الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
The fth generation (5G) is the next generation of wireless cellular networks that will
support a larger capacity and a higher data rate than the previous generations through
the emergence of new technologies and also by having a novel cellular architecture. As the
number of mobile subscribers and the number of wireless devices increase every year, and
the size of multimedia contents such as images, audios and videos continuously increases,
there is a continuous demand for a larger capacity wireless communication system that
can support high data rates. In addition to that the world’s trend is what is called green
communication to eliminate the environment pollution and decrease the cost of electricity
usage. The fourth generation (4G) system with its current technologies cannot face the
future requirements, because the band dedicated for wireless cellular communication is
nearly occupied and the 4G system was not built to be an energy ecient system. These
aspects encourage the researchers to think beyond the 4G and to have a 5G system. Many
researchers agree that massive multiple-input multiple-output (MIMO), cognitive radio,
spatial multiplexing and millimeter wave communication are promising technologies to be
used in the 5G system.
Massive MIMO technology is a very good technology to achieve the spectral and energy
eciencies requirements of the 5G system. MIMO is the technology of using multiple antennas
at both the transmitter and the receiver. This has the e ect of creating multiple
communication channels from the same time-frequency channel, where each communication
channel is identi ed by its propagation factor. MIMO technology is being used in the
4G, but with limited equal numbers of antennas at both the base station (BS) and the
mobile terminal for suitable terminal size. To maximize the bene ts of MIMO, increase
the system capacity and also keep small terminal size, massive MIMO technology has
been proposed, in which the BS has a very large number of antennas to serve many single
antenna terminals at the same time-frequency resources. There are many challenges
i
facing the practical deployment of massive MIMO such as pilot contamination, operation
in frequency division duplex (FDD) mode, accurate propagation model and hardware impairments.
The problem of pilot contamination is considered as the bottleneck of the massive MIMO
performance. This problem results during the process of channel estimation, if the same
pilot sequence is used by more than one terminal at the same time. This problem causes
interference during data transmission that exists even if we equipped the BS with an
unlimited number of antennas. Due to its importance, the pilot contamination problem
has been heavily investigated in many researches.
In this thesis, we propose two scenarios to mitigate the problem of pilot contamination.
In our scenarios, we try to decrease the number of interfering cells by avoiding the simultaneous
pilot transmission from all the cells. We also try to enhance the performance
of the low channel gain terminals located near the edges of the cells, which are severely
a ected by the problem of pilot contamination.
iiThe fth generation (5G) is the next generation of wireless cellular networks that will
support a larger capacity and a higher data rate than the previous generations through
the emergence of new technologies and also by having a novel cellular architecture. As the
number of mobile subscribers and the number of wireless devices increase every year, and
the size of multimedia contents such as images, audios and videos continuously increases,
there is a continuous demand for a larger capacity wireless communication system that
can support high data rates. In addition to that the world’s trend is what is called green
communication to eliminate the environment pollution and decrease the cost of electricity
usage. The fourth generation (4G) system with its current technologies cannot face the
future requirements, because the band dedicated for wireless cellular communication is
nearly occupied and the 4G system was not built to be an energy ecient system. These
aspects encourage the researchers to think beyond the 4G and to have a 5G system. Many
researchers agree that massive multiple-input multiple-output (MIMO), cognitive radio,
spatial multiplexing and millimeter wave communication are promising technologies to be
used in the 5G system.
Massive MIMO technology is a very good technology to achieve the spectral and energy
eciencies requirements of the 5G system. MIMO is the technology of using multiple antennas
at both the transmitter and the receiver. This has the e ect of creating multiple
communication channels from the same time-frequency channel, where each communication
channel is identi ed by its propagation factor. MIMO technology is being used in the
4G, but with limited equal numbers of antennas at both the base station (BS) and the
mobile terminal for suitable terminal size. To maximize the bene ts of MIMO, increase
the system capacity and also keep small terminal size, massive MIMO technology has
been proposed, in which the BS has a very large number of antennas to serve many single
antenna terminals at the same time-frequency resources. There are many challenges
i
facing the practical deployment of massive MIMO such as pilot contamination, operation
in frequency division duplex (FDD) mode, accurate propagation model and hardware impairments.
