Orbital-angular-momentum(OAM)multiplexing technology offers a significant dimension to enlarge communication capacity in free-space optical links.The coherent beam combining(CBC)system can simultaneously realize OAM m...Orbital-angular-momentum(OAM)multiplexing technology offers a significant dimension to enlarge communication capacity in free-space optical links.The coherent beam combining(CBC)system can simultaneously realize OAM multiplexing and achieve high-power laser output,providing substantial advantages for long-distance communication.Herein,we present an integrated CBC system for freespace optical links based on OAM multiplexing and demultiplexing technologies for the first time,to the best of our knowledge.A method to achieve flexible OAM multiplexing and efficient demultiplexing based on the CBC system is proposed and demonstrated both theoretically and experimentally.The experimental results exhibit a low bit error rate of 0.47%and a high recognition precision of 98.58%throughout the entire data transmission process.By employing such an ingenious strategy,this work holds promising prospects for enriching ultra-long-distance structured light communication in the future.展开更多
The theoretical lower bounds on mean squared channel estimation errors for typical fading channels are presented by the infinite-length and non-causal Wiener filter and the exact closed-form expressions of the lower b...The theoretical lower bounds on mean squared channel estimation errors for typical fading channels are presented by the infinite-length and non-causal Wiener filter and the exact closed-form expressions of the lower bounds for different channel Doppler spectra are derived. Based on the obtained lower bounds on mean squared channel estimation errors, the limits on bit error rate （BER） for maximal ratio combining （MRC） with Gaussian distributed weighting errors on independent and identically distributed （i. i. d） fading channels are presented. Numerical results show that the BER performances of ideal MRC are the lower bounds on the BER performances of non-ideal MRC and deteriorate as the maximum Doppler frequency increases or the SNR of channel estimate decreases.展开更多
Precodings using square-root decomposition,including Cholesky and G-To-Minus-Half(GTMH)precodings,are promising for eliminating the Faster-Than-Nyquist(FTN)-induced Intersymbol-Interference(ISI).However,the existing p...Precodings using square-root decomposition,including Cholesky and G-To-Minus-Half(GTMH)precodings,are promising for eliminating the Faster-Than-Nyquist(FTN)-induced Intersymbol-Interference(ISI).However,the existing precodings using square-root decomposition either ignore Interblock-Interference(IBI)or increase the signal power,deteriorating the Bit Error Rate(BER)performance for high-order modulations and severe ISI.To overcome these drawbacks,we adopt two approaches for constructing the circular ISI matrix.The first approach inserts a Cyclic Prefix/Suffix(CPS)after each precoded symbol block,while the second approach replaces the linear convolution of the FTN shaping and the matched filter by the circular convolution,resulting in the Circular FTN(CFTN).Using these two approaches,we propose three IBI-free precodings,i.e.,CPS-Cholesky,CFTN-Cholesky and CFTN-GTMH precodings.Furthermore,employing QR decomposition shows that the GTMH and Cholesky precodings can be converted interchangeably.Thus,we demonstrate that the GTMH precoding is essentially equivalent to the Cholesky precoding.Simulation results indicate that the BER performance of three IBI-free precodings approaches Nyquist performance for moderate ISI.However,as ISI intensifies,the CPS-Cholesky scheme increases the transmit power,causing BER performance degradation.In contrast,the CFTN-Cholesky and CFTN-GTMH precodings maintain optimal BER performance even for severe ISI.Considering 128-amplitude phase shift keying with a code rate of 1/2,the BER loss of CFTN-Cholesky and CFTN-GTMH precodings for the ideal BER of 10-5 is approximately 0.002 dB and 0.005 dB when packing factor is 0.7 and roll-offfactor is 0.3.To the best knowledge of the authors,this is the optimal performance achievable through precoding.展开更多
Quantization noise caused by analog-to-digital converter(ADC)gives rise to the reliability performance degradation of communication systems.In this paper,a quantized non-Hermitian symmetry(NHS)orthogonal frequency-div...Quantization noise caused by analog-to-digital converter(ADC)gives rise to the reliability performance degradation of communication systems.In this paper,a quantized non-Hermitian symmetry(NHS)orthogonal frequency-division multiplexing-based visible light communication(OFDM-VLC)system is presented.In order to analyze the effect of the resolution of ADC on NHS OFDM-VLC,a quantized mathematical model of NHS OFDM-VLC is established.Based on the proposed quantized model,a closed-form bit error rate(BER)expression is derived.The theoretical analysis and simulation results both confirm the effectiveness of the obtained BER formula in high-resolution ADC.In addition,channel coding is helpful in compensating for the BER performance loss due to the utilization of lower resolution ADC.展开更多
In high-speed railway(HSR)wireless communication,the rapid channel changes and limited high-capacity access cause significant impact on the link performance.Meanwhile,the Doppler shift caused by high mobility leads to...In high-speed railway(HSR)wireless communication,the rapid channel changes and limited high-capacity access cause significant impact on the link performance.Meanwhile,the Doppler shift caused by high mobility leads to the inter-carrier interference.In this paper,we propose a reconfigurable intelligent surface(RIS)-assisted receive spatial modulation(SM)scheme based on the spatial-temporal correlated HSR Rician channel.The characteristics of SM and the phase shift adjustment of RIS are used to mitigate the performance degradation in high mobility scenarios.Considering the influence of channel spatial-temporal correlation and Doppler shift,the effects of different parameters on average bit error rate(BER)performance and upper bound of ergodic capacity are analyzed.Therefore,a joint antenna and RIS-unit selection algorithm based on the antenna removal method is proposed to increase the capacity performance of communication links.Numerical results show that the proposed RIS-assisted receive SM scheme can maintain high transmission capacity compared to the conventional HSR-SM scheme,whereas the degradation of BER performance can be compensated by arranging a large number of RIS-units.In addition,selecting more RIS-units has better capacity performance than activating more antennas in the low signal-to-noise ratio regions.展开更多
