Patent Description:
The IEEE (Institute of Electrical and Electronics Enigneers) <NUM> Working Group is developing <NUM>. 11ax HE (High Efficiency) WLAN (Wireless Local Area Network) air interface in order to achieve a very substantial increase in the real-world throughput achieved by users in high density scenarios. OFDMA (Orthogonal Frequency Division Multiple Access) multiuser transmission has been envisioned as one of the most important features in <NUM>.

OFDM (Orthogonal Frequency Division Multiplexing) is a multiplexing technique that subdivides a system bandwidth into a plurality of orthogonal frequency subcarriers. In OFDM system, an input data stream is divided into several parallel substreams with a lower data rate (accordingly, increased symbol duration), and the substreams are modulated with respective orthogonal subcarriers and are transmitted. The increased symbol duration improves the robustness of OFDM system with respect to the channel delay spread. Further, introduction of a CP (Cyclic Prefix) is able to completely remove intersymbol interference so far as the CP duration is longer than the channel delay spread. Further, OFDM modulation may be realized by an efficient IFFT (Inverse Fast Fourier Transform) that makes a plurality of subcarriers usable with little complexity. In OFDM system, time and frequency resources are defined by OFDM symbols in a time domain and subcarriers in a frequency domain. OFDMA is a multiple access scheme that performs multiple operations of data streams to and from the plurality of users over the time and frequency resources of the OFDM system.

Studies are underway to perform frequency scheduling for OFDMA multiuser transmission in <NUM>. According to frequency scheduling, a radio communication access point apparatus (hereinafter simply "access point") adaptively assigns subcarriers to a plurality of radio communication station apparatuses (i.e., terminal ap-parartus, herein-after simply "stations") based on reception qualities of frequency bands of the stations (also called as "STAs"). This makes it possible to obtain a maximum multiuser diversity effect and perform communication quite efficiently.

Frequency scheduling is generally performed based on a Resource Unit (RU). A RU comprises a plurality of consecutive subcarriers. The RUs are assigned by an access point (AP) to each of a plurality of STAs with which the AP communicates. The resource assignment result of frequency scheduling performed by the AP shall be reported to the STAs as resource assignment information. However, unlike other OFDMA based mobile communication standards such as LTE (Long Term Evolution) and WiMAX (Worldwide Interoperability for Microwave Access), <NUM>. 11ax is packet oriented and does not support control channels for transmitting resource assignment information.

Patent Application <CIT> relates to backward compatibility between WLAN and HE-WLAN and signaling of resource assignments.

As flexibility in frequency scheduling increases, more signaling bits are needed to report the resource assignment information to STAs. This results in an increase of the overhead for reporting resource assignment information. So there is a relationship of trade-off between flexibility in frequency scheduling and overhead for reporting resource assignment information. A challenge is how to achieve flexible frequency scheduling while reducing an increase of the overhead for reporting resource assignment information.

It should be noted that general or specific disclosures may be implemented as a system, a method, an integrated circuit, a computer program, a storage medium, or any selective combination thereof.

With the transmission apparatus and transmission method of resource assignment information of the present disclosure, it is possible to achieve flexible frequency scheduling while supressing an increase of the overhead for reporting resource assignment information.

Various embodiments of the present disclosure will now be described in detail with reference to the annexed drawings. In the following description, a detailed description of known functions and configurations has been omitted for clarity and conciseness.

<FIG> illustrates an example format of PPDU (Physical layer Protocol Data Unit) <NUM> according to the prior art [see NPL <NUM> and <NUM>]. The PPDU <NUM> comprises a legacy preamble <NUM>, a non-legacy preamble (i.e., High Efficiency (HE) preamble) <NUM> and a data field <NUM>.

The data field <NUM> carries the payload for one or more STAs. For a specific STA in terms of single user transmission or a specific group of STAs in terms of multiuser MIMO transmission, the payload is carried on a designated resource in units of Resource Unit (RU) spanning a plurality of OFDM symbols. A RU may have different types depending on the number of constituent subcarriers per RU. OFDM symbols in the data field <NUM> shall use a DFT period of <NUM> and subcarrier spacing of <NUM>. The number of subcarriers per OFDM symbol depends on a size of channel bandwidth (CBW). For example, in case of CBW =<NUM>, the number of subcarriers per OFDM symbol is <NUM>. Therefore for a specific type of RU, the maximum number of RUs per OFDM symbol depends on a size of CBW as well.

<FIG> illustrates an example OFDMA structure of the data field <NUM> in case of CBW = <NUM> according to the prior art [see NPL <NUM> and <NUM>]. The <NUM> OFDMA supports four types of RUs. The Type I RU comprises <NUM> consecutive tones and has a bandwidth of about <NUM>. The Type II RU comprises <NUM> consecutive tones and has a bandwidth of about <NUM>. The Type III RU comprises <NUM> consecutive tones and has a bandwidth of about <NUM>. The Type IV RU comprises <NUM> consecutive tones and has a bandwidth of about <NUM>. The maximum number of Type I RUs, Type II RUs, Type III RUs and Type IV RUs which the <NUM> OFDMA is able to support is nine, four, two and one, respectively. A mix of different types of RUs can be accomodated in the <NUM> OFDMA. For example, the <NUM> OFDMA may be divided into one Type III RU <NUM>, three Type I RUs <NUM>, <NUM> and <NUM> as well as one Type II RU <NUM>.

<FIG> illustrates an example OFDMA structure of the data field <NUM> in case of CBW=<NUM> according to the prior art [see NPL <NUM> and <NUM>]. In addition to Type I RU, Type II RU, Type III RU and Type IV RU, the <NUM> OFDMA also supports Type V RU, which comprises <NUM> consecutive tones and has a bandwidth of about <NUM>. The maximum number of Type I RUs, Type II RUs, Type III RUs, Type IV RUs and Type V RUs which the <NUM> OFDMA is able to support is eighteen, eight, four, two and one, respectively. Similar to the <NUM> OFDMA, a mix of different types of RUs can also be accomodated in the <NUM> OFDMA.

<FIG> illustrates an example OFDMA structure of the data field <NUM> in case of CBW=<NUM> according to the prior art [see NPL <NUM> and <NUM>]. In addition to Type I RU, Type II RU, Type III RU, Type IV RU and Type V RU, the <NUM> OFDMA also supports Type VI RU, which comprises <NUM> consecutive tones and has a bandwidth of about <NUM>. The maximum number of Type I RUs, Type II RUs, Type III RUs, Type IV RUs, Type V RUs and Type VI RUs which the <NUM> OFDMA is able to support is thirty-seven, sixteen, eight, four, two and one, respectively. Similar to the <NUM> or <NUM> OFDMA, a mix of different types of RUs can also be accomodated in the <NUM> OFDMA.

Similar to the <NUM> OFDMA, the <NUM>+<NUM> OFDMA or <NUM> OFDMA also supports six types of RU, i.e., Type I RU, Type II RU, Type III RU, Type IV RU, Type V RU and Type VI RU. The maximum number of Type I RUs, Type II RUs, Type III RUs, Type IV RUs, Type V RUs and Type VI RUs which the <NUM>+<NUM> OFDMA or <NUM> OFDMA is able to support is seventy-four, thirty-two, sixteen, eight, four and two, respectively. Similar to the <NUM>, <NUM> or <NUM> OFDMA, a mix of different types of RUs can also be accomodated in the <NUM>+<NUM> OFDMA or <NUM> OFDMA.

