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Hervé Bonneville, Bruno Jechoux, Romain Rollet

MITMOT “ Mac and mImo Techniques for MOre Throughput” alliance proposal presentation in response to IEEE802.11n CFP. Hervé Bonneville, Bruno Jechoux, Romain Rollet Mitsubishi ITE 1, allee de Beaulieu, 35700 Rennes, France e-Mail: {bonneville,jechoux,rollet}@tcl.ite.mee.com

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Hervé Bonneville, Bruno Jechoux, Romain Rollet

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  1. MITMOT“Mac and mImo Techniques for MOre Throughput” alliance proposal presentationin response to IEEE802.11n CFP • Hervé Bonneville, Bruno Jechoux, Romain Rollet • Mitsubishi ITE1, allee de Beaulieu, 35700 Rennes, Francee-Mail: {bonneville,jechoux,rollet}@tcl.ite.mee.com Markus Muck, Marc de Courville, Jean-Noël Patillon, Stéphanie Rouquette-Léveil, Alexandre Ribeiro Dias, Karine Gosse, Brian Classon, Keith Blankenship Motorola Labs Parc les Algorithmes – Saint Aubin – 91193 Gif sur Yvette Cedex - France1301 E. Algonquin Rd, Schaumburg, IL 60196, USA e-Mail: {muck,courvill,patillon}@crm.mot.com,Brian.Classon@motorola.com Jechoux,Patillon Mitsubishi/Motorola

  2. Guide to MITMOT Proposal The complete proposal consists of the following four documents: • 11-04-1370-01-000n-mitmot-tgn-complete-proposal-response • Response to functional requirements, comparison criteria table. Includes also a technical overview • 11-04-1372-02-000n-mitmot-tgn-complete-proposal-detailed-description • Detailed technical description of the proposal • 11-04-1369-03-000n-mitmot-tgn-complete-proposal-presentation • This document • 11-04-1371-00-000n-mitmot-tgn-complete-proposal-sim-results • Detailed system simulation results (Excel spread sheet) • 11-04-1446-00-000n-mitmot-tgn-complete-proposal-short-presentation • Short overview presentation of the proposal Jechoux,Patillon Mitsubishi/Motorola

  3. Overall goal and positioning • Preserve compatibility with legacy IEEE802.11 system • Evolution: expand current WLAN application domain, offer a consistent solution to • Provide required QoS to support consumer electronics (multimedia home environment and VoIP enterprise) • Grant range extension for limited outdoor operation (hotspot) as well as full home coverage • Support heterogeneous traffic: increase overall peak data rate without jeopardizing lower data rates modes • Manage diversity (laptop/PDA/VoIP Phone) and evolution (independent STA/AP antenna configuration upgrade) of devices through asymmetric antenna configurations • Proven and simple solution: combine a highly efficient contention-free based MAC with robust yet low complexity open-loop MIMO PHY techniques Jechoux,Patillon Mitsubishi/Motorola

  4. .11n MAC: an evolutionary approach • Solutions: • Centralised on demand resource allocation with grouped resource announcements, • embedded in .11e superframe • providing contention free access for all type of .11n traffics • Aggregated PHY bursts made of short fixed size MAC-PDUs • 1 or multiple destinations and/or PHY modes • Enhanced ACK: low latency and low overhead selective retransmission • Benefits: • Actual QoS: guaranteed throughput, stringent delay constraints support • even in heavily loaded system • High efficiency and scalable architecture • Scenario SS16 (point to point): 86% - Extended SS6 (Hotspot): 67% • constant overhead when data rate increases • Efficient for heterogeneous traffics (bursty, VBR, CBR, high or low data rates) • without parameter tuning • Easy implementation, low power consumption Jechoux,Patillon Mitsubishi/Motorola

