Huseyin Dogukan Cavdar, NJIT
Date : December 4, 2006 (Monday)
Time : 11:00 AM
Location : ECE 202, NJIT

Abstract

Communication performance over a wireless channel should be considered according to two main parameters: energy and throughput, and the reliable data transfer is a key to these goals. The reliable node-to-node data transfer is performed by link layer protocols. One prominent approach is called Automatic Repeat Request (ARQ) protocol. The traditional ARQ protocols attempt to recover the erroneously transmitted frames by retransmitting those frames, regardless of the channel state. Since this channel state unaware behaviour may cause unnecessary retransmissions, traditional ARQ protocols are expected to be energy inefficient. Some ideas have been proposed such as stochastic learning automaton based ARQ, and channel probing based ARQ. However, these algorithms do not attempt to estimate the channel’s existing condition. Instead, the retransmission decision is made according to a simple feedback, on whether the previous packet was successful.

This thesis presents four proposed algorithms, which incorporates the channel state estimate in the feedback process to judiciously select a frame transmission/retransmission timing instant. Proposed protocol designs have been applied on Stop-and-Wait (S-W) ARQ, and the performance have been compared with respect to simple S-W ARQ, and the probing based S-W ARQ. In the probing based ARQ protocol, when the channel deteriorates, transmitter starts probing the channel periodically, but the periodicity is chosen arbitrarily, regardless of the fading state. In contrast, the proposed algorithms estimate the channel’s existing condition by using the feedbacks, and the probing interval is chosen according to the Average Fading Duration (AFD) of received signal level. Simulations are performed with Rayleigh Fading Channel as the transmission medium. The performance results show that at the cost of some additional delay, significant improvement on energy saving and throughput performance can be achieved when AFD based intelligent probing is done.

Committee Members:

Dr. Swades De (Supervisor)

Dr. Hongya Ge

Dr. Ali Abdi