460 likes | 693 Views
TDC 461 Basic Communications Systems. Class #4 24 April, 2001. Agenda. Computer Telephony Integration (CTI) Cordless Telephones Cellular Telephones Satellite Systems. Announcements:. Midterm exam next week
E N D
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
Shared Cabling • Voice Network Layout and Data Network Layout looks the same!!
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.
CTI Configuration • First Party Control • Third Party Control
CTI Third-Party ControlAlternative: Direct LAN Connection to PBX
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 • Base unit=> • Portable unit=> • Signaling carried between base and portable using out-of-band frequencies.
Cellular Technologies Cell 3 Cell 2 Cell 1
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 3 Cell 2 Cell 1
Cellular increases capacity using Frequency Reuse • 7-way Frequency Reuse: Chan 41-80 Chan 201-240 Chan 1-40 Chan 161-200 Chan 41-80 Chan 121-160 Chan 1-40 Chan 81-120 Chan 241-280 Chan 121-160 Chan 201-240 Chan 81-120
Mobile Telephone Switching Office (MTSO) • Interconnection=> • Switching=>. • Interconnection with wireline=> MTSO Mobile Office Trunks Central Office
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 • 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