Type-II Hybrid ARQ protocol and map receiver for DS-CDMA systems
Abstract
In this work, an analysis of a Type-II Hybrid ARQ Protocol in slotted DS-CDMA packet radio systems is performed, and a MAP receiver for Rayleigh fading DS-CDMA channels is designed. In the first part of this work, the application of a type-II hybrid ARQ protocol in a slotted direct-sequence code-division multiple-access (DS-CDMA) packet radio system is investigated. In the physical layer, packet error and packet success probabilities are computed using the improved Gaussian approximation technique, which accounts for the bit-to-bit error dependence within a packet. In the data-link layer, the systems with transmitter buffer length equal to 1 and greater than 1 are analyzed separately. For the first case, two-dimensional Markov chains are employed to model the system dynamic. Based on this model, the performance of the type-II hybrid ARQ protocol is upper and lower bounded by considering, respectively, a superior scheme and an inferior scheme. Steady state throughput and delay performances of the two bounding schemes are obtained. For the second case, Equilibrium Point Analysis (EPA) technique is employed to approximately compute the system performance including throughput and delay, and to analyze stability. Simulations are also performed to check the accuracy of the EPA technique. In the second part of this work, a decision-feedback MAP receiver is proposed for time-selective fading CDMA channels. The receiver consists of a sequence-matched filter and a MAP demodulator. Outputs samples (more than one per symbol) from the matched filter are fed into the MAP demodulator. The MAP demodulator exploits the channel memory by delaying the decision and using a sequence of observations. This receiver also rejects MAI and estimates channel fading coefficients implicitly to give good demodulation decisions. Moreover, computer simulations are performed to evaluate the BER performance of the receiver under various channel conditions.
Degree
Ph.D.
Advisors
Lehnert, Purdue University.
Subject Area
Electrical engineering|Systems design
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