Quantum key distribution(QKD)is a method for secure communication that utilizes quantum mechanics principles to distribute cryptographic keys between parties.Integrated photonics offer benefits such as compactness,sca...Quantum key distribution(QKD)is a method for secure communication that utilizes quantum mechanics principles to distribute cryptographic keys between parties.Integrated photonics offer benefits such as compactness,scalability,energy efficiency and the potential for extensive integration.We have achieved BB84 phase encoding and decoding,time-bin phase QKD,and the coherent one-way(COW)protocol on a planar lightwave circuit(PLC)platform.At the optimal temperature,our chip successfully prepared quantum states,performed decoding and calculated the secure key rate of the time-bin phasedecoding QKD to be 80.46 kbps over a 20 km transmission with a quantum bit error rate(QBER)of 4.23%.The secure key rate of the COW protocol was 18.18 kbps,with a phase error rate of 3.627%and a time error rate of 0.377%.The uniqueness of this technology lies in its combination of high integration and protocol flexibility,providing an innovative solution for the development of future quantum communication networks.展开更多
Overlapped x domain multiplexing(OVXDM) is a promising encoding technique to obtain high spectral efficiency by utilizing inter-symbol interference(ISI) intelligently. However, the computational complexity of maximum ...Overlapped x domain multiplexing(OVXDM) is a promising encoding technique to obtain high spectral efficiency by utilizing inter-symbol interference(ISI) intelligently. However, the computational complexity of maximum likelihood sequence detection(MLSD) increases exponentially with the growth of spectral efficiency in OVXDM, which is unbearable for practical implementations. In this paper, based on a novel path metric associating adjacent symbols, we propose a multi-bit sliding stack decoding(Multi-Bit SSD) algorithm to achieve multiple-bit decoding simultaneously in OVXDM. Theoretical analysis is provided for the algorithm, which indicates the relationship between the performance and parameters including multiplexing waveform, overlapping fold and sliding window size. Simulation results show that the proposed algorithm can achieve better decoding performance and higher spectral efficiency than conventional fast decoding algorithms.展开更多
The average bit error rate(ABER) performance of a decode-and-forward(DF) based relay-assisted free-space optical(FSO) communication system over gamma-gamma distribution channels considering the pointing errors is stud...The average bit error rate(ABER) performance of a decode-and-forward(DF) based relay-assisted free-space optical(FSO) communication system over gamma-gamma distribution channels considering the pointing errors is studied. With the help of Meijer's G-function, the probability density function(PDF) and cumulative distribution function(CDF) of the aggregated channel model are derived on the basis of the best path selection scheme. The analytical ABER expression is achieved and the system performance is then investigated with the influence of pointing errors, turbulence strengths and structure parameters. Monte Carlo(MC) simulation is also provided to confirm the analytical ABER expression.展开更多
An asynchronous transmission scenario for non-orthogonal multiple access(NOMA)user signals with arbitrary phase offset is investigated in this paper.To improve the system performance in the user power-balanced conditi...An asynchronous transmission scenario for non-orthogonal multiple access(NOMA)user signals with arbitrary phase offset is investigated in this paper.To improve the system performance in the user power-balanced conditions,we adopt a synthetic detection method at the receiver,i.e.,the jointly optimal maximal likelihood detection aided triangular successive interference cancellation(JO ML-TSIC)method.Analytical bit error rate(BER)solutions are obtained for a two-user case with the optimal,intentional onehalf symbol period time delay implemented between the user signals.Furthermore,closed-form BER solutions for the case using the triangular successive interference cancellation(TSIC)detection method are also derived for comparisons.Numerical results show that the JO ML-TSIC receiver for the asynchronous system outperforms the TSIC receiver as well as the synchronous successive interference cancellation(SIC)receiver in all the conditions concerned.The results also show that the superiority of the JO ML-TSIC receiver is strengthened when the signals experience flat Rayleigh fading channels compared to the TSIC and the synchronous SIC receivers.展开更多
Two-way relay networks have received lots of attention, thanks to its ability to overcome the loss in the spectral efficiency due to half-duplex transmission. Asymptotic performance analysis can provide valuable insig...Two-way relay networks have received lots of attention, thanks to its ability to overcome the loss in the spectral efficiency due to half-duplex transmission. Asymptotic performance analysis can provide valuable insights in- to practical system designs. However, this is a gap in two-way relay network. In this paper, the asymptotic performance is studied for multi-branch dual-hop two-way amplify-and-forward （AF） relaying networks in independently but not necessarily identically distributed （i.n.i.d.） Nakagami-m fading channels, with arbitrary m 〉 5. The approximate prob- ability density function （PDF） of the instantaneous dual-hop link power at high SNR region is derived. Then we present the asymptotic outage probability expression, and analyze the diversity order and coding gain. Simulations are per- formed to verify the tightness of the presented analysis at medium and high SNR regions.展开更多
