HK1244120B - Method and base station of frame structure for support of large delay spread deployment scenarios - Google Patents

Description

Method and base station for supporting frame structure with large delay spread deployment scenario

This application is a divisional application of PCT international application number PCT/US2010/048971, international application date September 15, 2010, Chinese national application number 201080050529.4, and entitled “Frame structure for supporting large delay spread deployment scenarios”.

Background of the Invention

In cellular radio interfaces based on orthogonal frequency division multiplexing (OFDMA), such as described in patent application Ser. No. 11/907,808 filed by Sassan Ahmadi and Hujun Yin on October 12, 2007, which is incorporated herein by reference in its entirety, the propagation of radio signals in large cell sizes and/or lower frequency bands can result in larger delay spreads, and thus, inter-symbol interference (ISI) effects in the received signal. In OFDM-based systems, ISI effects are mitigated by a cyclic prefix added to the beginning of the OFDM symbols. The larger the delay spread, the longer the cyclic prefix should be used to mitigate the ISI effects.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. However, the invention, together with objects, features, and advantages thereof, both as to organization and method of operation, may be best understood by reference to the following detailed description when read with the accompanying drawings, in which:

FIG1 is a schematic diagram of a wireless network according to an embodiment of the present invention;

FIG2 is a schematic diagram of an apparatus used in a wireless network according to an embodiment of the present invention;

FIG3 is a schematic diagram of a frame structure according to an embodiment of the present invention;

FIG4 is a schematic diagram of a superframe structure according to an embodiment of the present invention;

FIG5 is a schematic diagram of a superframe structure according to an embodiment of the present invention;

6, 6A and 6B are schematic diagrams of superframe structures according to an embodiment of the present invention;

7 is a schematic diagram of a superframe structure having a new preamble multiplexed with a legacy preamble according to an embodiment of the present invention;

8 is a diagram of a superframe structure with a supplementary preamble multiplexed with a legacy preamble according to an embodiment of the present invention, wherein the new preamble is hidden from legacy terminals;

FIG9 is a schematic diagram of a frame structure segmented in the time domain and/or frequency domain according to an embodiment of the present invention;

FIG10 is a schematic diagram of a frame structure in an FDD duplex mode according to an embodiment of the present invention;

11-13 are schematic diagrams of frame structures according to an embodiment of the present invention;

FIG14 is a table of OFDMA parameters according to an embodiment of the present invention; and

FIG15 is a flow chart of a method according to an embodiment of the present invention.

It will be understood that for simplicity and clarity of illustration, the elements shown in the drawings are not necessarily drawn accurately or to scale. For example, for clarity, the dimensions of some elements may be exaggerated relative to other elements, or several physical components may be included in a single functional block or element. Furthermore, where deemed appropriate, reference numerals are repeated in the drawings to indicate corresponding or similar elements. In addition, some blocks depicted in the drawings may be combined into a single function.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the present invention. However, it will be appreciated by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits are not described in detail to avoid obscuring the present invention.

Unless otherwise indicated, as will be apparent from the following discussion, it will be understood that throughout the specification, terms such as "process," "calculate," "calculate," "determine," etc., are used to refer to the actions and/or processing of a computer or computing system or similar electronic computing device that manipulates and/or transforms physical quantities (e.g., electronic physical quantities) represented as registers and/or memories of the computing device into other data similarly represented as physical quantities within the memory, registers, or other such information storage, transmission, or display devices of the computing system. In addition, the term "plurality" may be used throughout the specification to describe two or more components, devices, elements, parameters, etc.

Although the following detailed description may describe various embodiments of the present invention in relation to wireless networks utilizing Orthogonal Frequency Division Multiplexing (OFDM) modulation, the embodiments of the present invention are not limited thereto and, for example, may be implemented utilizing other modulation and/or coding schemes where applicable. Furthermore, although example embodiments are described herein with respect to wireless metropolitan area networks (WMANs), the present invention is not limited thereto and may be applied to other types of wireless networks where similar advantages may be achieved. These networks specifically include, but are not limited to, wireless local area networks (WLANs), wireless personal area networks (WPANs), and/or wireless wide area networks (WWANs).

The following embodiments of the invention may be used in various applications including transmitters and receivers of radio systems, however, the invention is not limited in this respect. Specifically included within the scope of the invention are radio systems including, but not limited to, network interface cards (NICs), network adapters, mobile stations, base stations, access points (APs), gateways, bridges, hubs, and cellular radiotelephones. Additionally, radio systems within the scope of the invention may include cellular radiotelephone systems, satellite systems, personal communication systems (PCS), two-way radio systems, two-way pagers, personal computers and related peripherals, personal digital assistants (PDAs), personal computing accessories, and essentially all existing and future systems to which the principles of the embodiments of the invention may be suitably applied.

1 , a wireless network 100 according to an embodiment of the present invention is schematically illustrated. Wireless network 100 may include a provider network (PN) 120, a base station (BS) 118, and one or more user or other stations 110, 112, 114, and/or 116, which may be, for example, mobile or fixed user stations. In some embodiments, base station 118, such as in a WLAN, may be referred to as an access point (AP), a terminal, and/or a node, and user stations 110, 112, 114, and/or 116 may be referred to as stations (STAs), terminals, and/or nodes. However, in this specification, the terms base station and user station are used as examples only, and their meaning in this regard is not intended to limit embodiments of the present invention to any particular type of network or protocol.

Wireless network 100 may facilitate wireless access between each subscriber station 110 , 112 , 114 , and/or 116 and PN 120 . For example, the wireless network 100 may be configured to use one or more protocols specified in the Institute of Electrical and Electronics Engineers (IEEE) 802.11™ Standard (“IEEE Standard Specification for Wireless LAN Media Access Control (MAC) and Physical Layer (PHY)”, 1999 Edition, reaffirmed on June 12, 2003) (such as IEEE 802.11a™-1999; IEEE 802.11b™-1999/Corl-2001; IEEE 802.11g™-2003 and/or IEEE 802.11n™), the IEEE 802.16™ Standard (“IEEE Standard for Local and Metropolitan Area Networks—Part 16: Air Interface for Fixed Broadband Wireless Access Systems,” October 1, 2004) (such as IEEE 802.16-2004/Corl-2005 or IEEE Std 802.16-2009, referred to herein as “IEEE Std 802.16-2009, the "WiMAX" standard), and/or one or more protocols specified in the IEEE 802.15.1™ standard ("IEEE Standard for Local and Metropolitan Area Networks—Specific Requirements Section 15.1: Wireless Medium Access Control (MAC) and Physical Layer (PHY) Specification for Wireless Personal Area Networks (WPANs™)," dated June 14, 2005), although the present invention is not limited in this respect and other standards may be used. In some embodiments, the attributes, compatibility, and/or functionality of wireless network 100 and its components may be defined in accordance with, for example, the IEEE 802.16 standard (which may be referred to, for example, as the Worldwide Interoperability for Microwave Access (WiMAX)). Alternatively, or in addition, wireless network 100 may use devices and/or protocols compatible with a Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) cellular network or any protocol for a WPAN or WWAN.

