communication sytems
Post on 05-Jul-2015
87 Views
Preview:
TRANSCRIPT
YuVa InnoVators
YuVa InnoVators
Purpose
Objectives
Expected Benefits
YuVa InnoVators
An overview of diversity techniques.
How diversity technique can be utilized for performance
improvement.
Provide MATLAB computing to understand the
performance improvement using diversity technique.
YuVa InnoVators
To acquire an update on the development of mobile phone technologies with potential for
supporting our own future carrier.
To learn about the present wireless communication condition in our country.
To demonstrate some latest technologies in communication field
How diversity techniques are used to improve the performance of the radio channel without
any increase in the transmitted power.
To evaluate the system performance degradation due to fading.
To undergo mathematical analysis and MATLAB simulation for analyzing the performance of
Raleigh fading channels.
To study Uniqueness of Mobile Radio Environment.
To overall basic knowledge about telecommunication.YuVa InnoVators
To know about the recent status of telecommunication sector
To work on the improvement of the communication services
Diversity is now being considered as one of the most
solution to mitigate the fading problem in wireless
communication.
YuVa InnoVators
Communication signifies transmission, reception and
processing of information by electric means.
YuVa InnoVators
YuVa InnoVators
An information source, presumably a person who creates a message.
The message, which is both sent by the information source and received by the destination.
A transmitter, a telephone instrument that captures an audio signal, converts it into an electronic signal, and amplifies it
for transmission through the telephone network.
A carrier or channel, which acts as a bridge between the transmitter and receiver. As the signal propagates through the
channel, it gets attenuated due to transmission loss and distorted due to various nonlinear effects and interference.
Channel can consist of a pair of wires, a coaxial cable or a radio link through free space
Noise, in the form of secondary signals that obscure or confuse the signal carried
Receiver It extracts the weakened and distorted signal from the channel, amplifies it and restores it to its original
form and then passes it into the message destination.
YuVa InnoVators
OPTICAL COMMUNICATION SYSTEM
RADIO COMMUNICATION
POWER LINE COMMUNICATIONS SYSTEMS
DUPLEX COMMUNICATION SYSTEM
TACTICAL COMMUNICATIONS SYSTEM
WIRELESS COMMUNICATION
YuVa InnoVators
The transfer of information over a distance without
the use of electrical conductors or "wires“
An electromagnetic signal is created, modulated,
amplified, and broadcast to one or more receivers that
can be fixed or mobile.
YuVa InnoVators
Every wireless system must have the basics of a transmitter
(modulation), receiver (demodulation) and a channel
(frequency) to transmit the signal from a stationary or mobile
reference. YuVa InnoVators
A TYPICAL GSM BASE STATIONYuVa InnoVators
High Frequency (HF) 3-30 MHz (PRIME BAND)
Very High Frequency (VHF) 30-300 MHz (PRIME BAND)
Ultra High Frequency (UHF) 300-3000 MHz (PRIME BAND)
Super High Frequency (SHF) 3-30 GHz (INCREASING USE)
Extremely High Frequency (EHF) 30-300 GHz (PROSPECTIVE USE)
YuVa InnoVators
SECURITY SYSTEMS
TELEVISION REMOTE CONTROL
CELLULAR TELEPHONY (PHONES AND MODEMS)
Wi–Fi
WIRELESS ENERGY TRANSFER
COMMUNICATIONS SATELLITEYuVa InnoVators
In telecommunications, modulation
is the process of conveying a
message signal inside another signal
that can be physically transmitted.
YuVa InnoVators
The aim of digital modulation is to transfer a digital
bit stream over an analog passband channel
The aim of analog modulation is to transfer an analog
baseband (or lowpass) signal
The aim of pulse modulation methods is to transfer a
narrowband analog signal
YuVa InnoVators
MODULATION
ANALOG MODULATION
AMPLITUDE MODULATION
FREQUENCY MODULATION
PHASE MODULATION
DIGITAL MODULATION
AMPLITUDE-SHIFT KEYING
FREQUENCY-SHIFT KEYING
PHASE-SHIFT KEYING
PULSE MODULATION
PULSE-AMPLITUDE MODULATION
PULSE-WIDTH MODULATION
PULSE-POSITION MODULATION
PULSE-CODE MODULATIONYuVa InnoVators
The modulation is applied continuously in response to the
analog information signal.
The amplitude of the carrier
signal is varied in accordance to the
instantaneous amplitude of the
modulating signal.
The frequency of the carrier
signal is varied in accordance to the
instantaneous frequency of the
modulating signal.
The phase shift of the carrier
signal is varied in accordance to the
instantaneous phase shift of the
modulating signal.
