상세정보

Because the imperfect channel state information (CSI) estimated in the receiver could degrade the bit error rate (BER) performance significantly, accurate channel estimation in the receiver in a high-speed mobility environment is critical to maintaining reliable system performance under extreme conditions. To track a fast time-varying channel, the traditional pilot based channel estimation algorithms need an abundance of extra resources to transmit pilot symbols, which may significantly reduce the spectral efficiency and the overall data rate. In order to preserve the spectral efficiency, decision directed (DD) channel tracking can be applied. It uses previously detected symbols and can therefore feed the channel estimation process with data that reflect current CSI. The propagation of errors due to incorrect detections remains a profound problem in the DD schemes.
In this dissertation, we propose an expectation-maximization (EM)-based poor slot update method for multiple-input multiple-output (MIMO) iterative detection and decoding (IDD) receivers to increase their channel tracking capability in fast time-varying channels. The poor slots that trigger error propagation in a frame are selected, the CSI is updated, and the updated recursive least squares (RLS) channel tracking algorithm is executed. The accurate channel tracking capability of this new channel updating technique contributes to a 3-dB improvement in the BER performance of an IDD receiver in a fast mobile environment (>180 km/h). we also demonstrate that an approximately 20-25% complexity reduction can be achieved under various conditions.

List of Figures iv
List of Tables vi
Abstract 1
1 Introduction 3
1.1 Overview of the Channel Tracking for MIMO IDD Receiver 3
1.2 Contributions of the Dissertation 7
1.3 Outline of the Dissertation 8
2 Backgrounds of the Channel Tracking for MIMO IDD Receiver 10
2.1 MIMO IDD Receiver for Time-Varying Channel 12
2.2 MIMO Time-Varying Channel 16
2.3 MIMODD-RLS Channel Tracking 17
3 EM-based Poor Slot Update Process for MIMO IDD Receiver 20
3.1 System Model 22
3.2 Selection of Poor Slot 24
3.3 EM-based Update 24
3.4 Updated RLS Channel Tracking 29
3.5 Summary of the EM-based Poor Slot Update Method 31
3.6 Simulation Results 32
3.6.1 BER and MSE performance comparison 33
3.6.2 Performance-Complexity Tradeoff of EPU-OFF 41
3.6.3 Effect of The Window Size 42
3.7 Chapter Summary and Conclusions 45
4 Low-Complexity MIMO IDD Receiver under Fast Time-Varying channel 46
4.1 Overview of Complexity of the IDD Scheme 48
4.2 Computational complexity of EM-based poor slot update 53
4.3 Computational complexity of STS-SD detector 54
4.4 Computational complexity of turbo decoder 56
4.5 Optimal IDD parameters 56
4.6 Simulation Results 60
4.7 Chapter Summary and Conclusions 61
5 Conclusions 64
Notation 66
Acronyms 69
Bibliography 72