John Ketchum, Bjorn A. Bjerke, and Irina Medvedev Qualcomm, Inc.

1. John Ketchum,Bjorn A. Bjerke, and Irina MedvedevQualcomm, Inc. 802.11n MIMO Link Performance: Some Simulation Results John Ketchum, et al., Qualcomm Incorporated

2. Presentation Outline • MIMO system overview • Link simulation overview • Preliminary simulation results: • Throughput and PER performance with 802.11n channel B and rate adaptation (CC67) • PER vs. SNR performance in AWGN (CC59) • Hardware prototype summary John Ketchum, et al., Qualcomm Incorporated

3. MIMO System Overview • 2x2 – 4x4 MIMO-OFDM: enables multiplexing of up to 4 spatial channels • OFDM structure identical to 802.11a/g (i.e., 52 subcarriers) • 802.11a/g constraint length 7, rate ½ convolutional code and punctured rates. • 802.11a/g QAM modulations + 256-QAM • Additional rates adopted to provide increased spectral efficiency • Two approaches to spatial multiplexing: • Eigensteering: • Full CSI operation; Tx & Rx steering based on SVD decomposition per OFDM subcarrier • Spatial spreading: • Partial CSI operation; Rx-only spatial processing • Separate coding/interleaving per data stream • Interleaving over single OFDM symbol: identical to 802.11a/g • Closed-loop PHY rate adaptation based on observed Rx SNR John Ketchum, et al., Qualcomm Incorporated

4. 4x4 MIMO Baseband System John Ketchum, et al., Qualcomm Incorporated

5. Extended 802.11a/g Rate Set Used in Simulations John Ketchum, et al., Qualcomm Incorporated

6. Closed-Loop Rate Adaptation • Forward link data rates determined by the STA and communicated to the AP. Rate adaptation algorithm determines the max. data rate supported per spatial stream, based on Rx SNR per subcarrier per stream computed from channel estimates. • Reverse link data rates determined by the AP and communicated to the STA. Rate adaptation algorithm identical to that operating in the STA. John Ketchum, et al., Qualcomm Incorporated

7. Simulation of Spatial Multiplexing Using Tx & Rx Eigensteering • Common MIMO Training Sequence broadcast by AP once every SCAP (Scheduled Access Period) (…,t0,t3,…). Forward link (FL) channel coefficients estimated by STA receiver • FL Dedicated MIMO Training Sequence (steered) transmitted by AP at t1=0.5 ms, immediately followed by FL data PPDU • Reverse link (RL) Dedicated MIMO Training Sequence transmitted by STA at t2=1.5 ms, immediately followed by RL data PPDU • Transmit and receive steering vectors derived from most recent channel estimates • Closed-loop rate adaptation: FL and RL data rates determined based on receive SNRs observed in previous frames John Ketchum, et al., Qualcomm Incorporated

8. Simulation Sequence • Channel estimation and rate control occurs over three SCAPs (2.048 ms each) • First SCAP: • STA receives Common MIMO Training Sequence • Computes channel estimate • Transmits Dedicated MIMO Training Sequence (steered) • AP receives Dedicated MIMO Training Sequence • Computes estimate of receive & transmit steering vectors • Second SCAP: • AP sends Dedicated MIMO Training Sequence (steered) • STA makes FL rate selection based on received Dedicated MIMO Training Sequence • STA sends Dedicated MIMO Training Sequence (steered) with DL rate selection • AP makes RL rate selection based on received dedicated MIMO Training Sequence • Third SCAP: • AP sends data PPDU based on rate choice in previous SCAP • Includes RL rate selection • STA sends data PPDU SCAP = Scheduled Access Period John Ketchum, et al., Qualcomm Incorporated

9. Simulation Parameters • 2x2 and 4x4 system configurations • IEEE 802.11n channel models B, D and E • IEEE 802.11n impairment models: • Time-domain channel simulator with 5x oversampling rate (Ts=10 ns) • Rapp nonlinear power amplifier model (IM1): • Total Tx power = 17 dBm; Psat = 25 dBm • 2x2 backoff = 11 dB per PA; 4x4 backoff = 14 dB per PA • Carrier frequency offset : -13.675 PPM (IM2) • Sampling clock frequency offset: -13.675 PPM (IM2) • Phase noise at both transmitter and receiver (IM4) • 100 channel realizations generated for each SNR point • In each channel realization the Doppler process evolves over three SCAPs to allow simulation of channel estimation, closed-loop rate adaptation and FL/RL data transmission in fading conditions John Ketchum, et al., Qualcomm Incorporated

10. Simulation Parameters (cont’d) • Stopping criterion: 10 packet errors or 400 packets transmitted per channel realization • Targeted packet error rate performance: mean PER <= 1% • Simulation results: • 2x2 and 4x4 systems • Packet size: 1000 B • Average throughput vs. SNR • Throughput distributions • Packet error rate distributions • Packet error rate vs. SNR in AWGN (“Fourier channel”) John Ketchum, et al., Qualcomm Incorporated

11. 2x2 Simulation Results: Average throughput vs. SNR John Ketchum, et al., Qualcomm Incorporated

12. 2x2 Throughput Distributions(Forward and Reverse Links) John Ketchum, et al., Qualcomm Incorporated

13. 2x2 Packet Error Rate Distributions (Forward and Reverse Links) John Ketchum, et al., Qualcomm Incorporated

