Design of Distributed Space-Time Block Codes for Relay Networks

다국어 초록 (Multilingual Abstract)

The fading effect often faced in wireless communications can cause severe attenuation in signal strength. To solve this problem, diversity techniques (in terms of spatial/time/frequency) have been considered. For example, spatial diversity can be achieved by using multiple antennas at the transmitter or the receiver or both. One important architecture that can efficiently exploit the multiple antennas is the space-time block coding (STBC). The realization of STBC requires more than one antenna at the transmitter. Unfortunately, the use of multiple antennas is not practical in many wireless devices due to the size limitation. Recently, the “cooperative diversity”, also known as “user diversity”, enables single-antenna mobiles in a multi-user environment to share their antennas and generate a virtual multiple-antenna transmitter that allows them to achieve transmit diversity. To apply concept of the STBC schemes to the cooperative communications, Laneman et al. suggest the use of “conventional” orthogonal STBC in a “distributed” fashion for practical implementation of user cooperation.
The pioneering works on distributed STBC (DSTBC) assume flat fading channels. This can be achieved by using multi-carrier techniques such as orthogonal frequency division multiplex (OFDM) to divide a whole spectrum into a set of narrower bands. Hence, the channel can be considered flat in each sub-band. However, for current wireless communications with single-carrier transmission, the frequency selective channels cannot be avoided. Thus, in this dissertation, we I will consider the application of DSTBC to frequency selective fading channels.
In the first part of ourmy thesis, we I present a new design of DSTBC to achieve full rate transmission and channel decoupling property as in conventional STBC by using zero-padding (ZP). Several receiver techniques in frequency domain are studied for the signal detection of the proposed DSTBC. The extension from ZP to unique-word (UW) will be proposed in the second part. Exploiting the properties of the UW, I will present in the third part of my thesis a method of channel estimation for relay networks.

목차 (Table of Contents)

• Chapter 1 Introduction = 1
• 1.1 Overview of STBC and DSTBC = 1
• 1.2 Contributions of this Dissertation = 2
• 1.3 Dissertation Structure = 3
• Chapter 2 Background = 4
• 2.1 Orthogonal STBCs = 4
• 2.2 Distributed STBCs = 6
• Chapter 3 Proposed DSTBC with ZP for Frequency Selective Fading Channels = 10
• 3.1 System Model = 10
• 3.2 Review of Current DSTBCs = 11
• 3.3 New Design of DSTBC for Frequency Selective Fading Channels in Single-Relay Systems = 12
• 3.3.1 Decoupling in Time-Domain = 15
• 3.3.2 Decoupling in Frequency-Domain = 15
• 3.4 New Design of DSTBC for Frequency Selective Fading Channels in Two-Relay Systems = 16
• 3.4.1 Decoupling in Time-Domain = 18
• 3.4.2 Decoupling in Frequency-Domain = 19
• Chapter 4 Proposed DSTBC with UW for Frequency Selective Fading Channels = 20
• 4.1 System Model and Data Block Structure = 20
• 4.2 New Design of DSTBC for Frequency Selective Fading Channels in Single-Relay Systems with UW Extension = 21
• 4.3 New Design of DSTBC for Frequency Selective Fading Channels in Two-Relay Systems with UW Extension = 23
• Chapter 5 Channel Estimation for Proposed DSTBC with UW = 24
• 5.1 Channel Estimation for UW-based DSTBC for Frequency Selective Fading Channels in Single-Relay Systems = 24
• 5.2 Channel Estimation for UW-based DSTBC for Frequency Selective Fading Channels in Two-Relay Systems = 26
• Chapter 6 Simulation Results = 27
• 6.1 Proposed DSTBC with ZP for Single-Relay Systems = 27
• 6.1.1 Performance Comparison for Various Combinations of Channel Lengths = 27
• 6.1.2 Performance Comparison for Different Equalizers = 29
• 6.2 Proposed DSTBC with ZP for Two-Relay Systems = 30
• 6.2.1 Performance Comparison for Various Combinations of Channel Lengths = 30
• 6.2.2 Performance Comparison for Different Equalizers = 33
• 6.3 Proposed DSTBC with UW for Single-Relay and Two-Relay Systems = 33
• Chapter 7 Conclusion = 35
• 7.1 Summary and Conclusion = 35
• 7.2 Future Works = 35
• Bibliography = 37