適用於WiMAX標準之有效停止視窗運算渦輪解碼器硬體架構設計

VLSI Design of Efficient Window-based Stopping Turbo Decoder for WiMAX Standard

魏志嘉(Chih-Chia Wei)

指導教授 ： 林承鴻

元智大學/電機通訊學院/電機工程學系/碩士(2012年)

摘要

隨著無線通訊產品功能日益強大，行動裝置對無線傳輸品質需求越來越高，因此錯誤更正碼也開始被納入於現代行動通訊標準中，例如：3GPP LTE、WiMAX。渦輪碼由Berrou在1993年提出，藉由兩個解碼器疊代運算、交換機率資訊，進而逼近薛農極限，然而隨著疊代運算次數增加，其消耗之功率也呈線性增加。因此，許多停止多餘疊代次數之研究文獻，也紛紛被提出。然而，至今鮮少有研究針對渦輪解碼內部分資訊框架收斂之情況下，停止其部分框架運算之研究。
此論文中提出一套停止視窗運算之技術，停止渦輪解碼過程內單一視窗之運算以減少功耗，再進而結合早疊代終結技術縮短解碼週期。使得本渦輪解碼器能在縮短之解碼週期內，額外針對內部收斂之視窗停止運算，進而達到低功率之渦輪解碼器設計。最後本論文利用TSMC 90nm CMOS製程實現硬體，在操作頻率為250MHz，晶片核心面積大小為0.69mm2。在採用早疊代終結技術及停止視窗運算技術之下，能夠在訊噪比為1.4 dB下額外減少43%之功率消耗，而付出之面積代價約為1.5%。最後，操作在最大疊代次數8之渦輪解碼器吞吐量為30.21 Mbps。

關鍵字

渦輪碼 ； 渦輪碼解碼器 ； 低功率 ； 停止機制

並列摘要

The convolutional turbo code (CTC) is one of the powerful forward error correction codes proposed by Berrou in 1993, which provides excellent performance. Thus the CTC was adopted for many wireless communication systems, such as 3GPP LTE and WiMAX. However, the power consumption is linearly increased with its iterative decoding. Therefore, many stopping criteria are proposed to avoid the redundant decoding. Nevertheless, there are few works discussing the criterion to stop the portion of computations within CTC decoding.
In this thesis, we propose a window-based stopping (WBS) algorithm to reduce the redundant computations of convergent information. Moreover, the early termination technique is also employed to terminate the redundant decoding. Finally, the proposed CTC decoder is implemented and fabricated in TSMC 90nm CMOS technology. The core size is about 0.69 mm2 with operating frequency 250 MHz. The proposed CTC decoder reduced about 43% power dissipation at Eb/N0 1.4 dB with 1.5% silicon area overhead. The throughput rate is 30.21 Mbps with maximum number of iteration 8.

並列關鍵字

turbo code ； low power ； stopping criterion

參考文獻

[1] C. Berrou, A. Glavieux, and P. Thitimajshima, “Near Shannon limit error-correcting coding and decoding: Turbo-codes,” in Proc. IEEE Int. Conf. Commum. (ICC), vol. 2, pp. 1064-1070, May 1993.

[2] 3rd Generation Partnership Project (3GPP). [Online]. Available: http://www.3gpp.org/

[3] C. Berrou and M. Jezequelm, “Non-binary convolutional codes for turbo coding,” Electron. Lett., vol.35, no.1, pp. 39-40, Jan. 1999

[4] Digital Video Broadcasting (DVB). [Online]. Available: http://www.dvb.org/

[5] Worldwide Interoperability for Microwave Access (WiMAX). [Online]. Available: http://www.wimaxforum.org/home/