The BER performance for an optimal circular 16-QAM constellation is theoretically derived and applied in wavelet based OFDM system in additive white Gaussian noise channel. Signal point constellations have been discus...The BER performance for an optimal circular 16-QAM constellation is theoretically derived and applied in wavelet based OFDM system in additive white Gaussian noise channel. Signal point constellations have been discussed in much literature. An optimal circular 16-QAM is developed. The calculation of the BER is based on the four types of the decision boundaries. Each decision boundary is determined based on the space distance d following the pdf Gaussian distribution with respect to the in-phase and quadrature components nI and nQ with the assumption that they are statistically independent to each other. The BER analysis for other circular M-ary QAM is also analyzed. The system is then applied to wavelet based OFDM. The wavelet transform is considered because it offers a better spectral containment feature compared to conventional OFDM using Fourier transform. The circular schemes are slightly better than the square schemes in most SNR values. All simulation results have met the theoretical calculations. When applying to wavelet based OFDM, the circular modulation scheme has also performed slightly less errors as compared to the square modulation scheme.展开更多
Orthogonal frequency division multiplexing （OFDM） is a special form of multi-carrier transmission that uses the policy of divide and rule. In this scheme, a large number of orthogonal, overlapping, narrow band sub-c...Orthogonal frequency division multiplexing （OFDM） is a special form of multi-carrier transmission that uses the policy of divide and rule. In this scheme, a large number of orthogonal, overlapping, narrow band sub-channels （subcarriers） are transmitted in parallel and divide the available transmission bandwidth. This techniqueis originally based on the Fast Fourier Transform of the information data. In order to improve the performance of the OFDM and overcome some limitations, an alternative OFDM approach based on the Wavelet Transform is proposed. In this paper, we study the performance of such systems in additive white Gaussian channel （AWGN）. MATLAB simulations are realized and performance comparisons are presented.展开更多
This work aims to study the effect of unwanted peaks and enhance the performance of wireless systems on the basis of tackling such peaks. A new proposition has been made based on wavelet transform method and its entro...This work aims to study the effect of unwanted peaks and enhance the performance of wireless systems on the basis of tackling such peaks. A new proposition has been made based on wavelet transform method and its entropy. Signals with large peak-to-average power ratio (PAPR) will be examined such as the ones that are considered as the major Orthogonal Frequency Division Multiplexing (OFDM) systems drawbacks. Furthermore, aspatial diversity Multiple-Input Multiple- Out-put (MIMO) technology is used to overcome the complexity addition that could arise in our proposition. To draw the best performance of this work, a MATLAB simulation has been used;it is divided into three main stages, namely, MIMO-OFDM symbols’ reconstruction based on wavelet transform, a predetermined thresholding formula, and finally, moving filter. This algorithm is called Peaks’ detection based Entropy Wavelet Transform;PD-EWT. Based on the simulation, and under some constrains such as the bandwidth occupancy and the complexity structure of the transceivers, a peak detection ratio has been achieved and reaches around 0.85. Comparing with our previously published works, the PD-EWT enhances detection ratio for 0.25 more peaks.展开更多
在正交频分复用(OFDM:Orthogonal Frequency Division Multiplexing)系统中,我们通常从频率域的角度估计信道衰落因子.在频率域,发射的信号在经历了乘性衰落的同时还经历了加性的噪声的干扰.不论我们采用哪种方法来估计乘性的衰落因子,...在正交频分复用(OFDM:Orthogonal Frequency Division Multiplexing)系统中,我们通常从频率域的角度估计信道衰落因子.在频率域,发射的信号在经历了乘性衰落的同时还经历了加性的噪声的干扰.不论我们采用哪种方法来估计乘性的衰落因子,加性噪声的干扰始终存在,从而影响了估计的质量.将小波去噪用于信道估计中以去除其中的加性干扰,从而在不增加复杂度的前提下,提高了信道估计的准确度,进而提高了整个系统的性能.同时证明了该方法适用于不同的信道环境(频率选择性衰落信道、平坦衰落信道、快衰落和慢衰落信道).展开更多
