MoCA Takes Spectrum Down a Notch
The newly added range covers frequencies from 500 to 1,500MHz. The original spectrum range for MoCA 1.1 was 850 to 1,500MHz.
Monk says there's not much difference between the chips supporting the different spectrum profiles; chips of both types are shipping.
The original range was a better fit for cable's available service spectrum, but it overlaps the L-band (950 to 2,150MHz), which is used by DirecTV and Dish, another MoCA member, to carry video signals from the dish to the satellite receiver. The original MoCA range didn't leave enough separation for proper filtering, says MoCA chief technology officer Anton Monk, who is also the VP of technology at MoCA chipmaker Entropic Communications Inc. (Nasdaq: ENTR).
He says MoCA went with the mid-RF approach over lower frequencies because tests showed that the latter environment is noisy and much more difficult to harness. Spectrum below 20MHz, for example, gets interference from powerlines.
AT&T Inc. (NYSE: T) has been able to make Home Phoneline Networking Alliance (HomePNA) work in lower frequencies for the U-verse TV service, but Monk believes the performance tradeoffs and the work necessary to perform a similar feat with MoCA are too great.
The mid-range approach offers "a very clean band, so it's away from any interference and powerline ingress interference issues," he says. "DirecTV wanted the same performance that cable is getting… without going to low frequencies."
The target performance, in the case of MoCA 1.1, is about 175 Mbit/s of net throughput. (The yet-to-be-ratified MoCA 2.0 platform is shooting for a basic mode that can pump out 400 Mbit/s, and an 800-Mbit/s enhanced mode: See MoCA 2.0 'Enhanced' Mode Target: 800 Mbit/s.)
DirecTV is eager to use MoCA not just for multiroom DVRs, but also to help fulfill its vision for RVU Alliance technology.
In that scenario, DirecTV will be looking to use MoCA and RVU to support thin-client video devices attached to a central video gateway/server. With that in place, DirecTV intends to ship its user interface over the home network to a wide range of remote clients, including IPTV set-tops, TVs, and PCs that can speak the RVU language.
DirecTV is championing RVU, but Verizon Communications Inc. (NYSE: VZ), still the heaviest MoCA user, is also a member of the RVU Alliance and is believed to be pursuing similar plans.
DirecTV has previously said it intends to deploy its whole-home DVR by the first quarter of 2010, but its Website indicates that the product is still in beta testing. A DirecTV spokesman says the company expects to launch it sometime in May. (See DirecTV Picks Entropic and DirecTV Preps Multiroom DVR.)
Can cable play in the new band?
Although the mid-RF approach is targeted to satellite companies, cable could use it as well. The problem, though, is that cable already uses that band to deliver video services on the outside plant, so there are some major interference issues that would need solving.
Monk says he's "heard of some interesting architectures floating around," including a "split gateway," that could tap into the lower MoCA band.
But that would require some extra work by the cable operator. "You'd have to isolate the inside of the house from the outside of the house," Monk explains.
— Jeff Baumgartner, Site Editor, Light Reading Cable