The demand for new mobile generation communication systems is to provide improved voice communication experience. The first step taken towards this aspect is the 2.5G, which gave users access to a data network (e.g. Internet access, MMS - Multimedia Message Service). However, users and applications demand more communication power. As a response to this demand 3rd Generation (3G) communication system with new standards and architecture has been developed. In antithesis, the new 4thGeneration (4G) communication system framework was established which would attain new levels of user experience and multi-service capacity by also integrating all the mobile technologies that exist (e.g.GSM - Global System for Mobile Communications, GPRS - General Packet Radio Service, IMT-2000 -International Mobile Communications, Wi-Fi - Wireless Fidelity, Bluetooth).

NTT DoCoMo, that has already a wide base of 3G mobile users, estimates the number of mobile communication terminals to grow in Japan from the actual 82.2 million to more than 500 million units by 2010. A multi-service platform is an essential property of the new mobile generation, not only because it is the main reason for user transition, but also because it will give telecommunication operators access to new levels of traffic. Voice will lose its weight in the overall user bill with the rise of more and more data services. Low-bit cost is an essential requirement in a scenario where high volumes of data are being transmitted over the mobile network. With the actual price per bit, the market for the new high demanding applications, which transmit high volumes of data (e.g. video), is not possible to be established. Also, it is necessary for Quality of service (QoS) framework that enables fair and efficient medium sharing among users with different requirements, supporting the different priorities of the services to be deployed. The core of this network is based on Internet Protocol version 6 - IPv6, the probable convergence platform of future services (IPv4 does not provide a suitable number of Internet addresses). The network should also offer sufficient reliability by implementing a fault-tolerant architecture and failure recovering protocols.

Objectives of 4G Networks

•  Should ensure the continuity of competitiveness of the 3G system for the future.
•  Higher data rates and quality of service are the main demand by users.
•  Complexity is very less.
•  Avoidance of unnecessary fragmentation of technologies for both paired and unpaired band operation.
•  Packet switching technology is provided over the wireless system by ensuring QoS parameters.

4G - Long Term Evolution (LTE)

4G/LTE (Fourth Generation / Long Term Evolution) is 4G technology and next stage in mobile network development. It provides users with high data speeds than 3G .The main goal of this generation is to offer specifications for a new radio-access technology geared to higher data rates, low latency and with greater spectral efficiency. The present LTE architectures has three methods as follows-

1. Voice over LTE (VoLTE)

This approach is mainly based on the IP Multimedia Subsystem (IMS) network, with very specific profiles for control and media planes of voice service on LTE defined by GSMA in PRD IR.92. Hence it results in the voice service (control and media planes) being delivered as data flows within the LTE data bearer. There is no dependency on (or ultimately, requirement for) the legacy Circuit Switch voice network which is to be maintained.

2. Circuit-switched fallback (CSFB)

In Circuit-switched fallback approach, LTE provides data services. When a voice call has to be received or initiated, it will fall back to the circuit switched domain. When using this solution, operators needs to upgrade the MSC instead of utilizing the IMS, and therefore, it can provide services quickly. But the disadvantage is longer call setup delay.

In Simultaneous voice and LTE approach, the handset works simultaneously both in the LTE and circuit switched modes. In LTE mode providing data services and the circuit switched mode providing the voice service. This kind of solution which is entirely based on the handset, which do not have special requirements on the network and even does not require the deployment of IMS either. The disadvantage of this solution is that the phone becomes expensive with high power consumption.

Applications of 4G LTE

1. Smart Grids
2. Connected Cars
3. Multimode Software Application
4. Online satellite mapping
5. Multiple User Videoconferencing
6. Location-based services
7. Tele-medicine
8. High definition TV channel (HDTV)
9. High Definition Video on demand
10. Video games on demand

Challenges of 4G LTE

•  Hardware compatibility - If the user is using 3G, then one has to change the phone to the smartphone with 4G capabilities.
•  Not all regions offer 4G network services.
•  Choose cell phone carrier that offers 4G LTE service.
•  Security, handoff delay, battery backup.