HK1226877B - Downlink subframe shortening method and apparatus in time-division duplex systems - Google Patents

Description

Method and device for shortening downlink subframe in time division duplex system

Technical Field

The technology disclosed herein relates generally to wireless communication networks, and more specifically to techniques for modifying subframe lengths in Time Division Duplex (TDD) systems.

Background

In a typical cellular radio system, end user radios or wireless terminals, also referred to as mobile stations and/or user equipment Units (UEs), communicate through a Radio Access Network (RAN) to one or more core networks. The Radio Access Network (RAN) covers a geographical area which is divided into cell areas, with each cell area being served by a base station, e.g. a Radio Base Station (RBS), which in some networks is also referred to as e.g. "NodeB" or "eNodeB". A cell is a geographical area which is provided with radio coverage by radio base station equipment at a base station site. Each cell is identified by an identity within the local radio area, which is broadcast within the cell. The base stations communicate over the air interface operating on radio frequencies with user equipment Units (UEs) within range of the base stations.

In some radio access networks, some base stations may be connected to a Radio Network Controller (RNC) or a Base Station Controller (BSC), for example, by landlines or microwave links. The radio network controller monitors and coordinates various activities of a plurality of base stations connected thereto. The radio network controller is typically connected into one or more core networks.

The Universal Mobile Telecommunications System (UMTS) is a third generation mobile communication system that has evolved from the global system for mobile communications (GSM). UTRAN is a radio access network using wideband code division multiple access (W-CDMA) for communication between UEs and base stations (referred to as NodeB in the UTRAN standard).

In a forum known as the third generation partnership project (3 GPP), telecommunications providers propose and agree on a generic third generation network and a specific UTRAN standard and study techniques to enhance wireless data rates and radio capacity. The 3GPP has undertaken to further evolve UTRAN and GSM based on radio access network technologies. Some versions of the evolved universal terrestrial radio access network (E-UTRAN) are proposed and continue to evolve the standard. Evolved universal terrestrial radio access network (E-UTRAN) includes Long Term Evolution (LTE) and System Architecture Evolution (SAE).

Long Term Evolution (LTE) is a variant of the 3GPP radio access technology, where radio base station nodes are connected to the core network through Access Gateways (AGWs), rather than Radio Network Controller (RNC) nodes. Generally, in LTE systems, the functionality of a Radio Network Controller (RNC) node is distributed between a radio base station node (referred to as eNodeB in the LTE standard) and an AGW. Thus, the radio access network (RNC) of the LTE system has a structure sometimes referred to as "flat", comprising radio base station nodes that do not report to the Radio Network Controller (RNC) node.

Transmissions and receptions from nodes, e.g. radio terminals like UEs in a cellular system such as LTE, may be multiplexed in the frequency or time domain or a combination of the above. In a Frequency Division Duplex (FDD) system, downlink and uplink transmissions occur in different, well separated frequency bands, as shown on the left in fig. 1. In Time Division Duplexing (TDD), downlink and uplink transmissions occur in different, non-overlapping time slots, as shown on the right in fig. 1. Thus, TDD can operate in unpaired spectrum, while FDD requires paired spectrum.

Typically, the signals transmitted in a communication system are organized in some form of frame structure. For example, as shown in fig. 2, LTE uses 10 equally sized subframes 0-9 of length 1 millisecond per radio frame.

In case of FDD operation, as shown in the upper part of fig. 2, there are two carrier frequencies, one for uplink transmission (fl) and one for downlink transmission (fDL). FDD may be either full duplex or half duplex, at least with reference to radio terminals in cellular communication systems. In the case of full duplex, the terminal may transmit and receive simultaneously, whereas in half duplex operation (see fig. 1), the terminal cannot transmit and receive simultaneously (although the base station is capable of receiving/transmitting simultaneously, i.e. receiving from one terminal while transmitting to another terminal). In LTE, a half-duplex radio terminal monitors/receives in the downlink link except when the uplink is explicitly instructed to transmit in a specific subframe.

In the case of TDD operation (as shown in the lower part of fig. 2), there is only a single carrier frequency, FUL/DL, and the uplink and downlink transmissions are separated in time and also on a cell basis. Since the same carrier frequency is used in both uplink and downlink transmissions, both the base station and the mobile terminal need to switch from transmitting to receiving and vice versa. An important aspect of TDD systems is to provide a sufficiently large guard time in case neither downlink nor uplink transmission occurs to avoid interference between uplink and downlink transmission. For LTE, special subframes (located at subframe 1 and, in some cases, subframe 6) provide this guard time. The TDD special subframe is divided into three parts: downlink part (DwPTS), Guard Period (GP), and uplink part (UpPTS). The remaining subframes are either allocated for uplink or downlink transmission.

Time Division Duplex (TDD) operation allows different asymmetries about the amount of resources allocated for uplink and downlink transmissions (by different downlink/uplink configurations), respectively. As shown in fig. 3, in LTE, there are seven different configurations. Each configuration has a different proportion of downlink and uplink subframes in each 10 ms radio frame. For example, as shown at the top of the figure, configuration 0 has two downlink subframes and three uplink subframes in each 5 ms half-frame, as indicated by the label "DL: UL 2: 3 "is indicated. Configurations 0, 1, and 2 have the same arrangement in each 5 ms half frame in the radio frame, while the remaining configurations are not the same. For example, configuration 5 has only a single uplink subframe and 9 downlink subframes, as identified by the label "DL: UL 9: 1 "is indicated. This configuration provides a range of uplink/downlink ratios to enable the system to select the configuration that best matches the previous traffic load.

To avoid significant interference between downlink and uplink transmissions between different cells, neighboring cells should have the same downlink/uplink configuration. Otherwise, as shown in fig. 4, uplink transmissions to base station 2, BS2 in one cell may interfere with downlink transmissions to base station 1, BS1 in a neighboring cell (and vice versa). In fig. 4, the uplink transmission of the UE in the right cell (identified as mobile station 1, MS1 in the figure) interferes with the downlink reception of the UE in the left cell (MS 2). To avoid this interference, the downlink/uplink asymmetry does not vary between cells. The downlink/uplink asymmetry configuration may be signaled as part of the system information and remain fixed for a long time.

