Variation of Spatial Protection Margins on Multihop Wireless Networks

In this paper, the effect of variation in the spatial protection margin, is investigated for multihop wireless networks under the interference avoidance protocol model and compared to single-hop communication network. Under the protocol model, the interference is avoided by the application of the exclusion range concept. This means that a spatial protection region (or a circular exclusion region) is specified around all receiving nodes so that any node other than the intended transmitter is not allowed to reuse the same frequency resource within this region. It is demonstrated that for an asymptotically infinite coverage area, the spatial reuse efficiency for a multihop design increases proportionally with the number of multiple hops per link, and with the spatial protection margin. However, under a finite coverage area, the monotonic increase of spatial reuse efficiency does not remain completely valid. In order to analyze the performance of such a system, a relation for the system throughput is derived from the Shannon capacity equation. It is found that the system throughput attains a peak when the value of spatial protection margin is nearly unity. The exact value of spatial protection margin when the throughput reaches its maximum is found to be a monotonically increasing function of the number of multiple hops and the pathloss exponent.