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This slide contain a modern communication system which convert a time multiplexed component of a signal into a frequency
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Transmultiplexer as Precodersin Modern Digital Communication
Presented By,
Nirnay Ranjan (1128731038)
Shashank Shukla (1128731058)
(ECE 3rd year)
Electronics & Communication
Engineering
Content
Summary
Introduction
Transmultiplexer System
Precoder
Controlling Bandwidth Efficiency
Optimizing for Noise
Blind Identification
Conclusion
Refrences
Naraina College Of Engg. & Technology , Electronics & Communication Engineering.Naraina College Of Engg. & Technology , Electronics & Communication Engineering.
Summary
This Seminar presents a system of modern communication which is
used to convert from time multiplexed components of a signal to a
frequency multiplexed version. In this Seminar we review the fundamental infrastructure behind these
methods. the transmultiplexer system is introduced and the
mathematical framework develope. we present the theory behind the
cancellation of multiuser interference and Amour system. We make
brief remarks on handling the effects of channel Noise.The
fundamentals behind blind identification of channels using
transmultiplexers is reviewed.
Naraina College Of Engg. & Technology , Electronics & Communication Engineering.
Introduction
Transmultiplexers have been known in digital communications
for many years.
Historically the transmultiplexer has been viewed as a system
that converts from time multiplexed components of a signal to
a frequency multiplexed version.
The role of transmultiplexers in digital communications has
gained new importance because of many recent results in filter
bank precoders.
Naraina College Of Engg. & Technology , Electronics & Communication Engineering.
Transmultiplexer System
Naraina College Of Engg. & Technology , Electronics & Communication Engineering.
A transmultiplexer is a structure that combines a collection of
signals into a single signal at a higher rate; i.e., it is the dual of
a filter bank.
Transmultiplexers were originally studied in the context of
converting time-domain-multiplexed (TDM) signals into
frequency domain multiplexed (FDM) signals with the goal of
converting back to time-domain-multiplexed signals at some
later point .
It includes discrete cosine transform processor used to receive
a linearly coded time division signal.
Block Diagram of Transmux System
In the given block diagram the symbol streams
are passed through the interpolation filters or
transmitter filters to produce the signals
Naraina College Of Engg. & Technology , Electronics & Communication Engineering.
In the above block diagram the received signal
are totally different from the input signal..
There are two reason behind this, the first is MUI
and second is ISI introduced by the Channel.
ISI is a form of distortion of a Signal in which
one symbol interferes with subsequent symbols
Naraina College Of Engg. & Technology , Electronics & Communication Engineering.Naraina College Of Engg. & Technology , Electronics & Communication Engineering.
Generalization of M-userTransmux
In this the M-sampled signal are transmitted through M different
channels.
This generalization has become important in the context of
multiuser communication over wireless communication.
Naraina College Of Engg. & Technology , Electronics & Communication Engineering.
Zero-Padding
Zero-Padding is a simple concept, used to
adding an additional Zeroes at the ending of
any time domain symbol stream.
Zero-Padding is used to increase the length
of a time domain symbol stream.
It is used to counter the IBI (Inter Block
Interference).
Naraina College Of Engg. & Technology , Electronics & Communication Engineering.
TransMux with Zero-Padding
Naraina College Of Engg. & Technology , Electronics & Communication Engineering.
Zero-Jamming
Zero-Jamming is a simple concept, used to
adding an additional Zeroes at the Begining
of the successive received signal.
It is used to counter the IBI (Inter Block
Interference).
Naraina College Of Engg. & Technology , Electronics & Communication Engineering.
TransMux With Zero-Jamming
Naraina College Of Engg. & Technology , Electronics & Communication Engineering.
Precoding
Precoding is a generalization of beamforming to support multi-
stream (or multi-layer) transmission in multi-antenna wireless
communications.
In point-to-point systems, precoding means that multiple data
streams are emitted from the transmit antennas with
independent and appropriate weightings such that the link
throughput is maximized at the receiver output.
Naraina College Of Engg. & Technology , Electronics & Communication Engineering.
Controlling Bandwidth Efficiency
This is known precisely as AMOUR systemdeveloped by Giannakis et al.
