The present invention relates generally to data communication, and more particularly, to data communication in wireless local area networks (WLAN).
In IEEE 802.11n development process, a Multi-MCS-Multi-Receiver Aggregation (MMRA) mechanism has been proposed to increase the wireless LAN (WLAN) efficiency.
Conventionally, MMRA and Single-MCS-Multi-Receiver Aggregation (SMRA) are treated as two independent communications mechanisms. Conventional solutions require at least two bits in the HT-SIG field of the PLCP Protocol Data Unit (PPDU) format to indicate the SMRA or MMRA. However, the HT-SIG field is running out of bits. Thus, there is a need for a method to unify SMRA and MMRA to save a bit from indicating SMRA and MMRA.
In one embodiment, the present invention provides a method to unify SMRA and MMRA to save a bit from indicating SMRA and MMRA.
As such, according to one embodiment of the present invention, in a method of communicating data over a wireless local area network according to a developing IEEE 802.11n standard for unifying Multi-MCS-Multi-Receiver Aggregation (MMRA) and Single-MCS-Multi-Receiver Aggregation (SMRA), the improvement comprises modifying SMRA format such that MMRA treats SMRA as a special case of MMRA, thereby unifying SMRA and MMRA.
The modification method further includes the steps of providing a modified PPDU format with MMRA signaling wherein in the modified PPDU format, HT-SIG-MMRA is placed at the end of HT-LTF, whereby the original HT-SIG format described in S.A. Mujtaba, “TGn Sync Proposal Technical Specification,” a contribution to IEEE.802.11, 11-04-889r1, November 2004, (incorporated herein by reference) is preserved while accommodating the variable length of HT-SIG-MMRA.
The modification step further includes the steps of using AGGRAGATION bit in HT-SIG such that it is used to indicate MRA, whether or not the operation is SMRA or MMRA. In addition, SMRA is moved from MAC layer to PHY layer, placed in the HT-SIG-MMRA Part, whereby SMRA is treated as a special case of MMRA which is a MMRA with only one Modulation and Coding Set, MCS, set.
These and other features, aspects and advantages of the present invention will become understood with reference to the following description, appended claims and accompanying figures.
In one embodiment, the present invention provides a method to unify SMRA and MMRA to save a bit from indicating SMRA and MMRA.
Initial 802.11 stations typically send frames in the order they are received. For throughput purposes, it is highly desirable to reorder frames so that they can coalesce into larger aggregated frames. Aggregation in TGnSync is a MAC-layer function that bundles several MAC frames into a single PLCP (Physical Layer Convergence Protocol) frame for transmission.
A single physical-layer frame contains several MAC layer frames. Several MAC frames are put into the same PLCP frame, with an appropriate delimiter between them. The delimiter has a small reserved field, a length field for the following MAC frame, a CRC to protect the delimiter, and a unique pattern to assist in recovering individual frames from the aggregate. MAC frames are put into the aggregate without modification, and contain the full header and MAC CRC. Even if one frame out of an aggregate is lost, it may be possible to successfully receive all the remaining frames.
However, the benefits of aggregation in TGnSync are not confined to pairs. Single-receiver aggregation is required; an optional extension allows aggregate frames to contain MAC frames for multiple receivers, in which case they are called Multiple Receiver Aggregate (MRA) frames. To distinguish multiple receiver aggregate frames from single-receiver aggregate frames, multiple-receiver frames start with a control item called the Multiple Receiver Aggregate Descriptor (MRAD). The initiator's aggregate frame starts with the aggregate descriptor, and is followed by the aggregated packets for each destination. (802.11 Wireless Networks: The Definitive Guide, Second Edition”, by Matthew Gast, Second Edition, Ch. 15, April 2005 ISBN: 0-596-10052-3).
In one embodiment, the present invention provides a method to unify SMRA and MMRA to save a bit from indicating SMRA and MMRA. In one example, changes in the conventional SMRA mechanism allow MMRA to treat SMRA as a special case of MMRA, thereby unifying SMRA and MMRA. In IEEE 802.11n development process, a Multi-MCS-Multi-Receiver Aggregation (MMRA) mechanism has been proposed to increase the wireless LAN (WLAN) efficiency, as described in the TGnSync Technical Proposal in the attached Appendix.
As noted, conventionally, MMRA and Single-MCS-Multi-Receiver Aggregation (SMRA) are treated as two independent communications mechanisms. SMRA provides Single Rate and Multiple Receiver Aggregation, while MMRA provides Multiple Receiver and Multiple Rate Aggregation. SMRA transmission format 100 is shown in
A conventional MMRA format 300 is illustrated in
Comparing the structure of HT-SIG-MMRA part and the MRAD in SMRA, it is observed that they are almost the same except that MRAD has an additional MAC header. If the SMRA format is moved to PHY layer, the MAC header is not necessary. As such, the present invention provides a format to unify the SMRA and MMRA mechanism. By unifying the SMRA and MMRA, one bit is saved for MMRA and SMRA indication in PHY layer of HT-SIG field.
In one implementation, an improved PPDU format 500 is utilized wherein the HT-SIG-MMRA 302 is placed to the end of HT-LTF 304, as shown in
In this way, the original HT-SIG format 301 (described in S.A. Mujtaba, “TGn Sync Proposal Technical Specification,” a contribution to IEEE.802.11, 11-04-889r1, November 2004, incorporated herein by reference) is maintained while accommodating the variable length of HT-SIG-MMRA 302.
Further, referring to the HT-SIG structure 600 in
In addition, the conventional SMRA format is changed to move it from MAC layer to PHY layer, where the SMRA 306 is placed in the HT-SIG-MMRA Part 302 as shown in
The present invention has been described in considerable detail with reference to certain preferred versions thereof; however, other versions are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained herein.