By Frédéric Lejay
The majority of communication systems are now designed around Internet Protocol (IP), which is the most standard and widely deployed architecture. By defining a clear separation between networks and services, IP offers interoperability and extensibility, resulting in lower up-front investments, maintenance cost savings and future proofing of long life products. M2M (machine-tomachine) applications remain the exception to the rule since they do not yet widely use IP technology.
One of the reasons that many M2M solutions do not use IP technology is because they cannot efficiently support IP from end-to-end. The burden on resourceconstrained devices and limited bandwidth networks has until now been considered a show stopper. Smart metering, with meter cost pressure and mostly non-IP last mile and local area networks, is no exception to this rule.
In order to make the benefits of IP available end-to-end, up to the meter and the home devices, Wavecom has designed an innovative technology which extends the IP network reach to include such systems. This IP extension – IPext – designed specifically to save resources (memory, CPU, battery life, bandwidth), enables standard TCP and UDP applications to be ported on any device connected over any non-IP network. This includes in particular low power RF networks, standard – such as ZigBee – or proprietary Power Line Communication (PLC) wired networks.
IPext provides a unique opportunity for the smart metering community to leverage the IP standard, while choosing the best “last mile” access and local area network technology suited to each specific smart metering application. By deploying standard IP applications, significant cost savings can be obtained, better and faster integration with information systems or consumer equipments can be reached, and investments are protected. By selecting the right network interface for each solution, power consumption, equipment cost or performance can be optimised.
Smart metering applications, by definition, require interconnecting meters, information systems, and possibly other devices such as data loggers, or even home devices. The choice of communication technologies, however, is complex and key. It will directly impact the cost of deployment and operation, as well as the quality of the solution. The technology choice will also determine how fast and easy – or how long and complex – the application development, porting and evolution will be.
The smart metering industry will go on investing significantly in communications technologies in the coming years. Futureproofing such investment can be achieved by relying on IP architecture and TCP and UDP transport protocols, the most widely deployed protocols today. The range of applications already available is almost unlimited, benefiting from a long list of popular application layer protocols (telnet, SNMP, SNTP, FTP, HTTP, etc.). The industry has invested important resources over several years to design, validate and deploy a wide range of TCP and UDP-based solutions, including in the metering area with DLMS/COSEM IPv4 transport layers, for example. IP-based applications represent the best transition path as communication technologies – in particular wireless – evolve. They will facilitate the integration of smart metering products with existing information systems, other machine networks including home automation, and even consumer applications.
On the other hand, smart metering applications have their specific constraints, often implying the use of specific wired and wireless networks, optimised for power consumption, coverage, deployment and operation costs. Many such networking technologies do not natively support IP networking. This is what IPext seeks to resolve.
How IPext works
Thanks to the IPext Gateway connected on one side to the IP network, and on the other side to one or more non-IP networks, standard TCP and UDP applications can run on non-IP devices and have access to the IP network resources. No IP stack is required on the device, and the underlying non-IP network remains unchanged. The application on the device is independent from the non-IP network, in the same way that IP applications are independent from their underlying IP network.
The simplicity and portability of the IPext technology resides in the principle of fully re-using the existing networking layer, and fully re-using existing IP routing and network. IPext can be easily be ported on any standard or proprietary solution, wired or wireless, whatever the topology (ad hoc, tree, mesh, etc.). IPext even allows the exact same application to run across heterogeneous networks.
The IPext Gateway runs the IP, TCP and UDP stacks. It is connected to an IP network and may host local IP applications. The RSP protocol, acting as a remote procedure call protocol, exposes the IPext Gateway TCP/UDP sockets Application Programming Interface (API) to the applications running on IPext devices. The IPext device does not need any IP, TCP nor UDP stack, but simply an RSP Client.
The IP application running on the IPext device is seen by the IP network as running on a port of the IPext Gateway. It can be a client or a server application.
Several IP applications can run on the same IPext device. The IPext Gateway can simultaneously manage several IPext devices, from one or from several non-IP networks.
