# Resilient Green Cellular IoT for Landslide Monitoring Using Voice Channels
## 4 Evaluation of VRTHI
### Improved Real-Time Communications  
VRITHI provides better real-time communication with less power consumption and less message delay. This section compares VRITHI with other prominent IoT protocols, such as MQTT, AMQP, CoAP, and XMPP.  
The MQTT protocol is based on publish-subscribe mechanism and uses cloud brokers for intercommunication among nodes. In MQTT, the subscriber continuously listens to the publisher. Whenever an event in the sensor is detected, it is disseminated immediately to the subscribers, as shown in Figure 10. However, listening continuously (or periodically) induces a lot of power consumption. In the figure, the grey area in MQTT indicates whether transceiver state is ON or OFF.  
AMQP, XMPP, and CoAP are other prominent protocols that can act in either publish-subscribe or request-reply mechanism. Primarily, they use a Request-Reply mechanism. AMQP is mostly used in a business messaging scenario where mobile handsets communicate with the back-office data centers. It can work in both TCP or UDP connections but requires higher resource utilization compared to other protocols. It needs a third party broker, such as Rabbit Messaging Queuing (RabbitMQ), for inter-node communications. XMPP uses XML-based messaging predominantly over TCP connection. However, they additionally need a jabber-id and broker server, such as AMQP, for communications. CoAP uses less energy as compared to these protocols. However, it also needs a polling mechanism and third-party broker (CoAP Mongoose server) for functioning. In Figure 10, the grey areas in AMQP, XMPP, CoAP indicate the period of polling for every 12 min. We can observe that, while an event is happening at the 15 th minute, it is disseminated only  
Figure 9: VRITHI leads to reduction of ratio of nodes under DoS attacks: (**a**) Before VRITHI, (**b**) After VRITHI.  
after a delay of 9 min during the next polling. Moreover, periodical polling results in higher power consumption.  
None of the above protocols provide direct peer-to-peer connection without the help of a brokerage service. This disadvantage of message delay is overcome by the VRITHI framework, along with reduced energy consumption. VRITHI follows an interrupt-based mechanism. In this, a node is in standby mode, and the data channel is disabled. Whenever there is an event in the sensor data, the control channel initiates an handshake with the appropriate node through their corresponding International Mobile Subscriber Number (IMSI). The data channels are then enabled. For IP communication to happen, the control channel is used to exchange their corresponding IP addresses and ports, as described in Section 4. In Figure 9(a), the grey area in VRITHI indicates the dissemination of interrupt as soon as the event is detected.  
During the course of communications, the assigned IP address may get changed by the cellular provider. In that case, the control channel takes care of updating it in the other node. Unlike other protocols, there is no need for a DNS or third party client in nodes memory which is helpful with nodes having only 2 KB RAM. We observe a specific node for the number of dynamic IPs assigned over 48 h during the peer-to-peer communication using sim5300E modem, and Figure 9(b) reflects the number of times IP address changes in four 12-h intervals.