Wireless Sensor Networks: Standards and Driving Forces

Maxim Osipov

OOO Siemens Corporate Technology, Embedded Systems

Volynskiy per. dom 3A liter A, 191186 St. Petersburg, Russia

Abstract. The paper will provide a state-of-the-art report of Wireless Sensor

Networking technologies, including ZigBee, WirelessHART, LowPower Blu-

etooth and others. The main advantages and drawbacks of these technologies

will be described, focusing on application-driven requirements. Special focus

will be put on standardization activities in the areas of WSN design itself, as

well as domain-specific WSN-related standards (Energy, Industry, Healthcare

and Environmental). A review of application frameworks will also be provided,

including OS-level platforms (TinyOS, Contiki OS).

1 Introduction

Following a period of relative stagnation, Wireless Sensor Networks now enjoy time

of rapid growth, facilitated by renewed interest in conservative resource consumption

and increasing usage of service infrastructures. Applications of WSN adopted now in

many areas, including Energy, Industry, Healthcare, Environmental Monitoring and

others. Among numerous advantages, provided by Wireless Sensor Networks, a spe-

cial emphasis can be put on possibility to create systems, optimized for environment

and thus consuming less of resources, easily deployable and offering non-intrusive

behavioral characteristics.

Introduction of WSN into the real life applications is following a number of

trends, including industrial efforts for standardization of technologies, governmental

activities to promote certain application scenarios, scientific research in the areas of

technological platforms for WSN (including radio data transmission, communication

network architectures and protocols, energy harvesting techniques, etc.). In this pa-

per, we will try to sketch a global picture of WSN technologies and applications from

a point of view of industrial adopters.

2 Communication Technologies

Wireless Sensor Network communication technologies include results of research and

development activities in the areas of radio communication, networking protocols,

software architectures and platforms. Development and standardization of WSN is

driven by several communities, including:

1. Internet community

Osipov M. (2009).

Wireless Sensor Networks: Standards and Driving Forces.

In Proceedings of the International Workshop on Networked embedded and control system technologies: European and Russian R&D cooperation,

pages 161-166

 SciTePress

2. Industrial associations

3. Technology groups

Often, standards development is going in similar directions and some standards over-

lap significantly in purpose and/or approach to implementation. Therefore knowledge

of existing WSN options, taking into account technical and marketing aspects, is

essential to select the right approach for a project or product.

2.1 IEEE 802.15.4

IEEE 802.15.4 is one of the most promising standards for Wireless Personal Area

Networks (WPAN). It is available since 2003 and serves as a basis for several higher

level protocols, including ZigBee, WirelessHART and 6LoWPAN. IEEE 802.15.4

[1] defines physical and MAC layers (including security) and supports star and peer-

to-peer topologies. Data transfer rate is up to 250 kb/s. Supported bands and modula-

tions are changing depending on a standard version (2003, 2006 and 2007 versions

available), but the most common is 2.4 GHz band with 16 channels. IEEE 802.15.4

can be used “as is” only for very simple applications].

2.2 6LoWPAN

IPv6 over Low power WPAN (6LoWPAN) is IETF working group, aiming to bring

IP networks (IPv6) and sensor networks together. The problem with integration of IP

and sensor networks is in significant overhead of IP protocol headers, which are not

suitable for IEEE 802.15.4 networks (with 127 bytes data frame). 6LoWPAN WG

has completed IETF RFC 4944 [2], defining a way for transmission of IPv6 packets

over IEEE 802.15.4 networks, basically using stateless headers compression. Usage

of IP is promoted by IP for Smart Objects (IPSO) Alliance as a native way for inte-

gration of sensor networks and smart objects with existing IT infrastructure.

2.3 ZigBee

ZigBee Allience is an industrial association, developing and promoting ZigBee proto-

col standard [3]. ZigBee protocol is a layer above IEEE 802.15.4, which provides

networking layer with support for different architectures, including star, tree and most

interesting – mesh topology. ZigBee specification is a mature one, first version re-

leased in 2004 and used by some commercial products. Special focus of the Alliance

is on application level standardization, i.e. definition of standard interfaces for differ-

ent application domains, including Home Automation, Smart Energy, Building Au-

tomation, Health Care and others.

2.4 Wireless HART

HART is an industrial protocol for communication between field instrumentation and

host systems. Wireless HART is a part of HART 7 Specification [4], and as ZigBee,

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provides extension over IEEE 802.15.4 layers with industrial specifics, such as neces-

sity for real-time operations. It defines communication network structure and neces-

sary components, such as Network Manager. Wireless HART uses channel hopping

TDMA protocol with 10 ms communication slots. HART specification includes also

application level elements, such as definition for formats of diagnostic information,

which are applicable for Wireless HART devices also.

2.5 ISA100

ISA100 Wireless Compliance Institute aims to define a complete set of industrial

wireless standards. One of these standards, ISA100.11a [5], is covering wireless

process control applications. From the maturity point of view, it is rather new (2008)

and very similar to Wireless HART from the technical perspective. This is also based

on IEEE 802.15.4-2006, uses channel hopping to increase robustness and provides

star topology for better response time and mesh topology for reliable communication.

Very interesting particularity of this standard is that it provides inter-networking

routing and frame format in accordance to IETF RFC 4944. Special attention is also

paid to interoperability with other families of standards (ZigBee, Wireless HART, etc.).

2.6 Bluetooth Low Energy

Development of Bluetooth Low Energy is currently ongoing and specification is

planned in the beginning of 2009. It is based on Nokia Webree and targeted to similar

applications as IEEE 802.15.4; advantage of Bluetooth Low Energy is availability

and cost of radio hardware (existing Bluetooth radios can be used in many cases).

