Broadband is defined as sustained rates above 128Kbps. It is a type of data transmission in which a single medium can carry several signals at once. Usually, it transmits by using frequency division multiplexing.
Similar to a telephone company's central office (CO), the headend is where the signals are processed and formatted for transmission onto the distribution network.
The distribution network is the trunk or backbone made of fiber and coaxial cabling that brings the signal to the subscriber drop.
Hybrid fiber coax (HFC) is a combination of fiber optics and coaxial cable. Each channel gets a 6MHz channel in the 50 to 860MHz range for downstream and in the 5 to 42MHz range for upstream.
DOCSIS (Data Over Cable Service Interface Specification) defines interface standards for cable modems and supporting equipment. Version 1.0 was the first standard, version 1.1 added VoIP, and version 2.0 should allow for a 30Mbps upstream path.
The cable modem termination system (CMTS) is a system of devices located in the headend that allows cable providers to offer high-speed Internet access.
With spectrum reuse, a cable company can place signals on a wire that it otherwise could not use because the signal is contained in the wire.
PPP over Asynchronous Transfer Mode (ATM) (PPPoA) is a routed solution. It requires no host-based software as with PPP over Ethernet (PPPoE). The customer premises equipment (CPE) routes packets to the aggregation router.
With PPPoE (RFC 2516), Ethernet frames are bridged over ATM as with RFC 1483 encapsulating PPP. The PPP session is established between the end user and the router.
DSL types are as follows:
Asymmetric DSL (ADSL) Designed for residential use, the downstream is faster than the upstream. It is rated for distances up to 18,000 feet.
Symmetric DSL (SDSL) Designed for business, the speed is the same in both directions. Distances can be up to 12,000 feet.
G.SHDSL Developed by the International Telecommunications Union (ITU), it is the first DSL technology developed as an international standard. It supports longer distances (28,000 feet) and is predicted to be the most adopted standard in the future.
ISDN DSL (IDSL) ISDL provides DSL over ISDN lines and its speed is similar to that of ISDN. Benefits of switching to IDSL are the always-on connection, flat-rate billing, and no call setup. Distances can be up to 18,000 feet.
Very high data rate DSL (VDSL) VDSL transmits data in the 13 Mbps to 55 Mbps range over short distances, usually between 1,000 and 4,500 feet.
High data rate DSL (HDSL) HDSL is used as a replacement for T1 or E1 services, and is limited to 12,000 feet.
