The 4g Mobile Networks Computer Science Essay
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 .
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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 .
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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:
1. Support for multimedia services like teleconferencing and wireless Internet.
2. Wider bandwidths and higher bitrates.
3. Global mobility and service portability.
4. Scalability of mobile network.
5. Entirely Packet-Switched networks.
6. Digital network elements.
7. Higher band widths to provide multimedia services at lower cost(up to 100 Mbps).
8. 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.
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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 Wireless Link
Cylinder Local Database
Telescopic/ educational satellite
Fixed wireless LAN
wireless LANProposed architecture of 4G
Property owners can install their own access points. Spreads infrastructure cost.
Reduced network access operational cost: Access points configure into access network.
Some access points may be moving (bus, train)
Multi hop also could reduce costs in heterogeneous 3G networks.
Figure 6: Overlay network
In this architecture, a user accesses an overlay network consisting of several universal access points (UAP). These UAPs in turn select a wireless network based on availability , QoS specifications, and user defined choices. A UAP performs protocol and frequency translation, content adaptation, and QoS negotiation-renegotiation on behalf of users. The over lay network, rather than the user or device, performs handoffs as the user moves from one UAP to another. A UAP stores user, network, and device information, capabilities, and preferences .Because UAPs can keep track of the various resources a caller uses, this architecture supports single billing and subscription.
A multimode device lets the user, device, or network initiate hand off between networks without the need for network modification or interworking devices.
An overlay network consisting of several universal access points (UAPs) that store user, network, and device information-performs a handoff as the user moves from one UAP to another.
A device capable of automatically switching between networks is possible if wireless networks can support a common protocol to access a satellite-based network and another protocol for terrestrial networks.
Wireless technology used in 4G
3. SMART ANTEENAS
1) Orthogonal Frequency Division Multiplexing (OFDM) :-
OFDM is multiplexing of the message signal with the orthogonal set of carrier waves. In this carrier signals are spaced equally which provides "orthogonality". Advantages of OFDM is high spectral efficiency, high resistance to RF interference, the multi-path distortion. In a standard terrestrial broadcasting there are high amounts of multipath-channels. Because of inter symbol interference (ISI) it becomes difficult to extract the original information. By the development of the fast Fourier transform (FFT). Shortly after an equalization algorithm was implemented in order to help suppress both ISI and inter subcarrier interference, which is caused by the channel impulse response and timing, frequency errors .
2) Ultra Wide Band (UWB):
An Ultra Wideband device works by emitting a series of short, low powered electrical pulses that are not directed at one particular frequency but rather are spread across the entire spectrum . As seen in Figure, Ultra Wideband uses a frequency of between 3.1 to 10.6 GHz. The pulse can be called "shaped noise" because it is not flat, but curves across the Spectrum. On the other hand, actual noise would look the same across a range of frequencies- it has no shape. For this reason, regular noise that may have the same frequency as the pulse itself does not cancel out the pulse. Interference would have to spread across the spectrum uniformly to obscure the pulse.
UWB provides greater bandwidth - as much as 60 megabits per second, which is 6 times faster than today's wireless networks. It also uses significantly less power, since it transmits pulses instead of a continuous signal. UWB uses all frequencies from high to low, thereby passing through objects like the sea or layers of rock. Nevertheless, because of the weakness of the UWB signal, special antennas are needed to tune and aim the signal.
Figure 7: Ultra wide Band
3) Smart Antenna:
Multiple "smart antennas" can be employed to help find, tune, and turn up signal information.
Figure 8: Figure illustrating different modes of MIMO antennas
There are two types of smart antennas:-
Switched Beam Antennas:
It have fixed beams of transmission, and can switch from one predefined beam to another when the user with the phone moves throughout the sector.
Figure 9: switched beam antenna transmission pattern
Adaptive Array Antenna:
It represent the most advanced smart antenna approach to date using a variety of new signal processing algorithms to locate and track the user, minimize interference, and maximize intended signal reception.
Figure 10: Adaptive array antenna transmission pattern
Smart antennas can thereby:
â€¢ Optimize available power
â€¢ Increase base station range and coverage
â€¢ Reuse available spectrum
â€¢ Increase bandwidth
â€¢ Lengthen battery life of wireless devices .
Although UWB and smart antenna technology may play a large role in a 4G system, advanced software will be needed to process data on both the sending and receiving side. This software should be flexible, as the future wireless world will likely be a heterogeneous mix of technologies.