  5. .11n PHY: a robust extension to MIMO • Goal: define new OFDM MIMO modes with the constraints to • handle asymmetric TX/RX antenna configurations with 1, 2 or 3 parallel streams • focus on open-loop for stability, avoiding calibration circuit or feedback signalling • Solution: exploit a hybrid combination of • Spatial Division Multiplexing (SDM) to increase spectrum efficiency and peak data rates • classical Space Time Block Coding (STBC) to improve link robustness or range for low to medium data rates (suited to small packet size e.g. VoIP) • Additional key features: • mandatory: 20MHz bandwidth, minimum of 2Tx antennas (up to 4Tx) • new two stage space and frequency interleaver design • Forward Error Correction scheme: • supports all .11a CC rates, adds low redundancy 5/6 (mandatory) • advanced optional scheme: binary turbo code derived from 3GPP • second 20MHz/128 carriers OFDM modulation (8% rate increase), with double duration guard interval (Hotspot: limited outdoor) • optional high rate 40MHz bandwidth/128 carriers modes (117% rate gain) • new nPLCP preambles: code overlay STS/orthogonal LTS Jechoux,Patillon Mitsubishi/Motorola

  6. Typical system performances • All QoS flows satisfied • Scenario XVI: Use the most efficient PHY mode (3x3 256QAM3/4, Ns=3) (*) bis stands for: “with fully backlogged TCP sources” Jechoux,Patillon Mitsubishi/Motorola

  7. PHY description and link performance Jechoux,Patillon Mitsubishi/Motorola

  8. PHY presentation outline The MitMot PHY layer proposal consists in an extension of IEEE802.11a PHY including several key new features: • 20MHz (mandatory), 40MHz (optional) bandwidth • Optional second OFDM modulation using 104 data subcarriers among 128 in 20MHz or 40MHz bandwidth • Multiple TX/RX antenna modes handling asymmetric antenna configuration (2, 3 or 4 transmit antennas, 2 or more receiving antennas) • Frequency and spatial interleaving • Advanced optional forward error correction scheme relying on turbo-codes • Improved preamble design for multi-antenna channel estimation and synchronization purposes • Link quality metric feedback for efficient link adaptation • Simulation Results & Conclusion Jechoux,Patillon Mitsubishi/Motorola

  9. OFDM modulations • 2 bandwidths support: 20&40MHz • 1st OFDM modulation based on IEEE802.11a for 20MHz • 48 data subcarriers, 64-point (I)FFT, 4 pilots • Reference PHY rate: 2TX: 120/144Mbps, 3-4TX: 180/216Mbps • 2nd OFDM modulation for 20MHz (optional): • duration of the guard interval and number of carriers doubled (0.8µs1.6µs) to absorb larger multipath delays with same total overhead (25%) • 104 data subcarriers, 128-point (I)FFT, 8 pilots • 8% increase on PHY rate: 2TX: 130/156Mbps, 3-4TX: 195/234Mbps • 3rd OFDM modulation for 40MHz (optional): • 104 data subcarriers, 128-point (I)FFT, 8 pilots • Guard interval duration: 0.8s • 117% increase on PHY rate: 2TX: 260/312Mbps, 3-4TX: 390/468Mbps Jechoux,Patillon Mitsubishi/Motorola

  10. 20MHz channels 40MHz channel 40MHz mode design choice • Methodology: • Choose to design single RF front-end architecture with on the fly reprogrammable filters able to address 20MHz and 40MHz • Derive compatible OFDM parameters • Proposition: • Preserve same number of poles (same frequency response in normalized frequency) band stop doubled at 40MHz • Reassign the center null carriers on the side ones to allow lower filter selectivity on the edges Jechoux,Patillon Mitsubishi/Motorola

  11. Multi-antenna scheme • Construction: transmission of 1, 2 or 3 parallel streams using, • Proposition: hybrid schemes relying on a combination of robust Space-Time Block Coding (STBC) and Spatial Division Multiplexing (SDM) • very simple transmitter implementation • very simple receiver implementations are possible as classical orthogonal designs are part of the proposed STBCs • e.g. design of low complexity ZF or MMSE equalizers • very good performance complexity tradeoff for robustness in asymmetric MIMO • Importance of configurations in which NTx≠ NRx • NTx > NRx e.g. between AP and mobile handset (in DL) • NTx < NRx e.g. between MT and AP (UL), or if MT have upgraded multi-antenna capabilities compared to AP (infrastructure upgrade cost) • Exploit all available transmit diversity when NTx> NRx to improve Tx reliability • 2, 3 or 4 transmit antennas • The number of receive antennas determines the maximum number of spatial streams that can be transmitted. • The capability of decoding 2 parallel data streams is mandatory • all the devices have to be able to decode all the modes where the number of spatial streams is lower or equal than the number of receive antennas in the device. • It is required for a device to exploit all its antennas in transmission even for optional modes. • 2 or more receive antennas • With STBC or STBC/SDM, asymmetric antenna configurations can be supported Jechoux,Patillon Mitsubishi/Motorola

