Outage probability for a zero forcing multiuser detector with random signature sequences

Salim Manji, Narayan B. Mandayam

Research output: Contribution to journalConference articlepeer-review

6 Scopus citations


The performance of linear interference suppression in a DS-CDMA (Direct-Sequence Code Division Multiple Access) system using random codes varies over the user population due to the random set of interfering sequences. As a result, the capacity of such systems depends on the distribution of the interfering signature sequences and consequently the distribution of the signal-to-interference ratio (SIR). For a zero-forcing or decorrelating solution, the SIR can be expressed in terms of the near-far resistance (NFR) associated with the detector. Using a statistical characterization of the NFR, we derive analytical bounds on the outage probability in such systems. The analysis is based on application of the Wilson-Hilferty approximation of the chi-squared distribution valid on the range 1≪K≪N where K is the number of users in a cell and N is the processing gain. We show that cell capacity can be upper and lower bounded by closed form expressions. We compare cell capacity using zero-forcing detection with conventional matched filter detection. Results show a ten fold capacity increase using zero-forcing detection in a single cell system and a three fold increase in a multiple cell system.

Original languageEnglish (US)
Pages (from-to)174-178
Number of pages5
JournalIEEE Vehicular Technology Conference
StatePublished - 1998
EventProceedings of the 1998 48th IEEE Vehicular Technology Conference, VTC'98. Part 3 (of 3) - Ottawa, Can
Duration: May 18 1998May 21 1998

All Science Journal Classification (ASJC) codes

  • Computer Science Applications
  • Electrical and Electronic Engineering
  • Applied Mathematics


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