LTE VS 4G

4G, known as 4^th generation of mobile communications, and LTE (Long Term Evolution) are 3GPP specifications for mobile broadband networks. Different eras of mobile communication are categorized into generations such as 1G, 2G, 3G, and 4G, where each generation has a number of technologies such as LTE. ITU (International Telecommunication Union) considers LTE-Advanced as the true 4G standard, while it also accepts LTE as a 4G standard.

Following specifications need to be met by any network to be considered as 4G:

·         Based on an all-IP packet switched network.

·         Peak data rates of up to approximately 100 Mbit/s for high mobility such as mobile access and up to approximately 1 Gbit/s for low mobility such as nomadic/local wireless access.

·         Dynamically share and use the network resources to support more simultaneous users per cell.

·         Scalable channel bandwidth 5–20 MHz, optionally up to 40 MHz.

·         Peak link spectral efficiency of 15 bit/s/Hz in the downlink, and 6.75 bit/s/Hz in the uplink (meaning that 1 Gbit/s in the downlink should be possible over less than 67 MHz bandwidth).

·         System spectral efficiency of up to 3 bit/s/Hz/cell in the downlink and 2.25 bit/s/Hz/cell for indoor usage.

·         Smooth handovers across heterogeneous networks.

·         Ability to offer high quality of service for next generation multimedia support

 What is the difference between 4G and LTE?

·        ·          LTE Advanced, which is also known as true 4G standard, is evolution of LTE standard. Therefore, LTE and LTE Advanced have compatibility, where LTE terminal can work in LTE Advanced network, and LTE Advanced Terminal can work in LTE network.

·         Capacities of true 4G standards are much higher when compared with LTE. LTE supports up to a maximum of 2.7 bps /Hz /cell, while LTE Advanced (True 4G) has a capacity of 3.7 bps /Hz /cell. Even though, both LTE and LTE-Advanced (true 4G) support the same spectral efficiency in downlink, uplink spectral efficiency is much higher with true 4G.

·          Both LTE and 4G are focused on data rate improvement. Peak downlink data rate of LTE is 300Mbps, while official 4G definition requires 1Gbps downlink data rate. Therefore, true 4G has much higher data rate when compared with LTE, in both uplink as well as in downlink.

·         LTE is known as 3GPP release 8, while true 4G is considered as 3GPP release 10, which is evolution of initial LTE technology.

·         LTE networks are being deployed around the world now, while true 4G networks are still pending for trials. This is simply due to the stability of LTE when compared with LTE-Advanced. Initial LTE standards are published in March 2008, whereas initial stages of LTE-Advanced (True 4G) were standardized in March 2010.

·         4G is the next generation of mobile broadband communication, whereas LTE is the basis for true 4G technologies such as LTE-Advanced.

3GPP LTE technologies

To reach the higher data rates and faster connection times LTE contains a new radio interface and access network compared to the previous cellular systems. During 3GPP organized workshops it was agreed that the technology solution chosen for the LTE air interface uses Orthogonal Frequency Division Multiplexing (OFDM) and to reach the agreed data levels, Multiple Input Multiple Output (MIMO) technologies together with high rate modulation were agreed. These new technologies enable LTE to operate more efficiently with respect to the use of spectrum, and also to provide the much higher data rates that are being required.

OFDM (Orthogonal Frequency Division Multiplex) 

 OFDM-based technology has been incorporated into LTE because it can achieve the targeted high data rates with simpler implementations involving relatively low cost and power-efficient hardware. It is good to notice that OFDMA is used in the downlink of LTE but for the uplink Single Carrier-Frequency Division Multiple Access (SC-FDMA) technology is used. SC-FDMA is technically similar to OFDMA but it suits better for handheld devices because it is less demanding on battery power.

