FIG. 1 is a schematic diagram illustrating a conventional FDD radio frame. In an FDD system, each radio frame lasts 10ms and includes 10 sub frames. Each sub frame lasts 1ms. Each sub frame is composed of two consecutive time slots, i.e., the k'th sub frame includes time slot 2k and time slot 2k+1, . Each time slots lasts 0.5ms. FIG. 2 is a schematic diagram illustrating a conventional TDD radio frame. In a TDD system, each radio frame lasts 10ms and includes two half frames. Each half frame lasts 5ms. Each half frame includes 8 subframes and 3 special fields. Each subframe lasts 0.5ms. The 3 special fields include downlink pilot time slot (DwPTS), guarding period (GP) and uplink pilot time slot (UpPTS). The 3 special fields last 1ms in all. Each subframe is composed of two consecutive time slots, i.e., the k'th sub frame includes time slot 2k and time slot 2k+1. A downlink transmission time interval (TTI) is defined in a sub frame.

There are 7 types of uplink/downlink (UL/DL) configurations for a TDD radio frame, as shown in Table 1. In the table, D represents a downlink sub frame, U represents an uplink sub frame, S represents a special sub frame including the 3 special fields.

Table 1

Configuration serial number

Switch-point periodicity

Sub-frame ID

0

1

2

3

4

5

6

7

8

9

0

5 ms

D

S

U

D

S

U

1

5 ms

D

S

U

D

S

U

D

2

5 ms

D

S

U

D

S

U

D

3

10 ms

D

S

U

D

4

10 ms

D

S

U

D

5

10 ms

D

S

U

D

6

10 ms

D

S

U

D

S

U

D

The first n OFDM symbols in each downlink subframe can be used for transmitting downlink control information, n is 0, 1, 2, 3 or 4. Downlink control information includes physical downlink control channel (PDCCH) and other control information. The other OFDM symbols may be used for transmitting physical downlink shared channel (PDSCH) or enhanced PDCCH (EPDCCH). In an LTE system, PDCCH and EPDCCH bear DCI for allocating uplink channel resourceses (referred to as UL Grant) and DCI for allocating downlink channel resources (referred to as DL Grant). In an LTE system, DCI of different UEs is transmitted individually. DL Grant and UL Grant in DCI are also transmitted individually.

In an LTE-advanced (LTE-A) system, multiple component carriers (CC) are aggregated to obtain larger working bandwidth, i.e., carrier aggregation (CA). The aggregated carriers constitute downlink and uplink links in the communication system, therefore larger transmission rates can be achieved. The CCs that are aggregated may adopt the same duplexing manner, i.e., all of the CCs may be FDD cells or all of the CCs may be TDD cells. Alternatively, the aggregated CCs may adopt different duplexing manners, i.e., there are FDD cells and TDD cells at the same time. A base station may configure a UE to work in multiple Cells which include a primary cell (Pcell) and multiple secondary cells (Scells). In an LTE CA system, HARQ-ACK and channel state information (CSI) in a Physical Uplink Control Channel is only transmitted in a Pcell.

The above LTE systems generally operate on the licensed band to avoid interference from other systems. Besides the licensed band, there are also unlicensed bands. Generally, unlicensed bands have already been allocated for other usages, e.g., radar systems and/or wireless local area network (WiFI) systems defined in 802.11 standards. WiFi systems of 802.11 family operate based on carrier sense multiple access/collision avoidance (CSMA/CA) mechanism. A mobile station (STA) has to check a radio channel before transmitting a signal, and can transmit the signal in the radio channel only when the radio channel remains idle for a certain period of time. The STA may use two mechanisms at the same time to detect the state of the radio channel. The STA may apply carrier sensing to the radio channel, and determine the radio channel is busy when signals from other STAs are detected or a detected signal power exceeds a pre-defined threshold. The a physical layer module in the STA may send a clear channel assessment (CCA) report to a higher layer module indicating the radio channel is busy. At the same time, WiFi systems of 802.11 family also introduce a virtual carrier sensing technique, i.e., a network allocation vector (NAV) which indicates the duration in which a radio channel is reserved. Each 802.11 frame includes a duration field, and the value of a NAV in the duration field can be used to determine signals cannot be sent to the radio channel.

LTE systems need more spectrum resources to meet the requirement of increasing mobile communications services. A possible solution is to deploy LTE systems on unlicensed bands. Since unlicensed bands are generally occupied for other usages, the interference level experienced by an LTE system operating on an unlicensed band is indefinite. Thus, the quality of service (QoS) of data transmission in the LTE system cannot be guaranteed. As such, unlicensed bands may be used for data transmission which has lower QoS requirements. In this situation, it is a yet to be solved problem in the industry as to how to reduce or avoid interference to an LTE system operating on an unlicensed band.

The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.

An objective of the present disclosure is to provide a method and a device of contending for channel resources in an LTE system, so as to reduce interference to the LTE system operating on an unlicensed band and to improve communication performances of the LTE system.

The technical schemes of the present disclosure are described as follows.

A method of contending for channel resources in long-term evolution (LTE) systems may include:

performing, by an LTE device, clear channel assessment (CCA) within bandwidth of a channel in an unlicensed band;

determining, by the LTE device, whether to perform data transmission according to a channel state obtained within the bandwidth; and performing data transmission in the channel when the channel state satisfies a pre-defined clear channel criterion.

In an example, the procedure of performing the CCA within the bandwidth of the channel in the unlicensed band may include: performing the CCA for N different types of signals respectively; the procedure of performing data transmission in the channel if the channel state satisfies the pre-defined clear channel criterion may include: judging whether the LTE device is to occupy the channel according to comparison results of CCA results of the N types of signals with N pre-defined CCA thresholds.

In an example, when N=2, the procedure of performing the CCA within the bandwidth of the channel in the unlicensed band may include: measuring signal power E_LAA of signals from the LTE system and signal power E_others of other signals; and the procedure of performing the data transmission in the channel when the channel state satisfies a pre-defined clear channel criterion may include: determining the channel state by applying different CCA thresholds to the signal power of the LTE system and the other signal power; performing data transmission using the channel if E_others is smaller than Th_others and E_LAA is smaller than Th_LAA; wherein Th_LAA and Th_others are pre-defined CCA thresholds.

In an example, when N=3, the procedure of performing the CCA within the bandwidth of the channel in the unlicensed band may include: measuring signal power E_intra of signals from an LTE system belonging to the same operator with the LTE device, signal power E_inter of signals from an LTE system from an operator different from the operator of the LTE device, and signal power E_others of other signals; the pre-defined clear channel criterion may include three CCA thresholds denoted as Th_intra, Th_inter, and Th_others; the procedure of performing the data transmission in the channel when the channel state satisfies a pre-defined clear channel criterion may include: determining the channel state by applying different CCA thresholds to the signal power E_intra, signal power E_inter and the signal power E_others; performing the data transmission using the channel if E_others is smaller than Th_others, E_inter is smaller than Th_inter and E_intra is smaller than Th_intra; wherein Th_intra, Th_inter and Th_others are pre-defined CCA thresholds.

In an example, the procedure of performing the CCA within the bandwidth of the channel in the unlicensed band may include: obtaining the channel state in all of time resources; the time resources may include alternating time segments A and time segments B;

performing, by the LTE device, the data transmission in the channel in response to a determination that the channel state obtained in time segments A is clear channel and a listen before talk (LBT) condition is satisfied;

stopping, by the LTE device, an LBT operation in time segments B in response to a determination that the channel state obtained in time segments A is clear channel and the LBT condition is not satisfied; or

continuing, by the LTE device, to monitor the channel state and updating a state of an LBT counter until the LBT counter is reset in response to a determination that the channel state obtained in time segments A is idle and the LBT condition is not satisfied.

In an example, in each of the time segments A, an LBT operation is re-started; or

re-starting an LBT operation if the LBT counter has returned to zero in each of the time segments A; continuing a previous LBT operation if the LBT counter has not returned to zero in each of the time segments A.

In an example, the procedure of performing the CCA in the bandwidth of the channel in the unlicensed band may include: obtaining a channel state in all of time resources which includes alternating time segments A and time segments B; obtaining, by the LTE device, the channel state on each orthogonal frequency division multiplexing (OFDM) symbol in time segments A, and performing data transmission using the channel from the n+1'th OFDM symbol when the channel state obtained in the n'th OFDM symbol is idle.

In an example, the LTE device may transmit a pilot signal which includes a pre-define sequence when the channel state is idle and an LBT condition is satisfied; wherein the pilot signal is composed of a basic sequence, the length of the basic sequence equals the length of an OFDM symbol or the length of a period in which the CCA is performed .

In an example, the LTE device may transmit a pilot signal which includes a pre-define sequence when the channel state is idle and an LBT condition is satisfied; wherein time domain mapping of the pilot signal takes a defined time point as a reference time point; the start and end timings of an OFDM symbol for transmitting the pilot signal is aligned to an OFDM symbol in a subframe according to a position of transmission start time of the pilot signal in an LTE subframe.

In an example, the LTE device may transmit a pilot signal including a pre-defined sequence when the channel state obtained is idle and an LBT condition is satisfied;

the LTE device may transmit the pilot signal in one comb of plural combs obtained by dividing subcarriers within bandwidth of the LTE communication system into groups; or

the LTE device may transmit the pilot signal in one of plural groups of sub bands within bandwidth of the LTE communication system, wherein sub bands in each group are distributed over the system bandwidth.

a global pilot signal sequence may be defined, a sequence segment of the pilot signal which is mapped to a frequency a fixed segment in the global pilot signal sequence.

In an example, the pilot signal may include one or plural complete OFDM symbols of an LTE system; if a time point at which an LBT condition is satisfied is not at a start position of an OFDM, a portion before the time point in the first OFDM symbol bearing the pilot signal is truncated.

In an example, a part A of the pilot signal corresponds to the first p OFDM symbols and occupies one subcarrier for transmitting a basic sequence A in every N subcarriers, and no signal is transmitted in the rest N-1 subcarriers, N is an integer, p is the number of OFDM symbols that only transmit the basic sequence A.

In an example, a part B of the pilot signal corresponds to OFDM symbols starting from the p+1'th OFDM symbol, and

the part B is transmitted independently of downlink data transmission; or

the part B supports transmission of demodulation reference signal and/or downlink data.

In an example, the part B of the pilot signal supports transmission of a demodulated reference signal, and

if CRS is to be mapped onto OFDM symbols corresponding to the part B in an LTE subframe, the CRS is transmitted on the same subcarrier of the pilot signals;

information in the pilot signal which is to be mapped to a fixed subcarrier is mapped to OFDM symbols which are not used for transmitting CRS;

if DMRS is to be mapped onto OFDM symbols corresponding to the part B in an LTE subframe, the DMRS is tranmitted on the same subcarrier of the pilot signals; and

information in the pilot signal which is to be mapped to a fixed position of a subcarrier is mapped to OFDM symbols not for transmitting DMRS.

In an example, the pilot signal may include a part A and a part B.

The part B includes OFDM symbols corresponding to fixed data, the number of OFDM symbols corresponding to part A varies according to the time at which the base station occupies the channel; or

the part A includes OFDM symbols corresponding to fixed data, the number of OFDM symbols corresponding to part B varies according to the time at which the base station occupies the channel.

In an example, the pilot signal may include a part A and a part B.

The base station may monitor the part A and the part B of a second base station.

A UE may monitor the part B of the pilot signal, or monitor the part B according to the minimum number of OFDM symbols of the part B, or monitor the part A according to the minimum duration of the part A and monitor the part B.

In an example, a pre-determined structure is used to map a pilot signal onto all or part of OFDM symbols of the part B of the pilot signal.

In an example, the procedure of the LTE device performing the CCA may include: performing CCA of signal power of different types of signals to obtain signal power of the different types of signals.

In an example, the procedure of performing the CCA for signal power of the different types of signals to obtain the signal power of different types of signals may include:

obtaining signal power of an LTE signal by monitoring the pilot signal, subtracting the signal power of the LTE signal from a total signal power detected to obtain a difference as signal power of signals of other wireless systems and the signal power of unidentifiable LTE systems; or

after detecting the signal power of the pilot signal, recovering the pilot signal using a pilot signal sequence and the signal power detected, subtracting the recovered pilot signal from an overall received signal to obtain the power of remaining signal as the signal power of other wireless systems and the signal power of unidentifiable LTE systems.

measuring signal power of different LTE systems or other wireless systems at different combs, wherein the combs are obtained by dividing subcarriers in the LTE bandwidth into plural groups; or

measuring signal power of different LTE systems or other wireless systems at different sub bands, wherein the sub bands are obtained by dividing system bandwidth on resources for channel state measurements into plural groups, and the sub bands in each group are distributed over the system bandwidth.

In an example, the method may also include: transmitting, by a base station of LTE devices, an indication in a primary cell for informing a UE of the LTE devices of the position to start monitoring the pilot signal.

In an example, after transmitting the indication in the primary cell by the base station of the LTE devices, by the base station may transmit a physical downlink shared channel (PDSCH) if the start timing of the PDSCH has arrived when the channel state is idle and an LBT condition is satisfied.

