Before delving into mobile phone systems, it may serve us well to recount some of the features of a fixed-line telephone. It is a device whose position is defined by the telephone jack in the wall (or some other permanent arrangement) that terminates a pair of wires from the serving central office. Some major points are:
- Ownership is established by the location; all charges to the telephone are billed to the owner of record who is responsible for their settlement. The fixed connection allows emergency services (such as E911) to provide an address and other details of the location.
- Voice service may be powered directly from the serving office; additional features are powered from the house/office power line. The telephone’s identity is established by a series of numbers specified in a national numbering plan that relate to the equipment itself and the serving office.
- The local connection to/from the telephone from/to the serving office is likely to be analog and duplex over a single pair of twisted copper wires equipped with hybrid transformers. Connections to other phones are made by switches at the central office and perhaps at higher level toll offices if the call is intended for another region.
- Once a connection is established, quality of service (QoS) will not be an issue, nor will traffic-dependent, time-varying congestion. The connecting arrangement will be maintained until the caller and/or the called party hang(s) up.
In contrast, a mobile phone is assigned ...