## 4 915 MHz/2400 MHz Bands' Performance in SG-oriented IoTs
### Scenario 2: Absence of 2400 MHz Co-Existing Devices  
A capital factor in the performance of wireless networks is their coexistence with other devices operating in the same frequency band. This second scenario evaluates the situation in which an IoT is deployed in an environment that presents the same amount of interference in both bands (set to \(-93.85\) dB).  
This will generally be the case in which the SG is placed in a remote area--hence, the absence of other interfering 2400 MHz devices. The rest of the variables will remain unaltered. As in the previous scenario, the PRR is greater for the 915 MHz band than for the 2400 MHz one (Figure 6a). However, the sheer differences that appeared in Scenario 1 are no longer present when both bands are subject to the same noise conditions. Nevertheless, the PRR for the 2400 MHz band is still much more affected by the resizing factor due to, mainly, a larger path loss, decreasing 2.25 times faster with \(\alpha\) than for the 915 MHz band.  
Figure 6b shows a general outlook of the MND results, whereas Figure 6c depicts a close-up of the first \(\alpha\) points. The results reveal a very interesting fact: in terms of MND, there are distances for which the 2400 MHz band is better suited than the 915 MHz one (and vice versa). When communicating devices are relatively far apart (e.g., greater than \(\alpha=0.996\) or \(\overline{D}_{in}=7.7\) m for a packet length of 6 B), the increment of path losses in the 2400 MHz band cannot be compensated by the higher transmission rate, thus resulting in larger MND values in this band. Conversely, when the resizing factor is small, the short number of packet losses does not play a major role in the MND, since the transmission rate is a more determining factor and presents a smaller value for the 915 MHz band. Therefore, when designing delay-sensitive networks, one should consider not only the transmission rate of the chosen band but also the \(\overline{D}_{in}\) of the deployment, incorporating it as a key design parameter.  
Since both the MND and the PCPT are affected by the number of retransmissions, they are strongly influenced by the packet losses, evaluated by the PRR. Therefore, the PCPT shows a similar tendency with \(\alpha\) than the MND. Again, there are specific values of \(\alpha\) for which SG-oriented IoT operating in the 2400 MHz band will benefit from a lower power consumption and vice versa. For example, for 6-byte long payloads, devices working in the 2400 MHz band will consume less energy if the network presents a small \(\overline{D}_{in}\) (specifically, values of \(\overline{D}_{in}\) smaller than 6.96 m or \(\alpha=0.9\)). This is explained by the behavior of the PRR along with the time that the transceiver requires to transmit a packet. When the PRR is relatively high for both bands, the much shorter transmitting times of the 2400 MHz band make the total power consumption smaller; power consumption strongly depends on the time the device is actively sending a packet. However, when the PRR drops abruptly (\(\alpha>0.9\)), these shorter times cannot compensate for the large number of losses.  
Furthermore, since bigger packets take longer times, the 2400 MHz especially benefits from a faster transmission rate when transmitting larger payloads. Finally, as \(\alpha\) grows, the power consumption in the 2400 MHz band greatly increases due to a corresponding decrease of the PRR. This increment leads to a PCPT up to 12 times higher for the 2400 MHz band than for the 915 MHz one for a 24-byte long payload.