Create In-house Network Using Buried Coaxial Cables

MoCA Introduction

MoCA (stands for Multimedia over Coax Alliance) is a technology that uses the existing coaxial cables already in most people’s homes. In essence, MoCA creates a wired Internet home network, but without the headache of drilling holes or running wires.

DOCSIS 3.0 used frequency band 5 MHz to 65 MHz for upstream and 85 MHz to 1002MHz for downstream, whereas DOCSIS 3.1 allocates 5 MHz to 204 MHz for upstream and 252 MHz to 1788MHz for downstream traffic. Gigabytes Internet plan may use spectrum defined by MoCA 2.5 (1125~1625MHz) and thus cannot co-exist with MoCA. MoCA network needs to be isolated from DOCSIS3.1.

Introduction on Screenbeam's website

Before purchasing any MoCA adpaters, check your house and understand coaxial cable layout in your house.

There should exist at least one coaxial socket where you want to put modem and wireless router and one coaxial socket where you want to wire your hardware (PC/WIFI extender/ethernet switch). Both coaxial sockets should be wired to N-way splitter at point of entry (likely in basement or garage). Common port of the splitter is connected to cable of ISP. There might be a cable booster between splitter's common port and ISP's cable. It is used to boost downlink signal as N-way splitter's IL is quite high.

N-way splitter plus cable booster might be problematic nowadays as uplink IL is way high so ISP does not like it. My modem used to have difficult to talk to ISP and uplink power was 57dBmV, which is out of recommended uplink power range (38~48dBmV for uplink and -7~7dBmV for downlink). The technician from my ISP simply removed booster and used 2-1 splitter instead of existing 8-way splitter. That brings down uplink power to 40dBmV-ish so the modem works just fine.

Checklist before investing on MoCA hardware:

1. Understand your coaxial network topology.

2. Verify uplink and downlink power by login into modem (192.168.100.1 for Netgear modem). You might need to rewire coaxial cables to less-ports splitter and disconnect cable booster (MoCA needs extra splitter supporting up to 1625MHz, most leacy splitter and booster only support freq up to 1002MHz), which means signal transmission in MoCA band may see extra attenuation.

Stop here if you don't fell comfortable to do this yourself and don't waste money.

Hardware to be purchased:

1. DOCSIS and MoCA co-exist configuration, if you find only one coaxial socket near modem and router.

   • Two MoCA adapters (better supports MoCA 2.5 to get highest speed). One may be enough if modem supports MoCA. But some modem only supports MoCA2.0 or lower version.
   • One MoCA compatible splitter for MoCA adapter 1. Some MoCA adapter bundle has this inlcuded.
   • Optional MoCA compatible splitter for MoCA adapter 2 if you cannot find a dedicated coaxial socket for this adapter.
   • At least two ethernet cables (CAT6).
   • Number of coaxial calbes (RG6/6U) = 6 (two splitters) or 4 (one splitter). You may already have one for the modem.
   • Optional coaxial cable meter if you don't know which cable goes to the point you want to install MoCA adapters.
   • Two POE filters that are MoCA compatible to prevent MoCA signal leaked to pubilc coaxial network and interfere your modem.

2. DOCSIS and MoCA isolated configuration, if you find two coaxial socket near modem and router. Best if possible. This means you need two dedicated coaxial sockets for MoCA.

   • Two MoCA adapters (better supports MoCA 2.5 to get highest speed).
   • At least two ethernet cables (CAT6).
   • Number of coaxial calbes (RG6/6U) = 2
   • Optional coaxial cable meter if you don't know which cable goes to the point you want to install MoCA adapters.
   • One coaxial cable coupler to hook up the two coaxial sockest for MoCA adapters. Or you can use MoCA compatible splitter comes with MoCA adapter, which introduces around 3.5dB IL. Just keep in mind less IL on link gives you better chance to achieve higher speed.

Typical in-house network topology without MoCA

Below is typical network topology, wireless router provides connectivity to every devices. Today's WIFI 6/7 router provides decent speed but signal degrades with distance and obstacles.

Also, it is worth noting most legacy splitters and booster do not support DOCSIS3.1 and MoCA bands. Your Internet plan is likely DOCSIS3.0 based if you find these.

MoCA co-exists with DOCSIS

If you have only one coaxial socket near your modem and router, this is the configuration for you.

Main drawback of this setup is it is not compatible with DOCSIS3.1. It may cause problem if ISP rolls out DOCSIS3.1 in the future. Though possiblity is low as they have to upgrade splitters for every household before they do that.

Also communication between MoCA adpaters go through two splitters, attenuated by port-to-port isolation (likely 20dB) on main splitter and then by IL (3.5dB) on splitter before modem. I had this setup when I was not familiar with coaxial cables layout and it worked suprisingly. Speed was around 60MB/s though. It works but not in optimal working condition. Need to emphasize coaxial splitter is designed for bi-directional communicatoin between "IN" and "OUT" ports. Communication between "OUTX" and "OUTY" is done through isolation spec of splitter. Coaxial splitter is not ideal hub for MoCA network like an ethernet switch for ethernet network.

MoCA isolated from DOCSIS

It should be preferred setup if you can find two coaxial sockets near modem and router.

Dedicated coaxial sockets allow MoCA network to work indepently and it avoids MoCA signal going through main splitter.

Rewiring is needed on entry of point. It is best to change splitters on MoCA path in the plot to coaxial cable coupler for 1:1 in/out to avoid 3.5dB attenuation.

Final Thoughts

In most cases, MoCA communication will go through main splitter behind the wall. Existing hardware (booster/splitter/filter) behind the wall will impact performance of MoCA without rewiring shown in the isolation configuration. Performance may not be as good as advertised.

You may want to check WIFI extender / mesher solution if it is diffcult to implement isolated MoCA network.

This article is not an advertisement of MoCA but rather a feasibility checklist before you invest into MoCA.

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