ICASSP '00 Proceedings of the Acoustics, Speech, and Signal Processing, 2000. on IEEE International Conference - Volume 05
A least-squares approach to blind channel identification
IEEE Transactions on Signal Processing
Blind equalization in antenna array CDMA systems
IEEE Transactions on Signal Processing
EURASIP Journal on Wireless Communications and Networking - Special issue on innovative signal transmission and detection techniques for next generation cellular CDMA systems
Blind multiuser detection for long-code CDMA systems with transmission-induced cyclostationarity
EURASIP Journal on Wireless Communications and Networking - Special issue on advanced signal processing algorithms for wireless communications
EURASIP Journal on Applied Signal Processing
Multicarrier block-spread CDMA for broadband cellular downlink
EURASIP Journal on Applied Signal Processing
Adaptive generalized rake reception in DS-CDMA systems
IEEE Transactions on Wireless Communications
Partial multiuser detection for CS-CDMA/CP over multipath channels and its comparison with DS-CDMA
ICC'09 Proceedings of the 2009 IEEE international conference on Communications
Partial multiuser detection for CS-CDMA/CP over multipath channels
IEEE Transactions on Communications
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We derive and compare several linear equalizers for the CDMA downlink under frequency selective multipath conditions: minimum mean-square error (MMSE), zero-forcing (ZF), and RAKE. MMSE and ZF equalizers are designed based on perfect knowledge of the channel. The downlink specific structure involves first inverting the multipath channel to restore the synchronous multi-user signal transmitted from the base-station at the chip-rate, and then correlating with the product of the desired user's channel code times the base-station specific scrambling code once per symbol to decode the symbols. ZF equalization restores orthogonality of the Walsh-Hadamard channel codes on the downlink but often suffers from noise gain because certain channel conditions (no common zeros) are not met; MMSE restores orthogonality only approximately but avoids excessive noise gain. We compare MMSE and ZF to the traditional matched filter (also known as the RAKE receiver). Our formulation generalizes for the multi-channel case as might be derived from multiple antennas and/or over-sampling with respect to the chip-rate. The optimal symbol-level MMSE equalizer is derived and slightly out-performs the chip-level but at greater computational cost. An MMSE soft hand-off receiver is derived and simulated. Average BER for a class of multi-path channels is presented under varying operating conditions of single-cell and edge-of-cell, coded and un-coded BPSK data symbols, and uncoded 16-QAM. These simulations indicate large performance gains compared to the RAKE receiver, especially when the cell is fully loaded with users. Bit error rate (BER) performance for the chip-level equalizers is well predicted by approximate SINR expressions and a Gaussian interference assumption.