However, applicability of this standard is limited to consumer devices, i.e. industrial

scenarios are not covered.

2.7 Other Solutions

There are many other solutions exist on a market, most of them proprietary and tar-

geted to certain specific applications. The list includes, but not limited to Z-Wave (the

main competitor to ZigBee), KNX RF, EnOcean and others. Often development of

particular technology is driven mostly by one company, and this makes investments

into this technology rather risky.

3 Wireless Sensor Platforms

Wiireless Sensor Platforms are hardware/software solutions to enable development of

WSN applications. These solutions usually have very special architecture due to ap-

plication requirements, i.e. include very low-power hardware (this means low per-

formance and small amount of memory) and low overhead software components,

including OS, drivers, protocol stacks, application services, etc. Usually, platforms

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are centered around particular operating system, which is adopted for WSN needs.

3.1 TinyOS

TinyOS is an open source component-based operating system, designed for embed-

ded Wireless Sensor Networks. TinyOS is written on nesC, a dialect of C designed

for sensor applications with limited resources. Due to openness, portability and com-

ponent architecture, TinyOS used in many projects and some ZigBee stack implemen-

tations use it as an underlying platform. However, TinyOS networking model is not

standard and without usage of some common protocol is more suited for research

activities, rather then industrial applications. Another limiting factor is usage of nesC

language – with all simplicity it is a new programming language to learn by developer.

3.2 Contiki OS

Contiki OS is another open source embedded platform for WSN applications. It is

implemented in C and similar to TinyOS, provides a broad spectrum of supported

hardware architectures, system modules and user tools. Very interesting particularity

of Contiki is IP networking stack, which actually led to IETF standard development

and IPSO Alliance creation. Contiki also used by Freaklabs FreakZ open source Zig-

Bee stack implementation project, so it has potential to cover both most perspective

WSN networking directions.

3.3 Linux

Linux is traditionally considered as a backbone for a modern networking infrastruc-

ture. In our days it is not only adopted in server equipment, but also used in network

appliances, such as routers, media streaming centers, etc. In the same time it is se-

lected by some manufacturers as a platform for mobile handsets. From author point of

view, this makes Linux an ideal platform for gateways between wireless sensor net-

works and traditional network infrastructures, including computer and mobile net-

works. The main blocking factor is the absence of proven implementations of WSN

protocols for Linux operating system. However, this situation is being changed by

Linux-ZigBee SourceForge.net project, which aims to develop a ZigBee (and more

generally – LoWPAN) protocols stack for Linux kernel.

4 Application Domains

Adoption of Wireless Sensor Network technologies is driven by application require-

ments. There are some “natural” areas where need in WSN obvious – for example

home automation, environmental monitoring or tracking applications. Other applica-

tions are “triggered” by specific governmental actions; a good example here is smart

metering technology.

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4.1 Energy (Metering)

Advanced Metering is a very hot topic in US and Europe, due to governmental plans

to update electricity grid and facilitate energy saving technologies. Electricity meter-

ing, is not connected directly to WSN topic, however there is a synergy with home

automation, which could bring significant benefits by enabling smart meters to com-

municate with in-house smart appliances, for example to schedule or control energy

consumption. This was understood by ZigBee Alliance and triggered development of

Smart Energy profile. However, state-level standards for metering are not yet devel-

oped, so it is not clear if WSN will be adopted at the end as an enabler technology for

Advanced Metering Infrastructures.

4.2 Industry (Manufacturing)

Wireless technologies in industrial automation are adopted rather slowly due to sig-

nificant products lifecycle and conservative approach to engineering. This area has

many specific requirements for reliability and real-time operation; main standardiza-

tion activities are done by International Society of Automation. However advantages

of WSN for industry are so significant, that 2 of most mature WSN standards (Wire-

less HART and ISA100.11a) are targeting industrial process control applications.

4.3 Health Care

In healthcare industry, most of the advantages of Wireless Sensor Networks are

usually connected to “personalized healthcare” concept. Development of standards in

this area is mostly driven by Continua Health Alliance, defining technologies and

interoperability requirements for the industry. There are specific requirements for

healthcare applications, mostly in the area of security and reliability of operation.

However from technology point of view, mostly common approaches and standards

are adopted, for example careful attention is paid to possibility of mobile technology

integration with healthcare services, and this means usage of Bluetooth (at the time of

writing, evaluation and selection of wireless technology by Continua was still in

progress).

4.4 Environmental Monitoring

This is a native application of Wireless Sensor Networks and it has a lot of attention

from research community. However, there are no significant moves to define com-

mon standards in this area, probably due to significant diversity of possible use cases.

For example, wireless sensor networks are adopted for pipeline infrastructures moni-

toring, dikes, bridges and pollution control.

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5 Conclusions

Wireless Sensor Networks standardization process is rapidly progressing, driven by

introduction of new application scenarios, market forces and governmental regulation

activities. The number of already published standards, often for similar (or same)

applications, raises concern for interoperability of different networking technologies.

Usage of common platforms for networking infrastructure may help to overcome this

potential problem and help to create single world wide “Internet of Things”.

References

1. IEEE Std. 802.15.4-2003, Wireless Medium Access Control (MAC) and Physical Layer

(PHY) Specifications for Low-Rate Wireless Personal Area Networks (LR-WPAN), IEEE,

2003.

2. G. Montenegro et al., “Transmission of IPv6 Packets over IEEE 802.15.4 Networks,” IETF

Internet draft, work in progress, September 2007.

3. ZigBee Specification, ZigBee Alliance, 2007.

4. HART Field Communication Protocol Specifications, Revision 7.0, HART Communication

Foundation, 2007.

5. ISA100.11a, Release 1, An Update on the First Wireless Standard Emerging from the

Industry for the Industry, ISA, 2007.

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