You need at least -62db RF-plan to roam between APs without loosing a call. Some devices are more picky than others (iphone 5c and higher give less problems). I observed that the scanning time of Android is often too high which makes roaming a bad user experience (but I have not tested the latest versions).
If you have no QoS and you are surrounded by many clients, you will experience problems in your call (either on the listening side or on the speaking side or on both sides). Not because of the bandwith requirements for a call but mainly because of the high sampling rate of VoIP and the jitter caused by retransmissions and the exponential back-off of the Wi-Fi protocol. This may result in dropping the call. The bandwidth requirements per call depend on the codec used. The traditional G711 codec results in a 64kbit/s connection whereas G729 is only 8 kbit/s. Skype uses a SILK codec, using between 6 and 40 kbit/s. Note, this is at the application layer. As a result of the overhead and inefficiency of the Wi-Fi protocol, the data rate on the Wi-Fi layer is much higher! 5Ghz is (much) better suitable for VoIP than 2,4Ghz. Especially with high number of active clients per AP. The downsize I experience from Wi-Fi calling on a smartphone is that all phones give priority to incomming 2G/3G/4G calls. No matter what device or app you use, your Wi-Fi calls drops if a person tries to reach you via the cellular network. But that won't bother you if your indoor reach is poor. I am surprised that mobile carriers in the US allow end-user networks in their VoIP communication path. That is unusual in the Netherlands (where we have less need for Wi-Fi calling as we have sound coverage and carriers are not offering Wi-Fi calling and will gladly install DAS instead in the case of bad indoor coverage which happens often as a result of e.g., foil on windows or because carriers move 2G/3G voice to high frequencies which penetrate badly through walls and windows). -Frans Op 16/10/15 om 21:34 schreef Howard, Christopher: > I'm honestly not surprised to hear that they are going to push wifi > calling and nothing else. They want to drop all cellular service > other than data, long term, in my opinion. > > I have AT&T myself, and ran the iOS 9 beta from the beginning, which > got me early access to AT&T wifi calling. Needless to say, it has not > been a pleasant experience. Calls drop all the time. > > For our wireless we have not had to do anything. Calls just work > without opening inbound ports (we don't limit much going outbound). > My calls run about 65kbps. > > The pain point is something you've already mentioned - roaming. If at > any time you roam from wifi to cell and there is no VoLTE service in > your area, the call dies. We apparently don't have VoLTE in > Chattanooga, TN. If I stay in my office I can usually hold a call, > and roaming from AP to AP is sometimes ok. Sometimes the roam between > APs is enough to drop the call. I've also noticed that if I get more > than 2 cell bars, the phone will want to go off of wifi calling on its > own. Even at home where I only have 1 AP and can be sitting 15 feet > from it, I'll drop calls because my phone decided to roam back to cell > during a live call. > > To directly answer your questions: > 1. I don't plan on doing anything special. We have enough free > bandwidth to handle a large number of 65kbps calls. > 2. Mine have been 65kbps or there about. > 3. We run both frequencies, but my phone tends to stay 5ghz. I don't > think we would change anything to support wifi calling. > 4. I'm not sure how we will get this across other than to let our > helpdesk know what to tell people when they call in about it. We'll > be looking into this more I'm sure. > 5. I'm a little surprised that carriers are being allowed to run calls > over end user networks. 911 is a big deal, and if our wifi is up > enough that the phone can do wifi calling, but there are issues going > on to prevent calls, who gets blamed here? In an emergency, it's too > much to troubleshoot what's going on and figure out that you have to > cut off your wireless to get a call through. As far as I know, > there's nothing we have to do in terms of uptime or anything. > > -Christopher > >> On Oct 16, 2015, at 2:14 PM, Smith, Todd <todd.sm...@camc.org >> <mailto:todd.sm...@camc.org>> wrote: >> >> Hello, >> >> Yesterday, a regional VP for AT&T Wireless told my Enterprise >> Architect and CIO that AT&T was not interested in pursuing a >> distributed antenna system with us and made it clear that they would >> not be moving forward with any DAS in the future. In seems, that >> Wi-Fi calling is the moving forward strategy for AT&T for poor >> cellular signal and presumably other carriers. I wasn’t in the >> meeting but I am confident that it has been reported accurately. >> >> Does this sound like anything that anyone else has heard? If so, how >> are other institutions handling this? It seems silly that our >> organization which is in the planning stages for a Wi-Fi wireless >> upgrade anyway would build in the necessary upgrades to accumulate >> cell carrier backhaul traffic for no compensation whatsoever. >> >> As usual, my job is to do or die, so I am trying to see what others >> might have done and if possible start a line of discussion to reason >> out the best way to handle poor cellular coverage in both older >> buildings as well as brand new LEEDS certified buildings. >> >> 1) Would you create a new SSID for cellular traffic with QoS >> enabled and open to the Internet with UDP 500 and 4500 open as well >> as more normal ports? >> 2) I can’t find any solid reference that details exactly how >> much bandwidth per call. I have literally read in the last couple of >> hours, everything from 2.5Kbps to 1Mbps to a general consensus from >> 60-128Kbps per call. >> 3) 2.4Ghz or 5Ghz or both? >> 4) Much of the discussion of seamless handover from cell to >> Wi-Fi involved HD Voice which seems to be provisioned as part of >> VoLTE and only available in some areas; i.e. not my coverage area. >> How to communicate to your normal users and any public that uses >> your Wi-Fi that when they switch between platforms; the call will be >> dropped? >> 5) Would we be responsible for maintaining redundant Internet >> connections just to support cell calls? Is there any requirement >> that would state that since we are providing cellular infrastructure >> that we are responsible for a certain minimum SLA? >> >> Is there any other questions or comments to think about? >> >> Todd >> >> >> >> >> >> ====================================================================== >> >> CONFIDENTIALITY NOTICE: The information contained in this >> message may >> be privileged and confidential. If this e-mail contains protected >> health information, you are hereby notified that any dissemination, >> distribution or copying of this communication is strictly prohibited, >> except as permitted by law. If you have received this communication in >> error, please notify the sender immediately by replying to this message >> and deleting it from your computer. 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