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Efficient Frame Format for MU Transmission

Efficient Frame Format for MU Transmission. Authors:. Date: 2010-11-08. Abstract. MU-MIMO is a key technique to attain at least 1 Gbps throughput at MAC SAP for Multi-STA.

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Efficient Frame Format for MU Transmission

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  1. Efficient Frame Format for MU Transmission Authors: Date: 2010-11-08

  2. Abstract • MU-MIMO is a key technique to attain at least 1 Gbps throughput at MAC SAP for Multi-STA. • However, the gain of MU-MIMO maybe shrink significantly due to mismatching of the lengths of co-transmission STA’s PSDU. • A sustainable frame format is proposed here to exploit the gain of MU-MIMO against the mismatching problem for co-transmission STAs

  3. The mismatching problem • The gain derived from MU-MIMO in actual scenario not only depends on the composite channel HMU-MIMO=[H1, H2,…Hn], but also on the buffer situation of each co-transmission STA • In 802.111ac, there must exist a mismatching problem for MU-MIMO transmission due to mismatching the lengths of co-transmission STA’s PSDU.

  4. An example for the mismatching problem • Related parameters are assumed here: • PSDU data length of STA1 is 2000 kb • STA1’s transmission rate is 500Mbps by using therefore 4ms is needed for STA1’s PSDU transmission • PSDU data length of STA2 is 800 kb • STA2’s transmission rate is the same as that of STA1, i.e. 500Mbps for SU-MIMO transmission, therefore 1.6ms is needed for STA2’s PSDU transmission • If MU-MIMO is used for STA1 and STA2, and their data rates are assumed identical, equal to 400Mbps, therefore 5ms and 2ms are needed respectively The mismatching problem appear. STA 1 STA1-PSDU STA 2 STA2-PSDU

  5. Transmission schemes for Multi-STA with mismatching lengths of their PSDU • Direct transmission by using SU-MIMO and MU-TXOP for each STA in turn • The transmission duration for the example is 5.6mswithout accounting for the overheads of preamble, SIFS, etc. SIFS header STA1-PSDU header STA2-PSDU

  6. Transmission schemes for Multi-STA with mismatching lengths of their PSDU • Direct transmission utilizing MU-MIMO • The LENGTH field in L-SIG is set according the maximum among the lengths of these multi-STA’s PSDU • The LENGTH field in each STA’s VHT-SIG-B is set according the actual length of the STA’s PSDU • The transmission duration for the example is 5ms

  7. A new frame format for efficient MU-MIMO transmission in 802.11ac • A new frame format with sustainable VHT-segment proposed here: • A series of VHT-segments with the maximum of 4 can be concatenated together to form a whole frame. • Each VHT-segment consists of VHT-SIG-A, VHT-STF, VHT-LTFs, VHT-SIG-B and VHT data • The set of co-transmission STA {STA1, … STAn} should be nested, i.e. set the set of the (i+1)-th segment is a subset of the i-th set

  8. The transmission scheme based on the proposed frame format • The transmission duration for the former example is 4.4ms, therefore a gain of more than 10% can be obtained.

  9. Details on the new frame format • A new frame format with sustainable VHT-segment proposed here: • The LENGTH field in L-SIG is set according to the total length of the whole frame consisted of all VHT-segments

  10. Details on the new frame format (con’t) • A new frame format with sustainable VHT-segment proposed here: • Each STA’s NSTS field in VHT-SIG-A implies whether its PSDU has been ended or not

  11. Details on the new frame format (con’t) • A new frame format with sustainable VHT-segment proposed here: • The length field in VHT-SIG-B of each VHT-segment indicates the actual length of VHT-data in current VHT-segment.

  12. Remarks • Although the transmission scheme based on the proposed frame format is somewhat like MU-TXOP, but it is superior to MU-TXOP due to omitting SIFS, L-STF and L-LTF. • Nevertheless, TXOP/MU-TXOP isn’t substitutable in providing continuous transmission with longer duration.

  13. References • Specification Framework for TGac, IEEE 802.11-09/0992r15, September 2010

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