5 ms·

Happy to see MoCA get a shout- out. I spent most of 2003-2015 working on the design of MoCA chips, starting before the v1.0 spec release up through v2.5. AMA

phonon 6y ago
How is MoCA 2.5 different from G.hn Wave 2?
- variaga 6y ago
  The main difference is that MoCA is designed to run over coaxial cable, and G.hn is meant for use over power lines. They have similar use cases ("route data over wires that already exist in your homes"), but different problems (MoCA: avoid interfering with your cable/satellite/cable modem feed, G.hn: deal with the absolutely abysmal signal quality on power lines, avoid accidentally broadcasting in the FM bands,...) From a modulation perspective, G.hn wave 2 and MoCA 2.0 are broadly similar. They both use OFDM as the main modulation and LDPC as the FEC. They both are scheduled networks (like 802.11, unlike wired ethernet) where a master node allocates transmission time slots to other nodes. The devil is in the details though and I'm not as familiar with the G.hn wave2 spec as MoCA, so the detail I can give you is limited.
  - vvanders 6y ago
    You alluded to it but the other difference is MoCA is shielded, EoP turns your house wires into a ton of radiating antennas across the frequency bands. I still have no idea how the FCC even approved the damn things after seeing what they do to the RF spectrum nearby.
    - variaga 6y ago
      Correct. Coax is nice and quiet in both directions. In home power wiring is basically a giant, poorly tuned antenna. I can tell you MOCA 1.0 can be made to work over powerline (at reduced bandwidth, if you rip out the RF frontend and run at baseband), and it can pass emissions, but it didn't work well enough (by % of households able to achieve >= target data rate) to be worth commercializing.
wolrah 6y ago
Why is MoCA still so rare and expensive? Is there a technical reason or is it just some combination of business reasons? It seems like it's been the obvious choice for no-new-wires home networking for years but you basically can't find it at retail and have to look for it even online.
- variaga 6y ago
  <normal disclaimer about this just being my opinion> I think there were a couple of contributing factors: - WiFi is still easier to install (where you can get a good signal), and built into phones/laptops/etc. so mostly all you have to do to get wireless networking is buy the router. For MoCA, you have to buy & install a box for every endpoint. Also, MoCA is limited to places you have coax, which is usually bedrooms & living rooms. If you need connectivity in the garage/attic/closet/kitchen, MoCA might require new wires anyway. - Lack of interest from MoCA developers. The main "customer" for MoCA chips was cable set-top-box vendors (Scientific Atlanta, etc.) for "multi-room PVR" products. That's where almost all MoCA networking chips made ended up. The cable/satellite vendors needed the deterministic performance of MoCA (vs WiFi) and they were always planning on putting a box in every room with a TV - which generally already aligns with where the cable taps are. They could also pre-configure the MoCA so it wouldn't interfere with some other stuff they might want to put on the cable (Example: DirecTV put its downlink from the dish squarely in the middle of the MoCA frequency band, so you had to configure MoCA to a different channel in DirecTV houses than e.g. Verizon). The market for bare Ethernet-Coax Bridges (ECB) was always tiny in comparison. - The chicken and egg problem. The consumer market for bare Ethernet-Coax gateways was smaller (see above) as it has to compete with both WiFi and "just run some new CAT-5" (as well as niche things like HPNA/G.hn) so it didn't get a lot of focus or advertising. In turn, this means most people have no idea that MoCA even exists, so they don't go looking for it. D.Link, Netgear, Linksys, etc. then decided that lack of demand meant it's not worth developing/advertising new/improved versions of the products, etc. MoCA was a very targeted solution for adding IP connectivity to things which were already wired together on a Coax network, and it did a great job at that. We sold 100s of millions of chips. MoCA was never meant to be all things to all people though, and while I personally use MoCA in my home I never got my own parents to use it - they just have the one computer hooked directly to their router, and WiFi for their iPad.

phonon 6y ago

How is MoCA 2.5 different from G.hn Wave 2?

variaga 6y ago
The main difference is that MoCA is designed to run over coaxial cable, and G.hn is meant for use over power lines. They have similar use cases ("route data over wires that already exist in your homes"), but different problems (MoCA: avoid interfering with your cable/satellite/cable modem feed, G.hn: deal with the absolutely abysmal signal quality on power lines, avoid accidentally broadcasting in the FM bands,...) From a modulation perspective, G.hn wave 2 and MoCA 2.0 are broadly similar. They both use OFDM as the main modulation and LDPC as the FEC. They both are scheduled networks (like 802.11, unlike wired ethernet) where a master node allocates transmission time slots to other nodes. The devil is in the details though and I'm not as familiar with the G.hn wave2 spec as MoCA, so the detail I can give you is limited.
- vvanders 6y ago
  You alluded to it but the other difference is MoCA is shielded, EoP turns your house wires into a ton of radiating antennas across the frequency bands. I still have no idea how the FCC even approved the damn things after seeing what they do to the RF spectrum nearby.
  - variaga 6y ago
    Correct. Coax is nice and quiet in both directions. In home power wiring is basically a giant, poorly tuned antenna. I can tell you MOCA 1.0 can be made to work over powerline (at reduced bandwidth, if you rip out the RF frontend and run at baseband), and it can pass emissions, but it didn't work well enough (by % of households able to achieve >= target data rate) to be worth commercializing.

wolrah 6y ago

Why is MoCA still so rare and expensive? Is there a technical reason or is it just some combination of business reasons? It seems like it's been the obvious choice for no-new-wires home networking for years but you basically can't find it at retail and have to look for it even online.

variaga 6y ago
<normal disclaimer about this just being my opinion> I think there were a couple of contributing factors: - WiFi is still easier to install (where you can get a good signal), and built into phones/laptops/etc. so mostly all you have to do to get wireless networking is buy the router. For MoCA, you have to buy & install a box for every endpoint. Also, MoCA is limited to places you have coax, which is usually bedrooms & living rooms. If you need connectivity in the garage/attic/closet/kitchen, MoCA might require new wires anyway. - Lack of interest from MoCA developers. The main "customer" for MoCA chips was cable set-top-box vendors (Scientific Atlanta, etc.) for "multi-room PVR" products. That's where almost all MoCA networking chips made ended up. The cable/satellite vendors needed the deterministic performance of MoCA (vs WiFi) and they were always planning on putting a box in every room with a TV - which generally already aligns with where the cable taps are. They could also pre-configure the MoCA so it wouldn't interfere with some other stuff they might want to put on the cable (Example: DirecTV put its downlink from the dish squarely in the middle of the MoCA frequency band, so you had to configure MoCA to a different channel in DirecTV houses than e.g. Verizon). The market for bare Ethernet-Coax Bridges (ECB) was always tiny in comparison. - The chicken and egg problem. The consumer market for bare Ethernet-Coax gateways was smaller (see above) as it has to compete with both WiFi and "just run some new CAT-5" (as well as niche things like HPNA/G.hn) so it didn't get a lot of focus or advertising. In turn, this means most people have no idea that MoCA even exists, so they don't go looking for it. D.Link, Netgear, Linksys, etc. then decided that lack of demand meant it's not worth developing/advertising new/improved versions of the products, etc. MoCA was a very targeted solution for adding IP connectivity to things which were already wired together on a Coax network, and it did a great job at that. We sold 100s of millions of chips. MoCA was never meant to be all things to all people though, and while I personally use MoCA in my home I never got my own parents to use it - they just have the one computer hooked directly to their router, and WiFi for their iPad.