An Efficient ARQ Protocol for Adaptive Error Control over Time-Varying Channels

  • Authors:

  • Hlaing Minn;Mao Zeng;Annamalai Annamalai, Jr.;Vijay K. Bhargava

  • Affiliations:

  • Department of Electrical and Computer Engineering, University of Victoria, Victoria, B.C., Canada V8W 3P6;Motorola Inc., U.S.A.;Bradley Department of Department of Electrical and Computer Engineering, Virginia Tech., U.S.A.;Department of Electrical and Computer Engineering, University of Victoria, Victoria, B.C., Canada V8W 3P6

  • Venue:
  • Wireless Personal Communications: An International Journal
  • Year:
  • 2001

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Abstract

This paper investigates a simple and efficient stop-and-wait (SW) automaticrepeat-request (ARQ) scheme with adaptive error control. In this scheme, thechannel state information (CSI) is extracted by monitoring the contiguouspositive acknowledgment (ACK) or negative acknowledgment (NAK) messages.Exploiting this CSI, we adapt the coding strategy to the changes in thechannel condition, and thus improve the throughput efficiency. In order tofacilitate the throughput analysis and parameters optimization, we model theadaptive system with a Markov chain. Using this analytical model and assuminga static channel, an exact throughput expression for the adaptive ARQ protocolis derived and suboptimal adaptive system parameters are obtained. Thesedesign parameters are applied to the adaptive system in a typical time-varyingmobile radio channel characterized by Rayleigh multipath fading on top oflognormal shadowing. The throughput performance of the proposed adaptiveSW-ARQ scheme in such a time-varying fading channel is evaluated by computersimulation. For slow fading channels, the proposed adaptive system can trackthe channel variations very well, hence much throughput improvement can beachieved over conventional nonadaptive SW-ARQ schemes for almost all SNRvalues considered. The simulation results also confirm the applicability ofthe adaptive system parameters, so-obtained by the throughput analysis instatic channel, to a time-varying mobile radio channel.