Multi Carrier Code Division Multiple Access (MC-CDMA) is a well known technique for high speed
wireless data transmission .Two advanced technology was included in the MC-CDMA structure, such as
orthogonal frequency division multiplex (OFDM) and the code division multiple access (CDMA),so that it
benefits from the robustness of OFDM against multipath environment and from the capability of multiuser
multiplexing services that is achieved via (CDMA) system. MC-CDMA is a multicarrier spread spectrum
system which is classified as the candidate scheme for future mobile radio systems. In this paper MCCDMA
system, with Rayleigh fading channel and 16QAM array modulation, was simulated to investigate
the effects of different parameters on the system performance, such as processing gain; number of paths;
number of users; interleaving; and coding ratio.MC-CDMA performances can be considerably improved
by proper selection of these parameters. As expected, results show that MC-CDMA has a better performance over CDMA system.
A DDRESSING T HE M ULTICHANNEL S ELECTION , S CHEDULING A ND C OORDINATION...pijans
We discuss a new multichannel coordination and sche
duling challenge called the Multichannel Scheduling
Cost (MSC). It is caused by the inability of the co
ntrol channel to schedule simultaneous transmission
s
resulting in data channels lying idle and their ban
dwidth underutilized. As a result, wasted bandwidth
increases as the number of data channels increases.
To address this challenge, a cyclic scheduling
Algorithm (CSA) is proposed. It employs one dedicat
ed signaling channel and 4 data channels. It is
premised on a proactive channel reservation scheme
which reduces the idleness of channels. The scheme
ensures that data channels are reserved while they
are still busy. The data channels are reserved whil
e
their remaining transmission duration is equal to t
he virtual carrier sensing duration. This gives the
next
pair sufficient time to reserve the current data ch
annel before it becomes available, limiting the MSC
to the
first cycle. The simulation results show a performa
nce benefit of the CSA scheme in addressing the eff
ects
of the MSC
Effect of Interleaved FEC Code on Wavelet Based MC-CDMA System with Alamouti ...IJCSEIT Journal
In this paper, the impact of Forward Error Correction (FEC) code namely Trellis code with interleaver on
the performance of wavelet based MC-CDMA wireless communication system with the implementation of
Alamouti antenna diversity scheme has been investigated in terms of Bit Error Rate (BER) as a function of
Signal-to-Noise Ratio (SNR) per bit. Simulation of the system under proposed study has been done in M-ary
modulation schemes (MPSK, MQAM and DPSK) over AWGN and Rayleigh fading channel incorporating
Walsh Hadamard code as orthogonal spreading code to discriminate the message signal for individual
user. It is observed via computer simulation that the performance of the interleaved coded based proposed
system outperforms than that of the uncoded system in all modulation schemes over Rayleigh fading
channel.
LTE QOS DYNAMIC RESOURCE BLOCK ALLOCATION WITH POWER SOURCE LIMITATION AND QU...IJCNCJournal
3GPP has defined the long term evolution (LTE) for 3G radio access in order to maintain the future
competitiveness for 3G technology, the system provides the capability of supporting a mixture of services
with different quality of service (QoS) requirements. This paper proposes a new cross-layer scheduling
algorithm to satisfy better QoS parameters for real time applications. The proposed algorithm takes care of
allocating resource blocks (RBs) with different modulation and coding schemes (MCS) according to target
bit error rate (BER), user equipment supportable MCS, queue stability constraints and available transmit
power constraints. The proposed algorithm has been valued, compared with an earlier allocation algorithm
in terms of service rate and packet delay and showed better performance regards the real time
applications.
Some of the key driving forces behind the transition from the UMTS based cellular system to the Long Term Evolution Advanced (LTE-A) are to improve the mean and the cell-edge throughput, improve the user fairness, and improve the quality of service (QoS) satisfaction for all users. In the latter system, relays appear as one of the most prominent enabler for improving the cell-edge user experience while increasing the system’s fairness.
In this white paper, we present the basics of relay deployments in LTE-A networks. Moreover, we analyze resource allocation problem for Relay Nodes (RN) deployments and present some of the solutions for improvement in system resource usage and QoS satisfaction. Afterwards, we introduce the capabilities of NOMOR’s LTE-A system level simulator and evaluate the performance of LTE-A relay systems under the described solutions.
A DDRESSING T HE M ULTICHANNEL S ELECTION , S CHEDULING A ND C OORDINATION...pijans
We discuss a new multichannel coordination and sche
duling challenge called the Multichannel Scheduling
Cost (MSC). It is caused by the inability of the co
ntrol channel to schedule simultaneous transmission
s
resulting in data channels lying idle and their ban
dwidth underutilized. As a result, wasted bandwidth
increases as the number of data channels increases.
To address this challenge, a cyclic scheduling
Algorithm (CSA) is proposed. It employs one dedicat
ed signaling channel and 4 data channels. It is
premised on a proactive channel reservation scheme
which reduces the idleness of channels. The scheme
ensures that data channels are reserved while they
are still busy. The data channels are reserved whil
e
their remaining transmission duration is equal to t
he virtual carrier sensing duration. This gives the
next
pair sufficient time to reserve the current data ch
annel before it becomes available, limiting the MSC
to the
first cycle. The simulation results show a performa
nce benefit of the CSA scheme in addressing the eff
ects
of the MSC
Effect of Interleaved FEC Code on Wavelet Based MC-CDMA System with Alamouti ...IJCSEIT Journal
In this paper, the impact of Forward Error Correction (FEC) code namely Trellis code with interleaver on
the performance of wavelet based MC-CDMA wireless communication system with the implementation of
Alamouti antenna diversity scheme has been investigated in terms of Bit Error Rate (BER) as a function of
Signal-to-Noise Ratio (SNR) per bit. Simulation of the system under proposed study has been done in M-ary
modulation schemes (MPSK, MQAM and DPSK) over AWGN and Rayleigh fading channel incorporating
Walsh Hadamard code as orthogonal spreading code to discriminate the message signal for individual
user. It is observed via computer simulation that the performance of the interleaved coded based proposed
system outperforms than that of the uncoded system in all modulation schemes over Rayleigh fading
channel.
LTE QOS DYNAMIC RESOURCE BLOCK ALLOCATION WITH POWER SOURCE LIMITATION AND QU...IJCNCJournal
3GPP has defined the long term evolution (LTE) for 3G radio access in order to maintain the future
competitiveness for 3G technology, the system provides the capability of supporting a mixture of services
with different quality of service (QoS) requirements. This paper proposes a new cross-layer scheduling
algorithm to satisfy better QoS parameters for real time applications. The proposed algorithm takes care of
allocating resource blocks (RBs) with different modulation and coding schemes (MCS) according to target
bit error rate (BER), user equipment supportable MCS, queue stability constraints and available transmit
power constraints. The proposed algorithm has been valued, compared with an earlier allocation algorithm
in terms of service rate and packet delay and showed better performance regards the real time
applications.
Some of the key driving forces behind the transition from the UMTS based cellular system to the Long Term Evolution Advanced (LTE-A) are to improve the mean and the cell-edge throughput, improve the user fairness, and improve the quality of service (QoS) satisfaction for all users. In the latter system, relays appear as one of the most prominent enabler for improving the cell-edge user experience while increasing the system’s fairness.
