自适应Viterbi译码器技术

The Technology of Adaptive Viterbi Decoding

随着现代通信技术的迅速发展,高速和高可靠性成为衡量信息传输质量的关键指标。信道编码技术能够对信道差错进行控制,降低误码率,实现可靠通信,具有重要的军事和民用意义。Viterbi译码算法及其实现技术是信道编码技术的一个重要组成部分,但是其存在自身的缺陷或不足。Viterbi译码算法的译码性能将会随着码的相关长度k增加而提高,但其实现的复杂度将以2k的比例增长。提出了一种自适应Viterbi译码算法——IAVA(Improved Adaptive Viterbi Algorithm)。该算法利用信噪比评估模块自适应地调整门限值的高低,并利用复杂度评估模块自适应地改变译码器的基状态数,从而合理利用硬件资源。当译码器工作于低信噪比环境中时门限被自动调高,保证译码性能的同时适当减少了译码器的复杂度;当工作于高信噪比环境中时门限被自动调低,此时译码器复杂度得到锐减,译码模式将切换到基-4模式从而提高了译码速度,因此在大动态信噪比环境下该算法具有优越的性能。

With the development of modern communication technology,high speed and high stability have come into being two key factors when measuring the quality of information tansmission.The technology of channel encoding,which can control the channel errors,reduce the code error rate,and ensure the stable communication,has a deep meaning in military affairs and civil applicaton.The Viterbi decoding algorithm and the methd of its implementation are important parts of the channel encoding.However,they have their own limitation as well.In 1the algorithm of Viterbi decoding,while the performance of decoding is improved with the increasing of length of the convolutional encoding,the complexity to implement it increases at the rate of 2k.A modified Viterbi decoding arithm IAVA is put forward.In the algorithm,while a SNR evaluating module is utilized to automatically adjust the gate-vaule,a complexity evaluating module is used to automatically adjust the decoder＇s radix mode,through which,the resource is reasonably used.When working at the condition of low SNR,the gatevaule is increased automatically.This way,reduces the decoding complexity while ensuring the good performance at the same time.When working at the condition of high SNR,the gata-vaule is decreased automatically to reduce the decoding complexity.In this working condition,the decoding mode is changed to radix-4 mode,which resultes in a rapid improvement in the decoding speed,thus the algorithm has a good performance in the condition of wide dynamic SNR.