National Taiwan University Dept Elect EngnLee, HuangHuangLeeChen, Kwang-ChengKwang-ChengChen2006-11-142018-07-062006-11-142018-07-062005-02http://ntur.lib.ntu.edu.tw//handle/246246/200611150121518We study access strategies for decorrelating detection applied in multi-rate direct-sequence code-division multipleaccess (DS/CDMA) systems, including multi-modulation (MM), multi-code (MC), and variable-spreading-length (VSL) schemes by jointly considering signal constellations and multiple-access interference. The mathematical analysis shows that when the number of active users is large, the MM scheme outperforms MC and VSL schemes especially for high-rate transmission. We also conclude that the design of modulation is important in MC and VSL schemes. Numerical analysis demonstrates that applying 4- PSK instead of 2-PSK in MC and VSL schemes can improve about 9 dB performance gain. In addition, by considering crosscorrelation of noise components, we propose a detector that minimizes the symbol error probability under the constraint that the complexity grows linearly with the number of active users as decorrelating detectors. Simulations show that about 4 dB performance gain over conventional decorrelating detectors can be achieved for multi-rate DS/CDMA communications.application/pdf521458 bytesapplication/pdfzh-TWDecorrelating multiuser detectioncode-division multiple-accessmulti-ratemulti-codevariable-spreadinglengthmulti-modulationjournal articlehttp://ntur.lib.ntu.edu.tw/bitstream/246246/200611150121518/1/3946.pdf