I’ve been tinkering with my Powerline adapters recently, on a mission to improve the bandwidth available to my office. I’ve been familiar with Powerline adapters for a long time, having started with some of those “up to 85Mbps” devices. Imagine my disappointment when I couldn’t get even 16Mbps through it on my slow ADSL internet at the time, I got 8Mbps!
I’m sure by now you’ve found countless internet articles written for clicks that don’t have any real scientific basis, probably telling you to mess with MTU settings and the such, forget all that. We’re going to make changes based on actual science here!
Why should you believe me? Because I managed to actually more than double my throughput from 130Mbps to 300Mbps on my less than stellar (read: old) wiring. Details on this are at the end of the post.
In this blog post we’ll go through some basics around the different Powerline standards and then get into the optimisations, feel free to skip ahead to the optimisations section if you’re not interested.
Standards
When Powerline adapters were a somewhat shiny and new concept, we saw standards come out such as HomePlug AV, later followed by HomePlug AV2 from the HomePlug Powerline Alliance (R.I.P), and more interestingly G.hn. I say interestingly as a lot of these standards are old, but we’re continuing to see incremental performance increases from G.hn, now sporting speeds of “up to” 2.4Gbps.
I say “up to” because, we’re actually talking about the speed of the Powerline rate here, which is different to the network transmission rate, or “bandwidth” we actually want to see. In summary, the conversion rate is typically around 30-35%. So if you’ve got 1000Mbps Powerline rate, then you should see around 300-350Mbps throughput. If this is the level of throughput ratio you’re already seeing, I suggest you stop now, you won’t magically increase your throughput further, but you might find some of these questionable guides that are available online result in nothing more than breaking your connection or causing issues with applications/services due to non-standard settings. However, if you are reaching the maximum speed of your device and there’s a faster version available, it could be worth the upgrade, if you can’t reach the maximum Powerline rate for your existing equipment, it’s less likely that you’ll see a meaningful performance uplift by replacing the hardware, if you’ll see any performance uplift at all.
Optimisations
Powerline adapters work by sending and receiving signals via your electrical wiring, so a good connection to this potential network is key. Here is some advice on optimising this connection, any why:
- Ensure your Powerline adapters are directly connected to the socket, not via a surge protector or extension lead. These devices will typically “stabilise” the “noise” on the power line (our data in this case), which will result in a lower throughput speed.
- Expanding on this, and something I only discovered recently, treat multi-plug wall sockets as if the Powerline adapter is on an extension lead, these neighbours generate an interference in the data signal. Whilst yes you’re not going to have a dedicated power network for data transmission (it’d be far easier and cheaper to just run ethernet at that point), the goal is to put some space between devices that are generating noise, this will lower the disruption to the data signal.
- Some sockets are “spurs” from an “upstream” socket rather than part of the core network loop, performance will be subpar on these compared to being part of the core ring network, as you’re beholden to the noise generated and filtered on that upstream socket(s) more so than a standard ring network.
- More Powerline devices in an environment can reduce interference by relaying the signal. This is because all Powerline devices will receive the signal on its way around the wiring, and perform both filtering of the existing noise on the line that isn’t network data, and amplify the signal again. This will only work if your devices are within the same ring network, as otherwise the connection will be traversing RCDs or even MCBs on your consumer unit/fuse board/electrical fuse box – whichever name you know it as.
- For those attempting to connect between different ring networks, more likely in modern electrical wiring than those houses of old, devices have started to reach the market that integrate into your fuse board. Devolo for example offer a “Magic 2 LAN DINrail” device that promises to boost internet performance via this integration, supporting three phases and earth as transmission channels too for a Powerline speed of up to 2400Mbps. I can’t comment on the performance of this product personally, but it’s an interesting evolution of Powerline technology.
- A second comment related to having multiple rings within your electrical wiring, but less related to Powerline itself. I’d like to share some guidance with those using Powerline adapters with built in Wifi. Whilst it’s tempting to put the Powerline adapter in the place you want the Wifi signal boost the most, if this is an upstairs office on a separate electrical ring, you could find improved performance by placing the Powerline adapter near your location, but in the room on the ground floor below. You would still receive a strong Wifi signal, but with the added potential benefit of increased bandwidth available via the Wifi due to the Powerline Adapter achieving greater speeds.
- MIMO-capable devices: A Powerline network is a Half-Duplex network, meaning the available bandwidth is split between send & receive traffic. It’s quite rare you’d have an application that would only be sending or receiving traffic, so instead your Powerline devices must time-share between sending and receiving. To elaborate further on this, a Powerline network is a “hub” network, instead of a “switch” network, which means that regardless of how many Powerline adapters you have within your network, only one may send traffic at a time. This is the case for a SISO (Single-Input Single-Output) network. Multiple-Input Multiple-Output (MIMO) capable devices utilise the multiple wires in your electrical circuits to send and receive signals simultaneously across the different wires, whilst it is still a hub network, you’ve got multiple paths to send and receive down, reducing network jitter and increasing throughput. In some scenarios, you might find MIMO results in a reduction of throughput, if this is the case, you would commonly have one or more dodgy/faulty wires in your circuit that are reducing the effectiveness of your Powerline network through packet loss and retransmission attempts.
