The 4g Mobile Networks Computer Science
The 4G mobile networks will surely convert the current mobile phone networks, in to point to point IP based networks through which every device in the world will have a unique IP address, which will allow communications from a mobile device to the core of the internet which is IP based, and back to the mobile device.
If 4G is implemented correctly, worldwide interoperability, high speed connectivity, and transparent end user performance on every mobile communications device in the world can be achieved .
It is expected that 4G is set to deliver data rates of up to 100 mbps to a roaming mobile device globally, and up to 1gbps to a stationary device.
Providing video conferencing, streaming picture perfect video and many more.
It is not the deployment of the phone networks but the traffic capacity needed to be expanded with advanced modulation and antenna technologies .
4G won't happen overnight, it is estimated if it is done correctly it will be implemented by 2012.
4G networks the Next Generation Networks (NGNs) are becoming fast and very cost-effective solutions for demanded IP built high-speed data capacities in the mobile network .
possible standards for the 4G system are 802.20, WiMAX (802.16), HSDPA, TDD UMTS, UMTS and future versions of UMTS .
The design is that 4G will be based on OFDM (Orthogonal Frequency Division Multiplexing).
Other technological aspects of 4G are adaptive processing and smart antennas, both of which will be used in 3G networks and enhance rates when used in with OFDM.
Currently 3G networks uses OFDM which is designed to send data over hundreds of parallel streams, thus increasing the amount of information that can be sent at a time over traditional CDMA networks .
4G an abbreviation for Fourth-Generation, is an upcoming milestone in wireless communications .
A 4G system will be able to provide an IP based solution where voice, data and streamed multimedia can be given to users on an "Anytime, Anywhere" basis, at higher data rates.
The approaching 4G (fourth generation) mobile communication systems are projected to solve still-remaining problems of 3G (third generation) systems and to provide a wide variety of new services, from high-quality voice to high-definition video to high-data-rate wireless channels.
One of the terms used to describe 4G is MAGIC-Mobile multimedia, Anytime anywhere, Global mobility support, Integrated wireless solution, and Customized personal service.
The 4G systems not only supports the next generation of mobile service, but also will support the already existing wireless networks .
4G wireless networks that support global roaming across multiple wireless and mobile networks-for example, from a cellular network to a satellite-based network to a high-bandwidth wireless LAN.
With this feature, users will have access to different services, increased coverage, the convenience of a single device, one bill with reduced total access cost, and more reliable wireless access even with the failure or loss of one or more networks.
4G networks will also feature IP interoperability for seamless mobile Internet access and bit rates of 50 Mbps or more .
The first analog cellular systems based on IMTS (Improved Mobile Telephone Service) which were developed in 1970.
The systems were "cellular" because coverage areas were split into smaller areas or cells .
FIRST GENERATION (1G):
Two key improvements were seen by 1G analog system during 1970's: 1) the invention of the microprocessor and 2) the digitization of the control link between the mobile phone and the cell site.
An AMPS (Advance Mobile Phone System) was first launched by US which is 1G mobile system, based on FDMA technology which allows users to make voice calls within one country .
Access technology used:
FDMA: Frequency Division Multiple Access (FDMA) is a technique whereby spectrum is divided up into frequencies and is assigned to users.
With FDMA, only one user can have access to the channel until the call is terminated another call cannot be initiated.
or until it is handed-off to a different channel.
A "full duplex "FDMA transmission requires two channels one for transmitting and the other for receiving.
FDMA has been used for first generation analog systems .
SECOND GENERATION (2G):
2G digital cellular systems were deployed by the end of 1980's.
These systems are digitized not only the control link but also the voice signal.
This system provided better quality and higher capacity at lower cost to consumers.
GSM (Global System for Mobile communication) was operated based on TDMA .
Access technology used:
TDMA: Time Division Multiple Access (TDMA) improves spectrum capacity by splitting each frequency into time slots which allows each user to access the entire radio frequency channel for the short period of call.
Other users share this same frequency channel at different time slots.
The base station continuously switches from user to user on the channel .
THIRD GENERATION (3G):
3G systems provide faster communication services, including voice, fax and internet, anytime and anywhere.
3G had opened the way to enabling innovative applications and services (e.g.
multimedia, entertainment, information and location-based services).
First 3G network was deployed in Japan in 2001 .
Access technology used:
CDMA: Code Division Multiple Access is based on "spread" spectrum technology.
which is suitable for encrypted transmissions, it has long been used for military purposes.
CDMA increases spectrum capacity by allowing all users to occupy all channels at the same time.
Transmissions are spread over the whole radio band, and each voice or data call are assigned a unique code to differentiate from the other calls carried over the same spectrum.
CDMA allows for a "soft hand-off", which means that terminals can communicate with several base stations at the same time .
Table 1: Short history of mobile technologies:
Figure 1: Comparison of different mobile technologies with corresponding coding techniques used 
What is 4G?
Fourth generation (4G) wireless was used by the Defense Advanced Research Projects Agency (DARPA), the same organization that deployed the wired Internet .
DARPA choose the distributed architecture for the wireless Internet that had proven so successful in the wired Internet.