The problem of pilot contamination is considered as the bottleneck of the massive MIMO
performance. This problem results during the process of channel estimation, if the same
pilot sequence is used by more than one terminal at the same time. This problem causes
interference during data transmission that exists even if we equipped the BS with an
unlimited number of antennas. Due to its importance, the pilot contamination problem
has been heavily investigated in many researches.
In this thesis, we propose two scenarios to mitigate the problem of pilot contamination.
In our scenarios, we try to decrease the number of interfering cells by avoiding the simultaneous
pilot transmission from all the cells. We also try to enhance the performance
of the low channel gain terminals located near the edges of the cells, which are severely
a ected by the problem of pilot contamination.
iiThe fth generation (5G) is the next generation of wireless cellular networks that will
support a larger capacity and a higher data rate than the previous generations through
the emergence of new technologies and also by having a novel cellular architecture. As the
number of mobile subscribers and the number of wireless devices increase every year, and
the size of multimedia contents such as images, audios and videos continuously increases,
there is a continuous demand for a larger capacity wireless communication system that
can support high data rates. In addition to that the world’s trend is what is called green
communication to eliminate the environment pollution and decrease the cost of electricity
usage. The fourth generation (4G) system with its current technologies cannot face the
future requirements, because the band dedicated for wireless cellular communication is
nearly occupied and the 4G system was not built to be an energy ecient system. These
aspects encourage the researchers to think beyond the 4G and to have a 5G system. Many
researchers agree that massive multiple-input multiple-output (MIMO), cognitive radio,
spatial multiplexing and millimeter wave communication are promising technologies to be
used in the 5G system.
Massive MIMO technology is a very good technology to achieve the spectral and energy
eciencies requirements of the 5G system. MIMO is the technology of using multiple antennas
at both the transmitter and the receiver. This has the e ect of creating multiple
communication channels from the same time-frequency channel, where each communication
channel is identi ed by its propagation factor. MIMO technology is being used in the
4G, but with limited equal numbers of antennas at both the base station (BS) and the
mobile terminal for suitable terminal size. To maximize the bene ts of MIMO, increase
the system capacity and also keep small terminal size, massive MIMO technology has
been proposed, in which the BS has a very large number of antennas to serve many single
antenna terminals at the same time-frequency resources. There are many challenges
i
facing the practical deployment of massive MIMO such as pilot contamination, operation
in frequency division duplex (FDD) mode, accurate propagation model and hardware impairments.
The problem of pilot contamination is considered as the bottleneck of the massive MIMO
performance. This problem results during the process of channel estimation, if the same
pilot sequence is used by more than one terminal at the same time. This problem causes
interference during data transmission that exists even if we equipped the BS with an
unlimited number of antennas. Due to its importance, the pilot contamination problem
has been heavily investigated in many researches.
In this thesis, we propose two scenarios to mitigate the problem of pilot contamination.
In our scenarios, we try to decrease the number of interfering cells by avoiding the simultaneous
pilot transmission from all the cells. We also try to enhance the performance
of the low channel gain terminals located near the edges of the cells, which are severely
a ected by the problem of pilot contamination.
iiThe fth generation (5G) is the next generation of wireless cellular networks that will
support a larger capacity and a higher data rate than the previous generations through
the emergence of new technologies and also by having a novel cellular architecture. As the
number of mobile subscribers and the number of wireless devices increase every year, and
the size of multimedia contents such as images, audios and videos continuously increases,
there is a continuous demand for a larger capacity wireless communication system that
can support high data rates. In addition to that the world’s trend is what is called green
communication to eliminate the environment pollution and decrease the cost of electricity
usage. The fourth generation (4G) system with its current technologies cannot face the
future requirements, because the band dedicated for wireless cellular communication is
nearly occupied and the 4G system was not built to be an energy ecient system. These
aspects encourage the researchers to think beyond the 4G and to have a 5G system. Many
researchers agree that massive multiple-input multiple-output (MIMO), cognitive radio,
spatial multiplexing and millimeter wave communication are promising technologies to be
used in the 5G system.
