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M. El Ghzaoui and S. Das
1 Introduction
The emergence of new services, such as IP telephony, video on demand, and data
exchange (Peer to Peer) and others …, are causing higher data rate requirements
over communication system. All these new services have been made possible thanks
to scientific advances in many fields such as microelectronics, signal processing,
digital communications, fiber optic development, and many more. Telecommunications operators must therefore develop and put in place the necessary infrastructure
that can allow access to these new technologies, for an increasing number of users,
while offering an increasing number of services. Thus, the deployment of wireless networks such as THz communication system will meet this constraint since it
offers a fairly wide bandwidth allowing more than 10 Gbps/s to be carried there [1].
However, the THz transmission channel is a difficult environment [2, 3]. Thus, the
current limits of the THZ system are essentially linked to those of the transmitters
and receivers [4]. So, communication over this THz channel appeals to innovative
challenges such as channel modeling, capacity analysis, modulation technics, and
other physical and link layer explanations [1, 5].
The communication channel is the main entity which transforms a transmitted
message to receiver. Different concepts of communication channels for the THz
system have been developed in recent years, intended for different research fields:
from electromagnetic propagation to information and communication theory. Understanding the THz channel: its physical parameters, properties, and modeling are
fundamental to the design of mobile communications systems. The THZ channel
is a frequency-selective channel [6, 7]. This frequency selectivity phenomenon is
aggravated by the presence of multiple paths effect. Due to the many reflections that
the signal can undergo in an urban environment, the receiver will receive a series of
echoes of varying amplitudes and delays. This problem of the multi-path channel is
critical in the case of a mobile radio channel, that is to say when the receiver and the
transmitter are not relatively fixed.
In order to meet these constraints and therefore to provide sufficient speed to
users to access these services, and to improve their transmission capacity. Many
techniques, often already used in radiofrequency transmissions, are proposed by the
literature in this sense [8]. This chapter will focus on OFDM modulation in the THz
context. This modulation is widely used in the context of radio communication to
enhance the spectral efficiency of the transmitted data and reduce multiple access
interference (MAI), thanks to the use of different frequency and orthogonal subcarriers between them. Furthermore, OFDM has received a lot of consideration in recent
years due to their capability to overcome frequency-selective fading by transmitting
data over narrow bands in parallel [9]. Indeed, the multi-carrier transmission systems
known under the name OFDM [10–12] are based on the principle of orthogonality of
the modulation filters. The OFDM modulation is carried out by an inverse discrete
Fourier transformation (IDFT). Let C j,k be the sequence of symbols to be sent at
the cadence Ts. These symbols generally belong to a finite alphabet resulting from
a given constellation. The initial data symbol is distributed over N parallel symbols,
M. El Ghzaoui and S. Das
1 Introduction
The emergence of new services, such as IP telephony, video on demand, and data
exchange (Peer to Peer) and others …, are causing higher data rate requirements
over communication system. All these new services have been made possible thanks
to scientific advances in many fields such as microelectronics, signal processing,
digital communications, fiber optic development, and many more. Telecommunications operators must therefore develop and put in place the necessary infrastructure
that can allow access to these new technologies, for an increasing number of users,
while offering an increasing number of services. Thus, the deployment of wireless networks such as THz communication system will meet this constraint since it
offers a fairly wide bandwidth allowing more than 10 Gbps/s to be carried there [1].
However, the THz transmission channel is a difficult environment [2, 3]. Thus, the
current limits of the THZ system are essentially linked to those of the transmitters
and receivers [4]. So, communication over this THz channel appeals to innovative
challenges such as channel modeling, capacity analysis, modulation technics, and
other physical and link layer explanations [1, 5].
The communication channel is the main entity which transforms a transmitted
message to receiver. Different concepts of communication channels for the THz
system have been developed in recent years, intended for different research fields:
from electromagnetic propagation to information and communication theory. Understanding the THz channel: its physical parameters, properties, and modeling are
fundamental to the design of mobile communications systems. The THZ channel
is a frequency-selective channel [6, 7]. This frequency selectivity phenomenon is
aggravated by the presence of multiple paths effect. Due to the many reflections that
the signal can undergo in an urban environment, the receiver will receive a series of
echoes of varying amplitudes and delays. This problem of the multi-path channel is
critical in the case of a mobile radio channel, that is to say when the receiver and the
transmitter are not relatively fixed.
In order to meet these constraints and therefore to provide sufficient speed to
users to access these services, and to improve their transmission capacity. Many
techniques, often already used in radiofrequency transmissions, are proposed by the
literature in this sense [8]. This chapter will focus on OFDM modulation in the THz
context. This modulation is widely used in the context of radio communication to
enhance the spectral efficiency of the transmitted data and reduce multiple access
interference (MAI), thanks to the use of different frequency and orthogonal subcarriers between them. Furthermore, OFDM has received a lot of consideration in recent
years due to their capability to overcome frequency-selective fading by transmitting
data over narrow bands in parallel [9]. Indeed, the multi-carrier transmission systems
known under the name OFDM [10–12] are based on the principle of orthogonality of
the modulation filters. The OFDM modulation is carried out by an inverse discrete
Fourier transformation (IDFT). Let C j,k be the sequence of symbols to be sent at
the cadence Ts. These symbols generally belong to a finite alphabet resulting from
a given constellation. The initial data symbol is distributed over N parallel symbols,