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      Abstract :
              This paper aims to identify and explore the different issues and challenges related to fourth
       generation networks. It starts with a brief Introduction, and then explains the edge of 4G technology
      over 3G, and defines 4G. , . It also provides a detailed insight on the vision of 4G, and also discusses
      about the advantages and applications of 4G technology. It also compares the 4G technology with all
      other technologies. and explains all its ,characteristics.

      This paper also focuses on key technologies to implement 4G technology. and also provide a technical
      Platform for implementing the technology as it provides a basic idea on OFDM since with its natural
      resistance to multipath fading and its ability to support extremely high data rates, orthogonal frequency
      division multiplexing (OFDM) is a major candidate for fourth-generation air interfaces. ,it consists
      characteristics   and benefits‟ of OFDM.

      it mainly explains the use of 4G having possessed “3G”

              We are seeing a massive demand for data, audio, image and video services on mobile phones.
      These require a faster rate of data transfer.
      Though the projected data rate of 3G is around 2 Mbps, the actual data rate is much slower, especially in
      crowded areas or when the network is congested. Further, data rates also depend on the user‟s activity
      (moving or steady state) and location (indoor/outdoor).
      As expected data services like multimedia are going to play an increasing role and will dominate the
      cellular traffic instead of voice in future.                                                                                             2
In such a scenario, the present 2G and 3G systems will saturate and have no room to survive. Also, the
demand for increasing data rates leads to higher bandwidth requirements. These factors force the cellular
industry to develop a common standard or system that over comes almost all limitations imposed by
previous cellular technologies.
4G services hold out the promise of end-to-end, totally IP (Internet protocol), packet-switched networks
that will be able to handle growing loads of wireless voice, data, video and audio transmissions more
efficiently, at lower cost and at higher performance levels i.e., 4G systems are expected to allow much
higher data rates of around 100 Mbps, higher bandwidth of the order of hundreds of megahertz, plenty
of services like data, audio and video(as shown in fig1),seamless connectivity and improved quality of
service keeping in mind that all existing networks can be merged or interconnected to form an all-in-

What is 4G?

        Fig 2 shows the concept of 4G cellular network. The future 4G infrastructure will consist of various
networks using Internet Protocol (IP) as a common protocol. So the users will be in control as they can choose
every application and environment. Accessing information any where, in time with seamless connections to a
wide range of information, data, pictures, video and so on will be the benefits of 4G infrastructure.                                                                                3
       One of the terms popularly used to describe 4G is „MAGIC‟, which stands for „Mobile
multimedia, anytime any where, Global mobility support, Integrated Wireless solutions and customized
personal services.‟
4G services will be dynamic and adaptable to the application. Faster response and quality are the
prerequisites for full-motion video, home entertainment and advance location-based services. The
expected data rate is 2 Mbps for vehicular applications. Such high data rates obviously require a high
bandwidth of the order of several hundreds of megahertz.

                                                      2G: was based on digital signal processing
1G: This process began with the designs in the
                                                      techniques and regarded as a revolution from
1970s that have become known as 1G. The
                                                      analogy to digital technology These 2G systems
earliest systems were implemented based on
                                                      provided circuit- switched data communication
analog technology and the basic cellular
                                                      services at a low speed. of 9.6 kbps The
structure of mobile communication.
                                                      competitive rush to design and implement                                                                                              4
digital systems led again to a variety of different        multimedia services requirements, together with
and incompatible standards such as GSM                     the coexistence of different services needing
,TDMA,CDMA,PDC.                                            different QoS and bandwidth.
                                                           Limitation of spectrum and its allocation.
2.5G: An interim step is being taken between               Difficult to roam across distinct service
2G and 3G, the 2.5G. It is basically an                    environment in different frequency bands.
enhancement of the two major 2G technologies               Lack        of    end-to-end     seamless    transport
to provide increased capacity on the 2G RF                 mechanism spanning a mobile sub-network and
(radio frequency) channels and to introduce                a fixed one.
higher throughput for data service, up to 384
kbps. GSM system enhancements like GPRS
                                                           Thus the limitations lead to development of new
and   EDGE        are     considered     to    be    2.5
                                                           generation of wireless technology i.e., 4G
technologies. GPRS is an attractive solution to
                                                           mobile communications .the 4G has wide range
mobile operators, because it does not require
                                                           of features compared to the different generations
the same degree of the investment as UMTS.
                                                           .and has much advantages and features

