TECHNICAL SEMINAR REPORT
SMART ANTENNA
NAME BHARATH KUMAR V
USN 1PE10EC019
VISVESVARAYA TECHNOLOGICAL UNIVERSITY
Belgaum-590014
Seminar Report
On
SMART ANTENNA Submitted in partial fulfillment of the requirements for the VIII Semester
Bachelor of Engineering
IN
ELECTRONICS AND COMMUNICATION ENGINEERING
For the Academic year
2013-2014
BY
BHARATH KUMAR V
1PE10EC019 UNDER THE GUIDANCE OF
Professor KAILASHNATH
Dept. of ECE, PESIT, BSC.
Department of Electronics and communication Engineering
PESIT, Bangalore South Campus HOSUR ROAD BANGALORE-560100
PESIT, Bangalore South Campus HOSUR ROAD
BANGALORE-560100
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
CERTIFICATE
This is to certify that the seminar entitled SMART ANTENNA is
a bonafide work carried out by BHARATH KUMAR V bearing register
number 1PE10EC019 in partial fulfillment for the award of Degree of
Bachelors (Bachelors of Engineering) in Electronics and Communication
Engineering of Visvesvaraya Technological University, Belgaum during the
year 2013-2014.
Signatures:
Seminar Guide Head of the Dept
Mr.Kailashnath Dr. Subhash Kulkarni HOD, ECE
PESIT, BSC
Bangalore-100
Examiners:
1.
2.
Dept. of E&C PESIT-BSC
Index
Sl. No. Topic Page No.
1.
2.
3.
4.
5.
6.
ABSTRACT
1:- Introduction
2:- Antenna and Antenna Systems
2.1:-Antenna
2.1.1:- Omnidirectional Antenna
2.1.2:- Directional Antenna
3:-Smart Antenna.
3.1:- Introduction of Smart Antenna
3.2:- History of Smart Antenna
3.3:- Types of Smart Antenna
3.3.1:- Adaptive Array
3.3.2:- Switched Beam
3.4:- Relative Benefits of Switched Beam and
Adaptive Array Systems
3.5:- Working of Smart Antenna
3.6:- Categories of Smart Antenna.
3.7:- Function of Smart Antenna
3.7.1:- Beamforming
3.7.2:- Direction of Arrival(DOA)
3.8:- Parameters affecting Antenna performance
3.9:- Applications of Smart Antenna.
3.10:- Advantages and Disadvantages of Smart
Antenna.
3.11:- Features and Benefit of Smart Antenna
4:- Conclusion
References
1
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1. Introduction
Wireless Communication is growing with a very rapid rate for several
years. The progress in radio technology enables new and improved
services. Current wireless services include transmission of voice, fax and
low-speed data. More bandwidth consuming interactive multimedia
services like video-on demand and internet access will be supported in
the future.
Wireless systems that enable higher data rates and higher capacities are
a pressing need. Wireless networks must provide these services in a wide
range of environments, dense urban, suburban, and rural areas.
Because the available broadcast spectrum is limited, attempts to increase
traffic within a fixed bandwidth create more interference in the system
and degrade the signal quality.
The solution to this problem is SMART ANTENNA. Today's modern
wireless mobile communications depend on adaptive "smart" antennas to
provide maximum range and clarity. With the recent explosive growth of
wireless applications, smart antenna technology has achieved widespread
commercial and military applications.
There is an ever-increasing demand on mobile wireless operators to
provide voice and high-speed data services. At the same time, operators
want to support more users per basestation in order to reduce overall
network cost and make the services affordable to subscribers. As a
result, wireless systems that enable higher data rates and higher
capacities have become the need of the hour.
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2. Antenna and Antenna System 2.1 – Antenna
An antenna (or aerial) is a transducer designed to transmit or receive
electromagnetic waves. In other words, antennas convert electromagnetic
waves into electrical currents and vice versa. Antennas are used in
systems such as radio and television broadcasting, point-to-point radio
communication, wireless LAN, radar, and space exploration. Antennas
are most commonly employed in air or outer space, but can also be
operated under water or even through soil and rock at certain
frequencies for short distances.
Physically, an antenna is simply an arrangement of one or more
conductors, usually called elements in this context. . In transmission, an
alternating current is created in the elements by applying a voltage at the
antenna terminals, causing the elements to radiate an electromagnetic
field. In reception, the inverse occurs: an electromagnetic field from
another source induces an alternating current in the elements and a
corresponding voltage at the antenna's terminals. Some receiving
antennas (such as parabolic types) incorporate shaped reflective surfaces
to collect EM waves from free space and direct or focus them onto the
actual conductive elements.