- More distance = more signal degradation. This is a simple one, the further the signal has to travel, the more likely it will degrade and not be received successfully by the other Powerline device(s). Whilst it can be tempting to put the Powerline adapter as near to the intended ethernet device(s) as possible, you could be adding significant additional distance between your Powerline devices, with additional, noise-introducing devices in-between. If you’re working with a single ring network, prior to the final placement of your Powerline devices, do some speed tests with the two Powerline devices on different sockets in their relevant rooms. This is because electrical wiring is run as a ring, running from your fuse board to an electrical socket, then onto the next, and the next, until eventually it has reached the last socket in the ring, and then it is connected again to the fuse board. Because of this, changing the socket used can potentially reduce metres off of the connection path, and reduce potentially a dozen different sources of electrical noise, as you could be moving your devices to sockets that are closer to each other, or have fewer additional sockets between them. If you’re trying to get a faster throughput, you could find a better result by getting the Powerline into the same room that you want it to be in, but running a longer ethernet, potentially trunked, concealed in skirting board, or even run under the carpet, to your intended destination.
- VDSL – Another technology that is sending data down a copper wire is VDSL, commonly known in the U.K. as FTTC internet. Unfortunately the frequency bands that VDSL and Powerline communicate on can overlap, depending on the VDSL profile used. This is a common problem if the phone line and power cables run too close to each other. Whilst there’s generic guidance to be had here around spacing and shielding of such cables, instead I’ll be focusing on Powerline adapter technology. Some vendors offer interference mitigation, either automatically or manually, that can be avoid interference with your VDSL connection, resulting in a lower likelihood of performance impact to your internet, whilst boosting Powerline performance through the reduction in noise on the electrical wires.
- Manufacturer differences – I hate to have a generic sounding item on this list, but it’s true. Each device manufacturer writes their firmware differently, with different tolerances and different performance/stability outputs from this. As part of my network troubleshooting, I swapped my 1200Mbps Netgear Powerline adapters for a pair of devolo 1200Mbps adapters. These devices both supported the same features such as MIMO, but the devolo cockpit software would allow me to see transmission & receive speeds on the Powerline that would give me a better base understanding of the network. But firstly, I put them in the existing place of my Netgear devices. I was unexpectedly, but pleasantly surprised to see that my throughput went from 120-130Mbps to 150-160Mbps and my jitter had noticeably smoothed too. My Netgear devices could provide a slightly lower minimum jitter figure, but the devolo devices more than made up for that with vastly improved average and maximum jitter values.
- Another potential increase in throughput can be gained by devices that will expand upon MIMO by also using Wifi as a send & receive option too. I would be cautious on this one, unless the Wifi signal is great, you’re likely going to risk increased packet loss and jitter via the use of wireless. Not to mention that 2.4Ghz has a longer/stronger signal range, at the trade-off of lower throughput vs 5/6Ghz frequencies, but 2.4Ghz only has 3 channels that don’t overlap, meaning you could quite easily reduce your Wifi experience by attempting this. If you do opt to use this, be sure you have a strong Wifi signal between the devices that is offering a consistent speed, and be sure to put this on a wireless channel that you aren’t using your own Wifi network on, to prevent interference.
Real-World Results
So, putting this all together. I migrated my Powerline adapters from Netgear to Devolo, and say an up to 30Mbps bandwidth improvement (from 130 up to 160Mbps), these devices were at opposite ends of the house. I migrated my front of house device to a single-socket electrical point and saw negligible increase in throughput. My devolo metrics had reported an increase in receive speed but not in transmission for the back of my house, so that was clearly my bottleneck at this point. Next, I moved my back of house Powerline adapter to the front of the next room, and ran a 10 metre ethernet cable to my desk. I saw a doubling of throughput on the devices. The Powerline Speed had gone from around 490-520Mbps receive and 380-400Mbps transmit to a solid 1000-1020Mbps send & receive on both devices. And my speed test then confirmed this, with speeds of around 300Mbps bandwidth. As the devices had a maximum theoretical Powerline speed of 1200Mbps, I was confident I’d found a true improvement.
I then moved to a nearer socket, a few metres away from the one I’d just used, I saw a reduction in Powerline speed to 800-820Mbps, but it was close enough that I could tuck a 5 metre ethernet lead under my carpet to my desk. If I want to increase this further, I can now look at G.hn standard devices that operate at up to 2400Mbps and see about further improvements, but I’m happy with my bandwidth uplift, and that’ll be a project for another day.
To close, some other notes about my environment. My house is nearing 100 years old, with all the electrical sockets in the house residing on a single ring, I’ve got a modern fuse box, but the wiring is decades old, some of it being the original retrofit of electrical cabling into the house. So this is by no means a “pristine lab” environment.
Michael Paul | @micoolpaul 
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