High-Throughput Enhancements for : Features and Performance

High-Throughput Enhancements for 802.11: Features and Performance
January 2005 doc.: IEEE /1404r4 January 2005 High-Throughput Enhancements for : Features and Performance Date: Authors: Notice: This document has been prepared to assist IEEE It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures < ieee802.org/guides/bylaws/sb-bylaws.pdf>, including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE Working Group. If you have questions, contact the IEEE Patent Committee Administrator at John Ketchum et al, Qualcomm John Ketchum et al, Qaulcomm

January 2005 Authors John Ketchum et al, Qualcomm

Qualcomm Proposal Documents
January 2005 Qualcomm Proposal Documents Original submissions (as revised) r1 High Throughput System Description and Operating Principles. r2 High Throughput Proposal Compliance Statement (this document.) r2 Link Level and System Performance Results for High Throughput Enhancements. r2 High Throughput Enhancements for : Features and Performance January Presentations: r4 Qualcomm Complete Proposal John Ketchum et al, Qualcomm

Maximize Throughput, QoS, and Spectral Efficiency
January 2005 Goals Maximize Throughput, QoS, and Spectral Efficiency Minimize complexity and assure backward compatibility Provide balance between TTM needs and 11n design longevity economics John Ketchum et al, Qualcomm

Throughput Comparison
January 2005 Throughput Comparison 0 dB: 120 m 10 dB: 60 m 20 dB: 30 m 30 dB: 15 m 37.5 dB: 10m SGI-52: 52 data subcarriers with short guard interval Results given with closed loop rate control SS-STBC can achieve 120Mbps at 30m (20dB) ES has > 6 dB advantage over other at 150 Mbps PHY throughput At 30 m (20 dB) ES has >50% PHY t’put advantage over others John Ketchum et al, Qualcomm

Proposal Summary: PHY Builds on 802.11a waveform
January 2005 Proposal Summary: PHY Builds on a waveform 20 MHz bandwidth with a/b/g spectral mask 802.11a modulation, coding, interleaving with expanded rate set Backward compatibility through legacy STF, LTF and SIG Supports a maximum of 4 wideband spatial streams Two forms of spatial processing Spatial Spreading (SS): modulation and coding per wideband spatial channel No calibration required SNR per wideband spatial stream known at Tx Eigenvector Steering (ES): via wideband spatial modes/SVD per subcarrier Tx and Rx steering Over the air calibration procedure required Rate adaptation enables sustained high rate operation PHY techniques proven in FPGA-based prototype John Ketchum et al, Qualcomm

January 2005 Spatial Spreading Spatial spreading for 2 Tx and 4 Tx uses Hadamard matrix No multiplies required to execute Matrix-Vector multiply Flexible number of spatial streams 1 ≤ Ns ≤ Ntx All transmit antennas used, regardless of stream count John Ketchum et al, Qualcomm

Spatial Spreading: Mandatory & Optional Features
January 2005 Spatial Spreading: Mandatory & Optional Features Mandatory Hadamard matrix-vector multiply at transmitter Cyclic transmit diversity at transmitter Receiver must be capable of handling spatially spread signals (zero-forcing, MMSE, etc.) Support for rate feedback in PLCP/MAC header Optional Rate feedback functionality John Ketchum et al, Qualcomm

Eigenvector Steering January 2005
Substantial throughput gains over baseline spatial spreading Full MIMO channel characterization required at Tx Tx steering using per-bin channel eigenvectors from SVD Rx steering renders multiple Tx streams orthogonal at receiver, allowing transmission of multiple independent spatial streams This approach maximizes both data rate and range Per-stream rate control and rate feedback required for robust high throughput operation John Ketchum et al, Qualcomm

Support for Eigenvector Steering
January 2005 Support for Eigenvector Steering Base standard mandatory features are required to support optional ES mode Independent rates per stream for up to four streams Modulation/coding/interleaving must support independent rates per stream Rate feedback Fields in PLCP header extension or MAC header MIMO training waveform design Must support steered reference Allows implicit channel state feedback in all PPDUs Tone interleaving (TGnSync) or Walsh cover (Qualcomm) Related elements such as signaling for mode control John Ketchum et al, Qualcomm

