Coding performance on the AX.25 radio packet

Abstract

AX.25 packet radio is a popular means of data communications which has found many wide spread applications. For error control, AX.25 packet radio currently uses the go-back-N ARQ scheme which makes no attempt to correct errors, but only re-transmits packets which have been received with errors. This can lead to a very inefficient system when the channel error rate becomes substantially large. It has been found that by adding forward error correction (FEC) to the packet, the system performance can be substantially improved. This thesis studies the performance of various BCH codes, the (23,12) Golay code, Reed-Solomon codes, and different rate convolutional codes with varying constraint lengths when used in conjunction with the go-back-N ARQ. Code combining and concatenation are also studied. The performance of these codes is based on throughput performance, code rate, and system complexity. It is found that the (255,187) Reed-Solomon and the 1/2 rate v=9 convolutional codes can greatly enhance the performance of the AX.25 packet radio system. These codes provide good throughput performance over a large range of bit error rates and both are readily implemented. In conclusion, error control codes should be included with the AX.25 packet radio in order to improve its performance over noisy channels.