Upload
ek-powell
View
148
Download
1
Tags:
Embed Size (px)
DESCRIPTION
pdp
Citation preview
15/7/2557 Power Delay Profile | GaussianWaves
http://www.gaussianwaves.com/2014/07/power-delay-profile/ 1/9
Channel Modelling Signal Processing Digital Modulations Matlab Codes
Estimation Theory Random Process Channel Coding Spread Spectrum
OFDM Pulse Shaping Book Reviews Tips & Tricks
(1 votes, average: 5.00 out of 5)
The Power Delay Profile gives the distribution of signal power
received over a multipath channel as a function of propagation
delays. It is obtained as the spatial average of the complex baseband
channel impulse response as
As discussed in the previous post, it can also be derived from
scattering function as given below
where denotes Doppler Frequency, denotes multipath
propagation delay, denotes the scattering function.
In a Power Delay Profile plot, the signal power of each multipath is
plotted against their respective propagation delays. A sample power
Power Delay Profile Mathuranathan July 9, 2014 Channel Modelling No Comment
,V
,V V
$$
]$0 V]
,V " V "
" V
" V
New users - Log in with:
Ebook Referred By Many
Around The World
Home Index Forums Video Lectures Buy Books Activity
Members Groups Feedback
15/7/2557 Power Delay Profile | GaussianWaves
http://www.gaussianwaves.com/2014/07/power-delay-profile/ 2/9
delay profile plot, shown below, indicates how a transmitted pulse
gets received at the receiver with different signal strength as it travels
through a multipath channel with different propagation delays (
and .
Power Delay Profile is usually supplied as a table of values obtained
from empirical data and it serves as a guidance to system design.
Nevertheless, it is not an accurate representation of the real
environment in which the mobile is destined to operate at. For
example, the 3GPP spec specifies the power delay profile for various
environments as follows.
V
V
V
Typical values for power delay profile listed in a 3GPP spec
Quirky Products !!!
Cordies - Desktop Cord
Manager
Search Articles
Search
Follow Us!
Digital Communication and
Signal Processing
2,909 Communication and Signal Processing
GaussianWaves
+ 133
15/7/2557 Power Delay Profile | GaussianWaves
http://www.gaussianwaves.com/2014/07/power-delay-profile/ 3/9
Maximum Excess Delay Definitionand applications
With Power Delay Profile, one can classify a multipath channel into
frequency selective or frequency non-selective category. The derived
parameter, namely, Maximum Excess Delay together with the
symbol time of each transmitted symbol, can be used to classify the
channel into frequency selective or non-selective channel.
Power Delay Profile can be used to estimated the average power of a
multipath channel, measured from the first signal that strikes the
receiver to the last signal whose power level is above certain
threshold. This threshold is chosen based on receiver design
specification and is dependent on receiver sensitivity and noise floor
at the receiver.
Maximum Excess Delay, also called Maximum Delay Spread, denoted
as , is the relative time difference between the first signal
component arriving at the receiver to the last component whose
power level is above some threshold. Maximum Delay Spread
and the symbol time peroid can be used to classify a channel
into frequency selective or non-selective category. This classification
can also be done using Coherence Bandwidth (a derived parameter
from Spaced Frequency Correlation Function which in turn is the
frequency domain representation of power delay profile).
Maximum Excess Delay is also an important parameter in mobile
positioning algorithm. The accuracy of such algorithm depends on
how well the Maximum Excess Delay parameter conforms with
measurement results from actual environment.
When a mobile channel is modeled as a FIR filter (tapped delay line
implementation), as in CODIT channel model[1], the number of taps
of the FIR filter is determined by the product of maximum excess
delay and the system sampling rate.
The Cyclic Prefix in a OFDM system is typically determined by the
maximum excess delay or by the RMS delay spread of that
environment [2].
