# On the Benefits of Listen before Talk Scheme for NB-Fi Networks
## 7 Numerical Results
### Results for 3 km  
Let us consider a wider network with an \(R=3\) km radius. In such a network, unlike an \(R=0.4\) km radius network, not all sensors can detect each other's transmissions: sensors do not sense the transmissions of other sensors that are too far away, and thus can start their transmission even if some other sensors in the network transmit their data.  
The sensing range depends on the subchannel occupied by the signal, which is determined by the rate in NB-Fi (see Table 3), and for the rates of 50 and 400 bps, the range is comparable with 3 km, while for the rates of 3200 and 25,600 bps, it is significantly lower. For 50 and 400 bps, the sensors have a high transmission range. Moreover, at low rates, they are highly likely to use non-overlapping subchannels. Thus, for such data rates, the results are almost the same as those obtained for an \(R=0.4\) km network radius, see Figure 8, which is why we only show the results for the 400 bps rate. At the same time, for the rates of 3200 and 25,600 bps, the results are significantly different.  
Figure 8: Performance evaluation results for R = 3 km and the data rate of 400 bps: (**a**) PLR, (**b**) delay, (**c**) throughput, (**d**) energy consumption.  
Let us consider the results for the 25.6 kbps rate, where the differences between the 0.4 km and 3 km radius scenarios are the most notable. Figure 9 shows the dependence of PLR, delay, throughput, and energy consumption on load. First, the PLR in the CSMA mode does not differ so much from the Aloha mode. Among the CSMA modes, non-persistent CSMA appears to be the least efficient, while \(p\)-persistent CSMA shows the best results. It happens because, when the channel is idle, in the \(p\)-persistent CSMA mode, the sensor only transmits with the probability \(p\). As a result, it transmits less frequently than when using non-persistent or persistent CSMA. We can also see the difference in average delay between the \(R=0.4\) km and \(R=3\) km scenarios. Results of the CSMA modes are more similar to the Aloha mode for \(R=3\) km than for \(R=0.4\) km because collisions happen with a higher probability. Throughput in all CSMA modes with a load of more than 40 packets/s becomes less than in the \(R=0.4\) km scenario, which happens due to more frequent collisions. A sensor's energy consumption also increases due to collisions. We can also see that the energy consumption varies for different types of CSMA in intense traffic. Non-persistent CSMA is not as efficient as in the \(R=0.4\) km scenario anymore, while \(p\)-persistent has the lowest energy consumption, which corresponds to the throughput results.  
To sum up, in a small network, to minimize PLR, the most efficient strategy is to use non-persistent CSMA and the highest data rate. The same strategy is efficient if we want to minimize the delay and energy consumption in a small network at a load below 100 frames per second. At higher rates, p-persistent CSMA with properly configured \(p\) is the best; however, at such loads, the PLR is close to 1. The maximal throughput is obtained  
Figure 9: Performance evaluation results for R = 3 km and the data rate of 25,600 bps: (a) PLR, (b) delay, (c) throughput, (d) energy consumption.  
with the non-persistent CSMA with frequency hopping and a 3200 bps rate. In a large network, the p-persistent CSMA is the most efficient for optimizing all the considered performance indicators.