Shi-Xin Cheng

Reduced-complexity soft-output Viterbi equalizer

In the classical soft-output Viterbi equalizer, the trace-back operation is required for computing the reliability information of the symbols on survivor paths. To reduce the complexity, a simplified algorithm is offered in this paper, which uses metric difference of merging paths to provide the reliability information. In this algorithm, the trace-back operation is avoided. Both forward and backward forms of this algorithm are provided. Simulation results show that the performance of this algorithm is close to the classical SOVA in both a binary GSM system and an 8-ary PAM system.

Simulation of uplink CDMA RAKE receiver with selective diversity and coding

The mobile radio environment is characterized by time variant multipath propagation and fading. The RAKE receiver is the preferred choice in CDMA communication systems. The receiver structure for the IS-95 uplink communication is presented, and a new selective diversity method using decision feedback is proposed. Simulation results demonstrate that this method can effectively suppress the effect of the interference only path (IOP) and reduce the complexity of the receiver. Antenna diversity and Viterbi decoding are also discussed. It is shown that channel coding is effective provided block interleaving is employed simultaneously. The GSM typical urban 6-path channel model is used in all of the simulations. The performance of the RAKE receiver in various conditions is analyzed by means of simulations.

Frame synchronization by decorrelation detection

Under a poor communication environment, to ensure the detectability for the necessary frame synchronization performance, the repeated transmission of the signature code in groups is greatly recommended. This paper analyses the detectability of the frame synchronization codes with such a frame scheme under an AWGN channel and a Rayleigh fading channel, by applying a decorrelation method to perform single observation detection, major decision detection and accumulation posterior detection. The analyses show that the accumulation posterior detection method can give a better performance under strict restrictions.

Developing performance of voice service in PRMA

An improvement of PRMA based on QoS is proposed. The system transacts communicating users and new users in different ways, which is always neglected. According to the simulation, the method improves the voice performance by reducing the probability of packet dropping, and channel utilization increases.