YuVa InnoVators
An analog carrier signal is
modulated by a digital bit stream
Considered as digital-to-analog
conversionYuVa InnoVators
AMPLITUDE-SHIFT KEYING (ASK)
FREQUENCY-SHIFT KEYING (FSK)
PHASE-SHIFT KEYING (PSK)YuVa InnoVators
Pulse modulation schemes aim at transferring a narrowband analog
signal over an analog baseband channel as a two-level signal by
modulating a pulse wave.
YuVa InnoVators
Essentially identical to coded OFDM (COFDM) and discrete
multi-tone modulation (DMT), is a frequency-division
multiplexing (FDM) scheme utilized as a digital multi-carrier
modulation method.
Orthogonal Frequency-Division Multiple Access (OFDMA)
is a multi-user version of the popular Orthogonal frequency-
division multiplexing (OFDM) digital modulation scheme.
YuVa InnoVators
AN OFDM (A) MODULATOR AND (B) DEMODULATOR
YuVa InnoVators
OFDM SIMULATION FLOWCHART
YuVa InnoVators
Flexibility of deployment across various frequency bands with little needed
modification to the air interface.
Averaging interferences from neighboring cells, by using different basic carrier
permutations between users in different cells.
Interferences within the cell are averaged by using allocation with cyclic
permutations.
Enables orthogonality in the uplink by synchronizing users in time and frequency.
Enables Single Frequency Network coverage, where coverage problem exists and
gives excellent coverage.
Offers Frequency diversity by spreading the carriers all over the used spectrum.
Offers Time diversity by optional interleaving of carrier groups in time. YuVa InnoVators
FADING
INTERFERENCE
ERROR BURST
FREQUENCY REUSES
NOISE LEVEL IN CELLULAR FREQUENCY BAND
PATH LOSS YuVa InnoVators
The fading is deviation of the attenuation that a carrier-
modulated telecommunication signal experiences over certain
propagation media.
The fading may vary with time, geographical position and/or
radio frequency, and is often modeled as a random process.
In wireless systems, fading may either be due to multipath
propagation or due to shadowing from obstacles affecting the
wave propagation.YuVa InnoVators
1. Multipath Spread Tm
It tells us the maximum delay between paths of significant power in the channel
2. Coherence Bandwidth (Δ)c
Gives an idea of how far apart –in frequency- for signals to undergo different degrees of fading
3. Coherence Time (t)c
Gives a measure of the time duration over which the channel impulse response is essentially invariant (highly correlated)
4. Doppler Spread Bd
It gives the maximum range of Doppler shifts
YuVa InnoVators
A MOBILE RADIO ENVIRONMENT (a) PROPAGATION LOSS(b) MULTIPATH FADING
YuVa InnoVators
FAST FADING vs. SLOW FADING
YuVa InnoVators
CO-CHANNEL INTERFERENCE
- Co-channel interference or CCI is crosstalk from two
different radio transmitters using the same frequency.
ADJACENT-CHANNEL INTERFERENCE
- Adjacent-channel interference or ACI is interference
caused by extraneous power from a signal in an adjacent
channel.
YuVa InnoVators
The core concept of the cellular mobile radio system.
Users in different geographic locations may
simultaneously use the same frequency .
The frequency reuse concept can be used in the time
domain and the space domain.
YuVa InnoVators
N-CELL REUSE PATTERNYuVa InnoVators
Tow-ray models for mobile radio environments
YuVa InnoVators
TIME DIVERSITY
FREQUENCY DIVERSITY
SPACE DIVERSITY
SPATIAL DIVERSITY
PATTERN DIVERSITY
POLARIZATION DIVERSITY
MULTIUSER DIVERSITY
COOPERATIVE DIVERSITYYuVa InnoVators
Time Diversity is used in digital communication systems
to combat that the transmissions channel may suffer from
error bursts due to time-varying channel conditions.
YuVa InnoVators
The signal is transferred using several frequency channels
or spread over a wide spectrum that is affected by
frequency-selective fading.
YuVa InnoVators
Antenna diversity, also known as space diversity, is any one of
several wireless diversity schemes that use two or more
antennas to improve the quality and reliability of a wireless
link. Often, especially in urban and indoor environments, there
is not a clear line-of-sight (LOS) between transmitter and
receiver. Instead the signal is reflected along multiple paths
before finally being received
YuVa InnoVators
YuVa InnoVators
Spatial diversity employs multiple antennas,
usually with the same characteristics, that are
physically separated from one another.
Depending upon the expected incidence of the
incoming signal, sometimes a space on the
order of a wavelength is sufficient.
YuVa InnoVators
Pattern diversity consists of two or more co-located antennas with different radiation patterns.This type of diversity makes use of directiveantennas that are usually physically separated bysome (often short) distance.
