In this paper, a time-varying channel prediction method based on conditional generative adversarial network(CPcGAN) is proposed for time division duplexing/frequency division duplexing(TDD/FDD) systems. CPc GAN utiliz...In this paper, a time-varying channel prediction method based on conditional generative adversarial network(CPcGAN) is proposed for time division duplexing/frequency division duplexing(TDD/FDD) systems. CPc GAN utilizes a discriminator to calculate the divergence between the predicted downlink channel state information(CSI) and the real sample distributions under a conditional constraint that is previous uplink CSI. The generator of CPcGAN learns the function relationship between the conditional constraint and the predicted downlink CSI and reduces the divergence between predicted CSI and real CSI.The capability of CPcGAN fitting data distribution can capture the time-varying and multipath characteristics of the channel well. Considering the propagation characteristics of real channel, we further develop a channel prediction error indicator to determine whether the generator reaches the best state. Simulations show that the CPcGAN can obtain higher prediction accuracy and lower system bit error rate than the existing methods under the same user speeds.展开更多
This paper presents a software simulator applicable to multipath fading channels in urban environments of mobile communication networks. The simulator is constructed by a two-state Markov model and several statistical...This paper presents a software simulator applicable to multipath fading channels in urban environments of mobile communication networks. The simulator is constructed by a two-state Markov model and several statistical models for simulating the characterizations of different environments. A core idea of the simulator is to construct a Rice distribution-based multipath fading module produced by a modified Gans Doppler power spectrum, and in combination with a Markov model to predict the time-dependent characteristics of packet in different radio circumstances. It can simply predict the packet performance of the future channel and evaluate the relations between the radio channel and the modulation schemes, error control protocols and channel coding. Simulation results demonstrate that it is a reliable and efficient method.展开更多
The influence of pulse repetition frequency(PRF) on performance of wireless digital time hopping spread spectrum(THSS) ultrawide bandwidth(UWB) radio systems with PPM in dense multipath fading environments is firstly ...The influence of pulse repetition frequency(PRF) on performance of wireless digital time hopping spread spectrum(THSS) ultrawide bandwidth(UWB) radio systems with PPM in dense multipath fading environments is firstly investigated. The receiver used in this UWB system is a hybrid selection/maximal-ratio combining(H-S/MRC) diversity receiver in which L strongest multipath components out of N multipath diversity branches are selected and combined using maximal-ratio combining. The exact expressions for the bit error rate(BER) of this UWB system are firstly derived by using the virtual branch technique in term of PRF, the number of multipath components selected and combined L, and multipath spread of the channel and then this BER performance is evaluated. With the computer simulation for impulses having different pulse shapes, numerical results show that PRF, as well as pulse shape and the number of multipath diversity branches selected and combined L, has much effect on the BER performance of this UWB system in dense multipath fading environments. As PRF increases, the BER performance of this UWB system is much degraded under the conditions of fixed L and pulse shape.展开更多
Hybrid direct sequence and slow frequency hopping spread spectrum multiple access systems (Hybrid DS/SFH SSMA) operating through nonselective slow Rayleigh fading channels was investigated. Multipath and Multiple acce...Hybrid direct sequence and slow frequency hopping spread spectrum multiple access systems (Hybrid DS/SFH SSMA) operating through nonselective slow Rayleigh fading channels was investigated. Multipath and Multiple access interference was taken into account. Expressions of the average error probability for the system were derived. Analytical and numerical results on the average probability of error were presented for the system examined. Random signature sequences and hopping patterns were employed for the system. The numerical results show the effects of the value of M for M ary frequency shift keying (MFSK) modulation and Reed Solomon (RS) coding on the system’s performance. The comparison between RS coded system and noncode system shows that error correction coding is essential to improve the system’s performance.展开更多
