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The true costs of fixed mobile convergence

The true costs of fixed mobile convergence

Now mobile is the new standard, and people are moving away from the clunky desk phones, we get a lot of questions from clients how to integrate mobile in a PBX. Especially the costs in conjunction with functionality are an important aspect.

Summarized, there are three flavors as alternative to give employees a separate mobile contract: VoIP apps, mobile on PBX and smart dial. In this blog, we will dive deeper in the differences and their advantages, while taking the global trends into account.

*These cellular cost are free on the business side, because in this scenario the employee calls with his own private sim card (in scenario 4 over the company PBX). Cost for the employee are only there, when he/she doesn’t have a ‘unlimited/fup’ calling plan, thus having two dollar signs, just as in scenario 0.

**Incoming calls for the SIM card number are always billed over MVNO airtime, thus always paying for the incoming leg. Sometimes employees don’t want their private calls routed over the company pbx for privacy reasons

***Incoming calls for the SIM card number are free, because it’s not routed over an PBX but delivered straight to the SIM card.

1. Mobile voip apps

These apps are already existing a long time, think of the consumer versions like Skype and Viber. Recent years the SIP voip apps are becoming more stable. The problem is, that they are not usable enough: If you are in a voip call, GSM calls always overruling, If the phone is locked you can not answer calls and the most important one: not all wifi / 4G networks are capable of handling voip calls, thus not knowing when to expect good quality.

2. Fixed mobile convergence / Mobile on PBX

This is almost the best solution, because it simulates a SIM card as a voip phone. Therefore you have almost all the functionality as you would have on a normal deskphone. Except, you have to port numbers. This is not convenient for most workers who already have a private contract, don’t have multi sim phones and don’t want to carry two mobile phones.

Furthermore the calling costs are much higher, this is because, mobile on pbx providers are always constructed via an MVNO. This party has to pay the MNO airtime costs, and cannot buy this traffic on the free wholesale market. When placing an outbound call it goes like this: Handset =$= Mvno =$= Mobile network.

3. Two leg call via PBX

Two leg call via PBX is a technique where the mobile app doesn’t call over IP, but initiates a two way call between the PBX, mobile handset and final destination. It works by letting the user choose a number to dial. After the app, sends a command to the pbx, with the handset number and the destination number. The PBX then first calls the handset, of the user who initiated the call and then calls the destination, following by connecting those calls together.  Why is this cheaper than Mobile on PBX? There is still airtime involved?

This is because when connecting the handset call to a final destination, technically you are doing a forward from the fixed network towards a mobile number. The costs of a forward, are much cheaper than the airtime costs of an MVNO, because you can buy it on the international market against better wholesale tariffs.

4. One leg call via PBX

This scenario is similar to scenario 3, but differentiates itself, in a way that the handset is setting up the call to the PBX. The pbx knows, to which destination it has to forward the call. (this is done by a mobile app that is submitting the destination number to the pbx separately or in the dialed pbx number). This scenario is especially useful when employees have a private sim card with unlimited calling plans. Because they already have that costs, business calls don’t raise those calls. This saves one leg calling costs.

Other forgotten aspects?

We are curious about your opinion. What do you think about this? Is this a complete overview of the situation?
How could new technologies (such as webrtc) bring positive change in stability and ultimate flexibility at the same time?

Update 16-07-2015

  • The Dutch MVNO firmtel.nl did not agree that the price of airtime cost to mobile in an MVNO scenario are higher than airtime bought on the wholesale market. We will investigate that with them and look for possibilities to publish actual rates from providers.
  • Added ‘Other PBX functionality’ and split the cost in outbound and inbound cellular calling costs.
  • Split ‘Smart dial + forward’ in Two leg call via PBX and one leg call via PBX.