Hey everyone, thanks for coming back to another chapter in Wi Fi fundamentals with location and analytics. This course will help you to muster the air. We have gone through frame types. And I wanted to give you a real life scenario that happens quite a lot in Wi Fi deployments, where to control frames, RTS requests to send and CTS clear to send comes handy. They're actually like traffic cops. Their main goal in life is to make order and silence the environment.
That's right, silent everyone in the network. When do we use them? Why do we use them? Well in different cases, such as the hidden note situation to understand RTS and CTS, we have to Go back to our Mac frame header. And remember the duration value field. The two by duration field indicates the remaining duration or time needed to transmit the frame.
This is the minimum time that the other stations need to wait before attempting to send their own frame. What is station here is the Wi Fi frame transmission by another station. It will set its own Neff timer network allocation vector, according to the duration value, which is in microseconds. And RTS duration value is usually longer than other frames. The reason is to make sure that the station or access point that sends it have enough time to complete its task whenever station sensor requests to send frame around access points with a Sif and then response with a clear to send frame. So when do we get to see RTS and CTS used.
In many cases we will focus on two scenarios, the hidden station and the hidden access point. Here we have two stations who can hear each other, but they're both connected to the same access point which hears both they can hear each other's frame and therefore can share the media using enough timer contention window and back off timer. Whenever both transmits, their frames collapse and their access point can acknowledge them. The solution is quite simple station a will send Then RTS frame with a long duration value. Our access point will pick it up and send its own CTS respond, which is the same duration value. Station B will hear that CTS respond and the act accordingly set up its own Neff timer, and so station a can send its transmission safely.
Our next scenario is hidden access point. We have two access point. Working on the same channel, we actually have a co channel interference, both are working on channel one. Access Point one transmits a frame to one of its stations in its BSS. At the same time access point to transmit a data frame. Both frames will collide Remember that both stations are choosing to listen to the same access point channel.
Although they are not connected and all transmissions in the overlapped coverage area are hurt. The solution is simple again. Access Point one will send an RTS frame along with its duration value. Its station will hear it and send a CTS frame. Since station one is an access point to coverage area or right access point will pick it CTS and set its own Neff timer to the duration when and now everyone can transmit safely. Coming up next is free space path loss where we will begin our journey to Three changing and location.
See you soon