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Figure 1
In a triple-play local-loop architecture, as illustrated in Figure 1, a single loop system carries the voice, data, and video traffic flow from residential and business customers to remote terminals (RTs) using standard telephony and DSL interfaces. The RTs are interconnected by access network feeder to the central office terminal (COT). Customers connected on copper pairs directly to the central office (CO) can receive all of the same services directly from the COT. The COT provides access to the public switched telephone network (PSTN) via a traditional Class-5 switch or softswitch (using VoIP with softswitch signaling), provides Internet access via a router, and provides access to video services via interconnection with a video head end.
BLC solutions, for example, combine two innovative technology approaches to deliver telcos a cost-effective, scalable, flexible architecture.
First, the solution leverages standard IP and Ethernet technologies. Technically, this approach rips out layers of complexity. Economically, it drastically reduces the cost of building and operating a high-bandwidth access network. In a BLC access network, all traffic between remote terminals and central offices is carried as IP packets across high-speed, fiber-based Ethernet links.
Second, the solution consolidates line access and aggregation functions into a single device. Specifically, the RTs and COTs integrate digital loop carrier (DLC), optical transport, DSL access multiplexer (DSLAM), and line access gateway (i.e., softswitch VoIP gateway) functionality into one network element.
Figure 2
In terms of traffic flow, residential and business customers connect to a BLC deployed in an RT or CO via traditional interfaces, such as analog/POTS lines, T1/E1, or DSL connections. Any non-IP traffic is converted to packets at the RT; for example, analog voice is converted to VoIP. RTs are connected to COs via fiber-based Ethernet links in whatever topology—ring, string, star, or tree—best suits the ILEC. IP-based traffic flows from the BLC RTs to the BLC COT in the CO. The BLC COT connects to Class-5 switches via a TR-08 or GR-303 interface and connects to Internet access routers, softswitches, and video head ends via Ethernet. The traffic flow in the BLC triple-play architecture is illustrated in Figure 2.
In Figure 2, the integration of key access and aggregation functions into a single network element simplifies network design and implementation and significantly reduces operational costs. The architecture in the figure also positions ILECs to move into new markets, such as expanded data services for businesses and video services for residential customers. It enables telcos to offer competitive analog voice and data services today while positioning them to compete with the full range of triple-play services, including VoIP, tiered data services, and a range of video services, in the near future.
Delivering these services will require more bandwidth than is available in today's distribution networks. Video, in particular, requires large amounts of bandwidth. It is important to plan today's networks to meet the bandwidth requirements for future video offerings.
