The number of subscribers for mobile          and further to fourth generation was the
communications has increased much             ability   to   support   advanced   and
faster than predicted. In the year 2010,      wideband services including e-mail, file
more than 1.8 billion mobile subscribers      transfers and distribution services like
are anticipated. The majority of traffic is   radio, TV and software provisioning, In
changing     from      speech     oriented    this paper we address about the 4TH G
communication         to        multimedia    mobile communications.
communication. The major step from            The Fourth Generation (4G) Mobile
second generation to third generation         Communications not only focuses on the


data-rate   increase    and     new      air
interface.4G   Mobile     converges      the
advanced          wireless         mobile
communications and high-speed wireless
access systems into an Open Wireless
Architecture (OWA) platform which
becomes the core of this emerging next
generation mobile technology. Based on
                                                        The advent of 4G wireless
this OWA model, 4G mobile will deliver
                                               systems has created many research
the best business cases to the wireless
                                               opportunities. The expectations from 4G
and                                mobile
                                               are high in terms of data rates, spectral
                                               efficiency, mobility and integration.
3-in-1                            product,
                                               Orthogonal       Frequency      Division
WCDMA/OFDM/WLAN                       3-in-1
                                               Multiplexing (OFDM) is proving to be a
product, etc. Asia-Pacific is the most
                                               possible multiple access technology to
dynamic market of new generation
                                               be used in 4G. But OFDM comes with
mobile communications with over $100
                                               its own challenges like high Peak to
Billion businesses in the next decade.
                                               Average Ratio, linearity concerns and
         The 4G mobile technology -
                                               phase noise. This paper proposes a
convergence of wireless mobile and
                                               solution to reduce Peak to Average Ratio
wireless access, will definitely drive this
                                               by clipping method. ATLAB as used to
growth. Any single-architecture wireless
                                               generate the OFDM signal to prove that
system, including 3G, HSDPA, WiMax,
                                               clipping does reduce Peak to Average
etc., is a transitional solution only, and
will be replaced by open wireless
architecture system very soon where
various different wireless standards can       INTRODUCTION:
be integrated and converged on this open       The      first   operational     cellular
platform.                                      communication system was deployed in
                                               the Norway in 1981 and was followed
                                               by similar systems in the US and UK.


These first generation systems provided       videoconferencing for mobile phones.
voice transmissions by using frequencies      When it became clear that the real killer
around     900     MHz      and    analogue   application was the Internet, 3G thinking
modulation.                                   had to evolve. As personal wireless
The second generation (2G) of the             handsets become more common than
wireless mobile network was based on          fixed telephones, it is
low-band digital data signaling. The          clear that personal wireless Internet
most popular 2G wireless technology is        access will follow and users will want
known as Global Systems for Mobile            broadband Internet access wherever they
Communications (GSM). The first GSM           go.
systems    used     a 25MHz       frequency
spectrum in the 900MHz band.
                    Planning for 3G started
in the 1980s. Initial plans focused on
multimedia        applications    such   as

2G 3G 4G


The objective of the 3G was to develop a        mobility users, to 1GHz for low mobility
new protocol and new technologies to            users, technologies that permit fast
further enhance the\mobile experience.          handoffs, an efficient delivery.
In contrast, the new 4G framework to be
established will try to accomplish new                  Migrating to 4G:
levels of user experience and multi-
                                                The fact that 4G mobile networks intend
service capacity by also integrating all
                                                to   integrate    almost     every wireless
the mobile technologies that exist (e.g.
                                                standard already in use, enabling its
GSM - Global System for Mobile
                                                simultaneous use and interconnection
Communications,       GPRS       -    General
                                                poses many questions not yet answered.
Packet Radio Service, IMT-2000 -
                                                The research areas that present key
International Mobile Communications,
                                                challenges to migrate current systems to
Wi-Fi - Wireless Fidelity, Bluetooth).In
                                                4G are many but can be summarized in
spite of different approaches, each
                                                the following: Mobile Station, System
resulting from different visions of the
                                                and Service. To be able to use 4G
future    platform        currently    under
                                                mobile networks a new type of mobile
investigation, the main objectives of 4G
                                                terminals     must    be     conceived.     The
networks can be stated in the following
                                                terminals to be adopted must adapt
                                                seamless to multiple wireless networks,
                                                each   with      different    protocols     and
                                                technologies. Auto reconfiguration will
                                                also be needed so that terminals can
              Multi-service platform;
                                                adapt to the different services available.
              Low bit cost
                                                This adaptation may imply that it must
                                                download automatically configuration
To achieve the proposed goals, a very
                                                software    from     networks     in      range.
flexible network that aggregates various
                                                Moreover terminals must be able to
radio access technologies, must be
                                                choose from all the available wireless
created. This network must provide high
                                                networks the one to use with a specific
bandwidth, from 50-100 MHz for high
                                                service. To do this it must be aware of


