Iterative multiuser joint decoding: Optimal power allocation and low-complexity implementation

Journal article
(Original article)

Publication Details

Author(s): Caire G, Müller R, Tanaka T
Journal: IEEE Transactions on Information Theory
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Publication year: 2004
Volume: 50
Journal issue: 9
Pages range: 1950-1973
ISSN: 0018-9448


We consider a canonical model for coded code-division multiple access (CDMA) with random spreading, where the receiver makes use of iterative belief-propagation (BP) joint decoding. We provide simple density-evolution analysis in the large-system limit (large number of users) of the performance of the BP decoder and of some suboptimal approximations based on interference cancellation (IC). Based on this analysis, we optimize the received user signal-to-noise ratio (SNR) distribution in order to maximize the system spectral efficiency for given user channel codes, channel load (users per chip), and target user bit-error rate (BER). The optimization of the received SNR distribution is obtained by solving a simple linear program and can be easily incorporated into practical power control algorithms. Remarkably, under the optimized SNR assignment, the suboptimal minimum mean-square error (MMSE) IC-based decoder performs almost as well as the more complex BP decoder. Moreover, for a large class of commonly used convolutional codes, we observe that the optimized SNR distribution consists of a finite number of discrete SNR levels. Based on this observation, we provide a low-complexity approximation of the MMSE-IC decoder that suffers from very small performance degradation while attaining considerable savings in complexity. As by-products of this work, we obtain a closed-form expression of the multiuser efficiency (ME) of power-mismatched MMSE filters in the large-system limit, and we extend the analysis of the symbol-by-symbol maximum a posteriori probability (MAP) multiuser detector in the large-system limit to the case of nonconstant user powers and nonuniform symbol prior probabilities. © 2004 IEEE.

FAU Authors / FAU Editors

Müller, Ralf Prof. Dr.-Ing.
Professur für Informationsübertragung

External institutions with authors

Institut Eurécom (EURECOM)
Kyoto University / 京都大学 Kyōto daigaku

How to cite

Caire, G., Müller, R., & Tanaka, T. (2004). Iterative multiuser joint decoding: Optimal power allocation and low-complexity implementation. IEEE Transactions on Information Theory, 50(9), 1950-1973.

Caire, Giuseppe, Ralf Müller, and Toshiyuki Tanaka. "Iterative multiuser joint decoding: Optimal power allocation and low-complexity implementation." IEEE Transactions on Information Theory 50.9 (2004): 1950-1973.


Last updated on 2018-12-12 at 14:23