IMPROVEMENT METHODS OF PROPAGATION ERROR FOR MULTIPLE-ACCESS INTERFERENCE SUCCESSIVE CANCELLATION TECHNIQUES IN DS CDMA/

In this paper, we propose several novel methods to decrease propagatio n error for multiple access interference cancellation techniques in as ynchronous DS/CDMA. To increase spectral efficiency, the system wherei n transmitting signal power of each user is assigned with exponential law and multiple access interference successive cancellation is used i n the receiver has been discussed. However, when the number of active users is increased, propagation error occurs in the receiver. Thus, th e improvement effect of spectral efficiency in the system has been deg raded. In this paper, we propose novel methods to decrease these propa gation errors for the system. These novel methods are quasi-maximum li kelihood method that means maximum likelihood in considering the signa l of the next user when the signal of the arbitrary user is demodulate d? feedback method that means the demodulation error of the stronger u sers in transmitting signal power is estimated after several users' de modulations and the error is corrected, and combination method that is a combination of quasi-maximum likelihood method and feedback method. And we evaluate their performances by computer simulation and show th at the combination method is effective for the reduction of the propag ation error.