Background
I’ve been living in my current house for a couple of years now. Being our first house, I didn’t exactly have the experience to evaluate all the little details like networkability. I had a vague idea that I could pay someone to pull CAT6 through the walls, but didn’t realize what a disruptive endeavor that would actually end up being.
Shortly after moving in, I decided to upgrade from my Netgear R7000 router to a Unifi-based system. This meant I had to get high-bandwidth wires to key places so that I could hook up my access points. Fortuantely, my house has a centrally located heating duct column that connects the attic to the crawlspace. With help, I was able to fish through some CAT6 and ceiling mount an access point right under the attic. Now I had pretty good WiFi coverage (UniFi stuff being pretty awesome), but the setup wasn’t complete. I wanted to have even better connectivity in the office, where I had my desktop rig. While I could maybe pull 400 Mbps through 5Ghz AC wifi, that was far shy of the gigabit speeds you would easily get with a physical wire.
I ruled out a bunch of potential solutions.. a dedicated wifi extender? Drilling more holes and mounting an AP just in the office room? Running outdoor-rated CAT6 up the wall on the outside and bringing it in to a box in the wall? All these ideas seemed like a lot of trouble, or were still limited in terms of overall bandwidth.
Then I remembered.. I have coax everywhere. I mean, literally everywhere. The previous owner was quite the Cable TV enthusiast, and when he had done is remodel, he made sure to have most rooms have at least two coax jacks. I vividly remember when the Comcast guy came the first time out, we found a 4-way and 8-way amped splitters out at the cable box so that every room (and even the detached garage) could be fed with sweet sweet cable TV. He told me that with so much splitting, he was doubtful he could get a good signal. I told him to unhook all the splitters and just connect the modem directly to the incoming feed.
My first thought was that maybe I could use the existing coax as a sort of fishing line to pull CAT6 through to the same places. I pulled out a few of the wall plates to see how much give there was but unfortunately, the coax was clearly securly attached to the studs.
Defeated, I went looking on the web to see if there was any way to use these coax wires to do IP networking. I mean, they’re getting up to gigabit speeds with Comcast right? If a cable modem can do that over long distances, seems something should exist to do this within the confines of a house.
Which leads me to…
How to use your existing coax to build a MoCA network
MoCA is a standard to enable data networking over residential coax. My understanding is that some cable providers in the US already install MoCA equipment. I’ve only ever used a self-purchased modem with Comcast, so I never encountered this tech. But here is the magical product:
This is the Actiontec Bonded MoCA 2.0 Ethernet to Coax Adapter sold in pairs at Amazon for around $150. These awesome devices let you use your coax to bridge your ethernet over your coax. Using this I was able to use the coax jack in my office to bring near gigabit speeds right to my desktop.
Topology
If you look closely, these adapters have a coax in and a coax out. That means they can be hooked in series with other devices that use the coax, and overlay the data network on the same cable.
Turns out this works even for the cable modem itself! These devices supposedly detect the frequency bands used by the cable modem, and use other bands to make sure things don’t conflict.
I use this exact setup. I have my main coax line come into a closet in the middle of the house. Here I have the cable modem, Unifi gateway, and switch. Before the coax hooks into the cable modem though, I have one of these devices in between. I then hook up one of the switch ports to the ethernet jack on the MoCA adapter which then uses the same coax line to spread the network out to other devices connected by coax.
Ok, that’s a mouthful. Here’s a picture instead..
As you can see the two ethernet switches here are connected to each other through the MoCA adapters, but the adapters are using the same coax line which feeds the cable modem! Maybe this is ho hum for people who are familiar with MoCA, but I’m still amazed this works.
Performance
From reading reviews, it sounds like your mileage may vary here, but most reports suggest that this works way better than your average WiFi (AC 5ghz) connection or powerline network.
In my case I get a solid 930Mbps between devices connected directly to the two switches in the diagram above (measured with iperf3). Ping time is also a consistent 3ms. I’ve used it for a good year now, and have never noticed any reliability issues.
That being said, I’ve read also that certain things can affect performance:
- Quality of the coax cable. RG6 is better shielded than RG59, but the latter is used in many earlier coax installs. I’m pretty sure I have some 59 in there as well.
- Run length and splitter signal loss: the farther the signal has to travel on a long coax run, the more signal you will lose. I currently have 3db loss at the splitter and approx 70-100ft of coax between the two adapters, and it works fine. I’ve read in a spec somewhere that MoCA devices like this should be able to survive at most 15db loss.
Other Notes
A couple more smaller considerations:
- Make sure your coax splitters support the full MoCA frequency range. Many old/cheap splitters do not, and can basically filter out the signal required for these devices to work. Basically look for splitters that are compatible with the 500-1650Mhz frequency range.
- Because MoCA works by pushing signal back out through coax (much like a cable modem), in theory the signal will also traverse back out the line that comes into your house. Some say the cable companies install filters on their end, but you never know. You can buy a “point of entry MoCA filter” like this to filter out those signals before they go back out to cable provider (and your neighbors).
In the works
As you can see from my diagram, currently I only have a pair of these on my network. But since I have so many coax jacks to play with, I’m planning to get a few more adapters to be able to place more access points.
Separately, the MoCA Alliance has already announced MoCA 2.5, which apparently can support a 2.5Gbps bridge using coax. This is an interesting development, but there no devices you can purchase quite yet. Very few people have 10GigE stuff at their house, and I expect the new 5GigE equipment to take a while to make it out to the market. Without something to actually use the 2.5Gbps supported by this standard, I don’t expect to see an adapter at this speed for quite a while. But when it does arrive, you can bet that I will jump on it immediately (unless I bite the bullet and pull CAT6 by then)
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