The coding-spreading tradeoff in CDMA systems

Venugopal V. Veeravalli, Ashok Mantravadi

Research output: Contribution to journalArticlepeer-review


General definitions of spreading and coding are given based on the notion of Shannon bandwidth introduced by Massey (1994), with the goal of distinguishing these operations for signaling with bandwidth redundancy. These definitions are shown to lead to a separation result: every bandwidth redundancy scheme can be expressed as a concatenation of coding followed by spreading. The coding-spreading tradeoff problem is then studied for a code division multiple access (CDMA) system in which the receiver processes the received signal by using a user-separating front-end, which feeds into autonomous single-user decoders. Under the single-user decoding setting, it is established that the linear minimum mean square error (LMMSE) front-end multiuser detector is optimum among all front-ends that are constrained to use only spreading information. Also, conditions are given for the single-user decoders to ignore spreading information without losing optimality. An example illustrating the coding-spreading tradeoff optimization for a direct sequence CDMA system with random spreading is given. Single-cell and multicell scenarios are considered in the optimization, and a comparison is made of the spectral efficiencies that can be achieved with the conventional matched filter and LMMSE front-ends.

Original languageEnglish (US)
Pages (from-to)396-408
Number of pages13
JournalIEEE Journal on Selected Areas in Communications
Issue number2
StatePublished - Feb 2002


  • Channel coding
  • Code division mnltiaccess
  • Land mobile radio cellular systems
  • Least mean square methods
  • Matched filters
  • Signal detection
  • Spectral efficiency
  • Spread spectrum communication

ASJC Scopus subject areas

  • Computer Networks and Communications
  • Electrical and Electronic Engineering


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