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, specializing in ad hoc control [ZigBee]. ZigBee was started in 2003 in conjunction with IEEE 802.15.4 standardization [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.
The ZigBee approach does have several down-sides, including reliance on a single wireless link technology, tight coupling with application profiles, along with Internet integration and scalability limitations. In 2009 the ZigBee Alliance announced that ZigBee will start to integrate IETF standards such as 6LoWPAN and ROLL into its future specifications. Earlier work has shown how ZigBee application profiles can be carried over UDP/IP and 6LoWPAN [ID-tolle-cap], which is covered in more detail in Section 5.4.3. The integration of IP technology into ZigBee provides a much wider range of networking possibilities, beyond just ad hoc control.
Machine-to-machine (M2M) communications has become a popular industry term for the remote monitoring and control of machines over the Internet. Traditionally, M2M systems include M2M modules (usually a cellular modem) integrated into embedded devices together with an Internet-based back-end system. The M2M module measures and controls the device, and communicates over IP with the back-end M2M service. More recently, M2M gateways to local embedded networked devices have become more common.
Thanks to native IP, 6LoWPAN networks can be connected to M2M services through simple routers and thus 6LoWPAN can be considered to be a natural extension of M2M. Machine-to-machine communications has been an important driving force in the development and growth of the Internet of Things, which has continued with the ETSI M2M standardization effort.
The Future Internet [Bauge08] is a term used to describe research into what the Internet architecture and protocols could look like in 10–20 years. The US National Science Foundation has a long-term initiative on Future Internet Design (FIND) which covers network architecture, principles as well as mechanism design [FIND]. Several European projects specialize in Future Internet research, for example the EU 4WARD project [4WARD], in cooperation with the European Future Internet Assembly [FIAssembly].
Although most of the research related to Future Internet does not consider embedded devices and networks, this aspect is starting to gain interest. The EU SENSEI project [SENSEI] for example specializes in making wireless sensor and embedded networks a part of the global Internet, both current and future. One of the subjects of the project is how wireless embedded networks and 6LoWPAN type functionality can be made an integral part of the Future Internet. Several examples throughout this book are taken from the SENSEI project as it has been doing leading work in this area.
The term Wireless Sensor Network (WSN) comes from an academic movement starting in the mid 1990s into research on low-power ad hoc wireless networked sensors and actuators. The US government was very interested in the application of low-power sensing in military and security applications, and provided extensive funding for the subject. The research area later developed into a widely popular subject with a large range of applications, and a huge collection of results and trials. These networks have traditionally been thought to be completely isolated, and thus typically Internet compatibility or standards were not taken into consideration. Instead each project has tended to produce its own optimized wireless, network and algorithm solutions.
Additionally most of the envisioned applications of sensor networks were created by university researchers, and they most often did not have a real market need. More recently the importance of standards, marketable applications and the importance of Internet services have encouraged the WSN community to become involved with 6LoWPAN standardization and the IPSO Alliance. The result is that a lot of the innovation produced through WSN research is starting to be applied to Wireless Embedded Internet technology, a good example being the IETF ROLL working group.
There is a strong trend of convergence in standardization, industry and research, as indicated above. This convergence is clearly steering towards an Internet-based approach as the requirements of modern-day embedded applications clearly demand it. 6LoWPAN has been a result of and catalyst for convergence to the Internet of Things.