The increasing reliance on interconnected Internet of Things(IoT)devices has amplified the demand for robust anonymization strategies to protect device identities and ensure secure communication.However,traditional an...The increasing reliance on interconnected Internet of Things(IoT)devices has amplified the demand for robust anonymization strategies to protect device identities and ensure secure communication.However,traditional anonymization methods for IoT networks often rely on static identity models,making them vulnerable to inference attacks through long-term observation.Moreover,these methods tend to sacrifice data availability to protect privacy,limiting their practicality in real-world applications.To overcome these limitations,we propose a dynamic device identity anonymization framework using Moving Target Defense(MTD)principles implemented via Software-Defined Networking(SDN).In our model,the SDN controller periodically reconfigures the network addresses and routes of IoT devices using a constraint-aware backtracking algorithmthat constructs new virtual topologies under connectivity and performance constraints.This address-hopping scheme introduces continuous unpredictability at the network layer dynamically changing device identifiers,routing paths,and even network topology which thwarts attacker reconnaissance while preserving normal communication.Experimental results demonstrate that our approach significantly reduces device identity exposure and scan success rates for attackers compared to static networks.Moreover,the dynamic schememaintains high data availability and network performance.Under attack conditions it reduced average communication delay by approximately 60% vs.an unprotected network,with minimal overhead on system resources.展开更多
The integration of satellite communication network and cellular network has a great potential to enable ubiquitous connectivity in future communication networks.Among numerous related application scenarios,the direct ...The integration of satellite communication network and cellular network has a great potential to enable ubiquitous connectivity in future communication networks.Among numerous related application scenarios,the direct connection of mobile phone to satellite has attracted increasing attention.However,the spectrum scarcity in the sub-6 GHz band and low spectrum utilization prevents its popularity.To address these problem,in this paper,we propose a dynamic spectrum sharing method for satellite network and cellular network based on beam-hopping.Specifically,we first develop a centralized dynamic spectrum sharing architecture based on beam-hopping,and propose a delay pre-compensation scheme for beam hopping pattern.Then,an optimization problem is formulated to maximize the overall capacity of the integrated network,with considering the service requirements,the fairness between beam positions and mixed co-channel interference,etc.To solve this problem,a polling-based dynamic resource allocation algorithm is proposed.Simulation results confirm that the proposed algorithm can effectively reduce the serious cochannel interference between different beams or different systems,and improve the spectrum utilization rate as well as system capacity.展开更多
Ferromagnetic semiconductor Ga_(1–x)Mn_(x)As_(1–y)P_(y) thin films go through a metal–insulator transition at low temperature where electrical conduction becomes driven by hopping of charge carriers.In this regime,...Ferromagnetic semiconductor Ga_(1–x)Mn_(x)As_(1–y)P_(y) thin films go through a metal–insulator transition at low temperature where electrical conduction becomes driven by hopping of charge carriers.In this regime,we report a colossal negative magnetoresistance(CNMR)coexisting with a saturated magnetic moment,unlike in the traditional magnetic semiconductor Ga_(1–x)Mn_(x)As.By analyzing the temperature dependence of the resistivity at fixed magnetic field,we demonstrate that the CNMR can be consistently described by the field dependence of the localization length,which relates to a field dependent mobility edge.This dependence is likely due to the random environment of Mn atoms in Ga_(1-x)Mn_(x)As_(1-y)P_(y) which causes a random spatial distribution of the mobility that is suppressed by an increasing magnetic field.展开更多
A scheme of a frequency-hopping frequency-synthesizer applied to a Bluetooth ratio frequency （RF） front-end is presented,and design of a voltage controlled oscillator （VCO） and dual-modulus prescaler are focused o...A scheme of a frequency-hopping frequency-synthesizer applied to a Bluetooth ratio frequency （RF） front-end is presented,and design of a voltage controlled oscillator （VCO） and dual-modulus prescaler are focused on.It is fabricated in a 0.18 μm mixed-signal CMOS （complementary metal-oxide-semiconductor transistor） process.The power dissipation of VCO is low and a stable performance is gained.The measured phase noise of VCO at 2.4 GHz is less than -114.32 dBc/Hz.The structure of the DMP is optimized and a novel D-latch integrated with ＂OR＂ logic gate is used.The measured results show that the chip can work well under a 1.8 V power supply.The power dissipation of the core part in a dual modulus prescaler is only 5.76 mW.An RMS jitter of 2 ps is measured on the output signal at 118.3 MHz.It is less than 0.02% of the clock period.展开更多