There are two fundamental types of antenna directional patterns, which,
with reference to a specific three dimensional (usually horizontal or
vertical) plane are either:
1. Omni-directional (radiates equally in all directions), such as a
vertical rod.
2. Directional (radiates more in one direction than in the other).
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2.1.1- Omnidirectional Antenna
Omni-directional usually refers to all horizontal directions with reception
above and below the antenna being reduced in favor of better reception
(and thus range) near the horizon.
Since the early days of wireless communications, there has been the
simple dipole antenna, which radiates and receives equally well in all
directions. To find its users, this single-element design broadcasts
omnidirectionally in a pattern resembling ripples radiating outward in a
pool of water. While adequate for simple RF environments where no
specific knowledge of the users' whereabouts is available, this unfocused
approach scatters signals, reaching desired users with only a small
percentage of the overall energy sent out into the environment.
Figure 2.1:- Omnidirectional Antenna and Coverage Patterns
Given this limitation, omnidirectional strategies attempt to overcome
environmental challenges by simply boosting the power level of the
signals broadcast. In a setting of numerous users (and interferers), this
makes a bad situation worse in that the signals that miss the intended
user become interference for those in the same or adjoining cells.
In uplink applications (user to base station), omnidirectional antennas
offer no preferential gain for the signals of served users. In other words,
Users have to shout over competing signal energy. Also, this single-
element approach cannot selectively reject signals interfering with those
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of served users and has no spatial multipath mitigation or equalization
capabilities.
Omnidirectional strategies directly and adversely impact spectral
efficiency, limiting frequency reuse. These limitations force system
designers and network planners to devise increasingly sophisticated and
costly remedies. In recent years, the limitations of broadcast antenna
technology on the quality, capacity, and coverage of wireless systems
have prompted an evolution in the fundamental design and role of the
antenna in a wireless system.
2.1.2- Directional Antenna
A "directional" antenna usually refers to one focusing a narrow beam in a
single specific direction. A single antenna can also be constructed to have
certain fixed preferential transmission and reception directions. As an
alternative to the brute force method of adding new transmitter sites,
many conventional antenna towers today split, or sectorize cells. A 360°
area is often split into three 120° subdivisions, each of which is covered
by a slightly less broadcast method of transmission.
All else being equal, sector antennas provide increased gain over a
restricted range of azimuths as compared to an omnidirectional antenna.
This is commonly referred to as antenna element gain and should not be
confused with the processing gains associated with smart antenna
systems.
While sectorized antennas multiply the use of channels, they do not
overcome the major disadvantages of standard omnidirectional antenna
broadcast such as co-channel interference
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All antennas radiate some energy in all directions in free space but
careful construction results in substantial transmission of energy in a
preferred direction and negligible energy radiated in other directions.
Figure 2.2 –
Directional Antenna and Coverage Pattern
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3. Smart Antenna
3.1- Introduction of Smart Antenna
Contrary to the name smart antennas consist of more than an antenna.
“A Smart Antenna is an antenna system which dynamically reacts to its
environment to provide better signals and frequency usage for wireless
communications”. There are a variety of smart antennas which utilize
different methods to provide improvements in various wireless
applications. This report aims to explain the main types of smart
antennas and there advantages and disadvantages.
The concept of using multiple antennas and innovative signal processing
to serve cells more intelligently has existed for many years. In fact,
varying degrees of relatively costly smart antenna systems have already
been applied in defense systems. Until recent years, cost barriers have
prevented their use in commercial systems. The advent of powerful low-
cost digital signal processors (DSPs), general-purpose processors (and
ASICs), as well as innovative software-based signal-processing techniques
(algorithms) have made intelligent antennas practical for cellular
communications systems.
Today, when spectrally efficient solutions are increasingly a business
imperative, these systems are providing greater coverage area for each
cell site, higher rejection of interference, and substantial capacity
improvements.
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Fig 3.1:- Smart Antenna System
Figure 3.2- Block Diagram of Smart Antenna
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3.2- History of Smart Antenna
Early smart antennas were designed for governmental use in military
applications, which used directed beams to hide transmissions from an
enemy. Implementation required very large antenna structures and time-
intensive processing and calculation.
