The Impact of ADSL Interoperability Testing on the DSL Market
Service Providers want ADSL modems that meet a standard set of interoperability tests and achieve a
guaranteed level of service. DSL Forum has produced an ADSL interoperability test specification, known as TR-048, which is supported by all key NEM's, Service Providers, access IC manufacturers and Independent Test Labs. Success in selling DSLAMs and modems to Service Providers is quickly becoming a simple matter of proving you can pass DSL Forum'sTR-048 interoperability tests. This is a new testing hurdle that suppliers need to conform to before they can sell their equipment.

Spirent’s TR-048 Interoperability Testing Solution
To ensure that DSLAMs and modems meet a minimum set of specifications when used together, ADSL Service Providers, Network Equipment Manufacturers and Independent Test Labs have come together at DSL Forum to produce the TR-048 ADSL Interoperability Test Plan.

Issues of control, consistency, repeatability, as well as automation, should be a concern to every TR-048 user. Spirent offers a solution that combines DLS physical layer with SmartBits™ traffic generation and analysis tools.

Physical Network Simulation
Wireline
A small variation in bit rate can mean a difference between passing or failing TR-048. Issues of noise floor, accuracy and repeatability are key technical issues that must be considered. In response to this, Spirent has developed a software-based compensation package, which is integrated with the DLS 400IA, to meet the accuracy, repeatability and requirements specific to TR-048. Customers who have a DLS 400A/N/HN can upgrade to the DLS 400IA system, which includes the additional testloops and software compensation package.

Noise
Real world noise has a dramatic impact on the performance of ADSL modems and DSLAMS. TR-048 has captured many of the worst case scenarios and specified a set of crosstalk, RFI, impulse and white noise test requirements. In response to these requirements, Spirent is developing the DLS 5200IA TR-048 Noise Impairment System. The DLS 5200IA, available in the summer of 2002, will provide all impairments specified in TR-048 including RFI and common mode noise injection. Other features include automation via Ethernet control, high accuracy and test repeatability, as well as ETSI / ANSI compliant crest factor.
For immediate test needs, the use of two DLS 5A01H Noise Impairment Generators, together with the DLS 5A17 TR-048 Noise Impairments CD-ROM, will allow for most TR-048 tests to be performed.
Table 1 compares the capabilities of both noise generation solutions and, for those who commit to the DLS 5A01H now, Spirent will offer an attractive upgrade program to the DLS 5200IA, once the TR-048 standard is finalized.