Request for Help: 802.11A Wireless Bridge Interference
By jeffreycentex on Apr 25, 2007 in Uncategorized
Post Tags: Wireless
OK, for the second item of the day, I want to make a general call for help in troubleshooting a particularly nasty 802.11A problem I am seeing between our office and branch office (basically, 1/4 of a mile down the road with LOS).
The wireless network works flawlessly for about 166 hours a week. However, everyday at about 4 PM, we get a few glitches in the data stream. When I look at the wireless performance data, I am getting about 15% of packet retries for about 5 minutes. This affects only the data (LAN) transfers and DFS replication. VOIP does not seem affected at all. On Wednesdays, however, this packet loss lasts considerably longer (for about an hour or so). This wreaks havoc with our CAD files (which are still being sent over the WAN).
During Normal Operations:
Strength: -53 dbm
Noise Level: -103 dbm
During the “Glitch”:
Strength: -90 dbm
Noise Level: -103 dbm
I have switched to all of the channels that the device (Tranzeo TR6) will support to no avail…
I’m working with the equipment provider, but I wanted to see if anyone out there has seen this..
I have tried to eliminate other interference sources, but there isn’t much that would cause problems throughout the 5 Ghz band…
Thanks for any help.
4 Comment(s)
By Stuart Clark on May 4, 2007 | Reply
From what you are reporting it certainly looks like an RF issue of some kind, especially given the degredation in signal strength -53 to -90 during the glitch. If your noise level stays constant though, that is puzzling.
Unfortunantly tranzeo does not have a “carrier busy” feature like Cisco gear that would enable you to sniff the 5a spectrum and get a sense of what the radio is seeing. This would be of limited use in this scenario anyway since it would take down the link while it ran.
My other thought would be whether or not you have done any load testing to try to simulate what high traffic volume looks like in a controlled setting?
We run tranzeo 5a gear to connect 4 locations back to an operations center, and our overall experience with Tranzeo has been positive. I’ve never seen such a wide variation in -dbm though. We have noticed that due to Tranzeo’s lack of any true QoS ability, when a link experiences high utilization performance degrades rather abruptly and noticably for users.
By Andy Black on Aug 30, 2007 | Reply
I have the same problem.
By jeffreycentex on Aug 30, 2007 | Reply
I solved the problem. It took two steps to do so:
1. Reduce the power to the lowest level.
- and -
2. Build a shelter for the unit to protect it from the afternoon heat of the sun.
The shelter was the last thing I have done and it has worked flawless since then. I built a cube from the “wire” furniture available at a local Target or Lowes and covered it with patio screen wire from Lowes. This allows air to flow in and around the unit and keeps the sun from heating the unit.
Before we placed the shelter on the branch, we did a surface temp scan and saw that the temperature was between 160~180 deg F during a reasonably hot day (ambient temp ~ 93 deg F).
By Andy Black on Aug 31, 2007 | Reply
Thanks man!
I did it!
Thanks a lot!