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This paper will explore the applications and services of emerging wireless technologies in 4G. The QOS mobile communications in 4G mobile networks include transmission delay, bit error rate, packet drop rate, transmission rate, end-to-end throughput etc. 4G technology will offer much advancement to the wireless market, including download link date rates well over 100Mbps, very efficient spectrum use. Fourth Generation is the next generation of wireless networks. 4G is all about an integrated global network it is an open wireless system approach. The 4G systems not only will support the next generation of mobile service, but also will support the fixed wireless networks.
Wireless technologies will provide information anywhere, anytime, at a low-cost to a large portion. The main research going on 4G is to provide high speed, high band-width and packet data communications. The next generation wireless system will be not only a voice medium but will have internet like functionality. Wireless technologies will provide information anywhere, anytime at a higher data rate than previous generations. 3G technologies have greater functionality than today's wireless systems. The current 3G devices are good, but they will have to improve in areas like imaging and processing power to support future 4G applications like three dimensional (3D), gaming, 16 megapixel smart cameras and high-definition (HD) camcorders . Applications like these will demand more processing power than the current 3G handsets offer. The fourth generation systems will support the next generation mobile communication service and also for fixed wireless networks. 4G networks will also feature IP interoperability for seamless mobile internet and bit rates of 50Mbps or more  . Current downlink data rates are less than 10 megabits per second (Mbps); 4G systems will offer downlink data rates well over 100 Mbps, an improvement of 10 times over 3G .Many wireless technologies are used in 4G: Orthogonal Frequency Division Multiplexing (OFDM), Ultra Wide Band (UWB), Smart Antennas and Internet Protocol (IPv6). By using OFDM it is high spectral efficiency; high resiliency. The performance is carried out by quality of service .
1. PRINCIPLES AND BACKGROUND THEROY:
In first generation of wireless technology during voice call a full band of the channels is not being used so, there are lulls when a typical user makes a call in circuit switching that lull is still being transmitted over the channel .
In 1G mobile Advance Mobile Phone System (AMPS) which allows making calls within our country. Frequency Division Multiple Access (FDMA) is an analog system. In FDMA technique first spectrum is divided in to different frequencies and only one subscriber can access a channel in any given time. When another subscriber want to access a channel then user has to access until the initial call is finished  .
In second generation they have developed digital cellular systems. These systems are digitized for control link and the voice signal. Global System for Mobile communications (GSM) was operated on digital system based TDMA. In Time Division Multiple Access (TDMA) spectrum will split each frequency into two slots. It allows each user to access within a short period of call at the same time other users are also using the same channel at different slots .
The third generation systems are faster communications services, including voice, fax and internet anytime and anywhere. In these systems Code Division Modulation Access is taken. CDMA increases capacity of spectrum and users occupy all channels at the same time. Code transmissions are spread over the whole band and each user will assign a unique code in order to differentiate from other  .
The expected features of 4G are much higher data around 100Mbps. It will improve quality of service. The upcoming features of 4G: 
Support for multimedia services like teleconferencing and wireless internet.
Wider bandwidths and higher bitrates.
Global mobility and service portability.
Higher band widths to provide multimedia service at lower cost up to 10Mbps.
Digital networks elements.
The first generation and second generation of mobile telephony were for voice transmission. In 3rd generation it will serve both voice transmission and data application and 4G will be a super enhanced version of 3G. 4G systems will be developed with software defined ratios i.e., with new protocols and all digital networks elements and for high bandwidth it will bring multimedia capability like high speed data access and video conferencing to the handset .
In the early 1980's 1G systems were developed and it is original analog cellular systems at the same time 2G mobile telephony were deployed in 1990's. The main difference between the systems is signal and modulation techniques: 
1G - Analog Signalling
2G - Digital Signalling
All these technologies are circuit-switched services. In digital signalling, packet data communication is taken in this voice or data is converted into binary code and divided into short segments. At the destination end output can be seen as all the segments are assembled in correct order and give back useful information . 3G development and thinking was started from 1991 most of the companies came with 3Gplus it is a extend performance for 4G  . Recently, several advancements have been introduced for 3G wireless communication systems to further enhance the data rate and the system performance (e.g., high speed downlink packet access (HSDPA)) in wideband code division multiple access (WCDMA) systems, . Universal Mobile Telecommunications System (UMTS) is projected to be the third-generation (3G) mobile phone technology. It offers broadband, packet-based transmission of text, voice, video, and multimedia at data rates that will reach 2 Mbps and greater.
3. WIRLESS TECHNOLOGIES:
There are different types of wireless technologies.
Global System for Mobile Communications (GSM)
Code Division Multiplication Access (CDMA).
Time Division Multiplication Access (TDMA).
These are used for 2G, 2.5G and eventually 3G. There are two approaches being used to develop 4G access techniques .
3XRTT - 4G and (W-CDMA), these are developed with software defined ratios.
