One of the first Radio Service and has been used widely across the globe for decades prior to the invention of cellular telephony. Following are the properties which differs wireless broadcasts from cellular telephony;
- The transmission is uni-directional, sent from the station towards users.
- The transmission information is same for all users
- The information is transmitted continuously
- In many cases, many transmitters transmit the same information at one time.
Examples are pay-TV or Pay-per-view services.
Similar like Broadcast service, the paging works unidirectional as well but unlike Radio broadcast there are some limitations. Following are the points regarding paging;
- The user can only receive the message and cannot reply to this message.
- The message is mostly initiated by call center, intended to and received by only single user.
- The amount of transmitted information is very small mostly in bits.
Examples are notifications from call centers to subscribers about receiving a text message or an image file or an audio file from any link or call number.
This is the most widely used wireless service so far and has been used for past decade with a persistent increase in subscription rate. Following are the properties of this service
- The transmission of information is bi-directional
- The user can initiate a session by calling or receiving a call from other user.
- The information transmitted is only between the users who are in active session.
Examples are mobile services
Trunking Radio System
An independent radio system which is not connected to the PSTN or any other public network mostly intended for designated purposes and designated individuals only. This kind of network is limited to the circle of its transmission. Most widely used by Government departments like Fire Brigade, Police, Emergency and Rescue etc. Following are the properties of this system;
- Group Calls – Conference Calls
- Call Priorities – Set priorities to calls like low, medium and high so the switch can drop low priority call against a high priority in case of emergency
- Relay Networks – The range can be extended by relaying the call to other BS and MS
The handset is directly connected to BS (Base set) with a wireless link which is further connected to PSTN. Following are the properties of this telephony
- The Base set doesn’t need to have any network functionality
- There is no central system, as the call doesn’t need to find the location of the user.
- There is no fees for the wireless link with the Base Set
Cordless systems have now evolved into wireless private branch exchanges wPABX.
Also known as Wi-Fi networks allow up to 11Mbits/s data rate and 802.11a standard extended this data rate up to 55Mbit/s
Personal Area Networks (PAN)
PANs are created for very smaller distances mostly less than a meter using blue tooth or body sensors.
Fixed Wireless Access (FWA)
Derived from Cordless or WLANs . Following are the properties of FWA
- There is no mobility of user device
- The BS must always serves multiple users over longer distances
Created over smaller distances without the use of any infrastructure with similar devices mostly laptops or mobiles. The advantage is that it is handy in emergency and is very fast to create. The disadvantage however, is the decreased performance.
Requirements for the Services
- Data Rate
- Range and number of users
- Energy Consumption
- Use of Spectrum
- Direction of transmission
- Service quality