The future of telephony and communications vs. Toll-Quality
What’s next in the world of telecom?
Let’s just say early one morning someone calls you as you’re about to leave for work. You pickup and start talking to the caller as you start out the door to get into your car. While you’re driving and talking you decide to turn on the news while you’re stuck in traffic. You finally make it to work and you’re still on the call which was placed to you before you left home. Now let’s suppose the thing you answered wasn’t even a phone but instead some multimedia device with the ability to traverse home broadband seamlessly with cellular, IP, and secured corporate networks without signal drops or service interruptions. Your local dial tone and long distance voice is a free side-benefit of the subscription you’ve bought for this multimedia gizmo. The package is some news, local channels, weather, financial information maybe, and some metropolitan concierge type information. Is this a pipe dream? For now definitely however the future is very bright and promises to be very exciting for media, communications, and hosted applications.
Building an infrastructure to support this sort of technology (known today as IP Multimedia Subsystem or just ‘IMS’) would be nothing short of a project like putting a man on the moon. It would rely on two things that are next to impossible to bring to life: a worldwide autonomous network and a global implementation of IPv6. The shorter run would be with v4 gateways and smaller starter network areas such as the east coast megalopolis.
Cellphones have paved the way for such a solution; by both lowering our expectations for “toll quality” voice and by adopting standards like 3G so we could get a taste of what is to come with mobile communications.
All of this sounds fun and even with the exception of newer wireless “last mile” connections we will still depend on traditional backbone technologies to deliver any of the advanced services to come in the future. Currently the priority pole in respect to Quality of Service has voice communications at the top with video at a close second and most everything else running at a lower level or QoS. This might not be the case for very much longer because as X over IP development progresses, better mechanisms for sending faxes and dial up communications are becoming more and more popular. Fax and dial are sort a mix of digital and analog communications and therefore require the most bandwidth and least compression to be successful. The sooner these become pure digital the sooner this hurdle will be cleared and the sooner what’s discussed in this article will become reality!
Let’s get back to the present for a little while. Telephone lines delivered over traditional TDM mechanisms have never lost contact with the concept and delivery of ‘toll quality’ voice and high quality dial-faxing. Over the past years however the beatings we’ve all endured by the use of cell phones have paved the way for many different types of compression-enabled voice transmission products. These have improved sound quality over most cell phones but are still classified as ‘near toll quality.’ That definition is what the telecommunications industry of today strives for in a market that is migrating to packet-based services for the future from the traditional circuit-based of old. In this day and age you will be hard pressed to pick up a phone anywhere, dial a number and the call complete without traversing at least one compressed span of network. Why compress? Simple — get more bang for your buck. If you can squeeze two calls into the same space that used to be required for one; you can sell the same network element twice and double your earnings. What about 4? or 8? Unfortunately the magnitude of compression is inversely proportional to the quality level of what you’re compressing, which is to say you lose sound quality as the compression tightens down so there is only so far you may go and still retain near toll-quality.
Before going that far let’s examine compression a litter deeper for the sake of clarification. Compression uses a coder/decoder (known as a ‘codec’) to remove unused bits in the transmission data stream as it is being transmitted and reinserts the bits while receiving. Different codecs compress at different rates therefore no one codec is the answer to all applications. The only codec that somewhat qualifies as a ‘one size fits all’ is generally referred to as the pulse code modulation (PCM) codec or as just ‘G.711.’ For fax and modem transmission G.711 is the best fit since it uses only analog to digital conversion and vice-versa with no compression. When transmitting voice only, the most popular industry standard codecs are G.723, G.726, and G.729. All of these codecs are considered to be adaptive differential pulse code modulation (ADPCM) codecs and each has different characteristics which fit different application needs. Video codecs are very similar.
In closing, we are on the verge of some really exciting things in the world of communications. Some of these are things we’ve never seen before converged with new technologies, and the rest are backed up with many years of proven traditional technology. At any rate, I can’t wait to build and be involved in the next phase.