In an example, the base station may continue obtaining the channel state if the channel stays busy before the start timing of the PDSCH, and perform data transmission using the channel when the channel is idle and the LBT condition is satisfied.

In an example, the method may also include: transmitting, by a base station of LTE devices, an indication in a primary cell for informing a UE of the LTE devices of the position to start blind detection of a physical downlink control channel (PDCCH)/enhanced PDCCH (EPDCCH) for receiving downlink data.

In an example, the method may also include:

configuring, via radio resource control (RRC) signaling, the first OFDM symbol for transmitting a PDSCH in the first subframe and the first OFDM symbol for transmitting a PDSCH in a subframe other than the first subframe within a time period in which the channel is used for data transmission; or

defining the start position of a PDSCH in the first subframe after the channel is occupied is the fourth OFDM symbol, and configuring the first OFDM symbol in a subframe other than the first subframe via RRC signaling; or

configuring via RRC signaling the first OFDM for transmitting a PDSCH in the first subframe after the channel is occupied, and defining data transmission from the first OFDM symbol in a subframe other than the first subframe after the channel is occupied; or

defining a start position of a PDSCH in the first subframe after the channel is occupied is the fourth OFDM symbol, and defining that data transmission starts from the first OFDM symbol in a subframe other than the first subframe after the channel is occupied.

In an example, an indication of 1 bit may be added in PDCCH/EPDCCH for indicating a PDSCH is mapped on to OFDM symbols starting from a semi-statically configured OFDM symbol or indicating a PDSCH is mapped from the first OFDM symbol.

An LTE device may include:

a channel assessment module, configured to perform clear channel assessment (CCA) within bandwidth of a channel in an unlicensed band; and

a data transmission module, configured to determine whether to perform data transmission according to the channel state obtained in the bandwidth, and occupy the channel to perform data transmission when the channel state satisfies a pre-defined idle criterion.

According to the method of various examples, an LTE device may perform CCA within the bandwidth of a channel in an unlicensed band, and determine whether to perform data transmission based on a channel state obtained through the CAA in the bandwidth of the channel. The LTE device may perform data transmission in the channel in response to a determination that the channel state satisfies a clear channel criterion. Compared with conventional mechanisms, various examples reserves radio channels for LTE devices, coordinates frequency occupation of an LTE device with other wireless communication systems, e.g., a WiFi system, thus can reduce or avoid interference to the LTE system from other wireless communication systems, and improve communication performances of the LTE system.

Other aspects, advantages, and salient features of the disclosure will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the disclosure.

Before undertaking the DETAILED DESCRIPTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms "include" and "comprise," as well as derivatives thereof, mean inclusion without limitation; the term "or," is inclusive, meaning and/or; the phrases "associated with" and "associated therewith, "as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term "controller" means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware or software, or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases.

The above and other aspects, features and advantages of certain exemplary embodiments of the present disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic diagram illustrating an LTE FDD frame;

FIG. 2 is a schematic diagram illustrating an LTE TDD frame;

FIG. 3 is a flowchart illustrating a method of contending for resources in an LTE system in accordance with examples of the present disclosure;

FIG. 4 is a schematic diagram illustrating allocation of channel assessment resources in accordance with examples of the present disclosure;

FIG. 5 is a schematic diagram illustrating allocation of channel assessment resources in accordance with examples of the present disclosure;

FIG. 6 is a schematic diagram illustrating a mapping scheme of a pilot signal in the time domain in accordance with examples of the present disclosure;

FIG. 7 is a schematic diagram illustrating a mapping scheme of a pilot signal in the time domain in accordance with examples of the present disclosure;

FIG. 8 is a schematic diagram illustrating a mapping scheme of a pilot signal in the frequency domain in accordance with examples of the present disclosure;

FIG. 9 is a schematic diagram illustrating a mapping scheme of a pilot signal in the frequency domain in accordance with examples of the present disclosure;

FIG. 10 is a schematic diagram illustrating reuse of the same pilot signal sequence by different frequence bands having different center frequencies in accordance with examples of the present disclosure;

FIG. 11 is a schematic diagram illustrating use of a global pilot signal sequence in accordance with examples of the present disclosure;

FIG. 12 is a schematic diagram illustrating allocation of frequency resources for CCA in accordance with examples of the present disclosure;

FIG. 13 is a schematic diagram illustrating allocation of frequency resources for CCA in accordance with examples of the present disclosure;

FIG. 14 is a schematic diagram illustrating allocation of frequency resources for CCA in accordance with examples of the present disclosure;

FIG. 15 is a schematic diagram illustrating a UE detecting a channel after receiving an indication from a Pcell in accordance with examples of the present disclosure;

FIG. 16 is a schematic diagram illustrating a UE directly transmitting a PDSCH after receiving an indication from a Pcell in accordance with examples of the present disclosure;

FIG. 17 is a schematic diagram illustrating a base station keeps monitoring a channel state in accordance with examples of the present disclosure;

FIG. 18 is a schematic diagram illustrating the structure of an LTE device in accordance with examples of the present disclosure;

FIG. 19 is a schematic diagram illustrating the structure of a pilot signal in the time domain in accordance with examples of the present disclosure;

FIG. 20 is a schematic diagram illustrating the structure of a subframe in an LTE system in accordance with examples of the present disclosure;

FIG. 21 is a schematic diagram illustrating a mapping relation of information in a pilot signal which is mapped to a fixed position in a subcarrier in the time domain in accordance with examples of the present disclosure;

FIG. 22 is a schematic diagram illustrating a mapping relation of information in a pilot signal which is mapped to a fixed position in a subcarrier in the time domain in accordance with examples of the present disclosure;

FIG. 23 is a schematic diagram illustrating a mapping relation of information in a pilot signal which is mapped to a fixed position in a subcarrier in the frequency domain in accordance with examples of the present disclosure;

FIG. 24 is a schematic diagram illustrating a length-variable pilot signal in accordance with examples of the present disclosure;

FIG. 25 is a schematic diagram illustrating sections A and sections B of a length-variable pilot signal in accordance with examples of the present disclosure; and

FIG. 26 is a schematic diagram illustrating sections A and sections B of a length-variable pilot signal in accordance with examples of the present disclosure.

Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the present disclosure as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the various embodiments described herein can be made without departing from the scope and spirit of the present disclosure. In addition, descriptions of well-known functions and constructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the present disclosure. Accordingly, it should be apparent to those skilled in the art that the following description of various embodiments of the present disclosure is provided for illustration purpose only and not for the purpose of limiting the present disclosure as defined by the appended claims and their equivalents.

It is to be understood that the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a component surface" includes reference to one or more of such surfaces.

Although ordinal numbers such as "first," "second," and so forth will be used to describe various components, those components are not limited herein. The terms are used only for distinguishing one component from another component. For example, a first component may be referred to as a second component and likewise, a second component may also be referred to as a first component, without departing from the teaching of the inventive concept. The term "and/or" used herein includes any and all combinations of one or more of the associated listed items.

The terminology used herein is for the purpose of describing various embodiments only and is not intended to be limiting. As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "has," when used in this specification, specify the presence of a stated feature, number, step, operation, component, element, or combination thereof, but do not preclude the presence or addition of one or more other features, numbers, steps, operations, components, elements, or combinations thereof.

The terms used herein, including technical and scientific terms, have the same meanings as terms that are generally understood by those skilled in the art, as long as the terms are not differently defined. It should be understood that terms defined in a generally-used dictionary have meanings coinciding with those of terms in the related technology.

According to various embodiments of the present disclosure, an electronic device may include communication functionality. For example, an electronic device may be a smart phone, a tablet personal computer (PC), a mobile phone, a video phone, an e-book reader, a desktop PC, a laptop PC, a netbook PC, a personal digital assistant (PDA), a portable multimedia player (PMP), an mp3 player, a mobile medical device, a camera, a wearable device (e.g., a head-mounted device (HMD), electronic clothes, electronic braces, an electronic necklace, an electronic appcessory, an electronic tattoo, or a smart watch), and/or the like.

According to various embodiments of the present disclosure, an electronic device may be a smart home appliance with communication functionality. A smart home appliance may be, for example, a television, a digital video disk (DVD) player, an audio, a refrigerator, an air conditioner, a vacuum cleaner, an oven, a microwave oven, a washer, a dryer, an air purifier, a set-top box, a TV box (e.g., Samsung HomeSync^TM, Apple TV^TM, or Google TV^TM), a gaming console, an electronic dictionary, an electronic key, a camcorder, an electronic picture frame, and/or the like.

According to various embodiments of the present disclosure, an electronic device may be a medical device (e.g., magnetic resonance angiography (MRA) device, a magnetic resonance imaging (MRI) device, computed tomography (CT) device, an imaging device, or an ultrasonic device), a navigation device, a global positioning system (GPS) receiver, an event data recorder (EDR), a flight data recorder (FDR), an automotive infotainment device, a naval electronic device (e.g., naval navigation device, gyroscope, or compass), an avionic electronic device, a security device, an industrial or consumer robot, and/or the like.

According to various embodiments of the present disclosure, an electronic device may be furniture, part of a building/structure, an electronic board, electronic signature receiving device, a projector, various measuring devices (e.g., water, electricity, gas or electro-magnetic wave measuring devices), and/or the like that include communication functionality.

According to various embodiments of the present disclosure, an electronic device may be any combination of the foregoing devices. In addition, it will be apparent to one having ordinary skill in the art that an electronic device according to various embodiments of the present disclosure is not limited to the foregoing devices.

A method and apparatus proposed in various embodiments of the present disclosure may be applied to various communication systems such as a long term evolution (LTE) mobile communication system, an LTE-advanced (LTE-A) mobile communication system, a licensed-assisted access (LAA)-LTE mobile communication system, a high speed downlink packet access (HSDPA) mobile communication system, a high speed uplink packet access (HSUPA) mobile communication system, a high rate packet data (HRPD) mobile communication system proposed in a 3^rdgeneration partnership project 2 (3GPP2), a wideband code division multiple access (WCDMA) mobile communication system proposed in the 3GPP2, a code division multiple access (CDMA) mobile communication system proposed in the 3GPP2, an institute of electrical and electronics engineers (IEEE) 802.16m communication system, an IEEE 802.16e communication system, an evolved packet system (EPS), and a mobile internet protocol (Mobile IP) system and/or the like.

Some examples will be described in detail with reference to the accompanying drawings.

In an unlicensed band, there may have been deployed other wireless communication systems, e.g., radar or WiFi systems. Thus, an LTE system operating on the unlicensed band may need to avoid interfer with the other wireless systems. Further, when there are plural LTE systems operating on the unlicensed band, e.g., plural LTE systems of different operators, interference between the plural LTE systems is also to be avoided.

In an unlicensed band, an LTE device may first obtain the state of a channel before transmitting signals to avoid interfering with other LTE devices or devices from other wireless systems. The LTE device may occupy the channel for signal transmission only when the channel is clear (i.e., idle). The LTE device as used herein may refer to a base station or a UE for simplicity. Since interference from other wireless communication systems is incontrollable in an unlicensed band, the QoS may be hard to achieve. According to various examples, a UE may be configured to operate under the carrier aggregation (CA) mode. A primary cell (Pcell) is a cell on a licensed band, and may be employed to ensure the QoS of the UE.

There may be plural types of wireless systems deployed on the unlicensed band, and different wireless systems may have different requirements for co-existence. For example, a WiFi system may work based on carrier sense multiple access with collision avoidance (CSMA/DA). When the signal strength detected by a WiFi device exceeds a threshold, the WiFi device cannot occupy the channel, i.e., only one device within an area is allowed to transmit signal. In contrast, the LTE system is designed to coordinate behaviors of base stations to achieve a frequency reuse factor of 1, i.e., plural base stations/UEs may transmit data at the same time. Thus, different wireless systems may have different working principles and different requirements for co-existence according to respective designs. According to various examples, an LTE device may monitor signals of the LTE system and signals from other wireless systems on an unlicensed band, and adjust transmission and reception of LTE signals accordingly.

In an example, a base station may configure a UE to work under the CA mode, and configure an LTE cell operating on an unlicensed band to be a secondary cell (Scell) of the UE. The UE may receive signaling from the base station and determine whether to perform data transmission in the Scell. Various examples may coordinate frequency occupation of an LTE system with other wireless communication systems such as WiFi systems, thus reduce or avoid interference between the LTE system and other communication systems.

FIG. 3 is a flowchart illustrating a method of contending for resources in an LTE system in accordance with examples of the present disclosure. The method may include the following procedures.

At block 301, an LTE device monitors signals within the bandwidth of a channel in an unlicensed band, i.e., performing clear channel assessment (CCA).

The CCA may be carried out in the time domain or in the frequency domain. The CCA may refer to measuring a total signal power in the bandwidth of the channel. In an example, when a signal sequence can be identified, the CCA may refer to measuring the power of a signal sequence. The signal sequence may identify signals from a wireless system, e.g., an LTE system operating on the unlicensed band. The LTE device may obtain information about plural types of signals from the CCA, and process subsequent data transmission according to the result of the CCA of the plural types of signals.