As personal wireless communications began to emerge, it was evident
that interference in wireless networks was limiting the total number of
simultaneous users the network could handle before unacceptable call
quality and blocking occurred. Since the narrow beams of the early
governmental smart antennas created less overall interference,
researchers began to explore the possibility of extending the use of smart
antennas to reduce overall network interference in commercial wireless
networks, thus increasing the total number of users a wireless system
could handle in a given block of spectrum. But the hardware and
processing technologies required to perform the complex calculations in
the very small spaces of time available in personal wireless
communications would prove to be a hurdle that was extremely difficult
to overcome. A few select companies have successfully developed and
introduced smart antenna technologies into commercial wireless
networks.
Antennas were used in 1888 by Heinrich Hertz (1857-1894) to prove the
existence of electromagnetic waves predicted by the theory of James
Clerk Maxwell. Hertz placed the emitter dipole in the focal point of a
parabolic reflector.
The origin of the word antenna relative to wireless apparatus is attributed
to Guglielmo Marconi. In 1895, while testing early radio apparatus in the
Swiss Alps, Marconi experimented with early wireless equipment.
A 2.5 meter long pole, along which was carried a wire, was used as a
radiating and receiving aerial element . Until then wireless radiating
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transmitting and receiving elements were known simply as aerials or
terminals. Marconi's use of the word antenna (Italian for pole) would
become a popular term for what today is uniformly known as the
antenna.
Smart Antennas Today
Today, smart antennas have been widely deployed in many of the top
wireless networks worldwide to address wireless network capacity and
performance challenges.
Several different versions of smart antennas are either in development or
available on the market today. Appliqué smart antenna systems can be
added to existing cell sites, enabling software-controlled pattern changes
or software-optimized antenna patterns that have produced capacity
increases of up to 35-94% in some deployments. Appliqué smart antenna
systems provide greater flexibility in controlling and customizing sector
antenna pattern beamwidth and azimuthal orientation over that of
standard sector antennas.
A second approach, embedded smart antennas, uses adaptive array
processing within the channel elements of a base station. The smart
antenna processing takes place in the base station signal path, using a
custom, narrow beam to track each mobile in the network. Embedded
smart antenna system trials have been proven to deliver 2.5-3 times the
capacity of current 2-2.5G base stations.
3.3- Types of Smart Antenna
The following are distinctions between the two major categories of smart
antennas regarding the choices in transmit strategy:
1).Adaptive array - an infinite number of patterns (scenario-based) that
are adjusted in real time .
2).Switched beam - a finite number of fixed, predefined patterns or
combining strategies (sectors).
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3.3.1- Adaptive Array
Adaptive antenna technology represents the most advanced smart
antenna approach to date. Using a variety of new signal-processing
algorithms, the adaptive system takes advantage of its ability to
effectively locate and track various types of signals to dynamically
minimize interference and maximize intended signal reception.
Both systems attempt to increase gain according to the location of the
user; however, only the adaptive system provides optimal gain while
simultaneously identifying, tracking, and minimizing interfering signals.
Figure 3.3:- Adaptive Array System:- Representative Depiction of a Main Lobe
Extending Toward a User.
3.3.2- Switched Beam
Switched beam antenna systems form multiple fixed beams with
heightened sensitivity in particular directions. These antenna systems
detect signal strength, choose from one of several predetermined, fixed
beams, and switch from one beam to another as the mobile moves
throughout the sector. Instead of shaping the directional antenna pattern
with the metallic properties and physical design of a single element (like a
sectorized antenna), switched beam systems combine the outputs of
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multiple antennas in such a way as to form finely sectorized (directional)
beams with more spatial selectivity than can be achieved with
conventional, single-element approaches.
Figure 3.4:-Switched Beam System
3.4- Relative Benefits of Switched Beam and Adaptive Array
Systems
Integration
Switched beam systems are traditionally designed to retrofit widely
deployed cellular systems. It has been commonly implemented as an add-
on or appliqué technology that intelligently addresses the needs of
mature networks
Range/coverage
Switched beam systems can increase base station range from 20 to 200
percent over conventional sectored cells, depending on environmental
circumstances and the hardware/software used. The added coverage can
save an operator substantial infrastructure costs and means lower prices
for consumers. Also, the dynamic switching from beam to beam
conserves capacity because the system does not send all signals in all
directions. In comparison, adaptive array systems can cover a broader,
more uniform area with the same power levels as a switched beam
system.
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Interference suppression
Switched beam antennas suppress interference arriving from directions
away from the active beam's center. Because beam patterns are fixed,
however, actual interference rejection is often the gain of the selected
communication beam pattern in the interferer's direction. Also, they are
normally used only for reception because of the system's ambiguous
perception of the location of the received signal (the consequences of
transmitting in the wrong beam being obvious). Also, because their
beams are predetermined, sensitivity can occasionally vary as the user
moves through the sector.
