IPIQ MOCA, Part Two: The Connected Home: Wiring (and Un-Wiring)
The first installment of this two-part series explored the trends that created the need for connected homes. It also introduced the technologies commonly used to deliver unified digital services throughout the home. In this installment, we’ll take a closer look at each network technology standard, and we’ll offer a description and practical guidelines regarding each.
Truth in Networking
In order to understand why hybrid architectures are often the most practical and cost-effective way to implement connected homes, it’s necessary to take a closer look at the capabilities, requirements and shortcomings of each commonly used home-networking technology. The strengths and weaknesses of each technology are summarized in Table 1, on the following page.
Theoretical vs. Actual
For any networking technology, there is always a difference between its theoretical and net throughput, or actual rate. Though often the number advertised outside the package, the theoretical rate is a maximum rate that is rarely, if ever, realized, even under the most ideal of conditions. What is really important is the actual data rate, or the rate actually realized in the home.
The amount of bandwidth actually available to the user is affected by two factors: First, every network technology must use part of its data stream to perform various overhead functions that insure data moves efficiently through the network and arrives intact. For wireless and powerline, the overhead can use up as much as 50 percent of the network’s advertised bandwidth. In addition, some of the remaining capacity is often lost due to non-ideal channel conditions and external interference, which forces the networked devices to re-transmit lost data frames.
This means that, while a typical 802.11n wireless network may have a rated capacity of 144Mbps, only about half of that is readily available for transporting AV media. Wireless networks also lose capacity as the distance between nodes increases, or as the speed increases. (Dual N routers have less physical distance strength than their older G cousins.) Electrical noise from radios, appliances or other sources can further reduce a wireless network’s capacity. Power line networks are also highly susceptible to external interference, so that even under normal conditions, a power line transceiver rated at 100Mbps may have its best-case useable capacity of around 50Mbps knocked down by another 25 percent, or even more.