Abstract:
A method comprises providing a frame, the frame including a downlink sub-frame and an uplink sub-frame, portions of the downlink sub-frame and uplink sub-frame being allocated for communication with a mobile station configured to operate utilizing a legacy IEEE 802.16 standard, and portions of the downlink sub-frame and uplink sub-frame being allocated for communication with a mobile station configured to operate utilizing the IEEE 802.16m standard; and using the frame to wirelessly communicate with a mobile station in at least one of the uplink and downlink directions. A method of using an 802.16m frame structure for multi-band operation is also provided, as well as an 802.16m frame structure for relay support.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present patent application is a continuation in part of U.S. patent application Ser. No. 12/331,847 filed on Dec. 10, 2008, which claims the benefit of U.S. Provisional Patent Application Ser. No. 61/012,680, filed on Dec. 10, 2007, the entire contents of the foregoing applications are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to wireless communication systems. 
       BACKGROUND 
       [0003]    The Worldwide Interoperability for Microwave Access Forum (WiMAX) has developed a specification that describes a radio interface for wireless data communications. This specification is known as the Institute of Electrical and Electronic Engineers (IEEE) 802.16e-2005 standard (referred to herein as the “IEEE 802.16e standard”) and is incorporated herein by reference. WiMAX is intended to provide higher capacity, allow greater communications distances and provide mobility (access across different access points). 
         [0004]    The Institute of Electrical and Electronics Engineers, Inc. (IEEE) 802.16 Broadband Wireless Access Working Group Task Group m (TGm) is chartered to develop an amendment to IEEE Standard 802.16, to be known as IEEE 802.16m: P802.16—IEEE Standard for Local and Metropolitan Area Networks—Part 16: Air Interface for Fixed Broadband Wireless Access Systems—Amendment: IEEE Standard for Local and Metropolitan Area Networks—Part 16: Air Interface for Fixed and Mobile Broadband Wireless Access Systems—Advanced Air Interface. The documents related to the IEEE 802.16m standard are available at http://www.ieee802.org/16/tgm/. These can be considered at any date by utilizing the services of the Internet Web Archive, available at http://www.archive.org/. For example, the following URL provides access to a copy of the IEEE 802.16m documents as they appeared on Dec. 10, 2007, the filing date of the application: http://web.archive.org/web/20071210/ieee802.org/16/tgm/, of which this application is a Continuation in Part. 
         [0005]    All documents, whether listed as contributed or official, listed in http://web.archive.org/web/20071210/ieee802.org/16/tgm/ are incorporated herein by reference in their entirety. 
         [0006]    Of particular relevance to the background of this application are those documents contributed to the above noted IEEE 802.16m working group by the inventors named herein. 
       SUMMARY OF THE INVENTION 
       [0007]    In some embodiments, the concepts of the present invention may be used in conjunction with the IEEE 802.16 standard, which is commonly referred to as the WiMAX standard, and in particular the next generation of the IEEE 802.16 standard commonly known as the IEEE 802.16m standard. 
         [0008]    Some embodiments described herein employ time division duplexing (TDD), and some embodiments employ frequency division duplexing (FDD). 
         [0009]    According to a first aspect, there is provided multiple types of systems or OFDMA transmission formats that can be multiplexed in time division fashion or frequency division fashion or both. Each frequency division segment can further be time division multiplexed across multiple systems. The same superframe format, frame format and smaller frame format can be applied to time division multiplexing, frequency division multiplexing and a mixture of both. The same synchronization channels and system parameters of the broadcast channel can be applied to time division multiplexing, frequency division multiplexing and a mixture of both. This aspect can be applied to a single hop system consisting of a base station and a mobile station, and multi-hop systems consisting of a base station, relay stations (or intermediate nodes) and mobile stations. This aspect can be applied to the transmission and multiplexing of multiple systems across each hop of a multi-hop network. 
         [0010]    According to a second aspect there is provided a transmission frame consisting of time division multiplexing (TDM) and/or frequency division multiplexing (FDM) of two or more systems or waveforms onto the same Radio Frequency (RF) carrier and bandwidth. A transmission frame consists of multiple equal-size smaller frames, where each smaller frame constitutes the basic unit of time-frequency resource definition, time-division duplex (TDD) partitioning between downlink and uplink, and time division multiplexing (TDM) between two or more OFDMA systems or formats. The start of the TDD downlink portion or uplink portion within a frame can be different for different systems that are multiplexed onto the same RF carrier and bandwidth. A superframe consists of multiple equal-size frames, where each frame is further divided into multiple equal-size smaller frames. The superframe boundary and duration can be different for different systems that are multiplexed onto the same RF carrier and bandwidth in TDM or FDM fashion. A transmission frame or superframe consists of a universal synchronization channel such as a universal preamble shared by multiple types of systems and system-specific synchronization channels or system-specific preambles used by the corresponding system. The system-specific synchronization channel occurs at a fixed location within the superframe of the corresponding system. The universal synchronization channel and system-specific synchronization channel puncture out one or more symbols of one or more designated smaller frames within a frame or superframe. A superframe consists of one or more system parameter broadcast channels at predefined locations within the superframe. The system parameter broadcast channels are superposed onto the same time-frequency resource within the superframe. The Hybrid ARQ (HARQ) acknowledgement (ACK) and retransmission timing of a system within a frame or superframe are defined by the ACK delay, retransmission delay, the number of parallel HARQ channels, the TDD Downlink (DL) to Uplink (UL) ratio and the TDM resource allocated to the system. This information is signaled by the base station in broadcast or unicast fashion to the mobile station and the mobile station deduces the HARQ ACK timing and retransmission timing based on this information. 
         [0011]    According to a third aspect, there is provided a superframe consisting of multiple equal-size frames, where each frame can be further divided into multiple equal-size smaller frames. A preamble frame or smaller frame is located in a predefined location within the superframe and defines the superframe boundary. A preamble frame or smaller frame consists of a common-synchronization channel and the cell-specific synchronization channel. The common-synchronization channel is scrambled by unique sequences to indicate the types of systems multiplexed onto the same RF carrier and bandwidth as that of the preamble frame or smaller frame. 
         [0012]    According to a fourth aspect, there is provided a system bandwidth divided into multiple segments with the same or different bandwidth. Each segment supports one or multiple systems or OFDMA transmission formats. A system, transmission format or time-frequency resource definition can span one or more segments. A base station can simultaneously support different types of systems or OFDMA transmission formats on different segments. The base station can transmit/receive in single carrier fashion, that is one center frequency and one Fast Fourier Transform (FFT) across multiple segments or in multi-carrier fashion, that is multiple center frequencies and FFTs across multiple segments. A mobile station can transmit/receive in single carrier fashion, that is one center frequency and one FFT across multiple segments or in multi-carrier fashion, that is multiple center frequencies and FFTs across multiple segments. A mobile station can transmit/receive on one or multiple segments using different center frequencies and FFT sizes from those of the base station. A mobile station performs synchronization and network entry on one or more specific segments implicitly indicated by the base station through the presence of preamble in that segment or explicitly indicated by the base station through system parameter broadcast signaling. A mobile station can be semi-statically or dynamically allocated to one or multiple segments after network entry. Guard bands or tones between segments can be semi-statically or dynamically included or excluded. One or more segments contain the universal synchronization channels and system parameter broadcast channels shared by multiple systems. Additional system-specific synchronization channels and system parameter broadcast channels can be located in the same or different sets of segments. The universal synchronization channels and system parameter broadcast channels can be located on the center frequency of the entire band, with predefined bandwidths. 
         [0013]    According to a fifth aspect, there is provided a node which transmits signals to its parent node and child node at the same time on the same RF carrier. A node receives signals from its parent node and child node at the same time on the same RF carrier. A node transmits a signal to its parent node and child node at the same time on the same RF carrier on global time-frequency resource zones. A node receives signals from its parent node and child node at the same time on the same RF carrier on global time-frequency resource zones. A set of orthogonal time-frequency sub-channels is defined in a global time-frequency resource zone. The set of sub-channels is shared by the transmission to parent node and child node or reception from parent node and child node. The global time-frequency resource zones may be configured within the DL sub-frame and/or UL sub-frame so that different Mobile Stations (MSs) may not use the same global zone for DL and UL transmissions, which can lead to interference issues. On a global time-frequency zone, either odd-hop or even-hop access nodes may use the zone for transmission to (or reception from) an MS. Two global time/frequency resource zones, one configured for odd-hop RS-to-MS communication and one configured for even-hop RS-to-MS communications may be configured for the DL sub-frame. Similarly, two global zones may be configured for the uplink sub-frame. A node simultaneously receives from (or transmits to) its parent node and child node using the same time-frequency resource. Data can be recovered using interference avoidance or interference removal. Global time-frequency resource zones are defined for signaling exchange between multiple nodes (BS, and/or RS, and/or MS) for self-configuration and self-organization operation. 
         [0014]    Embodiments may include a modified frame structure to the IEEE 802.16 standard thereby enabling backwards compatibility (also known as legacy support) for legacy systems (e.g. a deployed system such as that based on the IEEE 802.16e standard). In some embodiments, this modified frame structure may be used in conjunction with the IEEE 802.16m standard. 
         [0015]    According to a sixth aspect, there is provided a method comprising providing a frame, the frame including a downlink sub-frame and an uplink sub-frame, portions of the downlink sub-frame and uplink sub-frame being allocated for communication with a mobile station configured to operate utilizing a legacy IEEE 802.16 standard, and portions of the downlink sub-frame and uplink sub-frame being allocated for communication with a mobile station configured to operate utilizing the IEEE 802.16m standard; and using the frame to wirelessly communicate with a mobile station in at least one of the uplink and downlink directions. 
