Читать книгу Industry 4.0 Vision for the Supply of Energy and Materials - Группа авторов - Страница 45

MTC is a promising technology for connection of intelligent devices and appliances to the Internet and other networks. Given that 3GPP cellular systems were not primarily designed for machine-type communications, all MTC technical requirements in mobile and cellular technologies should be identified in advance. Some key requirements are as follows:

 Low complexity: MTC networks consist of heterogeneous connected devices from multiple vendor equipment and protocols [127]. Hence, a scalable MTC network architecture in a standard format is required to manage system heterogeneity and associated complexity [137]. 3GPP reduces MTC devices complexity by removing the unnecessary features of these devices. For instance, in 3GPP Release 12 and 13, a number of complexity reductions were identified for LTE. Such changes do not impact interoperability with normal 3GPP devices while maintaining IoT requirements.

 Increased energy efficiency: A majority of MTC devices are in small size, battery-powered, and located in remote areas. These features imply that recharging and replacement of batteries are infeasible. To prolong the MTC systems’ life cycle, optimization techniques are used to achieve power efficiency in MTC nodes’ sensing and data transmission [138]. These energy-efficient techniques could be applied in the application, network, and link layers.

 High coverage: Most industrial applications, such as smart metering and factory automation, require high levels of coverage, and their connectivity model succeeds where nearly the entire network elements are reachable. On the other hand, the large number of network nodes within a cell impacts the achieved QoS. In addition, the extended coverage of the wireless networks in indoor and industrial spaces is challenging and requires large number of base stations that would be very costly. 3GPP proposed a viable approach in Release 12 that improves MTC devices coverage, facilitates a scalable IoT system, and stipulates low complexity without significant increase in overall cost.

 Reliability: MTC wireless networks might be unreliable because of interference and noise from adjacent equipment, RF channel fluctuations, and machine interconnections [127]. Given that delivery of sensory data to applications should be reliable in terms of E2E delay [139], some possible solutions such as software reconfiguration of cognitive radios and spatial-temporal redundancy techniques are utilized to improve network reliability. For instance, cognitive radio software reconfiguration enables equipment and terminals to dynamically switch between various wireless modes and adapt to environment changes to decrease RF self-interference and external noise [127]. This technique is exploited in software-defined radio (SDR) systems.

 MTC user identification and control: Almost all MTC devices in the market are equipped with subscriber identification module (SIM) that contains crucial information about device profile, identity, and subscribed services. Since network operators support customized MTC services according to the subscription profile, it is essential to regulate access of MTC devices individually and based on the prior defined SIM profiles. MTC user identification impacts decisions of network operators for serving and access of MTC devices. 3GPP defines multiple UE categories in LTE to identify, isolate, and restrict access of MTC devices.

 Service enablement and exposure: To ensure connectivity and scalability of MTC systems in emerging industrial IoT, 3GPP requires third-party support to enable required services for MTC. In this context, ETSI and the oneM2M Global Initiative are standardization organizations that collaborate on E2E service enablement. Whereas ETSI focuses on enabling services across servers, gateways, devices, and standard service interfaces, oneM2M develops practical details to tackle requirements of the service layer for M2M communication [140, 141]. Since MTC systems should be able to deal with heterogeneous sensing, it is necessary that application platforms be connected to 3GPP core network via secure interfaces. Additionally, a privacy-preserving approach should be adopted to manage availability of personal information for IoT customers and applications [142].