Adaptive array technology currently offers more comprehensive
interference rejection. Also, because it transmits an infinite, rather than
finite, number of combinations, its narrower focus creates less
interference to neighboring users than a switched-beam approach.
3.5-Working of Smart Antenna
Traditional switched beam and adaptive array systems enable a base
station to customize the beams they generate for each remote user
effectively by means of internal feedback control. Generally speaking,
each approach forms a main lobe toward individual users and attempts
to reject interference or noise from outside of the main lobe.
Listening to the Cell (Uplink Processing)
It is assumed here that a smart antenna is only employed at the base
station and not at the handset or subscriber unit. Such remote radio
terminals transmit using omnidirectional antennas, leaving it to the base
station to separate the desired signals from interference selectively.
Typically, the received signal from the spatially distributed antenna
elements is multiplied by a weight, a complex adjustment of an
amplitude and a phase. These signals are combined to yield the array
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output. An adaptive algorithm controls the weights according to
predefined objectives. For a switched beam system, this may be primarily
maximum gain; for an adaptive array system, other factors may receive
equal consideration. These dynamic calculations enable the system to
change its radiation pattern for optimized signal reception.
Speaking to the Users (Downlink Processing) The task of transmitting in a spatially selective manner is the major
basis for differentiating between switched beam and adaptive array
systems. As described below, switched beam systems communicate with
users by changing between preset directional patterns, largely on the
basis of signal strength. In comparison, adaptive arrays attempt to
understand the RF environment more comprehensively and transmit
more selectively.
The type of downlink processing used depends on whether the
communication system uses time division duplex (TDD), which transmits
and receives on the same frequency (e.g., PHS and DECT) or frequency
division duplex (FDD), which uses separate frequencies for transmit and
receiving (e.g., GSM). In most FDD systems, the uplink and downlink
fading and other propagation characteristics
may be considered independent, whereas in TDD systems the uplink and
downlink channels can be considered reciprocal. Hence, in TDD systems
uplink channel information may be used to achieve spatially selective
transmission. In FDD systems, the uplink channel information cannot be
used directly and other types of downlink processing must be considered.
3.6- Categories of Smart Antenna
A smart antenna is a digital wireless communications antenna system
that takes advantage of diversity effect at the source (transmitter), the
destination (receiver), or both. Diversity effect involves the transmission
and/or reception of multiple radio frequency (RF) waves to increase data
speed and reduce the error rate.
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In conventional wireless communications, a single antenna is used at the
source, and another single antenna is used at the destination. This is
called SISO (single input, single output). Such systems are vulnerable to
problems caused by multipath effects. When an electromagnetic field (EM
field) is met with obstructions such as hills, canyons, buildings, and
utility wires, the wavefronts are scattered, and thus they take many
paths to reach the destination. The late arrival of scattered portions of
the signal causes problems such as fading, cut-out (cliff effect), and
intermittent reception (picket fencing). In a digital communications
system like the Internet, it can cause a reduction in data speed and an
increase in the number of errors. The use of smart antennas can reduce
or eliminate the trouble caused by multipath wave propagation.
Smart antennas fall into three major categories:--
1). SIMO (single input, multiple output)
2). MISO (multiple input, single output)
3). MIMO (multiple input, multiple output).
SIMO
SIMO (single input, multiple output) is an antenna technology for
wireless communications in which multiple antennas are used at the
destination (receiver). The antennas are combined to minimize errors and
optimize data speed. The source (transmitter) has only one antenna.
SIMO is one of several forms of smart antenna technology, the others
being MIMO (multiple input, multiple output) and MISO (multiple input,
single output).
In digital communications systems such as wireless Internet, it can
cause a reduction in data speed and an increase in the number of errors.
The use of two or more antennas at the destination can reduce the
trouble caused by multipath wave propagation.
SIMO technology has widespread applications in digital television (DTV),
wireless local area networks (WLANs), metropolitan area networks
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(MANs), and mobile communications. An early form of SIMO, known as
diversity reception, has been used by military, commercial, amateur, and
shortwave radio operators at frequencies below 30 MHz since the First
World War.
MISO
MISO (multiple input, single output) is an antenna technology for
wireless communications in which multiple antennas are used at the
source (transmitter). The antennas are combined to minimize errors and
optimize data speed. The destination (receiver) has only one antenna.
MISO is one of several forms of smart antenna technology, the others
being MIMO (multiple input, multiple output) and SIMO (single input,
multiple output).