A 10 Gbit/s recirculating system is configured with Chirped Fiber Bragg Grating (CFBG) for the dispersion compensation. For the first time, the transmission distance in the loop reaches 1000km with bit error rate of 1...A 10 Gbit/s recirculating system is configured with Chirped Fiber Bragg Grating (CFBG) for the dispersion compensation. For the first time, the transmission distance in the loop reaches 1000km with bit error rate of 10-9. The effect of the group delay ripple of the fiber grating is also investigated in the recirculating systems, and it is shown that the transmission distance is limited to 4 cycles (4× 167.1km ) in the loop with the power penalty fluctuation below 1.0dB. Thus the group delay ripple should be reduced to allow for the wavelength drift of ±5GHz.At the end of this letter, the principles are given for designing long haul recirculating systems with dispersion compensation CFBG.展开更多
Bit Error Probability (BEP) provides a fundamental performance measure for wireless diversity systems. This paper presents two new exact BEP expressions for Maximal Ratio Combining (MRC) diversity systems. One BEP exp...Bit Error Probability (BEP) provides a fundamental performance measure for wireless diversity systems. This paper presents two new exact BEP expressions for Maximal Ratio Combining (MRC) diversity systems. One BEP expression takes a closed form, while the other is derived by treating the squared-sum of Rayleigh random variables as an Erlang variable. Due to the fact that the extant bounds are loose and could not properly characterize the error performance of MRC diversity systems, this paper presents a very tight bound. The numerical analysis shows that the new derived BEP expressions coincide with the extant expressions, and that the new approximation tightly bounds the accurate BEP.展开更多
With the development of communication systems, modulation methods are becoming more and more diverse. Among them, quadrature spatial modulation(QSM) is considered as one method with less capacity and high efficiency. ...With the development of communication systems, modulation methods are becoming more and more diverse. Among them, quadrature spatial modulation(QSM) is considered as one method with less capacity and high efficiency. In QSM, the traditional signal detection methods sometimes are unable to meet the actual requirement of low complexity of the system. Therefore, this paper proposes a signal detection scheme for QSM systems using deep learning to solve the complexity problem. Results from the simulations show that the bit error rate performance of the proposed deep learning-based detector is better than that of the zero-forcing(ZF) and minimum mean square error(MMSE) detectors, and similar to the maximum likelihood(ML) detector. Moreover, the proposed method requires less processing time than ZF, MMSE,and ML.展开更多
Directional modulation(DM)is one of the most promising secure communication techniques.However,when the eavesdropper is co-located with the legitimate receiver,the conventional DM has the disadvantages of weak anti-sc...Directional modulation(DM)is one of the most promising secure communication techniques.However,when the eavesdropper is co-located with the legitimate receiver,the conventional DM has the disadvantages of weak anti-scanning capability,anti-deciphering capability,and low secrecy rate.In response to these problems,we propose a twodimensional multi-term weighted fractional Fourier transform aided DM scheme,in which the legitimate receiver and the transmitter use different transform terms and transform orders to encrypt and decrypt the confidential information.In order to further lower the probability of being deciphered by an eavesdropper,we use the subblock partition method to convert the one-dimensional modulated signal vector into a twodimensional signal matrix,increasing the confusion of the useful information.Numerical results demonstrate that the proposed DM scheme not only provides stronger anti-deciphering and anti-scanning capabilities but also improves the secrecy rate performance of the system.展开更多
Space-Time Block Coded(STBC)Orthogonal Frequency Division Multiplexing(OFDM)satisfies higher data-rate requirements while maintaining signal quality in a multipath fading channel.However,conventional STBCs,including O...Space-Time Block Coded(STBC)Orthogonal Frequency Division Multiplexing(OFDM)satisfies higher data-rate requirements while maintaining signal quality in a multipath fading channel.However,conventional STBCs,including Orthogonal STBCs(OSTBCs),Non-Orthogonal(NOSTBCs),and Quasi-Orthogonal STBCs(QOSTBCs),do not provide both maximal diversity order and unity code rate simultaneously for more than two transmit antennas.This paper targets this problem and applies Maximum Rank Distance(MRD)codes in designing STBCOFDM systems.By following the direct-matrix construction method,we can construct binary extended finite field MRD-STBCs for any number of transmitting antennas.Work uses MRD-STBCs built over Phase-Shift Keying(PSK)modulation to develop an MRD-based STBC-OFDM system.The MRD-based STBC-OFDM system sacrifices minor error performance compared to traditional OSTBC-OFDM but shows improved results against NOSTBC and QOSTBC-OFDM.It also provides 25%higher data-rates than OSTBC-OFDM in configurations that use more than two transmit antennas.The tradeoffs are minor increases in computational complexity and processing delays.展开更多
