UM E-Theses Collection (澳門大學電子學位論文庫)

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Performance analysis of HARQ schemes operating over time correlated fading channels

English Abstract

Wireless transmissions are generally affected by fading channels, interference and noise, and transmission errors are usually inevitable. Forward error correction (FEC) is one of the methods employed commonly to handle transmissions errors without any retransmission. Another approach for error correction is to use automatic repeat request (ARQ). In ARQ schemes, errors can be detected at the receiver and the receiver can send back acknowledgment (ACK) / non-acknowledgment (NACK) to the transmitter based on which the transmitter can decide whether there is a need for retransmission. Hybrid automatic repeat request (HARQ) is the combination of FEC and ARQ and has the capability to further enhance the performance. It has been applied in various systems, including WCDMA, CDMA 2000 and LTE, etc. In general, performance analysis is significant to understand the system behavior for better design and improved performance. Analysis of HARQ schemes however is still lacking due to the complexity of the schemes and the mathematical difficulties. This thesis focuses on the performance analysis of HARQ schemes. Specifically, there are two main contributions in this master thesis work. Firstly, an opportunistic cooperative hybrid automatic repeat request scheme with chase combining (HARQ-CC) is analyzed. Different from prior analyses, time correlated Rayleigh fading channels are considered. Based on moment generation function and Laplace transform, the outage probability and throughput in terms of long-term average v transmission rate (LATR) are derived in closed-forms for this opportunistic cooperative HARQ system. Secondly, the performance of hybrid automatic repeat request with incremental redundancy (HARQ-IR) in cooperative systems is analyzed. Different from prior analyses, time correlated Nakagami fading channels are considered. Due to the complexity of Nakagami distribution and cooperative HARQ-IR as well as the presence of time correlation, the analysis becomes very challenging. By adopting Gamma and Gaussian approximations, the outage probability and long-term average transmission rate (LATR) are derived. The accuracy of the analytical results for both HARQ-CC and HARQ-IR are validated by simulations. The impacts of various system parameters on the outage probability and LATR are discussed and the optimal transmission rate to maximize LATR subject to certain outage constraint is also found.

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Yang, Xuan Xuan


Faculty of Science and Technology


Department of Electrical and Computer Engineering




Wireless communication systems


Ma, Shao Dan

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