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DIGITAL
SUBSCRIBER LINE (DSL) 2
1.1 Introduction 2
1.1.1 ADSL (as an example of a
digital subscriber line) 2
1.2 Equipment Requirements for DSL 3
1.3 Advantages and Disadvantages of DSL 3
1.3.1 Advantages: 3
1.3.2 Disadvantages: 4
1.4 Prices from various providers of DSL 4
1.4.1 Lloyd Group xDSL PRICES (MVL:
Multiple virtual Lines) 4
1.4.2 Iprolink: INTERNET PRO-LINK
LIMITED. 4
1.4.3 Saturn ISP High Speed Plan 5
1.4.4 Other Saturn options 5
1.5 Comparisons with other technologies (offering similar
speeds) 6
1.5.1 ISDN 6
1.5.2 Cable Modems 6
1.5.3 Wireless Data Communication 6
1.6 Glossary of terms 7
1.6.1 DSL modem 7
1.6.2 Network Card (10baseT) 7
1.7 Bibliography 8
1.7.1 Web Sites: 8
1.7.2 Search Engines: 8
DSL (Digital Subscriber Line) is a technology for bringing high-bandwidth information to homes and small businesses over ordinary copper telephone lines. There are different variations of DSL, such as ADSL, HDSL, and RADSL. Assuming that the location of the line to be used for DSL is close enough to the Telephone Company the service will be considerably rapid. More typically, individual connections will provide from 1.5 MBps to 512 Kbps downstream and about 128 Kbps upstream. A DSL line can carry both data and voice signals and the data part of the line is continuously connected. DSL installations began in 1998 and will continue at a greatly increased pace during 1999 in a number of communities in the U.S. and elsewhere. Within a few years, DSL is expected to replace IDSN in many areas and to compete with the cable modem in bringing multimedia and 3-D graphics/ videos to homes and small businesses.
Phone services connect your home or small business to a telephone company office over copper wires that are wound around each other and called twisted pair. Traditional phone service was created to let you exchange voice information with other phone users and the type of signal used for this kind of transmission is called an analog signal. An input device such as a phone set takes an acoustic signal (which is a natural analog signal) and converts it into an electrical equivalent in terms of volume (signal amplitude) and pitch (frequency of wave change). The telephone company's signalling is already set up for this analog wave transmission, it's easier for it to use that as the way to get information back and forth between your telephone and the telephone company. That's why your computer has to have a modem so that it can ‘translate’ the analog signal and turn its values into the string of 0 and 1 values that is called digital information.
There is a technology called ADSL (Asymmetric Digital Subscriber Line) which is a form of DSL that Telecom NZ uses. ADSL is called "asymmetric" because most of its two-way bandwidth is devoted to the downstream direction[1], sending data to the user Only a small portion of bandwidth is available for upstream or user-interaction messages. However, most Internet and especially graphics- or multi-media intensive Web data need lots of downstream bandwidth, but user requests and responses are small and require little upstream bandwidth. Using ADSL, up to 6.0 megabits per second of data can be downloaded and about 600 Kbps upstream. In comparison with a 56K modem, the speed of ADSL is at least 10 times faster (at its slowest). The ADSL technology can be used in conjunction with a phone, as a set-aside amount of the line’s bandwidth is for phone use. (This is why it is called Assymetric)
DSL is peculiar in the way it is used, applying data communication to twisted pair copper cable. Twisted pair copper is the current standard that all phone lines are connected to. So the cost of installation to telephone companies is greatly reduced, compared to technology such as IDSN[2]. However repeaters are used a lot to maintain data speed over distances, especially with ADSL, which decreases in speed over short geographical distances, e.g; 5 kilometres.
Users, either at home or in business have to get new hardware installed in their computer (provided they have one) to communicate via the ISP (or Telephone Company). A network card is installed and a DSL modem is needed, which can be either purchased or rented from the ISP. Companies such as Motorola and Ericsson manufacture DSL modems. (See glossary). The modem used is similar to a network hub, which limits the data rate on the ‘computer side’.
Fortunately software is not needed for ADSL and it can be configured straight from the operating system (e.g; Windows 98 or NT). Although most operating systems will require drivers for the modem and network card, but as DSL is becoming more popular, newer operating systems will have the drivers loaded on them already.
As DSL uses existing phone lines (in most locations), it is an inexpensive set-up for telecommunication companies. The speed offered for customers means that audio and video files can be played from their Internet locations, without minimal fuss. In comparison to a 56K modem video files can be opened in larger screens with better quality. Video-conferencing can be used properly. Instead of worrying about intricate details like dialing a connection to the ISP every time in frustration, DSL is a dedicated line, which means it is constantly connected to the Internet. No more hassles or worries about the connection being lost halfway through a massive download .
The technology is quite new (in New Zealand that is), so as always with new technologies, DSL is still quite costly for most people in business and at home. Another problem associated with this technology is the massive amounts of data flow through ISP’s, as the DSL becomes increasingly popular.
MVL 128K Direct Connect Cost per Month Install Fee applies.
0 900.00
MVL 256K Direct Connection Cost per Month Install Fee applies.
0 1,800.00
MVL 512K Direct Connection Cost per Month Install Fee applies.
0 2,700.00
MVL 768K Direct Connection Cost per Month Install Fee applies.
0 3,600.00
MVL 768K Direct Connection Cost per Month Install Fee applies. MVL 768k connection delivered over standard copper the same as ADSL but more reliable.
