September 2012
Publication year: 2012
Source:Physical Communication, Volume 5, Issue 3
This paper addresses a novel Walsh–Hadamard (WH)-spread multicarrier code division multiple access (MC-CDMA) system which employs carrier interferometry (CI) codes in a multiuser environment. In frequency selective channels, phase characteristics of CI codes ensure better estimates of received WH-spread CI/MC-CDMA signals. Estimation of multiple access interference (MAI) becomes more reliable with time and frequency diversities of CI/MC-CDMA signals with spreading gain diversity of WH codes over multipath channels. Interference cancellation (IC) is done by taking hard and soft estimates of received data bits. Simulation results demonstrate that the proposed multiple access scheme with iterative decoding offer a significant performance gain over WH-spread MC-CDMA and CI/MC-CDMA over multipath channels. We observe that WH-spread CI/MC-CDMA maintains a stable envelope of the transmitted signal as that of CI/MC-CDMA. In an overloaded situation, the proposed multiple access scheme provides a low peak to the average power ratio (PAPR) compared to conventional MC-CDMA for multirate systems which supports simultaneous transmission of high and low data rate users.
Publication year: 2012
Source:Physical Communication, Volume 5, Issue 3