Reconfiguration between soft output Viterbi and log maximum a posteriori decoding algorithms

In third generation mobile communication standards (UMTS, cdma2000 and Japanese W-CDMA) different kinds of encoding are specified for different types of services and channels-convolutional, turbo, Reed-Solomon and CRC. Decoding may use any suitable algorithm, with prime candidates being versions of the Viterbi algorithm (with soft or hard output), and the maximum a posteriori probability algorithm, with its derivatives log-MAP and max-log-MAP. It would be advantageous to be able to select the optimum algorithm in any circumstance. The paper examines the reconfiguration between SOVA and log-MAP decoding algorithms. The performance of log-MAP is higher than SOVA, but with more complexity and delay. The two algorithms are analysed into component operations and blocks and the common parts are identified.