Note that use of a Type IV RU in context of <NUM> OFDMA implies a non-OFDMA configuration, which refers to a case where OFDMA is not used in the data field <NUM> of <FIG>. That is, the entire bandwidth of operation is scheduled for single user transmission or multiuser MIMO transmission. Similarly, use of a Type V RU in context of <NUM> OFDMA or a Type VI RU in context of <NUM> OFDMA implies a non-OFDMA configuration. In particular, use of two Type VI RUs in context of <NUM> or <NUM>+<NUM> OFDMA implies a non-OFDMA configuration.

Both continuous resoruce allocation and non-continuous resource allocation are possible in OFDMA frequency scheduling.

<FIG> illustrates an example of continuous resource allocation in the data field <NUM> according to the prior art [see NPL <NUM>]. As shown in <FIG>, a single RU is allocated to a specific STA in terms of single user transmission or a specific group of STAs in terms of multiuser MIMO transmission in one assignment,.

<FIG> illustrates an example of non-continuous resource allocation in the data field <NUM> according to the prior art [see NPL <NUM>]. In non-continuous resource allocation, more than one RUs which may be not continuous in the frequency domain can be allocated in one assignment for the purpose of achieveing frequency diversity effect. For example, three non-consecutive RUs <NUM>, <NUM> and <NUM> are allocated in one assignment.

With reference to <FIG>, the legacy preamble <NUM> comprises a L-STF (Legacy Short Training Field) <NUM>, a L-LTF (Legacy Long Training Field) <NUM> and a L-SIG (Legacy SIGnal field) <NUM> in order to keep backward compatibility with legacy standard <NUM>. 11a/g/n/ac. The L-STF <NUM> is used for start-of-packet detection, AGC (Automatic Gain Control) setting, initial frequency offset estimation and initial time synchronization. The L-LTF <NUM> is used for further fine frequency offset estimation and time synchronization. The L-LTF <NUM> is also used to generate channel estimates for receiving and equalizing the L-SIG <NUM>, HE-SIG-A (High Efficiency SIGnal A field) <NUM> and HE-SIG-B (High Efficiency SIGnal B field) <NUM>.

The HE preamble <NUM> comprises a first signal field (i.e., HE-SIG-A) <NUM>, a second signal field (i.e., HE-SIG-B) <NUM>, a HE-STF <NUM> and a HE-LTF <NUM>. The HE-STF <NUM> is used to retrain AGC. The HE-LTF <NUM> comprises a plurality of HE-LTF symbols and is used to generate MIMO (Multiple Input Multiple Output) channel estimates for receiving and equalizing the data field <NUM>. If the PPDU <NUM> is a DL OFDMA PPDU, both the HE-SIG-A <NUM> and the HE-SIG-B <NUM> contain resource assignment information and user specific information which are used for each scheduled STA to decode its payload in the data field <NUM> at designated resource [see NPL <NUM>]. If the PPDU <NUM> is a UL OFDMA PPDU, the HE-SIG-A <NUM> and HE-SIG-B <NUM> may contain neither resource assignment information nor user specific information since such information is preset by an AP and sent to scheduled STAs via a trigger frame which is carried in the data field of a previously transmitted DL PPDU [see NPL <NUM>]. Note that both HE-SIG-A <NUM> and HE-SIG-B <NUM> shall use a DFT period of <NUM> and subcarrier spacing of <NUM> in <NUM>.

Next, various embodiments for resource assignment in frequency scheduling will be explained in further details.

<FIG> illustrates an example of resource assignment according to a first embodiment of the present disclosure. The first embodiment is applicable to continous resource allocation where one or more RUs that are consecutive in the frequency domain are allocated in one assignment. In this example, there are eleven assignments in the <NUM> OFDMA. Each assignment, which is referenced by an assignment index, is addressed to either a specific STA in terms of single user transmission or a specific group of STAs in terms of multiuser MIMO transmission.

According to the first embodiment, the first assignment has a predetermined start position (e.g., the start tone index of a first RU (e.g., <NUM> as shown in <FIG>) which is known according to the size of CBW and the type of the first RU). And a start tone index of a subsequent assignment is next to the end tone index of its preceding assignment (i.e., there is no gap between consecutive assignments). The total number of assignments may be negotiated in advance between an Access Point (AP) and one or more station apparatus (STAs) or signaled to each STA in the HE-SIG-A field of DL PPDU or the trigger frame explicitly. However, assume that all available RUs are allocated, a STA can determine that an assignment is the last assignment if a last RU (e.g., <NUM> as shown in <FIG>) is allocated in this assignment. Consequently, signaling of the total number of assignments can be omitted.

According to the first embodiment, the start position of the first assignment is predetermined and the start position of a subsequent assignment can be determined from the end position of its preceding assignment. Therefore, it is enough to report the allocation bandwidth for each assignment. As a result, the overhead due to reporting resource assignment information for each assignment can be minimized.

According to the first embodiment, the resource assignment information includes a plurality of resource assignment indications, each of which corresponds to a particular assignment.

<FIG> illustrates a first example of resource assignment indication for one assignment according to the first embodiment of the present disclosure. The resource assignment indication for one assignment contains the number of allocated RUs and the type of each of allocated RUs, from which the allocation bandwidth for the assignment can be derived.

<FIG> illustrates a second example of resource assignment indication for one assignment according to the first embodiment of the present disclosure. In this example, only the same type of RUs can be allocated in one assignment. The resource assignment indication for the assignment contains the number of allocated RUs and the type of allocated RUs, from which the allocation bandwidth for the assignment can be derived.

<FIG> illustrates a third example of resource assignment indication for one assignment according to the first embodiment of the present disclosure. In this example, only a single RU can be allocated in one assignment. The resource assignment indication for the assignment contains the type of allocated RU only, from which the allocation bandwidth for the assignment can be derived.

In the above mentioned examples of the first embodiment, the number of allocated RUs and the RU type are indicated separately by using bit signalings.

According to the first embodiment, a two-bit signaling shown in Table <NUM> can be used to indicate the number of allocated RUs. Accroding to Table <NUM>, one RU to four RUs can be allocated in one assignment.

Additionally, a three-bit signaling shown in Table <NUM> can be used to indicate the RU type as follows:.

For example, the type of the RU (Type II RU) allocated in the first assignment as shown in <FIG> can be indicated by "<NUM>".

According to the first embodiment, in case of <NUM> non-OFDMA transmission, the number of allocated RUs shall be set to one and the type of allocated RUs shall be set to Type IV. In case of <NUM> non-OFDMA transmission, the number of allocated RUs shall be set to one and the type of allocated RUs shall be set to Type V. In case of <NUM> non-OFDMA transmission, the number of allocated RUs shall be set to one and the type of allocated RUs shall be set to Type VI. In case of <NUM>+<NUM> or <NUM> non-OFDMA transmission, the number of allocated RUs shall be set to two and the type of each of allocated RUs shall be set to Type VI. In this way, STA shall be able to determine whether an incoming DL PPDU <NUM> is an OFDMA PPDU or a non-OFDMA PPDU according to the resource assignment information without any dedicated signaling for such purpose.

