On The Performance Analysis And Design Of Cooperative ARQ Protocols In Relay Communication Models

In recent years, multi-user cooperative communications technology like cooperative diversity has become a hot topic in distributed wireless communication network for realizing the so-called "virtual antenna array" to greatly enhance the anti-fading performance for wireless communication system and improve resource efficiency and system capacity. Cooperative ARQ protocol extends the cooperative idea to the link layer ARQ design, wherein destination nodes may receive information from multiple links with the assistance from relay nodes to achieve diversity gain and the whole system performance improvement.At first, this thesis highlights the C-ARQ principle over relay communication model. Then the H-ARQ protocol, DF relay strategy C-ARQ protocol, AF relay strategy C-ARQ protocol are analyzed by using queuing theory with Poisson arrival assumption. And one improved C-ARQ is proposed based on H-ARQ protocol and DF relaying strategy C-ARQ protocol. Numerical results are presented to unveils that, the proposed improved C-ARQ protocol is the best, while DF relay strategy C-ARQ outperforms the AF C-ARQ relay strategy C-ARQ, the performance of the H-ARQ is the worst one. In addition, the thesis addresses the influence of data packet arrival rate on the system delay. It is shown that the system transmission delay will be prolonged with the increase in the data arrival rate. Meanwhile, a larger time slot between source node and relay node will give rise to a longer systen delay and the increase in the data frames in the relay node buffer.Secondly, truncated ARQ protocols are introduced by setting the maximum number of transmission attempt to reduce system latency. The impact of maximum number of transmission attempt on the truncated ARQ are investigated to show the performance degradation when comparing with the ARQ protocols without limit in the maximum transmission attempt number. It is shown through numerical simulation results that reliable transmission can not be guaranteed any more for truncated ARQ prptocols. Generally, a larger maximum transmission attempt number will lead to a better performance with the paid cost in the transmission efficiency.Finally, the C-ARQ protocols over relay communication model with multi-relay are focused, wherein relay selection may be selected by the source according to some predefined criteria, and the resultant performance is presented to highlight the ARQ protocols performance with different relay selection strategies. It is validated that the relay selection scheme based on instantaneous SNR seems to be superior to that based on fair mechanism in terms of the realized System transmission delay, waiting queue length. In additon, the relay selection schemes are re-examined by considering the paid cost with respect to different relays. The analysis in this thesis suggests that, although the relay selection scheme based on instantaneous SNR seems to be less economically efficient for every single transmission attempt, it tends to be more economical efficient than the fair relay selection scheme when multiple transmission attempts are considered, especially at low SNR region, wherein fair selection scheme generally needs more transmission attempt to secure the reliable delivery. Moreover, there exists a turning point between the total cost of data transmission and the relay selection scheme. It is shown that the fair relay selection tends to be inefficient within low SNR region and will become efficient within high SNR region. The analysis in this thesis may provide some useful reference for the price based relay selection in C-ARQ design.