Quality of service analysis for hybrid-ARQ

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Title: Quality of service analysis for hybrid-ARQ
Author: Gunaseelan, Nirmal K.
Abstract: Data intensive applications , requiring reliability and strict delay constraints , have emerged recently and they necessitate a different approach to analyzing system performance . In my work , I establish a framework that relates physical channel parameters to the queueing performance for a single -user wireless system . I then seek to assess the potential benefits of multirate techniques , such as hybrid -ARQ (Automatic Repeat reQuest ) , in the context of delay -sensitive communications . Present methods of analysis in an information theoretic paradigm define capacity assuming that long codewords can be used to take advantage of the ergodic properties of the fading wireless channel . This definition provides only a limited characterization of the channel in the light of delay constraints . The assumption of independent and identically distributed channel realizations tends to over -estimate the system performance by not considering the inherent time correlation . A finite -state continuous time Markov channel model that I formulate enables me to partition the instantaneous data -rate received at the destination into a finite number of states , representing layers in a hybrid -ARQ scheme . The correlation of channel has been incorporated through level crossing rates as transition rates in the Markov model . The large deviation principle governing the buffer overflow of the Markov model , is very sensitive to channel memory , is tractable , and gives a good estimate of the system performance . Metrics such as effective capacity and probability of buffer overflow , that are obtained through large deviations have been related to the wireless physical layer parameters through the model . Using the above metrics under QoS constraints , I establish the quantitative performance advantage of using hybrid -ARQ over traditional systems . I conduct this inquiry by restricting attention to the case where the expected transmit power is fixed at the transmitter . The results show that hybrid -ARQ helps us in obtaining higher effective capacity , but it is very difficult to support delay sensitive communication over wireless channel in the absence of channel knowledge and dynamic power allocation strategies .
URI: http : / /hdl .handle .net /1969 .1 /ETD -TAMU -2720
Date: 2009-05-15


Quality of service analysis for hybrid-ARQ. Available electronically from http : / /hdl .handle .net /1969 .1 /ETD -TAMU -2720 .

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