Patent Description:
In communication transmission interfaces using dynamic resource sharing, it is common for a resource management entity to schedule resource usage among one or more end-users at each of a sequence of scheduling intervals. The resource being shared may be, for example, time, codes, frequency, antennae to name a few, or combinations thereof (multiple dimensional resource). To allocate a multiple dimensional resource, the allocation of resources for each dimension is indicated.

In situations where the resource space is large, for example, broadband systems including multiple antennas wherein a relatively small resource granularity is to be accommodated, the assignment of resources is known to incur significant overhead. Exemplary such multiple-antenna systems are known as Multiple-input Multiple-Output (MIMO) Orthogonal Frequency-Division Multiplexing (OFDM) systems.

In addition to dividing data to be transmitted among frequencies, data may also be divided in time in a scheme called Time Division Multiplexing. Organizing data in frequency and time can be facilitated through the definition of a transmission unit, i.e., a frame.

As will be apparent to one of ordinary skill in the art, wireless broadband access systems using OFDM may be used to enable high speed data services. In particular, Orthogonal Frequency-Division Multiple Access (OFDMA) based broadband access air interfaces are known to allocate a two-dimensional resource (subchannel and OFDM symbol) in each frame in order to optimize frequency-time domain diversity. In addition, a sufficiently small resource granularity for accommodating small amounts of traffic per frame is employed, to support voice over Internet Protocol (VoIP) data, for example. Unfortunately, such OFDMA-based systems are known to incur significant resource allocation signaling overhead. That is, often a significant amount of resource allocation signaling bits are required to indicate, to the receiver of a frame, the location in the frame at which data relevant to the receiver may be found.

Document "<NPL>, discloses an air interface of fixed broadband wireless access systems supporting multimedia services. The medium access control layer supports a primarily point-to-multipoint architecture, with an optional mesh topology. The MAC is structured to support multiple physical layer specifications, each suited to a particular operational environment. For operational frequencies from <NUM>-<NUM>, the PHY is based on single-carrier modulation. For frequencies below <NUM>, where propagation without a direct line of sight must be accommodated, three alternatives are provided, using OFDM, OFDMA, and single-carrier modulation.

A need exists, therefore, for an improved method for allocating communication resources.

Since significant resources are required to indicate the location of relevant data in a vast resource space, the resource space may be logically divided into sub-resource spaces, or "channels". When allocating downlink or uplink resources to a terminal, a location for the resource may be identified first by the channel and then by a location within the channel, thereby saving allocation resources. A channel descriptor management message may be transmitted to define a plurality of channels within a given resource space. A subsequent resource allocation message may then allocate resources within at least one of the channels to a plurality of users.

In the figures which illustrate example embodiments of this invention:.

For the purposes of providing context for embodiments of the invention for use in a communication system, <FIG> shows a base station controller (BSC) <NUM> which controls wireless communications within multiple cells <NUM>, which cells <NUM> are served by corresponding base stations (BS) <NUM>. In general, each base station <NUM> facilitates communications using OFDM with Mobile Subscriber Stations (MSS), also called mobile and/or wireless terminals <NUM>, which are within the cell <NUM> associated with the corresponding base station <NUM>. The movement of the mobile terminals <NUM> in relation to the base stations <NUM> is known to result in significant fluctuation in channel conditions. As illustrated, the base stations <NUM> and mobile terminals <NUM> may include multiple antennas to provide spatial diversity for communications.

A high level overview of the mobile terminals <NUM> and base stations <NUM> upon which aspects of the present invention are implemented is provided prior to delving into the structural and functional details of the preferred embodiments.

With reference to <FIG>, a base station <NUM> is illustrated. The base station <NUM> generally includes a control system <NUM>, a baseband processor <NUM>, transmit circuitry <NUM>, receive circuitry <NUM>, multiple antennas <NUM> and a network interface <NUM>. The receive circuitry <NUM> receives radio frequency signals bearing information from one or more remote transmitters provided by the mobile terminals <NUM> (illustrated in <FIG>). Preferably, a low noise amplifier and a filter (not shown) cooperate to amplify and remove broadband interference from the signal for processing. Downconversion and digitization circuitry (not shown) then downconvert the filtered, received signal to an intermediate or baseband frequency signal, which is then digitized into one or more digital streams.

The baseband processor <NUM> processes the digitized received signal to extract the information or data bits conveyed in the received signal. This processing typically comprises demodulation, decoding and error correction operations. As such, the baseband processor <NUM> is generally implemented in one or more digital signal processors (DSPs) or application-specific integrated circuits (ASICs). The received information is then sent across a wireless network via the network interface <NUM> or transmitted to another mobile terminal <NUM> serviced by the base station <NUM>.

On the transmit side, the baseband processor <NUM> receives digitized data, which may represent voice, data or control information, from the network interface <NUM> under the control of control system <NUM> and encodes the data for transmission. The encoded data is output to the transmit circuitry <NUM>, where the encoded data is modulated by a carrier signal having a desired transmit frequency or frequencies. A power amplifier (not shown) amplifies the modulated carrier signal to a level appropriate for transmission and delivers the modulated carrier signal to the antennas <NUM> through a matching network (not shown). Modulation and processing details are described in greater detail below.

With reference to <FIG>, a mobile terminal <NUM>, is illustrated. The mobile terminal <NUM> may be configured, in a manner similar to base station <NUM>, to include a control system <NUM>, a baseband processor <NUM>, transmit circuitry <NUM>, receive circuitry <NUM>, multiple antennas <NUM> and user interface circuitry <NUM>. The receive circuitry <NUM> receives radio frequency signals bearing information from one or more base stations <NUM>. Preferably, a low noise amplifier and a filter (not shown) cooperate to amplify and remove broadband interference from the signal for processing. Downconversion and digitization circuitry (not shown) will then downconvert the filtered, received signal to an intermediate or baseband frequency signal, which is then digitized into one or more digital streams.

The baseband processor <NUM> processes the digitized received signal to extract the information or data bits conveyed in the received signal. This processing typically comprises demodulation, decoding and error correction operations. The baseband processor <NUM> is generally implemented in one or more DSPs and ASICs.

For transmission, the baseband processor <NUM> receives digitized data, which may represent voice, data or control information, from the control system <NUM>. The baseband processor <NUM> may then encode the digitized data for transmission. The encoded data is output to the transmit circuitry <NUM>, where the encoded data is used by a modulator to modulate a carrier signal that is at a desired transmit frequency or frequencies. A power amplifier (not shown) amplifies the modulated carrier signal to a level appropriate for transmission and delivers the modulated carrier signal to the antennas <NUM> through a matching network (not shown). Various modulation and processing techniques available to those skilled in the art are used for signal transmission between the mobile terminal <NUM> and the base station <NUM>.