)
)
/5)
Ratings
Simulation of Digital
Communication Systems
Using Matlab [eBook]
Second Edition -
10 votes
Simulation and Analysis of
White Noise in Matlab
- 7 votes
Simulation of OFDM system
in Matlab BER Vs Eb/N0 for
OFDM in AWGN channel
- 3 votes
Survey of Methods to
Compute Linear Convolution
- 2 votes
Computation of Power of a
Signal in Matlab
Simulation and Verification
- 2 votes
Polynomials, Convolution
and Toeplitz matrices
Connecting the dots
- 2 votes
Power and Energy of a signal
- 2 votes
On The Forums
How to generate an OFDM
signals with fixed sampling
frequency? by Preben
How is this envelope actually
created in AM? by
Premnath Deenadayalan
Digital Communications by
15/7/2557 Power Delay Profile | GaussianWaves
http://www.gaussianwaves.com/2014/07/power-delay-profile/ 4/9
Classification of Channel signalspreading in Time domain:
A channel is classified as Frequency Selective, if the maximum excess
delay is greater than the symbol time period, i.e, . This
introduces Inter Symbol Interference (ISI) into the signal that is being
transmitted, thereby distorting it. This occurs since the signal
components (whose power are above the threshold or the maximum
excess delay) due to multipath extend beyond the symbol time. ISI
can be mitigated at the receiver by an equalizer.
In a frequency selective channel , the channel output can be
expressed as the convolution of input signal and the channel impulse
response plus some noise.
On the other hand, if the maximum excess delay is less than the
symbol time period, i.e, , the channel is classified as
frequency non-selective or flat channel. Here, all the scattered
signal components (whose power are above the specified threshold
or the maximum excess delay) due to the multipath, arrive at the
receiver within the symbol time. This will not introduce any ISI, but
the received signal is distorted due to inherent channel effects like
SNR condition. Equalizers in the receiver are not needed. A time
varying non-frequency selective channel is obtained by assuming
that the impulse response . Thus the output of the
channel can be expressed as
Note, that the output of the channel can be expressed simply as
product of time varying channel response and the input signal. If the
channel impulse response is a deterministic constant, i.e, time in-
varying, then the non-frequency selective channel is expressed as
)
/5)
50 $0 V 40 30
)
/5)
$0 V $0FV
50 $0 V 40 30
$0 V40 V V 30
$0FV40 V V 30
$040 30
Ricardo Jnior
What is Phase of a Signal? by
Premnath
Deenadayalan
Frequency Response of
Rectangular Pulse by
Micky
Recent Comments
Mathuranathan Says: Check
this out
http://www.gaussianwaves.com/2...
Abdelrahman Salama Arbi
Says: how I can generate the
shadowing samples at d...
yasser Says: please where is
the article that illustrate t...
Mathuranathan Says: Hint
for you to solve : Sampling
Theorem spec...
yasser Says: an interview
question asked to me was
15/7/2557 Power Delay Profile | GaussianWaves
http://www.gaussianwaves.com/2014/07/power-delay-profile/ 5/9
follows by assuming
This is the simplest situation that can occur. In addition to that, if the
noise in the above equation is white Gaussian noise, the channel is
called Additive White Gaussian Noise (AWGN) channel.
Characterization of FrequencySelective Channels:
Average delay and the RMS delay spread are two most important
parameters that characterize a frequency selective channel. They are
derived from Power Delay Profile.
Average delay:
Simply the statistical mean of the delay that a signal undergoes when
transmitted over a multipath channel. For a frequency selective
WSSUS channel, the average delay is equal to the first moment of the
power delay profile . For a discrete channel it is calculated as
If the given PDP values are continuous in terms of time delays (as
given in the sample plot below), replace the summation with
integral and integrate it with respect to .
RMS delay spread:
RMS delay spread is equal to the second central moment of power
delay profile . It is similar to the standard deviation of a
statistical distribution. For a discrete channel it is given by
where,
$0 V $FV
50 $40 30
,V
Vc
V,V
,V
V
,V
U
V
V
c
Vc
,V
given a...
Subscribe To
Gaussianwaves Via Email
Enter your email address to
subscribe to this Website and
receive notifications of new
articles by email.
Join 90 other subscribers
Email Address
Subscribe
Designed & Powered By
Tags
advanced signal processing
advance statistical signal
processing AR ARMA ARMA model
Auto-Correlation Auto
regressive AWGN BPSK
Channel Coding Channel
Modelling cholesky
Cramer Rao Lower
Bound CRLB Cross-Correlation
Digital Modulations
Estimation FadingFisher Information Fisher
Matrix gray code Interleavers
15/7/2557 Power Delay Profile | GaussianWaves
http://www.gaussianwaves.com/2014/07/power-delay-profile/ 6/9
If the given PDP values are continuous in terms of time delays (as
given in the sample plot below), replace the summation with integral
and integrate it with respect to .