January 2005 Eigenvector Steering Some features are mandatory for devices supporting optional ES mode Messaging and sounding waveforms to support over-the-air calibration Transmit steering and computation of Tx steering vectors Real-time matrix-vector multiply capability Determine steering vectors from unsteered training sequence Steered training sequence Other optional Eigenvector Steering features Bi-directional steering: Both STAs in a corresponding pair use Eigenvector steering Uni-directional steering: Only one STA in corresponding pair (e.g. AP) use Eigenvector Steering John Ketchum et al, Qualcomm

Another Approach Space-Time Block Coding with Spatial Spreading
January 2005 Another Approach Space-Time Block Coding with Spatial Spreading Additional Tx diversity benefit of STBC with flexibility of SS Number of STBC streams decoupled from number of Tx antennas Can adjust power allocations in unequal diversity cases Possible compromise approach – best of both worlds John Ketchum et al, Qualcomm

Throughput Comparison
January 2005 Throughput Comparison 0 dB: 120 m 10 dB: 60 m 20 dB: 30 m 30 dB: 15 m 37.5 dB: 10m SGI-52: 52 data subcarriers with short guard interval Results given with closed loop rate control SS-STBC can achieve 120Mbps at 30m (20dB) ES has > 6 dB advantage over other at 150 Mbps PHY throughput At 30 m (20 dB) ES has >50% PHY t’put advantage over others John Ketchum et al, Qualcomm

Code Rates and Modulation
January 2005 Code Rates and Modulation Bits/subcarrier Bit/s/spatial chan1 Bit/s/spatial chan2 Code Rate Modulation 0.50 6 Mbit/s 7.2 Mbit/s r=1/2 BPSK 1.00 12 14.4 QPSK 1.50 18 21.7 r=3/4 2.00 24 28.9 16 QAM 2.50 30 36.1 r=5/8 3.00 36 43.3 3.50 42 50.6 r=7/12 64QAM 4.00 48 57.8 r=2/3 4.50 54 65 5.00 60 72.2 r=5/6 256 QAM 6.00 72 86.7 7.00 84 101.1 r=7/8 Notes: 1) short OFDM symbols; 2) expanded OFDM symbols with short guard interval John Ketchum et al, Qualcomm

January 2005 PHY Throughput vs SNR Throughput comparisons between TGn Sync Extended Rate Set and QCOM rate set for various parsing and codec configurations QC Eigenvector Steering Standard OFDM symbol; 2x2, 4x4 Channel B, no impairments System configurations simulated: 2,4 parallel encoders/decoders; QC rate set Single encoder/decoder; QC rate set Same as 2., but with single rate applied to all streams Single encoder/decoder, TGnSync Extended MCS John Ketchum et al, Qualcomm

January 2005 2x2 PHY Throughput vs SNR John Ketchum et al, Qualcomm

January 2005 4x4 PHY Throughput vs SNR John Ketchum et al, Qualcomm

802.11n PLCP Preamble/Header
January 2005 802.11n PLCP Preamble/Header Legacy portion 100% backward compatible HT portion supports up to four wideband spatial channels using Spatial Spreading (SS) or Eigenvector Steering (ES) PLCP header extension carries scrambler init and rate feedback John Ketchum et al, Qualcomm

Preamble Legacy Portion
January 2005 Preamble Legacy Portion Legacy portion of preamble transmitted using cyclic transmit diversity (no spatial multiplexing or eigenvector steering) Legacy SIGNAL field used to indicate HT Rate field set to unused value indicates HT Size/Request field indicates HT PPDU length. John Ketchum et al, Qualcomm