In OFDM modulation, the transmission band is divided into multiple, orthogonal carrier waves. Each carrier wave is modulated according to the digital data to be transmitted. Because OFDM divides the transmission band into multiple carriers, the bandwidth per carrier decreases and the modulation time per carrier increases. Since the multiple carriers are transmitted in parallel, the transmission rate for the digital data, or symbols, on any given carrier is lower than when a single carrier is used.

OFDM modulation utilizes the performance of an Inverse Fast Fourier Transform (IFFT) on the information to be transmitted. For demodulation, the performance of a Fast Fourier Transform (FFT) on the received signal recovers the transmitted information. In practice, the IFFT and FFT are provided by digital signal processing carrying out an Inverse Discrete Fourier Transform (IDFT) and Discrete Fourier Transform (DFT), respectively. Accordingly, the characterizing feature of OFDM modulation is that orthogonal carrier waves are generated for multiple bands within a transmission channel. The modulated signals are digital signals that have a relatively low transmission rate and are capable of staying within their respective bands. The individual carrier waves are not modulated directly by the digital signals. Instead, all carrier waves are modulated at once by IFFT processing.

In operation, OFDM is preferably used for at least downlink transmission from the base stations <NUM> to the mobile terminals <NUM>. Each base station <NUM> is equipped with "n" transmit antennas <NUM> and each mobile terminal <NUM> is equipped with "m" receive antennas <NUM>. Notably, the respective antennas can be used for reception and transmission using appropriate duplexers or switches and are so labeled only for clarity.

With reference to <FIG>, a logical OFDM transmission architecture will be described. Initially, the base station controller <NUM> (see <FIG>) will send data, which is to be transmitted to various mobile terminals <NUM>, to the base station <NUM>. The base station <NUM> may use channel quality indicators (CQIs) associated with the mobile terminals <NUM> to schedule the data for transmission as well as to select appropriate coding and modulation for transmitting the scheduled data. The CQls may be received directly from the mobile terminals <NUM> or determined at the base station <NUM> based on information provided by the mobile terminals <NUM>. In either case, the CQI for each mobile terminal <NUM> is a function of the degree to which the channel amplitude (or response) varies across the OFDM frequency band.

Scheduled data <NUM>, which is a stream of bits, is scrambled in a manner reducing the peak-to-average power ratio associated with the data using data scrambling logic <NUM>. A cyclic redundancy check (CRC) for the scrambled data is determined and appended to the scrambled data using CRC adding logic <NUM>. Next, channel coding is performed using channel encoder logic <NUM> to effectively add redundancy to the data to facilitate recovery and error correction at the mobile terminal <NUM>. Again, the channel coding for a particular mobile terminal <NUM> is based on the CQi associated with the particular mobile terminal <NUM>. In some implementations, the channel encoder logic <NUM> uses known Turbo encoding techniques. The encoded data is then processed by rate matching logic <NUM> to compensate for the data expansion associated with encoding.

Bit interleaver logic <NUM> systematically reorders the bits in the encoded data to minimize the loss of consecutive data bits. The resultant data bits are systematically mapped into corresponding symbols depending on the chosen baseband modulation by mapping logic <NUM>. Preferably, Quadrature Amplitude Modulation (QAM) or Quadrature Phase Shift Key (QPSK) modulation is used. The degree of modulation is preferably chosen based on the CQI for the particular mobile terminal <NUM>. The symbols may be systematically reordered, to further bolster the immunity of the transmitted signal to periodic data loss caused by frequency selective fading, using symbol interleaver logic <NUM>.

At this point, groups of bits have been mapped into symbols representing locations in an amplitude and phase constellation. When spatial diversity is desired, blocks of symbols are then processed by space-time block code (STC) encoder logic <NUM>, which modifies the symbols in a fashion making the transmitted signals more resistant to interference and more readily decoded at a mobile terminal <NUM>. The STC encoder logic <NUM> will process the incoming symbols and provide "n" outputs corresponding to the number of transmit antennas <NUM> for the base station <NUM>. The control system <NUM> and/or baseband processor <NUM>, as described above with respect to <FIG>, will provide a mapping control signal to control STC encoding. At this point, it may be assumed that the symbols for the "n" outputs are representative of the data to be transmitted and capable of being recovered by the mobile terminal <NUM>.

For the present example, assume the base station <NUM> has two antennas <NUM> (n = <NUM>) and the STC encoder logic <NUM> provides two output streams of symbols. Accordingly, each of the symbol streams output by the STC encoder logic <NUM> is sent to a corresponding IFFT processor <NUM>, illustrated separately for ease of understanding. Those skilled in the art will recognize that one or more processors may be used to provide such digital signal processing, alone or in combination with other processing described herein. The IFFT processors <NUM> will preferably operate on the respective symbols to provide an inverse Fourier Transform. The output of the IFFT processors <NUM> provides symbols in the time domain. The time domain symbols are grouped into frames, which are associated with a prefix by prefix insertion logic <NUM>. Each of the resultant signals is up-converted in the digital domain to an intermediate frequency and converted to an analog signal via the corresponding digital up-conversion (DUC) and digital-to-analog (D/A) conversion circuitry <NUM>. The resultant (analog) signals are then simultaneously modulated at the desired RF frequency, amplified and transmitted via the RF circuitry <NUM> and antennas <NUM>. Notably, pilot signals known by the intended mobile terminal <NUM> to be scattered among a plurality of sub-carriers. The mobile terminal <NUM>, whose operation is discussed in detail below, may measure the pilot signals for channel estimation.

Reference is now made to <FIG> to illustrate reception of the transmitted signals by a mobile terminal <NUM>. Upon arrival of the transmitted signals at each of the antennas <NUM> of the mobile terminal <NUM>, the respective signals are demodulated and amplified by corresponding RF circuitry <NUM>. For the sake of conciseness and clarity, only one of the two receive paths are described and illustrated in detail. Analog-to-digital (A/D) converter and down-conversion circuitry <NUM> digitizes and downconverts the analog signal for digital processing. The resultant digitized signal may be used by automatic gain control circuitry (AGC) <NUM> to control the gain of the amplifiers in the RF circuitry <NUM> based on the received signal level.