In digital communications systems such as wireless Internet, it can
cause a reduction in data speed and an increase in the number of errors.
The use of two or more antennas, along with the transmission of multiple
signals (one for each antenna) at the source, can reduce the trouble
caused by multipath wave propagation.
MISO technology has widespread applications in digital television (DTV),
wireless local area networks (WLANs), metropolitan area networks
(MANs), and mobile communications.
MIMO
MIMO (multiple input, multiple output) is an antenna technology for
wireless communications in which multiple antennas are used at both
the source (transmitter) and the destination (receiver). The antennas at
each end of the communications circuit are combined to minimize errors
and optimize data speed. MIMO is one of several forms of smart antenna
technology, the others being MISO (multiple input, single output) and
SIMO (single input, multiple output).
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In digital communications systems such as wireless Internet, it can
cause a reduction in data speed and an increase in the number of errors.
The use of two or more antennas, along with the transmission of multiple
signals (one for each antenna) at the source and the destination,
eliminates the trouble caused by multipath wave propagation, and can
even take advantage of this effect.
MIMO technology has aroused interest because of its possible
applications in digital television (DTV), wireless local area networks
(WLANs), metropolitan area networks (MANs), and mobile
communications.
3.7- Function of Smart Antenna
Smart antennas (also known as adaptive array antennas, multiple
antennas and recently MIMO) are antenna arrays with smart signal
processing algorithms used to identify spatial signal signature such as
the direction of arrival (DOA) of the signal, and use it to calculate
beamforming vectors, to track and locate the antenna beam on the
mobile/target.
Smart antennas have two main functions: DOA estimation and
Beamforming.
3.7.1- Beamforming
Beamforming is a signal processing technique used with arrays of
transmitting or receiving transducers that control the directionality of, or
sensitivity to, a radiation pattern. When receiving a signal, beamforming
can increase the receiver sensitivity in the direction of wanted signals
and decrease the sensitivity in the direction of interference and noise.
When transmitting a signal, beamforming can increase the power in the
direction the signal is to be sent. The change compared with an
omnidirectional receiving pattern is known as the receive gain (or loss).
The change compared with an omnidirectional transmission is known as
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the transmission gain. These changes are done by creating beams and
nulls in the radiation pattern. In electronics, gain is usually taken as
the mean ratio of the signal output of a system to the signal input of the
system.
Beamforming can be done with either radio or sound waves, and can also
be thought of as spatial filtering. As an everyday analogy, the human
brain uses a form of signal processing on its two sound transducers
(ears) and determines where the sound came from (sound localization). In
the comparable beamforming analogy, digital computers use signal
processing on an array of two (or generally more) electromagnetic sound
transducers (microphones) to determine the direction of maximum signal
strength, and thus the likely origin of the sound. A microphone with a
cord A microphone, sometimes called a mic (pronounced mike), is a
device that converts sound into an electrical signal. In
telecommunications, and particularly in radio, signal strength is the
measure of how strongly a transmitted signal is being received,
measured, or predicted, at a reference point that is a significant distance
from the transmitting antenna.
Beamforming takes advantage of interference to change the directionality
of the array. When transmitting, a beamformer controls the phase and
relative amplitude of the signal at each transmitter, in order to create a
pattern of constructive and destructive interference in the wavefront.
When receiving, information from different sensors is combined in such a
way that the expected pattern of radiation is preferentially observed.
Interference of two circular waves - Wavelength (decreasing bottom to
top) and Wave centers distance (increasing to the right).
In the receive beamfomer the signal from each antenna may be amplified
by a different "weight." Different weighting patterns (eg Dolph-Chebyshev)
can be used to achieve the desired sensitivity patterns. . A main lobe is
produced together with nulls and sidelobes. As well as controlling the
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main lobe width (the beam) and the sidelobe levels, the position of a null
can be controlled. This is useful to ignore noise or jammers in one
particular direction, while listening for events in other directions. A
similar result can be obtained on transmission. Jammer can refer to: A
device used in electronic warfare to inhibit or halt the transmission of
signals.
Figure3.5:- BeamForming Lobe.
Figure3.6:- Figure show pattern of Beamforming
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Beamforming techniques can be broadly divided into two categories:
A).Conventional (fixed) beamformers or switched beam smart
antennas.
