Receive Beamforming for Cognitive Radio MIMO System With Second-Order Statistics

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研究生：	張家豪 Chang, Chia-Hao
論文名稱：	Receive Beamforming for Cognitive Radio MIMO System With Second-Order Statistics 使用二階統計特性於多天線感知無線電系統之接收波束成形
指導教授：	吳仁銘 Wu, Jen-Ming
口試委員:
學位類別：	碩士 Master
系所名稱：	電機資訊學院 - 電機工程學系 Department of Electrical Engineering
論文出版年：	2010
畢業學年度：	99
語文別：	英文
論文頁數：	41
中文關鍵詞：	波束成形、干擾消除、感知無線電、多輸入多輸出
相關次數：	點閱：4 下載：0
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Cognitive Radio (CR) is a promising approach for improving
the utilization of the precious radio spectrum. The primary user and cognitive user regard each other as interference. The conventional null-space based method is receiving the data through the null-space of the interference channel. In this thesis, we present a receive beamforming approach in the receiver of the cognitive user to mitigate the interference from the primary user. This method can maximize the signal to interference and noise ratio (SINR) in the receiver of cognitive user. The simulation results show that the receive beamforming approach outperforms the null-space based method, no matter the receiver antennas of cognitive user are more or less than the antennas of primary user. This thesis also presents a method of channel estimation using the second order statistics for the cognitive receive beamforming.

感知無線電技術 (Cognitive Radio) 是個增進頻帶使用效率非常有前瞻性的方法。這個方法可以智慧的偵測並察覺哪些通訊頻帶沒有被使用，然後將第二使用者分配到沒有被使用的頻帶上。因為第一使用者和第二使用者會視對方為干擾，所以需要應用些方法將彼此的干擾消除掉。為了消除第二使用者對第一使用者造成的干擾，應用了傳送波束成形方法。這個方法使第二使用者的傳送端在傳送資訊前先乘上一個預編碼 (precoder) ，如此一來，可以使第二使用者傳送的資料沿著干擾通道的零空間傳送，不會對第一使用者造成任何干擾。第二使用者傳統上為了消除第一使用者對第二使用者造成的干擾，應用了基於零空間的波束成形方法，而這個方法是只在干擾通道的零空間上接收訊號，所以可以完全阻隔干擾。在本篇論文中，提出另一個應用在第二使用者接收端的波束成形方法去消除第一使用者造成的干擾。這個方法雖然不一定能把第一使用者造成的干擾完全消除，但是可以將第二使用者接收端的訊號對干擾及雜訊比 (SINR) 最大化。模擬的結果顯示出將第二使用者接收端的訊號對干擾及雜訊比 (SINR) 最大化的波束成形方法在錯誤率上會比基於零空間的波束成形方法低。以上的結果不管第二使用者的接收端天線數比第一使用者多或者是少都適用。這篇論文也介紹了一個使用二階統計特性的通道估計方法，而這個方法適用於本篇論文所提出的架構。

Contents
Abstract i
Contents ii
Introduction 1
1 Backgrounds and Motivations . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2 Thesis Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
System Model and Cognitive Transmit Beamforming 5
1 The Concept of Underlay Cognitive Radio Scenario . . . . . . . . . . . . . . 5
2 Channel Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3 Introduction of Environmental Learning and Channel Training . . . . . . . . 9
4 Transmit Beamforming for Cognitive Radio System . . . . . . . . . . . . . . 11
The Receive Beamforming Method 15
1 The Null-space Based Method . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2 Maximizing The Signal to Interference and Noise Ratio Method . . . . . . . 18
Cognitive Receive Beamforming With the Second Order Statistics Channel
Estimation 22
1 Eigenvector of The Effective Channel Between CU Transmitter and CU Receiver 22
2 Estimation of The Effective Channel Amplitude and Phase . . . . . . . . . . 24
Simulation and Results 27
1 Simulation Environments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
2 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
2.1 Comparing The BER with Different Number of Antennas in Null-space
Based Method and Receive Beamforming Method . . . . . . . . . . . 27
2.2 The Simulation Result of Phase Error in Estimating The Channel be-
tween CU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2.3 Variation of Signal to Interference Ratio (SIR) From PU . . . . . . . 35
Conclusion 38


List of Figures
1 Frequency band of MB-OFDM UWB system. . . . . . . . . . . . . . . . . . 6
2 The channel model between PU and CU. . . . . . . . . . . . . . . . . . . . . 7
3 The division of time frame in CU system. . . . . . . . . . . . . . . . . . . . . 10
1 The total time frame after adding the pilot training time symbols. . . . . . . 25
1 Ideal Rcr and Rc, ideal Hc with different number of antennas. SIR=10 dB. . 29
2 Estimated Rcr and Rc, ideal Hc with different number of antennas. SIR=10 dB. 30
3 Estimated Rcr and Rc, estimated Hc with different number of antennas.
SIR=10 dB, Pilot length = 10. . . . . . . . . . . . . . . . . . . . . . . . . . . 31
4 CU-Rx with 4 antennas in different channel condition, SIR=10 dB, Pilot
length = 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
5 CU-Rx with 3 antennas in different channel condition, SIR=10 dB, Pilot
length = 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
6 The phase error in estimating the channel between CU with different length
of pilot time symbols, SIR=10 dB . . . . . . . . . . . . . . . . . . . . . . . . 34
7 The BER of different SIR in CU-Rx based on nullspace method. . . . . . . . 35
8 The BER of different SIR in CU-Rx based on receive maximizing SINR method. 36

List of Tables
1 Simulation Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

                                

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