Lecture 48 : 5G SRS design – part IV

Okay, welcome back, so we have been discussing SRS and we will finish discussing most of it, okay, and rest of it we will discuss, finish discussing in the next class, okay. So, we will finish discussing this at least, this is what we have been discussing like a single port SRS, okay, I have not even discussed multiport SRS as of now, okay, the notion of multiport and SRS will come little later, okay, so that's what we will start doing that, we will first finish discussing this, okay. Now we have understood SRS, the notion of hopping, how hopping gets enabled, okay, and typically how many hops will be required for to sound out the complete bandwidth, okay, to sound out the maximum sounding bandwidth, okay, right, so and let's, I am going to put everything together, okay, and then understand like how, like how standard has defined this framework, okay, so we have actually understood most of it, now let's put together everything. So, what are we saying here, okay, so what is this BSRS, you look at this, we looked at this BSRS, BSRS is a 0, BSRS 1, 2, 3, we picked up these columns, okay, but I did not specifically define what each of this BSRS tells us, okay, right, so now if let's say what is this, this is the maximum sounding bandwidth which is MSRS 0, okay, now what are we saying here, this BSRS determines the number of PRBs, okay, within the actual sounding bandwidth, okay, that are sounded in each hop of a hopping cycle, okay, which is given by MSRS B for B is equal to BSRS, I will give this, we will discuss this in detail now, what values BSRS can take, it can take 0, 1, 2 and 3, right, okay, what we look at this, what are we saying, see MSRS is 0 is the maximum, correct, which the base station is interested in sounding, okay, now what are we saying, what are we writing over here and do not get carried away by this B is equal to BSRS MS, what am I saying here, what values BSRS can take 0, 1, 2 and 3, right, okay, so what does that mean, okay, the actual sounding bandwidth, okay, within that actual sounding bandwidth, how much you are going to sound out in each hop, okay, right, that is decided by BSRS, fine, okay, now so this is if let us say BSRS is 0, okay, which is this column, correct, okay, so or let us say BSRS is 2, I am picking this, okay, so bandwidth per hop is 12, right, okay, that is what this bullet is telling, the BSRS determines the number of PRBs within the actual sounding bandwidth that are sounded in each hop of a hopping cycle, okay, so how many PRBs will be sounded out, if BSRS is chosen as 2, 12, right, so bandwidth per hop is 12 PRBs, okay, right, now what I said, if B hop is 1, correct, okay, so now everything will come together, the actual bandwidth over which the hopping occurs, okay, is basically what I have said, okay, if B hop is 1, what will be the actual sounding bandwidth, okay, over which the hopping occurs is 24 PRBs, I have said B hop is 1, BSRS is 2, okay, maximum is SRS 0, understand this that maximum which needs to be sounded out is 48, actual is in basically actual bandwidth over which the hopping is occurring is 24 PRBs, because I have said B hop is 1, okay, if B hop is 1, what happens, then MSRS gets set as 1, okay, which is 24 PRBs, okay, right, so what is happening here, BSRS is 2, B hop is 1, okay, right, now B hop is less than BSRS, right, so hopping will happen, correct, okay, and how many hops it will take to sound out the complete bandwidth, so B hop is 1, okay, this is that is how I have set it, okay, so the actual bandwidth over which the hopping occurs is equal to MSRS 1, so this is the actual bandwidth over which the hopping will occur, over how many PRBs, that is 24 PRBs, okay, now how many, what is the, this MSRS 0 is how much, 40, 48, right, okay, so this is the maximum, okay, B hop is 1, so this is the actual bandwidth over which the hopping is happening, okay, so what I am saying here, maximum is this much, but I am sounding as a part of this hopping pattern, I am sounding out this actual bandwidth which is only 24 PRB, okay, right, and whatever I said this BSRS as 2, what is BSRS defining, number of PRBs within the actual bandwidth, this is 24, that are sounded in each hop of a hopping cycle, okay, right, so the actual bandwidth is 24, hopping bandwidth is 12, right, which is said by choosing BSRS as 2, right, that is what determines, okay, BSRS determines the number of PRBs within the actual sounding bandwidth, actual sounding bandwidth is 24 PRBs, right, this is actual not the maximum, okay, there is maximum, there is actual, then in that actual how much is hop, how much is sounded out in each hop, that is decided by BSR, right, okay, fine, clear, okay, so what is this? Now, okay, so this is in each hop, okay, what will happen here is that actual is 24, okay, hopping cycle will complete in basically how many it will require, what are we doing? Actual is 24, in each hop we are sounding out 12 PRBs, okay, so for sounding out the actual bandwidth how many hops you will need? 24, right, where is that 24 coming, yeah, right, V hop is set to 1, what is V hop tells