LTE, also known as Long Term Evolution, was introduced by 3GPP in order to improve the mobile phone standard and to cope with the needs and demands of future networks as they evolve and expand.

• GPRS: Service on a 2G network, offering basic data up to 56 kbps (comparable to dial-up speeds)
• EDGE: This is a 2.5G technology, provides higher data transfer rates compared to GPRS (2G). 2G can reach speeds of up to 144 Kbps.
• 3G: This technology provides higher data rates as compared with the predecessor 2G and 2.5G networks (EDGE & GPRS). 3G offers speeds of up to 21 Mbps.
• 4G: This term is based on LTE technologies and is the latest advancement in mobile data transfer. It is the most advanced technology available, and can reach speeds of up to 100 Mbps.

The 3GPP, or the 3G Partnership Project, is responsible for the standardization of LTE. LTE, like most emerging technologies, is in development and all major carriers and many important equipment manufacturers contribute to this through product research.

LTE gives a superior user experience when it comes to stability, throughput, and latency. The increased capacity will bring new and better services to users through high-speed access anytime, anywhere. Users will be able to stream data, video, and VoIP from anywhere with no delay.

LTE offers existing operators the advantage of running a future-proof network, offering higher capacity, increased throughput, and an improved user experience. This helps operators to create new business opportunities and revenue streams. LTE offers a low OPEX, and LTE networks deployed today can be utilized in conjunction with all legacy networks: GPRS, 2G, and 3G.

The LTE standards, as they stand, are not technically up to 4G specs. LTE would be more accurately classified as 3.9G. Technically speaking, LTE does not fulfill all requirements of the 4G definition. LTE advanced, the standards of which are still in development, would more accurately embody the standards for a 4G network.

LTE Advanced is a mobile system that goes beyond LTE in several ways. In addition to best-in-class performance in terms of peak and sustained data rates and corresponding spectral efficiencies, capacity, latency, and overall network complexity and QoS (Quality of Service) management, LTE Advanced networks target peak data rates of 100 Mbps for high mobility and up to 1Gbps for low mobility.

The goals set out for the LTE standards are to lower overall costs, improve quality of service and higher data, increase spectral efficiency, and create better integration with other open standards.

Today’s LTE networks are capable of offering data rates of up to 100 Mbps. This is debatable, however, because user experience could vary depending on the location and network load at that moment. The equipment itself allows for speeds of more than 300 Mbps and some equipment currently in development are touting speeds of up to 1Gbps in low mobility.

No, there is a large market for EDGE and 3G networks where these technologies will continue to provide broadband access to billions. LTE will be largely an evolutionary step in many ways, as many existing networks will migrate up from 3G to 4G capabilities in order to meet customer demands for capacity and speed. Although 3G and other legacy systems are currently satisfactory, all major carriers will need to be prepared to upgrade in the very near future, if they have not done so already.

LTE utilizes a flat architecture, also known as a distributed radio network architecture. In this topology, powerful “smart” base stations play a much greater role than they have in the past. They are responsible for RRM (Radio Resource Management) and several other high layer functions that were previously handled by a RNC (Radio Network Controller). This RRM is handled in the eNode-B (Evolved Node-B). The benefit to a flat architecture is that latency is reduced in this type of network.

Ans:- Figure shows LTE architecture

SON stands for Self-Organizing/Self-Optimizing Network. This feature of LTE supports the automatic configuration and optimization of new cells in an LTE network. SON is regarded as a important feature when installing femto-cells (aka pico-cell base stations) and for the efficient usage of resources in LTE.

The RAT (Radio Access Technology) of LTE is based on OFDMA (Orthogonal Frequency Division Multiple Access). MIMO (Multiple Input Multiple Output) antenna techniques are also used in LTE to increase over-air data rates. OFDMA has been used in the telecommunications industry for a long time, but advances in technology have allowed it to become a more economical, viable option for LTE.

LTE is using multiple techniques to increase spectral efficiency, some of which include MIMO, Higher order Modulation), and using OFDMA on variable spectrum bandwidth (up to 20 MHz)

The purpose of MIMO (Multiple Input Multiple Output) is to increase data rates over the air by utilizing a multiple antenna technique where spatial multiplexing is used in proportion to the number of antennas used. In MIMO, multiple transmitting antennas carry bit streams running parallel to one another, thus creating multiple channels. The receiver uses multiple antennas to extract each stream by cancelling the interference from other antennas when certain pre-determined conditions are satisfied.

