Spectral efficiency of CDMA with random spreading

Sergio Verdü, Shlomo Shamai

Research output: Contribution to journalArticlepeer-review

752 Scopus citations


The CDMA channel with randomly and independently chosen spreading sequences accurately models the situation where pseudonoise sequences span many symbol periods. Furthermore, its analysis provides a comparison baseline for CDMA channels with deterministic signature waveforms spanning one symbol period. We analyze the spectral efficiency (total capacity per chip) as a function of the number of users, spreading gain, and signal-to-noise ratio, and we quantify the loss in efficiency relative to an optimally chosen set of signature sequences and relative to multiaccess with no spreading. White Gaussian background noise and equal-power synchronous users are assumed. The following receivers are analyzed: a) optimal joint processing, b) single-user matched filtering, c) decorrelation, and d) MMSE linear processing.

Original languageEnglish (US)
Pages (from-to)622-640
Number of pages19
JournalIEEE Transactions on Information Theory
Issue number2
StatePublished - 1999

All Science Journal Classification (ASJC) codes

  • Information Systems
  • Computer Science Applications
  • Library and Information Sciences


  • Channel capacity
  • Code-division multiple access
  • Gaussian channels
  • Multiuser detection
  • Multiuser information theory
  • Spread spectrum


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