         [0016]    According to a seventh aspect, there is provided a method of operating a wireless communications network having multiple mobile stations and a serving base station, the multiple mobile stations including a first mobile station and a second mobile station, the method comprising dividing system bandwidth into a plurality of bandwidth segments, one for each mobile station; and the bandwidth segment associated with the first mobile station being configured to operate utilizing the IEEE 802.16m standard. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The invention will now be described in greater detail with reference to the accompanying diagrams, in which: 
           [0018]      FIG. 1  is a block diagram of a representative frame structure used in connection with some embodiments; 
           [0019]      FIG. 2  is a block diagram of a representative sub-frame structure used in connection with some embodiments; 
           [0020]      FIG. 3A  is a block diagram showing a representative frame structure where a legacy system and an IEEE 802.16m system share a common UL to DL switch time but have a different DL to UL switch time; 
           [0021]      FIG. 3B  is a block diagram showing a representative frame structure where a legacy system and an IEEE 802.16m system share a common DL to UL switch time but have a different UL to DL switch time; 
           [0022]      FIG. 4A  is a block diagram illustrating DL Hybrid Automatic Repeat Request (HARQ) round trip delay, with an IEEE 802.16m TDD ratio of 2:3; 
           [0023]      FIG. 4B  is a block diagram illustrating DL HARQ round trip delay, with an IEEE 802.16m TDD ratio of 3:2; 
           [0024]      FIG. 5A  is a block diagram illustrating UL HARQ round trip delay, with an IEEE 802.16m TDD ratio of 2:3; 
           [0025]      FIG. 5B  is a block diagram illustrating UL HARQ round trip delay, with an IEEE 802.16m TDD ratio of 3:2; 
           [0026]      FIG. 6  is a block diagram of a representative superframe structure used in connection with some embodiments; 
           [0027]      FIG. 7  is a block diagram of a representative alternative superframe structure used in connection with some embodiments; 
           [0028]      FIG. 8A  is a flowchart of exemplary steps for initial system access for an IEEE 802.16m Mobile Station (MS) according to one embodiment; 
           [0029]      FIG. 8B  is a flowchart of exemplary steps for initial system access for an IEEE 802.16m Mobile Station (MS) according to another embodiment; 
           [0030]      FIG. 9  is a block diagram of a representative frame structure where a superframe consists of K frames according to one embodiment; 
           [0031]      FIG. 10  is a block diagram of a representative frame structure where a superframe consists of P mini-slots according to one embodiment; 
           [0032]      FIG. 11A  is a block diagram of a first example multi-band scenario where the available IEEE 802.16m system bandwidth of 20 MHz  1200  is partitioned into multiple segments; 
           [0033]      FIG. 11B  is a block diagram showing a representative frame structure of the multi-band scenario illustrated in  FIG. 11A ; 
           [0034]      FIG. 11C  is a flowchart showing the steps for initial access for an IEEE 802.16m-enabled MS using the multi-band scenario of  FIGS. 11A and 11B ; 
           [0035]      FIG. 12A  is a block diagram showing a second example multi-band scenario where the available IEEE 802.16m system bandwidth is partitioned into multiple segments; 
           [0036]      FIG. 12B  is a block diagram showing a representative frame structure of the multi-band scenario illustrated in  FIG. 12A ; 
           [0037]      FIG. 12C  is a flowchart showing the steps for initial access for an IEEE 802.16m-enabled MS using the multi-band scenario of  FIGS. 12A and 12B ; 
           [0038]      FIG. 13A  is a block diagram showing a third example multi-band scenario where the available IEEE 802.16m system bandwidth is partitioned into multiple segments; 
           [0039]      FIG. 13B  is a block diagram showing a representative frame structure of the multi-band scenario illustrated in  FIG. 13A  showing a first option of where the preamble mini-slot could be located; 
           [0040]      FIG. 13C  is a block diagram showing a representative frame structure of the multi-band scenario illustrated in  FIG. 13A  showing a second option of where the preamble mini-slot could be located; 
           [0041]      FIG. 13D  is a flowchart showing the steps for initial access for an IEEE 802.16m-enabled MS using the multi-band scenario of  FIG. 13B ; 
           [0042]      FIG. 13E  is a flowchart showing the steps for initial access for an IEEE 802.16m-enabled MS using the multi-band scenario of  FIG. 13C ; 
           [0043]      FIG. 14A  is a block diagram showing a fourth example multi-band scenario where the available IEEE 802.16m system bandwidth is partitioned into multiple segments; 
           [0044]      FIG. 14B  is a block diagram showing a representative frame structure of the multi-band scenario illustrated in  FIG. 14A  showing a first option of where the preamble mini-slot could be located; 
           [0045]      FIG. 14C  is a block diagram showing a representative frame structure of the multi-band scenario illustrated in  FIG. 14A  showing a second option of where the preamble mini-slot could be located; 
           [0046]      FIG. 14D  is a flowchart showing steps for initial access for an IEEE 802.16m-enabled MS using the multi-band scenario of  FIG. 14B ; 
           [0047]      FIG. 14E  is a flowchart showing the steps for initial access for an IEEE 802.16m-enabled MS using the multi-band scenario of  FIG. 14C . 
           [0048]      FIG. 15  is a block diagram showing a first example of a frame structure to accomplish multi-hop relay, for TDD, provided in accordance with one embodiment; 
           [0049]      FIG. 16A  is a block diagram of a representative wireless communication network illustrating a second embodiment in TDD supporting multi-hop relay; 
           [0050]      FIG. 16B  is a block diagram illustrating DL and UL sub-frames for the second example shown in  FIG. 16A ; 
           [0051]      FIG. 17  is a block diagram showing further details of the second embodiment for multi-hop relay; 
           [0052]      FIG. 18  is a block diagram showing further details of a third embodiment for multi-hop relay, but for FDD; 
           [0053]      FIG. 19  is a block diagram showing further details of a fourth embodiment for multi-hop relay, also for FDD; and 
           [0054]      FIG. 20  is a block diagram showing further details of a fifth embodiment for multi-hop relay, also for FDD. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0055]    Although the concepts of the present invention may be used in various communication systems, in some embodiments these concepts can be particularly applicable to the IEEE 802.16 standard, which is commonly referred to as the WiMAX standard, and in particular the next generation of the IEEE 802.16 standard commonly known as the IEEE 802.16m standard. 
         [0056]      FIG. 1  shows a frame structure which provides legacy support, provided in accordance with one embodiment. The frame structure is segmented to provide a first set of zones specifically for legacy support, and a second set of zones designed for communication only with terminals operating under a new standard such as the IEEE 802.16m standard. The frame structure illustrated in  FIG. 1  is intended only as a representative example of one frame structure which could be used to provide legacy support to terminals operating under the IEEE 802.16e standard. Persons skilled in the art will appreciate that alternative frame structures could be employed to serve the same purpose. 
         [0057]    Embodiments of the present invention support both Time Division Duplexing (TDD) and Frequency Division Duplexing (FDD) modes.  FIG. 1  shows a representative frame structure for the case of TDD downlink and uplink transmission. For the case of FDD of downlink and uplink transmission, the downlink (DL) sub-frame  202  and uplink (UL) sub-frame  204  are on separate carrier frequencies rather than at separate time. The following description of DL sub-frame  202  and UL sub-frame  204  also apply to an FDD system. 
         [0058]    Operationally, the frame structure of  FIG. 1  supports both IEEE 802.16m and legacy systems by defining a legacy zone and an IEEE 802.16m zone whereby legacy zones are located at the beginning of the legacy DL sub-frame and the legacy UL sub-frame. The duration of the legacy zone and the IEEE 802.16m zone can be semi-statically or dynamically configured. 
         [0059]    In  FIG. 1 , a DL sub-frame  202  is shown, contiguous with a UL sub-frame  204 . The length of each sub-frame is designed to be compatible with legacy systems. DL sub-frame  202  is separated from UL sub-frame  204  by a Transmit Transition Gap (TTG)  206 , which is a buffer period between transmission and reception of frames which prevents downlink and uplink collisions. UL sub-frame  204  terminates with a Receive Transition Gap (RTG)  208  which performs a similar function as TTG  206 . 
         [0060]    DL sub-frame  202  is comprised of downlink preamble  210 , frame control header (FCH)  212 , which provides frame configuration information, MAP message  214 , legacy (i.e. 802.16e) data zone  216 , and IEEE 802.16m control and data zones  217 . 
         [0061]    UL sub-frame  204  is comprised of 802.16e UL ranging zone  218 , 802.16e UL control and data zones  220 , and IEEE 802.16m UL control and data zones  222 . 
         [0062]    Preamble  210 , FCH  212 , TTG  206 , RTG  208  and 802.16e UL ranging zone  218  are mandatory functions to support legacy MSs. 
         [0063]    MAP message  214 , 802.16e data zones  216 , and 802.16e UL control and data zones  220  are functions to support legacy 802.16e MSs when 802.16e data bursts are scheduled. 
         [0064]    IEEE 802.16m control and data zones  222  are functions to support IEEE 802.16m-enabled MSs when an IEEE 802.16m data burst is scheduled. 
         [0065]    Different TDD ratios can be configured for a legacy system and an IEEE 802.16m system. The DL/UL switch of legacy systems is broadcast in the Downlink Channel Descriptor/Uplink Channel Descriptor (DCD/UCD) and is synchronized across the network. In some embodiments, it should be almost statically configured. For IEEE 802.16m, the DL/UL switch should also be statically configured. IEEE 802.16m and legacy systems can have different TDD DL/UL switch times. 
         [0066]    Legacy system preamble  210  can be used by legacy terminals and IEEE 802.16m terminals for synchronization and system access. An additional IEEE 802.16m preamble (not shown), such as the common-synchronization channel, can be added to enhance the synchronization performance of IEEE 802.16m terminals. 
         [0067]      FIG. 2  is a block diagram of a representative sub-frame structure  300  used in connection with some embodiments.  FIG. 2  shows the case of time division duplexing (TDD) of downlink and uplink transmissions. For the case of FDD of downlink and uplink transmissions, the downlink and uplink sub-frames shown in  FIG. 2  are on separate carrier frequencies rather than separate time. The following description applies equally well to the DL and UL of an FDD system respectively. 
