MIMO Tutorial – Part One

I have posted part one of the MIMO tutorial. The first part is mostly concentrated on the capacity issues. You may think why even worry about capacity; We don’t seem to worry about the capacity of the traditional SISO links. We have to worry about the capacity possible with MIMO because that is the only way to know if this new-fangled technique requiring lots of antennas and receivers is even worth doing. And the conclusion is, no surprise, that MIMO is very much worth doing.

For same power that we might use in a regular link, if we just replace the transmitter and the receiver with a MIMO transmitter and a MIMO receiver, we have got ourselves as much as 3 to 4 times higher capacity. This is what we see when we went from 802.11 N to G. The gains came from the application of MIMO. You are already using MIMO in your router with its two antennas.

But what is MIMO, is it Multiple Access, NO. Is it modulation, No. Is it a type of receive signal processing like a rake receiver, No, again. It is just increasing the number of transmitters and receiver from one to many. The signal processing actually gets simpler, believe it or not.

MIMO is the future, but not for all applications. Line of sight links do not benefit from MIMO. So MIMO’s application is primarily in wireless phone and home networking.

As a topic to study, it seems complex and it is. Because you have to back track and start at the beginning by first looking at what it can offer. Then it very quickly leap frogs to trellis coding, block coding and these are not even for the purposes of error-correction. I will cover these in the next part.

Please let me know if it is easy to understand. MIMO does have a whole lot of new ideas, or actually old ideas combined in a new way. So it is confusing. Two books that I referred to a lot and like in order of preference are by Andrea Goldsmith (Stanford) and David Tse(Berkeley). David Tse actually has some terrific video movies on MIMO. Find them and watch them.

There are several other books that I used while writing this tutorial and I shall provide a list of these in part two.

BTW, if you have younger siblings or kids, be sure to look at my new Verbal Math books for kids. We have them in Kindle format now.

Posted in MIMO tutorial signal processing digital communications

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