TY - JOUR
T1 - Performance of coded DS-CDMA with pilot-assisted channel estimation and linear interference suppression
AU - Phoel, Wayne G.
AU - Honig, Michael L.
N1 - Funding Information:
Manuscript received September 25, 2000; revised October 1, 2001. This work was supported by a University Partnership in Research Grant from Motorola, Inc. and by the U.S. Army Research Office by Grant DAAD19-99-1-0288. This paper was presented in part at the Conference on Information Sciences and Systems (CISS), Johns Hopkins University, Baltimore, MD, March 1999, and IEEE Wireless Communications and Networking Conference (WCNC), Chicago, IL, September 2000.
PY - 2002/5
Y1 - 2002/5
N2 - We consider a direct sequence (DS-) code division multiple access (CDMA) system with orthogonally multiplexed pilot signals and minimum mean squared error (MMSE) data and channel estimation. Both flat and frequency-selective fading channels are considered. Large system analysis is used to optimize the pilot-to-data power ratio (PDR) and the code rate for a fixed bandwidth expansion. Specifically, the PDR is selected to minimize the probability of error subject to a constraint on transmitted power. When the MMSE filter estimates the channel of the desired user, but averages over the channels of the interferers (corresponding to an adaptive filter in moderate to fast fading), the optimal PDR is less than that for the matched filter (MF). That is, the MMSE filter benefits from allocating more power to the data. When the MMSE filter directly incorporates estimates of all users' channel coefficients, the optimal PDR is greater than that for the MF. System performance as a function of code rate is characterized through both probability of error and cutoff rate. The optimal code rate for the MMSE receiver is generally higher than that for the MF, and increases with load and E b/N O. In the presence of fading, and with channel estimation, the optimal code rate approaches zero for both MMSE and MF receivers, but the MMSE filter is more robust with respect to a suboptimal choice of code rate.
AB - We consider a direct sequence (DS-) code division multiple access (CDMA) system with orthogonally multiplexed pilot signals and minimum mean squared error (MMSE) data and channel estimation. Both flat and frequency-selective fading channels are considered. Large system analysis is used to optimize the pilot-to-data power ratio (PDR) and the code rate for a fixed bandwidth expansion. Specifically, the PDR is selected to minimize the probability of error subject to a constraint on transmitted power. When the MMSE filter estimates the channel of the desired user, but averages over the channels of the interferers (corresponding to an adaptive filter in moderate to fast fading), the optimal PDR is less than that for the matched filter (MF). That is, the MMSE filter benefits from allocating more power to the data. When the MMSE filter directly incorporates estimates of all users' channel coefficients, the optimal PDR is greater than that for the MF. System performance as a function of code rate is characterized through both probability of error and cutoff rate. The optimal code rate for the MMSE receiver is generally higher than that for the MF, and increases with load and E b/N O. In the presence of fading, and with channel estimation, the optimal code rate approaches zero for both MMSE and MF receivers, but the MMSE filter is more robust with respect to a suboptimal choice of code rate.
KW - Code division multiple access (CDMA)
KW - Fading channels
KW - Minimum mean squared error (MMSE) estimation
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U2 - 10.1109/TCOMM.2002.1006563
DO - 10.1109/TCOMM.2002.1006563
M3 - Article
AN - SCOPUS:0036578259
VL - 50
SP - 822
EP - 832
JO - IEEE Transactions on Communications
JF - IEEE Transactions on Communications
SN - 1558-0857
IS - 5
ER -