LTE Protocol Stack

Hello friends, today we will talk about air interface

protocol

s in LTE, it is a very big topic, so in this video we will only have an overview, we can divide the air interface

protocol

s into two parts, the user plane and the control, the user plane deals with the actual data flow, while the control plane is used to configure the user plane layers before the actual data flow. Let's talk about the user plan first. When data comes from ABC, it is stored in the P DCP buffer on a node B, so let's first talk about the P DCP layer.

PDC B stands for Packet Data Conversion Protocol. first tests performed by PD CBA header compression and handle decompression of IP data packets the data packets arriving to you note B from ABC are IP packets each IP packet has a 40 byte header these 40 bytes of IP header They don't have any meaningful information, so sending these 40 bytes of header along with the actual data in the interfaces represents a huge waste of resources; Also, in the case of a web call where the size of the actual data is very small compared to the IP header, this header incurs considerable overhead, so we need some mechanism to compress this header in the PDC insurer of the The transmitting end compresses this header using ROSC or robust header compression protocols at the receiving end.

Poly PVC decompresses this header. The second task is the maintenance of PD CB sequence numbers in the transmission and the PD CB layer assigns a sequence number to each packet before sending it to the next layer. i.e. RLC, this sequence number is used by the PDC P layer at the receiving end to align the packets in a sequential order before sending them to the higher layers at the time of PDC transfer, a source layer is sent in odo the sequence number of the last packet successfully received by UE to the target on node B, so the goal would be to be able to start transmitting data to Yui from that packet onwards.

This way you also know that the trees can synchronize the data flow at the time of transfer using the sequence number p d c b. The third task is data security if your data is not secure in your interface, someone can intercept this data, for example, online payment on your mobile phone will no longer be secure if there is no security mechanism, so that we must protect this data through integrity and encryption before transmitting it on its interface. come to our LC layer to learn the steps performed by RL, silly erasure, concatenation, segmentation and reassembly of our LCS d.

The use in the IP packet header is of fixed size, i.e. 40 bytes, but the data part is variable, for example in the case of the data part of a VoIP call. is small, but in the case of video streaming data, part of the IP packet is quite large. The available bandwidth on the air interface keeps changing very frequently due to the changing radio conditions and the changing number of you are below any node B, so our LC on the broadcast has to concatenate or segment these packets of data dynamically according to the current bandwidth on the air interface and the RLC at the receiving end reassembles this data, retransmits our use LCPD, this is the next task, if the data gets corrupted on our air interface, then our layer Transmit LC The entity has to send the data packet again, but this type of transmission is performed only when our LC is an acknowledgment mode.

Example of a Mr. LC is a data download using FTP. The next task is to reorder our LC data PDUs. Let me tell you the reason for this because The multi-retransmission order in which the packets are received at the receiver could be random, so RLC has to reorder all the packets before sending them to the higher layers. Now let's go to the Mac layer. The Mac layer is responsible for prioritization between various data streams for a given UE. We know that data packets of different flows have different priority according to their types, for example, VoIP call packets have the highest priority when the available bandwidth on the interface is not enough to carry all the data flows, there must be some entity that selectively sends the data belonging to higher priority transmission on the air interface this function is performed by Mac error correction through hark this is the next task hark means hybrid automatic repeat request is an error correction technique that has been taken from UMTS finally let's go to the physical layer it physically includes raw data before Modulation We cannot use raw data to modulate a carrier signal.

The data has to go through an encoding process before modulation. This processing is called physical hearing processing. This processing is necessary so that the receiver can detect any data errors caused during transmission on the air interface if direct. Error correction techniques are used. The receiver can decrypt the data at its end if there is any corruption at the latter. If the data can be corrected at the receiving end, then there is no need to retransmit the data. The physical error measures the interface for now the quality of the channel. Let me. I tell you the reason behind this due to mobility, multiple reflections from the environment and noise at the air interface.

The bandwidth available on the interface keeps changing very frequently, so we need some mechanism to measure the quality of the air interface to know the current bandwidth of the channel, so this is the reason behind this. Measurement now let's move on to the control plane. The most important layer in the control plane is our RC. You can estimate its importance from the fact that our LC layer initializes other layers like PCP, RLC, Mac and the physical layer, only the actual data transformation is carried out. I'll do it quickly. review the list of tasks performed by our RC layer.

The first task is transmitted from the system information in a cell. Our SIPs are transmitted by RC layer and SIP contains all the information related to the network and cell whenever we terminate or any UE moves. a new cell in idle mode decodes its broadcast information to get all the cell parameters such as cell bandwidth etc., the next task is to control the IRC connection, our UE OSI layer activates the RC connection with our silly Rafi note B note, it is mandatory for any contact to have RC connection before sending data packets to the network without RC connection EU can't send any data to the network when we don't have our C connection is said to be in idle mode the network task i.e. transition our layer of a node B state is activated which changes UE from Adam mode to connection mode and vice versa when there is an activity in the data flow for a particular Yui for a long time, our layer C of e note triggers our MC connection release for satuay and sends satuay to adalah state when we have some data to transmit, they can trigger RC connections in a process state.

The transition is made to save battery and ear interface resources. The next task is to page whenever there is some MT voice called RPS data which will be sent to any OE IRC layer of a node. B sends a pager message for Yui in the area you are tracking to activate initial security at the time of ROC connection setup. The RC layers of a node B exchange security keys and also decide the security algorithm to be used at the time of RC connection note integrity production is not done for DRP measurement setup and reporting. in connected mode.

Any OE has to perform many types of measurements, such as intra-frequency interference E and Inter measurements. All of these measurements are configured in the UE using the RC layer of e. note b The RZ layer of ue reports all measurements to RS a layer of e note B based on these measurements The RC layer of e note makes all decisions related to the transfer. Funny, let's go to the nesting layer. The mask layer is also part of NASA's control plane. The layer is composed of EMM and any SM layer. EMM stands for EPS Mobility Management and ESA stands for PS Session Management.

The EMM layer takes care of capacity-related scenarios, such as tracking each update, paging, security mode control and authentication, and other tasks like those handled by some Leones. best religious scenarios such as default EPS beer or contact activation EPA Office context modification PD and PD connectivity procedures and disconnection procedure etc. So this was all about the protocol

stack

in LTE for an interface in the next video we will talk about some other scenarios like RFC Connection and ends so keep two in and hit the like button if you enjoy the video and keep watching and waiting and you can subscribe to this chain.

See you soon.