Dropped and Garbled audio with SpectraLink 8440 Phones

[steve_dreher]

I have a site with 95 SpectraLink 8440 phones and 80 APs with a ZD 3000 running 9.6.1.0.15. We experience dropped audio for up to 8 seconds and then the call will come back. The SpectraLink phone logs show very high Tx and Rx retries. I was told this ZD load addressed dropped audio issues with SpectraLink but we continue to have issues. The SpectraLink phones are at 4.3.0 which is also the latest software. The inside APs are on the 5 GHz band to reduce interference with a separate customer WiFi and the outside APs are on 2.4.

[steve_dreher]

We have a 6 cabinet Toshiba CIX 670 PBX, a Ruckus ZD 3000 with 80 zf7363 and zf7762 APs, Cisco switches, and 95 SpectraLink 8440 phones. The best I could ever get is using 5 GHz on the inside APs and 2.4 GHz on the outside APs. To get you by while they fix this I suggest changing your APs to use 5 GHz only using channels 149-165 which is sub-band 4 on the phone. Use Auto for power on the phone and APs. You still get the hight Tx and Rx retries on the phone but it's less than 2.4 which seems to reduce the audio drops. Remember that 5 GHz has less range so if these phones are used outside, like mine, then they will not be able to go as far. That is why I had to keep my outside APs (zf7762) at 2.4 GHz. This is at a huge car dealership campus where it is spread out with multiple buildings and users walk all over the place outside too.

[matty_brown]

Hi Steve

Luckily for us, the majority of our phones are Mitel 5330e's which we have very little trouble with - and only 7 users on SpectraLink 8440's.

We're using 5 GHz sub-bands 1 and 2. For some reason, if we have all 4 sub bands enabled, we found that the phones would not work on channels 100+, so we decided to disable sub-bands 3 and 4.

We were advised to change our power settings to Auto both on the AP's and the phones, but that actually made things seem worse, so we changed the handsets back to their defaults, P5.

Have SpectraLink or Ruckus come back to you yet?

Cheers,

Matty Brown

[luke_sandberg]

I was using my co-worker's login when I started this post but now mine is fixed. SpectraLink made a site visit and we found one substantial issue. It seems that the Ruckus APs are not changing channels when another AP in close proximity is on the same channel. So we were getting co-channel interference. We then statically assigned the channels in an area and are currently testing this area before we static the channels for the whole campus. I don't think that is everything but is a big chunk of it. Ruckus did have a SpectraLink no-audio issue in an earlier software load. I would get the ZD to the latest and 4.3.0 on the 8440s. If you stay on 5 GHz the SpectraLink person recommended sub-band 1 and 4 only. If you have trouble having both enabled check in Services or System and there is a setting for optimize for compatibility or performance in the Ruckus ZD. That may need to be adjusted.

[matty_brown]

Yes, I noticed that too - back in June I pointed this out to our reseller, who in turn spoke to Ruckus, who replied "If there is no interference or less interference on the specific channel, Even though the APs are in auto mode, Unless the APs reach certain threshold value , They will not change the channel. They will remain in same channel."

I think the problem with this is that our WiFi is only really used for VoIP and therefor barely any bandwidth is used so I would think we're unlikely to hit their threshold values. I guess if we had laptops on WiFi sending file across the air, our AP's would move to cleaner channels.

I guess the only downside of manually configuring channels for your AP's is that if there are neighboring sites using 2.4GHz or 5GHz your AP's will not swap channels to avoid conflicts.

Let me know how your tests go - hopefully you're onto a winner there.

[matty_brown]

I noticed on Friday that a new firmware, v4.6.1 has been posted on SpectraLink's website on 02/10/2013.

We loaded it late on Friday to a couple of handsets and did a walk test. The results were promising - routes that would previously have resulted in high data loss were vastly improved. But we've been here before - I'm not getting my hopes up this time!!

All of our handsets have now been updated to the latest firmware... we'll see how it goes next week.