# Investigation of Data Quality Assurance across IoT Protocol Stack for V2I Interactions
## 4 Survey of Network Protocols  
The computing limitations of IoT devices have received extensive attention from academia and industry. These efforts have resulted in the development of several lightweight protocols to compensate for the constrained nature of IoT devices [81]. As a result, several application layer protocols have been developed to support communication in IoT networks, each with a unique and problem-specific communication solution. Various studies have employed a range of methodologies, including experiments [82, 83], simulations [84], and testbed implementation [85], to compare the performance of various protocols. These evaluations used several performance metrics such as bandwidth consumption, efficiency, energy consumption, latency, reliability, Round Trip Time (RTT), upload and download time, average response time, and throughput. With these metrics, more emphasis has been placed on investigating timeliness in the IoT application layer. [PERSON], [PERSON], and [PERSON] [81] performed an experiment by comparing the performance of three application layer protocols, CoAP, WebSocket, and MQTT, using different Internet connections. Protocol efficiency and RTT were the measured metrics. Their experiment showed that CoAP achieved the highest protocol efficiency and the lowest average RTT, closely followed by WebSocket. The performance of MQTT depended on QoS profiles. QoS1 generally achieved better RTT. Another set of comparisons was conducted via an experiment by [PERSON], [PERSON], and [PERSON] [82]. They measured the performance metrics of CoAP, MQTT, and REST HTTP using time and bandwidth consumption on a 4G cellular network with a speed of 6 Mbps and an Internet broadband connection with a speed of 50 Mbps. Their results showed that CoAP is faster among the protocols when transmitting payloads less than 10 kb. MQTT and CoAP outperformed REST HTTP when sending smaller payloads. With larger payloads, REST HTTP became the faster protocol. Additionally, the experiment showed bandwidth consumption is equally reduced in CoAP and MQTT when transmitting smaller payloads. With an increase in Payloads, REST HTTP consumed less bandwidth. Assessing these protocols over a 4G cellular network is favourable for CoAP and MQTT in V2I communications use cases requiring the broadcast of smaller payloads. In [PERSON], [PERSON], and [PERSON] [86], the transmission latency and throughput of various sensor data sizes and formats were studied using AMQP, DDS, MQTT, and XMPP over the web with MQTT outperforming the other protocols in latency. Another experiment was observed by [PERSON] and [PERSON] [87]; their study measured and compared the RTT for different loads using CoAP, MQTT, XMPP and WebSocket. CoAP and MQTT showed better response times. In another study, [PERSON] and [PERSON] [88] performed an analytical comparison between AMQP, CoAP, DDS, MQTT, MQTT-SN, XMPP, WebSocket, HTTP/1.1, HTTP/2.0, and RTP to investigate the most suitable IoT protocol for video transmission over LLN. Their comparative analysis showed that CoAP is the most appropriate protocol for video transmission due to its associated transport protocol (i.e., UDP), which supports best-effort packet delivery. A comparison between CoAP, MQTT, XMPP, and AMQP was observed by [PERSON] and [PERSON] [12]; their study revealed that CoAP, AMQP, and XMPP ensure reliability by some built-in features. In addition, AMQP and XMPP both benefit from the reliability provided by their associated transport protocols, e.g., TCP. On the other hand, reliability is provided using the various QoS in MQTT. Their research further showed that CoAP, MQTT, and XMPP all support real-time communication, while AMQP does not. + A study by [PERSON], [PERSON], and [PERSON] [89] compared the performance of AMQP, MQTT, and CoAP and found that MQTT exhibited high packet overhead, especially in 3G networks due to QoS requirements. At high message volumes, MQTT delivered superior throughput, while CoAP and MQTT (QoS 1 and 2) maximised bandwidth usage.