  12. Asymmetric Modes for a robust hybrid solution 2 transmit antenna schemes proposed 3 transmit antenna schemes proposed 4 transmit antenna schemes proposed Jechoux,Patillon Mitsubishi/Motorola

  13. Asymmetric MIMO motivation/illustration 2x23x2: 2.8dB5dB gain @PER=10-2 Simulation parameters • 20MHz bandwidth, 48 carriers • 64QAM, CC 2/3 and 5/6 • Packet size: 1000 bytes • Channel TGn D NLOS • MMSE MIMO detection, perfect CSI 2x24x2: 4.3dB7.5dB gain @PER=10-2 3x34x3: 2dB5.4dBgain @PER=10-2 Jechoux,Patillon Mitsubishi/Motorola

  14. Frequency and spatial interleaver • 2-step interleaving process • Interleaving prior to mapping • 802.11a like frequency interleaving with new parameters suitable to both OFDM modulations (48 and 104 subcarriers) • Interleaving prior to space-time coding • based on the frequency interleaver parameters to ensure adjacent bits are transmitted on different streams NSD : number of data subcarriers Jechoux,Patillon Mitsubishi/Motorola

  15. Data rate (Mbits/s) Data rate (Mbits/s) Number of spatial streams (NS) Number of spatial streams (NS) Modulation Modulation Coding rate (R) Coding rate (R) Coded bits per subcarrier per stream (NBPSC) Coded bits per subcarrier per stream (NBPSC) Coded bits/ symbol (NCBPS) Coded bits/ symbol (NCBPS) Data bits/ symbol (NDBPS) Data bits/ symbol (NDBPS) 6.5Mbps 1 BPSK 1/2 1 104 52 6Mbps 1 BPSK 1/2 1 48 24 13Mbps 1 QPSK 1/2 2 208 104 12Mbps 1 QPSK 1/2 2 96 48 19.5Mbps 1 QPSK 3/4 2 208 156 18Mbps 1 QPSK 3/4 2 96 72 24Mbps 1 16QAM 1/2 4 192 96 26Mbps 1 16QAM 1/2 4 416 208 36Mbps 1 16QAM 3/4 4 192 144 39Mbps 1 16QAM 3/4 4 416 312 48Mbps 1 64QAM 2/3 6 288 192 52Mbps 1 64QAM 2/3 6 624 416 60Mbps 1 64QAM 5/6 6 288 240 65Mbps 1 64QAM 5/6 6 624 520 72Mbps 2 16QAM 3/4 4 192 144 78Mbps 2 16QAM 3/4 4 416 312 96Mbps 2 64QAM 2/3 6 288 192 104Mbps 2 64QAM 2/3 6 624 416 108Mbps 2 64QAM 3/4 6 288 216 117Mbps 2 64QAM 3/4 6 624 468 120Mbps 2 64QAM 5/6 6 288 240 130Mbps 2 64QAM 5/6 6 624 520 144Mbps 2 256QAM 3/4 8 384 288 156Mbps 2 256QAM 3/4 8 832 624 Mode: 2-TX48 carriers20MHz Mode: 2-TX104 carriers20MHz Jechoux,Patillon Mitsubishi/Motorola

