Unit 1 network models & typical examples(part b)

1. Unit 1 - Part B
Network Examples
Using Telephone & Cable Networks
for
Data Transmission

2. 9-1 TELEPHONE NETWORK
 Telephone networks use circuit switching. The
telephone network had its beginnings in the late 1800s.
 The entire network, which is referred to as the plain old
telephone system (POTS), was originally an analog
system using analog signals to transmit voice.
Topics discussed in this section:
~ Major Components
~ LATAs’
~ Signaling
~ Services Provided by Telephone Networks

3. a) Major Components of a telephone system
The major components of Telephone system are :
1. Local Loop
it is the twisted-pair cable that connects the subscriber
telephone to the nearest end office or local central office.
2. Trunks
they are the transmission media that handle the
communication between offices.
3. Switching Offices
A switching office consists of switches, in that each switch
connects several local loops or trunks and allows a connection between
different subscribers. [ three types – End, Tandem and Regional ]

4. b) LATA stands for Local Access Transport Areas’
 LATA stands for Local Access Transport Areas’
 Intra-LATA services. (i.e. services within a LATA )
 Inter-LATA services. (i.e. services between LATAs’ )
Typical Structure of a LATA involving different switching offices

5. Point of presences (POPs)
Inter-LATA Services
Intra-LATA Services

6. c) Signalling
 The details involved in communication between two
ends on a telephone network can be broadly divided into
two :
~ Data Transfer
~ Signalling

7. Data transfer and Signaling networks

8. Layers in SS7 [ SS7 – Signaling System Seven ]
SS7 is a layered architecture
similar to Internet model that is
used in Signaling network of
Telephone System.

9. 9-2 DIAL-UP MODEMS
 Traditional telephone lines can carry frequencies
between 300 and 3300 Hz, giving them a bandwidth of
3000 Hz.
 But for realizing data communication the telephone
lines make use of only a signal bandwidth of 2400Hz
( ranging from 600 to 3000 Hz. )
Telephone line bandwidth

10. Modulation / demodulation
Modem
Note
stands for modulator/demodulator.

11. Modem Standards [ The V – Series ]
The V – Series :
 V.32
 V.32bis
 V.34bis
 V.90
 V.92

12. The V.32 and V.32bis constellation and bandwidth

13. Uploading and downloading in 56K modems
The downward stream data rate is higher since there is no
quantization error while downloading.

14. 9-3 DIGITAL SUBSCRIBER LINE
 After traditional modems reached their peak data rate,
telephone companies developed another technology,
DSL, to provide higher-speed access to the Internet.
 Digital subscriber line (DSL) technology is one of
the most promising for supporting high-speed digital
communication over the existing local loops.
Topics discussed in this section:
i) ADSL
ii) ADSL Lite
iii) HDSL
iv) SDSL
v) VDSL

15. Discrete Multitone Technique [ DMT ]
Discrete Multitone Technique [ DMT ] combines FDM & QAM.

16. Bandwidth division in ADSL

17. ADSL modem
DSLAM [ DSL Access Multiplexer ]

18. Summary of DSL technologies

19. 9-4 CABLE TV NETWORKS
The cable TV network originally started as a video
service provider, but now it has moved to the business
of Internet access.
Topics discussed in this section:
1. Traditional Cable Networks
2. Hybrid Fiber-Coaxial (HFC) Network

20. 1. Traditional cable TV network
Communication in the traditional cable
TV network is unidirectional.
Note

21. 2. Hybrid Fiber-Coaxial ( HFC ) Network
Communication in an HFC cable TV network
can be bidirectional.
Note
Fiber Cable

22. 9-5 CABLE TV FOR DATA TRANSFER
Cable companies are now competing with telephone
companies for the residential customer who wants
high-speed data transfer. In this section, we briefly
discuss this technology.
Topics discussed in this section:
Bandwidth
Sharing
CM and CMTS
Data Transmission Schemes: DOCSIS

23. Bandwidth division of coaxial cable by CATV
Sharing
 Both upstream and downstream bands are shared by the
subscribers.
 Upstream Data bandwidth is 37 MHz. This means that there are
only six channels (of 6MHz each ) available in the upstream
direction.
 Downstream data bandwidth is 200MHz. This means that there are
thirty-three channels (of 6 MHz each ) available in the downstream
direction.

24. Cable modem (CM) [ at Subscriber Premises ]

25. Cable modem transmission system (CMTS) [ at Company Premises ]