TelephoneTelephone

ServiceService

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PSTPSTNN

The Public Switched Telephone Network Worldwide A call may cross many telephone company

boundaries

Also Known as POTS Plain old telephone service “Old” “Uninteresting”

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PSTNPSTN

Importance

Corporate telephony spending is very high

Amount of use makes it very important

Deregulation is spurring price and product complexity

Management is exploding in complexity

Datacoms & telephony are managed together

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The Traditional Telephone The Traditional Telephone SystemSystem

Customer Premises Local Loop Switching Office

End Office Trunk Lines

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Customer PremisesCustomer Premises

Your home or office You control service on your premises

Beyond your premises, you need a telephone carrier

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Local LoopLocal Loop Line between your premises and the first

telephone company switching office Limits your transmission speed Usually a single twisted pair of copper wire Businesses may use higher-speed links “The Last Mile,” although often 2-4 miles

Customer Premises Switching Office

Local Loop

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Switching OfficesSwitching Offices

Connect Telephone Callers Can support many simultaneous connections

Connection

Switching OfficeLocalLoop

CustomerPremises

CustomerPremises

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Hierarchical Hierarchical Organization of Organization of SwitchesSwitches

Classes (1-5)

Class 5 Class 5

Class 4

Class 3

Class 4

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Trunk LinesTrunk Lines

Connect switching offices All lines except local loop

TrunkLine

LocalLoop

TrunkLines

LocalLoop

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Carriers in the United Carriers in the United StatesStates

Local Access and Transport Area (LATA) Intra-LATA Service

Local Exchange Carrier (LEC) Competitive Access Providers (CAPs)

Inter-LATA Service Inter-exchange Carriers (IXCs)

International Common Carriers (ICCs)

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Carriers in the United Carriers in the United StatesStates

POP

Point of presence

Located on LEC’s premises

Connects all customers of the LEC, CAPs, IXCs, ICCs

Allows new carriers to reach the total installed base, making competitive entry possible

Gives customers access to everyone else

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Carriers in Most Carriers in Most CountriesCountries

PTT Public Telephone and Telegraph (Authority) Traditional telephone monopoly carrier Government-owned Nationwide service

Ministry of Telecommunication Government ministry that oversees, regulates

the PTT

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Regulation in the Regulation in the United StatesUnited States

Nationally Federal Communications Commission (FCC) Sets interstate regulations, standards, prices Can set intrastate policies that affect the nation-

wide system Within States

Public Utilities Commissions (PUCs) Regulate most intrastate matters

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Deregulation in the Deregulation in the United StatesUnited States

Deregulation Relaxing rules that protect monopolies Fostering competition Competition should bring new services Competition should bring lower prices

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Deregulation in the Deregulation in the United StatesUnited States

Ma Bell The Bell System AT&T Had national monopoly on long-distance

service Owned LECs serving more than 80% of the

U.S. Population

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Deregulation in the Deregulation in the United StatesUnited States

Breaking Up Ma Bell (1983)

Justice Department antitrust suit

Results in agreement and Consent Decree

AT&T keeps long-distance service, equipment manufacturing

LECs divided among 7 Regional Bell Operating Companies (RBOCs)--”Baby Bells”

Court-administered limits on AT&T & RBOCs

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Deregulation in the Deregulation in the United StatesUnited States

Second Breakup of AT&T (1996)

AT&T given freedom by courts to enter intra-LATA competition for transmission service

AT&T moving increasingly into international competition for transmission services

Problem: also sells equipment (switches, etc.)

Sold equipment to firms with whom it was beginning to compete for transmission services

Competitors would stop buying equipment once competition began

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Deregulation in the Deregulation in the United StatesUnited States

Second Breakup of AT&T (1996)

Voluntarily divided the company

AT&T keeps transmission services

Lucent manufactures telephone equipment

NCR manufacturers computer equipment

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Deregulation in the Deregulation in the United StatesUnited States

Telecommunications Act of 1996 Congressional Act

Subjects intra-LATA service to open competition

Before, many PUCs had limited local competition

New competitors for service, including the local loop (dial tone service)

New freedom in pricing

Slowed by legal maneuvering

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Deregulation Trends in Deregulation Trends in the U.S.the U.S.

Customer Premises Most deregulated Once, you could not own modems or even

telephones Deregulated in the 1970s Now fully deregulated: you can do what your

like on your premises

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Deregulation Trends in Deregulation Trends in the U.Sthe U.S.

Data networking services Called value added networks (VANs) Deregulated in 1970s Now wide open

Inter-LATA service Deregulated in 1970s and 1980s Now, equal access: you get to choose your long-distance

carrier Now wide-open

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Deregulation Trends in Deregulation Trends in the U.S.the U.S.

