The document discusses performance comparisons of different receiver structures for high data rate ultra wideband communication systems. It analyzes Rake, MMSE, and Rake-MMSE receivers using MATLAB simulations on IEEE 802.15.3a channel models. The Rake-MMSE receiver combines advantages of Rake fingers and equalization to combat inter-symbol interference. Simulation results show the Rake-MMSE receiver achieves a lower bit error rate than Rake or MMSE receivers alone. The number of Rake fingers improves performance at low-medium SNR, while more equalizer taps help at high SNR.
Joint Timing and Frequency Synchronization in OFDMidescitation
With the advent of OFDM for WLAN
communications, as exemplified by IEEE 802.11a, it has become
imperative to have efficient and reliable synchronization
algorithms for OFDM WLAN receivers. The main challenges
with synchronization deal with the frequency offset and delay
spread introduced by the wireless channel. In this paper,
research is done into OFDM timing synchronization and
frequency synchronization techniques.
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.
Computationally Efficient Multi-Antenna Techniques for Multi-User Two-Way Wire...IJECEIAES
In this work, we are interested in implementing, developing and evaluating multi-antenna techniques used for multi-user two-way wireless relay networks that provide a good tradeoff between the computational complexity and performance in terms of symbol error rate and achievable data rate. In particular, a variety of newly multi-antenna techniques is proposed and studied. Some techniques based on orthogonal projection enjoy low computational complexity. However, the performance penalty associated with them is high. Other techniques based on maximum likelihood strategy enjoy high performance, however, they suffer from very high computational complexity. The Other techniques based on randomization strategy provide a good trade-off between the computational complexity and performance where they enjoy low computational complexity with almost the same performance as compared to the techniques based on maximum likelihood strategy.
Joint Timing and Frequency Synchronization in OFDMidescitation
With the advent of OFDM for WLAN
communications, as exemplified by IEEE 802.11a, it has become
imperative to have efficient and reliable synchronization
algorithms for OFDM WLAN receivers. The main challenges
with synchronization deal with the frequency offset and delay
spread introduced by the wireless channel. In this paper,
research is done into OFDM timing synchronization and
frequency synchronization techniques.
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.
Computationally Efficient Multi-Antenna Techniques for Multi-User Two-Way Wire...IJECEIAES
In this work, we are interested in implementing, developing and evaluating multi-antenna techniques used for multi-user two-way wireless relay networks that provide a good tradeoff between the computational complexity and performance in terms of symbol error rate and achievable data rate. In particular, a variety of newly multi-antenna techniques is proposed and studied. Some techniques based on orthogonal projection enjoy low computational complexity. However, the performance penalty associated with them is high. Other techniques based on maximum likelihood strategy enjoy high performance, however, they suffer from very high computational complexity. The Other techniques based on randomization strategy provide a good trade-off between the computational complexity and performance where they enjoy low computational complexity with almost the same performance as compared to the techniques based on maximum likelihood strategy.
Multi carrier equalization by restoration of redundanc y (merry) for adaptive...IJNSA Journal
This paper proposes a new blind adaptive channel shortening approach for multi-carrier systems. The
performance of the discrete Fourier transform-DMT (DFT-DMT) system is investigated with the proposed
DST-DMT system over the standard carrier serving area (CSA) loop1. Enhanced bit rates demonstrated
and less complexity also involved by the simulation of the DST-DMT system.
Performance Analysis of Various Symbol Detection Techniques in Wireless MIMO ...IOSR Journals
Wireless communication is one of the most effective areas of technology development of our time.
Wireless communications today covers a very wide array of applications. In this paper, we study the
performance of general MIMO system, the performance of Zero Forcing (ZF), Linear Least Square Estimator
(LLSE), V-BLAST/ZF, V-BLAST/LLSE of 4x4, 4x6 & 4x8 with 4-QAM & 16-QAM modulation in i i d Rayleigh
fading channel. We seen that SER performance of 4x8 antennas and 4-QAM modulation scheme outperforms
others. Result shows that for higher modulation schemes SER performance degrades as well as SER
performance increases for higher no of receiver antennas
Classical Discrete-Time Fourier TransformBased Channel Estimation for MIMO-OF...IJCSEA Journal
In this document, we look at various time domain channel estimation methods with this constraint of null carriers at spectrumborders.We showin detail howto gauge the importance of the “border effect” depending on the number of null carriers, which may vary from one system to another. Thereby we assess the limit of the technique discussed when the number of null carriers is large. Finally the DFT with the truncated singular value decomposition (SVD) technique is proposed to completely eliminate the impact of the null subcarriers whatever their number. A technique for the determination of the truncation threshold for any MIMO-OFDM system is also proposed.
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.
Using the Channel State Information (CSI) at the transmitter is fundamental for the precoder
design in Multi-user Multiple Input Single Output (MU-MISO-OFDM) systems. In Frequency
Division Duplex (FDD) systems, CSI can be just available at the transmitter through a limited
feedback channel [1], where we assume that each user quantizes its channel direction with a
finite number of quantization bits. In this paper, we consider a scalar quantization (SQ) scheme
of the Channel Direction Information (CDI). Although vector quantization (VQ) schemes [2],
[3] still outperform this scalar scheme in terms of quantization error and Sum rate, the former
scheme suffers from an exponential search complexity and high storage requirements at the
receiver for high number of feedback bits.
Localized Algorithm for Channel Assignment in Cognitive Radio NetworksIJERA Editor
Cognitive Radio has been emerged as a revolutionary solution to migrate the current shortage of spectrum
allocation in wireless networks. In this paper, an improved localized channel allocation algorithm based on
channel weight is proposed. A factor of channel stability is introduced based on link environment, which
efficiently assigns the best channels to the links. Based on the framework, a conflict resolution strategy is used to
make the scheme adaptable to different network conditions. Calculations indicate that this algorithm can reduce
the conflicts, increase the delivery rate and link assignment rate compared with the basic channel assignment
algorithm.
A QUANTITATIVE ANALYSIS OF HANDOVER TIME AT MAC LAYER FOR WIRELESS MOBILE NET...ijwmn
Extensive studies have been carried out for reducing the handover time of wireless mobile network at
medium access control (MAC) layer. However, none of them show the impact of reduced handover time
on the overall performance of wireless mobile networks. This paper presents a quantitative analysis to
show the impact of reduced handover time on the performance of wireless mobile networks. The proposed
quantitative model incorporates many critical performance parameters involve in reducing the handover
time for wireless mobile networks. In addition, we analyze the use of active scanning technique with
comparatively shorter beacon interval time in a handoff process. Our experiments verify that the active
scanning can reduce the overall handover time at MAC layer if comparatively shorter beacon intervals are
utilized for packet transmission. The performance measures adopted in this paper for experimental
verifications are network throughput under different network loads.
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.
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.
Tech report: Fair Channel Allocation and Access Design for Cognitive Ad Hoc N...Polytechnique Montreal
supplement to Globecom paper: L. T. Tan and L. B. Le, ``Fair Channel Allocation and Access Design for Cognitive Ad Hoc Networks,'' in 2012 IEEE Global Communications Conference (IEEE GLOBECOM 2012), Anaheim, California, USA, pp. 1162-1167, December, 2012.
CS Based Channel Estimation for OFDM Systems under Long Delay Channels Using ...IJERA Editor
Orthogonal frequency division multiplexing (OFDM) is a technique which are used in the next-generation wireless communication. Channel estimation in the OFDM technique is one of the big challenges, ever since high-resolution channel estimation can significantly improve the equalization at the receiver and consequently enhance the communication performances. Channel computation using superimposed pilot sequences is also a fully new area, idea for using superimposed pilot sequences has been proposed by various authors for different applications. In this paper, we are introduced a high accurate, low complexity compressive sensing (CS) based channel estimation namely Auxiliary information based Subspace Pursuit (ASP) in TFT-OFDM systems. ASP based channel estimation in TFT-OFDM system is based on two steps. First is, by exploiting the signal structure of recently proposed TDM-OFDM scheme, the supporting channel information is obtained. Second is, we propose the supporting information based subspace pursuit (SP) algorithm to use a very small amount of frequency domain pilots embedded in the OFDM block used for the exact channel estimation. Moreover, the obtained auxiliary channel information is adopted to reduce the complexity of the conventional SP algorithm. Simulation results demonstrate a important reduction of the number of pilots relative to least-squares channel estimation and supporting high-order modulations like 256 QAM.
In this paper, we analyzed a numerical evaluation of the performance of MIMO radio systems in the LTE network environment. Downlink physical layer of the OFDM-MIMO based radio interface is considered for system model and a theoretical analysis of the bit error rate of the two space-time codes (SFBC 2×1 and FSTD 4×2 codes are adopted by the LTE norm as a function of the signal to noise ratio. Analytical expressions are given for transmission over a Rayleigh channel without spatial correlation which is then compared with Monte-Carlo simulations. Further evaluated channel capacity and simulation results show throughput almost reaches to the capacity limit.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Performance Evaluation of Adaptive Continuous Wavelet Transform based Rake Re...IJECEIAES
This paper proposes an adaptive continuous wavelet transform (ACWT) based Rake receiver to mitigate interference for high speed ultra wideband (UWB) transmission. The major parts of the receiver are least mean square (LMS) adaptive equalizer and N-selective maximum ratio combiner (MRC). The main advantage of using continuous wavelet rake receiver is that it utilizes the maximum bandwidth (7.5GHz) of the UWB transmitted signal, as announced by the Federal Communication Commission (FCC). In the proposed ACWT Rake receiver, the weights and the finger positions are updated depending upon the convergence error over a period in which training data is transmitted. Line of sight (LOS) channel model (CM1 from 0 to 4 meters) and the Non line of sight (NLOS) channel models (CM, CM3 and CM4) are the indoor channel models selected for investigating in this research . The performance of the proposed adaptive system is evaluated by comparing with conventional rake and continuous wavelet transform (CWT) based rake. It showed an improved performance in all the different UWB channels (CM1 to CM4) for rake fingers of 2, 4 and 8. Simulations showed that for 8 rake fingers, the proposed adaptive CWT rake receiver has shown an SNR improvement of 2dB, 3dB, 10dB and 2dB respectively over CWT rake receiver in different UWB channels CM1, CM2, CM3 and CM4.
