System and method for spatial stream allocation in UL OFDMA

A method for establishing an uplink transmission. A recipient station receives a trigger frame. The trigger frame including at least one per user info field. Each of the at least one per user info field comprising at least a user identifier field identifying a STA to be allocated a resource unit, a resource unit allocation field for allocating a resource unit for the identified STA, and a spatial stream allocation field identifying a number of streams to be allocated for the identified STA. The recipient STA evaluating an order of the at least one per user info fields to determine a sequence of the allocated streams that matches the order of the at least one per user info fields. The recipient STA comparing the values from each of the resource unit allocation fields and grouping corresponding at least one per user info fields with matching values to identify members of a set STAs allocated to MU-MIMO. In some aspects, the spatial stream allocation field of the per user info fields comprises three bits.

FIELD OF THE INVENTION

The present invention pertains to the field of communication networks and in particular to a system and method for stations (STAs) to communicate over a communication network. In an aspect the present invention more particularly relates to a system and method for allocating streams for an uplink communication service period.

BACKGROUND

In communication networks, and in particular wireless communication networks, coordination is required between communicating devices. The coordination is managed by a network controller which sets the parameters for each device to use to avoid communication collisions or cross-talk.

In a downlink (DL) transmission the access point (AP) is both the data originator and network controller. Accordingly, the AP has control over the communication as it is both the controller and the point of transmission to listening STAs.

In an uplink (UL) transmission, however, the AP only acts as the network controller and the STAs are the data originators. In order to coordinate the STAs transmissions, the IEEE 802.11ax draft standard proposes that the AP may exercise UL control via the use of trigger frames that are sent to STAs. Upon receipt, each STA may process a received trigger frame to obtain the communication protocol to be followed. That STA may then apply the protocol when transmitting data to the AP, or in some cases to other STAs.

SUMMARY OF THE INVENTION

With the development of next generation wireless local-area networks (WLAN), there is additional flexibility in handling the identity of connected devices, as well as for providing new modes of connectivity for non-connected devices.

In accordance with an aspect of the present invention, there is provided a network for exchanging data over a communication network.

DETAILED DESCRIPTION OF THE INVENTION

The present application relates to a system and method for providing connectivity to a network. In particular, the present application relates to a system and method for triggering a connectivity service period and to allocate resources for that service period. In further particularity, the present application relates to a system and method for specifying a spatial stream allocation

The present application relates to a mechanism for a sender, or “Access Point (AP)”, to efficiently communicate to a recipient device (recipient STA) a protocol for conducting an uplink communication. In particular, the present application relates to a mechanism for an AP to efficiently select between a Single User Multiple Input Multiple Output (SU-MIMO) channel and a Multiple User Multiple Input Multiple Output (MU-MIMO) channel and in both cases to indicate a number of streams for each user. In the case of the MU-MIMO channel, the AP is further able to indicate a sequence of streams to the recipient STA in order to establish the uplink channel efficiently.

As would be readily appreciated by a worker skilled in the art, the present mechanism for communicating a protocol for conducting an uplink communication is suitable for SU/MU-MIMO scheduled on top of Orthogonal Frequency-Division Multiple Access (OFDMA) scheduling. For example, MU-MIMO may be scheduled on top of OFDMA scheduling, and both MU-MIMO and OFDMA require a protocol for conducting the uplink communication, irrespective of whether they are scheduled together or alone.

In a typical implementation each of the AP and the recipient STA comprise computing devices having at least one processor and memory. The at least one processor and memory operative to execute program code for generating the frame and fields described below. The AP further including a transmitter for transmitting the frame to the recipient STA. Each recipient STA further including a receiver for receiving the transmitted frame. The recipient STAs operative to process the received frame in order to identify parameters of the uplink transmission triggered by the AP.

FIG. 1illustrates a trigger frame100in a format as currently defined in the draft IEEE 802.11ax standard. The trigger frame100is used to allocate resources for uplink (UL) multiuser (MU) transmission, and to solicit an UL MU transmission at a specified interframe spacing (IFS) after the physical layer protocol data unit (PPDU) that carries the trigger frame100, as well as other information required for a responding device to send an UL MU transmission.