         [0068]    In some embodiments, a legacy frame  300  of 5 ms duration is comprised of eight mini-slots  306 ,  308 ,  310 ,  312 ,  314 ,  316 ,  318 ,  320  (also known as sub-frames). Mini-slots  306 ,  308 ,  310  and  312  comprise the DL sub-frame  301 , while sub-frames  314 ,  316 ,  318  and  320  comprise the UL sub-frame  303 . Each mini-slot contains six symbols, though this number can vary. 
         [0069]    In some embodiments, the first mini-slot (in this case mini-slot  306 ) is the preamble mini-slot. For the case of TDD, one symbol is punctured for use as TDD guard time, that is, TTG/RTG. The remaining 5 symbols consist of preamble, FCH and MAP and possibly legacy data zones. 
         [0070]    In some embodiments, the DL mini-slots start with the preamble mini-slots, and the UL mini-slots start with the legacy UL mini-slot. 
         [0071]    The IEEE 802.16m mini-slots  310 ,  312 ,  316 ,  318  and  320  contain both IEEE 802.16m control and data. The channelization, that is mapping of a logical channel to physical tones, for control and data is defined within each mini-slot. 
         [0072]    In some embodiments, an extended mini-slot can be defined by concatenating multiple adjacent or non-adjacent mini-slots. In the DL, the channelization is defined across the mini-slots within the extended mini-slot to improve time diversity for control and data. In the UL, the time is defined within a mini-slot. However, an MS can be assigned resources across the mini-slots within the extended mini-slot, to improve UL coverage. 
         [0073]    In both DL and UL, the extended basic resource unit (also called basic channel unit) within the extended mini-slot is defined by concatenation of B basic resource units, one from each mini-slot within the extended mini-slot; where B is the number of mini-slots within an extended mini-slot. The purpose of the extended basic channel unit is to allow scalability of resource size based on the number of mini-slots in the extended mini-slot and to allow the same control channel structure for mini-slots and extended mini-slots. 
         [0074]    The extended mini-slots and normal mini-slots can co-exist in the system in frequency division multiplexing (FDM) and/or time division multiplexing (TDM) fashion. Separate sets of OFDMA time/frequency resources are allocated to mini-slots and extended mini-slots. The channelization for control and data is defined within each set of OFDMA time/frequency resources. 
         [0075]    IEEE 802.16m TDD ratios are defined as M:N where M is the number of IEEE 802.16m DL mini-slots in a frame and N is the number of IEEE 802.16m UL mini-slots in a frame. In the example of  FIG. 2 , the TDD ratio is 2:3. 
         [0076]      FIG. 3A  is a block diagram showing a frame  400  where a legacy system and an IEEE 802.16m system share a common UL to DL switch time, but have a different DL to UL switch time. This case has some value where a legacy system profile doesn&#39;t support UL with more than a certain number of symbols, e.g. 21. 
         [0077]      FIG. 3B  is a block diagram showing a representative frame structure  450  where a legacy system and an IEEE 802.16m system share a common DL to UL switch time but have a different UL to DL switch time. This case has some value where a high DL:UL ratio is desired and where there is a desire to ensure the legacy system has lower latency in UL feedback/requests. 
         [0078]    Note that in some embodiments, the gap between an UL and DL sub-frame is always adjacent to a legacy mini-slot so that legacy users only need to search the first mini-slot for information. 
         [0079]      FIG. 4A  is a block diagram illustrating DL HARQ round trip delay, with an IEEE 802.16m TDD ratio of 2:3. The minimum HARQ ACK and Retrx (retransmission) delay and the number of HARQ channels are defined in system broadcast signaling which corresponds to particular partitioning of legacy, IEEE 802.16m, and TDD ratios (for the case of TDD). With these parameters defined, the precise HARQ timing can be deduced. In the embodiment of  FIG. 4A , ACK delay and retrx delay are four mini-slots, with two HARQ channels. 
         [0080]      FIG. 4B  is a block diagram illustrating DL HARQ round trip delay, with an IEEE 802.16m TDD ratio of 3:2. In the embodiment of  FIG. 4B , ACK delay and retrx delay are four mini-slots, with four HARQ channels. 
         [0081]      FIG. 5A  is a block diagram illustrating UL HARQ round trip delay, with an IEEE 802.16m TDD ratio of 2:3. In the embodiment of  FIG. 5A , ACK delay and retrx delay are four mini slots, with four HARQ channels. 
         [0082]      FIG. 5B  shows UL HARQ round trip delay, with an IEEE 802.16m TDD ratio of 3:2. In the embodiment of  FIG. 5B , ACK delay and retrx delay are four mini slots, with four HARQ channels. 
         [0083]    In the embodiments such as those illustrated in each of  FIGS. 4A ,  4 B,  5 A and  5 B, the first mini-slot is reserved for legacy systems. 
         [0084]    In  FIGS. 4A and 5B , each shaded block illustrates the corresponding DL tx/retrx and UL ACK. Similarly, in  FIGS. 5A and 5B  each shed block illustrates the corresponding UL tx/retrax and DL ACK. 
         [0085]      FIG. 6  is a block diagram of a representative example of a superframe structure.  FIG. 6  shows the case of time division duplexing (TDD) of downlink and uplink transmissions. For the case of frequency division duplexing (FDD) of downlink and uplink transmissions, the downlink and uplink sub-frames shown in  FIG. 6  are on separate carrier frequencies rather than separate time. The following description of DL sub-frames and UL sub-frames still apply to the DL and UL of an FDD system, respectively. 
         [0086]    In some embodiments, superframe  700  is comprised of K frames. In some embodiments, K=4. Superframe  700  is comprised of a plurality of frames  702 ,  704 , . . . and in this example, frames  702 ,  704  are of 5 ms duration. 
         [0087]    The first mini-slot  712  at the start of the superframe  700  or some predetermined fixed location within the superframe contains the IEEE 802.16m system parameter broadcast channels such as the primary and secondary broadcast channels and may also contain additional preamble (such as the common-sync channel) for IEEE 802.16m-only. In addition, the additional preamble for IEEE 802.16m-only (such as a common-sync channel) can be located at a fixed location within a superframe but separately from the primary/secondary broadcast channels. 
         [0088]    In this embodiment, each frame (such as frame  702 ) is comprised of a DL sub-frame  706  and a UL sub-frame  708 . Each sub-frame (such as DL sub-frame  706 ) is comprised of a number of mini-slots which, in this embodiment, is four. 
         [0089]    In this embodiment, each sub-frame is separated from each other by a gap, such as a TTG/RTG  710 . 
         [0090]    DL sub-frame  706  is comprised of DL mini-slots  712 ,  714 ,  716  and  718 . DL mini-slot  712  is reserved for a legacy DL preamble, FCH, MAP and legacy data. DL mini-slot  714  is a legacy DL mini-slot containing legacy DL data. DL mini-slot  716  is an IEEE 802.16m preamble mini-slot containing IEEE 802.16m primary and secondary broadcast channels. DL mini-slot  716  may also contain IEEE 802.16m preamble data such as a common-sync channel. DL mini-slot  718  is an IEEE 802.16m DL mini-slot containing IEEE 802.16m control and data. 
         [0091]    In this embodiment, UL sub-frame  708  is comprised of UL mini-slots  722 ,  720 ,  724 , and  726 . UL mini-slot  720  is a legacy UL mini-slot containing legacy UL data and control. UL mini-slots  722 ,  722 ,  724  and  726  are IEEE 802.16m UL mini-slots containing IEEE 802.16m control and data. 
         [0092]    Gap  710  separates frame  702  from frame  704 . Frame  704  is comprised of DL sub-frame  740  and UL sub-frame  742 . DL sub-frame  740  is comprised of DL mini-slots  730 ,  732 ,  734 , and  736 . DL mini-slot  730  is reserved for legacy DL preamble, FCH, MAP and legacy data. DL mini-slot  732  is a legacy DL mini-slot containing legacy DL data. DL mini-slots  734  and  736  are IEEE 802.16m DL mini-slots containing IEEE 802.16m control and data. 
         [0093]    DL sub-frame  740  is separated from UL sub-frame  742  by gap  710 . UL sub-frame  708  is comprised of UL mini-slots  750 ,  752 ,  754  and  756 . UL mini-slot  750  is a legacy UL mini-slot containing legacy UL data and control. UL mini-slots  752 ,  754  and  756  are IEEE 802.16m UL mini-slots containing IEEE 802.16m control and data. 
         [0094]      FIG. 7  is a block diagram of an embodiment of an alternative superframe structure as compared to the one illustrated in  FIG. 6 . The difference in this embodiment is that a common-sync channel/symbol  802  is located prior to the superframe  800  boundary. The common-sync channel/symbol can be contained within the IEEE 802.16m preamble mini-slot  804 . 
         [0095]      FIG. 8A  is a flowchart of exemplary steps for initial system access for an MS configured to support IEEE 802.16m according to one embodiment. 
         [0096]    At step  900 , the procedure is started. 
         [0097]    At step  902 , the IEEE 802.16m-enabled MS may perform coarse synchronization and superframe boundary detection using the IEEE 802.16m common-sync channel/symbol (if such channel/symbol exists). 
         [0098]    At step  904 , the IEEE 802.16m-enabled MS may perform fine synchronization and a cell search using the legacy preamble. 
         [0099]    At step  906 , the IEEE 802.16m-enabled MS may decode the legacy broadcast control channels, for example, FCH and MAP and therefore determine the location of the IEEE 802.16m zone from the legacy MAP. 
         [0100]    At step  908 , the IEEE 802.16m-enabled MS may decode the primary broadcast channel within the IEEE 802.16m zone. The primary broadcast channel can be transmitted at the beginning or at a predefined resource location within the IEEE 802.16m preamble mini-slot. (A superframe can consist of L frames, where L is predefined and the superframe boundary can be indicated in the legacy MAP in case there is no IEEE 802.16m common-sync channel. Otherwise, the superframe boundary is implied by the location of the common-sync channel detected in step  902 ). The primary broadcast channel can contain deployment-wide PHY parameters which do not change from one superframe to another. For example, system bandwidth, multi-carrier configuration, system time, etc. The primary broadcast channel can be encoded or employ repetition coding over multiple superframes to improve robustness. 
