As MoCA evolves from a feature to a market, and from curious little upstart to industry statesman, we feel it is incumbent on us to provide definition and explanation to some particularly cumbersome and vexing issues. These tend to be technical in nature but also have great and long term economic impact. For purposes of this paper, we will focus on the latter by explainging in lay terms the former.
Wired or wireless?
Wireless alternatives to home networking offer benefits of portability. The user can receive content any where in the house. However, high definition video is a challenge due to a number of factors including building materials, interference with other signals and the general nature of the technology which does not provide the stability for consistently high reliable transfer of multiple streams of HD video.
Wired alternatives tend to be more stable and generally provide the reliability required for high def video distribution. This begs the question, "what is the best wire?"
Phoneline, powerline or coax?
Phone line (as represented by HPNA) and powerline (as represented by HomePlug) are ubiquitous throughout the home. These mediums are more than adequate for voice, data and smart energy type applications. They are also prone to interference and generally are unable to sustain the reliable bandwidth needed for a whole home DVR solution.
Coax on the other hand, was designed for video and is found where the homeowner is most likely to watch TV. Coax is inherently secure as it is a shield medium. While coax does not offer the ubiquity of its wired counterparts (i.e., phone, powerline), outlets are found where entertainment is consumed. No, you won't find coax in every room, but who watches TV in the bathroom or from the refrigerator (OK, put your hands down. I get it). These rooms and the resulting applications are lean forward experiences, whereas wathcing TV is a lean back experience. Coax is found in the family room or bedroom, where watching TV is more comfortable and thus more likely.
It should be noted that all the wired home networking standards recommend coax in addition to their native medium for video applications.
MAC vs. PHY rate
Buyer beware. This is a "what you buy is not what you get" scenario.
Essentially there are two metrics for measuring performance. One is called the PHY rate (or physical layer) and the other the MAC rate (Media Access Controller). The former is the theoretical outlier for maximum performance that is possible, though not probable. It is rarely achieved even in pristine lab settings.
The MAC rate is the one that is important. It is the actual throughput that is realized. Pay TV operators design network topologies around actual, not theoretical, data rates.
When the large number on the product packageing states that this product is cabable of 200 and even 300 Megabits per second (Mbps) data rates, it is the PHY rate, not the MAC rate that is being touted. The consumer is seduced into thinking that more is better when in fact,more is often far less than advertised.
Performance vs. reliability
High performance is desirable of course, but so is reliability. Unreliable performance, not matter how great or high, is still insufficient and not a solution. What is required is high performance and consistent delivery of packets.
While many home networking technology standards are capable of high performance, reliability can be an issue becauase of interference issues and the nature of the medium. While no home networking standard considers reliability to be unimportant, only one is capable of the reliability required by service providers and home theatre installers and their customers.
If you drop a call on your cell phone, you can redial and finish the conversation. Annoying, but the experience is completed. Not so with video. Glitches, artifcats, latencies, all disrupt the movie/program and the expreience is not acceptable.
Interoperability vs. compatibility and coexistance
These terms are often used interchangeably but they are not the same.
Compatibility generally means coexistance meaning two technologies, products or services can reside on the same board or in the same system without interfering with each other's operation. Interoperability means each succeeding version of a networking specification can interact with the one previous.
Think of it as the differrence between living in a neighborhood (compatibility) and making friends with the neighbors (interoperability).
Interoperability includes backward compatibility. Backward compatibility does not always mean backward interoperable.
Interoperabality is essential for a technology to be a true standard as it assures operators and end users that their current investement is protected as next generation versions can be addedor layered in without disruption to existing equipment.
Who is really driving multiroom DVR? Subscribers or pay TV operators?
The end consumer in today's video distribution market is not the end user. It is the pay TV operator. This is to the subscriber's benefit as he/she is not responsible for evaluating and making technology decisions for which they are not trained or experienced. The operator and/or installer will set up the network, trouble shoot and pronounce ready for use.
While eventually there will be product that is easy to install and maintain for whole home DVR and other content sharing applications, for now, consider multiroom DVR one of those "don't try this at home," situations.
Solution or alternative?
To sum up, a complete and comprehensive home entertanment networking standard should offer high performance based on actual (MAC rate) throughputs, with reliable delivery of packets, that is backward interoperable with previous versions, and uses the homes existing coaxial cabling. There is only one such standard. MoCA.
The rest are merely alternatives.