In this white paper, we present the basics of relay deployments in LTE-A networks. Moreover, we analyze resource allocation problem for Relay Nodes (RN) deployments and present some of the solutions for improvement in system resource usage and QoS satisfaction. Afterwards, we introduce the capabilities of NOMOR’s LTE-A system level simulator and evaluate the performance of LTE-A relay systems under the described solutions.
One of the main challenges faced by the developing (3GPP-LTE-Advanced) standard is providing high throughput at the cell edge.
One solution to improve coverage is the use of fixed relays.
This presentation discusses about the WCDMA air Interface used in 3G i.e. UMTS. This Radio Interface has great capability on which Third Generation of Mobile Communication is built, with backward compatibility.
Duplexing mode, ARB and modulation approaches parameters affection on LTE upl...IJECEIAES
The next generation of radio technologies designed to increase the capacity and speed of mobile networks. LTE is the first technology designed explicitly for the Next Generation Network NGN and is set to become the de-facto NGN mobile access network standard. It takes advantage of the NGN's capabilities to provide an always-on mobile data experience comparable to wired networks. In this paper LTE uplink waveforms displayed with various duplexing mode, Allocated Resources Blocks ARB, Modulation types and total information per frame, QPSK and 16 QAM used as modulation techniques and tested under AWGN and Rayleigh channels, similarity and interference of the generated waveforms tested using auto-correlation and cross-correlation respectively.
COMPARATIVE PERFORMANCE ASSESSMENT OF VBLAST ENCODED 8×8 MIMO MC-CDMA WIRELES...pijans
The bit error rate performance of a V-Blast encoded 8x8 MIMO MC-CDMA wireless communication system
for different signal detection (MMSE and ZF) and digital modulation (BPSK, QPSK, DPSK, and 4QAM)
schemes for grayscale image transmission has been investigated in this paper. The proposed wireless system
employ ½-rated Convolution and cyclic redundancy check (CRC) channel encoding over the AWGN channel
and Walsh Hadamard code as an orthogonal spread code. The present Matlab based simulation study
demonstrates that the V-Blast encoded 8×8 MIMO MC-CDMA wireless system with the employment of 1⁄2-
rated convolution and cyclic redundancy check (CRC) channel encoding strategies shows good performance
utilizing BPSK digital modulation and ZF signal detection scheme in grayscale image transmission
Improving quality of service using ofdm technique for 4 th generation networkeSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Performance Comparison of Multi-Carrier CDMA Using QPSK and BPSK ModulationIOSR Journals
Abstract: MC-CDMA (Multi Carrier Code Division Multiple Access) plays an important role in modern wireless communications. Modern communication required an efficient spectrum usage and capacity and throughput.MC-CDMA provided the solution of these problems. MIMO refers to links with multiple antennas at the transmitter and receiver side. CDMA systems combined with multiple antennas is a promising technique, beyond 3G and 4G wireless communications. MIMO provides spatial diversity, which mitigates the fading. The usage of multiple antennas can significantly improve the performance of wireless communication system. This work also derives simulation through MATLAB of average bit error rate verses bit energy to noise ratio of multicarrier code division multiple access over Rayleigh channel using QPSK and BPSK modulation additive white Gaussian noise. Keywords: AWGN,BER,MC-CDMA, QPSK Modulation, Rayleigh Channel.
ABSTRACT : Performance enhancement of smart antennas versus their complexity for commercial wireless
applications. The goal of the study presented in this paper is to investigate the performance improvement
attainable using relatively simple smart antenna techniques when applied to the third-generation W-CDMA air
interface. Methods to achieve this goal include fixed multi beam architectures with different beam selection
algorithms (maximum power criterion, combined beams) or adaptive solutions driven by relatively simple direction
finding algorithms. After comparing these methods against each other for several representative scenarios, some
issues related to the sensitivity of these methods are also studied, (e.g., robustness to environment, mismatches
originating from implementation limitations, etc.). Results indicate that overall, conventional beam forming
seems to be the best choice in terms of balancing the performance and complexity requirements, in particular
when the problem with interfering high-bit-rate W-CDMA 3g users is considered.
Outage and throughput performance of cognitive radio based power domain based...TELKOMNIKA JOURNAL
This paper considers power domain based multiple access (PDMA) in cognitive radio network to serve numerous users who intend to multiple access to core network. In particular, we investigate the effect of signal combination scheme equipped at PDMA end-users as existence of direct link and relay link. This system model using relay scheme provides performance improvement on the outage probability of two PDMA end-users. We first propose a simple scheme of fixed power allocation to PDMA users who exhibit performance gap and fairness. Inspired by PDMA strategy, we then find signal to noise ratio (SNR) to detect separated signal for each user. In addition, the exact expressions of outage probability are derived in assumption that receiver can cancel out the interference completely with successive interference cancellation (SIC). By exploiting theoretical and simulation results, both considered combination schemes (Maximal Ratio Combining (MRC) and Selection Combining (SC) can achieve improved performance of two PDMA users significantly.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Topics covered in this presentation:
1. RF spectrum and GSM specifications
2. FDMA and TDMA
3. Digital Voice Transmission
4. Channel coding, Interleaving and Burst formatting
5. GMSK
6. Frame structure of GSM
7. Corrective actions against multipath fading
STUDY OF VARIOUS INTERNET OF THINGS PLATFORMSIJCSES Journal
Internet of Things is a technological revolution which provides the vision of connected world of Things.Devices, people and systems are connected with one another in such a way that they can communicate with each other over Internet. So the form of communication from human-human is now turned into humanhuman,human-things and things- things. Variety of platforms are now a days available that can support
entire development to deployment of IoT applications and systems. In this paper, we will first start with the introduction of IoT platforms as well as IoT middle ware and then will discuss various IoT platforms,compare various IoT platforms and will end up with the conclusion.
One of the main challenges faced by the developing (3GPP-LTE-Advanced) standard is providing high throughput at the cell edge.
One solution to improve coverage is the use of fixed relays.
This presentation discusses about the WCDMA air Interface used in 3G i.e. UMTS. This Radio Interface has great capability on which Third Generation of Mobile Communication is built, with backward compatibility.
Duplexing mode, ARB and modulation approaches parameters affection on LTE upl...IJECEIAES
The next generation of radio technologies designed to increase the capacity and speed of mobile networks. LTE is the first technology designed explicitly for the Next Generation Network NGN and is set to become the de-facto NGN mobile access network standard. It takes advantage of the NGN's capabilities to provide an always-on mobile data experience comparable to wired networks. In this paper LTE uplink waveforms displayed with various duplexing mode, Allocated Resources Blocks ARB, Modulation types and total information per frame, QPSK and 16 QAM used as modulation techniques and tested under AWGN and Rayleigh channels, similarity and interference of the generated waveforms tested using auto-correlation and cross-correlation respectively.