B).Adaptive beamformers or adaptive array smart antennas
Conventional beamformers use a fixed set of weightings and time-delays
(or phasing’s) to combine the signals from the sensors in the array,
primarily using only information about the location of the sensors in
space and the wave directions of interest. In contrast, adaptive
beamforming techniques, generally combine this information with
properties of the signals actually received by the array, typically to
improve rejection of unwanted signals from other directions. This process
may be carried out in the time or frequency domains. Smart Antenna
refers to a system of antenna arrays with smart signal processing
algorithms that are used to identify the direction of arrival (DOA) of the
signal, and use it to calculate beamforming vectors, to track and locate
the antenna beam on the mobile/target. ... Smart Antenna refers to a
system of antenna arrays with smart signal processing algorithms that
are used to identify the direction of arrival (DOA) of the signal, and use it
to calculate beamforming vectors, to track and locate the antenna beam
on the mobile/target. ...
As the name indicates, an adaptive beamformer is able to adapt
automatically its response to different situations. Some criterion has to
be set up to allow the adaption to proceed such as minimising the total
noise output. Because of the variation of noise with frequency, in wide
band systems it may be desirable to carry out the process in the
frequency domain. An adaptive beamformer is signal processing system
often used with an array of radar antennae (or phased array) in order to
transmit or receive signals in different directions without having to
mechanically steer the array. ... Frequency domain is a term used to
describe the analysis of mathematical functions with respect to
frequency.
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3.7.2- Direction of Arrival (DOA)
Direction of Arrival (DOA) denotes the direction from which usually a
propagating wave arrives at a point, where usually a set of sensors are
located. This set of sensors forms what is called a sensor array. Often
there is the associated technique of beamforming which is estimating the
signal from a given direction. Various engineering problems addressed in
the associated literature are as follows: A wave crashing against the
shore a wave is a disturbance that propagates. Beamforming is the
process of delaying the outputs of the sensors in an arrays aperture and
adding these together, to reinforce the signal with respect to noise or
waves propagating in different directions.
Find the direction relative to the array where the underwater sound
source is located.
Directions of different sound sources around you are also located
by you using a process similar to those used by the algorithms in the
literature.
Radio telescopes use these techniques to look at a certain location
in the sky.
Recently beamforming has also been used in RF applications such
as wireless communication. Compared with the spatial diversity
techniques, beamforming is preferred in terms of complexity. On the
other hand beamforming in general has much lower data rates. In
multiple access channel (CDMA,FDMA,TDMA) beamforming is
necessary & sufficient.
The smart antenna system estimates the direction of arrival of the signal,
using any of the techniques like MUSIC (Multiple Signal Classification) or
ESPRIT (Estimation of Signal Parameters via Rotational Invariant
Techniques) algorithms,Matrix Pencil method or their derivatives. They
involve finding a spatial spectrum of the antenna/sensor array, and
calculating the DOA from the peaks of this spectrum. MUSIC involves
calculation of eigenvalues and eigenvectors of an autocorrelation matrix
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of the input vectors from the receiving antenna array. These calculations
are computationally intensive. Matrix Pencil is very efficient in case of
real time systems, and under the correlated sources. In mathematics, a
number is called an eigenvalue of a matrix if there exists a nonzero vector
such that the matrix times the vector is equal to the same vector
multiplied by the eigen value.In linear algebra, the eigenvectors (from the
German eigen meaning own) of a linear operator are non-zero vectors
which, when operated on by the operator, result in a scalar multiple of
themselves.
3.9- Application of Smart Antenna
Smart Antenna is used in number of fields. It has number of
Applications. Here are some of the fields where Smart Antenna used:-
1). MOBILE COMMUNICATION.
2).WIRELESS COMMUNICATION. 3). RADAR. 4).SONAR
APPLICATION OF SMART ANTENNAS TO MOBILE
COMMUNICATIONS SYSTEMS
Smart or adaptive antenna arrays can improve the performance of
wireless communication systems. An overview of strategies for achieving
coverage, capacity, and other improvements is presented, and relevant
literature is discussed. Multipath mitigation and direction finding
applications of arrays are briefly discussed, and potential paths of
evolution for future wireless systems are presented. Requirements and
implementation issues for smart antennas are also considered.
Smart antennas are most often realized with either switched-beam or
fully adaptive array antennas. An array consists of two or more antennas
(the elements of the array) spatially arranged and electrically
interconnected to produce a directional radiation pattern. In a phased
array the phases of the exciting currents in each element antenna of the
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array are adjusted to change the pattern of the array, typically to scan a
pattern maximum or null to a desired direction.
A smart antenna system consists of an antenna array, associated RF
hardware, and a computer controller that changes the array pattern in
response to the radio frequency environment, in order to improve the
performance of a communication or radar system.
