COMT 3911 Cellular/PCS, Wireless Data Technical Issues COMT 391 Wireless

COMT 3912 Overview Cell Layout Site Survey Signaling Mobile Operation

COMT 3913 System Block Diagram Cellular/PCS MobileBTSBSCMTSOPSTN Data Bases forward reverse BTSBase Tranceiver Station BSCBase Station Controller MTSOMobile Telephone Switching Office Radio LinkBearer Trunk Signaling Trunk

COMT 3914 Frequency Reuse Pattern

COMT 3915 Example: AMPS 50MHz spectrum 30kHz per channel per direction 832 total full-duplex channels 4, 7, and 12 cell clusters used

COMT 3916 AMPS cont. 832 channels (2 frequencies per channel) –Forward: MHz –Reverse: MHz –Forward/Reverse Spacing: 45MHz –Adjacent Channel Spacing: 30kHz –21 Control Channels per group Cell Sizes: 2-20km

COMT 3917 Antenna Placement - high Good Coverage Co-Channel Interference Problems

COMT 3918 Buildings as Boundaries Cell Limits Defined Possible Adjacent Channel Interference

COMT 3919 Interference Co-Channel Interference Adjacent Channel Interference Outside Sources

COMT Signaling Channels Dedicated Control Channels (CC) –Mobile will scan for the strongest control channel when first switched on –System Identification –Number of Paging and Access Channels Paging Channels (PC) –Used to Initiate Calls to a Mobile Access Channels (AC) –Used to Initiate Calls from a Mobile

COMT Call Setup from Mobile Mobile receives AC numbers over PC Mobile finds the strongest AC Mobile signals (dials) over the AC to the Base Station and the MTSO MTSO transmits the Bearer Channel No.

COMT Mobile-Originated Call, AMPS MobileBTSBSCMTSOPSTN RCC MIN, ESN, dialed no validation FCC Ch No, SAT code, Power FVC SAT RVC SAT FVC RVC Conversation

COMT Call Setup to Mobile PSTN delivers call to MTSO MTSO transmits Mobile ID over all Paging Channels Mobile acknowledges on the strongest Access Channel MTSO selects the voice channel to use MTSO sends voice channel number to mobile

COMT 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.

COMT Call Handoff cont… Current base station at MTSO command sends signal to mobile giving the new channel assignment. Mobile tunes to the new channel. Previous base station clears the call path.

COMT Mobile Handset ESN - Electronic Serial Number Programmable NAM (Number Assignment Module) Contains among other things –System ID –First control channel to scan –System selection preferences –MIN (Mobile Identification Number)

COMT 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: internal mobile number

COMT Hand-Off MTSO BS MS

COMT Roaming Mobile MTSO Mobile MTSO Mobile

COMT Roaming Details MTSO BS MS MTSO HLR VLR Request Response Billing Information Service Profile Current Location Temporary Directory Number

COMT Intersystem Hand-Off MTSO BS MS MTSO

COMT The “Shoe-Lace” Effect BS MS

COMT Multi-System Tandem MTSO BS MS MTSO

COMT The “Trombone” Effect MTSO BS MS MTSO Fixed Station

COMT Security/Fraud Issues Security –Privacy of Conversations –Denial of Service Fraud –Illegally obtained ESN/MINs –Roaming-related (“tumbling” ESNs)

COMT Classes of Standards Analog Cellular –FDMA - Frequency Division Multiple Access Digital Cellular –FDMA –TDMA - Time Division Multiple Access –CDMA - Code Division Multiple Access

COMT Access Methods Frequency Time Frequency Time Frequency Time FDMA TDMA CDMA

COMT Standards Content Frequency Bands Channel Assignments Voice Encoding Access Method and Frame Structure Signaling Structure

COMT Wireless LAN Short range Single channel (“half-duplex”) Packet-based –Signaling packets –Bearer packets Authentication against back-end data base