ADSL (Asymmetric Digital Subscriber Line) is a highly popularized form of a DSL technology. As the name implies, ADSL is ‘asymmetric’ in terms of upload and download speeds it provides. This has been one of the key reasons for its popularity since ADSL provides higher downstream frequency bandwidth (138 kHz – ۱۱۰۴ kHz) compared to upstream frequency bandwidth (26.075 kHz – ۱۳۷٫۸۲۵ kHz).
Generally, ADSL is provided using the same infrastructure used for voice connectivity; thus, it requires an ADSL splitter for discriminating the two voice and data bandwidths. The splitter is usually connected at the customer premises, and the split data signals are fed into an ADSL modem or a router, for the purpose of modulation and demodulation. The main drawback of the ADSL is the attenuation of signals over extended distances.
ADSL can generally be distributed over short distances from the last mile telephone exchange; this typically varies in the range of 4 to 5km. For the exchange side, it terminates with a digital subscriber line access multiplexer (DSLAM), which is another kind of frequency splitter that separates the voice band signal from the telephony network. Then, the data is routed over the telephone company’s data network, and it finally reaches the data backbone based Internet Protocol.
ADSL is a full duplex data communication solution and is usually deployed using a pair of wires (Copper), based on either frequency division duplex (FDD), time-division duplex (TDD), or echo-cancelling duplex (ECD) technologies. There are several types of ADSL technologies available today, such as ADSL 2 and ADSL 2+. These types have evolved with higher data rates. ADSL2 has speeds of up to 12,000kbps and ADSL 2+ with speeds of up to 24,000 kbps.
Broadband was initially introduced as a differentiation from dial-up service and offers greater ‘bandwidth’ than the older narrowband technologies. It can be either in the format of DSL or Cable. The International Telecommunications Union (ITU) has defined broadband as a connection that provides rates higher than the standard rate of 1.5Mbps.
Moreover, broadband transmission technologies were intended to utilize the vast bandwidth offered by fiber optics. Broadband provides access to the highest quality Internet services for streaming media, gaming, VoIP (Internet phone), and interactive services. Broadband connections ensure the instant access to range of online information, email, instant messaging, and certain other communications services which are available over the internet. Many of these current and newly developing services require to transfer much greater amounts of data that are not feasible with any dial up connection services.
Today, many different forms of digital subscriber line (DSL) services are available such as SDSL (symmetric Digital Subscriber Line), HDSL (High-bit-rate Digital Subscriber Line). The basis of all of these technologies ensures that digital information is sent over high-bandwidth channels.
What is the difference between ADSL and Broadband?
• ADSL is a type of broadband solution; thus both have similar characteristics in terms of the network architecture.
• ADSL connections are best applied in situations where there is a very high demand for downstream, whereas broadband can provide solutions to a variety of demands independent from the bandwidth limitations for upstream and downstream.
• Broadband is diversified in many transmission technologies such as cable, DSL, Mobile/wireless, but ADSL uses only DSL technology that runs on copper cables.
• ADSL may not be available in all areas, because of the distance limitation factor from the last mile exchange, but Broadband provides services using many other types of technology such as cable, satellite, which can cater irrespective of the distance limitations.