Switched-beam antenna systems are the simplest form of smart antenna.
By selecting among several different fixed phase shifts in the array feed,
several fixed antenna patterns can be formed using the same array. The
appropriate pattern is selected for any given set of conditions. An
adaptive array controls its own pattern dynamically, using feedback to
vary the phase and/or amplitude of the exciting current at each element
to optimize the received signal.
Smart or adaptive antennas are being considered for use in wireless
communication systems. Smart antennas can increase the coverage and
capacity of a system. In multipath channels they can increase the
maximum data rate and mitigate fading due to cancellation of multipath
components. Adaptive antennas can also be used for direction finding,
with applications including emergency services and vehicular traffic
monitoring. All these enhancements have been proposed in the literature
and are discussed in this paper. In addition, possible paths of evolution,
incorporating adaptive antennas into North American cellular systems,
are presented and discussed. Finally, requirements for future adaptive
antenna systems and implementation issues that will
influence their design are outlined.
Range extension
In sparsely populated areas, extending coverage is often more important
than increasing capacity. In such areas, the gain provided by adaptive
antennas can extend the range of a cell to cover a larger area and more
users than would be possible with omnidirectional or sector antennas.
Dept. of E&C PESIT-BSC
Interference reduction and rejection
In populated areas, increasing capacity is of prime importance. Two
related strategies for increasing capacity are interference reduction on
the downlink and interference rejection on the uplink. To reduce
interference, directional beams are steered toward the mobiles.
Interference to co-channel mobiles occurs only if they are within the
narrow beamwidth of the directional beam. This reduces the probability
of co-channel interference compared with a system using omnidirectional
base station antennas.
Interference can be rejected using directional beams and/or by forming
nulls in the base station receive antenna pattern in the direction of
interfering co-channel users.
Interference reduction and rejection can allow N c (which is dictated by
co-channel interference) to be reduced, increasing the capacity of the
system.
Interference reduction can be implemented using an array with steered or
switched beams. By using directional beams to communicate with
mobiles on the downlink, a base station is less likely to interfere with
nearby co-channel base stations than if it used an omnidirectional
antenna.
There will be a small percentage of time during which co-channel
interference is strong, e.g., when a mobile is within the main beam of a
nearby co-channel base station.
This can be overcome by handing off the mobile within its current cell to
another channel that is not experiencing strong co-channel interference.
3.10- Advantages and Disadvantages of Smart
Antenna. Advantages
Dept. of E&C PESIT-BSC
Increased number of users
Due to the targeted nature of smart antennas frequencies can be reused
allowing an increased number of users. More users on the same
frequency space means that the network provider has lower operating
costs in terms of purchasing frequency space.
Increased Range
As the smart antenna focuses gain on the communicating device, the
range of operation increases. This allows the area serviced by a smart
antenna to increase. This can provide a cost saving to network providers
as they will not require as many antennas/base stations to provide
coverage.
Geographic Information
As smart antennas use ‘targeted’ signals the direction in which the
antenna is transmitting and the gain required to communicate with a
device can be used to determine the location of a device relatively
accurately. This allows network providers to offer new services to devices.
Some services include, guiding emergency services to your location,
location based games and locality information.
Security
Smart antennas naturally provide increased security, as the signals are
not radiated in all directions as in a traditional omni-directional antenna.
This means that if someone wished to intercept transmissions they would
need to be at the same location or between the two communicating
devices.
Reduced Interference
Interference which is usually caused by transmissions which radiate in
all directions are less likely to occur due to the directionality introduced
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by the smart antenna. This aids both the ability to reuse frequencies and
achieve greater range.
Increased bandwidth
The bandwidth available increases form the reuse of frequencies and also
in adaptive arrays as they can utilize the many paths which a signal may
follow to reach a device.
Easily integrated
Smart antennas are not a new protocol or standard so the antennas can
be easily implemented with existing non smart antennas and devices.
Disadvantages
Complex
A disadvantage of smart antennas is that they are far more complicated
than traditional antennas. This means that faults or problems may be
harder to diagnose and more likely to occur.
More Expensive
As smart antennas are extremely complex, utilizing the latest in
processing technology they are far more expensive than traditional
antennas. However this cost must be weighed against the cost of
frequency space.
Larger Size
Due to the antenna arrays which are utilized by smart antenna systems,
they are much larger in size than traditional systems. This can be a
problem in a social context as antennas can be seen as ugly or unsightly.