In this paper, the channel estimation techniques for Orthogonal Frequency Division Multiplexing （OFDM） systems based on pilot arrangement are studied and we apply Low Density Parity Check （LDPC） codes to the syste...In this paper, the channel estimation techniques for Orthogonal Frequency Division Multiplexing （OFDM） systems based on pilot arrangement are studied and we apply Low Density Parity Check （LDPC） codes to the system of IEEE 802.16a with OFDM modulation. First investigated is the influence of channel cstimation schemes on LDPC-code based OFDM system in static and multipath fading channels. According to the different propagation environments in 802.16a system, a dynamic channel estimation scheme is proposed. A good irregular LDPC code is designed with code rate of 1/2 and code length of 1200. Simulation results show that the performance of LDPC coded OFDM system proposed in this paper is better than that of the convolution Turbo coded OFDM system proposed in IEEE standard 802.16a.展开更多
Fading and inter-symbol interference (ISI) arising from multipath effects are a common source of both latency and packet errors in wireless communications. Test methods often require large environments to produce long...Fading and inter-symbol interference (ISI) arising from multipath effects are a common source of both latency and packet errors in wireless communications. Test methods often require large environments to produce long delays that are enough to affect the communications between a transmitter and receiver. This paper presents a simple, compact test method to produce and isolate effects from multipath interference simulating these effects produced by discrete distances. Signals with controlled delays can be created and combined using multiple antennas in two isolated small (2 foot/60 cm) cubes constructed with microwave absorber. We demonstrated this with a pulsed RF signal and a signal from an 802.11 n access point with an internal antenna. This method can be further extended to provide a compact test-bed for almost any wireless interference or coexistence test.展开更多
Wireless networks are characterized by nodes mobility, which makes the propagation environment time-varying and subject to fading. As a consequence, the statistical characteristics of the received signal vary continuo...Wireless networks are characterized by nodes mobility, which makes the propagation environment time-varying and subject to fading. As a consequence, the statistical characteristics of the received signal vary continuously, giving rise to a Doppler power spectral density (DPSD) that varies from one observation instant to the next. This paper is concerned with dynamical modeling of time-varying wireless fading channels, their estimation and parameter identification, and optimal power control from received signal measurement data. The wireless channel is characterized using a stochastic state-space form and derived by approximating the time-varying DPSD of the channel. The expected maximization and Kalman filter are employed to recursively identify and estimate the channel parameters and states, respectively, from online received signal strength measured data. Moreover, we investigate a centralized optimal power control algorithm based on predictable strategies and employing the estimated channel parameters and states. The proposed models together with the estimation and power control algorithms are tested using experimental measurement data and the results are presented.展开更多
信道均衡(Channel Equalization,CE)技术作为一种高效抗多径方法,在卫星通信领域有着广泛的应用价值。为提高均衡算法性能,提出一种基于面向判决的最小均方(Decision-Directed Least Mean Square,DD-LMS)算法及判决反馈均衡(Decision Fe...信道均衡(Channel Equalization,CE)技术作为一种高效抗多径方法,在卫星通信领域有着广泛的应用价值。为提高均衡算法性能,提出一种基于面向判决的最小均方(Decision-Directed Least Mean Square,DD-LMS)算法及判决反馈均衡(Decision Feedback Equalizer,DFE)算法的自适应均衡技术。该技术基于导频训练序列方案及最小二乘法进行信道估计,在时域对畸变码元进行补偿;基于信号传输速率及信道特性设置导频数据结构,自适应切换信道均衡模式及步长因子,实现最优均衡性能。在遥测多径衰落信道下,该自适应均衡算法误码率为10^(-5)时约有0.5 dB增益,具有良好的系统稳定性。为满足实际应用需求,基于现场可编程门阵列(Field Programmable Gate Array,FPGA)平台进行实现,仿真及实测结果验证了该算法的有效性。展开更多