One dimensional periodic hopping model is useful to understand the motion of microscopic particles in thermal noise environment. In this research, by formal calculation and based on detailed balance, the explicit expr...One dimensional periodic hopping model is useful to understand the motion of microscopic particles in thermal noise environment. In this research, by formal calculation and based on detailed balance, the explicit expressions of the limits of mean velocity and diffusion constant of this model as the number of internal mechanochemical sates tend to infinity are obtained.These results will be helpful to understand the limit of the one dimensional hopping model.At the same time, the work can be used to get more useful results in continuous form from the corresponding ones obtained by discrete models.展开更多
A flexible-rigid hopping mechanism which is inspired by the locust jumping was proposed, and its kinematic characteris- tics were analyzed. A series of experiments were conducted to observe locust morphology and jumpi...A flexible-rigid hopping mechanism which is inspired by the locust jumping was proposed, and its kinematic characteris- tics were analyzed. A series of experiments were conducted to observe locust morphology and jumping process. According to classic mechanics, the jumping process analysis was conducted to build the relationship of the locust jumping parameters. The take-offphase was divided into four stages in detail. Based on the biological observation and kinematics analysis, a mechanical model was proposed to simulate locust jumping. The forces of the flexible-rigid hopping mechanism at each stage were ana- lyzed. The kinematic analysis using pseudo-rigid-body model was described by D-H method. It is confirmed that the proposed bionic mechanism has the similar performance as the locust hind leg in hopping. Moreover, the jumping angle which decides the jumping process was discussed, and its relation with other parameters was established. A calculation case analysis corroborated the method. The results of this paper show that the proposed bionic mechanism which is inspired by the locust hind limb has an excellent kinematics performance, which can provide a foundation for design and motion planning of the hopping robot.展开更多
Beam hopping technology provides a foundation for the flexible allocation and efficient utilization of satellite resources,which is considered as a key technology for the next generation of high throughput satellite s...Beam hopping technology provides a foundation for the flexible allocation and efficient utilization of satellite resources,which is considered as a key technology for the next generation of high throughput satellite systems.To alleviate the contradiction between resource utilization and co-frequency interference in beam hopping technology,this paper firstly studies dynamic clustering to balance traffic between clusters and proposes cluster hopping pool optimization method to avoid inter-cluster interference.Then based on the optimization results,a novel joint beam hopping and precoding algorithm is provided to combine resource allocation and intra-cluster interference suppression,which can make efficient utilization of system resources and achieve reliable and near-optimal transmission capacity.The simulation results show that,compared with traditional methods,the proposed algorithms can dynamically adjust to balance demand traffic between clusters and meet the service requirements of each beam,also eliminate the co-channel interference to improve the performance of satellite network.展开更多
End hopping is an active and effective technology for defending against adversaries in the network warfare.Synchronization is a key technology of end hopping.However,the common synchronization methods are insufficient...End hopping is an active and effective technology for defending against adversaries in the network warfare.Synchronization is a key technology of end hopping.However,the common synchronization methods are insufficient for end hopping.Based on timestamp synchronization,this paper proposes a novel method of Distributed Timestamp Synchronization(DTS)to improve the capacity of synchronization.DTS uses a list of timestamp servers which are located all over the Internet to synchronize timestamp,and a list of clock offsets to adjust the synchronized timestamp.DTS can overcome the main deficiencies(request overwhelming and boundary failure)of timestamp synchronization.Experiments show that DTS is a feasible synchronization technology for end hopping.展开更多