         [0101]    At step  910 , the IEEE 802.16m-enabled MS may decode the secondary broadcast channel within the IEEE 802.16m zone. The secondary broadcast channel can be transmitted at the beginning of a predefined resource location within the IEEE 802.16m preamble mini-slot. The secondary broadcast channel can be encoded in one superframe. The secondary broadcast channel can contain essential PHY parameters for the proper decoding of PHY frame and PHY traffic and control channel within the corresponding superframe. The information (channelization, zones configuration) can change every superframe. 
         [0102]    At step  912 , the IEEE 802.16m-enabled MS can decode the system parameter broadcast messages. The system parameter broadcast messages can be sent on a regular traffic channel, and contain physical layer and MAC layer MAC system parameters that are semi-statically configured, e.g. HO parameters, power control parameters, etc. 
         [0103]    Note that the IEEE 802.16m-enabled MS can also decode the legacy system broadcast messages (i.e. DCD and UCD) within the legacy DL zone to obtain common system information shared between the legacy system and IEEE 802.16m system. The primary and secondary broadcast channel can be superposed onto the same OFDMA time/frequency resource and successive decoding can be employed to decode the primary and secondary broadcast channels. 
         [0104]    At step  914 , the procedure terminates. 
         [0105]      FIG. 8B  is a flowchart of exemplary steps for initial system access for an IEEE 802.16m Mobile Station (MS) according to another embodiment. 
         [0106]    At step  950 , the procedure is started. 
         [0107]    At step  952 , the IEEE 802.16m-enabled MS performs coarse synchronization and superframe boundary detection using the common-sync symbol. The MS then detects if the legacy support is enabled or disabled through scrambling sequence detection on the common-sync symbol. 
         [0108]    At step  954 , the IEEE 802.16m-enabled MS performs fine synchronization and cell search using the legacy preamble. 
         [0109]    At step  956 , the IEEE 802.16m-enabled MS decodes the primary broadcast channel. The primary broadcast channel is transmitted at a predefined resource location within the preamble mini-slot. The primary broadcast channel contains deployment-wide PHY parameters which don&#39;t change from one superframe to another. For example, system bandwidth, multi-carrier configuration, system time, etc. The primary broadcast channel can be encoded or employ repetition coding over multiple superframes to improve robustness. 
         [0110]    At step  958 , the IEEE 802.16m-enabled MS decodes the secondary broadcast channel. The secondary broadcast channel is transmitted at a predefined resource location within the preamble mini-slot. The secondary broadcast channel is encoded in one superframe. It contains essential PHY parameters for the proper decoding of the PHY frame and PHY traffic and control channel within the corresponding superframe. The information (channelization, zones configuration) can change every superframe. 
         [0111]    At step  960 , the IEEE 802.16m-enabled MS decodes the system parameter broadcast messages. The system parameter broadcast messages are sent on a regular traffic channel. They contain PHY/MAC system parameters that are semi-statically configured, e.g. HO parameters, power control parameters, etc. 
         [0112]    The primary and secondary broadcast channels can be superposed onto the same OFDMA time/frequency resource and successive decoding can be employed to decode to primary and secondary broadcast channels. 
         [0113]    At step  970 , the procedure terminates. 
         [0114]    Persons skilled in the art will appreciate that instead of the TDM of IEEE 802.16m and legacy resources in a frame as described in  FIGS. 1-8B , the IEEE 802.16m and legacy resources can also be Frequency Division Multiplexed (FDM). 
         [0115]    A set of physical subcarriers are reserved for legacy systems. 
         [0116]    Those reserved sub-carriers are bypassed by the IEEE 802.16m resource definition, i.e. the IEEE 802.16m logical subchannel resource only maps to the non-reserved physical sub-carriers. 
         [0117]    The sub-carrier reserved for legacy systems can be dynamically changed from frame to frame. 
         [0118]    In the case of Partially Used Sub-Carrier (PUSC) channelization or distributed channelization of the legacy system, a number of major subgroups or zones are reserved for the legacy system, so that the legacy logical subchannel resource maps to those reserved subgroups. 
         [0119]    In the case of band Adaptive Modulation and Coding (AMC) or localized channelization of the legacy system, the number of localized resource units or tiles can be dynamically assigned to legacy systems and IEEE 802.16m systems. 
         [0120]      FIGS. 1-8B  and corresponding description may enable a person of ordinary skill in the art to realize the following advantageous functionality. 
         [0121]    A transmission frame consists of time division multiplexing (TDM) and/or frequency division multiplexing (FDM) of two or more systems or waveforms onto the same RF carrier and bandwidth. 
         [0122]    A transmission frame consists of multiple equal-size smaller frames, where each smaller frame constitutes the basic unit of time-frequency resource definition, time-division duplex (TDD) partitioning between downlink and uplink, and time division multiplexing (TDM) between two or more OFDMA systems or formats. 
         [0123]    The start of the TDD downlink portion or uplink portion within a frame can be different for different systems that are multiplexed onto the same RF carrier and bandwidth. 
         [0124]    A superframe consists of multiple equal-size frames, where each frame is further divided into multiple equal-size smaller frames. The superframe boundary and duration can be different for different systems that are multiplexed onto the same RF carrier and bandwidth in TDM or FDM fashion. 
         [0125]    A transmission frame or superframe consists of a universal synchronization channel such as a universal preamble shared by multiple types of systems and system-specific synchronization channels or a system-specific preamble used by the corresponding system. The system-specific synchronization channel occurs at a fixed location within the superframe of the corresponding system. The universal synchronization channel and system-specific synchronization channel puncture out one or more symbols of one or more designated smaller frames within a frame or superframe. 
         [0126]    A superframe consists of one or more system parameter broadcast channels at a predefined location within the superframe. The system parameter broadcast channels are superposed onto the same time-frequency resource within the superframe. 
         [0127]    The Hybrid ARQ (HARQ) acknowledgement (ACK) and retransmission timing of a system within a frame or superframe are defined by the ACK delay, retransmission delay, the number of parallel HARQ channels, the TDD DL:UL ratio and the TDM resources allocated to the system. This information is broadcast by the base station to the mobile station and the mobile station deduces the HARQ ACK timing and retransmission timing based on this information. 
         [0128]      FIGS. 9 and 10  are block diagrams showing alternative frame structures used in connection with other embodiments. In both figures, a superframe is shown consisting of multiple equal-size frames, where each frame can be further divided into multiple equal-size smaller frames. As well, a preamble frame or smaller frame can be located in a predefined location within the superframe and defines the superframe boundary. 
         [0129]      FIGS. 9 and 10  show cases of TDD of downlink and uplink transmissions when legacy support is disabled for the case of single band operation. For the case of FDD of downlink and uplink transmissions, the downlink and uplink sub-frames shown in  FIGS. 9 and 10  are on separate carrier frequencies rather than separate time. The following description of DL sub-frame and UL sub-frame still apply to the DL and UL of an FDD system, respectively. 
         [0130]      FIG. 9  is a block diagram showing a representative frame structure where a superframe  1000  consists of K frames  1002 ,  1004 ,  1006 , and  1008  according to an embodiment. 
         [0131]    Each frame (e.g. frame  1002 ) consists of J mini-slots  1010 ,  1012 , . . .  1024 . J can be set to 8 to align with the legacy support mode. The TDD DL-to-UL and UL-to-DL switches are defined within a frame. The DL/UL partition is defined in units of mini-slots. 
         [0132]    The first mini-slot  1010  at the start of the superframe  1000  is the preamble mini-slot. The preamble mini-slot is defined such that an IEEE 802.16m-enabled MS performs the same synchronization and cell search procedure as in the case where legacy support is enabled. The preamble mini-slot  1010  contains a common-sync symbol  1026 , followed by a cell-specific preamble symbol  1028  which can be the same structure as the legacy preamble, the primary broadcast channel and the secondary broadcast channel. 
         [0133]    The common-synchronization channel is scrambled by unique sequences to indicate the types of systems multiplexed onto the same RF carrier and bandwidth as that of the preamble frame or smaller frame. Thus, different scrambling sequences can be used in the common-sync symbol  1026  to indicate whether legacy support is enabled or disabled. 
         [0134]      FIG. 10  is a block diagram showing a representative frame structure where a superframe  1100  consists of P mini-slots  1102 ,  1104 , . . .  1132  according to an embodiment. 
         [0135]    The TDD DL/UL partition is defined in units of mini-slots. The TDD ratios are defined by M:N where M is the number of adjacent DL mini-slots followed N adjacent UL mini-slots. 
         [0136]    The first mini-slot  1102  at the start of the superframe  1100  is the preamble mini-slot  1102 . The preamble mini-slot  1102  is defined such that an IEEE 802.16m-enabled MS performs the same synchronization and cell search procedure as in the case where legacy support is enabled. The preamble mini-slot  1102  contains a common-sync symbol  1134 , followed by a cell-specific preamble symbol  1136  which can be the same structure as the legacy preamble, the primary broadcast channel and the secondary broadcast channel. 
         [0137]    Different scrambling sequences are used in the common-sync symbol  1134  to indicate whether legacy support is enabled or disabled. 
         [0138]    The following description sets out a frame structure for IEEE 802.16m multi-band operation, which is applicable to the following cases: 1) IEEE 802.16m MSs operating on a smaller or equal bandwidth than the IEEE 802.16m BS;  2 ) legacy MSs operating on a smaller or equal bandwidth than the IEEE 802.16m BS. 
         [0139]    In single carrier mode, a single wideband FFT that spans the system bandwidth is used at the BS. The BS supports MSs (legacy MSs and IEEE 802.16m MSs) with different bandwidth capabilities up to the system bandwidth. This mode is suitable for the case of contiguous spectrum allocation. 
         [0140]    In multi-carrier mode, the system bandwidth is segmented into multiple smaller bands. A separate Fast Fourier Transform (FFT) and filter is used at each band. This mode supports MSs with different bandwidth capabilities up to the system bandwidth. This mode is suitable for the case of non-contiguous spectrum allocation and for operator carrier-upgrade scenarios. 