OFDM, also known as Orthogonal Frequency Division Multiplexing, is a method of encoding digital data on multiple carrier frequencies, and is used in LTE and other advanced wireless systems. This is where a significant number of closely spaced orthogonal sub-carrier signals are used to carry data streams. In OFDM a high-rate bit stream is multiplexed into a number of narrow band subcarriers and transmitted over parallel subcarriers which do not interfere with any other subcarrier in the cell. The orthogonality of subcarriers prevents crosstalk between them.

The purpose of IP mobility is to allow mobile users to move from one network to another and maintain an ongoing session without re-allocation of IP addresses or re-initialization of the session when the user changes geographical areas. LTE uses one of two available options: GTP (GPRS Tunneling Protocol) or MIP (Mobile IP).

E-UTRAN
Evolved UMTS Terrestrial Radio Access Network (E-UTRAN) is the official 3GPP-commissioned name for LTE’s radio access network. Quite the contrary to legacy systems, the E-UTRAN is made up of only one type of node, the eNode-B.

eNode-B
eNode-B (Evolved Node B) is the only mandatory node in the radio access network (RAN) of an LTE network. The eNode-B has its own control functionality embedded, therefore eliminating the need for an Radion Network Controller (RNC). This advanced, high-functioning base station manages 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. eNode-B also handles admission control, scheduling, enforcement of QoS, cell information broadcast, and much more.

Mobility Management Entity (MME)
Critical to LTE network functionality, the MME is located in the Evolved Packet Core (EPC) and manages session states, UE/user identities, user security parameters, roaming, and other bearer management functions.

Serving Gateway (S-GW)
The Serving Gateway (S-GW) is responsible for handovers from neighboring eNode-Bs. It routes and forwards user data packets across the user plane, and acts as the anchor for mobility between LTE and other 3GPP technologies (2G and 3G).

Packet Data Network Gateway (P-GW)
The PDN Gateway (P-GW) provides connectivity to the UE (User Equipment) by serving as the anchor/termination point of exit and entry of traffic for the UE. The P-GW supports the following functions: packet filtering for each UE, charging support, policy enforcement, lawful interception, and packet screening. The P-GW is also responsible for acting as a mobility anchor between 3GPP and non-3GPP networks (like WiMAX).

Home Subscriber Server (HSS)
The Home Subscribe Server acts as an IMS database as well as a database in EPC. The purpose of the HSS is to maintain storage of integrated subscriber data storage and management. HSS provides support by managing the routing/roaming procedures and solving authentication, authorization, naming/addressing resolution, location dependencies, and more.

Evolved Packet Core (EPC)
3GPP defined the Evolved Packet Core (EPC) as the IP-based core network in release 8 for use by an LTE network and other access network technologies. The EPC has a flat, all-IP core network architecture designed to efficiently give access to various services such as the ones provided in IMS (IP Multimedia Subsystem). EPC consists essentially of a Mobility Managment Entity (MME) and various Gateways for the routing of user data.

S1
S1 is a interface between eNode-B and the Evolved Packet Core (EPC). S1 has two important jobs: the S1-MME is used to exchange signaling messages between the eNB and the MME; the S1-U is the transport of user datagrams between the eNB and the Serving Gateway (S-GW).

X2
X2 is the interface between two eNode-Bs in E-UTRAN. User data and signaling messages are exchanged between two eNode-Bs over an X2.

On most current 4G networks, the 4G part of the network is set aside and used for data transfer. Typically, 3G or even 2G is used for voice calls. In a LTE system, the IMS (IP multimedia subsystem) is powerful enough to handle data transfer and support all voice call features. IMS is also scalable to serve very large subscriber bases, and provides operators the ability to offer additional services that can integrate voice calls with enhanced features like presence, instant messaging, and video content.

The initial costs of deployment for LTE networks are typically higher, although the OPEX will prove to be profitable in the long run. LTE networks utilizes very different RAT (Radio Access Technologies) and multiple antenna techniques and therefore cannot simply be implemented as an upgrade to existing.

Although there are limits, coexistence with 2G and 3G networks is possible. The LTE standards support seamless mobility with GSM and UMTS networks. Additionally, LTE standards support interoperability with non-3GPP networks like WiMAX and WLAN . The degree of mobility is obviously dependent on the innate capabilities of the mobile device as well.