<FIG> illustrates an example of resource assignment according to a second embodiment of the present disclosure. The second embodiment is also applicable to continous resource allocation where one or more RUs that are consecutive in the frequency domain can be allocated in one assignment. In this example, there are ten assignments in the <NUM> OFDMA. Each assignment is addressed to either a specific STA in terms of single user transmission or a specific group of STAs in terms of multiuser MIMO transmission.

According to the second embodiment, a start position of the first assignment may be variable and a gap may exist between consective assignments. In this embodiment, the start tone index of an assignment is always larger than the end tone index of its preceding assignment. The total number of assignments may be negotiated in advance between an AP and one or more STAs or signaled to each STA in the HE-SIG-A field of DL PPDU or the trigger frame explicitly.

According to the second embodiment, the start position of the first assignment is variable and the start position of a subsequent assignment cannot be derived only from the end position of its preceding assignment. Therefore, in addition to allocation bandwidth, it is necessary to report start position for each assignment.

According to the second embodiment, the resource assignment information includes a plurality of resource assignment indications, each of which corresponds to a particular assignment.

<FIG> illustrates a first example of resource assignment indication for one assignment according to the second embodiment of the present disclosure. The resource assignment indication for one assignment contains the assignment offset, the number of allocated RUs and the type of each of allocated RUs. As illustrated in <FIG>, for the first assignment, the assignment offset <NUM> is relative to the start tone index of the first Type I RU. For each of the remaining assignments, the assignment offset (e.g., <NUM>) is relative to the end tone index of its preceding assignment. The start position for a subsequent assignment can be determined according to the assignment offset and the end tone index of its preceding assignment. Further, the allocation bandwidth for the assignment can be determined according to the number of allocated RUs and the type of each of allocated RUs.

<FIG> illustrates a second example of resource assignment indication for one assignment according to the second embodiment of the present disclosure. In this example, only the same type of RUs can be allocated in one assignment. The resource assignment indication for the assignment contains the assignment offset, the number of allocated RUs and the type of allocated RUs. The start position for the assignment can be determined according to the assignment offset and the end tone index of its preceding assignment. Further, the allocation bandwidth for the assignment can be determined according to the number of allocated RUs and the type of allocated RUs.

<FIG> illustrates a third example of resource assignment indication for one assignment according to the second embodiment of the present disclosure. In this example, only a single RU can be allocated in one assignment. The resource assignment indication for the assignment contains the assignment offset and the type of allocated RU. The start position for the assignment can be determined according to the assignment offset and the end tone index of its preceding assignment. Further, the allocation bandwidth for the assignment can be determined according to the type of allocated RU.

If reception quality of a RU is very poor for all scheduled STAs, the AP may not allocate the RU to them. This RU with poor reception quality is not used for resource assignment and becomes a gap between two assignments in this embodiment. The number of unused RUs that form a gap can be one or plural. As a result, the second embodiment provides more flexibility in frequency scheduling than the first embodiment. The overhead of reporting resource assignment information will slightly increase compared to the first embodiment. However, such overhead increase is not so siginificant.

In the above mentioned examples of the second embodiment, the assignment offset, the number of allocated RUs and the RU type are indicated separately by using bit signalings.

According to the second embodiment, if the assignment offset is not larger than three Type I RUs, a two-bit signaling shown in Table <NUM> can be used to indicate the assignment offset in units of the smallest RU (i.e., Type I RU).

For example, for the first assignment as shown in <FIG>, the assignment offset <NUM> (e.g., an offset of two Type I RUs) can be indicated by "<NUM>".

Two-bit signaling shown in Table <NUM> can be used to indicate the number of allocated RUs, An alternative two-bit signaling is shown in Table <NUM>. According to Table <NUM>, zero RU to three RUs can be allocated in an assignment. When no RU is allocated in an assignment, the assignment is called a "dummy assignment" with zero RU allocation.

Two-bit signaling shown in Table <NUM> makes it possible to indicate an offset that is larger than three Type I RUs. For example, if there is an offset of five Type I RUs between a first assignment and a second assignment, this offset can be indicated by inserting a "dummy assignment" with zero RU allocation. More specifically, the "dummy assignment" located between the first assignment and the second assignment has an offset of three RUs and the second assignment has an offset of two RUs. Then, total offset will be five Type I RUs in this case. In addition, two-bit signaling shown in Table <NUM> can also make it possible to omit an explicit signaling of the total number of assignments. For example, if no last RU(s) (e.g., <NUM> as shown in <FIG>) is allocated to any STA, a "dummy assignment" with zero RU allocation, which has some offset can be used to indicate such unused resource (RU). In this case, the STA is able to determine that the dummy assignment is the last assignment.

According to the second embodiment, in case of <NUM> non-OFDMA transmission, the number of allocated RUs shall be set to one and the type of allocated RU shall be set to Type IV. In case of <NUM> non-OFDMA transmission, the number of allocated RUs shall be set to one and the type of allocated RU shall be set to Type V. In case of <NUM> non-OFDMA transmission, the number of allocated RUs shall be set to one and the type of allocated RU shall be set to Type VI. In case of <NUM>+<NUM> or <NUM> non-OFDMA transmission, the number of allocated RUs shall be set to two and the type of each of allocated RUs shall be set to Type VI. In this way, STA shall be able to determine whether incoming DL PPDU <NUM> is an OFDMA PPDU or a non-OFDMA PPDU according to the resource assignment information without any dedicated signaling for such purpose.

<FIG> illustrates an example of resource assignment according to a third embodiment of the present disclosure. The third embodiment is applicable to both continuous resource allocation and non-continuous resource allocation where one or more RUs which may not be consecutive in the frequency domain can be allocated in an assignment. The third embodiment enables even more flexibility in frequency scheduling than the first embodiment and the second embodiment. In this example, there are ten assignments in the <NUM> OFDMA. Each assignment is addressed to either a specific STA in terms of single user transmission or a specific group of STAs in terms of multiuser MIMO transmission.

According to the third embodiment, the total number of assignments may be negotiated in advance between an AP and one or more STAs, or signaled to each STA in the HE-SIG-A field of DL PPDU or the trigger frame explicitly.

According to the third embodiment, the resource assignment information includes a plurality of resource assignment indications, each of which corresponds to a particular assignment.

<FIG> illustrates a first example of resource assignment indication for one assignment according to the third embodiment of the present disclosure. For each assignment, the resource assignment indication contains the number of allocated RUs and the type and position information of each of allocated RUs,.

<FIG> illustrates a second example of resource assignment indication for one assignment according to the third embodiment of the present disclosure. In this example, only a single RU can be allocated in one assignment. For the assignment, the resource assignment indication contains the type and position information of allocated RU.

According to the third embodiment, the type and position of an allocated RU are jointly signalled in a single signaling field. That is, a single signaling field can be used to indicate both position and type of each of allocated RUs. <FIG> illustrates a signaling of the RU type and position information according to the third embodiment of the present disclosure. Encoding of the RU type and position information is performed for RUs which <NUM> OFDMA can support, followed by encoding for additional RUs which <NUM> OFDMA can support, encoding for additional RUs which <NUM> OFDMA can support, and encoding for additional RUs which <NUM> and <NUM>+<NUM> OFDMA can support in this order.

