A. Mirbagheri (Canada) and Y.C. Yoon (USA)
CDMA, Channel estimation, LMMSE, Pilot channels
This paper examines pilot-channel-aided (PCA) adaptive implementations of a recently proposed linear minimum mean-square error (LMMSE) receiver for interference suppression and multipath reception in long-code direct sequence code-division multiple-access (DS-CDMA) sys tems. Pilot channels, already existent in the forward link and recently incorporated in the reverse link, refer to dedi cated code-multiplexed channels orthogonal to the traffic channel. The accuracy of channel estimation in the re verse link is strongly dependent on the pilot channel power, which often constitutes a small portion of the mobile user signal power. Higher levels of pilot power improve the per formance in channel estimation but compromise the capac ity of the traffic channel. In this paper, a new algorithm is proposed that jointly utilizes the statistics of both the traffic and pilot channels. It is shown that, at the expense of increased computational complexity, the proposed algo rithm can suppress interference and perform multipath di versity combining while maintaining a low level of pilot power. Simulation results demonstrate that, under the ex amined scenarios, the proposed algorithm can reduce the pilot power by half and still perform equal to, or even bet ter than, the conventional PCA algorithm which utilizes only the statistics of the pilot channel. Such savings in pi lot power translate into substantial improvements in system and channel capacity on the reverse link.
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