Dedicated Dial-in access Cost per Month Install Fee applies. 100.00 exc. GST
Digital Leased Circuit (DDS-Digital Data Service).
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DDS Installation |
$400.00 |
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Monthly fee DDS (per 64kbps) |
$ 95.00 |
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Router Installation |
$ 500.00 |
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Monthly fee |
$ 150.00 |
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Bulk Data
charges |
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Inside Internet Pro-Link NZ Limited |
FREE |
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Inside New
Zealand |
$ 0.15 /MB |
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International
off-peak (11pm-7am) |
$ 0.65 /MB |
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International
peak (7am-11pm) |
$ 1.45 /MB |
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Saturn's standard high speed plan |
$114.95 |
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512kbps downstream/128kbps upstream speed |
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$175 worth of monthly traffic |
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The plan is significantly cheaper if a customer also takes Saturn telephone or Cable TV services (see below).
Traffic Charges
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International traffic charge |
$0.35 /MB |
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National traffic charge |
$0.035 /MB |
· After the monthly traffic allowance is exceeded, the user is charged per Megabyte at the above rates
· Internet traffic is classed as national or international by the IP address e.g; www.yahoo.com would be classed as international, because it is an American IP address, but www.accessnz.co.nz would be considered as national.
· Speed Upgrade: The service can be upgraded to 2 Mbps downstream/256kbps upstream speed for an additional $30 per month.
· Monthly traffic upgrade: You can upgrade to $350 worth of traffic for an additional $25 a month.
A positive point to note about Saturn’s cable service is the fact that Saturn TV users can get cheaper Internet: only recommended for the serious channel/ Internet surfers.
Installation
A standard connection to Saturn's High Speed service is $350. This includes the call-out charge for a technician to configure the PC, an Ethernet/ Network card (as mentioned above) and installation of the cable modem itself. Installed cable modems are leased from the company.
The low profile cable modem can be wall or desk mounted and supports Windows, Mac, and UNIX operating systems and workstations. High Speed - 64 QAM demodulation provides 30 Mbps of downstream bandwidth in a single 6 MHZ channel for efficient use of the RF spectrum. This is twice the frequency of standard UTP and STP’s (Twisted Pair copper wire)
ISDN is a telephone company technology that provides digital service typically in increments of 64Kbps channels. ISDN has been around for many years, but it's popularity is now only beginning to increase due to the limitations of analog modems and the rise of Internet usage. ISDN requires the phone company to install services within their phone switches to support this digitally switched connection service. This service initially got off to a slow start and was stalled by high costs, lack of standards and low acceptance rate by consumers.
Cable modems are devices that attach to the cable TV network connection in a home. Along with xDSL, it is still in the early stages of development. There are a number of challenges faced by this industry, including return path capabilities, customer service issues and standards. However, potential bandwidth estimates range upwards of 30Mbps from the service provider to subscriber. Cable networks are inherently different in design than telephone networks. Cable networks are broadcast oriented, with each subscriber in an area receiving the same signals as all others in that area. xDSL is circuit oriented so that each connection is independent of all others. Cable networks are inherently hierarchical in nature and thus require two paths, one for downstream and one for upstream. This requires either a second cable plant for upstream or a second frequency band allocated onto the existing system.
There are a number of different wireless schemes proposed, planned and implemented throughout the world. Wireless access technology takes shape in a number of different forms such as via a satellite TV service provider or a cellular phone network. Wireless systems can provide ubiquitous access to a large number of subscribers in a relatively large area. Bandwidth can range from a few kilobits a second to many megabits and be either symmetrical or asymmetrical. Like all other technologies, there can be deployment issues which may include spectrum licensing, interference and noise problems, or bandwidth limitations.
A modem that connects through a digital subscriber line to a computer. It sends digital messages and doesn’t have to demodulate any analog signals like the slower 33K and 56K modems. This modem looks similar to a network hub.
Device that connects a computer to a network of other computers through a hub ( or in this case through a DSL modem
ADSL - (Asymmetric Digital Subscriber Line) is the most popular form of DSL technology.
ADSL Lite - A lower data rate version of Asymmetric Digital Subscriber Line (ADSL)
CDSL - Consumer Digital Subscriber Line (CDSL) is a proprietary technology trademarked by Rockwell International.
EtherLoop - EtherLoop is currently a proprietary technology from Nortel, short for Ethernet Local Loop.
HDSL - High Bit-rate Digital Subscriber Line (HDSL) is generally used as a substitute for T1/E1.
IDSL - ISDN based DSL developed originally by Ascend Communications.
RADSL - Rate Adaptive Digital Subscriber Line (RADSL) is any rate adaptive DSL modem, but may specifically refer to a proprietary modulation standard designed by Globespan Semiconductor.
SDSL - Symmetric Digital Subscriber Line (SDSL) is a 2-wire implementation of (HDSL).
VDSL - Very High Bit-rate Digital Subscriber Line (VDSL) is proposed for shorter local loops, perhaps up to 3000 ft.
These variations of DSL courtesy of a web-site: www.dsl.com
www.dsl.com DSL forum page
www.adsl.com Another forum, mostly dedicated to ADSL
www.zdnet.com Huge amounts of information on data communications
www.saturn.co.nz Saturn Communiactions
www.lloyd.co.nz Lloyd Group communications consultants and providers
www.clear.net.nz CLEAR Communications LTD
www.telecom.co.nz Telecom NZ