Massive MIMO technology is a very good technology to achieve the spectral and energy
eciencies requirements of the 5G system. MIMO is the technology of using multiple antennas
at both the transmitter and the receiver. This has the e ect of creating multiple
communication channels from the same time-frequency channel, where each communication
channel is identi ed by its propagation factor. MIMO technology is being used in the
4G, but with limited equal numbers of antennas at both the base station (BS) and the
mobile terminal for suitable terminal size. To maximize the bene ts of MIMO, increase
the system capacity and also keep small terminal size, massive MIMO technology has
been proposed, in which the BS has a very large number of antennas to serve many single
antenna terminals at the same time-frequency resources. There are many challenges
i
facing the practical deployment of massive MIMO such as pilot contamination, operation
in frequency division duplex (FDD) mode, accurate propagation model and hardware impairments.
The problem of pilot contamination is considered as the bottleneck of the massive MIMO
performance. This problem results during the process of channel estimation, if the same
pilot sequence is used by more than one terminal at the same time. This problem causes
interference during data transmission that exists even if we equipped the BS with an
unlimited number of antennas. Due to its importance, the pilot contamination problem
has been heavily investigated in many researches.
In this thesis, we propose two scenarios to mitigate the problem of pilot contamination.
In our scenarios, we try to decrease the number of interfering cells by avoiding the simultaneous
pilot transmission from all the cells. We also try to enhance the performance
of the low channel gain terminals located near the edges of the cells, which are severely
a ected by the problem of pilot contamination.
iiThe fth generation (5G) is the next generation of wireless cellular networks that will
support a larger capacity and a higher data rate than the previous generations through
the emergence of new technologies and also by having a novel cellular architecture. As the
number of mobile subscribers and the number of wireless devices increase every year, and
the size of multimedia contents such as images, audios and videos continuously increases,
there is a continuous demand for a larger capacity wireless communication system that
can support high data rates. In addition to that the world’s trend is what is called green
communication to eliminate the environment pollution and decrease the cost of electricity
usage. The fourth generation (4G) system with its current technologies cannot face the
future requirements, because the band dedicated for wireless cellular communication is
nearly occupied and the 4G system was not built to be an energy ecient system. These
aspects encourage the researchers to think beyond the 4G and to have a 5G system. Many
researchers agree that massive multiple-input multiple-output (MIMO), cognitive radio,
spatial multiplexing and millimeter wave communication are promising technologies to be
used in the 5G system.
Massive MIMO technology is a very good technology to achieve the spectral and energy
eciencies requirements of the 5G system. MIMO is the technology of using multiple antennas
at both the transmitter and the receiver. This has the e ect of creating multiple
communication channels from the same time-frequency channel, where each communication
channel is identi ed by its propagation factor. MIMO technology is being used in the
4G, but with limited equal numbers of antennas at both the base station (BS) and the
mobile terminal for suitable terminal size. To maximize the bene ts of MIMO, increase
the system capacity and also keep small terminal size, massive MIMO technology has
been proposed, in which the BS has a very large number of antennas to serve many single
antenna terminals at the same time-frequency resources. There are many challenges
i
facing the practical deployment of massive MIMO such as pilot contamination, operation
in frequency division duplex (FDD) mode, accurate propagation model and hardware impairments.
The problem of pilot contamination is considered as the bottleneck of the massive MIMO
performance. This problem results during the process of channel estimation, if the same
pilot sequence is used by more than one terminal at the same time. This problem causes
interference during data transmission that exists even if we equipped the BS with an
unlimited number of antennas. Due to its importance, the pilot contamination problem
has been heavily investigated in many researches.
