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Telephone Service. 2 PSTN l The Public Switched Telephone Network l Worldwide l A call may cross many telephone company boundaries l Also Known as POTS.

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Presentation on theme: "Telephone Service. 2 PSTN l The Public Switched Telephone Network l Worldwide l A call may cross many telephone company boundaries l Also Known as POTS."— Presentation transcript:

1 Telephone Service

2 2 PSTN l The Public Switched Telephone Network l Worldwide l A call may cross many telephone company boundaries l Also Known as POTS l Plain old telephone service l Old Uninteresting

3 3PSTN l Importance l Corporate telephony spending is very high l Amount of use makes it very important l Deregulation is spurring price and product complexity l Management is exploding in complexity l Datacoms & telephony are managed together

4 4 The Traditional Telephone System l Customer Premises l Local Loop l Switching Office l End Office l Trunk Lines

5 5 Customer Premises l Your home or office l You control service on your premises l Beyond your premises, you need a telephone carrier

6 6 Local Loop l Line between your premises and the first telephone company switching office l Limits your transmission speed l Usually a single twisted pair of copper wire l Businesses may use higher-speed links l The Last Mile, although often 2-4 miles Customer PremisesSwitching Office Local Loop

7 7 Switching Offices l Connect Telephone Callers l Can support many simultaneous connections Connection Switching Office Local Loop Customer Premises Customer Premises

8 8 Hierarchical Organization of Switches l Classes (1-5) Class 5 Class 4 Class 3 Class 4

9 9 Trunk Lines l Connect switching offices l All lines except local loop Trunk Line Local Loop Trunk Lines Local Loop

10 10 Carriers in the United States l Local Access and Transport Area (LATA) l Intra-LATA Service l Local Exchange Carrier (LEC) l Competitive Access Providers (CAPs) l Inter-LATA Service l Inter-exchange Carriers (IXCs) l International Common Carriers (ICCs)

11 11 Carriers in the United States l POP l Point of presence l Located on LECs premises l Connects all customers of the LEC, CAPs, IXCs, ICCs l Allows new carriers to reach the total installed base, making competitive entry possible l Gives customers access to everyone else

12 12 Carriers in Most Countries l PTT l Public Telephone and Telegraph (Authority) l Traditional telephone monopoly carrier l Government-owned l Nationwide service l Ministry of Telecommunication l Government ministry that oversees, regulates the PTT

13 13 Regulation in the United States l Nationally l Federal Communications Commission (FCC) l Sets interstate regulations, standards, prices l Can set intrastate policies that affect the nation- wide system l Within States l Public Utilities Commissions (PUCs) l Regulate most intrastate matters

14 14 Deregulation in the United States l Deregulation l Relaxing rules that protect monopolies l Fostering competition l Competition should bring new services l Competition should bring lower prices

15 15 Deregulation in the United States l Ma Bell l The Bell System l AT&T l Had national monopoly on long-distance service l Owned LECs serving more than 80% of the U.S. Population

16 16 Deregulation in the United States l Breaking Up Ma Bell (1983) l Justice Department antitrust suit l Results in agreement and Consent Decree l AT&T keeps long-distance service, equipment manufacturing l LECs divided among 7 Regional Bell Operating Companies (RBOCs)--Baby Bells l Court-administered limits on AT&T & RBOCs

17 17 Deregulation in the United States l Second Breakup of AT&T (1996) l AT&T given freedom by courts to enter intra- LATA competition for transmission service l AT&T moving increasingly into international competition for transmission services l Problem: also sells equipment (switches, etc.) l Sold equipment to firms with whom it was beginning to compete for transmission services l Competitors would stop buying equipment once competition began

18 18 Deregulation in the United States l Second Breakup of AT&T (1996) l Voluntarily divided the company l AT&T keeps transmission services l Lucent manufactures telephone equipment l NCR manufacturers computer equipment

19 19 Deregulation in the United States l Telecommunications Act of 1996 l Congressional Act l Subjects intra-LATA service to open competition l Before, many PUCs had limited local competition l New competitors for service, including the local loop (dial tone service) l New freedom in pricing l Slowed by legal maneuvering

20 20 Deregulation Trends in the U.S. l Customer Premises l Most deregulated l Once, you could not own modems or even telephones l Deregulated in the 1970s l Now fully deregulated: you can do what your like on your premises

21 21 Deregulation Trends in the U.S Deregulation Trends in the U.S. l Data networking services l Called value added networks (VANs) l Deregulated in 1970s l Now wide open l Inter-LATA service l Deregulated in 1970s and 1980s l Now, equal access: you get to choose your long-distance carrier l Now wide-open

22 22 Deregulation Trends in the U.S. l Intra-LATA Service l Least deregulated l Some prior deregulation l Deregulation really began in earnest only with the Telecommunications Act of 1996

23 23 Deregulation in Other Countries l Varies Considerably l Few countries as deregulated as U.S. l Prices generally higher than U.S. l Services available in U.S. may not be available l Customer premises usually deregulated most l Basic voice telephone service usually deregulated least