Physical layer key generation(PKG)technology leverages reciprocal channel randomness to generate shared secret keys.However,multipath fading at the receiver may degrade the correlation between legitimate uplink and do...Physical layer key generation(PKG)technology leverages reciprocal channel randomness to generate shared secret keys.However,multipath fading at the receiver may degrade the correlation between legitimate uplink and downlink channels,resulting in a low key generation rate(KGR).In this paper,we propose a PKG scheme based on the pattern-reconfigurable antenna(PRA)to boost the secret key capacity.First,we propose a reconfigurable intelligent surface(RIS)based PRA architecture with the capability of flexible and reconfigurable antenna patterns.Then,we present the PRA-based PKG protocol to improve the KGR via mitigation of the effects of multipath fading.Specifically,a novel algorithm for estimation of the multipath channel parameters is proposed based on atomic norm minimization.Thereafter,a novel optimization method for the matching reception of multipath signals is formulated based on the improved binary particle swarm optimization(BPSO)algorithm.Finally,simulation results show that the proposed scheme can resist multipath fading and achieve a high KGR compared to existing schemes.Moreover,our findings indicate that the increased degree of freedom of the antenna patterns can significantly increase the secret key capacity.展开更多
基金supported in part by the National Science Fund for Distinguished Young Scholars under Grant 61925102in part by the National Natural Science Foundation of China(62201087&92167202&62101069&62201086)in part by the Beijing University of Posts and Telecommunications-China Mobile Research Institute Joint Innovation Center。
文摘In this paper, a time-varying channel prediction method based on conditional generative adversarial network(CPcGAN) is proposed for time division duplexing/frequency division duplexing(TDD/FDD) systems. CPc GAN utilizes a discriminator to calculate the divergence between the predicted downlink channel state information(CSI) and the real sample distributions under a conditional constraint that is previous uplink CSI. The generator of CPcGAN learns the function relationship between the conditional constraint and the predicted downlink CSI and reduces the divergence between predicted CSI and real CSI.The capability of CPcGAN fitting data distribution can capture the time-varying and multipath characteristics of the channel well. Considering the propagation characteristics of real channel, we further develop a channel prediction error indicator to determine whether the generator reaches the best state. Simulations show that the CPcGAN can obtain higher prediction accuracy and lower system bit error rate than the existing methods under the same user speeds.
基金Supported by the National Natural Science Foundation of China (40474055)
文摘This paper presents a software simulator applicable to multipath fading channels in urban environments of mobile communication networks. The simulator is constructed by a two-state Markov model and several statistical models for simulating the characterizations of different environments. A core idea of the simulator is to construct a Rice distribution-based multipath fading module produced by a modified Gans Doppler power spectrum, and in combination with a Markov model to predict the time-dependent characteristics of packet in different radio circumstances. It can simply predict the packet performance of the future channel and evaluate the relations between the radio channel and the modulation schemes, error control protocols and channel coding. Simulation results demonstrate that it is a reliable and efficient method.
文摘The influence of pulse repetition frequency(PRF) on performance of wireless digital time hopping spread spectrum(THSS) ultrawide bandwidth(UWB) radio systems with PPM in dense multipath fading environments is firstly investigated. The receiver used in this UWB system is a hybrid selection/maximal-ratio combining(H-S/MRC) diversity receiver in which L strongest multipath components out of N multipath diversity branches are selected and combined using maximal-ratio combining. The exact expressions for the bit error rate(BER) of this UWB system are firstly derived by using the virtual branch technique in term of PRF, the number of multipath components selected and combined L, and multipath spread of the channel and then this BER performance is evaluated. With the computer simulation for impulses having different pulse shapes, numerical results show that PRF, as well as pulse shape and the number of multipath diversity branches selected and combined L, has much effect on the BER performance of this UWB system in dense multipath fading environments. As PRF increases, the BER performance of this UWB system is much degraded under the conditions of fixed L and pulse shape.