Performance enhancement of audio transmission based on LMMSE methodnooriasukmaningtyas
The research in wireless communication has developed rapidly for the last
decades as a result of raising the demand for efficient data transmission with
more security and accuracy. This paper proposed a system based on the
special multiplexing (SM) technique and linear minimum mean square error
(LMMSE) detection method with the assistance of the hamming code as well
as the interleaving techniques for a better enhanced performance of an audio
transmission. Moreover, the comparison was done between the two systems
for different antenna configurations and with the presence of two types of
modulation: binary phase shift key and quateradure phase shift key. These
systems are employed by Matlab simulation to show significant results in
terms of enhancing the Rayleigh fading channel capacity, bit error rate
(BER) and security as well as in recovering the transmitting audio signals.
Each system has advantages than the others in one performance term respect
to the other terms. The simulation results have provided to prove and discuss
our analysis.
Performance Analysis of Rake Receivers in IR–UWB System IOSR Journals
Suppression of interference in time domain equalizers is attempted for high data rate impulse
radio (IR) ultra wideband communication system. The narrow band systems may cause interference with UWB
devices as it is having very low transmission power and the large bandwidth. SRAKE receiver improves system
performance by equalizing signals from different paths. This enables the use of SRAKE receiver techniques in IR
UWB systems A semi analytical approach is used to investigate the BER performance of SRAKE receiver on
IEEE 802.15.3a UWB channel models. Study on non-line of sight indoor channel models (both CM3 and CM4)
illustrates that bit error rate performance of SRake receiver with NBI performs better than that of Rake receiver
without NBI
Multi carrier equalization by restoration of redundanc y (merry) for adaptive...IJNSA Journal
This paper proposes a new blind adaptive channel shortening approach for multi-carrier systems. The
performance of the discrete Fourier transform-DMT (DFT-DMT) system is investigated with the proposed
DST-DMT system over the standard carrier serving area (CSA) loop1. Enhanced bit rates demonstrated
and less complexity also involved by the simulation of the DST-DMT system.
Performance Analysis of Various Symbol Detection Techniques in Wireless MIMO ...IOSR Journals
Wireless communication is one of the most effective areas of technology development of our time.
Wireless communications today covers a very wide array of applications. In this paper, we study the
performance of general MIMO system, the performance of Zero Forcing (ZF), Linear Least Square Estimator
(LLSE), V-BLAST/ZF, V-BLAST/LLSE of 4x4, 4x6 & 4x8 with 4-QAM & 16-QAM modulation in i i d Rayleigh
fading channel. We seen that SER performance of 4x8 antennas and 4-QAM modulation scheme outperforms
others. Result shows that for higher modulation schemes SER performance degrades as well as SER
performance increases for higher no of receiver antennas
Classical Discrete-Time Fourier TransformBased Channel Estimation for MIMO-OF...IJCSEA Journal
In this document, we look at various time domain channel estimation methods with this constraint of null carriers at spectrumborders.We showin detail howto gauge the importance of the “border effect” depending on the number of null carriers, which may vary from one system to another. Thereby we assess the limit of the technique discussed when the number of null carriers is large. Finally the DFT with the truncated singular value decomposition (SVD) technique is proposed to completely eliminate the impact of the null subcarriers whatever their number. A technique for the determination of the truncation threshold for any MIMO-OFDM system is also proposed.
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.
Using the Channel State Information (CSI) at the transmitter is fundamental for the precoder
design in Multi-user Multiple Input Single Output (MU-MISO-OFDM) systems. In Frequency
Division Duplex (FDD) systems, CSI can be just available at the transmitter through a limited
feedback channel [1], where we assume that each user quantizes its channel direction with a
finite number of quantization bits. In this paper, we consider a scalar quantization (SQ) scheme
of the Channel Direction Information (CDI). Although vector quantization (VQ) schemes [2],
[3] still outperform this scalar scheme in terms of quantization error and Sum rate, the former
scheme suffers from an exponential search complexity and high storage requirements at the
receiver for high number of feedback bits.
Localized Algorithm for Channel Assignment in Cognitive Radio NetworksIJERA Editor
Cognitive Radio has been emerged as a revolutionary solution to migrate the current shortage of spectrum
allocation in wireless networks. In this paper, an improved localized channel allocation algorithm based on
channel weight is proposed. A factor of channel stability is introduced based on link environment, which
efficiently assigns the best channels to the links. Based on the framework, a conflict resolution strategy is used to
make the scheme adaptable to different network conditions. Calculations indicate that this algorithm can reduce
the conflicts, increase the delivery rate and link assignment rate compared with the basic channel assignment
algorithm.
A QUANTITATIVE ANALYSIS OF HANDOVER TIME AT MAC LAYER FOR WIRELESS MOBILE NET...ijwmn
Extensive studies have been carried out for reducing the handover time of wireless mobile network at
medium access control (MAC) layer. However, none of them show the impact of reduced handover time
on the overall performance of wireless mobile networks. This paper presents a quantitative analysis to
show the impact of reduced handover time on the performance of wireless mobile networks. The proposed
quantitative model incorporates many critical performance parameters involve in reducing the handover
time for wireless mobile networks. In addition, we analyze the use of active scanning technique with
comparatively shorter beacon interval time in a handoff process. Our experiments verify that the active
scanning can reduce the overall handover time at MAC layer if comparatively shorter beacon intervals are
utilized for packet transmission. The performance measures adopted in this paper for experimental
verifications are network throughput under different network loads.
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.
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.
Tech report: Fair Channel Allocation and Access Design for Cognitive Ad Hoc N...Polytechnique Montreal
supplement to Globecom paper: L. T. Tan and L. B. Le, ``Fair Channel Allocation and Access Design for Cognitive Ad Hoc Networks,'' in 2012 IEEE Global Communications Conference (IEEE GLOBECOM 2012), Anaheim, California, USA, pp. 1162-1167, December, 2012.
CS Based Channel Estimation for OFDM Systems under Long Delay Channels Using ...IJERA Editor
Orthogonal frequency division multiplexing (OFDM) is a technique which are used in the next-generation wireless communication. Channel estimation in the OFDM technique is one of the big challenges, ever since high-resolution channel estimation can significantly improve the equalization at the receiver and consequently enhance the communication performances. Channel computation using superimposed pilot sequences is also a fully new area, idea for using superimposed pilot sequences has been proposed by various authors for different applications. In this paper, we are introduced a high accurate, low complexity compressive sensing (CS) based channel estimation namely Auxiliary information based Subspace Pursuit (ASP) in TFT-OFDM systems. ASP based channel estimation in TFT-OFDM system is based on two steps. First is, by exploiting the signal structure of recently proposed TDM-OFDM scheme, the supporting channel information is obtained. Second is, we propose the supporting information based subspace pursuit (SP) algorithm to use a very small amount of frequency domain pilots embedded in the OFDM block used for the exact channel estimation. Moreover, the obtained auxiliary channel information is adopted to reduce the complexity of the conventional SP algorithm. Simulation results demonstrate a important reduction of the number of pilots relative to least-squares channel estimation and supporting high-order modulations like 256 QAM.
In this paper, we analyzed a numerical evaluation of the performance of MIMO radio systems in the LTE network environment. Downlink physical layer of the OFDM-MIMO based radio interface is considered for system model and a theoretical analysis of the bit error rate of the two space-time codes (SFBC 2×1 and FSTD 4×2 codes are adopted by the LTE norm as a function of the signal to noise ratio. Analytical expressions are given for transmission over a Rayleigh channel without spatial correlation which is then compared with Monte-Carlo simulations. Further evaluated channel capacity and simulation results show throughput almost reaches to the capacity limit.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Performance Evaluation of Adaptive Continuous Wavelet Transform based Rake Re...IJECEIAES
This paper proposes an adaptive continuous wavelet transform (ACWT) based Rake receiver to mitigate interference for high speed ultra wideband (UWB) transmission. The major parts of the receiver are least mean square (LMS) adaptive equalizer and N-selective maximum ratio combiner (MRC). The main advantage of using continuous wavelet rake receiver is that it utilizes the maximum bandwidth (7.5GHz) of the UWB transmitted signal, as announced by the Federal Communication Commission (FCC). In the proposed ACWT Rake receiver, the weights and the finger positions are updated depending upon the convergence error over a period in which training data is transmitted. Line of sight (LOS) channel model (CM1 from 0 to 4 meters) and the Non line of sight (NLOS) channel models (CM, CM3 and CM4) are the indoor channel models selected for investigating in this research . The performance of the proposed adaptive system is evaluated by comparing with conventional rake and continuous wavelet transform (CWT) based rake. It showed an improved performance in all the different UWB channels (CM1 to CM4) for rake fingers of 2, 4 and 8. Simulations showed that for 8 rake fingers, the proposed adaptive CWT rake receiver has shown an SNR improvement of 2dB, 3dB, 10dB and 2dB respectively over CWT rake receiver in different UWB channels CM1, CM2, CM3 and CM4.
Performance enhancement of audio transmission based on LMMSE methodnooriasukmaningtyas
The research in wireless communication has developed rapidly for the last
decades as a result of raising the demand for efficient data transmission with
more security and accuracy. This paper proposed a system based on the
special multiplexing (SM) technique and linear minimum mean square error
(LMMSE) detection method with the assistance of the hamming code as well
as the interleaving techniques for a better enhanced performance of an audio
transmission. Moreover, the comparison was done between the two systems
for different antenna configurations and with the presence of two types of
modulation: binary phase shift key and quateradure phase shift key. These
systems are employed by Matlab simulation to show significant results in
terms of enhancing the Rayleigh fading channel capacity, bit error rate
(BER) and security as well as in recovering the transmitting audio signals.
Each system has advantages than the others in one performance term respect
to the other terms. The simulation results have provided to prove and discuss
our analysis.
