Cellular Telephone Service
Topics Covered
Service Definition
Service Architecture Overview
Cell Sites
Mobile Telephone Switching Office
Transmission Channels
Voice Channels

Cellular Technologies
Advanced Mobile Phone Service (AMPS)
Amps Was The First North American Cellular System.
Operates In The 800-MHz Region (824 To 849 MHz, And
869 To 894 MHz).
AMPS Employs A Channel Bandwidth Of 30 kHz.
Later Versions Of AMPS (AMPS/IS-41) Incorporate
Transparent Roaming Techniques Adapted From GSM
(See The Next Slide).

Cellular Technologies -
Continued
Global System For Mobile Communication (GSM)
A Pan-European System, GSM Is A Second-Generation
Digital, Cellular, Land Mobile Telephone System..
Operates In The 900-MHz Region (890 To 915 MHz, And
935 To 960 MHz).
GSM-900 Employs 200 kHz Channels Separated By 45 MHz.
Each Channel Is Time-Divided To Create Eight Subchannels
(FD/TDMA).

Cellular Technologies -
Continued
Global System For Mobile Communication (GSM)
GSM-1800 And GSM-1900 Employ The Same Technology
And Operate In The PCS Bands (Personal
Communications Service Around 1.8 GHz In Europe And 1.9
GHz In North America).
GSM Pioneered Automatic Roaming Techniques, Mobile-
Assisted Handover, Subscriber Authentication, And User
Privacy.

Cellular Technologies -
Continued
Digital AMPS (D-AMPS And NA-TDMA)
D-AMPS, Defined By Telecommunications Industries
Association Interim Standard 54.
D-AMPS Employs AMPS Frequencies.
It Provides Three Digital Channels (TDMA) In A 30-kHz
Channel, And Employs A Combination Of Analog And
Digital Control Channels.
Dual-Mode Terminals Operate With AMPS Or D-AMPS To
Facilitate The Evolution Of AMPS To A Higher-Capacity
Digital System.

Cellular Technologies -
Continued
Digital AMPS (D-AMPS And NA-TDMA)
NA-TDMA Is Defined By Telecommunications Industries
Association Interim Standard 136.
NA-TDMA Operates In Two Frequency Bands.
At AMPS Frequencies, It Provides Six Digital Channels In A
30-kHz Channel, And Employs A Combination Of Analog
And Digital Control Channels.
Dual-Mode Terminals Operate In Analog Or Digital Modes.
At PCS Frequencies (Around 1.9 GHz), NA-TDMA Provides
Six Digital Channels In A 30-kHz Channel, And Uses Digital
Control Channels Exclusively.

Cellular Technologies -
Continued
Digital AMPS (D-AMPS And NA-TDMA)
In The Digital Mode, Automatic Roaming, Mobile-Assisted
Handoff, Terminal Authentication, And User Privacy Are
Provided.
DQPSK (Differential Quaternary Phase-Shift Keying) Is
Employed.

Cellular Communications
Cellular Telephony Provides
Communications Services To Hand-
Held Portable Phones And
Interconnects With The Public
Telephone Network By Using Radio
Transmissions That Are Based On A
System Of Cells And Antennas.

Cellular
A Wireless Design Method Where Multiple
Transmitters Are Strategically Placed
Throughout A Geographical Area To Provide
Two Functions.
To Radiate The Area With An Adequate
Signal.
To Make The Size Of The Radiated Area
Adequate To Accommodate The Number
Of Users.

Cell Layout – Antenna Location
- Cell Site Antenna
- “Fade” Area
Cell
Cell
Cell
Cell
Cellular Telephony Is Provided By A Series Of Directional
Antennae Providing Area Coverage In The Form Of
Hexagonal Cells.

Cell Coverage
Closely-Spaced Hexagons Provide More
Efficient Area Coverage Than Would
Closely-Spaced Circles.
Directional Antennae Are Used To
Radiated The Coverage Area.

Antenna
Cellular Components
Hut/
”Doghouse”
MTSO
AC
SMS
HLR
VLR
MTSO
Class 5 Switch
The Transmit And Receive Center For The
Geographical Area Called A Cell.
AC
SMS
HLR
VLR

Sample Cellular Antennae

Cellular Components
Each Cell Site Contains:
Transmitter
2 Receivers Per Cell
Cell Site Controller
An Antenna
Voice/Data Land Links To The MTSO
Loops From MTSO To Class 5 CO

Cell Site
Antenna
Hut/
”Doghouse”
The Transmit And Receive Center For The
Geographical Area Called A Cell.
The Cell Shape Is Roughly Hexagonal.

