LTE (long term evolution) is everywhere and its time you understood the LTE basics. If you’re not already using your smartphone on this new and improved network, chances are you will be doing so soon. But before you can appreciate LTE, you must fully understand it. To help accomplish this, let’s go over the LTE basics.
What is LTE?
LTE is the next generation of mobile broadband technology, and successor to the now outdated 3G network. LTE follows UMTS 3G technology. It also carries data rates of 100 Mbps and works with IP. The main advantages LTE brings include low latency, higher network throughput, increased data transfer speed, better cost efficiency and overall improvements compared to the 3G network.
LTE Basics – Architecture
So, what is LTE made of? The technologies that comprise the LTE network architecture include OFDM (orthogonal frequency division multiplexing) for downlink, SC-FDMA (single carrier – frequency division multiple access) for uplink, MIMO (multiple input multiple output) and SAE (system architecture evolution).
LTE Network Elements
You can’t tackle the LTE basics without discussing network elements. For LTE, there are four:
Evolved Node B (eNB) is the only mandatory node in the radio access network (RAC) of LTE. The eNB is a complex base station that handles radio communications with multiple devices in the cell and carries out radio resource management and handover decisions. There is no need for a centralized radio network controller in LTE. Main functions include:
- Supports air interface
- Provides radio resource management functions
The Serving Gateway (SGW) routes and forwards user data packets, and serves as the mobility anchor for the user plane during the inter-eNodeB handovers. SGW also acts as the anchor for mobility between LTE and other 3GPP technologies. The SGW terminates the downlink data path and triggers paging when downlink data arrives for the UE that is in an idle state. It manages and stores UE contexts, e.g. parameters of the IP bearer service, network internal routing information. It also performs replication of the user traffic in case of lawful interception. Main functions include:
- Provides mobility
- Responsible for routing and forwarding
The Packet Data Network Gateway (PDN GW) is the point of exit and entry of traffic for the UE, providing connectivity from the UE to external packet data networks. A UE may have simultaneous connectivity with more than one PGW for accessing multiple PDNs. The PGW performs policy enforcement, packet filtering for each user, charging support, lawful interception and packet screening. The PGW also acts as the anchor for mobility between 3GPP and non-3GPP technologies such as WiMAX and 3GPP2 (CDMA 1X and EvDO). Main functions include:
- Provides connectivity to the internet
- Provides QoS and mobility between 3G and non-3G networks
Mobility Management Entity (MME) plays an important role in LTE EPC architecture. In fact, MME is the main signaling node in the EPC. According to LTE University, LTE MME is responsible for initiating paging and authentication of the mobile device. MME retains location information at the tracking area level for each user and then selects the appropriate gateway during the initial registration process. MME connects to the evolved node b (eNB) through the S1-MME interface and connects to S-GW through the S11 interface. Multiple MMEs can be grouped together in a pool to meet increasing signaling load in the network. MME also plays a vital part in handover signaling between LTE and 2G/3G networks. Main functions include:
- Manages mobility and provides security
- Operates in control plane and provides authentication [1]
There is no arguing that LTE is a complex network, to say the least. But its many components and facets are what will allow for improved speed and data rates. LTE came about to meet the demands of today’s wireless customer who want speed, and want it now. Hopefully these LTE basics put the network into terms you can understand.