Embodiments of the present invention may enable next generation mobile WiMAX systems (e.g., based on the IEEE 802.16m standard) to efficiently support very high mobility and low latency applications, such as Voice over Internet Protocol (VoIP), interactive gaming over the air interface, deployment in larger cell sizes or lower frequency bands, and/or "multi-hop" relay operation, while allowing backward compatible operation and integration with baseline standards (e.g., legacy mobile WiMAX systems based on IEEE Std 802.16-2009).

In some embodiments, base station 118 may manage and/or control wireless communications between subscriber stations 110, 112, 114, and/or 116 and between subscriber stations 110, 112, 114, and/or 116 and provider network 120. Subscriber stations 110, 112, 114, and/or 116 may, in turn, facilitate various service connections of other devices (not shown) to wireless network 100 via a private or public local area network (LAN), although embodiments are not limited in this respect.

2 , a schematic diagram illustrates an apparatus 130 used in a wireless network according to an embodiment of the present invention. For example, apparatus 130 may be a terminal, device, or node (e.g., one of user stations 110, 112, 114, and/or 116, base station 118, and/or provider network 120 described in FIG1 ) in a wireless network (e.g., wireless network 100 described in FIG1 ) that communicates with other terminals, devices, or nodes. As described in one or more embodiments of the present invention, apparatus 130 may include a controller or processing circuit 150 that includes logic (e.g., including hard circuitry, a processor, and software, or a combination thereof) for determining an erroneous frame detection rate and/or adjusting frame detection sensitivity. In some embodiments, apparatus 130 may include a radio frequency (RF) interface 140 and/or a media access controller (MAC)/baseband processor circuit 150.

In one embodiment, RF interface 140 may include a component or combination of components suitable for transmitting and/or receiving single-carrier or multi-carrier modulated signals (e.g., including complementary code keying (CCK) and/or orthogonal frequency division multiplexing (OFDM) symbols), although embodiments of the present invention are not limited to any particular over-the-air interface or modulation scheme. RF interface 140 may include, for example, a receiver 142, a transmitter 144, and/or a frequency synthesizer 146. Interface 140 may include bias control, a crystal oscillator, and/or one or more antennas 148 and/or 149. In another embodiment, RF interface 140 may utilize an external voltage-controlled oscillator (VCO), surface acoustic wave filter, intermediate frequency (IF) filter, and/or RF filter, as desired. Due to the variety of possible RF interface designs, an extended description thereof is omitted.

Processing circuitry 150 can communicate with RF interface 140 to process received and/or transmitted signals and may include, for example, an analog-to-digital converter 152 for downconverting received signals and a digital-to-analog converter 154 for upconverting signals for transmission. Furthermore, processing circuitry 150 may include baseband or physical layer (PHY) processing circuitry 156 for PHY link layer processing of corresponding received/transmitted signals. Processing circuitry 150 may include, for example, processing circuitry 159 for media access control (MAC)/data link layer processing. Processing circuitry 150 may include a memory controller 158 for communicating with processing circuitry 159 and/or base station management entity 160, for example, via interface 155.

In some embodiments of the present invention, PHY processing circuitry 156 may include a frame construction and/or detection module in combination with additional circuitry, such as a buffer memory, to construct and/or deconstruct superframes as described in the previously described embodiments. Alternatively or additionally, MAC processing circuitry 159 may share processing for some of these functions or perform these processes independently of PHY processing circuitry 156. In some embodiments, MAC and PHY processing may be integrated into a single circuit as desired.

The apparatus 130 may be, for example, a base station, access point, user station, device, terminal, node, hybrid coordinator, wireless router, NIC and/or network adapter for a computing device, mobile station, or other device suitable for implementing the methods, protocols, and/or architectures described herein. Thus, the functionality and/or specific configurations of the apparatus 130 described herein may be included or omitted in various embodiments of the apparatus 130 as appropriate. In some embodiments, the apparatus 130 may be configured to be compatible with protocols and frequencies associated with one or more of the IEEE 802.11, 802.15, and/or 802.16 standards for WLANs, WPANs, and/or broadband wireless networks, although embodiments of the present invention are not limited in this respect.

Embodiments of device 130 may be implemented using a single-input single-output (SISO) architecture. However, as shown in FIG2 , some implementations may include multiple antennas (e.g., antennas 148 and 149) that transmit and/or receive using adaptive antenna technology (for beamforming or spatial division multiple access (SDMA)) and/or using multiple-input multiple-output (MIMO) communication technology.

The components and features of the station 130 may be implemented using any combination of discrete circuits, application specific integrated circuits (ASICs), logic gates, and/or single-chip architectures. Additionally, where appropriate, features of the device 130 may be implemented using microcontrollers, programmable logic arrays, and/or microprocessors, or any combination thereof. Note that hardware, firmware, and/or software elements may be collectively or individually referred to herein as "logic" or "circuitry."

It should be appreciated that the example device 130 shown in the block diagram of FIG2 may represent one functional descriptive example of many possible implementations. Therefore, the division, omission, or inclusion of block functions described in the accompanying drawings does not infer that hardware components, circuits, software, and/or elements for implementing these functions must be divided, omitted, or included in embodiments of the present invention.