Signal detection plays an essential role in massive Multiple-Input Multiple-Output(MIMO)systems.However,existing detection methods have not yet made a good tradeoff between Bit Error Rate(BER)and computational complex...Signal detection plays an essential role in massive Multiple-Input Multiple-Output(MIMO)systems.However,existing detection methods have not yet made a good tradeoff between Bit Error Rate(BER)and computational complexity,resulting in slow convergence or high complexity.To address this issue,a low-complexity Approximate Message Passing(AMP)detection algorithm with Deep Neural Network(DNN)(denoted as AMP-DNN)is investigated in this paper.Firstly,an efficient AMP detection algorithm is derived by scalarizing the simplification of Belief Propagation(BP)algorithm.Secondly,by unfolding the obtained AMP detection algorithm,a DNN is specifically designed for the optimal performance gain.For the proposed AMP-DNN,the number of trainable parameters is only related to that of layers,regardless of modulation scheme,antenna number and matrix calculation,thus facilitating fast and stable training of the network.In addition,the AMP-DNN can detect different channels under the same distribution with only one training.The superior performance of the AMP-DNN is also verified by theoretical analysis and experiments.It is found that the proposed algorithm enables the reduction of BER without signal prior information,especially in the spatially correlated channel,and has a lower computational complexity compared with existing state-of-the-art methods.展开更多
Due to the high complexity of the pairwise decoding algorithm and the poor performance of zero forcing（ ZF） /minimum mean square error（ MMSE） decoding algorithm, two low-complexity suboptimal decoding algorithms, ...Due to the high complexity of the pairwise decoding algorithm and the poor performance of zero forcing（ ZF） /minimum mean square error（ MMSE） decoding algorithm, two low-complexity suboptimal decoding algorithms, called pairwisequasi-ZF and pairwise-quasi-MMSE decoders, are proposed. First,two transmit signals are detected by the quasi-ZF or the quasiMMSE algorithm at the receiver. Then, the two detected signals as the decoding results are substituted into the two pairwise decoding algorithm expressions to detect the other two transmit signals. The bit error rate（ BER） performance of the proposed algorithms is compared with that of the current known decoding algorithms.Also, the number of calculations of ZF, MMSE, quasi-ZF and quasi-MMSE algorithms is compared with each other. Simulation results showthat the BER performance of the proposed algorithms is substantially improved in comparison to the quasi-ZF and quasiMMSE algorithms. The BER performance of the pairwise-quasiZF（ pairwise-quasi-MMSE） decoder is equivalent to the pairwiseZF（ pairwise-MMSE） decoder, while the computational complexity is significantly reduced.展开更多
By introducing orthogonal frequency division multiplexing （OFDM） technology, a visible light communication （VLC） system using a 5~5 white LED array is studied in this paper. The OFDM transmitter and receiver are m...By introducing orthogonal frequency division multiplexing （OFDM） technology, a visible light communication （VLC） system using a 5~5 white LED array is studied in this paper. The OFDM transmitter and receiver are modeled through MATLAB/Simulink tool. The electrical-optical-electrical （EOE） response of the VLC channel, which is also the re- sponse of the detector, is derived based on Lambert＇s lighting model. Then the modeling on the overall OFDM/VLC system is established by combining the above three models together. The effects of the factors which include the digital modulation, Reed-Solomon （RS） coding, pilot form, pilot ratio （PR） and communication distance on the bit error rate （BER） of the system are discussed. The results show that through the use of RS coding, block pilot, quad- rate phase shift keying （QPSK） modulation and a suitable pilot ratio about 1/3, under the communication rate about 550 kbit/s, the BER can be dropped to below 10^-5, and the communication distance can reach 0.9 m.展开更多
An OOK-NRZ visible light communication (VLC) system is designed by using a single white LED and a 550 nm visible photodetector. The emitting model of the single LED is established, and the general expression of the de...An OOK-NRZ visible light communication (VLC) system is designed by using a single white LED and a 550 nm visible photodetector. The emitting model of the single LED is established, and the general expression of the detector's output signals under OOK modulation is deduced. With the selected LED, detector and other related parameters, the designed communication system is optimized and its performance is analyzed. The optimized communication distance between the LED and the detector is 0.54 m at the communication bit rate of 1 Mbit/s. With the best communication distance, when the signal-to-noise ratio (SNR) is larger than 6.5 dB, the bit error rate (BER) can drop to 10-4. The analytical model and theory presented in this paper can be of certain practical meanings in the design of similar communication systems.展开更多
This paper presents a performance study of the distributed coordination function （DCF） of 802.11 networks considering erroneous channel and capture effects under non-saturated traffic conditions employing a basic ac...This paper presents a performance study of the distributed coordination function （DCF） of 802.11 networks considering erroneous channel and capture effects under non-saturated traffic conditions employing a basic access method.The aggregate throughput of a practical wireless local area network （WLAN） strongly depends on the channel conditions.In a real radio environment,the received signal power at the access point from a station is subjected to deterministic path loss,shadowing,and fast multipath fading.The binary exponential backoff （BEB） mechanism of IEEE 802.11 DCF severely suffers from more channel idle time under high bit error rate （BER）.To alleviate the low performance of IEEE 802.11 DCF,a new mechanism is introduced,which greatly outperforms the existing methods under a high BER.A multidimensional Markov chain model is used to characterize the behavior of DCF in order to account both non-ideal channel conditions and capture effects.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.62305388)the Postgraduate Scientific Research Innovation Project of Hunan Province(Grant No.QL20230007).
