Broadband Internet Access Solutions Lecture 12. Definition Broadband can be defined as transferring multiple channels of (data) over a single link. A.

Broadband Internet Access Solutions

Lecture 12

Definition Broadband can be defined as

transferring multiple channels of (data) over a single link. A form of multiplexing

In contrast baseband transmission only allows a single signal at a time on any link.

Possible Broadband Selections

Always on? Shared >500Kb

DSL avail?

Service guaranteed

Satellite or ISDN

DSL via Modem

Cable avail?

Cable

ISDNLeased Line

DSL

ISDN available?

ISDN

No

Yes Yes YesYes

Yes

Yes

Yes

No No No No No

No

Location/Availability 97% of UK population has access

to ADSL (BT claim) Increasing to 99.6% Cable has limited availability Leased Line cost can be excessive Satellite has severe cost /upload

problems

Cable Utilise Fibre Optic Technology Lower Contention Costs are lower than DSL Geographic problems –limited access Offers a stable and reliable access

technology Down traffic to consumer easier than

getting upstream traffic from consumer

Cable broadband

DSL – Digital Subscriber Lines DSL offers the ability to access

Broadband over existing copper cables

DSL uses the unused bandwidth on current telephone lines

Up to 2MHz is available on current telephone lines – up to 3Km distance

DSL 2 MHz minus the telephone

bandwidth leaves 1.5 MHz for data. Most current solutions offer up to

2Mbps downlink with 256 kbps uplink.

Contention Ratio is a problem – 10:1 is good 20:1 is adequate and up to 50:1 is acceptable.

DSL

Exchange

Up to 3Km

Telephone

DSL or ADSL Modem

DSL technology uses the same physical cable for telephone and data transmission

ADSL or SDSL?• Asymmetric or symmetric?• ADSL

• allows voice and data on the cable at the same time• Different upload and download speeds• 256kbps, 512kbps, 1024 kbps (= 1 Mbps), and 2

Mbps kbps. (download)• 256 kbps (upload)

• SDSL• No simultaneous voice use• Same upload and download speed• 256kbps, 512kbps, 1024 kbps, 2048 kbps (both

ways)• Up to 8 Mbps available soon

Useful information http://www.adslguide.org.uk/

News about broadband http://www.bt.com/broadband/

BT wholesale broadband http://www.ispa.org.uk/

Internet service providers association

ISDN Fully digital, integrates voice and

data over a common digital technology.

Requires an ISDN line and a terminal adapter (TA)

ISDN2 – or basic rate interface offers 2 x 64kbits for data or voice 1 x D channel for control

Leased Line Traditional route for Business to

have always-on Internet connectivity

Leased lines are expensive Contention ratio is of course 1:1 This is a major attraction over DSL System set up is a non-trivial task

Leased Line Designing using leased line

techniques requires skills in WAN technologies

Leased lines can either use Digital Signalling level channels (DSO) Synchronous Optical Networking(Sonet)

This offers a range of speed from 64 kbits/sec Up to 10 Gbits/sec

Leased Line rates

Line Type Capacity

DS0 64 Kbits/sec

DS1 1.544 Mbits/sec

DS2 6.213 Mbits/sec

DS3 44.736 Mbits/sec

DS4 274.176 Mbits/sec

OC-1 51.84 Mbits/sec

OC-3 274.176 Mbits/sec

OC-12 622.08 Mbits/sec

OC-48 2,488.32 Mbits/sec

OC-192 10GBits/sec

Satellite Location is a major problem for a

broadband connection Need to be near an exchange

Satellite theoretically removes the need for any physical cabling

Customer Premises Satellite Interface (CPSI) is a new open standard which avoids buying a unique decoder from each supplier.

Satellite access

Al-Chalabi and Stewart (Chaltel Ltd) -2001

Two-way Satellite

• Typical speeds – 1Mbps download 256k upload

• Higher speeds available

Satellite footprint

One-way satellite Current system require two

connections A coaxial feed from the receiver disk A telephone connection

The use of a tunnelling protocol allows the phone link to identify the consumers request to the ground station and hence onto the satellite downlink.

Satellite Latency

Latency on such a system is very high 0.25 seconds for the 35,000 km link

to the satellite 56 kbps maximum on the phone link.

basic browsing not ideal for serious users of multimedia.

Questions left unanswered Broadband – what technology will

be used in the future? Unbundling the local loop! Will this

enhance the adoption of DSL technology

What is the impact on all this for Multimedia?

Conclusions Broadband is needed for more

utilisation of multimedia on the Internet. Consumers or Business influence on the

technology adoption for broadband very limited.

It is probable that it will be Broadband Service Providers and the Infrastructure Providers that will have the most influence.