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A “High Throughput” Partial Proposal

A “High Throughput” Partial Proposal. Patrik Eriksson, Anders Edman, Christian Kark Wavebreaker AB, Norrkoping, Sweden patrik.eriksson@acreo.se

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A “High Throughput” Partial Proposal

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  1. A “High Throughput” Partial Proposal Patrik Eriksson, Anders Edman, Christian Kark Wavebreaker AB,Norrkoping, Sweden patrik.eriksson@acreo.se Scott Leyonhjelm, Mike Faulkner, Melvyn Pereira,Jason Gao, Aaron Reid,Tan Ying,Vasantha Crabb. Australian Telecommunication Co-operative Research Centre, Melbourne, Australia. scott.leyonhjelm@vu.edu.au Patrik Eriksson et. al., WaveBreaker AB

  2. Presentation Outline • Proposal Executive Summary • Proposed Frame Format • Proposed PHY Design • Comparison Criteria • Conclusion Patrik Eriksson et. al., WaveBreaker AB

  3. Proposal Executive Summary • Fully backward compatible with 802.11a/g • All enhancements are simple extensions to 11a/g OFDM structure. • STS and LTS sequences are used in conjunction with progressive cyclic delay per antenna • Higher Data Throughput due to combination of PHY technologies • MIMO-OFDM - Spatial Multiplexing, up to 3 transmit spatial streams (mandatory), 4 spatial streams (optional) • Fast Rate adaptation on a per stream (mandatory) or a per subgroup (optional) level • Higher order modulation - 256QAM (mandatory) • Higher Data Throughput due to combination of MAC enhancements • Frames with NO short and long training sequences (mandatory) • Frame aggregation (mandatory) • Shorter SIFS, down to 8 us. (Optional) • Minimising Hardware Complexity • Frame format designed to increase available time for inverting channel estimate. Patrik Eriksson et. al., WaveBreaker AB

  4. Presentation Outline • Proposal Executive Summary • Proposed Frame Format • Proposed PHY Design • Comparison Criteria • Conclusion Patrik Eriksson et. al., WaveBreaker AB

  5. 802.11a OFDM Frame format STS LTS Sig D1 D2 STS1 LTS1 S2 LTS1a LTS1b LTS1c S3 D1 D2 Dn STS2 LTS2 S2 LTS2a LTS2b LTS2c S3 D1 D2 Dn 802.11n MIMO - Type 1 STS3 LTS3 S2 LTS3a LTS3b LTS3c S3 D1 D2 Dn STS4 LTS4 S2 LTS4a LTS4b LTS4c S3 D1 D2 Dn S3 D1 D2 Dn S3 D1 D2 Dn 802.11n MIMO - Type 2 S3 D1 D2 Dn S3 D1 D2 Dn STS1 LTS1 Sigi D1 D2 Dn D1 STS2 LTS2 Sig D2 Dn 802.11n MIMO - Type 3 D1 STS3 LTS3 Sig D2 Dn STS4 LTS4 Sig D1 D2 Dn LTS4b LTS4c S3 S3 S3 S3 D1 D1 LTS4a D1 D2 S2 D1 LTS3c D2 LTS3b LTS3a S2 LTS2c LTS2b LTS2a S2 LTS1c LTS1b LTS1a S2 D2 D2 Proposed Frame Format 3 new MIMO frame types are proposed: • MIMO - Type 1 frames with Training. • Re-Synchronisation • Note that the STS, LTS and Sig2 sequence can be received by legacy equipment. • S3 is positioned to increase time allowed for calculating and inverting channel estimate • MIMO - Type 2 frames without Training. • Preferred for Data carrying frames • MIMO – Type 3 frames with Training. • RTS/CTS frames in 5GHz band • Note that the STS, LTS and Sig and Data sequence can be received by legacy equipment. • S3 is positioned to increase time allowed for calculating and inverting channel estimate Patrik Eriksson et. al., WaveBreaker AB

