THROUGHPUT AND BIT ERROR RATE ANALYSIS OF LUBY TRANSFORM CODES WITH LOW AND MEDIUM NODAL DEGREE DISTRIBUTIONS

I Joe Louis Paul,J Raja,S Radha

doi:10.3844/ajassp.2014.1584.1593

Abstract

This study presents two degree distributions namely low and medium nodal degree distributions aiming to build a low overhead Luby Transform (LT) codes. The motivation is to design a fast encoder/decoder especially for real-time multimedia streaming and multicasting applications using LT codes. The key idea of this study is to restrict the average degree of the transmitted encoded symbols as minimal. The impacts of low and medium degree encoded symbols on the performance of LT codes over an Additive White Gaussian Noise channel (AWGN) have been analyzed by the means of Bit Error Rate (BER), encoder/decoder delay, ripple size, throughput, overhead and bandwidth utilization as the performance metrics. Simulation results show that the proposed nodal degree distributions for LT codes achieve better throughput and BER performance at low overhead and delay with minimal decoding iterations by having a constantly decreasing ripple in comparison with conventional Robust Soliton Distribution (RSD) based LT codes.

Highlights

For achieving reliable data delivery in cellular mobile and wireless broadcasting applications, the AutomaticLuby Transform (LT) codes are the first realization of digital Fountain codes, designed for erasure channels to transmit the data reliably
The performance of LT codes using Low Degree Distribution (LDD), Medium Degree Distribution (MDD) and Robust Soliton Distribution (RSD) are studied over Additive White Gaussian Noise channel (AWGN) channel with Binary Phase Shift Keying (BPSK)
RSD has been implemented with the number of input source symbols K = 100 and tested for varying the failure probability of the LT process δ and a positive constant c that affects the probability of generating degree 1 encoded symbols

Summary

Introduction

Luby Transform (LT) codes are the first realization of digital Fountain codes ( called as rateless codes), designed for erasure channels to transmit the data reliably. The assumption is ofencoded message symbols N, slightly larger than K. that both transmitter and receiver should know the Recently, LT codes find its suitability in many applications due to its simple and efficient, exclusive OR (XOR) based implementations of both encoder and prior knowledge about channel conditions. This may not be feasible like in Internet, where the channel condition is always time-varying. Adaptive coding is decoder (Byers et al, 1998; Cataldi et al, 2009)

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