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Cellular and PCS Technical Issues
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Overview• Cell Layout• Signaling• Mobile Handset Operation
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System Block Diagram
Mobile BTS BSC MTSO PSTN
Data Bases
forward
reverse
BTS Base Tranceiver StationBSC Base Station ControllerMTSOMobile Telephone Switching Office
Radio Link Voice TrunkData Trunk
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Frequency Reuse Pattern
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First Generation Standards• AMPS - United States• TACS - UK• NTT - Japan• NMT - Scandanavia• MATS-E - France• C-450 - Germany• GSM - global
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North American AMPS system
• 50MHz spectrum• 30kHz per channel per direction• 832 total full-duplex channels• 4, 7, and 12 cell clusters used
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AMPS Specifics• 832 channels (2 frequencies per
channel)– Forward: 869-894 MHz– Reverse: 824-849MHz– Forward/Reverse Spacing: 45MHz– Adjacent Channel Spacing: 30kHz– 21 Control Channels per group
• Cell Sizes: 2-20km
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Mobile-Originated CallMobile BTS BSC MTSO PSTN
RCC MIN, ESN, dialed novalidation
FCC Ch No, SAT code, Power
FVC SAT
RVC SATFVCRVC
Conversation
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Call Handoff• Base Stations monitor the signal
strength• If strength drops below hand-off level,
all base stations are asked to look for the mobile; strongest becomes new BS
• MTSO instructs the new base station to activate a voice channel to receive the handoff; BS starts transmitting the Supervisory Audio Tone.
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Call Handoff cont…• Current base station at MTSO
command sends signal to mobile giving the new channel assignment.
• Mobile send a signaling tone burst, and tunes to the new channel.
• Previous base station clears the call path.
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Mobile Handset• ESN - Electronic Serial Number• Programmable NAM (Number
Assignment Module)• Contains among other things
– System ID– First control channel to scan– A/B system selection– MIN (Mobile Identification Number)
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Mobile Identification Number
• MIN1 - Mobile System Id (3 digits)– US: Area Code– International: Mobil Carrier
Identifcation• MIN2 - Station Number
– US: NXX and line number– International: international mobile
number
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Hand-Off
MTSO
BSBS
MSMS
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Roaming
Mobile
MTSO
MobileMobile
Mobile
Mobile
MTSO
MobileMobile
Mobile
Mobile
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Intersystem Hand-Off
MTSO
BSBS
MSMS
MTSO
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The “Shoe-Lace” Effect
BSBS
BSBS
BSBS
BSBS
MS
MS
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Multi-System Tandem
MTSO
BS BS
MS MS
MTSOMTSO MTSO MTSO
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Automatic Roaming
MTSO
BS
MS
MTSO
HLR
HLR VLR
Request
Response
Billing InformationService Profile
Current LocationTemporary Directory Number
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The “Trombone” Effect
MTSO
BS
MS
MTSO
Fixed Station
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Second Generation SystemsCOMT 220
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Classes of Standards• Analog Cellular
– FDMA - Frequency Division Multiple Access
• Digital Cellular– FDMA– TDMA - Time Division Multiple Access– CDMA - Code Division Multiple Access
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Access MethodsFr
eque
ncy
TimeFr
eque
ncy
TimeFr
eque
ncy
Time
FDMA
TDMA
CDMA
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Systems and Frequencies• Advanced mobile phone service (AMPS)
– 824 to 849 MHz and 869 to 894 • Digital-advanced mobile phone service
(D-AMPS)– 824 to 849 MHz and 869 to 894
• Global system for mobile communications (GSM)– 450 MHz, 890 to 960 MHz, 1.8 GHz, 1.9
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Systems cont.• Personal communications service
(PCS)– 1.9 GHz
• Nextel and other specialized mobile radio (SMR)– 816 MHz to 866 MHz
• Cellular digital packet data (CDPD)– 824 to 894 MHz, 1.8 GHz to 1.9 GHz
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3rd Generation Wireless ServiceCOMT 220
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“3G” Definition• From the FCC Web Site:
– 144 kbps (vehicular traffic) to 2 Mbps for indoor traffic
– Common billing and user profile services– Bandwidth on demand– Fixed and variable bit rates– Multimedia store-and-forward messaging
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Background• ITU Specifications
– FPLMTS (future public land mobile telecommunication systems)
– IMT-2000
• Frequency bands identified at the 1992 and 200 World Radio Conferences
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Technical Specs• Wideband CDMA (5MHz channel)• CDMA2000 (1.25-15MHz channels)
– Based on TIA/EIA 95 B• CMDA Time Division Duplex• TDMA Single Carrier• DECT (TDMA/FDMA)
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Frequencies• ITU Recommendations:
– 1885-2025 MHz– 2110-2200 MHz– 806-960 MHz– 1710-1885 MHz (1755-1850 studied
by NTIA)– 2500-2690 MHz (Studied by FCC)
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