Satellite mobile system and space-airground integrated network have a prominent superiority in global coverage which plays a critical role in remote and non-land regions, as well as emergency communications. However, ...Satellite mobile system and space-airground integrated network have a prominent superiority in global coverage which plays a critical role in remote and non-land regions, as well as emergency communications. However, due to the gradual angle attenuations of the satellite antennas, it is difficult to achieve full frequency multiplex among different beams as terrestrial 5G network. Multi-color frequency reuse is widely adopted in both academic and industry. Beam hopping scheme has attracted the attention of researchers recently due to the allocation flexibility. In this paper, we focus on analyzing the performance benefits of beam hopping compared with multi-color frequency reuse scheme in non-uniform user and traffic distributions in satellite system. Aerial networks are also introduced to form a space-airground integrated network for coverage enhancement,and the capacity improvement is analyzed. Besides,additional improved techniques are provided to make comprehensive analysis and comparisons. Theoretical analysis and simulation results indicate that the beam hopping scheme has a prominent superiority in the system capacity compared with the traditional multicolor frequency reuse scheme in both satellite mobile system and future space-air-ground integrated network.展开更多
In this paper,a property of Frequency Hopping (FH) sequence set with No Hit Zone (NHZ) is analyzed. Based on matrix transform and mapping methods,respectively,two classes of NHZ FH sequences are presented. These NHZ F...In this paper,a property of Frequency Hopping (FH) sequence set with No Hit Zone (NHZ) is analyzed. Based on matrix transform and mapping methods,respectively,two classes of NHZ FH sequences are presented. These NHZ FH sequences have good Hamming auto-correlation and Hamming cross-correlation properties. FH Code-Division Multiple Access (FH-CDMA) communication systems employing such NHZ FH sequences will eliminate multiple-access interference if the maximum time delay is shorter than the length of the NHZ.展开更多
Attacking time-sensitive targets has rigid demands for the timeliness and reliability of information transmission, while typical Media Access Control（MAC） designed for this application works well only in very light-...Attacking time-sensitive targets has rigid demands for the timeliness and reliability of information transmission, while typical Media Access Control（MAC） designed for this application works well only in very light-load scenarios; as a consequence, the performances of system throughput and channel utilization are degraded. For this problem, a feedback-retransmission based asynchronous FRequency hopping Media Access（FRMA） control protocol is proposed. Burst communication, asynchronous Frequency Hopping（FH）, channel coding, and feedback retransmission are utilized in FRMA. With the mechanism of asynchronous FH, immediate packet transmission and multi-packet reception can be realized, and thus the timeliness is improved.Furthermore, reliability can be achieved via channel coding and feedback retransmission. With theories of queuing theory, Markov model, packets collision model, and discrete Laplace transformation, the formulas of packet success probability, system throughput, average packet end-to-end delay, and delay distribution are obtained. The approximation accuracy of theoretical derivation is verified by experimental results. Within a light-load network, the proposed FRMA has the ability of millisecond delay and 99% reliability as well as outperforms the non-feedback-retransmission based asynchronous frequency hopping media access control protocol.展开更多
This paper deals with the follower jamming(FJ)resistance for the frequency hopping(FH)communication system over additive white Gaussian noise(AWGN)channel.Conventional FH systems are susceptible to be jammed by FJ,and...This paper deals with the follower jamming(FJ)resistance for the frequency hopping(FH)communication system over additive white Gaussian noise(AWGN)channel.Conventional FH systems are susceptible to be jammed by FJ,and multi-pattern frequency hopping(MPFH)has good resistance to FJ.To further improve the FJ rejection capability of MPFH,we propose a wide gap multi-pattern frequency hopping(WGMPFH)scheme.WGMPFH uses channels to represent messages,and the data channel and complementary channel are hopping on orthogonal frequency slots according to wide gap FH patterns.The transmitted signal lures FJ to aim at the data channel and the complementary channel is away from FJ by adopting wide gap frequency patterns.FJ does not affect the complementary channel but increases the signal energy in the data channel,thus the effect of FJ is reduced.Its bit error rate(BER)is derived under FJ and the effects of three FJ parameters(tracking success probability,jamming duration ratio and jamming bandwidth ratio)on the BER performance of WGMPFH are investigated versus the co nventional FH/BFSK and MPFH system.Numerical and simulation results show that when under the worst-case FJ,the proposed WGMPFH outperforms the MPFH by about 1-3 dB and outperforms the conventional FH/BFSK by more than 4 dB.The proposed WGMPFH shows superior jamming rejection performance under FJ especially in severe signal-to-jamming ratio(SJR).展开更多