  16. Mode: 2-TX104 carriers40MHz Mode: 3/4-TX48 carriers20MHz Jechoux,Patillon Mitsubishi/Motorola

  17. Mode: 3/4-TX104 carriers20MHz Mode: 3/4-TX104 carriers40MHz Jechoux,Patillon Mitsubishi/Motorola

  18. Forward Error Correction scheme • Proposed FEC scheme: • Mandatory: all IEEE802.11a CC with additional 5/6 puncturing pattern • Introduction of an optional advanced coding scheme: parallel binary turbo code with mother rate 1/3 with 3G polynomials (rate ½, 2/3, ¾, 5/6 achieved with puncturing). • TCs are stable, well-understood technology yielding good performance with known IPR landscape • Implementation features and advantages: • Adaptable block sizes relying on segmentation: breaks padded sequence into 2048-bit segments plus at most one segment of length 512, 1024, or 1536 bits  yields simple construction of corresponding interleavers • Constituent encoders left unterminated: it helps preserving exact code rate. Negligible performance degradation; scrambling performed before padding insertion • “Parallel window” decoder architecture easily scaled to meet latency requirements: • For a 2048-bit information block implementation, 10ms per iteration possible on 2001 FPGA scales to 1.25ms per iteration on current ASIC (higher clock rate and smaller window size) • Interleavers parallelized to avoid memory contentions without performance penalty Jechoux,Patillon Mitsubishi/Motorola

  19. Gain of Turbo vs. Convolutional Codes • Average PER vs SNR comparison on channel D • Left: STBC 2x2, 64QAM, R=1/2, N=2048 bits, no tail, rand. intlv. • Right: SDM 2x2, 64QAM, R=3/4, N=2048 bits, no tail, rand. intlv. • Conclusions: • The gain remains between 2-3 dB on TGN-D channel even with severe puncturing Jechoux,Patillon Mitsubishi/Motorola

  20. Preamble Design • nSTS : time synchronization, frequency offset, AGC • Code overlay time domain sequence design on finite alphabet {0,±1, ±j} leads to simple cross correlator implementation • nLTS : synchronization refinement, channel estimation • Orthogonal design instead of cyclic shift approach: Walsh-Hadamard weighting leads to greater accuracy for CIR estimation Jechoux,Patillon Mitsubishi/Motorola

  21. Short Training Sequence Preamble • Time domain design using alphabet {0,±1, ±j} • nSTS choice criteria: Spectral & auto/cross-correlation properties • Frame definition: nSTS are weighted by ±1, nSTS doubled @40MHz • Exploitation: time synchronization, Automatic Gain Control, freq offset Jechoux,Patillon Mitsubishi/Motorola

  22. Performances: Time Synchronization • Typical time synchronization performances for 2x2 antennas case • Typical time synchronization performances for 4x4 antennas case • Time synchronization very reliable for 4x4 antennas case even for very low SNR (< 0dB) • Important for hybrid 4x4 antennas modes, since they work for very low SNR • Good reliability even for channel with large delay spread (TGe) • Time synchronization reliable for 2x2 antennas case Jechoux,Patillon Mitsubishi/Motorola

  23. Long Training Sequence preamble • Focus on a orthogonal design allowing • easier tradeoff between quality/complexity for CSI estimation: frequency domain only estimation is possible • Inclusion of time confinement constraint into the estimator possible yielding a more robust estimator avoiding the important noise enhancement using ZF approaches with Cyclic Shift based methods • Definition in frequency domain from alphabet {0, ±1} • LTS over 56 subcarriers to further improve the accuracy of the channel estimator using time confinement constraint LTS(#-28…#+28) = {-1, 1, -1, 1, 1, 1, 1, -1, -1, 1, 1, 1, -1, 1, 1, -1, -1, -1, -1, 1, 1, -1, 1, 1, -1, 1, -1, -1, 0, -1, -1, -1, 1, -1, 1, -1, -1, -1, 1, 1, 1, 1, -1, -1, 1, 1, 1, 1, 1, 1, 1, 1, 1, -1, -1, 1, -1} Jechoux,Patillon Mitsubishi/Motorola

  24. Link quality metric feedback for efficient link adaptation • Accurate PER prediction tools are available: • E.g. Shannon capacity at RX output, exp-ESM effective SNR • yields several dBs gain w.r.t. SNR or ACK-based link adaptation • Observation: only the RX can predict PER accurately (knowledge of processing, interference) • Proposal: • Feedback current link quality metric • 1 dedicated PDU for initial calibration so that feedback can be mapped on PER in multiple vendor environment Jechoux,Patillon Mitsubishi/Motorola

