Wireless Controller Dynamic TPC

[rick505d3]

Hi,

1. Just trying to understand the dynamic TPC on the Cisco 5500 controller on the 5 GHz band and 20 MHz wide channels (keeping the example simple). The default settings enable TPC adjustments between the Max (30 dbm) and Min (-10 dbm) power levels on an AP when it sees 3 or more neighbours at -70 dbm or better. 

Reading Cisco docu and blog posts, the 4 AP's may all be on different 5 GHz channels say 36, 44, 52, 60 and TPC still runs reducing the power level on all AP when they meet the algorithm criteria. The example channel are all different and deliberately picked as non-adjacent. There is no RF overlap. Will TPC run in this case and why?

2. In dense AP deployments data and VoIP over Wireless (Cisco 8821 handsets), this document http://www.cisco.com/c/dam/en/us/td/docs/voice_ip_comm/cuipph/8821/english/Deployment/8821_wlandg.pdf on page 28 suggests setting Max and Min Power levels to 16 dbm and 11 dbm respectively for rugged environments. I am troubleshooting Voice quality for one such deployment where The TPC (TPC 1) threshold is set to -65 dbm (yes higher than the default - 70 dbm) and a good number of AP's see neighbour AP at this level or better. Dynamic TPC runs and reduces the power on these AP's. On quite a few AP, the power level is at the lower Min Power level (11 dbm). This indicates to me that if allowed some if these AP's may have gone down further if Min Power level was say 0 or -10 dbm. Since the TPC settings are applied at the controller level, this would be impacting all data clients on the 5 GHz band. Also having TCP threshold set to -65 dbm instead of default -70 dbm may increase co-channel interference as a neighbour may be seen at say - 68 dbm but TPC will not run for it. What is the best practice / optimal TPC settings for voice over wireless deployments on 5 GHz band.

3. Any suggestion that may help troubleshoot and improve the voice quality issue in (2) above?

Regards, 

Rick. 

[patoberli]

1: if TPC is enabled, it will run.

2: never done any voice deployments, can't help here. Only thing I once learned, many years ago, was to exclude clients on the 5 GHz band and only allow voice clients to it, because of your mentioned reason. With todays software, where you can run QoS on an application basis on the controllers/AP side, this might not anymore be the recommended setup (exclude clients from 5 GHz).

3: If you run voice on it's own SSID, mark it as Platinum on the WLANs configuration. If that is, for whatever reason, not possible and the voice and data clients share the SSID, enable AVC and prioritize voice traffic (Skinny (named cisco-voice), SIP, ...).