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Principal Sponsors:
 | Digital Subscriber Line (DSL) Testing |
1. Need for xDSL Loop Prequalification
Using xDSL transmission techniques allows rapid provisioning of high-speed data and voice services. The ability to leverage the existing OSP is a significant advantage given its ubiquity—in serving or being connected to every home and every business. In addition, utilization of the OSP eliminates the need for major investments to upgrade the OSP, as would be required with alternative architectures such as fiber in the loop or hybrid fiber/coax. Deploying xDSL service is dependent on the quality and design of the OSP; thus, prequalification of copper loops is necessary to determine if the loop is capable of supporting xDSL transmission.
The use of the existing OSP to deliver high-speed data or voice is indeed the prime advantage of xDSL, but it also presents a number of deployment challenges. The ability to use xDSL is dependent on the design and quality of the plant, which was, in many cases, designed decades ago to deliver plain old telephone service (POTS). The design of the OSP presents a number of obstacles that can impair or prohibit xDSL transmissions. For instance, all xDSL technologies are blocked by the presence of load coils in the loop, and performance can be impacted by factors such as the length of the loop and the presence of bridge taps. The same impairments affect HDSL transport, which is used almost exclusively for DS1 access (replacing repeatered T1), ISDN, and digital added main line (DAML), increasingly deployed as a result of copper exhaustion.
The inability to prequalify copper loops accurately has been a significant obstacle for the local exchange carriers (LECs). Prequalification is critical because xDSL deployment is dependent on the design and quality of the OSP, and xDSL technologies are blocked by the presence of load coils. Prequalification is the testing of loops to determine if the loop is capable of supporting xDSL transmission prior to attempting to provide service—a hot topic in the industry. The ability to qualify a loop without having to dispatch technicians to either the central office (CO) or the customer's premises will result in significant cost savings for the LEC. The significant number of xDSL services projected by the industry implies a strong need for an automated testing capability to handle the growing line volume. As a result, the current manual methods for testing loops will not be able to keep pace in the face of doubling and quadrupling line volumes and will necessitate an automated testing solution.
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