  25. Mode (Mbps) / STC SNR for PER=10-1 Mode (Mbps) / STC SNR for PER=10-1 120 / SDM-STBC 30dB 120 / SDM (fluor. Eff.) 35dB 96 / SDM-STBC 25.5dB 120 / SDM 35dB 48 / SDM-STBC 17dB 96 / SDM 28dB 48 / STBC 18dB 12 / SDM-STBC 7dB 12 / STBC 5dB Mode (Mbps) / STC SNR for PER=10-1 Mode (Mbps) / STC SNR for PER=10-1 180 / SDM-STBC (Flour. Eff.) 29dB 120 / SDM 24dB 180 / SDM-STBC 29dB 96 / SDM 20dB 48 / STBC 14.5dB 120/ SDM-STBC 23dB 12 / STBC 2dB 96 / SDM-STBC 19dB Performance illustration for TGnD channel (CC67) • Performance improvements for 2x2  2x4 and 4x2  4x4 antennas 2x2 4x2 2x4 4x4 Jechoux,Patillon Mitsubishi/Motorola

  26. Mode/Mbps Mode/Mbps Mode/Mbps SNR for PER=10-1 SNR for PER=10-1 SNR for PER=10-1 120 120 180 (effect) 24dB XXX  36dB  29dB 30dB 96 96 25.5dB 20dB 180 XXX  36dB  29dB 120 35dB  25.5dB  23dB 48 48 17dB 14.5dB 96 27.5dB  21dB  19dB 12 12 2dB 7dB 48 18dB  14dB  11dB 12 5dB  4.5dB  3.5dB Simulation results - TGnD • 4RX antennas: Full Diversity gain for all streams: 120 Mbps lowers SNR ~ 35dB  25.5dB  23dB • Assymetric modes: #TX antennas < #RX antennas vs #RX antennas < #TX antennas # TX antennas > # RX antennas  Update AP # TX antennas < # RX antennas  Update MT Jechoux,Patillon Mitsubishi/Motorola

  27. Limited outdoor environment: Hotspot support • Benefit of 20MHz 128 carriers mode using a 32 samples cyclic prefix: • 8% overall rate increase • designed to cope with larger channels for more efficient outdoor environment operations • Illustration for channel F: no error floor in performance for higher rates modes Jechoux,Patillon Mitsubishi/Motorola

  28. Antenna configuration Data rate (Mbits/s) PER carrier offset = -40ppm PER carrier offset = 0ppm PER carrier offset =+40ppm 2x2 12Mbps 0.0003 0.0003 0.0002 2x2 48Mbps 0.0016 0.0016 0.0018 2x2 96Mbps 0.0039 0.0037 0.0042 2x2 120Mbps 0.0297 0.0183 0.0298 3x3 12Mbps 0.0002 0.0001 ~0 3x3 120Mbps 0.0043 0.0045 0.0050 3x3 180Mbps 0.0963 0.0617 0.0974 4x4 12Mbps ~0 ~0 ~0 4x4 48Mbps 0.0001 0.0001 0.0001 4x4 96Mbps 0.0016 0.0016 0.0019 4x4 120Mbps 0.0021 0.0021 0.0022 4x4 180Mbps 0.0023 0.0024 0.0029 Simulation results – Offset compensation • No significant impact at 10% PER in channel E (NLOS) • Impact of carrier frequency offset and symbol clock offset at SNR=50dB in channel E (LOS): • Small degradation of the PER performance • High data rate modes are more impacted: • PER (+40ppm)=112/100xPER (0ppm)@48Mbps • PER (+40ppm)=163/100xPER (0ppm)@120Mbps • High data rate modes are less impacted if spatial diversity: • 3x3: PER (+40ppm)=158/100xPER (0ppm)@180Mbps • 4x4: PER (+40ppm)=121/100xPER (0ppm)@180Mbps Jechoux,Patillon Mitsubishi/Motorola

  29. MAC Description Jechoux,Patillon Mitsubishi/Motorola

  30. ECCF overview • ECCF: “Extended Centralised Coordination Function” • Functions are distributed over 4 sub-layers 802.2 LLC 802.2 LLC ECCF MAC Legacy 802.11 MAC Packet Sequence Number Assignments MAC Header Compression LLCCS Sequence Number Assignments Fragmentation Encryption MDU Header + CRC SAR Segment Sequence Number Assignments Segmentation/Re-Assembly Error and Flow Control MIS Encryption MPDU Header Signalling Insertion MLS PHY PHY Jechoux,Patillon Mitsubishi/Motorola