In this thesis, we propose two scenarios to mitigate the problem of pilot contamination.
In our scenarios, we try to decrease the number of interfering cells by avoiding the simultaneous
pilot transmission from all the cells. We also try to enhance the performance
of the low channel gain terminals located near the edges of the cells, which are severely
a ected by the problem of pilot contamination.
iiThe fth generation (5G) is the next generation of wireless cellular networks that will
support a larger capacity and a higher data rate than the previous generations through
the emergence of new technologies and also by having a novel cellular architecture. As the
number of mobile subscribers and the number of wireless devices increase every year, and
the size of multimedia contents such as images, audios and videos continuously increases,
there is a continuous demand for a larger capacity wireless communication system that
can support high data rates. In addition to that the world’s trend is what is called green
communication to eliminate the environment pollution and decrease the cost of electricity
usage. The fourth generation (4G) system with its current technologies cannot face the
future requirements, because the band dedicated for wireless cellular communication is
nearly occupied and the 4G system was not built to be an energy ecient system. These
aspects encourage the researchers to think beyond the 4G and to have a 5G system. Many
researchers agree that massive multiple-input multiple-output (MIMO), cognitive radio,
spatial multiplexing and millimeter wave communication are promising technologies to be
used in the 5G system.
Massive MIMO technology is a very good technology to achieve the spectral and energy
eciencies requirements of the 5G system. MIMO is the technology of using multiple antennas
at both the transmitter and the receiver. This has the e ect of creating multiple
communication channels from the same time-frequency channel, where each communication
channel is identi ed by its propagation factor. MIMO technology is being used in the
4G, but with limited equal numbers of antennas at both the base station (BS) and the
mobile terminal for suitable terminal size. To maximize the bene ts of MIMO, increase
the system capacity and also keep small terminal size, massive MIMO technology has
been proposed, in which the BS has a very large number of antennas to serve many single
antenna terminals at the same time-frequency resources. There are many challenges
i
facing the practical deployment of massive MIMO such as pilot contamination, operation
in frequency division duplex (FDD) mode, accurate propagation model and hardware impairments.
The problem of pilot contamination is considered as the bottleneck of the massive MIMO
performance. This problem results during the process of channel estimation, if the same
pilot sequence is used by more than one terminal at the same time. This problem causes
interference during data transmission that exists even if we equipped the BS with an
unlimited number of antennas. Due to its importance, the pilot contamination problem
has been heavily investigated in many researches.
In this thesis, we propose two scenarios to mitigate the problem of pilot contamination.
In our scenarios, we try to decrease the number of interfering cells by avoiding the simultaneous
pilot transmission from all the cells. We also try to enhance the performance
of the low channel gain terminals located near the edges of the cells, which are severely
a ected by the problem of pilot contamination.
iiThe fth generation (5G) is the next generation of wireless cellular networks that will
support a larger capacity and a higher data rate than the previous generations through
the emergence of new technologies and also by having a novel cellular architecture. As the
number of mobile subscribers and the number of wireless devices increase every year, and
the size of multimedia contents such as images, audios and videos continuously increases,
there is a continuous demand for a larger capacity wireless communication system that
can support high data rates. In addition to that the world’s trend is what is called green
communication to eliminate the environment pollution and decrease the cost of electricity
usage. The fourth generation (4G) system with its current technologies cannot face the
future requirements, because the band dedicated for wireless cellular communication is
nearly occupied and the 4G system was not built to be an energy ecient system. These
aspects encourage the researchers to think beyond the 4G and to have a 5G system. Many
researchers agree that massive multiple-input multiple-output (MIMO), cognitive radio,
spatial multiplexing and millimeter wave communication are promising technologies to be
used in the 5G system.
