Wireless LAN (Voice)

Samphos Ngak · ‎08-09-2013

With Shankar Ramanathan

Welcome to the Cisco Support Community Ask the Expert conversation. This is an opportunity to learn and ask questions about how to monitor, troubleshoot, and configure voice over WLAN on Cisco Unified Wireless Network and 792x/9971 phones with Cisco experts Saravanan Lakshmanan and Shankar Ramanathan.

Additionally, the experts will cover relevant issues such as one-way voice, two-way failure (no voice), “robotic” or choppy voice quality, network busy, and leaving service area.

Saravanan Lakshmanan is a customer support engineer at the Cisco Technical Assistance Center, specializing in wireless technologies and solving high-severity and critical wireless issues for Cisco customers and partners. He is an expert in debugging and troubleshooting Cisco Wireless LAN controllers; wireless LAN services; unified access points; wireless LAN security; autonomous access points (Aps); voice over Wi-Fi (VoWifi); authentication, authorization, and accounting (AAA); and radio frequency (RF) technologies. As a technical content engineer, he creates and edits documentation to enhance product serviceability. During more than 10 years of engineering experience, he has served as QA specialist for the Cisco Wireless business unit and before that as a senior software specialist in QA for Motorola’s wireless engineering infrastructure team. Saravanan is a frequent contributor to Cisco’s internal forums as well as the external Cisco Support Community. He holds a bachelor of engineering degree from Annamalai University in Chidambaram, India.

Shankar Ramanathan is a customer support engineer at the Cisco Technical Center specializing in Cisco voice over wireless LAN (VoWLAN) technologies, including 792x and 9971 phones. Prior to joining Cisco in November 2011, he worked as a wireless network engineer at Elan Technologies, responsible for RF wireless network planning, simulation, propagation path analysis, and optimization of Wi-Fi 802.11 mesh and WiMax (802.16 d/e) networks for various system integration and automation projects. Shankar holds a master of science degree in electrical engineering specializing in communications and signal process from the State University of New York, Buffalo. He is CCNA certified (number 410004168640IMZF) and has four years of industry experience.

Remember to use the rating system to let Saravanan and Shankar know if you have received an adequate response.

Because of the volume expected during this event, Saravanan and Shankar might not be able to answer each question. Remember that you can continue the conversation on the Wireless, sub-community forum shortly after the event. This event lasts through August 23, 2013. Visit this forum often to view responses to your questions and the questions of other Cisco Support Community members.

jawad-mukhtar · ‎08-11-2013

What basic things to be kept in mind while configuring Voice over WLAN

Jawad

Saravanan Lakshmanan · ‎08-12-2013

Hi Jawad

Cisco 7925 Voice Design & Deployment Guide

http://www.cisco.com/en/US/docs/voice_ip_comm/cuipph/7925g/7_0/english/deployment/guide/7925dply.pdf

Configuring the Cisco Unified Wireless LAN Controller and Access:-

Follow cisco's best practice for WLC starting from Page - 61.

It has recommended - WLAN, Datarate, FSR, QoS, EDCA, 802.1p, Voice CAC, RRM config.

Thanks

Saravanan

Rasika Nayanajith · ‎08-13-2013

Thanks for releasing updated (for 7.x) deployment guide 7925. I would like to clarify the below

1. Why is it recomended to disable Video CAC ? Let's say If someone need to optimize their wireless to support both voice/video what should we select here. I noticed EDCA set to "optimzed voice & video" with video CAC disabled is general recommendation in this guide.

2. In U-APSD section (page 28), it is stated these phone utilize U-APSD as long as WMM enable on AP & power save mode enable on the Phone. Is this true or still do we need to enable this feature on a voice wlan using below command.

config wlan uapsd compliant-client enable

Rasika

Saravanan Lakshmanan · ‎08-13-2013

Hi Rasika

Good questions!!!

Have notified it BU, will be responded.

