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