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Introduction :
The First generation wireless mobile communication systems were introduced in early eighties
and second generations systems in the late 1980s were intended primarily for transmission of
voice. The initial systems used analog frequency modulation where as the second as well as the
subsequent mobile systems use digital communication techniques with time division
multiplexing (TDM), frequency division multiplexing (FDM) or the code division multiple
access (CDMA).
The third generation wireless systems which are just getting introduced in the world
markets offer considerably higher data rates, and allow significant improvements over the 2G
systems. The 3G Wireless systems were proposed to provide voice and paging services to
provide interactive multimedia including teleconferencing and internet access and variety of
other services.
However, these systems offer wide area network (WAN) coverage of 384 kbps peak rate
and limited coverage for 2 Mbps. Hence providing broadband services would be one of the major
goals of the 4G Wireless systems.
A descendant to 2G and 3G aiming to provide the very high data transfer rates. This
technology can provide very speedy wireless internet access to not only stationary users but also
to mobile users.
This technology is expected to trounce the deficiencies of 3G technology in terms of
speed and quality. 4G can be best described in one word “MAGIC”, which stands for Mobile
multimedia Anytime Anywhere Global mobility support, integrated wireless and personalized
services
4G, short for fourth-generation wireless communication systems, has engaged the
attention of wireless operators, equipment makers (OEMs), investors, and industry watchers
around the world. 4G refers to the next generation of wireless technology that promises higher
data rates and expanded multimedia services. Since, at this point, 4G is more of an aspiration
than a standard, there is not an agreement yet on what should constitute 4G.
Since the ITU is a major force in the standardization of telecommunications technologies, it’s
worth looking at the ITU’s performance goals for 4G:
The framework for 4G systems should fuse elements of current cellular systems
with nomadic wireless-access systems and personal-area networks in a seamless
layered architecture that is transparent to the user.
Data rates of 100 Mbps for mobile applications and 1 Gbps for nomadic
applications should be achievable by the year 2010.
Worldwide common spectrum and open, global standardization should be
pursued.
As another viewpoint, the Wireless World Research Forum (WWRF) defines a 4G
network as one that operates on Internet technology, combines it with other applications and
technologies such as WiFi and WiMAX, and runs at speeds ranging from 100 Mbps (in cellphone
networks) to 1 Gbps (in local WiFi networks). There is some debate among standards
bodies and industry watchers as to whether WiMAX is, or will become, a full-fledged 4G
technology competitive with 4G wireless.
The telecommunication companies like NTT Docomo from Japan and Sprint Nextel were
also deploying 4G wireless technologies from the early 2006 along with 3G mobile technologies.
The flexibility of 4G technologies to be used in combination with GSM and CDMA has provided
it an edge over other technologies. The reason is that the high broadband capability of 4G not
only increases data streaming for stationary users but also for mobile users.4G can be efficiently
combined with cellular technologies to make consistent use of smart phones. The digital cameras
attached in smart phones can be used to establish video blogs in scattered geographical regions.
This gives the manufactures the opportunity to produce more affordable user friendly 4G
compatible devices. Famous iPod is one such device that supports the working of video blogs.
Hence 4G is capable of providing new horizon of opportunity for both existing and startup
telephone companies.
Currently marketed technologies such as LTE (Long Term Evolution) and WiMAX have
been around for a few years and are being marketed as 4G whilst not meeting the requirements
set by the ITU. It was recently announced that these services could continue to be marketed as
4G as they are precursors to the IMT-Advanced, 4G standard whilst also operating on the same
basis of technology; however, these should really be considered as "Pre-4G" or "3.9G" as they
technically do not offer the required data rates of (stationary) 1Gbps.
The ITU has recognised two standards that are planned to meet the 4G IMT-Advanced
requirements put forward by the two groups, 3GPP and IEEE. These are the LTE Advanced and
WirelessMAN-Advanced (WiMAX-Advanced) standards and will almost certainly abandon the
old spread system technology found in 3G systems for OFDMA and other equalisation schemes,
use MIMO technology, channel-dependant scheduling and dynamic channel allocation all
technologies that are being found on new, modern wireless networking equipment.
