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 decisionfeedback
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 the negligible decision delay.