Nakul, I think you mentioned 5G architecture is very similar to 4G, but are there any major differences that you can point us to? Absolutely. There are many differences between 4G and 5G at all levels of the hierarchy, network being one of them. By now we know that when we speak of network, we have to speak individually of RAN, the access network, versus the core network. Now, fully understanding those technical differences requires some deeper engineering contexts, but we're not going to do that yet. Let me plan to explain those differences at a sufficiently higher level. If you think of the core network, LTE core network, was what they called the component-based architecture, meaning that to facilitate a certain LTE service, you had to have a specific software running on specific hardware and you couldn't do without it. That also meant that not only you are deployments were not very flexible, they were somewhat rigid interoperability between two different vendors. Although they would provide the same or similar service, interoperability would be a challenge. 5G moves away from that paradigm in that it makes the core network architecture what they call service-based architecture, in that the focus is on the service that is being provided, rather than what software or what hardware is responsible for providing that service. One way to understand that is that communication commands between two different coordinate were components. In 4G, they follow some specific protocols, specific language, so to speak whereas in 5G, most of the communication, if not all, has been translated from some rigid inflexible protocols into generic interaction commands. Those generic commands can then be translated onto generic software and generic software can run on generic hardware. The rigidity that you had an LTE in terms of close dependence of service on software and hardware that has largely been taken away. One simpler way to understand that would be, let's say a book returning an arcane language like Latin, which only a few people in the world by now would be able to understand. You would need that specific knowledge about the language, the grammar, and sentence structure, etc. Only a few people woould be able to really read and appreciate that book. Whereas the same book, when translated into a general language such as English or Hindi or Chinese, or languages that are understood by a hundreds of millions of people across the globe. Suddenly with one translation, the applicability of that book grows exponentially or even beyond. You can think of 4G here and 5G unit works in a similar way 4G had to follow certain rigid rules in the core network. Whereas 5G, gets rid of most of those rules, at least for the better and making the whole architecture flexible in what is technically known as service-based architecture. That's for the core network, where most of the changes are. For the radio access network, well, there are a few major changes and it occurs to me that we will actually be talking about, some of those key changes in that the first change wouldn't be massive MIMO, in that we wouldn't be limited to just few antennas as we were in LTE. 5G cellphone towers, will be able to have many more antennas than before, and this is something we will spend a good deal of time talking about in one of the later modules. Another round relative change that I can think of is something that is called virtualization. That is, your cell phone tower doesn't have to have all the intelligence needed for its operation. Some of that intelligence can be safely moved away from the tower into a node somewhere in the Cloud. That has its own benefits, are something that we are also going to touch up on here, one of the later modules. At a high level, these are some of the crucial differences between 4G and 5G as far as the network architecture is concerned. Understood. What about non-standalone and standalone? I think that I get how it works in general, but I am curious is the network operators today need to choose which one to use at some time and choose the other one for another time? Yes, the network operators do have to make that choice whether they want to deploy 5G in NSA or non-standalone mode, or SA or standalone mode. There are as always, multiple engineering factors that feed into the network operator's decision. But one of the most fundamental factors that I would say is a pertinent to the architecture itself, in that if you quickly recall the mental picture of NSA versus SA side-by-side, you will notice that in an NSA network, you had just a few select 5G base station where the demand was the highest. Whereas in, if I do standalone network, you would have to have every single base station 5G capable. Whereas, doing that sounds easy on paper or in theory, think about what you would have to undergo as a network operator in order to actually accomplish that. That is, you would not only need to upgrade your core network from 4G to 5G in order for it to operate as a standalone network. But if you have, let's say 10,000 LD base stations in the country like the size of the United States, you would have to go and upgrade each and every one of those 10,000 base stations from 4G to 5G. A task that is neither simple nor cheap, nor something quick to do. It takes, as I mentioned, a few quarters worth of planning, a few millions of dollars of infrastructure investment, and maybe a few $100 million of additional expenditure in buying the spectrum. This is to be able to operate your network as a standalone network. If an operator has the resources and the budget to do that well and good, they will definitely deploy standalone network. In fact, there are some standalone deployments in different countries around the world. Although a more prevalent option at this point is non-standalone. Simply because in an NSA network, you can continue operating with your basic LTE network and add 5G as an additional layer on top of 4G, so that wherever there is extra demand, your 5G network helps meet that demand. Something that 4G cannot do. But where there is little demand, you are underlying layer 4G can continue to serve you as if nothing happened. This is perhaps the most important consideration that operators keep in mind when deciding what it says NSE or deciding between NSA versus SA. There are many other technical factors as well regarding the frequency of operation, a possibility of cell densification, etcetera. But those topics are better discussed in a more advanced class.