3G: 3G is deploying a new system with new
                                                           4G: Edge over 3G
services instead of only providing higher data                       It is commonly said that 4G is the super-
up to 2 Mbps and broader bandwidth. Based on               enhanced version of 3G.4G systems will be
intelligent DSP techniques, various multimedia             deployed        with     software    –defined     radios,
data communications services are transmitted by            allowing equipment upgrades for new protocols
convergent 3G networks. The 3G system would                and services via software upgrades. In addition,
have higher quality voice channels. The 3G                 4G holds the promise of worldwide roaming
system will have features like fast internet               using      a        single   handheld       device.   To
surfing advanced value added service and video             summarise,4G means fully converged services,
telephony .The technologies that are used to               ubiquitous cellular access, diverse user devices,
boost the speed are UMTS and W-CDMA .                      autonomous             networks       and       software
Problems associated with 3G:                               The main aim of 3G was to provide multimedia,
Difficulty     in      continuously        increasing   multirate, cellular communications any time and
bandwidth       and     high   data    rate   to    meet   any where. It‟s uneconomical to meet this                                                                                               5
requirement         with only cellular radio.4G                radio.4G systems will extend the scenario to an
systems      will extend the scenario to an IP                 IP network that integrates broadcast ,cellular ,
network      that   integrates   broadcast, cellular           cordless ,WLAN/PAN and fixed wire.
          “4G is a network of networks” with which users will be in control. They will be able to decide the right s
As can be seen in the picture above, the main requirements for 4G are as follows:

      Peak data rate of 100Mbps for high mobility applications such as mobile access
      Approx. 1Gbps for low mobility applications such as nomadic/local wireless access

   4G TECHNICAL PERSPECTIVES:                                                                                      6
                     In    the    4G     wireless        computer will send a packet to the 4G-IP
networks, each node will be assigned a 4G-IP             address of the cell phone targeting on its home
address (based on IPv6), which will be formed            address. Then a directory server on the cell
by a permanent “home” IP address and a                   phone‟s home network will forward this packet
dynamic “care-of” address that represents its            to the cell phone‟s care-of address through a
actual location . When a device (computer) in            tunnel, mobile IP; moreover, the directory
the Internet wants to communicate with another           server will also inform the computer that the cell
device (cell phone) in the wireless network, the         phone‟s         care-of        address        (real
location), so next packets can be sent to the cell phone directly. The idea is that the 4G-IP address (IPv6)
can carry more information than the IP address (IPv4) that we use right now. IPv6 means Internet
Protocol Version 6 including 128 bits, which is 4 times more than 32bits IP address in IPv4. 32 bits IP.
Moreover, in 4G wireless network, not only has it IPv6 transmission protocol, but also be supported by

    4G is the Fourth Generation Wireless Network Communications Technology standard. When
       implemented, users of 4G devices will have the ability to access to applications ranging from
       basic voice communications to seamless real-time streaming video. Although it is in the research
       and development stage, 4G is expected to be globally available to the public between 2006 and
       2010.                                                                              7

Unlike previous standards such as 3G (Third Generation), 4G is based entirely on packet switched
networks. In addition, all 4G networks will be digital and will provide higher bandwidths of up to
100Mbps. 4G is actually a collection of previous standards as opposed to an entirely new standard.
Standards such as 3G C-CDMA, LAS-CDMA, UWB *7 and Network-LMD


                   This    new   generation   of    protocol) as a common protocol so that users are
wireless is intended to complement and replace      in control because they will be able to choose
the 3G systems, perhaps in 5 to 10 years.           every application and environment. Based on
Accessing information anywhere, anytime, with       the developing trends of mobile communication,
a seamless connection to a wide range of            4G will have broader bandwidth, higher data
information and services, and receiving a large     rate, and smoother and quicker handoff and will
volume of information, data, pictures, video,       focus on ensuring seamless service across a
and so on, are the keys of the 4G infrastructure.   multitude of wireless systems and networks.
The future 4G infrastructures will consist of a     The below figure describes the process included
set of various networks using IP (Internet          in      4G        mobile       communications                                                                               8

               The key concept is integrating      to the personal preference of different users and
the 4G capabilities with all of the existing       support the users' traffic, air interfaces, radio
mobile    technologies     through     advanced    environment, and quality of service. Connection
technologies. Application adaptability and being   with the network applications can be transferred
highly dynamic are the main features of 4G         into various forms and levels correctly and
services of interest to users. These features      efficiently. The dominant methods of access to
mean services can be delivered and be available    this    pool                                    of
information will be the mobile telephone, PDA,     4G systems will be fully IP-based wireless
and laptop to seamlessly access the voice          Internet.   This   all-encompassing   integrated
communication,       high-speed      information   perspective shows the broad range of systems
services, and entertainment broadcast services.    that the fourth generation intends to integrate,
                                                   from satellite broadband to high altitude
                 The fourth generation will        platform to cellular 3G and 3G systems to WLL
encompass all systems from various networks,       (wireless local loop) and FWA (fixed wireless
public to private; operator-driven broadband       access) to WLAN (wireless local area network)
networks to personal areas; and ad hoc             and PAN (personal area network), all with IP as
networks. The 4G systems will interoperate with    the integrating mechanism. With 4G, a range of
2G and 3G systems, as well as with digital         new services and models will be . examined for
(broadband) broadcasting systems. In addition,     their interface with the design of 4G systems                                                                                    9
                                                        signals are the subset of the main signal. In
Multiplexing:         Method of sharing a               OFDM first the signal itself is split into
bandwidth        with other independent data            independent channels, modulated by data and
OFDM is a combination of both modulation and            then re-multiplexed to create the OFDM carrier.
multiplexing. Multiplexing generally refers to          OFDM is a special case of Frequency Division
independent signals, those produced by different        multiplex (FDM).As an analogy, a FDM
sources. So it is a question of how to share the        channel is a flow out of a faucet, in contrast the
spectrum with these users. In OFDM the                  OFDM signal is like a shower. In a faucet all
question    of     multiplexing   is   applied   to     water comes in a big stream and cannot be
independent signals but these independent               subdivided