Performance Analysis of Rake Receivers in IR–UWB System IOSR Journals
Suppression of interference in time domain equalizers is attempted for high data rate impulse
radio (IR) ultra wideband communication system. The narrow band systems may cause interference with UWB
devices as it is having very low transmission power and the large bandwidth. SRAKE receiver improves system
performance by equalizing signals from different paths. This enables the use of SRAKE receiver techniques in IR
UWB systems A semi analytical approach is used to investigate the BER performance of SRAKE receiver on
IEEE 802.15.3a UWB channel models. Study on non-line of sight indoor channel models (both CM3 and CM4)
illustrates that bit error rate performance of SRake receiver with NBI performs better than that of Rake receiver
without NBI
Performance Analysis of Rake Receivers in IR–UWB SystemIOSR Journals
ABSTRACT : Suppression of interference in time domain equalizers is attempted for high data rate impulse radio (IR) ultra wideband communication system. The narrow band systems may cause interference with UWB devices as it is having very low transmission power and the large bandwidth. SRAKE receiver improves system performance by equalizing signals from different paths. This enables the use of SRAKE receiver techniques in IR UWB systems A semi analytical approach is used to investigate the BER performance of SRAKE receiver on IEEE 802.15.3a UWB channel models. Study on non-line of sight indoor channel models (both CM3 and CM4) illustrates that bit error rate performance of SRake receiver with NBI performs better than that of Rake receiver without NBI Keywords – Bit error rate, Impulse radio, Non-line of sight, SRAKE receiver, Ultra wideband (UWB)
Intersymbol interference caused by multipath in band limited frequency selective time dispersive channels distorts the transmitted signal, causing bit error at receiver. ISI is the major obstacle to high speed data transmission over wireless channels. Channel estimation is a technique used to combat the intersymbol interference. The objective of this paper is to improve channel estimation accuracy in MIMO-OFDM system by using modified variable step size leaky Least Mean Square (MVSSLLMS) algorithm proposed for MIMO OFDM System. So we are going to analyze Bit Error Rate for different signal to noise ratio, also compare the proposed scheme with standard LMS channel estimation method.
Turbo Detection in Rayleigh flat fading channel with unknown statisticsijwmn
The turbo detection of turbo coded symbols over correlated Rayleigh flat fading channels generated
according to Jakes’ model is considered in this paper. We propose a method to estimate the channel
signal-to-noise ratio (SNR) and the maximum Doppler frequency. These statistics are required by
the linear minimum mean squared error (LMMSE) channel estimator. To improve the system convergence, we redefine the channel reliability factor by taking into account the channel estimation
error statistics. Simulation results for rate 1/3 turbo code and two different normalized fading rates
show that the use of the new reliability factor greatly improves the performance. The improvement
is more substantial when channel statistics are unknown.
CHANNEL ESTIMATION AND MULTIUSER DETECTION IN ASYNCHRONOUS SATELLITE COMMUNIC...ijwmn
In this paper, we propose a new method of channel estimation for asynchronous additive white Gaussian noise channels in satellite communications. This method is based on signals correlation and multiuser interference cancellation which adopts a successive structure. Propagation delays and signals amplitudes are jointly estimated in order to be used for data detection at the receiver. As, a multiuser detector, a single stage successive interference cancellation (SIC) architecture is analyzed and integrated to the channel estimation technique and the whole system is evaluated. The satellite access method adopted is the direct sequence code division multiple access (DS CDMA) one. To evaluate the channel estimation and the detection technique, we have simulated a satellite uplink with an asynchronous multiuser access.
Noise uncertainty effect on multi-channel cognitive radio networks IJECEIAES
Achieving high throughput is the most important goal of cognitive radio networks. The main process in cognitive radio is spectrum sensing that targets getting vacant channels. There are many sensing methods like matched filter, feature detection, interference temperature and energy detection which is employed in the proposed system; however, energy detection suffers from noise uncertainty. In this paper a study of throughput under noise fluctuation effect is introduced. The work in this paper proposes multi-channel system; the overall multi-channel throughput is studied under noise fluctuation effect. In addition, the proficiency of the network has been examined under different number of channels and sensing time with noise uncertainty.
A novel delay dictionary design for compressive sensing-based time varying ch...TELKOMNIKA JOURNAL
Compressive sensing (CS) is a new attractive technique adopted for Linear Time Varying channel estimation. orthogonal frequency division multiplexing (OFDM) was proposed to be used in 4G and 5G which supports high data rate requirements. Different pilot aided channel estimation techniques were proposed to better track the channel conditions, which consumes bandwidth, thus, considerable data rate reduced. In order to estimate the channel with minimum number of pilots, compressive sensing CS was proposed to efficiently estimate the channel variations. In this paper, a novel delay dictionary-based CS was designed and simulated to estimate the linear time varying (LTV) channel. The proposed dictionary shows the suitability of estimating the channel impulse response (CIR) with low to moderate Doppler frequency shifts with acceptable bit error rate (BER) performance.
Bit Error Rate Performance of MIMO Spatial Multiplexing with MPSK Modulation ...ijsrd.com
Wireless communication is one of the most effective areas of technology development of our time. Wireless communications today covers a very wide array of applications. In this, we study the performance of general MIMO system, the general V-BLAST architecture with MPSK Modulation in Rayleigh fading channels. Based on bit error rate, we show the performance of the 2x2 schemes with MPSK Modulation in noisy environment. We also show the bit error rate performance of 2x2, 3x3, 4x4 systems with BPSK modulation. We see that the bit error rate performance of 2x2 systems with QPSK modulation gives us the best performance among other schemes analysed here.
Analysis of Space Time Codes Using Modulation TechniquesIOSR Journals
Abstract: In this Paper, Analysis of channel codes for improving the data rate and reliability of communication over fading channels using multiple transmit antennas has been considered. The codes, namely ’Space Time Codes’ render full diversity and amend coding gain. Performance criteria for designing such codes, under this assumption that the fading is slow and nonselective frequency, is also analysed. Under this research, Study of Frame Error Rate(FER) and outage capacity is compared for different no. Of transmit and receive antennas as well as for different modulation techniques. According to theoretical results FER decreases with increasing SNR and No. Of receiving antennas. Numerical and practical result shows that FER decreases with increasing SNR and no. Of receiving antennas. Keywords: Space time Block Codes ,Space time trellis Codes,Frame Error Rate(FER),Outage capacity,Pairwise Error Probability
A novel and efficient mixed-signal compressed sensing for wide-band cognitive...Polytechnique Montreal
In cognitive radio (CR) networks, unlicensed (cognitive) users can exploit the licensed frequency bands by using spectrum sensing techniques to identify spectrum holes. This paper proposes a distributed compressive spectrum sensing scheme, in which the modulated wide-band converter can apply compressed sensing (CS) directly to analog signals at the sub-Nyquist rate and the central fusion receives signals from multiple CRs and exploits the multiple-measurements-vectors (MMV) subspace pursuit (M-SP) algorithm to jointly reconstruct the spectral support of the wide-band signal. This support is then used to detect whether the licensed bands are occupy or not. Finally, extensive simulation results show the advantages of the proposed scheme. Besides, we also compare the performance of M-SP with M-orthogonal matching pursuit (M-OMP) algorithms.
Indexed-channel estimation under frequency and time-selective fading channels...IJECEIAES
Index modulation (IM) techniques have been employed in different communication systems to improve bandwidth efficiency by carrying additional information bits. In high-mobility communication systems and under both time-selective and frequency-selective fading channels with Doppler spread, channel variations can be tracked by employing pilot-aided channel estimation with minimum mean-squared error estimation. However, inserting pilot symbols among information symbols reduces the system's spectral efficiency in pilot-aided channel estimation schemes. We propose pilot-aided channel estimation with zero-pilot symbols and an energy detection scheme to tackle this issue. Part of the information bit-stream is conveyed by the indices of zero-pilot symbols leading to an increase in the system's spectral efficiency. We used an energy detector at the receiver to detect the transmitted zero-pilot symbols. This paper examines the impacts of diversity order on the zero-pilot symbol detection error probability and the mean-squared of error estimation. The impacts of pilot symbols number and the zero-pilot symbol number on the mean-squared error of the minimum mean-squared error (MMSE) estimator and the system error performance are also investigated in this paper.
Multi-carrier Equalization by Restoration of RedundancY (MERRY) for Adaptive ...IJNSA Journal
This paper proposes a new blind adaptive channel shortening approach for multi-carrier systems. The performance of the discrete Fourier transform-DMT (DFT-DMT) system is investigated with the proposed DST-DMT system over the standard carrier serving area (CSA) loop1. Enhanced bit rates demonstrated and less complexity also involved by the simulation of the DST-DMT system.
In this paper, three beamforming design are considered for multi user MIMO system. First, transmit
beamformers are fixed and the receive (RX) beamformers are calculated. Transmit beamformer (TX-BF)is
projectedas a null space of appropriate channels. It reduces the interference for each user. Then the receiver
beamformer is determined which maximize the SNR. This beamforming design provides less computation time.
The second case is joint TX and RX beamformer for SNR maximization. In this transmitter and receiver
beamformer are calculated using extended alternating optimization (EAO) algorithm. The third one is joint
transmitter and receiver beamforming for SNR and SINR maximization using EAO algorithm. This algorithm
provides better error performance and sum rate performance. All the design cases are simulated by using
standard multipath channel model. Our simulation results illustrate that compared to the least square design and
zero forcing design, the joint TX and RX beamforming design using EAO algorithm provides faster
beamforming and improved error performance and sum rate.
MIMO Channel Estimation Using the LS and MMSE AlgorithmIOSRJECE
Wireless Communication Technology has developed over the past few yearsfor other objectives.The Multiple InputMultiple Output (MIMO) is one of techniques that is used to enhancethe data rates, in which multiple antennas are employed both the transmitter and receiver. Multiple signals are transmitted from different antennas at the transmitter using the same frequency and separated space. Various channel estimation techniques are employed in order to judge the physical effects of the medium present. In this paper, we analyze and implementvarious estimation techniques for MIMO Systems such as Least Squares (LS), Minimum Mean Square Error (MMSE),these techniques are therefore compared to effectively estimate the channel in MIMO System. The results demonstrate that SNR required to support different values of bit error rate varies depending on different low correlation between the transmitting and the receiving antennas .In addition, it is illustrated that when the number of transmitter and receiver antennas increases, the performance of TBCE schemes significantly improves. The Same behavior isalso observed for MIMO system. Performance of both MMSE and LSestimation are the same for allkinds of modulation at small value of SNR but the more we increase the SNR value the more performance gap goes on increasing.
Adaptive blind multiuser detection under impulsive noise using principal comp...csandit
In this paper we consider blind signal detection for an asynchronous code division multiple
access (CDMA) system with Principal component analysis (PCA) in impulsive noise. The blind
multiuser detector requires no training sequences compared with the conventional multiuser
detection receiver. The proposed PCA blind multiuser detector is robust when compared
with knowledge based signature waveforms and the timing of the user of interest. PCA is
a statistical method for reducing the dimension of data set, spectral decomposition of the
covariance matrix of the dataset i.e first and second order statistics are estimated.