The trigger frame100is generated by an AP and transmitted to a recipient STA. The recipient STA reading the trigger frame100to determine a type of transmission (SU or MU-MIMO), and if a MU-MIMO transmission, an identity of the users as well as an order of their streams in the transmission, among other information required for the communication.

Multiple User (MU) transmission includes both OFDMA and/or MU-MIMO. Single User (SU) transmission is not limited to SU-MIMO, but rather, it means the transmission is only targeted to one user. One user UL transmission, that is, UL-SU transmission, does not require a trigger frame because it is targeted for only one recipient, however, sending a trigger frame can be beneficial with UL-SU with one RU allocation.

As indicated, the trigger frame100currently includes a number of defined fields, as well as a number of fields that remain to be defined. Additional fields not currently illustrated may also be included when the format is finalised. The current trigger frame100includes a frame control field105, a duration field110, a Receiver Address (RA) field115, a Transmitter Address (TA) field120, a common info field125, a plurality of per user info fields130(one for each user), a padding field135, and a Frame Check Sequence (FCS) field140.

FIG. 2illustrates an embodiment of a format for the per user info fields130indicated inFIG. 1, as currently defined in the IEEE 802.11ax standard. The per user info fields130ofFIG. 2each include a user identifier field205, a Resource Unit (RU) allocation field210, a coding type field215, a Modulation and Coding Set (MCS) field220, a Dual Carrier Modulation (DCM) field225, a Spatial Stream (SS) allocation field230, and a trigger dependent per user info field235.

The user identifier field205indicates the association identifier (AID) of the STA to be allocated an RU in the current per user info field130. The RU allocation field210indicates the RU(s) allocated to the STA identified in the user identifier field205.

The SS allocation field230is intended to indicate the spatial streams of the High Efficiency (HE) trigger-based PPDU response of the STA identified by the user identifier field205in that per user info field130. It has been proposed that the SS allocation field230represent the number of allocated streams for both the SU-MIMO case as well as the MU-MIMO case. In the case of MU-MIMO, the SS allocation field230will further indicate the order of the streams. The format of the SS allocation field230has not yet been further defined by the IEEE 802.11ax standard.

The present application proposes a format for the SS allocation field230included in each per user info field130. In a first aspect, the present application provides for the SS allocation field230having a constant size such that the number of bits in the SS allocation field230is equal for both a SU-MIMO allocation and for a MU-MIMO allocation. A constant size for the SS allocation field230conveniently provides a constant byte length for the per user info field130regardless of whether the SS allocation field230is indicating a SU-MIMO or MU-MIMO allocation.

In a second aspect, the maximum number of streams to allocate per STA for SU-MIMO is 8 streams. The maximum number of allocated streams per STA for MU-MIMO is 4 streams. Thus, a minimum number of required bits to indicate the number of allocated streams for SU-MIMO is 3 bits and for MU-MIMO is 2 bits. Referring toFIG. 3, in an implementation, the first and second aspect may be combined, and a constant 3 bits may be assigned to the SS allocation field230. This arrangement allows for constant size per user info fields130, with only minimal additional space for the redundant extra bit in the case of MU-MIMO.

In a third aspect, there is a need to identify whether the STA identified in the user identifier field205is to be allocated as an SU-MIMO or MU-MIMO. One option would be to allocate additional bits in the SS allocation field230to indicate whether the STA identified in the user identifier field205is to be allocated as a SU-MIMO or MU-MIMO. The present application provides for eliminating the need to assign designated bits to identity SU-MIMO or MU-MIMO. Instead, the recipient STA may determine the allocation by evaluating the RU allocation field210for all of the per user info fields130. The recipient STA may group STA(s) based upon the indicated RU in the RU allocation field210. Where more than one STA is allocated to the same RU, then all of the STA(s) with the common RU belong to a group of MU-MIMO STAs, and the recipient STA may flag or identify their corresponding per user info fields130as being allocated to MU-MIMO scheduling. Where an STA has a unique RU (or a unique set of RU depending upon the case) allocated to it by the RU allocation field210, then that recipient STA may flag or identify that STA as being allocated to SU-MIMO scheduling.