In an example, the CCA may be carried out on all frequencies in the system bandwidth. In another example, the CCA may be carried out on some of frequencies in the system bandwidth. When the CCA is carried out on some of the frequencies, the frequencies may be distributed over plural sub bands of the system bandwidth, or the frequencies may be all of frequencies in a sub band on the system bandwidth. The system bandwidth may refer to a range of frequencies that may be used for data transmission within channel width. For example, when the channel bandwidth of an LTE system is 20MHz, the system bandwidth may be about 18MHz.

At block 302, the LTE device may determine whether to perform data transmission according to a channel state obtained within the bandwidth; and perform data transmission in the channel when the channel state satisfies a pre-defined clear channel criterion.

Since the LTE system adopts a fixed frame structure, i.e., each subframe lasts 1ms and has fixed start timing and end timing, and an LTE device may detect an available channel at any time, the LTE device may transmit a signal for occupying the channel before transmitting communicational signals. The signal for occupying the channel is referred to herein as pilot signal. If the LTE device does not transmit any signal before the timing of data transmission, the channel may be occupied by other devices operating on the unlicensed band.

The LTE device may monitor the channel state on the unlicensed band, and may generate a random number N when detecting the channel is occupied. The LTE device may continue monitoring the channel state and occupy the channel after N times when the channel state obtained by CCA is idle. The above process may be referred to as an LBT process, and the counter may be referred to as an LBT counter. The above takes a down counter as an example. The initial value of an LBT counter may be set as N. Each time when the channel state obtained by CCA is idle, the counting value of the LBT counter may be decreased by 1. When the LBT counter counts down to 0, the LTE device may occupy the channel. The above method may also be implemented using other methods that generate similar results. For example, an up counter may be adopted, and the initial value of the up counter may be set as 0. The LTE device may occupy the channel when the LBT counter counts to N.

The mechanism of the present disclosure is hereinafter described in detail with reference to the following examples.

Example one

Within the bandwidth of a channel in an unlicensed band, there may be signals from other LTE cells and/or other wireless systems. An LTE device may take influences from the signals of other LTE cell and/or the signals from other wireless systems into consideration when deciding whether to occupy the channel for data transmission. Since LTE systems are based on a working principle different from those of other wireless systems, signals from LTE cells and signals from other wireless systems may be handled differently.

Various examples may adopt a total of N CCA thresholds as the clear channel criteria for the CCA of N types of signals. N is an integer larger than 1. It may be determined whether a type of signals exists in the channel based on the CCA value of the type of signals and the CCA threshold of the type of signals. An LTE device may determine whether to occupy the channel by comparing the CCA value of each of the N types of signals with the CCA threshold of the type of signals.

In an example, the N types of signals may be different components of the overall received signal, i.e., the N different signals may compose the overall received signal. For example, LTE signals may be determined to be one type of signals, and signals other than LTE signals may be determined to be another type of signals. In an example, the N types of signals may not be different components of the overall received signal. For example, LTE signals may be determined to be one type of signals, and the overall received signal may be determined to be another type of signals. The CCA values of the N types of signals may be denoted as E_k, and corresponding CCA threshold as Th_k, k may be 0,1, ... , N-1. When the CCA values of the N types of signals are all smaller than corresponding CCA thresholds, i.e., E_k is smaller than Th_k, the LTE device may occupy the channel for data transmission. If any one of the CCA values is not smaller than corresponding CCA threshold, the LTE device cannot occupy the channel.

In an example, it may be supposed N equals 2. Within the bandwidth of a channel on an unlicensed band, it may be supposed that an LTE device may differentiate signal power from the LTE system with signal power from other systems in the CCA. The signal power from the LTE system may be denoted as E_LAA, and the signal power from other systems may be denoted as E_others. The signal power from the LTE system may be the total power of signals from LTE systems, or may be the total power of identifiable signals from LTE systems, or may be the total power of signals from LTE systems of the same operator, or may be the total power of idendtifiable signals from LTE systems of the same operator.

The other signal power may be the total power of signals from other wireless systems within the bandwidth, or may be the power of signals from other wireless systems and the power of unidentifiable signals from LTE systems, or may be the sum of signal power of LTE system of other operators and signal power from other wireless systems, or may be signal power of LTE system of other operators, or signal power of LTE systems of other operators and power of unidentifiable signals from LTE systems. In an example, when the k'th method of determining the power from LTE systems is adopted, the other power may also be determined using the k'th method. In other examples, the powers may be determined using different methods.

Different thresholds may be used to determine whether a channel is idle according to the signal power of LTE systems and the other power, Th_LAA and Th_others may be pre-defined. When the CCA value E_others is smaller than Th_others, a determination may be made that there is no requirement for co-existence with other wireless systems. When the CCA value E_LAA is smaller than Th_others, a determination may be made that there is no LTE device that is transmitting data within a short distance from the LTE device.

In an example, the Th_others may be stricter than Th_LAA. That is, as long as the signal power from other wireless systems reaches a relatively low value, the LTE device may avoid occupying the channel so as to avoid generating interference to signals from the other wireless systems. Regarding signals from LTE systems, the LTE device may occupy the channel unless the signal power from LTE systems is strong. This is because the frequency reuse factor of LTE systems is designed to be 1, and a series of methods have been specified to increase the frequency reuse factor.

The following is examples of processing signals from LTE systems and signals from other wireless systems using different CCA thresholds.

When E_others is smaller than Th_others, and E_LAA is smaller than Th_LAA, the LTE device may occupy the channel for data transmission.

When E_others equals or exceeds Th_others, or when E_LAA equals or exceeds Th_LAA, the LTE device may not occupy the channel. If E_others is smaller than Th_others, interference to signals from other wireless systems is avoided. If E_LAA is smaller than Th_LAA, interference to other LTE systems is avoided. If both E_others and E_LAA equal to or exceed respective thresholds, the interference to other wireless systems and the interference to other LTE systems are both avoided.

Example two

The following takes N equals to 3 as an example of the method of processing CCA results of N different types of signals using N CCA thresholds as clear channel criteria as described in exampe one. It may be supposed that N equals 3, and within the bandwidth of a channel on an unlicensed band, an LTE device can perform CCA for power of LTE systems from the same operator (denoted as E_intra), power of LTE systems from other operators (denoted as E_inter) and other power (denoted as E_others) respectively. The power from LTE systems of the same operator may refer to the total power of signals from LTE systems of the same operator, or may be the total power of identifiable signals from LTE systems of the same operator. The power from LTE systems of other operators may refer to the total power of signals from the LTE systems of other operators, or may be the total power of identifiable signals from the LTE systems of other operators. The other power may be the total power of signals from other wireless systems within the bandwidth, or may be the power of signals from other wireless systems and the power of unidentifiable signals from LTE systems of the same operator, or may be the total power of signals from other wireless systems and unidentifiable signals from LTE systems of other operators, or may be the power of signals from other wireless systems and unidentifiable signals from LTE systems.

Different thresholds may be defined for the signal power of LTE systems of the same operation, the signal power of LTE systems of other operators and the other signal power respectively, which are denoted as Th_intra, Th_inter, and Th_others. When the CCA value E_others is smaller than Th_others, a determination may be made that there is no requirement for coexistence with other wireless systems. When the CCA value E_inter is smaller than Th_inter, a determination may be made that there is no LTE device of another operator that is transmitting data within a short distance from the LTE device. When the CCA value E_intra is smaller than Th_intra, a determination may be made that there is no LTE device of the same operator that is transmitting data within a short distance from the LTE device.

In an example, the Th_others may be stricter than Th_intra and Th_inter. That is, as long as the power of other signals reaches a relatively small value, the LTE device may avoid occupying the channel, so as to avoid generating interference to signals from other wireless systems. In an example, Th_inter may be stricter than Th_intra, and this is because LTE systems of different operators are generally hard to be coordinated. As long the the signal strength of LTE systems of other operators reaches a relatively small value, the LTE device may avoid occupying the channel, so as to avoid generating interference to LTE systems of other operators. Regarding signals from LTE systems of the same operator, the LTE device may not occupy the channel only when the signals from LTE systems of the same operator is strong because it is relatively easy to coordinate LTE systems of the same operator.

When E_others is smaller than Th_others, E_inter is smaller than Th_inter, and E_intra is smaller than Th_intra, the LTE device may occupy the channel for data transmission.

In other cases, the LTE device may not occupy the channel. When E_intra is larger than or equal to Th_intra, interference to other LTE systems of the same operator may be avoided. When E_inter is larger than or equal to Th_inter, interference to LTE systems of other operators may be avoided. When E_others is larger than or equal to Th_others, interference to other wireless systems may be avoided.

Example three

In order to co-exist with other LTE systems and other wireless systems on an unlicensed band, an LTE device may check the state of the channel before transmitting a signal, and occupy the channel only when the channel is idle. When the LTE device is to transmit data, the LTE device may check the state of the channel on all of time resources, and occupy the channel when the channel state detected is idle and a listen before talk (LBT) condition is satisfied. In an example, as shown in FIG. 4, time resources may be divided into time segments A and time segments B. The LTE device may occupy the channel only when the channel state obtained in time segments A is idle and the LBT condition is satisfied. When the LTE device determines the channel can be occupied according to a detection result in a time segment A, the LTE device may occupy resources in a remaining portion of the time segment A and resources in the next time segment B, or the LTE device may occupy resources in the remaining portion of the time segment A and resources in multiple subsequent successive time segments A and time segments B. The time segments A and time segments B may occur periodically, and a time segment A and an adjacent time segment B may form a basic structure. The duration of the basic structure may equal to the duration of one or multiple subframes. In an example, the total duration of a time segment A and a time segment B may be variable, but the total duration may be within a limit so that other devices may have the opportunity to occupy the channel.

The LTE device may obtain the channel state on the unlicensed band, and set the number in an LBT counter to be a random value when determining the channel is busy. The LTE device may continue to monitor the channel, and decrease the number in the LBT counter when a condition is satisfied. For example, the LTE device may detect within a time unit that the channel is idle, and decrease the number in the LBT counter by 1. For example, according to regulations of unlicensed bands in Europe, a TU should be at least 20us. A device may check the channel through CCA within a TU, and occupy the channel if the channel is found to be idle. If the channel is found to be busy, the device may start an extended CCA (ECCA) process, i.e., generate a random number N and set a CCA T counter. Each time when the device finds the channel remains idle within a TU, the device may decrease the number in the counter by 1. If the device finds the channel is busy, the device may keep the number in the counter unchanged. When the counter counts down to 0, the device may occupy the channel.

In a time segment A, the LTE device may check the channel state, and start LTE transmission when the LBT condition is satisfied. The LTE do not occupy resources of a time segment B if the LBT condition is not satisfied in the time segment A. For example, a time segment A may be corresponding to the first three OFDM symbols in a subframe. The LTE device may start LTE transmission only when the channel is detected to be idle in the first three OFDM symbols of the subframe and the LBT condition is satisfied. If the LBT condition is not satisfied in the first three OFDM symbols, the LTE device cannot perform data transmission using subsequent OFDM symbols in the subframe. A benefit of defining the time segment A to be corresponding to the first three OFDM symbols may be that, when a base station detects a channel an LBT condition is satisfied within a time segment A, the base station may reuse the conventional PDSCH structure for data transmission in subsequent OFDM symbols in the subframe. Supposing the time spot at which a determination is made that the LBT condition is satisfied is at the n'th OFDM symbol, the base station may instruct a UE to start PDSCH transmission from the n+1'th OFDM symbol, n may be 1, 2 or 3. If the above LBT method is used in uplink transmission, according to a physical mapping scheme of a PUSCH in a subframe having a short cyclic prefix (CP), a demodulation reference signal (DMRS) is mapped onto the 4'th single carrier frequency division multiple access (SCFMA) symbol. According to the above method in which a time segment A includes 3 SCFDMA symbols, DMRS transmission may not be affected, thus the performances of demodulating PUSCH can be guaranteed.

The following provides two examples of processing time segments B.

According to an example, when an LTE device obtains a channel state in a time segment A and an LBT condition is not satisfied, the LTE device may not perform LTE transmission within a time segment B. In the time segment B, the LTE device may suspend LBT operations, i.e., no longer monitor the channel state.

According to another example, after obtaining a channel state in a time segment A and an LBT condition is not satisfied, an LTE device may not perform LTE transmission within a time segment B. The LTE device may continue monitoring the channel state within the time segment B, and decrease the number in an LBT counter by 1 each time the LTE device detects the channel is idle in a TU, and stop the LBT operations until the LBT counter counts down to zero. Within the time segment B, although the LBT counter counts down to zero, the LTE device cannot perform LTE data transmission.

Another issue may arise that within another time segment A, the LBT counter of the LTE device may have not counted to zero, and a method may be used to process the LBT.

In an example, the LBT operation may be restarted in each time segment A. For example, according to regulations on unlicensed bands in Europe, a method of performing LBT based on CCA/ECCA may discard the previous ECCA counting operation, and restart a CCA/ECCA operation.