Thanks

Saravanan

Shankar Ramanathan · ‎08-13-2013

HI Rasika,

On question#1:

No need to enable ACM for video for 792x deployments since just SCCP (call control) will utilize this queue (low bandwidth).

The 792x will always send TSPEC for video / UP4 for SCCP (call control) regardless of ACM enabled or disabled for video though.

For our current video endpoints (e.g. DX650, Cius), we do not recommend to enable ACM for video, primarily as they do not support TSPEC and if done then the quality would degrade from UP5 to best effort.

For a video call, both voice and video are sent as DSCP AF41 / WMM UP5

On Question#2: I discussed this with the BU folks, as of now it appears that 792x(cisco phones) doesnt seem be require this command for enabling wlan uapsd compliance. Might be for non-cisco phones but I will dig on this further and let you know.

migilles · ‎08-13-2013

Yes that command or U-APSD seems to be something specific for 3rd party clients; not required for 792x phones, which is probably why it is available in the CLI only.

So what is stated in my 7925G/7926G Deployment Guide holds true, 792x phones will utilize U-APSD when WMM is enabled; regardless of the status of this other command.

For Video CAC, if utilizing video heavily and you have clients capable of video calls and also support TSPEC where you want to preserve that queue and bandwidth for the video traffic, then you could optionally turn on ACM for video and change the allocation percentages as necessary.

But as mentioned above, you woud probably not want to do that if you plan on deploying clients capable of video clients that do not support TSPEC (e.g. DX650, Cius).

Hope that helps clear things up.

Shankar, thanks for posting my comments from our discussion earlier.

wjenkins · ‎08-13-2013

I do have some questions about the 7925 deployment guide.

First of all let me say it is a great source of information on what is required to deploy a 7925 phone. And the CLI "config auto-configure voice" command in v7.4 is a great way to simplify the voice configuration required on the WLC.

From what I understand the Advanced Network Profile setting allows you to select which channels to scan, the maximum TxPower level for each channel and the minimum physical rate.

1) Is the 7925 by default scanning all of the 2.4GHz (14) channels and all of the 5GHz (23) channels or a total of 37 channels?

From what I understood it is recommended to only scan a maximum of 12 channels.

2) Does the phone only scan 802.11a when set to 802.11a and only 802.11b/g when set to 802.11b/g?

3) All of the channels max TxPower is configured for 17dB yet there are places in the 7925 deployment guide that indicates that the maximum TxPower for the 7925 phone is 16dB. What is the correct max TxPower and should the advanced network profile be set to match?

4) If deploying in a challenging enviroment that requires a 6Mbps data rate as recommended should the minimum physical rate be set to 6Mbps also?

5) Is the only way to change the advanced network profile settings using the Web GUI?

Oh and just on a side note. It is no longer possible to set the session timeout to 86400 seconds as shown in an example in the document. The maximum now is 65535 seconds.

Thanks!

migilles · ‎08-14-2013

Below inline are answers to your questions (marked MG: in bold).

1) Is the 7925 by default scanning all of the 2.4GHz (14) channels and all of the 5GHz (23) channels or a total of 37 channels?

MG: This depends on the 802.11 mode configured in the netowrk profile, but if set to an "Auto" mode (Auto-RSSI, Auto-a, Auto-bg), then yes all channels would be scanned assuming all channels are enabled in the advanced section of the network profile.

If set to 802.11a then only 5 GHz channels would be scanned assuming those channels are enabled.

If set to 802.11bg then only 2.4 GHz channels would be scanned assuming those channels are enabled.

From what I understood it is recommended to only scan a maximum of 12 channels.

MG: It is recommended to only utilize 8-12 channels for a 5 GHz WLAN deployment.

Once APs have been discovered using the same SSID locally configured on the phone, then those channels will be moved into the highest priority scan list.

Discovered channels are scanned more frequently than non-discovered channels.

5 GHz channels must be passively scanned then actively scanned per 802.11h.

2.4 GHz channels can simply be actively scanned.

CCX neighbor list data can also help to populate the phone's neighbor list data, where channels could be scanned sooner if not discovered yet.

