Network Architecture and Evolution from 3G

In this section, we will give you an introduction of the network architecture in. If you look at the picture here on the right, the network architecture in LTE is essentially composed of two main parts. You have the Radio Access Network, which is also known as the Ran in abbreviation, which is also known as the evolved Utra network or E-utran, or known in an abbreviated form. On the top you have the award packet core known as the EPC, and EPC is what is the core network architecture. The EPC and the Ran, they work hand in hand with each other to deliver LTE service to a given subscriber. So there are just two main moving parts on a very high level and utran the focus of this course will be the EPC. In the next slide, we will add a lot more detail to this architecture and look at slightly lower level architecture of the LTE. This picture shows the architecture. It may look a little daunting here, but just bear with me And we will walk through each of these network elements and describe the functions and how they work with each other. So starting from the left hand side, you have the utran within this red box here, and to the left of it is within this red box is the EPC. If you remember from the previous slide, Utran and the work. With each other to deliver service. Now, these are the two boxes with a lot more detail inside each of them. If we focus on the trend, you have what is called a enodeb here and your you can actually have more than one enodebs. And these Enode B's are able to communicate with each other. And the reason they are able to do that is because three Gbps wanted to make the architecture a lot more distributed and flat. So the rather than the enode B talking to the for every small thing they have the ability to talk amongst themselves and perform some of the functionality that way. Then you have the mobile equipment, which in technical terms is called a user equipment here. And this user equipment is able to connect to the Enodeb. The Enodeb in general, based on the architecture is connected to a network element within the which is called me or mobility management entity. The mobility management entity is in turn connected to a element which is called Home Subscription server or HSS. And the HSS is connected to a network element called a Pxf, which stands for Policy Charging Rate Function. The MMD is also connected to a network element, which is called a serving gateway or abbreviated as GW. The GW is connected to a network element which is called a P gateway or a packet gateway. The packet gateway in turn is connected to the PCF network element, and the Packet Gateway is also able to access the outside world or as we can call it, a packet data network outside the bounds here represented as this cloud. Now these these network elements, you may notice some of these network elements are connected via dashed or dotted lines, whereas some of them are connected by a solid line. Here you have the legend. The solid line represents a user plane connections, whereas the dotted or dashed represents control plane. Now you may wonder what user, plane and control plane are. So let's shed some light on what the differences are. So imagine you have a or a user equipment here that is getting there, is trying to get service by connecting to the enodeb and say they want to open a web browser and go to Google.com. Now in order. For the UAE to be able to access and open up a Web session towards Google.com. A lot of things need to happen between the UAE, the Enodeb and the EPC for before the UAE can even access that Web page. So that part of communication is actually referred to as signaling. Signaling is all the communication that happens before the user is able to actually access data so the control plane can be used synonymously as signaling and the actual user traffic, you know, the user that when they are searching on Google.com, the queries that happen on towards Google and the results they get in return, all those are part of the user plane. So as you can see, the Enodeb has a control plane connection to the but has a user plane connection to the serving gateway and the has a control plane connection to the gateway and also has a control plane to the HSS, which in turn has a control plane to the PCF. The PCF has a control plane towards the gateway. So if you look at this picture here, you can see that the lower half is all user plane because it's all solid, whereas the the top half is all control plane traffic. I have also summarized some of the functions of each of these network elements here at the bottom. And we will as the course progresses, we will talk a lot more in detail about each of these network elements and walk through some of these functions. But for now, if you want to pause this lecture and just maybe read through some of these points here that may be useful, if not, you can continue to proceed and we will indeed talk about some of them here in the following slides. To give you a little more historical perspective of we have on the x axis listed the different three technologies. You have the GSM, you have UMTS, and then you have LTE. And then here we are listing the different domains and the different services that were meant to be served by the network. So you have GSM that was a circuit switched only network and you were serving voice SMS, low rate data for the most, for the most part in terms of applications. When you went into the UMTS, you started slowly migrating towards the packet switched network and your main applications in this scenario were voice and SMS, and you started seeing the emergence of data because the data consumption started increasing among users. So data started showing up here when we moved towards LTE, we are completely in the packet. Switched domain means we are in all architecture and the main applications that are using LTE are data voice over IP or voice over LTE and SMS. So here's another picture that adds a little more detail into the previous slide. And here at the bottom, you have the different networks, you have the GSM, GPUs. Then we had the GPUs with IMS, and then we have the fourth generation. Now you can see each of these networks have in common an access network, which in most cases is called the Radio Access Network. This is the network that the user equipment or the mobiles directly attaches to. So access network is common across all these generations. Now, if you look at the second generation, the access network was connected to a circuit switched domain, whereas in the third generation you see it being connected to both a circuit and a packet. And same here with when it was introduced in third generation. Whereas in the fourth generation it's only connected to the packet switched domain because you have completed your migration from a circuit to a packet based network entirely as you move from 3G to 4G. Now if you look at the layer three here, essentially the circuit was connected to a PSTN for delivering voice services. In the third generation you had connected to PSTN for voice, whereas you had it connected to an IP for data because you were able to see the emergence of packet switched domain come in and around the third generation. In the third generation with the IMS, you saw the emergence of IP multimedia system where your packet switched domain was able to talk to your IMS, which further talked to your IP protocol. And you also have a direct link between here as well. But in the fourth generation your packet switched domain is entirely talking to your IMS for all your voice services and for data. You strictly talk to an IP protocol because it's an all IP architecture. So as you can see, as you have progressed from left to right, the number of layers has remained the same. But within each layer there is a lot more simplification and it is moved all towards an all IP communication. IMS operates in all IPS, so by 4G you are in an all domain. And if there are some legacy networks that you still want to talk to in time domain, the IMS has network elements that are able that are able to do the translation and talk to the PSTN if needed. Here we show the evolution of 3G architecture. You have at the bottom. You have the different 3G technologies. The one we are talking about here is the or evolved packet system or EPC, which is released eight, nine, ten, 11. And you have the Enodeb, which is part of the access network. You have Node B and Node B here as part of some prior releases, and those were controlled again by a distributed control center. In case of Pre-4g, this was referred to as an RNC or a radio network controller. The radio network controller is was connected to something that was called a sgsn and that sgsn was connected to a GSN. Whereas if you compare that with the 4G architecture, it looks like these layers have essentially disappeared because there is nothing here and there is the here, the serving gateway and the gateway that we that we are a little familiar based on the old network architecture slide that we had reviewed a little while back. Now, again, the dotted is the control plane and the solid is the user plane. So you can see here in 4G, your control plane terminates at the and your user plane or the actual user traffic is terminated at the serving gateway. So the aim of this picture was just to show you how the architecture has progressed through different releases and how it has become a lot more simpler and a lot more distributed. What indeed actually happened was 3G took a lot of the functionality that was happening here and it pushed it out to the enodeb, to the edge and to the in a sense, getting rid of the middle network elements, making it a little making for a little flat architecture, which helps obviously reduce latency and increase throughput. So this wraps up the section on the network architecture overview. Next, we will take a slightly deeper view of the Radio Access network in the next section.