文摘Orbital-angular-momentum(OAM)multiplexing technology offers a significant dimension to enlarge communication capacity in free-space optical links.The coherent beam combining(CBC)system can simultaneously realize OAM multiplexing and achieve high-power laser output,providing substantial advantages for long-distance communication.Herein,we present an integrated CBC system for freespace optical links based on OAM multiplexing and demultiplexing technologies for the first time,to the best of our knowledge.A method to achieve flexible OAM multiplexing and efficient demultiplexing based on the CBC system is proposed and demonstrated both theoretically and experimentally.The experimental results exhibit a low bit error rate of 0.47%and a high recognition precision of 98.58%throughout the entire data transmission process.By employing such an ingenious strategy,this work holds promising prospects for enriching ultra-long-distance structured light communication in the future.
文摘The theoretical lower bounds on mean squared channel estimation errors for typical fading channels are presented by the infinite-length and non-causal Wiener filter and the exact closed-form expressions of the lower bounds for different channel Doppler spectra are derived. Based on the obtained lower bounds on mean squared channel estimation errors, the limits on bit error rate （BER） for maximal ratio combining （MRC） with Gaussian distributed weighting errors on independent and identically distributed （i. i. d） fading channels are presented. Numerical results show that the BER performances of ideal MRC are the lower bounds on the BER performances of non-ideal MRC and deteriorate as the maximum Doppler frequency increases or the SNR of channel estimate decreases.
基金supported in part by National Natural Science Foundation of China under Grants 62071002 and 62471004in part by"Double First-Class"Discipline Creation Project of Surveying Science and Technology under Grants CHXKYXBS03 and GCCRC202306+1 种基金in part by Anhui Provincial Natural Science Foundation under Grant 2408085QF207in part by Anhui Provincial University Distinguished Research and Innovation Team Foundation under Grant 2024AH010003.
文摘Precodings using square-root decomposition,including Cholesky and G-To-Minus-Half(GTMH)precodings,are promising for eliminating the Faster-Than-Nyquist(FTN)-induced Intersymbol-Interference(ISI).However,the existing precodings using square-root decomposition either ignore Interblock-Interference(IBI)or increase the signal power,deteriorating the Bit Error Rate(BER)performance for high-order modulations and severe ISI.To overcome these drawbacks,we adopt two approaches for constructing the circular ISI matrix.The first approach inserts a Cyclic Prefix/Suffix(CPS)after each precoded symbol block,while the second approach replaces the linear convolution of the FTN shaping and the matched filter by the circular convolution,resulting in the Circular FTN(CFTN).Using these two approaches,we propose three IBI-free precodings,i.e.,CPS-Cholesky,CFTN-Cholesky and CFTN-GTMH precodings.Furthermore,employing QR decomposition shows that the GTMH and Cholesky precodings can be converted interchangeably.Thus,we demonstrate that the GTMH precoding is essentially equivalent to the Cholesky precoding.Simulation results indicate that the BER performance of three IBI-free precodings approaches Nyquist performance for moderate ISI.However,as ISI intensifies,the CPS-Cholesky scheme increases the transmit power,causing BER performance degradation.In contrast,the CFTN-Cholesky and CFTN-GTMH precodings maintain optimal BER performance even for severe ISI.Considering 128-amplitude phase shift keying with a code rate of 1/2,the BER loss of CFTN-Cholesky and CFTN-GTMH precodings for the ideal BER of 10-5 is approximately 0.002 dB and 0.005 dB when packing factor is 0.7 and roll-offfactor is 0.3.To the best knowledge of the authors,this is the optimal performance achievable through precoding.
基金supported by the National Natural Science Foundation of China(No.62201508)the Zhejiang Provincial Natural Science Foundation of China(Nos.LZ21F010001 and LQ23F010004)the State Key Laboratory of Millimeter Waves of Southeast University,China(No.K202212).
文摘Quantization noise caused by analog-to-digital converter(ADC)gives rise to the reliability performance degradation of communication systems.In this paper,a quantized non-Hermitian symmetry(NHS)orthogonal frequency-division multiplexing-based visible light communication(OFDM-VLC)system is presented.In order to analyze the effect of the resolution of ADC on NHS OFDM-VLC,a quantized mathematical model of NHS OFDM-VLC is established.Based on the proposed quantized model,a closed-form bit error rate(BER)expression is derived.The theoretical analysis and simulation results both confirm the effectiveness of the obtained BER formula in high-resolution ADC.In addition,channel coding is helpful in compensating for the BER performance loss due to the utilization of lower resolution ADC.
