In broadband technology, which is the cheapest and most easily applied is ADSL (Asymmetric Digital Subscriber Line). ADSL rapidly sending signals via a regular phone connection with a speed of 512 kbps (upstream) and 8 Mbps (downstream). ADSL is one of xDSL family together with HDSL, SHDSL, SSDSL, VDSL and others. Telephone lines xDSL family of office (outposts) phone into homes using a frequency of 4 kHz for voice analog signal delivery. DSL uses ordinary telephone lines to send digital signals high speed. On DSL There are different types of DSL. For example Asymetric DSL (ADSL) for the purpose of fast internet access, for the companies, there is High speed DSL (HDSL), Single Pair HDSL (SHDSL), synchonized symetric DSL (SSDSL) and a combination of optical fiber Very High DSL (VDSL). To condense these terms emua known as xDSL. ISDN (Integrated Services Digital Network), which has two types, namely 1B (64 kbps) and 2B (128 kbps) is also one of the xDSL family. The American term for ISDN known as IDSL (Intermediate DSL). The description of xDSL can be seen in Table 1 below.
ADSL history
Research on how high-speed data transfer using the telephone line has long been done by experts. While research technology is ADSL (Asymmetric Digital Subscriber Line) was first started in 1989 were carried out by the company Bell Core. Then in early 1990 the various trials conducted in the United States, Europe and Japan. At that time the ADSL technology applications is only limited to the VOD (Video On Demand = witnessing an event (TV programs, video films and the like) in accordance with our wishes only). Because at high speed to access VOD pen downloading (from the server to the user) is required, whereas access speed uploader's (from user to server) is not so emphasized. In other words, the access speeds to download and upload on VOD different (asymmetric). But at that time the ADSL technology developed by Bell Core is not so progressed. Can be said to suffer from congestion. This is due to several reasons, among others: the current server operating costs are very expensive, ADSL technology for VOD itself is still immature and has not received a warm welcome from customers. In 1995, the Internet is growing so rapidly. The need for high-speed access at a low cost is one of the conditions for the advancement of the Internet itself in the future. Then research on ADSL technology re-performed by experts.
ADSL Modem
ADSL itself is actually just a MODEM that we use to access the Internet with "dial up connection" and not a connection system / network. ADSL technology is a technology MODEM. The difference between conventional ADSL modem with modem easiest we have encountered is the speed of transferring (uploading / downloading) data. Although both use a common phone lines as lines of communication, the speed of the ADSL modem ranges from 1.5 Mbps to 9 Mbps. A striking difference between the two speeds (conventional modem and ADSL) dikerenakan differences in the use of frequencies to send signals / data. In the conventional modem to use frequencies below 4 kHz, while the ADSL modem is used frequencies above 4 kHz. ADSL modems generally use frequencies between 34 kHz to 1104 kHz (see Figure 2). This is the main cause of the difference in the speed of transferring signals / data between a conventional modem and ADSL modem
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