5stemsinc

  A cellular network is made up of some cells. The cell covers a geographical area whose base station conforms to 802.11 AP which helps mobile users to connect to the network. There is an air interface of the physical and link layer protocols between the mobile and the base station. All these base stations are connected to the mobile switching centre which connects the cells to the wide area net, manages call setup, and handles mobility. There is a radio spectrum that is allocated to base stations and a particular area and which now needs to be shared. There are 2 techniques for sharing mobile-to-base station radio spectrum. 1. Combined FDMA/TDMA It divides the spectrum into frequency channels and divides each channel into time slots. 2. Code Division Multiple Access This allows the re-use of the same spectrum on all cells. Two frequency bands are used to improve net efficiency, one forward channel for the cell site to the subscriber and one reverse channel for the cell sit