In the HE preamble of DL PPDU, assignment information regarding RUs of <NUM> OFDMA is allocated first, followed by assignment information regarding additional RUs of <NUM> OFDMA, assignment information regarding additional RUs of <NUM> OFDMA, and assignment information regarding additional RUs of <NUM> OFDMA in this order. This provides a technical advantage that a receiver of the resource assignment information (i.e., STA) that only supports CBW= <NUM> has to decode only a first part (i.e., assignment information regarding RUs of <NUM> OFDMA) of the resource assignment information, and it can disregard the remaining part of the resource assignment information. Similarly, a STA that supports CBW= <NUM> has to decode only a first and second parts (i.e., assignment information regarding RUs of <NUM> OFDMA and <NUM> OFDMA) of the resource assignment information. Further, a STA that supports CBW= <NUM> has to decode a first, second and third parts (i.e., assignment information regarding RUs of <NUM> OFDMA, <NUM> OFDMA and <NUM> OFDMA) of the resource assignment information. Lastly, a STA that supports CBW= <NUM> has to decode the resource assignment information as a whole. In this way, decoding workload at a STA supportting a smaller channel bandwidth (CBW) can be significantly lowered.

According to the signaling of the RU type and position information illustrated in <FIG>, in one embodiment, an eight-bit signaling is used to indicate the type and position of an alllocated RU. So, the overhead of reporting resource assignment information further increases compared to the second embodiment. Alternatively, signaling whose length is variable depending on CBW may be used. In more details, four-bit signaling, six-bit signaling, seven-bit signaling and eight-bit signaling can be used when CBW = <NUM>, CBW = <NUM>, CBW = <NUM> and CBW = <NUM>+<NUM> or <NUM>, respectively. As a result, an increase of the overhead of reporting resource assignment information due to much more flexible frequency scheduling is reduced. For example, the type and position information of the RU allocated to the first assignment of <NUM> OFDMA as illustrated in <FIG> can be indicated by "<NUM>".

According to the signaling of the RU type and position information illustrated in <FIG>, in order to decode the type and position of each of the allocated RUs, a STA supporting CBW up to <NUM> only needs to maintain a four-bit look up table. Likewise, a STA supporting CBW up to <NUM> only needs to maintain a six-bit look up table and a STA supporting CBW up to <NUM> only needs to maintain a seven-bit look up table. As a result, the memory required for decoding the type and position information of each of allocated RUs is minimized for STAs with different PHY capabilities in terms of supported CBW.

According to the third embodiment, in case of <NUM> non-OFDMA transmission, the number of allocated RUs shall be set to one and the type and position of allocated RU shall be set to the first Type IV RU. In case of <NUM> non-OFDMA transmission, the number of allocated RUs shall be set to one and the type and position of allocated RU shall be set to the first Type V RU. In case of <NUM> non-OFDMA transmission, the number of allocated RUs shall be set to one and the type and position of allocated RU shall be set to the first Type VI RU. In case of <NUM>+<NUM> or <NUM> non-OFDMA transmission, the number of allocated RUs shall be set to two and the type and position of allocated RUs shall be set to the first Type VI RU and the second Type VI RU, respectively. Consequently, STA shall be able to determine whether incoming DL PPDU <NUM> is an OFDMA PPDU or a non-OFDMA PPDU according to the resource assignment information without any dedicated signaling for such purpose.

<FIG> illustrates an example of information content of HE-SIG-A <NUM> and HE-SIG-B <NUM> of DL PPDU <NUM> according to the present disclosure. Common control information is included in both the HE-SIG-A for non-OFDMA transmission and the HE-SIG-A for OFDMA transmission. According to the present disclosure, the information contained in the HE-SIG-A <NUM> for non-OFDMA transmission differs from the HE-SIG-A <NUM> for OFDMA transmission. In case of non-OFDMA transmission, in addition to the common control information, the HE-SIG-A field <NUM> contains resource assignment information and user specific information for single user transmission or multiuser MIMO transmission. The HE-SIG-B field <NUM> does not exist in case of non-OFDMA transmission in the data field <NUM>. In case of OFDMA transmission in the data field <NUM>, in addition to the common control information, the HE-SIG-A field <NUM> contains resource assignment indication and user specific information for the first assignment, and the HE-SIG-B field <NUM> contains resource assignment indication and user specific information for each of the remaining assignments.

According to the present disclosure, common control information includes CBW and GI (Guard Interval), etc. The user specific information is required for each scheduled STA to decode its payload, e.g., Group ID, Nsts (i.e., the number of space-time streams) and MCS (Modulation and Coding Scheme), etc..

According to the present disclosure, common control information further includes an assignment set ID that maps a plurality of resource assignments indicated by resource assignment information to scheduled STAs, which will be detailed later. As a result, after decoding HE-SIG-A <NUM> of a DL PPDU <NUM>, if a STA determines that it is not addressed by the PPDU <NUM>, it will ignore the remaining of the PPDU <NUM> and reduce its power consumption.

According to the present disclosure, the common control information may further include an Allocation Defined flag in conjunction with the assignment set ID. Assume a first DL PPDU and a subsequent second DL PPDU are associated with the same assignment set ID. The Allocation Defined flag of the second DL PPDU shall be set if the resource assignment information contained in the first DL PPDU can be reused by the second DL PPDU. In that case, the resource assignment information for the second DL PPDU can be ommited, and thus signaling overhead can be reduced.

According to the present disclosure illustrated in <FIG>, the HE-SIG-A <NUM> contains similar information for non-OFDMA transmission and OFDMA transmission in the data field <NUM>. This would reduce implementation complexity of STA.

According to the present disclosure illustrated in <FIG>, when non-OFDMA transmission is performed in the data field <NUM>, the HE-SIG-B <NUM> does not exist. As a result, STAs need not to decode HE-SIG-B <NUM>, which leads to a reduced power consumption of STAs.

<FIG> illustrates an example sequence of excuting OFDMA transmission in a radio communication system according to the present disclosure. The radio communication system comprises an AP <NUM> and a plurality of STAs (e.g., <NUM>) which are associated with AP <NUM>, AP <NUM> performs frequency scheduling using the plurality of RUs in the radio communication system.

Prior to initiatation of DL OFDMA transmission, AP <NUM> determines possible combinations of STAs that can be addressed by a DL OFDMA PPDU by assigning STAs to DL assignment sets and to specific assignment indices within those sets. One assignment set is identified by an assignment set ID and refers to a plurality of STAs and a plurality of assignment indices where each of the plurality of assignmentm indices is addressed to one or more of the plurality of STAs. For example, one assignment set comprises two STAs (STA1 and STA2) and two assignments where the first assignment is addressed to STA1 and the second assignment is addressed to STA2. Then AP <NUM> transmits an Assignment Set ID Management frame <NUM> to STA <NUM> to assign or change its assignment indices corresponding to one or more DL assignment sets of which STA <NUM> is a member.

Prior to initiatation of UL OFDMA transmission, AP <NUM> determines the possible combinations of STAs that transmit a UL OFDMA PPDU by assigning STAs to UL assignment sets and to specific assignment indices within those sets. Then AP <NUM> transmits an Assignment Set ID Management frame <NUM> to STA <NUM> to assign or change its assignment indices corresponding to one or more UL assignment sets of which STA <NUM> is a member.