specifications of all the networks in             Services available in this new mobile
terms of bandwidth, QoS supported,                generation like videoconference have
costs and respect to user preferences.            restricted time constraints and QoS
Terminal mobility will be a key factor to         needs that must not be perceptible
the success of 4G networks. Terminals             affected by handoffs. To avoid these
must be able to provide wireless services         problems new algorithms must be
anytime, everywhere. This implies that            researched and a prevision of user
roaming between different networks                mobility will be necessary, so as to avoid
must be automatic and transparent to the          broadcasting at the same time to all
user. There are two major issues in               adjacent antennas what would waste
terminal mobility, location management            unnecessary resources. Another major
and   handoff       management        Location    problem relates to security, since 4G
management deals with tracking user               pretends to join many different types of
mobility,     and    handling     information     mobile technologies, as each standard
about original, current and (if possible)         has its own security scheme, the key to
future cells. Moreover it must deal with          4G systems is to be highly flexible.
authentication        issues     and      QoS     Services also pose many questions as 4G
assurances.         Handoff      management       users may have different operators to
primary objective is to maintain the              different services and, even if they have
communications        while     the    terminal   the same operator, they can access data
crosses wireless network boundaries. In           using different network technologies.
addition, 4G networks, in opposition to           Actual billing using flat rates, time or
the other mobile generations, must deal           cost per bit fares, may not be suitable to
with vertical and horizontal handoffs,            the new range of services. At the same
i.e., a 4G mobile client may move                 time it is necessary that the bill is well
between different types of wireless               understood by operator and client. A
networks (e.g. GSM and Wi-Fi) and                 broker system would be advisable to
between cells of the same wireless                facilitate the interaction between the user
network (e.g. moving between adjacent             and the different service providers.
GSM cells). Furthermore, many of the              Another challenge is to know, at each
                                                  time, where the user is and how he can


be contacted. This is very important to     this framework, each user has a unique
mobility management. A user must be         identifier served by personal mobile
able to be reached wherever he is, no       agents that make the link from users to
matter the kind of terminal that is being   Internet.
used. This can be achieved in various
ways one of the most popular being the
use of a mobile-agent infrastructure. In


      Multi-technology Approach:

      Orthogonal Frequency Division Multiplexing (OFDM)

      Open wire less Architecture(OWA)

      Multiple-input multiple-output ( MIMO )


Increasing demand for high performance                unlikely all the channels will fade
4G broadband wireless mobile calls for                simultaneously.
use of multiple antennas at both base
                                                      OFDM is chosen over a single carrier
station and subscriber ends. Multiple
                                                      solution due to lower complexity of
Antenna       technologies      enable        high
                                                      equalizers     for    high    delay        spread
capacities     suited   for     Internet       and
                                                      channels or high data rates. A broadband
multimedia        services       and          also
                                                      signal is broken down into multiple
dramatically      increase       range         and
                                                      narrowband carriers (tones), where each
reliability. This design is motivated by
                                                      carrier is more robust to multipath. In
the growing demand for broadband
                                                      order to maintain orthogonality amongst
wireless Internet access. The challenge
                                                      tones, a cyclic prefix is added which has
for wireless broadband access lies in
                                                      length greater than the expected delay
providing a comparable quality of
                                                      spread.      With    proper       coding     and
service for similar cost as competing
                                                      interleaving         across        frequencies,
wire   line     technologies.     The        target
                                                      multipath turns into an OFDM system
frequency band for this system is 2 to 5
                                                      advantage      by      yielding      frequency
GHz due to favorable propagation
                                                      diversity. OFDM can be implemented
characteristics and low radio-frequency
                                                      efficiently by using FFT's             at     the
(RF) equipment cost. The broadband
                                                      transmitter and receiver .At the receiver,
channel is typically non LOS channel
                                                      FFT reduces the channel response into a
and includes impairments such as time
                                                      multiplicative constant on a tone-by-tone
selective fading and frequency-selective
                                                      basis .With MIMO, the channel response
fading.      Multiple   antennas        at     the
                                                      becomes a matrix. Since each tone can
transmitter      and    receiver        provide
                                                      be    equalized        independently,         the
diversity in a fading environment. By
                                                      complexity of space time equalizers is
employing multiple antennas, multiple
spatial channels are created and it is


Multipath remains an advantage for a        the rank distribution of the channel
MIMO-OFDM system since frequency            matrices across frequency tones, thereby
selectivity caused by multipath improves    increasing capacity.


