Analyzing space/capacity tradeoffs of cooperative wireless networks using a probabilistic model of interference

  • Authors:
  • Hermann Simon Lichte;Stefan Valentin;Holger Karl;Imad Aad;Joerg Widmer

  • Affiliations:
  • University of Paderborn, Paderborn, Germany;University of Paderborn, Paderborn, Germany;University of Paderborn, Paderborn, Germany;DoCoMo Euro-Labs, Munich, Germany;DoCoMo Euro-Labs, Munich, Germany

  • Venue:
  • Proceedings of the 12th ACM international conference on Modeling, analysis and simulation of wireless and mobile systems
  • Year:
  • 2009

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Abstract

Interference limits throughput in wireless networks. To protect themselves against interference, many wireless protocols create areas around receivers in which no node is allowed to transmit. If such an exclusion area is small, more transmissions can proceed simultaneously but observe higher interference, creating a tradeoff between network capacity and link capacity. Link capacity can be improved by cooperative diversity techniques, exploiting stochastically independent retransmissions by a relay node. But for this relay to work, it has to receive the original transmission, again consuming space. Hence, cooperation influences the network/link capacity tradeoff as it invests more space to increase link capacity. This paper characterizes the tradeoff when cooperation is used. We derive a closed-form solution for the expected total interference caused by the k-closest nodes. We use this result to reformulate the outage capacity equations for direct, Non-Cooperative Relaying (NCR), and Selection Decode-and-Forward (SDF) transmission as functions of exclusion areas. We find that by using SDF, capacity gains over direct transmission are highest when exclusion areas are smallest. This result suggests that cooperation is a key technique to improve capacity in networks with powerful/sophisticated receivers that are able to cope well with high interference.