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 CORE Network ADSL ADSL Internet ADSL Connection Existing Copper 1.5 to 9 Mbps Internet 16 to 640 kbps ADSL Connection

Advantages Connectivity – always connected Ease of use Reliability Security Speed

Create Multiple Channel Echo Cancellation FDM Upstream Downstream Upstream Downstream POTS POTS Frequency 1 Mhz Frequency 1 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

Fig. 1 ADSL Problem Splitter ADSL Phone modem Phone Telephone line Voice (only) Splitter Voice + ADSL ADSL (only) ADSL modem Phone Phone Fig. 1 ADSL Problem

Fig. 2 ADSL Problem Splitter ADSL Filter ADSL Phone modem Phone Telephone line Voice (+ ADSL leakage) Splitter Voice + ADSL ADSL (only) ADSL Filter ADSL modem Phone Phone Fig. 2 ADSL Problem

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.