VOIP handover

[casperdacat]

Hi,

we have recently implemented a voip solution: Siemens WL2 handsets, Trapeze MX200 controller, Trapeze MP422A antenna's, 3Com 5500 ei PoE switches and a Siemens HiPath 3800 hybrid pbx. Our supplier checked the configuration of all devices (handsets, LAN, pbx etc) and tells us all is well configured for voip (Vlan, QoS etc) but when a user roams between antenna's, we get a short interruption during the handover: 0,5 to 1 s. Our supplier tells us this is default behaviour. Is that correct? I thought voip was mature enough to provide seamless (<50ms) handover?

Any thoughts on this would be welcome...

PS we use our wireless LAN for voice only at this point

Thanx,
Fred

 

[whykap]

This is not a voip issue, this is clearly a wirelless issue. Either the handsets or the APs do not handle the switch over properly causing the delay/interruption.

If your manufacturer tells you this is default behaviour ask for documentation on this. If this was clearly defined to you ahead of time you are kind of stuck. If not it would be your choice how to proceed.

A properly designed and implemented wirelless network that is handling voice as well would not behave the way you are describing it.
Having multiple manufacturers in the picture you got a lot to work with and there is going to be a lot of finger pointing. Put the pressure on the implementation team especially if the caveat above was not presented to you ahead of time.

 

[casperdacat]

Hi,

thanks for replying. In fact all equipment is provided and installed by the same supplier/implementation team. Just the 3Com LAN equipment is not but they stated well ahead of time that this would not be an issue. We didn't ask to get different brands of equipment, it was presented to us as being a reliable solution. The supplier did not state the handover behaviour before the deal was signed so I guess I'll put pressure to have the look things over.

Thanks!

 

[rfpup]

Have a look at it regarding Wi-Fi phone sets

http://www.trapezenetworks.com/products/interoperability/

 

[whykap]

Siemens is not even mentioned as a tested product.

 

[casperdacat]

Yes it noticed that... damn this doesn't look good. Could a slow handover be the result of insufficient wireless coverage (the signal being not strong enough)? We have AP's at a distance of only 30 meter in a direct line of sight and even then we get a short hickup when handover occurs... I also get the impression only the communication from the handset to the other end gets interrupted, never the other way around. Does that make any sense?

Thx, Fred

 

[rfpup]

You may try one/two of the Wi-fi phones which have passed interoperability tests of trapezenetworks registering to HiPath and simulate the same situation when you face the problem with Siemens WiFi phones

Then you can judge and raise a problem to Siemens/trapezenetwork

 

[whykap]

There's a lot of reasons that could happen including the one you mention. Without proper documentation, discovery and troubleshooting it is just speculation.
Unfortunately I am not familiar with the interoperability of these products so I can't help you there. The team that sold you and installed this is your go to people.
The fact that the wireless controller manufacturer does not have the phones you have there as a supported brand excludes them from supporting this implementation. Unless they directly sold you this solution.
I am not saying this is not fixable but it might take a lot of man hours if it is feasible.

Some of the reasons can be insufficient wireless coverage, too much coverage causing the AP's to step all over each other, product incompatibility, bugs on the firmware/software of the phones, controller or AP's, radio interference from other sources, etc etc etc

 

[casperdacat]

Thank you all for your replies! I just wanted to let you know most of our roaming problems have been solved by now. Main reason was the number of APs, there were not enough of them so the signal was too weak to get a clean handover. We now have 44 APs where we initially only had 33! We also upgraded the firmware on the Trapeze controller and all of a sudden, we got a far better coverage as well.
I also upgraded all Siemens WL2 wifi phones and limited the wifi channels to 1-6-11 which helped in getting an even better (faster) handover.
In the end, it seems like a load of (small) different upgrades resolved my problem. It took us about 3 months to fine tune, but now we've got an acceptable voip wlan setup.

Fred