This article is about orthogonal frequency-division multiplexing with quadrature amplitude modulation combined with code division multiplexing access for complex data transmission. It aims to present a method which us...This article is about orthogonal frequency-division multiplexing with quadrature amplitude modulation combined with code division multiplexing access for complex data transmission. It aims to present a method which uses two interfering subsets in order to improve the performance of the transmission scheme. The idea is to spread in a coherent manner some data amongst two different codes belonging to the two different subsets involved in complex orthogonal frequency-division multiplexing with quadrature amplitude modulation and code division multiplexing access. This will improve the useful signal level at the receiving side and therefore improve the decoding process especially at low signal to noise ratio. However, this procedure implies some interference with other codes therefore creating a certain noise which is noticeable at high signal to noise ratio.展开更多
Contrary to the other multi-carrier modulation systems, the coherent optical orthogonal frequency division multiplexing communication system with an offset quadrature amplitude modulation (CO-OFDM-OQAM) possesses inhe...Contrary to the other multi-carrier modulation systems, the coherent optical orthogonal frequency division multiplexing communication system with an offset quadrature amplitude modulation (CO-OFDM-OQAM) possesses inherent imaginary interference (IMI). This has an important impact on the channel estimation process. Currently, a variety of frequency-domain channel estimation methods have been proposed. However, there are various problems that still exist. For instance, in order to reduce the influence of IMI, it is necessary to insert more guard intervals between the training sequence and the payload, leading to the occupation of excessive spectrum resources. In order to address this problem, this work designs a high spectral efficient frequency-domain channel estimation method for the polarization-division-multiplexing CO-OFDM-OQAM systems. First, the working principle of the proposed method is described in detail. Then, its spectral efficiency, power peak-to-average ratio, and channel estimation performance are studied based on simulations. The simulation results show that the proposed method improves the spectral efficiency without worsening the power peak-to-average ratio. The channel estimation capability of this method is verified in three scenarios of long-distance transmissions, including back-to-back, 100 km, and 200 km transmissions. .展开更多
Orthogonal frequency division multiplex/offset QAM (OFDM/OQAM) has been proven to be a promising multi-carrier modulation (MCM) technique for the transmission of signals over multipath fading channels. However, OFDM/O...Orthogonal frequency division multiplex/offset QAM (OFDM/OQAM) has been proven to be a promising multi-carrier modulation (MCM) technique for the transmission of signals over multipath fading channels. However, OFDM/OQAM has also the intrinsic disadvantage of high peak-to-average-power ratio (PAPR) that should be alleviated. This paper focuses on the reduction of the clipping noise and out-of band radiation caused by the clipping process. The basic principle is to estimate the clipping noise and then eliminate it from the received signal. Analysis and simulation results show that, with one time iteration, the proposed method can effectively improve the bit error ratio (BER) performance.展开更多
传统的正交频分复用/偏移正交幅度调制(OFDM/OQAM)系统波形自适应设计主要针对具有非指数型时延功率谱和非U型多普勒功率谱的信道模型对波形进行优化,而实际中,波形自适应设计会因不同的信道模型产生不同的信道匹配准则系数。结合地空...传统的正交频分复用/偏移正交幅度调制(OFDM/OQAM)系统波形自适应设计主要针对具有非指数型时延功率谱和非U型多普勒功率谱的信道模型对波形进行优化,而实际中,波形自适应设计会因不同的信道模型产生不同的信道匹配准则系数。结合地空信道模型和扩展高斯函数的特性,在传统基于信干噪比(SINR)优化的OFDM/OQAM系统波形自适应算法的基础上提出一种新的OFDM/OQAM系统波形自适应设计算法。该算法引入信道匹配系数β,通过信道匹配准则建立波形时频域间隔与信道最大多径时延、最大多普勒频移的关系,再结合传统SINR优化函数计算扩展因子参数,将参数反馈给发送端并调整发送端和接收端的滤波器达到波形自适应的目的。仿真结果表明,4QAM和16QAM调制下,信道匹配系数β的引入在系统误码性能上均有1. 0 d B以上的改善。展开更多
The performance of an OFDM/OQAM system under phase noise is analyzed. The analysis helps to direct the design of low cost tuners through specifying the required phase noise characteristics. Discrete time formulation o...The performance of an OFDM/OQAM system under phase noise is analyzed. The analysis helps to direct the design of low cost tuners through specifying the required phase noise characteristics. Discrete time formulation of OFDM/OQAM is first derived with the square root raised cosine (SRRC) filter as the pulse-shaping filter. Then the effect of multiplicative phase noise is equivalently represented as additive white Gaussian noise (AWGN), the variance of which is given analytically. We can observe that the same result as OFDM/QAM system is derived. Lastly, all the analytical results are verified by the bit error rate (BER) degradation through Monte Carlo simulation.展开更多
Orthogonal frequency division multiplex/offset QAM (OFDM/OQAM) and N-continuous OFDM are both improved multi-carrier modulation (MCM) techniques for the transmission of signals over multipath fading channels. In this ...Orthogonal frequency division multiplex/offset QAM (OFDM/OQAM) and N-continuous OFDM are both improved multi-carrier modulation (MCM) techniques for the transmission of signals over multipath fading channels. In this paper, we aim to compare these two techniques with respect to out-of-band radiation, bit error ratio (BER) and calculation complexity. Analysis and simulation results show that, compared to the N-continuous OFDM, the OFDM/OQAM has lower out-of-band radiation, calculation consumption and similar BER performance.展开更多
Orthogonal frequency division multiplex/offset QAM (OFDM/OQAM) has been proven to be a promising multi-carrier modulation (MCM) technique for the transmission of signals over multipath fading channels. However, OFDM/O...Orthogonal frequency division multiplex/offset QAM (OFDM/OQAM) has been proven to be a promising multi-carrier modulation (MCM) technique for the transmission of signals over multipath fading channels. However, OFDM/OQAM has also the intrinsic disadvantage of high peak-to-average-power ratio (PAPR) that should be alleviated. In this paper, a novel selective mapping (SLM) method is proposed for OFDM/OQAM system. Since the pulse shape may cover a few OFDM symbols, the basic principle of the proposed method is to apply the SLM method in the range of the most relevant OFDM symbols. Analysis and simulation results show that, compared to the existing SLM algorithms for OFDM/OQAM system, the proposed method has better PAPR performance and lower computation complexity.展开更多
文摘This article is about orthogonal frequency-division multiplexing with quadrature amplitude modulation combined with code division multiplexing access for complex data transmission. It aims to present a method which uses two interfering subsets in order to improve the performance of the transmission scheme. The idea is to spread in a coherent manner some data amongst two different codes belonging to the two different subsets involved in complex orthogonal frequency-division multiplexing with quadrature amplitude modulation and code division multiplexing access. This will improve the useful signal level at the receiving side and therefore improve the decoding process especially at low signal to noise ratio. However, this procedure implies some interference with other codes therefore creating a certain noise which is noticeable at high signal to noise ratio.
