CELLULAR RADIO

Identifying the cellular radio system Describes the principles and characteristics of cellular radio Draw a block of unit moblile communication' Explain the functions of each block of the mobile communicationsDifferentiate control channels and voice channels Identifying the types and characteristics of the antenna

OBJECTIVE :

INTRODUCTION

Cellular Radio Communications System is     a two-way form of communication.

using radio waves

cellular phone can be connected to the telephone system,where it is connected to the world.

Bell Telephone Company, the AT & T has

     create a cellular radio system at the end of the 70s and

fully implemented in early 1980.

Known as ‘Advanced Mobile Phone Service’(AMPS).

CELLULAR RADIO PRINCIPLES

Each cell consists of a receiver and transmitter with low power called 'Radio Base Station' (RBS) .     enable it to provide services  to the user in the coverage of several square kilometers.

Sel

MTSO

There are transmitter and receiver where it divides its services to smaller areas called “CELL”

The smaller the radius of a cell, the higher the available bandwidth. So, in highly populated urban areas, there are cells with a radius of a few hundred metres, while huge cells of up to thirty kilometres provide coverage in rural areas.

Each cell is connected by telephone lines or microwave to the Main Control Center, known as ‘Mobile Telephone Switching Office’(MTSO).

CHARACTERISTICS OF CELLULAR RADIO COMMUNICATION SYSTEM When user moves out of one cell to another

cell, they automatic switching system  to the another  RBS.

Recipients in each cell will monitor the signal strength of

the mobile unit. When signal strength falls to a level below the prescribed level, or reference, then it will automatically be switched to a higher level through the nearest RBS.

BASIC COMPONENT OF RADIO CELLULAR COMMUNICATION SYSTEM

I. Unit Mobile : Is a consumer devices that used      to make and receive calls.

II. Radio Base Station (RBS):

Is an outside station-guard cells Controller that received instructions from the MTSO.

 using the radio channel that      found in every cell including the       voice channels and control channels

Supervise the call which includes monitoring     on speech quality and measurement     on the strength of the voice signal.

Send and receive voice signals and      data from/to consumers.

as an interface between users and systems.

III. Mobile Telephone Switching Office (MTSO):

A mobile switching center, as the heart of the system

Perform the switching operation   between cellular networks and public telephone network.

Receive and process data received from the RBS include

 the status of mobile units, diagnostic data, information for billing, data text and so on.

implementing supervisory that determine and updating

the locations of mobile units when there

is movement from one  cell to cell.

Implementing the flow to determine the appropriate cells and the necessary radio channels

 when a call is to be made.

CELLULAR PHONE UNIT

Transmiter

Frequency Synthesizer

Receiver

Logic Unit

Control Unit Cellular Phone CELLULAR PHONE BLOCK DIAGRAM

TRANSMITTER.Low-

power FM transmitters, frequency range 825MHz to 845 MHz.Has

a transmission channel 666 at a distance of 30 kHz each other.

Power  emissions:Mobile radio = 3 WMobile phone = 500 mW

FREQUENCY SYNTHESIZER.

To generate the signals for the use of transmitter and

receiverUsing

a PLL circuit (Phase Locked Loop), where the hablor oscillator provide the frequency needed.

RECEIVER.It is dual-

conversion superhetrodin.

Frequency Range= 870.03 MHz to 870.98 MHz.

there are 666 channel

receiver at 30 kHz frequency

range of each other.

For each channel, the frequency of transmission and receiving distinguished at a distance of 45 MHz. For example; at a frequency transmission channel is 825.03MHz while the frequency of acceptance for Channel 1 is 870.03 MHz, then the difference between them is 45 MHz.

LOGIC UNIT.Consist of main control

circuit for cellular unitThis part is using a

microprosessor (RAM &ROM.)

Contains an additional circuit which is used to interpret signals from

the MTSO or cells, and to generate control signals for

the transmitter and receiver.  

CONTROL UNIT .

Consist of speaker, microphone and keypad(touch-tone).

Microprocessor used to control the LCD display and indicators in

unit mobile.microprocessor memory is

 capable of storing the frequently called numbers and

the automatic dialing system.

3.3 RADIO CHANNEL

•Control Channel

•Voice Channel

Radio Channelis a two way radio transmission path between the RBS(Radio Base Station) and mobile units

Each channel uses different frequencies for transmissionfrom the RBSanother transmission from mobile unit to RBSUse different frequencies to

avoid interference or overlapping signal  between transmitter and receiverFrequency @ the same channel can be used by other cells that are far away from each other

Control ChannelEach cell has one (1) control channel that is used only for transmission of data (not voice)Control channel continuously control the flow of data when the mobile unit is ONWhen the user moves from one cell to another cell, the terminals will be adjusted to a new control channel automatically within the operating system.Control channel with the best reception quality will be selected and set of mobile terminals will then be adjusted to this channel until the quality of reception decreases.

Voice ChannelChannel which

brought conversation signal and used during conv

ersation took place

Each cell usually has between 7 to 23 voice channels

Besides bringing the conversation signals, this channel also route to:

*Tone generator SAT (Supervisory Audio Tone)* Data Message*Signaling tone detection *Ringing order delivery

At Radio Base Station (RBS), there are TWO(2) types of antenna used:- Omnidirectional DirectionalAntenna is used as a medium

of communication between the receiver

and transmitter signal.

Antenna

Antenna has a stability of sending and receiving signals.Used in less populated areas/rural areasThe coverage area round in shape and every coverage area circle end would overlap between one anotherUsing only one element.

Omnidirectional Antenna

Coverage area for omnidirectional antenna

Antenna that have a directional nature, where transmission is in a certain direction.Requires three antennas arranged so that each antenna near a corner of 120 coverageUsed in large areas such as urban, town

Directional Antenna

Directional Antena

Omnidirectional DirectionalCoverage area = Circle-shaped area  and overlap each other

Coverage area = Balanced coverage area and are arranged in a hexagonal and non-overlapping

 antenna beam = 360 each RBS

 antenna beam = 120 each RBS

RBS = located at the middle of cell.

RBS = located at the edge of cell

Used = in rural areas/low population area

Used = in urban/town areas or high population area

COMPARISON

QUIZ 21) What is the basic component of radio

cellular communcation system?2) Cellular radio principles is

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3) Differentiate directional and omnidirectional antenna.

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