The ratio of RMS delay spread and symbol time duration quantifies
the strength of Inter Symbol Interference. This ratio determines the
complexity of the equalizer required at the receiver. Typically, when
the symbol time period is greater than 10 times the RMS delay
spread, no ISI equalizer is needed in the receiver.
A sample power delay profile is plotted below. Average delay, RMS
delay spread, and the maximum excess delay ( given a threshold of
100 dBm ) are all marked.
References:
[1] Andermo, P.G.; Larsson, G., Code division testbed, CODIT, Universal
Personal Communications, 1993. Personal Communications:
Gateway to the 21st Century. Conference Record., 2nd International
Conference on , vol.1, no., pp.397,401 vol.1, 12-15 Oct 1993
V
c
,VV
,V
V
Power Delay Profile with Mean delay, RMS delay spread,
Maximum Excess Delay
Matched Filter MatlabCode Matlab Codes matrixalgebra Maximum
Likelihood Estimation
Minimum Variance Unbiased
Estimator MLE Multi-carrier
Modulation OFDM
Orthogonal Frequency
Division Multiplexing
oversampling PDF positive definite
Power spectral Density
PSD Pulse Shaping Random
Process Random Variables
Rayleigh Reed Solomon Codes
Score SignalProcessing SpreadSpectrum
15/7/2557 Power Delay Profile | GaussianWaves
http://www.gaussianwaves.com/2014/07/power-delay-profile/ 7/9
5Like Tweet 1 2StumbleUpon
submit
[2] Huseyin Arslan, Cognitive Radio, Software Dened Radio, and Adaptive
Wireless Systems, pp. 238, 2007, Dordrecht, Netherlands, Springer.
Share this:
Share
More
autocorrelation function, average delay, AWGN, channel modeling, CoherenceBandwidth, Coherence Time, Doppler Power Spectrum, Fading, flat fading, frequencynon-selective, Frequency selective, Maximum excess delay, mean delay, multipath,Power Delay Profile (PDP), RMS delay spread, scattering function, spaced-frequencycorrelation function, spaced-time correlation function
About Mathuranathan
Mathuranathan Viswanathan - Founder and Author @
gaussianwaves.com which has garnered worldwide readership.
He is a masters in communication engineering and has 7 years
of technical expertise in channel modeling and has worked in
various technologies ranging from read channel design for
hard drives, GSM/EDGE/GPRS, OFDM, MIMO, 3GPP PHY layer
and DSL. He also specializes in tutoring on various subjects like
signal processing, random process, digital communication
etc..,He can be contacted at [email protected]
View all posts by Mathuranathan
15/7/2557 Power Delay Profile | GaussianWaves
http://www.gaussianwaves.com/2014/07/power-delay-profile/ 8/9
Statistical Characteristics of
Multipath Channels Scattering
Function
Sampling a Signal in Matlab
Sampling Theorem Bandpass
or Intermediate or Under
Sampling 3 comments
Simulation and Analysis of White
Noise in Matlab 10 comments
Power and Energy of a signal
2 comments
Simulation of Rayleigh Fading (
Clarkes Model sum of
sinusoids method) 4 comments
ALSO ON GAUSSIANWAVES WHAT'S THIS?
Comments Community Login
Sort by Best Share
Start the discussion
Be the first to comment.
Subscribe
Favorite
Copyright Notice
The articles and the
programming codes
appearing in this
website are the
intellectual properties
of the respective
authors and are
licensed under
Creative Commons :
Attribution-
NonCommercial-
15/7/2557 Power Delay Profile | GaussianWaves
http://www.gaussianwaves.com/2014/07/power-delay-profile/ 9/9
Copyright 2014. GaussianWaves
ShareAlike 3.0
License. If you copy
and reproduce the
works, then you must
attribute the works to
the respective
authors. Copyright
infringements will be
dealt with severly.