PROSPECTIVITY OF ASYMMETRIC DIGITAL SUBSCRIBER LINE TECHNOLOGY Dr. Ayman Ahmed Abu Samra

Transcription

1 PROSPECTIVITY OF ASYMMETRIC DIGITAL SUBSCRIBER LINE TECHNOLOGY Dr. Ayman Ahmed Abu Samra ABSTRACT: Users of the Internet require more and more speed of data transfer to be able to deal easily with websites or any information they like, without delays. But the most challenging part in the way between far servers and the user, at his home, is still the link between subscriber and the network. This paper presents the current position of Asymmetric Digital Subscriber Line (A) technology among other x schemes and among all other solutions for homes and small business. The paper makes a comparison between all types of x. It compares the price of A service with competitive T1 service. It also compares the prices in Arab countries with the prices in Western countries. The paper studies the market of service all over the glob and in the Middle East. KEYWORDS: A, AM, broadband, bandwidth, distance, service, business, market 1. INTRODUCTION The "Internet universe" comprises an estimated 500 million users and new thousands discover the internet every day. This growing number of users, require more services and more applications. These applications contain more and more multimedia. All of the above needs more bandwidth. However, today, many users feel they are getting bandwidth less than what they should. Many solutions like Dialup modem, Line-modem, ISDN, Satellite, and x were deployed and implemented to satisfy the Internet users needs. Some solutions are expensive, others require new infrastructure, others do not offer the desired speed. This paper makes a comparison between all of x. It compares the price of A service with competitive T1 service. It also compares the prices in Arab countries with the prices in Western countries. The paper studies the market of service all over the glob and in the Middle East. It makes analysis and gives a recommendation that, A service is a good solution for small business, and home office broadband connection in our region and the Arab Internet Service Providers and the Arab Telecommunication companies should be interested to create a service market like that in other countries. Islamic University of Gaza, Palestine, Assistant Professor I-14

2 technology, which stands for Digital Subscriber Line will allow providers to offer service bundles that include voice, Internet, and local area network (LAN) services, all using existing phone lines. is expected to replace ISDN in many areas and to compete with the cable modem in bringing multimedia and 3-D to homes and small businesses. 2. WHAT IS AND A?, which stands for Digital Subscriber Line, provides high-speed Internet access using regular telephone lines. It has the ability to move data over the phone lines at speeds up to 6Mb/s or 140 times quicker than the fastest analog modems available today (56,000 bits per second). In addition to its very high speed, has many benefits over analog connections. Unlike dial-up connections that require analog modems to "dial-in" to the Internet Service Provider every time the user wants to obtain access to the Internet, connections are always on. That means no more logging on and off. Another benefit is the ability to use the telephone at the same time you are accessing the Internet. A is Asymmetric. It has faster downstream and slower upstream. A is a fastgrowing technology. Depending on the level of service offered by A provider, the A modem can download data at speeds ranging from 256 Kilobits per second up to 8 Megabits per second [1]. 3. A Applications Asymmetric Digital Subscriber Line (A) can supply the necessary bandwidth for applications such as fast access to the Internet, video conferencing, interactive multimedia, and Video-on-Demand. This technology is designed to solve the most severe bottleneck in the data access network between the Central Office and the customer. 4. HOW WORKES? Because analog transmission only uses a small portion of the available amount of information that could be transmitted over copper s, the maximum amount of data that you can receive using ordinary modems is about 56 Kbps (thousands of bits per second). (With ISDN, which one might think of as a limited precursor to, you can receive up to 128 Kbps.) The ability of a computer to receive information is constrained by the fact that the telephone company filters information that arrives as digital data, puts it into analog form for your telephone line, and requires your modem to change it back into digital. In other words, the analog transmission between your home or business and the phone company is a bandwidth bottleneck. Digital Subscriber Line is a technology that assumes digital data does not require change into analog form and back. Digital data is transmitted to your computer directly as digital data and this allows the phone company to use a much wider bandwidth for transmitting it to you. Meanwhile, if you choose, the signal can be separated so that some of the I-15

3 bandwidth is used to transmit an analog signal so that you can use your telephone and computer on the same line and at the same time. 5. A TECHNOLOGY Most of modem makers are using one of two modulation technologies, either Discrete Multitone Technology (DMT) or Carrierless Amplitude Modulation (CAP)[2]. Figure 1 CAP modulation CAP operates by dividing signals on the telephone line into three distinct bands (Figure 1). Voice conversations are carried in the 0-4 khz (kilohertz) band, as they are in all POTS circuits. The upstream channel (from the user back to the server) is carried in a band between khz. The downstream channel (from the server to the user) begins at 240 khz and goes up to a point that varies depending on a number of conditions (line length, line noise, number of users in a particular telephone company switch) but has a maximum of about 1.5 Mhz (megahertz). This system, with the three channels widely separated, minimizes the possibility of interference between the channels on one line, or between the signals on different lines. Figure 2 DMT modulation DMT also divides signals into separate channels, but doesn't use two fairly broad channels for upstream and downstream data. Instead, DMT divides the data into 247 separate channels (Fig 2), each 4 khz wide. One way to think about it is to imagine that the phone company divides your copper line into 247 different 4 khz lines and then attaches a modem to each one. You get the equivalent of 247 modems connected to your computer at once! Each channel is monitored and, if the quality is too impaired, the signal is shifted to another channel. This system constantly shifts signals between different channels, searching for the best channels for transmission and reception. In addition, some of the lower channels (those starting at about 8 khz, are used as bidirectional channels, for upstream and downstream I-16