AMOUR means A Mutually-Orthogonal Usercode-Receiver.
From the figure of transmux,it consists of Mindependent symbol stream. If these have to beseparated successfully later, then the spacingbetween the samples of sk (n) must be at least Mtimes larger than the spacing T between the symbolsentering the channels Ck (n).
Naraina College Of Engg. & Technology , Electronics & Communication Engineering.
The “Bandwidth expansion Factor” is given by,
Γ=P/M=M+L/M
It is price paid ,in terms of redundancy which allowsequalization of FIR channels of order n.
A slight variation of the redundant transmultiplexersystem is obtain when we make each user look likeK users.This can be done by blocking the mth user
K-fold.
Γ^= P^/MK=MK+L/MK
Naraina College Of Engg. & Technology , Electronics & Communication Engineering.
Naraina College Of Engg. & Technology , Electronics & Communication Engineering.
Optimizing For Noise
It is known that noise can never be eliminated
completely, but can only be reduced to optimum
value .
Consider a transmultiplexer. Assume that the filters
have order < P so E (z) and R (z) are constants.
All systems described in the preceding paragraphs
fall under the category of zero-forcing equalizers .
Naraina College Of Engg. & Technology , Electronics & Communication Engineering.
Block Diagram Of TRANSMUX In Polyphase Form
Naraina College Of Engg. & Technology , Electronics & Communication Engineering.
Consider a TransMux with Reciever and transmitter filters R(z) and
E(z) respectively.
The Transfer Function from Input to Output is the prouct of
E(z)Cb(z)R(z),where Cb(z) is the blocked version of channel.
The condition for perfect recovery in absence
of noise can be attained by
EAR=I
E is said to be the left inverse of AR which
used minimize the channel noise at the
reciever output.
Since P>M this same left inverse is not unique.
Naraina College Of Engg. & Technology , Electronics & Communication Engineering.
Blind Identification
In mobile communication, the channel transfer
functions are unknown and have to be estimated.
Such estimation can be done either with the help of
training signals or by blind identification methods.
It is well known that with non redundant systems
(P = M) blind identification is not possible unless we
use fourth order moments.
Naraina College Of Engg. & Technology , Electronics & Communication Engineering.Naraina College Of Engg. & Technology , Electronics & Communication Engineering.
Consider again the single channel system of Fig. 10.Assume
as that the channel is FIR with order ≤ L, that the receiver filters
have order ≤ P −1, and that the transmitting filters have order ≤
M − 1.
Figure 11 shows the path from the transmitted symbols to the
channel output y(n).For convenience we consider the blocked
version y(n) as indicated. With the vector s(n) as defined in the
figure,we then have
Naraina College Of Engg. & Technology , Electronics & Communication Engineering.
Where A is defined as
This is a full-banded Toeplitz
matrix representing the FIR
channel of order ≤ L.
Naraina College Of Engg. & Technology , Electronics & Communication Engineering.
Conclusion
As all know that no system whether in
communication field or electronic field is perfect.
In this topic One problem which was not addressed
in this review is the minimization of redundancy in
the precoder.
Another important aspects was not defined is
resistance to channel nulls.
Naraina College Of Engg. & Technology , Electronics & Communication Engineering.
References:-
A tutorial review of “Transmultiplexer as precoder”.
Akansu, A. N., Duhamel, P., Lin, X., and Courville, M. de. “Orthogonaltransmultiplexers in communications: a review,” IEEE Trans. SP, April1998.
Giannakis, G. B. “Filter banks for blind channel identification and equalization,”IEEE Signal Processing Letters.
Giannakis, G. B., Wang, Z., Scaglione, A., and Barbarossa, S., “Amour—generalized multicarrier transceivers for blind CDMA regardless of multipath,”IEEE Trans. Comm., pp 2064–2076, Dec. 2000.
Precoding Techniques for Digital Communication Systems www.springer.com
Precoding - Wikipedia the free encyclopedia
www.en.wikipedia.org
Decimation (Digital Filter Design Toolkit) - LabVIEW 2013 Digital Filter DesignToolkit Help - National Instruments
www.zone.ni.com
www.google.com
Naraina College Of Engg. & Technology , Electronics & Communication Engineering.