That brings us to the benefit that is facilitated by massive MIMO, and that is in technical terms known as beamforming. Now, some of you might realize this that when we discussed some of the key advantages of millimeter-wave in the previous module. We do discuss beamforming to certain extent without naming names, without seeing that it is beamforming. But now we are at a point where we can explicitly learn what beamforming is and why we do so. You will be able to recall some of the fundamentals that we did discuss when talking about some of the fundamental benefits of millimeter-wave. How can we begin to understand beamforming? Well, as I had mentioned previously, once you have an antenna array, a panel of multiple antennas, you basically have two choices. You can either let all the individual antennas do their own thing and let them operate as individual entities or you can make some or all of those antennas work together in unison, and that working in unison has the potential to achieve some of the benefits which are called beamforming and something that we're going to talk about next. Legacy technologies in general, like LTE or Wi-Fi they're limited in terms of how many antennas they can have. Typically they have four antennas. Furthermore, their antennas don't necessarily work together in unison. As a result, the energy that the antennas on a typical entity in eNode B, for example, would look something like this. Something like a wide balloon. This is the rough shape of a transmitted wireless signal from an entity eNode B. That is because the antennas don't necessarily work together in unison. If you have a user that you want to serve and is located here. That is fine because the wireless signal reaches that user but at the same time, it reaches many other points that it isn't relevant at. This would essentially be some tremendous wastage of energy in lateral directions because that is not where your user is, your user is located over here. But because this is how the shape of the transmitted wireless signal looks like or coverage, in other words, this is how the coverage of wireless signal looks like. [inaudible] you end up sending some energy and not just in the desired direction but also in a lot of undesired directions leading to a lot of wasted energy. However, with the advent of 5G and massive MIMO, you will have an antenna panel. That panel looks mostly like a rectangle with many individual antenna elements. If you could make them work together in unison by executing some smart signal processing algorithms on the back-end. What you can achieve is you can make those antennas transmit their energy as one unit only in the direction of interests. That is the direction where your user is located. Let's say this is where your user is. Then beamforming entails that those antenna elements will focus their transmitted energy as a sharp narrow beam focused only in other design direction of interest towards the user. Because there is this one sharp beam of energy, there is no wastage in lateral directions. So that is the fundamental premise of beamforming rather than sending your energy in all the directions wherein it may not be necessary, rather focus your energy as a sharp B only in the direction where it is necessary. If your user is located here, you will send your beam of energy precisely in this direction and not in the entire space. That is the fundamental premise of beamforming, a focusing transmitted signal only in the desired direction and thus leading to a narrow beam. This is something that we had also alluded to when discussing some of the fundamental benefits of millimeter-wave. We are going to not only talk more about beamforming and its advantages but we're also going to tie the two together as to what relationship millimeter-wave and a massive MIMO share. But for the time being, let's continue talking about the benefits of beamforming. Going back to this schematic, one of the fundamental benefits of beamforming can be explained as follows. Going back to Module 1, I hope you'll remember that we had talked about a specific metric of wireless systems, that is signal to noise ratio. This is your desired signal and denominator would be noise. We have also established that in order to improve the performance of a wireless system, it would help to maximize the signal to noise ratio, ie., for a given noise level, maximize the level at which the desired signal is received. As you may have already guessed, by avoiding wastage in lateral directions, by focusing your outward energy only in the direction where it is indeed useful by forming a sharp narrow focus to beam you can clearly see that beamforming improves the level of the desired signal at the receiver. Thereby, it improves the numerator of the ratio, and thereby it improves SNR. Improvement in SNR and thereby improvement in spectral efficiency, and thereby improvement in user speed or throughput is one of the fundamental benefits of beamforming. But that is not the end, there are a few more benefits, we are going to talk about, although this would be the most fundamental of the model.