24 24 Deregulation in Other Countries l World Trade Organization (WTO) l Agreement in 1997 on Telecommunications Services l Agreement to open domestic (internal) competition l Not total deregulation l Not all countries sign l Timetable for deregulation may be long l Encouraging but not decisive

25 25 Deregulation in Other Countries l Europe 1998 l European Community l Has been breaking down many national monopolies l As of January 1998, high degree of domestic telecommunication competition is mandated

26 26 International Service l Provided by international common carriers (ICCs) l Each pair of countries negotiates which ICCs may provide service l Each pair of countries negotiates settlement charges on calls l This bilateral negotiation often brings uneven pricing when you call nearby countries

27 27 Customer Premises Equipment l Private Branch Exchanges (PBXs) l Internal telephone network l PBX is the switch l Wiring to individual telephones l Telephones themselves l Lines to carriers for incoming, outgoing calls PBX Company Phones Carriers

28 28 Building Telephone Wiring l In the Basement l Line from carrier l Termination Equipment protects carrier line l PBX l Wiring bundle (many pairs) out of PBX Termination Equipment PBX Wiring Bundle

29 29 Building Telephone Wiring l Between Floors l Vertical riser spaces Vertical Riser Spaces

30 30 Building Telephone Wiring l Wiring Closets l Break up bundle l Sub-bundle goes to next floor l Other wires are for distribution on floor Wiring Closet

31 31 Building Telephone Wiring l Horizontal Distribution on Floors l Run wires through false ceilings, conduits l Drop down to faceplate phone jacks Wiring BundleSingle Line Wallplate

32 32 Telephone Wiring and LAN Wiring l LAN Wiring Based on Building Wiring l Cat5 UTP wiring bundles l 8-wire bundles l 100 meter limitation l Sufficient to get from wiring closet to station l Vertical Distribution l Distance limitations sufficient to reach internetting device in basement

33 33 PBX Networks l PBXs at different sites work together l Connected by leased lines l You can dial any telephone in the firm Leased Line

34 34 PBX User Services l Speed Dialing l Dial a number using a 1- or 2-digit code l Last Number Redial l Easy redial of last number called l Display of Called Number l Display shows the number you dialed l Allows you to check for dialing errors

35 35 PBX User Services l Camp On l You dial another number l You get a busy signal l You hit the camp on button l You hang up l When the called party hangs up, your phone rings l You pick it up l Called partys phone rings

36 36 PBX User Services l Call Waiting l You are on the phone l Hold l Place someone on hold l ANI l Automatic Number Identification l Displays number of calling extension when your phone rings l Conferencing l 3-party calling

37 37 PBX User Services l Call Transfer l You will be away from you desk l Calls go automatically to a phone near you l Call Forwarding l Someone calls you l Voice Mail l Can leave messages

38 38 PBX Attendant Services l Operator Assistance l In-house operators to handle problems l Automatic Call Distribution l Call comes in from outside l Automatically goes to correct extension l Message Center l Leave message with operator for anyone in the building

39 39 PBX Attendant Services l Paging l Broadcasts call for person over loudspeakers l Nighttime Call Handling l Special functions for nighttime calls l E.g., transfer control to guard station l Change Requests l Automated adding, dropping, changing of numbers once information is typed in

40 40 PBX Management Services l Automatic Route Selection l For outgoing calls l Automatically selects the lowest-cost line l Call Restriction l Prevent certain numbers from calling out, making long-distance calls, etc. l Call Detail Reporting l Reports with detailed charges go to departments

41 41 Voice Response l Customer calls in l Gets a recording that gives them a menu of choices l Caller hits button on phone to select a menu choice l Not voice recognition! l Reduces operator time l Can upset customers l Can also be used in product support

42 42 Carrier Services and Pricing l Tariffs l Filed by carriers, approved by authority l Lets customer know the details of the service to be provided l Lets customer know exactly what price they should pay l Provides recourse in disputes l Deregulation is generating many untariffed services for faster response to competition

43 43 Local Calling l Within local area l Flat rate pricing l Fixed payment per month l No charge per call l Message unit pricing l Charged message units for each call in local area l Depends on distance and duration l Penalizes Internet access, other resource hogs

44 44 Toll Calls l Long-distance calls l Inter-LATA or Intra-LATA l Priced per minute l Price based on distance l International calls l Prices depend primarily on country called l Prices depend less on distance than on country called l Price may be lower calling from one country than from the other in the pair

45 45 Toll Calls l Direct Distance Dialing l Most common method l Collect Calls l Called party pays if accepts calls l Pays more than direct dial rate l 800/888 Numbers l Area codes are with 800 or 888 l Pays less than direct dial rates to support customers l 900 Numbers l Caller pays l Pays more than direct dial rate l Called company can charge for user service

46 46 Toll Calls l WATS l Wide Area Telephone Service l Company can call out from site, to phones throughout the WATS service area l Pay less than direct dial rates l Universal Availability l Personal telephone number for person l Will reach you wherever you are physically l Some day given at birth?

