Dealing with echo on a PRI; can HPEC help?

Hey everyone. I have pretty consistent echo problems on my PRI that I have been unable to completely eliminate via conventional means. If I greatly dampen the txgain and rxgain signals, I can mute the echo enough that it is fairly unnoticeable, but it comes at the cost of call quality–especially if someone dials in to check voicemail. (In those scenarios, the messages become practically inaudible because they are hit twice.)

Using a setting of 128 or 256 on echocancel provides varying levels of success–there is always very noticeable echo in the beginning (the sidetone is loud and delayed in the beginning) but within 15-20 seconds the echo cancellation kicks in. However, the call will then intermittently experience echo, as the echocancel algorithm is unable to perfectly anticipate and cancel it.

At this point, I’ve got echo to fairly acceptable levels, by both dampening the txgain and use of echocancel, but I would like to have it completely eliminated. Has anyone used HPEC to echocancel on a PRI line? If you have, has it been effective in eliminating echo? Also, what sort of computational hit does it generate? Digium says the following:

“Digium recommends that users requiring 8 channels at 1024 taps run a PC comparible to a 3.0 GHz Pentium 4, while users only requiring 4 channels at 1024 taps may run a 2.5 GHz Pentium Celeron. The CPU requirements are such that it is impractical to operate this echo canceller at 1024 taps for a full T1 or E1 of channels.”

Any help would be greatly appreciated.


I have also been fighting the same issues. My echo reports only appear to be when a caller makes a Long Distance call. I have been unsuccessful in eliminating echo using echocancel of any setting ranging from 64 - 256. I read on that if your are getting echo on long distance calls that it should be set to 256, but I haven’t had any luck.

I was also wondering in HPEC would be worthwhile.

HPEC will work on a PRI. However due to the amount of CPU required, you won’t be able to have 23 concurrent calls with it echocancelling on each. If you only have echo on LD calls, you could assign a few channels for LD only and apply HPEC to them so it doesn’t bog the machine down trying to apply it to all channels.