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9.1 Chapter 9 Using Telephone and Cable Networks for Data Transmission Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction.

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Presentation on theme: "9.1 Chapter 9 Using Telephone and Cable Networks for Data Transmission Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction."— Presentation transcript:

1 9.1 Chapter 9 Using Telephone and Cable Networks for Data Transmission Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2 9.2 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. Major Components LATAs (Local-Access Transport Areas) Signaling Services Provided by Telephone Networks Topics discussed in this section:

3 9.3 Figure 9.1 A telephone system first 3 digits next 4 digits toll offices intermmediate switching offices

4 9.4 LATA: Local-Access Transport Area IXC: Inter-eXchange Carriers (AT&T, MCI, Sprint, Verizon) POP: Point Of Presence (a switch office)

5 9.5 Intra-LATA services are provided by local exchange carriers (LECs). Since 1996, there are two types of LECs: incumbent local exchange carriers(ILEC) and competitive local exchange carriers (CLEC). Note

6 9.6 Figure 9.2 Switching offices in a LATA

7 9.7 Figure 9.3 Point of presences (POPs)

8 9.8 The tasks of data transfer and signaling are separated in modern telephone networks: data transfer is done by one network, signaling by another. Note

9 9.9 Figure 9.4 Data transfer and signaling networks

10 9.10 Figure 9.5 Layers in SS7

11 9.11 9-2 DIAL-UP MODEMS Traditional telephone lines can carry frequencies between 300 and 3300 Hz, giving them a bandwidth of 3000 Hz. All this range is used for transmitting voice, where a great deal of interference and distortion can be accepted without loss of intelligibility. Modem Standards Topics discussed in this section:

12 9.12 Figure 9.6 Telephone line bandwidth

13 9.13 Modem stands for modulator/demodulator. Note

14 9.14 Figure 9.7 Modulation/demodulation

15 9.15 Figure 9.8 The V.32 and V.32bis constellation and bandwidth Modulation: 32-QAM, 5 bits / baud 4 bits for data, 1 extra bit for error detection Baud rate: 2400, Data rate: 9600 bps Modulation: 128-QAM, 7 bits / baud 6 bits for data, 1 extra bit for error detection Baud rate: 2400, Data rate: 14400 bps V.32 V.32bis V.34bis: 28.8 Kbps with a 960-point constellation 33.6 Kbps with a 1664-point constellation

16 9.16 Figure 9.9 Uploading and downloading in 56K modems 33.6 Kbps 56 Kbps No quantization error at ISP (no sampling), higher SNR Quantization error at user side 8000 * (8-1) = 56000 bps, 8-bit samples, 1 bit for control (V.90)

17 9.17 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. ADSL ADSL Lite HDSL SDSL VDSL Topics discussed in this section: (often referred to as xDSL)

18 9.18 ADSL is an asymmetric communication technology designed for residential users; it is not suitable for businesses. Note

19 9.19 The existing local loops can handle bandwidths up to 1.1 MHz. Note

20 9.20 ADSL is an adaptive technology. The system uses a data rate based on the condition of the local loop line. Note

21 9.21 Figure 9.10 Discrete multitone technique C1-C5 not used, providing a gap between voice and data 1 baud / Hz 15 bits / Hz 24 * 15 * 4K = 1.44 Mbps (500K max. provided normally) 224 * 15 * 4K = 13.4 Mbps (8 Mbps max. provided normally)

22 9.22 Figure 9.11 Bandwidth division in ADSL

23 9.23 Figure 9.12 ADSL modem Used at the subscribers premises

24 9.24 Figure 9.13 DSLAM Used at the telephone company site

25 9.25 Table 9.2 Summary of DSL technologies

26 9.26 9-4 CABLE TV NETWORKS The cable TV network started as a video service provider, but it has moved to the business of Internet access. In this section, we discuss cable TV networks per se; in Section 9.5 we discuss how this network can be used to provide high-speed access to the Internet. Traditional Cable Networks Hybrid Fiber-Coaxial (HFC) Network Topics discussed in this section:

27 9.27 Figure 9.14 Traditional cable TV network Cable TV officeunidirectional Up to 35 amplifiers between the head end and the subscriber premises

28 9.28 Communication in the traditional cable TV network is unidirectional. Note

29 9.29 Figure 9.15 Hybrid fiber-coaxial (HFC) network RCH: Regional cable head, serves up to 400,000 subscribers Modulation distribution done here Each cable serves up to 1,000 subscribers 1.Reduces the need for amplifiers to 8 or less 2.Makes the cable network bi-directional

30 9.30 Communication in an HFC cable TV network can be bidirectional. Note

31 9.31 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. Bandwidth Sharing CM and CMTS Data Transmission Schemes: DOCSIS Topics discussed in this section:

32 9.32 Figure 9.16 Division of coaxial cable band by CATV Frequency range: 5 to 750 MHz (approximate) Divide into 3 bands: video, downstream data, and upstream data > 80 channels 6 MHz each 64-QAM, 6 bits/baud,1 baud / Hz 30 Mbps (5 bits/Hz * 6 MHz) 27 Mbps specified by standard Divide into 6 MHz channels QPSK used for modulation 2bits / baud, 1baud / Hz 12 Mbps upstream 6 channels shared by subscribers using timesharing

33 9.33 Downstream data are modulated using the 64-QAM modulation technique. Note

34 9.34 The theoretical downstream data rate is 30 Mbps. Note

35 9.35 Upstream data are modulated using the QPSK modulation technique. Note

36 9.36 The theoretical upstream data rate is 12 Mbps. Note

37 9.37 Figure 9.17 Cable modem (CM)

38 9.38 Figure 9.18 Cable modem transmission system (CMTS)


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