基金supported in part by National Natural Science Foundation of China under Grant 62461024Jiangxi Provincial Natural Science Foundation of China under Grant 20224ACB202001.
文摘In high-speed railway(HSR)wireless communication,the rapid channel changes and limited high-capacity access cause significant impact on the link performance.Meanwhile,the Doppler shift caused by high mobility leads to the inter-carrier interference.In this paper,we propose a reconfigurable intelligent surface(RIS)-assisted receive spatial modulation(SM)scheme based on the spatial-temporal correlated HSR Rician channel.The characteristics of SM and the phase shift adjustment of RIS are used to mitigate the performance degradation in high mobility scenarios.Considering the influence of channel spatial-temporal correlation and Doppler shift,the effects of different parameters on average bit error rate(BER)performance and upper bound of ergodic capacity are analyzed.Therefore,a joint antenna and RIS-unit selection algorithm based on the antenna removal method is proposed to increase the capacity performance of communication links.Numerical results show that the proposed RIS-assisted receive SM scheme can maintain high transmission capacity compared to the conventional HSR-SM scheme,whereas the degradation of BER performance can be compensated by arranging a large number of RIS-units.In addition,selecting more RIS-units has better capacity performance than activating more antennas in the low signal-to-noise ratio regions.
基金supported by the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0300701)the National Key Research and Development Program of China(Grant No.2018YFA0306403)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB43000000).
文摘Quantum key distribution(QKD)is a method for secure communication that utilizes quantum mechanics principles to distribute cryptographic keys between parties.Integrated photonics offer benefits such as compactness,scalability,energy efficiency and the potential for extensive integration.We have achieved BB84 phase encoding and decoding,time-bin phase QKD,and the coherent one-way(COW)protocol on a planar lightwave circuit(PLC)platform.At the optimal temperature,our chip successfully prepared quantum states,performed decoding and calculated the secure key rate of the time-bin phasedecoding QKD to be 80.46 kbps over a 20 km transmission with a quantum bit error rate(QBER)of 4.23%.The secure key rate of the COW protocol was 18.18 kbps,with a phase error rate of 3.627%and a time error rate of 0.377%.The uniqueness of this technology lies in its combination of high integration and protocol flexibility,providing an innovative solution for the development of future quantum communication networks.
基金supported by the Fundamental Research Funds for the Central Universities under grant 2016XD-01
文摘Overlapped x domain multiplexing(OVXDM) is a promising encoding technique to obtain high spectral efficiency by utilizing inter-symbol interference(ISI) intelligently. However, the computational complexity of maximum likelihood sequence detection(MLSD) increases exponentially with the growth of spectral efficiency in OVXDM, which is unbearable for practical implementations. In this paper, based on a novel path metric associating adjacent symbols, we propose a multi-bit sliding stack decoding(Multi-Bit SSD) algorithm to achieve multiple-bit decoding simultaneously in OVXDM. Theoretical analysis is provided for the algorithm, which indicates the relationship between the performance and parameters including multiplexing waveform, overlapping fold and sliding window size. Simulation results show that the proposed algorithm can achieve better decoding performance and higher spectral efficiency than conventional fast decoding algorithms.
基金supported by the National Natural Science Foundation of China(No.61474090)the Fundamental Research Funds for the Central Universities(No.JB160105)the 111 Project of China(No.B08038)
文摘The average bit error rate(ABER) performance of a decode-and-forward(DF) based relay-assisted free-space optical(FSO) communication system over gamma-gamma distribution channels considering the pointing errors is studied. With the help of Meijer's G-function, the probability density function(PDF) and cumulative distribution function(CDF) of the aggregated channel model are derived on the basis of the best path selection scheme. The analytical ABER expression is achieved and the system performance is then investigated with the influence of pointing errors, turbulence strengths and structure parameters. Monte Carlo(MC) simulation is also provided to confirm the analytical ABER expression.
基金supported by the National Natural Science Foundation of China (Grant No. 62022019)
文摘An asynchronous transmission scenario for non-orthogonal multiple access(NOMA)user signals with arbitrary phase offset is investigated in this paper.To improve the system performance in the user power-balanced conditions,we adopt a synthetic detection method at the receiver,i.e.,the jointly optimal maximal likelihood detection aided triangular successive interference cancellation(JO ML-TSIC)method.Analytical bit error rate(BER)solutions are obtained for a two-user case with the optimal,intentional onehalf symbol period time delay implemented between the user signals.Furthermore,closed-form BER solutions for the case using the triangular successive interference cancellation(TSIC)detection method are also derived for comparisons.Numerical results show that the JO ML-TSIC receiver for the asynchronous system outperforms the TSIC receiver as well as the synchronous successive interference cancellation(SIC)receiver in all the conditions concerned.The results also show that the superiority of the JO ML-TSIC receiver is strengthened when the signals experience flat Rayleigh fading channels compared to the TSIC and the synchronous SIC receivers.