HT Portion HT-SIG conveys rates, MIMO training type and length
January 2005 HT Portion HT-SIG conveys rates, MIMO training type and length MIMO training can be either steered training or direct training Uses Walsh functions to establish orthogonality among eigenmodes or Tx antennas Uses unique training sequence on each mode or Tx antenna to ensure equal levels at Rx Used by Rx STA to calculate Rx steering Used by Rx STA to calculate Tx steering when using ES John Ketchum et al, Qualcomm

Legacy and MIMO Training for 2, 3, and 4 Tx
January 2005 Legacy and MIMO Training for 2, 3, and 4 Tx STS: a STS LTS: a LTS L_SIG: a SIGNAL HT-SIG: Extended SIGNAL MTSn: MIMO training symbol for Tx antenna n CDx: x ns cyclic delay Shows unsteered MIMO training John Ketchum et al, Qualcomm

Modulation/Coding/Interleaving
January 2005 Modulation/Coding/Interleaving Proposal specifies parallel coding/decoding to support multiple rates in parallel Legacy BCC with extended rates/puncturing patterns to provide expanded MCS set Tail per stream per PPDU– requires parallel decoding for best performance Alternative is tail per stream per OFDM symbol Small increase in overhead, allows single-decoder architecture John Ketchum et al, Qualcomm

Alternative Modulation/Coding/Interleaving
January 2005 Alternative Modulation/Coding/Interleaving Simplified single-decoder architecture Parse/demux must be coordinated with puncture patterns John Ketchum et al, Qualcomm

No advanced coding included in proposal
January 2005 Advanced Coding No advanced coding included in proposal Advanced coding must support eigenvector steering Multiple streams with significantly different SNRs Requires multiple independent code rates or high tolerance to large SNR variance. Single coder/decoder architectures are more feasible with advanced coding such as Turbo codes. John Ketchum et al, Qualcomm

Summary of MAC Objectives
January 2005 Summary of MAC Objectives Enhanced efficiency built on e Ensure high QoS and high throughput Support MIMO operation with limited overhead Limit introduction of new features Minimize burden on transmit and receive processing John Ketchum et al, Qualcomm

Reduced Complexity PHY Implementations
January 2005 doc.: IEEE /1404r4 January 2005 Reduced Complexity PHY Implementations MAC design choices must not impose excessive complexity on PHY implementation Allow low complexity PHY implementations for low capability devices, e.g., VoIP phone, PDA. Fewer antennas. MIMO processing delay. Delayed decoding. Permit STA designs with reduced PHY complexity Limit on reception of Aggregate frames, Limit on reception of Aggregate PPDUs, Turn-around time for Block Ack. Turn-around time for estimation of steering vectors. John Ketchum et al, Qualcomm John Ketchum et al, Qaulcomm

MAC Throughput vs Range
January 2005 MAC Throughput vs Range Throughput above the MAC of 100 Mbps is achieved at: 5.25 GHz : 2x2 – 29 m, 4x4 – 47 m 2.4 GHz: 2x m, 4x4 -75 m. Highest throughput of all proposals. John Ketchum et al, Qualcomm

Mandatory Enhancements to 802.11e
January 2005 MAC Elements Summary Mandatory Enhancements to e Aggregation Frame Aggregation to a single RA. PPDU Aggregation: Reduced or zero IFS Adaptive Coordination Function (ACF) Multi-poll enhancement to HCCA No Immediate Ack for Block Ack Request and Block Ack Low latency Data rate feedback from Rx to Tx Enhanced rate adaptation Very low overhead John Ketchum et al, Qualcomm

Aggregation Significant performance gains at higher date rates:
January 2005 Aggregation Significant performance gains at higher date rates: 25-60% greater throughput for PHY rates of Mbps Key Attributes: Frame Aggregation to a single RA. PPDU Aggregation: Reduced or zero IFS John Ketchum et al, Qualcomm

Adaptive Coordination Function
January 2005 Adaptive Coordination Function SCAP (Scheduled Access Period) initiated by SCHED message Acts as consolidated multi-STA poll Indicate TA, RA, start offset and duration of TXOP. Permits effective PPDU Aggregation Improved battery management Eliminate Immediate ACK for Block Ack frames MIMO training in SCHED message functions as broadcast sounding waveform for channel estimation and SVD calculation John Ketchum et al, Qualcomm

