An emerging technology is one that offers a relatively undiscovered method to solve a daunting wireless problem in a cost-effective way. The methods or technology itself may be non-conventional, but emerging technologies that become mainstream are typically more evolutionary than revolutionary.
This is because a technology cannot succeed by itself – it must bring the whole sector with it. This paper presents an overview survey of emerging wireless technologies – 802.11(wi-fi), 802.15.4 (Zigbee)and 802.16 (wi-max).

WI-FI:
Wi-Fi is a popular technology that allows an electronic device to exchange data wirelessly using radio waves over a computer network including high speed internet connections. A device that can use Wi-Fi can connect to a network resource such as the Internet via a wireless networl access point Such an access point has a range of about 20 meters (65 feet) indoors and a greater range outdoors.

Wi-Fi works with no physical wired connection between sender and receiver by using radio frequency (RF) technology, a frequency within the electromagnetic spectrum associated with radio wave propagation. When an RF current is supplied to an antenna, an electromagnetic field is created that then is able to propagate through space. The cornerstone of any wireless network is an access point (AP). The primary job of an access point is to broadcast a wireless signal that computers can detect and "tune" into. In order to connect to an access point and join a wireless network, computers and devices must be equipped with wireless network adapters
Wi-Fi allows cheaper deployment of local area networks (LANs). Also spaces where cables cannot be run, such as outdoor areas and historical buildings, can host wireless LANs Manufacturers are building wireless network adapters into most laptops. The price of chipsets for Wi-Fi continues to drop, making it an economical networking option included in even more devices

WIMAX:
802.16, better known as WiMAX. The IEEE approved the 802.16 standards in June2004 .This technology supports speeds as high as 70Mbps and a range of up to 48 kilometers. WiMAX can be used forwireless networking like the popular WiFi. WiMAX allows higher data rates over longer distances, efficient use of bandwidth, and avoids interference almost to a minimum.WiMAX can be termed partially a successor to the Wi-Fiprotocol. Current technologists envision a WiMAX receiver in a person’s home, with a WiFi transmitter to serve in-home connections, and longer term having laptops and personal devices capable of transmitting directly to WiMAX towers
WiMAX uses microwave radio technology to connect computers to the Internet. WiMAX works very much like cell phone technology in that reasonable proximity to a base station is required to establish a data link to the Internet. Users within 3 to 5 miles of the base station will be able to establish a link using non line- of-sight (NLOS) technology with data rates as high as 75Mbps. Users up to 30 miles away from the base station with an antenna mounted for line-of-sight (LOS) to the base station will be able to connect at data rates approaching 280Mbps .
Technical aspects of 802.16a that are instrumental in powering robust performance include following characteristics: • Power: Varies with band. Profiles from 100 Mw up to 2W
• Spectrum: Initially 3.5 GHz licensed and 5.8 GHz unlicensed bands
• Actual realizable data rates are ~ 2b/Hz
• Maximum range ~2Km for indoor Non-LOS cellular service at 3.5 GHz
ZIGBEE:

ZigBee is one of the newest technologies enabling Wireless Personal Area Networks (WPAN). ZigBee is the name of a specification for a suite of high level communication protocols using small, low-power digital radios based on the IEEE 802.15.4 standard. ZigBee protocols are intended for use in embedded applications requiring low data rates and low power consumption. Though WPAN implies a reach of only a few meters, 30 feet in the case of ZigBee, the network will have several layers, so designed as to enable intrapersonal communication within the network, connection to a network of higher level and ultimately an uplink to the Web. Applications include wireless light switches, electrical meters with in-home-displays, traffic management systems, and other consumer and industrial equipment that requires short-range wireless transfer of data at relatively low rates. The technology defined by the ZigBee specification is intended to be simpler and less expensive than other WPAN’S, such as Bluetooth. Zigbee has disadvantage such as,replacement with Zigbee compliant appliances can be costly and it covers small distance