The quality of your voice calls depend on multiple factors: potentially the most significant is the combination of phone devices you select and your office network or networks where those devices are used.
The following table gives a qualitative hierarchy of how each combination of phone device plus network type determines the overall quality. In a nutshell: the more the voice traffic to and from devices and across your network is separated / preferred compared to other data traffic, the better the overall quality. Naturally this assumes that the bandwidth, download and upload, is sized sufficiently for voice data.
|Device and network pair type||Device description||Network description||What quality can you expect? What purpose is the deployment type good for?|
|Dedicated phone device on separated specialised wired network||SIP Deskphone wired||office with dedicated optimised wired network only for voice SIP calls||Classic best approach for a larger scale specialised business call center|
|Partly dedicated device on separated specialised wireless network||softphone on tablet or smartphone (principally intended for use with voice calls - limited other apps and data connections in use)||office with dedicated optimised wireless network only for voice SIP calls||
Best for unified communications deployment where answering and making calls are mixed with lots of other tasks
|Non-dedicated device on a non-separated optimised wired network||softphone on laptop, tablet or smartphone||office with an optimised wired network shared by voice SIP devices and other data traffic||The laptop with softphone variant is good for a call center also. Even a large team can be very effective like this without dedicated deskphones (compare with the top of the table - the classic call center).|
|Non-dedicated device on a separated optimised wireless network||softphone on laptop, tablet or smartphone||office with dedicated optimised wireless network only for voice SIP calls||Also good for a unified communications deployment where the business users want to use devices for very mixed tasks. More effort has to be put into optimisation to achieve good results - but that is perfectly possible.|
|Non-dedicated browser-based phone on a non-separated optimised wired network||Browser webRTC softphone||office with an optimised wired network shared by voice SIP devices and other data traffic||For a small number of users with really fantastic network (symetric high bandwidth ...), this can be good. But when the number of users rises, it gets more and more difficult to achieve reliable high quality. For smaller teams it has the advantage of ease of initial setup.|
|Dedicated device on a shared non-optimised wired network||SIP Deskphone wired||home, small office, cafe, public hotspot, hotel wifi||If your network gives you limited ability to control and optimise for VoIP/SIP, then a dedicated hardphone is going to give better results.|
|Non-dedicated device on a shared non-optimised wired network||softphone on laptop/desktop (wired)||home, small office, cafe, public hotspot, hotel wifi||The results will be hard to predict and could well be haphazard - with issues occurring that are difficult or impossible to isolate - simply not enough control of the network.|
|Non-dedicated device on a shared non-optimised wireless network||softphone on laptop, tablet or smartphone||home, small office, cafe, public hotspot, hotel wifi||More difficult still - the only difference to the category above is now we have a poor wireless network instead of a poor wired network.|
Note that the device / local network combination is not the only factor effecting your call quality. But what is certain is that without getting this factor right, you can not hope to achieve a truly optimised VoIP telephony deployment.