Wireless Ad Hoc and Sensor Networks
Wireless Ad Hoc and Sensor Networks Wireless Ad Hoc and Sensor Networks
Optimized Energy and Delay-Based Routing 41112 × 10510Overhead (OEDSR vs OEDR)oedsroedrOverhead (bytes)8642040 50 60 70 80 90Number of nodes100FIGURE 8.44Overhead with network size.Even though the distance to the BS from each node is included in the costfactor calculation, the total overhead for the OEDSR is still lower than theOEDR, due to the way the RNs are selected.To understand the effect of channel fading during routing, another simulationrun was carried out but with fading channels. Channel fading wasintroduced during routing for the OEDSR in a random manner. The channelfading causes the noise level in the terrain to go up, which in turn, increasesthe percentage of packets lost. With channel fading, the signal-to-noise ratio(SNR) has to be increased because of an increase in the threshold for successfulpacket reception. Otherwise, the packet is dropped. It can beobserved from Figure 8.45 that the number of packets lost increases as thereceived SNR threshold is increased. When the threshold is set greater than20 dB, the percentage of packets lost is greater than 20%, that is, one out ofevery five packets transmitted are lost and have to be retransmitted. Thisalso increases the amount of energy consumed because more packets haveto be transmitted from the node. These results clearly show that protocolsfor ad hoc network cannot be directly deployed for WSNs.Example 8.9.4: Mobile NetworkThe simulation was run for networks with 40, 50, 70, and 100 nodesrandomly distributed in an area of size 2000 × 2000 m with node mobility.
412 Wireless Ad Hoc and Sensor Networks3530Channel fadingOEDSR% of packets dropped25201510510 12 14 16 18 20 22 24 26 28Noise level (dB)30FIGURE 8.45Packets dropped with channel fading.Node mobility is generated in a random manner for each node but waskept the same when testing protocols.Figure 8.46 shows the comparison of energy consumed by the OEDSRand the OEDR for a mobile network. As expected and observed in previousscenarios, the energy consumed using the OEDSR increases significantlyas the number of nodes increases in the network, because the nodes inthe network move in a random fashion. Due to this, the different routeshaving varying number of RNs are selected at different times. However,the energy consumed in the OEDSR is far less compared to the OEDRdue to the reasons mentioned in the static node case.The average E2E delay is still lower for the OEDSR when compared tothe OEDR as observed in Figure 8.47. Even with node mobility, fewernodes are selected as RNs in the OEDSR protocol, whereas the numbersof RNs are significantly more with the OEDR, which in turn, increase theE2E delay. The E2E delay includes the wake-up time for a node, apartfrom the transmission time. Therefore, with more RNs, waking, processing,and queuing times go up increasing the E2E delay.It can be observed from Figure 8.48 that the number of collisions in thenetwork is fewer for the OEDSR when compared with the OEDR. TheOEDR uses more RNs to transmit data from the CHs to the BS. Moreover,when selecting the MPR nodes, the nodes send information to their onehopand two-hop neighbors, and this increases the number of signals
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Optimized Energy <strong>and</strong> Delay-Based Routing 41112 × 10510Overhead (OEDSR vs OEDR)oedsroedrOverhead (bytes)8642040 50 60 70 80 90Number of nodes100FIGURE 8.44Overhead with network size.Even though the distance to the BS from each node is included in the costfactor calculation, the total overhead for the OEDSR is still lower than theOEDR, due to the way the RNs are selected.To underst<strong>and</strong> the effect of channel fading during routing, another simulationrun was carried out but with fading channels. Channel fading wasintroduced during routing for the OEDSR in a r<strong>and</strong>om manner. The channelfading causes the noise level in the terrain to go up, which in turn, increasesthe percentage of packets lost. With channel fading, the signal-to-noise ratio(SNR) has to be increased because of an increase in the threshold for successfulpacket reception. Otherwise, the packet is dropped. It can beobserved from Figure 8.45 that the number of packets lost increases as thereceived SNR threshold is increased. When the threshold is set greater than20 dB, the percentage of packets lost is greater than 20%, that is, one out ofevery five packets transmitted are lost <strong>and</strong> have to be retransmitted. Thisalso increases the amount of energy consumed because more packets haveto be transmitted from the node. These results clearly show that protocolsfor ad hoc network cannot be directly deployed for WSNs.Example 8.9.4: Mobile NetworkThe simulation was run for networks with 40, 50, 70, <strong>and</strong> 100 nodesr<strong>and</strong>omly distributed in an area of size 2000 × 2000 m with node mobility.
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