Dept. of E&C PESIT-BSC
Location
The location of smart antennas needs to be considered for optimal
operation. Due to the directional beam that ‘swings’ from a smart
antenna locations which are optimal for a traditional antenna are not for
a smart antenna. For example in a road context, smart antennas are
better situated away from the road, unlike normal antennas which are
best situated along the road.
3.11- Features and Benefit of Smart Antenna
Feature of Smart Antenna
1).Signal gain - Inputs from multiple antennas are combined to optimize
available power required to establish given level of coverage.
2).Interference Rejection - Antenna pattern can be generated toward
co-channel interference sources, improving the signal-to-interference
ratio of the received signals.
3).Spatial diversity-Composite information from the array is used to
minimize fading and other undesirable effects of multipath propagation.
4).Power efficiency- Combines the inputs to multiple elements to
optimize available processing gain in the downlink (toward the user)
Benefit of Smart Antenna
1).Better range/coverage- Focusing the energy sent out into the cell
increases base station range and coverage. Lower power requirements
also enable a greater battery life and smaller/lighter handset size.
2).Increased capacity- Precise control of signal nulls quality and
mitigation of interference combine to frequency reuse reduce distance (or
cluster size),improving capacity. Certain adaptive technologies (such as
Dept. of E&C PESIT-BSC
space division multiple access) support the reuse of frequencies within
the same cell.
3).Multipath rejection- Can reduce the effective delay spread of the
channel, allowing higher bit rates to be supported without the use of an
equalizer.
4).Reduced expense- Lower amplifier costs, power consumption, and
higher reliability will result.
4. Conclusion
This report aims to explain the basic concept of Smart Antenna and some of its Application.
First Question arises what is Smart Antenna?
A smart antenna combines an antenna array with a digital signal-
processing capability to transmit and receive in an adaptive, spatially sensitive manner. Or In other words Smart Antenna is an Array of antenna which is used to optimize its reception and transmit pattern.
There are two types of Smart Antenna:-
1). Switched Beam- Switched beam antenna systems form multiple fixed beams with heightened sensitivity in particular directions. These antenna systems detect signal strength, choose from one of several
predetermined, fixed beams, and switch from one beam to another as the mobile moves throughout the sector.
2). Adaptive Array- Adaptive antenna technology represents the most
advanced smart antenna approach to date. the adaptive system takes advantage of its ability to effectively locate and track various types of signals to dynamically minimize interference and maximize intended
signal reception.
Both systems attempt to increase gain according to the location of the user; however, only the adaptive system provides optimal gain while
simultaneously identifying, tracking, and minimizing interfering signals.
Smart antenna works in two processes. First one is Uplinking and second one is Downlinking
There are 2 categories of Smart Antenna:-
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1). SIMO (Single Input Multiple Output)
2). MISO (Multiple Input Single Output)
3).MIMO (Multiple Input Multiple Output)
Basically Smart antenna has two functions :-
1).Beamforming-
2).Direction of Arrival
Smart antenna is used in various fields the most important is named below:-
1). Mobile Communication
2). Wireless Communication
3). RADAR
4).SONAR
There are some of the factors which affects the performance of Smart
Antenna . These factors reduce the Quality of Smart Antenna.Factors are:-
1).Resonant Frequency
2).Gain
3).Impedance
4).Bandwidth
5).Polarization
6).Transmission and Reception
Merits of Smart Antenna
1). Increased number of users.
2). Increased Range
3). Security
4). Reduced Interference.
Dept. of E&C PESIT-BSC
Demerits of Smart Antenna:-
1). Complex
2). Expensive
3). Large Size
4). Location
References
1). www.wikipedia.com
2). www.statemaster.com
3). www.iec.org
4). http://www.iec.org/online/tutorials/smart_ant/
5).W. L. Stutzman and G. A. Thiele, Antenna theory and
Design, John Wiley & Sons, New York, 1981.
6). D. Johnson and D. Dudgeon, Array Signal Processing,
Prentice-
Hall, Englewood Cli_s, NJ, 1993
7). http://www.smartanteenas.googlepages.com
8). Michael Chryssomallis “Smart antennas” IEEE antenna and
propagation magazine” Vol 42 No 3 pp 129-138, June 2000.
9). D. Johnson and D. Dudgeon, Array Signal Processing,
Prentice-
Hall, Englewood Cli_s, NJ, 1993
10). Special issue on blind identi_cation and estimation," IEEE
Proceedings, mid-1998.
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11). R Kronberger,H Lindermerier,J Hopf “Smart antenna
applications on vehicles with low profile array antenna” Proc
IEEE Vol 53 pp1-3 September 2003.
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