Microwave Ovens and WiFi Routers

I never cease to wonder about the electromagnetic spectrum. Much of it is invisible to our senses, and yet, we have reached a stage when it is quite impossible to survive without it.

The microwave oven in out kitchens sends out waves at around 2.45 GHz (2,450,000,000,000 vibrations/second!), heating up food at the molecular level. The ubiquitous WiFi that keeps us connected to the internet - and the rest of the world - are "harmonized" worldwide in the 2.4 and 5GHz bands. Even without getting into the world of electronic waves that send signals across great distances (radio, satellite and space probes), getting a grip on regular household devices seems complicated enough!

Both the equipment's - the microwave oven and the WFi router - produce signals in the Industrial, Scientific and Medical (ISM) bands that have been allotted by ITU for non-communication purposes. There seem to be 12 frequency ranges in the ISM band that ranges all the way from 6.78 MHz to 245 GHz. Out of this, home equipment like ovens and WiFi routers use the frequency range 2.45-2.5 GHz.

Since a licence is not required for equipment produced in this range, the part of the spectrum is also crowded with radio-communication services, including amateur satellite services. Thanks to this dual-use, the WiFi equipment you purchase from one country country is likely to interfere with the microwave oven imported from another country. So, if you are heating a mug of coffee in your microwave oven, your internet connection may get disrupted.

International standards - especially IEEE 802.11 a/b/g/n - tries to deal with this problem:

• 802.11a supports bandwidth up to 54 Mbps and signals in a regulated frequency spectrum around 5 GHz. More expensive, usually used by businesses. Higher frequency makes it difficult to penetrate walls, so its best for open areas.
• 802.11b supports bandwidth up to 11 Mbps, comparable to traditional Ethernet. Usually for home networks.
• 802.11g supports bandwidth up to 54 Mbps; uses the 2.4 GHz frequency for greater range
• 802.11n is an improvement on 802.11g in the amount of bandwidth supported by utilizing multiple wireless signals and antennas (called MIMO technology) instead of one.

It is still mind boggling to think that we have actually figured out ways to precisely control devices that produce more than a trillion vibrations per second! How do we do it? And why is it that microwave ovens need chunky magnetrons to produce the same kind of signals that are produced by lightweight WiFi routers?

In an emergency, can I rig up my WiFi router to heat up a mug of coffee? :)

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LINKS

ITU - http://www.itu.int/en/Pages/default.aspx
http://www.itu.int/itu-t/recommendations/rec.aspx?

https://www.howtogeek.com/171869/why-does-running-my-microwave-kill-my-wi-fi-connectivity/

Wireless Standards - https://www.lifewire.com/wireless-standards-802-11a-802-11b-g-n-and-802-11ac-816553

WiFi and Basic Needs

This illustration says it all.

It might be stretching things a bit, but it does indicate how staying connected seems to have becomesome sort of a desperate, visceral need. We now choose hotels and eateries based on their ability to provide reliable bandwidth as much as the quality of accomodation or food. There is now a joke going around that, even at home, the best way to have a family get-together is to switch off the wireless router!

In an earlier post, I had figured that all WiFi devices talk to each other in the 2.4 GHz frequency, and that as per international protocols this band is divided into 79 channels (each 1 MHz wide) which the devices can change up to 1600 times per second, just to keep a data connection going.

I still have no idea how the scientists managed to create anything that sends out 1,000,000,000 vibrations per second, let alone how they go about slicing it like a cake and passing it around with all the icing and toppings intact.

Perhaps it is easier to understand things that are happening at an individual device level. Here are two parameters from my WiFi analyser:

The first screenshot shows that the signal strength ranges from -100 dBm (decibel milliwatts) to -40 dBm. The key unit here is that of power - Watts. It takes a thousandth (1/1000) of a Watt to send out signal equal to 0 dB.

The negative sign comes from the log scale. To quote WirelessAnnonymous:

Under a log 10 scale, a value of -2 represents 10 to the -2 power, which equals 0.01. Likewise, a negative dBm means that you're applying a negative exponent in your power calculations; 0 dBm equals 1 mW of power, so -10 dBm equates to 0.1 mW, -20 dBm equates to 0.01 mW, and so forth. It's a lot easier, and more useful in some calculations, to describe a weak signal as -100 dBm as opposed to 0.0000000001 mW.

The following shot illustrates how the signal strengh drops the further you move away from a router. The closest ones are sending out signals stronger than -50dBm while the farthest ones have the green bands diminishing into the -90 dBm range.



Then you have the next most important thing: the media access control (MAC) address.

When you have millions of data signals riding piggypack on radio waves, it is necessary to ensure that they reach the right destinations. For this, each WiFi device comes with a unique MAC address and they all use the address resolution protocol (ARP) to avoid cross-talk. If we compare the whole set up to city traffic, MAC represents the final destinations (a mall, home or fuel station). Vehicles (data packets) traveling along the roads (the internet protocol/IP) are capable of reaching anywhere but get an entry only to those places which have a matching MAC address.

This brings us to the next basic need - how do we stay safe from the carjackers, and hackers hiding in the dark streets?

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REFERENCES & LINKS

* Reading signal strength -- http://www.tomshardware.com/forum/9782-43-read-signal-strength
* How to Geek - MAC Address - http://www.howtogeek.com/169540/what-exactly-is-a-mac-address-used-for/
* Ask Leo: IP address vs. MAC address -- https://askleo.com/whats_the_difference_between_a_mac_address_and_an_ip_address/