In LTE, the downlink is based on Orthogonal Frequency Division Multiplexing (OFDM) and the uplink is based on discrete fourier transform spread (DFT-spread) OFDM, also known as single carrier frequency division multiple access (SC-FDMA). Available in 3GPP documents "evolved Universal Radio Access (E-UTRA)", Physical channels and modulation "(evolved Universal Terrestrial Radio Access (E-UTRA)"), 3GPP TS 36.211, V11.3.0, at www.3gpp.org. The Transmission Time Interval (TTI) in both cases is equal to a1 millisecond subframe consisting of 14 OFDM symbol intervals in the downlink and 14 SC-FDMA symbol intervals in the uplink, given a normal length of cyclic prefix. The portions of the OFDM and SC-FDMA symbols transmitted in these symbol intervals may be used to carry user data in physical channels known as Physical Downlink Shared Channel (PDSCH) and Physical Uplink Shared Channel (PUSCH). In future wireless communication systems, the length of the sub-frames may be significantly reduced to reduce user data delay. Further, both the downlink and uplink in future wireless systems may be based on OFDM.

An important priority of current wireless system evolution and the development of future wireless communication systems is higher bit rates and shorter delays, especially as applied in cell scenarios. Higher bit rates can be achieved by using higher carrier frequencies, for example, where wide spectrum resources are available. Moreover, TDD (time division duplex) is still gaining increased interest. With dynamic TDD systems, i.e. systems where the TDD configuration from one subframe to the next is not necessarily static, the downlink or uplink bit rate can be increased immediately by adaptively changing the relation between the number of intervals for downlink (from eNodeB to UE) and uplink (from UE to eNode B). Within a cell, the propagation delay will be small, so that a small guard interval can be used when switching from downlink to uplink. Accordingly, there is a need for improved techniques for switching between downlink and uplink in dynamic TDD systems while maintaining minimal interference between downlink and uplink transmissions and keeping control signaling to a minimum.

Disclosure of Invention

The fixed relationship between uplink and downlink in Time Division Duplex (TDD) systems results in inflexible radio resource utilization. Dynamic TDD systems allow for more flexible use of these resources. In various embodiments of the present invention, a guard interval for switching between uplink and downlink subframes is created by shortening the downlink subframe. This is done by omitting one or more symbols at the end of the downlink subframe transmission interval, i.e. by not transmitting during one or more symbol intervals at the end of the subframe interval. Signaling is included in a downlink grant (grant) message sent to the UE indicating that the UE downlink subframe is one or several OFDM (or SC-FDMA) symbols shorter than the normal subframe, wherein transmission of the subframe ends one or several OFDM (or SC-FDMA) symbol intervals earlier than the normal subframe.

Although several embodiments are described below in the context of an LTE system in which the uplink corresponds to transmissions from the UE to the eNode B, it will be appreciated that the techniques of the present disclosure may be applied to other wireless systems and do not necessarily depend on a particular hierarchical arrangement between the LTE enodebs and the UEs.

Accordingly, example methods according to the present disclosure are applicable to receiving node implementations configured to receive data from a transmitting node in subframes occurring at defined subframe intervals and having a predetermined number of symbol intervals. In an LTE system, this receiving node may be a UE, the subframe being a downlink subframe. The example method includes determining that a received subframe is to be shortened relative to a predetermined number of symbol intervals, and in response to the determination, ignoring a last portion of the received subframe by ignoring one or more symbols at an end of the received subframe when processing the received subframe.

In some embodiments, the receiving node determines that the received subframe is to be shortened by receiving a message from the transmitting node containing subframe-shortening information indicating that the received subframe is to be shortened. The subframe-shortening information, which is received in the grant message transmitted in the beginning portion of the received subframe, may consist of, for example, a single bit indicating that the received subframe is to be shortened by omitting a predetermined number of symbols, or may include a plurality of bits indicating a plurality of symbols to be ignored at the end of the received subframe. In other embodiments or other instances, the receiving node may determine that the receive subframe is to be shortened without explicit signaling from the transmitting node, e.g., by determining that the transmit subframe is scheduled to be transmitted in an interval of consecutive (contiguous) and overlapping receive subframes.

Another example method is suitable for implementation in a transmitting node configured to transmit data to a receiving node occurring at a defined subframe interval and having a predetermined duration (e.g., a predetermined number of symbols). In an LTE system, the node is an LTE eNodeB, and the subframes are also downlink subframes. The example method includes transmitting a message to a receiving node containing subframe-shortening information indicating that a subframe is to be shortened relative to a predetermined number of symbol intervals. The method further includes shortening the subframe by omitting one or more symbols at the end of the subframe when transmitting the subframe. The subframe-shortening information may be transmitted in the grant information in the first portion of the subframe, and may consist of a single bit indicating that the subframe is to be shortened by omitting a predetermined number of symbols from the end of the subframe, or may include a plurality of bits indicating a certain number of symbols to be omitted from the subframe.

Corresponding structures, i.e. receiving and transmitting nodes, configured to implement one or more of the methods summarized above are also detailed in the following description.

Of course, the present invention is not limited to the above features and advantages. Indeed, those skilled in the art will recognize additional features and advantages upon reading the following detailed description, and upon viewing the accompanying drawings.

Drawings

Fig. 1 illustrates frequency division duplex, half duplex frequency division, and time division duplex transmissions.

Fig. 2 shows the uplink/downlink time/frequency structure of LTE for the case of Frequency Division Duplex (FDD) and Time Division Duplex (TDD).

Fig. 3 is a diagram illustrating an example of seven different downlink/uplink configurations for Time Division Duplex (TDD) in Long Term Evolution (LTE).

Fig. 4 illustrates an example of interference for uplink/downlink (UL/DL) interference in Time Division Duplex (TDD).