Figure 11: Anteena as both transmitter & reciever
The Internet Protocol (IP) is a protocol which data is sent from one computer to another on the internet. Each computer (known as a host) on the Internet has at least one IP that uniquely identifies it from all other computers on the Internet. When you send or receive data, the data gets divided into little chunks called packets. Each of these packets contains both the sender's Internet address and the receiver's address. Any packet is sent first to a gateway computer that understands a small part of the Internet. The gateway computer reads the destination address and forwards the packet to an adjacent gateway that in turn reads the destination address and so forth across the Internet until one gateway recognizes the packet as belonging to a computer within its immediate neighborhood or domain. That gateway then forwards the packet directly to the computer whose address is specified. Because a message is divided into a number of packets, each packet can, if necessary, be sent by a different route across the Internet. Packets can arrive in a different order than the order they were sent in. The Internet Protocol just delivers them. It's up to another protocol, the Transmission Control Protocol (TCP) to put them back in the right order. IP is a connectionless protocol and TCP, the connection-oriented protocol that keeps track of the packet sequence in a message. The most widely used version of IP today is Internet Protocol Version 4 (IPv4). However, IP Version 6 is also beginning to be supported. In order to provide wireless services at anytime and anywhere, terminal mobility is a must in 4G infrastructures, terminal mobility allows mobile client to roam across boundaries of wireless networks.
Figure 12: IP layout
Software defined ratio :
Software Defined Radio (SDR) benefits from today's high processing power to develop multi-band, multi-standard base stations and terminals. Although in future the terminals will adapt the air interface to the available radio access technology, at present this is done by the infrastructure. Several infrastructure gains are expected from SDR. For example, to increase network capacity at a specific time (e.g. during a sports event), an operator will reconfigure its network adding several modems at a given Base Transceiver Station (BTS). SDR makes this reconfiguration easy. In the context of 4G systems, SDR will become an enabler for the aggregation of multi-standard pico /micro cells. For a manufacturer, this can be a powerful aid to providing multi-standard, multi-band equipment with reduced development effort and costs through simultaneous multi-channel processing.
The existing security schemes for wireless systems are inadequate for 4G networks. The key concern in security designs for 4G networks is flexibility. As the existing security schemes are mainly designed for specific services, such as voice service, they may not be applicable to 4G environments that will consist of many heterogeneous systems. Moreover, the key sizes and encryption and decryption algorithms of existing schemes are also fixed. They become inflexible when applied to different technologies and devices (with varied capabilities, processing powers, and security needs). As an example, Tiny SESAME is a lightweight reconfigurable security mechanism that provides security services for multimode or IP-based applications in 4G networks.
4G in normal life:-
Figure: view of in building to global applications of 4G and corresponding coding techniques used
Using 4G networks allows cities to deploy cameras and backhaul them wirelessly. And instead of having to backhaul every camera, cities can backhaul every third or fifth or tenth camera, using the other cameras as router/repeaters. These cameras can also serve as fixed infrastructure Location application.
4G location applications:
4G location applications will be based on visualized, virtual navigation schemes that will support a remote database containing graphical representations of streets, buildings and another physical characteristic of a large metropolitan area . Which is accessed by subscribers in vehicles.
A paramedic assisting a victim of a traffic accident in a remote location could access medical records (X-rays) and establish a video conference so that a remotely based surgeon could provide 'on-scene' assistance .
Traffic Control During Disaster:
4G networks can allow officials to access traffic control boxes to change inland traffic lanes to green. lights could also be forced to red to prevent civilians from driving into harm's way.
In the event of natural disasters restoring communications quickly is essential. With wideband wireless mobile communications, limited and even total communication capability(including Internet and video services) could be set up within hours instead of days or even weeks required at present for restoration of wire line communications .
Threats for implementing the 4G Network:
Because deployment of 4G wireless technology is not expected until 2012 or even later, developers will hopefully have time to resolve issues involving multiple heterogeneous networks such as Access, Handoff, Location coordination, Resource coordination to add new users, Support for multicasting, support for quality of service, Wireless security and authentication, Network failure and backup, and Pricing, billing. Network architectures will play a key role in implementing the features required to address these issues .
Figure: Broader applications of 4G
Currently 4G is still under research in many countries and the trail version has been implemented in countries like united states. Certain companies are working collectively for the integration of the currently existing technology to create the unique standard called 4G which is compatible with all the wireless networks. Figure below shows the companies which are having active participation in the 4G project.
Figure: Member companies in implementing 4G project
Attempts have been made to reduce a number of technologies to a single global standard. Projected 4G systems offer this promise of a standard through its key concept of integration. Future wireless networks will need to support diverse IP multimedia applications to allow sharing of resources among multiple users. The fourth generation promises to fulfill the goal of PCC (personal computing and communication)-a vision that affordably provides high data rates everywhere over a wireless network. Although 4G wireless technology offers higher bit rates and the ability to roam across multiple heterogeneous wireless networks, several issues require further research and development. It is not clear if existing 1G and 2G providers would upgrade to 3G or wait for it to evolve into 4G, completely bypassing 3G in some countries. The answer probably lies in the perceived demand for 3G and the ongoing improvement in 2G networks to meet user demands until 4G arrives .
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