Voice-over-Wi-Fi

Voice-over-Wi-Fi is the same as VoIP (Voice-over-IP) but over a wireless Wi-Fi network and can be seen as the replacement of a DECT network. Instead of using a DECT telephone, a similar device with a Wi-Fi chipset or even smartphones with what is referred to as a SIP (Session Initiation Protocol) client is used. A SIP client is a fragment of software that ensures that you can also communicate through the telephone exchange internally by using your smartphone.

 

Benefits of VoWiFi

If the Wi-Fi network is used, VoWiFi offers the possibility of making significant cost savings in addition to offering more mobility and flexibility.

  • You only need to install one network instead of several (DECT, beepers, WLAN, telemetrics, etc.).
  • This means that less cabling is required.
  • This, in turn, leads to fewer switch ports.
  • Fewer devices (base stations, controllers and switches) also means lower energy costs.

In addition, you are less dependent on a telephone exchange and it is easier to choose alternative or cheaper solutions in addition to traditional telephony.

 

Technical challenges

VoWiFi, however, is not self-evident and there are a few technical challenges precisely because we use multiple applications over one network that is open to everyone. This is where selecting the right technology and a partner with expertise is vital. VoWiFi is seen as being "new", but Multicap has already been installing VoWiFi networks since 2004 and, therefore, definitely has the required know-how and expertise to offer support within this context.

The telephony quality will greatly depend on the following:

  • The roaming options of the client;
  • The interference in the environment that will result in jitter (variable delay);
  • The end-to-end Quality-of-Service support (client - wireless network - cabled network - PBX);
  • The quality of the device itself (microphone, loudspeaker and/or wireless chipset).

 

Roaming

The transition from one access point (AP) to another is called roaming. The client (i.e. the telephone) is responsible for taking the decision when and to which AP it will switch. A client will perform an active or passive scan to discover nearby access points to ensure that this at least is performed correctly. This means that the client cannot do anything else during this time. Moreover, the strength of the signal is not the only thing that is important. Whether an AP is the right choice can also depend on the load on that AP (number of clients and the bandwidth and applications that they use). The client, naturally, will not be aware of this information.

We all also want a secure network, but security is always linked to a specific “cost”. In the case of roaming, this means that the full authentication and agreements related to the use of encryption keys must be carried out again if a client switches from one AP to another one. This will, therefore, have an impact on the speed with which the system can change between access points.

Depending on the codec that is used, a package is created every 20 or 30 ms in a typical scenario. If one package is missing, the previous packages are injected automatically again in some systems, which the human ear will not hear. If several packages, however, are missing, we will notice this very quickly.

It is crucial for a good experience that the switch between the APs takes place at the right moment, that the correct AP is selected and that the switch takes place sufficiently fast.

 

Quality-of-Service

Voice packages are small packages that must be delivered fast. It is, therefore, crucial that the packages are given priority. So not only the roaming has to go fast but everything.

Quality-of-Service is the collective name for a number of standards that can ensure that there is a distinction with regard to priority depending on traffic type. WMM (wireless MultiMedia) or 802.11e are related standards. Existing technologies of 802.1p (differentiated services code point; DSCP), Terms of Service (ToS) and DiffServ (differentiated services) are translated for the wireless network with regard to this issue.

The objective is to understand end-to-end which priority a specific package has. The package must, however, be either tagged by the sender (here, therefore, the PBX and/or the telephone) using the correct code or the network must have a mechanism to identify, classify and tag this traffic itself. A system that works correctly will have both mechanisms.

 

VoWiFi Networks

Predictability and consistency are the most important qualities of a VoWiFi network. It can't be subject to variable power, antenna's, channels etc because this will lead to dropped connections and calls.

These are the parts where the Meru Networks solution fits perfectly which is why we advise this solution for a VoWiFi network.

If these variables are met, you can simply replace your DECT network with a VoWiFi network!