RELIABILITY-BASED HYBRID-ARQ USING CONVOLUTIONAL CODES By ABHINAV ROONGTA A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA

of Dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy RELIABILITY-BASED HYBRID-ARQ USING CONVOLUTIONAL CODES By Abhinav Roongta August 2005 Chair: John M. Shea Major Department: Electrical and Computer Engineering In this work we develop selective-retransmission hybrid-ARQ protocols for communication systems that use soft-input soft-output (SISO) decoders. The schemes that we propose are based on reliability-based hybrid-ARQ that use the estimated a posteriori probabilities at the output of the SISO decoder to adaptively determine the set of bits to be retransmitted in response to error detection. First we show the performance of the proposed scheme for nonfading additive white Gaussian noise channels without any interference. We begin by evaluating the performance of a simple reliability-based hybrid ARQ scheme that uses fixed rate convolutional codes in the forward channel and exploits their time-correlation properties to achieve smaller retransmission requests. Then we extend our work where rate-compatible punctured convolutional (RCPC) codes are used in the forward channel and arithmetic coding is used in the feedback channel. We compare the performance of the proposed scheme with the common approach to hybrid-ARQ that uses punctured convolutional codes. The results show that the proposed RB-HARQ scheme achieves better performance than a hybrid-ARQ scheme that uses only RCPC codes.