  31. 802.11 MAC Super Frame CFP CP CFP MTF ECCF PCF/HCCA DCF/EDCA CAP ECCF CAP ECCF ECCF Beacons Beacons Beacon Information CF Parameter Set ECCF Parameter Set Frame structure and timing • 802.11 MAC Super Frame & Beacon kept for compatibility. • A part of the Contention Free Period (CFP) or some Controlled Access Periods (CAP) are used to inset ECCF periods. • Resource scheduling performed on a per MTF basis (fixed duration: e.g.2 ms). • Variable duration Time Intervals (TI) dynamically allocated to STAs within an MTF. Jechoux,Patillon Mitsubishi/Motorola

  32. 802.11 MAC Super Frame CP MTF MTF … CAP ECCF DCF/EDCA CAP ECCF DCF/EDCA ECCF Beacons Beacons Beacon Information CF Parameter Set ECCF Parameter Set Example of .11e and ECCF peaceful coexistence • ECCF scheme is flexible enough to easily handle backward compatibility • Question: how to have clean coexistence of .11e QoS STA and .11n ECCF STA • Practical case: mixed environment, .11n stations + .11e VoIP terminals • Solution: • the RRM reserves time for legacy stations every 10 ms using insertion into CAP method • granularity of ECCF reservation (MTF) is 2ms • several ECCF MTF can be embedded in superframe • VoIP .11e stations are able to operate Jechoux,Patillon Mitsubishi/Motorola

  33. MTF MPDU MPDU MPDU MPDU PGPM Data Data Data Data PGPM TI#0 TI#1 TI#2 TI#3 TI#4 Frame structure and timing (cont.) • MTF composition defined in a specific MPDU = PGPM • Variable duration TI constituted of one MPDU = data unit exchanged with the PHY layer as in legacy 802.11 (i.e. one PLCP preamble per MPDU) • MPDU contains two parts: signalling and data • contents defined by the emitter (source STA) • data and signalling can be intended for one or more destination STAs • Multiple MCS / Multiple flows / Multiple destinations aggregation • Possible long PHY bursts (up to 1ms) Jechoux,Patillon Mitsubishi/Motorola

  34. PGPM Header TID STA#1 ->STA#2 TID STA#4 ->RRM,STA#3 HSCS MPDU MPDU MPDU Header Signalling HSCS Data STA#1 STA#2 MTF structure (detailed) • Each resource is described at the beginning of an MTF in the PGPM • MPDU signalling part (variable length): • Includes resource requests, Error Control signalling,... • Includes description of data blocks (if any) MTF structure example PGPM Signalling DPD STA#2 Data Block to STA#2 MPDU Header Signalling RR ->RRM FB ->STA#3 HSCS Sent by RRM STA#4 All RRM, STA#3 (TI #0) (TI #1) (TI #2) Jechoux,Patillon Mitsubishi/Motorola

  35. LLC LLCCS SAR Fixed size segments (2 possible lengths) MPEGflow HDR MIS-PDU CRC HDR MIS-PDU CRC SDU VOIP flow HDR CRC HDR CRC SDU TCP flow SDU HDR MIS-PDU CRC HDR MIS-PDU CRC HDR MIS-PDU CRC ... ... Data Block#2 Data Block #1 Data Block #3 (*) LLC packet sequence number (**) Segment sequence numbers MPDU Header Signalling HSCS • An MPDU may aggregate several data blocks sent by a station Aggregated MPDU, up to 1ms Aggregation ... • MPDU description part has a dedicated protection (HSCS) • Possible Multiple MCS / Multiple flows / Multiple destinations • In particular, description part can use a robust PHY mode • Sequence numbers: 2 levels • (*) at LLC level (LLCCS-PDU), and (**) at segment level (MIS-PDU) • SAR is easy to implement Jechoux,Patillon Mitsubishi/Motorola