COMPARATIVE PERFORMANCE ASSESSMENT OF VBLAST ENCODED 8×8 MIMO MC-CDMA WIRELES...pijans
The bit error rate performance of a V-Blast encoded 8x8 MIMO MC-CDMA wireless communication system
for different signal detection (MMSE and ZF) and digital modulation (BPSK, QPSK, DPSK, and 4QAM)
schemes for grayscale image transmission has been investigated in this paper. The proposed wireless system
employ ½-rated Convolution and cyclic redundancy check (CRC) channel encoding over the AWGN channel
and Walsh Hadamard code as an orthogonal spread code. The present Matlab based simulation study
demonstrates that the V-Blast encoded 8×8 MIMO MC-CDMA wireless system with the employment of 1⁄2-
rated convolution and cyclic redundancy check (CRC) channel encoding strategies shows good performance
utilizing BPSK digital modulation and ZF signal detection scheme in grayscale image transmission
Improving quality of service using ofdm technique for 4 th generation networkeSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Performance Comparison of Multi-Carrier CDMA Using QPSK and BPSK ModulationIOSR Journals
Abstract: MC-CDMA (Multi Carrier Code Division Multiple Access) plays an important role in modern wireless communications. Modern communication required an efficient spectrum usage and capacity and throughput.MC-CDMA provided the solution of these problems. MIMO refers to links with multiple antennas at the transmitter and receiver side. CDMA systems combined with multiple antennas is a promising technique, beyond 3G and 4G wireless communications. MIMO provides spatial diversity, which mitigates the fading. The usage of multiple antennas can significantly improve the performance of wireless communication system. This work also derives simulation through MATLAB of average bit error rate verses bit energy to noise ratio of multicarrier code division multiple access over Rayleigh channel using QPSK and BPSK modulation additive white Gaussian noise. Keywords: AWGN,BER,MC-CDMA, QPSK Modulation, Rayleigh Channel.
ABSTRACT : Performance enhancement of smart antennas versus their complexity for commercial wireless
applications. The goal of the study presented in this paper is to investigate the performance improvement
attainable using relatively simple smart antenna techniques when applied to the third-generation W-CDMA air
interface. Methods to achieve this goal include fixed multi beam architectures with different beam selection
algorithms (maximum power criterion, combined beams) or adaptive solutions driven by relatively simple direction
finding algorithms. After comparing these methods against each other for several representative scenarios, some
issues related to the sensitivity of these methods are also studied, (e.g., robustness to environment, mismatches
originating from implementation limitations, etc.). Results indicate that overall, conventional beam forming
seems to be the best choice in terms of balancing the performance and complexity requirements, in particular
when the problem with interfering high-bit-rate W-CDMA 3g users is considered.
Outage and throughput performance of cognitive radio based power domain based...TELKOMNIKA JOURNAL
This paper considers power domain based multiple access (PDMA) in cognitive radio network to serve numerous users who intend to multiple access to core network. In particular, we investigate the effect of signal combination scheme equipped at PDMA end-users as existence of direct link and relay link. This system model using relay scheme provides performance improvement on the outage probability of two PDMA end-users. We first propose a simple scheme of fixed power allocation to PDMA users who exhibit performance gap and fairness. Inspired by PDMA strategy, we then find signal to noise ratio (SNR) to detect separated signal for each user. In addition, the exact expressions of outage probability are derived in assumption that receiver can cancel out the interference completely with successive interference cancellation (SIC). By exploiting theoretical and simulation results, both considered combination schemes (Maximal Ratio Combining (MRC) and Selection Combining (SC) can achieve improved performance of two PDMA users significantly.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Topics covered in this presentation:
1. RF spectrum and GSM specifications
2. FDMA and TDMA
3. Digital Voice Transmission
4. Channel coding, Interleaving and Burst formatting
5. GMSK
6. Frame structure of GSM
7. Corrective actions against multipath fading
STUDY OF VARIOUS INTERNET OF THINGS PLATFORMSIJCSES Journal
Internet of Things is a technological revolution which provides the vision of connected world of Things.Devices, people and systems are connected with one another in such a way that they can communicate with each other over Internet. So the form of communication from human-human is now turned into humanhuman,human-things and things- things. Variety of platforms are now a days available that can support
entire development to deployment of IoT applications and systems. In this paper, we will first start with the introduction of IoT platforms as well as IoT middle ware and then will discuss various IoT platforms,compare various IoT platforms and will end up with the conclusion.
The semantic Web service discovery has been given massive attention within the last few years. With the
increasing number of Web services available on the web, looking for a particular service has become very
difficult, especially with the evolution of the clients’ needs. In this context, various approaches to discover
semantic Web services have been proposed. In this paper, we compare these approaches in order to assess
their maturity and their adaptation to the current domain requirements. The outcome of this comparison
will help us to identify the mechanisms that constitute the strengths of the existing approaches, and
thereafter will serve as guideline to determine the basis for a discovery approach more adapted to the
current context of Web services.
ADVANCES IN HIGHER EDUCATIONAL RESOURCE SHARING AND CLOUD SERVICES FOR KSAIJCSES Journal
Cloud represents an important change in the way information technology is used. Cloud makes it possible
to access work anywhere anytime and to share it with anyone [1]. It is changing the way people
communicate, work and learn [2]. In this changing environment, it is important to think about the
opportunities and risks of using the cloud in the education field, and the lessons we can learn from the
previous uses of this technology in the education field. In order to gain the benefits of the cloud to be used
in educational system in KSA, a comprehensive study on scientific literatures in this paper. This paper also
presents the significant information such as the findings, the case studies, related frameworks and
supporting also the tools associated to the migration of organizational resources to cloud
A vague improved markov model approach for web page predictionIJCSES Journal
Today most of the information in all areas is available over the web. It increases the web utilization as
well as attracts the interest of researchers to improve the effectiveness of web access and web utilization.
As the number of web clients gets increased, the bandwidth sharing is performed that decreases the web
access efficiency. Web page prefetching improves the effectiveness of web access by availing the next
required web page before the user demand. It is an intelligent predictive mining that analyze the user web
access history and predict the next page. In this work, vague improved markov model is presented to
perform the prediction. In this work, vague rules are suggested to perform the pruning at different levels of
markov model. Once the prediction table is generated, the association mining will be implemented to
identify the most effective next page. In this paper, an integrated model is suggested to improve the
prediction accuracy and effectiveness.
Security in Mobile Ad Hoc Network became very important due to the nature of wireless communication
between the nodes and the rapid movement of node which make Mobile Ad hoc Network vulnerable to
Attackers. Jamming is a DoS attack’s special category used in wireless networks. The attacker disrespects
the medium access control (MAC) protocol and transmits on the shared channel; either periodically or
continuously to target all or some communication, respectively. Distributed coordination function (DCF)
and Point coordination function (PCF) are the two different media access control (MAC) mechanisms
which are specified by the IEEE 802.11standard. PCF can achieve higher throughput than DCF due to the
nature of contention-free, therefore, this paper investigate the impact of PCF when integrated into the
TORA – Based MANET and how it can improve the performance of the network. OPNET – Based
simulation scenarios were created and the simulation was run and the results were collected which
investigate that PCF provided a good functionality to improve deficiency caused by the Jammers this by
increasing the throughput and decreasing the delay which is affected by the Jammers. PCF was a good
improvement with different levels of Jammers’ transmission power.
This course was developed to assist Supervisors, Quality Staff or additional Leadership in delivering effective feedback sessions to staff. Deck also includes a list of do's and don'ts, as well as proven communication methods.
Jpeg image compression using discrete cosine transform a surveyIJCSES Journal
Due to the increasing requirements for transmission of images in computer, mobile environments, the
research in the field of image compression has increased significantly. Image compression plays a crucial
role in digital image processing, it is also very important for efficient transmission and storage of images.
When we compute the number of bits per image resulting from typical sampling rates and quantization
methods, we find that Image compression is needed. Therefore development of efficient techniques for
image compression has become necessary .This paper is a survey for lossy image compression using
Discrete Cosine Transform, it covers JPEG compression algorithm which is used for full-colour still image
applications and describes all the components of it.