Principal component analysis makes no assumption on the independence of the data vectors
PCA searches for linear combinations with the largest variances and when several linear
combinations are needed, it considers variances in decreasing order of importance. PCA
improves SNR of signals used for differential side channel analysis. In different to other
approaches, the linear minimum mean-square-error (MMSE) detector is obtained blindly; the
detector does not use any training sequence like in subspace methods to detect multi user
receiver. The algorithm need not estimate the subspace rank in order to reduce the
computational complexity. Simulation results show that the new algorithm offers substantial
performance gains over the traditional subspace methods.
ADAPTIVE BLIND MULTIUSER DETECTION UNDER IMPULSIVE NOISE USING PRINCIPAL COMP...csandit
In this paper we consider blind signal detection for an asynchronous code division multiple access (CDMA) system with Principal component analysis (PCA) in impulsive noise. The blind multiuser detector requires no training sequences compared with the conventional multiuser detection receiver. The proposed PCA blind multiuser detector is robust when compared with knowledge based signature waveforms and the timing of the user of interest. PCA is a statistical method for reducing the dimension of data set, spectral decomposition of the covariance matrix of the dataset i.e first and second order statistics are estimated.
Principal component analysis makes no assumption on the independence of the data vectors PCA searches for linear combinations with the largest variances and when several linear combinations are needed, it considers variances in decreasing order of importance. PCA
improves SNR of signals used for differential side channel analysis. In different to other approaches, the linear minimum mean-square-error (MMSE) detector is obtained blindly; the detector does not use any training sequence like in subspace methods to detect multi user
receiver. The algorithm need not estimate the subspace rank in order to reduce the computational complexity. Simulation results show that the new algorithm offers substantial performance gains over the traditional subspace methods.
Similar to Performance Analysis of Ultra Wideband Receivers for High Data Rate Wireless Personal Area Network System (20)
ON THE PROBABILITY OF K-CONNECTIVITY IN WIRELESS AD HOC NETWORKS UNDER DIFFER...graphhoc
We compare the probability of k-Connectivity of an ad hoc network under Random Way Point (RWP),City Section and Manhattan mobility models. A Network is said to be k Connected if there exists at least k edge disjoint paths between any pair of nodes in that network at any given time and velocity. Initially, for each of the three mobility models, the movement of the each node in the ad hoc network at a given velocity and time are captured and stored in the Node Movement Database (NMDB). Using the movements in the NMDB, the location of the node at a given time is computed and stored in the Node
Location Database (NLDB).
The Impact of Data Replication on Job Scheduling Performance in Hierarchical ...graphhoc
In data-intensive applications data transfer is a primary cause of job execution delay. Data access time depends on bandwidth. The major bottleneck to supporting fast data access in Grids is the high latencies of Wide Area Networks and Internet. Effective scheduling can reduce the amount of data transferred across the internet by dispatching a job to where the needed data are present. Another solution is to use a data replication mechanism. Objective of dynamic replica strategies is reducing file access time which leads to reducing job runtime. In this paper we develop a job scheduling policy and a dynamic data replication strategy, called HRS (Hierarchical Replication Strategy), to improve the data access efficiencies. We study our approach and evaluate it through simulation. The results show that our algorithm has improved 12% over the current strategies
DISTANCE TWO LABELING FOR MULTI-STOREY GRAPHSgraphhoc
An L (2, 1)-labeling of a graph G (also called distance two labeling) is a function f from the vertex set V (G) to the non negative integers {0,1,…, k }such that |f(x)-f(y)| ≥2 if d(x, y) =1 and | f(x)- f(y)| ≥1 if d(x, y) =2. The L (2, 1)-labeling number λ (G) or span of G is the smallest k such that there is a f with
max {f (v) : vє V(G)}= k. In this paper we introduce a new type of graph called multi-storey graph. The distance two labeling of multi-storey of path, cycle, Star graph, Grid, Planar graph with maximal edges and its span value is determined. Further maximum upper bound span value for Multi-storey of simple
graph are discussed.
Impact of Mobility for Qos Based Secure Manet graphhoc
Secure multicast communication in Mobile Adhoc Networks (MANETs) is challenging due to its inherent characteristics of infrastructure-less architecture with lack of central authority, limited resources such as bandwidth, energy and power. Several group oriented applications over MANETs create new challenges to routing protocols in terms of QOS requirements. In many multicast interactions, due to its frequent node mobility, new member can join and current members can leave at a time. It is necessary to choose a routing protocol which establishes true connectivity between the mobile nodes. The pattern of movement of members is classified into different mobility models and each one has its own distinct features. It is a crucial part in the performance of MANET. Hence key management is the fundamental challenge in achieving secure communication using multicast key distribution for mobile adhoc networks. This paper describes the impact of mobility models for the performance of a new cluster-based multicast tree algorithm with destination sequenced distance vector routing protocol in terms of QOS requirements such as end to end delay, energy consumption and key delivery ratio. For simulation purposes, three mobility models are considered. Simulation results illustrate the performance of routing protocol with different mobility models and different mobility speed under varying network conditions.
A Transmission Range Based Clustering Algorithm for Topology Control Manetgraphhoc
This paper presents a novel algorithm for clustering of nodes by transmission range based clustering (TRBC).This algorithm does topology management by the usage of coverage area of each node and power management based on mean transmission power within the context of wireless ad-hoc networks. By reducing the transmission range of the nodes, energy consumed by each node is decreased and topology is formed. A new algorithm is formulated that helps in reducing the system power consumption and prolonging the battery life of mobile nodes. Formation of cluster and selection of optimal cluster head and thus forming the optimal cluster taking weighted metrics like battery life, distance, position and mobility is done based on the factors such as node density, coverage area, contention index, required and current node degree of the nodes in the clusters
A Battery Power Scheduling Policy with Hardware Support In Mobile Devices graphhoc
A major issue in the ad hoc networks with energy constraints is to find ways that increase their lifetime. The use of multihop radio relaying requires a sufficient number of relaying nodes to maintainnetwork connectivity. Hence, battery power is a precious resource that must be used efficiently in order to avoid early termination of any node. In this paper, a new battery power scheduling policy based on dynamic programming is proposed for mobile devices.This policy makes use of the state information of each cell provided by the smart battery package and uses the strategy of dynamic programming to optimally satisfy a request for power. Using extensive simulation it is proved that dynamic programming based schedulingpolicyimproves the lifetime of the mobile nodes.Also a hardware support is proposed to succeeds in distinguishing between real-time and non-real-time traffic and provides the appropriate grade of service, to meet the time constraints associated with real time traffic.
A Review of the Energy Efficient and Secure Multicast Routing Protocols for ...graphhoc
This paper presents a thorough survey of recent work addressing energy efficient multicast routing protocols and secure multicast routing protocols in Mobile Ad hoc Networks (MANETs). There are so many issues and solutions which witness the need of energy management and security in ad hoc wireless networks. The objective of a multicast routing protocol for MANETs is to support the propagation of data from a sender to all the receivers of a multicast group while trying to use the available bandwidth efficiently in the presence of frequent topology changes. Multicasting can improve the efficiency of the wireless link when sending multiple copies of messages by exploiting the inherent broadcast property of wireless transmission. Secure multicast routing plays a significant role in MANETs. However, offering energy efficient and secure multicast routing is a difficult and challenging task. In recent years, various multicast routing protocols have been proposed for MANETs. These protocols have distinguishing features and use different mechanisms.
Case Study On Social Engineering Techniques for Persuasion Full Text graphhoc
There are plenty of security software in market; each claiming the best, still we daily face problem of viruses and other malicious activities. If we know the basic working principal of such malware then we can very easily prevent most of them even without security software. Hackers and crackers are experts in psychology to manipulate people into giving them access or the information necessary to get access. This paper discusses the inner working of such attacks. Case study of Spyware is provided. In this case study, we got 100% success using social engineering techniques for deception on Linux operating system, which is considered as the most secure operating system. Few basic principal of defend, for the individual as well as for the organization, are discussed here, which will prevent most of such attack if followed.
Breaking the Legend: Maxmin Fairness notion is no longer effective graphhoc
In this paper we analytically propose an alternative approach to achieve better fairness in scheduling mechanisms which could provide better quality of service particularly for real time application. Our proposal oppose the allocation of the bandwidth which adopted by all previous scheduling mechanism. It rather adopt the opposition approach be proposing the notion of Maxmin-charge which fairly distribute the congestion. Furthermore, analytical proposition of novel mechanism named as Just Queueing is been demonstrated
I-Min: An Intelligent Fermat Point Based Energy Efficient Geographic Packet F...graphhoc
Energy consumption and delay incurred in packet delivery are the two important metrics for measuring the performance of geographic routing protocols for Wireless Adhoc and Sensor Networks (WASN). A protocol capable of ensuring both lesser energy consumption and experiencing lesser delay in packet delivery is thus suitable for networks which are delay sensitive and energy hungry at the same time. Thus a smart packet forwarding technique addressing both the issues is thus the one looked for by any geographic routing protocol. In the present paper we have proposed a Fermat point based forwarding technique which reduces the delay experienced during packet delivery as well as the energy consumed for transmission and reception of data packets.
Fault tolerant wireless sensor mac protocol for efficient collision avoidancegraphhoc
In sensor networks communication by broadcast methods involves many hazards, especially collision. Several MAC layer protocols have been proposed to resolve the problem of collision namely ARBP, where the best achieved success rate is 90%. We hereby propose a MAC protocol which achieves a greater success rate (Success rate is defined as the percentage of delivered packets at the source reaching the destination successfully) by reducing the number of collisions, but by trading off the average propagation delay of transmission. Our proposed protocols are also shown to be more energy efficient in terms of energy dissipation per message delivery, compared to the currently existing protocol.