Fig. 5 shows a portion of an example LTE network, including multiple User Equipments (UEs).

Fig. 6 illustrates downlink and uplink timing in a TDD system.

Fig. 7 shows an uplink-downlink configuration according to the 3GPP specifications.

Fig. 8 shows details of frame structure type 2 (for a switching point period of 5 milliseconds), as specified by 3GPP.

Fig. 9 shows shortening of the uplink OFDM symbol after the downlink subframe.

Fig. 10 shows shortening of a downlink subframe before an uplink subframe.

FIG. 11 illustrates an example method process flow diagram in accordance with the presently disclosed technology.

FIG. 12 is a process flow diagram illustrating another example method.

FIG. 13 is a block diagram illustrating components of an example user device.

Fig. 14 shows a block diagram of an example base station.

Detailed Description

In the following description, for purposes of explanation and limitation, specific details are set forth of particular embodiments of the invention, and it will be appreciated by one skilled in the art that other embodiments may be utilized in addition to the specific details. Further, detailed descriptions of well-known methods, nodes, interfaces, circuits, and devices in some instances are omitted so as not to obscure the description with unnecessary detail. Those skilled in the art will appreciate that the described functionality may be implemented in one or several nodes. Some or all functions described may be implemented using hardware circuitry (e.g., analog and/or discrete logic gates interconnected to perform the specified function, ASICs, PLAs, etc.), and likewise some or all functions may be implemented using software programs and data in conjunction with one or more digital microprocessors and a general purpose computer. Where nodes that communicate using the air interface are described, it will be appreciated that those nodes also have suitable radio communications circuitry. Moreover, the techniques can additionally be considered to be embodied entirely within any form of computer-readable memory, including non-transitory embodiments such as solid-state memory, magnetic disk, or optical disk containing an appropriate set of computer instructions that would cause a processor to perform the described techniques.

Hardware implementations of the invention can include, or encompass, without limitation, Digital Signal Processor (DSP) hardware, a reduced instruction set processor, hardware (e.g., digital or analog) circuitry including, but not limited to, an Application Specific Integrated Circuit (ASIC), and/or one or more Field Programmable Gate Arrays (FPGAs), and, where appropriate, a state machine capable of performing such functions.

With respect to computer implementations, a computer is generally understood to include one or more processors or one or more controllers, and the terms computer, processor, and controller are used interchangeably. When provided by a computer, processor or controller, the functions may be provided by a single dedicated computer or processor or controller, by a single shared computer or processor or controller, or by a plurality of individual computers or processors or controllers, some of which may be shared or distributed. Furthermore, the terms "processor" or "controller" also refer to other hardware capable of performing such functions and/or executing software, such as the example hardware described above.

Referring now to the drawings, fig. 5 illustrates an exemplary mobile communication network for providing wireless communication services to a mobile terminal 100. Three mobile terminals 100, referred to in 3GPP terminology as "user equipment" or "UE", are shown in fig. 5. The mobile terminal 100 may comprise, for example, a cellular telephone, a personal digital assistant, a smart phone, a palm top computer, a handheld computer, a machine type communication/machine to machine (MTC/M2M) device or other device having wireless communication capabilities. It is noted that the term "mobile terminal," as used herein, refers to a terminal operating in a mobile communications network and does not necessarily imply that the terminal itself is mobile or otherwise movable. Thus, the terms used herein should be understood to be interchangeable with the term "wireless device" and may refer to a terminal installed in a fixed configuration, such as in certain machine-to-machine applications, as well as a removable device, a device installed in a motor vehicle, and the like.

The mobile communications network includes a plurality of geographic cell regions or sectors 12. Each geographic cell region or sector 12 may be served by a base station 20, which in the context of an LTE radio access network is referred to as an eNodeB, formally referred to as an evolved universal terrestrial radio access network or E-UTRAN. One base station 20 provides service in multiple geographic cell regions or sectors 12. The mobile terminal 100 receives signals from the base station 20 on one or more Downlink (DL) channels and transmits signals to the base station 20 on one or more Uplink (UL) channels.

In an LTE network, the base station 20 is an eNodeB and may be connected to one or other enodebs through an X2 interface (not shown). The eNodeB is also connected to the MME130 through an S1-MME interface, and may be connected to one or more other network nodes, such as a serving gateway (not shown).

For purposes of illustration, several embodiments of the present invention may be described in the context of the EUTRAN system. However, those skilled in the art will appreciate that several embodiments of the present invention may be more generally applicable to other wireless communication systems.

As discussed above, in a TDD (time division duplex) system, both the downlink and uplink use the same frequency. Assuming full duplex operation is not possible, both the UE and the eNodeB must then switch between transmission and reception. An illustration of the timing between downlink and uplink is given in fig. 6, which shows the subframe transmission and reception times (times) versus time at both the UE and eNodeB, which can be measured in terms of OFDM (or SC-FDMA) symbol indices. Due to the propagation delay, which may vary as the UE moves in the coverage of the eNodeB, the downlink subframe transmitted by the eNodeB is received at the UE after a delay. A fast fourier transform, FFT, window in the UE receiver is aligned to the received subframe such that the data portion of the subframe falls completely within the FFT window, while the cyclic prefix, CP, portion of the subframe overlaps with the FFT window edge. The uplink subframe transmitted by the UE may be transmitted only after the UE has completed switching time from reception to transmission mode and received at the eNodeB after a propagation delay. The timing of UE transmissions is controlled by the eNodeB such that the data-carrying parts of consecutive uplink subframes from multiple UEs do not overlap each other and fall within the FFT window of the eNodeB receiver. Again, the portion of the subframe that includes the cyclic prefix, CP, may overlap with the edge of the eNodeB FFT window.

