Defining the terms when talking about wireless A range of wireless technologies has recently emerged, targeted at low power, low data-rate networking. Wireless sensor networking, monitoring and control are the most often cited applications. As with many new technologies, the associated nomenclature is unfamiliar to all but those closely associated with development of the technology. We hope this column will clarify the differences among commonly used terms associated with low data-rate wireless networking. Wireless sensor networking Wireless sensor networking includes three distinct components. The first component is a sensor or an actuator. Many sensors and actuators are part of systems that need regular monitoring, thus the need for networking. In many cases, wiring costs prevent sensor networking; and in other cases prevent placement of sensors. Power constraints are also a concern. Often there is no ability to power the sensor in its desired location. One solution is to use battery power to operate the sensor and connect it wirelessly to a network. Unfortunately, until very recently, radio technologies, power sources and reliable and redundant networking protocols were not available to meet these needs. This is changing as a variety of technologies, standards and specifications are being created to enable the emerging Wireless Sensor Networking marketplace. Mesh networking Mesh networking refers to a specific type of network topology. Unlike hub-and-spoke networks or tree networks that must rely on an ultra-reliable connection to a single other node in the network, each node in a mesh network can be connected to multiple other nodes in the network, thus the term 'mesh.’ This multiple connection model theoretically gives mesh networks higher reliability than their hub-and-spoke and tree-based counterparts because there is not a single point of failure. As applied to wireless sensor networks, mesh networking is available in a variety of implementations from numerous vendors, each with advantages and consequences. In general, they share common attributes: - Networks can self-form based on the connectivity available in the physical deployment
- Network connections change over time as conditions change
- Routing of messages is hidden from the installer.
IEEE 802.15.4 IEEE 802.15.4 is a global standard created by the Institute of Electrical and Electronic Engineers. IEEE 802.15.4 was created primarily to address the needs of the wireless sensing and actuation marketplace. IEEE 802.15.4 defines the physical layer – also known as PHY or the radio; and the Medium Access Sublayer – known as the MAC or the software that controls the radio. A key characteristic and differentiator of IEEE 802.15.4 allows the creation of mesh networks and the operation of a many devices in a way that maximizes coexistence within commonly available radio frequency bands. Currently, the IEEE 802.15.4 standard is being used in a range of standards and specifications that define multi-hopping mesh networks such as ZigBee, Wi-HART, TinyOS and IETF Lo-WPAN. The ISA SP-100 committee is considering this standard as a preferred physical layer. Organizations ZigBee – The ZigBee specification defines a specific mesh network built on top of IEEE 802.15.4 radios. The primary focus of the ZigBee Alliance has been home and commercial building automation, with a recent focus on industrial monitoring. WINA – Industrial sites include a multitude of wireless devices and systems at work: WiFi, RFID/RTLS asset tracking, cell phones, pagers, point-to-point radio modems, wireless surveillance camera systems and wireless field transmitters. When used together in the same physical location, a potential coexistence, interoperability and performance train wreck looms. The Wireless Industrial Networking Alliance was formed to provide best practices and guidelines to address these issues. ISA SP-100 – The ISA SP-100 committee is a standards-making body within ISA chartered with the creation of wireless standards, best practices and tutorial content for the process control industry. The first draft of the ISA-100 standard is expected in early 2007, with final approval in early 2008, and initial product availability late in 2008. Mesh networking is being considered for this standard, along with other topologies. | 