Enhancing qo s and qoe in ims enabled next generation networksgraphhoc
Managing network complexity, accommodating greater numbers of subscribers, improving coverage to support data services (e.g. email, video, and music downloads), keeping up to speed with fast-changing technology, and driving maximum value from existing networks – all while reducing CapEX and OpEX and ensuring Quality of Service (QoS) for the network and Quality of Experience (QoE) for the user. These are just some of the pressing business issues faced by mobileservice providers, summarized by the demand to “achieve more, for less.” The ultimate goal of optimization techniques at the network and application layer is to ensure End-user perceived QoS. The next generation networks (NGN), a composite environment of proven telecommunications and Internet-oriented mechanisms have become generally recognized as the telecommunications environment of the future. However, the nature of the NGN environment presents several complex issues regarding quality assurance that have not existed in the legacy environments (e.g., multi-network, multi-vendor, and multi-operator IP-based telecommunications environment, distributed intelligence, third-party provisioning, fixed-wireless and mobile access, etc.). In this Research Paper, a service aware policy-based approach to NGN quality assurance is presented, taking into account both perceptual quality of experience and technologydependant quality of service issues. The respective procedures, entities, mechanisms, and profiles are discussed. The purpose of the presented approach is in research, development, and discussion of pursuing the end-to-end controllability of the quality of the multimedia NGN-based communications in an environment that is best effort in its nature and promotes end user’s access agnosticism, service agility, and global mobility
Simulated annealing for location area planning in cellular networksgraphhoc
LA planning in cellular network is useful for minimizing location management cost in GSM network. In fact, size of LA can be optimized to create a balance between the LA update rate and expected paging rate within LA. To get optimal result for LA planning in cellular network simulated annealing algorithm is used. Simulated annealing give optimal results in acceptable run-time
Secure key exchange and encryption mechanism for group communication in wirel...graphhoc
Secured communication in ad hoc wireless networks is primarily important, because the communication signals are openly available as they propagate through air and are more susceptible to attacks ranging from passive eavesdropping to active interfering. The lack of any central coordination and shared wireless medium makes them more vulnerable to attacks than wired networks. Nodes act both as hosts and routers and are interconnected by Multi- hop communication path for forwarding and receiving packets to/from other nodes. The objective of this paper is to propose a key exchange and encryption mechanism that aims to use the MAC address as an additional parameter as the message specific key[to encrypt]and forward data among the nodes. The nodes are organized in spanning tree fashion, as they avoid forming cycles and exchange of key occurs only with authenticated neighbors in ad hoc networks, where nodes join or leave the network dynamically.
Simulation to track 3 d location in gsm through ns2 and real lifegraphhoc
In recent times the cost of mobile communication has dropped significantly leading to a dramatic increase in mobile phone usage. The widespread usage has led mobiles to emerge as a strong alternative for other applications one of which is tracking. This has enabled law-enforcing agencies to detect overspeeding vehicles and organizations to keep track its employees. The 3 major ways of tracking being employed presently are (a) via GPS [1] (b) signal attenuation property of a packet [3] and (c) using GSM Network [2]. The initial cost of GPS is very high resulting in low usage whereas (b) needs a very high precision measuring device. The paper presents a GSM-based tracking technique which eliminates the above mentioned overheads, implements it in NS2 and shows the limitations of the real life simulation. An accuracy of 97% was achieved during NS2 simulation which is comparable to the above mentioned alternate methods of tracking.
Coverage and Connectivity Aware Neural Network Based Energy Efficient Routing...graphhoc
There are many challenges when designing and deploying wireless sensor networks (WSNs). One of the key challenges is how to make full use of the limited energy to prolong the lifetime of the network, because energy is a valuable resource in WSNs. The status of energy consumption should be continuously monitored after network deployment. In this paper, we propose coverage and connectivity aware neural network based energy efficient routing in WSN with the objective of maximizing the network lifetime. In the proposed scheme, the problem is formulated as linear programming (LP) with coverage and connectivity aware constraints. Cluster head selection is proposed using adaptive learning in neural networks followed by coverage and connectivity aware routing with data transmission. The proposed scheme is compared with existing schemes with respect to the parameters such as number of alive nodes, packet delivery fraction, and node residual energy. The simulation results show that the proposed scheme can be used in wide area of applications in WSNs.
An Overview of Mobile Ad Hoc Networks for the Existing Protocols and Applicat...graphhoc
Mobile Ad Hoc Network (MANET) is a collection of two or more devices or nodes or terminals with
wireless communications and networking capability that communicate with each other without the aid of
any centralized administrator also the wireless nodes that can dynamically form a network to exchange
information without using any existing fixed network infrastructure. And it’s an autonomous system in
which mobile hosts connected by wireless links are free to be dynamically and some time act as routers at
the same time, and we discuss in this paper the distinct characteristics of traditional wired networks,
including network configuration may change at any time , there is no direction or limit the movement and
so on, and thus needed a new optional path Agreement (Routing Protocol) to identify nodes for these
actions communicate with each other path, An ideal choice way the agreement should not only be able to
find the right path, and the Ad Hoc Network must be able to adapt to changing network of this type at any
time. and we talk in details in this paper all the information of Mobile Ad Hoc Network which include the
History of ad hoc, wireless ad hoc, wireless mobile approaches and types of mobile ad Hoc networks, and
then we present more than 13 types of the routing Ad Hoc Networks protocols have been proposed. In this
paper, the more representative of routing protocols, analysis of individual characteristics and advantages
and disadvantages to collate and compare, and present the all applications or the Possible Service of Ad
Hoc Networks
An Algorithm for Odd Graceful Labeling of the Union of Paths and Cycles graphhoc
In 1991, Gnanajothi [4] proved that the path graph n
P with n vertex and n −1edge is odd graceful, and
the cycle graph Cm with m vertex and m edges is odd graceful if and only if m even, she proved the
cycle graph is not graceful if m odd. In this paper, firstly, we studied the graphCm∪Pn when m = 4, 6,8,10
and then we proved that the graphCm∪Pn
is odd graceful if m is even. Finally, we described an
algorithm to label the vertices and the edges of the vertex set ( ) m n
V C ∪P and the edge set ( ) m n
E C ∪P .
ACTOR GARBAGE COLLECTION IN DISTRIBUTED SYSTEMS USING GRAPH TRANSFORMATIONgraphhoc
A lot of research work has been done in the area of Garbage collection for both uniprocessor and
distributed systems. Actors are associated with activity (thread) and hence usual garbage collection
algorithms cannot be applied for them. Hence a separate algorithm should be used to collect them. If we
transform the active reference graph into a graph which captures all the features of actors and looks like
passive reference graph then any passive reference graph algorithm can be applied for it. But the cost of
transformation and optimization are the core issues. An attempt has been made to walk through these
issues.
A Proposal Analytical Model and Simulation of the Attacks in Routing Protocol...graphhoc
In this work we have devoted to some proposed analytical methods to simulate these attacks, and node mobility in MANET. The model used to simulate the malicious nodes mobility attacks is based on graphical theory, which is a tool for analyzing the behavior of nodes. The model used to simulate the Blackhole cooperative, Blackmail, Bandwidth Saturation and Overflow attacks is based on malicious nodes and the number of hops. We conducted a simulation of the attacks with a C implementation of the proposed mathematical models.
UiPath Test Automation using UiPath Test Suite series, part 3DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 3. In this session, we will cover desktop automation along with UI automation.
Topics covered:
UI automation Introduction,
UI automation Sample
Desktop automation flow
Pradeep Chinnala, Senior Consultant Automation Developer @WonderBotz and UiPath MVP
Deepak Rai, Automation Practice Lead, Boundaryless Group and UiPath MVP
Welocme to ViralQR, your best QR code generator.ViralQR
Welcome to ViralQR, your best QR code generator available on the market!
At ViralQR, we design static and dynamic QR codes. Our mission is to make business operations easier and customer engagement more powerful through the use of QR technology. Be it a small-scale business or a huge enterprise, our easy-to-use platform provides multiple choices that can be tailored according to your company's branding and marketing strategies.
Our Vision
We are here to make the process of creating QR codes easy and smooth, thus enhancing customer interaction and making business more fluid. We very strongly believe in the ability of QR codes to change the world for businesses in their interaction with customers and are set on making that technology accessible and usable far and wide.
Our Achievements
Ever since its inception, we have successfully served many clients by offering QR codes in their marketing, service delivery, and collection of feedback across various industries. Our platform has been recognized for its ease of use and amazing features, which helped a business to make QR codes.
Our Services
At ViralQR, here is a comprehensive suite of services that caters to your very needs:
Static QR Codes: Create free static QR codes. These QR codes are able to store significant information such as URLs, vCards, plain text, emails and SMS, Wi-Fi credentials, and Bitcoin addresses.
Dynamic QR codes: These also have all the advanced features but are subscription-based. They can directly link to PDF files, images, micro-landing pages, social accounts, review forms, business pages, and applications. In addition, they can be branded with CTAs, frames, patterns, colors, and logos to enhance your branding.
Pricing and Packages
Additionally, there is a 14-day free offer to ViralQR, which is an exceptional opportunity for new users to take a feel of this platform. One can easily subscribe from there and experience the full dynamic of using QR codes. The subscription plans are not only meant for business; they are priced very flexibly so that literally every business could afford to benefit from our service.
Why choose us?
ViralQR will provide services for marketing, advertising, catering, retail, and the like. The QR codes can be posted on fliers, packaging, merchandise, and banners, as well as to substitute for cash and cards in a restaurant or coffee shop. With QR codes integrated into your business, improve customer engagement and streamline operations.
Comprehensive Analytics
Subscribers of ViralQR receive detailed analytics and tracking tools in light of having a view of the core values of QR code performance. Our analytics dashboard shows aggregate views and unique views, as well as detailed information about each impression, including time, device, browser, and estimated location by city and country.
So, thank you for choosing ViralQR; we have an offer of nothing but the best in terms of QR code services to meet business diversity!
UiPath Test Automation using UiPath Test Suite series, part 4DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 4. In this session, we will cover Test Manager overview along with SAP heatmap.
The UiPath Test Manager overview with SAP heatmap webinar offers a concise yet comprehensive exploration of the role of a Test Manager within SAP environments, coupled with the utilization of heatmaps for effective testing strategies.
Participants will gain insights into the responsibilities, challenges, and best practices associated with test management in SAP projects. Additionally, the webinar delves into the significance of heatmaps as a visual aid for identifying testing priorities, areas of risk, and resource allocation within SAP landscapes. Through this session, attendees can expect to enhance their understanding of test management principles while learning practical approaches to optimize testing processes in SAP environments using heatmap visualization techniques
What will you get from this session?
1. Insights into SAP testing best practices
2. Heatmap utilization for testing
3. Optimization of testing processes
4. Demo
Topics covered:
Execution from the test manager
Orchestrator execution result
Defect reporting
SAP heatmap example with demo
Speaker:
Deepak Rai, Automation Practice Lead, Boundaryless Group and UiPath MVP
Builder.ai Founder Sachin Dev Duggal's Strategic Approach to Create an Innova...Ramesh Iyer
In today's fast-changing business world, Companies that adapt and embrace new ideas often need help to keep up with the competition. However, fostering a culture of innovation takes much work. It takes vision, leadership and willingness to take risks in the right proportion. Sachin Dev Duggal, co-founder of Builder.ai, has perfected the art of this balance, creating a company culture where creativity and growth are nurtured at each stage.
