Delay estimation of code-spread CDMA systems

Delay estimation of a code-spread code division multiple access (CS-CDMA) system using low-rate maximum free distance (MFD) convolutional codes for bandwidth expansion is studied. Using the repetitive structure of the low-rate MFD codes, the codewords are first permuted using a criterion based on the Cramer-Rao bound that results in good delay estimation properties. Thereafter, an approximate maximum-likelihood estimator that jointly estimate the channel gain, the codewords and the delay is used. Using the derived algorithm we show that it is in fact possible to estimate the delay in a code-spread system.