1. Digital Subscriber Line (DSL)
What is it?
DSL is a technology for bringing high-bandwidth connections to homes and small business
First Installations started in 1998
A DSL can carry both data and voice signals, and the data part is continuously connected
Speed can go as high as 6.1 Mbps
Typical speeds are between 128 Kbps and 1.54 Mbps

2. Digital Subscriber Line (DSL)
How it works
POTS and DSL
Two wire analog
Voice uses analog frequencies 0 to 3400 Hertz
DSL uses analog frequencies above 4000 Hertz
DSL Technology
Uses advanced modulation technologies on existing communications networks for high speed networking between a subscriber and a Telco
Assumes digital data does not require conversion to analog form and back

3. Digital Subscriber Line (DSL)
How it works
DSL Access Multiplexer (DSLAM) and Splitter Technology
DSLAM combines the channels (bit streams) coming upstream from the users and splits data into cannels going down stream to the users (Multiplexing)
Splitter vs. Splitterless
Splitter uses four wires – two for voice, two for data
The splitter is at the customer site
Splitterless uses two wires
Splitter is at DSLAM
Uses filters for voice – Low-Pass Filter - filters everything above 4000 Hrtz

4. Digital Subscriber Line (DSL)
Types of DSL
ADSL (Asymmetrical Digital Subscriber Line)
HDSL (High-Bit-Rate Digital Subscriber Line)
SDSL (Symmetrical Digital Subscriber Line)
RADSL (Rate Adaptive Digital Subscriber Line)
VDSL (Very High-Data-Rate Digital Subscriber Line)

5. Digital Subscriber Line (DSL)
ADSL
Most common DSL
Distance from CO limited to 18,000 feet
Each line direct to DSLAM
Bandwidth
Upload – 64 Kbps to 640 Kbps (1.54 Mbps, If less than 12,000 feet)
Download – up to 9 Mbps
Two primary modulation implementations
CAP (Carrierless Amplitude Phase Modulation)
DMT (Discrete MultiTone)

6. Digital Subscriber Line (DSL)
ADSL Modulation Technologies
CAP (Carrierless Amplitude Phase Modulation)
Separates Voice, Upload and Download into distinct bands
Bands Widely seperated
Default ANSI standard
Developed by AT&T
Uses a technique similar to QAM (Quadrature Amplitude Modulation)

7. Digital Subscriber Line (DSL)
ADSL Modulation Technologies
DMT (Discrete MultiTone)
KHz each
First channel (0 to KHz) voice
Each channel can be either upload or download
Each channel can carry 0 to 60 Kbps
Uses QAM (Quadrature Amplitude Modulation)

8. Digital Subscriber Line (DSL)
HDSL (High-Bit-Rate Digital Subscriber Line)
The earliest variation of DSL to be widely used
Symmetrical
Data rate 2.048
13728 feet (4.2 km (2.6 mi)) without repeater
Separate phone line
Used to deliver t-1 circuit
Requires 2 independent twisted pairs

9. Digital Subscriber Line (DSL)
SDSL (Symmetrical Digital Subscriber Line)
Single twisted pair
10,000 feet (3 km (1.86 mi)) without repeater
768 kbps maximum in both direction
RADSL (Rate Adaptive Digital Subscriber Line)
Adapts the transmission speed depending on the distance to the CO

10. Digital Subscriber Line (DSL)
VDSL (Very High-Data-Rate Digital Subscriber Line)
Data rates
12.9 Mbps to 52.8 Mbps download
1.5 Mbps to 2.3 Mbps upload
Maximum distance 4,500 feet (1.35 km (0.83 mi)
Will require fiber to the neighborhood or fiber to the curb before it could be widely available

11. Digital Subscriber Line (DSL)
Advantages
Operates over ordinary two-wire phone lines
Service is always connected
Enables high bandwidth and push technologies
Faster than analog, ISDN or wireless access
Cost effective to implement, requiring no expensive infrastructure build-outs (Except to alleviate distance restrictions)
Utilizes existing copper wire infrastructure
Service is the same for small and large companies alike
Utilizes standardized premise products such as splitters, DSL modems and PC cards
Access to other broadband services such as ATM
Allows rapid file transfer and faster downloads
Allows constant access to and shared files

12. Digital Subscriber Line (DSL)
Disadvantages
Distance sensitive
Not yet available everywhere
Splitters require in-house installation

13. Cable Modem Technology
Cable Modem Termination System (CMTS)
Data Over Cable Service Interface Specifications (DOCSIS)
CMTS enables as many as 1,000 users to connect to the Internet through a single 6-MHz channel
Performance does not depend on distance

14. Cable Modem Technology
Disadvantages
Is not available everywhere
Subscriber density affects performance