tdc 461 basic communications systems
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TDC 461Basic Communications
Systems
Class #4
24 April, 2001
Agenda • Computer Telephony Integration (CTI)
• Cordless Telephones
• Cellular Telephones
• Satellite Systems
Announcements:
• Midterm exam next week– You can bring one 8.5”x11” sheet of Exam will
be multiple choice, true false, fill-in-the-blank, and short answer. You will have to diagram a solution to at least one problem, so be prepared.
– Exam will last until 7:30pm.– Review guide on the web.
Computer Telephony Integration (CTI)
• The concept:
– Integrate PBX with computer services to
– Integrate voice cabling with data cabling to
save money
Why CTI?
PBX System Layout
Public SwitchedTelephone Network
Punchdown block
Station SetStation Set Station Set Station Set
Station Set Station Set Station Set
PBX
Punchdown /Patch Panel IVR Voice Mail ACD
LAN System Layout
LAN Switch
Router Internet
T-1
File Server Web ServerDatabase Server
Hub / LAN Switch
Client Client Client Client
Client Client Client
Shared Cabling
• Voice Network Layout and Data Network
Layout looks the same!!
Non-Integrated PBX & LAN
Workstation Phone Workstation PhoneWorkstation Phone
LAN SwitchFile ServerPBX/ACD
DataVoice
Voice/Data Adjunct Services(with no PBX modifications)
• Some voice/data convergence can be accomplished without PBX changes.
• LAN servers can connect to PBX by standard voice trunks.
• Examples
Unified Messaging
• Users utilize a single desktop application to receive and send
• Voice mail can be recorded/heard through PBX telephone set or PC microphone/speaker.
Unified Messaging
Workstationw/ Mail software
Phone Workstationw/ Mail software
PhoneWorkstationw/ Mail software
LAN SwitchIntegrated
Mail Server
Trunks
PSTNInternet
Router
PBX
Phone
FAX Server
FAX Server
Workstationw/ FAX software
Phone Workstationw/ FAX software
PhoneWorkstationw/ FAX software
LAN SwitchFAX Server
Trunks
PSTNInternet
Router
Fax Machine
PBX
CTI Configuration
• First Party Control –
• Third Party Control– –
CTI First-Party ControlIndividual connections to desktops
AgentPhone
AgentPhone
LAN SwitchFile ServerPBX/ACD
w/ CTI
DataVoice
AgentWorkstation
w/ CTI
AgentPhone
AgentWorkstation
w/ CTI
AgentWorkstation
w/ CTI
CTI Control Link
CTI Third-Party ControlConnect through CT Server
AgentPhone
AgentPhone
LAN Switch
CT ServerPBX/ACDw/ CTI
DataVoice
AgentWorkstation
w/ CTI
AgentPhone
AgentWorkstation
w/ CTI
AgentWorkstation
w/ CTI
CTI Control Link
CTI Third-Party ControlAlternative: Direct LAN Connection to PBX
AgentPhone
AgentPhone
LAN SwitchCT ServerPBX/ACD
w/ LAN card
DataVoice
AgentWorkstation
w/ CTI
AgentPhone
AgentWorkstation
w/ CTI
AgentWorkstation
w/ CTI
CTI Applications
• Intelligent Call Assignment for ACD
• Data lookups triggered by calling number (ANI / DNIS)
• Linking database records and PBX call records
• Intelligent Voice Response Unit / Faxback
• Control voice calls via PC applications
CTI Software Configuration
• CTI Software required on: – – –
• All CTI functions and messaging defined by CTI Applications Programming Interface (API)
CTI APIs • Telephony Services API (TSAPI)
– –
• Telephony API (TAPI)– –
• CallPath –
• Java Telephony API (JTAPI)–
CTI Summary
• Advantages
–
• Disadvantages
– .
–
Cordless Telephones
Cordless Telephones
Base unit=>
Portable unit=>
Signaling carried between base and portable using out-of-band frequencies.
Cellular Technologies
Cell 1
Cell 2
Cell 3
Previous Wireless SystemsSingle Powerful Transmitter
Wireless Before CellularProblem: Limited Capacity
• Before 1981:– FDM– Limited number of users:– Very limited capacity
Cellular Services• 728 Mobile Service Areas (MSAs) defined
by the FCC in the United States.
• 2 Cellular carriers in each MSA– A Carrier : – B Carrier :
•
Cellular Concept:Many Low Power Base Stations
Cell 1
Cell 2
Cell 3
Cellular increases capacity using Frequency Reuse
• 7-way Frequency Reuse:–
–
– Chan81-120 Chan
201-240
Chan161-200Chan
121-160
Chan41-80
Chan1-40
Chan241-280
Chan1-40
Chan81-120
Chan121-160
Chan41-80
Chan201-240
Mobile Telephone Switching Office (MTSO)
• Interconnection=>• Switching=>.• Interconnection with
wireline=>
MTSOMTSO
CentralCentralOfficeOffice
Mobile Office Trunks
Cellular Network Signaling• Registration
– • Call Handoff
– • Roaming
–
Call Handoff• Caller moves from one cell to another:
Cellular Systems• Advanced Mobile Phone System (AMPS)
• IS-54B Digital Cellular (TDMA)
Personal Communications Systems (PCS)
• Combines voice and data services
• Intelligent network
• Code Division Multiple Access (CDMA)
Personal Communications Systems (PCS)
• Smart PCS equipment=>
How to Share Airwaves?
• Frequency Division Multiple Access (FDMA) –
How to Share Airwaves?
• Time Division Multiple Access (TDMA) – – – – Example: For 3 voice channels,
• Voice Channel 1: data bytes #1, #4, #7, #10, …
• Voice Channel 2: data bytes #2, #5, #8, #11, …
• Voice Channel 3: data bytes #3, #6, #9, #12, ...
How to Share Airwaves?• Code Division Multiple Access (CDMA)
– – – – Example:
• Voice channel 1: ‘0’ = 0101100, ‘1’ = 1010011• Voice channel 2: ‘0’ = 1100110, ‘1’ = 0011001
How to Share Airwaves?• Advantages:
– FDMA: – TDMA: – CDMA:
Satellite Systems
Satellite Systems
• Satellites are big repeaters in the sky
Advantages to Satellites• Coverage
– Geosynchronous satellite=>
• Distance Insensitivity –
• Scalability–
Disadvantages to Satellites• Propagation Delay
–
–
• Weather –
Satellite Orbits• Geosynchronous Earth Orbit (GEO)
– Orbits 22,300 miles above earth– Appears to be motionless from Earth– Uses: TV, telephony, intelligence
• Low Earth Orbit (LEO)– Orbits 100-1000 miles above earth– Satellite rises and sets in ~15 minutes when viewed from Earth– Advantage: Much smaller propagation delay– Uses: New voice/data networks
Example: Iridium• Iridium is LEO network
– Built by consortium lead by Motorola– Constellation of 66 LEO satellites
• 11 satellites in each of 6 different polar orbits
– Provides voice communications from anyplace to anyplace on Earth.– 12 Gateways provide interconnection to international public telephone
networks– Commercial service started in Nov. 1998
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