A new quadrature coded OFDM system is proposed. The transmitted data symbols are grouped in such format that the in phase side and the quadrature side of the symbols are arranged in opposite order. By analysis an...A new quadrature coded OFDM system is proposed. The transmitted data symbols are grouped in such format that the in phase side and the quadrature side of the symbols are arranged in opposite order. By analysis and simulation, the performance of the new system can be improved greatly, as well as the harmful influences on the system owing to frequency offset can be reduced effectively, which can combat the disadvantages of OFDM system.展开更多
High Peak-to-Average Power Ratio(PAPR)is one of the major drawbacks of Orthogonal Frequency DivisionMultiplexing(OFDM)systems.This paper presents the structures of the particular bit sequences leading to the maximumPA...High Peak-to-Average Power Ratio(PAPR)is one of the major drawbacks of Orthogonal Frequency DivisionMultiplexing(OFDM)systems.This paper presents the structures of the particular bit sequences leading to the maximumPAPR(PAPR_(max))in Carrier-Interferometry OFDM(CI/OFDM)and Pseudo Orthogonal Carrier-Interferometry OFDM(PO-CI/OFDM)systems for Binary Phase Shift Keying(BPSK)modulation.Furthermore,the simulation and analysisof PAPR_(max) and PAPR cumulative distribution in CI/OFDM and PO-CI/OFDM systems with 2048 sub-carriers are pre-sented in this paper.The results show that the PAPR of OFDM system with large number of sub-carriers reduced evidentlyvia CI approaches.展开更多
Multi-Access Interference's (MAI's) effect on parallel acquisition performance of DS-Multi-carrier CDMA system under the typical indoor radio channel is discussed in the paper. Moreover, a comparison of acqui...Multi-Access Interference's (MAI's) effect on parallel acquisition performance of DS-Multi-carrier CDMA system under the typical indoor radio channel is discussed in the paper. Moreover, a comparison of acquisition performance impairment produced by the MAI in DS-MC-CDMA and DS-Single-carrier CDMA is also made. Results are given in terms of average acquisition time obtained by means of simulations and theory analysis.展开更多
This paper mainly focuses on performance analysis of the previously proposedSTFT based 2-D timing approach to OFDM systems and presents simulations results of its performancein AWGN and multipath fading environment an...This paper mainly focuses on performance analysis of the previously proposedSTFT based 2-D timing approach to OFDM systems and presents simulations results of its performancein AWGN and multipath fading environment and its robustness against the duration of Channel ImpulseResponse (CIR) and frequency offset. Simulation results suggest that a revised version of Short-TimeFourier Transform (STFT) can be used to greatly reduce computational complexity, especially athigher SNR.展开更多
The estimate of signals parameters is very important in wireless communications. In this paper, we combine subspace based blind channel estimation algorithm with the extension of the JADE WSF algorithm to jointl...The estimate of signals parameters is very important in wireless communications. In this paper, we combine subspace based blind channel estimation algorithm with the extension of the JADE WSF algorithm to jointly estimate the Angles of Arrival ( AOAs ) and delays of multipath signals arriving at an antenna array in Code Division Multiple Access ( CDMA ) systems. Our approach uses a collection of estimates of a consistent chip sample of space time vector channel. The channel estimates are assumed to have constant path AOA and delay over a finite number of symbols. Unlike the traditional MUltiple SIgnal Classification ( MUSIC ) and Estimation of Signal Parameters via Rotational Invariance Techniques ( ESPRIT ) algorithms for the estimation of signals parameters, the proposed method can work when the number of paths exceeds the number of antennas. The Cramer Rao Bound ( CRB ) and simulations are provided.展开更多
In this paper we study the subcarrier and bit allocation strategies for downlink OFDMA system.Our opti-mization objective is to find optimum subcarrier and bit assignment minimizing the total transmitted power with th...In this paper we study the subcarrier and bit allocation strategies for downlink OFDMA system.Our opti-mization objective is to find optimum subcarrier and bit assignment minimizing the total transmitted power with the con-straints on BER and data rate for all users.We divide this problem into three steps:resource allocation,subcarrier assign-ment and single-user power and bit allocation.For the first two steps we propose new algorithms.Various loading schemesconstitute by combining these algorithms as well as algorithms proposed in Ref.[6].Simulation results demonstrate thatour proposed suboptimal loading scheme can achieve performance closer to the near optimal algorithm in Ref.[8]withmuch lower complexity than schemes in Ref.[6].展开更多
A new technique that uses Discrete Fractal Brownian Motion to describe a fingerprint is presented. By computing certain fractal parameters, a fingerprints core and delta fields can be roughly detected. Experimental re...A new technique that uses Discrete Fractal Brownian Motion to describe a fingerprint is presented. By computing certain fractal parameters, a fingerprints core and delta fields can be roughly detected. Experimental results demonstrate this method to be not only more efficient than the single fractal dimension method, but also more noise resistant than the traditional schemes.展开更多
The design and analysis of special type beam former, the Butler matrix, toachieve orthogonal beam-forming networks is presented in this paper. A 4 X 4 microstrip planar arrayantenna is assumed to simulate a 4 X 4 Butl...The design and analysis of special type beam former, the Butler matrix, toachieve orthogonal beam-forming networks is presented in this paper. A 4 X 4 microstrip planar arrayantenna is assumed to simulate a 4 X 4 Butler matrix to demonstrate orthogonal beam forming andbeam steering. The dimensions of rectangular patches in the planar array are chosen according to theDolph-Chebyshev current distribution in order to minimize the side-lobe level ratio for a givenvalue of beamwidth. The simulations are carried out using an antenna design and analysis softwarePCAAD. It is shown that orthogonal beams can be formed to cover about 163° angle with a constantbeam crossover level and high directivity.展开更多
文摘A new quadrature coded OFDM system is proposed. The transmitted data symbols are grouped in such format that the in phase side and the quadrature side of the symbols are arranged in opposite order. By analysis and simulation, the performance of the new system can be improved greatly, as well as the harmful influences on the system owing to frequency offset can be reduced effectively, which can combat the disadvantages of OFDM system.