Time alignment techniques for experimental sensor dataIJCSES Journal
Experimental data is subject to data loss, which presents a challenge for representing the data with a
proper time scale. Additionally, data from separate measurement systems need to be aligned in order to
use the data cooperatively. Due to the need for accurate time alignment, various practical techniques are
presented along with an illustrative example detailing each step of the time alignment procedure for actual
experimental data from an Unmanned Aerial Vehicle (UAV). Some example MATLAB code is also
provided.
STUDY ON THE PATH TRACKING AND POSITIONING METHOD OF WHEELED MOBILE ROBOTIJCSES Journal
As a kind of wheeled mobile robot used in intelligent logistics system, AGV is mainly used for automatic
material transportation, the precise positioning and path tracking is the assu- rance of accurate material
transportation. In this article, the laser coordinate positioning technology is used to realize accurate
positioning for AGV, a new method of target reference point selection is put forward, and path tracking is
implemented in combination with the kinematics model of single steering wheel AGV, the objective function
that AGV successfully reaches the destination accurately according to the preset trajectory is completed
finally. The study is in trial stage, and obtains good operation effectiveness.
This presentation was developed to introduce new hires to the Quality & Training Department staff and to clearly define account expectations for call monitoring.
This report discusses the planning Associate in
nursing the implementation of an OFDM system
in several information module schemes like MQPSK,
M-QAM. First, a short introduction is
provided by explaining the background and the
specification of the project. Then the report deals
with the system model, every block of the OFDM
system is represented (IFFT, FFT, Cyclic prefix,
modulation / reception, Channel estimation, bit
error rate). System design is analyzed. The
transmission techniques, further because the
system parameters for transmission and reception
are explained well. Finally, the results are
provided.
Index modulation is one of the promising techniques for future communications systems due to many improvement over the classical orthogonal frequency division multiplexing systems such as single RF chain, increased throughput for the same modulation order, achieved tradeoff between the efficiencies of the power and the spectral, and elimination of inter-channel interference. Many forms of index modulation researches exist where symbols are conveyed in antennas, subcarriers, time slots, and the space-time matrix. Spatial modulation is one member of index modulation family where symbols are conveyed in activating transmit/receive antennas. In this paper, a modification to a standard multiple input single output scheme by integrating spatial modulation using simplified mathematical procedure is achieved. In the transmitter side, data and activation symbols are distributed simultaneously using mathematical module and floor functions. At the receiver, a simplified maximum likelihood detector is used to obtain transmitted pair of symbols. To verify this, MATLAB simulink is used to simulate a downlink system where spatial modulation is applied to a base station. Results for different transmit antenna number and modulation order are obtained in the form of bit error rate versus signal to noise ratio.
Performance of Wideband Mobile Channel with Perfect Synchronism BPSK vs QPSK ...Editor Jacotech
Direct-sequence code-division multiple access (DS-CDMA) is
currently the subject of much research as it is a promising
multiple access capability for third and fourth generations
mobile communication systems. The synchronous DS-CDMA
system is well known for eliminating the effects of multiple
access interference (MAI) which limits the capacity and
degrades the BER performance of the system. In this paper,
we investigate the bit error rate (BER) performance of a
synchronous DS-CDMA system over a wideband mobile
radio channel. The BER performance is affected by the
difference in path length ΔL and the number of arriving
signals N. Furthermore, the effect of these parameters is
examined on the synchronous DS-CDMA system for different
users’ number as well as different processing gain Gp. In this
environment and under the above conditions the performances
of the BPSK (Binary Phase Shift Keying) and the QPSK
(Quadrature Phase Shift Keying) modulations are compared.
The promising simulation results showed the possibility of
applying this system to the wideband mobile radio channel.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
A SEMI BLIND CHANNEL ESTIMATION METHOD BASED ON HYBRID NEURAL NETWORKS FOR UP...ijwmn
The paper describes how to improve channel estimation in Single Carrier Frequency Division Multiple
Access (SC-FDMA) system, using a Hybrid Artificial Neural Networks (HANN). The 3rd Generation
Partnership Project (3GPP) standards for uplink Long Term Evolution Advanced (LTE-A) uses pilot based
channel estimation technique. This kind of channel estimation method suffers from a considerable loss
ofbitrate due to pilot insertion; all data frame sent contains reference signal. The HANN converts data
aided channel estimator to semi blind channel estimator. To increase convergence speed, HANN uses some
channel propagation Fuzzy Rules to initialize Neural Network parameters before learning instead of a
random initialization, so its learning phase ismore rapidly compared to classic ANN.HANN allows more
bandwidth efficient and less complexity. Simulation results show that HANN has better computational
efficiency than the Minimum Mean Square Error (MMSE) estimator and has faster convergence than
classic Neural Networks estimators.
A significant problem in Multicarrier Code Division Multiple Access (MC-
CDMA) system is the possibility of high Peak to Average Power Ratio (PAPR). This is due
to the cumulative sum of N subcarrier peaks in the transmitted signals which reduces Power
efficiency, resolution and battery life. In this paper a technique is proposed to make use of
Inverse Discrete Cosine Transform (IDCT) and Inverse Discrete Wavelet Transform
(IDWT) based Multicarrier Code Division Multiple Access (MC-CDMA) system. This
system is in combination with Modified Exponential Companding with Clipping Transform
(MECCT) technique which reduces PAPR and that is analyzed over Additive White
Gaussian Noise (AWGN) channel, Rayleigh and Stanford University Interim (SUI)
multipath fading channel.
International Journal of Engineering Research and Applications (IJERA) is a team of researchers not publication services or private publications running the journals for monetary benefits, we are association of scientists and academia who focus only on supporting authors who want to publish their work. The articles published in our journal can be accessed online, all the articles will be archived for real time access.
Our journal system primarily aims to bring out the research talent and the works done by sciaentists, academia, engineers, practitioners, scholars, post graduate students of engineering and science. This journal aims to cover the scientific research in a broader sense and not publishing a niche area of research facilitating researchers from various verticals to publish their papers. It is also aimed to provide a platform for the researchers to publish in a shorter of time, enabling them to continue further All articles published are freely available to scientific researchers in the Government agencies,educators and the general public. We are taking serious efforts to promote our journal across the globe in various ways, we are sure that our journal will act as a scientific platform for all researchers to publish their works online.
Performance evaluation of high mobility OFDM channel estimation techniques IJECEIAES
In wireless communication, Orthogonal Frequency Division Multiplexing (OFDM) has been adopted due to its robustness to multipath fading and high data rate transmissions. At the other hand, the performance of OFDM systems severely degraded due to multi-path fading and Doppler frequency shifts in mobile systems, which causes inter-carrier-interference (ICI). Thus, Estimation of channel parameters is required at the receiver using a pre designed estimator where pilot tones are inserted in each OFDM symbol. In this paper, a random pilot data are generated and inserted in each OFDM symbol at equally spaced locations. The performance test of Least Square (LS) and Linear Minimum Mean Square (LMMSE) estimation methods are proposed with Discrete Fourier Transform (DFT) based on both LS and LMMSE, where different ITU channel models are considered in order to compare their performance for data transmission in high mobile systems with different Doppler frequencies exceeds 200 Hz and minimal number of pilots.
