1. daisuke.takeda@toshiba.co.jp noritaka.deguchi@toshiba.co.jp
Month 2000
The sensitivity of performance to antenna element spacing when using the n Channel Model
Corporate Research & Development Center
Toshiba Corporation
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2. Objective 802.11n channel model
Month 2000
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 AS is less than 15 degree (Model B, 1st-cluster).
The maximum AS is more than 50 degree (Model F, 2nd-cluster).
Matlab channel model assumes 0.5l as typical example.
(1)
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3. Objective (cont’d) Small AS case Large AS case Spatial Correlation
Month 2000
Objective (cont’d) d d
Small AS case
Antenna distance is critical issue. (especially when antenna spacing d is small)
Large AS case
Antenna distance is not so critical.
Spatial Correlation
Spatial correlation is governed by Bessel Function.
AS affects spatial correlation.
(may not be pure Bessel Function) r
J0(2p d /l) d
How much does antenna spacing affect PER performance?
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4. Simulation Parameters
Month 2000
Simulation Parameters
Table 1 Simulation Parameters
Data Rate (per antenna)
6Mbps, 54Mbps
Number of Antenna
2x2, 3x3, 4x4
Antenna Shape
Linear Array
Antenna Spacing
(0.3, 0.5, 1, 1.5, 5) x l
Algorithm
MMSE-BLAST
Channel Model
802.11n (B,C,D,E)
Channel Estimation
Ideal
Synchronization
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5. Fig.1 Channel Model B (LOS)
Month 2000
Fig.1 Channel Model B (LOS)
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6. Fig.2 Channel Model D (LOS)
Month 2000
Fig.2 Channel Model D (LOS)
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7. Performance Difference from 0.5l in Model B [dB]
Month 2000
Table 2
Performance Difference from 0.5l in Model B [dB]
at a PER of 10-2
0dB – 2dB
2dB – 4dB
> 4dB
Table 3
Performance Difference from 0.5l in Model C [dB]
at a PER of 10-2
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8. Performance Difference from 0.5l in Model D [dB]
Month 2000
Table 4
Performance Difference from 0.5l in Model D [dB]
at a PER of 10-2
0dB – 2dB
2dB – 4dB
> 4dB
Table 5
Performance Difference from 0.5l in Model E [dB]
at a PER of 10-2
--- We have not got yet
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9. From Simulation Results
Month 2000
From Simulation Results
The performance difference is serious for Model B.
Due to Narrow AS.
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.
(54Mbps experiences large differences).
In 54Mbps, Throughput performance will be seriously affected.
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10. Conclusions Performance varies appreciably with antenna spacing.
Month 2000
Conclusions
Performance varies appreciably with antenna spacing.
It depends on channel models, data rate and number of antennas.
The difference between 0.5l and 1.0l shows 6dB.
The comparison criteria must specify antenna separation.
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.
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11. Month 2000
End
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12. Fig.3 Channel Model C (LOS)
Month 2000
Fig.3 Channel Model C (LOS)
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13. Fig.4 Channel Model E (LOS)
Month 2000
Fig.4 Channel Model E (LOS)
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14. Spatial Correlation for Model B, Tap #3
Month 2000
Spatial Correlation for Model B, Tap #3
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