Controle de Erros em Redes ATM sem Fio

Abstract

ATM networks have been designed considering the use of optical links in the physical layer, which present low bit error rate. The main problem in implementing wireless ATM networks is the high and variable bit error rate in the radio link. To overcome this problem, it is necessary to use an additional error control mechanism in the wireless link. The traditional techniques for error control are ARQ (Automatic Repeat Request) and FEC (Forward Error Correction). Using FEC or ARQ techniques in the wireless link decreases the residual bit error rate, increases the delay in transmitting a packet and decreases the throughput, due to overhead of the error control mechanisms. This paper presents a comparison of the performances of ARQ and FEC techniques in wireless ATM networks considering adaptive and non-adaptive systems and real-time and nonreal time applications. The criteria to compare the performances are: the delay to transmit a PDU (Protocol Data Unit), for real-time applications, and, for non-realtime applications, the throughput and the average and maximum cell transference delays.