you? V hop tells you the actual bandwidth, correct, V hop is 1 that will tell you give you MSRS, it will become 1, okay, so the actual bandwidth if you look at MSRS 1 that becomes how much? 24 PRBs, right, fine, okay, this 24 PRBs will be sounded out in how many hops, okay, that is decided by BSRS, that is how much is BSRS? BSRS is 12, correct, okay, 24 is actual, 12 you are sounding out in each hop, how many hops you will need? 2, fine, correct, okay, so that is what is this, okay, so there is an intricate relationship, it takes some time to like to crystallize things, okay, so now if I set V hop as 0, correct, okay, now what will happen? Actual bandwidth, so now actual bandwidth is equal to the maximum bandwidth, right, that is how you are going to, in this case you are sounding out the maximum bandwidth, okay, so what am I saying? V hop is 0, actual bandwidth over which the hopping occurs is equal to the 48 PRBs, now how many hops you will need in this case? That is the formula, okay, okay, so hopping cycle will complete in how many hops? In each hop you are sounding out 12, actual is 48, you will need, that is the formula, N1 into N2, okay, N1 into N2 is 4 hops, okay, so there is generic formula, I will give you that, sorry, okay, so this, how does this come? That is what you are asking, okay, in general a hopping cycle completes in, this is product, pi and it runs from where? B is equal to B hop plus 1 to B SRS, look at these values, okay, right, so let us look at this, this example, okay, what was B hop? 0, so B will run from 1 to, what is B SRS? B SRS is set to 2, what comes here? This will run from 1 to 2, what will you have? N1 into N1 into N2, okay, so that is how it works, okay, you see, it is little involved, okay, so you have the notion of maximum sounding bandwidth, you have actual sounding bandwidth and the bandwidth sounded out in each hop and let us move on from here, so we will take 1 or 2 more examples and then it will become clear, okay. So, again the same, this table remains same, okay, so this we are considering intra and inter slot frequency hopping, okay, taking examples to understand it better, that is all, okay. Now, so this case 1 and case 2, what is this? SRS with B hop is equal to 0, right, so the actual bandwidth, sounding bandwidth is equal to the maximum sounding bandwidth, right, okay, correct, so fine, so B hop is 0 and what is B SRS? Is I have set it to 2, right, so we just did this example, how many hops it will need? 4, right and no repetition, okay, so what is happening here? Here, you see this, it is basically being done over, this is one hopping cycle, so in one hopping cycle, so you need 4, this one, it will be done in 4 hops, okay, but so this is basically you are hopping, where are we hopping? This is one hopping cycle, okay, so we are hopping over, so there are 4 hops, okay, why they are not showing up? Look at this, this is offset, you look at this gap, okay, so this is one hopping cycle, right, okay, correct, so I was getting a few that both of them are same, they are not same, this is one hop, this is 13 symbol and this is 14 symbol, okay, right, so you have 4 hops, okay, so SRS with B hop is 0 and B SRS is 2, okay, so how many hops will need? That is the example we took in the last slide, 4 hops, how many hops we are taking? This is first hop, this is the second hop, yeah, this is coming over here, okay, 13th and 14th symbol, right, again 13th and 14th symbol, right, so you are doing this, you are sounding out this channel in 14th hop, correct, in 4 hops, okay, right, that is how we have set it and the repetition is 1, so this is one wherein you are sounding out the complete, this is one hopping cycle, this is the next one begins, so when I say this hopping cycle, so over this is one, this is the beginning of the next one, that is what I am saying, okay, do not get confused by that this is also part of this hopping cycle, no, okay, hopping cycle consists of these 4 hops, right, the next hopping cycle will consist of again next 4 hops, okay, fine. Now, here so same B SRS is 2, but we have set as a repetition factor of 2, right, so what is happening? We are repeating, that is all, okay, so this again, so in the hopping cycle is going to increase because we have allowed repetition of a factor of 2, okay, fine and the number of hops required to sound out the maximum bandwidth is 4, that is all, right, okay, so this is an example, okay, we take one more example, okay, to make things more clear for us, okay, so this is inter-slot hopping, again like the figures were drawn by different students, so different colours, that is all, okay, so the same table SRS with B hop is equal to 0 and B SRS is 2, right, so what are we doing here, okay, so the number of hops required to sound the 48 PRBs, okay, is 4 hops, okay, so again this is slightly different example, so again you require 4 hops, so we are doing it in 4 hops, 1, 2, 3 and 4, okay, in the case 2, what is happening over here is, okay, that this same, so we have said B hop is equal to 1, B hop is equal to, so what will happen and B SRS is 2, okay, whereas this NRRC which is coming, okay, correct, so what is this, what will happen here, one second, so in this case B hop is 1, B SRS is 2, okay and NRRC is 0, so B hop is 1, what happens when B hop is 1, okay, so you will have the actual sounding bandwidth is 24, not 48, okay, so now you see the difference between, this will basically make the difference clear between the maximum sounding bandwidth and the actual sounding bandwidth, okay, so the maximum sounding bandwidth is 48, actual sounding bandwidth with B hop is 24, right, but you still need to sound out the maximum sounding bandwidth, correct, okay, right, so if I am setting B hop to 1, what is the actual sounding bandwidth? 