Asynchronous CDMA systems with random spreadingpart I: Fundamental limits

Journal article
(Original article)

Publication Details

Author(s): Cottatellucci L, Müller R, Debbah M
Journal: IEEE Transactions on Information Theory
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Publication year: 2010
Volume: 56
Journal issue: 4
Pages range: 1477-1497
ISSN: 0018-9448


Spectral efficiency for asynchronous code division multiple access (CDMA) with random spreading is calculated in the large system limit allowing for arbitrary chip waveforms and frequency-flat fading. Signal-to-interference and noise ratios (SINRs) for suboptimal receivers, such as the linear minimum mean square error (MMSE) detectors, are derived. The approach is general and optionally allows even for statistics obtained by undersampling the received signal. All performance measures are given as a function of the chip waveform and the delay distribution of the users in the large system limit. It turns out that synchronizing users on a chip level impairs performance for all chip waveforms with bandwidth greater than the Nyquist bandwidth, e.g., positive roll-off factors. For example, with the pulse shaping demanded in the UMTS standard, user synchronization reduces spectral efficiency up to 12% at 10 dB normalized signal-to-noise ratio. The benefits of asynchronism stem from the finding that the excess bandwidth of chip waveforms actually spans additional dimensions in signal space, if and only if the users are desynchronized at chip-level. The analysis of linear MMSE detectors shows that the limiting interference effects can be decoupled both in the user domain and in the frequency domain such that the concept of effective interference spectral density arises. This generalizes and refines Tse and Hanly's concept of effective interference. In Part II, the analysis is extended to any linear detector that admits a representation as multistage detector and guidelines for the design of low complexity multistage detectors with universal weights are provided. © 2006 IEEE.

FAU Authors / FAU Editors

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

External institutions with authors

Institut Eurécom (EURECOM)
University of South Australia

How to cite

Cottatellucci, L., Müller, R., & Debbah, M. (2010). Asynchronous CDMA systems with random spreadingpart I: Fundamental limits. IEEE Transactions on Information Theory, 56(4), 1477-1497.

Cottatellucci, Laura, Ralf Müller, and Merouane Debbah. "Asynchronous CDMA systems with random spreadingpart I: Fundamental limits." IEEE Transactions on Information Theory 56.4 (2010): 1477-1497.


Last updated on 2018-23-10 at 21:50