AMR編碼及IEEE 802.16a標準之Reed-Solomon解碼器於數位訊號處理器之實現

Abstract

近年來，多媒體與無線通訊已成為市場上非常重要的發展趨勢，IEEE 802.16a通訊標準主要在於實現無線網路上能夠傳輸高品質的多媒體的目標，在本篇論文中，我們將會實現語音與Reed-Solomon編碼機制於TI DSP平台上。 本篇論文的重點之一，在於多媒體編碼的部分，我們將討論第三代無線通訊系統中所採用的語音標準「適應性多速率編碼(AMR)」，它提供了多樣的編碼模式來因應各種通道所產生的影響；另一個重點為IEEE 802.16a無線通訊標準中前向誤差改正編碼機制的部分，由於Reed-Solomon編碼高度的修正能力，因而被IEEE 802.16a採用於前向誤差改正編碼的程序之一。 在論文中，首先我們將簡單描述AMR語音標準與IEEE 802.16a FEC部分的演算法與架構，並且針對數位訊號處理器(DSP)平台的特性，改善AMR語音編碼與Reed-Solomon解碼器的執行效率，進而實現於DSP平台上。我們的實現平台核心為德州儀器公司所發展的數位訊號處理器，程式經過改進後，AMR語音編碼器在DSP平台上可以達到每秒22.78K位元的處理速率，解碼器則可達到每秒31.84K位元，而在IEEE 802.16a中Reed-Solomon解碼器的部分，在DSP平台上甚至可以達到每秒176.4K位元的處理速度，但這些測試數據都包括電腦與DSP之間資料傳輸所花費的時間，若扣除後將會更加快速。此外，我們也對原先的程式加以比較，在AMR編碼方面進步了65.94%，在Reed-Solomon解碼器方面也比原先實現的版本進步了96.44%。

Multimedia and wireless communication have been two very important trends in the recent years. Transmitting high quality multimedia data over wireless channel is the target of the IEEE 802.16a standard. In this thesis, we will implement a speech coding scheme and a Reed-Solomon coding scheme on TI DSP. One focus of this thesis is Adaptive Multi Rate (AMR), the speech coding standard of 3GPP. It provides various coding modes match the channel error rates. Another focus of this thesis is the Forward Error Correction (FEC) scheme of the IEEE 802.16a wireless communication standard. The Reed-Solomon coding is adopted by the IEEE 802.16a because of its high capability of correcting errors. We first describe the basic structure and algorithm of the AMR speech coding and the FEC in IEEE 802.16a. Then, we adopt and modify fast scheme to accelerate the programs of the AMR speech codec and Reed-Solomon decoder to match the architecture of the DSP baseboard. We further implement them on the DSP platform, which contains the Texas Instruments (TI) TMS320C6416 digital signal processor (DSP). The processing rate of the AMR codec on the DSP platform reaches 22.78 Kbytes/sec for the encoder and 31.84 Kbytes/sec for the decoder. And the Reed-Solomon decoder reaches up to 176.4 Kbytes/sec. Moreover, those processing rates includes of the data transfer time between the host and the DSP board. It can be much faster if the data transfer time is excluded. In addition, the AMR speech codec after our improvement is 65.94% faster for the encoder and 61.31% faster for the decoder than the original one. The Reed-Solomon decoder is 96.44% faster than the original one.