In another example, a processing method for a time segment A may be selected according to the instant state of the LBT counter. According to the method of processing the time segment B, the LBT counting state may reflect the state of the LBT counter at the end of the last time segment A, or may reflect the result obtained by continuing updating the LBT counting state in the time segment B. If the previous LBT operation has completed, i.e., the LBT counter is reset, the LBT operation may be restarted. For example, according to the regulations on the unlicensed bands in Europe, when the ECCA counter returns to zero, the CCA/ECCA operation may be restarted to process the channel occupation. In an example, a device may perform CCA of a channel in a TU, and occupy the channel after detecting the channel is idle, or start an ECCA process after detecting the channel is busy. If the previous LBT operation is not completed, i.e., the LBT counter has not returned to zero, the previous LBT process is continued. For example, according to a method based on CCA/ECCA, when an ECCA counter has not returned to zero, the ECCA counting operation of the previous time segment A may be continued when the ECCA counting process has not returned to zero. That is, within a new time segment A, each time the device detects the channel remains idle within a TU, the device may decrease the number in the counter by 1. When detecting the channel is busy in a TU, the device may keep the number in the counter unchanged. When the counter returns to zero, the device may occupy the channel.

Example four

Similar to example three, time resources of a channel on an unlicensed band are divided into alternating time segments A and time segments B according to the structure as shown in FIG. 4. After detecting the channel is idle in a time segment A, an LTE device may occupy the channel. When the LTE device determines the channel can be occupied according to a detection result in a time segment A, the LTE device may occupy resources in a remaining portion of the time segment A and resources in the next time segment B, or the LTE device may occupy resources in the remaining portion of the time segment A and resources in multiple subsequent successive time segments A and time segments B. Multiple opportunities of occupying the channel may be provided by configuring multiple OFDM symbols within a time segment A. When the channel is busy in all of the multiple OFDM symbols within a time segment A, the LTE device may not occupy the channel. Different from example three, it is supposed in example four that an LBT counting operation is not started after the channel is detected to be busy. The time segments A and time segments B may occur periodically, and a time segment A and an adjacent time segment B may form a basic frame structure. The duration of the basic frame structure may equal to the duration of one or multiple subframes. In an example, the total duration of a time segment A and a time segment B may be variable, but the total duration may be within a limit so that other devices may have the opportunity to occupy the channel.

There may be multiple OFDM symbols within a time segment A. For example, a time segment A may be corresponding to the first three OFDM symbols in a subframe. A benefit of defining the time segment A to be corresponding to the first three OFDM symbols may be that, when a base station detects the channel is idle within a time segment A, the base station may perform PDSCH transmission in subsequent OFDM symbols in the subframe. Supposing the time spot at which a determination is made that the LBT condition is satisfied is at the n'th OFDM symbol, the base station may instruct a UE to start PDSCH transmission from the n+1'th OFDM symbol. Supposing the above LBT method is used in uplink transmission, according to a physical mapping scheme of PUSCH in a subframe having a short CP, DMRS is mapped onto the 4'th SCFDMA symbol. Thus, the method does not affect DMRS transmission, and guarantees performances of PUSCH demodulation.

As shown in FIG. 5, the following provides two examples of the method of obtaining a channel state.

According to an example, an LTE device may perform channel detection in each OFDM symbol one after another within a time segment A, stop channel detection after detecting the channel is idle in the n'th OFDM symbol, and occupy the channel from the n+1'th OFDM symbol. According to this example, the first OFDM symbol of the subframe to which the time segment A belongs cannot be used for LTE transmission.

According to another example, in addition to the method of the above example, channel detection may also be performed in the last OFDM symbol of the previous subframe of the time segment A, i.e., the LTE device may perform channel detection in the last OFDM symbol in the previous subframe of the time segment A and in each OFDM symbol within the time segment A, step channel detection after detecting the channel is idle in an OFDM symbols, and occupy the channel from the next OFDM symbol. According to this example, if the channel is detected to be idle in the last OFDM symbol of the previous subframe of the time segment A, all of OFDM symbols in the subframe corresponding to the time segment A can be used for LTE transmission.

According to the above examples, in each basic frame composed of a time segment A and a time segment B, the time segment A configured to include multiple OFDM symbols provides more opportunities for an LTE device to obtain channel states, and thus increases the success ratio in resource contention.

Example five

In an unlicensed band, in order to co-exist with other LTE systems and other wireless systems, an LTE device may detect the channel state before transmitting a signal (i.e., LBT), and maintains an LBT counter. In an example, when detecting the channel is busy, the LTE device may set the number in the LBT counter to be a random value. The LTE device may continue to monitor the channel, and decrease the number in the LBT counter when a condition is satisfied. For example, the LTE device may detect within a TU that the channel is idle, and decrease the number in the LBT counter by 1. For example, according to regularions on unlicensed bands in Europe, a TU is at least 20us. In a WiFi system, a device may obtain a channel state and perform an operation on a backoff counter every 9 us.

The time spot at which an LTE device detects a channel is idle and an LBT condition is satisfied may not be at the boundary of a subframe or the boundary of any of the first 3 OFDM symbols, thus conventional LTE standards do not support data transmission from that time spot. In order to occupy the channel, the LTE device may transmit a pilot signal which includes a known sequence within the time interval until the LTE device is able to transmit data. There may be a random length of time from the time the LBT condition is satisfied to the time the LTE device is able to transmit PDSCH, the pilot signal may have the ability to effectively support a variable-length structure. In an example, the pilot signal may be composed of a basic sequence. In an example, the basic sequence may be corresponding to the duration of an OFDM symbol. In another example, since the TU is a short time period, the time spot at which an LTE device detects the channel is idle and the LBT condition is satisfied may not be the boundary of an OFDM symbol. In order to transmit a complete basic sequence in a pilot signal, the basic sequence may last a short time period. For example, the length of the basic sequence may equal to the length of a CCA time period, i.e., equal to the length of a TU. In an example, when the length of the TU is 1/N of the length of an OFDM symbol and a CP, i.e., the duration of each OFDM symbol and CP may accommodate N complete basic sequences, N is an integer. That is, the duration of an OFDM symbol and corresponding CP may be divided into N CCA time periods. As such, some of the time spots at which the channel occupation condition is satisfied may be at the boundary of the OFDM symbol.

The pilot signal may include multiple repititions of the same basic sequence. If the length of the pilot signal is not an integer times of the length of the basic sequence, the pilot signal may include multiple complete repititions of the basic sequence and an incomplete repitition of the basic sequence. When such structure including repititions is adopted, the CP may not be added for each basic sequence. In an example, the pilot signal may be composed of multiple different basic sequences. A CP may be added for each of the basic sequences. In an example, when the duration of a basic sequence equals the duration of an OFDM symbol, the duration of a CP may also equal to a CP of the corresponding OFDM symbol in the subframe of the LTE system. The basic sequences of the pilot signal may be mapped to different subcarriers, so that the LTE device may obtain information of more subcarriers through measurements of the pilot signal. In an example, the basic sequence may be mapped onto different subcarrier positions in the frequency domain to obtain multiple different time domain basic sequences.

According to the above analysis, the start time of the pilot signal may be random, and may not be at the boundary of an OFDM symbol or a subframe. In order to enable the LTE device to know the exact timing of the pilot signal when detecting the pilot signal, the time domain mapping process of the pilot signal may be according to a fixed reference time point. In an example, the reference time point may be the boundary of a subframe. In another example, the reference time point may be the ending position of the n'th OFDM symbol in a subframe, e.g., n may be 3. For example, it may be configured that the reference time point for transmitting the pilot signal is corresponding to the boundary of a basic sequence. In an example, supposing a pilot signal is composed of one or plural OFDM symbols, start timing and ending timing of OFDM symbols of the pilot signal is aligned to corresponding OFDM symbols in a subframe according to the position in an LTE subframe to which the transmission time of the pilot signal is mapped to. According to the method, the pilot signal may be used for obtaining the timing of a subframe. Regarding a method in which a pilot signal is composed of multiple different basic sequences, the order of the basic sequences corresponding to the reference time point in the pilot signal may be defined. FIG. 6 is a schematic diagram illustrating a mapping scheme of a pilot signal in the time domain. It may be supposed that LTE data transmission can only start from a starting position of a subframe with the boundary of the subframe as the reference time point of the pilot signal. That is, the pilot signal may end at a boundary of the subframe no matter when is the starting time point of the pilot signal. The upper drawing is a schematic diagram of the longest pilot signal. The lower drawing is a schematic diagram illustrating the actually transmitted pilot signal at the time point when the channel is detected to be idle. The actually transmitted pilot signal only includes a portion of basic sequences, which are equivalent to CP, at the start position, and the basic sequences end at the boundary of the subframe. In fact, pilot signal in the lower drawing is equivalent to the pilot signal shown in the upper drawing in which the portion before the time point at which the channel is detected to satisfy the LBT condition is truncated.

FIG. 7 is a schematic diagram illustrating a mapping scheme of another pilot signal in the time domain. It is supposed LTE data transmission may start from the fourth OFDM symbol at the latest. The end position of the third OFDM symbol in the subframe may be used as the reference time point, i.e., the pilot signal may end at the end position of the third OFDM symbol in the subframe no matter which time point is the start position of the pilot signal. The upper drawing is a schematic diagram illustrating the longest pilot signal. The drawing at the middle is a schematic diagram illustrating the actually transmitted pilot signal at the time spot when the channel is detected to be idle. The actually transmitted pilot signal may only include a portion of the basic sequence, which is equivalent to the CP, at the start position. It may be supposed that the data transmission may start from the second OFDM symbol in the subframe, thus the pilot signal is not transmitted within the second and the third OFDM symbols in the subframe. The lower drawing is a schematic diagram illustrating the actually transmitted pilot signal at the time point when the channel is detected to be idle. The beginning part of the pilot signal only includes a portion of the basic sequence, which is equivalent to the CP. It may be supposed that the time point when the channel is detected to be idle is within the second OFDM symbol of the subframe, and data transmission begins from the fourth OFDM symbol of the subframe. In fact, the pilot signals in the middle and lower drawings are equivalent to the pilot signal shown in the upper drawing in which the portion before the time point at which the channel is detected to satisfy the LBT condition is truncated.

The following is an example of a mapping scheme of a pilot signal in the frequency domain.

In an example, a basic sequence of a pilot signal may occupy all of subcarriers of the LTE system. Accordingly, the length of the basic sequence equals the length of an OFDM symbol.

In another example, subcarriers in the whole LTE bandwidth may be divided into N Combs. The k'th Comb may occupy the k'th subcarrier in every N subcarriers. N is an integer, and k may be 0, 1,... , N-1. An LTE device may transmit the pilot signal in one of the Combs, and transmit no signal in other Combs. According to the method, the length of a basic sequence may be reduced to 1/N of the length of an OFDM symbol. As shown in FIG. 8, the LTE bandwidth is divided into two Combs. The pilot signal may occupy only one of every two subcarriers. Since DC is to be inserted into LTE downlink transmission, DC may be regarded as a subcarrier, and the k'th Comb may be mapped to the k'th subcarrier in every N subcarriers. For example, the pilot signal may be mapped onto subcarriers 2k and -2k-1, k may be 0, 1, ..., M/2-1. M is the number of available subcarriers within the system bandwidth. According to the method, multiple LTE devices may transmit pilot signals on different Combs, and measure signals from other wireless systems exclusing LTE systems on a Comb that is not used by the LTE devices.

In an example, multiple groups of sub bands may be allocated on the LTE bandwidth, and each sub band may be distributed in the system bandwidth. Each sub band may include multiple successive subcarriers, e.g., subcarrier resources of one or plural successive physical resource blocks (PRB). An LTE device may transmit the pilot signal only on one goup of sub bands. As shown in FIG. 9, the central frequency of a WiFi signal may be any frequency points having an interval of 5MHz. The central part of each sub band of 5MHz in the LTE bandwidth, e.g., about 6 PRBs, may be used for measuring signals from other wireless systems, thus the pilot signal may be mapped onto other frequency resources. According to the method, multiple LTE devices may transmit pilot signals on different sub band groups, and measure signals from other wireless systems exclusing LTE systems on a sub band group that is not used by the LTE devices.

Different LTE cells may have different sequences for the pilot signal. For example, the different sequences may be corresponding to the physical cell identities (PCID) of the LTE cells. For another example, different LTE operators may use different pilot signals. For yet another example, all LTE systems may have the same sequence for pilot signal, in which the sequence can only identify signals from LTE systems.

The pilot signal may be defined according to LTE system bandwidth, i.e., a pilot signal sequence may be reused by bands having different central frequencies. Referring to FIG. 10, pilot signal sequences at different frequencies may be denoted by

numerals

1, 2, 3 and 4. Supposing system bandwidth of multiple cells may partially overlap with each other, e.g., the cells may belong to different operators. Supposing an LTE device may need to detect pilot signals of the cells whose bandwidths partially overlap with each other, the LTE device may detect 4 different sequence segments to detect the pilot signals within a sub band of 5MHz.

