doc.: IEEE /1404r0 Submission November 2004 John Ketchum, et al, QualcommSlide 1 High-Throughput Enhancements for : Features and Performance John Ketchum, Sanjiv Nanda, Rod Walton, Steve Howard, Mark Wallace, Bjorn Bjerke, Irina Medvedev, Santosh Abraham, Arnaud Meylan, Shravan Surineni QUALCOMM, Incorporated 9 Damonmill Square, Suite 2A Concord, MA Phone: Fax:

doc.: IEEE /1404r0 Submission November 2004 John Ketchum, et al, QualcommSlide 2 Goals Maximize Throughput, QoS, and Spectral Efficiency Minimize complexity and assure backward compatibility Provide balance between TTM needs and 11n design longevity economics

doc.: IEEE /1404r0 Submission November 2004 John Ketchum, et al, QualcommSlide 3 Throughput Comparison 0 dB: 120 m 10 dB: 60 m 20 dB: 30 m 30 dB: 15 m 37.5 dB: 10m Results given with closed loop rate control, except STBC-OL 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 SGI-52: 52 data subcarriers with short guard interval

doc.: IEEE /1404r0 Submission November 2004 John Ketchum, et al, QualcommSlide 4 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

doc.: IEEE /1404r0 Submission November 2004 John Ketchum, et al, QualcommSlide 5 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 ≤ N s ≤ N tx –All transmit antennas used, regardless of stream count

doc.: IEEE /1404r0 Submission November 2004 John Ketchum, et al, QualcommSlide 6 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

doc.: IEEE /1404r0 Submission November 2004 John Ketchum, et al, QualcommSlide 7 Eigenvector Steering 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

doc.: IEEE /1404r0 Submission November 2004 John Ketchum, et al, QualcommSlide 8 Support for Eigenvector Steering Base standard mandatory features are required to support optional ES mode –Per-stream rate control 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

doc.: IEEE /1404r0 Submission November 2004 John Ketchum, et al, QualcommSlide 9 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

doc.: IEEE /1404r0 Submission November 2004 John Ketchum, et al, QualcommSlide 10 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

doc.: IEEE /1404r0 Submission November 2004 John Ketchum, et al, QualcommSlide 11 Throughput Comparison 0 dB: 120 m 10 dB: 60 m 20 dB: 30 m 30 dB: 15 m 37.5 dB: 10m Results given with closed loop rate control, except STBC-OL 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 SGI-52: 52 data subcarriers with short guard interval

doc.: IEEE /1404r0 Submission November 2004 John Ketchum, et al, QualcommSlide n 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

doc.: IEEE /1404r0 Submission November 2004 John Ketchum, et al, QualcommSlide 13 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.

doc.: IEEE /1404r0 Submission November 2004 John Ketchum, et al, QualcommSlide 14 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

doc.: IEEE /1404r0 Submission November 2004 John Ketchum, et al, QualcommSlide 15 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

doc.: IEEE /1404r0 Submission November 2004 John Ketchum, et al, QualcommSlide 16 Alternative Modulation/Coding/Interleaving Simplified single-decoder architecture Parse/demux must be coordinated with puncture patterns

doc.: IEEE /1404r0 Submission November 2004 John Ketchum, et al, QualcommSlide 17 Advanced Coding No advanced coding included in proposal Advanced coding must support independent rates per stream for eigenvector steering. Single coder/decoder architectures are more feasible with advanced coding such as Turbo codes.

doc.: IEEE /1404r0 Submission November 2004 John Ketchum, et al, QualcommSlide 18 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

doc.: IEEE /1404r0 Submission November 2004 John Ketchum, et al, QualcommSlide 19 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.

doc.: IEEE /1404r0 Submission November 2004 John Ketchum, et al, QualcommSlide 20 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 Low latency –Data rate feedback from Rx to Tx Enhanced rate adaptation Very low overhead

doc.: IEEE /1404r0 Submission November 2004 John Ketchum, et al, QualcommSlide 21 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

doc.: IEEE /1404r0 Submission November 2004 John Ketchum, et al, QualcommSlide 22 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 –Eliminate Immediate ACK for Block Ack frames –MIMO training in SCHED message functions as broadcast sounding waveform for channel estimation and SVD calculation

doc.: IEEE /1404r0 Submission November 2004 John Ketchum, et al, QualcommSlide 23 Adaptive Coordination Function Benefits –ACF offers 50% to 100% throughput gain over EDCA & HCCA depending on traffic model –ACF meets and exceeds QoS requirements with greater efficiency ScenarioThroughput (Mbps) Scenario 1 – 5.25 GHz SGI-52 HCF Scenario 1 – 5.25 GHz SGI-52 ACF Scenario 6 – 5.25 GHz HCF44.72 Scenario 6 – 5.25 GHz ACF69.42

doc.: IEEE /1404r0 Submission November 2004 John Ketchum, et al, QualcommSlide 24 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

doc.: IEEE /1404r0 Submission November 2004 John Ketchum, et al, QualcommSlide 25 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.

doc.: IEEE /1404r0 Submission November 2004 John Ketchum, et al, QualcommSlide 26 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.

doc.: IEEE /1404r0 Submission November 2004 John Ketchum, et al, QualcommSlide 27 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 STBC IP status needs to be clarified –ES should be an Optional Feature that can provide significant longevity to the 11n standard.

doc.: IEEE /1404r0 Submission November 2004 John Ketchum, et al, QualcommSlide 28 Summary Qualcomm proposal builds on existing a,g,e design Two PHY operating modes exceed TGn throughput requirements at 30 meters –Spatial Spreading –Eigenvector Steering provides best rate/range performance Simple MAC enhancements take full advantage of HT PHY –Required for 100 Mbps throughput in realistic operating environments –QoS-sensitive applications are not satisfied with EDCA