Still 4G is not clearly defined or documented anywhere what are the basic requirements
to build 4G wireless technology, like 3G is clearly defined in IMT-2000 (International Mobile
Telecommunications 2000). IMT-Advanced is the closest where some of the 4G requirements
can be found. For supporting high data rate and high mobility in fast moving car
(60kilometers/hours) or fast moving trains (250 km/hr) and it is predicted that the new potential
wireless system will support 100 Mbps on mobility and 1 Gbps approximately on without
mobility at lower cost. This potential new wireless system could be developed by 2010. Its
characteristics should be like high degree of commonality of design worldwide to provide
backward compatibility, compatibility of services within IMT-Advanced and with the fixed
networks, high quality, and small terminal suitable for worldwide use, worldwide roaming
capability, capability to run high data rate multimedia applications within a wide range of
services and terminals.
Evolution of 4G Technology :
In order to make smooth transition from 3G to 4G the mobile communication companies are
promoting Super 3G/LTE. The companies are upgrading 3G Technology by initializing the
introduction of High Speed Downlink Packet Access (HSDPA) service, which increases the
downlink data rate of packet services, and by finalizing specifications for High Speed Uplink
Packet Access (HSUPA), which enhances uplink speed. HSDPA and HSUPA cover area by 3-4
times relative to W-CDMA and by providing the high transmission rate with low cost per bit
transmission. The main objective of the Super 3G is to construct simple, low cost system by
removing the complexity from wireless network and mobile handsets. The 3G provides packet
and voice services separately where as Super 3G is based on ALL-IP network covering both
packet and voice services. As from diagram we can infer that by the 2010 we would be able to
achieve the 1 Gbps in motion at low speed and 100 Mbps at high speed. On December 25, 2006,
NTT DOCOMO became the first in the world to achieve a packet signal speed of 5 Gbps in an
outdoor test in a low-speed environment (10 km/h). The test was undertaken to demonstrate the
expected maximum transmission speed in an actual cell environment, taking into account
interference from peripheral cells.
We are steadily approaching towards 4G wireless technologies by upgrading the current
3G technology by increasing the data rate speed and by reducing the cost of transmission which
is the main objective of 4G wireless technology.
There are some key components for the successful deployment of the 4G wireless technology.
Multipath phenomena in CDMA can tolerate long delay but it does not capture the entire energy,
only fraction of the energy of the multipath signal because of limited no. of capability of taking
the signal. In OFDM as from the below figure it can be understand the long guard band interval
is long enough to absorb all inter-symbols-interference.
Orthogonal Frequency Division Multiplexing (OFDM) not only provides clear
advantages for physical layer performance, but also a framework for improving layer 2
performance by proposing an additional degree of freedom. Using ODFM, it is possible to
exploit the time domain, the space domain, the frequency domain and even the code domain to
optimize radio channel usage. It ensures very robust transmission in multi-path environments
with reduced receiver complexity.
In OFDM, a data stream is split into Nc parallel lower data streams (a few kHz) that are
modulated on separate subcarriers. The split the signal is called orthogonal subcarriers and
these subcarriers are modulated by Inverse Discrete Fourier Transformation (IDFT) and hence
it does not affect the signals on multipath effects. The long guard band is inserted between each
OFDM symbol to absorb all inter signal symbols interference. This significantly improves the
physical layer performance. The OFDM signal is also compatible with other enhancement
technologies like smart antennas and MIMO.
Multiple access technology (Orthogonal Frequency Division Multiple Access; OFDMA)
can also be used for modulation of OFDM. In this case, each OFDM signal symbol can transmit
information to/from several users using a different set of subcarriers (subchannels). This not only
provides additional flexibility for resource allocation (increasing the capacity), but also enables
cross-layer optimization of radio link usage.
(B) Implementation of MIMO (multiple inputs, multiple outputs).
In order to improve the communication performance between sender and receiver, the multiple
antennas are used at both transmitter and receiver end. MIMO multiplex the signals from the
multiple transmitting antennas as it is suitable for OFDM because time symbols can be processed
independently after OFDM waveform is correctly designed for the channel. This aspects of
OFDM reduces the complexity while transmission and makes processing simple. The signal
transmitted by m antennas and signal received by n antennas and the processing of the received
signal may produce significant performance improvement such as range, quality of received
signal and spectrum efficiency. Hence MIMO is more efficient when many multiple path signals
are received. The gain in spectrum efficiency is directly related to the minimum number of
antennas in the link. The MIMO enables significant increase in the data throughput and link
range with additional bandwidth or transmit power. It achieves this by higher spectral efficiency
more bits per second per hertz of bandwidth) and link reliability or diversity (reduced fading).