Massive MIMO technology is a very good technology to achieve the spectral and energy
eciencies requirements of the 5G system. MIMO is the technology of using multiple antennas
at both the transmitter and the receiver. This has the e ect of creating multiple
communication channels from the same time-frequency channel, where each communication
channel is identi ed by its propagation factor. MIMO technology is being used in the
4G, but with limited equal numbers of antennas at both the base station (BS) and the
mobile terminal for suitable terminal size. To maximize the bene ts of MIMO, increase
the system capacity and also keep small terminal size, massive MIMO technology has
been proposed, in which the BS has a very large number of antennas to serve many single
antenna terminals at the same time-frequency resources. There are many challenges
i
facing the practical deployment of massive MIMO such as pilot contamination, operation
in frequency division duplex (FDD) mode, accurate propagation model and hardware impairments.
The problem of pilot contamination is considered as the bottleneck of the massive MIMO
performance. This problem results during the process of channel estimation, if the same
pilot sequence is used by more than one terminal at the same time. This problem causes
interference during data transmission that exists even if we equipped the BS with an
unlimited number of antennas. Due to its importance, the pilot contamination problem
has been heavily investigated in many researches.
In this thesis, we propose two scenarios to mitigate the problem of pilot contamination.
In our scenarios, we try to decrease the number of interfering cells by avoiding the simultaneous
pilot transmission from all the cells. We also try to enhance the performance
of the low channel gain terminals located near the edges of the cells, which are severely
a ected by the problem of pilot contamination.
iiThe fth generation (5G) is the next generation of wireless cellular networks that will
support a larger capacity and a higher data rate than the previous generations through
the emergence of new technologies and also by having a novel cellular architecture. As the
number of mobile subscribers and the number of wireless devices increase every year, and
the size of multimedia contents such as images, audios and videos continuously increases,
there is a continuous demand for a larger capacity wireless communication system that
can support high data rates. In addition to that the world’s trend is what is called green
communication to eliminate the environment pollution and decrease the cost of electricity
usage. The fourth generation (4G) system with its current technologies cannot face the
future requirements, because the band dedicated for wireless cellular communication is
nearly occupied and the 4G system was not built to be an energy ecient system. These
aspects encourage the researchers to think beyond the 4G and to have a 5G system. Many
researchers agree that massive multiple-input multiple-output (MIMO), cognitive radio,
spatial multiplexing and millimeter wave communication are promising technologies to be
used in the 5G system.
Massive MIMO technology is a very good technology to achieve the spectral and energy
eciencies requirements of the 5G system. MIMO is the technology of using multiple antennas
at both the transmitter and the receiver. This has the e ect of creating multiple
communication channels from the same time-frequency channel, where each communication
channel is identi ed by its propagation factor. MIMO technology is being used in the
4G, but with limited equal numbers of antennas at both the base station (BS) and the
mobile terminal for suitable terminal size. To maximize the bene ts of MIMO, increase
the system capacity and also keep small terminal size, massive MIMO technology has
been proposed, in which the BS has a very large number of antennas to serve many single
antenna terminals at the same time-frequency resources. There are many challenges
i
facing the practical deployment of massive MIMO such as pilot contamination, operation
in frequency division duplex (FDD) mode, accurate propagation model and hardware impairments.
The problem of pilot contamination is considered as the bottleneck of the massive MIMO
performance. This problem results during the process of channel estimation, if the same
pilot sequence is used by more than one terminal at the same time. This problem causes
interference during data transmission that exists even if we equipped the BS with an
unlimited number of antennas. Due to its importance, the pilot contamination problem
has been heavily investigated in many researches.
In this thesis, we propose two scenarios to mitigate the problem of pilot contamination.