MIMO (Multiple Input Multiple Output)

Today’s mobile networks are very noisy environments. Without noise, an infinite amount of information could be transmitted over a finite amount of spectrum. To minimize the effects of noise and to increase the spectrum utilization and link reliability, LTE uses MIMO technique to send the data. The basic idea of MIMO is to use multiple antennas at receiver end and use multiple transmitters when sending the data. Before sending the data, the transmitter converts serial bit streams output by the source into multiple parallel sub streams. Then transmitter sends them via different transmit antennas using the same time slot and the same frequency band. After receiving data, the receiver separates out the original sub streams from the mixed signals using the non-correlation of signals on multiple receive antennas caused by multipath in the transmission. This leads to significant increases in achievable data rates and throughput.

SAE (System Architecture Evolution)

With the very high data rate and low latency requirements for 3G LTE, it is necessary to evolve the system architecture to enable the improved performance to be achieved. One change is that a number of the functions previously handled by the core network have been transferred out to the periphery. Essentially this provides a much "flatter" form of network architecture. In this way latency times can be reduced and data can be routed more directly to its destination. 

SAE - The Core Network for LTE

LTE Architecture and Network Elements

The 3GPP evolution for the 3G mobile system defined the UTRAN Long Term Evolution (LTE) and System Architecture Evolution (SAE) network. These standards define an all-IP network as a base for the LTE/SAE. The LTE/SAE does not have separate packet switched data traffic and circuit switched voice network. Both data and user plane communicates over the same network, which is called Evolved Packet System (EPS) network. 

LTE/SAE network includes many new network elements like MME and SAE GW. Only remaining element in radio access network is (enhanced) eNode B.

The figure shows the evolved system architecture of LTE

eNB

eNode B (eNB) is the base station in the LTE/SAE network that interfaces with the UE and hosts the PHYsical (PHY), Medium Access Control (MAC), Radio Link Control (RLC), and Packet Data Control Protocol (PDCP) layers. It also hosts Radio Resource Control (RRC) functionality corresponding to the control plane. Its main functions are

•  Radio resource management
•  IP header compression and encrypting of user data stream
• Selection of an MME at UE attachment
•  Routing of user  plane data towards SAE gateway
• Measurement and measurement reporting configuration for mobility and scheduling

Mobility Management Entity (MME)

The main task of MME is to take care signaling of control plane, and especially for mobility management and idle-mode handling.  It is also manages and stores UE context for the idle state, for example UE/user identities, UE mobility state and user security parameters.

Serving Gateway (SGW)

The SGW routes and forwards user data packets, while also acting as the mobility anchor for the user plane during inter-eNB handovers and as the anchor for mobility between LTE and other 3GPP technologies (terminating S4 interface and relaying the traffic between 2G/3G systems and PDN GW).

Packet Data Network Gateway (PDN GW)

The PDN GW provides connectivity to the UE to external packet data networks by being the point of exit and entry of traffic for the UE. A UE may have simultaneous connectivity with more than one PDN GW for accessing multiple PDNs. The PDN GW performs policy enforcement, packet filtering for each user, charging support, lawful Interception and packet screening. 

Both SGW and PDN GW gateways are used to process the user-plane data and handle the tasks related to the mobility management inside LTE and between other 3GPP radio technologies.

Home Subscriber Server (HSS)

Home Subscriber Server (HSS) can be compared to Home Location Register (HLR) in UMTS network. It contains the subscription-related information, performs authentication and authorization of the user, and can provide information about the subscriber's location and IP information.

Policy and Charging Rules Function (PCRF)

Policy and Charging Rules Function (PCRF) is the generic name for the entity within the LTE SAE EPC which detects the service flow, enforces charging policy. For applications that require dynamic policy or charging control, a network element entitled the Applications Function, AF is used.

LTE network combined with GSM and UMTS networks will be complex because the network will have so many symbiotic relationships between the various elements within the system. For example voice handover between LTE and UMTS networks is not possible to do. Facing these challenges will generate work for years to come.

Benefits of LTE

LTE which is currently in development phase can really take over the global mobile network because it has the capability to transition the 3G technology to 4G technology keeping the price factor at the minimum level. Most mobile developers across the world know that their consumers are always looking for faster speeds so that they can access their data and information at lightning speed and they can provide this through LTE network. There are many new mobile applications that are currently not available on 3G technology but with the help of LTE they can be available on the 4G technology.

