Examples of Current wireless System
Wireless and mobile networks are being used in diverse areas such as travel, education, stock trading, military, package delivery, disaster recovery, and medical emergency care. There are many wireless systems which makes our life easy to communicate in all around the world.
Paging systems are unidirectional wireless communications systems.
They are characterized by the following properties
- The user can only receive information, but cannot transmit. Consequently, a “call” (message) can only be initiated by the call center, not by the user.
- The information is intended for, and received by, only a single user.
- The amount of transmitted information is very small amount of transmitted information is very small.
Cellular Telephone system:
- Cellular telephony is the economically most important form of wireless communications. It is characterized by the property:
- The information flow is bidirectional.
- A user can transmit and receive information at the same time.
- Cordless telephony describes a wireless link between a handset and a BS that is directly connected to the public telephone syste
- The main difference from a cellphone is that the cordless telephone is associated with, and can communicate with, only a single BS (see Figure 1.4).
- There is thus no mobile switching center; rather, the BS is directly connected to the PSTN.
This has several important consequences
- The BS does not need to have any network functionality. When a call is coming in from the PSTN, there is no need to find out the location of the MS.
- Similarly, there is no need to provide for handover between different BSs.
- There is no central system. A user typically has one BS for his/her apartment or business under control, but no influence on any other BSs.
- The fact that the cordless phone is under the control of the user also implies a different pricing structure: there are no network operators that can charge fees for connections from the MS to the BS; rather, the only occurring fees are the fees from the BS into the PSTN.
- Cordless systems have also evolved into wireless Private Automatic Branch exchanges (PABXs) (see Figure 1.5).
- In its most simple form, a PABX has a single BS that can serve several handsets simultaneously – either connecting them to the PSTN or establishing a connection between them.
- In its more advanced form, the PABX contains several BSs that are connected to a central control station. Such a system has essentially the same functionality as a cellular system; it is only the size of the coverage area that distinguishes such a full functionality wireless PABX from a cellular network.