Hey everyone, thanks for coming back to Wi Fi fundamentals with location and analytics. This course will help you to muster the air. The common topic is one of the most fundamental stuff you need to know decibels and dBm. This is the unit we measure signal strength. But as you will see, it is not an absolute unit. DPS are used to measure the relative power between two devices.
Why do you need to know that because it influences everything. If you want to double your access point coverage, you can do it knowing the Bayes rule. If you want to calculate ranging, you will need to muster the dBm language. And if you're reading a spec sheet of an access point and even an external antenna, you will Once you understand it's gain which is also in DPS. decibels are everywhere in WiFi. What will you learn when we will take a look at DPS that their basic form?
How do we use it? When do we use it? We will look at them in Wi Fi networks and we will learn the B's must know rules. We will also take a look at the six DB rule. Most of our life we use absolute units. We measure power using VAT and mini VAT.
We measure length using centimeters and meters. We measure a weight using grams and kilograms. DPS are relative, they measure the difference or the change in power between two sources. Why do we use DPS because It is much more simple to express the ratio between two power levels than doing all the complicated mathematical function that is involved. Let's see an example. Let's assume that we have a signal sent with a power of eight, but instead of calculating an increase of 4000 times signal, we can say that it has been increased in 36 Db or that the antenna of the transmitting device has a 36 dB gain.
If the signal has been decreased due to attenuation in the scale of 100,000 times, we can just say that it had been decreased in minus 50 db. That simple DB is are used in different flavors in Wi Fi BACnet only, we use them also to describe a cables loss or antennas gain when it transmits. In Wi Fi we use the dBm scale at decibel relative to one millivolt one milliwatt equals zero dBm there is a reference remember it. So in the case where you see a plus sign or no sign at all, it indicates the output signal is larger than the reference than zero dBm. If you see the minus sign that indicates that the output signal is less than the reference. So in our case our access point has 20 dBm transmission power, which is 20 dBm stronger than the reference are at access our station has that loss of minus 70 Db m in relation to the reference which is zero dBm or one millivolt.
Is there an easy way to calculate dBm and what is the six DB rule that we have mentioned before. All of that is coming in part two