文摘Contrary to the other multi-carrier modulation systems, the coherent optical orthogonal frequency division multiplexing communication system with an offset quadrature amplitude modulation (CO-OFDM-OQAM) possesses inherent imaginary interference (IMI). This has an important impact on the channel estimation process. Currently, a variety of frequency-domain channel estimation methods have been proposed. However, there are various problems that still exist. For instance, in order to reduce the influence of IMI, it is necessary to insert more guard intervals between the training sequence and the payload, leading to the occupation of excessive spectrum resources. In order to address this problem, this work designs a high spectral efficient frequency-domain channel estimation method for the polarization-division-multiplexing CO-OFDM-OQAM systems. First, the working principle of the proposed method is described in detail. Then, its spectral efficiency, power peak-to-average ratio, and channel estimation performance are studied based on simulations. The simulation results show that the proposed method improves the spectral efficiency without worsening the power peak-to-average ratio. The channel estimation capability of this method is verified in three scenarios of long-distance transmissions, including back-to-back, 100 km, and 200 km transmissions. .
文摘Orthogonal frequency division multiplex/offset QAM (OFDM/OQAM) has been proven to be a promising multi-carrier modulation (MCM) technique for the transmission of signals over multipath fading channels. However, OFDM/OQAM has also the intrinsic disadvantage of high peak-to-average-power ratio (PAPR) that should be alleviated. This paper focuses on the reduction of the clipping noise and out-of band radiation caused by the clipping process. The basic principle is to estimate the clipping noise and then eliminate it from the received signal. Analysis and simulation results show that, with one time iteration, the proposed method can effectively improve the bit error ratio (BER) performance.
文摘传统的正交频分复用/偏移正交幅度调制(OFDM/OQAM)系统波形自适应设计主要针对具有非指数型时延功率谱和非U型多普勒功率谱的信道模型对波形进行优化,而实际中,波形自适应设计会因不同的信道模型产生不同的信道匹配准则系数。结合地空信道模型和扩展高斯函数的特性,在传统基于信干噪比(SINR)优化的OFDM/OQAM系统波形自适应算法的基础上提出一种新的OFDM/OQAM系统波形自适应设计算法。该算法引入信道匹配系数β,通过信道匹配准则建立波形时频域间隔与信道最大多径时延、最大多普勒频移的关系,再结合传统SINR优化函数计算扩展因子参数,将参数反馈给发送端并调整发送端和接收端的滤波器达到波形自适应的目的。仿真结果表明,4QAM和16QAM调制下,信道匹配系数β的引入在系统误码性能上均有1. 0 d B以上的改善。
文摘The performance of an OFDM/OQAM system under phase noise is analyzed. The analysis helps to direct the design of low cost tuners through specifying the required phase noise characteristics. Discrete time formulation of OFDM/OQAM is first derived with the square root raised cosine (SRRC) filter as the pulse-shaping filter. Then the effect of multiplicative phase noise is equivalently represented as additive white Gaussian noise (AWGN), the variance of which is given analytically. We can observe that the same result as OFDM/QAM system is derived. Lastly, all the analytical results are verified by the bit error rate (BER) degradation through Monte Carlo simulation.
文摘Orthogonal frequency division multiplex/offset QAM (OFDM/OQAM) and N-continuous OFDM are both improved multi-carrier modulation (MCM) techniques for the transmission of signals over multipath fading channels. In this paper, we aim to compare these two techniques with respect to out-of-band radiation, bit error ratio (BER) and calculation complexity. Analysis and simulation results show that, compared to the N-continuous OFDM, the OFDM/OQAM has lower out-of-band radiation, calculation consumption and similar BER performance.
文摘Orthogonal frequency division multiplex/offset QAM (OFDM/OQAM) has been proven to be a promising multi-carrier modulation (MCM) technique for the transmission of signals over multipath fading channels. However, OFDM/OQAM has also the intrinsic disadvantage of high peak-to-average-power ratio (PAPR) that should be alleviated. In this paper, a novel selective mapping (SLM) method is proposed for OFDM/OQAM system. Since the pulse shape may cover a few OFDM symbols, the basic principle of the proposed method is to apply the SLM method in the range of the most relevant OFDM symbols. Analysis and simulation results show that, compared to the existing SLM algorithms for OFDM/OQAM system, the proposed method has better PAPR performance and lower computation complexity.