By allowing standard IP applications to run on non-native IP devices, IPext drastically simplifies smart metering application design and deployment and contributes to investment protection:
- Application design is standard and portable, using a BSD-like TCP/UDP socket APIs: applications are easily developed and portable across usual operating systems; re-use is maximised for both IP and non-IP networks
- Applications are network independent: there is no need to learn about the non-IP network specificities; no need to modify the non-IP network; routing capabilities, including mesh when available, are unchanged; no network specific application profile is required
- Applications operate on heterogeneous devices, across heterogeneous non-IP and IP networks, using standard IP addresses and ports.
IPext has been designed to optimise the scarce network and device resources by re-using the existing networking and transport layers of the IP and non-IP network:
- IP without IP overhead for battery and bandwidth savings: 1 byte overhead for TCP data sending, a few bytes to establish a TCP connection, far below TCP and IP requirements
- No IP routing in the devices: with the IPext Gateway IP address used to address all attached IPext devices, IPext can be deployed on IPv4, IP routing is not impacted and remains located in the IP network. As a counterpart, as for a NAT architecture, IPext devices are not individually addressed by an IP address but at application level
- Minimal – software only – impact: few kilobytes of code, low data memory, no significant CPU requirement, no real time constraints, no OS required on the IPext device.
With such combined performance, simplicity and flexibility, IPext can be introduced now and smoothly. IPext can coexist with legacy devices and applications. When needed, non-IP applications can be used in conjunction with IP-based applications.
Alter natives to IPext
Today, the main alternatives to IPext for providing IP access to non-IP networks are:
- To define IP networking evolution as ongoing through IETF with 6lowPAN and ROLL. These specifications aim at integrating all devices in the IPv6 network. The counterpart of this approach is to imply trade-offs on routing and networking capabilities, losing part of the specificities and optimisation of each network technology.
- To design an application level gateway that connects to the IP world on one side but that is designed specifically for the non-IP network on the other side. Application level gateways have the drawback of requesting a specific design of the gateway and the devices – such as the meters – for each network technology. It makes the gateway more and more complex as it handles different non-IP networks, for example PLC and low power RF, and various applications, for example metering and home automation. Interoperability requirements result usually in an application profile specification for each application on each network technology.
Typical IPext use in smart metering
IPext perfectly answers to the increasing demand in smart metering for interconnecting a variety of devices (data loggers, meters, home displays, domestic appliances, etc.) to an information system, by offering IP end-to-end.
A typical implementation of IPext is depicted below for a multi-energy smart metering infrastructure. GPRS cellular network access is used by concentrators, home gateways or meters to connect to the information system through IP. This IP network is then extended over PLC or over low power RF technologies (ZigBee or any proprietary technology) to electricity, water and gas meters, but also domestic appliances. With IPext, the same IP application can run on all meters for data collection, whatever the retained architecture. As IPext is not exclusive, a standard ZigBee application can also be deployed when preferred.
Smart metering applications require connecting meters, possibly of various types (electricity, gas, water or heat), concentrators, and even additional home devices (display, domestic appliances, etc.) across access networks and local and home area networks. For technical, historical and economical reasons, and despite standardisation efforts, the network technologies are numerous, and will remain numerous.
IP, the reference architecture for telecommunication applications, is a powerful way to simplify smart metering application development and deployment, while keeping open the choice for the right connectivity for each specific application. Unfortunately, the burden of IP was until now a show stopper for use in limited resource devices and networks.
By extending the IP network to such resource limited devices and networks, IPext is a key building block for smart metering. With IPext, smart metering users can select their preferred networking technologies, including PLC and low power RF – such as ZigBee or any proprietary solution – without impacting their application. Combining IPext to IP offers a unique opportunity to significantly lower smart metering solution design and deployment costs, protect investments and offer improved time-to-market. In addition, this is the opportunity to better integrate the smart metering infrastructure to existing systems, thus to extend the smart metering services range.
And, as interoperability is key to IP and to smart metering, Wavecom is pushing IPext as a free and widely available technology, with a rich eco-system of industry players providing IPext solutions.