Low earth orbit(LEO) satellite communications can provide ubiquitous and reliable services,making it an essential part of the Internet of Everything network. Beam hopping(BH) is an emerging technology for effectively ...Low earth orbit(LEO) satellite communications can provide ubiquitous and reliable services,making it an essential part of the Internet of Everything network. Beam hopping(BH) is an emerging technology for effectively addressing the issue of low resource utilization caused by the non-uniform spatio-temporal distribution of traffic demands. However, how to allocate multi-dimensional resources in a timely and efficient way for the highly dynamic LEO satellite systems remains a challenge. This paper proposes a joint beam scheduling and power optimization beam hopping(JBSPO-BH) algorithm considering the differences in the geographic distribution of sink nodes. The JBSPO-BH algorithm decouples the original problem into two sub-problems. The beam scheduling problem is modelled as a potential game,and the Nash equilibrium(NE) point is obtained as the beam scheduling strategy. Moreover, the penalty function interior point method is applied to optimize the power allocation. Simulation results show that the JBSPO-BH algorithm has low time complexity and fast convergence and achieves better performance both in throughput and fairness. Compared with greedybased BH, greedy-based BH with the power optimization, round-robin BH, Max-SINR BH and satellite resource allocation algorithm, the throughput of the proposed algorithm is improved by 44.99%, 20.79%,156.06%, 15.39% and 8.17%, respectively.展开更多
A novel frequency hopping(FH) sequences generator based on advanced encryption standard(AES) iterated block cipher is proposed for FH communication systems.The analysis shows that the FH sequences based on AES algorit...A novel frequency hopping(FH) sequences generator based on advanced encryption standard(AES) iterated block cipher is proposed for FH communication systems.The analysis shows that the FH sequences based on AES algorithm have good performance in uniformity, correlation, complexity and security.A high-speed, low-power and low-cost ASIC of FH sequences generator is implemented by optimizing the structure of S-Box and MixColumns of AES algorithm, proposing a hierarchical power management strategy, and applying ...展开更多
Based on the anti-jamming performance of differential frequency hopping(DFH)systems in Additive White Gaussian Noise(AWGN)channel,Fountain code is introduced to the DFH systems as the outer error correcting code in th...Based on the anti-jamming performance of differential frequency hopping(DFH)systems in Additive White Gaussian Noise(AWGN)channel,Fountain code is introduced to the DFH systems as the outer error correcting code in this paper to investigate the improvements against partial-band jamming over AWGN channel.The performance of Fountain coded DFH is theoretically analyzed and numerically simulated.The total frequency of hopping in the simulation is 16,and results show that,on one hand,when exact jamming state information(JSI)is available,and the number of jamming frequency is n=16,the bit error rate(BER)of 10~3 is achieved with the signal to interference ratio(SIR)approximately 7.5 dB over AWGN channel,and the performance improves about 1-1.5dB compared with the no-coded system.When the number of jamming frequency is n=2,the performance increases 15-17dB.On the other hand,when JSI is unavailable,a joint JSI estimation and decoding algorithm is proposed.The BER of 103 is achieved with jamming-frequency n 16,SIR=8dB and signal noise ratio(SNR)10dB over AWGN channel.It's proved that this algorithm provides robust anti-jamming pertbrmance even without JSI.The anti-jamming performance of Fountain coded DFH systems is obviously superior to no-coded DFH systems.展开更多
In order to achieve fast synchronization of the modulation hopping system, a synchronization scheme called short code to guide long code is adopted, and the initial synchronization hops and service hops are designed i...In order to achieve fast synchronization of the modulation hopping system, a synchronization scheme called short code to guide long code is adopted, and the initial synchronization hops and service hops are designed in detail.According to the system requirements for short code in the properties of time-varying, safety and balance, an algorithm to design wide-gap chaos short code based on TOD is proposed.Synchronization performance analysis shows that the algorithm has good performance, the initial synchronization time and the later entering network synchronization time are short, additionally, maximum synchronization time difference and synchronization maintaining time are long, all of which meet the needs of normal communications, and further verify the synchronization scheme feasible.展开更多
基金supported by the National Key Research and Development Program of China(Project No.2022YFB3104300).
