The Average Number Of Hops To Reach The Sink Node Case Study

The average number of hops to reach the sink node is shown in Figure [fig_M1]. In Sink-PathCC, the number of hops to reach the sink node does not change significantly with an increase on the node density. On the other hand, CoopSink increases the number of hops to reach the sink by over 40% when the number of nodes increases from 50 to 100. While Sink-PathCC demands for ≈7 hops to reach the sink, CoopSink requires nearly 17 hops when n = 100, an increase of nearly 142%. Clearly, Sink-PathCC provides a short path to reach the sink node as compared to CoopSink.
When using CoopSink, |Hi, j|+2 transmissions are needed to transpose a CC-link while |Hi, j|+1 are needed when using Sink-PathCC. Thus, Sink-PathCC reduces the number of transmissions
As already mentioned, CoopSink and Sink-PathCC use different strategies to establish CC-link. Figure [fig_M3] shows the performance of the CoopSink and Sink-PathCC in terms of connectivity to the sink node. The y-axis shows the connectivity with the sink node when employing CoopSink, Sink-PathCC and without the use of CC. On average, CoopSink increases the connectivity to the sink node by nearly 50% while Sink-PathCC attains an average of 44%. This results from the fact that the CC model used by Sink-PathCC does not allow the source node to take part in the second step of the CC. Hence, Sink-PathCC does not have as many nodes to improve the transmission range as the CoopSink. Nevertheless, the difference between the two strategies becomes negligible at higher node density. In fact, with 100 nodes, both strategies provide similar results, with a difference of ≈1% between the
Figure [fig_M5] show the average energy cost of the helper nodes for different node density. For both techniques, as the node density increases, the cost of the helper nodes decrease significantly. As the topology gets denser, the source node improve the chance of selecting suitable helper nodes to compose the CC-link. When n = 50 nodes, CoopSink outperforms Sink-PathCC by less than 6%. With 100 nodes, CoopSink reduces the average cost of helper nodes by nearly 9% as compared to Sink-PathCC. Although Sink-PathCC demands more power of the helper nodes as compared to CooSink, Sink-PathCC provides higher energy savings for the source node. Clearly, there is a trade-off between reducing power consumption of the source node in detriment of the helper nodes. One may argue that with higher node density, the source node may have several helpers to select. Thus, even if some of its helper run out of batteries, the source node would still be able to select other helpers. On the other hand, the task of selecting suitable helpers is a time consuming task, particularly in CoopSink. Hence, this work seeks for an energy balance alternative that would not place a higher burden on the helpers or on the source