ADSL Modem Performance in an ISP Trial

About the Avalon Trial

Avalon Networks is an ISP in Iowa City, IA. Our interest in ADSL is primarily in replacing existing hi-cap services and expanding into the apartment complex market. Avalon ordered LADS lines in the summer of 97 after a fight with the PUC and USWest over deletion of the LADS tariff. We received working lines in the fall of '97. Our initial experience with one ADSL modem vendor was quite poor, and this drove us to run an in-house trial. Because of an interest in the results of this trial, we presented this data at DSLcon 98. This web page is an attempt to recap that talk for those who could not attend.

Testing Process

Copper Wire Evaluation
The copper wire used in this trial was evaluated by a number of methods. Our goal was to characterize the wire as much as possible.

Live circuit tests
Each of the modems was tested on live copper loops. Goals were to test speed, distance, and reliability.

Modem bench tests
The goal of these tests were to evaluate performance of the router/bridge engine in the ADSL modems.

Conclusions

1) We found wide variability in the performance of the ADSL products we tested. The early versions of many of these products had various reliability problems, but by the end of the trial, many of these had been improved.

2) The single most important variable for us in this trial was distance. Several of the modems (Netspeed and USR) failed to reach our magic number of 15K feet that we need to cover our planned deployment area. Overall, DMT modems went farther, due to their ability to shift down to lower speeds. The best performer in this category was the yet unreleased Pairgain Falcon DMT product.

3) CAP based products tended to be the most mature. For a current deployment, we would feel most comfortable using Westell, Pairgain, or Paradyne modems. All three worked without significant flaws.

Last updated: 4/3/98