8/3/2019 Ece401 Lecture 2

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BY: NAVJOT KAUR

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No physical link or wire

Radio Communication

Examples of Wireless Communication

Systems used in everyday life areGarbage door opener, remote controllersfor home entertainment equipment,cordless telephones, walkie-talkie, pagersand cellular telephones.

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Mobile: Any radio terminal that could bemoved during operation and is attachedto a high moving (speed) mobile platform

e.g. a cellular telephone in a fast movingvehicle.

Subscriber: A user who pays subscriptioncharges for using a mobile

communication system.

Roamer: A mobile station which operatesin a service area other than that from

which the service has been subscribed.

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Base Station: A fixed station in a mobileradio system for radio communicationwith mobile stations. They are located at

the center or on the edge of a coveragearea (or region) and consist of radiochannels and transmitter and receiverantennas mounted on a tower

Forward Channel: Radio channel used forthe transmission of information from thebase station to mobile.

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Reverse Channel: Radio channel used forthe transmission of information from themobile to base station.

 Control Channel: Radio channels used forthe transmission of call setup, callrequest, call initiation, and other controlpurposes.

Handoff:  The process of transferring amobile station from one channel or basestation to another.

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Mobile Switching Center (MSC): Switchingcenter which coordinates the routing of calls in a large service area. In a cellular

radio system, the MSC connects the basestations and the mobiles to the PSTN orother network. An MSC is also calledMobile Telephone Switching

Office(MTSO).   Transceiver: A device which is capable of 

simultaneously transmitting andreceiving radio signals.

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It may be classified in three categories: Simplex Systems e.g. pager.

Half Duplex system e.g. Walkie-Talkie, Radio Systems.

Full Duplex system e.g. Telephones

Simplex Systems: Paging systems, in whichmessages are received but notacknowledged, are simplex systems.

Half Duplex Systems: Half duplex radio

systems allow two-way communication, butuse the same radio channel for bothtransmission and reception. But at any time,a user can only transmit or receiveinformation.

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 The fundamentals features of this systemare: Push-to-talk Release-to-listen

Full Duplex Systems: Such systemsallows simultaneous radio transmissionand reception between a subscriber anda base station, by providing twosimultaneous but separate channels(Frequency division duplexing or FDD) oradjacent time slots in a single radiochannel (Time division duplexing or TDD)

for communication to and from the user..

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Frequency Division Duplexing or FDD: FDDprovides simultaneous radio transmissionchannels for the subscriber and the base

station so that they both may constantlytransmit by simultaneously receiving signalfrom one another.

 Time Division Duplexing or TDD: In this type

a single radio channel is shared in such away with respect to time so that a portion of time is used to transmit from the basestation to the mobile and the remaining time

is used to transmit from the mobile to thebase station.