24, right, fine, and B SRS is 2, B SRS is 2, correct, so what are we doing, okay, so in each hop, we are basically sounding out 12, right, okay, so you see this, okay, so this is we are sounding out this 12, okay, correct, and so this is basically say and what are we saying over here, this NRRC is set to 0, okay, what this NRRC tells us is as follows and decides the position of actual sounding bandwidth within the maximum, okay, so what did we say, okay, there is maximum sounding bandwidth, there is actual sounding bandwidth, okay, right, so and within that actual sounding bandwidth, we are sounding out the bandwidth in each hop, 3 different like hierarchy, okay, this is the hierarchy, okay, so now what is happening? Actual sounding bandwidth is only 24, but you need to sound out the maximum sounding bandwidth also, right, correct, how does that happen? That is configured by NRRC, this is the parameter which was missing till now, okay, so what is happening when NRRC is 0, so this factor NRRC tells, gives the offset of actual sounding bandwidth in terms of multiple of 4 PRBs, okay, let us look at this, okay, so B hop is 1, actual sounding bandwidth is 24, right, when NRRC is set to 0, which part of the bandwidth you are sounding out? The bottom half, okay, because the total sounding bandwidth is 48, right, if you set NRRC to 0, right, what does that mean? The offset for the actual sounding bandwidth is 0, if NRRC is set to 6, what will happen? It will move by 24 PRB, so that is the later half, right, okay, so this NRRC tells us the actual bandwidth, this B hop, right, so the actual bandwidth belongs to which part of the maximum sounding bandwidth, right, okay, that is decided by NRRC and this gives the offset in terms of multiple of 4, okay. So, here this is the complete configuration, you set NRRC to 0, right, okay, we have set B hop to 1, correct, which means the actual sounding bandwidth is 24, maximum sounding bandwidth is 48, but you, so you need to sound out the maximum sounding bandwidth, right, okay, now you will, so how will you do that? In the first half, you set NRRC to 0, so that you sound out the bottom part of the maximum sounding bandwidth, in the second part, okay, you set the NRRC to 6, so that you sound out the second half of the maximum sounding bandwidth, because this gives the offset in terms of multiple of 4, okay, so 6 into 4, 24, so you move on to the second one and do the repeat operation, whatever you are doing here, right, okay. So, we have, so if you look at it, how have we done all this exercise? I could not have told you to begin from here. So, I have given you information in parts, right, okay, MSRS 0, B hop, MSRS 0 tells us the maximum sounding bandwidth, B hop tells us the actual sounding bandwidth, okay, right, but you need to sound out the maximum sounding bandwidth, okay, and how do you do that? How are they related? They are related using this basically, so what will, which part of the maximum sounding bandwidth you will sound out using actual sounding bandwidth is set by NRRC 0, right, okay, and within that, all these hopping patterns are defined, right, okay, so and we know the formula that how many hops you will be able to complete the whole operation, that is what we have discussed, correct, okay, so that this is how this whole SRS business works, okay, fine, so and if you look at it that we have only discussed that there is only one port SRS, in the sense that like if there is a multi-antenna user, okay, how will it transmit multiple ports, you remember SRS can be transmit, needs to be transmitted from multiple ports also, okay, right, as of now if you look at this, what have we said, there is a SRS as a comm structure, correct, and that comm structure can be used by different users, okay, correct, and each user will be offset using, will use a different comm, okay, so that different user can sound out the bandwidth part simultaneously, right, this user is, one user is using one comm, other user will use the other comm with an offset, okay, right, and that is how different users will sound out the bandwidth, okay, uplink bandwidth. Now, so let us move on to see how this multiple ports can be sounded out using the SRS, before that this was missing, so NRLC has a configurable range of 0 to 67, because why? Offset can, if the complete bandwidth is being sounded out, right, okay, so if I say that how many, what are the maximum number of ERBs which can