Because of these properties MIMO has become current theme of wireless research.
The main purpose of the radio communication depends on the advancements of the antennas
which refer to smart or intelligent antennas. In early 90s, in order to meet growing data rate
needs of the data communication, many transmission techniques were proposed such as spatial
multiplexing which increases the bandwidth conservation and power efficiency. Spatial
multiplexing provides the multiple deployment of antennas at the transmitting and receiving end
and then independent streams of data can be transmitted as requested by the user can be
transmitted simultaneously from the all transmitting antennas. Thus increasing the throughput
into multiple folds with minimum number of the transmitting and receiving antennas.
There are two types of smart antennas which are switched beam smart antennas and
adaptive array smart antennas. Switched beam systems have several available fixed beam
patterns which help in making decisions as to which beam to access at any given point of time
based on the requirements of the system. While adaptive arrays allow the antenna to steer the
beam to any direction of interest while simultaneously nulling interfering signals.
The reliability in transmitting high speed data in the fading channel can be improved by
using more antennas at the transmitter or at the receiver. This is called transmit or receive
diversity. Both transmit/receive diversity and transmit spatial multiplexing are categorized into
the space-time coding techniques, which does not necessarily require the channel knowledge at
the time of transmitting the signals. The other category is closed-loop multiple antenna
technologies which use the channel knowledge at the transmitter.
(D) SDR (Software-Defined Radio)
A basic SDR produces a radio that is capable of receiving and transmitting a different form of
radio protocol (sometimes referred to as a waveform) as per the needs just by running different
software. A SDR will allow to increase network capacity at specific time (e.g. during a sports
event) and the operator can reconfigure its network by adding several modems at a given Base
Transceiver Station (BTS). SDR will allow reconfigure network structure as per the needs. At the
present SDR implementation is done by the infrastructure which develops multi-band, multistandard
base stations and terminals. SDR can be a powerful aid for manufacturer by providing
multi-standard, multi-band equipment with reduced development effort and costs through
simultaneous multi-channel processing. Software radios have significant utility for the military
and cell phone services, both of which must serve a wide variety of changing radio protocols in
real time. In the long term, software-defined radio is expected by its proponents to become the
dominant technology in radio communications.
4G Technology Features :
(A)Incomparable Speed
The majority of internet users choose a particular ISP over another because of the speed it offers.
Even though I’ve used some slow and frustrating internet connections before I’ve also used a lot
of super fast internet connections and I’m a great fan of the 3G technology. With all I’ve read so
far the 4G mobile internet technology will be at least 10 times faster than the 3G mobile internet
technology and that alone is enough speed than any individual will need.
(B) Advanced Security
One thing about most forms of broadband internet technology despite their great speed is their
security weakness. A lot of them have one or two features that make them highly vulnerable and
even though the 4G internet technology is not perfect when it comes to security it has been
designed in a way that makes it cover the weakness of other technologies.
If you’re an internet user concerned a lot about security, with 4G, you really have no need to
worry.
© Reliability and Effectiveness Irrespective of the Weather Condition
The final thing I love the most about the 4G mobile internet technology is how reliable it is and
also the fact that it isn’t affected by the weather.
It can be really frustrating to be enjoying your broadband internet connection only to start
experiencing problems due to harsh weather conditions. The 4G technology addresses all these
and it won’t in any way be affected by the weather.
(D) Transfer Rate
One of the things that changes from each generation of computers to the next is the speed at
which they can transfer and process data. For instance, a third generation computer and computer
network could transfer data up to 2 megabits per second. Fourth generation computers improved
on that speed, with the ability to transfer data at up to 100 megabits per second. This higher
bandwidth sets these two generations apart from previous ones, which could barely transfer data
fast enough for streaming video.
Wireless Technology
3G and 4G computers and computer networks are some of the first to offer truly wireless
capabilities. Wireless Internet works off of radio signals, the same kind used by cell phones. 3G
computers have the ability to use and receive these wireless signals and thus you can make calls
over a 3G computer or you can use wireless Internet. 4G computers and their networks take this
further, adding power to the amount of data that can be transferred and the additional reception
that 4G systems can provide.