14. 4x4 Simulation Results: Average throughput vs. SNR John Ketchum, et al., Qualcomm Incorporated

15. 4x4 Throughput Distributions(Forward and Reverse Links) John Ketchum, et al., Qualcomm Incorporated

16. 4x4 Packet Error Rate Distributions (Forward and Reverse Links) John Ketchum, et al., Qualcomm Incorporated

17. Per-Eigenmode Data Rate Distributions • Distribution of data rates picked by the rate selection algorithm in a 4x4 system (Forward Link) • Independent data rates per stream (eigenmode) • SNR = 20, 30, 40, 50 dB • Legend: • 0: Eigenmode does not support transmission • 1: BPSK (0.5 bps/Hz) • 2, 3: QPSK (1.0 - 1.5 bps/Hz) • 4, 5, 6: 16-QAM (2.0 - 3.0 bps/Hz) • 7, 8, 9, 10: 64-QAM (3.5 - 5.0 bps/Hz) • 11, 12: 256-QAM (6.0 - 7.0 bps/Hz) John Ketchum, et al., Qualcomm Incorporated

18. 4x4, Channel B, SNR = 20 dB John Ketchum, et al., Qualcomm Incorporated

19. 4x4, Channel B, SNR = 30 dB John Ketchum, et al., Qualcomm Incorporated

20. 4x4, Channel B, SNR = 40 dB John Ketchum, et al., Qualcomm Incorporated

21. 4x4, Channel B, SNR = 50 dB John Ketchum, et al., Qualcomm Incorporated

22. Packet Error Rate vs. SNR in AWGN • 2x2 and 4x4 Fourier matrix channels as specified by CC59 • Perfect synchronization and channel estimation; no impairments • Fixed rates (rate adaptation turned off) • Simulation results obtained with the following rates: • BPSK, R=1/2 (6 Mbps per stream), • QPSK, R=3/4 (18 Mbps per stream) • 16-QAM, R=3/4 (36 Mbps per stream) • 64-QAM, R=3/4 (54 Mbps per stream) • 256-QAM, R=7/8 (84 Mbps per stream) • Packet size: 1000 B John Ketchum, et al., Qualcomm Incorporated

23. 2x2 PER vs. SNR John Ketchum, et al., Qualcomm Incorporated

24. 4x4 PER vs. SNR John Ketchum, et al., Qualcomm Incorporated

25. Acquisition Performance • Probability of detection • Frequency estimate error variance • Frequency estimate error distributions • 40 ppm timing and frequency offset @5.25 GHz • 1000 channel realizations, 20 trials per channel realization John Ketchum, et al., Qualcomm Incorporated

26. Short Training Sequence Detection Performance in TGn Channels John Ketchum, et al., Qualcomm Incorporated

27. Frequency Estimation Performance in TGn Channels John Ketchum, et al., Qualcomm Incorporated

28. Frequency Error CDF SNR = 10 dB John Ketchum, et al., Qualcomm Incorporated

29. MIMO WLAN Prototype John Ketchum, et al., Qualcomm Incorporated

30. Qualcomm MIMO WLAN Prototype • Fully operational hardware prototype of 802.11n MIMO WLAN modem • Supports four antennas for Tx/Rx • Processing implemented in two Virtex-II Xilinx FPGAs • FPGA board has four channels that are digitized using four 12-bit A/D converters • All signal processing is real-time • IF sampled at 80 MHz is converted to complex baseband at 20 MHz sampling rate • FFT and spatial processing runs at peak rate of 250 kHz • Multiple parallel convolutional decoders run at 80 MHz clock to provide high-speed decoding • Fully operational hardware channel estimation and tracking • Supports stationary and low-mobility operation • Closed-loop rate control performs real-time rate adjustments • Performance matches results of detailed simulations • Operates in PCS band (1930 – 1950 MHz) • 0 dBm per antenna Tx power to limit interference to PCS users per experimental license John Ketchum, et al., Qualcomm Incorporated

31. MIMO WLAN Prototype John Ketchum, et al., Qualcomm Incorporated

32. MIMO WLAN Prototype John Ketchum, et al., Qualcomm Incorporated

33. MIMO WLAN Measured Performance • Measurements made in Qualcomm’s Concord MA offices • Renovated mill building with brick outer walls, sheet-rock on metal studs inner walls • 41.2 m x 16.8 m, 3.2 m high floor-to-ceiling walls • Measured values indicate error-free physical-layer data rates achieved • All rates reflect communications between AP and stations • Measurements made at 1940 MHz • Measurement results extrapolated to 2.4 GHz and 5.25 GHz unlicensed bands • Data rates scaled to reflect operation in SNRs were modified to reflect 17 dBm total Tx power, and increased path loss at 2.4 GHz (1.6 dB) and 5.25 GHz (8.4 dB) • Resulting median/minimum physical layer data rates: • 2.4 GHz: 310/198 Mbps • 5.25 GHz: 225/120 Mbps John Ketchum, et al., Qualcomm Incorporated

34. Measured PHY Data Rates John Ketchum, et al., Qualcomm Incorporated

35. Extrapolated PHY Data Rates John Ketchum, et al., Qualcomm Incorporated

36. Summary • Eigenvector steered mode supports high throughput operation in 2x2 and 4x4 configurations • Stable wideband spatial channels synthesized from eigenmodes easily support 256 QAM under full PHY impairments • High throughput eigenvector steering operation proven in hardware prototype John Ketchum, et al., Qualcomm Incorporated