PERFORMANCE OF MIMO MC-CDMA SYSTEM WITH CHANNEL ESTIMATION AND MMSE EQUALIZATIONTamilarasan N
The quality of a wireless link can be described by three basic parameters, namely transmission rate, transmission range
and transmission reliability. With the advent of multiple-input multiple-output (MIMO) assisted Multicarrier code
division multiple access (MC-CDMA) systems, the above-mentioned three parameters may be simultaneously
improved. The MC-CDMA combined with the MIMO technique, has become a core technology for future mobile radio
communication system. However, possible potential gain in spectral efficiency is challenged by the receiver’s ability to
accurately detect the symbol due to inter symbol interference (ISI). Multipath propagation, mobility of transmitter,
receiver and local scattering cause the signal to be spread in frequency, different arrival time and angle, which results in
ISI in the received signal. This will affect overall system performance. The use of MC-CDMA mitigates the problem of
time dispersion. However, still it is necessary to remove the amplitude and phase shift caused by channel. To solve this
problem, a multiple antenna array can be used at the receiver, not only for spectral efficiency or gain enhancement, but
also for interference suppression. This can be done by the, efficient channel estimation with strong equalization. This
paper proposes MIMO MC-CDMA system, Minimum mean square error (MMSE) equalization with pilot based
channel estimation. The simulation result shows improved Bit error rate (BER) performance when the sub carrier (SC)
and antenna configuration were increased
Channel Estimation Techniques in MIMO-OFDM LTE SystemsCauses and Effects of C...IJERA Editor
There is an increasing demand for high data transmission rates with the evolution of the very large scale integration (VLSI) technology. The multiple input multiple output-orthogonal frequency division multiplexing (MIMO-OFDM) systems are used to fulfill these requirements because of their unique properties such as high spectral efficiency, high data rate and resistance towards multipath propagation. MIMO-OFDM systems are finding their applications in the modern wireless communication systems like IEEE 802.11n, 4G and LTE. They also offer reliable communication with the increased coverage area. The bottleneck to the MIMO-OFDM systems is the estimation of the channel state information (CSI). This can be estimated with the help of any one of the Training Based, Semiblind and Blind Channel estimation algorithms. This paper presents various channel estimation algorithms, optimization techniques and their effective utilization in MIMO-OFDM for modern wireless LTE systems.
BER Performance of OFDM-QAM over AWGN and RICAIN Channels Using Error Correct...IJERA Editor
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Terzaghi's soil bearing capacity theory, developed by Karl Terzaghi, is a fundamental principle in geotechnical engineering used to determine the bearing capacity of shallow foundations. This theory provides a method to calculate the ultimate bearing capacity of soil, which is the maximum load per unit area that the soil can support without undergoing shear failure. The Calculation HTML Code included.
Courier management system project report.pdfKamal Acharya
It is now-a-days very important for the people to send or receive articles like imported furniture, electronic items, gifts, business goods and the like. People depend vastly on different transport systems which mostly use the manual way of receiving and delivering the articles. There is no way to track the articles till they are received and there is no way to let the customer know what happened in transit, once he booked some articles. In such a situation, we need a system which completely computerizes the cargo activities including time to time tracking of the articles sent. This need is fulfilled by Courier Management System software which is online software for the cargo management people that enables them to receive the goods from a source and send them to a required destination and track their status from time to time.
TECHNICAL TRAINING MANUAL GENERAL FAMILIARIZATION COURSEDuvanRamosGarzon1
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Ideal for homeowners, contractors, engineers, and anyone interested in modern plumbing solutions, this guide provides valuable insights into why trenchless pipe repair is becoming the preferred choice for pipe rehabilitation. Stay informed about the latest advancements and best practices in the field.
Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
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introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
COLLEGE BUS MANAGEMENT SYSTEM PROJECT REPORT.pdfKamal Acharya
The College Bus Management system is completely developed by Visual Basic .NET Version. The application is connect with most secured database language MS SQL Server. The application is develop by using best combination of front-end and back-end languages. The application is totally design like flat user interface. This flat user interface is more attractive user interface in 2017. The application is gives more important to the system functionality. The application is to manage the student’s details, driver’s details, bus details, bus route details, bus fees details and more. The application has only one unit for admin. The admin can manage the entire application. The admin can login into the application by using username and password of the admin. The application is develop for big and small colleges. It is more user friendly for non-computer person. Even they can easily learn how to manage the application within hours. The application is more secure by the admin. The system will give an effective output for the VB.Net and SQL Server given as input to the system. The compiled java program given as input to the system, after scanning the program will generate different reports. The application generates the report for users. The admin can view and download the report of the data. The application deliver the excel format reports. Because, excel formatted reports is very easy to understand the income and expense of the college bus. This application is mainly develop for windows operating system users. In 2017, 73% of people enterprises are using windows operating system. So the application will easily install for all the windows operating system users. The application-developed size is very low. The application consumes very low space in disk. Therefore, the user can allocate very minimum local disk space for this application.
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PERFORMANCE EVALUATION OF MC-CDMA SYSTEM OVER RAYLEIGH FADING CHANNEL
1. International Journal of Computer Science & Engineering Survey (IJCSES) Vol.6, No.3, June 2015
DOI:10.5121/ijcses.2015.6302 9
PERFORMANCE EVALUATION OF MC-CDMA
SYSTEM OVER RAYLEIGH FADING CHANNEL
A. M. Abdulsattar1
, A. D. Alwazzan2
and K. M.Quboa2
1
Alhdba University College, Mousel, Iraq
2
Mousel University, Mousel, Iraq
ABSTRACT
Multi Carrier Code Division Multiple Access (MC-CDMA) is a well known technique for high speed
wireless data transmission .Two advanced technology was included in the MC-CDMA structure, such as
orthogonal frequency division multiplex (OFDM) and the code division multiple access (CDMA),so that it
benefits from the robustness of OFDM against multipath environment and from the capability of multiuser
multiplexing services that is achieved via (CDMA) system. MC-CDMA is a multicarrier spread spectrum
system which is classified as the candidate scheme for future mobile radio systems. In this paper MC-
CDMA system, with Rayleigh fading channel and 16QAM array modulation, was simulated to investigate
the effects of different parameters on the system performance, such as processing gain; number of paths;
number of users; interleaving; and coding ratio.MC-CDMA performances can be considerably improved
by proper selection of these parameters. As expected, results show that MC-CDMA has a better
performance over CDMA system.
KEYWORDS
CDMA, OFDM, MC-CDMA, Rayleigh fading, Convolutional Encoder.
1. INTRODUCTION
People use mobile not only for making their calls but also to transmit and receive different data
types like: music, video, games and many other applications. Due to the large number of people
request for different communication services, the multiple access technique has been necessary to
deal with all requests. The mobile radio channel is considered as one of the difficult channels to
deal with. The multipath effect is one of the complicated problems in mobile radio channel and
heavily affects the system performance due to the effect of Inter symbol Interference (ISI). Many
communication systems used techniques that are known as orthogonal frequency division
multiplexing (OFDM) and code division multiple access (CDMA) [1]. OFDM and CDMA
techniques are used in high speed wireless communications. One of the advanced technique for
broadband wireless communication is Multi-Carrier Code Division Multiple Access (MC-
CDMA)[2]. MC-CDMA system benefits from the robustness of OFDM against multipath
environment and from the capability of multiuser multiplexing services that is achieved via
(CDMA)system[2,3].In this paper MC-CDMA performance under Rayleigh fading
channelusing16-QAM array modulation, was evaluated for different system parameters such as
number of users, number of paths, processing gain, ratio of convolutional encoder, and
interleaver.
