Abstract
The problem of synchronous multiuser receiver design in the case of direct-sequence single-antenna code division multiple access (DS-CDMA) uplink networks is studied over frequency selective fading channels. An exact expression for the bit error rate (BER) is derived in the case of BPSK signaling. Moreover, an algorithm is proposed for finding the finite impulse response (FIR) receiver filters with block memory such that the exact BER of the active users is minimized. Several properties of the minimum BER FIR filters with block memory are identified. The algorithm performance is found for scenarios with different channel qualities, spreading code lengths, receiver block memory size, near-far effects, and channel mismatch. For the BPSK constellation, the proposed FIR receiver structure with block memory has significant better BER with respect to and near-far resistance than the corresponding minimum mean square error (MMSE) filters with block memory.
Highlights
CDMA is a multiple access technique where the user separation is done neither in frequency, nor in time, but rather through the use of codes
The case of receiver filters with block memory of a direct-sequence single-antenna code division multiple access (DS-CDMA) system has been studied for blind equalization in [13], and the problem of CDMA receiver design has been studied in [14], the problem of minimum bit error rate (BER) receiver filter design for multiuser CDMA systems has to the best of our knowledge not been treated in the literature for communication over frequency selective channels
The BER versus Eb/ N0 performances of the minimum mean square error (MMSE) and the minimum BER DS-CDMA systems are shown in Figure 3 for different number of users N
Summary
CDMA is a multiple access technique where the user separation is done neither in frequency, nor in time, but rather through the use of codes. The case of receiver filters with block memory of a DS-CDMA system has been studied for blind equalization in [13], and the problem of CDMA receiver design has been studied in [14], the problem of minimum BER receiver filter design for multiuser CDMA systems has to the best of our knowledge not been treated in the literature for communication over frequency selective channels. In this contribution, a general framework based on the discrete-time equivalent low-pass representation of signals is provided. Three appendices contain proofs and tools used in the article throughout
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