The arrival of Voice over IP as a method of transmitting voice over cellular networks has to be dealt with by the various regulators and anti-trust authorities sooner or later and a piece this week in the International Herald Tribune suggests that the European Commission has just completed an investigation of this technology. The next step is some form of regulation.
What’s difficult to understand about this idea is that it is actually wasteful of network resources. A cellular operator using W-CDMA or CDMA is likely to squeeze voice into a circuit which could carry the equivalent of about 12 kilobits per second of data. Decent VoIP takes at least 48 kbps and most minimum’s are 64 kbps, and higher quality fixed line systems take up to 128 kbps to carry a VoIP conversation. So if all cellular networks sent all of their voice over IP all of the time, the strain on the networks could be 5 to ten times what it is today.
The big issue is that like the fixed telephone network before it, cellular voice is switched, which means that a certain virtual amount of capacity is reserved from end to end across the air interface, the switches and across the backhaul and all the way back out to the phone that it is calling. If no-one speaks, then the silence still takes up 12 kbps or more, whereas in VoIP the coding of the signal is designed to mix all the voice and data packets in together and it is all sent to a router which prioritizes each packet and gets it across the network and it doesn’t go through the voice switches at all which could eventually become redundant. If there are periods of silence, a null value is sent in a couple of bits and the rest of the capacity can be used by another conversation or another data process until someone speaks.
The trouble is that laying an IP signal on the data portion of cellular networks is quite a new phenomena, and only a tiny portion of the bandwidth is used in this way. Once LTE (Long Term Evolution) networks arrive in around 2011 and beyond and replace 3G, then the whole network will have IP data built into it over an OFDM layer rather like wi-fi and WiMAX have now and then everything will be packet switched instead of circuit switched. What we have now is a hybrid of CDMA switching and an IP data channel shared by everyone at a base station using HSDPA ‘ a bit of each really.
But it is the network pricing that is causing problems. Cellular operators offer mobile web with their best effort on data rates, which can be as high as 3.6 Mbps and data limits between 1 GB of data a month and 15 GBs for prices as low as £10 or £15 a month. Per bit this is dramatically lower than the price it charges for voice. If a customer chooses to send voice over that data network using something like Skype, it might not give a particularly clear voice, but it would cost nothing extra for each call and someone could talk all month to anywhere in the world and not go beyond their data limit and bypass roaming charges in the process.
The natural solution is to block voice (VoIP) so that only web pages and music and video can be sent over the broadband wireless line, not voice, and this is what the European Commission has been investigating. The argument is that operators cannot have all that data revenue but ban one type of data which is not harder to deal with than other real time data.
What happens in all these cases is that the EC will send out questionnaires to carriers and VoIP rivals and major customers to form a picture of what tools and techniques are being used for filtering and blocking VoIP traffic.
If the cellular operators find that they are reduced purely to the role of carriers of data bits, they will rapidly find new breed of operator selling voices services on top of their broadband data services ‘ something which led to a whole raft of rivals when this happened in fixed networks, and to the crash in the pricing of fixed voice.
Earlier this year 3 UK began to offer Skype over its network as part of its X Series of services, and is now using that throughout its European operations, and this has led to more flat rate data services from 3 competitors ‘ but so far it has not led to rival VoIP services.
In the US the operators have used tight control of their intellectual property to prevent rivals appearing who offer VoIP over their services, claiming patent breaches, and this may be the only way that European cellular operators can legally stop services emerging here. The patents in question ‘ how to interconnect to their specific network ‘ were largely obvious.
T-Mobile UK and mobile VoIP player Truphone reached for lawyers this Summer over this same issue with T-Mobile refusing to agree interconnect fees for Truphone customers, because it did not have its own network to support. Other deals have emerged in Europe where VoIP services work hand in hand with cellular operators, whereas others block traffic.
Right now most VoIP offers some kind of bridge from the fixed world to the cellular network, and delivers its voice as a circuit switched service which the cellular operators can then charge a little for, but it makes more sense for them to come in on a data carrier without the cellular operator even knowing, and deliver voice for free as part of the monthly data payment.
It is understood that several cellular operators have clauses in their customer contracts which allow them to block VoIP services over 3G, or to exclude VoIP traffic from monthly data bundles. These would have to be dropped I the European Commission finds that it is anti-competitive, which is what is likely to happen here.
The powerful cellular lobby will work hard to try to get permission to continue to block VoIP calls, but eventually, as their data delivery becomes more efficient, all cellular voice will be carried as IP packets and at that point it will have to allow interconnection with all other VoIP services.