Initially, the digitized signal is provided to synchronization logic <NUM>, which includes coarse synchronization logic <NUM>, which buffers several OFDM symbols and calculates an auto-correlation between the two successive OFDM symbols. A resultant time index corresponding to the maximum of the correlation result determines a fine synchronization search window, which is used by fine synchronization logic <NUM> to determine a precise framing starting position based on the headers. The output of the fine synchronization logic <NUM> facilitates frame acquisition by frame alignment logic <NUM>. Proper framing alignment is important so that subsequent FFT processing provides an accurate conversion from the time domain to the frequency domain. The fine synchronization algorithm is based on the correlation between the received pilot signals carried by the headers and a local copy of the known pilot data. Once frame alignment acquisition occurs, the prefix of the OFDM symbol is removed with prefix removal logic <NUM> and resultant samples are sent to frequency offset correction logic <NUM>, which compensates for the system frequency offset caused by the unmatched local oscillators in the transmitter and the receiver. Preferably, the synchronization logic <NUM> includes frequency offset and clock estimation logic <NUM>, which is based on the headers to help estimate such effects on the transmitted signal and provide those estimations to the correction logic <NUM> to properly process OFDM symbols.

At this point, the OFDM symbols in the time domain are ready for conversion to the frequency domain using FFT processing logic <NUM>. The results are frequency domain symbols, which are sent to processing logic <NUM>. The processing logic <NUM> extracts the scattered pilot signal using scattered pilot extraction logic <NUM>, determines a channel estimate based on the extracted pilot signal using channel estimation logic <NUM> and provides channel responses for all sub-carriers using channel reconstruction logic <NUM>. In order to determine a channel response for each of the sub-carriers, the pilot signal is essentially multiple pilot symbols that are scattered among the data symbols throughout the OFDM sub-carriers in a known pattern in both time and frequency. <FIG> illustrates an exemplary scattering of pilot symbols among available sub-carriers over a given time and frequency plot in an OFDM environment.

Continuing with <FIG>, the processing logic <NUM> compares the received pilot symbols with the pilot symbols that are expected in certain sub-carriers at certain times to determine a channel response for the sub-carriers in which the pilot symbols were transmitted. The results are interpolated to estimate a channel response for most, if not all, of the remaining sub-carriers for which pilot symbols were not provided. The actual and interpolated channel responses are used to estimate an overall channel response, which includes the channel responses for most, if not all, of the sub-carriers in the OFDM channel.

The frequency domain symbols and channel reconstruction information, which are derived from the channel responses for each receive path are provided to an STC decoder <NUM>, which provides STC decoding on both received paths to recover the transmitted symbols. The channel reconstruction information provides equalization information to the STC decoder <NUM> sufficient to remove the effects of the transmission channel when processing the respective frequency domain symbols.

The recovered symbols are placed back in order using symbol de-interleaver logic <NUM>, which corresponds to the symbol interleaver logic <NUM> of the transmitter. The de-interleaved symbols are then demodulated or de-mapped to a corresponding bitstream using de-mapping logic <NUM>. The bits are then de-interleaved using bit de-interleaver logic <NUM>, which corresponds to the bit interleaver logic <NUM> of the transmitter architecture. The de-interleaved bits are then processed by rate de-matching logic <NUM> and presented to channel decoder logic <NUM> to recover the initially scrambled data and the CRC checksum. Accordingly, CRC logic <NUM> removes the CRC checksum, checks the scrambled data in traditional fashion and provides it to the de-scrambling logic <NUM> for de-scrambling using the known base station de-scrambling code to recover the originally transmitted data <NUM>.

in parallel to recovering the data <NUM>, a CQI, or at least information sufficient to create a CQI at the base station <NUM>, is determined and transmitted to the base station <NUM>. As noted above, the COI may be a function of the carrier-to-interference ratio (C/I), as well as the degree to which the channel response varies across the various sub-carriers in the OFDM frequency band. The channel gain for each sub-carrier in the OFDM frequency band being used to transmit information may be compared relative to one another to determine the degree to which the channel gain varies across the OFDM frequency band. Although numerous techniques are available to measure the degree of variation, one technique is to calculate the standard deviation of the channel gain for each sub-carrier throughout the OFDM frequency band being used to transmit data.

<FIG> provide one specific example of a communication system that could be used to implement embodiments of the invention. It is to be understood that embodiments of the invention can be implemented with communications systems having architectures that are different than the specific example, but that operate in a manner consistent with the implementation of the embodiments as described herein.

The known Media Access Control (MAC) layer is used to enable features in the physical (PHY) layer in an OFDMA air interface framework. Frames are a format used to transmit "bursts" of data over the air interface between the base station <NUM> and the mobile terminal <NUM>. The mobile terminal <NUM> is, for example, any known wireless device such as a cellular telephone, a computer with a wireless modern or a Personal Digital Assistant (PDA). Various types of information elements (IE) are included in the frame to provide a structure within the frame for defining where downlink information and uplink information are located within the frame. Each IE defines a rectangle in the (time, sub-channels) grid used to carry a specific sub-burst.

In overview, in accordance with embodiments of the invention, schemes for allocating resources in an OFDMA-based wireless network are provided, which OFDMA-based wireless network operates in accordance with the IEEE Broadband Metropolitan Area Networks Standard (IEEE P802.16e/D5a-<NUM>). One of skill in the art will appreciate, however, that the broader embodiments of the invention are not limited in this regard but are equally applicable to other wireless technologies, including Multi-carrier CDMA (C-CDMA) and, even, to Wireline technology. It should further be appreciated that embodiments of the invention are as applicable to uplink communications as they are to downlink communications.

<FIG> shows a schematic diagram of an example frame used in conjunction with embodiments of the invention. Details are shown for a frame labeled "Frame N" <NUM> which is preceded by Frame "N-<NUM>" and followed by "Frame N+<NUM>", all of which form part of an ongoing sequence of frames. The Frame N <NUM> has a two dimensional appearance which is represented in terms of a rows and columns. The rows are designated by logical subchannel numbers L, L+<NUM>,. , L+<NUM> and the columns are designated by OFDM symbol numbers M, M+<NUM>,. Logical subchannels are designated groupings of active sub-carriers. Active sub-carriers are any one of data sub-carriers for data transmission, pilot sub-carriers for synchronization or sub-carriers that do not involve direct transmission, but are used as transition guards between parts of the frame.

A base station <NUM> provides a structure for frames, such as the Frame N <NUM> of <FIG>, by transmitting messages on a broadcast connection to the mobile terminals <NUM> that are within range. The messages are known as Downlink Channel Descriptor (DCD) MAC management messages and Uplink Channel Descriptor (UCD) MAC management messages. UCD and DCD MAC management messages contain Type/Length/Value (TLV) encoded elements. Notably, UCD MAC management messages and DCD MAC management messages may be considered to be relatively long; UCD MAC management message length may be over <NUM> bytes and DCD MAC management message length may be over <NUM> bytes. MAC management messages on broadcast, basic or initial ranging connections are known to be neither fragmented nor packed. Therefore, it is necessary to transmit a long MAC management message all at once, that is, without fragmentation. The resource allocation for a long DCD/UCD message may be considered to be a burden for a base station <NUM>, and the transmission of a long DCD/UCD message may be necessarily delayed if sufficient bandwidth is unavailable. Moreover, available resource in a frame may be less than that required to transmit a DCDIUCD MAC management message. As such, DCD/UCD messages are typically transmitted relatively infrequently.

