So returning now to our example, let's do the SIRs for the first iteration, using the, using the power levels that we just changed to. So, we know that the noise in the receivers or their values that we had before, and here are the transit powers that we did before, 1.4, 1.5 and 2.68. So now the transfer powers aren't same at the each of them anymore, so we're not going to have 2 milliwatts everywhere. They're going to be different values now and we are going to see how that plays out. So with our equation to measure SIR at link A and if we start off remember again we have direct times the transmit power so 0.9 times 1.4. That's the signal and interference is 0.1 not times 1.4 but times 1.5 because that's B's transfer power right now, 0.1 times 1.50 plus 0.2 times 2.68, and then we add 0.1, which is the noise in the receiver. And I'm not going to write the milliwatts out, because we saw before how they cancel out. So then we do this, we're going to get 1.26 divided by 0.786, which is going to give us 1.60. So now we can move on to B. We saw the direct is .8, time 1.5. [SOUND] The indirect from A is .1. We multiply that by 1.4, plus the indirect from C, which is .1. We multiply that by 2.68, [SOUND] and then we add 0.2 onto that. And if we do that out, we get 1.20 divided by 0.608, which is 1.97. And now let's move on to C, the direct transfer power is 0.9 times the gain which is 2.68 divided by 0.2 which is indirect from A times A's transmit that is 1.40 plus the indirect from B which is 0.2 times 1.50 direct transmit plus the noise in the receiver which is Upon 3. And we get 2.412 divided by 0.880 which is 2.75. So now we'll move onto the second iteration and we'll update the power levels used in the SIR stat we'll just compute it. So A would feed back the value of 1.6 to transmitter A, which has a desired SIR of 1.8. And remember, our equation is that the next power is equal to the ratio times the current power. So first let's calculate the ratio for each of these guys in here. So for A, the ratio is going to be the desired over the measured, and the desired is 1.8 and the measured is 1.6. For B, the desired is 2.0 and the measured is 1.97. So we have 2.0 divided by 1.97. For C, the desired is 2.2, and the measured is 2.75. So it's 2.2 divided by 2.75. So this is interesting because now, for A, the ratio is greater than one, whereas before, we had it as less than one. For B It's greater than one, whereas before it was less than one. And for C, it's less than one, whereas before it was greater than one. So they've switched, and now we expect A and B's transmit powers to go up, because their SIRs are too low, and C's transmit power to go down because its SIR right now is too high. So this is a process of Overshooting and undershooting, which will likely occur many times till we hit the equilibrium levels. So we've undershot in for A and B because we're too low, and we've overshot for C because the SIR is too high, and so this we expect it to look something like this, where each of the SIRs will kind of go like this over time, until the eventually hit where they need to be. So now let's do these power updates, so we can, so the transmit powers for A, B, and C are 1.4, 1.5 and 2.68 respectively. So you take 1.8 divided by 1.6, multiply that by 1.40, and we would get 1.58 millawatts, to be the new power level. Multiply this by 1.50 and we get 1.52, so really close. So you see B is very close to where it needs to be. This power level didn't change much at all, because of that. And, then for C, multiply this by 2.69, and we get 2.15 milliwatts. So that's how the updates are computed. So now, iteration two will move on and we will compute now the SIRs, just like we did before. So we have our noise values, and we have our transit powers. And so we'll start off with, like, A and we'll do that again. So, for A we have direct gain 0.9 times 1.58 and at the interference we have 0.1 times 1.52 from B plus 0.2 times 2.15 from C plus 0.1 milli watts In the receiver, and this we get 1.422 divided by 0.682, which is 2.08. Now, for B, we have a direct of 0.8 times 1.52, indirect, or interference of .8 times 1.52 plus .1 for C times 2.15 plus .2 of noise. And for that we get 1.216 divided by .573, which is 2.13, and then for C, we have a direct of 0.9 times 2.15, and we divide that by the indirect interference, 0.2 times 1.58 plus 0.2 times 1.52 [lus the noise of 0.3, and we do that out, we get 1.935 divided by 0.920, which is 2.10.
