telecommunications systems (part 2) school of business eastern illinois university © abdou illia,...
TRANSCRIPT
Telecommunications systems(Part 2)
School of BusinessEastern Illinois University
© Abdou Illia, Spring 2007
(Week 12, Thursday 3/29/2007)
T-1
Digital Subscriber Line (DSL)Cellular Telephone System
Integrated Services Digital Network (ISDN)
2Learning Objectives
Describe and compare types of connections offered by telephone companies
Explain Cellular Telephone System
T-1 Leased lines
4Trunk lines
Trunk lines = Type of transmission lines that connect nodes.
Trunk lines operate at speed from 56 kbps to 40+ Gbps
Trunk lines
T-1 1.544 MbpsT-3 45 MbpsSONET768 40+ Gbps
Synchronous Optical Network
5T-1 Lines
Computer TelephoneSwitch
TelephoneSwitch
TelephoneSwitch
Server
AccessLine
T-1 Trunk Line (1.544 Mbps)
T-1 Leased Line (1.544 Mbps)End-to-End Circuit with Trunk Line Speed
TrunkLine
6T-1 Leased lines
T-1 Leased lines:– Extend T-1 trunk line speeds to end-to-end circuits
between two locations (e.g. 2 customer offices)
– Require fiber optic or at least a special data-grade twisted Pair (Note: fiber optic is used for T-3 and SONET)
Data-Grade Twisted Pair
Q: What is the difference between T-1 Trunk line and T-1 Leased line?Q: In T-1 Leased lines, what kind of TP is used to connect a customer to the 1st telephone switch?
7T-1 Lines
The customer can request Fractional T-1 lines that offer low-speed choices, typically:
128 bps 256 kbps 384 kbps 512 kbps 768 kbps
T-1 Costs depend on distance:– ~$350-400/mo for local connection (non long-distance)– ~$1200/mo plus 2.50/mile for long-distance connection
Digital Subscriber Line - DSL
9Digital Subscriber Line (DSL)
Standard telephone line (Cat 1 UTP)– Capable of handling more than 3.1 Khz bandwidth
DSL exploits Standard telephone line’s “extra capacity” to transmit data without disturbing the line’s ability to transmit voice
Bandwidth usage for some Asymmetric DSL (ADSL) services:
– 0 - 4 Khz band for Voice conversation– Upstream data transmission in 25 – 160 Khz band– Downstream data transmission in 240 – 1500 Khz band
DSL uses filters (splitters) to separate voice and data signals– Typically a filter is needed for each analog device (telephone, fax, etc.)
10Digital Subscriber Line (DSL)
DataWAN
PSTN
DSLAM*
DSLModem
Splitter
Telephone
Telephone CompanyEnd Office Switch
Standard telephone line
PC
* DSL Access Multiplexer: (1) mixes data from many customers and (2) forwards mixed packets
UserEnd
11Digital Subscriber Line (DSL)
DataWAN
PSTN
DSLAM
DSLModem
Splitter
Telephone
UserEnd
Telephone CompanyEnd Office Switch
PC
Q: On the user end, what elements are needed to establish a DSL connection?
12Digital Subscriber Line (DSL)
DSL speed: 256 kbps – 24000 kbps
Digital Subscriber Lines (DSLs)– Asymmetric DSL (ADSL)
Standard ADSL– Downstream (to customer): 256 kbps to over 1.5 Mbps– Upstream (from customer): 64 kbps or higher
ADSL2– Downstream (to customer): 5 Mbps to aver 12 Mbps– Upstream (from customer): 1 Mbps to 3.5 Mbps
Q: How can a 3.5 Mbps upstream speed be achieved with Cat 1 UTP ?
13Digital Subscriber Line (DSL)
Digital Subscriber Lines (DSLs)– HDSL (High-rate DSL)
Needed in business. (ADSL primarily for home and small business access.)
Maximum range: 3 kilometers
Symmetric speed over voice-grade twisted pair
– HDSL: symmetric 768 kbps
– HDSL2: symmetric 1.544 Mbps or symmetric 2.3 Mbps
14
Summary Questions
1. What is the difference between a T-1 Trunk line and T-1 Leased line?
Answer: A T-1 trunk line only runs between two switches within the telephone network. T-1 Leased lines extend T-1 trunk line speeds to end-to-end circuits between 2 locations.
2. In T-1 Leased lines, what kind of twisted pair wire is used to connect a customer to the 1st telephone switch?
Answer: Data-grade TP which is a category 2 TP.
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Summary Questions
3) On the user end, what elements are needed to establish a DSL connection?
