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Understanding 6LoWPAN: The wireless embedded Internet (Part 2)

Posted: 22 Sep 2011     Print Version  Bookmark and Share

Keywords:6LoWPAN  Internet Engineering Task Force  ZigBee 

What is 6LoWPAN? It is a set of standards defined by the Internet Engineering Task Force (IETF), which creates and maintains all core Internet standards and architecture work. A straightforward technical definition of 6LoWPAN would be: 6LoWPAN standards enable the efficient use of IPv6 over low-power, low-rate wireless networks on simple embedded devices through an adaptation layer and the optimisation of related protocols.

The IETF 6LoWPAN working group was officially started in 2005, although the history of embedded IP goes back farther. Throughout the 1990s it was assumed that Moore's law would advance computing and communication capabilities so rapidly that soon any embedded device could implement IP protocols. Although partially true, and the Internet of Things has grown rapidly, it did not hold for cheap, low-power microcontrollers and low-power wireless radio technologies.

The vast majority of simple embedded devices still make use of 8bit and 16bit microcontrollers with very limited memory, as they are low-power, small and cheap. At the same time, the physical trade-offs of wireless technology have resulted in short-range, low-power wireless radios which have limited data rates, frame sizes and duty cycles such as in the IEEE 802.15.4 standard.

Early work on minimising Internet protocols for use with low-power microcontrollers and wireless technologies includesµIP from the Swedish Institute of Computer Science [Dunkels03] and NanoIP from the Centre for Wireless Communications [Shel03]. The IEEE 802.15.4 standard released in 2003 was the biggest factor leading to 6LoWPAN standardisation. For the first time a global, widely supported standard for low-power wireless embedded communications was available [IEEE802.15.4]. The popularity of this new standard gave the Internet community the needed encouragement to standardise an IP adaptation for such wireless embedded links.

6LoWPAN and other related standards

Figure 1: The relation of 6LoWPAN to related standards and alliances.

The first 6LoWPAN specifications were released in 2007, first with an informational RFC [RFC4919] specifying the underlying requirements and goals of the initial standardisation, and then with a standard track RFC [RFC4944] specifying the 6LoWPAN format and functionality. Through experience with implementations and deployments, the 6LoWPAN working group continued with improvements to header compression [ID-6lowpan-hc], 6LoWPAN Neighbour Discovery [ID-6lowpan-nd], use cases [ID-6lowpan-uc] and routing requirements [ID-6lowpan-rr].

In 2008 a new IETF working group was formed, Routing over Low-power and Lossy Networks (ROLL)[ROLL]. This working group specifies routing requirements and solutions for low-power, wireless, unreliable networks. Although not restricted to use with 6LoWPAN, that is one main target.

In 2008 ISA began standardisation of a wireless industrial automation system called SP100.11a (also known as ISA100), which is based on 6LoWPAN. An overview of ISA100 is given in Chapter 7.

Recent activities related to 6LoWPAN include the IP for Smart Objects (IPSO) Alliance founded in 2008 to promote the use of IP in smart objects and Internet of Things business [IPSO], and the IP500 Alliance which is developing a recommendation for 6LoWPAN over IEEE 802.15.4 sub-GHz radio communications [IP500]. Figure 1.3 shows the relations between related standards bodies and alliances. The Open Geospatial Consortium (OGC) specifies IP-based solutions for geospatial and sensing applications. In 2009 the European Telecommunication Standards Institute (ETSI) [ETSI] started a working group for standardisingM2M, which includes an end-to-end IP architecture compatible with 6LoWPAN.

6LoWPAN and other trends
There are several other trends to take into consideration when thinking about the Internet of Things. These include ZigBee, machine-to-machine (M2M) communications, the Future Internet, and wireless sensor networks (WSNs). This section looks into how each of these trends relates to the Internet of Things and 6LoWPAN in particular.

ZigBee is a protocol specification from an industry special interest group called the ZigBee Alliance, specialising in ad hoc control [ZigBee]. ZigBee was started in 2003 in conjunction with IEEE 802.15.4 standardisation [IEEE802.15.4], and specifies a vertical protocol stack solution with similarities to Bluetooth. The protocol mainly makes use of IEEE 802.15.4 features, adding ad hoc networking, service discovery and application protocol profiles on top of that. ZigBee has been successful for multi-vendor ad hoc applications such as home automation.

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