3 , a schematic diagram of a frame 300 structure according to an embodiment of the present invention is shown. Frame 300 (e.g., a radio frame) may be, for example, a portion of a communication transmitted and/or received in wireless network 100. In some embodiments, frame 300 may describe a periodically repeating segmented structure of a larger communication signal or stream. In some embodiments, repeating frame 300 may include, for example, substantially different information during substantially each separate transmission. Frame 300 may be defined according to, for example, IEEE Standard 802.16-2009 or a Mobile WiMAX profile, and may include broadband wireless access technologies according to, for example, IEEE Standard 802.16-2009 or a Mobile WiMAX profile. According to the Mobile WiMAX profile, the duration or Transmission Time Interval (TTI) of frame 300 may be, for example, approximately 5 ms. Other frame or radio frame sizes, such as 2, 2.5, 4, 8, 10, 12, and 20 ms, may be used as specified in IEEE Standard 802.16-2009.

In some embodiments, frame 300 may be transmitted and/or received, for example, according to a time division duplex (TDD) mode or scheme. Other time and/or frequency schemes (e.g., frequency division duplex (FDD) mode or scheme) may be used according to embodiments of the present invention.

Frame 300 may include an integer number of OFDM symbols or other multiplexed symbols. The number of OFDM symbols per frame may be determined, for example, based on a selection of OFDM numerology (e.g., subcarrier spacing, cyclic prefix length, sampling frequency, etc.). In some embodiments, the OFDM numerology may be determined, set, or obtained, for example, based on bandwidth and sampling frequency (e.g., or based on an oversampling factor for a mobile WiMAX profile). In various embodiments, substantially different OFDM numerologies may be used, which may result in substantially different numbers of OFDM symbols in frame 300.

In some embodiments, the frame 300 may include idle symbols and/or idle time slots. In one embodiment, the frame 300 may include one or more switching periods 302 and/or 304, for example, to change between pre-designed downlink (DL) transmissions 306 and pre-designed uplink (UL) transmissions 308 when a TDD duplexing mode or scheme is used. In other embodiments, for example, when an FDD duplexing scheme is used, the frame 300 may include substantially no idle symbols, idle time slots, and/or switching periods 302 and/or 304, because the DL transmissions 306 and UL transmissions 308 may be sent at substantially the same or overlapping times (e.g., via different frequencies or network channels).

In some embodiments, the TTI or duration of a frame 300 may be, for example, approximately 5 ms. The round trip time (RTT) (e.g., the time interval between two consecutive pre-scheduled DL transmissions 306 to a particular wireless node) may be, for example, approximately 10 ms. Wireless networks (e.g., wireless network 100) with rapidly changing channel conditions and/or small coherence times (e.g., fast-moving mobile stations or nodes, such as cars with speeds exceeding approximately 120 kilometers per hour (km/h)) may utilize mechanisms that support relatively high mobility under changing channel conditions. For example, embodiments of the present invention may support wireless networks 100 with relatively small round trip times to substantially enable feedback of rapidly changing channel conditions between user stations 110, 112, 114, and/or 116, such as mobile stations, and base station 118. Other durations may be used.

The current IEEE Std 802.16-2009 specification standard frame structure may include limitations such as relatively long TTIs, which are generally not suitable for supporting relatively fast feedback and low access latency (e.g., less than 10 ms), which may be used by, for example, emerging radio access technologies.

Embodiments of the present invention may include or utilize a modified version of frame 300 to support lower latency operation while maintaining backward compatibility, for example, with the IEEE Std 802.16-2009 specification frame structure. Frame 300 structure may be used, for example, in next-generation Mobile WiMAX systems and devices (e.g., including the IEEE 802.16m standard). In some embodiments, frame 300 structure or portions thereof may be transparent to legacy terminals (e.g., operating according to the Mobile WiMAX profile and IEEE Std 802.16-2009) and may be used only for communications between base stations, subscriber stations, and/or mobile stations, all of which operate according to the IEEE 802.16m standard.

According to embodiments of the present invention, wireless network 100 and its components that can communicate using a new frame structure (e.g., as described in accordance with FIG. 3-15 ) can be backward compatible with a baseline network that can communicate using a legacy frame structure (e.g., as described in accordance with the Mobile WiMAX profile and based on IEEE Std 802.16-2009). In some embodiments, backward compatibility can include, for example, enabling legacy terminals (e.g., that can communicate using legacy and/or baseline frame structures) to operate in the wireless network without significantly impacting the performance and operation of the terminals relative to the legacy network. In some embodiments, new (e.g., non-legacy) terminals or subscriber stations that utilize a new (e.g., non-legacy) frame structure can operate in the legacy network without significantly impacting the performance and operation of the terminals relative to the wireless network. For example, the new terminals can be "backward compatible." In some embodiments, for example, wireless network 100 can substantially simultaneously support both legacy and new (e.g., non-legacy) terminals (where time division multiplexing of new and legacy frames overlaps within the same frame). In some embodiments, wireless network 100 can enable seamless communication, mobility, and handover between legacy and new terminals. As used herein, the terms "new," "evolved," "updated," and "next generation" are used only in contrast to "old," "legacy," or "current," etc. For example, a "new" standard may be the standard in use at the time of filing this application, and a "legacy" system may be a system in use before and for a period of time after the date of filing this application; a "new" system is one implemented or developed after the "legacy" system, typically including improvements and updates. "New," "evolved," "updated," etc. systems are typically backwards compatible, allowing them to be used with "old," "legacy," or existing systems or standards.

According to an embodiment of the present invention, the new frame structure may include new synchronization and broadcast channels to extend the capabilities of IEEE Std 802.16-2009 by, for example, enhancing system acquisition and/or enhancing unit selection at low signal-to-interference-plus-noise ratios (SINRs). According to IEEE Std 802.16-2009, broadcast channels (e.g., DL channel descriptors and UL channel descriptors) are generally not located in predetermined positions within a frame, and mobile stations are required to decode common control channels (e.g., MAPs) to acquire system configuration information.

According to an embodiment of the present invention, the new frame structure may include, for example, a superframe, which includes an integer number of radio frames, which may include synchronization and/or broadcast information and/or messages, such as system configuration information, which may simplify the operation of the wireless network 100 and further reduce the overhead and acquisition latency of the wireless network.

