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Friday, October 30, 2020

An Expert Explains: Why does an internet connection become unreliable in the rain?

Why does your internet connection become unreliable and your cell phone start giving trouble when it rains? The reason lies in the nature of electrical force — and the ways in which bad weather disrupts its working.

Written by Varun Makhija | Updated: September 24, 2020 11:14:40 am
India monsoon, rains and internet, monsoon and internet connection, india rains, rains cell phone connectivity, indian expressOn a road in New Delhi on August 28, 2020. (Express Photo: Amit Mehra)

As the monsoon begins to officially retreat, many in India will be looking forward to some relief from a phenomenon that they have come to expect whenever it rains: Internet connections become unstable, and cell phone networks deteriorate. Why does this happen?

In the 1860s, the Scottish physicist James Maxwell predicted the existence of a new kind of ‘electromagnetic’ waves that travel at a speed of ~300 million metres/second. A couple of decades on, Heinrich Hertz experimentally verified Maxwell’s theory and, in 1895, Sir Jagadish Chandra Bose demonstrated for the first time wireless communication with electromagnetic waves over a distance of 23 metres in Calcutta, establishing the foundation of a modern system of communication.

To understand how we communicate or send messages today via the Internet across continents – and then how this communication is disrupted – we first need to understand the fundamental nature of electrical force.

The Expert

Varun Makhija is Assistant Professor of Physics in the University of Mary Washington.

Electrons in communication

There are three fundamental building blocks, or ‘Lego bricks’ that nature uses to make all matter – two kinds of quarks, and the electron. For our purposes, we need to discuss only the electron.

All matter consists of many, many electrons. Like the other Lego bricks, electrons have a property called mass, which indicates how strongly the gravitational force acts on them, and is therefore directly related to their weight.

Another property of electrons called electric charge indicates how strongly the electrical force acts on them. The electron’s charge also decides the strength of the electrical force they apply on other objects that, too, have a charge (like the two other Lego bricks, for instance). This force, like the force of gravity, acts at a distance. So, two electrons separated by a long distance apply electrical forces without ever making contact. Since an electron is charged, the space around it is filled with an electric field.

If you imagine that an electron lives in an ocean it creates, you can, if you wiggle the electron, initiate a wave in this ocean. This is similar to throwing a stone in a still pond, which creates ripples that travel away from it. When this wave passes by another electron that happens to be in our electron’s ocean, this other electron will bounce up and down – as you might when an ocean wave washes over you.

This is how we communicate. An electromagnetic wave is initiated at some location by wiggling electrons, which then washes over electrons at some distant location. The word ‘signal’ specifically means electromagnetic waves. The electrons in your eyes can also respond to these waves, provided the wavelength – the distance between peaks in the wave – is within a specific range. In this particular wavelength range, electromagnetic waves are visible to us; they are light! The most basic form of long-distance communication – flashing a bright light and using Morse Code – uses the transfer of electromagnetic waves from one location to another.

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Optical fibres & the rain

These concepts equip us to understand the only mode of communication that matters anymore, the Internet. This is essentially a vast network of computers across the world that can transfer electromagnetic waves to each other, and therefore communicate.

There are two primary ways to transport waves — by optical fibre, and cellular towers (via satellite link). Optical fibres are long, thin glass rods of thickness less than human hair. Light is confined in the rod due to the phenomenon of total internal reflection. When light travelling from a denser medium to a less dense one (for instance, from glass to air) hits the surface between two transparent media at a critical angle, it is entirely reflected back into the denser medium. This way, electromagnetic waves are trapped inside the fibre, and travel down the length of it. Splicing or joining hundreds of thousands of kilometres of fibres together, and burying them underground or undersea, allows communication across the globe. The electromagnetic waves used for communication (infrared waves) are generated by lasers, and have a slightly longer wavelength than visible light, so they are invisible to us.

The optical fibre network in India was initiated by VSNL, and is currently owned and developed by Tata Communications. All Internet Service Providers connect in some way to this ‘Tier 1’ network, and eventually to your home. These secondary connections are not necessarily optical, and involve several electrical components. (Note: Electrical cables transfer electrons rather than electromagnetic waves, but that’s a topic for another day!) Electrical components are also required along the entire optical fibre network to amplify and switch the light on and off for digital communications.

Monsoon rain might interrupt this subterranean network in many ways. The combination of water seeping into the ground and landslides can damage the various electric components in the network, or cause physical damage at locations where the fibres are spliced together.

There can also be similar damage, or power outages at intermediate locations, where your local service provider connects to the Tier 1 optical network, and then to your home. The fibre has a core, cladding, and plastic protective coating and is held in a watertight protective enclosure, so the signal transmission is least affected by rain. The coating is removed while joining two fibres. At locations where fibres begin or end (known as ‘splice boxes’) there is a possibility of fibres being exposed to rain water, causing a reduction in signal strength . Additionally, water molecules may find a way via micro cracks in the fibres, eventually affecting the life of the fibre.

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Cell phones in the rain

When your cell phone is connected to the Internet, electromagnetic waves travel from your device through the air to a cell tower. You could think of this as a giant antenna. The electrons in this antenna bounce up and down. When they do this, they produce their own electromagnetic waves, which travel to a central location managed by your service provider. At this location, the waves get ‘processed’ in some way, and are sent either to the optical fibre network (the Internet) or another phone (phone call, text message, etc.).

There are various kinds of processing that might occur. For instance, one important difference between the electromagnetic waves emitted from your phone and those from the laser that travels in the optical fibre is the wavelength. The radio waves emitted from, and received by your phone, are approximately a metre long. In contrast, the infrared waves that travel through the fibre network are approximately a millionth of a metre in length. Note that neither of these wavelengths affects the electrons in your eye, since they are not visible wavelengths (around 500 billionths of a metre long).

Somehow, the message from your phone needs to be ‘translated’ from radio to infrared waves. If you were using Morse Code, you might imagine that the radio waves detected by your provider flash on and off, containing your message. The laser managed by your provider needs to be made to produce the same sequence of flashes that travel through the fibre network.

The reasons for interruption in this communication chain during the monsoon are different compared to the optical fibre network.

The radio waves travelling between your phone and the cell tower can make electrons in water drops wiggle, interrupting communication. The size and number of rain drops reduce the signal strength due to the scattering of the radio waves, while water vapour in the atmosphere absorbs the radio waves, converting them to heat (like in your microwave oven).

Further, heavy monsoon rain, wind, and lightning can cause damage to cell towers, resulting in interruptions in the area they cover. Note that this is also why you find yourself without any signal in some areas – there is no cell tower nearby. But perhaps the most common cause of interruption is ‘jamming’. When too many people try to communicate through signal processing locations at the same time, some messages get lost.

Getting that favourite meme from its author’s computer to yours is, therefore, an effort that involves electromagnetic waves travelling many thousands of kilometres. It is an extraordinary achievement of modern science, and it would seem amazing that it works at all! Perhaps this can ease your frustration somewhat the next time your Internet goes off during a rainstorm!

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