Pilot Symbol Aided Channel Estimation in OFDM

This report discusses the concept of pilot symbol aided channel estimation technique in the field of OFDM telecommunication system. It covers different types of pilot symbol estimation techniques, their impact on the future of telecommunication, and advantages and disadvantages of pilot symbol estimation. The report also explores the applications of pilot symbol estimation technique in mobile radio, broadcasting, and telecommunication systems.

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Mobile and Satellite
Communication Systems

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Table of Contents
Introduction...........................................................................................................................................2
Concept of pilot symbol aided channel technique in OFDM..................................................................2
Different types of pilot symbol channel estimation technique..............................................................4
Block type pilot estimation................................................................................................................4
Comb type pilot estimation...............................................................................................................5
The impact of the pilot symbol estimation on the future of telecommunication..................................6
Applications of pilot symbol estimation technique...............................................................................7
Advantages and disadvantages of the pilot symbol estimation.............................................................7
Advantages........................................................................................................................................7
Disadvantage.....................................................................................................................................7
Conclusion.............................................................................................................................................7
References.............................................................................................................................................9

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Introduction
The term pilot symbol aided channel is defined as the technique which is used in the
telecommunication system for improving the performance of communication channels.
The fundamental concept of this estimation technique is to multiplex training symbols
known to the receiver into the data stream [1]. However, by using such kind of
technique the receiver is able to evaluate the channel at any time period. The purpose of
this report is to describe the concept of pilot symbol aided channel estimation technique
in the field of OFDM telecommunication system. It is observed that such kind of
estimation technique is used in the mobile radio and broadcasting applications. This
report is divided into several sections which include the concept of pilot symbol
estimation, different types of pilot symbol technique, the impact of this technique on the
future of communication and advantages and disadvantages of pilot symbol estimation.
Concept of pilot symbol aided channel technique in OFDM
The term OFDM refers to the orthogonal frequency division multiplexing system which
is a communication method utilized for transmitting data or signals over indoor and
outdoor wireless networks. Mainly, the OFDM technique uses the fundamental concept
of pilot symbol estimation process for improving the performance of the
communication scheme. It is analysed that the pilot symbol estimation is used for a
single carrier system with fading channels which is mainly utilized in the field of
broadcasting applications [2]. Moreover, the filtering process used by pilot estimation
needs channel statistics for controlling and managing the efficiency of communication
networks used in the OFDM. The channel parameters in the OFDM can be collected with
the help of interpolation and the optimum interpolation is identified by the channel
statistics which are usually difficult to collect signals and data.

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The pilot symbol aided estimation is a time domain and various kinds of interpolation
filters are used for managing the performance of the OFDM system. A recent study
identified that pilot symbol estimation deliver robust estimates even for severe channel
situations and also suitable for OFDM channel systems [3]. The transmitter structure of
the OFDM system includes various key factors such as outer encoder, symbol mapper,
multiplexer, and pilot insertion. The below figure indicates the transmitter model of
coded OFDM technique and the pilot arrangement for OFDM system in the frequency-
time grid.
It is observed that every OFDM symbol vector in the frame is modulated with the help of
subcarrier signals using the concept of Fourier transform and guard interval process. In
the case of pilot arrangement Nf can be selected as the larger to the length of the
channel and Nt can be chosen by satisfying the channel coherence time [4].
The below equation shows the grid selection in pilot symbol estimation:

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The receiver section of the OFDM system involves various components, for example,
FFT system, pilot extraction, equalizer, channel estimation, outer decoder and so on.
The FFT is defined as the fast Fourier transform which is used in the field of pilot
symbol estimation for controlling and managing the input signals.
A recent study identified that for increasing the correctness of the network
approximation it is very important to add virtual pilot using an iterative channel and
data detection process [5]. Therefore, the pilot symbol estimation technique is sufficient
for controlling and managing the channel estimation errors occurred in the field of
OFDM communication systems.
Different types of pilot symbol channel estimation technique
It is observed that there are major two kinds of pilot symbol estimation techniques used
in the field of telecommunication systems which includes:
 Block type estimation
 Comb type estimation
Block type pilot estimation
In such kind of method, OFDM symbols are transferred occasionally where altogether
sub-carriers are utilized as aviators. If the station is continuous at the time of chunk
then there will be no network approximation fault produce in the signals transmitted
from one source to another [6]. It is analysed that the estimation process for OFDM can
be performed with the help of LSE and MMSE techniques. If inter symbol in the system
is removed by the protector intermission so, medium representation can be described
as:
Y= XFh+ W