基金supported by the Major State Basic Research Development Program of China(973 Program No.2012CB316100)the National Natural Science Foundation of China(No.61032002)the Fundamental Research Funds for the Central Universities(No.2010XS21)
文摘Two-way relay networks have received lots of attention, thanks to its ability to overcome the loss in the spectral efficiency due to half-duplex transmission. Asymptotic performance analysis can provide valuable insights in- to practical system designs. However, this is a gap in two-way relay network. In this paper, the asymptotic performance is studied for multi-branch dual-hop two-way amplify-and-forward （AF） relaying networks in independently but not necessarily identically distributed （i.n.i.d.） Nakagami-m fading channels, with arbitrary m 〉 5. The approximate prob- ability density function （PDF） of the instantaneous dual-hop link power at high SNR region is derived. Then we present the asymptotic outage probability expression, and analyze the diversity order and coding gain. Simulations are per- formed to verify the tightness of the presented analysis at medium and high SNR regions.
基金the National 863 High Technology Development Program of China (No.2001 AA122012)
文摘A 10 Gbit/s recirculating system is configured with Chirped Fiber Bragg Grating (CFBG) for the dispersion compensation. For the first time, the transmission distance in the loop reaches 1000km with bit error rate of 10-9. The effect of the group delay ripple of the fiber grating is also investigated in the recirculating systems, and it is shown that the transmission distance is limited to 4 cycles (4× 167.1km ) in the loop with the power penalty fluctuation below 1.0dB. Thus the group delay ripple should be reduced to allow for the wavelength drift of ±5GHz.At the end of this letter, the principles are given for designing long haul recirculating systems with dispersion compensation CFBG.
基金Supported by the National Natural Science Foundation of China (No.60572059)Foundation of Guangdong Province for Ph.D. (No. 5300707).
文摘Bit Error Probability (BEP) provides a fundamental performance measure for wireless diversity systems. This paper presents two new exact BEP expressions for Maximal Ratio Combining (MRC) diversity systems. One BEP expression takes a closed form, while the other is derived by treating the squared-sum of Rayleigh random variables as an Erlang variable. Due to the fact that the extant bounds are loose and could not properly characterize the error performance of MRC diversity systems, this paper presents a very tight bound. The numerical analysis shows that the new derived BEP expressions coincide with the extant expressions, and that the new approximation tightly bounds the accurate BEP.
基金supported in part by The Science and Technology Development Fund, Macao SAR, China (0108/2020/A3)in part by The Science and Technology Development Fund, Macao SAR, China (0005/2021/ITP)the Deanship of Scientific Research at Taif University for funding this work。
文摘With the development of communication systems, modulation methods are becoming more and more diverse. Among them, quadrature spatial modulation(QSM) is considered as one method with less capacity and high efficiency. In QSM, the traditional signal detection methods sometimes are unable to meet the actual requirement of low complexity of the system. Therefore, this paper proposes a signal detection scheme for QSM systems using deep learning to solve the complexity problem. Results from the simulations show that the bit error rate performance of the proposed deep learning-based detector is better than that of the zero-forcing(ZF) and minimum mean square error(MMSE) detectors, and similar to the maximum likelihood(ML) detector. Moreover, the proposed method requires less processing time than ZF, MMSE,and ML.
基金supported by National Natural Science Foundation of China(No.62171445)。
文摘Directional modulation(DM)is one of the most promising secure communication techniques.However,when the eavesdropper is co-located with the legitimate receiver,the conventional DM has the disadvantages of weak anti-scanning capability,anti-deciphering capability,and low secrecy rate.In response to these problems,we propose a twodimensional multi-term weighted fractional Fourier transform aided DM scheme,in which the legitimate receiver and the transmitter use different transform terms and transform orders to encrypt and decrypt the confidential information.In order to further lower the probability of being deciphered by an eavesdropper,we use the subblock partition method to convert the one-dimensional modulated signal vector into a twodimensional signal matrix,increasing the confusion of the useful information.Numerical results demonstrate that the proposed DM scheme not only provides stronger anti-deciphering and anti-scanning capabilities but also improves the secrecy rate performance of the system.
基金supported by the Excellent Foreign Student scholarship program,Sirindhorn International Institute of Technology.
文摘Space-Time Block Coded(STBC)Orthogonal Frequency Division Multiplexing(OFDM)satisfies higher data-rate requirements while maintaining signal quality in a multipath fading channel.However,conventional STBCs,including Orthogonal STBCs(OSTBCs),Non-Orthogonal(NOSTBCs),and Quasi-Orthogonal STBCs(QOSTBCs),do not provide both maximal diversity order and unity code rate simultaneously for more than two transmit antennas.This paper targets this problem and applies Maximum Rank Distance(MRD)codes in designing STBCOFDM systems.By following the direct-matrix construction method,we can construct binary extended finite field MRD-STBCs for any number of transmitting antennas.Work uses MRD-STBCs built over Phase-Shift Keying(PSK)modulation to develop an MRD-based STBC-OFDM system.The MRD-based STBC-OFDM system sacrifices minor error performance compared to traditional OSTBC-OFDM but shows improved results against NOSTBC and QOSTBC-OFDM.It also provides 25%higher data-rates than OSTBC-OFDM in configurations that use more than two transmit antennas.The tradeoffs are minor increases in computational complexity and processing delays.
