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What's New in MoCA 2?

7/19/2010 9:53 AM

By now, it’s nearly a foregone conclusion that providers will take advantage of a somewhat eponymous technology - MoCA, for Multimedia Over Coax Alliance - to handle the business of moving the bits of video, voice and data over the coaxial cables that already interconnect our various cable gadgets.

Last month, a second version of the MoCA spec emerged, which seemed a good enough reason to take a closer look at what’s happening in this interconnectable world of Ethernet, Wi-Fi and its 802.11 flavors, HomePlug and HPNA.

Know going in that there’s little truth in networking, at least as it relates to the advertising speeds emblazoned upon the boxes in the homenetworking aisle. If it sounds too good to be true (500 Megabits per second!), it usually is.

Here’s why. In any communications network, there’s such a thing as MAC and PHY. “MAC” stands for Media Access Control. “PHY” stands for “physical.” In raw terms, “PHY” is the gross and “MAC” the net.

In tech terms, the “physical layer,” or “PHY,” is where bits are modulated and coded. The media-access control, or “MAC,” is where the stuff happens for multiple devices on a network to communicate - how they get access, how they listen, how they request a slice of the PHY, for transmitting.

Those activities of the MAC create overhead, in the form of extra bits, moving through the network - in other words, taking up room. Service providers, for that reason, are much more interested in the MAC rate than the PHY rate.

Which takes us back to MoCA 2.0, likely to be the wired home-networking method of choice by multichannel video operators (cable, satellite and telco). Here’s what’s new: a throughput pop from 175 Mbps to 400 Mbps and, in “enhanced mode,” 800 Mbps. That’s the MAC rate. (PHY rates are 700 Mbps and 1.4 Gbps.)

Also interesting, from a “green” perspective: The 2.0 version of MoCA includes sleep and standby modes for networked devices. This is good, because set-tops, modems and their ilk do draw power, and don’t currently have either mode.

Remember, “specifications” are blueprints. From there, specs like MoCA 2.0 go to chip manufacturers, then to device manufacturers, to build. Translation: Add about 18 months, realistically, until you’ll see MoCA 2.0-based gear in homes.

But it’s coming, and that’s good, because it’ll be needed for homes simultaneously flinging five or so HD streams to connected screens.

September