Dev Dives: Train smarter, not harder – active learning and UiPath LLMs for do...UiPathCommunity
💥 Speed, accuracy, and scaling – discover the superpowers of GenAI in action with UiPath Document Understanding and Communications Mining™:
See how to accelerate model training and optimize model performance with active learning
Learn about the latest enhancements to out-of-the-box document processing – with little to no training required
Get an exclusive demo of the new family of UiPath LLMs – GenAI models specialized for processing different types of documents and messages
This is a hands-on session specifically designed for automation developers and AI enthusiasts seeking to enhance their knowledge in leveraging the latest intelligent document processing capabilities offered by UiPath.
Speakers:
👨🏫 Andras Palfi, Senior Product Manager, UiPath
👩🏫 Lenka Dulovicova, Product Program Manager, UiPath
Essentials of Automations: Optimizing FME Workflows with ParametersSafe Software
Are you looking to streamline your workflows and boost your projects’ efficiency? Do you find yourself searching for ways to add flexibility and control over your FME workflows? If so, you’re in the right place.
Join us for an insightful dive into the world of FME parameters, a critical element in optimizing workflow efficiency. This webinar marks the beginning of our three-part “Essentials of Automation” series. This first webinar is designed to equip you with the knowledge and skills to utilize parameters effectively: enhancing the flexibility, maintainability, and user control of your FME projects.
Here’s what you’ll gain:
- Essentials of FME Parameters: Understand the pivotal role of parameters, including Reader/Writer, Transformer, User, and FME Flow categories. Discover how they are the key to unlocking automation and optimization within your workflows.
- Practical Applications in FME Form: Delve into key user parameter types including choice, connections, and file URLs. Allow users to control how a workflow runs, making your workflows more reusable. Learn to import values and deliver the best user experience for your workflows while enhancing accuracy.
- Optimization Strategies in FME Flow: Explore the creation and strategic deployment of parameters in FME Flow, including the use of deployment and geometry parameters, to maximize workflow efficiency.
- Pro Tips for Success: Gain insights on parameterizing connections and leveraging new features like Conditional Visibility for clarity and simplicity.
We’ll wrap up with a glimpse into future webinars, followed by a Q&A session to address your specific questions surrounding this topic.
Don’t miss this opportunity to elevate your FME expertise and drive your projects to new heights of efficiency.
Key Trends Shaping the Future of Infrastructure.pdfCheryl Hung
Keynote at DIGIT West Expo, Glasgow on 29 May 2024.
Cheryl Hung, ochery.com
Sr Director, Infrastructure Ecosystem, Arm.
The key trends across hardware, cloud and open-source; exploring how these areas are likely to mature and develop over the short and long-term, and then considering how organisations can position themselves to adapt and thrive.
Accelerate your Kubernetes clusters with Varnish CachingThijs Feryn
A presentation about the usage and availability of Varnish on Kubernetes. This talk explores the capabilities of Varnish caching and shows how to use the Varnish Helm chart to deploy it to Kubernetes.
This presentation was delivered at K8SUG Singapore. See https://feryn.eu/presentations/accelerate-your-kubernetes-clusters-with-varnish-caching-k8sug-singapore-28-2024 for more details.
GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using Deplo...James Anderson
Effective Application Security in Software Delivery lifecycle using Deployment Firewall and DBOM
The modern software delivery process (or the CI/CD process) includes many tools, distributed teams, open-source code, and cloud platforms. Constant focus on speed to release software to market, along with the traditional slow and manual security checks has caused gaps in continuous security as an important piece in the software supply chain. Today organizations feel more susceptible to external and internal cyber threats due to the vast attack surface in their applications supply chain and the lack of end-to-end governance and risk management.
The software team must secure its software delivery process to avoid vulnerability and security breaches. This needs to be achieved with existing tool chains and without extensive rework of the delivery processes. This talk will present strategies and techniques for providing visibility into the true risk of the existing vulnerabilities, preventing the introduction of security issues in the software, resolving vulnerabilities in production environments quickly, and capturing the deployment bill of materials (DBOM).
Speakers:
Bob Boule
Robert Boule is a technology enthusiast with PASSION for technology and making things work along with a knack for helping others understand how things work. He comes with around 20 years of solution engineering experience in application security, software continuous delivery, and SaaS platforms. He is known for his dynamic presentations in CI/CD and application security integrated in software delivery lifecycle.
Gopinath Rebala
Gopinath Rebala is the CTO of OpsMx, where he has overall responsibility for the machine learning and data processing architectures for Secure Software Delivery. Gopi also has a strong connection with our customers, leading design and architecture for strategic implementations. Gopi is a frequent speaker and well-known leader in continuous delivery and integrating security into software delivery.
State of ICS and IoT Cyber Threat Landscape Report 2024 previewPrayukth K V
The IoT and OT threat landscape report has been prepared by the Threat Research Team at Sectrio using data from Sectrio, cyber threat intelligence farming facilities spread across over 85 cities around the world. In addition, Sectrio also runs AI-based advanced threat and payload engagement facilities that serve as sinks to attract and engage sophisticated threat actors, and newer malware including new variants and latent threats that are at an earlier stage of development.
The latest edition of the OT/ICS and IoT security Threat Landscape Report 2024 also covers:
State of global ICS asset and network exposure
Sectoral targets and attacks as well as the cost of ransom
Global APT activity, AI usage, actor and tactic profiles, and implications
Rise in volumes of AI-powered cyberattacks
Major cyber events in 2024
Malware and malicious payload trends
Cyberattack types and targets
Vulnerability exploit attempts on CVEs
Attacks on counties – USA
Expansion of bot farms – how, where, and why
In-depth analysis of the cyber threat landscape across North America, South America, Europe, APAC, and the Middle East
Why are attacks on smart factories rising?
Cyber risk predictions
Axis of attacks – Europe
Systemic attacks in the Middle East
Download the full report from here:
https://sectrio.com/resources/ot-threat-landscape-reports/sectrio-releases-ot-ics-and-iot-security-threat-landscape-report-2024/
PHP Frameworks: I want to break free (IPC Berlin 2024)Ralf Eggert
In this presentation, we examine the challenges and limitations of relying too heavily on PHP frameworks in web development. We discuss the history of PHP and its frameworks to understand how this dependence has evolved. The focus will be on providing concrete tips and strategies to reduce reliance on these frameworks, based on real-world examples and practical considerations. The goal is to equip developers with the skills and knowledge to create more flexible and future-proof web applications. We'll explore the importance of maintaining autonomy in a rapidly changing tech landscape and how to make informed decisions in PHP development.
This talk is aimed at encouraging a more independent approach to using PHP frameworks, moving towards a more flexible and future-proof approach to PHP development.
Assuring Contact Center Experiences for Your Customers With ThousandEyes
Performance Analysis of Ultra Wideband Receivers for High Data Rate Wireless Personal Area Network System
1. ! " #!#
10.5121/jgraphhoc.2010.2104 31
Bikramaditya Das*
and Susmita Das, Member, IEEE*
*
Department of Electrical Engineering, National Institute of Technology,
Rourkela -769008, India
adibik09@gmail.com
sdas@nitrkl.ac.in
ABSTRACT
For high data rate ultra wideband communication system, performance comparison of Rake, MMSE and
Rake-MMSE receivers is attempted in this paper. Further a detail study on Rake-MMSE time domain
equalizers is carried out taking into account all the important parameters such as the effect of the number
of Rake fingers and equalizer taps on the error rate performance. This receiver combats inter-symbol
interference by taking advantages of both the Rake and equalizer structure. The bit error rate
performances are investigated using MATLAB simulation on IEEE 802.15.3a defined UWB channel
models. Simulation results show that the bit error rate probability of Rake-MMSE receiver is much better
than Rake receiver and MMSE equalizer. Study on non-line of sight indoor channel models illustrates
that bit error rate performance of Rake-MMSE (both LE and DFE) improves for CM3 model with smaller
spread compared to CM4 channel model. It is indicated that for a MMSE equalizer operating at low to
medium SNR values, the number of Rake fingers is the dominant factor to improve system performance,
while at high SNR values the number of equalizer taps plays a more significant role in reducing the error
rate.
KEYWORDS
UWB, Rake receiver, MMSE, Rake-MMSE, Bit Error Rate, LE, DFE.
1. INTRODUCTION
Ultra-wideband (UWB) has recently evoked great interest and its potential strength lies in its
use of extremely wide transmission bandwidth. Furthermore, UWB is emerging as a solution for
the IEEE 802.15a (TG3a) standard which is to provide a low complexity, low cost, low power
consumption and high data-rate among Wireless Personal Area Network (WPAN) devices. An
aspect of UWB transmission is to combat multipath propagation effects. Rake receivers can be
employed since they are able to provide multipath diversity [1-3]. Another aspect is to eliminate
or combat the inter-symbol interference (ISI) which distorts the transmitted signal and causes bit
errors at the receiver, especially when the transmission data rate is very high as well as for
which are not well synchronized. In [1] and [3], the “rake decorrelating effect” was mentioned
as a way to combat ISI. Combination of spatial diversity combining and equalization is a well
established scheme for frequency selective fading channels. In [5], a combined rake and
equalizer structure was proposed for high data rate UWB systems. In this paper, the
performance of a rake-MMSE-equalizer receiver similar to [5] is investigated for different
number of rake fingers and equalizer taps using a semi-analytical approach. We propose at first
2. ! " #!#
32
to study time equalization with combined Rake-MMSE equalizer structure. We show that, for a
MMSE equalizer operating at low to medium SNR’s, the number of Rake fingers is the
dominant factor to improve system performance, while, at high SNR’s the number of equalizer
taps plays a more significant role in reducing error rates[7-8]. We show that for high frequency
selective channels such as the CM4 one, a linear equalizer structure is not sufficient and must be
replaced by a decision feedback equalizer (DFE) structure. Furthermore, we propose a simple
recursive gradient based algorithm to implement the equalizer structures.
The rest of the paper is organized as follows. In Section 2 we study the signals and system
model for IEEE UWB channel modelling. Section 3 is devoted principles of equalizations and
receiver structure. In section 4 we study performance analysis for Rake-MMSE receiver.