基金supported by Major Project of Science and Technology Research Program of Chongqing Education Commission of China(Grant No.KJZD-M201900601)China Postdoctoral Science Foundation(Grant No.2021MD703932)Project Supported by Engineering Research Center of Mobile Communications,Ministry of Education,China(Grant No.cqupt-mct-202006)。
文摘Signal detection plays an essential role in massive Multiple-Input Multiple-Output(MIMO)systems.However,existing detection methods have not yet made a good tradeoff between Bit Error Rate(BER)and computational complexity,resulting in slow convergence or high complexity.To address this issue,a low-complexity Approximate Message Passing(AMP)detection algorithm with Deep Neural Network(DNN)(denoted as AMP-DNN)is investigated in this paper.Firstly,an efficient AMP detection algorithm is derived by scalarizing the simplification of Belief Propagation(BP)algorithm.Secondly,by unfolding the obtained AMP detection algorithm,a DNN is specifically designed for the optimal performance gain.For the proposed AMP-DNN,the number of trainable parameters is only related to that of layers,regardless of modulation scheme,antenna number and matrix calculation,thus facilitating fast and stable training of the network.In addition,the AMP-DNN can detect different channels under the same distribution with only one training.The superior performance of the AMP-DNN is also verified by theoretical analysis and experiments.It is found that the proposed algorithm enables the reduction of BER without signal prior information,especially in the spatially correlated channel,and has a lower computational complexity compared with existing state-of-the-art methods.
基金The National Natural Science Foundation of China(No.6157110861201248)+1 种基金the Open Research Fund of National Mobile Communications Research Laboratory of China(No.2011D18)China Postdoctoral Science Foundation(No.2012M511175)
文摘Due to the high complexity of the pairwise decoding algorithm and the poor performance of zero forcing（ ZF） /minimum mean square error（ MMSE） decoding algorithm, two low-complexity suboptimal decoding algorithms, called pairwisequasi-ZF and pairwise-quasi-MMSE decoders, are proposed. First,two transmit signals are detected by the quasi-ZF or the quasiMMSE algorithm at the receiver. Then, the two detected signals as the decoding results are substituted into the two pairwise decoding algorithm expressions to detect the other two transmit signals. The bit error rate（ BER） performance of the proposed algorithms is compared with that of the current known decoding algorithms.Also, the number of calculations of ZF, MMSE, quasi-ZF and quasi-MMSE algorithms is compared with each other. Simulation results showthat the BER performance of the proposed algorithms is substantially improved in comparison to the quasi-ZF and quasiMMSE algorithms. The BER performance of the pairwise-quasiZF（ pairwise-quasi-MMSE） decoder is equivalent to the pairwiseZF（ pairwise-MMSE） decoder, while the computational complexity is significantly reduced.
基金supported by the Innovation Fund for Technology Based Firms of Changchun of China (No.10ZC04)
文摘By introducing orthogonal frequency division multiplexing （OFDM） technology, a visible light communication （VLC） system using a 5~5 white LED array is studied in this paper. The OFDM transmitter and receiver are modeled through MATLAB/Simulink tool. The electrical-optical-electrical （EOE） response of the VLC channel, which is also the re- sponse of the detector, is derived based on Lambert＇s lighting model. Then the modeling on the overall OFDM/VLC system is established by combining the above three models together. The effects of the factors which include the digital modulation, Reed-Solomon （RS） coding, pilot form, pilot ratio （PR） and communication distance on the bit error rate （BER） of the system are discussed. The results show that through the use of RS coding, block pilot, quad- rate phase shift keying （QPSK） modulation and a suitable pilot ratio about 1/3, under the communication rate about 550 kbit/s, the BER can be dropped to below 10^-5, and the communication distance can reach 0.9 m.
基金supported by the Innovation Fund For Technology Based Firms of Changchun, China (No.10ZC04)
文摘An OOK-NRZ visible light communication (VLC) system is designed by using a single white LED and a 550 nm visible photodetector. The emitting model of the single LED is established, and the general expression of the detector's output signals under OOK modulation is deduced. With the selected LED, detector and other related parameters, the designed communication system is optimized and its performance is analyzed. The optimized communication distance between the LED and the detector is 0.54 m at the communication bit rate of 1 Mbit/s. With the best communication distance, when the signal-to-noise ratio (SNR) is larger than 6.5 dB, the bit error rate (BER) can drop to 10-4. The analytical model and theory presented in this paper can be of certain practical meanings in the design of similar communication systems.
文摘This paper presents a performance study of the distributed coordination function （DCF） of 802.11 networks considering erroneous channel and capture effects under non-saturated traffic conditions employing a basic access method.The aggregate throughput of a practical wireless local area network （WLAN） strongly depends on the channel conditions.In a real radio environment,the received signal power at the access point from a station is subjected to deterministic path loss,shadowing,and fast multipath fading.The binary exponential backoff （BEB） mechanism of IEEE 802.11 DCF severely suffers from more channel idle time under high bit error rate （BER）.To alleviate the low performance of IEEE 802.11 DCF,a new mechanism is introduced,which greatly outperforms the existing methods under a high BER.A multidimensional Markov chain model is used to characterize the behavior of DCF in order to account both non-ideal channel conditions and capture effects.