2) Does the phone only scan 802.11a when set to 802.11a and only 802.11b/g when set to 802.11b/g?

MG: See above.

If set to 802.11a then only 5 GHz channels would be scanned assuming those channels are enabled.

If set to 802.11bg then only 2.4 GHz channels would be scanned assuming those channels are enabled.

3) All of the channels max TxPower is configured for 17dB yet there are places in the 7925 deployment guide that indicates that the maximum TxPower for the 7925 phone is 16dB. What is the correct max TxPower and should the advanced network profile be set to match?

MG: Don't worry about the 17 dBm option for 5 GHz so much in the advanced network profile.

The max tx power for 5 GHz is up to 16 dBm, where it is up to 17 dBm for 2.4 GHz.

4) If deploying in a challenging enviroment that requires a 6Mbps data rate as recommended should the minimum physical rate be set to 6Mbps also?

MG: Yes as outlined in the guide, it is recommended to enable 6 Mbps as a mandatory/required data rate if deploying 7925 in a rugged environment.

This allows ACKs and beacons to be sent at that rate.

5) Is the only way to change the advanced network profile settings using the Web GUI?

MG: Yes primarily via 7925 webpage, but you could also use our Bulk Deployment Utility (BDU), which can be used to make changes in mass.

http://www.cisco.com/web/software/282074239/14006/792xBD.1-0-Readme.pdf

Rasika Nayanajith · ‎08-14-2013

Hi Shankar/migilles

Thanks for the clarification. In surmmary, this is my representation of your responses, is this correct ?

1. If video clients support TSPEC, you have to enable video CAC to control % RF given to video within wireless environment.

2. If video clients does not support TSPEC, there is no difference between BE traffic & Video traffic coming from client, so no point of configuring video CAC.

Rasika

migilles · ‎08-14-2013

Not quite right.

My changes are in bold below.

1. If video clients support TSPEC, you can optionally enable video CAC to control % RF given to video within wireless environment.

2. If video clients do not support TSPEC, then it is NOT recommended to enable video CAC as the priority of the upstream & downstream video and audio streams for a video call (both streams to be sent as DSCP AF41 & WMM UP5) as well as upstream & downstream call control frames (SCCP/SIP) would be downgraded from UP5 (video) or UP4 (call control) to best effort quality if Video CAC is enabled.

Rasika Nayanajith · ‎08-14-2013

Hi MG,

1. if Video CAC is optional, without enabling it from where I can control % bandwidth for such traffic(ie WMM UP 5 or AF41). I can only see a place to set a % RF bandwidth only when ACM enable under Wireless ->802.11a/b/g/n ->media->video -> ACM.

2. I understand your point. Does this mean in this scenario (video client is not TSPEC capable), AF41/WMM UP5 traffic can goes into network as it is once you disable video CAC on AP.

Rasika

migilles · ‎08-15-2013

For #1, Yes if Video CAC is optional, then you can not control what traffic is sent using the AC_VI queue.

If you want to control the traffiic then yes you would enable video CAC.

But then again, you need weigh the pros and cons as you may not have TSPEC capable clients and they may be forced to use the best effort queue if you enable Video CAC.

For #2, yes if you don't enable Video CAC, then clients do not have to send TSPEC request for that queue in order to send traffic tagged as WMM UP4 or WMM UP5 in that AC_VI queue.

Shankar Ramanathan · ‎08-12-2013

Hi Jawad,

This doc by Aaron has simple guidelines for reliable phone performance

https://supportforums.cisco.com/docs/DOC-26863

Also check out

http://www.cisco.com/en/US/docs/wireless/technology/vowlan/troubleshooting/VoWLAN_Troubleshooting_Checklist.html

Saravanan Lakshmanan · ‎08-13-2013

Hi Jawad

Are you looking anything in specific to voice deployment that is not addressed in the guide.

Thanks

Saravanan