Fundamental limits and scaling behavior of cooperative multicasting in wireless networks

Ashish Khisti*, Uri Erez, Gregory W. Wornell

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


A framework is developed for analyzing capacity gains from user cooperation in slow-fading wireless networks when the number of nodes (network size) is large. The framework is illustrated for the case of a simple multipath-rich Rayleigh-fading channel model. Both unicasting (one source and one destination) and multicasting (one source and several destinations) scenarios are considered. We introduce a meaningful notion of Shannon capacity for such systems, evaluate this capacity as a function of signal-to-noise ratio (SNR), and develop a simple two-phase cooperative network protocol that achieves it. We observe that the resulting capacity is the same for both unicasting and multicasting, but show that the network size required to achieve any target error probability is smaller for unicasting than for multicasting. Finally, we introduce the notion of a network "scaling exponent" to quantify the rate of decay of error probability with network size as a function of the targeted fraction of the capacity. This exponent provides additional insights to system designers by enabling a finer grain comparison of candidate cooperative transmission protocols in even moderately sized networks.

Original languageEnglish
Pages (from-to)2762-2770
Number of pages9
JournalIEEE Transactions on Information Theory
Issue number6
StatePublished - Jun 2006


  • Ad hoc networks
  • Cooperative diversity
  • Multicasting
  • Outage capacity
  • Scaling laws
  • Sensor networks
  • Wireless networking


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