be sounded out together, 68 into 4, okay, 272, that is the number which was there, right, so it has a range like that, okay. So, till now we have discussed SRS for a single port transmission, okay, we will now discuss SRS for multiport transmission, okay, and that will bring us to a closure, I will discuss only little bit today and then we will continue discussing this in the next class, okay, what are we doing here? This we have finished, okay, we are going to discuss this SRS for multiport transmission and how are they defined, okay, so let us look at this and let this figure what is showing, being shown here, okay, now this antenna port for SRS, okay, usual port numbering, okay, so it starts from 100, okay, and goes up to like how many maximum SRS ports can be sounded out, 4, right, SRS are designed for that, so they are numbered starting from 100, okay, what are we saying here? That is the first key information I am giving you, this multiple ports are all multiplexed on to the same comp, okay, right, and what do we mean by that, okay, so we have a, what is this? This is a 2 symbol SRS and what is, so there is, this is one comp, you look at, forget this for some time, this is another example, okay, right, what am I saying here? This is one comp, right, okay, correct and all the, what this bullet is saying? All the ports are multiplexed on to the same comp, okay, what do we mean by that? You remember DMRS, okay, how did we multiplex different port DMRS, we use something called code division multiplexing, right, they were defined on the same resource elements, but what did we do? How did we multiplex? We used code division multiplexing, frequency division multiplexing, so what are we saying here? The different ports of SRS will use the same resource element, that is what, that is the constraint which is being imposed by the standard, okay, right, so multiple ports are all multiplexed on to the same comp and so the number of antenna ports denoted as NAP for an SRS resource may be configured as 1, 2 or 4, maximum of 4 SRS ports, okay, right. On the left, on this, okay, what have we done? All the 4 ports are mapped to the same comp in each OFDM symbol and this comp has a comp spacing of 2. This is a comp spacing, right, okay, it can have 1, 2 or 4, right, okay, so the comp spacing of 2, okay, right, so all 4 ports are mapped to same comp in each OFDM symbol with a comp spacing of 2 and so how will it be mapped, okay, right, so what are we saying here that on the same subcarrier, we will have to create 4 different ports, okay, right, you see this all these green color, what is this green color telling 100 to 10123, okay, all of these ports are mapped on to the same port, how are they created that we will discuss, some kind of code division multiplexing has to happen, like it happened for the DMRS, right, okay. And here, look at this, on the right, different port pairs are mapped to 2 different comps each with the spacing of 4, look at this, okay, on the red one, how many ports are mapped? 2 ports and on the green one, how many ports are mapped? 2 ports, okay, how are they, so we will have to create some kind of code division for that, so that you can differentiate these 2 ports, we have to make them orthogonal, these 2 ports using some code division multiplexing, okay, here again, there will be 2 ports, okay, we will have to again differentiate them using some kind of code division multiplexing. So, we will have to here for this example, we will have to create 2 CDM, just for an example, I will tell you what exactly they are, how they are multiplexed, okay, right, remember this DMRS, if 2 ports are there, you have to create a sequence like this, plus 1, plus 1, plus 1, minus 1, right, that is the orthogonality, something similar needs to be done, but in a different way, okay, right, here how many, right, you will have to create 4 different sequences, we did that, right, okay, we understood that in detail for DMRS, okay, correct, so what the key point to take away from here is all the 4 ports are mapped on to the same resource elements over here, it is a same COM basically, okay, here on one COM, 2 ports are mapped, on another port, 2 COMs are mapped, here on the same COM, all the 4 ports are mapped, okay, and how are they multiplexed, we will see that later, okay, right, so I will stop here, okay, so what are we saying in 5G NR, all antenna ports are sounded in every OFDM symbol of the SRS resource, okay, so you see this in each symbol, we are actually sounding out all 4 ports, so we are defining over 2 symbols, here 2 ports are defined, here 2 ports are defined, here 2 ports are defined, right, okay, so what are we saying, all the symbols will basically sound out all different ports, wherever they are defined, wherever the SRS is defined, in whatever symbol SRS is defined, okay, all the OFDM symbol will sound out all the antenna ports, fine, okay, that is this last bullet, what are we saying, all antenna ports are sounded in every OFDM symbol of the SRS resource, okay, we will stop here, we will continue discussing this in the next class, okay, thank you.