Fixed allocations of uplink and downlink subframes are used in LTE release 11 and are defined in "evolved universal Radio Access (E-UTRA)", Physical channels and modulation, "(" evolved universal Terrestrial Radio Access (E-UTRA) "), 3GPP TS 36.211, V11.3.0, available at www.3gpp.org. Some predetermined allocations are then specified as shown in fig. 7, where uplink-downlink configurations 0-6 are shown, along with their respective periods of either 5 ms or 10 ms. In the diagram shown in fig. 7, each subframe number 0-9 is indicated by a subframe designated as either "D", "U", or "S", corresponding to downlink, uplink, and special subframes, respectively. The specific subframe is inserted between consecutive downlink and uplink subframes. Details of the special sub-frame are shown in fig. 8. The special subframe downlink and uplink include both OFDM and SC-FDMA symbols, respectively, with a guard interval therebetween. The guard interval is used by the UE to transmit a timing advance such that uplink symbols are received within the FFT window of the eNodeB, as shown in fig. 6. The guard interval also provides time for the transmit and receive circuitry of the eNodeB and UE to switch from downlink mode to uplink mode.

In the dynamic TDD system, according to the semi-static configuration shown in fig. 7, the relationship between the number of downlink subframes and uplink subframes is not fixed, but may be flexibly configured depending on current needs. For example, the UE may treat each subframe as a downlink subframe unless it is explicitly instructed to transmit in a given subframe. The dynamic TDD approach is described in U.S. patent application publication 2011/0149813a1 entitled "flexible subframes" issued on 23/6/2011, which is incorporated herein by reference in its entirety. When dynamic TDD is used, the eNodeB sends control signals to the UE indicating when and how to schedule to receive (i.e., downlink assignments) and when and how to transmit in the uplink (i.e., uplink grants). In LTE, this control signaling is also carried by the Physical Downlink Control Channel (PDCCH) or Enhanced Physical Downlink Control Channel (EPDCCH). The downlink assignment is transmitted in the same subframe as the user data is transmitted, while the uplink grant is transmitted in some subframes before the UE is scheduled to transmit in the uplink.

The fixed relationship between the uplink and the downlink results in an inflexible utilization of radio resources. However, with dynamic TDD, the amount of control signaling will increase significantly if all UEs have to know which subframe is used as downlink and uplink subframe, respectively. Further, in dynamic TDD, a guard interval is required between consecutive downlink and uplink subframes to allow the UE circuitry to switch from downlink to uplink mode.

The guard interval may be created by omitting one or several OFDM symbols in the uplink subframe. According to the method, the base station includes signaling in the UL grant indicating that the UE should transmit a subframe that is shorter than one or several OFDM (or SC-FDMA symbols) of the normal subframe, wherein the transmission of the subframe begins at one or several OFDM (or SC-FDMA) symbol intervals later than the normal subframe.

The subframe timing according to this latter approach is depicted in fig. 9, where a series of subframes are flexibly scheduled, where one subframe is scheduled for uplink use, two other subframes are scheduled for downlink use, and the remaining subframes are not scheduled. An uplink grant is transmitted in subframe n (n =5 in fig. 9) in the downlink, and the grant indicates that the UE is to transmit in subframe n + g (g =5 in fig. 9) in the uplink. If the eNodeB transmits in subframe n + g-I (subframe 9) in the downlink, the UE must omit one or several OFDM (or SC-FDMA) symbols from the uplink subframe n + g (subframe 10 in FIG. 9) from its transmission start to create a short guard interval. A "subframe-shortening message" is thus included in the uplink grant, indicating to the UE that it needs to omit one or more symbols from the start of the uplink subframe transmission. As shown at the bottom of fig. 9, the uplink subframe extends the subframe interval, which includes 14 symbol intervals numbered 0-13. Each of these symbol intervals normally carries OFDM (or SC-FDMA) symbols. However, the OFDM symbols may be omitted from one or more symbol intervals starting from the subframe interval. In the example shown in fig. 9, the guard interval is created by omitting two OFDM symbols at the beginning of the subframe interval.

Another approach is to create a guard interval by omitting one or more symbols from the end of the downlink subframe transmission. In systems utilizing redundant coding, the receiving UE may treat these omitted OFDM symbols as "punctured" symbols and reconstruct the data that would normally be carried by those symbols using normal decoding techniques. Alternatively, the receiving UE may decode data in the remaining portion of the subframe while operating around symbol intervals that do not carry data. In either case, if the guard interval is created by omitting one or several OFDM symbols in the downlink, the eNodeB needs to transmit control information to all UEs indicating that the last OFDM symbol of the subframe is omitted and therefore should be ignored by the UE. Thus, according to this method, signaling is included in the downlink grant instructing the eNodeB to transmit a subframe that is one or several OFDM (or SC-FDMA) symbols shorter than the normal subframe, and wherein the transmission of this subframe terminates earlier than the one or several OFDM (or SC-FDMA) symbol intervals with which the normal subframe would. Note that this indication needs to signal all UEs scheduled for this subframe.

Note that the UE may blindly detect whether the last OFDM symbol or symbols have been omitted. However, if the UEs are not well separated from each other, another UE may transmit in the uplink during these last downlink OFDM symbols, causing interference. This interference may lead to unreliable detection of OFDM symbol omission, which may cause performance degradation.

Fig. 10 illustrates a subframe shortening method applied to a downlink. The uplink grant is transmitted in downlink in subframe n (n =5 in fig. 10) and indicates that the first UE will transmit in subframe n + g (g =5 in fig. 10) in uplink. The eNodeB transmits in subframe n + g-l (subframe 9) in the downlink and thus omits one or several OFDM (or SC-FDMA) symbols from the end of its transmission of downlink subframe 9. A "subframe-shortening message" is thus included in the downlink grant in downlink subframe 9, indicating to one or more UEs scheduled for the downlink subframe that one or more symbols are omitted from the end of the downlink subframe transmission. Note that one or more UEs scheduled to receive the shortened subframe may be different from one or more UEs scheduled to receive in the next subframe.

