Wireless Ad Hoc and Sensor Networks

482 Wireless Ad Hoc and Sensor Networksaverage 30% of the readers will be switched off for each time intervalwhereas the other 30% transmit at full power. Hence, readers in full powerhave a greater probability of attaining the desired range, whereas theaverage detection range is sacrificed for this achievement. The relativelypoor performance in average detection range compared to DPC and PPCBeta(2, 2) can be observed in Figure 10.11.Although the percentage of time a target range is achieved is low forBeta(2, 2), it provides the best average detection range of all three algorithms.DAPC with the selective backoff scheme finds a balance betweenthe two evaluation metrics. These show that there is a trade-off betweenpercentage times the target range and average detection range areachieved.The average detection range and percentile plots can also be producedby fixing the number of readers and varying the minimum distancebetween any two readers. Shown in Figure 10.12 and Figure 10.13, DAPCis seen to converge as the minimum distance between any two readersdecreases, which again verifies the theoretical conclusions for the powerupdate scheme. With the same explanation as discussed previously, PPCwith Beta(0.1, 0.1) performs better in achieving desired range, whereasBeta(2, 2) gives better average detection range.100Network with 15 nodesPercentage of time achieving desired range9080706050403020PPC beta (0.1, 0.1)10PPC beta (2, 2)DAPC05 6 7 9 11 14Minimum distance between readers (meters)FIGURE 10.12Percentage of time the target range is achieved with minimum distance.