<FIG> illustrates an example format of Assignment Set ID Management frame <NUM> or <NUM> according to the present disclosure. The frame <NUM> comprises a Directionality field <NUM>, a Membership Status Array field <NUM> and an Assignment Index Array field <NUM>. The Directionality field <NUM> indicates whether OFDMA assignment sets are for DL or UL. STA <NUM> may be assigned to multiple sets by setting multiple subfields of the Membership Status Array field <NUM> to <NUM> in the frame <NUM>. An assignment index in each assignment set of which STA <NUM> is a member is indicated by the associated subfield in the Assignment Index Array field <NUM> in the frame <NUM>. For each Set ID, AP <NUM> may assign the same assignment index to multiple STAs. STA <NUM> shall have only one assignment index in each set of which it is a member.

According to the present disclosure, the AP <NUM> may transmit the Assignment Set ID management frames to STA <NUM> when it associates with the AP <NUM>. In addition, the AP <NUM> may transmit the Assignment Set ID management frames to STA <NUM> periodically or if necessary.

If only a specific combination of STAs is allowed to communicate with the AP <NUM> in an OFDMA transmission for a period of time, a simple management frame can be used instead of the Assignment Set ID management frame to indicate an assignment index for each STA. In this case, the assignment set ID in the HE-SIG-A of DL PPDU or the trigger frame can be omitted.

If AP <NUM> has buffered data addressed to STA <NUM>, AP <NUM> selects a DL assignment set of which STA <NUM> is a member and determines DL resource required to transmit the data addressed to STA <NUM> based on the data size and QoS (Quality of Service) requirement. Then AP <NUM> transmits a DL OFDMA PPDU <NUM> which includes the data addressed to STA <NUM>, assignment set ID of the selected DL assignment set as well as other control information (e.g., resource assignment information) which is required by STA <NUM> to decode its data inside the DL OFDMA PPDU <NUM>. Note that when a subsequent DL OFDMA PPDU which includes the same assignment set ID as the DL OFDMA PPDU <NUM> is transmitted, if the resource assignment information contained in the DL OFDMA PPDU <NUM> can be reused by the subsequent DL OFDMA PPDU, the Allocation Defined flag in the subsequent DL OFDMA PPDU shall be set and then resource assignment information needs not to be included in the subsequent DL OFDMA PPDU.

If STA <NUM> has buffered data addressed to AP <NUM>, STA <NUM> may perform ADDTS Request/Response frame exchange <NUM> with AP <NUM> to request transmission bandwidth for its data. ADDTS Request frame may also include information on RUs, for example, channel quality information to show which RUs are prefereble or not prefereble for the STA <NUM>. Then AP <NUM> selects a UL assignment set of which STA <NUM> is a member and determines UL resource according to the requested transmission bandwidth by STA <NUM>. After that, AP <NUM> transmits a trigger frame <NUM> to STA <NUM> which includes assignment set ID of the selected UL assignment set as well as other control information (e.g., resource assignment information) which is required by STA <NUM> to transmit its data. Note that when a subsequent trigger frame which includes the same assignment set ID as the trigger frame <NUM> is transmitted, if the resource assignment information contained in the trigger frame <NUM> can be reused by the subsequent trigger frame, the Allocation Defined flag in the subsequent trigger frame shall be set and then resource assignment information needs not to be included in the subsequent trigger frame. The trigger frame may also include UL transmission power control information and UL transmission duration information. After receiving the trigger frame <NUM>, STA <NUM> transmits a UL OFDMA PPDU <NUM> to send its data using the designated resource accordingly. STA <NUM> may control its transmission power based on the transmission power control information so that, at the AP <NUM>, large variation between reception power from each STA can be avoided.

<FIG> is a block diagram illustrating example configuration of AP <NUM> according to the present disclosure. The AP <NUM> comprises a controller <NUM>, a scheduler <NUM>, a message generator <NUM>, a message processor <NUM>, a PHY processor <NUM> and an antenna <NUM>. The controller <NUM> is a MAC protocol controller and controls general MAC protocol operations.

For DL OFDMA transmission, scheduler <NUM> performs frequency scheduling under the control of the controller <NUM> based on channel quality indicators (CQIs) from STAs and assigns data for STAs to RUs. Examples of a CQI-based scheduling method include the Max CIR method and the proportional-fairness method. Scheduler <NUM> also outputs the resource assignment results to the message generator <NUM>. The message generator <NUM> generates corresponding common control information, resource assignment information, user specific information and data for scheduled STAs, which are formulated by the PHY processor <NUM> into an OFDMA PPDU and transmitted through the antenna <NUM>. The resource assignment information can be configured according to the above mentioned embodiments. On the other hand, the message processor <NUM> analyzes the received CQIs from STAs through the antenna <NUM> under the control of the controller <NUM> and provides them to scheduler <NUM> and controller <NUM>. These CQIs are received quality information reported from the STAs. Further, each STA can measure received quality on a per RU basis using the received SNR, received SIR, received SINR, received CINR, received power, interference power, bit error rate, throughput and MCS whereby a predetermined error rate can be achieved. Furthermore, the CQI may also be referred to as "CSI" (Channel State Information).

For UL OFDMA transmission, scheduler <NUM> performs frequency scheduling under the control of the controller <NUM> based on transmission bandwidth request from STAs and assigns resource for scheduled STAs for UL data transmission. At the same time, scheduler <NUM> may also perform time scheduling to determine duration of UL OFDMA frame or transmission opportunity (TXOP) in which STAs have a right to perform UL OFDMA frame exchanges. Scheduler <NUM> also outputs the resource assignment results to the message generator <NUM>. The message generator <NUM> generates a trigger frame including common control information, resource assignment information and user specific information, which is formulated by the PHY processor <NUM> into a DL PPDU and transmitted through the antenna <NUM>. On the other hand, the message processor <NUM> analyzes the received transmission bandwidth request from STAs through the antenna <NUM> and provides them to scheduler <NUM> and controller <NUM>. The antenna <NUM> can be comprised of one antenna port or a combination of a plurality of antenna ports.

<FIG> is a block diagram illustrating example configuration of STA <NUM> according to the present disclosure. STA <NUM> comprises a controller <NUM>, a message generator <NUM>, a message processor <NUM>, a PHY processor <NUM> and an antenna <NUM>. The controller <NUM> is a MAC protocol controller and controls general MAC protocol operations. The antenna <NUM> can be comprised of one antenna port or a combination of a plurality of antenna ports.

For UL OFDMA transmission, the message processor <NUM> analyzes the received trigger frame from AP <NUM> through the antenna <NUM> and provides common control information, resource assignment information and user specific information to controller <NUM>. The resource assignment information can be configured according to the above mentioned embodiments. The message generator <NUM> generates data under the control of the controller <NUM>, which are formulated by the PHY processor <NUM> under the control of the controller <NUM> into an UL OFDMA PPDU in such a way that the data is transmitted at the designated resource. The UL OFDMA PPDU is transmitted through the antenna <NUM>.

For DL OFDMA transmission, the message processor <NUM> estimates channel quality from the received DL PPDU through the antenna <NUM> and provides them to controller <NUM>. The message generator <NUM> generates CQI message, which is formulated by the PHY processor <NUM> into an UL PPDU and transmitted through the antenna <NUM>.

<FIG> illustrates an example of resource assignment according to a fourth embodiment of the present disclosure. The fourth embodiment is applicable to continous resource allocation where one or more RUs that are consecutive in the frequency domain can be allocated in one assignment. In this example, there are nineassignments (#<NUM> to #<NUM>) in the <NUM> OFDMA. Each assignment is addressed to either a specific STA in terms of single user transmission or a specific group of STAs in terms of multiuser MIMO transmission.