In a fourth aspect, as indicated above the SS allocation field230is intended to indicate the spatial streams of the High Efficiency (HE) trigger-based PPDU response of the STA identified by the user identifier field205in that per user info field130. In the case of MU-MIMO, an order of the streams for scheduling also needs to be indicated. In order to minimize a length of the SS allocation field230, and accordingly each of the per user info fields130making up the trigger frame100, the present application provides for not including this information in the SS allocation field230. Instead, the present application proposes indicating the stream ordering by a sequence order of the per user info fields130having the same RU in the RU Allocation field210within the trigger frame100. Accordingly, a recipient STA may determine its own position in the sequence of the allocated streams by evaluating the trigger frame100and in particular the recipient STA's position within the relative order of the user identifier fields205in the per user info fields130having the same RU in the RU Allocation field210within the trigger frame100. Conforming the stream order with the order of the per user info fields130within the trigger frame obviates the need for assigning extra bits to indicate the order of the streams for MU-MIMO. This conforming is further advantageous as the trigger frame100is intended to be used for both SU-MIMO and MU-MIMO communications. Eliminating the need for assigning extra bits that are only relevant MU-MIMO avoids the inefficiency of allocating additional bits that are irrelevant for SU-MIMO communication.

FIG. 4illustrates a trigger frame400in a format as currently defined in the draft IEEE 802.11ax standard. As described above trigger frame400is used to allocate resources for uplink (UL) multiuser (MU) transmission, and to solicit an UL MU transmission at a specified interframe spacing (IFS) after the physical layer protocol data unit (PPDU) that carries the trigger frame400, as well as other information required for a responding device to send an UL MU transmission.

As also described above in relation toFIG. 1, the trigger frame400is generated by an AP and transmitted to a recipient STA. The recipient STA reading the trigger frame400to determine a type of transmission (SU or MU-MIMO), and if a MU-MIMO transmission, an identity of the users as well as an order of their streams in the transmission, among other information required for the communication.

As illustrated inFIG. 4, the trigger frame400currently includes a number of defined fields. Additional fields not currently illustrated may also be included when the format is finalised. The current trigger frame400includes a frame control field405, a duration field410, a Receiver Address (RA) field415, a Transmitter Address (TA) field420, a common info field425, a plurality of per user info fields430(one for each user), a padding field435, and a Frame Check Sequence (FCS) field440.

FIG. 5illustrates an embodiment of a format for each per user info field430, as currently defined in the IEEE 802.11ax standard. The per user info fields430ofFIG. 4each include a AID12 field505(which is an example of an user identifier field), a Resource Unit (RU) allocation field510, a coding type field515, a Modulation and Coding Set (MCS) field520, a Dual Carrier Modulation (DCM) field525, a Spatial Stream (SS) allocation field530, a target Received Signal Strength Indication (RSSI) field540(which represents the strength of the received signal), a reserved field545and a trigger dependent per user info field535. As illustrated inFIG. 4, in this embodiment, bits have been assigned to the fields within each per user info field130, with the SS allocation field530being assigned 6 bits. In this embodiment, the first 3 bits of the 6 bit SS allocation represents the number of streams and remaining three bits represents the beginning stream. For example, the STA corresponding to the AID12 field is scheduled with 2 streams indicated by the first 3 bits, and the beginning stream is the third stream indicated by the remaining three bits, then the STA of the AID12 field is scheduled over the third and fourth streams. However, as described above, one aspect of the present application is to reduce the SS allocation to a constant 3 bits, which allows for a constant size per user info fields130. Accordingly, in one embodiment, and redefining the currently defined IEEE 802.11 ax standard, SS field530of the info field430depicted inFIG. 5, is assigned 3 bits.