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Hot from the PAN

Wireless technology is gathering momentum. Bluetooth is gaining widespread acceptance and popularity, while technologies such as ultra-band network and Zigbee are coming up fast. Dominic K reports on the technologies that make personal area networking possible.

Individuals today carry multiple intelligent computer devices ranging from smart cellular telephones to personal digital assistants (PDAs). This is where personal area networking or PAN comes into the picture. The reach of a PAN is typically a few hundred metres. As the name suggests, PAN is used for communication among personal devices for interpersonal communication, or for connecting to a higher level network and the Internet. PAN cannot be related or compared to its native brothers such as LAN or WAN. It is a concept that adds convenience and enhances lifestyle comforts through high technological innovation and research.

The concept unveiled

The goal of a PAN is to facilitate seamless connectivity between home or business devices and systems. They network with each other, inter-operate, and provide a routing function to connect individuals beyond the personal network.

The routing may be via a GSM handset, or through an access point to a landline or a corporate network. One of the concepts to be understood when talking about a PAN is a ‘personal bubble.’ The bubble is defined as the effective radius of wireless range, which is defined to be 100 metres for Class One transmitters. Similarly, the defined parameter for Class Two and Three is 10 metres and one metre respectively.

Currently, work is underway on a concept that will extend a PAN over a wider area; it is called wireless PAN (WPAN).

WPAN

One of the essential concepts in WPAN technology is known as plugging-in. Plugging-in is what happens when any two WPAN-equipped devices come into the designated proximity, or within a few kilometres of a central server, and hence start to communicate with each other as if connected by a cable. The other feature is the ability of an individual device to lock out other devices selectively. This prevents interference as well as unauthorised access to information.

"Zigbee is redefining both star and mesh network topologies, along with a variety of data security features and inter-operable application profiles" - Ganesh Guruswamy Country Manager & Director Freescale Semiconductor India

WPAN technology is currently in its infancy, and is under development trials to further explore the technology. 2.4 GHz in digital modes is expected to be the operating frequency. Every device in a WPAN will be able to plug-in to any other device in the same WPAN, provided they are within physical range of one another.

Further, WPANs worldwide will be inter-connected. For example, an archaeologist on a survey site in India can use a PDA to directly access the databases at the Department of Archaeology, University of Cambridge, Britain, and transfer his findings to the specific database.

A WPAN consists of a dynamic group of less than 255 devices that communicate within about a 33-foot range. Unlike with wireless LANs, only devices within this limited area typically participate in the network, and no online connection with external devices is defined. One device is selected to assume the role of the controller during WPAN initialisation, and this controller device mediates communication within the WPAN. The controller broadcasts a beacon that lets all devices synchronise with each other, and allocates time-slots for the devices.

Each device attempts to join the WPAN by requesting a time-slot from the controller. The controller authenticates the devices and assigns time-slots for each device to transmit data. The data may be sent to the entire WPAN using the WPAN destination address, or it may be directed to a particular device.

The 802.15 working group is defining different versions for devices that have different requirements. 802.15.3 focusses on high-bandwidth (about 55 Mbps) low-power MAC and physical layers, while 802.15.4 deals with low-bandwidth (about 250 Kbps) extra-low power MAC and physical layers.

Bluetooth analysis

Bluetooth is designed for one-to-one static links, and is based on frequency-hopping radio links between various devices. Bluetooth PAN helps individuals connect and disconnect on the fly. Users can move only within their defined personal bubble if they want to stay connected.

For mobility, PAN demands that the connection becomes a mobile router, which is mostly a GSM or a Digital Enhanced Cordless Telecommunications handset. Further, Bluetooth offers limited bandwidth coverage. The highest throughput achieved via one-to-one connection at its maximum asymmetric throughput is of 721 Kbps (approximately).

The dominant driving force for Bluetooth acceptance is mobile phone manufacturers, more so in the GSM arena; GSM manufacturing players have thrown their resources behind the Bluetooth concept.

Ultra-wide band (UWB) technology is considered to be best-suited for short-range applications with regards to PAN. It is a fast, power-efficient, low-cost and non-interfering wireless alternative ideal for inter-device communications.

UWB and Zigbee explored

Ultra-wideband, also known as impulse or carrierless radio technology, is one of one of the most promising radio technologies ever. Unlike conventional radio systems, which operate within a relatively narrow bandwidth, ultra-wideband (UWB Modulation) operates across a wide range of frequency spectra by transmitting a series of extremely narrow (10-1000 ps) and low power pulses. (Ultra-wideband should not be confused with spread spectrum technology, which is used by other WLAN standards such as 802.11b.)

Zigbee is yet another open standards-based wireless technology. It dedicatedly addresses the needs of remote monitoring, and control and sensory network applications. Zigbee is considered to be the next-generation Bluetooth technology.

States Ganesh Guruswamy, Country Manager and Director, Freescale Semiconductor India: “The technology supports low data rates and low power consumption. It is redefining both star and mesh network topologies, along with a variety of data security features and inter-operable application profiles.”