It's 2012 now, we're all driving flying cars, wearing reflective clothing, the world is scheduled to end in a few more months, and we're all carrying around computers (called "smartphones") in our pockets. With that backdrop, let's look at our voice communications yesterday, now, and tomorrow.
Before we go back to the future, let's look at the past: analog. Speech is nothing more than sound-waves — oscillations of pressure transmitted through the air and received by specialized "vibration receptors" that we call "ears". In telecommunications these vibrations are picked up by a microphone and translated into electrical impulses. On the receiving end these electrical impulses are translated back into sound waves by a speaker, at which point your ear picks up the vibrations and the process is complete.
With cellular telephony we're living in the digital age. After the microphone "hears" your voice it's translated into a digital signal — one's and zero's. Just like CDs and MP3s, digital voice takes up a lot less bandwidth, meaning more of us can talk using the same cell tower or the same circuit.
Today's cellular telephony, however, is a sort of hybrid between the old analog phone systems and futuristic digital phone systems of "the future".
The Now: VoIP
Today some of us have Voice Over IP at home. You might get phone service from your Internet Service Provider (cable, DSL, even fixed wireless), or you might do like I do and supply your own VoIP provider. VoIP isn't like traditional phones that are based on completing an electrical circuit between you and the person on the other end of the line. In circuit-based systems you have to have a physical circuit for each and every person using the phone system. (That's where the "all circuits busy" message, and eventually the "busy signal" originated.)
VoIP, as its name implies, uses Internet technologies to break up your voice into packets, then send them whizzing across the web to the person on the other end of the call where they are reassembled and played back. Using the network this way is much more efficient and more conversations can be packed into the same circuits.
VoIP, however, has some overhead requirements. Your network connection must be fairly quick (100Kbps up should do) and latency must be low (preferably in the double-digits). VoIP is also somewhat resource intensive on the client: you've got to have enough processing power to put all those bits back together properly — and quickly — on each end of the call.
These are all likely reasons why not many of us use "traditional VoIP" on our smartphones today.
The Future: VoLTE
As our cellular networks get faster (speed) and quicker (latency), and our handsets get higher-end processors, the possibility of VoIP on our handsets gets closer to reality. Many of us thought HSPA+ and LTE would be the realization of those physical requirements — which they still may be.
As they are currently deployed HSPA+ and LTE are fairly well matched —though LTE has more room to grow than HSPA+. LTE, however, has an ace up its sleeve that may be fatal to HSPA+ and GSM networks — and CDMA, too.
Voice over LTE is the future. VoLTE shares many of the same benefits that VoIP does, but instead of relying on the hardware at the ends of the call (your smartphone), VoLTE offloads the heavy lifting to the network. Doing so lets VoLTE calls be described as VoIP HD. Calls are crisp and clear, and reportedly sound amazing. Not only that, VoLTE includes the ability to cancel echos and background noise on the back end, not the handset itself.
Some smartphones today have two microphones, one listens to your voice, the other listens to the ambient noise and removes that noise from the call using algorithms and hardware. This requires additional hardware, processing power, and time on the handset. The VoLTE solution eliminates that by putting all the work on your carrier's network instead.
Will we see CDMA and GSM go away and the spectrum they occupied re-purposed for LTE? Will this happen before or after we see handsets capable of VoLTE? When will we see handsets capable of VoLTE? In short, we don't know, but if you'd like to weigh-in, let us know your thoughts in the comments!