At the bottom of fig. 10, details of shortening the downlink subframe are shown. Like the uplink subframe shown in fig. 9, the downlink subframe shown in fig. 10 extends the subframe interval including 14 symbol intervals numbered 0-13. Each of these symbol intervals normally carries an OFDM (or SC-FDMA) symbol. In a shortened downlink subframe, OFDM symbols may be omitted from one or more symbol intervals at the end of the subframe interval, thus creating a guard interval. In the example shown in fig. 10, the guard interval is created by omitting two OFDM symbols at the end of the subframe interval.

In some embodiments, the subframe-shortening message in the downlink grant includes only a single bit that signals whether the last OFDM (or SC-FDMA) symbol of the downlink transmission was omitted. In these embodiments, the UE may be preconfigured either by hard-programming or semi-static, e.g., by RCC signaling, with a predetermined number of symbols being ignored if a subframe-shortening message is received. A somewhat more flexible approach may be used in which the subframe-shortening message explicitly indicates the number of omitted OFDM (or SC-FDMA). Using this approach, if the round trip time is small, only one OFDM (or SC-FDMA) needs to be omitted, whereas for UEs with large round trip times, the eNodeB may need to omit multiple OFDM symbols. In some embodiments, the eNodeB may be configured to always use the same indication based on the cell size. In other embodiments, the round trip time for each UE is estimated and continuously tracked in the eNodeB so that the subframe-shortening message can adjust the round trip time for each individual UE.

For example, assume that two bits are used for the subframe-shortening message. In this example, a bit sequence of "00" may be used to signal that no downlink OFDM (or SC-FDMA) omission is made. A sequence of "01" may be used to indicate omission of one OFDM (or SC-FDMA) symbol, a sequence of "10" indicates omission of two OFDM (or SC-FDMA), and a sequence of "11" indicates omission of three OFDM (or SC-FDMA) symbols. Alternatively, the number of omitted OFDM symbols, as indicated by one or more bits of the subframe-shortening message, may be semi-statically configured by higher layers.

It will be appreciated that a downlink grant may contain grants for several subframes. If these downlink subframes are consecutive, only the last of the simultaneously scheduled subframes requires signaling for subframe shortening.

In addition, a dynamic TDD system may be configured with several pairs of subframes fixed for the uplink and thus never used for the downlink. One or more of these fixed uplink subframes may occur in a multi-subframe downlink grant for the UE. In this case, the UE cannot receive during the fixed uplink subframe, but can continue thereafter. Here, the UE may either continue to receive all remaining subframes according to its downlink grant, or consider one subframe in a grant "punctured" by a fixed uplink subframe, such that the entire downlink transmission effectively includes one less subframe than indicated by the downlink grant. In any case, the UE must know to ignore one or more OFDM (or SC-FDMA) symbols of the subframe preceding the fixed uplink subframe. The need for such subframe shortening does not have to be signaled to the UE, since the UE already knows the fixed uplink subframe. If flexible subframe shortening is used, a default number of omitted OFDM (or SC-FDMA) symbols may be used. Alternatively, subframe shortening according to the last received subframe-shortening message within a downlink grant for a particular UE may be assumed.

In the above, various techniques for transmitting and receiving shortened subframes are described in the context of an LTE system. However, it should be understood that these techniques are more generally applicable to TDD wireless links between wireless nodes, and do not rely on wireless nodes having UE-to-base station relationships found in LTE systems. Fig. 11 thus illustrates a method 1100 suitable for implementation in a wireless node, i.e., a receiving node configured to receive data in subframes occurring at defined subframe intervals and having a particular length. If the method is implemented in the LTE context, the receiving node may be a UE communicating with an eNodeB.

As shown at block 1110, the method may begin by receiving configuration information from a transmitting node specifying a predetermined number of symbols to omit from a downlink subframe if a shortened subframe is transmitted. In fig. 11, this operation is illustrated by dashed lines, indicating that this operation is not present in every embodiment or every instance of the described method.

As shown at block 1120, the method includes determining that a received subframe is shortened with respect to a predetermined length, e.g., with respect to a predetermined number of symbol intervals. As discussed above, this may be done in some embodiments or in some instances by receiving a message, such as a downlink grant message including subframe-shortening information. However, in other embodiments or in other instances, the receiving node may determine that the received subframe is to be shortened by determining that the fixed uplink subframe is consecutive and overlaps the received subframe.

At block 1130, the method continues by ignoring the last portion of the received subframe in response to determining that the received subframe is shortened. In some embodiments, the predetermined duration of the subframe is a predetermined number of symbol intervals, in which case omitting the last portion of the received subframe comprises ignoring one or more symbol intervals at the end of the received subframe. Note that as the term is used herein, a subframe interval consists of a specific number (e.g., 14) of symbol intervals, each of which normally carries a transmitted signal. When a subframe is shortened, the one or more subframe intervals do not carry transmitted symbols.

As described above, determining to shorten the received subframe may include receiving a message from the transmitting node including subframe-shortening information indicating that the received subframe is shortened. In some embodiments, the message is received in a grant message in the first portion of the received subframe. In some embodiments, the subframe-shortening information consists of a single bit indicating that the received subframe is shortened by omitting a predetermined number of symbols at the end of the subframe. In some of these embodiments, the receiving node receives configuration information from the transmitting node, as shown at block 1110, the configuration information specifying a predetermined number prior to receiving the grant message. In other embodiments, the subframe-shortening information received from the transmitting node specifies a number of symbols omitted from the end of the received subframe.

In some embodiments, the receiving node decodes data from the received subframe by treating one or more omitted symbols at the end of the subframe interval as punctured data. If the original data is encoded using conventional redundant coding techniques, the punctured data may be reconstructed using conventional decoding techniques. In other embodiments, the receiving node retrieves the decoded data from the first shortened subframe by demapping data symbols from the received subframe and decoding the demapped data symbols according to a demapping pattern that ignores symbol intervals that are omitted at the end of the subframe interval.

Fig. 12 illustrates a method 1200 implemented in a wireless node from the other end of the link corresponding to the receiving node of fig. 11. Thus, the method illustrated in fig. 12 is suitable for implementation in a transmitting node configured to transmit data in subframes occurring at defined subframe intervals and having a predetermined duration, e.g. a predetermined number of symbol intervals. In the LTE context, the transmitting node may be an eNodeB.

