Chapter 9 Using Telephone and Cable Networks for Data Transmission

Chapter 9 of Data Communications and Networking by Behrouz A. Forouzan, titled "Using Telephone and Cable Networks for Data Transmission", covers how telephone and cable networks are used for transmitting data. Here are detailed notes from the chapter:

1. Telephone Network

• Structure:

  • Telephone networks use circuit switching and were originally designed for voice communication.

  • The network is now both digital and analog.

• Major Components:

  1. Local Loops: Twisted-pair cables connecting the subscriber’s telephone to the nearest switching office.

  2. Trunks: Transmission media that connect switching offices, usually through fiber-optic cables.

  3. Switching Offices: Hierarchical switching levels for managing communication within the network.

• Signaling System Seven (SS7): A protocol used for signaling, responsible for call setup, routing, and teardown. It operates in multiple layers similar to the OSI model.

2. Dial-up Modems

• Definition: A modem modulates and demodulates signals to allow digital data to be transmitted over analog telephone lines.

• Modem Standards:

  • V.32: 9600 bps.

  • V.32bis: 14,400 bps.

  • V.90: 56 kbps download, 33.6 kbps upload.

  • V.92: Newer standard, allowing up to 48 kbps upload speed.

3. Digital Subscriber Line (DSL)

• Technology: A technology that provides high-speed access to the Internet over existing telephone networks.

• DSL Types:

  1. Asymmetric DSL (ADSL): Higher speed downstream (up to 6.1 Mbps) and slower upstream (640 kbps).

  2. ADSL Lite: Simplified version of ADSL without the need for a splitter.

  3. High-bit-rate DSL (HDSL): Used for symmetric data rates (1.5 to 2 Mbps) over two twisted pairs.

  4. Symmetric DSL (SDSL): Provides equal upstream and downstream speeds (768 kbps).

  5. Very-high-bit-rate DSL (VDSL): Achieves very high speeds (up to 55 Mbps) over short distances.

• DSL Modems and DSLAM:

  • DSL Modem: Installed at the customer’s premises, separating voice and data communication.

  • DSLAM (Digital Subscriber Line Access Multiplexer): Installed at the telephone company, it packetizes data and routes it to the Internet.

4. Cable TV Networks

• Traditional Cable TV: Initially designed to deliver video services using unidirectional coaxial cables.

• Hybrid Fiber-Coaxial (HFC) Networks: Second-generation cable networks use a combination of fiber-optic and coaxial cables to support bidirectional data transmission.

5. Cable TV for Data Transfer

• Cable networks are used to provide high-speed Internet access.

• Bandwidth Division: The cable’s bandwidth is divided into:

  1. Video Band: For TV channels.

  2. Downstream Data Band: For data coming from the Internet to the subscriber (using 64-QAM modulation, with up to 30 Mbps data rate).

  3. Upstream Data Band: For data sent from the subscriber to the Internet (using QPSK modulation, with a theoretical maximum of 12 Mbps).

• Cable Modem (CM) and Cable Modem Transmission System (CMTS):

  • Cable Modem: Installed at the subscriber’s premises, it handles data modulation/demodulation.

  • CMTS: Installed at the distribution hub, it connects the cable network to the Internet and handles upstream and downstream traffic.

6. Data Transmission Protocols (DOCSIS)

• DOCSIS (Data Over Cable Service Interface Specification): The standard that defines protocols for data transmission over HFC networks. It controls how the cable modem and CMTS communicate, ensuring efficient data transmission.

7. Summary

• Telephone and cable networks, initially designed for voice and video, are now also used for high-speed Internet access.

• Technologies such as DSL and cable modems enable fast data transmission by utilizing existing infrastructure, each having its own strengths and limitations for upstream and downstream communication.

These notes provide a detailed understanding of how telephone and cable networks facilitate data transmission【7:0†source】【7:1†source】【7:4†source】【7:9†source】【7:10†source】.