Asymmetric Digital Subscriber Line

(ADSL)

Table of Contents

Introduction Advantages Drawbacks Conclusion

Introduction High speed data link. Pure network connection. Coming with different schemes:

CAP, QAM, and DMT. Using special modems called

endpoints

Server

Internet

CORENetwork

ADSLExisting Copper

ADSL

1.5 to 9 Mbps

16 to 640 kbps

ADSL Connection

Advantages Connectivity – always connected Ease of use Reliability Security Speed

FDM

POTS POTS

Upstream UpstreamDownstream Downstream

Echo Cancellation

FrequencyFrequency 1 Mhz1 Mhz

Create Multiple Channel

Nyquist’s Theorem

Maximum data rate = 2H log2 V bits/sec

H = low-pass filter of bandwidth

V = signal discrete levels

Drawbacks Availability Signal leaking Cost of installation and equipment Not standardization

Splitter

ADSL modem

Phone

Phone

Telephone line

Voice + ADSL

Voice (only)

ADSL (only)

Fig. 1 ADSL Problem

Splitter

ADSL modem

Phone

Phone

Telephone line

Voice + ADSL

Voice (+ ADSL leakage)

ADSL (only)

Fig. 2 ADSL Problem

ADSL Filter

Conclusion ADSL is a high speed access to

internet. ADSL has advantages but it also has

limitations. ADSL needs to extend the access

distance. ADSL might improve the speed. ADSL needs to be standardized.