A DSL modem and splitter(s) to separate regular analog channel from the DSL data channels.
4) ADSL provides for higher downstream speeds than upstream speeds. (a) Is this good for web service? (b) Is it good for videoconferencing?
a) Asymmetric speeds are good for web service because http requests tend to be small but downloaded material are large.
(b) It is not good for videoconferencing, which needs high speed in both directions.
16Twisted Pair wires
Cellular Telephone System
18Cells, Cellsites, MTSO
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PSTN
Mobile TelephoneSwitching Office
Cellsite
Metropolitan service area is divided into cells.
Cellsite in each cell communicateswith cellphones.
MTSO controls all cellsites,links cellular system to PSTN.
19Cellular Telephone: The big picture
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PSTN
Mobile TelephoneSwitching Office
Cellsite
Cellsite main components:- Transceiver- Devices for supervising cellphones’ operation (initiating calls, terminating calls, etc.)
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20Why cells?
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PSTN
Mobile TelephoneSwitching Office
Cellsite
Why cells?So channels can be reused in different cells.
Channel reuse allows more customersto be supported.
Channel47
21Mobility
Handoff– Switching service from one cellsite to another when
users move from cells to cell in a system (city)
Roaming– Switching service from one MTSO to another when
users move from one system (city) to another.
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Handoff
22Generations of Cellular Technology
Generation 1G 2nd 3G
Year 1980 1990 2002
Signaling Analog Digital Digital
Data Transfer RateData transfer
is difficult;~5 kbps
10 kbps30 kbps to500 kbps
Technology
FrequencyDivision
Multiplexing
FDM
CodeDivision
MultiplexingCDM
CodeDivision
MultiplexingCDM
23Summary Questions
1) In cellular technology, what is:a) A cell?b) A cellsite?
2) What is the benefit of using cells instead of a large geographical area?
3) What are the main functions of a Mobile Telephone Switching Office (MTSO)?
4) Distinguish between handoff and roaming.
Integrated Services Digital Network- ISDN
25Integrated Services Digital Network
PersonalComputer
Desktop Telephone
2.64 kbps B ChannelAnalog Voice SignalOn Telephone Wires
1.64 kbps B Channel
Digital SignalOn Serial Cable
(1010)
ISDNWallJack
(RJ-45)
Original idea: one voice channel, one data channel
26Integrated Services Digital Network
PersonalComputer
Desktop Telephone
“ISDN Modem”
64 kbps B ChannelDigital Signal
On Serial Cable(1010)
Internal DSUConverts Serial Port
Signal to DigitalB Channel
Signal at 64kbps
(1010)
All-digitalService
(1101001..)
ISDNWallJack
(RJ-45)
The Data ChannelUses 232 Serial Cable
27Integrated Services Digital Network
PersonalComputer
Desktop Telephone
64 kbps B ChannelAnalog Voice SignalOn Telephone Wires
“ISDN Modem”
Internal CodecConverts
Analog VoiceSignal to Digital
B ChannelSignal at 64 kbps
(000010000))
All-digitalService
(1101001..)
ISDNWallJack
(RJ-45)
The Voice ChannelUses Home Telephone Cord
28Integrated Services Digital Network
PersonalComputer
Desktop Telephone
“ISDN Modem”
64 kbps B ChannelDigital Signal
On Serial Cable(1010)
Internal DSUConverts Serial Port
Signal to DigitalB Channel
Signal at 64kbps
(1010)
All-digitalService
(1101001..)
ISDNWallJack
(RJ-45)
BondingUse Both B Channels for DataSend and Receive at 128 kbps
29Integrated Services Digital Network
Dial Up: Not always connected– Do not have to pay for full-time use– Good if usage is small per day, say to upload sales data
from retail once per night
30ISDN Costs
Must install an ISDN line– Will cost more than telephone line
Actually, could use your existing phone line– But then would need one B channel for telephony
31ISDN Costs
Need “ISDN modem” (expensive)
Costs for standard ISDN service– $40/mo plus $1.00/minute for usage
ISDN tend to be used as a backup service. Example: Most banks communicate with headquarters using T-1, SONET, etc. If these services fails, they activate the ISDN connection.
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Summary Questions
5. (a) What is the highest speed you can have to and from an ISP using ISDN? (b) Is ISDN an always-active service? (c) How is it likely to be used in corporations? Why?
(a) With bonding, ISDN can provide 128 kbps Internet access.
(b) ISDN is NOT an always-on service. It is a dial-up service like ordinary telephone service.
(c) It is likely to be a backup service because ISDN payments are modest except when the service is being actively used