• Table Of Contents

Electronics Basics

Frequency, Time period

<aside> 👉 Time Period

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If we think about a swinging pendulum, its time period is the minimum amount of time it takes to reach back to its position from where it started off (one iteration)

<aside> 👉 Frequency

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• It’s the number of oscillations in a second.
• Opposite of time period viz. $f = 1/T_{time-period}$
• The SI unit is Hertz (Hz)

Difference b/w Bandwidth, Throughput and Speed

<aside> 👉 Bandwidth

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• It’s a range of frequencies, and is the difference between the upper and lower frequency
• $B = u_{upper} - u_{lower}$
• Different from frequency as the latter indicates number of cycles in unit time ($cycles/seconds$), while on the other hand, Bandwidth is used to showcase the amount of data that can be transferred in unit time theoretically($bits/seconds$)

<aside> 👉 Throughput

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• While the bandwidth is a theoretical amount, it may/ may not connote to the real-life readings because there are a lot of other factors at play.
• Throughput is the actual amount of data passing through media (considering all the devices)

<aside> 👉 Speed

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It’s a generic term used interchangeably with bandwidth and throughput

Attenuation: Relationship b/w frequency and range of wireless signals

As the frequency increases, the distance b/w each consecutive high/ trough decreases (the wavelength), and lower wavelength waves are easily absorbed by objects, to keep up with the signal loss (attenuation) we need to provide more and more power, which is not possible because we provide constant power supply, which is why, the range of high frequency waves is less.

Relationship b/w data rate and frequency

If the frequency is high, it means more to-and-fro motions in a second, and we can fit more data in them, which is why we say the more the frequency, the better the data rates.

Classification of EM Waves

• Electromagnetic waves can be classified based by the region of frequency they operate on, and this classification is known as EM Spectrum.
• EM spectrum is divided into different bands with different names: Radio waves, microwaves, infrared, visible light, ultraviolet, X-Rays and Gamma rays.

Wireless Basics

Major players in the Wireless game

<aside> 👉 IEEE

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• IEEE (Institute Of Electrical and Electronics Engineers) is an organisation that does work, improvements and standardisation in the electronics space.
• It has various committees working on different technologies, and each committee is split further into working groups

<aside> 👉 Wi-Fi Alliance

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• An not-for-profit alliance of companies, vendors, consumers, researchers and other interested parties which strive to make the wireless technologies better.
• Has a vendor certification process where vendors give their devices to this body for testing and potential certification
• This alliance has a lot of responsibilities such as watching over the developments being done in the 802.11 space, standardisation, addressing security problems, ensuring interoperability etc.

What is IEEE 802.11

<aside> 👉 Basics

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• The 802 committee aims to build standards and stuff in the LAN related space, and the .11 working group (802.11) specially works for the WLAN
• IEEE 802.11 is the standard laid out by IEEE, which is a sub-part of the 802 IEEE standard.
• It’s neither a single technology, nor a single standard, rather its a collection of original defined standards and the amendments made to it over time.
• 802.11 is a standard, and 802.11a, 802.11n etc are amendments

<aside> 👉 The Amendments Of 802.11

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• We refer to the IEEE 802.11 amendments by suffixing the same with some code, such as 802.11ac, 802.11ax etc, where the code represents a specific amendment
• There are a lot out there: 802.11b, 802.11a, 802.11g, 802.11n, 802.11ac, 802.11ax etc viz. bagnac ax

<aside> 👉 Generational names for 802.11 amendments

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• The amendments codes were very confusing, so WiFi alliance came up with generational names
  • Devices with 802.11ax and WPA-3 of 802.11i support are classified as Wi-Fi 6 certified
  • Devices with 802.11ac support are classified as Wi-Fi 5 certified
  • Devices with 802.11n support are classified as Wi-Fi 4 certified
  • Devices with previous versions will not be rebranded
• The classification is based on highest capability offered by that piece of hardware. For example, a device certified with WiFI-6 will always be WiFi-6, whether connected to a 802.11ax network or a 802.11ac network.

<aside> 👉 Frequency bands in the 802.11 standard

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• Wireless transmission is also a type of EM spectrum
• A frequency band is delimited by a lower and upper limit frequency. A system operating under this frequency band means the waves which will be emitted by the system, will have its frequency under this range
• There are more frequency bands than just 2.4 and 5 GHz, some are proprietary, and some are very uncommon.
• When our frequency is lower, our throughput will be lower, the range will be more and the capacity of carrying data will be lower
• Some bands are proprietary and we need to get a license in order for our routers to operate in that frequency band, others are known as ISM bands.

WLAN

Wireless concepts: Antenna Diversity, Spatial Streams and Beamforming

<aside> 👉 Antenna Diversity

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<aside> 👉 Spatial Streams (Concept)

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• In the antenna diversity concept, we had assumed both the antennas transmit the same signal, but it’s not the case always