In order to reduce the overhead of pilot signal detection, a global pilot signal sequence may be set, such that sequence segment of a pilot signal mapped onto a specific frequency position is a fixed part of the global pilot signal sequence which is independent of the position of the central frequency of the bandwidth. For example, a long sequence may be set for a start position of an unlicensed band. Each segment of the long sequence may be corresponding to a specific frequency in the unlicensed band. A LTE cell may take a segment of the long sequence corresponding to the central frequency of the LTE cell and use the segment as the pilot signal sequence of the cell. As shown in FIG. 11, by using the global pilot signal sequency, sequences of pilot signals within a sub band of 5MHz may be in the same form, which reduces the detection overhead.

It may be supposed that a pilot signal may be composed of one or plural complete LTE OFDM symbols. The basic sequence on an OFDM symbol in a pilot signal may occupy all of subcarriers of the OFDM symbol, or may only occupy some of the subcarriers of the OFDM symbol. For example, the basic sequence may be mapped to 1 of every 6 subcarriers. No signal or other information may be transmitted on the other subcarriers excluding the subcarriers on which the basic sequence is mapped onto. For example, a base station may transmit downlink control information or downlink data on the subcarriers. The basic sequences transmitted in OFDM symbols of the pilot signal may be the same or different sequences. The basic sequence transmitted in an OFDM symbol of the pilot signal may be one sequence, or may include plural sub sequences each of which may have different functions. For example, within one OFDM symbol, two hierarchies of signals for synchronization may be transmitted, which are equivalent to PSS and SSS in conventional LTE systems.

In an example, in the first p OFDM symbols in the pilot signal, a basic sequence A may be transmitted in one subcarrier in every N subcarriers, and no signal may be transmitted in the other N-1 subcarriers in every N subcarriers. N may be an integer. From the perspective of the time domain, the above method divides the length of an OFDM symbol into N equal parts, and the same signal or different phase offsets of the same signal may be transmitted in the N equal parts. Subsequent OFDM symbols of the pilot signal may reuse a basic sequence and other information at different frequencies. For example, a base station may transmit control information or downlink data on those subcarriers. The part of the pilot signal within the first p OFDM symbols is referred to as part A, and the subsequent OFDM symbols except the first p OFDM symbols of the pilot signal are referred to as part B. The basic sequence A transmitted in an OFDM symbol may be a single sequence or may include plural sub sequences. The signals transmitted in the p OFDM symbols in the part A are the same signals, i.e., the basic sequence A. With respect to the part B, the basic sequence transmitted and/or subcarrier mapping scheme of the part B may be different from that of the part A. In an example, in the part B includes plural OFDM symbols, the plural OFDM symbols may transmit the same or different basic sequences and/or use the same or different subcarrier mapping schemes. The part A may be used for enabling the channel occupation, and may also be sued for automatic gain control (AGC), synchronization, cell identification, operator identification, or the like. The part B may also be used for AGC, synchronization, cell identification, operator identification, or the like. The value of p may be a pre-defined value, e.g., p may be 1. In an example, the value of p may be decided by the position of the time point at which it is determined a channel occupation condition is satisfied in the OFDM symbol. For example, if the time point at which the channel occupation condition is satisfied is close to the head of the OFDM symbol, i.e., the remaining time in the first OFDM symbol is enough to transmit information of the basic sequence A, the value of p may be set to be a small value, e.g., p may be set to be 1. If the time point at which the channel occupation condition is satisfied is close to the end of the OFDM symbol, i.e., the remaining time in the first OFDM symbol is not enough to transmit the information of the basic sequence A, the value of p may be increased by 1, e.g., p may be set to be 2, so that the second OFDM symbol of the pilot signal is only used for transmitting the basic sequence A. In an example, the value of p may be decided by the position of the time point at which the channel occupation condition is satisfied in the OFDM symbol. If the time point is within the first OFDM symbol in the pilot signal, p may be set to 1, it cannot be guaranteed that a receiving device is able to receive the basic sequence A. If the time point is at the boundary of an OFDM symbol, the value of p may be set to be 0, i.e., the basic sequence A is not to be transmitted in the pilot signal.

FIG. 19 is a schematic diagram illustrating a mapping scheme of a pilot signal. It may be supposed that a pilot signal includes 3 OFDM symbols. According to the above scheme, the timing of the pilot signal is aligned to the boundary of an OFDM symbol corresponding to the current frame. That is, an LTE device detects the channel occupation condition is satisfied within the n'th OFDM symbol of a subframe, the end timing of the k'th OFDM symbol of the pilot signal may be aligned to the end timing of the n+p'th OFDM symbol of the subframe. k may be 0, 1, ..., K-1. K may be the number of OFDM symbols for transmitting the pilot signal. In the n'th OFDM symbol of the subframe, the time point at which the channel occupation condition is satisfied may not be at the start position of the n'th OFDM symbol. The portion before the time point at which the channel occupation condition is satisfied in the first OFDM symbol of the pilot signal may be truncated, and the end timing of the OFDM symbols of the pilot signal may be unchanged. For example, in FIG. 19, a part close to the start of the first OFDM symbol of the pilot signal is truncated.

According to the pilot signal as shown in FIG. 19, although a portion close to the start of the first OFDM symbol may be truncate, a receiving device may still be able to receive the information of the basic sequence A sent in the OFDM symbol as long as the time point is close to the start of the OFDM symbol. According to the above description, the basic sequence A may only occupy one of N subcarriers of the first OFDM symbol of the pilot signal. Accordingly, in the time domain, it may be equivalent to dividing the time length of an OFDM symbol into N equal sub blocks, and the same sequence or different phase offsets of the same sequence may be transmitted in the sub blocks. As such, as long as the receiving device is able to receive at least one of the sub blocks, the receiving device may obtain information transmitted in the pilot signal. If the time point at which the channel occupation condition is detected to be satisfied is close to the end of an OFDM symbol, e.g., the remaining part of the first OFDM symbol may be not enough to transmit a sub block, the receiving device is unable to obtain information of the basic sequence A transmitted in the first OFDM symbol. In an example, the signal transmitted in the first OFDM symbol may be transmitted in the second OFDM symbol of the pilot signal. As such, the information of the basic sequence A may be transmitted in a duration of one OFDM symbol.

In an example, supposing transmission of the pilot signal starts from the start timing of the CP of an OFDM symbol, the LTE device may start transmission of the pilot signal from the first OFDM symbol of the pilot signal, or from the second OFDM symbol assuming that the remaining time in the first OFDM symbol is 0.

The following illustrates a formation method of a pilot signal in the time domain. Since the time point at which the channel occupation condition is satisfied within a subframe may be random, only a hind part of the first subframe may be remained after the channel is occupied. In order to make full use of the hind part of the subframe for data transmission, as many as cell-specific reference signals (CRS) may be transmitted under a CRS-based transmission mode, or as many as demodulation reference signals (DMRS) may be transmitted under a DMRS-based transmission mode, so as to improve the accuracy of channel estimation. Therefore, the following structure of the pilot signal may be designed to avoid conflict between CRS and DMRS as much as possible to optimize the data transmission performances.

Taking a CP having a normal duration as an example, FIG. 20 is a schematic diagram illustrating positions to which CRS and DMRS are mapped within a subframe. When 1 or 2 CRS ports are configured,

OFDM symbols

0, 4, 7 and 11 may be used for CRS transmission. When 4 CRS ports are configured,

OFDM symbols

0, 1, 4, 7, 8 and 11 may be used for CRS transmission. DMRSs may be mapped to

OFDM symbols

5, 6, 12 and 13. The time domain structure of the pilot signal should be designed to avoid conflict between CRSs and/or DMRSs.

The following is an example of a formation method of pilot signals. In a pilot signal, a part A is used only for transmitting a basic sequence A, and has no functions related with corresponding OFDM symbols of an LTE subframe, i.e., OFDM symbols in the part A of the pilot signal may not be used for transmitting other signals. The number of OFDM symbols in the part A may be denoted as p. Since the time point at which the channel occupation condition is determined to be satisfied may be a random position within a subframe and transmission of a pilot signal may generally start from a position within an OFDM symbol, the duration of the transmission of the pilot signal in the first p OFDM symbols may be shorter than the total length of p OFDM symbols and longer than the total length of p-1 OFDM symbols.

A part B of the pilot signal may be independent from downlink data transmission, i.e., OFDM symbols in the part B may not be used in transmitting downlink data and control information scheduling downlink data transmission and corresponding DMRS. In other words, the part B of the pilot signal may not be used for transmitting CRS and DMRS.

In an example, the part B of the pilot signal may also be used for transmitting demodulation reference signals in such OFDM symbols, including CRS and/or DMRS. For example, a formation method may be as follows.

1) If CRS is to be mapped to OFDM symbols in an LTE subframe corresponding to the part B, the CRS may be transmitted in the same subcarrier in such subsequent OFDM symbols of the pilot signal in part B.

As such, CRS transmissions may have reduced intervals at the start position where the channel starts to be occupied, and the mapping positions of the CRS in LTE subframes are not changed. CRS-based operations, e.g., synchronization tracing, data demodulation, etc., may be optimized.

2) in the part B, information of the pilot signal to be mapped to fixed subcarriers may only be mapped onto OFDM symbols which is not used for CRS transmission.

It may be required that certain information in the pilot signal be mapped to fixed subcarriers, so that a receiving device does not have to perform blind detection to obtain the positions of the subcarriers when receiving the information, which can reduce the complexity of the receiving device. For example, the pilot signal may include a signal for synchronization purposes to provide reference for synchronization, i.e., similar to the coarse synchronization reference signals of PSS/SSS in LTE systems. Such signal is generally mapped onto fixed carriers. Such information that is to be mapped to fixed subcarriers is not suitable to be transmitted in OFDM symbols which is used for transmitting CRS. CRS may be mapped to an arbitrary subcarrrier as PCID changes. This may result in a confliction between the CRS and the information that is to be mapped to fixed subcarriers for certain PCID.

It may be assumed that p equals 1, i.e., only the first OFDM symbol of the pilot signal is used for transmitting the basic sequence A. Since the time point at which the channel occupation condition is satisfied may be a random position in a subframe, as shown in FIG. 21, an OFDM symbol in an LTE subframe corresponding to the p+1'th OFDM symbol of the pilot signal may not include CRS, thus the OFDM symbol may be used for transmitting the information that is to be mapped to fixed subcarriers. In another example, as shown in FIG. 22, an OFDM symbol in an LTE subframe corresponding to the p+1'th OFDM symbol of the pilot signal may include CRS, the OFDM symbol may not be used for transmitting the information which is to be mapped to fixed subcarriers. In other words, the information to be mapped to fixed subcarriers can only be transmitted in an OFDM symbol which is at the hind part and does not transmit CRS, e.g., the p+2'th OFDM symbol. According to the above examples, the different positions of the time point at which the channel occupation condition is satisfied within a subframe result in that the position of an OFDM symbol to which information to be mapped to fixed subcarriers within the pilot signal is variable. In FIG. 21 and 22, the synchronization signal is an example of the information to be mapped to fixed subcarriers.

According to the above method, conflict between the sequence of the pilot signal and the CRS may be avoided, and the pilot signal may still transmit CRS according to the CRS structure of LTE systems. As such, CRS transmissions may have reduced intervals at the start position when the channel is occupied, and CRS-based operations, such as synchronization tracing, data demodulation, etc., may be optimized.

3) If DMRS is to be mapped to OFDM symbols in an LTE subframe corresponding to the part B, the DMRS may be transmitted in the same subcarrier in subsequent OFDM symbols of the pilot signal.

According to the method, the probability of transmitting DMRS within the time the channel is occupied may be increased while the mapping positions of DMRS in the LTE subframe is unchanged. As such, DMRS-based data demodulation may be optimized.

4) In the part B, information of the pilot signal to be mapped to fixed subcarriers may only be mapped onto REs which is not used for DMRS transmission of OFDM symbols.

In order to avoid conflict with DMRS, information to be mapped to fixed subcarriers in the pilot signal may use subcarriers excluding the subcarriers occuped by DMRS within an OFDM symbol. As shown in FIG. 23, such subcarriers within a PRB may be divided into two groups, and each group may include 3 successive subcarriers. There may be two pairs of subcarriers in the 6 subcarriers, the subcarrier interval of subcarriers in a pair is 6, i.e., the two pairs of subcarriers in the boxes labeled by '1' and '2'. Resources corresponding to each of the two pairs of subcarriers may be one subcarrier in every 6 subcarriers in the full bandwidth, and each pair of subcarriers may be prioritized for transmitting the information that is to be mapped to fixed subcarriers.

According to the above, if mapping of DMRS is not considered, the structure of the pilot signal may be determined according to the above limitations 1) and 2), i.e., the pilot signal is transmitted in symbols not including CRS, to make the mapping of the sequence of the pilot signal more flexible. In an example, if the influence of DMRS is taken into consideration, the structure of the pilot signal may be determined according to the above 4 limitations, i.e., the sequence of the pilot signal is transmitted in REs excluding REs that are used for transmitting DMRS in symbols not including CRS. In an example, the part B of the pilot signal may not be used for downlink data transmission. In an example, the part B of the pilot signal may be allowed to be used for downlink data transmission. In an example, CRS REs, DMRS REs and REs to which the basic sequence of the pilot signal is mapped may be removed during rate matching. In an example, REs to which the information to be mapped onto fixed subcarriers may also be removed.

