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

2. 9.3 ADSL Technology ADSL = Asymmetrical Digital Subscriber Line Allows user to use both the phone and the internet at the same time Provides higher speeds than modems No need for new wiring, uses the existing telephone line

3. Performance is highly affected by the distance from the central office (limited to about 5 Km after which service can not be offered) Performance is also affected by the condition of the local loop (Quality of the local loop, existence of voice signal amplifier) Bandwidth versus distanced over category 3 UTP for DSL. 9-3 DIGITAL SUBSCRIBER LINE

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

5. Bandwidth division in ADSL Channels No. Frequency

6.  1.1 MHz is divided into 256 channels  Each channel is about 4 KHz  One channel (channel 0) allocated for voice  Channel 1-5 are not used to separate voice signal and data signals  two channels for control one for upstream and one for downstream  24 channels for upstream  224 channels for downstream  Why higher rate is allocated for downstream?  To be suitable for the WWW applications  Upstream handles just user requests but downstream handles transfer of web pages 9-3 DIGITAL SUBSCRIBER LINE

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

8. Figure 9.12 ADSL modem  Filter separates the voice from the data  ADSL modem is connected to the Ethernet card

9. Figure 9.13 DSLAM Digital subscriber line access multiplexer (DSLAM) ISP

10. DSLAM Digital Subscriber Line Access Multiplexer Located at the telephone company DSLAM takes connections from many customers and combines them onto a single high capacity connection to the internet Packetizes the data to be sent to the Internet (ISP server) Provides other services like routing or dynamic IP address assignment for customers