2. MC-CDMA SYSTEM
To support high data rates services, several 4G systems utilizes MC-CDMA to minimize the inter
symbol interference (ISI) that occurs when transmission through multipath wireless channels are
2. International Journal of Computer Science & Engineering Survey (IJCSES) Vol.6, No.3, June 2015
used. The OFDM, as a kind of multicarrier modulation, is an efficient low complex technique
modulated multiple subcarriers using digital signal processing (DSP).
sub-streams was achieved by the multi
high data rate stream already injected at system input.
different sub-carrier as shown in Figure 1
Figure 1.
One of the important targets in using multicarrier transmission based on OFDM technique is that
the mobile radio channel can be cons
type fading which is already considered
[4].
2.1 REVERSE LINK DS-CDMA
A mathematical description of a
system configuration, including transmitting
2.
Figure 2.
Let us considering K independent users e
2
Where is the power of the transmitted
represents the spreading pseudorandom sequence ,
modulated carrier. Due to asynchronous uplink transmission, the l
different transmitters represented here by
carrier. The user,
s data signal is a
International Journal of Computer Science & Engineering Survey (IJCSES) Vol.6, No.3, June 2015
The OFDM, as a kind of multicarrier modulation, is an efficient low complex technique
modulated multiple subcarriers using digital signal processing (DSP). A multiple parallel low
by the multi-carrier system through serial to parallel conversi
already injected at system input. Each sub-stream is modulated on a
as shown in Figure 1.
Figure 1. Basic diagram of an Multicarrier System .
in using multicarrier transmission based on OFDM technique is that
the mobile radio channel can be considered as time-invariant during one OFDM symbol with flat
which is already considered here in this paper by assuming Rayleigh fading
DMA SYSTEM MODEL
A mathematical description of a reverse link DS-CDMA system will be discussed here. The main
including transmitting and receiving side (base station), is shown
Figure 2. Reverse link DS-CDMA System Model.
independent users each of them transmits a signal in the form.
1
power of the transmitted signal, represents thedata bit stream sequence,
pseudorandom sequence , represents the angular frequency
carrier. Due to asynchronous uplink transmission, the lack of synchronism between
represented here by the time delay , represents the phase angle of the
s data signal is an NRZ-L sequence of duration
International Journal of Computer Science & Engineering Survey (IJCSES) Vol.6, No.3, June 2015
10
The OFDM, as a kind of multicarrier modulation, is an efficient low complex technique
multiple parallel low-rate
conversion of the
stream is modulated on a
in using multicarrier transmission based on OFDM technique is that
one OFDM symbol with flat
Rayleigh fading channel
CDMA system will be discussed here. The main
is shown in Figure
sequence,
angular frequency of the
ack of synchronism between
he phase angle of the
duration !, taking
3. International Journal of Computer Science & Engineering Survey (IJCSES) Vol.6, No.3, June 2015
values" 1#, #1$. If is the chip period, then
factor for user k. By considering the desired user as
interference (MAI) comes mainly
signal formula at the input of the receiver
%
Where & is the complex low pass equivalent impulse response of the the transmitted channel
and n(t) is Additive White Gaussian Noise (AWGN)
at the input of the receiver after Considering (1) and (2)
% ' ' 2
()
*)+,
-,
+.
/
0
Where ∅ ,*)
is the phase of the multipath component,
of multipath components. α3,*)
is
the magnitude of the 4 multipath
2.2 OFDM BASIC SYSTEM
The OFDM system block diagram
Figure 3
Binary data was generated and coded using convolutional
converted from bits to symbols using M
was inserted into modulated signal , then symbols are converted from serial to parallel substream
with size equal to the number of subcarriers.
The cyclic prefix (CP) was added to eliminate ISI and inter carrier
transmission purposes, data was converted from parallel to serial one.
received signal, after CP removing,
circuit to get the useful data and pilots which are use
signal is equalized depending on the channel es
channel. The equalized signal is back converted from parallel to serial st
demodulated, deinterleaved, and decoded in order to recover the original bits[
International Journal of Computer Science & Engineering Survey (IJCSES) Vol.6, No.3, June 2015
is the chip period, then 5 67
68
is the processing gain (PG) or the spreading
By considering the desired user as k=0, then the introduced multiple access
mainly from the contribution of all other users. Equation (
of the receiver.
& 0 2
is the complex low pass equivalent impulse response of the the transmitted channel
ive White Gaussian Noise (AWGN). Equation (3) gives the formula
of the receiver after Considering (1) and (2)[5] [6].
,*)
9 ,*)
: ; < 9 ,*)
:< 9= >
3
is the phase of the multipath component, ,*)
is the path delay, and @ is the number
is a random process with Rayleigh distribution which represents
multipath .
block diagram is shown in Figure 3.
Figure 3. The block diagram of an OFDM System.
Binary data was generated and coded using convolutional encoder. After interleaving data was
converted from bits to symbols using M-arry modulation. For channel estimation purposes pilots
was inserted into modulated signal , then symbols are converted from serial to parallel substream
ber of subcarriers. Those substreams are modulated using IFFT circuit.
was added to eliminate ISI and inter carrier interference
transmission purposes, data was converted from parallel to serial one. At the receiver sid
after CP removing, is converted from serial to parallel, then signal is fed into FFT
circuit to get the useful data and pilots which are used to estimate the effect of the
signal is equalized depending on the channel estimation information to compensate the effect of
channel. The equalized signal is back converted from parallel to serial stream. The signal is
, and decoded in order to recover the original bits[7].
International Journal of Computer Science & Engineering Survey (IJCSES) Vol.6, No.3, June 2015
11
or the spreading
multiple access
Equation (2) gives the
is the complex low pass equivalent impulse response of the the transmitted channel
. Equation (3) gives the formula of the signal
> ,*)
:
is the number
which represents
encoder. After interleaving data was
. For channel estimation purposes pilots
was inserted into modulated signal , then symbols are converted from serial to parallel substream
substreams are modulated using IFFT circuit.
interference (ICI ) . For
At the receiver side, the
is converted from serial to parallel, then signal is fed into FFT
d to estimate the effect of the channel. The
timation information to compensate the effect of
ream. The signal is
4. International Journal of Computer Science & Engineering Survey (IJCSES) Vol.6, No.3, June 2015
12
2.3 MC-CDMA SYSTEM MATHEMATICAL MODEL
MC-CDMA scheme spreads the original data on large bandwidth by using a given spreading code
and converts the high rate of serial stream to parallel low rate substream then transmits N chips
simultaneously by assigning each chip to a separate carrier, by using OFDM transmitter, so that
each input symbol is transmitted on N subcarriers. By correlating the signal samples at the OFDM
outputwith the code sequence used for signal dispreading, the transmitted symbol will be
extracted at theoutput of the receiver.MC-CDMA transmitter system is shown by figure 4, where
aB
[i] represents binary data input sequence belong to the uth
user at ith
time.
Figure 4. MC-CDMA transmitter.
Considering the case where the length of processing gain PG is equal to the number of subcarrier
Nc(Nc=PG ), the ith
input dataaB[i], is first copied to Nc subchannels and then multiplied by the
spreading codeCG
B which corresponds to the uth
user, modulated by Nc subcarriers, then summed
and digitized to generate the transmitted MC-CDMA signalxI[i] which is given by [9].
xI[i] ' XG[i]e
KLMNO
PQ
RS-,
I+.