In our scenarios, we try to decrease the number of interfering cells by avoiding the simultaneous
pilot transmission from all the cells. We also try to enhance the performance
of the low channel gain terminals located near the edges of the cells, which are severely
a ected by the problem of pilot contamination.
iiThe fth generation (5G) is the next generation of wireless cellular networks that will
support a larger capacity and a higher data rate than the previous generations through
the emergence of new technologies and also by having a novel cellular architecture. As the
number of mobile subscribers and the number of wireless devices increase every year, and
the size of multimedia contents such as images, audios and videos continuously increases,
there is a continuous demand for a larger capacity wireless communication system that
can support high data rates. In addition to that the world’s trend is what is called green
communication to eliminate the environment pollution and decrease the cost of electricity
usage. The fourth generation (4G) system with its current technologies cannot face the
future requirements, because the band dedicated for wireless cellular communication is
nearly occupied and the 4G system was not built to be an energy ecient system. These
aspects encourage the researchers to think beyond the 4G and to have a 5G system. Many
researchers agree that massive multiple-input multiple-output (MIMO), cognitive radio,
spatial multiplexing and millimeter wave communication are promising technologies to be
used in the 5G system.
Massive MIMO technology is a very good technology to achieve the spectral and energy
eciencies requirements of the 5G system. MIMO is the technology of using multiple antennas
at both the transmitter and the receiver. This has the e ect of creating multiple
communication channels from the same time-frequency channel, where each communication
channel is identi ed by its propagation factor. MIMO technology is being used in the
4G, but with limited equal numbers of antennas at both the base station (BS) and the
mobile terminal for suitable terminal size. To maximize the bene ts of MIMO, increase
the system capacity and also keep small terminal size, massive MIMO technology has
been proposed, in which the BS has a very large number of antennas to serve many single
antenna terminals at the same time-frequency resources. There are many challenges
i
facing the practical deployment of massive MIMO such as pilot contamination, operation
in frequency division duplex (FDD) mode, accurate propagation model and hardware impairments.
The problem of pilot contamination is considered as the bottleneck of the massive MIMO
performance. This problem results during the process of channel estimation, if the same
pilot sequence is used by more than one terminal at the same time. This problem causes
interference during data transmission that exists even if we equipped the BS with an
unlimited number of antennas. Due to its importance, the pilot contamination problem
has been heavily investigated in many researches.
In this thesis, we propose two scenarios to mitigate the problem of pilot contamination.
In our scenarios, we try to decrease the number of interfering cells by avoiding the simultaneous
pilot transmission from all the cells. We also try to enhance the performance
of the low channel gain terminals located near the edges of the cells, which are severely
a ected by the problem of pilot contamination.
iiThe fth generation (5G) is the next generation of wireless cellular networks that will
support a larger capacity and a higher data rate than the previous generations through
the emergence of new technologies and also by having a novel cellular architecture. As the
number of mobile subscribers and the number of wireless devices increase every year, and
the size of multimedia contents such as images, audios and videos continuously increases,
there is a continuous demand for a larger capacity wireless communication system that
can support high data rates. In addition to that the world’s trend is what is called green
communication to eliminate the environment pollution and decrease the cost of electricity
usage. The fourth generation (4G) system with its current technologies cannot face the
future requirements, because the band dedicated for wireless cellular communication is
nearly occupied and the 4G system was not built to be an energy ecient system. These
aspects encourage the researchers to think beyond the 4G and to have a 5G system. Many
researchers agree that massive multiple-input multiple-output (MIMO), cognitive radio,
spatial multiplexing and millimeter wave communication are promising technologies to be
used in the 5G system.
Massive MIMO technology is a very good technology to achieve the spectral and energy
eciencies requirements of the 5G system. MIMO is the technology of using multiple antennas
at both the transmitter and the receiver. This has the e ect of creating multiple
communication channels from the same time-frequency channel, where each communication
channel is identi ed by its propagation factor. MIMO technology is being used in the
4G, but with limited equal numbers of antennas at both the base station (BS) and the
mobile terminal for suitable terminal size. To maximize the bene ts of MIMO, increase
the system capacity and also keep small terminal size, massive MIMO technology has
been proposed, in which the BS has a very large number of antennas to serve many single
antenna terminals at the same time-frequency resources. There are many challenges
i
facing the practical deployment of massive MIMO such as pilot contamination, operation
in frequency division duplex (FDD) mode, accurate propagation model and hardware impairments.