The Frame N <NUM> of <FIG> includes a DL subframe <NUM>, a transmit-receive transition guard (TTG) <NUM> and a UL subframe <NUM>.

The DL subframe <NUM>, as is typical, includes a preamble <NUM>, a Frame Control Header (FCH) <NUM>, a downlink (DL) mapping component (i.e., a DL-MAP <NUM>) and an uplink (UL) mapping component (i.e., an UL-MAP <NUM>). Furthermore, the DL subframe <NUM> includes two subsidiary DL mapping components (sub-DL-MAP1 <NUM> and sub-DL-MAP2 <NUM>) and a subsidiary UL mapping component (sub-UL-MAP1 <NUM>). As is known, information elements in the DL-MAP <NUM> may reference information elements in the sub DL-MAPs <NUM>, <NUM> and information elements in the sub DL-MAPs <NUM>, <NUM> may reference locations in the resource space of the DL subframe <NUM>. Similarly, information elements in the UL-MAP <NUM> may reference information elements in the sub-UL-MAP <NUM> and information elements in the sub-UL-MAP <NUM> may reference locations in the UL subframe <NUM>.

The UL subframe <NUM> contains UL information allocated to designated regions <NUM> of the UL subframe in which specific mobile terminals <NUM> may transmit data back to the base station <NUM>. The UL subframe <NUM> also includes fast feedback channels <NUM> that are used to allow the mobile terminals <NUM> to report information to the base station <NUM>. For example, a fast feedback channel <NUM> can be designated as a channel to be used to indicate the air Interface channel quality between the base station <NUM> and the mobile terminal <NUM>.

Following the UL subframe <NUM> is a receive/transmit transition guard (RTG) <NUM>. Frames N-<NUM> and N+<NUM> have a similar composition.

The data frame of <FIG> is an example of a time division duplex (TDD) data frame. It is to be understood that embodiments of the Invention are also applicable to frequency division duplex (FDD) operation and OFDMA operation.

It is typical that much of the DL subframe <NUM> is a continuous resource space addressed by the DL-MAP <NUM>, which includes information elements that refer to locations of resource units within the resource space. However, according to an embodiment of the Invention, a structure for the resource space may be determined that involves dividing the resource space into a plurality of sub-resource spaces. Determining the structure for the resource space may involve defining the sub-resource spaces, called channels herein. The division of the resource space may, for instance, be based on measured traffic statistics.

Conventionally, when referencing resource units in the DL-MAP, each resource units is described by a DL-MAP Information Element which includes OFDMA symbol offset (<NUM> bits), sub-channel offset (<NUM> bits), number of OFDMA symbols (<NUM> bits) and number of sub-channels (<NUM> bits). By using such a mechanism, the minimum, or basic, DL resource unit is one sub-channel (or mini-sub-channel) x one OFMDA symbol. Assuming <NUM> mobile terminals are assigned DL resources in each frame, <NUM> bits in the DL-MAP will be used for region assignments. This results in large overhead.

Determining a definition for a given sub-resource space, or channel, may involve, in part, assigning a Channel InDex (CHID) to a region of the resource space of the DL subframe <NUM>. Determining a given channel definition may also involve determining the geometry of the region of the DL subframe to be occupied by the given channel. Channel definitions, once determined, may then be broadcast in a DCD MAC management message.

Notably, while channel definitions can be updated and declared slowly through infrequent system configuration broadcast messages (e.g., DCD MAC management messages) channel definitions may also be updated and declared dynamically through resource allocation signaling (e.g., DL-MAP) on a per-frame basis or a few frame basis.

The DL subframe <NUM>, as illustrated in <FIG>, contains DL data in channels <NUM> of the DL subframe <NUM> to be transmitted to one or more mobile terminals <NUM>. The channels <NUM> of the DL subframe <NUM> are identified as channel <NUM><NUM>-<NUM>, channel <NUM><NUM>-<NUM>, channel <NUM><NUM>-<NUM>, channel <NUM><NUM>-<NUM>, channel <NUM><NUM>-<NUM>, channel <NUM><NUM>-<NUM>, channel <NUM><NUM>-<NUM> and channel <NUM><NUM>-<NUM>.

The resource space, and, consequently, the channels <NUM> of the DL subframe <NUM>, is known to contain protocol data units (PDU). PDUs are known to include some or all of the following: a MAC header, MAC sub-headers and a MAC payload.

Information elements included in the DL-MAP <NUM> or SUB-DL-MAP <NUM>, <NUM> may be employed to indicate an allocation of a set of sub-channels and OFDM symbols, within a channel, for a particular sub-burst destined for a particular mobile terminal <NUM>. Exemplary such allocations are illustrated in <FIG> for channel <NUM><NUM>-<NUM> and channel <NUM><NUM>-<NUM>. Channel <NUM><NUM>-<NUM> includes sub-bursts <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM>. Channel <NUM><NUM>-<NUM> includes sub-bursts <NUM>, <NUM> and <NUM>. Both channel <NUM><NUM>-<NUM> and channel <NUM><NUM>-<NUM> include some <NUM>. 16D DL traffic <NUM>.

As shown in <FIG>, each channel may include multiple sub-bursts and each sub-burst may be mapped into to the channel following the known frequency-first-one-dimension mapping rule. If some part of a channel is partially occupied (for example by MAPs and <NUM>. 16D DL traffic or any other assignment using a regular IE), the frequency-first-one-dimension mapping rule is still valid.

It is proposed herein that a PHY PDU associated with a mobile terminal <NUM> may be mapped to more than one channel. An example is illustrated in <FIG> wherein insufficient room is left in channel <NUM><NUM>-<NUM> to schedule an entire PDU. The final sub-burst <NUM> of channel <NUM><NUM>-<NUM> may be mapped to channel <NUM><NUM>-<NUM>.

It is also proposed herein to allow a PHY PDU associated with a mobile terminal <NUM> to be non-consecutively mapped. For example, some slots may be reserved for certain transmissions, including retransmissions. An example is illustrated in <FIG> wherein an intervening sub-burst <NUM> is allocated to slots among slots that are allocated to a long sub-burst <NUM>.

It is further proposed that a mobile terminal <NUM> may prevent unnecessary MAP processing by introducing a "done" bit.

It is proposed herein to allow each sub-burst (or layer in MIMO) to use distinct Downlink interval Usage Code (DIUC), repetition and boosting. The related overhead can be reduced by introducing a transmission control group. A transmission control group may, for example, include all sub-bursts that use the same DIUC, boosting and repetition to use one DiUC/boosting/repetition transmission code for the entire transmission control group of sub-bursts.

