Introduction to Powerline communications (g.hn) and Devolo Magic 2

Santa brought me a couple of new powerline adaptors so I will share some experience with Devolo Magic 2 - a kit that is advertised for a speed of 2400 Mbps. The speed is the theoretical maximum uplink and downlink added together.

Introduction

Throught the ages engineers had the dream to use power networks for data communication. However, this showed out to be notoriously difficult and power line communication has been reinvented time and again. I think there are few products that disappoints as much as these becuase you will seldom achieve even close to the speed on box but in certain ideal cases. The reality is that the powerline network is very noise and it is hard to do anything.

The standard

g.hn is a fairly new standard for powerline communications developed by ITU (International Telecommunications Union in Geneva). It replaces e.g. AV2 and whatever is in the market and it your best option if you need to fallback on this technology.

g.hn supports multiple media such as

• Powerline
• Telephone lines
• Coaxial

The standard has very efficient error corretion (LDPC) and advanced support for topologies, relays, gateways, interconnection between various media. MIMO is an obvious part. It uses OFDM and various orders of QAM. Good coexistence with e.g. VDSL is build into the standard.

The standard promises more robustness and speed than ever.

Why do I need it?

My house has stone walls and 3 floors and WiFi penetrates badly. Due to the size of the house I need at least 2 access points. WiFi repeaters is usually a bad idea - I tried it.

Powerline allows me to connect two mesh routers using cable without trying to pull Ethernet from the top of the house to the basement which would be an extremly challenging project.

When will it work well?

Powerline can work well when

1. All 3 pins in the socket are connected
2. The two devices are on the same phase
3. The distance between the devices is not too long e.g. < 30 meters

Needless to say my house is a good candidate but never expect huge speeds.

What does the speed indication mean?

In powerline communication it is normal to display the speed (Mbps) of the radio up and down link. This is different from througput (Mbps) but it is important not to confuse them because confusing them will lead to much disappointmen as througput is much lower.

Devolo Magic 2

In radio technology there is nothing magical, it is all physics and probability calculus. When it is designed well it will work well. Devolo is no different and this kit is not based on the paranormal.

The Devolo Magic 2 has a nice and modern user interface. To maximise speed I disabled all VDSL safeguards(I do not need them) and turned on maximum power and MIMO.

I measured the throgput using Ookla and a diretly connected computer. This speed is really ok for my purpose:

The physical speed according to Devolo was

We see that the actual throughput is <20% of the radio link and this is normal.

Conclusion

The Devolo has been running stably for a week now and it has not disappointed and it was precisely what I expected with respect to performance. Thanks to the upgrade from AV2 to g.hn I more than doubled the throughput in the basement and the Internet experience is now ok.