The problem of pilot contamination is considered as the bottleneck of the massive MIMO
performance. This problem results during the process of channel estimation, if the same
pilot sequence is used by more than one terminal at the same time. This problem causes
interference during data transmission that exists even if we equipped the BS with an
unlimited number of antennas. Due to its importance, the pilot contamination problem
has been heavily investigated in many researches.
In this thesis, we propose two scenarios to mitigate the problem of pilot contamination.
In our scenarios, we try to decrease the number of interfering cells by avoiding the simultaneous
pilot transmission from all the cells. We also try to enhance the performance
of the low channel gain terminals located near the edges of the cells, which are severely
a ected by the problem of pilot contamination.
iiThe fth generation (5G) is the next generation of wireless cellular networks that will
support a larger capacity and a higher data rate than the previous generations through
the emergence of new technologies and also by having a novel cellular architecture. As the
number of mobile subscribers and the number of wireless devices increase every year, and
the size of multimedia contents such as images, audios and videos continuously increases,
there is a continuous demand for a larger capacity wireless communication system that
can support high data rates. In addition to that the world’s trend is what is called green
communication to eliminate the environment pollution and decrease the cost of electricity
usage. The fourth generation (4G) system with its current technologies cannot face the
future requirements, because the band dedicated for wireless cellular communication is
nearly occupied and the 4G system was not built to be an energy ecient system. These
aspects encourage the researchers to think beyond the 4G and to have a 5G system. Many
researchers agree that massive multiple-input multiple-output (MIMO), cognitive radio,
spatial multiplexing and millimeter wave communication are promising technologies to be
used in the 5G system.
Massive MIMO technology is a very good technology to achieve the spectral and energy
eciencies requirements of the 5G system. MIMO is the technology of using multiple antennas
at both the transmitter and the receiver. This has the e ect of creating multiple
communication channels from the same time-frequency channel, where each communication
channel is identi ed by its propagation factor. MIMO technology is being used in the
4G, but with limited equal numbers of antennas at both the base station (BS) and the
mobile terminal for suitable terminal size. To maximize the bene ts of MIMO, increase
the system capacity and also keep small terminal size, massive MIMO technology has
been proposed, in which the BS has a very large number of antennas to serve many single
antenna terminals at the same time-frequency resources. There are many challenges
i
facing the practical deployment of massive MIMO such as pilot contamination, operation
in frequency division duplex (FDD) mode, accurate propagation model and hardware impairments.
The problem of pilot contamination is considered as the bottleneck of the massive MIMO
performance. This problem results during the process of channel estimation, if the same
pilot sequence is used by more than one terminal at the same time. This problem causes
interference during data transmission that exists even if we equipped the BS with an
unlimited number of antennas. Due to its importance, the pilot contamination problem
has been heavily investigated in many researches.
In this thesis, we propose two scenarios to mitigate the problem of pilot contamination.
In our scenarios, we try to decrease the number of interfering cells by avoiding the simultaneous
pilot transmission from all the cells. We also try to enhance the performance
of the low channel gain terminals located near the edges of the cells, which are severely
a ected by the problem of pilot contamination.
iiThe fth generation (5G) is the next generation of wireless cellular networks that will
support a larger capacity and a higher data rate than the previous generations through
the emergence of new technologies and also by having a novel cellular architecture. As the
number of mobile subscribers and the number of wireless devices increase every year, and
the size of multimedia contents such as images, audios and videos continuously increases,
there is a continuous demand for a larger capacity wireless communication system that
can support high data rates. In addition to that the world’s trend is what is called green
communication to eliminate the environment pollution and decrease the cost of electricity
usage. The fourth generation (4G) system with its current technologies cannot face the
future requirements, because the band dedicated for wireless cellular communication is
nearly occupied and the 4G system was not built to be an energy ecient system. These
aspects encourage the researchers to think beyond the 4G and to have a 5G system. Many
researchers agree that massive multiple-input multiple-output (MIMO), cognitive radio,
spatial multiplexing and millimeter wave communication are promising technologies to be
used in the 5G system.