As shown at block 1210, the illustrated method may begin with transmitting configuration information to a receiving node, the configuration information specifying a predetermined number of symbols omitted from a downlink subframe if a shortened downlink subframe is transmitted. In fig. 12, the operation is shown with dashed lines indicating that the operation is not present in every embodiment or every instance of the illustrated method.

As shown at block 1220, the method includes transmitting, to a receiving node, a message including subframe-shortening information indicating subframes transmitted by the transmitting node during which a subframe interval is to be shortened. In the LTE context, for example, the receiving node is a UE. In some embodiments, the message is transmitted in a grant message in the first portion of the subframe.

As shown at block 1230, the method continues by shortening the subframe by omitting the end portion of the subframe when transmitting the subframe. In some embodiments, the duration of the subframe interval is a predetermined number of symbol intervals, in which case the last part of the subframe when transmitted includes one or more symbols omitted at the end of the subframe.

In some embodiments, the subframe-shortening information sent to the receiving node specifies a number of symbols omitted from the end of the subframe. In other embodiments, the subframe-shortening message consists instead of a single bit indicating that the subframe is shortened by omitting a predetermined number of symbols from the end of the subframe. In some of these embodiments, prior to transmitting the grant message, the transmitting node transmits configuration information to the receiving node, the configuration information specifying a number of symbols omitted from the end of the subframe.

In the LTE context, if a guard interval is created by puncturing one or several OFDM symbols in the downlink, the eNodeB can send a control message to the UEs scheduled in the current subframe. By the UE-specific signaling, a significant reduction in signaling overhead can be achieved. The message should preferably be transmitted together with the downlink assignment. However, if the signaling is done with an Enhanced Physical Downlink Control Channel (EPDCCH) in the same subframe as where the handover occurred, the UE cannot know whether the EPDCCH with the last OFDM symbol or an omitted symbol needs to be decoded. In some embodiments, this may be handled by performing blind decoding of EPDCCH without, with one, or several omitted symbols.

Several of the methods described above and generally shown in fig. 11 and 12 may be implemented using radio circuitry and electronic data processing circuitry provided in the receiving node and the corresponding transmitting node, respectively, corresponding to the mobile terminal and the base station. Fig. 13 illustrates features of an example receiving node 1300, in this case embodied as a mobile terminal, according to several embodiments of the present invention. The mobile terminal 1300, which may be a UE configured for operation in an LTE system, includes a transceiver 1320 for communicating with one or more base stations, and processing circuitry 1310 for processing signals transmitted and received by the transceiver 1320. The transceiver 1320 includes a transmitter 1325 coupled to one or more transmit antennas 1328 and a receiver 1330 coupled to one or more receiver antennas 1333. The same one or more antennas 1328 and 1333 may be used for both transmitting and receiving. The receiver 1330 and the transmitter 1325 use known radio processing and signal processing components and techniques typically in accordance with a particular telecommunications standard, e.g. the 3GPP standard for LTE. Since many of the details and engineering tradeoffs associated with such circuit designs and implementations are well known and not necessary for a comprehensive understanding of the invention, additional details are not shown.

The processing circuitry 1310 includes one or more processors 1340 coupled to one or more memory devices 1350, including a data storage memory 1355 and a program storage memory 1360. Processor 1340, identified in FIG. 13 as CPU1340, may be a microprocessor, microcontroller, or digital signal processor in some embodiments. More generally, the processing circuit 1310 may include a processor/firmware combination, or dedicated digital hardware, or a combination thereof. The memory device 1350 may include one or more types of memory, such as Read Only Memory (ROM), random access memory (ram), cache memory, flash memory devices, optical storage devices, and so forth. In addition, since various details and engineering tradeoffs associated with the design of baseband processing circuits for mobile devices are well known and not necessary for a comprehensive understanding of the invention, additional details are not shown herein.

Typical functions of the processing circuit 1310 include modulation and encoding of transmitted signals, and demodulation and decoding of received signals. In several embodiments, the processing circuitry 1310 is adapted, using suitable program code stored in the program memory 1360, for example, to control the transmitter 1325 and receiver 1330 and to perform the techniques described above for processing received subframes, including shortened subframes.

Accordingly, in various embodiments described herein, the processing circuitry is configured to perform one or more of the techniques described in detail above. Likewise, other embodiments include a mobile terminal (e.g., an LTE UE) that includes one or more such processing circuits. In some cases, these processing circuits are configured with suitable program code stored in one or more memory devices to implement one or more of the techniques described herein. Of course, it will be appreciated that not all of the steps of these techniques may be performed in a single microprocessor or even a single module.

Mobile terminal 1300 of fig. 13 may be understood as an example of a wireless device configured for operation in a wireless communication network and comprising a plurality of functional modules, each of which may be implemented using analog and/or digital hardware, or processing circuitry configured with appropriate software and/or firmware, or a combination thereof. For example, in some embodiments, a mobile terminal includes transceiver circuitry including receiver circuitry for receiving data in subframes occurring at defined subframe intervals and having a predetermined number of symbol intervals, and determination circuitry for determining that a received subframe is to be shortened relative to the predetermined number of symbol intervals, and subframe processing circuitry, responsive to the determination circuitry, for ignoring one or more symbols at the end of the received subframe when processing the received subframe. It will be appreciated that several of the variations described above in connection with the method illustrated in fig. 11 are equally applicable to the mobile terminal implementation described herein.