         [0141]    Allowing IEEE 802.16m MSs with different bandwidth capabilities has implications on system overhead. First, a guard band is required between adjacent bands within the system bandwidth. Second, IEEE 802.16m preamble and broadcast signaling has to be present in the bands that support the corresponding types of IEEE 802.16m MSs. 
         [0142]    Within the system bandwidth, there can be zero or multiple legacy-only bands, zero or multiple mixed (legacy plus IEEE 802.16m) bands and zero or multiple IEEE 802.16m-only bands. 
         [0143]    It should be noted that enabling IEEE 802.16m MSs to operate with different bandwidth capabilities may have implications on system overhead. A guard band is required between adjacent bands within the system bandwidth. In addition, an IEEE 802.16m preamble and broadcast signaling has to be present in the bands that support the corresponding types of IEEE 802.16m MSs. 
         [0144]    For a given IEEE 802.16m deployment bandwidth, three scenarios are described. 
         [0145]    In Scenario 1 (legacy support case) where an IEEE 802.16m system bandwidth is larger than the bandwidth supported by the legacy MS. In this case the IEEE 802.16m system and legacy system are overlaid in both FDM and TDM fashion. 
         [0146]    In Scenario 2 where IEEE 802.16m system bandwidth is larger than the bandwidth supported by the IEEE 802.16m-enabled MS. 
         [0147]    In Scenario 3 which is a combination of scenarios 1 and 2. In this case, the combination of proposed schemes for scenarios 1 and 2 can be used. 
         [0148]      FIGS. 11A-14E  show the case of TDD of downlink and uplink transmission. For the case of FDD of downlink and uplink transmission, the downlink and uplink sub-frames shown in  FIGS. 11A-14C  are on separate carrier frequencies rather than separate time. The following description of DL sub-frame and UL sub-frame still apply to the DL and UL of an FDD system respectively. 
         [0149]      FIG. 11A  is a block diagram showing a first example multi-band scenario (see Scenario 1 above) where the available IEEE 802.16m system bandwidth of 20 MHz  1200  is partitioned into multiple segments  1202 ,  1204  and  1206 . The IEEE 802.16m DL/UL transmission is on a single carrier with an FFT covering the entire bandwidth. 
         [0150]    There are two 5 MHz legacy-only bands (in this case represented by segments  1202  and  1204 ) and one 10 MHz IEEE 802.16m-only band  1206 . Guard band  1208  separates legacy support segment  1202  and legacy support segment  1204 . Guard band  1210  separates legacy support segment  1204  and non-legacy support segment  1206 . Any non-legacy support segments should be adjacent to each other in order to avoid the guard band. 
         [0151]    Any legacy MS in the network (in this example, legacy MS 1  and legacy MS 2 ) operate with 512-FFT at 5 MHz bandwidth. 
         [0152]    Any IEEE 802.16m-enabled MS (in this example, MS 3 ) operates with 1K FFT at 10 MHz. 
         [0153]      FIG. 11B  shows the frame structure of the multi-band scenario  1200  illustrated in  FIG. 11A . Frames  1252  and  1254  are legacy frames where legacy and IEEE 802.16m transmission is TDM as previously defined (these frames are meant to correspond with legacy support segments  1202  and  1204  in  FIG. 11A ). Frame  1256  comprises a non-legacy frame (meant to correspond with non-legacy support segment  1206  in  FIG. 11A ), where the frame structure is as previously defined, except that the IEEE 802.16m preamble may not be transmitted on the preamble mini-slot. 
         [0154]    Frame structure  1250  is comprised of DL mini-slots  1201  and UL mini-slots  1203 . Required guard bands  1257  separate the frames. Optional guard bands  1259  are only required if the occurrence of legacy and IEEE 802.16m mini-slots are not synchronized across sectors. 
         [0155]    The IEEE 802.16m sub-channel is either defined (i.e. mapped to physical sub-carriers) across the segments available for IEEE 802.16m on a mini-slot by mini-slot basis or defined within each segment. Correspondingly, the IEEE 802.16m control channels are either defined across the available segments for IEEE 802.16m to indicate the sub-channel resource allocation across the available segments, or defined within each segment to indicate the sub-channel resource within each segment. 
         [0156]    There are different options for where the IEEE 802.16m preamble mini-slot can be located. 
         [0157]    Option 1: The IEEE 802.16m preamble mini-slot  1258  is located in the non-legacy support segment  1256 . It coincides with the legacy preamble mini-slot in time. This option is shown in  FIG. 11B . 
         [0158]    Option 2: The IEEE 802.16m preamble mini-slot is located in the non-legacy support segment  1256 . The IEEE 802.16m preamble mini-slot  1260 ,  1262  does not coincide with the legacy preamble mini-slot in time. At the time when the legacy preamble mini-slot is transmitted, there may be no transmission on the non-legacy support segment. This allows the BS transmit power to concentrate on the legacy preamble transmission. This can improve the coverage of the system for initial access. This option is not shown. 
         [0159]    Option 3: The IEEE 802.16m preamble mini-slot and common-sync are located in the legacy support segment  1252  in the same way as the single-band case (i.e. in legacy preamble DL mini-slot  1262 ). This is recommended since after preamble detection, an IEEE 802.16m-enabled MS would not have knowledge of the overall system bandwidth, where the non-legacy support segment can be found, and whether legacy support is enabled. In addition, this option allows the IEEE 802.16m-enabled MS to use the same synchronization and cell search, and initial access procedures for both single band and multi-band operations. At the time when the legacy preamble is transmitted, and/or when the IEEE 802.16m common-sync symbol is transmitted, and/or when the IEEE 802.16m primary/secondary broadcast channels are transmitted, there may be no transmission on the non-legacy support segment. This can allow the BS transmit power to concentrate on the preamble transmission and broadcast channel transmission. This can improve the coverage of the system for initial access. 
         [0160]      FIG. 11C  is a flowchart showing the steps for initial access for an IEEE 802.16m-enabled MS using the multi-band scenario of  FIGS. 11A and 11B . 
         [0161]    At step  1275 , the process begins. 
         [0162]    At step  1280 , an IEEE 802.16m-enabled MS detects the IEEE 802.16m common-sync, the legacy preamble and performs synchronization and cell search. 
         [0163]    At step  1285 , the IEEE 802.16m-enabled MS decodes the primary broadcast channel and the secondary broadcast channel on the IEEE 802.16m preamble mini-slot. 
         [0164]    At step  1290 , the IEEE 802.16m-enabled MS decodes the system parameter broadcast messages. The information in these channels and messages indicates the overall system bandwidth, the legacy and non-legacy support segments and their corresponding IEEE 802.16m mini-slots, FFT size, and guard bands. 
         [0165]    At step  1295 , the process ends. 
         [0166]      FIG. 12A  is a block diagram showing a second example multi-band scenario (Scenario 1) where the available IEEE 802.16m system bandwidth of 20 MHz  1300  is partitioned into multiple segments  1302 ,  1304  and  1306 . 
         [0167]    One or more 5 MHz segments of the spectrum are defined as legacy support segments (in this case segments  1302  and  1304 ). Guard band  1308  separates legacy support segment  1302  and legacy support segment  1304 . Guard band  1310  separates legacy support segment  1304  and non-legacy support segment  1306 . Any non-legacy support segments should be adjacent to each other in order to avoid the guard band. 
         [0168]    In this example, legacy MS 1  and legacy MS 2  operate with 512-FFT at a 5 MHz bandwidth. 
         [0169]    The IEEE 802.16m-enabled MS 3    1316  operates with 1K FFT at a 10 MHz bandwidth. The IEEE 802.16m DL/UL transmission is on multiple carriers, e.g. carrier  1  with 512-FFT, carrier  2  with 512-FFT, carrier  3  with 1k-FFT. This means that an IEEE 802.16m-enabled MS such as MS 3    1316  may simultaneously transmit/receive on one or multiple segments/carriers by performing multi-carrier decoding using multiple FFT sizes or single carrier wideband decoding using the 2K-FFT. 
         [0170]      FIG. 12B  shows a representative frame structure of the multi-band scenario  1300  illustrated in  FIG. 12A . Multi-band scenario  1350  is comprised of DL mini-slots  1351  and UL mini-slots  1353 . 
         [0171]    Segments  1352  and  1354  comprise legacy support segments where legacy and IEEE 802.16m transmission is TDM as previously defined. Segment  1356  comprises a non-legacy support segment, where the frame structure is as previously defined, except that the IEEE 802.16m preamble may not be transmitted on the preamble mini-slot. Required guard bands  1359  separate the segments. 
         [0172]    The IEEE 802.16m sub-channel is defined (i.e. mapped to physical sub-carriers) within each segment. The IEEE 802.16m control channels are defined within each segment to indicate the sub-channel resource allocation across that segment. 
         [0173]    There are different options for where the IEEE 802.16m preamble mini-slot can be located. 
         [0174]    Option 1: The IEEE 802.16m preamble mini-slot  1358  is located in the non-legacy support segment  1356 . It coincides with the legacy preamble mini-slot in time. This is shown in  FIG. 12A . 
         [0175]    Option 2: The IEEE 802.16m preamble mini-slot is located in the non-legacy support segment  1356  but does not coincide with the legacy preamble mini-slot in time. As such, any of mini-slots  1370 ,  1372  or  1374  could be used. At the time when the legacy preamble mini-slot is transmitted, there may be no transmission on the non-legacy support segment. This allows the BS transmit power to concentrate on the legacy preamble transmission. This can improve the coverage of the system for initial access. This is not shown in  FIG. 12A . 
         [0176]    Option 3: The IEEE 802.16m preamble mini-slot and common-sync is located in the legacy support segment  1352  in the same way as the single-band case, i.e. in either of DL mini-slot  1360  or  1362 . This is the recommended since after preamble detection, an IEEE 802.16m-enabled MS would not have knowledge of the overall system bandwidth, where the non-legacy support segment can be found, and whether legacy support is enabled. In addition, this option allows the IEEE 802.16m-enabled MS to use the same synchronization and cell search, and initial access procedures for both single band and multi-band operations. At the time when the legacy preamble is transmitted, and/or when the IEEE 802.16m common-sync symbol is transmitted, and/or when the IEEE 802.16m primary/secondary broadcast channels are transmitted, there may be no transmission on the non-legacy support segment. This allows the BS transmit power to concentrate on the preamble transmission and broadcast channel transmission. This can improve the coverage of the system for initial access. 
