Joint AMC-ARQ transmission in wireless systems with finite-length transmit buffers

Adaptive modulation and coding (AMC) and automatic repeat request (ARQ) are two of the most important techniques to overcome the limitations of the wireless channel, and to thereby improve quality of service (QoS) over wireless networks. Traditionally, the performance of these two techniques have been designed and analyzed separately. In this thesis, we develop a novel cross-layer design of joint AMC-ARQ transmission for wireless systems and analyze its performance while taking into account the finite-length buffer constraint at the transmitter. This work differs from previous works in that it considers the effect of the transmitter buffer size and the different ARQ strategies in the design and performance analysis. In particular, a new buffer-assisted AMC strategy is presented in which the data rate is selected based on channel fading conditions as well as the status of the transmit buffer. We carry out detailed performance analysis of the proposed systems with different traffic arrival patterns and buffer management strategies, based on the Markov chain theory. Mathematical analysis and simulations show that an all retransmit (AR) retransmission strategy achieves the best performance and power efficiency amongst all retransmission strategies. The results also indicate that a partial retransmit (PR) strategy would provide a fair tradeoff between improved performance and increased receiver complexity. Further, we show that the buffer-assisted AMC technique can improve the transmission reliability when compared to the traditional channel-based AMC strategy.