CELLULAR RADIO

OBJECTIVE : 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 communications Differentiate control channels and voice channels  Identifying the types and characteristics of the antenna

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 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 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.

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

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.

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. implementing supervisory that determine and updating the locations of mobile units when there is movement from one   cell to cell. 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 the flow to determine the appropriate cells and the necessary radio channels  when a call is to be made.

CELLULAR PHONE UNIT

cellular phone block diagram 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 W Mobile phone = 500 mW

Frequency synthesizer. To generate the signals for the use of transmitter and receiver Using a PLL circuit (Phase Locked Loop), where the hablor oscillator provide the frequency needed.

receiver. It is dual-conversion superhetrodin. 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. there are 666 channel receiver at 30 kHz frequency range of each other. Frequency Range= 870.03 MHz to 870.98 MHz.

Logic unit. Consist of main control circuit for cellular unit This 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.  

Consist of speaker, microphone and keypad(touch-tone). 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 Channel is a two way radio transmission path between the RBS(Radio Base Station) and mobile units Each channel uses different frequencies for transmission from the RBS another transmission from mobile unit to RBS Use different frequencies to avoid interference or overlapping signal  between transmitter and receiver Frequency @ the same channel can be used by other cells that are far away from each other

Control Channel Each 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 ON When 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.

Each cell usually has between 7 to 23 voice channels Channel which brought conversation signal and used during conversation 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

Antenna At Radio Base Station (RBS), there are TWO(2) types of antenna used:- Omnidirectional Directional Antenna is used as a medium of communication between the receiver and transmitter signal.

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

Coverage area for omnidirectional antenna

Directional 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 coverage Used in large areas such as urban, town

Directional Antena

COMPARISON Omnidirectional Directional Coverage 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

QUIZ 2 What is the basic component of radio cellular communcation system? Cellular radio principles is __________________________________________ __________________________________________ Differentiate directional and omnidirectional antenna.

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