4 information. Monitoring and sorting out the information on the bidirectional channels, and keeping up with the quality of all 247 channels, makes DMT more complex to implement than CAP, but gives it more flexibility on lines of differing quality. 6. A EQUIPMENT A uses two pieces of equipment (Figure 3), one on the customer end, and one at the Internet Service Provider, telephone company or other provider of services. At the customer's location there is a modem, which may also provide other services. The service provider has a Access Multiplexer, or AM to receive customer connections. Figure 3 A equipment Modem: It is the point where data from the user's computer or network is connected to the line. The transceiver can connect to a customer's equipment in several ways, though most residential installation uses USB or 10-baseT Ethernet connections. While most of the A modems sold by ISPs and telephone companies are simply transceivers, the devices used by businesses may combine network routers, network switches or other networking equipment in the same platform. AM: The AM at the access provider is the equipment that really allows to happen. A AM takes connections from many customers and aggregates them onto a single, high-capacity connection to the internet. AMs are generally flexible and able to support multiple types of in a single central office and different varieties of protocol and modulation -- both CAP and DMT, for example -- in the same type of. In addition, the AM may provide additional functions including routing or dynamic IP address assignment for the customers. The AM provides one of the main differences between user service through A and through cable modems. Because cable modem users generally share a network loop that runs through a neighborhood, additional users mean lowered performance in many instances. A provides a dedicated connection from each user back to the AM, meaning that users won't see a performance decrease as new users are added--until the total number of users begin to saturate the single, high-speed connection to the Internet. At that I-17

5 point, an upgrade by the service provider can provide additional performance for all the users connected to the AM. 7. TYPES OF Most technologies require that a signal splitter be installed at a home or business, requiring the expense of a phone company visit and installation. However, it is possible to manage the splitting remotely from the central office. This is known as splitterless, " Lite", "G.Lite. Table 1 shows the different types. Table 1: Summary of types Type I C G.Lite H S Description ISDN Digital Subscriber Line Consumer "Splitterless" High bit-rate Digital Subscriber Line Symmetric Data Rate Downstream; Upstream Distance Limit 128 Kbps 18,000 1 Mbps downstream; less upstream From Mbps to 6 Mbps, depending on the subscribed service Mbps duplex on two twisted-pair lines; Mbps duplex on three twisted-pair lines Mbps duplex (U.S. and Canada); Mbps (Europe) on a single duplex line downstream and upstream 18,000 18,000 12,000 12,000 Application Similar to the ISDN BRI service but data only (no voice on the same line) Splitterless home and small business service; similar to Lite The standard A; sacrifices speed for not having to install a splitter at the user's home or business T1/E1 service between server and phone company or within a company; WAN, LAN, server access Same as for H but requiring only one line of twisted-pair For small businesses, doesn't allow you to use the phone at the same time I-18

6 Table 1: (continued) A Asymmetric Digital Subscriber Line RA Rate- Adaptive V Very high Digital Subscriber Line to 6.1 Mbps downstream; 16 to 640 Kbps upstream Adapted to the line, 640 Kbps to 2.2 Mbps downstream; 272 Kbps to Mbps upstream 12.9 to 52.8 Mbps downstream; 1.5 to 2.3 Mbps upstream; 1.6 Mbps to 2.3 Mbps downstream Mbps at 18,000 feet; Mbps at 16,000 feet; Mpbs at 12,000 feet; Mbps at 9,000 feet Not provided 4,500 feet at Mbps; 3,000 feet at Mbps; 1,000 feet at Mbps Used for Internet and Web access, motion video, video on demand, remote LAN access Similar to A ATM networks; Fiber to the Neighborhood 8. ANALYSIS It is seen that each type of has its own characteristics and we can make some comments and conclusions. Very high bit-rate (V) -- This is a fast connection, but works only over a short distance. Symmetric (S) -- This connection, used mainly by small businesses, doesn't allow you to use the phone at the same time, but the speed of receiving and sending data is the same. Rate-Adaptive (RA) -- This is a variation of A, but the modem can adjust the speed of the connection, depending on the length and quality of the line. This type is very good for home and small businesses. Although subscribers needed to be located within 3.5km from the local exchange in order to be able to receive A. With rate adaptive, reach is extended to around 5.5km. RA has a high performance, secure access with download speeds of up to 512K and upstream performance of 256K. I-19

