In this paper, an efficient multiuser detection scheme with low decision delay is proposed for asynchronous variable processing gain (VPG) DS/CDMA systems in mobile radio channels without any restrictions on processing gains. An equivalent synchronous single bit rate DS/CDMA system is first formulated to break up the detection problem into the blocks of finite length called processing windows. A low delay multipath-combining decision-feedback multiuser detector (LDMCDF) is then proposed based on the equivalent system model. Since the LDMCDF makes the decisions for data bits every processing window, the decision delay is less than the interval of one processing window. The effect of the processing window length on the performance of the LDMCDF is evaluated, and the simulation results show that the LDMCDF provides good performance with negligible decision delay.
Proceedings of the 1999 VTC - Fall IEEE VTS 50th Vehicular Technology Conference 'Gateway to 21st Century Communications Village', v.5, pp.3004 - 3008