47 47 Electronic Switching Services l Switches are Computers l Can provide services beyond switching through software l Can provide PBX-like user services to carrier customers l ISDN standardizes these services and allow them to work worldwide. (Integrated Services Digital Network)

48 48 Electronic Switching Services l Automatic Number Identification (ANI) l You see the number of the person calling you l Lets you screen calls l Lets companies route caller to personal service representative automatically l Concerns about privacy l Can be blocked, so that receiver will not see your number l Receiver can refuse calls from blocked ANI

49 49 Cellular Telephones l Original Mobile Telephones l One transmitter/receiver l Limited number of channels l For good service can support about 20 subscribers per channel Transmitter/ Receiver Mobile Phone

50 50 Cellular Telephones l Divide Region into Cells l One cellsite per cell l Channels can be reused in non-adjacent cells No Yes No Yes No Yes No Uses Channel 232 Can Reuse Ch. 232? Channel 232 Used in 4 cells

51 51 Cellular Telephones l Reuse l Without reuse, only 20 users per channel for good service l If reused 4 times, 80 subscribers per channel l Reuse Rule (Rough) l Reuse factor = Number of cells / 7 l If 20 cells, reuse factor is about 3

52 52Handoffs l When you move to another cell l You are transferred automatically to that cells cellsite

53 53Roaming l Take your cellphone to another city l Use it there to send and receive l Not always possible technically l May be limited procedurally because of high rates of cellular fraud in some areas l Dont confuse this with handoff, which takes place within a cellular system between cells

54 54Control l Mobile Telephone Switching Office l Controls cellsites, handoffs, etc. l Calls go to/from MTSO l Connects to POP at LEC to link to traditional telephone (wireline) carriers MTSO POP at LEC

55 55 Placing a Call l Enter number, hit send l Cellphone broadcasts request l Several cellsites receive, send to MTSO l MTSO assigns cellphone to cellsite with loudest signal l MTSO sends message to cellphone, telling it what incoming, outgoing channels to use

56 56 Receiving a Call l MTSO has each cellsite broadcast cellphones ID number l Cellphone transmits a response l Responses from cellsites go to MTSO l MTSO selects loudest cellsite l MTSO sends message to cellphone, giving channels and telling the cellphone to ring

57 57 First Generation Cellular l Analog Operation l Limits services and signal quality l How Many Subscribers can it support? l Large Cells (20-40 per city) l 20 cells, and frequency reuse is about 3 (20/7) l 832 channels, and with frequency reuse, 2,496 available channels l 20 users per available channel, then only about 50,000 subscribers per system l Engineering tricks can extend, but only somewhat

58 58 First Generation Cellular l United States l AMPS standard l Elsewhere l Many incompatible standards l Use different radio bands l Limits multinational roaming

59 59 Second Generation Cellular l What it is l Digital instead of analog for better service l Still uses large cells l Still has about the same number of channels l In the United States l Retrofitting existing analog systems with some digital channels l CDPD (Cellular Digital Packet Data) is the most common technology l Not widely used l Elsewhere in the World l Standardizing almost completely on GSM - General System for Mobile (communication)

60 60 Third-Generation Cellular l Personal Communication Service (PCS) l Or Personal Communication Network (PCN) l Smaller cells l More frequency reuse l More channels l About 2,500 l Digital, like 2nd generation l 3rd generation companies usually offer more services at a price similar to that of 1st generation instead of dropping prices

61 61 Third-Generation Cellular l Most of World l Standardized on DCS Technology l Based on GSM l U.S. l FCC did not specify a standard! l Different carriers use different technologies l Many have standardized on DCS l Your cellphone may not work with another carrier l Limits roaming

62 62 Potential System Capacity Category 1st Gen3nd Gen Cells/City 30 100? Channel reuse ~4 ~14 Channels 8002,500 Effective channels3,200 35,000 Subscribers 60,000 700,000 This analysis is inexact but illustrative

63 63 U.S. PCS Standards l Coordinated by the TIA TR-45 Committee l 3 standards selected l DCS (Digital Communications Service) l Based on GSM l Time division multiplexing l 2-3 times as many simultaneous calls as first generation in the same bandwidth

64 64 Personal Service Telephones l On the road l Personal cellphone acts like 3d generation cellphone l At home l Cellphone acts like cordless telephone l No cellular charges when you use it l At work l Wireless PBXs treat it like a business phone l No cellular charges

65 65 Traditional Communications Satellites l In geosynchronous orbit l Appear to be stationary l Far from the ground (22,300 miles) l Need much power to send/receive l Need dish antennas to concentrate signals l Must point dish at the satellite l Impractical for portable telephony

66 66 LEO Satellites l Low Earth Orbit Satellites l Only 100 to 200 miles above the earth l Need far less power to reach than 22,300 mile geosynchronous satellites l Can get by with omnidirectional antenna l Can use phone of reasonable size, cost l Access anywhere Omnidirectional Antenna

67 67 LEO Satellites l Satellites circle the earth every 90 minutes l Handoffs between satellites serving you l Like cellular, except you are (relatively) stationary and the transmitter/receiver moves

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