Collectively they are capable of discriminating alarge portion of angle space and can provide ahigher gain versus a single omni directionalradiator.
YuVa InnoVators
Multiple versions of a signal are transmitted and received via
antennas with different polarization.
LINEAR CIRCULAR ELLIPTICALYuVa InnoVators
Achieves antenna diversity gain by using the
cooperation of distributed antennas belonging to
each node.
Cooperative diversity is a cooperative multiple
antenna technique for improving or maximizing
total network channel capacities for any given set
of bandwidths .
YuVa InnoVators
SELECTION COMBINING
SWITCHING COMBINING
EQUAL GAIN COMBINING
MAXIMAL-RATIO COMBININGYuVa InnoVators
Of the N received signals, the strongest signal is selected.
Any additional gain diminishes rapidly with the increasing number of
channels.
YuVa InnoVators
• The receiver switches to another signal when current signal drops below apredefined threshold.
• This is a less efficient technique than selection combining.
YuVa InnoVators
All the received signals are summed coherently.
YuVa InnoVators
• The received signals are weighted with respect to their SNR
and then summed.
YuVa InnoVators
Use of multiple antennas at both the transmitter and
receiver to improve quality (BER) or data rate
(bits/sec).
One of several forms of smart antenna technology.
Core scheme of MIMO: space-time coding (STC)
Two main functions of STC: diversity & multiplexingYuVa InnoVators
Spatial Diversity: Increased SNR Spatial Multiplexing: Increased rate
Receive and transmit diversity mitigates fading and significantly
improves link quality
Spatial multiplexing yields substantial increase in spectral
efficiencyYuVa InnoVators
YuVa InnoVators
YuVa InnoVators
Diversity plays an important role in combating fading and co-channel
interference and avoiding error bursts. It is based on the fact that
individual channels experience different levels of fading and
interference. Multiple versions of the same signal may be transmitted
and/or received and combined in the receiver. Alternatively, a
redundant forward error correction code may be added and different
parts of the message transmitted over different channels. Diversity
techniques may exploit the multipath propagation, resulting in a
diversity gain, often measured in decibels.YuVa InnoVators
Comparison of the Performance of a wireless Communication System using Antenna Diversity
YuVa InnoVators
SNR KNo. of receiving
antenna (Rx.)
BER-Floor for a Un-
coded System
40dB 0dB
2 10-5
3 10-7
4 10-8
5 10-10
6 10-12
The improvement of performance of a Wireless System using Multiple Antenna
(Diversity) System
YuVa InnoVators
Comparison of Performance between one (L=1) and six receiving (L=6) Antenna of wireless Communication System using Maximum Ratio
Combining Diversity Method YuVa InnoVators
SNR KNo. of receiving
antenna (Rx.)
BER-Floor for the
System
50dB 0dB
1 10-5
6 10-22
Comparison of Performance between one (L=1) and six receiving (L=6) Antenna of wireless Communication System
YuVa InnoVators
Comparison of Performance between one (L=1) and eight receiving (L=8) Antenna of wireless Communication System using Maximum
Ratio Combining Diversity Method YuVa InnoVators
Comparison of Performance between one (L=1) and eight receiving (L=8) Antenna of wireless Communication System
SNR KNo. of receiving
antenna (Rx.)
BER-Floor for the
System
60dB 0dB
1 10-4
8 10-34
YuVa InnoVators
Comparison of Performance for different diversity schemes of a Wireless Communication System using Maximum Ratio Combining (MRC).
YuVa InnoVators
Comparison of Performance for different diversity schemes of a Wireless Communication System.
SNR KNo. of receiving
antenna (Rx.)
BER-Floor for the
System
60dB 0dB
1 10-4
2 10-10
4 10-20
6 10-27
8 10-35
YuVa InnoVators
The diversity is used to provide the receiver with several replicas of the samesignal. Diversity techniques are used to improve the performance of the radiochannel without any increase in the transmitted power. As higher as thereceived signal replicas are de correlated, as much as the diversity gain
Among different combining techniques MRC has the best performance andthe highest complexity, SC has the lowest performance and the leastcomplexity.
BER performance of a Multi-antenna system for both Coded and Un-codedsystem considering several number of Receiving Antenna. From the bothfigures it is noticed that there is remarkable improvement in the achievableprobability of bit error as number of receiving antenna increase. The BER ismeasured as 10-5 , 10-7 , 10-8 ,10-10 , and 10-12 for Receiving AntennaNumbers 2, 3, 4, 5 and 6 respectively. Also it is revealed that Bit-Error-Rate of a Multi-Antenna System is 10-23, 10-30 , 10-38 , 10-47 and 10-56
for Receiving Antenna Numbers 2, 3, 4, 5 and 6 respectively.YuVa InnoVators
top related