Analysis of Active Interference Cancellation for Cognitive Radio MB-OFDM UWB Speaker: 王貞傑 Professor: 吳仁銘教授 date:

Outline Introduction to cognitive radio in ultra wideband AIC algorithm Simulation Conclusion

Introduction to cognitive radio

Spectrum utilization

Resource :spectrum UWB : GHz Wimax : GHz, GHz IEEE802.11a : GHz

Employ multi-band orthogonal frequency division multiplexing (MB-OFDM)

Cognitive Radio object 1) highly reliable communication 2) efficient utilization of the radio spectrum “Cognitive Radio” does what? 1) sense the spectral environment over a wide available band 2) use the spectrum only if communication does not interfere with licensed user. multiple signal dimensions : time, frequency, physical space, and user networks

“Cognitive Radio” Task 1) Radio-scene analysis 2) Channel-state estimation and predictive modeling 3) Transmit-power control and dynamic spectrum management => feedback

Interference avoidance method Non-rectangular windows Active interference canceling (AIC)

AIC algorithm

turning off the interfering tones: the inter-carrier interference may limit the notch depth to 5-10 dB AIC (active interference cancellation tones)

Over-sampling Why over-sampling MB-OFDM based interference Over-sampling rate = r

Minimization

MIMO AIC

Minimization

 唯一解 : 利用錯開頻帶，來消除所要干擾主要頻帶 的訊號，頻帶間不重複利用，否則 det =0  頻帶間有重複 (overlap) ，則造成有無限多組解

Simulation

Picture parameter Axis explanation & Input Parameter re-sampling rate Vs AIC number Turn-off Vs AIC with different re-sampling rate Comparison in different re-sampling rate Different protected sub-carriers MIMO AIC

Axis explanation: X-axis : sub-carrier index ( over-sampling ) Y-axis: power spectrum Input : QPSK ( a + j*b ) Random Number of fft =128

Parameter: over-sampling rate ( r ) protect-band sub-carriers AIC number

Picture parameter Axis explanation & Input Parameter re-sampling rate Vs AIC number Turn-off Vs AIC with different re-sampling rate Comparison in different re-sampling rate Different protected sub-carriers MIMO AIC

Protected spectrum 3 sub-carriers R=2 Turn-off

Protected spectrum 3 sub-carriers R=2 AIC

 With using 5 tones of AIC, It reaches the best performance.  more than 5 tones, e.g. 7 tones, performance goes back.

Protected spectrum 3 sub-carriers R=3 Turn-off

Protected spectrum 3 sub-carriers R=3 AIC

 With using 7 tones of AIC, It reaches the best performance.  more than 7 tones, e.g. 9 tones, performance goes back.

Protected spectrum 3 sub-carriers R=4 AIC

 With using 9 tones of AIC, It reaches the best performance.  more than 9 tones, e.g. 11 tones, performance goes back.

Protected spectrum 3 sub-carriers AIC R=5 best in 9 tones Protected spectrum 3 sub-carriers AIC R=6 best in 9 tones

Protected spectrum 3 sub-carriers AIC R=7 best in 9 tones Protected spectrum 3 sub-carriers AIC R=8 best in 11 tones

Protected spectrum 3 sub-carriers AIC R=100 best in 11 tones Protected spectrum 3 sub-carriers AIC R=50 best in 11 tones

#AIC r12348

Picture parameter Axis explanation & Input Parameter re-sampling rate Vs AIC number Turn-off Vs AIC with different re-sampling rate Comparison in different re-sampling rate Different protected sub-carriers MIMO AIC

Comparison in different re-sampling rate(1/4) R=2 R=3

Comparison in different re-sampling rate(2/4) R= 4 R=5

Comparison in different re-sampling rate(3/4) R=6 R=7

Comparison in different re-sampling rate(4/4) R=8

Picture parameter Axis explanation & Input Parameter re-sampling rate Vs AIC number Turn-off Vs AIC with different re-sampling rate Comparison in different re-sampling rate Different protected sub-carriers MIMO AIC

Protected spectrum 3 sub-carriers AIC R=4 Protected spectrum 5 sub-carriers AIC R=4

Protected spectrum 7 sub-carriers AIC R=4 Protected spectrum 9 sub-carriers AIC R=4

Protected spectrum 11 sub-carriers AIC R=4 Protected spectrum 13 sub-carriers AIC R=4

Picture parameter Axis explanation & Input Parameter re-sampling rate Vs AIC number Turn-off Vs AIC with different re-sampling rate Comparison in different re-sampling rate Different protected sub-carriers MIMO AIC

2Tx AIC Protected spectrum 4 sub-carriers R=4 AIC 6 sub-carriers Channel? No

2Tx AIC

Conclusion AIC 壓縮能力大約 100 ~ 130 dB AIC sub-carrier 不是越多越好，適用即可。越遠 的 sub-carrier 影響越小。

Reference Hirohisa Yamaguchi, “ Active Interference Cancellation Technique for MB-OFDM Cognitive Radio” 2004 Danijela Cabric, Shridhar Mubaraq Mishra, Robert W. Brodersen, “ Implementation Issues in Spectrum Sensing for Cognitive Radios” J. Mitola III, “Cognitive radio for flexible mobile multimedia communications,” in 1999 IEEE International Workshop on Mobile Multimedia Communications, Nov. 1999, pp J. Mitola III, “Cognitive radio an integrated agent architecture for software defined radio,” PHD thesis, KTH Royal Institute of Technology, Stockholm, Sweden, Federal Communications Commission, “ Spectrum Policy Task Force,”Rep. ET Docket no , Nov

Simon Haykin, “Cognitive Radio: Brain-Empowered Wireless Communications” IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS, VOL. 23, NO. 2, FEBRUARY 2005