Benefits of ACF ACF versus HCF with Frame Aggregation
January 2005 Benefits of ACF ACF versus HCF with Frame Aggregation Throughput Gain in Scenario 1: 70% John Ketchum et al, Qualcomm

Benefits of ACF ACF Features No Immediate ACK SCHED
January 2005 Benefits of ACF ACF Features No Immediate ACK For BlockAckRequest and BlockAck MAC Efficiency Gain over HCF with Frame Aggregation: ~18% SCHED PPDU Aggregation with Reduced and Zero IFS Multi-Poll MAC Efficiency Gain over HCF with Frame Aggregation : ~7% Low latency closed loop operation Achieve higher PHY rates due to smaller backoff and MIMO Mode Control Mean PHY Rate Gain over HCF: ~35% John Ketchum et al, Qualcomm

January 2005 Data Rate Feedback John Ketchum et al, Qualcomm

Benefit of Data Rate Feedback
January 2005 Benefit of Data Rate Feedback 16-bit field in PLCP header extension specifies up to four preferred rates Tx PHY rate is maximized after single ACK received Accurate PHY rate tracking for time varying channels Substantial throughput gains: Scenario 1: 41% 82.6 Mbps versus 58.7 Mbps Scenario 6: 46% 81.5 Mbps versus 55.9 Mbps John Ketchum et al, Qualcomm

Benefit of Eigensteering
January 2005 doc.: IEEE /1404r4 January 2005 Benefit of Eigensteering Comparison of Spatial Spreading only with closed loop MIMO Mode Selection Sample Gains: 30% throughput gain in Scenario 1. 40% in Scenario 4. John Ketchum et al, Qualcomm John Ketchum et al, Qaulcomm

Goals Maximize Throughput, QoS, and Spectral Efficiency
January 2005 doc.: IEEE /1404r4 January 2005 Goals Maximize Throughput, QoS, and Spectral Efficiency Eigenvector Steering (ES) and rate feedback provide the highest throughput and QoS performance. ES should be an Optional Feature that can provide significant longevity to the 11n standard. Provision for optional ES in n requires a few mandatory and some specified optional features. John Ketchum et al, Qualcomm John Ketchum et al, Qaulcomm

Goals Minimize complexity and assure backward compatibility
January 2005 doc.: IEEE /1404r4 January 2005 Goals Minimize complexity and assure backward compatibility Builds on a waveform 20 MHz bandwidth with a/b/g spectral mask 802.11a modulation, coding, interleaving with expanded rate set Backward compatibility through legacy STF, LTF and SIG Provision for optional ES in n requires a few mandatory and some specified optional features. John Ketchum et al, Qualcomm John Ketchum et al, Qaulcomm

January 2005 Goals Provide balance between TTM needs and 11n design longevity economics Both Spatial Spreading and Spatial Spreading with Space Time Block Coding are good mandatory alternatives that meet TTM objectives ES should be an Optional Feature that can provide significant longevity to the 11n standard. John Ketchum et al, Qualcomm

Summary Qualcomm proposal builds on existing 802.11a,g,e design
January 2005 Summary Qualcomm proposal builds on existing a,g,e design 802.11n can enable new markets & applications: Multimedia distribution in the home Enhanced enterprise applications (e.g. VoD, Video Conf.) These applications require: High throughput  SS/ES, ACF, rate feedback High QoS  SS/ES, ACF, rate feedback Maximized range  ES Maximum spectral efficiency  ES SS/ES + rate feedback + ACF meet the requirements associated with these new markets & applications: Highest network capacity: greater than 100 mbps above the MAC inside 30 m (20 MHz, 2x2, 5 GHz) Reliable coverage QoS: Less than 50 ms latency with “ZERO packet loss” John Ketchum et al, Qualcomm

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