broadband strategies handbook.pdf - Khazar University

challenges by extending distances and reducing interference, while increasingbit rates up to 100 Mbit/s for distances less than 300 meters.In Israel, incumbent operator Bezeq has been rolling out VDSL2 as partof its NGN deployment, with coverage to around half the households by theend of 2010 (Bezeq Group 2011). It was advertising bandwidth of 100 Mbit/sfor DSL connections on its website in March 2011. Bezeq plans to offer up to200 Mbit/s through VDSL bonding, which uses two copper pairs per subscriber.23While DSL technology has evolved with ever-increasing data rates andremains the most popular wireline broadband technology in terms of subscriptions,its biggest constraint is bandwidth deterioration as the distancefrom the exchange increases, as shown in figure 5.9.Cable ModemCable modems provide subscribers with access to broadband services overcable television (CATV) networks. CableLabs developed standards for cablemodem technology in the late 1990s. 24 The technical guidelines are calledData over Cable Service Interface Specification (DOCSIS). The DOCSISguidelines have been progressively enhanced in terms of functionality (forexample, support for IPv6) and speed (figure 5.10). The latest version is 3.0,with a slightly different European implementation (EuroDOCSIS). DOCSIShas been approved as an ITU recommendation. 25The first DOCSIS specification was version 1.0, issued in March 1997,which uses the subscriber’s copper wire telephone line for upstream traffic.Beginning in April 1999 with the DOCSIS 1.1 revision, cable operatorsFigure 5.9 Speed of DSL and Distance from ExchangeMbit/s25201510theoretical maxspeed at 2 km iscirca 14Mbit/s500 1 2 3 4 5distance from exchange (km)ADSL2+ADSL1Source: Ofcom.Note: Theoretical maximum speed at 2 kilometers is about 14 Mbit/s.224 Broadband Strategies Handbook