Unequal power allocation to the turbo-encoder output bits with applicationto CDMA systems

Traditional Turbo-codes with binary phase-shift keying modulation assign eq ual noise margins to the Turbo-encoder output bits. It is shown that by usi ng unequal power allocation (UPA) among the encoder output streams, one can improve the code performance especially for large block lengths, On the ot her hand, there has been a growing interest in the application of Turbo-cod es for signaling over a code-division multiple-access (CDMA) channel. A usu al practice in CDMA systems for matching of rate is based on repeating the encoder output bits. This feature can be used to provide UPA with a negligi ble increase in the complexity. Simulation results are presented showing a noticeable improvement in the bit-error-rate performance.