Local Decoding of Walsh Codes to Reduce CDMA Despreading ComputationCDMA Cell Sites Are Power-HungrySuboptimal Walsh Decoder with FeedbackTest SetupBit Error Rate and Power UsageWalsh Decoder FHTFHT Recombine AlgebraLocal Decoding of Walsh Codes to Reduce CDMA Despreading ComputationMatthew DohertyCDMA Cell Sites Are Power-Hungry• Code Division Multiple Access– Moves multiple access problem to DSP• Computation uses more power than other standards (TDMA, GSM, etc.)Orthogonal coding functionsImage removed due to copyright restrictions.Please see: http://upload.wikimedia.org/wikipedia/commons/ f/f7/Cdma_orthogonal_signals.svg__________________________________________________________________Suboptimal Walsh Decoder with FeedbackWalshDecoderBit Error RateDetectorSymbols BitsBER• Exploit structure of Walsh codes to estimate bits using fewer symbols• Use feedback to choose number of symbols to use and maintain bit error rateTest SetupTest Vectors in Block RAMWalshDecoderBER DetectorVGAFeedback PathSyncDCMControl Buffer BufferEnablerBufferBit Error Rate and Power Usage Images removed due to copyright restrictions.Please compare the 1-day and 5-day trends in the stock index of your choice, for example, usinghttp://finance.yahoo.com/q/bc?s=%5eIXIC&t=1d&c=BitWalsh Decoder FHTSame algorithm as FFT but with real (1 or -1) coefficientsImage removed due to copyright restrictions.Please see http://etoile.berkeley.edu/~jrg/ngst/fft/fft15b.xbmFHT Recombine Algebra• FFT butterfly structurey0 = x0 + x1y1 = x0 − x1Image removed due to copyright restrictions.Please see
View Full Document