# Enhancing the Reliability of Cellular Internet of Things through Agreement
## 6 Conclusions  
As the IoT is applied in various applications, a large number of IoT PUs need to communicate through wireless networks. According to the comparison of [PERSON] et al. [21], among general wireless access technologies such as Bluetooth, Zigbee, WiFi, LoRa, and cellular. Cellular is the best choice to provide wireless access with quality of service (QoS) for a large number of IoT PUs [21]. The comparisons of wireless access techniques for IoT networks are shown in Table 1.  
Because CIoT can provide security between connected PUs [5]. In order to provide these applications with high security, a highly reliable CIoT environment is required to support these large-scale applications. In this research, a CIoT platform MECIoT that integrates MEC is proposed to improve the flexibility and reliability of the network topology. In addition, the agreement problem is one of the important issues to discuss improving the reliability of the system in a distributed system, and it has been extensively studied. The topology of the network is an important factor that affects the complexity of solving agreement problem. All past protocols may not be suitable to solve the agreement problem of the new MECIoT environment. In this research, CIoTAP is proposed to solve the agreement problem that PUs may fail in MECIoT. According to the proofs of the optimality of CIoTAP in Section 5, CIoTAP has the following features. * (Feature of _Access-tier_): \(n_{Bj}>\lfloor(n_{Bj}-1)/2\rfloor+f_{Bj}\) where \(n_{Bj}\) is the number of CIoT PUs,\(f_{Bj}\) is the total number of faulty CIoT PUs allowed within the coverage of \(BS_{j}\) at the _Access-tier_. The condition, \(n_{Bj}>\lfloor(n_{Bj}-1)/2\rfloor+f_{Bj}\), is used to describe the number of CIoT PUs within the coverage of \(BS_{j}\) in _Access-tier_. * (Feature of _MEC-tier_): \(n_{Mj}>\lfloor(n_{Mj}-1)/3\rfloor+2f_{Mj}\) where \(n_{Mj}\) is the number of MEC PUs,\(f_{Mj}\) is the total number of faulty MEC PUs allowed in MEC cloud \(E_{j}\) of MEC-tier. This feature indicates the number of MEC PUs required to execute the agreement problem in the MEC cloud \(E_{j}\). * (Feature of _Cloud-tier_): The (Feature of _Cloud-tier_) is similar to the (Feature of _MEC-tier_) that \(n_{C}>\lfloor(n_{C}-1)/3\rfloor+2f_{C}\) where \(n_{C}\) is the number of Cloud PUs, and \(f_{C}\) is the total number of Cloud PUs allowed in the _Cloud-tier_. This feature, \(n_{C}>\lfloor(n_{C}-1)/3\rfloor+2f_{C}\), is used to indicate the total number of Cloud PUs required by the _Cloud-tier_ to achieve agreement. The agreement problem has been extensively studied over the past two decades. Many graceful agreement protocols have been proposed with various network topologies [10; 11; 20; 22; 23; 24; 25; 26; 27; 28]. In [28], the network topology is Broadcasting Network (BCN); in [11; 23], the network topology is Fully Connected Network (FCN); in [10], the network topology is Cloud Computing environment (CC); in [20], the network topology is the Integrated Fog Cloud IoT (IFCIoT). However, the existence of abnormal PUs in the network topology is assumed by these studies [10; 11; 20; 22; 23; 24; 25; 26; 27; 28]. Table 2 shows a comparison of these protocols. Among them, only the CIoTAP proposed in this research can be used in a cellular network that implements mobile edge computing and IoT, so that all normal PUs can reach the agreement and provide a highly reliable CIoT platform. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **Bluetooth** & **Zigbee** & **WiFi** & **LoRa** & **Cellular** \\ \hline Spectrum & Unlicensed & Unlicensed & Unlicensed & Unlicensed & Licensed \\ Connectivity & Small & Medium & Large & Massive & Massive \\ Range & Short & Short & Medium & Long & Long \\ Power & Low & Low & High & Low & Low \\ Delay & Short & Short & Short & Short & Short \\ Security & Low & Medium & Medium & Medium & High \\ Mobility & Not & Not & Not & Yes & Yes \\ Cost & Low & Low & Low & High & Low \\ \hline \hline \end{tabular}
\end{table}