文摘High Peak-to-Average Power Ratio(PAPR)is one of the major drawbacks of Orthogonal Frequency DivisionMultiplexing(OFDM)systems.This paper presents the structures of the particular bit sequences leading to the maximumPAPR(PAPR_(max))in Carrier-Interferometry OFDM(CI/OFDM)and Pseudo Orthogonal Carrier-Interferometry OFDM(PO-CI/OFDM)systems for Binary Phase Shift Keying(BPSK)modulation.Furthermore,the simulation and analysisof PAPR_(max) and PAPR cumulative distribution in CI/OFDM and PO-CI/OFDM systems with 2048 sub-carriers are pre-sented in this paper.The results show that the PAPR of OFDM system with large number of sub-carriers reduced evidentlyvia CI approaches.
文摘Multi-Access Interference's (MAI's) effect on parallel acquisition performance of DS-Multi-carrier CDMA system under the typical indoor radio channel is discussed in the paper. Moreover, a comparison of acquisition performance impairment produced by the MAI in DS-MC-CDMA and DS-Single-carrier CDMA is also made. Results are given in terms of average acquisition time obtained by means of simulations and theory analysis.
文摘This paper mainly focuses on performance analysis of the previously proposedSTFT based 2-D timing approach to OFDM systems and presents simulations results of its performancein AWGN and multipath fading environment and its robustness against the duration of Channel ImpulseResponse (CIR) and frequency offset. Simulation results suggest that a revised version of Short-TimeFourier Transform (STFT) can be used to greatly reduce computational complexity, especially athigher SNR.
文摘The estimate of signals parameters is very important in wireless communications. In this paper, we combine subspace based blind channel estimation algorithm with the extension of the JADE WSF algorithm to jointly estimate the Angles of Arrival ( AOAs ) and delays of multipath signals arriving at an antenna array in Code Division Multiple Access ( CDMA ) systems. Our approach uses a collection of estimates of a consistent chip sample of space time vector channel. The channel estimates are assumed to have constant path AOA and delay over a finite number of symbols. Unlike the traditional MUltiple SIgnal Classification ( MUSIC ) and Estimation of Signal Parameters via Rotational Invariance Techniques ( ESPRIT ) algorithms for the estimation of signals parameters, the proposed method can work when the number of paths exceeds the number of antennas. The Cramer Rao Bound ( CRB ) and simulations are provided.
文摘In this paper we study the subcarrier and bit allocation strategies for downlink OFDMA system.Our opti-mization objective is to find optimum subcarrier and bit assignment minimizing the total transmitted power with the con-straints on BER and data rate for all users.We divide this problem into three steps:resource allocation,subcarrier assign-ment and single-user power and bit allocation.For the first two steps we propose new algorithms.Various loading schemesconstitute by combining these algorithms as well as algorithms proposed in Ref.[6].Simulation results demonstrate thatour proposed suboptimal loading scheme can achieve performance closer to the near optimal algorithm in Ref.[8]withmuch lower complexity than schemes in Ref.[6].
文摘A new technique that uses Discrete Fractal Brownian Motion to describe a fingerprint is presented. By computing certain fractal parameters, a fingerprints core and delta fields can be roughly detected. Experimental results demonstrate this method to be not only more efficient than the single fractal dimension method, but also more noise resistant than the traditional schemes.
文摘The design and analysis of special type beam former, the Butler matrix, toachieve orthogonal beam-forming networks is presented in this paper. A 4 X 4 microstrip planar arrayantenna is assumed to simulate a 4 X 4 Butler matrix to demonstrate orthogonal beam forming andbeam steering. The dimensions of rectangular patches in the planar array are chosen according to theDolph-Chebyshev current distribution in order to minimize the side-lobe level ratio for a givenvalue of beamwidth. The simulations are carried out using an antenna design and analysis softwarePCAAD. It is shown that orthogonal beams can be formed to cover about 163° angle with a constantbeam crossover level and high directivity.
