# Signal Strength, Quizzes, and BSSID / SSID / ESSID
###### tags: `elearning` `Multimedia Wireless Network`
###### Note Page : [:link:](https://hackmd.io/@YTL0307/HJEb6jWCo)

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## **Signal Strength**
- The changes in a signal strength is measured in a unit called dB (decibel) and dBm or decibels in relation to a milliwatt, which is the unit that is used to measure the absolute value of the signal strength in a location.
- A logarithmic scale is used to measure the signal strength in a Wi-Fi network as opposed to a linear scale.
- The rule of 3s and 10s is used to measure the changes in the signal strength.
- Essentially, it uses small numbers to represent big changes.
- As the Wi-Fi signal strength is very low, the dBm scale dips into negatives.
- For instance, if you move up from a signal strength of minus 70 dBm to minus 67 dBm, there is an increase or gain of plus 3 dB in signal strength.
- Similarly, when you move down from minus 70 dBm to minus 73 dBm, there is a loss of minus 3 dB in signal strength.
- Therefore, every time you go down 3 dB, you reduce your signal strength by half and when you go up by 3 dB, you double your signal strength
- This is the rule of 3s.
- A different rule applies to the rule of 10s.
- Every time you go down 10 dB, you reduce your signal strength by 10 times and when you go up 10 dB, you gain 10 times more than your signal strength.
- Another alternative measurement unit to measure signal strength can be the milliwatt (mW), which is very precise.
- However, as the Wi-Fi transmission power is very low, using mW for denoting Wi-Fi signal strength gives the numeric value of the signal strength with many decimal places and can be cumbersome to understand and use in real time.
- You can also see that the table shows some "good" signal strengths. However, the term "good" is highly relative and is not an established value by any rules or means.
- These can serve as just rough guidelines.
- You can refine these numbers with your own experiences of what a "good" signal strength means.
- From minus 80 dBm values and lower, the Wi-Fi signal strength becomes highly unreliable, such that at minus 90 dBm, it is completely taken over by the noise floor or the background noise.

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## **Quizzes**

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## **BSSID / SSID / ESSID**
- Wi-Fi devices are marked with a unique identifier that helps to differentiate between them.