The 4G Mobile communications will be        HomeRF, Wireless ATM, etc) are
based on the Open Wireless Architecture     available. When the users move to the
(OWA) to ensure the single terminal can     mobile zone (i.e. Highway, Beach,
seamlessly and automatically connect to     Remote area, etc.), the same terminal
the local high-speed wireless access        can automatically switch to the wireless
systems when the users are in the           mobile networks (i.e.GPRS, W-CDMA,
offices, homes, airports or shopping        cdma2000,     TD-SCDMA,       etc.).This
centers   where   the   wireless   access   converged wireless communications can
networks (i.e. Wireless LAN, Broadband      provide the following advantages.
Wireless Access, Wireless Local Loop,


_                                           infrastructure of mobile communications
Greatly increase the spectrum efficiency    with optimal spectrum efficiency and
mostly ensures the highest data-rate to     resource management. In fact, this OWA
the wireless terminal. Best share the       model had already been accepted by
network     resources    and     channel    most wireless industries, for example,
utilization optimally manages the service   the W-CDMA/W-LAN/Bluetooth 3-in-1
quality and multimedia applications. 3G     terminal is being designed in many
wireless LAN and other wireless access      companies. The global 4G Mobile R&D
technologies will be converged into 4G      focuses on the following Open Wireless
mobile platform to deliver the best         Architecture:



The goal of 4th Generation (4G) mobile                            technologies and services have been
communications          technologies                is     to     appearing as of late. A scrutiny on the
realize wireless communications at the                            market trends, along with a close watch
same high data rate as is made possible                           on carrier reaction as to the introduction
through     use         of        the         fiber-optic         of      the   Mobile   Number    Portability
transmission systems that are available                           (MNP) system planned for October 24,
today.    Realization             of      4G       mobile         2006, is of vital importance at this time
communications is foreseen in the early                           for all those interested in this business
2010s,      but          various               precursor          field

                             In        this    paper        we    by seamless handover and the additional
present     the     evolution                 of         mobile   data communications capacity (although
communications               through               all      its   very small) advanced and opened the
generations. From the initial speech                              doors to future developments Some of the
vocation to an IP-based data network,                             developments was brought by generation
several steps were made. From the analog                          2.5 namely by GPRS, which improved
voice centric first generation to the digital                     data communications by supporting IP in
second generation, the goal was to                                the GSM infrastructure. With the third
enhance the voice experience of a user, by                        generation the goal changed from voice-
improving         the         quality              of       the   centric to data-centric. Moreover total
communication            while            using           more    ability became an objective to pursuit. In
efficiently the installed capacity. At the                        this generation it is possible to combine
same time the enhanced mobility provided                          voice,        lntermedia   applications   and


mobility in a never experienced manner.                  [3] ITU-R PDNR WP8F, “Vision,
However, the global mobility, while an                   Framework and Overall Objectives of
important objective, was never really                    the Future Development of IMT-2000
reached.      At     the     same       time     new     and
applications demand more bandwidth and                   Systems beyond IMT-2000,” 2002.
lower   costs.      The      newcomer          fourth-   [4] “2G – 3G Cellular Wireless data
generation tries to address this problem by              transport terminology”, Arc Electronics
integrating        all      different      wireless      www.arcelect.com/2G-
technologies. In spite of all the evolving               3G_Cellular_Wireless.htm
technologies the final success of new                    [5]      Schiller,     J.,      “Mobile
mobile generations will be dictated by the               Communications”, slides
new services and contents made available                 http://www.jochenschiller.de/
to users. These new applications must                    [6] Tachikawa, Keiji, “A perspective on
meet user expectations, and give added                   the      Evolution        of     Mobile
value over existing offers.                              Communications”,                   IEEE
                                                         Communications Magazine,
           6. References:                                October 2003, pp. 66-73

  [1] “Mobile cellular, subscribers per                  [7] Hui, Suk Yu, and Yeung, Kai Hau,

100           people”,              International        “Challenges in the Migration to 4G

Telecommunication           Union       Statistics,      Mobile          Systems”,          IEEE

2002                                                     Communications

   http://www.itu.int/ITU-                               Magazine, December 2003, pp. 54-

D/ict/statistics/at_glance/cellular02.pdf                59eamless handover and the additional

[2] Kim, Y., Jeong, B.J., Chung, J.,                     data communications

Hwang, C., Ryu, J.S., Kim, K., Kim,
Y.K.,       “Beyond            3G:        Vision,
Requirements, and
Enabling           Technologies”,           IEEE
Communications             Magazine,       March
2003, pp. 120-124



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