David Boswarthick, Omar Elloumi, Olivier Hersent   M2M Communications  A Systems Approach (2012, Wiley)

David Boswarthick, Omar Elloumi, Olivier Hersent M2M Communications A Systems Approach (2012, Wiley)

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Chapter 5: ETSI M2M Services Architecture
Chapter 5
ETSI M2M Services Architecture
Omar Elloumi1 and Claudio Forlivesi2
1Alcatel-Lucent, Velizy, France
2Alcatel-Lucent, Antwerp, Belgium
5.1 Introduction
As with every vision, the M2M promise has taken time to materialize. The early phases have been dedicated to refining the vision, testing new business models, developing standalone solutions to test concept feasibility, and also overcoming the limitations of insufficient interoperability. The use of horizontal service platforms, as a means for an operator to provide value-added services, or for an application provider to have a modular and future-proof application enablement strategy, is an integral part of the M2M vision. A recent report from the Yankee Group on the US carriers' perspective on M2M, A Closer Look at M2M Carrier Strategy, very clearly depicts the fact that providing value-added services based on horizontal platforms is becoming a business imperative for telecom operators:
Carriers view value-added services as new differentiators. As all four major carriers have increased their coverage across the U.S., network availability is diminishing as a key differentiator. Overlapping coverage areas increase price competition, as solution providers have more carrier options in various geographies and can shop around for the cheapest price on a per-contract basis. The trend among all four carriers is to promote flexible, easy channels and robust device management services in order to attract business. 
(Source: Yankee Group)
The components of such a horizontal platform may vary based on the targeted M2M applications. For instance, the support of location services is needed for fleet-tracking applications but not for smartmetering. Additionally, a stepwise approach is being adopted by the operators who are in the process of deploying horizontal M2M platforms. The original focus primarily targets connectivity and activation, basic data mediation, device management, and security. Figure 5.1 provides an overview of the M2M basic horizontal service platform components. These can be grouped into the following categories.
Figure 5.1 Typical components of a horizontal M2M service platform. Source: Yankee Group
		Data mediation functions: Allow for basic data collection, storage, and subscription/notification on events pertaining to data availability. Additionally, further complex data functions, such as data aggregation, and analytics, can be provided.
		Communications: Hides network transport specificities as well as communication protocols from the applications. Communication functions include name-to-network address translation, bearer selection (SMS, data bearers) and establishment, protocol translation, etc.
		Management functions: Provides applications with configuration management (CM), fault, and performance management (PM) (such as battery level monitoring) as well as firmware and application software upgrade. Management functions are an important aspect of M2M, especially when considering the relatively long lifetime of M2M devices (more than 20 years for smart meters).
		Context: Provides access to other functions such as location, provisioning (device activation, security key bootstrapping, etc.), and billing functions.
This chapter will focus on the standardization work taking place in the ETSI Technical Committee Machine to Machine (ETSI TC M2M). This technical committee aims to provide a standards-based foundation for the deployment of such horizontal platforms.
The chapter is structured as follows. First, it provides the high-level system architecture and explains the generic framework used to build the horizontal platform service capabilities (SC). This framework is then further examined to show individual service capabilities. A motivational and a functional description are also provided for the principal capabilities. Second, an introduction to representational state transfer (REST) and the motivation underpinning the use of REST as an architecture style are provided. The rest of the chapter focuses on resource structure, as well as interface procedures, which are explained using an example.
5.2 High-Level System Architecture
High-level system architecture provides an overview of the components of a system, as well as the relationship between the individual components. It provides the starting point for a stepwise approach to the description of the functional architecture. This second presentation of the architecture provides a more formal description of the interactions between functions within the system, where each function can be mapped onto components of the high-level system architecture.
ETSI TC M2M has adopted the following high-level system architecture which allows for a common understanding of the system that is under standardization (see Figure 5.2). This high-level architecture fully endorses the need for M2M service capabilities that are exposed toward applications, be it in the network, the device or in the gateway. One important aspect of this high-level system view is that it provides an end-to-end representation of an M2M system. However, not all elements of this architecture are targeted as standardization work in ETSI TC M2M. That group fully recognizes that M2M communications will maximize the usage of already deployed access and core networks as well any other form of local and personal area networks. Additionally, the ongoing work on mobile network improvements for M2M currently underway in 3GPP and 3GPP2 is considered as a means to improve the delivery of M2M services as opposed to must-have features. As such, ETSI TC M2M, at least in Release 1 of its set of specifications, does not rely on the ongoing 3GPP and 3GPP2 network improvement for M2M, because the implementations must be based on existing network deployments. However, it is expected that subsequent M2M standards releases will increasingly seek to optimize these network improvements.
Figure 5.2 M2M high-level system architecture overview. Reproduced by permission of ETSI
The M2M high-level system architecture (Figure 5.2) includes the concept of the M2M device domain, as well as the network and applications domain.
The M2M device domain is composed of the following elements:
		M2M device: a device that runs M2M application(s), referred to in the rest of this chapter as device applications (DAs), using M2M service capabilities and network domain functions. M2M devices can connect to the M2M core in the following manner:
		Scenario 1 \u201cdirect connectivity\u201d: The M2M device is equipped with a WAN communication module and accesses directly the operator access network. Examples of such devices include a smart meter that is directly connected to a GSM/GPRS infrastructure. In this case, the M2M device performs procedures such as registration, authentication, authorization, management, and provisioning with the network and applications domain.
		Scenario 2 \u201cgateway as a network proxy\u201d: The M2M device connects to the network and applications domain via an M2M gateway. M2M devices connect to the M2M gateway using the M2M area network. This case is applicable for \u201clow-cost\u201d devices that only run applications and make use of M2M SC available in the M2M gateway in order to perform the same procedures as in Scenario 1.
		M2M area network: a generic term referring to any network technology providing physical and MAC layer connectivity between different M2M devices connected to the same M2M area network or allowing an M2M device to gain access to a public network via a router (not shown in Figure 5.2) or a gateway. Examples of M2M area networks include wireless personal area networks, such as IEEE 802.15.x, Zigbee, Bluetooth, etc., or local networks such as PLC (powerline communications) or WiFi. While several M2M area networks are based