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Here, X= diag { X(0),….. X(N-1)}
Y= [Y(0),……….. Y(N-1)]T
W= [W(0),……. W(N-1)]T
In such kind of pilot symbol estimation technique tones or signals are introduced into
complete subcarriers of experimental ciphers with a retro in time. However, the chunk
kind of pilot symbol estimation technique is additional effective for incidence discerning
networks and reduces the rate of estimation errors from the OFDM channels. Therefore,
in the field of pilot symbol estimation, the consumers first evaluate the channel and
after that use the similar estimation system with the complete blocks.
Comb type pilot estimation
In such kind of pilot symbol estimation technique, the pilot arrangements are mainly
distributed in every OFDM blocks. Such kind of estimation has a larger re-transmission
degree due to which this technique is widely used in the field of telecommunication
channels [7]. However, comb type pilot estimation deliver accurate confrontation to
debauched disappearing networks due to which certain sub-carriers involve the
experimental data or signals which will be determined by using the interpolating
system. As compared to the block pilot symbol estimation the comb estimation
technique is more effective for selecting frequency in the telecommunication system.
It is identified that in the comb pilot estimation pilots or signals are located at several
subcarriers in every OFDM character. In the field of comb pilot symbol estimation, the
network transmission system changes effective from one chunk to another due to which
channel estimation used in the current block cannot be utilized for the next block. So,
the comb-type pilot estimation can be used in the field of communication systems for
estimating the network transmission purpose in every block [8]. In the case of comb
pilot estimation, the pilot data is initially removed from the obtained sign and the
transferred channel is determined from the established blocks. Moreover, the channel
responses of the carrier signals which contain signals are interpolated with the help of
recent pilot channel replies.

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The impact of the pilot symbol estimation on the future of telecommunication
It is observed that the pilot symbol is one of the effective techniques which are now
used in the field of OFDM techniques. In the future generation of telecommunication
networks, pilot symbol estimation will positively affect the communication system.
Moreover, such kind of technique will change the way of communication and improve
the overall performance of the telecommunication networks in a future generation [9].
In this modern era, the rate of estimation error is very high due to which consumers are
not able to receive the effective signals but pilot type estimation technique address such
kind of problems and reduce the rate of estimation errors. In the future generation of
telecommunication, this technique will reduce the estimation errors in an effective
manner and monitor the overall efficiency of the communication channels [12].
With the help of such techniques, consumers can estimate the channel performance by
inserting pilot tones into all subcarriers of the OFDM systems. In the case of fast fading
channels, pilot symbol estimation technique will be used for providing better resistance
to the telecommunication networks [10]. The future of telecommunication networks
will adopt the pilot estimation technique in order to select the sensitive frequency for
data communication and increase the overall effectiveness of the system in a positive
manner [11]. Therefore, it is suggested that the by using pilot symbol estimation
process the future telecommunication networks will effectively improve the
performance of the communication and reduce risks factors that increase issues while
transferring data from one block to another.

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Applications of pilot symbol estimation technique
There are various applications of pilot symbol estimation approach which are described
below:
 Mobile radio system
 Broadcasting applications
 Telecommunication applications
 Reducing estimation errors from the networks
Advantages and disadvantages of the pilot symbol estimation
Advantages
 More effective
 Very reliable rather than other estimation techniques
 It has the ability to improve the overall performance of the communication
systems
 Reduce the rate of estimation errors and provide an effective frequency to the
communication channels
Disadvantage
 Very expensive
 Take more time for estimation
 Very complex rather than other
Conclusion
From the above discussion, it is concluded that the pilot symbol estimation is one of the
appropriate techniques for OFDM communication channels where it improves the
efficiency of the system. This report described the concept of pilot symbol estimation
along with their impact on the future generation of the telecommunication system. It is
identified that the in future the pilot symbol estimation will change the way of
interaction and improve the performance of telecommunication networks in an
effective manner. This study is based on the telecommunication system and readers and
the students can enhance their skills in the field of pilot symbol estimation technique.

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References
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Communications (ICC), vol. 5, no. 6, pp. 1-6, 2016.
[9]. W.O., Popoola, Z. Ghassemlooy and, B.G., Stewart, “Pilot-assisted PAPR reduction
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[11]. M. Yu and, P., Sadeghi, “A study of pilot-assisted OFDM channel estimation
methods with improvements for DVB-T2,” IEEE Transactions on Vehicular
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