  6. STS1 LTS1 Sig D1 D2 Dn D1 STS2 LTS2 Sig D2 Dn D1 STS3 LTS3 Sig D2 Dn STS4 LTS4 Sig D1 D2 Dn LTS4c Sig3 Sig3 Sig3 D2 D2 Sig3 LTS4b D1 D1 LTS4a D2 D2 LTS3c LTS2b D1 D1 Sig2 LTS1a LTS1b LTS1c Sig2 Sig2 LTS2c Sig2 LTS3a LTS3b LTS2a Proposed Frame Format 802.11a compatible MIMO part of frame Type 2 MIMO Frame (DATA) Length field faked Sig symbol MIMO data length R4 – indicates MIMO Extra time for inverting CE • Sig2 Symbol - Specify MIMO transmission Mode • Adaptive Loading Mode • MIMO mode • Indicate if Sig3 and Data symbols are present • Sig3 Symbol – supports MIMO transmission • Reverse link CSI info • Data Rate used in transmission • Data length • Request for retraining Patrik Eriksson et. al., WaveBreaker AB

  7. Example of RTS/CTS frame transfer: SIFS= 8-16us n*4 us AP: Type3 Type2 Type2 Type1 RTS Data Data Training Type3 Type1 STA: ACK ACK CTS Training Time Training required for initially establishing fast rate adaptation Data carrying with no Training sequence Request for Training sequence • Used for • Re-transmission • Re-synchronising during a RTS/CTS transmission, and • Extending the duration of thetransmission (CTS to self) Updated rate information Proposed Frame Format Patrik Eriksson et. al., WaveBreaker AB

  8. Proposed Frame Format • Proposed frame format compared to 802.11a • MAC Efficiency 61% vs 47% • PSDU Size = 1.5kbyte • Frame Aggregation • 9kbyte PSDU size • MAC efficiency >80% Patrik Eriksson et. al., WaveBreaker AB

  9. Proposed Frame Format To Achieve Goodput of >100Mbps for PER 10%, PHY average rate =144Mbps • Single Frame Transmission Mode • PSDU Size = 5kbyte packet • RTS/CTS Transmission Mode • Packet Size > 2kbyte • Transmission Length = 10kbyte • Frame Aggregation • Increases MAC efficiency • Proposed max. PSDU 16kbyte Patrik Eriksson et. al., WaveBreaker AB

  10. Proposed Frame Format Implementation Details of the Frame Format proposal • Channel Models in 802.11n are slowly moving (low Doppler) • Channel sufficiently stable for at least 50 symbols (MSE <-35dB) • Channel F with 40kph Doppler Component • Type 2 packets have NO training sequences • Initial STS/LTS sets up Timing grid • Transmissions start at 4us intervals • Receiver uses fast power detection algorithms to determine if packet (sig3 symbol) is present or not • Frequency offset and sampling time offsets must flywheel over non-transmission periods • Implementation Requirements • Time, frequency offsets tracked via 4 pilots • Channel Tracking Patrik Eriksson et. al., WaveBreaker AB

  11. Presentation Outline • Proposal Executive Summary • Proposed Frame Format • Proposed PHY Design • Comparison Criteria • Conclusion Patrik Eriksson et. al., WaveBreaker AB

  12. Demux Encode Punct Inter. Map Mux FFT CP Mux Cyclic Delay Encode Punct Inter. Map FFT CP Cyclic Delay Data Bits Scramble To DACs Encode Inter. Map FFT CP Cyclic Delay Punct Encode Punct Inter. Map FFT CP Cyclic Delay Adaptive Loading Info from Sig3 Symbol ‘CSI’ field Pilots STS and LTS Preambles Proposed PHY Design Parallel Spatial Multiplexing Architecture • Scalable architecture - supports up to 3 (mandatory) or 4 (optional) antennas • The mapping function expanded to include 256QAM • Cyclic Delay is implemented with a progressive 1 sample delay /per antenna • Fast Rate Adaptation Patrik Eriksson et. al., WaveBreaker AB

  13. Proposed PHY Design Fast Rate Adaptation Concept => Higher Average Data Throughput • Based on Closed loop feedback of CSI transported by ACK frame • Optimises Data rate to channel condition on a per packet basis • Low implementation cost vs High performance gain • Small impact on MAC efficiency • 4 bits per spatial stream • Overcomes spatial multiplexing singularity in LOS conditions • Naturally falls back to transmission of a single stream Patrik Eriksson et. al., WaveBreaker AB

