MIT 6 111 - LOCAL DECODING OF WALSH CODES (10 pages)

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LOCAL DECODING OF WALSH CODES



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LOCAL DECODING OF WALSH CODES

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Pages:
10
School:
Massachusetts Institute of Technology
Course:
6 111 - Introductory Digital Systems Laboratory
Introductory Digital Systems Laboratory Documents

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LOCAL DECODING OF WALSH CODES TO REDUCE CDMA DESPREADING COMPUTATION Matt Doherty TA Kyeong Jae Lee 6 111 Introductory Digital Systems Laboratory May 18 2006 Abstract As field programmable gate arrays FPGAs continue to become more powerful and more flexible computer scientists are looking to them to combine the flexibility of software with the performance afforded by the specialization of hardware An algorithm for local decoding of CDMA Walsh codes has been translated from software to hardware and the problems and benefits associated with the translation have been analyzed In software the algorithm saves valuable computation but in hardware this computation savings results directly in power savings as well The system uses a VGA display to show in real time the decoder s bit error rate the received signal s signal to noise ratio and an estimate of the power being consumed by the device The project is a successful proof of concept not only that complex software algorithms can be implemented in hardware but also that significant power savings can be realized in CDMA base stations today through the use of a different decoding algorithm 1 Table of Contents 1 0 Introduction 3 2 0 Module Description Implementation 4 3 0 Testing Debugging 9 4 0 Conclusion 10 5 0 Bibliography 10 List of Figures 1 Labkit block diagram 4 2 Walsh decoder block digram 4 3 Bahl s 256 chip FHT design 5 4 Bahl s single FHT stage 6 5 Screenshot of VGA display 7 2 1 0 Introduction As field programmable gate arrays FPGAs continue to become more powerful and more flexible computer scientists are looking to them to combine the flexibility of software with the performance afforded by the specialization of hardware The project described herein is one such computer scientist s implementation of a software algorithm in hardware and analysis of the problems and benefits associated with the translation Code division multiple access CDMA is a wireless standard that relies on orthogonal Walsh codes to multiplex



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