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

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.

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INDEX TERMS

Primary Classification:
  E. Data
  E.4 CODING AND INFORMATION THEORY
      Subjects: Formal models of communication

General Terms:
Design, Performance, Theory

Keywords:
capacity analysis, cooperative communication, interference, relaying protocols, spatial reuse