Confirming the difference between MIMO and channel width

[thething55]

I have been preparing for a CCNA however, I have decided to take a break from this to learn about some other areas of interest I have around layer 1 and layer 2 networking.

Now, I already know about MIMO (2x2, 3x3,etc) and channel spacing (20,40,80,160,etc MHz) and I am trying to find out if they are the same thing or different technologies however, I seem to be reading conflicting information. Now channel width is an easy one, you simply use a larger width in your frequency to obtain a greater speed however, some websites state that MIMO use the SAME CHANNEL/Frequency on every antenna while some other sites seem to suggest that MIMO uses DIFFERENT CHANNELS/Frequencies on each antenna to communicate which sounds very similar to increasing the channel width.

My question is are these different and if so, does MIMO use identical channels across its antennas or does each antenna use a different channel?

[GR8-Ride]

MIMO and channel bandwidth are two very separate items.   Perhaps the best way to understand the differences between MIMO and channel bandwidth is to refer back to the original technical definitions of MIMO (two types).

 

The first is Space-Time Block Coding.   This is where duplicate data streams are sent from multiple antennas, with the intent of ensuring that at least one clean signal reaches the end device (or is received from the end device).   The purpose behind STBC is to improve signal to noise ratio, with the goal of improving the modulation and coding scheme for the WiFi connection.    This is one form of MIMO, and it uses the same frequency and channel size for each antenna.   STBC works even if the client device only has a single RF antenna.

 

The second type is Spatial Multiplexing.   There is where unique data streams are sent from multiple antennas, with the intent of doubling (or tripling) effective throughput.   This is done by carefully co-ordinating the received signals and reassembling the data stream.   Antenna spacing is critical, as the distance between antennas needs to be a multiple of the wavelength, in order for it to be effective.   Again, SM uses the same frequency and channel bandwidth for each antenna.

 

Hopefully this helps.

 

 

 

Patrck

[thething55]

Thank you for the information. I was was fairly confident that they were different and that MIMO uses the same frequencies. It was just one or two sites which either worded it bad or was just wrong