         [0177]      FIG. 12C  is a flowchart showing the steps for initial access for an IEEE 802.16m-enabled MS using the multi-band scenario of  FIGS. 12A and 12B . 
         [0178]    At step  1375 , the process begins. 
         [0179]    At step  1380 , an IEEE 802.16m-enabled MS detects the IEEE 802.16m common-sync, the legacy preamble and performs synchronization and cell search on one of the legacy segments. 
         [0180]    At step  1385 , the IEEE 802.16m-enabled MS decodes the primary broadcast channel and the secondary broadcast channel on the IEEE 802.16m preamble mini-slot. 
         [0181]    At step  1390 , the IEEE 802.16m-enabled MS decodes the system parameters and broadcast messages. The information in these channels and messages indicate the overall system bandwidth, the legacy and non-legacy support segments and their corresponding IEEE 802.16m mini-slots, FFT size, and guard bands. 
         [0182]    At step  1395 , the process ends. 
         [0183]      FIG. 13A  is a block diagram showing a third example multi-band scenario (see Scenario 2 above) where the available IEEE 802.16m system bandwidth of 20 MHz  1400  is partitioned into multiple segments  1402 ,  1404  and  1406 . 
         [0184]    In  FIG. 13A , there are three types of IEEE 802.16m-enabled MSs, supporting 5 MHz, 10 MHz and 20 MHz bandwidths respectively. An IEEE 802.16m-enabled MS 1  (a first type of IEEE 802.16m-enabled MS) operates with 512-FFT on 5 MHz segment  1402 . An IEEE 802.16m-enabled MS 2  (a first type of IEEE 802.16m-enabled MS) operates with 512-FFT on 5 MHz segment  1404 . An IEEE 802.16m-enabled MS 3  (a second type of IEEE 802.16m-enabled MS) operates with 1k-FFT on 10 MHz segment  1406 . An IEEE 802.16m-enabled MS 4  (a second type of IEEE 802.16m-enabled MS) operates with 1k-FFT on 5 MHz segments  1402  and  1404 . An IEEE 802.16m-enabled MS 5  (a third type of IEEE 802.16m-enabled MS) operates with 2k-FFT on 5 MHz segments  1402  and  1404 , and 10 MHz segment  1406 . 
         [0185]    Guard band  1408  separates 5 MHz segment  1402  and 5 MHz segment  1404 . Guard band  1410  separates 5 MHz segment  1404  and 10 MHz segment  1406 . To minimize the number of guard bands, the number of segments should be minimized 
         [0186]    In this example, the IEEE 802.16m enabled BS transmits/receives on a single carrier using 2k-FFT operation. 
         [0187]    An IEEE 802.16m sub-channel can be defined within each segment illustrated in  FIG. 13A . An MS can be assigned a sub-channel resource in segments that have bandwidth equal to or smaller than the MS bandwidth capability. 
         [0188]    For example, a 5 MHz MS can be assigned to either of MHz segments  1402 ,  1404  by the BS signaling the center frequency of the corresponding segment in a slower fashion (through unicast control signaling after network entry). A 10 MHz MS can be assigned to either of the two 5 MHz segments  1402 ,  1404  or to the 10 MHz segment  1406  by the BS signaling the center frequency of the two 5 MHz segments  1402 ,  1404  or the 10 MHz segment  1406  in a slower fashion (through unicast control signaling after network entry). A 20 MHz MS can be assigned to any of the 5 MHz segments  1402 ,  1404  and 10 MHz segment  1406  dynamically since the center frequency does not change. 
         [0189]      FIG. 13B  shows further details of the multi-band scenario  1400  illustrated in  FIG. 13A  showing a first option of where the preamble mini-slot could be located. Multi-band scenario  1540  is comprised of DL mini-slots  1451  and UL mini-slots  1453 . 
         [0190]    Segments  1452  and  1454  comprise 5 MHz segments. Segment  1456  comprises a 10 MHz segment. Optional guard bands  1459  separate the segments. A guard band is not required if all the frequency subcarriers are assigned to a wideband MS. For example, the guard band between two 5 MHz segments is not required if both segments are assigned to a 10 MHz MS. The existence of guard tones on each mini-slot is signaled through a broadcast channel, e.g. the secondary broadcast channel. 
         [0191]    In this first option, preamble mini-slot  1461  is located at the center of the RF frequency to minimize detection time. The bandwidth where the preamble mini-slot is transmitted should be the minimum of the bandwidth capacity of the IEEE 802.16m-enabled MSs. 
         [0192]      FIG. 13C  shows a representative frame structure of the multi-band scenario  1400  illustrated in  FIG. 13A  showing a second option of where the preamble mini-slot could be located. Multi-band scenario  1480  is comprised of DL mini-slots  1491  and UL mini-slots  1493 . 
         [0193]    Segments  1482  and  1484  comprise 5 MHz segments. Segment  1486  comprises a 10 MHz segment. Optional guard bands  1489  separate the segments. 
         [0194]    In this second option, preamble mini-slot  1481  is located at one or multiple segments (two segments are illustrated in  FIG. 13C ). In this case, the MS has to search the preamble over multiple possible choices of segments, which can be a preferred option to align with the legacy support mode where the preamble is located at one or multiple segments. 
         [0195]      FIG. 13D  is a flowchart showing the steps for initial access for an IEEE 802.16m-enabled MS using the multi-band scenario of  FIG. 13B . 
         [0196]    At step  1420 , the process begins. 
         [0197]    At step  1422 , an IEEE 802.16m-enabled MS detects the common-sync and cell-specific preamble on the IEEE 802.16m preamble mini-slot on one of the segments and performs synchronization and cell search. 
         [0198]    At step  1424 , the IEEE 802.16m-enabled MS decodes the primary broadcast channel and the secondary broadcast control channels on the IEEE 802.16m preamble mini-slot. The information in these channels includes system bandwidth, bandwidth segments, reserved tones, and guard tones. 
         [0199]    At step  1426 , the IEEE 802.16m-enabled MS performs initial network entry on one of the segments based on the MS bandwidth capability as well as the recommended initial network entry segment(s) indicated by the BS in the primary/secondary broadcast channel. Note that the BS can designate one or multiple segments as the initial network entry segments. 
         [0200]    At step  1428 , the process ends. 
         [0201]      FIG. 13E  is a flowchart showing the steps for initial access for an IEEE 802.16m-enabled MS using the multi-band scenario of  FIG. 13C . 
         [0202]    At step  1430 , the process begins. 
         [0203]    At step  1432 , an IEEE 802.16m-enabled MS detects the common-sync and cell-specific preamble on the IEEE 802.16m preamble mini-slot on one of the segments and performs synchronization and cell search. 
         [0204]    At step  1434 , the IEEE 802.16m-enabled MS decodes the primary broadcast channel and the secondary broadcast control channels on the IEEE 802.16m preamble mini-slot. The information in these channels includes system bandwidth, bandwidth segments, reserved tones, and guard tones. 
         [0205]    At step  1436 , an MS performs initial network entry on one of the segments based on the MS bandwidth capability as well as the recommended initial network entry segment(s) indicated by the BS in the primary/secondary broadcast channel. Note that BS can designate on or multiple segments as the initial network entry segments. Those segments designated for network entry can be the same or different than the segments containing the preamble mini-slot. 
         [0206]    At step  1438 , the process ends. 
         [0207]      FIG. 14A  is a block diagram showing a fourth example multi-band scenario (see Scenario 2 above) where the available IEEE 802.16m system bandwidth of 20 MHz  1500  is partitioned into multiple segments  1502 ,  1504  and  1506 . 
         [0208]    In  FIG. 14A , multiple segments  1502 ,  1504  and  1506  support an IEEE 802.16m-enabled MS having three different bandwidth capabilities (in this case, 5 MHz, 10 MHz and 20 MHz bandwidth respectively). An IEEE 802.16m-enabled MS 1  (a first type of IEEE 802.16m-enabled MS) operates with 512-FFT on 5 MHz segment  1502 . An IEEE 802.16m-enabled MS 2  (also a first type of IEEE 802.16m-enabled MS) operates with 512-FFT on 5 MHz segment  1504 . An IEEE 802.16m-enabled MS 3  (a second type of IEEE 802.16m-enabled MS) operates with 1k-FFT on 10 MHz segment  1506 . 
         [0209]    An IEEE 802.16m-enabled MS 4  (also a second type of IEEE 802.16m-enabled MS) operates with 1k-FFT on 5 MHz segments  1402  and  1404  or on 10 MHz segment  1506 . In other words, MS 4  can simultaneously decode two adjacent 5 MHz segments or one 10 MHz segment. 
         [0210]    An IEEE 802.16m-enabled MS 5  (a third type of IEEE 802.16m-enabled MS) operates with 2k-FFT on 5 MHz segments  1502  and  1504 , and 10 MHz segment  1506 . In other words MS 5  can simultaneously decode multiple segments each with a corresponding FFT size or can perform wideband decoding with a single 2k-FFT. 
         [0211]    Guard band  1508  separates 5 MHz segment  1502  and 5 MHz segment  1504 . Guard band  1510  separates 5 MHz segment  1504  and 10 MHz segment  1506 . To minimize the number of guard bands, the number of segments should be minimized. 
         [0212]    In this example, the IEEE 802.16m-enabled BS transmits/receives on multiple carriers each with the corresponding FFT size of each segment. 
         [0213]    An IEEE 802.16m sub-channel can be defined within each segment illustrated in  FIG. 14A . An MS can be assigned a sub-channel resource in segments that have bandwidths equal to or smaller than the MS bandwidth capability. 