Intra-LATA Service Least deregulated Some prior deregulation Deregulation really began in earnest only with

the Telecommunications Act of 1996

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International ServiceInternational Service Provided by international common carriers

(ICCs)

Each pair of countries negotiates which ICCs may provide service

Each pair of countries negotiates settlement charges on calls

This bilateral negotiation often brings uneven pricing when you call nearby countries

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Customer Premises Customer Premises EquipmentEquipment

Private Branch Exchanges (PBXs) Internal telephone network PBX is the switch Wiring to individual telephones Telephones themselves Lines to carriers for incoming, outgoing calls

PBX

CompanyPhones

Carriers

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Building Telephone Building Telephone WiringWiring

In the Basement Line from carrier Termination Equipment protects carrier line PBX Wiring bundle (many pairs) out of PBX

Termination Equipment

PBX

Wiring Bundle

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Building Telephone Building Telephone WiringWiring

Between Floors Vertical riser spaces

Vertical Riser Spaces

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Building Telephone Building Telephone WiringWiring

Wiring Closets Break up bundle Sub-bundle goes to next floor Other wires are for distribution on floor

Wiring Closet

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Building Telephone Building Telephone WiringWiring

Horizontal Distribution on Floors Run wires through false ceilings, conduits Drop down to faceplate phone jacks

Wiring BundleSingle Line

Wallplate

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Telephone Wiring and Telephone Wiring and LAN WiringLAN Wiring

LAN Wiring Based on Building Wiring Cat5 UTP wiring bundles

8-wire bundles 100 meter limitation

Sufficient to get from wiring closet to station Vertical Distribution

Distance limitations sufficient to reach internetting device in basement

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Cellular TelephonesCellular Telephones Original Mobile Telephones

One transmitter/receiver Limited number of channels For good service can support about 20

subscribers per channel

Transmitter/Receiver

MobilePhone

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Cellular TelephonesCellular Telephones

Divide Region into Cells One cellsite per cell Channels can be reused in non-adjacent cells

No

No

YesNo

Yes

No

No

Yes

No

UsesChannel

232

Can ReuseCh. 232?

Channel 232Used in 4 cells

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Cellular TelephonesCellular Telephones

Reuse Without reuse, only 20 users per channel for

good service If reused 4 times, 80 subscribers per channel

Reuse Rule (Rough) Reuse factor = Number of cells / 7 If 20 cells, reuse factor is about 3

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HandoffsHandoffs

When you move to another cell You are transferred automatically to that cell’s

cellsite

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RoamingRoaming

Take your cellphone to another city

Use it there to send and receive

Not always possible technically

May be limited procedurally because of high rates of cellular fraud in some areas

Don’t confuse this with handoff, which takes place within a cellular system between cells

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ControlControl

Mobile Telephone Switching Office Controls cellsites, handoffs, etc. Calls go to/from MTSO Connects to POP at LEC to link to traditional

telephone (wireline) carriers

MTSO

POP atLEC

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Placing a CallPlacing a Call

Enter number, hit send Cellphone broadcasts request Several cellsites receive, send to MTSO MTSO assigns cellphone to cellsite with

loudest signal MTSO sends message to cellphone, telling

it what incoming, outgoing channels to use

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Receiving a CallReceiving a Call

MTSO has each cellsite broadcast cellphone’s ID number

Cellphone transmits a response Responses from cellsites go to MTSO MTSO selects loudest cellsite MTSO sends message to cellphone, giving

channels and telling the cellphone to ring

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First Generation First Generation CellularCellular

Analog Operation Limits services and signal quality

How Many Subscribers can it support? Large Cells (20-40 per city) 20 cells, and frequency reuse is about 3 (20/7) 832 channels, and with frequency reuse, 2,496

available channels 20 users per available channel, then only about

50,000 subscribers per system Engineering tricks can extend, but only

somewhat

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First Generation First Generation CellularCellular

United States AMPS standard

Elsewhere Many incompatible standards Use different radio bands Limits multinational roaming

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Second Generation Second Generation CellularCellular

What it is Digital instead of analog for better service Still uses large cells Still has about the same number of channels

In the United States Retrofitting existing analog systems with some digital

channels CDPD (Cellular Digital Packet Data) is the most common

technology Not widely used

Elsewhere in the World

Standardizing almost completely on GSM - General System for Mobile (communication)

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Third-Generation Third-Generation CellularCellular

Personal Communication Service (PCS) Or Personal Communication Network (PCN)

Smaller cells More frequency reuse

More channels About 2,500

Digital, like 2nd generation 3rd generation companies usually offer more

services at a price similar to that of 1st generation instead of dropping prices

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Third-Generation Third-Generation CellularCellular

Most of World Standardized on DCS Technology Based on GSM

U.S. FCC did not specify a standard! Different carriers use different technologies Many have standardized on DCS Your cellphone may not work with another

carrier Limits roaming

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Wide Area Wireless NetworksWide Area Wireless Networks(next class meeting)(next class meeting)

Review of multiplexing spread spectrum cellular generations

Comparison of Wi-Fi and cellular New generation: 4G WiMAX and LTE

Wi-Fi and cellular convergence mobile computing growth

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Traditional Traditional Communications Communications SatellitesSatellites

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

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LEO SatellitesLEO Satellites

Low Earth Orbit Satellites Only 100 to 200 miles above the earth Need far less power to reach than 22,300 mile

geosynchronous satellites Can get by with omnidirectional antenna Can use phone of reasonable size, cost Access anywhere

OmnidirectionalAntenna

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LEO SatellitesLEO Satellites

Satellites circle the earth every 90 minutes Handoffs between satellites serving you Like cellular, except you are (relatively)

stationary and the transmitter/receiver moves