Cell Site
The Cell Consists Of An Antenna, A Hut And A
“Doghouse”.
“Doghouse” Contains The Transmitting And
Receiving Electronics.

A Sectored Cell
Each Cell Consists Of As Many As 128 Channels Per
Cell.
“Doghouse” Contains The Transmitting And
Receiving Electronics.
Two To Six Sectors.
A Maximum Of 128 Channels Per Cell & 70
Channels Per Cell On Average.

A Sectored Cell
A Minimum Of One Control Channel Is Provided,
Dedicated Control Channel (DCCH), To Control The
Mobiles.

Cell Sites
Cell Boundaries Are Neither Uniform Nor
Constant.
Usage Density
Landscape

Cellular Service Architecture
Dedicated Control Channel (DCCH)
Voice Channel
MTSO
AC
SMS
HLR
VLR
Class 5 Switch

Cellular Telephone Handset
Provides The Interface Between The User And The Cellular
System.
Dial-First - Each Cellular System Can Support Only
A Limited Number Of Talk Paths At A Time.
Dial Tone Received After The SEND Button Is Pressed.

Cellular Telephone Handset
Identification Codes
Each Mobile Is Assigned Four Permanent
Identification Codes.

Cellular Telephone Handset
Identification Codes
Mobile Identification Number (MIN) – A 10-Digit
Directory Number Assigned To Each Mobile
Subscriber. It Is Stored As A 34-Bit Code That Consists Of:
- Area Code – Three Digits That Identify The
Mobile Telephone’s Home Service Area.
- Exchange Code – Three Digits That Identifies The
Mobile Telephone Service Office (MTSO) Of The
Home Service Provider Within The Given Area
Code.
- Subscriber Number – Four Digits That Identify
The Mobile Scriber.

Cellular Telephone Handset
Identification Codes
Electronic Serial Number (ESN) – A 32-Bit Code
Assigned To The Mobile Station Equipment By The
Manufacturer.
ESN Is A Unique Identification Number Embedded In A
Wireless Phone By The Manufacturer.
Each Time A Call Is Placed, The ESN Is
Automatically Transmitted To The Base
Station So The Wireless Carrier's
Mobile Switching Office Can Check
The Call's Validity.

Cellular Telephone Handset
Identification Codes
Station Class Mark (SCM) – A 4-Bit Code That
Describes The Capabilities Of The Mobile Station,
Including.
Bit 1 Tells The Cell Tower Whether Your Cell
Phone Uses The Older 666 Channel Cellular
System Or The Newer 832 Channel Cellular
System.
Bit 2 Tells The System Whether Your Cellular
Telephone Is A Mobile Unit Or A Voice
Activated Cellular Telephone.

Cellular Telephone Handset
Identification Codes
Station Class Mark (SCM) – Continued.
Bits 3 And 4 Tell The Cell Tower What Power
Your Cellular Phone Should be Using.

Cellular Telephone Handset
Identification Codes
System Identifier (SID) – A 15-Bit Code Assigned By
By The FCC That Identifies Cellular Geographic
Service Area In Which The Service Provider Is
Licensed .
It Is Used To Determine If A Mobile System Is
Operating In Its Home Area.
If The SID Stored In The Mobile Telephone And The
Serving Cell Do Not Match, The Mobile Is Roaming.

Cellular Telephone Handset
Logic/Control
Numeric Assignment Module (NAM) – Used For
Programmable Assignment Of Unit’s Telephone
Number.
Electronic Serial Number (ESN) – Unique Fixed
Number For Each Unit.
Carrier Records Both Numbers In The HLR At
The Time Service Is Setup.

Cellular Service Architecture
Class 5 Switch MTSO
HLR
VLR
MTSOs Track Mobiles
That Are (1)
Operating In Their
Home Area, And (2)
Roamers.

Cellular Telephone
Communications Channels
Two Types Of Channels Are Provided –
Setup/Data Channels – Transmits Data Used To Set
Up All Calls.
Voice Channels – Provides Message Paths And
Carries Signals Needed For Call Supervision – i.e.,
To Signal Changes In State And To Maintain The
Connection..

Cellular Telephone
Communications Channels
- Continued -
The Supervisory Signals Are:
Supervisory Audio Tone (SAT) – An Out-Of
-Band, Continuous Tone (5,700, 6,000 Or
6,300 Hz), The SAT Is Present Whenever
A Call Is In Progress.
Absence Of The SAT Tone Indicates That One Of
The Parties Has Gone On-Hook.
Nearby Cells Are Assigned Different SATs To
Assist In Distinguishing Between Signals.

