# Evaluation of IEEE802.15.4g for Environmental Observations
## 4 Analysis
### Line of Sight Scenario
#### 4.1.2 RX at 700 m  
Considering the RX node at 700 m, we approach to the limit of the radio link. Figure 8 shows that high data rates are not capable of delivering any packet, making them unusable for similar distances. From Figure 8a, with short packets, we see that most OFDM radio settings have a poor or nonexistent PDR. The reference 2 FSK-50 has a PDR of 83%. Only OFDM2-100 presents a PDR of 92%. O-QPSK radio settings have a high reliability, with 3 out of 4 PDR values of 100% and the remaining (OQPSK-12.5) of 94%. 2 FSK-FEC-100 has 100% PDR. Therefore, we highlight 2 FSK-FEC-100 and O-QPSK since they have the highest PDR and highest data rate in their technology. Increasing the packet size to 2047 B, we see from Figure 8b that the PDR slightly drops in comparison to small packets. Nonetheless, it is still around 80% for some radio settings. The reference is at 58% PDR, being matched by OFDM2-50 and outperformed by all O-QPSK PHYs and 2 FSK-FEC-50 and 2 FSK-FEC-100. We highlight the highest PDR of each technology, therefore 2 FSK-FEC-50 and OQPSK-50. It is notable that for OFDM2-50, the PDR concerning long packets is 59% whereas for short packets is only 23%. This is counterintuitive since short packets should have a higher PDR than long packets due to is lower probability of getting a wrong symbol throughout the complete received frame. Therefore, this effect can be attributed to interference that occurred only in that precise moment. For the following radio setting tested, OFDM2-100, we see how the PDR for short packets increased to 92%, using the same frequency as OFDM2-50, which shows that the interference is no longer present. Figure 8: Line of Sight, 700 m. Only O-QPSK and FSK radio settings are able to provide the highest reliability. This node is close to the limits of the coverage. OFDM radio settings have a poor performance at this distance, but the difference is that OFDM transmissions are at least 3 dBm weaker that the rest of the PHYs. (**a**) PDR at 700 m from TX with packets of 127 B. Highest reliability achieved with 2 FSK-FEC-100, OQPSK-6.25, OQPSK-12.5 and OQPSK-50. The reference has 83% PDR. OFDM2-100 has also higher reliability than the reference; (**b**) PDR at 700 m from the TX with packets of 2047 B. The reference has 58% PDR, while 2 FSK-FEC-50 94% PDR and OQPSK-50 100% PDR; (**c**) Maximum amount of 127 B packets that can be correctly sent within an hour. 4 FSK-FEC-200 and 2 FSK-100 can send 239 and 253 short packets. OFDM2-100 can send up to 285 packets, while the reference only 138 packets; (**d**) Maximum amount of 2047 B packets that can be correctly sent within an hour. OFDM2-100 and OQPSK-50 can send up to 10 packets, while the reference 2 FSK-50 just 6 packets; (**e**) Average electric charge consumption per packet of 127 B. OFDM2-100 consumes the less electric charge, 964 uC while 2 FSK-50 consumes 2178 uC; (**f**) Average electric charge consumption per packet of 2047 B. OFDM2-100 and OQPSK-50 are the less electric charge-hungry radio setting, consuming 26.8 mC and 29.1 mC respectively while 2 FSK-50 consumes almost the double, 47.5 mC. Ref. [17] shows that a link of 3.5 km can be obtained with this technology. They were in the Highlands of Scotland and the router node with that link was located at the top of a hill ([[https://mountainsensing.org/deployment/router-nodes/](https://mountainsensing.org/deployment/router-nodes/)]([https://mountainsensing.org/deployment/router-nodes/](https://mountainsensing.org/deployment/router-nodes/))). In our case, our link did not arrive to one kilometer, mainly due to the obstacle the ground poses at that distance (the Fresnel radius to that distance is 9.29 m and the nodes are at 1.8 m above the ground). Now, considering the maximum amount of packets that can be transmitted under the duty cycle regulation with short packets. Figure 8c shows that OFDM2-100 is the radio setting that can send up to 285 short packets within an hour. Not far behind we have 4 FSK-FEC-200 and 2 FSK-100 capable of transmitting 239 and 253 short packets per hour.