The orthogonal space-frequency block coding (OSFBC) with orthogonal frequency division multiplexing (OFDM) system reduces complexity in the receiver which improves the system performance significantly. Motivated by th...The orthogonal space-frequency block coding (OSFBC) with orthogonal frequency division multiplexing (OFDM) system reduces complexity in the receiver which improves the system performance significantly. Motivated by these advantages of OSFBC-OFDM system, this paper considers a secure wireless multicasting scenario through multiple-input multiple-output (MIMO) OFDM system employing OSFBC over frequency selective α-μ fading channels. The authors are interested to protect the desired signals from eavesdropping considering the impact of the number of multicast users and eavesdroppers, and the fading parameters α and μ. A mathematical model has been developed based on the closed-form analytical expressions of the probability of non-zero secrecy multicast capacity (PNSMC) and the secure outage probability for multi-casting (SOPM) to ensure the security in the presence of multiple eaves-droppers. The results show that the security in MIMO OSFBC OFDM system over α-μ fading is more sensitive to the magnitude of α and μ and this effect increases in the high signal-to-noise ratio (SNR) region of the main channel.展开更多
A new non-orthogonal space-time-frequency code (STFC) was proposed. In conjunction with orthogonal frequency-division multiplexing (OFDM), it is appropriate for the application on frequency-selective fading channels. ...A new non-orthogonal space-time-frequency code (STFC) was proposed. In conjunction with orthogonal frequency-division multiplexing (OFDM), it is appropriate for the application on frequency-selective fading channels. On the basis of the existing non-orthogonal STC, frequency diversity is studied and a new non-orthogonal STFC is further designed. Monte-Carlo simulations show that the non-orthogonal STFC-OFDM has the advantage of large diversity order, high bandwidth efficiency and better BER performance when compared with the orthogonal STC/STFC-OFDM and non-orthogonal STC-OFDM systems.展开更多
Non-orthogonal multiple access(NOMA) is a new access method to achieve high performance gains in terms of capacity and throughput, so it is currently under consideration as one of the candidates for fifth generation(5...Non-orthogonal multiple access(NOMA) is a new access method to achieve high performance gains in terms of capacity and throughput, so it is currently under consideration as one of the candidates for fifth generation(5 G) technologies. NOMA utilizes power domain in order to superimpose signals of multiple users in a single transmitted signal. This creates a lot of interference at the receive side. Although the use of successive interference cancellation(SIC) technique reduces the interference, but to further improve the receiver performance, in this paper, we have proposed a joint Walsh-Hadamard transform(WHT) and NOMA approach for achieving better performance gains than the conventional NOMA. WHT is a well-known code used in communication systems and is used as an orthogonal variable spreading factor(OVSF) in communication systems. Application of WHT to NOMA results in low bit error rate(BER) and high throughput performance for both low and high channel gain users. Further, it also reduces peak to average power ratio(PAPR) of the user signal. The results are discussed in terms of comparison between the conventionalNOMA and the proposed technique, which shows that it offers high performance gains in terms of low BER at different SNR levels, reduced PAPR, high user throughput performance and better spectral efficiency.展开更多
为了提高卫星通信的频谱利用效率,提出基于认知无线电的非连续正交频分复用(Non-continuous Orthogonal Frequency Division Multiplexing,NC-OFDM)卫星通信方法,研究了NC-OFDM子载波分配方法、系统建模仿真和对授权用户的干扰分析。基...为了提高卫星通信的频谱利用效率,提出基于认知无线电的非连续正交频分复用(Non-continuous Orthogonal Frequency Division Multiplexing,NC-OFDM)卫星通信方法,研究了NC-OFDM子载波分配方法、系统建模仿真和对授权用户的干扰分析。基于频谱感知的子载波分配方法实现了NC-OFDM卫星通信系统对频谱空洞的有效利用,系统仿真结果和干扰分析表明,NC-OFDM卫星通信能够提高频谱利用率,并且在采用频谱感知和自适应信道接入技术的条件下,NC-OFDM卫星通信系统能够与授权用户实现频谱兼容。展开更多