Cellular Telephone
Communications Channels
- Continued -
The Supervisory Signals Are:
Signaling Tone (ST) – An Out-Of-Band Tone
Burst (10 kHz).
Among Other Things, The Signaling Tone Is
Used To Initiate Ringing, To Signal Hand Off
To Another Cell Site, And To Disconnect.

Cellular Handset Registration
MTSO
AC
SMS
HLR
VLR
Over-The-Air Registration Carried Out Each Time
The Mobile Unit Is Turned On.
Registration Required Before Call Can Be Made.

Cellular Handset Registration
MTSO
AC
SMS
HLR
VLR
Over-The-Air Registration Uses The Data Control
Channel – Not The Voice Channel.
Mobile Unit Passes Its Telephone Number Stored
In Its NAM And Its ESN To The MTSO.
MTSO Uses The DBs To Verify Mobile’s Authenticity.

Cellular Handset Registration
The Base Station & Mobile Unit Uses The Control
Channel To Support Incoming And Outgoing Calls.
Used To Monitor Signal Quality.
Used To Register.
Used Only When The Station Is “Off-The-Hook”.
For Incoming Calls, The System Uses The
Control Channel To Alert The Station Of A Call.

Cellular Location Registers
MTSO
HLR
VLR
Home Location Register – Contains Customer-Based
Information (NAM, ESN, Etc.) For Customers
Whose Telephone Numbers Belong To The Carrier
And That Are Located Within The Area Code.
Visitor Location Register Contains Customer-Based
Information (NAM, ESN, Etc.) For Roaming Customers .
Registration Supported By Both HLR & VLR.

Registration Non-Roaming
DCCH
MTSO
HLR
MTSO Verifies Handset Authenticity Using HLR.
Once Registration Is Complete, Service Is Allowed.

Home Location Register
HLR
Home Location Register (HLR) Is The Main
Database Of Permanent Subscriber Information For
A Mobile Network.
HLR Contains Pertinent User Information, Including
Telephone Number, ESN, Address, Account Status,
And Preferences.

Registration Roaming – Case 1
DCCH
MTSO
VLR
A Customer Record Exists At The VLR.
Unit Is Registered Using VLR-Located Customer
Record.

Registration Roaming – Case 2
DCCH
MTSO
VLR
Class 5 Switch
No Customer Record Exists At The VLR.
MTSO Communicates With Home-System And
Registers The Unit In The VLR.

VLR
Visitor Location Register
If The User Is Out Of The Home Area, The Area
VLR Sends Out A Request For Information
Required To Process The Call.
User Information Passed From The Home HLR
Includes Telephone Number, ESN, Address, Account
Status, And Some Preferences.

Cellular Signal Strength
Cell Site 1
Freq. Group 1
Cell Site 2
Freq. Group 2
Cell Site 4
Freq. Group 4
Cell Site 3
Freq. Group 3
Cell Site 5
Freq. Group 5
MTSO
A Mobile Unit’s Signal May Be Received By More
Than One Cell Site At A Time.

Cellular Signal Strength
MTSO
Signal May Be Received By More Than One Cell
Site At A Time.
MTSO Compares Signal Strengths And Specifies
Which Cell Site To Use.

Cellular Handoff
MTSO
As Mobile Unit Moves Around Coverage Area,
The MTSO Changes The Antenna Used.
The MTSO Uses The SAT Signal Strength To
To Determine Whether, And How To Switch
The Call To Another Antenna.
Handoff Requires About 0.2 Seconds.

Roaming
The Ability For Cellular Phone Users To Make
Or Receive Calls On Other Service Providers‘
Networks When Outside The Coverage Area Of
Their Own Cellular Network Service Provider
Visitor Location Register.

Short Message Service
Short Message Service (SMS) Applications
Include Two-Way Point-To-Point Messaging.
SMS Is Also Used For Paging.
Supports Alphanumeric Messages.

Authentication Center
Because Radio Signals Can Be Accessed By
Virtually Anyone.
Authentication Involves Two Functional
Entities.
SIM
The Authentication Center
The SIM And AC Contain A Secret Key And
They Pass Randon Numbers Between Them.

Some Cellular Standards
EIA/TIA 95B – Digital Over-The Air Standard.
EIA/TIA 136 (Supports DCCH).