What are LTE protocols and specifications

LTE network architecture

The increase in transmission rates and short connection times are the most important features that distinguish LTE from UMTS and HSPA. In addition to the modern improvements in transmission technology, the network architecture of the mobile network operators is also subject to some changes. First and foremost, it is about the savings in the exchange of information between the base station and the core network. In addition, for reasons of cost, simple integration into the existing cellular networks is sought.
The radio access network and the core network were largely redesigned for LTE. The number of network nodes and interfaces were reduced in order to get a simple architecture with self-configuring base stations.
A leaner architecture reduces the number of signaling messages. This speeds up the establishment of the connection. The connection establishment now only takes 100 ms. With UMTS / HSPA it was 1 to 2 seconds. Latency and connection times have also been reduced. Response times between sender and receiver of 20 to 30 ms and less are possible. This is also sufficient for real-time applications.

EPS - Evolved Packet System

The LTE network architecture is called Evolved Packet System (EPS) designated. It is in the radio access network Evolved UMTS Terrestrial Radio Access Network (EUTRAN) and the core network Evolved Packet Core (EPC) divided. The EPC is completely packet-oriented and relies on the Internet Protocol (IP).
It should be noted that the following description is a greatly simplified representation.

In the EUTRAN, the mobile devices are called User equipment, LTE UE for short. The function of the base stations is derived from the UMTS network architecture and therefore bear the name eNode-B. In the LTE network architecture, the base stations are connected to their neighboring base stations and the core network. The X2 interface between the base stations enables quick handover.
For the registration of the participants in the network and their localization is the Management Mobility Entity (MME) responsible. The MME accesses the Home Subscriber Service (HSS) to. If the device has a valid account, it will be given a Serving Gateway (SGW) assigned. From there there is a connection to the PDN-GW, which establishes the connection to the Internet and assigns an IP address to the end device.
In the core network there is also the PCRF (Policy and Charging Rules Function). The services that are specified in the tariff are regulated here.

In order to be able to handle the growing data traffic in the cellular network, a broadband connection of the base stations to the core network is necessary. For this purpose, directional radio and fiber optics are preferred. An LTE base station with three sectors requires around 240 Mbit / s. That is a multiple of what is sufficient with UMTS and GSM. For this reason, the network operators are forced to expand their fiber optic lines. In this way, fiber optics are also moving closer to the customer in the mobile network.

LTE relay base station (relay node)

With LTE Advanced, relay stations (RelayNode) are set up on the network side, which receive, decode, process and transmit the mobile radio signal. In this way, the ranges of the base stations (eNodeB) can be increased and network coverage improved. This enables faster connections, especially at the cell edges. The signal runtimes increase somewhat, but this is offset by a significantly better wireless connection. The relay stations work in both downlink and uplink directions. The relay is completely invisible to the end device.

A relay base station is a complete LTE base station that is connected to the LTE core network via another LTE base station. However, operating a relay base station does not increase the network capacity; instead, part of the capacity is diverted. With the relay base station, only the capacity of an LTE cell is distributed more evenly over the coverage area, thus improving overall reception.

Overview: LTE

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