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Full-duplex ADSL communication is usually achieved on a wire pair by either frequency-division duplex (FDD), echo-cancelling duplex (ECD), or time-division duplex (TDD). FDD uses two separate frequency bands, referred to as the upstream and downstream bands. The upstream band is used for communication from the end user to the telephone central ...
Upstream speeds are also important to users of peer-to-peer software. Residential services often have higher downstream rates than upstream, while business services are often symmetric. ADSL and cable modems are asymmetric , with the upstream data rate much lower than that of its downstream.
Digital subscriber line (DSL; originally digital subscriber loop) is a family of technologies that are used to transmit digital data over telephone lines. [1] In telecommunications marketing, the term DSL is widely understood to mean asymmetric digital subscriber line (ADSL), the most commonly installed DSL technology, for Internet access.
ITU G.992.3 is an ITU (International Telecommunication Union) standard, also referred to as ADSL2 or G.dmt.bis.It optionally extends the capability of basic ADSL in data rates to 12 Mbit/s downstream and, depending on Annex version, up to 3.5 Mbit/s upstream (with a mandatory capability of ADSL2 transceivers of 8 Mbit/s downstream and 800 kbit/s upstream). [1]
In order to combine voice telephone service with downstream and upstream ADSL signals the bandwidth is split into discrete parts using frequency-division multiplexing (FDM). In this case: 0–4 kHz is for voice, 26–138 kHz is the upstream band and 138–1104 kHz is the downstream band.
G.992.5 (also referred to as ADSL2+, G.dmt.bis+, and G.adslplus) [1] is an ITU-T standard for asymmetric digital subscriber line (ADSL) broadband Internet access. The standard has a maximum theoretical downstream sync speed of 24 megabits per second (Mbit/s). Utilizing G.992.5 Annex M upstream sync speeds of 3.3 Mbit/s can be achieved.
Another factor reducing throughput is deliberate policy decisions made by Internet service providers that are made for contractual, risk management, aggregation saturation, or marketing reasons. Examples are rate limiting , bandwidth throttling , and the assignment of IP addresses to groups.
A symmetric digital subscriber line (SDSL) is a digital subscriber line (DSL) that transmits digital data over the copper wires of the telephone network, where the bandwidth in the downstream direction, from the network to the subscriber, is identical to the bandwidth in the upstream direction, from the subscriber to the network.