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Macrocell-Wide Behavior of the Orthogonality Factor in WCDMA Downlinks

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Author

  • N B Mehta
  • Andreas Molisch
  • L Greenstein

Summary, in English

The orthogonality factor (OF) quantifies the loss of orthogonality between the signals transmitted simultaneously on a wideband code division multiple access (WCDMA) downlink due to multipath dispersion. It is one of the fundamental parameters that determines the signal-to-interference-plus-noise ratio at the output of the Rake receiver and, consequently, it has a significant impact on downlink system capacity. The OF depends greatly on the delay profile of the multipath channel between the mobile and its serving base station; this profile varies considerably from one location in the cell to another. In this paper, we study how the statistical properties of the small-scale-fading-averaged OF vary over the entire macrocellular area. We use an ensemble of channel profiles at different locations in a cell generated from an implementation of the comprehensive COST259 channel model, which incorporates results from several experimental investigations. We show that the small-scale-fading-averaged OF is itself a random variable whose statistics depend on the mobile's distance from its serving base station. The large observed variance of the OF indicates that using a single value for all users in downlink capacity analyses and simulations, as has been the practice, may lead to erroneous conclusions. Finally, we propose a simple model that closely matches the statistics of the OF as a function of mobile-to-base distance, thus obviating the need to set up the complicated channel model every time OF values are to be generated.

Publishing year

2006

Language

English

Pages

3394-3399

Publication/Series

IEEE Transactions on Wireless Communications

Volume

5

Issue

12

Document type

Journal article

Publisher

IEEE - Institute of Electrical and Electronics Engineers Inc.

Topic

  • Electrical Engineering, Electronic Engineering, Information Engineering

Keywords

  • wideband code division multiple access
  • land mobile
  • fading channels
  • multipath channels
  • radio propagation factors
  • Rayleigh channels
  • Rake receivers
  • cellular radio
  • COST259
  • channel profile
  • time-varying channels
  • statistics
  • radio receivers
  • orthogonality factor

Status

Published

ISBN/ISSN/Other

  • ISSN: 1536-1276