According to the above, the time point at which the channel occupation condition is satisfied may be at a random position within a subframe, i.e., a base station may occupy the channel at any OFDM symbol. In order to reduce processing overhead of UEs, a base station may start transmitting downlink data and/or scheduling information of the downlink data from a position selected from a few OFDM symbols. Accordingly, a UE may detect the signal from the base station and receive the downlink data and/or the scheduling information based on the few possibilities. The i'th OFDM symbol from which transmission of downlink data and/or scheduling information of the downlink data may start may be denoted as k_i, i = 0, 1, ... , M-1, M is the total number of OFDM symbols from which transmission of downlink data and/or scheduling information of the downlink data may start. It may be supposed that k₀<k₁< ... <k_M _-1. The pilot signal may have a variable length, i.e., the number of OFDM symbols in the pilot signal may be changed. If a downlink signal sent by a base station before an OFDM symbol from which transmission of downlink data and/or corresponding scheduling information is started is defined as a pilot signal, the length of the pilot signal may equal to a time different between the time point from at the base station obtained the channel and the time from which transmission of downlink data and/or corresponding scheduling information is started.

FIG. 24 is a schematic diagram illustrating a variable length pilot signal. Supposing a base station starts to transmit downlink data and/or corresponding scheduling information from OFDM symbol k_x, the pilot signal may end at a start point of the OFDM symbol k_x. The minimum duration of the pilot signal may be long enough to allow operations, such as synchronization, cell identification, or the like, to be completed based on the pilot signal. The maximum duration of the pilot signal may be short enough so that the start time of the pilot signal is before the OFDM symbol k_x _-1, and that the part of the pilot signal before the OFDM symbol k_x _-1 is not enough to allow operations, such as synchronization, cell identification, or the like, to be completed based on the part of the pilot signal. The OFDM symbols k_x and k_x _-1 are the indice of two successive OFDM symbols from which transmission of downlink data and/or corresponding scheduling information starts.

In the above structure of the pilot signal, the total number of OFDM symbols of the pilot signal may be denoted as L. A part A of the pilot signal may be used only for transmitting the basic sequence A, and a part B may be used for transmitting the basic sequence and other information. The number of OFDM symbols of the part A may be denoted as p, and that of the part B denoted as q. L may change according to the time point at which the base station occupies the channel, and p and q may be determined according to L. Supposing the end timing of the pilot signal is at a start time of OFDM symbol k_x, the part A of the pilot signal may be before the start time of OFDM symbol k_x - q, and the part B of the pilot signal may be between the start time of OFDM symbol k_x - q and the start time of OFDM symbol k_x. In fact, since timings of LTE devices are not perfectly synchronized, a device may detect the pilot signal of another base station within proximity of the ideal timing of the pilot signal.

In an example, a first pilot signal may adopt a fixed value for q, such that the value of p is decided by the time point at which the base station occupies the channel. The part B of the first pilot signal, the value of q may be larger than or equal to a minimum value q_min to allow functions, such as synchronization, cell identification, operator identification, etc., to be fulfilled. For example, q may be 1 or 2. According to the structure of the pilot signal used, the duration of the part A may be set to be 0, or the duration of the part A may be set to be larger or equal to a minimum value q_min. Referring to the structure as shown in FIG. 25, it may be assumed that q may be defined to always be 1, and the value of p may change within 1 to 4.

A base station may detect signals from other base stations or from other operators and implement other functions by detecting a part A of a pilot signal. In an example, the base station may search for the signal of the part A at all possible timings, e.g., all of timings before the start time of OFDM symbol k_x - q and within the maximum length of the pilot signal. In another example, the base station may search for the signal of the part A according to the minimum length p_min of the part A, e.g., within a time period having a length of p_min before the start time of OFDM symbol k_x - q. In an example, the base station may detect signals from other base stations or from other LTE operators and implement other functions according to the part B of q OFDM symbols of the pilot signal. In another example, the base station may detect signals from other base stations or from other LTE operators and implement other functions by searching for the signal of the part B according to the minimum number q_min of OFDM symbols in the part B of the pilot signal, i.e., searching in a range between the start time of OFDM symbol k_x -q_min and the start time of OFDM symbol k_x. In an example, the base station may detect signals from other base stations or from other LTE operators and implement other functions according to the part A and part B.

Since the length of the part A may be changed, in order to reduce the complexity of a UE, the UE according to an example may not search for the part A, only search for q OFDM symbols in the part B of the pilot signal to implement functions such as synchronization, cell detection, or the like. In another example, the UE may search for the signal of the part B according to the minimum number of OFDM symbols q_min in the part B of the pilot signal, i.e., searching in the range between the start time of OFDM symbol k_x -q_min and the start time of OFDM symbol k_x, to implement functions such as synchronization, cell detection, or the like. In another example, the UE may implement functions such as synchronization, cell detection, or the like by searching for the part B of the pilot signal and searching for the signal of the part A according to the minimum duration p_min of the part A, i.e., searching a range of p_min OFDM symbols from the start time of OFDM symbol .

In an example, a first pilot signal may adopt a fixed value for p, such that the value of q is decided by the time point at which the base station occupies the channel. In the part B of the pilot signal, the value of q may be larger than or equal to a minimum value q_min to allow functions, such as synchronization, cell identification, operator identification, etc., to be fulfilled. For example, q_min may be 1 or 2. According to the structure of the pilot signal used, the duration of the part A may be set to be 0, or the duration of the part A may be set to be larger or equal to a minimum value p_min. FIG. 26 is a schematic diagram illustrating such a structure. It may be supposed that p is defined to always be 1, and the duration of the part A may be allowed to approximate 0. The value of q may change within the range between 1 and 4, and q_min may be 1. In an example, when a minimum duration p_min of the part A is defined, the number of OFDM symbols may be decreased as much as possible. In an example, the value of p may be one of two successive values p1 and p2, and p2 = p1 + 1. From the OFDM symbol which includes the time point the base station starts to occupy the channel, if the length of time during which the part A may be transmitted within

successive OFDM symbols is larger than or equal to p_min, the duration of the part A may be p1; if the length of time is smaller than p_min, the duration of the part A may be p2.

A base station may detect signals from other base stations or from other operators and implement other functions by detecting a part A of a pilot signal. In an example, the end position of the pilot signal may be the start position of OFDM symbol k_x. The number of OFDM symbols in the part A is fixed to be p, but the part A may still appear before the start time of OFDM symbol k_x -q_min and at all timings within the maximum length of the pilot signal depending on the time at which the base station starts to occupy the channel. Accoringly, the base station has to perform blind detection for the part A at all possible timings. In an example, the base station may detect signals from other base stations or from other LTE operators and implement other functions based on OFDM symbols which may belong to the part B of the pilot signal. In an example, the base station may detect signals from other base stations or from other LTE operators and implement other functions by detecting the signal of the part B based on the minimum number q_min of OFDM symbols in the part B, i.e., the part between the start time of OFDM symbol k_x -q_min and the start time of OFDM symbol k_x. In an example, the base station may detect signals from other base stations or from other LTE operators and implement other functions according to the part A and part B.

Since the timing at which the part A may appear is variable, in order to reduce the complexity of UE, a UE may not search for the part A, and check possible OFDM symbols of the part B of the pilot signal to implement functions such as synchronization, cell detection and the like. In an example, the UE may detect the signal of the part B according to the minimum length q_min of the part B of the pilot signal, i.e., the part between the start position of OFDM symbol k_x -q_min and the start position of OFDM symbol k_x, to implement functions such as synchronization, cell detection, and the like.

According to the above first structure of pilot signals, if signals such as CRS and DMRS are not transmitted in the part B, the basic sequence of the pilot signal may be mapped onto q OFDM symbols of the part B. According to the method, the mapping scheme of the part B may be independent from the OFDM symbol position from which the base station starts to transmit downlink data and/or corresponding scheduling information.

According to the above second structure of pilot signals, if signals such as CRS and DMRS are not transmitted in the part B, the basic sequence of the pilot signal may be mapped onto q OFDM symbols of the part B. The scheme of mapping the basic sequence to the part B may be defined according to the maximum value of q, and the last q OFDM symbols of the mapping structure of the part B determined according to the maximum value of q is truncated according to the actual value of q. As such, the mapping structure of the part B may be independent from the position of the OFDM symbol from which the base station starts to transmit downlink data and/or corresponding scheduling information. In an example, in the last q_min OFDM symbols of the part B, the mapping structure of the basic sequence may be fixed and may be independent from the position of the OFDM symbol from which the base station starts to transmit downlink data and/or corresponding scheduling information.

According to the above two structures of the pilot signal, if CRS and/or DMRS is to be transmitted in the part B of the pilot signal, only those OFDM symbols that does not include CRS in the part B may be used for transmitting information that is to be mapped to fixed subcarriers within the pilot signal, and conflict between the information and DMRS. According to the method, the mapping structure of the part B may be related with the position of the OFDM symbol from which the base station starts to transmit downlink data and/or corresponding scheduling information. In this case, the OFDM symbol k_x from which the base station starts to transmit downlink data and/or corresponding scheduling information may be selected such that the position of at least a portion of OFDM symbols that does not include CRS of the part B is fixed. For example, the k_x may be selected such that OFDM symbol k_x -1 does not include CRS, such that it is certain that the last OFDM symbol of the part B does not include CRS. For another example, the k_x may be selected such that OFDM symbols k_x -1 and k_x -2 do not include CRS, such that it is certain that the last two OFDM symbols of the part B do not include CRS. The mapping structure of the basic sequence of the pilot signal on the OFDM symbols that do not include CRS may be independent from the OFDM symbol from which the base station starts to transmit downlink data and/or corresponding scheduling information.

Example six

In an unlicensed band, in order to co-exist with other LTE systems and other wireless systems, an LTE device may detect the channel state before transmitting a signal (i.e., LBT). It may be supposed that an LTE device detects channel state in a time unit (TA), i.e., CCA. If the channel is idle, the LTE device can occupy the channel. If the channel is busy, the LTE device cannot occupy the channel. There may be signals from LTE systems or other wireless systems on the bandwidth of a channel in an unlicensed band. The CCA may be performed for different types of signals respectively. For example, signals from LTE systems and signals from other wireless systems may be regarded as the different types of signals. For another example, LTE signals from the same operator, LTE signals from different operators, and signals from other wireless systems may be regarded as the different types of signals.

It may be supposed that the signals from the two types of systems may be searched for on the same time resources and the same frequency resources.

Supposing the LTE device is to transmit a pilot signal which includes a defined sequence before transmitting data, the LTE device may judge whether the signal from the LTE system exists. Different LTE cells may have different pilot signals. For example, a pilot signal may be corresponding to the physical cell identity (PCID) of an LTE cell. For another example, different pilot signals may be used to identify different LTE operators, i.e., different LTE operators may use different pilot signals. For yet another example, all LTE systems may have the same pilot signal, thus the pilot signal can only identify signals from LTE systems.

There may be some LTE devices are transmitting pilot signals on the resources on which the LTE device is performing the channel state detection, the power of these LTE signals may be obtained by detecting the pilot signals. But there may be other LTE devices are transmitting LTE data, and the power of these LTE signals cannot be obtained by detecting the pilot signals.

Supposing LTE systems operating on the unlicensed band use a unique sequence for the pilot signals, the LTE device may obtain the power of LTE signals by detecting pilot signals, and subtract the power of the LTE signals from the overall signal power detected. The difference may be regarded as the approximate value of the power of signals from other wireless systems and signals from unidentifiable LTE systems. In another example, an interference cancellation method may be adopted. After detecting the power of a pilot signal, the pilot signal may be recovered using the sequence of the pilot signal and the detected power. Then the recovered pilot signal may be subtracted from the overall received signal, and the remaining signal may be regarded as approximately including signals from other wireless systems and signals from other unidentifiable LTE systems. Therefore, the power of the signals from other wireless systems and the signals from unidentifiable LTE systems may be obtained by measuring the remaining signal. In an example, the unique sequence for pilot signals may refer to that all LTE systems operating on the unlicensed band, no matter which operators they belong, uses the same sequence for their pilot signals. In another example, the unique sequence for pilot signals may refer to LTE systems of the same operator operating on the unlicensed band use the same sequence for pilot signals, and devices of an operator may attempt to detect the power of LTE signals from the same operator.

Supposing LTE systems operating on the unlicensed band may use multiple sequences for pilot signals, an LTE device may detect the power of the multiple sequences, and the detected power of the multiple sequences may be subtracted from the overall detected signal power to obtain approximate power of signals from other wireless systems and signals from unidentifiable LTE systems. In another example, an interference cancellation method may be adopted. After detecting the power of a pilot signal, the pilot signal may be recovered using the sequence of the pilot signal and the detected power. Then the recovered pilot signal may be subtracted from the overall received signal, and the remaining signal may be regarded as approximately including signals from other wireless systems and signals from other unidentifiable LTE systems. Therefore, the power of the signals from other wireless systems and the signals from unidentifiable LTE systems may be obtained by measuring the remaining signal. The above multiple sequences may refer to LTE systems of the same operator adopt multiple sequences for pilot signals, or may refer to multiple operators configure multiple different sequences for pilot signals, and an LTE device may attempt to detect LTE signals from multiple operators.

