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A wide variety of different wireless data technologies now exist, some in direct competition with one another, others designed to be optimal for specific applications. Wireless technologies can be evaluated by a variety of different metrics described below.

Of the standards evaluated, these can be grouped as follows: (Reference : Comparison of wireless data standards)

UWB, Bluetooth, ZigBee, and Wireless USB are intended for use as so called Wireless PAN systems. They are intended for short range communication between devices typically controlled by a single person. A keyboard might communicate with a computer, or a mobile phone with a handsfree kit, using any of these technologies.

WiFi is the most successful system intended for use as a WLAN system. A WLAN is an implementation of a LAN over a microcellular wireless system. Such systems are used to provide wireless Internet access (and access to other systems on the local network such as other computers, shared printers, and other such devices) throughout a private property. Typically a WLAN offers much better bandwidth and latency than the user's Internet connection, being designed as much for local communication as for access to the Internet, and while WiFi may be offered in many places as an Internet access system, access speeds are usually more limited by the shared Internet connection and number of users than the technology itself. Other systems that provide WLAN functionality include DECT and HIPERLAN.

GPRS, EDGE and 1xRTT are bolt-ons to existing 2G cellular systems, providing Internet access to users of existing 2G networks (it should be noted that technically both EDGE and 1xRTT are 3G standards, as defined by the ITU, but are generally deployed on existing networks.) 3G systems such as EV-DO, W-CDMA (including HSDPA and HSUPA) provide combined circuit switched and packet switched data and voice services as standard, usually at better data rates than the 2G extensions. All of these services can be used to provide combined mobile phone access and Internet access at remote locations. Typically GPRS and 1xRTT are used to provide stripped down, mobile phone oriented, Internet access, such as WAP, multimedia messaging, and the downloading of ring-tones, whereas EV-DO and HSDPA's higher speeds make them suitable for use as a broadband replacement.

Pure packet-switched only systems can be created using 3G network technologies, and UMTS-TDD is one example of this. Alternatively, next generation systems such as WiMAX also provide pure packet switched services with no need to support the circuit switching services required for voice systems. WiMAX is available in multiple configurations, including both NLOS and LOS variants. UMTS-TDD, WiMAX, and proprietary systems such as Canopy are used by Wireless ISPs to provide broadband access without the need for direct cable access to the end user.

Some systems are designed for point-to-point line-of-sight communications, such as RONJA and IrDA; once 2 such nodes get too far apart to directly communicate, they can no longer communicate. Other systems are designed to form a wireless mesh network using one of a variety of list of ad-hoc routing protocols. In a mesh network, when 2 nodes get too far apart to directly communicate, they can still indirectly communicate through intermediate nodes.

The purpose of Wi-Fi is to hide complexity by enabling wireless access to applications and data, media and streams. The main aims of Wi-Fi are the following:

• make access to information easier
• ensure compatibility and co-existence of devices
• eliminate cabling and wiring
• eliminate switches, adapters, plugs, pins and connectors.

The term "Wi-Fi" suggests "Wireless Fidelity", comparing with the long-established audio recording term "High Fidelity" or "Hi-Fi", and "Wireless Fidelity" has often been used in an informal way, even by the Wi-Fi Alliance itself, but officially the term does not mean anything.

Wi-Fi networks have limited range. A typical Wi-Fi home router using 802.11b or 802.11g with a stock antenna might have a range of 32 m (120 ft) indoors and 95 m (300 ft) outdoors. Range also varies with frequency band. Wi-Fi in the 2.4 GHz frequency block has slightly better range than Wi-Fi in the 5 GHz frequency block. Outdoor range with improved (directional) antennas can be several kilometres or more with line-of-sight.

WiMAX, the Worldwide Interoperability for Microwave Access, is a telecommunications technology that provides wireless data in a variety of ways, from point-to-point links to full mobile cellular type access. It is based on the IEEE 802.16 standard, which is also called WirelessMAN.

Within the marketplace, WiMAX's main competition comes from existing widely deployed wireless systems such as UMTS and CDMA2000, as well as a number of Internet oriented systems such as HIPERMAN.

3G cellular phone systems usually benefit from already having entrenched infrastructure, being upgraded from earlier systems. Users can usually fall back to older systems when they move out of range of upgraded equipment, often relatively seamlessly.

The major cellular standards are being evolved to so-called 4G, high bandwidth, low latency, all-IP networks with voice services built on top. With GSM/UMTS, the move to 4G is the 3GPP Long Term Evolution effort. For AMPS/TIA derived standards such as CDMA2000, a replacement called Ultra Mobile Broadband is under development. In both cases, existing air interfaces are being discarded, in favour of OFDMA for the downlink and a variety of OFDM based techniques for the uplink, much akin to WiMAX.

In some areas of the world the wide availability of UMTS and a general desire for standardization has meant spectrum has not been allocated for WiMAX: in July 2005, the EU-wide frequency allocation for WiMAX was blocked.

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Posted by Charley Lim