Connection Speed, Bandwidth and Download Time

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"Bandwidth (the width of a band of electromagnetic frequencies) is used to mean (1) how fast data flows on a given transmission path, and (2), somewhat more technically, the width of the range of frequencies that an electronic signal occupies on a given transmission medium. Any digital or analog signal has a bandwidth" (What Is?, 2002). In digital systems, bandwidth is expressed as data speed in kilo/bits per second (k/bps).

Long before the Web was invented, connections to the Internet were made using modems . Modems began with download speeds of 2.4 to 9.6 kbps, then 14.4, 28.8, 33.6 and, finally somewhere around 56-58 kbps. Thus, a modem that works at 57,600 bps has twice the bandwidth of a modem that works at 28,800 bps. They are now essentially as fast as telephone line technology will allow them to be. The Web however, has become a platform for a wide variety of multimedia applications such as video on demand, downloadable music files and rich graphics. In order to download these applications as quickly as users demand, requires speeds that are beyond the physical capabilities of any modem. The Web of today requires broadband.

"Broadband is a high-capacity communications pipeline capable of delivering simultaneously a range of voice, video and data services to the home in a truly interactive reliable manner" (Broadband Daily, 2002). "Broadband isn't a single technology. Rather, it's the name for any form of high-speed access" (.Net, 2002c). Typically broadband access is 10 times faster than modem dial-up and is permanently connected.

Broadband is available as either Asynchronous Digital Subscriber Line (ADSL), cable or satellite . The most popular option is ADSL, which uses existing telephone lines to provide access at 512Kbps. Cable is similar, except that connections are made via fibre-optic cables underground. Although broadband speeds are much faster than those for modems, ADSL and cable connections are "contended", meaning than other people in close geographical proximity can share the same bandwidth. "The average contention ratio for these services is expected to be 50:1, or 50 users sharing the same bandwidth" (.net, 2002c). Another problem is that no matter how fast the connection to a users computer is, if any point between the user and a website is running slowly, the time taken to view a web page will still be slow because bandwidth has no influence on external factors.

Until recently, due to high cost, broadband was a luxury mainly confined to business users but its availability is increasing. "For the first time yet, broadband connections have accounted for more than half of all Internet connections in the US, according to the latest State of the Web Report from Nielsen/Netratings" (.net, 2002a) and "South Korea is massively ahead of the UK" also with over 50 per cent of connections available via broadband (Mullen, A. as cited by Oliver, 2002. p33).

In the UK however, the rollout of broadband has been much slower. British Telecom has been at the mercy of scathing reports over its more than slow handling of "local-loop unbundling", which will allow competitors to provide their own broadband access. ADSL and cable modems are being made available in densely populated areas first, and then will spread to more remote parts of the country over the next few years. ADSL will reach 50 per cent of the population by the end of this year, which means it will not be available in most of Scotland, Northern Ireland or Wales. Even in ADSL-enabled areas, access will only be available to users who live within 3.5km of the exchange. At the time of writing, The Register reported that "BT Wholesale has announced the broadband registration trigger levels for a further 169 exchanges". (Richardson, T. 2002).

With regard to broadband access in the UK, it appears that it will arrive, but for the majority of users, not anytime soon. Therefore, websites still have to be designed with speed as the number one consideration. My view however, is that because the US market is overcoming the bandwidth problem before the rest of the world, we will see an American drive towards more multimedia-rich web-based applications such as video on demand which can be downloaded with ease across the Atlantic. For a significant proportion of the world however, such US-driven websites will be even slower to access than those that are currently online, only adding to user frustration. It is critical therefore that web designers take heed of the advice from the leaders in the field of usability to ensure the advances in the US don't have detrimental effects on web usability for the rest of the world.

According to Nielsen, a web page should not exceed 3KB in size if it is to download in one second, the "required response time for hypertext navigation". The importance of creating pages with fast download times cannot be over emphasized. Even mid-band connection speeds provided by leased lines are "insufficient for decent response times". "The web requires at least T-1 speed to work well." (Nielsen, 1997).

According to studies cited by Nielsen (1997), 0.1 second "is about the limit for having the user feel that the system is reacting instantaneously, meaning that no special feedback is necessary except to display the result." 1.0 second "is about the limit for the user's flow of thought to stay uninterrupted, even though the user will notice the delay" and 10 seconds "is about the limit for keeping the user's attention focused on the dialogue." Waits longer than 10 seconds will result in users performing other tasks as they wait for their computers to finish processing.


Publication Date: Friday 6th June, 2003
Author: Ukwdc View profile

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