, n 0,1, … , Nc 1 4
Where XG[i] ' aB[i]
-,
B+.
CG
B
5
Where CG
B
is the spreading code given by (6).
CG
B
C.
B
, C,
B
, … , C^_-,
B
6
The transmitted signal, xn[i]in (4) has a similar formula as that of the OFDM transmitted
signal,except that it contains the multiuser multiplexing capability which is introduced basically
by the CDMA technology. For simplicity, the index (i) could be omitted in case of one OFDM
symbol and assuming multipath fading channel consists of L-paths, then the received signal, yI,
is given by (7).
yI ' hI,*
b-,
*+.
xI-* wI … 7
5. International Journal of Computer Science & Engineering Survey (IJCSES) Vol.6, No.3, June 2015
13
Where hI,* represents the channel impulse response of the lth
path at time n and wI is the noise
component. Without inter carrier interference(ICI ),the received signal in the frequency domain is
given by (8):
YG f' H*
.
e
-
KLMhN
PQ
b-,
*+.
i XG WG
αmXG WG … (8)
WhereWG is the noise component in frequency domain, L represents the number of paths,
AndαGrepresents the multipath fading effect and is given by (9).
αj ' H*
.
e
-
KLMhk
PQ
b-,
*+.
9
Where H*
.
represents the channel transfer function.
If the channel is assumed to be time invariant during the symbol period, then it could be easily
compensated by frequency domain equalizer, where the output of the equalizer is given by (10).
X = H-1
YT
(10)
WhereH-1
is the estimated invers channel transfer function.
Based on equations (7,8,10), Figure 5shows the channel estimation and equalization system for
MC-CDMA receiver which is already adopted in this paper.
Figure 5. MC-CDMA receiver.
3. SIMULATION AND RESULTS
The system simulation is carried out using MC-CDMA Simulator, designed and built in
MATLAB to study the performance of MC-CDMA system for different lengths of processing
gain, number of paths, coding ratios of the convolutional encoder, number of users and
interleaver.
3.1 MC-CDMA SIMULATOR
In this section, a simulator built for the uplink scenario of MC-CDMA system is described. It is
composed of four basic units to simulate the transmitter, channel, receiver and BER calculator.
6. International Journal of Computer Science & Engineering Survey (IJCSES) Vol.6, No.3, June 2015
14
3.1.1 TRANSMITTER SECTION
MC-CDMA transmitter block diagram is shown in Figure 6.
Figure 6. Structure of the MC-CDMA transmitter.
The information bits are generated at 1 in Figure 6 for number of users. These binary bits are
coded by using a convolutional encoder with different coding ratios of 1/2, 2/3 and 3/4.
Convolutional encoder is performed according to IEEE 802.11a standard and is built as shown in
Figure 7with six Shift Registers (SR)[10].
Figure 7. Convolutional encoder structure.
Higher rates (2/3 & 3/4) are derived from the same structure by employing “puncturing”. Some of
the encoded bits in the transmitter will be omitted using Puncturing procedure, thus reducing the
number of transmitted bits and increasing the coding rate. At the receiver a “zero” will be inserted
into the convolutional decoder on the place of the omitted bits. In this case Viterbi algorithm is
recommended for the decoder. Table (1) shows the specifications of the IEEE 802.11a
Convolutional encoder[10].
Table 1. The IEEE 802.11a Convolutional encoder specifications.
The coded bits are interleaved by using an interleaver. The interleaved bits are modulated
(mapped) to data symbols according to the symbol modulation type which transforms the binary
bits into complex data symbols according to the value of modulation index (M). In this paper; 16-
QAM modulation type is taken into consideration. The spreading operation was performed using
Gold code, which is chosen here due to its good cross correlation property, which is an essential
7. International Journal of Computer Science & Engineering Survey (IJCSES) Vol.6, No.3, June 2015
15
requirement for CDMA system, where many users share the same medium and to assuring the
ability for the receiver to distinguish between them especially in the reverse-link (uplink) case
where the transmission is subject to asynchronous behavior between the different transmitted
users [11].Figure 8 show a Gold code generated by using two preferred Pseudo Noise (PN) codes.
Polynomials combination are used (5,2) and (5,4,3,2) configurations to generate the Gold code
with PG=31.
Figure 8. Gold code generation.
The polynomials are fixed while the initial conditions of the registers are varying to generate a
group of codes where each code is allocated for a specific user. Table (2) shows the properties of
the Gold code used in the simulator where the processing gain of 31, 63, 127 and 255 are taken
into consideration. In this paper, the processing gain of 127 is chosen as an upper limit because
more higher processing gain leads to decreasing in the transmission bit rates.
Table 2. Code polynomials.
Figure 9a shows the Gold code waveform for the first user of 31 chips. The Gold code has the
best autocorrelation function when there is no lagging between its chips (chip index = 0) as
shown in Figure 9b where the autocorrelation value is equal to the length of the code.
Autocorrelation & cross correlation values are bounded by either 1, t Lo or t Lo 2 where
Lo is the number of shift registers and t Lo is given by (11)[11].
t Lo q
2 brs, /u
1 , for odd Lo
2 brsu /u
1 , for even Lo
11 #
(a) Gold code for first user.
8. International Journal of Computer Science & Engineering Survey (IJCSES) Vol.6, No.3, June 2015
16
(b) Autocorrelation of first Gold code.
Figure 9. Characteristics of first user Gold code.
The second user Gold code waveform is shown by Figure 10a.For the case of 31 Gold code,
figure 10b shows the cross correlation between two Gold codes . The cross correlation values are
either -1,-9 or 7.
.
(a) Gold code for second user.
(b) Crosscorrelation between first and second user.
Figure 10. Correlation between two users.
A specific Gold code is allocated for each user. The spreading process is achieved by multiplying
each symbol by its allocated code as shown in Figure 11and checked at point 3 in Figure 6.
Figure 11. Spreading Process.
9. International Journal of Computer Science & Engineering Survey (IJCSES) Vol.6, No.3, June 2015
17
The pilot insertion process is used to insert pilots with known values in the transmitter and the
receiver units. This could be done by choosing a Comb type estimator proposed in this paper. In
the proposed Comb type, the number of pilots is chosen to be 12, because in IEEE802.11a
standard it is specified that only 48 subcarriers are used for data in the OFDM symbol and the 16
subcarriers, including nulls, to achieve a 64-point for the IFFT implementation. Figure 12 show
the replacement of the 12 data subcarriers by those of 12 pilots and checked at point 4 in Figure 6.
Figure 12. Pilot insertion in Comb type.
The serial stream is converted into 64 parallel substreams which are equal to the size of IFFT
circuit. The IFFT circuit modulates each chip of data to the subcarrier where the IFFT circuit
ensures the orthogonality between subcarriers and checked at point 5 in Figure 6.The parallel
substreams are reconverted to serial streams. The cyclic prefix(CP) is added by copying the last
part with length of 16 (equivalent to Ts/4) resulting in 80 bits symbol length as shown in Figure
13.
Figure 13. Adding cyclic prefix.
Finally the MC-CDMA symbols are transmitted to the mobile radio channel at point 6 in Figure
6.
