Let's move onto the next question. In the previous question, we've touched upon the satellite radio systems a little bit . Well, in the satellite radio systems number of cells or number of base stations are quite important to the capacity of the system or a network. Well, one question is increasing the number of cells, or increasing the number of base agents will increase the capacity of the system? Or increase the success for communication pairs? Numbers of communication pairs. That is actually the question. Difficult to this slide. You'll see there's actually two persons making conversation to each other. Imagine one is in the center of radio system. One is the base station, the other one is terminal. In they're given a rectangular area. There is one base station and one more terminal communicating with each other. Of course, this mobile terminal where they send their signal to their base station and base station will deliver this signal to the other base station. But this given area assuming the capacity of this base station is just equal to one. Meaning that only one mobile can be supported. But however, this given area, what happens if the number of communication demanding? A demanding communication pair will be increasing or demanding such communication with the world increasing. Then, the only thing that we can do is or the direct solution that we can do is actually we can increase number of create vision. For example, in the given area, we could put more base stations, like this. So in the given rectangular area, we put four base stations, which is four times the number of base stations. Each will support one more terminal each. So for the very happy case, in this given area, now we can support four mobile terminal simultaneously by installing four pay stations. However, if they are using the same radio channel, each pay station will make some interference each other, like this, if the interference level is acceptable still, we can support four times number of mobiles, four times number of mobile terminals in the given area. Well, of course, in the radio communication signal, the signal power will decrease as the radio signal travel some distances. And in engineering terms, this is called path loss. And the path loss is actually denoted by some number like 3, 4, 5, or 6 so as number goes to large the pathless amount will be larger. So the signal power will be decreasing very rapidly. So in this cellular radio system as pathless becomes large, perhaps interference will be small so the installation of four bay station will support four mobile terminals simultaneously. That means in the end we can support four times the capacity is compared to the original case where we have just one mobile terminal, one by station. Well, in network this is called the cell splitting technique. One cell is splitting to multiple cells. Well this is very entity wizard or entity wizard but the question is if we increase bay stations 10x or some more number of bays that will be installed then capacitor will still be increasing. That is actually our fundamental question in this slide sets. Well, you see actually in the closed area, and users actually are located randomly and then we have one, two, three, four, or six base stations. Then, we want to increase base station density to support user demand. So not only we have a base station intensity, I cannot count how many base stations are installed here. But let's say they are triple, three times the capacity has been increased compared to the original, that figures. The question is whether this increasing number of base station will increase the capacity. Linearally, or in other ways. Well, after some accurate calculations, my research group, Middle Net published the research paper in a journal, in a conference. There is actually someone in the next slide to answer such a question. Can we increase the capacity, why the interface is a little bit lower level or another way of making such question is, will capacitors increase if bay installation of more bay stations then will it also generate interfaces? So when you increase the bay stations, then distance between mobile terminal and base will be shrinking. But at the same time, the interference from other bases will be also increasing. So we cannot answer directly whether such capacity increment will be in which formula. If we go to the next slide, after some accurate calculations we found that the capacity increment will be such a logarithmic scale. So if you at this plot thing here the horizontal x-axis is for the number of base stations per given area while in the y-axis vertical line shows the area capacity in a given area, how many mobile terminals can you support simultaneously? You see different plotting here, first curve and second curve than the other curve. And this plotting is all based on the level of the [INAUDIBLE], level of the interference filtering or level of the power decrease when the wireless waves that travels over the distance. As it becomes high, you have a more capacity. Why? Because interference will be much more filtered than it would be reduced. But in any curve, you see patterns. In the beginning when you install more base stations, the increment will be proportional to the base station intensity, then you increase. But however as it increases more, the area capacity will be saturated like this function. Well, [INAUDIBLE] radio system has been Has been evolved over these couple of decades. And then, we start with the first generation system and second generation system and future nor system. And currently we are in the fourth generation system and preparing for the fifth generation. And according to the area capacity, according to the base station intensity, we can divide each generation in this region. First, second, up to third generation, when you increase more base stations, the capacity will increase linearly. So they're very much proportionate to the base station density, the capacity, and base station denseness are very much linear proportional to each other. But however, as system becomes 4G or 5G, I understand that as they increase more base stations, area capacity will increase not as but with the logarithmic function. That means there is a sum saturation at the point. Of course, as there is more pay stations, the capacity will increase, but increasing speed will be very much slow. Well, we're actually preparing for the 5G systems. Where user demand becomes increasing day by day. So question is, installation of more base is not enough because with such low user demand increase. So we need to have other way of technique to improve the capacity or to improve the area capacity that will be handled in the next questions. Thank you.