Fig. 14 is a schematic illustration of an example transmitting node 1400, in this case implemented as a base station (in which a method embodying one or more of the techniques described above may be implemented). A computer program for controlling a base station to perform one or more of the methods described herein is stored in program storage 1430, which includes one or several memory devices. Data used during execution of methods embodying the present technology is stored in a data storage 1420, which also includes one or more memory devices. During execution of a method embodying the present technology, program steps are retrieved from the program storage 1430 and executed by a Central Processing Unit (CPU) 1410 that retrieves (retrieve) required data from the data storage 1420. Output information resulting from performing methods embodying the present invention may be stored back in data storage 1420 or sent to an input/output (I/O) interface 1440, which may include a transmitter for transmitting data to other nodes (e.g., RNC) as needed. Likewise, input/output (I/O) interface 1440 may include a receiver for receiving data from other nodes, e.g., for use by CPU 1410. Together, CPU1410, data storage 1420, and program storage 1430 form processing circuitry 1460. The base station 1400 further includes radio communication circuitry 1450, including a receiver circuit 1452 and a transmitter circuit 1455 suitable for communicating with one or more mobile terminals according to well-known designs and techniques.

According to several embodiments of the present invention, the generic base station apparatus 1400 and more specifically the radio communication circuitry 1450 is configured to transmit data in subframes occurring at defined subframe intervals and having a predetermined number of symbol intervals. The processing circuit 1460 is configured to control the receiver circuit and the transmitter circuit 1455 in the radio communication circuit 1450 to transmit, by the transmitter circuit 1455, a message to the second wireless node including subframe-shortening information, the subframe-shortening information indicating that a subframe is to be shortened. The processing circuit 1460 is further configured to control the transmitter circuit 1455 to transmit the shortened subframe to the second wireless node by omitting an end portion of the subframe when transmitting the subframe.

Accordingly, in various embodiments of the invention, the processing circuitry is configured to perform one or more of the techniques detailed above. Likewise, other embodiments include a base station that includes one or more such processing circuits. In some cases, these processing circuits are configured with suitable program code (stored in one or more suitable memory devices) to implement one or more of the techniques described herein. Of course, it will be appreciated that all of the steps of these techniques need not all be performed in a single microprocessor or even in a single module.

The base station 1400 of fig. 14 may also be understood as an example of a wireless device configured to operate in a wireless communication network and comprising several functional modules, each of which may be implemented using analog and/or digital hardware, or processing circuitry with appropriate software and/or firmware, or a combination thereof. For example, in some embodiments, the base station comprises radio communication circuitry comprising transmitter circuitry, receiver circuitry for receiving data in subframes occurring at defined subframe intervals and having a predetermined number of symbol intervals, and grant-transmission circuitry for transmitting, by the transmitter circuitry, a grant message to the second wireless node containing subframe-shortening information indicating that a subframe is to be shortened. The base station according to these embodiments further comprises a controller circuit for controlling the transmitter circuit to omit an end portion of the subframe when transmitting the subframe. It will be appreciated that several variations of the method described above in connection with fig. 12 may be equally applied to the base station implementation described herein.

Examples of several embodiments of the present invention have been described above in detail with reference to the description of the attachment of specific embodiments. Since it is, of course, not possible to describe every conceivable combination of components or techniques, those skilled in the art will recognize that many further modifications may be made to the embodiments described above without departing from the scope of the present invention. For example, it will be readily appreciated that although the above embodiments are described with reference to a 3GPP network, embodiments of the present invention may also be applied to similar networks, such as successor networks to a 3GPP network having the same functional components. Thus, in particular, the term 3GPP and related or related terms used in the above description and in the drawings and the claims that are currently or later appended should be construed accordingly.

Notably, modifications and other embodiments of the disclosed invention will occur to those skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the present disclosure. Although specific terms may have been employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims (24)

1. A method (1100) in a receiving node configured to receive data from and transmit data to a transmitting node in a subframe of a time division duplex system, the subframe having a predetermined number of symbol intervals, the method comprising:

receiving a subframe from the transmitting node, wherein a grant message is included in a beginning portion of the received subframe, the grant message containing subframe-shortening information indicating that the received subframe is to be shortened relative to the predetermined number of symbol intervals;

determining (1120) that the received subframe is to be shortened relative to the predetermined number of symbol intervals based on the subframe-shortening information; and

in response to the determination, ignoring (1130) a last portion of the received subframe by ignoring one or more symbols at an end of the received subframe when processing the received subframe.

2. The method (1100) of claim 1, wherein the subframe-shortening information consists of a single bit indicating that the received subframe is to be shortened by omitting a predetermined number of symbols.

3. The method (1100) of claim 2, further comprising, prior to receiving the message, receiving (1110) configuration information from the transmitting node, wherein the configuration information specifies a number of symbols to be ignored at the end of the received subframe.

4. The method (1100) of claim 1, wherein the subframe-shortening information specifies a number of symbols to be ignored at the end of the received subframe.

5. The method (1100) of any of claims 1-4, wherein the method further comprises decoding data from the received subframe, wherein the decoding comprises processing one or more data symbols corresponding to the ignored symbols as punctured data symbols.

6. The method (1100) of any of claims 1-4, wherein the method further comprises retrieving decoded data from the received subframe, wherein the retrieving comprises demapping data symbols from the received subframe according to a demapping pattern omitting the ignored symbols and decoding the demapped data symbols.

7. A method (1200) in a transmitting node configured to transmit data to and receive data from a receiving node in a subframe of a time division duplex system, the subframe having a predetermined number of symbol intervals, the method comprising:

transmitting (1220) a subframe to the receiving node, the subframe comprising a grant message in a start portion of the subframe, the grant message containing subframe-shortening information indicating that the subframe is to be shortened relative to the predetermined number of symbol intervals;

wherein the subframe is shortened (1230) by omitting one or more symbols at the end of the subframe when transmitting the subframe.

8. The method (1200) of claim 7, wherein the subframe-shortening information consists of a single bit indicating that the subframe is to be shortened by omitting a predetermined number of symbols.

9. The method (1200) of claim 8, further comprising transmitting (1210) configuration information to the receiving node before transmitting the grant message, wherein the configuration information specifies a number of symbols to be omitted at the end of the subframe.

10. The method (1200) of claim 7, wherein the subframe-shortening information specifies a number of symbols to be omitted at the end of the subframe.