         [0214]    For example, a 5 MHz MS can be assigned to either of the 5 MHz segments  1502 ,  1504  by the BS signaling the center frequency of the corresponding segment in a slower fashion (through unicast control signaling after network entry). A 10 MHz MS can be assigned to either the two 5 MHz segments  1502 ,  1504  or the 10 MHz segment  1506  by the BS signaling the center frequency of the two 5 MHz segments  1502 ,  1504  or the 10 MHz segment  1506  in a slower fashion (through unicast control signaling after network entry). A 20 MHz MS can be assigned to any of the 5 MHz segments  1502 ,  1504  and 10 MHz segment  1506  dynamically since the center frequency does not change. 
         [0215]      FIG. 14B  shows a representative frame structure of the multi-band scenario  1500  illustrated in  FIG. 14A  showing a first option of where the preamble mini-slot could be located. Multi-band scenario  1550  is comprised of DL mini-slots  1551  and UL mini-slots  1553 . 
         [0216]    Segments  1552  and  1554  comprise 5 MHz segments. Segment  1556  comprises a 10 MHz segment. Required guard bands  1559  separate the segments. 
         [0217]    In this first option, preamble mini-slot  1561  is located at the center of the RF frequency to minimize detection time. The bandwidth where the preamble mini-slot is transmitted should be the minimum of the bandwidth capacity of the IEEE 802.16m-enabled MSs. 
         [0218]      FIG. 14C  shows further details of the multi-band scenario  1500  illustrated in  FIG. 14A  showing a second option of where the preamble mini-slot could be located. Multi-band scenario  1580  is comprised of DL mini-slots  1591  and UL mini-slots  1593 . 
         [0219]    Segments  1582  and  1584  comprise 5 MHz segments. Segment  1586  comprises a 10 MHz segment. Required guard bands  1589  separate the segments. 
         [0220]    In this second option, preamble mini-slot  1581  is located at one or more segments (two segments are illustrated in  FIG. 14C ). In this case, the MS has to search the preamble over multiple possible choices of segments, which can be a preferred option to align with the legacy support mode where the preamble is located at one or more of the segments. 
         [0221]      FIG. 14D  is a flowchart showing the steps for initial access for an IEEE 802.16m-enabled MS using the multi-band scenario of  FIG. 14B . 
         [0222]    At step  1520 , the process begins. 
         [0223]    At step  1522 , an IEEE 802.16m-enabled MS detects the common-sync and cell-specific preamble on the IEEE 802.16m preamble mini-slot on one of the segments and performs synchronization and cell search. 
         [0224]    At step  1524 , the IEEE 802.16m-enabled MS decodes the primary broadcast channel and the secondary broadcast control channel on the IEEE 802.16m preamble mini-slot. The information in these channels includes system bandwidth, bandwidth segments, reserved tones, and guard tones. 
         [0225]    At step  1526 , an MS performs initial network entry on one of the segments based on the MS bandwidth capability as well as the recommended initial network entry segment(s) indicated by the BS in the primary/secondary broadcast channel. Note that the BS can designate one or more segments as the initial network entry segments. 
         [0226]    At step  1528 , the process ends. 
         [0227]      FIG. 14E  is a flowchart showing the steps for initial access for an IEEE 802.16m-enabled MS using the multi-band scenario of  FIG. 14C . 
         [0228]    At step  1530 , the process begins. 
         [0229]    At step  1532 , an IEEE 802.16m-enabled MS detects the common-sync and cell-specific preamble on the IEEE 802.16m preamble mini-slot on one of the segments and performs synchronization and cell search. 
         [0230]    At step  1534 , the IEEE 802.16m-enabled MS decodes the primary broadcast channel and the secondary broadcast control channel on the IEEE 802.16m preamble mini-slot. The information in these channels includes system bandwidth, bandwidth segments, reserved tones, and guard tones. 
         [0231]    At step  1536 , an MS performs initial network entry on one of the segments based on the MS bandwidth capability as well as the recommended initial network entry segment(s) indicated by the BS in the primary/secondary broadcast channel. Note that the BS can designate one or more segments as the initial network entry segments. Those segments designated for network entry can be the same or different than the segments containing the preamble mini-slot. 
         [0232]    At step  1538 , the process ends. 
         [0233]      FIGS. 11A to 14E  and corresponding description above may enable a person of ordinary skill in the art to realize the following advantageous functionality. 
         [0234]    A system bandwidth can be divided into multiple segments with each segment having the same or different bandwidths. Each segment can support one or multiple systems or OFDMA transmission formats. A system, transmission format or time-frequency resource definition can span one or more segments. 
         [0235]    A base station can simultaneously support different types of systems or OFDMA transmission formats on different segments. The base station can transmit/receive in single carrier fashion, that is one center frequency and one FFT across multiple segments or in multi-carrier fashion, that is multiple center frequencies and FFTs across multiple segments. 
         [0236]    A mobile station can transmit/receive in single carrier fashion, that is one center frequency and one FFT across multiple segments or in multi-carrier fashion, that is multiple center frequencies and FFTs across multiple segments. 
         [0237]    A mobile station can transmit/receive on one or multiple segments using different center frequencies and FFT sizes from the base station. 
         [0238]    A mobile station can be semi-statically or dynamically allocated to one or multiple segments after network entry. 
         [0239]    Guard bands or tones between segments can be semi-statically or dynamically included or excluded. 
         [0240]    One or more segments contain the universal synchronization channels and system parameter broadcast channels shared by multiple systems. Additional system-specific synchronization channels and system parameter broadcast channels can be located in the same or different sets of segments. 
         [0241]    The universal synchronization channels and system parameter broadcast channels can be located on the center frequency of the entire band, with a predefined bandwidth. 
         [0242]      FIG. 15  is a block diagram showing a first example of a frame structure to accomplish multi-hop relay, for TDD, provided in accordance with one embodiment. This first example illustrates separate DL and UL access zones  1602 ,  1604  and relay zones  1606 ,  1608 . An access zone is used to enable a BS/RS to communicate with an MS. A relay zone is used to enable a BS/RS to communicate with an RS. 
         [0243]    In the DL sub-frame  1600  at the BS, one or multiple DL mini-slots  1601 ,  1603 ,  1605  are used for the DL access zone, and one or multiple DL mini-slots  1607  are used for DL relay zone. In the DL sub-frame  1600  at the RS, one or multiple DL mini-slots  1609 ,  1611 ,  1613  are used for the DL access zone, and one or multiple DL mini-slots  1615  are used for the DL relay zone. 
         [0244]    In the UL sub-frame at the BS, one or multiple UL mini-slots  1617 ,  1619  are used for the UL access zone and one or multiple UL mini-slots  1621 ,  1623  are used for UL relay zone. In the UL sub-frame at the RS, one or multiple UL mini-slots  1625 ,  1627  are used for the UL access zone and one or multiple UL mini-slots  1629 ,  1631  are used for the UL relay zone. 
         [0245]      FIG. 16A  is a block diagram of a representative example of a wireless communication network illustrating a second embodiment in TDD supporting multi-hop relay. In  FIG. 16A , the concept of a global zone is introduced. 
         [0246]    Global transmission zones are defined for simultaneous transmission to parent node and child node. Global reception zones are defined for simultaneous reception from parent node and child node. MSs may use global zones for transmission/reception to an access node (e.g. an RS or BS). But a given global zone may be used either for reception or transmission by all the mobiles to avoid interference. Therefore, global zones may be defined within the DL sub-frame or the UL sub-frame so that the mobiles are allowed only to use them for UL or DL transmissions. These global zones may be configured to be used for MS communication in either odd-hop nodes or even-hop nodes. Two DL global zones can be configured, one for odd-hop RSs to MSs transmission and the other for even-hop RSs to MS communications. Similarly two global zones may be configured in the UL sub-frame. 
         [0247]    Within each global zone, the transmissions to/from the parent and child nodes use the same set of compatible channelization structures in order to overlay the resources allocated to the parent and child nodes. 
         [0248]    For the case of a dedicated pilot, one solution is to define the same tile structure for parent and child to transmit/receive. 
         [0249]    For the case of common pilot, one solution is to define an orthogonal common pilot structure for parent and child. 
         [0250]    Transmission on global zones can be scheduled by one or more nodes involved in the global zone transmission/reception, and/or a parent node of those nodes involved in transmission/reception, and/or by the base station under a centralized scheduler. 
         [0251]    In addition to global zones, separate non-global zones can be configured, such as an access zone that can be configured for parent RS/BS to MS communication, and relay zone that can be configured for parent RS/BS to child RS communication. 
         [0252]    In addition to data communication between BS, MS and RS, global zones can also be used for transmission/reception of signaling information among different nodes for network self-configuration and self-organization operation. 
         [0253]    In the example of  FIG. 16A , wireless communication network  1700  is comprised of MS 1    1702 , BS 1    1704 , RS 1    1706 , MS 3    1708 , RS 2    1710 , and MS 2    1712 . In  FIG. 16A , T 1 A refers to a DL access zone for transmission to an MS, T 1 R refers to a DL relay zone (for communications from parent to child), T 1 G refers to a DL global zone (where a first or odd-hop RS receives a communication from both child and parent; and a second or even-hop RS transmits to both child and parent, T 2 A refers to a UL access zone (for transmission from an MS), T 2 R refers to a UL relay zone (for communications from child to parent), and T 2 G refers to a UL global zone (where a first or odd-hop RS transmits to both child and parent; and a second or even-hop RS receives from both child and parent). The designation SC refers to a subchannel. 
         [0254]      FIG. 16B  is a block diagram illustrating DL and UL sub-frames  1750 ,  1760  for the second example shown in  FIG. 16A . DL sub-frame T 1   1750  is comprised of zone T 1 A  1752 , zone T 1 R  1754 , and zone T 1 G  1756 . UL sub-frame  1760  is comprised of zone T 2 A  1762 , zone T 2 R  1764 , and zone T 2 G  1766 . 
         [0255]    In this second example technique, a global zone is defined for a node (e.g., an RS) to simultaneously transmit to its parent node (e.g. a BS or a parent RS) and child node (e.g., a child RS or MS). Another global zone is defined for a node (e.g., an RS) to simultaneously receive from its parent node (e.g. a BS or a parent RS) and child node (e.g., a child RS or MS). 
