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The sensitivity of performance to antenna element spacing when using the 802.11n Channel Model

The sensitivity of performance to antenna element spacing when using the 802.11n Channel Model. daisuke.takeda@toshiba.co.jp noritaka.deguchi@toshiba.co.jp. Corporate Research & Development Center Toshiba Corporation. The Concern.

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The sensitivity of performance to antenna element spacing when using the 802.11n Channel Model

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  1. The sensitivity of performance to antenna element spacing when using the 802.11n Channel Model daisuke.takeda@toshiba.co.jp noritaka.deguchi@toshiba.co.jp Corporate Research & Development Center Toshiba Corporation Daisuke Takeda (Toshiba Corporation)

  2. The Concern Antenna spacing used for simulations is not currently specified in the Comparison Criteria document. Daisuke Takeda (Toshiba Corporation)

  3. Objective • 802.11n channel model • Uniform linear array is mentioned in doc-940r1. D=2pd / l ( d: Antenna spacing, l: Wavelength ) • In doc-940r1, angular spread is defined for each channel model. • The minimum angular spread is less than 15 degree (Model B, 1st-cluster). • The maximum angular spread is more than 50 degree (Model F, 2nd-cluster). • Matlab channel model assumes 0.5l astypical parameter but it is not mandatory in Comparison Criteria. (1) Daisuke Takeda (Toshiba Corporation)

  4. Objective (cont’d) • Small angular spread • Antenna spacingis critical issue. (especially when antenna spacing d is small) d d • Large angular spread • Antenna spacing is not so critical. • SpatialCorrelation • Spatial correlation is governed by Bessel Function. • Angular spread affects spatial correlation. (may not be pure Bessel Function) r J0(2p d/l) d How much does antenna spacing affect PER performance? Daisuke Takeda (Toshiba Corporation)

  5. Simulation Parameters Table 1 Simulation Parameters Daisuke Takeda (Toshiba Corporation)

  6. Fig.1 Channel Model B (LOS) Daisuke Takeda (Toshiba Corporation)

  7. Fig.2 Channel Model D (LOS) Daisuke Takeda (Toshiba Corporation)

  8. Table 2 • Performance Improvement from 0.5l in Model B [dB] • at a PER of 10-2 0dB – 2dB 2dB – 4dB > 4dB • Table 3 • Performance Improvement from 0.5l in Model C [dB] • at a PER of 10-2 Daisuke Takeda (Toshiba Corporation)

  9. Table 4 • Performance Improvement from 0.5l in Model D [dB] • at a PER of 10-2 0dB – 2dB 2dB – 4dB > 4dB • Table 5 • Performance Improvement from 0.5l in Model E [dB] • at a PER of 10-2 Not yet simulated. Not yet simulated. Daisuke Takeda (Toshiba Corporation)

  10. From Simulation Results • The performance difference is significant for Model B. • Due to narrow angular spread. • The performance difference for 0.5l and 1.0l spacing is 6dB at a PER of 10-2. ( 54Mbps, 3x3 case ). • Performance differences increase with the number of antennas. • The difference increases with data rate. • In 54Mbps, throughput performance will be seriously affected. Daisuke Takeda (Toshiba Corporation)

  11. Conclusions • Performance varies appreciably with antenna spacing (by up to 6dB!) • It depends on channel model, data rate and number of antennas. • The comparison criteria must specify antenna spacing. • A fair comparison of proposals can only occur if the same antenna geometry and spacing are employed by everyone. • Hence, these parameters should be specified in the Comparison Criteria document for both the transmitter and receiver. Daisuke Takeda (Toshiba Corporation)

  12. End Daisuke Takeda (Toshiba Corporation)

  13. Possible Solution? Antenna spacing should be specified as follows? • Antenna Aperture : (m-1) x d • m : The number of antennas • d : Antenna spacing is 0.5l (precise value to be decided). Daisuke Takeda (Toshiba Corporation)

  14. Fig.3 Channel Model C (LOS) Daisuke Takeda (Toshiba Corporation)

  15. Fig.4 Channel Model E (LOS) Daisuke Takeda (Toshiba Corporation)

  16. Spatial Correlation for Model B, Tap #3 Daisuke Takeda (Toshiba Corporation)

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