部分传输序列算法（PTS）是抑制非连续正交频分复用（NC-OFDM）系统中峰值功率平均比（峰均比,PAPR）的有效算法之一,但该算法存在着搜索最优相位集合时计算复杂度高的问题。针对该问题,提出了一种改进的离散粒子群优化PTS的峰均比抑制...部分传输序列算法（PTS）是抑制非连续正交频分复用（NC-OFDM）系统中峰值功率平均比（峰均比,PAPR）的有效算法之一,但该算法存在着搜索最优相位集合时计算复杂度高的问题。针对该问题,提出了一种改进的离散粒子群优化PTS的峰均比抑制算法。改进算法将整个粒子群体划分为多个子群,增加了粒子的多样性,使得相位因子朝着最优解快速收敛,避免了因陷入局部最优解而导致早熟的现象,可获取更优的相位因子。仿真结果表明,在降低传统PTS算法复杂度的同时,改进算法可获得优于传统粒子群优化PTS算法0.3~0.4 d B的PAPR性能改善,从而证明了该算法的有效性。展开更多
文摘The orthogonal space-frequency block coding (OSFBC) with orthogonal frequency division multiplexing (OFDM) system reduces complexity in the receiver which improves the system performance significantly. Motivated by these advantages of OSFBC-OFDM system, this paper considers a secure wireless multicasting scenario through multiple-input multiple-output (MIMO) OFDM system employing OSFBC over frequency selective α-μ fading channels. The authors are interested to protect the desired signals from eavesdropping considering the impact of the number of multicast users and eavesdroppers, and the fading parameters α and μ. A mathematical model has been developed based on the closed-form analytical expressions of the probability of non-zero secrecy multicast capacity (PNSMC) and the secure outage probability for multi-casting (SOPM) to ensure the security in the presence of multiple eaves-droppers. The results show that the security in MIMO OSFBC OFDM system over α-μ fading is more sensitive to the magnitude of α and μ and this effect increases in the high signal-to-noise ratio (SNR) region of the main channel.
基金National Natural Science Foundation ofChina(No.60 3 72 0 76)
文摘A new non-orthogonal space-time-frequency code (STFC) was proposed. In conjunction with orthogonal frequency-division multiplexing (OFDM), it is appropriate for the application on frequency-selective fading channels. On the basis of the existing non-orthogonal STC, frequency diversity is studied and a new non-orthogonal STFC is further designed. Monte-Carlo simulations show that the non-orthogonal STFC-OFDM has the advantage of large diversity order, high bandwidth efficiency and better BER performance when compared with the orthogonal STC/STFC-OFDM and non-orthogonal STC-OFDM systems.
基金supported by Priority Research Centers Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education, Science and Technology (2018R1A6A1A03024003)
文摘Non-orthogonal multiple access(NOMA) is a new access method to achieve high performance gains in terms of capacity and throughput, so it is currently under consideration as one of the candidates for fifth generation(5 G) technologies. NOMA utilizes power domain in order to superimpose signals of multiple users in a single transmitted signal. This creates a lot of interference at the receive side. Although the use of successive interference cancellation(SIC) technique reduces the interference, but to further improve the receiver performance, in this paper, we have proposed a joint Walsh-Hadamard transform(WHT) and NOMA approach for achieving better performance gains than the conventional NOMA. WHT is a well-known code used in communication systems and is used as an orthogonal variable spreading factor(OVSF) in communication systems. Application of WHT to NOMA results in low bit error rate(BER) and high throughput performance for both low and high channel gain users. Further, it also reduces peak to average power ratio(PAPR) of the user signal. The results are discussed in terms of comparison between the conventionalNOMA and the proposed technique, which shows that it offers high performance gains in terms of low BER at different SNR levels, reduced PAPR, high user throughput performance and better spectral efficiency.
文摘为了提高卫星通信的频谱利用效率,提出基于认知无线电的非连续正交频分复用(Non-continuous Orthogonal Frequency Division Multiplexing,NC-OFDM)卫星通信方法,研究了NC-OFDM子载波分配方法、系统建模仿真和对授权用户的干扰分析。基于频谱感知的子载波分配方法实现了NC-OFDM卫星通信系统对频谱空洞的有效利用,系统仿真结果和干扰分析表明,NC-OFDM卫星通信能够提高频谱利用率,并且在采用频谱感知和自适应信道接入技术的条件下,NC-OFDM卫星通信系统能够与授权用户实现频谱兼容。
文摘部分传输序列算法（PTS）是抑制非连续正交频分复用（NC-OFDM）系统中峰值功率平均比（峰均比,PAPR）的有效算法之一,但该算法存在着搜索最优相位集合时计算复杂度高的问题。针对该问题,提出了一种改进的离散粒子群优化PTS的峰均比抑制算法。改进算法将整个粒子群体划分为多个子群,增加了粒子的多样性,使得相位因子朝着最优解快速收敛,避免了因陷入局部最优解而导致早熟的现象,可获取更优的相位因子。仿真结果表明,在降低传统PTS算法复杂度的同时,改进算法可获得优于传统粒子群优化PTS算法0.3~0.4 d B的PAPR性能改善,从而证明了该算法的有效性。