  36. ECCF period (within CAP or CFP) MTF (2ms) MTF (2ms) PGPM PGPM PGPM CTI CTI CTI ACK RG-STA A CTI location RG-STA A CTI Location RG-STA B RG-STA A CTI Location RRM RR RR STA A RR STA B Data RR via in band signalling RG Signalling TIs (Resource announcement + Contention) Successful contention ACK RR via contention Resource request (RR) and resource grant (RG) Resource allocation scheme Jechoux,Patillon Mitsubishi/Motorola

  37. Enhanced ACK & Flow control • Performed on a per-flow basis (src STA, dst STA, priority) • Operated independently from the aggregation • Feedback sent upon request from source or triggered by receiver • May be sent in-band or out-band • May be cumulative when no errors (compact) or selective with bit map bloc otherwise (accurate) • Flow control • Negotiated minimum window size (throughput guaranty) • or signaled Jechoux,Patillon Mitsubishi/Motorola

  38. Aggregated MPDUs (PHY bursts) SID1, Pr1 SID1, Pr1 SID2 , Pr3 Src STA SID Priority Seq Nb -> N HDR HDR HDR MIS-PDU MIS-PDU MIS-PDU CRC CRC CRC Flags Dst STA (SID 2) Cumulative Ack SIE Data In band feedback message SID SDU N LLC Priority Seq Nb -> M Flags MISPU Bit Map (32 bits) Selective Ack SIE Dst STA (SID1) HDR HDR HDR HDR HDR HDR HDR HDR HDR HDR MIS-PDU MIS-PDU MIS-PDU MIS-PDU MIS-PDU MIS-PDU MIS-PDU MIS-PDU MIS-PDU MIS-PDU CRC CRC CRC CRC CRC CRC CRC CRC CRC CRC Feedback message SDU M -1 SDU M LLC Preamble + MAC Header SID: Short station IDentifier Enhanced ACK Jechoux,Patillon Mitsubishi/Motorola

  39. 802.11 MAC Super Frame CFP CP ECCF DCF/EDCA/ECCF PCF/HCCA CAP(ECCF) CAP(ECCF) N- Beacon N- Beacon Legacy Beacon Legacy Beacon CF-Poll CF-Poll High range dedicated .11n Beacon • Goal: Enable materialisation of new PHY mode range • Proposal: Introduction of a dedicated beacon • Transmitted with MIMO 2Tx, 1 flow, BPSK STBC CC1/2 (6 Mbps) • Include all legacy system Information • Add ECCF specific elements • Green Field Case • N Beacon only is transmitted • Mixed Mode • Dual Beacon, Legacy kept as is • an N Beacon immediately after legacy one • Valid for both Mixed Mode and Green Field • Gain of 6db => ~50% Range increase for .11n stations • BSS overlapping avoided by DFS as per 802.11h Jechoux,Patillon Mitsubishi/Motorola

  40. System Performance Jechoux,Patillon Mitsubishi/Motorola

  41. ECCF Robustness • MAC Efficiency vs PER (Scenario I bis, IV, VI bis) • Slight impact of the PER on MAC efficiency • retransmission with low signalling SR-ARQ • MAC efficiency: • Robust vs PER • > 60% even for harsh conditions (*) • High performance even in bad radio conditions Results valid whatever the application packet size (c.f.segmentation) (*) PER for 134 bytes packets, 1E-1 equivalent to 9.5E-1 for 4000 bytes or 6.9E-1 for 1500 bytes packets Jechoux,Patillon Mitsubishi/Motorola

  42. ECCF Scalability • Goodput at MAC SAP vs PHY data rate (point-to-point scenario) • linear variation • MAC efficiency: • Constant vs PHY rate • High level: [76% ; 86%] • Fully scalable for high bit rates Results valid whatever the application packet size (c.f.segmentation) Jechoux,Patillon Mitsubishi/Motorola

  43. Mixed traffic handling • Capacity usage at MAC-SAP vs. Number of VoIP sessions • 1 TCP data flow transmitted using MIMO 3x3_64QAM2/3 (Ns=3) [144Mbit/s] • VoIP: 120-byte packets emitted every 10 ms (2x96kbit/s) • n VoIP sessions, using either 2x2_64QAM2/3 (Ns=1) [48Mbit/s] or 2x2_16QAM1/2 (Ns=1) [24 Mbit/s] • MAC Efficiency between 78% and 55% • 30 VoIP sessions + at least 65 Mbit/s of TCP traffic Jechoux,Patillon Mitsubishi/Motorola