According to the fourth embodiment, the total number of assignments may be negotiated in advance between an AP and one or more STAs or may be explicitly signaled to each STA in the HE-SIG-A field of DL PPDU or the trigger frame.

Unlike the first and second embodiments where the start tone index of an assignment is always larger than the end tone index of its preceding assignment, there is no such restriction in the fourth embodiment. The start tone index and the end tone index of an assignment can be smaller than the first tone index of another preceding assignment. As a result, the scheduling flexibility is improved in the fourth embodiment.

According to the fourth embodiment, the resource assignment information includes a plurality of resource assignment indications, each of which corresponds to a particular assignment.

<FIG> illustrates a first example of resource assignment indication for one assignment according to the fourth embodiment of the present disclosure. The resource assignment indication for one assignment contains the number of allocated RUs, the position and type of the first allocated RU and the type of each of remaing allocated RUs. In other words, each resource assignment indication contains position and type information of the first RU only and type information of each of the remaining RUs. The start position for an assignment can be determined according to the position of the first allocated RU. Further, the allocation bandwidth for the assignment can be determined according to the number of allocated RUs and the type of each of allocated RUs.

<FIG> illustrates a second example of resource assignment indication for one assignment according to the fourth embodiment of the present disclosure. In this example, only the same type of RUs can be allocated in one assignment. The resource assignment indication for the assignment contains the number of allocated RUs and the position and type of the first allocated RU. The start position for an assignment can be determined according to the position of the first allocated RU. Further, the allocation bandwidth for the assignment can be determined according to the number of allocated RUs and the type of the first allocated RU.

Two-bit signaling shown in Table <NUM> can be used to indicate the number of allocated RUs, and three-bit signaling shown in Table <NUM> can be used to indicate the RU type. The type and position of the first allocated RU can be jointly signalled in a single signaling field as illustrated in <FIG>.

<FIG> illustrates another example of information content of HE-SIG-A <NUM> and HE-SIG-B <NUM> of DL PPDU according to the present disclosure. According to the present disclosure, the HE-SIG-B field <NUM> does not exist in the DL PPDU in case of single user transmission. In case of multiuser transmission, the HE-SIG-B field <NUM> exists in the DL PPDU and contains resource assignment information (i.e., resource assignment indication for each assignment), followed by user specific information for each assignment. The HE-SIG-B field <NUM> is encoded on a per <NUM> subband basis. For CBW = <NUM>, <NUM>, <NUM> or <NUM>+<NUM>, the number of <NUM> subbands carrying different content is two.

An example structure of the HE-SIG-B field <NUM> in <FIG> in case of CBW = <NUM> is illustrated in <FIG>. The HE-SIG-B field <NUM> comprises two portions: HE-SIG-B1 <NUM> and HE-SIG-B2 <NUM>. The HE-SIG-B1 <NUM> is transmitted over the first <NUM> subband channel <NUM> and a duplicate of the HE-SIG-B <NUM> is transmitted over the third <NUM> subband channel <NUM> while the HE-SIG-B2 <NUM> is transmitted over the second <NUM> subband channel <NUM> and a duplicate of the HE-SIG-B2 <NUM> is transmitted over the fourth <NUM> subband channel <NUM>.

According to the present disclosure, resource assignment indication for one assignment that is fully located within a <NUM> subband channel should be carried in one of the HE-SIG-B <NUM><NUM> and HE-SIG-B2 <NUM> that is transmitted over the same <NUM> subband channel. In more details, the HE-SIG-B1 <NUM> should carry resource assignment indications for the assignments (e.g., <NUM>) that are fully located within the first <NUM> subband channel <NUM> or the third <NUM> subband channel <NUM>. The HE-SIG-B2 <NUM> should carry resource assignment indications for the assignments (e.g., <NUM>) that are fully located within the second <NUM> subband channel <NUM> or the fourth <NUM> subband channel <NUM>. In this way, even if control signaling in a <NUM> subband channel (e.g., <NUM> or <NUM>) is corrupted due to interference, the DL PPDU in another <NUM> subband channel (e.g., <NUM> or <NUM>) can be decoded correctly.

According to the present disclosure, for the assignments (e.g., <NUM>) that span across two or more neighboring <NUM> subband channels, the corresponding resource assignment indications can be carried either in the HE-SIG-B1 <NUM> or in the HE-SIG-B2 <NUM> such that data amount of the HE-SIG-B1 <NUM> and data amount of the HE-SIG-B2 <NUM> become similar in size. Since smaller one of the HE-SIG-B1 and the HE-SIG-B2 will be appended padding bits until their payload sizes become the same, the padding efficiency of HE-SIG-B field can be improved or maximized according to this embodiment.

<FIG> is a flow chart illustrating a method for distributing resource assignment information into the HE-SIG-B field according to the present disclosure. The method shown in <FIG> starts at Step <NUM>. At Step <NUM>, resource assignment indications for the assignments that are fully located in any <NUM> subband channel over which the HE-SIG-B1 is transmitted are included (i.e., mapped) in the HE-SIG-B1. At Step <NUM>, resource assignment indications for the assignments that are fully located in any <NUM> subband channel over which the HE-SIG-B2 is transmitted are included (i.e., mapped) in the HE-SIG-B2. Note that the sequential order of Step <NUM> and Step <NUM> may be interchangeable. At Step <NUM>, resource assignment indications for the assignments that span across two or more neighboring <NUM> subband channels are included (i.e., mapped) in either the HE-SIG-B1 or the HE-SIG-B2 so that data amount of the HE-SIG-B1 and data amont of the HE-SIG-B2 become similar in size. This method stops at Step <NUM>.

According to the method illustrated in <FIG>, resource assignment indications for the above four assignments should be distributed into the HE-SIG-B as follows:.

By distributing resource assignment indications between the HE-SIG-B1 and the HE-SIG-B2, data amount of the HE-SIG-B1 and data amount of the HE-SIG-B2 become similar in size, thus improving padding efficiency in the HE-SIG-B field.

<FIG> illustrates a first example format of the HE-SIG-B1 <NUM> or the HE-SIG-B2 <NUM> in <FIG> in case of CBW = <NUM>. The HE-SIG-B1 <NUM> or the HE-SIG-B2 <NUM> comprises a common field <NUM> and a user-specific field <NUM>. The common field <NUM> comprises a first resource assignment subfield <NUM>, a second resource assignment subfield <NUM>, a CRC (Cyclic Redundancy Check) subfield <NUM> and a tail bits subfield.

In context of the HE-SIG-B <NUM><NUM>, the first resource assignment subfield <NUM> contains a RU arrangement pattern index which indicates a specific RU arrangement in the frequency domain (including MU-MIMO (Multiuser Multiple Input Multiple Output) related information) for the first <NUM> subband channel <NUM> in <FIG>. The mapping of RU arrangement pattern indices and the corresponding RU arrangement patterns is predetermined. An example mapping of RU arrangement pattern indices and the corresponding RU arrangement patterns is shown in Table <NUM>. Note that RUs are arranged from lower frequency to higher frequency in the frequency domain within a <NUM> subband channel and Type I RUs and Type II RUs can be used for SU-MIMO transmission only.