         [0256]    The different zones shown in  FIGS. 16A and 16B  are: 
         [0257]    DL Access Zone (T 1 A): This is the BS/RS to MS DL transmission zone in the DL sub-frame at time slot T 1 . 
         [0258]    DL Relay Zone (T 1 R): This is the BS/RS to RS DL relay zone in the DL sub-frame at time slot T 1 , which can be used exclusively for transmission from a parent BS/RS to a child RS. 
         [0259]    Global Zone in DL sub-frame (T 1 G): This is a common zone within the DL sub-frame at time slot T 1 , in which an RS can transmit/receive data to both parent BS/RS and child RS. This zone also can be used by an access RS/BS to send data to an MS. 
         [0260]    UL Access Zone (T 2 A): This is the MS to BS/RS UL transmission zone in the UL sub-frame at time slot T 2 . 
         [0261]    UL Relay Zone (T 2 R): This is the RS to BS/RS UL relay zone in the UL sub-frame at time slot T 2 , which can be used exclusively for transmission from a child RS to a BS/RS. 
         [0262]    UL Global Zone in UL sub-frame (T 2 G): This is the common zone within the UL sub-frame at time slot T 2 , in which an RS can transmit/receive data to both parent RS/BS and child RS. This zone also can be used by an MS to transmit data to an access RS/BS. 
         [0263]    There are two options for resource multiplexing in the global zones: 
         [0264]    Option 1: Different OFDMA time/frequency (or subchannel) resource is assigned to different simultaneous transmissions to/from different nodes. This option does not improve resource multiplexing but will improve latency. In  FIG. 16A , T 1 G-SCx and T 1 G-SCy describes different subchannel resource X and Y in the global zone at time T 1 . 
         [0265]    Option 2: the same OFDMA time/frequency (or subchannel) resource is assigned to different simultaneous transmissions to/from multiple nodes. Interference avoidance or removal is used to separate the transmissions. This option provides resource multiplexing gain in addition to latency improvement. In this case, in  FIG. 16A , SCx and SCy have the same time/frequency resource, SCa and SCb have the same time/frequency resource, SCz and SCv have the same time/frequency resource, and SCw and SCu have the same time/frequency resource. In one embodiment, SCx, SCy, SCa and SCb all have the same time/frequency resource. SCz, SCv, SCw and SCu all have the same time/frequency resource. 
         [0266]    In this second example shown in  FIGS. 16A and 16B , the BS and the RS in the second hop can communicate with the MS in the global zones but the RS in the first hop can only use the access zones T 1 A and T 2 A to communicate with the MSs. Alternatively, a global zone can also be configured such that the first hop RS can use global zones to communicate with its MSs but the BS and the second hop RSs can only use access zones T 1 A and T 2 A to communicate with their MSs. Relay zones T 1 R and T 2 R are used for the BS to transmit to and receive from the RS respectively. Other relay zones may be defined for the first hop RS to transmit to and receive from the second hop RS. 
         [0267]      FIG. 17  is a block diagram showing further details of the second embodiment for multi-hop relay. As illustrated, multiple global zones can be defined where there are multiple RSs. In the example of  FIG. 17 , a global zone is defined for each RS (in this case two) for transmission and another global zone is defined for each RS (in this case two) for reception. Thus global transmit zones  1802 ,  1806  are defined at a BS  1801  (or parent RS), along with global receive zones  1806 ,  1808 . Similarly, global transmit zones  1812 ,  1816  are defined at an RS  1803 , along with global receive zones  1810 ,  1814 . Finally, at child RS  1805 , global transmit zones  1820 ,  1824  are defined, along with global receive zones  1822 ,  1826 . In all cases in this example, TTGs and RTGs are employed to prevent downlink and uplink collisions. 
         [0268]    Within each global zone, the transmissions to/from the parent and child nodes use the same set of compatible channelization structures in order to overlay the resource allocated to the parent and child nodes. 
         [0269]    MSs may receive or transmit in a global zone from their access nodes. However, in a given global zone, either all the MSs transmit or all the MSs receive. This may be achieved by assigning the global zones within the downlink sub-frame or uplink sub-frame. When the global zone is in the downlink sub-frame, MSs can only receive (from their access nodes) and when it is in the uplink sub-frame, MSs can only transmit. 
         [0270]    In addition to global zones, transmission to/from the child MS can be performed on separate non-global zones. 
         [0271]      FIG. 18  is a block diagram showing further details of a third embodiment for multi-hop relay, but this time for FDD. The technique illustrated includes a first Two Hops aspect. 
         [0272]    Communications between an RS  1902  with its parent node and with its child node occur at different time slots T 1  and T 2 . 
         [0273]    At time T 1 , RS  1902  communicates with its parent node BS  1904  (or parent RS) using frequency F 2  on DL and frequency F 1  on UL. 
         [0274]    At time T 2 , the RS communicates with its child node (e.g. MS or child RS) using frequency F 2  on DL and frequency F 1  on UL 
         [0275]    BS  1904  can communicate with MS  1906  on time T 1  or T 2 . T 2  is preferred for better reuse of OFDMA resources that are used by RS  1902  to communicate with MS  1906 . 
         [0276]      FIG. 19  is a block diagram showing further details of a fourth embodiment for multi-hop relay, also for FDD. The technique illustrated includes a second Two Hops aspect. 
         [0277]    At time T 1 , RS  2002  can simultaneously receive on the UL on F 1  from MS/child RS  2008  and receive on the DL on F 1  from BS/parent RS  2004  on the global zone. 
         [0278]    At time T 1 , RS  2002  can simultaneously transmit on the DL to MS  2008  on F 2  and transmit on the UL to BS/parent RS  2004  on F 2  on the global zone. 
         [0279]    At time T 2 , BS/parent RS  2004  transmits/receives to/from MS  2006  on F 2  for DL and F 1  for UL. 
         [0280]    At time T 1 , there are two options for resource multiplexing in the global zones: 
         [0281]    Option 1: different OFDMA time/frequency resources are assigned to different transmissions to/from different nodes. This option does not improve resource multiplexing but will improve latency. 
         [0282]    Option 2: the same OFDMA time/frequency resource is assigned to multiple transmissions to/from multiple nodes. Interference cancellation with or without a directional antenna can be used to separate the transmissions. This option provides resource multiplexing gain in addition to latency improvement. 
         [0283]      FIG. 20  is a block diagram showing further details of a fifth embodiment for multi-hop relay, also for FDD. The technique illustrated includes a more than Two Hops aspect. 
         [0284]    At a particular time slot, an RS transmits simultaneously to its parent node and child node on the same carrier frequency. An RS receives simultaneously from its parent node and child node on another carrier frequency. An RS and its next hop RS (parent or child) use alternate carrier frequency for transmission and reception. This is explained in the example below. 
         [0285]    At time T 1 , intermediate RS  2106  uses F 1  for transmission to its child and parent nodes (i.e. BS  2110  and access RS  2102 ) on a global zone and uses F 2  for reception from its child and parent nodes on a global zone. Its next hop RS, i.e. access RS  2102 , uses F 2  for transmission to its child and parent nodes (i.e. intermediate RS  2106  and MS  2104 ) on a global zone and uses F 1  for reception from its child and parent nodes on a global zone. 
         [0286]    BS  2110  can transmit/receive to/from MS  2112  on T 1  or T 2 . F 2  is for DL and F 1  is for UL. T 2  is preferred for better reuse at the OFDMA resource. 
         [0287]    At time T 2 , intermediate RS  2106  transmits/receives to/from MS  2108  on F 2  for DL and F 1  for UL. 
         [0288]    At time T 1 , there are two options for resource multiplexing in the global zones: 
         [0289]    Option 1: a different OFDMA time/frequency resource is assigned to different transmissions to/from different nodes. This option does not improve resource multiplexing but will improve latency. 
         [0290]    Option 2: the same OFDMA time/frequency resource is assigned to multiple transmissions to/from multiple nodes. Interference cancellation with or without a directional antenna can be used to separate the transmissions. This option provides resource multiplexing gain in addition to latency improvement. 
         [0291]    The same frame structure same as that defined for multi-hop relay can be used to support network coding. Global zones as described above can be defined for a network node to simultaneously multicast the transmission to both parent node(s) and child node(s), as well as receive simultaneous transmissions from parent node(s) and child node(s). 
         [0292]      FIGS. 15 to 20  and the corresponding descriptions above may enable a person of ordinary skill in the art to realize the following advantageous functionality. 
         [0293]    A node can transmit signals to its parent node and child node at the same time on the same RF carrier. A node can receive signals from its parent node and child node at the same time on the same RF carrier. 
         [0294]    A node can transmit signals to its parent node and child node at the same time on the same RF carrier on global time-frequency resource zones. A node can receive signals to its parent node and child node at the same time on the same RF carrier on global time-frequency resource zones. 
         [0295]    A set of orthogonal time-frequency sub-channels can be defined in a global time-frequency resource zone. The set of sub-channels is shared by the transmission to parent node and child node or reception from parent node and child node. 
         [0296]    Global time-frequency resource zones may be configured within the DL sub-frame and/or UL sub-frame so that different MSs may not use the same global zone for DL and UL transmissions that can lead to interference issues. On a global time-frequency zone, either odd-hop or even-hop access nodes may use the zone for transmission to (or reception from) an MS. Two global time/frequency resource zones, one configured for odd-hop RS to MS communication and one configured for even-hop RS to MS communications may be configured for the DL sub-frame. Similarly two global zones may be configured for the uplink. 
         [0297]    A node receives from (or transmits to) its parent node and child node using the same time-frequency resource. Data can be recovered using interference avoidance or interference removal. 
         [0298]    Global time-frequency resource zones are defined for signaling exchanges between multiple nodes (BS, and/or RS, and/or MS) for self-configuration and self-organization operation. 
         [0299]    What has been described is merely illustrative of the application of the principles of the invention. Other arrangements and methods can be implemented by those skilled in the art without departing from the spirit and scope of the present invention.