<FIG> illustrates an exemplary grouping. A first group <NUM> includes Normal mode sub-bursts, a second group <NUM> includes Chase sub-bursts and a third group <NUM> includes Chase Combining-Incremental Redundancy (CC-IR) sub-bursts.

Advantages of the above embodiments of the invention include a reduction of overhead. As discussed above, each region assignment, that is, assignment of a location for a sub-burst in the DL subframe <NUM>, in a resource space that has not been divided into channels, may require <NUM> bits. In contrast, region assignment for the DL subframe <NUM> in a resource space that has been divided into channels may be shown to require fewer than <NUM> bits. Furthermore, the possibility of un-utilized resource at the end of a channel is minimized through the allowance of mapping a PDU across a channel boundary.

The above embodiments may be implemented through the use of the following exemplary enhanced format for a DL assignment DL MAP information element.

The enhanced information element format for DL assignment DL MAP references a normal sub-burst IE format (mode = <NUM>). An exemplary normal sub-burst IE format follows.

The enhanced information element format for DL assignment DL MAP references a Chase Hybrid Automatic Request (H-ARQ) sub-burst IE format (mode = <NUM>). An exemplary Chase H-ARQ sub-burst IE format follows.

The enhanced information element format for DL assignment DL MAP references a Incremental Redundancy (IR) Chase Combining (CC) H-ARQ sub-burst IE format (mode = <NUM>). An exemplary IR CC H-ARQ sub-burst IE format follows.

The enhanced information element format for DL assignment DL MAP references a MIMO sub-burst IE format (mode = <NUM>). An exemplary MIMO sub-burst IE format follows.

The enhanced information element format for DL assignment DL MAP references a MIMO Chase H-ARQ sub-burst IE format (mode = <NUM>). An exemplary MIMO Chase H-ARQ sub-burst IE format follows.

The enhanced information element format for DL assignment DL MAP references a MIMO IR CC H-ARQ sub-burst IE format (mode = <NUM>). An exemplary MIMO IR CC H-ARQ sub-burst IE format follows.

The enhanced information element format for DL assignment DL MAP references a STC H-ARQ sub-burst IE format (mode = <NUM>). An exemplary STC H-ARQ sub-burst IE format follows.

The enhanced information element format for DL assignment DL MAP references a Normal Convolution Turbo Code (CTC) sub-burst IE format (mode = <NUM>). An exemplary Normal CTC sub-burst IE format follows.

The enhanced information element format for DL assignment DL MAP references a MIMO CTC sub-burst IE format (mode = <NUM>). An exemplary MIMO CTC sub-burst IE format follows.

The enhanced information element format for DL assignment DL MAP references a MIMO IR CTC H-ARQ sub-burst IE format (mode = <NUM>). An exemplary MIMO IR CTC H-ARQ sub-burst IE format follows.

The enhanced information element format for DL assignment DL MAP references a Closed Loop (CL) MIMO sub-burst IE format (mode = <NUM>). An exemplary CL MIMO sub-burst IE format follows.

The enhanced information element format for DL assignment DL MAP references a CL MIMO (CTC) sub-burst IE format (mode = <NUM>). An exemplary CL MIMO (CTC) sub-burst IE format follows.

The enhanced information element format for DL assignment DL MAP references a CL MIMO Chase H-ARQ sub-burst IE format (mode = <NUM>). An exemplary CL MIMO Chase H-ARQ sub-burst IE format follows.

The enhanced information element format for DL assignment DL MAP references a CL MIMO CC H-ARQ sub-burst IE format (mode = <NUM>). An exemplary CL MIMO CC H-ARQ sub-burst IE format follows.

The enhanced information element format for DL assignment DL MAP references a CL MIMO IR CTC H-ARQ sub-burst IE format (mode = <NUM>). An exemplary CL MIMO IR CTC H-ARQ sub-burst IE format follows.

In overview, using a two-step process, it may be shown that the total overhead involved in resource allocation may be reduced as compared to known resource allocation methods. In the first step, the base station <NUM> defines a plurality of sub-resource spaces within a communication resource space. When performing subsequent resource allocation, the base station may refer to the sub-resource space for the allocation rather than describing in full the location within the resource. In particular, while the sub-resource spaces may be defined relatively infrequently in DCD messages, the allocation of the sub-resources spaces may be updated relatively frequently in scheduling messages.

As discussed above, a frame may be considered to have a resource. According to the present invention, a mapping component of the frame (e.g., a DL-MAP) includes information elements that define a plurality of channels. It has been proposed above to define the plurality of channels as occupying the resource in a contiguous manner. It is proposed in the following to define the channels as occupying the resource in an overlapping manner. To this end, the channels are defined to be in a hierarchy of layers, where each successively defined layer has a plurality of channels with a channel size that is smaller than the channel size of the channels of the previous layer.

Given that the resource may be considered to be made up of resource units, the minimum size for a channel in this hierarchical scheme may be predetermined as the size of the smallest resource unit.

<FIG> illustrates a frame of channels defined using a hierarchical channel definition scheme, such that the frame is organized into five depths. At depth <NUM>, a first channel <NUM> (channel ID = <NUM>) occupies the entirety of the available resource. At depth <NUM>, two channels <NUM>, <NUM> (channel ID = <NUM>, <NUM>) each occupy a half of the available resource. At depth <NUM>, four channels <NUM>, <NUM>, <NUM>, <NUM> (channel ID = <NUM>, <NUM>, <NUM>, <NUM>) each occupy a quarter of the available resource. At depth <NUM>, eight channels <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> (channel ID = <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) each occupy an eighth of the available resource. At depth <NUM>, <NUM> channels <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> (channel ID = <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) each occupy a sixteenth of the available resource. Notably, in this exemplary case, the smallest resource unit is a sixteenth of the available resource. Furthermore, the bit-length of the channel ID, that is, the number of bits required to uniquely identify each channel in the scheme, may be determined by adding one to the base-<NUM> logarithm of the maximum depth.

The maximum depth for the hierarchical channel definition scheme in the example of <FIG> is <NUM>. The bit-length of the channel ID may, therefore, be determined as log<NUM>(<NUM>)+<NUM> = <NUM> bits.

Although the channel definitions overlap, allocation of resources to various channels need not overlap. <FIG> illustrates a scenario in which only a limited number of hierarchically defined channels are allocated. In particular, the allocated channels include: a first quarter-resource space channel (CHID = <NUM>) <NUM>; a second quarter-resource space channel (CHID = <NUM>) <NUM>; a third quarter-resource space channel (CHID = <NUM>) <NUM>; a first sixteenth-resource space channel (CHID = <NUM>) <NUM>; a second sixteenth-resource space channel (CHID = <NUM>) <NUM>; a third sixteenth-resource space channel (CHID = <NUM>) <NUM>; and a fourth sixteenth-resource space channel (CHID = <NUM>) <NUM>.

