Feature: IIOT
Figure 2: Device-to-cloud connection
switch-off by the end of 2025. Te question then is how to migrate from 2G to the newer LTE or 5G networks with minimal costs and disruption. Tankfully for system owners there are options that can transparently migrate their existing 2G (and/or PSTN dial-up) devices onto a modern Ethernet, LTE or 5G network, allowing their legacy systems to continue to operate seamlessly.
A replacement system Te operation mode of most 2G-based M2M systems in essence mirrors that of landline-based dial-up PSTN networks; see its connection sequence in Figure 1. Each device is connected to a modem, which uses a protocol
known as the ‘Hayes’ or ‘AT’ command set. Tis defines a series of serial interface commands that can be used to obtain a connection to a remote device, transfer data across that connection and, subsequently, disconnect the call. To migrate these legacy devices onto an Ethernet, LTE or 5G
network, the AT modems must be replaced with devices that support the AT command-set via a serial interface, but which can then use an IP network to replicate the functionality of the dial-up system. Tis means that the connection, data transfer and disconnection command sequences need to be supported, but,
more importantly, it means there’s a mechanism to create a virtual point-to-point serial connection through the IP network. In reality there are rarely only two devices involved, and most
of these systems have an architecture where a large number of remote devices will try to dial in to a single central server via one or more dial-up numbers. It is therefore also necessary to replicate concepts such as ‘number engaged’, in order to retain the same communications network characteristics at both the remote and server sites. Advantech offers a solution here, with a combination of edge
routers loaded with an AT modem emulator application and its WebAccess/virtual private network (VPN) server; see Figure 2. Tis allows seamless migration of equipment connected to legacy 2G (or dial-up PSTN) systems onto current-generation cellular networks.
Advantech solutions WebAccess/VPN provides an authenticated and secure network upon which the system functionality is built. It allows creation and operation of a virtual private network within the Ethernet or cellular communications system, without requiring the user to have any detailed knowledge of how to configure or maintain the
Figure 3: The ICR-2000 router setup
www.electronicsworld.co.uk March 2024 39
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