Conference Paper

Further study on joint estimation of multiple access interferencein DS-CDMA systems

Xian Jiaotong Univ., Xian
DOI: 10.1109/ICCT.1998.740957 Conference: Communication Technology Proceedings, 1998. ICCT '98. 1998 International Conference on, Volume: vol.2
Source: IEEE Xplore

ABSTRACT To further extend the results of Feng Li et al. in which we proposed a joint estimation algorithm, this paper shows that the parameters and multiple access interference (MAI) estimated by the algorithm approaches to the true value as the length of the information sequence expands. With the algorithm, the estimation of MAI produced by the users of strong power is more accurate, thus their MAIs to the users of weak power can be effectively cancelled, making the bit error rate (BER) decrease. As a consequence, the joint estimation algorithm achieves a better near-far resistance capacity and outperforms the conventional single-user detector

0 Reads
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Consider a Gaussian multiple-access channel shared by K users who transmit asynchronously independent data streams by modulating a set of assigned signal waveforms. The uncoded probability of error achievable by optimum multiuser detectors is investigated. It is shown that the K -user maximum-likelihood sequence detector consists of a bank of single-user matched filters followed by a Viterbi algorithm whose complexity per binary decision is O(2^{K}) . The upper bound analysis of this detector follows an approach based on the decomposition of error sequences. The issues of convergence and tightness of the bounds are examined, and it is shown that the minimum multiuser error probability is equivalent in the Iow-noise region to that of a single-user system with reduced power. These results show that the proposed multiuser detectors afford important performance gains over conventional single-user systems, in which the signal constellation carries the entire burden of complexity required to achieve a given performance level.
    IEEE Transactions on Information Theory 02/1986; 32(1-32):85 - 96. DOI:10.1109/TIT.1986.1057121 · 2.33 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Under the assumptions of symbol-synchronous transmissions and white Gaussian noise, the authors analyze the detection mechanism at the receiver, comparing different detectors by their bit error rates in the low-background-noise region and by their worst-case behavior in a near-far environment where the received energies of the users are not necessarily similar. Optimum multiuser detection achieves important performance gains over conventional single-user detection at the expense of computational complexity that grows exponentially with the number of users. It is shown that in the synchronous case the performance achieved by linear multiuser detectors is similar to that of optimum multiuser detection. Attention is focused on detectors whose linear memoryless transformation is a generalized inverse of the matrix of signature waveform crosscorrelations, and on the optimum linear detector. It is shown that the generalized inverse detectors exhibit the same degree of near-far resistance as the optimum multiuser detectors. The optimum linear detector is obtained
    IEEE Transactions on Information Theory 02/1989; 35(1-35):123 - 136. DOI:10.1109/18.42183 · 2.33 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Compensating for near/far effects is critical for satisfactory performance of DS/CDMA systems. So far, practical systems have used power control to overcome fading and near/far effects. Another approach, which has a fundamental potential in not only eliminating near/far effects but also in substantially raising the capacity, is multiuser detection and interference cancellation. Various optimal and suboptimal schemes have been investigated. Most of these schemes, however, get too complex even for relatively simple systems and rely on good channel estimates. For interference cancellation, estimation of channel parameters (viz. received amplitude and phase) is important. We analyze a simple successive interference cancellation scheme for coherent BPSK modulation, where the parameter estimation is done using the output of a linear correlator. We then extend the analysis for a noncoherent modulation scheme, namely M-ary orthogonal modulation. For the noncoherent case, the needed information on both the amplitude and phase is obtained from the correlator output. The performance of the IC scheme along with multipath diversity combining is studied
    IEEE Journal on Selected Areas in Communications 07/1994; 12(5-12):796 - 807. DOI:10.1109/49.298053 · 3.45 Impact Factor