With reference to Table <NUM>, for example, the first resource assignment subfield <NUM> may contain a RU arrangement patern index <NUM> to indicate a specific RU arrangement for the first <NUM> subband channel where five Type I RUs followed by one Type III RU in the frequency domain, and each of five Type I RUs is used for SU-MIMO (Single User Multiple Input Multiple Output) transmission while the Type III RU is used for MU-MIMO transmission with two users multiplexed. The second resource assignment subfield <NUM> indicates the RU arrangement in the frequency domain and MU-MIMO related information for the third <NUM> subband channel <NUM> in <FIG>.

In context of the HE-SIG-B2 <NUM>, the first resource assignment subfield <NUM> indicates the RU arrangement in the frequency domain and MU-MIMO related information for the second <NUM> subband channel <NUM> in <FIG>. The second resource assignment subfield <NUM> indicates the RU arrangement in the frequency domain and MU-MIMO related information for the fourth <NUM> subband channel <NUM> in <FIG>. It should be noted that the RU arrangement signalled by the first resource assignment subfield <NUM> and the second resource assignment subfield <NUM> does not involve the center Type I RU <NUM> as illustrated in <FIG>, which is located between two adjacent <NUM> subband channels.

The user-specific field <NUM> comprises a plurality of BCC (Binary Convolutional Coding) blocks <NUM>. Each of the BCC blocks <NUM> except the last BCC block <NUM>-N comprises a first user-specific subfield, a second user-specific subfield, a CRC subfield and a tail bits subfield. The last BCC block <NUM>-N may comprise a single user-specific subfield. Each of user-specific subfields in the user-specific field <NUM> carries per-user allocation information (e.g., STA identifier for addressing and the information necessary for decoding the PPDU <NUM> such as the number of spatial streams and modulation and coding scheme, etc). For each RU assigned for SU-MIMO transmission, there is only a single corresponding user-specific subfield. For each RU assigned for MU-MIMO transmission with K users multiplexed, there are K corresponding user-specific subfields. The ordering of user-specific subfields in the user-specific field <NUM> is compliant with the RU arrangement signalled by the first resource assignment subfield <NUM> and the second resource assignment subfield <NUM>.

According to the present disclosure, one of the user-specific subfields of the user-specific field <NUM> in each of the HE-SIG-B1 <NUM> and the HE-SIG-B2 <NUM> is used to carry per-user allocation information for the center Type I RU <NUM> as illustrated in <FIG>. The user-specific subfield for the center Type I RU shall be located at a predetermined position in the user-specific field <NUM>. For example, the user-specific subfield for the center Type I RU is the last user-specific subfield <NUM> in the user-specific field <NUM>.

According to the present disclosure, the number of the user-specific subfields in the user-specific field <NUM> except the user-specific subfield for the center Type I RU can be derived from the first resource assignment subfield <NUM> and the second resource assignment subfield <NUM> in the common field <NUM>.

In case of CBW = <NUM> or <NUM>+<NUM>, there is a center Type I RU that is located between two adjacent <NUM> subband channels for every <NUM>. As a result, there are two center Type-I RUs in total in case of CBW = <NUM> or <NUM>+<NUM>. In this case, according to the present disclosure, two of the user-specific subfields of the user-specific field <NUM> in each of the HE-SIG-B1 <NUM> and the HE-SIG-B2 <NUM> are used to carry per-user allocation information for the two center Type I RUs, respectively. Each of the two user-specific subfields for the center Type I RUs shall be located at a predetermined position in the user-specific field <NUM>. For example, the user-specific subfield for a first center Type I RU is the last user-specific subfield in the user-specific field <NUM> while the user-specific subfield for a second center Type I RU is the second last user-specific subfield in the user-specific field <NUM>.

<FIG> illustrates a second example format of the HE-SIG-B1 <NUM> or the HE-SIG-B2 <NUM> in <FIG> in case of CBW = <NUM>. The HE-SIG-B <NUM><NUM> or the HE-SIG-B2 <NUM> comprises a common field <NUM> and a user-specific field <NUM>. The common field <NUM> comprises a first resource assignment subfield <NUM>, a second resource assignment subfield <NUM>, a presence of allocation information for center RU subfield <NUM>, a CRC subfield <NUM> and a tail bits subfield. The user-specific field <NUM> comprises a plurality of BCC blocks <NUM>. Each of the BCC blocks <NUM> except the last BCC block <NUM>-N comprises a first user-specific subfield, a second user-specific subfield, a CRC subfield and a tail bits subfield. The last BCC block <NUM>-N may comprise a single user-specific subfield. Each of the user-specific subfields in the user-specific field <NUM> carries per-user allocation information.

The first resource assignment subfield <NUM>, the second resource assignment subfield <NUM> and each of user-specific subfields are defined in the same way as their respective counterparts in <FIG>.

According to the present disclosure, the presence of allocation information for center RU subfield <NUM> in the common field <NUM> is used to indicate whether there is a user-specific subfield for the center Type I RU in the user-specific field <NUM>. If a user-specific subfield for the center Type I RU is present in the user-specific field <NUM>, its position in the user-specific field <NUM> shall be predetermined. For example, the user-specific subfield for the center Type I RU is the last user-specific subfield <NUM> in the user-specific field <NUM>.

According to the present disclosure, the number of user-specific subfields in the user-specific field <NUM> can be derived from the first resource assignment subfield <NUM>, the second resource assignment subfield <NUM> and the presence of allocation information for center RU subfield <NUM> in the common field <NUM>.

Compared with the first example format of the HE-SIG-B1 <NUM> or the HE-SIG-B2 <NUM> as illustrated in <FIG> where the user-specific subfield for the center Type I RU is included in both the HE-SIG-B1 <NUM> and the HE-SIG-B2 <NUM>, the second example format as illustrated in <FIG> enables more flexible arrangement of user-specific subfield for the center Type I RU in the HE-SIG-B1 <NUM> and the HE-SIG-B2 <NUM>. For one example, the user-specific subfield for the center Type I RU may be included in either of the HE-SIG-B1 <NUM> and the HE-SIG-B2 <NUM> for the purpose of keeping load balancing between the HE-SIG-B1 <NUM> and the HE-SIG-B2 <NUM> and improving channel efficiency. In other words, the user-specific subfield for the center Type I RU may be included in either of the HE-SIG-B1 <NUM> and the HE-SIG-B2 <NUM> so that the difference in terms of the number of user-specific subfields between the HE-SIG-B <NUM><NUM> and the HE-SIG-B2 <NUM> is minimized. For another example, the user-specific subfield for the center Type I RU may be included in both of the HE-SIG-B1 <NUM> and the HE-SIG-B2 <NUM> for the purpose of improving reliability for decoding the user-specific subfield for the center Type I RU.

In case of CBW = <NUM> or <NUM>+<NUM>, the presence of allocation information for center RU subfield <NUM> in the common field <NUM> needs to indicate whether there is a user-specific subfield for each of the two center Type I RUs in the user-specific field <NUM>. If the user-specific subfield for only one of the two center Type I RUs is present in the user-specific field <NUM>, its position in the user-specific field <NUM> shall be predetermined. For example, the user-specific subfield for the center Type I RU is the last user-specific subfield in the user-specific field <NUM>. If the user-specific subfield for each of the two center Type I RUs is present in the user-specific field <NUM>, the two user-specific subfields for the center Type I RUs shall be located at the predetermined positions in the user-specific field <NUM>. For example, the user-specific subfield for a first center Type I RU is the last user-specific subfield in the user-specific field <NUM> while the user-specific subfield for a second center Type I RU is the second last user-specific subfield in the user-specific field <NUM>.

