PDF of this tutorialThe copper local loop is going digital. The local loop, the twisted-pair network that delivers telephony services to homes and small to medium-sized businesses, is evolving to become a broadband network capable of delivering high-speed data and other value-added communication services (see Figure 1). To date, the local loop has bottlenecked service provider’s high-speed backbone networks. Existing analog technology in the local loop limits the bandwidth between the subscriber and the central office (CO) to 56 kbps. But by integrating new technologies into today’s twisted-pair, local-loop network, service providers are discovering that the same lines that deliver standard telephony services or 56–kbps, dial-up data access can now economically deliver high-speed data plus multiple voice connections. DSL technology is enabling this new generation of service. Historically, high-speed data service has primarily been delivered via T1 lines to businesses. A 1.5–Mbps high-speed data service delivered via a traditional T1 line is typically priced at $350 to $650 per month. With DSL over the copper local loop, service providers are now offering 1.5–Mbps data service for $140 per month (see Figure 2).
Figure 1. The Local Loop
Figure 2. The Local Loop with DSL
Offering high-speed data service over the copper local loop is achieved by integrating DSL equipment at the subscriber premises and at the edge of the service-provider backbone network, typically at the CO. With DSL technology integrated into the local loop, information is transmitted as digital signals at much higher frequencies than for traditional analog telephony transmission. This enables more communications traffic to be transmitted over an existing twisted pair. But installing and managing this network requires new local-loop management tools and strategies optimized for broadband digital transmission and rapid network deployment.
