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.
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