Referring to FIG4 , a superframe 400 structure according to an embodiment of the present invention is schematically illustrated. In some embodiments, a transmission between terminals or nodes may include, for example, one or more superframes 400. A superframe 400 may include or be divided into a fixed and/or predetermined number of frames 410. In other embodiments, the number of frames 410 in each of two or more superframes 400 may be different. The number M of frames 410 within a superframe 400 (e.g., M may be an integer, where M=2, 3, 4, etc.) may be a design parameter and may be specified in a standard specification, and may be fixed for a specific profile and deployment, for example. In some embodiments, the number of frames 410 within a superframe 400 may be determined by one or more factors, including, but not limited to, a target system acquisition time, a maximum allowable distance between two consecutive preambles (e.g., a synchronization channel), a minimum number of preambles that can be averaged during system acquisition for preamble detection, and/or a maximum allowable distance between two consecutive broadcast channels (e.g., a system configuration information or paging channel).

In one embodiment, substantially each superframe 400 may be divided into or include two or more (e.g., four (4)) frames 410. Other numbers of divisions, partitions, or frames may be used. The length of each frame 410 may be, for example, approximately 5 ms, for example, to establish backward compatibility with systems that comply with IEEE Std 802.16-2009. Other frame or radio frame lengths may be used. Each frame 410 may be further divided or subdivided into two or more (e.g., eight (8)) subframes 420. Other numbers of divisions may be used. The length of the subframes 420 may determine the TTI for terminals that comply with the new standard and, for example, constitute the superframe 400 and/or frame 410 structure. The start and end of each TTI may be substantially aligned or synchronized with, for example, a subframe boundary. Each TTI may contain an integer number of subframes (e.g., typically one or two subframes). Each subframe 420 may be divided into or include a fixed number of OFDM symbols 430. In one embodiment, each subframe 420 may be divided into or include, for example, six (6) OFDM symbols, such that the number of OFDM symbols 430 within a subframe (e.g., the length of the subframe 420) is compatible with resource block sizes (e.g., subchannels) corresponding to various permutation schemes specified in, for example, IEEE Std 802.16-2009.

In other embodiments, there may be other or alternative numbers, lengths, sizes, and/or variations of superframes 400, frames 410, subframes 420, and/or OFDM symbols 430. The numbers used herein are given for illustrative purposes only. In another embodiment, the length of frame 410 (e.g., approximately 5 ms) and the number of OFDM symbols 430 (e.g., six (6)) may be set to establish backward compatibility with systems, devices, and/or transmissions that comply with IEEE Std 802.16-2009.

For example, a permutation scheme defined in accordance with current standard specifications may include, for example, a number of time slots from one to six for transmitting signals and/or resource blocks. The physical boundaries of the resource blocks may, for example, be aligned with subframe boundaries. In some embodiments, each physical resource block may be substantially contained within a single subframe 420. In other embodiments, each physical resource block may be substantially contained within two consecutive subframes.

Those skilled in the art will appreciate that embodiments of the present invention, including, for example, the superframe 400 structure, may be applied with both TDD and FDD duplexing schemes or modes. In FDD duplexing mode, each of the DL and UL transmissions may be transmitted simultaneously, for example, on a corresponding frequency or channel. In TDD duplexing mode, each of the DL and UL transmissions may be transmitted at substantially non-overlapping intervals, for example, on substantially the same frequency or channel (e.g., according to a time division multiplexing (TDM) scheme). In the TDD duplexing mode of operation and within any frame 410, the subframe 420 may be configured to be static for DL and UL transmissions (e.g., DL transmission 306 and UL transmission 308), for example, under each deployment. The DL and UL transmissions may be separated by idle time and/or idle symbols, which are used to switch between DL and UL transmissions (e.g., during switching periods 302 and/or 304).

In one embodiment of the present invention, a "legacy zone" and a "new zone" may include, for example, periods, portions, or zones of DL or UL transmissions specifically designed to communicate substantially only with legacy terminals or new terminals, respectively. In the TDD duplex mode of IEEE Standard 802.16-2009, each DL transmission 306 and UL transmission 308 may be further divided into two or more permutation zones. In some embodiments, the number of consecutive OFDM or other symbols 430 in a frame 410 may be referred to as, for example, a permutation zone (e.g., permutation zone 310 described with reference to FIG. 3 ). A permutation zone may, for example, include several consecutive OFDM symbols (e.g., in DL and UL transmissions 306 and 308 described with reference to FIG. 3 ) that use substantially the same permutation (e.g., partial use of subchannels (PUSC) for distributed allocation of subcarriers, adaptive modulation and coding (AMC) for localized allocation of subcarriers, etc.).

According to an embodiment of the present invention, a frame may include or be divided into a legacy zone and a new zone (other terminology may be used). In one embodiment, legacy terminals and new terminals may communicate using the legacy zone and the new zone, respectively. In some embodiments, new terminals may communicate using the legacy zone and the new zone. Legacy terminals typically communicate only using the legacy zone. In one embodiment, within a frame, each DL transmission may be further divided into two or more zones, for example, including a DL transmission legacy zone and a DL transmission new (e.g., non-legacy) zone, and each UL transmission may be further divided into two or more zones, for example, including a UL transmission legacy zone and a UL transmission new (non-legacy) zone.

Embodiments of the present invention may provide for dividing a frame into subframes (e.g., where transport block or zone boundaries may be synchronized with subframe boundaries). According to IEEE Std 802.16-2009, transport block or zone boundaries may start and end at any OFDM symbol within a frame boundary. According to embodiments of the present invention, new zones may utilize new and more efficient resource allocation and feedback mechanisms. The total number of OFDM symbols within a frame may vary based on OFDM numerology. To maintain backward compatibility with legacy mobile WiMAX systems, the same frame size and OFDMA numerology (e.g., or OFDMA parameters) may be used for both IEEE 802.16m systems and legacy mobile WiMAX systems. Those skilled in the art will appreciate that all permitted numerologies and/or frame sizes specified in the 802.16e-2005 standard may be used according to embodiments of the present invention.

Embodiments of the present invention may provide a superframe structure that is compatible with legacy standards such as IEEE Std 802.16-2009 and/or other standards. For example, the superframe structure may include a subset of features specified in the Mobile WiMAX profile or may be compatible therewith (e.g., may be backward compatible with the Mobile WiMAX profile).

Embodiments of the present invention may provide a superframe structure that may be divided into several frames including, for example, one or more legacy synchronization channels (e.g., IEEE Std 802.16-2009 preambles), new synchronization channels (e.g., IEEE 802.16m preambles), broadcast channels (BCHs), medium access protocols (MAPs), or common control channels (CCCHs) in new and legacy zones corresponding to each frame or an integer number of frames.

