Radio frequency is a term that refers to alternating current (AC) having characteristics such that, if the current is input to an antenna, an electromagnetic (EM) field is generated suitable for wireless broadcasting and/or communications. These frequencies cover a significant portion of the electromagnetic radiation spectrum, extending from nine kilohertz (9 kHz),the lowest allocated wireless communications frequency (it's within the range of human hearing), to thousands of gigahertz(GHz).
When an RF current is supplied to an antenna, it gives rise to an electromagnetic field that propagates through space. This field is sometimes called an RF field; in less technical jargon it is a "radio wave." Any RF field has a wavelength that is inversely proportional to the frequency. In the atmosphere or in outer space, if f is the frequency in megahertz and sis the wavelength in meters, then
The frequency of an RF signal is inversely proportional to the wavelength of the EM field to which it corresponds. At 9 kHz, the free-space wavelength is approximately 33 kilometers (km) or 21 miles (mi). At the highest radio frequencies, the EM wavelengths measure approximately one millimeter (1 mm). As the frequency is increased beyond that of the RF spectrum, EM energy takes the form of infrared (IR), visible, ultraviolet (UV), X rays, and gamma rays.
Many types of wireless devices make use of RF fields. ...
Many types of wireless devices make use of RF fields. Cordless and cellular telephone, radio and television broadcast stations, satellite communications systems, and two-way radio services all operate in the RF spectrum. Some wireless devices operate at IR or visible-light frequencies, whose electromagnetic wavelengths are shorter than those of RF fields. Examples include most television-set remote-control boxes, some cordless computer keyboards and mice, and a few wireless hi-fi stereo headsets. (SearchNetworking.com)
2. Wireless Architecture
WAP Architecture is divided into several layers. This is often called the 'WAP Stack'. (Bharadwaj) The technical description of each layer of the wireless architecture is explained below.
Wireless Application Environment (WAE)
The goal of WAE is to establish an environment that allows users to build applications that can be used over a wide variety of wireless systems that can be implemented efficiently.
In the WAP model, WAE would be the application environments that sends and receives requests from the Clients to the Gateway to the Origin Server.
Wireless Session Protocol (WSP)
The Wireless Session Protocol is the layer that deals with communication between client and proxy or server. The WSP provides dialog between client and server.
Wireless Transaction Protocol (WTP)
The Wireless Transaction Protocol, in a simple definition, deals with the transaction of data. WTP handles