A new access technology is developing it is called as Large-Area-Synchronized Code Division Multiple Access (LAS-CDMA). LAS-CDMA will support for all the advanced technologies for 4G. . 1XRTT for 2.5G and 3G
3.1 INTERNET SPEEDS:
2G - 28Kbps
3G - 2Mbps
4G - 100Mbps
3G networks are 200 times faster than 2G networks.
4. QUALITY OF SERVICE (QoS):
In wireless networks quality of service (QoS) refers to the measure of the performance, the transmission quality and service availability. The reliability of 4G is 99.99% with the help of QOS in 4G networks we can overcome the major problem: varying rate channel characteristics, bandwidth allocation and network levels this makes the network more flexible  .
Varying rate channel (VRC) characteristics must be considered to meet user demand. This refer to 4G applications at same time it will be varying bandwidth and transition rate, according to the flexibility and scalability this networks are designed. In order to avoid unnecessary network failure poor coverage, dropped calls and more fault tolerance capabilities are taken in 4G. In 2G and 2.5 we see less faults tolerance. These network support interoperability between disparate networks technology by using techniques like Large-Area-Synchronized Code Division Multiple Access (LAS-CDMA) signalling .
QoS support can occur at the packet transaction, circuit, user and network levels.
Transaction level QoS describes both the packet loss rate and time taker to complete a transaction .
Circuit level QoS includes blocking calls of new and existing calls. Call routing and location management are two circuit level attributes .
User level QoS it mainly depends on user mobility and application type in complete wireless system the end to end communication between two users will likely involve multiple wireless networks .
The best advanced applications in 4G system is location based services. 4G location applications would be based on visualization, virtual navigation schemes that would support a remote database containing graphical representations of streets, buildings and other large metropolitan area. This data base could be accessed by a subscriber in a moving vehicle equipped with the appropriate wireless device.eg: one would be able to see the layout of a building during an emergency rescue. This type of application is sometimes called as "Telegeoprocessing" 
Telegeoprocessing means it is a combination of Geographical Information Systems (GIS) and Global Positioning Systems (GPS) these works in high capacity wireless mobile systems .
5.1 VIRTUAL NAVIGATION:
A remote data base contains the graphical representation of stress, buildings and physical characteristics of a large metropolis. In these blocks of data are transmitted in rapid sequence to a vehicle a rendering program permits the occupants to visualize the environmental ahead. They may also virtually see the internal layout of building to plan an emergency rescue  .
5.2 TELE MEDICINE:
A paramedic assisting a victim of a traffic accident in a remote location could access medical records like X-rays and conference so that a remotely based surgeon could provide 'on scene' assistance. In such a circumstance, the paramedic could relay the victims recorded locally back to the hospital in real time, for review by the surgeon  . Patient will be able to take general readings, like temperature, pulse and blood glucose levels and send them directly to a doctor for evaluation. With these applications, child will be able to take their blood glucose reading at school and that reading would then be automatically forwarded to you .
5.3 LOCALIZED/PERSONALIZES INFORMATION:
These services are more used for internet usage, income brackets and mobile professional segments. This provide users with general news, financial news, location guides, mobile commerce and travel services, it is used for individuals that they spend longer than about 32 minutes browsing the internet .
This type of application involves messaging. These services are important to all users, especially mobile professional. It includes short messaging services (SMS), email, video conferencing and fax .
It includes personal digital assistant (PDA), currency exchange, calendars, call management and address books. These applications are more relevant to the income brackets and mobile professional .
These services may include chat, photo trading, gaming, streaming audio and streaming video and are mainly on page segment (18years old or younger) .
5.7 MOBILE COMMERCE (M-COMMERCE):
The ability for subscribers to purchase gas, food from vending machines using a wireless device. E.g.: If a person wants to purchase an item for a vending machine user must dial a number or accessing the code with the item which is most lively marked on the vending machine. The vending machine should be connected to public switched telephone network through a modem. The wireless service provider would pass the information to the vending company and this pass information to vending machine. The user account would be billed for items purchased from credit card .
5.8 TRAFFIC CONTROL:
In some major cities thy have deployed cameras on traffic lights and send those images back to a central command centre , this is done using fiber , 4Glocation applications will be based on visualization, virtual navigation schemes that will support a remote database .
5.9 CONTEXT AWARENESS:
This is based on sense information so that to adapt with the user profile. For ex: when a user was travelling in a car and as he/she passed by an electronic poster about real estate in which the user is interested in, the details about that real estate deal will be automatically automated in users local device for instance mobile .
This paper describes some important new technologies, approaches and applications to wireless communications. Orthogonal Frequency Division Multiplexing (OFDM), Ultra Wide Band (UWB) these two has improved spectral efficiency. In future wireless network will need to support diverse IP multimedia applications to allow sharing of resources among multiple users. There must be a low complexity of implementation and an efficient means of negotiation between the end users and the wireless infrastructure. Applications and services for 4G are still being defined.