5 , a schematic diagram of a superframe 500 structure according to an embodiment of the present invention is shown. In one embodiment, superframe 500 may include a legacy preamble 502, which may be referred to as a primary synchronization channel (PSCH), for example. In some embodiments, superframe 500 may include an additional or supplemental preamble 504, for example, to improve system timing acquisition and cell selection for new terminals. Supplemental preamble 504 may be referred to as a secondary synchronization channel (SSCH), for example. A synchronization channel may include a sequence that may be used and/or decoded by both base stations and mobile stations to acquire frame timing and/or scheduling.

In some embodiments, the new preamble 504 may be effectively or partially transparent, unreadable, or undetectable to legacy terminals, while the legacy preamble 502 may be detectable by both legacy and new terminals. In some embodiments, the superframe 500 may include a broadcast channel (BCH) 506. The broadcast channel may contain information that may include, for example, system configuration information, paging, and/or other broadcast-type information, and may be sent by a base station to all mobile stations in the network and/or in the surrounding area.

As shown in FIG5 , a supplemental or new preamble 504 (e.g., an SSCH) may be located at a fixed position in the new zone or the legacy zone. In one embodiment of the present invention, for example, the new preamble 504 may be located at a fixed offset, which may be referred to as "SSCH_OFFSET." SSCH_OFFSET may be a measure of the position of the new preamble 504 in each frame, for example, relative to the location of the legacy preamble. In some embodiments, the legacy preamble in a mobile WiMAX system may be located in the first OFDM symbol of each frame (as shown in FIG9 ). The value of SSCH_OFFSET may be included and broadcast as part of the system configuration information. In some embodiments, when the new preamble 504 is detected by a mobile terminal, SSCH_OFFSET may be used to locate the start of the frame. In one embodiment, when SSCH_OFFSET = 0, there may be no legacy preamble 502, which may indicate that the network does not support legacy terminals. In some embodiments, the new synchronization channel and the broadcast channel may span the minimum system bandwidth (BW). In some embodiments, the legacy synchronization channel typically spans the entire system BW, an example of which is shown in FIG9 . The region pre-designated for conveying the new preamble 504 (e.g., via multiple subcarriers) may be, for example, transparent and/or ignored by legacy terminals. The scheduler for downlink base station or terminal transmissions typically does not allocate user/system traffic/control/signaling in the region pre-designated for conveying the new preamble 504.

In another embodiment of the present invention, for example, the new preamble 504 may be located at the beginning of a new frame, where the new frame may be positioned at a fixed offset relative to the legacy frame. In one embodiment, the fixed offset may be referred to as, for example, "FRAME_OFFSET" and may be fixed within the frame timing. In some embodiments, the value of FRAME_OFFSET may be set by a network operator or administrator (e.g., rather than broadcast). New mobile terminals may detect the new preamble 504, which may indicate the beginning of a new frame and other information channels, such as those relative to the beginning of the new frame (e.g., as shown in FIG6 ). For example, the timing or periodicity of the BCH 506 may be substantially aligned with the timing or periodicity of the superframe 500 transmission.

In various embodiments, the superframe 500 may have substantially different structures, which may be distinguished, for example, based on the relative positions of the legacy preamble 502 and/or the new preamble 504 in the superframe 500 and/or other characteristics or design considerations of the frame structure (e.g., DL scan latency, physical layer overhead, and other information). Those skilled in the art will appreciate that although three options for the superframe 500 structure are described, including options I, II, and III, various other structures and/or variations thereof may be used in accordance with embodiments of the present invention.

The following description may include embodiments that may be referred to individually or collectively as Option 1. Option 1 and other "options" given herein are merely examples and are not limiting.

In some embodiments, the new preamble 504 and/or BCH 506 may be positioned substantially at the beginning of each superframe 500, e.g., in the first frame of each superframe 500 in a communication stream. In such embodiments, the legacy preamble 502 and the new preamble 504 may be positioned separately (e.g., spaced or offset along the length of the superframe 500). In such embodiments, the impact or visibility of the new preamble 504 on legacy terminals (e.g., which typically only detect the legacy preamble 502) and their operations (such as system acquisition) may be minimized. The new preamble 504 may be repeated periodically at any desired frequency (e.g., substantially every frame). The BCH 506 may include system configuration information, a paging channel, and/or other broadcast information. In some embodiments, the BCH 506 may be synchronized with the superframe 500 interval and may appear every integer number of superframes. In some embodiments, new terminals may use the new preamble 504 (e.g., exclusively or in addition) to improve system timing acquisition and fast cell selection. For example, the new preamble 504 may include unit identification (ID) information or code and may be used by the new terminal for frame timing acquisition. For example, the unit ID code may include a concatenated base station group ID code, base station ID code, sector ID code, and/or other codes or information, such as for simplifying unit ID detection (e.g., performing a structured search).

According to the embodiments of the present invention described with reference to Option 1, the new preamble 504 may be minimally detectable by legacy terminals because the new preamble 504 may be separated from the legacy preamble 502. In some embodiments, to minimize physical layer overhead (layer 1 overhead), such as may be increased by transmitting the new preamble 504 using OFDM symbols, the new preamble 504 may be transmitted, for example, with limited (e.g., minimum) bandwidth or time or by scheduling user traffic using additional subcarriers corresponding to the same OFDM symbols, as shown in FIG.

The following description may include embodiments that may be referred to individually or collectively as Option II.

6 , a superframe 600 structure according to an embodiment of the present invention is schematically illustrated. In some embodiments for TDD duplex mode, the superframe 600 may be divided into, for example, four frames having a pre-specified legacy period, interval, or zone and a new or non-legacy period, interval, or zone. In one embodiment, the legacy frame 610 may be further divided into subframes, which include, for example, a DL transmission legacy zone 612 and a UL transmission legacy zone 616. The new frame 620 may start at a fixed offset (e.g., FRAME_OFFSET) relative to the start of the legacy frame. The value of FRAME_OFFSET may be an integer number of subframes and may be determined based on the length or time ratio of DL transmission to UL transmission (e.g., in TDD duplex mode). For example, when FRAME_OFFSET = _Toffset and _Tsubframe indicates the length of the subframe and _Tf indicates the frame length, the minimum and maximum allowed values for _Toffset may be determined as follows:

T _offset <áT _f

0≤á≤1: frame portion allocated to DL

Example: a = 0.625, corresponding to DL:UL = 5:3

_{nTsubframe≤áTf - Toffset} , l≤n<7

T _offset = mT _subframes , 0≤m<(number of DL subframes)-n

In some embodiments, legacy terminals may communicate using legacy frames 610 , and new terminals may communicate using new frames 620 and/or legacy frames 610 .