  14. Forward Link Punct/ Map Channel Estimation Data Bits Data Bits Tx Rx SNR (Link Margin/layer) Calculate Maximum Rate Possible on a per layer basis Reverse Link Decode Sig3 Symbol ‘Rev CSI’ field Encode Sig3 Symbol ‘Rev CSI’ field Proposed PHY Design • Rate Adaptation Concept • The STA determines the maximum rate per layer (mandatory) or subgroup of carriers (optional) and this is communicated back to the AP, and vice-versa. • Adaptive rate can vary from 0Mbit/s through to 72Mbits/s on a per layer basis. • Fast Adaptation handled at PHY layer, reported to MAC Patrik Eriksson et. al., WaveBreaker AB

  15. STS STS STS LTS LTS LTS LTS*exp (jp/3) LTS*exp (j2p/3) LTS LTS*exp (j2p/3) LTS*exp (jp/3) LTS Proposed PHY Design • Short Training Sequences • 802.11a STS transmitted on each stream • Cyclic delay ensures good performance characteristics for AGC function • Long Training Sequences • Based on current LTS definitions • Orthogonality between TX antennas achieved via Cyclic Delay and ‘Phase Loading’ • Channel Estimation achieved by combining received LTS’s TX1 TX2 TX3 Patrik Eriksson et. al., WaveBreaker AB

  16. Proposed PHY Design • For >100 Mbps Goodput @ 10m: 3 data streams required • For >3*3 MIMO : Channel estimation and equalisation begins to dominate • Analog increases slightly less than linear due to reuse of functions Patrik Eriksson et. al., WaveBreaker AB

  17. Presentation Outline • Proposal Executive Summary • Proposed Frame Format • Proposed PHY Design • Comparison Criteria • Conclusion Patrik Eriksson et. al., WaveBreaker AB

  18. Comparison Criteria –CC58 • RTS/CTS frame transmission mode achieves a goodput of more than 100Mbps, • The single frame transmission mode achieves a maximum goodput of 80Mbps when the average PHY data rate is 288Mbps !. To get >100Mbps • With frame aggregation a 5.5kbyte packet size transmitted at a average PHY data rate of 144Mbps • With channel bonding (optional) the average PHY data rate is increased by a factor 1.8 Just! with no impairments Patrik Eriksson et. al., WaveBreaker AB

  19. Comparison Criteria • CC59 –AWGN Channel • Observation : the capacity is a linear function of the number of transmit data streams. Patrik Eriksson et. al., WaveBreaker AB

  20. Comparison criteria • CC80- The modifications required for a legacy 802.11 PHY are; • The scalable architecture supports up to 3 (mandatory) or 4 (optional) antennas • Rate adaptation modifies the puncturing and Constellation Mapping on a stream basis, • Include 256 QAM • Cyclic Delay implemented with a progressive 1 sample delay /per antenna • The LTS preambles are modified versions of the 802.11a/g defined sequences Patrik Eriksson et. al., WaveBreaker AB

  21. Presentation Outline • Proposal Executive Summary • Proposed Frame Format • Proposed PHY Design • Comparison Criteria • Conclusion Patrik Eriksson et. al., WaveBreaker AB

  22. Conclusion – Key Features • Higher Data Throughput due to combination of PHY technologies • MIMO-OFDM – 1 to 3 data streams using Spatial Multiplexing • Rate Adaptation • Higher order modulation – 256QAM • Higher Data Throughput due to combination of MAC enhancements • Frames with NO training sequences • Frame aggregation – up to 16kbytes/packet Patrik Eriksson et. al., WaveBreaker AB

  23. Conclusion • Backward Compatibility is ensured by • Operation within a 20MHz bandwidth with the same 802.11a/g spectral mask. • Single and RTS/CTS frame transmission modes are fully compatible with legacy 802.11a/g devices. • All Low Functional Requirements are met • Low Overhead Frame formats to increase MAC efficiency • 100Mbps Goodput @ 10m achieved when • 20MHz and >=3 transmit data streams • > 144Mbps Average PHY data rate • With Rate Adaptation! Patrik Eriksson et. al., WaveBreaker AB

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