That being said, resources may also be allocated to overlapping channels, as illustrated in <FIG>, wherein the allocated channels in the resource space <NUM> include: a first quarter-resource space channel (CHID = <NUM>) <NUM>; a second quarter-resource space channel (CHID = <NUM>) <NUM>; a third quarter-resource space channel (CHID = <NUM>) <NUM>; a fourth quarter-resource space channel (CHID = <NUM>) <NUM>; and a sixteenth-resource space channel (CHID = <NUM>) <NUM>. Notably, since the sixteenth-resource space channel <NUM> overlaps the first quarter-resource space channel <NUM>, the allocation of first quarter-resource space channel <NUM> is understood to only relate to the region of the resource not allocated to the sixteenth-resource space channel <NUM>.

In a non-hierarchical channel definition scheme, the available resource may be divided into multiple channels of non-uniform size. The non-uniform size of the channels may be based, for instance, on traffic statistics. Notably, the non-uniform size is not a whole number multiple of the size of a resource unit.

A plurality of channel defined according to a non-hierarchical channel definition scheme is illustrated in <FIG>, wherein the defined channels in the resource space <NUM> include: four twelfth-resource space channels <NUM>, <NUM>, <NUM>, <NUM>; six eighteenth-resource space channels <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>; and twelve thirty-sixth-resource space channels <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>,<NUM>, <NUM>.

Alternatively, channels may be defined using a hybrid hierarchical/non-hierarchically scheme. The resource plane may be divided into N parts, where N will often be two. In a first option, a first part uses a non-hierarchical channel definition and a second part uses a hierarchical channel definition.

Definition of a plurality of channels defined using this first option the hybrid hierarchical/non-hierarchically channel definition scheme is illustrated in <FIG>, wherein the defined channels in the first part of a resource space <NUM> include: four <NUM>/<NUM>-resource space channels <NUM>, <NUM>, <NUM>, <NUM>; and six sixteenth-resource space channels <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. The defined channels in the second part of the resource space <NUM> include <NUM> sixty-fourth-resource space channels <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>.

in a second option, both parts use a hierarchical channel definition, but the hierarchical channel definition of the first part uses a different maximum depth than the hierarchical channel definition of the second part.

Definition of a plurality of channels using this second option of the hybrid hierarchical/non-hierarchically channel definition scheme is illustrated in <FIG>, wherein the defined channels of a first part of a resource space <NUM> have a maximum depth of <NUM> and include: two quarter-resource space channels <NUM>, <NUM>. The defined channels of a second part of the resource space <NUM> have a maximum depth of <NUM> and include eight sixteenth-resource space channels <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>.

<FIG> illustrates a plurality of-channels <NUM>, a first DL access information element (DL_access_IE) <NUM> and a second DL access information element <NUM>. The first DL_access_IE <NUM> includes a DUIC; a <NUM>-bit Channel type = <NUM>; a <NUM>-bit CHID = <NUM>; and a CID. The second DL_access_IE <NUM> includes a DUIC; a <NUM>-bit Channel type = <NUM>; a <NUM>-bit CHID = <NUM>; a <NUM>-bit indication of the number of channels referred to = <NUM> (two channels); and a CID. As will be apparent to one of skill in the art, logical channels are shown in the plurality of channels <NUM>.

Notably, in operation, a DL_access_IE is normally associated with each of the channels in the plurality of channels <NUM>. it should be clear to a person of ordinary skill in the art that the first DL_access_IE <NUM> and the second DL_access_IE <NUM> are merely presented as exemplary DL access information elements.

In some scenarios without irregular assignment, the overhead of DL resource allocation can be further reduced. Initially, the base station <NUM> may provide a Channel ID list corresponding to the plurality of channels <NUM>. Subsequently, the base station <NUM> may provide a plurality of DL access information elements in the same order as the channels in the Channel ID list. In such a case, the CHID field may be omitted and the overhead may be reduced further as a result. See, for example, the downlink resource allocation scheme shown in <FIG>, which provides a channel definition <NUM> and a plurality of corresponding DL access information elements that enable the reduced overhead, given that the channels are assigned in order. As will be apparent to one of skill in the art, logical channels are shown.

In <FIG>, DL_access_IE information elements for type <NUM> channels are illustrated. The DL access_IE information elements for the type <NUM> channels are as follows. DL_access_IE <NUM> includes: a DUIC; a <NUM>-bit channel type = <NUM>; a <NUM>-bit number of type <NUM> channels = <NUM> (<NUM> channel); and a CID. DL_access_IE <NUM> includes: a DUIC; a <NUM>-bit channel type = <NUM>; a <NUM>-bit number of type <NUM> channels = <NUM> (<NUM> channels); CID. DL_access_IE <NUM> includes: a DUIC; a <NUM>-bit channel type = <NUM>; a <NUM>-bit number of type <NUM> channels = <NUM> (<NUM> channels); and a CID. DL_access_IE <NUM> includes: a DUIC; a <NUM>-bit channel type = <NUM>; a <NUM>-bit number of type <NUM> channels = <NUM> (<NUM> channels); and a CID. DL_access_IE <NUM> includes: a DUIC; a <NUM>-bit channel type = <NUM>; a <NUM>-bit number of type <NUM> channels = <NUM> (<NUM> channel); and a CID. DL_access_IE <NUM> includes: a DUIC; a <NUM>-bit channel type = <NUM>; a <NUM>-bit number of type <NUM> channels = <NUM> (<NUM> channels); and a CID.

<FIG> provides another exemplary channel definition <NUM>, wherein a DL-MAP occupies a portion of a type <NUM> channel with CHID = <NUM>, some resources are assigned to soft hand off (SHO) mobile terminals <NUM> and some mobile terminals <NUM> are allocated both a type <NUM> channel and a type <NUM> channel.

In particular, channel <NUM> is partially occupied by DL-MAP; the remaining portion of channel <NUM> is allocated to a mobile terminal <NUM> in a DL_access_IE <NUM> that includes: a DUIC; an OFDMA symbol offset; a sub-channel offset; a number of OFDMA symbols; a number of sub-channels; and a CID.

Channel <NUM> is assigned to a mobile terminal <NUM> in a DL_access_IE <NUM> that includes: a DUIC; a <NUM>-bit channel type = <NUM>; a <NUM>-bit CHID = <NUM>; and a CID.

Channel <NUM> is assigned to a mobile terminal <NUM> in a DL_access_IE <NUM> that includes: a DUIC; a <NUM>-bit channel type = <NUM>; and a CID. Note that a CHID is not necessary.