According to an embodiment of the present invention, such as in Option III, the start of the new frame 620 and the legacy frame 610 may be offset by a fixed value, such as a frame offset 622 or an offset interval (eg, a fixed duration and/or number of subframes).

6 depicts the relative positions of a new frame 620 and a legacy frame 610 according to one embodiment, for example, in TDD duplex mode. For example, in TDD duplex mode, the legacy frame 610 structure may begin with a DL transmission 612 and end with a UL transmission 616. For example, the new frame 610 structure may begin with a DL transmission 614, followed by a UL transmission 618, and end with a DL transmission 614.

In some embodiments, each new frame 610 may include a new preamble (eg, SSCH), for example, in a subframe at the beginning or start of the frame 610 .

In other embodiments, each superframe 600 may include a superframe header (SFH) 624, for example, in a subframe at the beginning or start of the superframe 600. For example, the SFH 624 may include a new preamble and a broadcast channel.

For example, K and 6-K (K=1, 2, ..., 6) may indicate the number of OFDM symbols allocated to the new preamble and the broadcast channel, respectively. The number of OFDM symbols allocated to the new preamble and the legacy preamble may be as low as one OFDM symbol per channel. In one embodiment, the remaining OFDM symbols available in the SFH 624 subframe may be allocated for, for example, user traffic, control, and/or control and signaling information, which may minimize system layer 1 overhead.

The SFH 624 may include a new preamble sequence and broadcast information (eg, including system configuration information and a paging channel). In some embodiments, legacy frames and new frames may have a fixed frame offset 622, which may be configurable by a network operator.

In some embodiments of the present invention, the legacy area and the new area may be offset by a fixed number of subframes. In actual deployment, the offset value may be substantially stable or fixed. Due to the dynamic nature of network traffic in practice, in some frames, the legacy area may not be used, while the new area may be fully loaded or vice versa. In some embodiments, pointers in the IEEE 802.16m common control channel may be designed and/or used, for example, to point to or indicate subframes in the legacy area that are not used by legacy terminals. For example, when the legacy area and/or the new area division are fixed, resources (e.g., subframes) may be dynamically allocated frame by frame to maximize the use of physical resources that may otherwise not be used.

The following description may include embodiments that may be referred to individually or collectively as Option III.

7 , a superframe 700 structure is schematically illustrated having a new preamble 704 multiplexed with a legacy preamble 702, according to an embodiment of the present invention. In some embodiments, the new preamble 704 may be multiplexed with the legacy preamble 702, for example, every M frames (e.g., where M may be the number of frames within the superframe 700). For example, the first OFDM symbol of the first frame 710 in the superframe 700 may include the new preamble 704, and the M-1 subsequent frames 710 in the superframe 700 may include the legacy preamble 702. In some embodiments, common control channel (e.g., including DL and UL MAPs) and/or frame control header (FCH) 708 and BCH 706 transmissions may occur, for example, at intervals between superframes 700 and frames 710, respectively.

Acquisition of the legacy preamble 702 (e.g., by a legacy terminal) may be suspended due to an interruption in the periodic reception of the legacy preamble 702. Because the new preamble 704 and the legacy preamble 702 may share, for example, physical resources and may be transmitted substantially simultaneously or at overlapping times or locations within the superframe 700, additional physical resources are generally not required to include the new preamble within the superframe 700 structure. Additionally, in some embodiments, the location of the new preamble 704 may be fixed within a periodic number (one or more) of frames 710.

In some embodiments, there is substantially no impact on layer 1 overhead when the new preamble 704 and the legacy preamble 702 are code division multiplexed, e.g., in substantially the same OFDM symbol. In these embodiments, some legacy preambles 702 may be transmitted consecutively, and other legacy preambles 702 may overlap with the new preamble 704, e.g., according to the multiplexing schemes discussed herein.

In some embodiments, the new preamble 704 may be multiplexed with the legacy preamble 702 using, for example, a code division multiplexing (CDM) scheme. For example, as shown in FIG7 , the CDM scheme may include code division multiplexing the new preamble 704 and the legacy preamble 702, for example, substantially every M frames 710.

In one embodiment, the new preamble 704 and legacy preamble 702 sequences may overlap and be transmitted (e.g., by a new base station or terminal) every M frames, for example, according to the following equation:

y _k = _uk + X _k u′ _k , where _uk , u′ _k , X _k may indicate the k th primary synchronization sequence, the k th new synchronization sequence, and the k th spreading function. Other (eg, linear) combinations may be used.

For example, the spreading functions may include a set of robust spreading functions that may substantially cover the new synchronization sequence.Other multiplexing schemes or combinations thereof may be used.

In one embodiment, the legacy preamble 702 and the new preamble 704 may be code-division multiplexed, for example, every fixed number of frames (e.g., M=1, 2, 3...). In these embodiments, the legacy terminal may experience or include a small degradation in the energy of the legacy preamble every M frames. The new terminal may detect and extract the new preamble 704 that encroaches on or overlaps the legacy preamble 702. As proposed herein, the new preamble may be referred to as, for example, a "new preamble," a "new synchronization channel," a "SSCH," and a "secondary synchronization channel," and the new system, profile, and/or standard may be referred to as, for example, an "evolved version" of a baseline system standard.

8 , a superframe 800 structure is schematically shown having a new preamble 804 multiplexed with a legacy preamble 802 according to an embodiment of the present invention, wherein the legacy preamble 802 may be hidden from legacy terminals.

In some embodiments, the overlap of the new preamble 804 on the legacy preamble 802 may, for example, increase the interference level or, for example, the value of thermal interference 820 (IoT). The goal is to find the minimum signal to interference + noise ratio (SINR) required to properly detect the legacy preamble, or the maximum IoT tolerated by the legacy terminal (which results in the maximum power that can be used for the new preamble).