Simulation results are discussed in Section 5. Section 6 concludes the paper.
2. SIGNALS AND SYSTEM MODEL
For a single user system, the continuous transmitted data stream is written
+∞
−∞=
−=
k
sTktpkdts ).().()( (1)
Where d(k) are stationary uncorrelated BPSK data and Ts is the symbol duration. Throughout
this paper we consider the application of a root raised cosine (RRC) transmit filter p(t) with roll-
off factor = 0.3. The UWB pulse p(t) has duration Tuwb (Tuwb < Ts ).
The channel models used in this paper are the model proposed by IEEE 802.15.3a Study Group
[10]. In the normalized models provided by IEEE 802.15.3a Study Group, different channel
characteristics are put together under four channel model scenarios having rms delay spreads
ranging from 5 to 26 nsec. For this paper four channel models, derived from the IEEE 802.15
channel modelling working group. In IEEE 802.15.3a working group, the UWB channel is
further classified into four models. Channel model 1 (CM1) represents LOS and distance from 0
to 4 m UWB channel, while channel model 2 (CM2) represents NLOS and distance from 0 to 4
m UWB channel. Distance from 4 m to 10 m and NLOS UWB channel is modelled as CM3 and
distance over 10 m NLOS UWB channels are all classified into the extreme model CM4.
The impulse response can be written as
=
−=
M
p
pp thth
0
)(.)( τδ (2)
Parameter M is the total number of paths in the channel.
3. PRINCIPLE OF RECEIVERS STRUCTURE
3.1. RAKE RECEIVER
Rake receivers are used in time-hopping impulse radio systems and direct sequence spread
spectrum systems (DS-SS) for matched filtering of the received signal [9]. The receiver
structure consists of a matched filter that is matched to the transmitted waveform that represents
one symbol, and a tapped delay line that matches the channel impulse response. It is also
possible to implement this structure as a number of correlators that are sampled at the delays
related to specific number of multipath components; each of those correlators can be called
“Rake finger.” A Rake receiver structure is shown in Fig.1.
3. ! " #!#
33
Figure.1. UWB RAKE receiver structure
The received signal first passes through the receiver filter matched to the transmitted pulse and
is given by
)().(.)(
)(*)()(*)(*)()(
tnTktmhkd
tptntpthtstr
is
k i
i
Λ∞+
−∞=
+−−=
−+−=
τ
(3)
Where p(-t) represents the receiver matched filter, “*” stands for convolution operation and
n(t) is the additive white Gaussian noise (AWGN) with zero mean and variance N0/ 2 . Also,
m (t ) = p (t ) * p ( −t ) and n (t ) = n (t ) * p ( −t ) .
Combining the channel impulse response (CIR) with the transmitter pulse shape and the
matched filter, we have
)(.)(*)(*)()(
0
~
i
M
i
i tmhtpthtpth τ−=−=
=
(4)
The output of the receiver filter is sampled at each Rake finger. The minimum Rake finger
separation is Tm = Ts / Nu , where Nu is chosen as the largest integer value that would result in
Tm spaced uncorrelated noise samples at the Rake fingers
( ) ( )( ) ( )kdtTknhtTnv is
k
ls ... 0
'
~
0
'
++−=++
+∞
−∞=
ττ (5)
where l is the delay time corresponding to the lth
Rake finger and is an integer multiple of Tm.
Parameter t0 corresponds to a time offset and is used to obtain the best sampling time. Without
loss of generality, t0 will be set to zero in the following analysis.
3.2. MMSE STRUCTURE
In reality the noise component due to the physical channel cannot be ignored. In the presence of
additive Gaussian noise at the receiver input, the output of the equalizer at the nth
sampling
instant is given by
−=
−=
N
NK
knkn rbyˆ (6)
The mean square error (MSE) for the equalizer having 2N+1 taps, denoted by J(N) is
−=−=
−=
−
2
2
ˆ)(
N
Nk
knknnn rbxEyxENJ (7)
J(N) with respect to the equalizer coefficients (bk) is obtained by the following differentiation:
0
)(
=
kdb
NdJ
(8)
Equation (7) leads to the necessary condition for the minimum MSE given by
4. ! " #!#
34
xrr RbR = xrr RRb 1−
= (9)
WHERE
T
xrxrxrxr NRRNRR ))()....0()....(( −= (10)
)0()()2(
)1()1()12(
...
...
)2().......().......0(
2 −−
+−+−
=
rrNr
rrr
rrr
r
RNRNR
RNRNR
NRNRR
R (11)
3.3. RAKE-MMSE STRUCTURE
The receiver structure is illustrated in Fig. 2 and consists in a Rake receiver followed by a linear
equalizer. As we will see later on, a structure gives better performances over UWB channels
when the number of equalizer taps is sufficiently large. The received signal first passes through
the receiver filter matched to the transmitted pulse (3). The output of the receiver filter is
sampled at each Rake finger. The minimum Rake finger separation is Tm = Ts / Nu , where Nu is
chosen as the largest integer value that would result in Tm spaced uncorrelated noise samples at
the Rake fingers(4). In a first approach, complete channel state information (CSI) is assumed to
be available at the receiver. For general selection combining, the Rake fingers ( ’s) are selected
as the largest L (L Nu) sampled signal at
Figure.2. UWB RAKE-MMSE receiver structure
the matched filter output within one symbol time period at time instants l ,l = 1, 2, ..., L . A
feasible implementation of multipath diversity combining can be obtained by a selective-Rake
(SRake) receiver, which combines the L best, out of Nu, multipath components. Those L best
components are determined by a finger selection algorithm. For a maximal ratio combining
(MRC) Rake receiver, the paths with highest signal-to-noise ratios (SNRs) are selected, which is
an optimal scheme in the absence of interfering users and intersymbol interference (ISI). For a
minimum mean square error (MMSE) Rake receiver, the “conventional” finger selection
algorithm is to choose the paths with highest signal-to-interference-plus-noise ratios (SINRs)
[2]. The received signal sampled at the l th
Rake finger in the nth
data symbol interval is given by
equation (5).
The Rake combiner output at time t = n.Ts is
( ) ( )'
ls
L
1l
l
'
ls
L
1l
l T.nn.T.nv.]n[y τβτβ
Λ
+++=
==
(12)
Choosing the correct Rake finger placement leads to the reduction of ISI and the performance
can be dramatically improved when using an equalizer to combat the remaining ISI.
Considering the necessary tradeoff between complexity and performance, a sub-optimum
classical criterion for updating the equalizer taps is the MMSE criterion.
5. ! " #!#
35
4. PERFORMANCE ANALYSIS
In this part, due to the lack of place we will only discuss the matrix block computation of linear
equalizers. Furthermore, we suppose perfect channel state information (CSI). Assuming that the
n data bit is being detected, the MMSE criterion consists in minimizing
)()(
2
−
Λ
ndndE
(13)
where d( n ) is the equalizer output. Rewriting the Rake output signal, one can
distinguish the desired signal, the undesired ISI and the noise as
( )( )
( )'
ls
L
1l
l
'
ls
~
nk
L
1l
l
'
l
~L
1l
l
T.nn.
)k(d.T.knh.)n(d.)(h.)n(y
τβ
τβτβ
Λ
++
+−+=
=
≠ ==
(14)
where the first term is the desired output. The noise samples at different fingers, n (n.Ts + l ), l
= 1... L, are uncorrelated and therefore independent, since the samples are taken at
approximately the multiples of the inverse of the matched filter bandwidth. It is assumed that
the channel has a length of (n1 + n2 + 1).Ts. That is, there is pre-cursor ISI from the subsequent
n1 symbols and post-cursor ISI from the previous n2 symbols, and n1 and n2 are chosen large
enough to include the majority of the ISI effect. Using (8), the Rake output can be expressed
now in a simple form as
( ) ( ) ( )
[ ] ( )nnnd
nnkndndny
T
n
k
nk
k
~
~
0
0 ..)(
2
1
+=
+−+=
≠
−=
φ
αα
(15)
where coefficient K’s are obtained by matching (14) and (15).
T
21nn )]n-...d(n)....d(n).n[d(nd[n]and +== ]......[ 21 0 αααφ
The superscript denotes the transpose operation. The output of the linear equalizer is obtained as
( ) ( ) ( )ncncrnycnd TT
k
kr
r ηγ +=−=
−=
Λ 2
1
.)( (16)
where c = [c−K1 ...c0 ...c K 2] contains the equalizer taps. Also
[ ] [ ] [ ] [ ][ ]TTTT
KndndKndn 21 ...... −+= φφφγ
[ ] ( ) ( ) ( )
T
KnnnnKnnn =+= 2
~~
1
~
......η (17)
The mean square error (MSE) of the equalizer,
( ) [ ] [ ]−−
2
ncncndE TT
ηγ (18)
which is a quadratic function of the vector c, has a unique minimum solution. Here, the
expectation is taken with respect to the data symbols and the noise. Defining matrices R, p and
N as
[ ] [ ][ ]n.nE T
γγ=R (19)
6. ! " #!#
36
( ) [ ][ ]n.ndE γ=p (20)
[ ] [ ][ ]n.nE T
ηη=N (21)
The equalizer taps are given by
pNRc .)( 1−
+= (22)
and the MMSE is
pNRpJ T
d .)( 12
min
−
+−= σ (23)
])([
22
ndEd =σ
Evaluating the expectation over R and p with respect to the data and the noise, we have
[ ] [ ] 1,1,0
21212
...... ++++− == KKKKji
T
KK rRp ααα
(24)
Where
1nn,1nnk,lji,j,i
T
j,i 2121
]f[FandFr ++++== φφ
−≠−
−=−
=
ijkl
ijkl
flk
,0
,1
(25)
[ ] [ ][ ] I..
2
N
n.nEN 1KK
L
1l
2
l
0T
21 ++
=
== βηη
(26)
Where I is the identity matrix. This Rake-equalizer receiver will eliminate ISI as far as the
number of equalizer’s taps gives the degree of freedom required. In general, the equalizer output
can be expressed as
( ) ( ) )(.)(.