  44. Delay performances • IEEE TGn Usage models : Scenario I (Home) • Traffic classification based on priority level (VoIP > TCP) • Delay comparison for different error rate [cdf(d>D)] • Strong QoS constraints of VoIP reached: • with a simple centralised scheduling • an efficient ACK • Max delay below 20 ms for QoS traffic Jechoux,Patillon Mitsubishi/Motorola

  45. Scenario 1bis Performance 53 Mbps 76 % MAC Efficiency Non-QoS goodput (171%) 17 53 Mpbs CC Targets QoS goodput (100%) Satisfied QoS flows (100%) Metrics 139 Mbps Average PHY rate Simulation results for Scenarios 1 • Scenario 1: • all data flow transmitted using MIMO 3x2 64QAM 3/4 (Ns=2) or 2x2 16QAM 3/4 (Ns=1) • Modified scenario 1bis: • Infinite TCP sources + PHY modes (36 - 180 Mbit/s) • All QoS requirements can be achieved with 106 Mbit/s at PHY • 76% MAC efficiency • 106 Mbit/s available at MAC-SAP (139 Mbit/s avg at PHY) Jechoux,Patillon Mitsubishi/Motorola

  46. Scenario 4 Performance 73 % MAC Efficiency 9 Mbps 18 CC Targets QoS goodput (100%) Satisfied QoS flows (100%) 121 Mpbs (27%) Non-QoS goodput Metrics 178 Mbps Average PHY rate Simulation results for Scenario 4 • Scenario 4: • PHY modes 108 - 180 Mbit/s • 73% MAC efficiency • 130 Mbit/s available at MAC-SAP (178 Mbit/s avg at PHY) Jechoux,Patillon Mitsubishi/Motorola

  47. Performance Scenario 6 bis 58 Mbps (292%) 67 % MAC Efficiency Non-QoS goodput 39 45 Mpbs CC Targets QoS goodput (100%) Satisfied QoS flows (100%) Metrics 155 Mbps Average PHY rate Simulation results for Scenarios 6 • Scenario 6: • all data flow transmitted using MIMO 3x3 64QAM2/3 (Ns=2) or 2x2 64QAM5/6 (Ns=1). • Modified scenario 6bis: • Infinite TCP sources + PHY modes (48 - 180 Mbit/s) • QoS requirements can be achieved with 92 Mbit/s at PHY • 67% MAC efficiency • 103 Mbit/s available at MAC-SAP (155 Mbit/s avg at PHY) Jechoux,Patillon Mitsubishi/Motorola

  48. Results conclusion • QoS requirements supported (throughput and delay) • In all scenarios • High level MAC efficiency • Above 65 % in all scenarios • Efficient with QoS flows as non QoS flows • Very good scalability • Constant efficiency versus PHY rate • Backward compatibility • Flexibility ensured, without context-dependent tuning • Full support of all mandatory 11n simulations scenarios with a 120 Mbps PHY layer Jechoux,Patillon Mitsubishi/Motorola

  49. Differentiators • Resource allocation mechanism is highly dynamic • QoS provided without use of traffic profiles (TSPECS) • Enhanced transparency and predictability through broadcast grouped resource announcement • yields clean low power implementation and low overhead • Inherent clean split between legacy and .11n devices at MAC level • no need for mixed-modes transmission mode definition • High Efficiency independent of application packet size through segmentation • Robustness to error through retransmission mechanism on segmented packets • .11n specific beacon enables materialization of new PHY mode range prediction • Build in support for asymmetric TX/RX antenna configurations to accommodate various terminal sizes (PDA/Phone) offering a scalable and evolutionary solution • New preamble definition: allowing easier tradeoff between quality/complexity for CSI estimation avoiding the important noise enhancement using ZF approaches • Open-loop link quality feedback for easier and better link adaptation Jechoux,Patillon Mitsubishi/Motorola

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