In one embodiment of the present invention, the signal _ys received at the s-th subcarrier may be calculated as shown in the following equation. In one embodiment, the new preamble 804 associated with each new base station or relay station may be substantially different, for example, to enable a mobile station to distinguish, detect, and/or select different base stations or relay stations in the network. In some embodiments, because the received power 822 of the new preamble 804 may be determined, or the received power 822 of the new preamble 804 may be proportional to the IoT 820, it is desirable to maximize the degree to which the IoT 820 allows legacy terminals to correctly detect the legacy preamble 802 at a minimum SINR level. In some embodiments, optimization of the IoT 820 value may be performed, for example, according to the following equation:

IoT＝|H _s，k X _k u′ _k | ²

Each item can be defined as follows:

y _s : signal received at the sth subcarrier

u _k : legacy preamble sequence sent by the kth BS

Hs _,k : multipath channel impulse response

u' _k : new preamble sequence sent by the kth BS

X _k : kth expansion function

_Ws : noise received at the sth subcarrier

_SINRs : Signal to Interference + Noise Ratio for legacy terminals

Inter-cell interference due to new and legacy preambles

Other criteria for IoT value optimization may be used. In some embodiments, when legacy preambles 702 and 802 are code division multiplexed, sending new preambles 704 and 804, respectively, may have substantially no impact or minimal impact on the physical layer overhead of the system sending them.

In these embodiments, overlapping the new preamble 804 on the legacy preamble 802 may limit the received power 822 of the new preamble 704 due to additional interference from neighboring base stations or relay stations transmitting the new preamble and may potentially interfere with or hide the legacy terminal's system acquisition of the legacy preamble 802. The impact of the additional interference may be minimized, for example, by utilizing a robust preamble detection algorithm that has minimal sensitivity to transient degradation of preamble power.

Those skilled in the art will appreciate that each of the three options for embodiments of the superframe structure and/or its partitioning (e.g., including the embodiments described with reference to each of options I, II, and III) can be applied to both TDD and FDD duplexing schemes. The size and distribution of the new and legacy zones, and their corresponding DL and UL transmissions and/or subframes, may depend on, for example, a number of factors, including but not limited to the distribution of new and legacy terminals, network load, and performance optimization for new and legacy terminals.

10 , a schematic diagram illustrates a frame 1000 structure in FDD duplex mode according to an embodiment of the present invention. Frame 1000 may include subframe 1030. In some embodiments, superframe 1000 may include a legacy preamble 1002, a new preamble 1004, and a BCH 1006, which may be transmitted whenever an integer number of superframes are transmitted. In one embodiment, legacy preamble 1002, new preamble 1004, and/or BCH 1006 may be located at the beginning of frame 1000. According to an embodiment of the present invention, in FDD duplex mode, DL transmission 1016 and UL transmission 1018 may occur substantially simultaneously, for example, at different frequencies (e.g., DL frequency F1 1024 and UL frequency F2 1026, respectively).

11-13 , frame structures 1100, 1120, 1200, 1220, 1300, and 1320 according to embodiments of the present invention and their corresponding subframes 1110, 1130, 1210, 1230, 1310, and 1330 are schematically illustrated. In FIG11 , the TDD frame 1100 is shown as having a DL/UL ratio of 4:3, and an FDD frame 1120 having a cyclic prefix of ¼ of the useful OFDM symbol length for a 5, 10, or 20 MHz channel bandwidth. TDD frame 1100 may consist of seven subframes 1110, each consisting of six OFDM symbols, and FDD frame 1120 may have the same configuration as the TDD frame to maximize commonality, or may consist of six subframes 1110, each consisting of six OFDM symbols, and one subframe 1130, consisting of seven OFDM symbols. As an example, for an OFDM symbol duration of 114.386 microseconds (Tb) and a CP length of 1/4Tb, the lengths of the six-symbol subframe 110 and the seven-symbol subframe 1130 are 0.6857 ms and 0.80 ms, respectively. In this case, the transmit-receive transmission gap (TTG) and receive-transmit transmission gap (RTG) are 139.988 microseconds and 60 microseconds, respectively.

In FIG12 , a TDD frame 1200 is shown with a DL/UL ratio of 3:2, and an FDD frame 1120 with a CP of ¼ Tb for a 7 MHz channel bandwidth. TDD frame 1200 may consist of five six-symbol subframes 1210, and FDD frame 1220 may have the same structure as the TDD frame to maximize commonality, or may consist of four six-symbol subframes 1210 and one seven-symbol subframe 1230. Assuming an OFDM symbol duration of 160 microseconds and a CP length of ¼ Tb, the lengths of the six-symbol subframe 1210 and the seven-symbol subframe 1230 are 0.960 ms and 1.120 ms, respectively. TTG and RTG are 140 microseconds and 60 microseconds, respectively.

In Figure 13, a TDD frame 1300 is shown with a DL/UL ratio of 4:2, and an FDD frame 1320 with a CP of 1/4 Tb for an 8.75 MHz channel bandwidth. TDD frame 1300 has four six-symbol subframes 1310 and two seven-symbol subframes 1330, while FDD frame 1320 has three six-symbol subframes 1310 and three seven-symbol subframes 1330. Assuming an OFDM symbol duration of 128 microseconds and a CP length of 1/4 Tb, the lengths of the six-symbol subframes 1310 and seven-symbol subframes 1330 are 0.768 ms and 0.896 ms, respectively. The number of OFDM symbols in a subframe may be related to, for example, the length of each OFDM symbol and/or the cyclic prefix value. However, to simplify system implementation, it is desirable that all subframes within a frame have the same size and consist of the same number of OFDM symbols. Embodiments of the present invention may be used with any suitable OFDM numerology. Those skilled in the art will recognize that while various parameters (eg, duplex mode, cyclic prefix value, OFDMA numerology, etc.) may be used in accordance with the embodiments described herein, suitable variations may be used, as described in the variations of Figures 11-13.

Referring to Figure 14 , which is a table of OFDMA parameters according to an embodiment of the present invention, Figure 14 lists parameters for a 1/4 CP. A quarter CP length is equal to 22.85 microseconds (for bandwidths of 5, 10, or 20 MHz), corresponding to a cell size of approximately 5 km. Therefore, delay spread can be reduced by up to 22.85 microseconds.

15 , which is a flowchart of a method according to an embodiment of the present invention.

