Introduction to Wireless Networks
To fulfill the demand of personal communication new networking techniques accommodated by mobile and data users around the world
Cellular telephone system:
- The cellular telephone system is responsible for providing coverage throughout a particular territory, called a coverage region or market.The interconnection of many such systems defines a wireless network.
- It is capable of providing service to mobile users throughout a country or continent
- To provide wireless communications within a particular geographic region (a city, for example), an integrated network of base stations must be deployed to provide sufficient radio coverage to all mobile users.as shown in figure8.1
- The base stationsmust be connected to a central hub called the mobile switching center (MSC).
- The MSC provides connectivity between the public switched telephone network (PSTN) and the numerous base stations, and ultimately between all of the wireless subscribers in a system.
- The PSTN forms the global telecommunications grid which connects conventional (landline) telephone switching centers (called central offices) with MSCs throughout the world
- Tb connect mobile subscribers to the base stations, radio links are established using a carefully defined communication protocol called common air interface (CAl) which in essence is a precisely defined handshake communication protocol
- The common air interface specifies exactly how mobile subscribers and base stations communicate over radio frequencies and also defines the control channel signaling methods
- At the base station, the air interface portion (i.e., signaling and synchronization data) of the mobile transmission is discarded, and the remaining voice traffic is passed along to the MSC on fixed networks
- Each base station may handle on the order of 50 simultaneous calls, a typical MSC is responsible for connecting as many as 100 base stations to the PSTN (as many as 5,000 calls at one time), so the connection between the MSC and the PSTN requires substantial capacity at any instant of time