(a provocative post for my friend Andrea)
We know UMTS CS uses almost the same codecs as GSM. On the air interface voice codecs streams use data rates between 12–28 kbit/s, depending on the spreading factor.
Since 3G launch, in order to switch towards the full packet switched world, several techniques based on complicated “real-time rate adaptive dynamic switch etc.. etc.. codecs ” have been studied and released for voice coding.
They are all meant to allow operators to reduce the impact on network capacity.
4th generation codec rate adaptation for VoIP over LTE has been clearly defined in the 3GPP Rel-9 specifications. The use of VADs and CNG has contributed to reduce bandwidth requirements as well.
To make it short, air interface bandwidth required by new VoIP codecs is really low; AMR WB (which is like “HiFI voice call”) can reach 6,6 kbps only.
Not so much considering the throughput evolution curve (see figure below from AT&T, taken from http://www.atis.org).
I believe we are not that far to say that VoIP on wireless can be optimized and shrunk enough so that full packet switched networks can think to manage it in terms of capacity in the next years (providing making some CAPEX investments on backhauling).
The fact is that we shouldn’t simply think of a block migration of voice from one technology to the other.
Let’s consider a couple of other aspects, not strictly technology related.
Are packet users more hungry of conversations using mouth or using fingers?
Look at this interesting Nielsen report.
Now, supposing packet based wireless networks have sufficient bandwidth to carry IP data also for mobile IP voice in indoor coverage, if you had to choose between using the terminal for IP voice over fixed lines and you mobile, which terminal would you use? As for myself, if the QoS is good enough, I’d definitely go for the mobile wireless.
So, from one side we can think of voice over mobile decreasing, both for social behaviours and for very low prices of VoIP over fixed lines. (I see young people not so interested as in the past in talking on the phone. They can sit next to each other and digitally chat. Just spend a few hours in a park close to secondary schools and you’ll see that yourself).
On the contrary, people will increase working on the move (even in offices, see people running up and down in open spaces), so if you could make cheap VoIP also on your mobile, why should you sit and pick up a fixed line phone?
The decrease of voice from teens can somehow compensate the increase voice on mobility of business?
If I were a teen I’d probably have at least 5 different free VoIP mobile apps on my device , each implementing a set of sophisticated coding.
If I were a business man, in the future era of tiered plans, I’d join a “platinum” data plan with fantastic voice quality “network allowed”.
Are these fixed line stuff on desk still going to survive for a long time?