Broadband Today a staff Report to
Download 276.36 Kb.
|
- Navigate this page:
- TABLE 2: DSL Technologies
*kbps (kilobits per second) & Mbps (Megabits per second) Source: http://www.cablemodems.com/whatis.html Not Without ProblemsDespite the expanded capacity, technical problems for providing advanced services over cable HFC networks remain. Return path transmission interference results from noise generated at the connection points between the trunk-distribution line connection and the distribution line-drop connections. In addition, a cable network is a shared medium, wherein subscribers in a particular area share capacity. As a result, data transmissions are potentially more vulnerable to interference and degradation caused by the actions of any individual subscriber's equipment. Further, as previously mentioned, transmission speeds degrade as more subscribers are online. C. Telephone Company Broadband-- Digital Subscriber Lines (xDSL)22 Digital Subscriber Line (DSL)—sometimes referred to as xDSL because of the variety of DSL technologies and implementations—is the telecommunications carriers’ version of broadband access. DSL is quickly emerging as an economic solution to provide high speed Internet access to end users—both residential and small to midsized businesses. With DSL, the average analog connection of 56.6 kbps can be upgraded to 1.5 Mbps or higher.23 DSL technology upgrades the performance of the standard twisted pair (the copper line connecting most homes and businesses) to carry high capacity data transmission. The technology expands the amount of frequency used over the copper line, whereby the line’s higher frequencies are used to transmit the data and the lower frequencies are free to transmit voice or fax transmissions.24 Thus, DSL is able to function on a line simultaneously with standard voice and fax services and avoids the installation of a new separate line. Because the technology works over the existing telephone plant, DSL is significantly less expensive to deploy on a broad scale than other approaches, such as new fiber or cable construction.25 In addition, the cost structure of DSL enables providers to serve both residential and business customers economically.26 Since phone lines are nearly ubiquitous in the United States, DSL providers are not limited to one market segment (e.g. business or residential) as are some other broadband access providers.27 Despite the promise of DSL to deliver broadband access to businesses and consumers, there are several technical issues with regard to the widespread implementation of DSL.28 One of the primary inhibitors is signal attenuation, also known as the distance limitation. Attenuation describes the dissipation of signal strength as it travels over the copper line. DSL utilizes a higher frequency that is more susceptible to attenuation than ordinary voice transmission.29 Consequently, the various DSL technologies detailed below have distance limitations ranging from 4,000 to 18,000 feet from the telephone company’s central office.30 “These limitations may ease as technologies improve, but as a practical matter, DSL is currently limited to locations within a three-mile maximum loop from the central office.”31 Although there are several versions of DSL service, there are two general categories, symmetrical and asymmetrical (see Table 2). Symmetrical versions offer the same data rates upstream and downstream and are best suited for business applications such as video-conferencing.32 Asymmetrical versions offer different data rates upstream and downstream and are ideal for residential users who receive a lot of data but do not originate or send much (e.g. Internet surfers).33 One such version is called asymmetric digital subscriber line (ADSL). As ADSL does not interfere with the basic voice service, the user can simultaneously browse the Internet or watch a movie while talking on the telephone.34 According to some reports, ADSL provides a competitive advantage over cable modem Internet access in the following areas:35
TABLE 2: DSL Technologies
Directory: pub -> Bureaus pub -> Preparation of Papers for ieee transactions on medical imaging pub -> Forthcoming meetings and conferences pub -> Asilomar Conference on Circuits, Systems & Computers, Pacific Grove, ca, November 1978, pp. 55 58 pub -> Forthcoming meetings and conferences pub -> Harmonised compatibility and sharing conditions for video pmse in the 7 9 ghz frequency band, taking into account radar use Bureaus -> I. statutory framework Bureaus -> Before the Federal Communications Commission Bureaus -> July 21, 2000 fcc filings july 13 In the Matter of Numbering Resource Optimization Download 276.36 Kb. Share with your friends:
| |||||||||||||||||||||||||||||||||||