<FIG> illustrates a third example format of the HE-SIG-B1 <NUM> or the HE-SIG-B2 <NUM> in <FIG> in case of CBW = <NUM>. The HE-SIG-B1 <NUM> or the HE-SIG-B2 <NUM> comprises a common field <NUM> and a user-specific field <NUM>. The common field <NUM> comprises a first resource assignment subfield <NUM>, a second resource assignment subfield <NUM>, a CRC subfield <NUM> and a tail bits subfield. The user-specific field <NUM> comprises a plurality of BCC blocks <NUM>. Each of BCC blocks <NUM> except the last BCC block <NUM>-N comprises a first user-specific subfield, a second user-specific subfield, a CRC subfield and a tail bits subfield. The last BCC block <NUM>-N may comprise a single user-specific subfield. Each of user-specific subfields in the user-specific field <NUM> carries per-user allocation information.

According to the present disclosure, whether the CRC subfield <NUM> in the common field <NUM> is masked by a predefined binary sequence (i.e., whether a XOR (Exclusive OR) is applied to the CRC subfield <NUM> and a predefined binary sequence) is used to indicate whether there is a user-specific subfield for the center Type I RU in the user-specific field <NUM>. For example, if the CRC subfield <NUM> in the common field <NUM> is not masked with a predefined binary sequence, there is no user-specific subfield for the center Type I RU in the user-specific field <NUM>. Otherwise there is a user-specific subfield for the center Type I RU in the user-specific field <NUM>.

Alternatively, instead of the CRC subfield <NUM> in the common field <NUM>, whether the CRC subfield of a specific BCC block in the user-specific field <NUM> is masked by a predefined binary sequence is used to indicate whether there is a user-specific subfield for the center Type I RU in the user-specific field <NUM>. For example, if the CRC subfield <NUM> of the first BCC block <NUM>-<NUM> is not masked by a predefined binary sequence, there is no user-specific subfield for the center Type I RU in the user-specific field <NUM>. Otherwise there is a user-specific subfield for the center Type I RU in the user-specific field <NUM>.

If a user-specific subfield for the center Type I RU is present in the user-specific field <NUM>, its position in the user-specific field <NUM> shall be predetermined. For example, the user-specific subfield for the center Type I RU is the last user-specific subfield <NUM> in the user-specific field <NUM>.

According to the present disclosure, the number of user-specific subfields in the user-specific field <NUM> except the user-specific subfield for the center Type I RU can be derived from the first resource assignment subfield <NUM> and the second resource assignment subfield <NUM> in the common field <NUM>.

Compared with the second example format of the HE-SIG-B1 <NUM> or the HE-SIG-B2 <NUM> as illustrated in <FIG>, the third example format as illustrated in <FIG> does not need a signaling subfield in the common field to signal the presence of user-specific subfield for the center Type I RU in the user-specific field. In other words, the signaling bits required by the third example format is reduced compared with the second example format.

In case of CBW = <NUM> or <NUM>+<NUM>, whether the CRC subfield <NUM> in the common field <NUM> (or the CRC subfield <NUM> in the user-specific field <NUM>) is masked by one of the three predefined binary sequences is used to indicate whether there is a user-specific subfield for each of the two center Type I RUs in the user-specific field <NUM>. For example, if the CRC subfield <NUM> in the common field <NUM> (or the CRC subfield <NUM> in the user-specific field <NUM>) is not masked by one of three predefined binary sequences, there is no user-specific subfield for the center Type I RU in the user-specific field <NUM>. If the CRC subfield <NUM> in the common field <NUM> (or the CRC subfield <NUM> in the user-specific field <NUM>) is masked by a first predefined binary sequence, there is a user-specific subfield for a first center Type I RU in the user-specific field <NUM>. If the CRC subfield <NUM> in the common field <NUM> (or the CRC subfield <NUM> in the user-specific field <NUM>) is masked by a second predefined binary sequence, there is a user-specific subfield for a second center Type I RU in the user-specific field <NUM>. If the CRC subfield <NUM> in the common field <NUM> (or the CRC subfield <NUM> in the user-specific field <NUM>) is masked by a third predefined binary sequence, there is a user-specific subfield for each of the two center Type I RUs in the user-specific field <NUM>. If the user-specific subfield for only one of the two center Type I RUs is present in the user-specific field <NUM>, its position in the user-specific field <NUM> shall be predetermined. For example, the user-specific subfield for the center Type I RU is the last user-specific subfield in the user-specific field <NUM>. If the user-specific subfield for each of the two center Type I RUs is present in the user-specific field <NUM>, the two user-specific subfields for the center Type I RUs shall be located at the predetermined positions in the user-specific field <NUM>. For example, the user-specific subfield for a first center Type I RU is the last user-specific subfield in the user-specific field <NUM>; while the user-specific subfield for a second center Type I RU is the second last user-specific subfield in the user-specific field <NUM>.

In the foregoing embodiments, the present invention is configured with hardware by way of example, but the invention may also be provided by software in cooperation with hardware.

In addition, the functional blocks used in the descriptions of the embodiments are typically implemented as LSI devices, which are integrated circuits. The functional blocks may be formed as individual chips, or a part or all of the functional blocks may be integrated into a single chip. The term "LSI" is used herein, but the terms "IC," "system LSI," "super LSI" or "ultra LSI" may be used as well depending on the level of integration.

In addition, the circuit integration is not limited to LSI and may be achieved by dedicated circuitry or a general-purpose processor other than an LSI. After fabrication of LSI, a field programmable gate array (FPGA), which is programmable, or a reconfigurable processor which allows reconfiguration of connections and settings of circuit cells in LSI may be used.

Should a circuit integration technology replacing LSI appear as a result of advancements in semiconductor technology or other technologies derived from the technology, the functional blocks could be integrated using such a technology. Another possibility is the application of biotechnology and/or the like.

Claim 1:
A communication apparatus (<NUM>) comprising:
a receiver configured to receive a signal (<NUM>) that contains a legacy preamble (<NUM>), a non-legacy preamble (<NUM>), and a data field (<NUM>),
wherein
- the non-legacy preamble comprises a HE-SIG-A field (<NUM>) and a HE-SIG-B field (<NUM>) indicating assignments of a plurality of resource units, RUs, (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) in a frequency domain;
- the HE-SIG-B field includes a user specific field (<NUM>; <NUM>; <NUM>) including a plurality of user fields (<NUM>-<NUM> to <NUM>-N; <NUM>-<NUM> to <NUM>-N; <NUM>-<NUM> to <NUM>-N); and
- each of the plurality of RUs being allocated to a user field or a group of user fields for multiuser-multiple input multiple output, MU-MIMO, transmission in the plurality of user fields, respectively; and
- the user fields are arranged such that the corresponding RUs are arranged in increasing order of frequency;
circuitry configured to decode at least a part of the data field based on the non-legacy preamble,
characterized in that
the HE-SIG-B field comprises a common field (<NUM>; <NUM>; <NUM>) indicating the assignments of the plurality of RUs.