11. A receiving node (1300) comprising a receiver circuit (1330) configured to receive data from a transmitting node in a subframe of a time division duplex system and a transmitter circuit (1325) configured to transmit data to the transmitting node in a subframe of the time division duplex system, the subframe having a predetermined number of symbol intervals, the receiving node (1300) further comprising a processing circuit (1310) configured to control the receiver circuit (1330) and to process a subframe received from the transmitting node, characterized in that the processing circuit (1310) is further configured to:

receiving, via the receiver circuit (1330), a subframe from the transmitting node, wherein a grant message is included in a starting portion of the received subframe, the grant message containing subframe-shortening information indicating that the received subframe is to be shortened relative to the predetermined number of symbol intervals;

determining, based on the subframe-shortening information, that the received subframe is to be shortened relative to the predetermined number of symbol intervals; and

in response to the subframe-shortening information, ignoring one or more symbols at the end of the received subframe when processing the received subframe.

12. The receiving node (1300) of claim 11, wherein the subframe-shortening information consists of a single bit indicating that the received subframe is to be shortened by omitting a predetermined number of symbols.

13. The receiving node (1300) of claim 12, wherein the processing circuit (1310) is further configured to receive, via the receiver circuit (1330), configuration information from the transmitting node prior to receiving the message, wherein the configuration information specifies a number of symbols to be ignored at the end of the received subframe.

14. The receiving node (1300) of claim 11, wherein the subframe-shortening information specifies a number of symbols to be ignored at the end of the received subframe.

15. The receiving node (1300) of any of claims 11-14, wherein the processing circuit (1310) is further configured to decode data from the received subframe, wherein the decoding comprises processing one or more data symbols corresponding to the ignored symbols into punctured data symbols.

16. The receiving node (1300) of any of claims 11-14, wherein the processing circuit (1310) is further configured to retrieve decoded data from the received subframe, wherein the retrieving comprises demapping data symbols from the received subframe according to a demapping pattern omitting the ignored symbols and decoding the demapped data symbols.

17. A transmitting node (1400) comprising a transmitter circuit (1455) configured to transmit data to a receiving node in a subframe of a time division duplex system and a receiver circuit (1452) configured to receive data from the receiving node in a subframe of a time division duplex system, the subframe having a predetermined number of symbol intervals, and the transmitting node further comprising a processing circuit (1460) configured to control the transmitter circuit (1455), characterized in that the processing circuit (1460) is further configured to:

transmitting, via the transmitter circuitry, a subframe to the receiving node, the subframe comprising a grant message in a starting portion of the subframe, the grant message containing subframe-shortening information indicating that the subframe is to be shortened relative to the predetermined number of symbol intervals; and

control the transmitter circuitry to shorten the subframe by omitting one or more symbols at the end of the subframe when transmitting the subframe.

18. The transmitting node (1400) of claim 17, wherein the subframe-shortening information consists of a single bit indicating that the subframe is to be shortened by omitting a predetermined number of symbols.

19. The transmitting node (1400) of claim 18, wherein the processing circuit (1460) is further configured to transmit, via the transmitter circuit (1455), configuration information to the receiving node prior to transmitting the message, wherein the configuration information specifies a number of symbols to be omitted at the end of the subframe.

20. The transmitting node (1400) of claim 17, wherein the subframe-shortening information specifies a number of symbols to be omitted at the end of the subframe.

21. A receiving node configured to receive data from and transmit data to a transmitting node in a subframe of a time division duplex system, the subframe having a predetermined number of symbol intervals, the receiving node comprising one or more processing circuits which, when executed by the one or more processing circuits, cause the one or more processing circuits to:

receiving a subframe from the transmitting node, wherein a grant message is included in a beginning portion of the received subframe, the grant message containing subframe-shortening information indicating that the received subframe is to be shortened relative to the predetermined number of symbol intervals;

determining, based on the subframe-shortening information, that the received subframe is to be shortened relative to the predetermined number of symbol intervals; and

in response to the determination, ignoring a last portion of the received subframe by ignoring one or more symbols at an end of the received subframe when processing the received subframe.

22. A transmitting node configured to transmit data to and receive data from a receiving node in a subframe of a time division duplex system, the subframe having a predetermined number of symbol intervals, the transmitting node comprising one or more processing circuits which, when executed by the one or more processing circuits, cause the one or more processing circuits to:

transmitting a subframe to the receiving node, the subframe including a grant message in a beginning portion of the subframe, the grant message containing subframe-shortening information indicating that the subframe is to be shortened relative to the predetermined number of symbol intervals;

wherein the subframe is shortened by omitting one or more symbols at the end of the subframe when the subframe is transmitted.

23. A non-transitory computer readable medium having a computer program stored thereon, the computer program comprising computer program code which, when executed by a receiving node configured to receive data from a transmitting node and transmit data to the transmitting node in a subframe of a time division duplex system, the subframe having a predetermined number of symbol intervals, causes the receiving node to perform the steps of:

receiving a subframe from the transmitting node, wherein a grant message is included in a beginning portion of the received subframe, the grant message containing subframe-shortening information indicating that the received subframe is to be shortened relative to the predetermined number of symbol intervals;

determining, based on the subframe-shortening information, that the received subframe is to be shortened relative to the predetermined number of symbol intervals; and

in response to the determination, ignoring a last portion of the received subframe by ignoring one or more symbols at an end of the received subframe when processing the received subframe.

24. A non-transitory computer readable medium having stored thereon a computer program comprising computer program code which, when executed by a transmitting node configured to transmit data to and receive data from a receiving node in a subframe of a time division duplex system, the subframe having a predetermined number of symbol intervals, causes the transmitting node to perform the steps of:

transmitting a subframe to the receiving node, the subframe including a grant message in a beginning portion of the subframe, the grant message containing subframe-shortening information indicating that the subframe is to be shortened relative to the predetermined number of symbol intervals;

wherein the subframe is shortened by omitting one or more symbols at the end of the subframe when the subframe is transmitted.