According to the design of the pilot signal, only some of all subcarriers of an OFDM symbol of the pilot signal may be used for transmitting the defined sequence, and the other subcarriers may be used for transmitting other signals. Therefore, the power of LTE signals detected based on the sequences of pilot signals may be weighted. For example, supposing the defined sequence for pilot signals occupy only half of subcarriers of an OFDM symbol, and supposing EPRE of other signals is identical to EPRE of the defined sequence, 3dB may be added to LTE signal power detected using the sequence of the pilot signal, and the result may be taken as the estimated overall LTE signal power.

It may be supposed that there is a time period which is only used for channel state detection and transmitting pilot signals and cannot be used for transmitting LTE data. For example, according to the method of dividing time into time segments A and segments B as shown in FIG. 4, time segments A may be used for channel detection and transmitting pilot signals and cannot be used for transmitting LTE data. While ensuring synchronization between the cells, an LTE device may obtain the power of LTE systems by detecting pilot signals in time segments A, and subtract the detected power of LTE signals from overall detected power. The difference may be regarded to be the approximate power from other wireless systems. In another example, an interference cancellation method may be adopted. An LTE device may obtain the power of LTE systems by detecting pilot signals in time segments A, recover the pilot signal using the sequence of the pilot signal and detected power, and subtract the recovered pilot signal from the overall received signal. The remaining signal may be approximiately regarded as the sum of signals from other wireless systems and signals from unidentifiable LTE systems. Therefore, the power of the signals from other wireless systems and the power of signals from the unidentifiable LTE systems by measuring the remaining signal.

It may be supposed that signals from LTE systems and from wireless systems are detected on the same time resources and different frequency resources. Through frequency division, an LTE device may detect power from different systems on different frequency resources. Detection of LTE systems may be not based on detection of pilot signals.

Within the resources for channel state measurement, subcarriers on the full LTE bandwidth may be divided into N Combs, and N is an integer. An LTE device may transmit LTE signals on one of the N Combs, thus measure signal power of different LTE systems and other wireless systems on different Combs. For example, on one Comb, all LTE devices may not transmit signals, and the power on that Comb reflects characteristics of signal from other wireless systems. On other Combs, each LTE device may transmit signal on one of the Combs, e.g., different LTE operators may transmit LTE signals using resources of different Combs. Thus, different LTE systems may be detected on different Combs.

As shown in FIG. 12, subcarriers on the whole LTE bandwidth may be divided into two Combs. One of the Combs may be used for LTE transmission, thus includes power of LTE signals. The other of the Combs may have no signal transmitted by LTE systems, thus may be used for obtaining signal power from other systems. The multiplexing method of the two Combs is the same with that of of LTE uplink SRS. For example, supposing uplink SRS detection is performed using the last symbol of a previous subframe of subframe n, SRS transmission may not be configured on one of Combs of SRS symbols so that the resources may be used for measuring signals from other wireless systems.

As shown in FIG. 13, subcarriers on the whole LTE bandwidth may be divided into three Combs. LTE systems may not transmit signal on one of the Combs, so that signal power of other systems may be obtained from the Comb. The other two Combs may be used by two operators respectively, so that an LTE device may obtain the power of LTE signals from different operators.

In an example, the whole bandwidth of the system on the resources for channel state measurement may be divided into plural groups of sub bands. Each group of sub bands may be distributed over the system bandwidth. Each sub band may include plural successive subcarriers, e.g., one or plural successive subcarriers of PRB. An LTE device may transmit LTE signals on one of the sub band groups so as to measure signal power from different LTE systems or other wireless systems on different sub bands. As shown in FIG. 14, two groups of sub bands may be allocated. Since central frequencies of WiFi signals may be any frequencies with a spacing of 5MHz and bandwidths of two WiFi signals may have an overlapping bandwidth of 1MHz, a sub band group for measuring signals from other wireless systems may be at the center of sub bands each of which has a bandwidth of 5MHz, e.g., covering about 6 PRBs; and the other sub band group may be used for measuring the power of other LTE systems.

According to the scheme of obtaining time segments A and time segments B, supposing the channel detection operation is performed within time segments A, according to the above method of measuring the power of different types of signals in a frequency division manner, resources for measuring other wireless systems may be reserved only within time segments A, thus resources needed may be reduced.

Example seven

In order to co-exist with other LTE systems and other wireless systems on an unlicensed band, an LTE device may check the state of a channel before transmitting a signal, and occupy the channel only when the channel is idle and an LBT condition is satisfied. As such, a base station cannot determine beforehand whether it can occupy the channel, thus cannot inform a UE of the precise time to start receive information from the bandwidth of the channel. In an example, the UE may be instructed to perform continuous blind detection on the bandwidth of the channel, but this is power consuming. The following is a few examples of transmitting instruction information in a Pcell to reduce the processing overhead of the UE.

In an example, an indication may be transmitted in a Pcell, e.g., through PDCCH or EPDCCH. The indication may be used for informing the UE of the position to start detecting pilot signals. For example, the indication may be transmitted in subframe n of the Pcell to inform the UE to start pilot signal detection from a time point in subframe n+k. The k may be larger than or equal to 0. The value of k and the time point within the subframe k from which the channel state detection may be started may be determined according to the time delay adopted by the UE in processing PDCCH/EPDCCH. For example, supposing the indication is transmitted in PDCCH and the PDCCH is mapped onto the first m OFDM symbols in subframe n, if k is 0, the UE may start pilot signal detection after the m'th OFDM symbol in subframe n of the LTE cell on the unlicensed band after receiving the indication in subframe n from Pcell. If k is larger than 0, the UE may start pilot signal detection from the start position of subframe n+k of the LTE cell on the unlicensed band. In another example, after receiving the indication from the Pcell, the UE may start channel detection from the 4'th OFDM symbol in subframe n+k, as shown in FIG. 15. For example, supposing the indication is transmitted in EPDCCH, k may be larger than or equal to 1.

The indication for instructing the UE to detect pilot signal may inexplicitly specify the first position at which the PDSCH may be transmitted in the time period the channel is occupied. For example, if the base station may complete CCA within the first m OFDM symbols in subframe n+k, the first PDSCH may be transmitted as early as in subframe n+k. If the base station may complete CCA within a time period after the first m OFDM symbols in subframe n+k, the first PDSCH may be transmitted as early as in subframe n+k. Even if the UE detects the indication in the Pcell, that does not necessarily mean the base station transmitted the pilot signal. In fact, whether the pilot signal can be transmitted and the start time of the pilot signal may be decided by the channel state detected by the base station.

If the start timing of PDSCH has arrived when the channel is idle and an LBT condition is satisfied, there is no time to transmit the pilot signal. In an example, as shown in FIG. 16, the base station may directly transmit the PDSCH. In another example, the base station may continuously transmit the pilot signal until the next start timing of PDSCH before transmitting PDSCH.

If the channel stays busy before the start timing of PDSCH, the base station cannot occupy the channel. As shown in FIG. 17, the base station may not transmit the indication again for instructing the UE to detect pilot signal, and continue channel state detection, and occupy the channel when the channel is idle and the LBT condition is satisfied. In another example, if the base station is to continue channel state detection, the base station may transmit the indication again in subframe n+1 in the Pcell to instruct the UE to detect the pilot signal in subframe n+1+k.

After receiving the indication in the Pcell, the UE may start detect the pilot signal at a time point determined by the LTE device. The UE may not have to start detect the pilot signal from a long time beforehand because the start timing of PDSCH is generally in one of the first 4 OFDM symbols from the start position of a subframe and a short pilot signal segment may be enough to enable UE synchronization and AGC and the like. If the time-frequency synchronization and AGC, etc. of the UE are in good state, the UE may skip pilot signal detection and directly detect PDCCH/EPDCCH to receive downlink data.

If the UE detects a valid pilot signal after receiving the instruction from the Pcell, the UE may start monitoring PDCCH/EPDCCH in the subframe which includes the first PDSCH to receive downlink data. If the UE does not detect the pilot signal, the UE may not monitor PDCCH/EPDCCH in the subframe including the PDSCH because a possible reason for detecting no pilot signal may be the base station did not occupy the channel. In an example, the UE may monitor PDCCH/EPDCCH in the subframe which includes the PDSCH. This may be applied to two situations. In a first situation, the base station may have no time to transmit a pilot signal and directly transmits PDSCH because the start timing of PDSCH has arrived when the channel is idle and the LBT condition is satisfied. In a second situation, the UE may miss the pilot signal transmitted by the base station, but may still have the opportunity to correctly receive the PDSCH because the PDSCH may be re-transmitted according to HARQ. Another indication may be transmitted in PDCCH/EPDCCH in the Pcell to inform the UE of whether the base station has successfully occupied the channel. Therefore, the UE may determine whether to perform blink detection for PDCCH/EPDCCH to receive downlink data according to the obtained instruction.

In an example, an indication may be transmitted in a Pcell, e.g., through PDCCH or EPDCCH. The indication may be used for informing the position at which the UE may start blind detection of PDCCH/EPDCCH to receive downlink data. For example, the indication may be transmitted in Pcell subframe n to instruct the UE to start blind detection of PDCCH/EPDCCH from subframe n+k to receive downlink data. The k may be larger than 0. The value of k may be determined according to a time delay adopted by the UE for PDCCH/EPDCCH processing. After detecting the Pcell indication, the UE may monitor PDCCH/EPDCCH and corresponding PDSCH in one or plural subframes in the time period after the channel is occupied. Even if the UE detects the indication in the Pcell, that does not necessarily mean the base station transmitted the pilot signal. On possibility may be that the base station may have occupied the channel but the UE is not scheduled in the current subframe. Another possibility may be that the base station may have not successfully occupied the channel for data transmission because the channel is busy.

Supposing the base station supports transmitting a pilot signal, the above Pcell indication may inexplicitly specifying the position of the pilot signal. In fact, the time period before the start position of the PDSCH specified by the indication may be the time position at which the pilot signal may be transmitted. In an example, according to the Pcell indication, the UE may directly monitor PDCCH/EPDCCH to receive downlink data without monitoring the pilot signal. In another example, the UE may choose to receive the pilot signal according to the need.

Example eight

In order to co-exist with other LTE systems and other wireless systems on an unlicensed band, an LTE device may check the state of a channel before transmitting a signal, and occupy the channel only when the channel is idle and an LBT condition is satisfied. The time during which the LTE device occupies the channel may be the duration of one or plural subframes. For example, according to regulations of Europe, the channel occupation time may reach 10 to 13 ms, which may be about 4ms according to regulations of Japan.

Supposing the CCA on the bandwidth of a channel on an unlicensed band may continue until the first m OFDM symbols in a subframe and m is smaller than or equal to 3, transmission of the PDSCH in the first subframe after the LTE device occupies the channel may not start from the first OFDM symbol. In subframes other than the first subframe after the LTE device occupies the channel, the LTE device may start transmitting data or control signal from the first OFDM symbol so as to keep occupying the channel.

According to the above analysis, the start OFDM symbol of PDSCH transmission in the first subframe within the time the LTE device occupies the channel may be different from that in a subframe other than the first subframe. The following illustrates a method of processing a OFDM symbol from which PDSCH transmission starts.

According to the method, a start OFDM symbol of a PDSCH in the first subframe and the start OFDM symbol of a PDSCH in a subframe within a time period in which the channel is occupied may be configured via radio resource control (RRC) signaling.

In another example, in order to maximize the probability of an LTE device successfully occupying a channel, the first three OFDM symbols in a subframe may all be used for CCA. Accordingly, the fourth OFDM symbol may be defined as the start position of PDSCH in the first subframe after the channel is occupied. The start OFDM symbol of PDSCH in a subframe other than the first subframe after the channel is occupied may be configured via RRC signaling. In an example, the RRC signaling for configuring the start OFDM symbol of PDSCH in an Scell in LTE CA systems may be reused.

In another example, the RRC signaling for configuring the start OFDM symbol of PDSCH in an Scell in LTE CA systems may be reused to configure the start OFDM symbol of PDSCH in the first subframe after the channel is occupied. The LTE device may be configured to start transmitting data from the first OFDM symbol in a subframe other than the first sub frame after the channel is occupied.

In an example, in order to maximize the probability of an LTE device successfully occupying a channel, the first three OFDM symbols in a subframe may all be used for CCA. Accordingly, the fourth OFDM symbol may be defined as the start position of PDSCH in the first subframe after the channel is occupied. In an example, in order to enabling occupying a channel using PDSCH, it may be regulated that an LTE device always regards data transmission starts from the first OFDM symbol in a subframe other than the first subframe after the channel is occupied. Therefore, the positions of the start OFDM symbols of PDSCH in subframes on the unlicensed band may be determined without using RRC signaling.