0
10 nwindqndqnd
i
+−+=
=
Λ
(27)
.with nnn cq α=
The variance of w( n ) is
( ) 2
.. 0
1
2
1
22
2
1
N
Ec p
L
l
K
Ki
inw
=
=−=
βσ (28)
Where Ep is the pulse energy.
the case of DFE, assuming error free feedback, the input data vector can be written in
the form of
]]...1[][]...[[][ 21 Kn
TT
DFE dndndKndn −−Φ+Φ=γ
(29)
Using the same approach as for the linear equalizer, the MMSE feedforward taps for tap
equalizer are obtained as
DFEDFEDFEDFE pNRC 1
)( −
+= (30)
Where ]0....0....[ 01 ccC KDFE −=
Also
=
2K
T
F
DFE
IU
UR
R
(31)
7. ! " #!#
37
Where RF=(K1+1) square matrix with its element defined by (19) .Matrix U is defined
by
1K1,........
,.....1ij
1
2
]u[
+=
== KiU
(32)
Matrix NDFE and vector DFEp are given by
]0........0.......K[p
OO
OI2/N
N
01DFE
KK1K,K
L
1l
K,1KK
2
l0
DFE
2,212
2111
αα
β
=
=
+
=
++
(33)
Where matrix 0 is the all zero matrix.
The MMSE feedback taps are then obtained in terms of feed forward taps and matrix U.
[c1………….ck2]=[c-K1……………c0]UT
(34)
Conditioned on a particular channel realization, h= [h1………hI],an upper bound for the
probability of error using the chernoff bound technique given by
)
2
/1
exp()ˆ(
min
2
min
J
J
hddP d
nn
σ−
−≤≠ (35)
An exact BER expression with independent noise and ISI terms can be expressed as a series
expansion is given by
∏
≠
==
×
−
−=≠
2
1
0
1
0
22
)cos(
)sin()2/exp(2
2
1
)ˆ(
N
n
Nn
n
z
zodd
z
nn zwq
z
zwqwz
hddP
π
(36)
Note that ISI comes from the interfering symbols in the range of N1Ts and N2Ts. Parameter z and
w determine the accuracy of the error rate given by (35). Set the qi’ s that are within the span of
the feedback taps to be 0, which corresponds to zero post-cursor ISI for the span of feedback
taps.
5. SIMULATION STUDY AND ANALYSIS
5.1. Signal Waveform
The pulse shape adopted in the numerical calculations and simulations is the second derivative
of the Gaussian pulse given by
))(t/exp(-2])(t/4-[1=w(t) 22
επεπ (37)
5.2. Channel Model Parameter (IEEE 802.15.3a)
As we mentioned it before, we study the case of UWB channels CM3 and CM4 channel models.
We have used an oversampling factor of eight for the root raised cosine (RRC) pulse. According
8. ! " #!#
38
to this sampling rate, time channel spread is chosen equal to 100 for CM4 and 70 for CM3, this
corresponds to respectively 12 =100 / 8 and 9 = 70 / 8 transmitted symbols. This choice enables
to gather 99% of the channel energy. The coherence bandwidths of CM3 and CM4 simulation
are 10.6 MHz and 5.9 MHz respectively. The data rate is chosen to be 200 Mbps, one of the
optional data rates proposed for IEEE standard. The size of the transmitted packets is equal to
2560 BPSK symbols including a training sequence of length 512. CIR remains constant over the
time duration of a packet. The root raised cosine (RRC) pulse with roll off factor α =0.5 is
employed as the pulse-shaping filter. The CM3 and CM4 indoor channel model is adopted in
simulation. The simulated channel impulse responses for CM3 and CM4 are shown in figure
4 and figure 6. The power delay profiles for CM3 and CM4 are plotted in figure 5and figure
7 respectively: The simulation parameter settings for the two channel models are listed in
Table.1. The pulse waveform and power spectral density are showed as figure 3.
Table.1 Parameter Settings for IEEE UWB Channel Models
Scenario Λ(1/ns) λ (1/ns) Γ (1/ns) γ (1/ns) ξσ (dB) ςσ (dB) gσ (dB)
CM3 0.0067 2.1 14 7.9 3.3941 3.3941 3
CM4 0.0067 2.1 24 12 3.3941 3.3941 3
-1 -0.5 0 0.5 1
x 10
-9
-0.5
0
0.5
1
TIME
AMPLITUDE
0 2 4 6
x 10
10
0
0.05
0.1
0.15
0.2
FREQUENCY
AMPLITUDE
4 6 8 10 12 14 16
x 10
9
-120
-100
-80
-60
-40
-20
0
FREQUENCY
PSD
Figure.3. Second derivative of Gaussian pulse
Figure.4. Channel Impulse Response of CM3 (NLOS)
9. ! " #!#
39
Figure.5. Power Delay Profile of CM3 Channel model
Figure.6. Channel Impulse Response of CM4 (NLOS)
Figure.7. Power Delay Profile of CM4 Channel model
5.3. BER ANALYSIS
In the case of time domain equalization, we have at first to optimize the number of Rake fingers
and the number of equalizer taps. The Rake fingers are regularly positioned according to time
channel spread and the number of fingers. For example, in the case of CM4 channel, with L =
10. Figure.8 and figure.9 show the effect rake, MMSE and Rake-MMSE using Monte-Carlo
simulation. The Rake combiner output at time t = n.Ts. The BER simulation results obtained
using CM3 channel data is shown in figure.(8). As expected, using an MMSE equalizer to
compensate for ISI, a relative improvement is observed. The major comparison lies in the Rake-
MMSE receiver versus the Rake receiver. Rake-MMSE receiver has around1.8dB performance
improvement compared to a channel with rake receivers for CM3 channel.
10. ! " #!#
40
0 2 4 6 8 10 12 14 16
10
-5
10
-4
10
-3
10
-2
10
-1
10
0
SNR(dB)
BER
CM3 CHANNEL
RAKE-MMSE
rake
MMSE
Figure.8. Performance of UWB receivers for CM3 channel model
0 2 4 6 8 10 12 14 16
10
-5
10
-4
10
-3
10
-2
10
-1
10
0
SNR(dB)
BER
CM4 CHANNEL
RAKE-MMSE
MMSE
rake
Figure.9. Performance of UWB receivers for CM4 channel model
Using CM4 channel data, the simulation results obtained as shown in figure.9.Using Rake-
MMSE, i.e. Rake-MMSE and a rake receiver a gain of around 4dB is observed. This result can
be explained by considering the fact that at high SNR’s it is mainly the ISI that affects the
system performance whereas at low SNR’s the system noise is also a major contribution in
system degradation (more signal energy capture is required). The performance dramatically
improves when the number of Rake fingers and the equalizer taps are increased simultaneously
in Rake-MMSE receiver. Performance of UWB Rake-MMSE-receiver for different number of
equalizer taps and rake fingers for CM3 channel model as shown in figure.10. At 10-3
BER floor
DFE provides more than 2dB SNR improvement than that of LE for CM3 channel model.
11. ! " #!#
41
0 5 10 15 20 25 30
10
-4
10
-3
10
-2
10
-1
10
0
SNR(dB)
BER
K=10,L=10,LE CM3
K=10,L=10,DFE CM3
Figure.10. Performance of UWB rake-MMSE-receiver for different number of equalizer taps
and rake fingers for CM3 channel model
0 5 10 15 20 25 30
10
-4
10
-3
10
-2
10
-1
10
0
SNR(dB)
BER
K=20,L=1,LE CM4(upperbound)
K=20,L=1,LE CM4
K=3,L=20,LE CM4
K=20,L=10,LE CM4
K=3,L=10,DFE CM4
K=3,L=20,DFE CM4
K=20,L=10,DFE CM4
DFE
LE
Figure.11. Performance of UWB rake-MMSE-receiver for different number of equalizer taps
and rake fingers for CM4 channel model
At low to medium SNR’s, however, the receiver with more Rake fingers outperforms the one
that has more equalizer taps but fewer Rake fingers. This result can be explained by considering
the fact that at high SNR’s it is mainly the ISI that affects the system performance whereas at
low SNR’s the system noise is also a major contribution in system degradation (more signal
energy capture is required). The performance dramatically improves when the number of Rake
12. ! " #!#
42
fingers and the equalizer taps are increased simultaneously, i.e. K = 20, L = 10 as shown in
figure.11. As expected the receiver has better performance over CM3 with smaller delay spread
than CM4. Again BER performance observed on different UWB NLOS channel models
(CM3 and CM4) shows that LE fails to perform satisfactorily at high SNR’s due to
presence of zeros outside the unit circle. These difficulty BER floor can be overcome
DFE structure. A DFE outperforms a linear equalizer of the same filter length, and the
performance further improve with increase in number of equalizer taps.DFE
performances are computed by Monte-Carlo computer simulations, using a training
sequence with length 500.
6. CONCLUSION
UWB is emerging as a solution for the IEEE 802.15a (TG3a) standard which is to
provide a low complexity, low cost, low power consumption and high data-rate among
Wireless Personal Area Network (WPAN) devices. For high data rate short range, the
receivers combats inter-symbol interference by taking advantage of the Rake and
MMSE equalizer structure by using different UWB channel models CM3 and CM4. For
a MMSE equalizer operating at low to medium SNR’s, the number of Rake fingers is
the dominant factor to improve system performance, while, at high SNR’s the number
of equalizer taps plays a more significant role in reducing error rates. One can observe a
BER floor at high SNR’s the receiver has better performance over CM3 with smaller
delay spread thanCM4 in non-line of sight indoor channel models . Rake-MMSE
receiver has around1.8dB performance improvement compared to a channel with rake
receivers for CM3 channel model. Again BER performance observed on different UWB
channel models (CM3 and CM4) shows that DFE outperforms a LE of the same filter
length, and the performance further improve with increase in number of equalizer taps.
It is concluded that increasing the number of rake fingers performance become superior
at low to medium SNR. These architecture has opened up new directions in designing
efficient time domain equalizers for UWB system and can be implemented in DSP
processors for real - time applications.
REFERENCES
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for MMSE Rake Receivers in Impulse Radio Ultra-Wideband Systems", in Proc IEEE WCNC
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13. ! " #!#
43
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Authors
Bikramaditya Das received his B.Tech in Electronics and Telecommunications
Engineering from the University of B.P.U.T, Rourkela, Orissa, India, in 2007.
From 2008 to till now he is a research Fellow under the Department of Electrical
Engineering at the N.I.T, Rourkela, India. He is a Member IEI.
Dr.Susmita Das, Ph.D, is Associate Professor of Electrical Engineering, NIT,
and Rourkela, India. She has twenty years of teaching and research experience
and has many research papers to her credit. She is Member IEEE, Fellow IETE,
LM ISTE and Member IEI. Her research interests include Wireless
Communication, DSP, and Application of Soft Computing Techniques etc.