Massive MIMO technology is a very good technology to achieve the spectral and energy
eciencies requirements of the 5G system. MIMO is the technology of using multiple antennas
at both the transmitter and the receiver. This has the e ect of creating multiple
communication channels from the same time-frequency channel, where each communication
channel is identi ed by its propagation factor. MIMO technology is being used in the
4G, but with limited equal numbers of antennas at both the base station (BS) and the
mobile terminal for suitable terminal size. To maximize the bene ts of MIMO, increase
the system capacity and also keep small terminal size, massive MIMO technology has
been proposed, in which the BS has a very large number of antennas to serve many single
antenna terminals at the same time-frequency resources. There are many challenges
i
facing the practical deployment of massive MIMO such as pilot contamination, operation
in frequency division duplex (FDD) mode, accurate propagation model and hardware impairments.
The problem of pilot contamination is considered as the bottleneck of the massive MIMO
performance. This problem results during the process of channel estimation, if the same
pilot sequence is used by more than one terminal at the same time. This problem causes
interference during data transmission that exists even if we equipped the BS with an
unlimited number of antennas. Due to its importance, the pilot contamination problem
has been heavily investigated in many researches.
In this thesis, we propose two scenarios to mitigate the problem of pilot contamination.
In our scenarios, we try to decrease the number of interfering cells by avoiding the simultaneous
pilot transmission from all the cells. We also try to enhance the performance
of the low channel gain terminals located near the edges of the cells, which are severely
a ected by the problem of pilot contamination.
iiThe fth generation (5G) is the next generation of wireless cellular networks that will
support a larger capacity and a higher data rate than the previous generations through
the emergence of new technologies and also by having a novel cellular architecture. As the
number of mobile subscribers and the number of wireless devices increase every year, and
the size of multimedia contents such as images, audios and videos continuously increases,
there is a continuous demand for a larger capacity wireless communication system that
can support high data rates. In addition to that the world’s trend is what is called green
communication to eliminate the environment pollution and decrease the cost of electricity
usage. The fourth generation (4G) system with its current technologies cannot face the
future requirements, because the band dedicated for wireless cellular communication is
nearly occupied and the 4G system was not built to be an energy ecient system. These
aspects encourage the researchers to think beyond the 4G and to have a 5G system. Many
researchers agree that massive multiple-input multiple-output (MIMO), cognitive radio,
spatial multiplexing and millimeter wave communication are promising technologies to be
used in the 5G system.
Massive MIMO technology is a very good technology to achieve the spectral and energy
eciencies requirements of the 5G system. MIMO is the technology of using multiple antennas
at both the transmitter and the receiver. This has the e ect of creating multiple
communication channels from the same time-frequency channel, where each communication
channel is identi ed by its propagation factor. MIMO technology is being used in the
4G, but with limited equal numbers of antennas at both the base station (BS) and the
mobile terminal for suitable terminal size. To maximize the bene ts of MIMO, increase
the system capacity and also keep small terminal size, massive MIMO technology has
been proposed, in which the BS has a very large number of antennas to serve many single
antenna terminals at the same time-frequency resources. There are many challenges
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facing the practical deployment of massive MIMO such as pilot contamination, operation
in frequency division duplex (FDD) mode, accurate propagation model and hardware impairments.
The problem of pilot contamination is considered as the bottleneck of the massive MIMO
performance. This problem results during the process of channel estimation, if the same
pilot sequence is used by more than one terminal at the same time. This problem causes
interference during data transmission that exists even if we equipped the BS with an
unlimited number of antennas. Due to its importance, the pilot contamination problem
has been heavily investigated in many researches.
In this thesis, we propose two scenarios to mitigate the problem of pilot contamination.
In our scenarios, we try to decrease the number of interfering cells by avoiding the simultaneous
pilot transmission from all the cells. We also try to enhance the performance
of the low channel gain terminals located near the edges of the cells, which are severely
a ected by the problem of pilot contamination.