## 5 Proposed Scheme
### Simulation Results and Discussion
#### 6.2.2 Discussion on Overall System Performance  
Figure 5 depicts the outage probability of the overall system for different values of distance from the eNB to D2D-Rx. When the distance increases, the channel gain decreases and thus increases outage probability. The significance of the proposed scheme is that, because of the FFR scheme with FRF of 2, the proposed scheme provides high utilization of resources within the distance of 100 m. Thus, the proposed scheme helps to reduce the outage probability by minimizing uplink interference. However, RRA scheme dramatically increases the outage probability with the increase of distance due to the expansion of path-loss. This results in degradation of SINR. In Figure 6, the outage probability of the system under varying threshold SINR is shown. The value of definite value of SINR threshold is varied from \(-15\) dB to \(25\) dB. The proposed scheme has very low outage probability as compared to other existing schemes. It can be seen that, with the SINR threshold of 17 dB, the system outage value for the proposed scheme, FRF of 1 scheme, and RRA scheme are 0.0989, 0.125, and 0.20, respectively. This implies that the proposed scheme minimizes outage probability by means of joint resource allocation and power control method. Figure 5: Overall system outage probability with varying distance from eNB to D2D-Rx. Figure 6: System outage probability with varying SINR threshold. Performance result for the system throughput at varying number of available D2D pairs is depicted in Figure 7. We observed that with the increase of D2D pairs, RA scheme achieved very less throughput because there is high rate of interference; in contrast, the proposed scheme yields highest throughput by maximizing the system capacity. Comparing to RA scheme, our proposed scheme provides a 4.38 throughput gain as compared with RRA scheme and a 1.45 throughput gain as compared with RA with FRF of 1. The throughput gain of D2D communications at maximum number of available D2D pairs is higher than that of the overall system throughput; this is because as the D2D pairs increases cellular user throughput decreases. In Figure 8, the throughput of the D2D users and cellular users over varying cellular user coverage distance. As expected, throughput of the D2D users is decreases with the increase of cellular coverage distance. This is because of the fact that D2D-Rx received more uplink interference from cellular users. However, as the cellular coverage distance increases throughout of the cellular users increases. It is observed that cellular user in the proposed scheme can afford more capacity as compared with other existing schemes. Figure 8: Throughput of D2D user and cellular user at varying cellular user coverage distance. Figure 7: System outage probability with varying number of available D2D pairs. Figure 9 shows the outage probability of cellular user over varying number of available D2D pairs at different SINR threshold values. It is seen from the Figure that the outage probability at threshold SINR value of 10 dB is higher than other values. Due to the increase of threshold SINR value, system capacity decreases dramatically. The average energy consumption of the overall system with varying number of D2D pairs is shown in Figure 10. Our result shows that with the increase of number of D2D users, power consumption is increases. The worse case is the RA scheme which has upper bound of energy consumption. This is due to the fact that RA scheme could not reduce the uplink interference and this leads to subcarrier synchronization error. However, the energy consumption of the proposed scheme is very less as compared with other existing schemes. During the discovery of D2D pairs which can simultaneously share the same cellular resource, optimal synchronization of subcarriers is achieved by the proposed scheme. Therefore, our proposed scheme increases the success rate of transmission and is favorable for low-energy devices.