At operation 1500, a processor in a terminal divides each frame into two or more subframes. The frame (e.g., frame 410 described with reference to FIG. 4 or other frames) may be backward compatible with a baseline system profile and, for example, defined according to a baseline standard system (e.g., IEEE Std 802.16-2009 or a Mobile WiMAX profile). Consequently, compared to a frame divided into subframes, a subframe (e.g., subframe 420 described with reference to FIG. 4 ) may be shorter, thereby enabling faster processing and transmission/reception with a smaller periodicity. Transmissions based on the subframe structure may provide over-the-air communications with a periodicity on the scale of several subframes, rather than the relatively longer periodicity of several frames.

At operation 1505 , the transmitter may transmit one or more subframes during a pre-designated downlink transmission (eg, the pre-designated DL transmission 306 described with reference to FIG. 3 ).

At operation 1510 , the transmitter may transmit one or more subframes during a pre-designated uplink transmission (eg, the pre-designated UL transmission 308 described with reference to FIG. 3 ).

At operation 1515, the transmitter may transmit one of a plurality of subframes including a legacy preamble for communicating with, for example, a legacy terminal operating according to a baseline system profile during a pre-designated legacy transmission period or zone (e.g., legacy zones 612 and/or 616 described with reference to FIG. 6).

In operation 1520, the transmitter may transmit one of a plurality of subframes including a new preamble for communicating with a new (e.g., non-legacy) terminal operating, for example, according to an evolved or newer version of a baseline system standard (such as the IEEE 802.16m standard) during a pre-designated new (e.g., non-legacy) transmission period or zone (e.g., new zones 614 and/or 618 described with reference to FIG. 6 ).

In various embodiments, the first and second signals may be transmitted in TDD duplex mode or FDD duplex mode. In some embodiments, when transmitting in TDD duplex mode, operations 1505 and 1510 may be performed at substantially different time intervals or frame positions, such that the first and second signals are transmitted separately. In other embodiments, when transmitting in FDD duplex mode, operations 1505 and 1510 may be performed in substantially overlapping time periods, such that the first and second signals are transmitted on substantially different frequencies and/or channels.

In some embodiments, a subframe may be further divided into two or more (eg, six) information carrying, multiplexing, and/or OFDM symbols.

In some embodiments, the first and second signals may include a legacy preamble for communicating with legacy terminals operating according to a baseline system profile and a new preamble for communicating with new (e.g., non-legacy) terminals operating according to a second system standard and/or an evolution of the baseline system. In one embodiment, each of the first and second subframes may be pre-designated for communication with both legacy and non-legacy terminals, or with one of a legacy terminal or a non-legacy terminal. For example, in operation 1510, one of the two or more subframes may be pre-designated for communication with both legacy and non-legacy terminals.

In some embodiments, the start of frames pre-designated for communication with legacy and non-legacy terminals may be offset, for example, by a fixed number of subframes.

In some embodiments, a superframe may be defined. For example, a superframe may include two or more frames (e.g., the frames described in operation 1500) that may be transmitted consecutively. In one embodiment, the new preamble may be transmitted substantially once during each superframe transmission. In one embodiment, the new preamble may be transmitted substantially once per frame.

According to an embodiment, such as Option I described herein, the legacy preamble and the new preamble may be transmitted separately at substantially fixed intervals along the length of the frame, for example.

In one embodiment, the process may perform operations 1500, 1505, and 1510 without performing operations 1515 and 1520. In another embodiment, the process may perform operations 1500, 1515, and 1520 without performing operations 1505 and 1510. In another embodiment, the process may perform operations 1500, 1505, 1510, 1515, and 1520. The process may perform other sequences, orders, and/or permutations of the operations described herein.

Although the present invention has been described with reference to a limited number of embodiments, it will be appreciated that many variations, modifications, and other applications of the present invention may be made. Embodiments of the present invention may include other devices for performing the operations herein. Such devices may integrate the elements discussed, or may include optional components for implementing the same purpose. It will be understood by those skilled in the art that the appended claims are intended to cover all such modifications and changes that fall within the true spirit of the present invention.

Claims (9)

1. A method for base station to relay station (RN) transmission based on Orthogonal Frequency Division Multiple Access (OFDMA) technology, the method comprising: The frame is divided into multiple subframes, each subframe including a time slot for transmitting signals within a resource block, wherein a cyclic prefix (CP) of a predetermined length is appended to each symbol of the subframe, some of the multiple subframes are downlink subframes for pre-specified downlink transmission, and some of the multiple subframes are uplink subframes for pre-specified uplink transmission, some of the multiple subframes each include 6 symbols, and some of the multiple subframes each include 7 symbols; Transmit one or more subframes from the plurality of subframes during a pre-specified downlink transmission; and One or more of the plurality of subframes are transmitted during a pre-specified uplink transmission. 2. The method of claim 1, wherein the cyclic prefix has a useful symbol length of one-quarter. 3. The method of claim 1, wherein the length of the cyclic prefix is selected based on the channel delay spread. 4. The method of claim 1, wherein the method further comprises using time-division duplex mode to transmit subframes. 5. The method of claim 1, wherein the method further comprises using frequency division duplex mode to transmit subframes. 6. A base station configured to perform relay station (RN) transmission according to Orthogonal Frequency Division Multiple Access (OFDMA) technology, the base station comprising: A processing circuit is configured to divide a frame into multiple subframes, each subframe including a time slot for transmitting signals within a resource block, wherein a cyclic prefix (CP) of a predetermined length is appended to each symbol of the subframe, some of the multiple subframes being downlink subframes for pre-specified downlink transmission, and some of the multiple subframes being uplink subframes for pre-specified uplink transmission, some of the multiple subframes each including 6 symbols, and some of the multiple subframes each including 7 symbols; and Physical layer circuitry for transmitting one or more of the plurality of subframes during a pre-specified downlink transmission and for transmitting one or more of the plurality of subframes during a pre-specified uplink transmission. 7. The base station of claim 6, wherein the cyclic prefix has a useful symbol length of one-quarter. 8. A computer-readable medium having instructions stored thereon, the instructions causing the processor, when executed by a processor of a computer, to perform the method as described in any one of claims 1 to 5. 9. An apparatus for base station to relay station (RN) transmission according to orthogonal frequency division multiple access (OFDMA) technology, comprising means for performing the method as described in any one of claims 1 to 5.