According to the above three examples, the UE may have to know the position of the first subframe after the channel is occupied. The indication for instructing the UE to search for pilot signal in example seven may inexplicitly specify the first position at which the PDSCH may be transmitted in the time period when the channel is occupied. Supposing the channel stays busy before the start timing of PDSCH in the first possible PDSCH and the base station continues monitoring the channel state instead of transmitting new Pcell indication informing the UE to monitor the pilot signal, the base station may transmit the PDSCH within a subframe after the first PDSCH subframe. In this example, in thr first PDSCH subframe after the base station occupies the channel, in order to avoid confusion, the base station may configure the start OFDM symbol of PDSCH according to the method for a subframe other than the first subframe within the time period when the channel is occupied. In another example, the base station may transmit information in PDCCH/EPDCCH to specify the current PDSCH subframe is the first subframe after the channel is occupied.

In some cases, the UE may not know the exact position of the first subframe after the channel is occupied. Indication may be added in PDCCH/EPDCCH to specify the start position of the scheduled PDSCH. For example, 2-bit information may be added to dynamically specify the start OFDM symbol of PDSCH.

In an example, indication of 1 bit may be added. The RRC signaling for configuring a start OFDM symbol of PDSCH in an Scell in LTE CA systems may be reused to semi-statically configure the position of the start OFDM symbol of PDSCH. The 1-bit indication may dynamically specify whether PDSCH is mapped from the first OFDM symbol or from the start OFDM symbol semi-statically configured. According to the method, the first subframe after the channel is occupied may also provide the base station with two options of the start OFDM symbol. This is beneficial when an LTE device has occupied the channel before the subframe starts. The two options of a start OFDM symbol are still provided for a subframe other than the first subframe after the channel is occupied so as to support self-scheduling on the bandwidth of the channel on the unlicensed band using the PDCCH.

Corresponding to the above method, various examples also provide an LTE deivce capable of executing the method. FIG. 18 is a schematic diagram illustrating the structure of an LTE device in accordance with examples of the present disclosure. The LTE device may include:

a channel assessment module 1801, configured to perform clear channel assessment (CCA) within bandwidth of a channel in an unlicensed band; and

a data transmission module 1802, configured to determine whether to perform data transmission according to the channel state obtained in the bandwidth, and occupy the channel to perform data transmission when the channel state satisfies a pre-defined idle criterion.

Meanwhile, an inner structure of an LTE device (not shown) in an LTE system according to an embodiment of the present disclosure will be described below.

The LTE device includes a transmitter, a controller, a receiver, and a storage unit.

The controller controls the overall operation of the LTE device. More particularly, the controller controls the LTE device to perform an operation related to an operation of contending for channel resources in the LTE system, so as to reduce interference to the LTE system operating on an unlicensed band and to improve communication performances of the LTE system according to an embodiment of the present disclosure. The operation related to the operation of contending for the channel resources in the LTE system, so as to reduce the interference to the LTE system operating on the unlicensed band and to improve the communication performances of the LTE system according to an embodiment of the present disclosure is performed in the manner described with reference to FIGS. 1 to 26, and a description thereof will be omitted herein.

The transmitter transmits various signals and various messages, and the like to other LTE devices and other devices, and the like included in the LTE system under a control of the controller. The various signals, the various messages, and the like transmitted in the transmitter have been described in FIGS. 1 to 26 and a description thereof will be omitted herein.

The receiver receives various signals, various messages, and the like from other LTE devices and other devices included in the LTE system under a control of the controller. The various signals, the various messages, and the like received in the receiver have been described in FIGS. 1 to 26 and a description thereof will be omitted herein.

The storage unit stores a program related to an operation of contending for channel resources in the LTE system, so as to reduce interference to the LTE system operating on an unlicensed band and to improve communication performances of the LTE system according to an embodiment of the present disclosure, various data, and the like.

The storage unit stores the various signals and the various messages which the receiver receives from the other LTE devices and other devices, and the like.

While the transmitter, the controller, the receiver, and the storage unit are described in the LTE device as separate units, it is to be understood that this is merely for convenience of description. In other words, two or more of the transmitter, the controller, the receiver, and the storage unit may be incorporated into a single unit. The LTE device may be implemented with one processor.

In addition, various modules of various examples may be integrated into one processing unit, or may be in the form of standalone physical entities. In other examples, two or more of the modules may be integrated into one unit. The integrated units may be implemented by hardware or software modules. The modules of various examples may be within the same terminal or network node, or may be distributed into multiple terminals or network nodes.

In addition, each example may be implemented by data processing program executed by a data processing device such as a computer. Thus, data processing program is part of the present disclosure. Data processing program stored in a storage medium may be executed after being read out from the storage medium or after being installed or copied to a storage device (e.g., a hard drive or memory) in a data processing device. Thus, such storage medium is also part of the present disclosure. The storage medium may include any recording mechanisms, such as paper storage medium (e.g., a paper tape), magnetic storage medium (e.g., floppy disks, hard drive, flash memory), optical storage medium (e.g., CD-ROM), magneto-optical storage medium (e.g., MO), and the like.

Various examples also provide a storage medium which stores the data processing program for executing any of various examples of the method.

The method procedures may be implemented by a data processing program, or by hardware, e.g., logic gates, on-off switches, application specific integrated circuit (ASIC), programmable logic controller and embedded micro-controllers, or the like. Such hardware capable of implementing the method may also be part of the present disclosure.

The foregoing are only preferred examples of the present disclosure and are not for use in limiting the protection scope thereof. All modifications, equivalent replacements or improvements in accordance with the spirit and principles of the present disclosure shall be included in the protection scope of the present disclosure.

Certain aspects of the present disclosure may also be embodied as computer readable code on a non-transitory computer readable recording medium. A non-transitory computer readable recording medium is any data storage device that can store data, which can be thereafter read by a computer system. Examples of the non-transitory computer readable recording medium include read only memory (ROM), random access memory (RAM), CD-ROMs, magnetic tapes, floppy disks, optical data storage devices, and carrier waves (such as data transmission through the Internet).The non-transitory computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. In addition, functional programs, code, and code segments for accomplishing the present disclosure can be easily construed by programmers skilled in the art to which the present disclosure pertains.

It can be appreciated that a method and apparatus according to an embodiment of the present disclosure may be implemented by hardware, software and/or a combination thereof. The software may be stored in a non-volatile storage, for example, an erasable or re-writable ROM, a memory, for example, a RAM, a memory chip, a memory device, or a memory integrated circuit (IC), or an optically or magnetically recordable non-transitory machine-readable (e.g., computer-readable), storage medium (e.g., a compact disk (CD), a digital video disc (DVD), a magnetic disk, a magnetic tape, and/or the like).A method and apparatus according to an embodiment of the present disclosure may be implemented by a computer or a mobile terminal that includes a controller and a memory, and the memory may be an example of a non-transitory machine-readable (e.g., computer-readable), storage medium suitable to store a program or programs including instructions for implementing various embodiments of the present disclosure.

The present disclosure may include a program including code for implementing the apparatus and method as defined by the appended claims, and a non-transitory machine-readable (e.g., computer-readable), storage medium storing the program. The program may be electronically transferred via any media, such as communication signals, which are transmitted through wired and/or wireless connections, and the present disclosure may include their equivalents.

An apparatus according to an embodiment of the present disclosure may receive the program from a program providing device which is connected to the apparatus via a wire or a wireless and store the program. The program providing device may include a memory for storing instructions which instruct to perform a content protect method which has been already installed, information necessary for the content protect method, and the like, a communication unit for performing a wired or a wireless communication with a graphic processing device, and a controller for transmitting a related program to a transmitting/receiving device based on a request of the graphic processing device or automatically transmitting the related program to the transmitting/receiving device.

While the present disclosure has been shown and described with reference to various embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents.

Claims

A method of contending for channel resources in a long-term evolution (LTE) system, comprising:

performing, by an LTE device, clear channel assessment (CCA) within bandwidth of a channel in an unlicensed band;

determining, by the LTE device, whether to perform data transmission according to a channel state obtained within the bandwidth; and performing data transmission using the channel when the channel state satisfies a pre-defined clear channel criterion.
The method of claim 1, wherein

performing the CCA within the bandwidth of the channel in the unlicensed band comprises: performing CCA for N types of signals respectively;

wherein performing the data transmission in the channel when the channel state satisfies the pre-defined clear channel criterion comprises: comparing CCA measuremnet results of the N types of signals with respective pre-defined CCA thresholds, and judging whether the LTE device is to occupy the channel according to results of the comparing; wherein N is the number of types of the signals.
The method of claim 1, wherein

wherein performing the CCA within the bandwidth of the channel in the unlicensed band comprises: monitoring the channel state in all of time resources; the time resources comprises alternating time segments A and time segments B;

wherein determining whether to perform the data transmission comprises:

performing, by the LTE device, the data transmission in the channel in response to a determination that the channel state obtained in time segments A is idle and a listen before talk (LBT) condition is satisfied;

stopping, by the LTE device, an LBT operation in time segments B in response to a determination that the channel state obtained in time segments A is idle and the LBT condition is not satisfied; or

continuing, by the LTE device, monitoring the channel state and updating a state of an LBT counter until the LBT counter returns to zero in response to a determination that the channel state obtained in time segments A is idle and the LBT condition is not satisfied.
The method of claim 1, wherein

performing the CCA within the bandwidth of the channel in the unlicensed band comprises: monitoring the channel state in all of time resources which includes alternating time segments A and time segments B; obtaining, by the LTE device, the channel state on each orthogonal frequency division multiplexing (OFDM) symbol in time segments A, and performing data transmission using the channel from the n+1'th OFDM symbol when the channel state obtained in the n'th OFDM symbol is idle.
The method of claim 1, further comprising:

transmitting, by the LTE device, a pilot signal which includes a pre-defined sequence when the channel state is idle and an LBT condition is satisfied; wherein the pilot signal is composed of a basic sequence, the length of the basic sequence equals to the length of an OFDM symbol or the length of time during which the CCA is performed.
The method of claim 1, further comprising: transmitting, by the LTE device, a pilot signal which includes a pre-defined sequence when the channel is idle and an LBT condition is satisfied; wherein time domain mapping of the pilot signal takes a fixed time point as a reference time point; the start and end timings of an OFDM symbol in which the pilot signal is transmitted are aligned to an OFDM symbol in a subframe according to a position of a transmission start time of the pilot signal in an LTE subframe.
The method of claim 1, further comprising:

transmitting, by the LTE device, a pilot signal including a pre-defined sequence when the channel is idle and an LBT condition is satisfied;

transmitting, by the LTE device, the pilot signal in one comb which is one of plural combs obtained by dividing subcarriers on bandwidth of the LTE communication system into groups; or

transmitting, by the LTE device, the pilot signal in one group of sub bands which is one of plural groups of sub bands within bandwidth of the LTE communication system, wherein sub bands in each group are distributed over the system bandwidth.
The method of claim 1, further comprising:

transmitting, by the LTE device, a pilot signal including a pre-defined sequence when the channel is idle and an LBT condition is satisfied;

setting a global pilot signal sequence, wherein a sequence segment of the pilot signal mapped onto a frequency is a fixed segment in the global pilot signal sequence.
The method of claim 1, wherein:

the pilot signal comprises one or plural complete OFDM symbols of an LTE system; if a time point at which a channel occupation requirement is satisfied is not a start position of an OFDM symbol, a portion before the time point in the first OFDM symbol in OFDM symbols for transmitting the pilot signal is truncated.
The method of claim 1, wherein performing the CCA by the LTE device comprises: performing the CCA for signal power of different types of signals respectively to obtain the signal power of the different types of signals.
The method of claim 1, further comprising: transmitting, by a base station of LTE devices, an indication in a primary cell for informing a UE of the LTE devices of the position to start monitoring the pilot signal.
The method of claim 1, further comprising: transmitting, by a base station of LTE devices, an indication in a primary cell to inform a UE of the LTE devices of the position to start blind detection of a physical downlink control channel (PDCCH)/enhanced PDCCH (EPDCCH) for receiving downlink data.
The method of claim 1, further comprising:

configuring, via radio resource control (RRC) signaling, the first OFDM symbol for transmitting a PDSCH in the first subframe and the first OFDM symbol for transmitting a PDSCH in a subframe other than the first subframe within a time period in which the channel is occupied for data transmission; or

defining the start position of a PDSCH in the first subframe after occupying the channel is the fourth OFDM symbol, and configuring the start OFDM symbol in a subframe other than the first subframe via RRC signaling; or

configuring via RRC signaling the first OFDM for transmitting a PDSCH in the first subframe after the channel is occupied, and defining data transmission starts from the first OFDM symbol in a subframe other than the first subframe after the channel is occupied; or

defining a start position for transmitting a PDSCH in the first subframe after the channel is occupied is the fourth OFDM symbol, and defining that data transmission starts from the first OFDM symbol in a subframe other than the first subframe after the channel is occupied.
The method of claim 1, further comprising: adding an indication of 1 bit in PDCCH/EPDCCH for indicating a PDSCH is mapped according to a semi-statically configured start OFDM symbol or indicating a PDSCH is mapped from the first OFDM symbol.
A long-term evolution (LTE) device adapted to perform the method of one of claims 1 to 14.