正交频分复用(OFDM,Orthogonal Frequency Division Multiplexing)与单载波信号广泛应用于短波通信领域。针对低信噪比和多径环境下OFDM与单载波信号识别效率低的问题,本文提出了基于小波脊线的信号识别算法。本文推导了常用信号对应的...正交频分复用(OFDM,Orthogonal Frequency Division Multiplexing)与单载波信号广泛应用于短波通信领域。针对低信噪比和多径环境下OFDM与单载波信号识别效率低的问题,本文提出了基于小波脊线的信号识别算法。本文推导了常用信号对应的小波脊线幅度和脊点位置,并分析了小波脊线幅度和脊点形态。通过理论推导和仿真测试证明了OFDM与单载波信号对应小波脊线具有不同特征,对小波脊线差分、中值滤波、并利用其熵作为特征值能够有效的进行OFDM信号与单载波信号的识别。仿真结果证明该算法对输入信号点数要求低,在低信噪比和短波中等信道下识别效果具有稳健性和有效性。展开更多
文摘The BER performance for an optimal circular 16-QAM constellation is theoretically derived and applied in wavelet based OFDM system in additive white Gaussian noise channel. Signal point constellations have been discussed in much literature. An optimal circular 16-QAM is developed. The calculation of the BER is based on the four types of the decision boundaries. Each decision boundary is determined based on the space distance d following the pdf Gaussian distribution with respect to the in-phase and quadrature components nI and nQ with the assumption that they are statistically independent to each other. The BER analysis for other circular M-ary QAM is also analyzed. The system is then applied to wavelet based OFDM. The wavelet transform is considered because it offers a better spectral containment feature compared to conventional OFDM using Fourier transform. The circular schemes are slightly better than the square schemes in most SNR values. All simulation results have met the theoretical calculations. When applying to wavelet based OFDM, the circular modulation scheme has also performed slightly less errors as compared to the square modulation scheme.
文摘Orthogonal frequency division multiplexing （OFDM） is a special form of multi-carrier transmission that uses the policy of divide and rule. In this scheme, a large number of orthogonal, overlapping, narrow band sub-channels （subcarriers） are transmitted in parallel and divide the available transmission bandwidth. This techniqueis originally based on the Fast Fourier Transform of the information data. In order to improve the performance of the OFDM and overcome some limitations, an alternative OFDM approach based on the Wavelet Transform is proposed. In this paper, we study the performance of such systems in additive white Gaussian channel （AWGN）. MATLAB simulations are realized and performance comparisons are presented.
文摘This work aims to study the effect of unwanted peaks and enhance the performance of wireless systems on the basis of tackling such peaks. A new proposition has been made based on wavelet transform method and its entropy. Signals with large peak-to-average power ratio (PAPR) will be examined such as the ones that are considered as the major Orthogonal Frequency Division Multiplexing (OFDM) systems drawbacks. Furthermore, aspatial diversity Multiple-Input Multiple- Out-put (MIMO) technology is used to overcome the complexity addition that could arise in our proposition. To draw the best performance of this work, a MATLAB simulation has been used;it is divided into three main stages, namely, MIMO-OFDM symbols’ reconstruction based on wavelet transform, a predetermined thresholding formula, and finally, moving filter. This algorithm is called Peaks’ detection based Entropy Wavelet Transform;PD-EWT. Based on the simulation, and under some constrains such as the bandwidth occupancy and the complexity structure of the transceivers, a peak detection ratio has been achieved and reaches around 0.85. Comparing with our previously published works, the PD-EWT enhances detection ratio for 0.25 more peaks.
文摘在正交频分复用(OFDM:Orthogonal Frequency Division Multiplexing)系统中,我们通常从频率域的角度估计信道衰落因子.在频率域,发射的信号在经历了乘性衰落的同时还经历了加性的噪声的干扰.不论我们采用哪种方法来估计乘性的衰落因子,加性噪声的干扰始终存在,从而影响了估计的质量.将小波去噪用于信道估计中以去除其中的加性干扰,从而在不增加复杂度的前提下,提高了信道估计的准确度,进而提高了整个系统的性能.同时证明了该方法适用于不同的信道环境(频率选择性衰落信道、平坦衰落信道、快衰落和慢衰落信道).
文摘正交频分复用(OFDM,Orthogonal Frequency Division Multiplexing)与单载波信号广泛应用于短波通信领域。针对低信噪比和多径环境下OFDM与单载波信号识别效率低的问题,本文提出了基于小波脊线的信号识别算法。本文推导了常用信号对应的小波脊线幅度和脊点位置,并分析了小波脊线幅度和脊点形态。通过理论推导和仿真测试证明了OFDM与单载波信号对应小波脊线具有不同特征,对小波脊线差分、中值滤波、并利用其熵作为特征值能够有效的进行OFDM信号与单载波信号的识别。仿真结果证明该算法对输入信号点数要求低,在低信噪比和短波中等信道下识别效果具有稳健性和有效性。
