This cavalier approach extends to HomePlug adapters (also known as powerline adapters). For people who have problems with wireless, HomePlug adapters can be a Godsend. HomePlugs send data over the electrical mains system; an adapter connected to your router is plugged into the nearest three pin socket. Plug another into a socket elsewhere in the house or office, connect it to the computer with an Ethernet cable and voila – you are connected to the internet. In some locations, the wireless signal can be unreliable, perhaps not reaching throughout the building. However, HomePlugs invariably work.
Homeplugs are available in different speeds. Aside from some very early devices, the first widely available models ran at 85 Mbit/s; the most common devices today are 200 Mbit/s. Adapters that also run at 500 Mbit/s and 1000 Mbit/s are also available, both of which are often described as ‘gigabit’ adapters. For instance, the Netgear XAV5101 500 Nano is labelled ‘Powerline AV500 Gigabit’. Tech-savvy readers might want to pause a second to think about that: an adapter that has a maximum speed of 500 Mbits/s is described as gigabit (i.e. 1000 Mbit/s), a speed that it is unable to run at. How can that be? It’s a good question. The Netgear does have a gigabit Ethernet adapter inside, one that can run at 10/100/1000 Mbit/s, only it can’t actually utilise the latter speed. In other words, the term gigabit is not being used in the conventional sense (meaning 1000 Mbit/s) but perhaps simply to mean ‘fast’. This is not to unfairly target Netgear – other brands are equally creative in their labelling.
Dig a little deeper and things get even more murky. Powerline speeds are quoted as duplex; in other words, 500 Mbit/s actually means 250 Mbit/s in each direction simultaneously. So, if you buy a ‘gigabit’ Powerline adapter in the hope of connecting a computer at 1000 Mbit/s, you will in fact be restricted to 250 Mbit/s – a quarter of the implied speed. However, that is only a theoretical maximum speed, and in practice it will be a lot less. Here’s why.
Powerline adapters run over the mains wiring system. Mains systems are not perfect; the specification for electrical wiring was drawn up a century ago and of course was not designed to carry relatively weak, high speed data signals – something that couldn’t even be envisaged in those days. Because of this and other considerations, the wiring system in a typical house or office will be very ‘noisy’ and this affects the ability of Powerline adaptors to operate in an optimal fashion. Additionally, they do not like extensions and surge protectors, plus can pick up interference from other electrical devices that are in use.
Whilst the adaptors do incorporate circuitry to try and cope with these problems, the bottom line is that they run slower than their rated or theoretical speeds, typically at only a third to a half of the rated speed. So, you buy a pair of gigabit powerline adaptors, which turn out to be rated at only half that speed i.e. 500 Mbit/s rather than 1000 Mbit/s. Then you find that that the speed quoted is duplex, meaning it is a maximum of 250 Mbit/s in one direction. Finally, the local circumstances dictate that it will probably max out at a third to a half of that theoretical speed, i.e. 83-125 Mbit/s. Let’s split the difference, and say that you get 100, which is how 1000 Mbit/s becomes 100 Mbit/s.
Does this mean that Powerline adaptors are no good? No, far from it! There are often situations when it is not possible to install Ethernet cable and wireless simply doesn’t work, perhaps because of range or interference issues. Here, Powerline adaptors offer a unique and practical solution. In many situations, the relatively low throughput is not an issue, as it will still be somewhat higher than the broadband connection. Besides computers, it’s often a very good solution for other devices that need an internet connection, such as gaming boxes and TV set top boxes. Where it may fall down is when it is used for connecting a server or a NAS box, particularly in a business environment. Here, it is the technology of last resort for when no other solution is available.