3.1.2. MOBILE RADIO CHANNEL SECTION
To include the effect of the multipath fading channel and Additive White Gaussian Noise
(AWGN), the mobile radio channel is divided into two parts as shown in Figure 14.Multipath
Rayleigh fading channel is considered in this paper. The uplink case is taken into consideration
where each user is affected by certain multipath channel and the faded signals from different
users are added together. The last step is represented by adding the AWGN effect before the
signal reaches the receiver. All the processes which established at the transmitter site was
reversed at the receiver site to get the transmitted message by considering perfect carriers and
symbol synchronization.
10. International Journal of Computer Science & Engineering Survey (IJCSES) Vol.6, No.3, June 2015
18
Figure 14. Channel section.
3.2 BER EVALUATION
The BER calculation is performed by comparing the transmitted information bits with the
received bits. The BER process was evaluated using Monty Carlo principle by taking 200 BER
iterations and taking the average to get more accurate results. Finally the BER is plotted for
different values of Eb/N0 to illustrate the performance of the MC-CDMA system. The system
design parameters used in this MC-CDMA simulator are summarized in Table (3) and the basic
flowchart is shown in Figure 15.
Table 3. Summary of simulation parameters.
11. International Journal of Computer Science & Engineering Survey (IJCSES) Vol.6, No.3, June 2015
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….. to be continued
12. International Journal of Computer Science & Engineering Survey (IJCSES) Vol.6, No.3, June 2015
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Figure 15. MC-CDMA simulator flowchart.
3.3 PERFORMANCE OF MC-CDMA:
3.3.1 EFFECT OF PROCESSING GAIN ON BER:
The effect of varying the processing gain (PG) on the performance of the MC-CDMA are shown
in Figure 16 by varying PGfrom 31 to 63, and 127 for 2 users. It is clear from Figure 16 that BER
becomes more better as PG increased.
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Figure 16. Effect of processing gain on MC-CDMA performance.
3.3.2 EFFECT OF NUMBER OF PATHS ON BER
Figure 17 shows the effect of number of channel paths on the BER of the system for 2 users for
1,2,3 and 4 paths.It is clear that more degradation in system performance occurs as the number of
paths increases.
Figure 17. Effect of number of paths on MC-CDMA performance.
3.3.3 EFFECT OF CODE RATIO OF CONVOLUTIONAL ENCODER ON BER:
Convolutional encoder is used to handle the deep fading caused by the channel. Figure 18shows
the effect of using different coding ratios for 2 users.
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Figure 18. Effect of coding ratio on MC-CDMA performance.
From Figure 18, it is clear that for reference level BER = 10-3
at the receiver, the Eb/No needs to
be 11 dB , 13.5 dB , and 15.5 dB for code ratio of (1/2), for (2/3) and for (3/4) respectively. Also
it could be noticed that for Eb/N0 less than 6 dB the system performance is better in case of no
coding.
3.3.4 EFFECT OF NUMBER OF USERS ON BER:
Figure 19shows the effect of increasing the number of active users on the system performance.
From Figure 19, it is shown that the system is failed to response to more than 2 users, since we
deal here with a conventional detector, because diversity based detector using Rake receiver is out
of the scope of this paper. By using 16-QAMarray modulation and a convolutional encoder of
coding ratio (1/2),we can achieve a best MC-CDMA system performance when applying
interleaver technique as shown in Figure 20.
Figure 19. Effect of number of users on MC-CDMA performance.
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Figure 20. Effect of interleaver on MC-CDMA performance.
4. CONCLUSION
The combination between OFDM technology and CDMA technology resulting an attractive high
speed wireless MC-CDMA communication system. The obtained results showns that the
performance of the MC-CDMA is affected by different parameters such as processing gain,
number of paths, number of active users, coding ratio of convolutional encoder, and
interleaver.MC-CDMA system performance becomes better by increasing the processinggain,
decreasing number of paths, and decreasing the coding ratio. As the number of users increases,
multi access interference(MAI) increases, causing a degradation in system performance. We can
conclude also, depending on the obtained results, that MC-CDMA system performance look
better for higher processing gain lower code ratio using interleaver.
REFERENCES
[1] H.Schulze and C.Luders, Theory and Applications of OFDM and CDMA. Southern Gate, Chichester:
John Wiley and Sons Ltd,2005.
[2] K.Fazel and S. Kaiser, Multi-Carrier and Spread Spectrum Systems. Southern Gate, Chichester: John
Wiley and Sons Ltd,2003.
[3] A.Mourad, On The System Level Performance of MC-CDMA Systems in The Downlink” Ph.D.
dissertation, Rennes Univ.,France, 2006.
[4] W.M.Abdul-Latef, “Performance Improvement of Cellular Communication Systems Using MIMO –
OFDM”, M.S. thesis, Dept. Elect. Eng., Mosul Univ., Iraq, 2006.
[5] Reem Sultan “ Evaluating the Capaciyt of CDMA using SDMATechnique”,Thesis at the University
of Mosul, College of Engineering.2012.
[6] U.S.Goni, and A.M.Turkmani, “BER performance of a direct-sequence CDMA system in multipath
fading mobile radio channels with Rake reception,” Vehicular Technology Conference, 1994 IEEE
44th, ISSN: 1090-3038, Vol.2, pp.747 – 751, Stockholm, 1994.
[7] S.Cho, J. Kim, W.Y.Yang and C.G. Kang " MIMO-OFDM Wireless Communications With
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[9] W.G.Jeon, K.H.Chang and Y.S. Cho, "An Equalization Technique For OFDM and MC-CDMA in a
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[10] IEEE Std. 802.11a-1999, "Part 11: Wireless LAN Medium AccessControl (MAC) and Physical Layer
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Authors
1.A.M Abdulsattar was born in Mousel-Iraq on 1954. Lecturer at Alhdba University
College-Mousel-Iraq. R&D contribution and consultant in wireless communication.
Received BSc degrees from MTC College-Baghdad in 1977. Received MSc and Ph.D.
degrees from ENSAE-France in 1979 and 1983 respectively. From 1983 to 1987
Lecturer at MTC College–Baghdad- Iraq. From 1987 to 2004 Researcher at Industrial
sector for development of Electronic and Communication systems. From 2004 to 2006
contribute in development of a privet sector companies for wireless applications. From
2006 to 2015, Lecturer at Mousel University and Alhdba university college-Mousel-
Iraq.Having many Publications in local and International magazines in the digital communication sector.
2.A. D. Alwazzanwas born in Mousel- Iraq on 1985. Working for privet sector in wireless communication
services. He received the B.Sc. degree from University of Mosul, Mosul, Iraq in 2008,the M.Sc. degree
from University of Mosul, Mosul, Iraq, in 2012.Consultant in wireless communication.
3. KAYDAR MAJEED QUBOA was born in Mosul, Iraq, in 1953. He received the B.Sc.
degree from University of Mosul, Mosul, Iraq, in 1976, the M.Sc.degree from
University of Mosul, Mosul, Iraq, in 1979 and the Ph.D. degree from the University of
Salford, Greater Manchester, United Kingdom, in 1990, all in electrical engineering. He
joint the Electrical Engineering Department, College of Engineerin, University of Mosul
since 1977. He was the Head of Communication Engineering Department, College of
Elrectronics, University of Mosul, from 2002 to 2006. Now he is an Asst. Professor in
Electrical Engineering Department, University of Mosul, Mosul, Iraq. His area of interest
is the effects of EMF on biological materials.