Part of channel <NUM> is occupied by an irregular assignment; the remaining portion of channel <NUM> is assigned to a mobile terminal <NUM> in a DL_access_IE <NUM> that includes: a DUIC; an OFDMA symbol offset; a sub-channel offset; a number of OFDMA symbols; a number of sub-channels; and a CID.

Channel <NUM> is assigned to a mobile terminal <NUM> in a DL access_IE <NUM> that includes: a DUIC; a <NUM>-bit channel type = <NUM>; and a CID.

Channel <NUM> is assigned to a mobile terminal <NUM> in a DL_access_IE <NUM> that includes: a DUIC; a <NUM>-bit channel type = <NUM>; and a CID.

Type <NUM> channel <NUM> and type <NUM> channel <NUM> are assigned to a mobile terminal <NUM> in a DL_access_IE <NUM> that includes: a DUIC; a <NUM>-bit channel type = <NUM>; a further <NUM>-bit channel type = <NUM>; a <NUM>-bit CHID = <NUM>; a <NUM>-bit number of type <NUM> channels = <NUM>; and a CID.

Type <NUM> channels <NUM> and <NUM> are assigned to a mobile terminal <NUM> in a DL_access_IE <NUM> that includes: a DUIC; a <NUM>-bit channel type = <NUM>; a <NUM>-bit number of type <NUM> channels = <NUM>; and a CID. Note that, due to consecutive assignments, the CHID is unnecessary.

The following provides an "enhance" DL MAP information element in accordance with an embodiment of the invention. This information element may be used by a base station <NUM> to indicate the DL resource allocation by using a two step DL resource assignment method.

Wherein:
Num_Assignment is Number of assignments in the IE.

The Assignment_code values are explained as follows.

CHID is channel index defined in the DCD message.

Num_Channels is number of type <NUM> channel(s) assigned.

The following provides DCD channel encoding in accordance with an embodiment of the invention.

It is recognized that, occasionally, irregular assignments will occur. An exemplary irregular assignment is a SHO, which requires synchronized resource assignment across all members in active set of a mobile terminal <NUM>. in such cases, the DL access information element is required to be explicit about the location with the resource that is to be allocated. An exemplary format for such a DL access information element follows.

In the current <NUM>. 16e draft standard (p802.16e/D5), DL and UL resource or data burst assignment is performed by layer <NUM> or MAC control messages called DL/UL-MAP messages. The DL/UL-MAP messages are encapsulated in the physical layer OFDMA region called the DL/UL-MAP region. Each DL/UL-MAP region contains one DL/UL-MAP message. Within the DL/UL MAP message, there are one or more broadcast, multicast or unicast information elements that contain information for one or more Mobile Subscriber Station (MSS, mobile terminals <NUM>). The information elements are used for, among other things, assigning DL/UL OFDMA regions for mobile terminals <NUM> to receive/transmit DL/UL traffic or MAC messages.

The current DL/UL-MAP designs have many shortcomings including the following. First, there is no more room to define new lEs due to the limited number of IE type indicators, called the Downlink Interval Usage Code (DIUC) and Uplink Interval Usage Code (UIUC). The DIUC/UIUC is <NUM> bits in length, thus allowing only up to <NUM> types of IEs. To alleviate the problem, one of the DIUC/UIUC values (i.e., <NUM>) is reserved for extending the IE types. When a DIUC/UIUC is set to <NUM>, an extended DIUC/UIUC (also <NUM> bits) is included to indicate up to an additional <NUM> new IE types. Currently, in the draft standard, all the <NUM> plus <NUM>, i.e. <NUM> DIUC/UIUC values have been used. Therefore, new lEs cannot be introduced. Second, there is no explicit indication of whether a broadcast IE is designated to all mobile terminals <NUM> or only those mobile terminals <NUM> in certain modes of operation (Normal, Sleep or Idle).

As will be apparent to one skilled in the art, a mobile terminal <NUM> can be in Normal mode, Sleep mode or Idle Mode. A mobile terminal <NUM> in Normal mode continuously processes the DL/UL-MAP messages and can be assigned DL or UL resource or burst at any time. A mobile terminal <NUM> in sleep mode operates in cycles of a sleep interval followed by a listening interval. During the sleep interval, the mobile terminal <NUM> is not available to the base station <NUM> for DL traffic. However, the mobile terminal <NUM> may initiate UL traffic transmission during sleep interval. During listening interval, the mobile terminal <NUM> operates as in Normal mode. Sleep mode reduces the mobile terminal <NUM> battery consumption compared to Normal mode. For Idle mode, the mobile terminal <NUM> is not available for DL traffic and cannot initiate UL traffic. Furthermore, the mobile terminal <NUM> does not perform Hand Off. The mobile terminal <NUM> listens to paging signaling from the base station <NUM> during a designated paging interval. Idle Mode therefore provides the most power saving for the mobile terminal <NUM>.

When a mobile terminal <NUM> is in Sleep mode - listening interval, or Idle Mode - paging interval, the mobile terminal <NUM> is required to decode the DUUL-MAP message in order to receive unicast traffic (for sleep mode) or relevant broadcast traffic (for both sleep mode and idle mode). However, when the mobile terminal <NUM> receives an IE with broadcast connection identifier (broadcast CID), the mobile terminal <NUM> has to demodulate and decode the DL OFDMA region assigned by this IE, even though the DL broadcast traffic carried in that OFDMA region is not designated to the mobile terminal <NUM>.

This is not power efficient for mobile terminals <NUM> in Sleep and Idle Modes since a given mobile terminal <NUM> has to demodulate and decode all DL broadcast traffic or messages.

The current DL and UL lEs are encapsulated in a DL-MAP and a separate UL-MAP. For the case of unicast burst assignment to the same mobile terminal <NUM> on both DL and UL, the <NUM>-bit basic connection identifier (basic CID) of that mobile terminal <NUM> will appear twice, once in the DL-MAP and a second time in the UL-MAP. This may be considered to be unnecessary overhead.

According to the current design, a mobile terminal <NUM> in either Normal mode, Sleep mode - listening interval or Idle mode - paging interval is required to demodulate and decode all the DL and UL MAP regions and associated messages, even though many of the information elements contained in the MAP regions are not designated to that mobile terminal <NUM>. The DL-MAP region and the UL-MAP region may be long and span multiple OFDMA symbols, this is not power efficient for an mobile terminal <NUM> in Idle mode and Sleep mode.

It is proposed herein to provide hierarchical MAP structures for broadband mobile wireless metropolitan area networks. Advantageously, the hierarchical MAP structures may be shown not to impact the operation of <NUM>. 16d mobile terminals and should be transparent to the <NUM>. 16d mobile terminal.