The video talking about the benefits of the LTE Technology：

The reason why LTE is more powerful than the normal CDMA and GSM networks is because LTE uses radio spectrum that allows more data to transfer at the same bandwidth used by any 3G equipment or device. Hence, users are bound to get more data transfer at the same speed which will definitely bring down the overall cost of the network providers.

                                                                                                                                

Today, people need more options for mobile browsing apart from using their desktops and laptops and therefore they need some technology that can provide them with speedier internet access. In the future where people would prefer to buy mobile phones instead of desktops and laptops speedy internet is a necessity and therefore LTE is really important to people who want to stay connected at excellent browsing speeds.

Long Term Evolution (LTE) network is also available on 3G networks and many mobile service providers provide it to their users where they provide seamless transition to their consumers and then use the regular CDMA and GSM networks for backup. LTE was first designed for quick data transfer by 3GPP (3rd Generation Partnership Project). However, leading mobile providers and equipment manufacturers joined the team in the year 2009 and created a Voice over LTE via Generic Access (VoLGA) Forum.

With the advent of LTE wireless broadband at lightning speeds will become a reality for the consumers. However, mobile service providers will have to upgrade their equipments before they actually transition their technology from 3G to 4G. The LTE technology is certainly more efficient than the current technology that we are using at the moment.

What are the advantages of using a 4G network rather than a 3G network?

1.      For 4G network, it carries data only so it allows for more broadband width availability so that more data can be sent quickly.

2.      The speed is much faster in 4G.

3.       The range of availability for 3G networks is 10 miles at best, while it is 30 miles for 4G.

4.      There is now no disruption when transferring data from one coverage area to the next one in a 4G network.

5.       There are more devices and applications available or soon to be available in 4G.

6.      There is the anticipation of a high-definition, digital television along with applications for online games, improved GPS, and telemedicine.

Overview of LTE

The recent increase of mobile data usage and emergence of new applications such as MMOG (Multimedia Online Gaming), mobile TV, Web 2.0, streaming contents have motivated the 3rd Generation Partnership Project (3GPP) to work on the Long-Term Evolution (LTE). LTE is part of the GSM evolutionary path for mobile broadband, following EDGE, UMTS, HSPA (HSDPA and HSUPA combined) and HSPA Evolution (HSPA+).  Although HSPA and its evolution are strongly positioned to be the dominant mobile data technology for the next decade, the 3GPP family of standards must evolve toward the future. HSPA+ will provide the stepping-stone to LTE for many operators.

The goal of LTE was to increase the capacity and speed of wireless data networks using new DSP (digital signal processing) techniques and modulations that were developed around the turn of the millennium. A further goal was the redesign and simplification of the network architecture to an IP-based system with significantly reduced transfer latency compared to the 3G architecture. The LTE wireless interface is incompatible with 2G and 3G networks, so that it must be operated on a separate wireless spectrum. 

The following video has provide a brief introduction of the LTE network:

In view of the fact that there are a number of differences between the operation of the uplink and downlink, these naturally differ in the performance they can offer.These highlight specifications give an overall view of the performance that LTE will offer. It meets the requirements of industry for high data download speeds as well as reduced latency. It also provides significant improvements in the use of the available spectrum.

PARAMETER	DETAilS
Peak downlink speed 64QAM (Mbps)	100 (SISO), 172 (2x2 MIMO), 326 (4x4 MIMO)
Peak uplink speeds (Mbps)	50 (QPSK), 57 (16QAM), 86 (64QAM)
Data type	All packet switched data (voice and data). No circuit switched.
Channel bandwidths (MHz)	1.4,   3,   5,   10,   15,   20
Duplex schemes	FDD and TDD
Mobility	0 - 15 km/h (optimised), 15 - 120 km/h (high performance)
Latency	Idle to active less than 100ms Small packets ~10 ms
Spectral efficiency	Downlink:   3 - 4 times Rel 6 HSDPA Uplink:   2 -3 x Rel 6 HSUPA
Access schemes	OFDMA (Downlink) SC-FDMA (Uplink)
Modulation types supported	QPSK,   16QAM,   64QAM (Uplink and downlink)