文摘Hybrid direct sequence and slow frequency hopping spread spectrum multiple access systems (Hybrid DS/SFH SSMA) operating through nonselective slow Rayleigh fading channels was investigated. Multipath and Multiple access interference was taken into account. Expressions of the average error probability for the system were derived. Analytical and numerical results on the average probability of error were presented for the system examined. Random signature sequences and hopping patterns were employed for the system. The numerical results show the effects of the value of M for M ary frequency shift keying (MFSK) modulation and Reed Solomon (RS) coding on the system’s performance. The comparison between RS coded system and noncode system shows that error correction coding is essential to improve the system’s performance.
基金Supported by Jiangsu University Natural Science Re-search Fund (05KJB510090), National Natural Science Foundation of China (No.60472104).
文摘In this paper, the channel estimation techniques for Orthogonal Frequency Division Multiplexing （OFDM） systems based on pilot arrangement are studied and we apply Low Density Parity Check （LDPC） codes to the system of IEEE 802.16a with OFDM modulation. First investigated is the influence of channel cstimation schemes on LDPC-code based OFDM system in static and multipath fading channels. According to the different propagation environments in 802.16a system, a dynamic channel estimation scheme is proposed. A good irregular LDPC code is designed with code rate of 1/2 and code length of 1200. Simulation results show that the performance of LDPC coded OFDM system proposed in this paper is better than that of the convolution Turbo coded OFDM system proposed in IEEE standard 802.16a.
文摘Fading and inter-symbol interference (ISI) arising from multipath effects are a common source of both latency and packet errors in wireless communications. Test methods often require large environments to produce long delays that are enough to affect the communications between a transmitter and receiver. This paper presents a simple, compact test method to produce and isolate effects from multipath interference simulating these effects produced by discrete distances. Signals with controlled delays can be created and combined using multiple antennas in two isolated small (2 foot/60 cm) cubes constructed with microwave absorber. We demonstrated this with a pulsed RF signal and a signal from an 802.11 n access point with an internal antenna. This method can be further extended to provide a compact test-bed for almost any wireless interference or coexistence test.
文摘Wireless networks are characterized by nodes mobility, which makes the propagation environment time-varying and subject to fading. As a consequence, the statistical characteristics of the received signal vary continuously, giving rise to a Doppler power spectral density (DPSD) that varies from one observation instant to the next. This paper is concerned with dynamical modeling of time-varying wireless fading channels, their estimation and parameter identification, and optimal power control from received signal measurement data. The wireless channel is characterized using a stochastic state-space form and derived by approximating the time-varying DPSD of the channel. The expected maximization and Kalman filter are employed to recursively identify and estimate the channel parameters and states, respectively, from online received signal strength measured data. Moreover, we investigate a centralized optimal power control algorithm based on predictable strategies and employing the estimated channel parameters and states. The proposed models together with the estimation and power control algorithms are tested using experimental measurement data and the results are presented.
基金Project supported by the National Key Research and Development Program of China(Nos.2022YFB2902202,2022YFB2902205)the National Natural Science Foundation of China(No.U22A2001)。
文摘Physical layer key generation(PKG)technology leverages reciprocal channel randomness to generate shared secret keys.However,multipath fading at the receiver may degrade the correlation between legitimate uplink and downlink channels,resulting in a low key generation rate(KGR).In this paper,we propose a PKG scheme based on the pattern-reconfigurable antenna(PRA)to boost the secret key capacity.First,we propose a reconfigurable intelligent surface(RIS)based PRA architecture with the capability of flexible and reconfigurable antenna patterns.Then,we present the PRA-based PKG protocol to improve the KGR via mitigation of the effects of multipath fading.Specifically,a novel algorithm for estimation of the multipath channel parameters is proposed based on atomic norm minimization.Thereafter,a novel optimization method for the matching reception of multipath signals is formulated based on the improved binary particle swarm optimization(BPSO)algorithm.Finally,simulation results show that the proposed scheme can resist multipath fading and achieve a high KGR compared to existing schemes.Moreover,our findings indicate that the increased degree of freedom of the antenna patterns can significantly increase the secret key capacity.
