# Sustainable IoT Sensing Applications Development through GraphQL-Based Abstraction Layer
## 7 Energy-Wave Problem and High Power Communication
### Communication Setup and Test Findings  
We designed experiment scenarios to test our assumption and suggested high power communications. We used four Zolertia Z1 IoT motes with a custom small external antennas to enable short hop ranges in lab environment, running on Contiki OS for IoT. IETF standard ReST-based CoAP protocol is often used in modern IoT applications, thus we used Contiki implementation [35] of this request-response protocol for our IoT communications. In all the trials, there was a sender node providing in-field sensing service in response to periodic requests by a client installed on a server laptop, sent via Z1 mote acting as IoT gateway node. In each experiment trial, the client made 100 requests for sensors' data and variation in frequency of requests massages was done to check effect of different data load on the IoT system. We used two topologies for connectivity experiments, in which sender and receiver gateway were placed 12 m away in an indoor/home environment. In first scenario, low transmission power equal to \(-25\) dbm (0.0032 mW) was set to restrict direct connectivity. Connectivity for data communication was provided by placing two z1 motes in between at equal distances with same transmission powers (\(-25\) dbm) to act as intermediate forwarders. We made sure that each mote had connectivity range only to next forwarder and communication was really happening via multi-hop path. In the other scenario, we switched off intermediate motes and increased the transmission powers to \(-15\) dbm (0.0316 mW), which was sufficient to provide direct connectivity between in-filed sensing server and gateway node. The intervals between periodic request messages were varied as 10, 5, 1 and 0.5 s providing message sending rates 0.1, 0.2, 1 and 2 per second, respectively. We measured average round trip delays, average energy consumption by sender per request-response message exchange, average response receiving rate achieved at receiver gateway per second and duty cycling to be done by sender node per request-response exchange. All the results comparisons in Figure 13 are on the same set of experiments and variations. The only difference is of transmission powers to provide connectivity between sender and receiver. We consider the results in Figure 13 one by one. **Delay:** Average delay for direct connectivity case Figure 13a is much less on all the request sending rates. The average for all four sending rate experiments is 0.62 s for direct connectivity case, whereas it is 8.5 s for hop-by-hop case. The high power case is five times better at low sending rates and 15 times less on high data rates in comparison to multi-hop communication. Its values are not much affected by more load in shape of high message rates on the system, whereas hop-by-hop architecture suffers by the load and delays are increased on high data rates. **Response Receive Rate:** The response receiving rate on increasing request rates in Figure 13b are very encouraging and, on high data rates, direct connectivity scenario delivers all the data in time. The hop-by-hop case suffers severely at high load rates and is unable to deliver the data even in reasonable time. On two requests per second rate, direct transmission delivers at two packets per second, whereas hop-by-hop communication is only able to deliver at 0.45 packets per second. It is 4 times less than request sending rate as well as delivery rate of multi-hop case. On high data sending rates of 1 and 2, to complete the total 100 request/response exchanges, direct connectivity case needed 100 and 50 s, whereas hop-by-hop communication took 253 and 244 s, respectively. This is one of the major reasons for high energy usage for three-hop case because it has to run for 2.5-5 times longer, utilising the extra power. **Energy Consumption:** Now, if look at the energy consumption of both the cases Figure 13c, it is more interesting to observe these results.