Hello, today we are going to talk about principles steps of WIFI dimensioning
The process of planning and sizing a WI-FI network is carried out in four stages:
1) Sizing by radio coverage: determines the radius and area of WI-FI cells.
2) Capacity sizing: determines the number of access points in each network cell
3) Sizing on the number of switches required.
4) Wiring design: choice of cable type and AP power
Cover sizing
Considering that the radio waves are transported in the air and undergo significant losses in intensity along their path, the knowledge of the characteristics of the pair of WI-FI devices used for the link will make it possible to calculate the theoretical distance of this link, in free space, ie without obstacles.
Power output
The power of the transmitted signal is called the Equivalent Isotropic Radiated Power (EIRP). It is noted Tx on the diagram. It depends on the device-cable-antenna chain: the transmitting device (the access point AP) transmits the signal with a certain power noted Px, the cable connecting the device to the antenna loses a part noted L, and the antenna also provides additional power, denoted G.
By expressing these powers in deciBel (dB), the EIRP is obtained by simple addition:
EIRP = AP power - Cable losses + Antenna power,
either: Tx = Px - L + G.
Cable losses = cable length * loss per meter
Receiving sensitivity
It determines the minimum power threshold that must be received to have a certain data rate. The lower the reception sensitivity, the farther the signal can be picked up. Above -90dBm, this is high reception sensitivity. The reception sensitivity is given for each device.
In order for the received signal to be intelligible to the receiver, the latter must have sufficient sensitivity. Here again, it is the device-cable-antenna assembly that must be taken into account.
The effective sensitivity Rx is an addition of the sensitivity of the device Sx (another characteristic with the power) and the gain of the antenna G, from which we subtract the cable losses L. The gain of the antenna and the cable losses are those used in the previous power calculations.
The effective power of the received signal must be greater than the sensitivity of the assembly, otherwise the signal cannot be used.
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