Analysis of IEEE 802.11 Transmission Overheads
Delve into a detailed analysis of transmission overheads in IEEE 802.11 networks, focusing on downlink simultaneous transmissions. Explore comparisons between various technologies such as OFDMA and DL MU-MIMO, including aspects like adaptive user selection and signaling overhead efficiency. Gain insights into small packet throughput considerations and the impact on different transmission scenarios.
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November 2014 doc.: IEEE 802.11-14/1436r0 Overhead Analysis for Simultaneous Downlink Transmissions Date: 2014-11-01 Authors: Name Hanqing Lou Affiliations Address 2 Huntington Quadrangle; 4th Floor, South Wing; Melville, NY, USA; 11747 Phone email Pengfei Xia Interdigital Communications Joseph Levy Submission Slide 1 Interdigital Communications
November 2014 doc.: IEEE 802.11-14/1436r0 Abstract Downlink simultaneous transmissions is an important candidate technology in IEEE 802.11ax. Continuing our analysis in 1186r2, we perform a comparison of transmission overhead for downlink OFDMA, and DL MU-MIMO employing adaptive user selection and simultaneous ACK. We also perform a comparison of simultaneous ACK and staggered ACK signaling overhead for downlink OFDMA. Submission Slide 2 Interdigital Communications
September 2014 doc.: IEEE 802.11-14/1436r0 Comparison Methodology Link level PER simulation results MU-MIMO: ZF transmit beamforming per subcarrier OFDMA/SU: Single user transmit beamforming per subcarrier PER curve (Nt x Nr x Nu): 4 x 1 x 1 (single user transmit beamforming), 4 x 1 x 2, 4 x 1 x 3, 4 x 1 x 4 (zero forcing transmit beamforming) Sum throughput comparison For each SNR point, consider the maximum sum throughput (per user throughput x number of users) satisfying PER<=1% Determine the TXOP duration by taking into account the MCS, as well as signaling overhead: BA, BAR, SIFS, DIFS, ACK, backoff, etc. Fixed packet size and same varying SNR for all users Submission Slide 3 Interdigital Communications
September 2014 doc.: IEEE 802.11-14/1436r0 Analysis Parameters Four transmit antennas (AP), one receive antenna (STA) Control frame: MCS 0; Data frame: MCS 0~8 adaptive AMPDU aggregation: no; MSDU size: 36/1508 bytes [6] Number of simul. users: SU (1), OFDMA (4), MU-MIMO (1 ~ 4) MU-MIMO/SU Bandwidth: 20 MHz ( 52 data tones) OFDMA Bandwidth: 20 MHz total, 5 MHz (13 data tones) each user OFDMA/MU-MIMO: simultaneous ACK MU-MIMO: no impairments other than channel estimation noise, ideal user adaptation, no training/feedback overhead Parameter BA (bytes) BAR (bytes) ACK (bytes) Value 32 24 14 Parameter DIFS ( s) SIFS ( s) Avg backoff ( s) Value 34 16 27 Submission Slide 4 Interdigital Communications
November 2014 doc.: IEEE 802.11-14/1436r0 Small Packet Throughput Analysis OFDMA is suitable for small packet size transmissions MU-MIMO is highly penalized due to large signaling overhead Submission Slide 5 Interdigital Communications
November 2014 doc.: IEEE 802.11-14/1436r0 Large Packet Throughput Analysis MU-MIMO may provide certain gains More sensitive to channel impairments and user adaptation algo OFDMA may be combined with open-loop/closed-loop SU/MU-MIMO Submission Slide 6 Interdigital Communications
November 2014 doc.: IEEE 802.11-14/1436r0 Different ACK Options Staggered ACK Also known as channel based ACK [9] Same as that for DL MU-MIMO in 802.11ac Baseline ACK scheme Data PPDU (AP -> STA 1) Block ACK Request PPDU (AP -> STA 2) Block ACK Request PPDU (AP -> STA 3) Block ACK Request PPDU (AP -> STA 4) Block ACK PPDU (STA1-> AP) Block ACK PPDU (STA2-> AP) Block ACK PPDU (STA3-> AP) Block ACK PPDU (STA4-> AP) Data PPDU (AP -> STA 2) Data PPDU (AP -> STA 3) Data PPDU (AP -> STA 4) Simultaneous ACK Also known as subchannel based ACK [9] Multiple ACK transmitted simultaneously in the freq domain Each ACK occupies the same channel resource block as the data BlockACK STA1-> AP Data PPDU (AP -> STA 1) BlockACK STA2-> AP Data PPDU (AP -> STA 2) BlockACK STA3-> AP Data PPDU (AP -> STA 3) BlockACK STA4-> AP Data PPDU (AP -> STA 4) Interdigital Communications Submission Slide 7
November 2014 doc.: IEEE 802.11-14/1436r0 ACK Overhead Analysis for DL OFDMA Scheme ( 4 users) Staggered ACK Simultaneous ACK Overhead 648 s 128 s Significant throughput enhancement from simultaneous ACK Similarly, simultaneous ACK may be considered for DL MU-MIMO Submission Slide 8 Interdigital Communications
November 2014 doc.: IEEE 802.11-14/1436r0 Conclusion DL MU-MIMO Suitable for large packets and high SNR May suffer from a large feedback overhead DL OFDMA Potential efficiency improvement over single user transmissions Suitable for small packet transmissions ACK Simultaneous ACK may reduce overhead and improve the throughput substantially Submission Slide 9 Interdigital Communications
November 2014 doc.: IEEE 802.11-14/1436r0 References 1. 2. 3. 4. 5. IEEE 802.11-14/0839r1, Discussion on OFDMA in IEEE 802.11ax, Jinsoo Ahn, July 2014. IEEE 802.11-13/1382r0, Discussion on OFDMA in HEW, Jinsoo Choi et. al., November 2013. IEEE 802.11-14/0804r1, Envisioning 11ax PHY Structure - Part I, Jinsoo Choi et. al., July 2014. IEEE 802.11-14/0801r0, Envisioning 11ax PHY Structure - Part II, Jinsoo Choi et. al., July 2014. IEEE 802.11-13/1395r2, Simultaneous Transmission Technologies for HEW, Koichi Ishihara et. al., November 2013. IEEE 802.11-14/0571r3, Evaluation Methodology, Ron Porat et. al., July 2014. G. Bianchi, Performance analysis of the IEEE 802.11 distributed coordination function, IEEE JSAC, vol. 18, no. 3, August 2000. IEEE 802.11-14/0980r2, Simulation Scenarios, Simone Merlin et. al., July 2014. IEEE 802.11-14/1211r0, ACK procedure for OFDMA, Yongho Seok et. al., September 2014. IEEE 802.11-12/0103r0, Sequence detection for parallel ACK, T. Kim et. al., Jan. 2012. IEEE 802.11-14/1186r2, Comparisons of Simultaneous Downlink Transmissions, P. Xia et. al., Sept. 2014. 6. 7. 8. 9. 10. 11. Submission Slide 10 Pengfei Xia, Interdigital Communications