                                          Fig.9: OFDM Principles
As shown in the fig.5 the signal is split into               OFDM can also be as a multiple access
orthogonal sub carriers, on each of which the signal    technology (Orthogonal Frequency Division
is “narrowband” (a few KHz) and therefore immune        Multiple Access; OFDMA). In this case, each
to multipath effects, Provided a guard interval is
                                                        OFDM symbol can transmit information to/from
guarded between each OFDM symbol. OFDM also
                                                        several users using a different set of subcarriers
provides a frequency diversity gain increasing the
                                                        (sub   channels).   This   not   only     provides
physical layer performance. It is also compatible
                                                        additional flexibility for resource allocation
with other enhancement technologies, such as smart
antenna and MIMO.
                                                        (increasing the capacity), but also enables cross-
                                                        layer optimization of radio link usage.

OFDM Characteristics:
 High peak-to-average power levels.                                                                                  10
 Preservation of orthogonality in severe multi-path.
 Efficient FFT based receiver structures.
 Enables efficient TX and RX diversity.
 Adaptive antenna arrays without joint Equalization.
 Support for adaptive modulation by sub carrier.
 Frequency Diversity.
 Robust against narrow-band interference.
 Efficient for simulcasting.
 Variable/Dynamic Bandwidth.
 Used for highest speed Applications.
 Supports dynamic packet Access.

OFDM Benefits:
 High-spectral efficiency.
 Resistance to frequency selective fading.

.   Advantages of 4G
      Support for interactive 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.

Applications                                             a large metropolitan area. This data base could
                                                         be accessed by subscribers in vehicles.
Location application. 4G location applications
                                                         Virtual navigation and telegeoprocessing.
will be based on visualized, virtual navigation
                                                         You will be able to see the internal layout of a
schemes that will support a remote database
                                                         building during an emergency rescue. This type
containing graphical representations of streets,
buildings and another physical characteristic of                                                                                      11
of application is some time referred to as                 present    for     restoration   of    wire   line
„telegeoprocessing‟.                                       communications.
A remote database will contain the graphical               Limitations
representation of streets, buildings and physical          Although the concept of 4G communications
characteristics of a large metropolis. Blocks of           shows much promise, there are still limitations
this database will be transmitted in rapid                 that must be addressed. A major concern is
sequence to a vehicle, where a rendering                   interoperability     between     the     signaling
program will permit the occupants to visualize             techniques that are planned for use in 4G
the    environment     ahead.    They      may     also    (3XRTT and WCDMA).
„virtually‟ see the internal layout of buildings to        Cost is another factor that could hamper the
plan an emergency rescue or engage hostile                 progress of 4G technology. The equipment
elements hidden in the building.                           required to implement the next-generation
Telemedicine. A paramedic assisting a victim               network are still very expensive.
of a traffic accident in a remote location could           A Key challenge facing deployment of 4G
access medical records (X-rays) and establish a            technologies is how to make the network
video conference so that a remotely based                  architectures compatible with each other. This
surgeon could provide „on-scene‟ assistance.               was one of the unmet goals of 3G.
Crisis management application. In the event                AS regards the operating area, rural areas and
of     natural   disasters     where      the     entire   many buildings in metropolitan areas are not
communications infrastructure is in disarray,              being served well by existing wireless networks
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

“IT IS A REVOLUTION –NOT EVOLUTION”                                                                        12

    Hui, Suk Yu, and Yeung, Kai Hau, “Challenges in the Migration to 4G Mobile Systems”, IEEE
    Magazine, December 2003, pp. 54-59eamless handover and the additional data communications
    Janny Hu,Willie W. Lu ,“Open Wireless Architecture - The Core to 4G Mobile
     Communications”. In Proceedings of ICCT, 2007
    .
    Juuso Pesola, Sami Pönkänen,”Location-aided Handover in Heterogeneous Wireless Networks”.
     In Wireless Personal Communications ,Volume 30 , Issue 2-4 ,September 2004

    “2G – 3G Cellular Wireless data transport terminology”, Arc Electronics
    Schiller, J., “Mobile Communications”, slides

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