Bandwidth

Accessing Internet over Power Lines

The power lines, are present in almost all the localities (including rural homes). Is it possible to access Internet through these all-reaching power lines? And more importantly, is it feasible? We’ll look at both the technology (Called as BPL – Broadband Over Power Lines / PLC – Power Line Communications) and its advantages/dis-advantages, in this article.

Is it possible to access Internet over the Power Lines?

In short, Yes. The technology for transmitting data along with power has been there for quite some time. Earlier, the SCADA signals used to be transmitted along the power lines in order to take some important readings. Now, Internet access is possible through power lines, as data (Through RF signals) can be bundled along with electric current to enable Internet access along with power, with the same power lines.

There have even been some announcements of deployments of BPL here and there. But the main reason that we do not see large scale deployments is because of the Interference issue – BPL (Broadband over Power Lines) interferes with Short wave / Low range wireless communications (Ham radio’s included).

What kind of technology is used to enable Internet over Power Lines?

The basic principle used to carry electric current and data (Through RF Signals) is that, they vibrate at different frequencies and hence don’t interfere with each other.

There are three types of Power Lines – The High Voltage Lines (that carry – Hundreds of Kilo Watts), Medium Voltage Lines (Few Kilo Watts) and Low Voltage Lines (Few hundred Watts). Power is transmitted in all the three type of lines starting from power stations to the subscriber homes.

Since power in High Voltage Lines vibrate at multiple frequencies across the spectrum, data cannot be transmitted using them. So, a separate cable (Like Optical Fiber Cable) needs to be used along this stretch to carry data, separately from the power lines.

Data can be transmitted (In the form of RF signals, the same kind used in wireless networks) over Medium Voltage lines but there is a distance limitation. So, repeaters are used to amplify these signals and they are re-transmitted from multiple locations.

Transformers convert the medium voltage current in to low voltage current that is suitable for individual home consumption. But data (RF signals) cannot travel through the transformers. Hence, some specialized equipments (like CT Couplers) are used for RF signals to bypass the transformers. From there on, they go in to the home wiring using the low voltage power lines.

Some times, wireless access points are installed in the poles itself, and the data is carried through the wireless medium (as Wi-Fi signals), in to the homes. But normally, they are taken in to homes along with the low voltage power lines.

There are power line modems that connect to the electrical power supply at one end and computers at the other – through CatV Twisted Pair Copper Cables (And RJ-45 Jacks), to enable Internet connectivity.

Are there any Standards & What are the speeds that can be achieved for Internet over Power Lines?

Earlier, it was 3.1 Mbps Internet connectivity that would be shared among multiple users. But these days, since the IEEE 1901 Standard for BPL technology has been released, speeds of up to 200/ 500 Mbps is possible and data signals can travel distances of up to 1500 meters.

What are the advantages of accessing Internet over Power Lines?

Since the power lines reach almost every home (mostly), new cables need not be laid at many locations to enable copper/ fiber based Internet connectivity. This reduces the time and cost of laying new cables. This is especially very useful in rural/ hilly areas which are not connected by copper cables for broadband access.

There are equipments available to calculate the amount of Internet bandwidth consumed by each user, over these power lines. The RF technology used to carry data over power lines is well understood and reliable. BPL technologies can be used only for the last mile connectivity, in places which are not already connected with existing cables.

What are the disadvantages of transmitting Internet over Power Lines?

The main disadvantage is the Interference caused due to the BPL technologies to Short Wave/ Low range communications, including Ham Radios. These frequencies are used even by Governments during emergencies and are reserved, in most countries. Another disadvantage is the maturity of other forms of broadband technologies.

Even in rural areas, mobile broadband technologies have started to penetrate along with copper cables (for DSL) and Satellite based Broadband access. Due to large number of subscribers for these technologies, the cost of Internet access through the alternate Internet access technologies is coming down rapidly.

If electric power is cut, the Internet (and telephony, if VOIP/ IP Telephony is used) also gets terminated. In most of the areas, power is provided using State run companies or exclusive monopoly based power companies, some of which may not be in a position to give good support/ trouble shooting.

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