7 G.Lite which was developed by Compaq Computer Corp., Intel Corp., and Microsoft Corp. encountered major problems in field tests. Data-connection rates were hindered, due in part to the poor quality of copper wiring in most households. And signaling problems between the phone line and the modem forced carriers to install an expensive passive component called a microfilter in every phone jack[13]. A is the type that provide high data rate over a reasonable. It is the best choice, among all types, for small business and home offices. It does not need many devices and the devices that needed is not expensive[2], [5], [6]. A service is a good solution for our region because of the following reasons: Most companies in our region have workers less than 200 or 250 so they belong to small business according to UK or USA standards[14]. Many areas inside and surround cities in Arab countries do not have access to fiber networks and won't in the foreseeable future due to the tremendous capital cost of laying it out. But what about the price of the A service compared to the competitive service T1. Table 2 makes a comparison in the price between A and T1 technology. Table 2: a comparison of the price between A and T1 technology Technology Bandwidth Price/month Company Download / Upload A Mbps/384 $69.95 Covad [7] Kbps T1 384Kbps 1.5 Mbps / 384Kbps 1.5 Mbps $499 Covad [7] It is clear from table 2 that, A is more cost effective and it is not a problem that the upload stream less than the download stream as users need download stream much more. So it expected to be the choice of home users and small business managers without competition. Could ISDN service be competitive to A service? of course not because ISDN works like a dial up telephone, the WAN link is brought up just for a duration of the call, and it will be very expensive to hold the line on all the time. Another reason that, the Basic Rate Interface (BRI) ISDN has a data rate 128 Kbps. It is much less than A can provide. What about the prices in Arab and Western countries? And how the price affect the number of A subscribers? Table 3 makes a comparison for residential A service prices in some Arab countries and some Western countries. I-20

8 Table 3: a comparison for residential A service prices in some Arab and some western countries. Country Bandwidth Price/month Price/month Company in US $ USA 1.5Mbps $ Covad[7] UK 512Kbps Bulldog[10] Egypt 512Kbps LE Soficom[11] Saudi Arabia 256Kbps SR Sahara[12] As can be seen there is a wide gap between prices in Arab countries and Western countries. As 512Kbps connection is offered in the UK with 42% the price in Egypt. Or the subscriber in Saudi Arabia should pay, for much less data rate, nearly 5 times the price that the subscriber should pay in USA for a wider bandwidth. As it will be seen when studying the market the total number of A subscribers in Arab countries is still very small. It is a result of the high price. So we call on Telecommunication companies in Arab countries to offer the A service for the public with reasonable cost. 10. MARKET market is quickly gaining acceptance as a viable way to meet the ever-increasing demand foe more bandwidth. The fastest growth in this market has been in South and East Asia region, where the annual growth is 321.7% [3]. All over the globe, broadband subscribers now are 35.9 million and the top 10 countries (ASA, South Korea, Japan, Germany, China, Taiwan, Canada, France, Spain, Italy) account for 86% of them[3]. South Korea could be a good example for Arab countries where the communication infrastructure is still limited. This country continues to hold first place in global rankings of penetration of main phone lines. Over 28% of South Korea s main phone lines provide connection[3].the total subscribers in South Korea is 6.4 million[3]. In the Middle East market grew by 262% in 2002 led by the United Arab Emirates (708%) with a total subscribers of 16,180. Israel s growth is 270% with a total subscribers of 150,000 [3]. While Palestinian National Authority territory, until writing this paper, has no service. 11. FUTURE is expected to dominate the broadband access market. In Western Europe, for example, A accounted for 56 percent of broadband connections in technology is expected to reach a 63 % market share of the estimated 38 million European households expected to have a broadband connection by In the United States, some studies suggest that broadband penetration will reach 41 % by 2006[8]. I-21

9 12. CONCLUSION The total number of A service subscribers in Arab countries still very small because the service is still very limited or expensive. So we call on Telecommunication companies in Arab countries to offer the A service for the public with reasonable cost. A service is a good solution for small business, and home office broadband connection in our region. Arab Internet Service Providers and Telecommunication companies should be interested to create a service market like that in other countries 13. REFERENCES [1] Website: [2] Website: [3] Website: [4] Website: [5] Website: [6] Website: [7] [8] [10] Website: www. Bulldogdsl.com [11] Website: [12] Website: [13] Website: [14] Muhammed Ibrahim Migdad, Performance Analysis of Small-Scale Industries, Submission for the degree of Philosophy Development & Project Planning Center, University of Bradford, 1999, pp 76 I-22