8.2 Impact of Transmission Rate and Forwarding Strategy on OR Performance
In this section, we discuss the factors that affect the one-hop performance in terms of throughput and delay of OR. These factors include rate and forwarding strategy, which further includes candidate selection, prioritization and coordination.
The impacts of transmission rate on the performance of opportunistic routing are twofold. On the one hand, different rates achieve different transmission ranges, which lead to different neighborhood diversity. Explicitly, high-rate causes short transmission range, then in one hop, there are few neighbors around the sender, which presents low neighborhood diversity. Low-rate is likely to have long transmission range, therefore achieves high neighborhood diversity. So from the diversity point of view, low rate may be better. On the other hand, although low rate brings the benefit of larger one-hop distance, which results in higher neighborhood diversity and fewer hop counts to reach the destination, it is still possible to achieve a low effective end-to-end throughput or high delay because it needs more time to transmit a packet at lower rate. So it is nontrivial to decide which rate is indeed better.
Besides the inherent rate-distance, rate-diversity and rate-hop tradeoffs, which affect the performance of opportunistic routing, the forwarding strategy will also have an impact on the performance. That is, for a given transmission rate, different candidate forwarding ...