<FIG> presents a hierarchical MAP structure <NUM> in accordance with an embodiment of the invention. As will be apparent to one of skill in the art, the regions shown are logical regions rather than actual physical space defined by sub-channels and OFDMA symbols. The hierarchical MAP structure <NUM> includes a Root Map, which contains a Frame Control Header (FCH) <NUM>, which, in turn, contains a DL-MAP, as is the case in the current <NUM>. 16d standard, for the purpose of backward compatibility.

Since the DL-MAP may be processed by mobile terminals <NUM> that intend to listen to DL traffic or messages including mobile terminals <NUM> in Normal mode, mobile terminals <NUM> in Sleep mode - listening interval and mobile terminals <NUM> in Idle mode - Paging interval, the DL-MAP may be used as the Root MAP <NUM> to: point to additional DL/UL-MAP regions <NUM>, which only need to be processed by specific groups of mobile terminals <NUM>; point to DL broadcast regions <NUM>; point to DL multicast-broadcast service (MBS) regions <NUM>; and contain DL IEs that are addressed to both <NUM>. 16d subscriber stations and to <NUM>. 16e Mobile Subscriber Stations, e.g., MIMO_DL_Basic_IE, etc. To target to a specific group of mobile terminals, each pointer may be associated with a multicast ID or an applicable allocation code, where the allocation code indicates a group of mobile terminals to which the message in the broadcast region is applicable.

The DL broadcast regions <NUM> may be divided into four types:.

In this way, a mobile terminal <NUM> operating in certain mode may only need to process the corresponding region and messages instead of having to process all broadcast regions and messages.

Additionally, a particular one of the MBS regions <NUM> may be demodulated and decoded by mobile terminals <NUM> that are subscribed to the associated MBS.

As illustrated in <FIG> the additional MAP regions <NUM> may include:.

In this way, a particular type of mobile terminal only needs to process the corresponding MAP lEs instead of having to process all the MAP IEs.

It is proposed herein to provide hierarchical MAP structures which include an Enhanced MAP message (an "EN-MAP") that includes unicast IEs for all <NUM>. 16e mobile terminals in Normal mode or Sleep mode - listening interval. One characteristic of the EN-MAP message may be a lack of generic MAC header when the EN-MAP message is transmitted. A proposed EN-MAP format follows.

As illustrated above, an EN-MAP message may contain one or more EN-MAP information elements named EN-MAP_IE. Each EN-MAP_IE information element may contains an IE type field of <NUM> bits. The IE type field allows a number of types of information elements to be supported by the EN-MAP message. For each unicast resource allocation, the DL/UL resource allocations may be combined together into the same information element whenever possible to reduce MAC overhead, i.e., when the same basic CID for both DL and UL is used for the DL/UL resource allocation. An exemplary format for an EN-MAP _IE information element follows.

The <NUM>-bit IE_Type may be encoded according to the following.

An exemplary format for a UL access information element (EN-MAP type = 0b <NUM> ) follows.

An exemplary format for a DL/UL access information element (EN-MAP type = 0b <NUM>) follows.

The Root MAP <NUM> may include an MSS_region_IE information element to point to broadcast message regions specifically for <NUM>) all <NUM>. 16e mobile terminals or <NUM>) all <NUM>. 16e Sleep mode mobile terminals or <NUM>) all <NUM>. 16e Idle mode mobile terminals. The MSS_region_IE may include an Applicability Code field to indicate which type of region is pointed to by the information element. The MSS_region_IE information element may also be used to point to the region for the EN-MAP message. An exemplary format for a MSS region IE information element follows.

A Skip_IE information element may be provided in the Root MAP, to allow an <NUM>. 16e mobile terminal to disregard, i.e., avoid processing, regions designated for <NUM>. 16d subscriber stations. The Skip_IE information element may be used to toggle the enabling and disabling of processing of regions designated by information elements following the Skip_IE information element. An exemplary Skip_IE information element format follows.

16e mobile terminal may sequentially process information elements and, if applicable, the associated regions designated by the information elements in the Root MAP. When the first Skip_IE information element is encountered, the mobile terminal may not process the region designated by information elements following the Skip_IE information element. When a second Skip_IE information element is encountered, the mobile terminal reverts back to processing the region designated by the information elements following the Skip_IE information element, when applicable. When the next Skip_IE information element is encountered, the mobile terminal again disables processing of regions designated by subsequent information elements. This procedure may continue until the end of the Root MAP.

Advantageously, by implementing aspects of the present invention, both backward compatibility with <NUM>. 16d subscriber stations and power saving and overhead reduction for <NUM>. 16e mobile terminals can be achieved. In particular, <NUM>. 16d subscriber stations may be expected to ignore any newly introduced information elements.

Unicast information designated for <NUM>. 16d subscriber stations may be skipped for power saving purposes by <NUM>. 16e mobile terminals <NUM>. Also, <NUM>. 16e mobile terminals <NUM> in certain modes (Normal, Sleep, Idle) may only process the relevant regions designated for the mobile terminal.

Advantageously, aspects of the invention reduce resource allocation signaling overhead by dividing resource space into sub-resource spaces with reasonable size, shape. Furthermore, aspects of the invention reduce power consumption of mobile terminals by enhancing allocation signaling.

Claim 1:
A method executed by a mobile terminal (<NUM>) for operating in a downlink Orthogonal Frequency-Division Multiplexing, OFDM, resource space allocated by a cell (<NUM>), the method comprising:
receiving a channel descriptor management message from the cell (<NUM>) of a base station (<NUM>), the channel descriptor management message indicating to the mobile terminal (<NUM>) the downlink OFDM resource space allocated by the cell (<NUM>), wherein the message comprises a format for a DL subframe, the DL subframe including an OFDM resource space, the message further providing a hierarchical definition for a plurality of sub-resource spaces within the OFDM resource space, each sub-resource space having an associated sub-resource space identifier and being individually allocatable, the plurality of sub-resource spaces comprising a definition of a first sub-resource space in a first layer of a hierarchy of layers of the OFDM resource space and a definition of a second sub-resource space in a second layer of the hierarchy of layers, where the second sub-resource space is positioned within the first sub-resource space, wherein the second layer of the hierarchy of layers has a plurality of channels with a channel size that is smaller than a channel size of the first layer of a hierarchy of layers, wherein each layer of the hierarchy of layers occupies the entirety of the OFDM resource space, and
receiving the DL subframe from the cell (<NUM>) of the base station (<NUM>), wherein the DL subframe comprises a respective sub-burst within at least one of the plurality of sub-resource spaces within the OFDM resource space corresponding to the mobile terminal (<NUM>), the DL subframe further comprising a downlink mapping component that includes information for the mobile terminal (<NUM>) indicating where the respective sub-burst for the mobile terminal (<NUM>) is located in the OFDM resource space.