Title :
On the spectral efficiency of large CDMA systems using higher order modulation
Author :
Prätor, Oliver ; Fettweis, Gerhard P.
Author_Institution :
Inst. of Mobile Commun. Syst., Dresden Univ. of Technol., Germany
Abstract :
The spectral efficiency of large CDMA systems using higher order modulation schemes is investigated. Therefore, the asymptotic analysis for single cell systems and random spreading codes is used to obtain the signal-to-interference-and-noise ratio (SINR) after the matched filter (MF) and linear minimum mean-squared-error (LMMSE) receiver. Then the concepts of capacity and cut-off rate are applied to determine the optimum spectral efficiency with coding and modulation. It is shown that with a MF receiver higher order modulation in combination with coding has no advantage. In contrast, beyond a particular signal-to-noise ratio (SNR) threshold the spectral efficiency of a CDMA system can be improved with larger constellations when deploying an LMMSE receiver. Depending on the SNR an optimum modulation scheme exists, which was shown for a number of QAM constellations.
Keywords :
3G mobile communication; code division multiple access; least mean squares methods; matched filters; quadrature amplitude modulation; radio receivers; random codes; CDMA systems; QAM constellations; SINR; SNR; higher order modulation; linear minimum mean-squared-error; matched filter; random spreading codes; signal-to-interference-and-noise ratio; signal-to-noise ratio; single cell systems; spectral efficiency; Amplitude modulation; Detectors; Interference; Matched filters; Mobile communication; Modulation coding; Multiaccess communication; RAKE receivers; Signal analysis; Signal to noise ratio;
Conference_Titel :
Personal, Indoor and Mobile Radio Communications, 2003. PIMRC 2003. 14th IEEE Proceedings on
Print_ISBN :
0-7803-7822-9
DOI :
10.1109/PIMRC.2003.1260319