Two characteristics have emerged: end-to-end Internet Protocol (IP), and peer-to-peer networking.
IP based networks possess gate ways which transmits data in terms of packets from source to destination using header which contains destination address peer-to-peer network, where every device is both a transceiver and a router/repeater for other devices in the network.
4G technology is significant because users joining the network add mobile routers to the network infrastructure.
Because users carry much of the network with them, network capacity and coverage is dynamically shifted to accommodate changing user patterns .
Users will automatically hop away from congested routes to less congested routes.
This permits the network to dynamically and automatically self-balance capacity, and increase network utilization .
4G systems are intended to replace the 3G systems, perhaps in 3 to 5 years.
Accessing information anywhere, anytime, with a seamless connection to a wide range of information and services, and receiving a large volume of information, data, pictures, video, and so on, are the keys of the 4G infrastructures.
4G will have broader bandwidth, higher data rate, and smoother and quicker handoff and will focus on ensuring tremendous service across a multitude of wireless systems and networks .
Why 4G is required ?
We may question that why we require 4G if 3G systems are working well.
It is because of basically two reasons that one is substantial growth in overall number of subscribers and other is massive demand of new data services like data, audio, image or video(interactive or non- interactive).
Though the projected data rate is around 2Mbps in 3G, the actual data rates are slower, the data services like multimedia are going to play modest role and will dominate the cellular traffic instead of voice in future.
In such scenario the present 1G & f2G systems will saturate and will have no room to survive.
Also the demand for increasing data rates leads to higher band width requirement.
These factors cause the cellular industry to develop a common standard for a system that can work to overcome almost all the limitations imposed by the previous cellular technologies.
The expected features of 4G systems are as follows:
Support for multimedia services like teleconferencing and wireless Internet.
Wider bandwidths and higher bitrates.
Global mobility and service portability.
Scalability of mobile network.
Entirely Packet-Switched networks.
Digital network elements.
Higher band widths to provide multimedia services at lower cost(up to 100 Mbps).
Tight network security.
Figure 2: Technology convergence to 4G
4G mobile phone and internal building blocks:
Figure3: sample view of the 4G mobile phone
Figure 4: Basic internal blocks of the 4G mobile
Figure below shows the basic concept of 4g network.
The 4G infrastructure is the integration of networks using IP.
Because of which users will be able to choose every application, environment and obtaining services, receiving a large volume of information, data, pictures, video and so on .
Figure 4: concept of integration of several networks 
Figure: Standards and Components supported by 4G network
Architecture in prospects:
End-to-end Service Architectures for 4G Mobile Systems:-
4G is an IP based point to point system.
End-to-end service architectures should have the following desirable properties:
1 Open service and resource allocation model.
2 Open capability negotiation and pricing model.
3 Trust management: Managing trust relationships among clients and service providers,
and between service providers, based on trusted third party monitors .
4 Collaborative service constellations.
5 Service fault tolerance.
Figure: 4G network with wide interoperability
The service middleware is decomposed into three layers; i.e.
user support layer, service support layer and network support layer.
The criterion for using a layered approach is to reuse the existing subsystems in the traditional middleware.
The user support layer has autonomous agent aspects that traditional service middleware lacks.
It consists of 4 sub-systems: 'Personalization', 'Adaptation', 'Community' and 'Coordination', to provide mechanisms for context awareness and support for communities and coordination.
Introduction of this functional layer enables the reduction of unnecessary user interaction with the system and the provision of user-centric services realized by applying agent concepts, to support analysis of the current context, personalization depending on the user's situation, and negotiation for service usage.
The middle layer, the service support layer, contains most functionality of traditional middleware.
The bottom layer, the network layer supports connectivity for all-IP networks.
The dynamic service delivery pattern defines a powerful interaction model to negotiate the conditions of service delivery by using three subsystems: 'Discovery & Advertisement', 'Contract Notary' and 'Authentication & Authorization'.
Cellular Multi hop Communications: Infrastructure-Based Relay
Figure 5: Layer decomposition of Middleware Architecture
It is clear that more fundamental enhancements are necessary for the very ambitious throughput and coverage requirements of future networks.
Some major modifications in the wireless network architecture are to be made like advanced transmission techniques and antenna technologies, which will enable effective distribution and collection of signals to and from wireless users .
In a Multi hop network, a signal from a source reach's its destination in multiple hops through the use of "relays" .
Since we are here concerned with infra structure-based networks, either the source or destination is a common point in the network base station.
The potential advantage of relaying is that it allows substituting a poor-quality single-hop wireless link with a composite, two or more hop, better-quality link whenever possible.
Relaying is not only efficient in eliminating black spots throughout the coverage region , but it may extend the high data rate coverage range of a single BS; therefore cost effective high data rate coverage may be possible through the augmentation of the relaying capability in conventional cellular networks.
Figure below shows the network architecture view of basic 4G network.
The architecture of both the transmitter and the receiver is same but coming to transmitter the system possess multiple antennas.
The data within the communication system is manipulated digitally.
Here we use multiple antenna architecture design to achieve multiple data patterns to achieve the data more accurately.
Figure: 4G network Architecture
Figure: Different 4G layered network models
Legends used in the diagram:
Bi-directional block arrow