## 5 Performance Analysis of Proposed Schemes: MRS-ST-BL and MRS-SD-BL
### Results
#### 5.3.1 Impact of Different Battery Levels of Relays on Throughput
The graph shows the average throughput of all schemes initially increases with the increase in search radius, except for Direct scheme which remains constant. The throughput of MRS-ST with a relay having full battery power (the blue line with square) and a relay having different battery power (the dashed blue line) gradually decreases for large search radius as expected. The reason is that, with the increase in search radius, more devices are being probed, and also the length of link from a source to a relay and that from the relay to a destination increases. For large search radius, the throughput of MRS-ST and HRS with varying battery level are reduced compared to the throughput of MRS-ST and HRS with full battery. For other schemes, the throughput remains unchanged for large values of search radius. Next, we present the performance of our proposed schemes MRS-ST-BL and MRS-SD-BL to overcome such reduction in throughput. Figure 3b illustrates the average throughput of various relay selection schemes as the search radius increases. A relay for each of the schemes have different battery power levels. The proposed schemes MRS-ST-BL and MRS-SD-BL, which take battery power of devices into consideration for selection of a relay are compared against existing schemes MRS-ST, MRS-SD, HRS and M-Nearest schemes with relays having different battery power levels. We also analyzed the performance of modified version of HRS, HRS-RP, in which relay selection is done considering battery power of devices. The important result is that the throughput of our proposed scheme MRS-ST-BL is greater than that of MRS-ST-WFB for large values of search radius. Figure 4: Average throughput of different schemes when Shape = 1.01 and Scale = 0.01 in a network having width of 100 m. (**a**) Different battery power levels not considered in relay selection; (**b**) Different battery power levels considered in relay selection. Figure 4 depicts the average throughput of different schemes as the search radius increases for a weak social trust scenario (Shape = 1.01, Scale = 0.01) among users in a network with high node density. The key observation from this figure is that the varying battery power level of a relay significantly affect the performance of all relay selection schemes, when social trust among the users in the network are weak. Additionally, our proposed scheme MRS-ST-BL significantly increases the throughput of D2D communications when relay devices have varying battery levels. Figure 4a illustrates the average throughput comparison of existing schemes MRS-ST and MRS-SD (our previous work [10]), HRS [12] and generic schemes, with the increase in radius of search ring. The average throughput of these schemes with a relay having full battery power is compared against throughput of the schemes with a relay having varying battery power. Figure 4a shows that the average throughput of all schemes initially increases with the increase in search radius, except for Direct scheme which remains constant. The blue line with squares represents the throughput of MRS-ST with a relay having full battery and the dashed blue line represents the throughput of MRS-ST with a relay having varying battery level. The green line with squares represents the throughput of MRS-SD with a relay having full battery and the dashed green line represents a relay with varying battery level. The red line with squares represents the throughput of HRS with a relay having full battery and the dashed red line represents a relay having varying battery level. The throughput of MRS-ST and HRS, that have relay with and without varying battery power levels, gradually decrease for large search radius. This is because with the increase in search radius, more devices are being probed and also the length of link from a source to a relay and that from the relay to a destination increases. Interestingly, the throughput of MRS-ST, MRS-SD and HRS significantly decreases when a relay has varying battery power compared to the schemes when relays have full battery.