Working groups on 4G wireless technology:
There are many groups who work together for the enhancement of the cellular technology. There
are 3 groups who are working for deployment of 4G wireless technology.
4.1 3GPP (The Third Generation Partnership Project)
4.2 3GPP2 (The Third Generation Partnership Project 2)
4.3 WiMAX
3GPP (The 3rd Generation Partnership Project):
The 3rd Generation Partnership Project (3GPP) is body which is formed by collaborating the
groups of the telecommunications associations to develop upcoming a globally applicable third
generation (3G) mobile phone specification within the scope of International Mobile
Telecommunications-2000 project of the International Telecommunication Union (ITU). 3GPP
standardization major focus is on Radio, Core Network and Service architecture. 3GPP is
working to upgrade the mobile communication by increasing the data rate and reducing the
cost. As from the figure above it states that 3GPP focus on mobile communication since 2007
and 3GPP is working in that direction which will lead to enter in the 4G technology by the 2011.
3GPP2 (The 3rd Generation Partnership Project):
Again there is another working group on mobile communication is called the Third Generation
Partnership Project 2 (3GPP2) is formed by collaborating third generation (3G)
telecommunications specifications-setting project comprising North American and Asian interests developing global specifications for ANSI/TIA/EIA-41. Cellular Radio
telecommunication Intersystem Operations network evolution to 3G and global specifications for
the radio transmission technologies (RTTs) supported by ANSI/TIA/EIA-41. 3GPP2 is the
standardization group focuses on CDMA 2000 which includes the set of 3G standard based on
earlier 2G CDMA technology.
WiMAX:
As we can see in the above figure that WiMAX is using the some of the major key component of
4G technology which is defined in IMT-Advance. WiMAX is using the OFDM modulation
technique for transmission of the signals but other features of the 4G technology such as MIMO,
smart antennas capabilities and IP mobility which are not available in the WiMAX. As it is
shown in figure in the WiMAX section in 2008 Mobile WiMAX is using SISO and 60-65% of
SIMO with frequency spectrum of the10MHz. And in 2009 WiMAX will be using SIMO/MIMO
and data rate of 23/46 Mbps in downlink and data rate of 12 Mbps in uplink with frequency
spectrum of 10 MHz In 2011 WiMAX will be able to achieve the 100 Mbps with high mobility
which is defined in the IMT Advance. In 2011 WiMAX will fully enter into 4G technology
because it is expected that the WiMAX will using all the major key component of the 4G
technology. At present WiMAX is one of the potential candidate for the 4G technology. WiMAX
has served as a catalyst for 3GPP (Third Generation Partnership Project) and 3GPP2 to
accelerate their next round of innovation, adopting OFDM modulation and implementing MIMO
and other smart antenna technologies with high mobility. Both 3GPP and 3GPP2 camps have
clearly defined their paths toward 4G.
Mobile WiMAX was being commercialized in 2007 and It had been expected that the
WiMAX will have several advantages, including throughput, cost, time-to-market. It does seem
to have a time-to-market advantage over LTE (Long Term Evolution) and UMB (Ultra Mobile
Broadband). However, the first generation of mobile WiMAX technologies without MIMO
enhancements will not be able to deliver significantly higher throughput as compare to 3.5G
technologies such as HSDPA (High-Speed Downlink Packet Access), which has already been
deployed commercially. WiMAX vendor had predicted the cost advantages of the WiMAX.
Mobile company sprint claims that Mobile WiMAX will deliver a cost-per-bit performance of 10
times EVDO (Evolution-Data Optimized). The spectral efficiency of WiMAX is better but the
coverage area of the WiMAX is smaller, possibly at only half to one-quarter the cell radius of an
equivalent HSPA (High-Speed Packet Access) cell.
Over period of time WiMAX will improve by increasing throughput and lower cost, but
3GPP and 3GPP2 technologies are also evolving to support higher throughput, lower latency and
better economics by leveraging MIMO and other smart antenna technologies, wider spectrum
bands and eventually OFDM modulation. 3GPP and 3GPP2 are still getting stronger support
from technology companies, and they are already being integrated into laptops and other
embedded devices.