Testing Broadband Services End-To-End

America's Network, Sept 1, 2001 by Chris Bohrson

Improving Broadband QoS

The broadband service provider who owns reliable information on service issues owns the consumer.

While current business practices are straining at current subscriber levels, broadband providers must now find ways to effectively scale business practices to mass deployment levels. The cost and quality of qualification, provisioning and service assurance processes need to make business sense at levels of millions of subscribers.

With the rapid growth of the Internet and the subsequent need for reliable information, Teradyne brings proven experience to service providers. Teradyne is an industry leader in qualifying and testing broadband services. The company has nine years of experience in IP protocol testing and nearly 30 years experience in providing customer care systems. Teradyne presently has more than 110 million access lines under test supporting voice services, providing reliable and actionable information to customer care call centers worldwide.

ILEC Case Study -- Layer 1

Testing the physical plant for broadband services

The last mile connection from the CO (Central Office) to the subscriber is considered the weakest link in the network in that it is made up of a physical copper twisted pair, originally designed to carry voice and now used for carrying broadband DSL. This poses challenges for DSL service providers for qualification and provisioning testing.

Qualification Testing: Using insertion loss rather than length to qualify Lines

Qualification Testing:
False Red and False Green Detection

Metric Actual Celerity   Pilot Results            Business Impact

False Red and False      30% Reduction in         13% increase in lines
 Green Detection          False Reds               ready for DSL now

                         20% Reduction in False   Reduction in
                          Greens and lines with    Provisioning Truck
                          potentially service      Rolls
                          affecting physical
                          faults

                         65% Reduction in         Reduction in manual
                          Indeterminate Lines      engineering efforts
                                                   to qualify lines.

Current methods of checking the DSL pre-qualification status rely primarily on records systems containing the loop construction including overall length, gauge mix and presence and length of bridged taps. These systems, while having varying levels of accuracy fundamentally rely on being able to identify presence of impairments (like load coils) and use length as a predictor of DSL speed for a "clean" line. For smaller deployments, the record system qualification approach was adequate. However, as DSL rollout ramps-up, these systems face three challenges:

1. The stored records are incomplete or in some cases inaccurate.

2. For lines beyond 12 Kft, length is not a very accurate predictor of DSL line speed.

3. There may be physical faults present that will disrupt DSL service that are not detectable by current line test systems.

To solve this problem, Teradyne developed Celerity - a single-ended, automated test system that uses insertion loss (rather than length) to predict DSL speed. Celerity is unique in that it can measure the loss of the line with a single-ended test through the existing voice switch to enable accurate pre-qualification. This approach has been proven accurate in the toughest situations, including through the 5ESS switch test bus on lines with bridged taps. Along with this information, the DSL impairments that exist in the network are identified prior to making a commitment to deliver service to a customer.

Qualification and Provisioning Testing:
Load Coil Detection

Metric        Actual Celerity Pilot Results   Business Impact

Load Coil     Above 99% Accuracy              Reduced Truck Rolls for
 Detection                                     maintenance

                                              Increased successful
                                               subscriber turn-ups
Provisional Testing: Splitter Detection

Metric        Actual Celerity Pilot Results   Business Impact

Splitter      Above 98% Accuracy              10% Call reduction at
 Detection                                     Call Center

                                              10% Truck roll reduction

Trial results have shown that because record systems have missing or inaccurate data and rely on length to qualify a line for DSL these systems often result in inaccurate qualification assessments leading to false greens, lines incorrectly qualified, and false reds, lines incorrectly disqualified. In the case of lines with bridged taps this is particularly critical. Many ILECs disqualify lines with a bridged tap despite the fact that this line may qualify for DSL service. This is unfortunate as the ILEC either takes this line out of circulation (limiting revenue) or incurs the cost of removal. In addition, as the inaccuracies of these systems are known by many providers, a high proportion of the lines require a costly manual assessment of the loop make up where the system is unsure whether the line qualifies or not.