文摘The increasing reliance on interconnected Internet of Things(IoT)devices has amplified the demand for robust anonymization strategies to protect device identities and ensure secure communication.However,traditional anonymization methods for IoT networks often rely on static identity models,making them vulnerable to inference attacks through long-term observation.Moreover,these methods tend to sacrifice data availability to protect privacy,limiting their practicality in real-world applications.To overcome these limitations,we propose a dynamic device identity anonymization framework using Moving Target Defense(MTD)principles implemented via Software-Defined Networking(SDN).In our model,the SDN controller periodically reconfigures the network addresses and routes of IoT devices using a constraint-aware backtracking algorithmthat constructs new virtual topologies under connectivity and performance constraints.This address-hopping scheme introduces continuous unpredictability at the network layer dynamically changing device identifiers,routing paths,and even network topology which thwarts attacker reconnaissance while preserving normal communication.Experimental results demonstrate that our approach significantly reduces device identity exposure and scan success rates for attackers compared to static networks.Moreover,the dynamic schememaintains high data availability and network performance.Under attack conditions it reduced average communication delay by approximately 60% vs.an unprotected network,with minimal overhead on system resources.
基金supported in part by the National Key Research and Development Program of China under Grant 2018YFA0701601in part by the National Natural Science Foundation of China under Grant 61922049 and Grant 61941104in part by the Tsinghua University-China Mobile Communications Group Company Ltd.,Joint Institute.
文摘The integration of satellite communication network and cellular network has a great potential to enable ubiquitous connectivity in future communication networks.Among numerous related application scenarios,the direct connection of mobile phone to satellite has attracted increasing attention.However,the spectrum scarcity in the sub-6 GHz band and low spectrum utilization prevents its popularity.To address these problem,in this paper,we propose a dynamic spectrum sharing method for satellite network and cellular network based on beam-hopping.Specifically,we first develop a centralized dynamic spectrum sharing architecture based on beam-hopping,and propose a delay pre-compensation scheme for beam hopping pattern.Then,an optimization problem is formulated to maximize the overall capacity of the integrated network,with considering the service requirements,the fairness between beam positions and mixed co-channel interference,etc.To solve this problem,a polling-based dynamic resource allocation algorithm is proposed.Simulation results confirm that the proposed algorithm can effectively reduce the serious cochannel interference between different beams or different systems,and improve the spectrum utilization rate as well as system capacity.
基金This work was supported by the National Science Foundation Grant No.DMR 1905277.
文摘Ferromagnetic semiconductor Ga_(1–x)Mn_(x)As_(1–y)P_(y) thin films go through a metal–insulator transition at low temperature where electrical conduction becomes driven by hopping of charge carriers.In this regime,we report a colossal negative magnetoresistance(CNMR)coexisting with a saturated magnetic moment,unlike in the traditional magnetic semiconductor Ga_(1–x)Mn_(x)As.By analyzing the temperature dependence of the resistivity at fixed magnetic field,we demonstrate that the CNMR can be consistently described by the field dependence of the localization length,which relates to a field dependent mobility edge.This dependence is likely due to the random environment of Mn atoms in Ga_(1-x)Mn_(x)As_(1-y)P_(y) which causes a random spatial distribution of the mobility that is suppressed by an increasing magnetic field.
文摘A scheme of a frequency-hopping frequency-synthesizer applied to a Bluetooth ratio frequency （RF） front-end is presented,and design of a voltage controlled oscillator （VCO） and dual-modulus prescaler are focused on.It is fabricated in a 0.18 μm mixed-signal CMOS （complementary metal-oxide-semiconductor transistor） process.The power dissipation of VCO is low and a stable performance is gained.The measured phase noise of VCO at 2.4 GHz is less than -114.32 dBc/Hz.The structure of the DMP is optimized and a novel D-latch integrated with ＂OR＂ logic gate is used.The measured results show that the chip can work well under a 1.8 V power supply.The power dissipation of the core part in a dual modulus prescaler is only 5.76 mW.An RMS jitter of 2 ps is measured on the output signal at 118.3 MHz.It is less than 0.02% of the clock period.
基金ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.10701029） and the Shanghai Key Laboratory for Contemporary Applied Mathematics （No.SGST09DZ2272900）.
文摘One dimensional periodic hopping model is useful to understand the motion of microscopic particles in thermal noise environment. In this research, by formal calculation and based on detailed balance, the explicit expressions of the limits of mean velocity and diffusion constant of this model as the number of internal mechanochemical sates tend to infinity are obtained.These results will be helpful to understand the limit of the one dimensional hopping model.At the same time, the work can be used to get more useful results in continuous form from the corresponding ones obtained by discrete models.
基金This work is financially supported by the National Natural Science Foundation of China （Grant No. 51075014）.
文摘A flexible-rigid hopping mechanism which is inspired by the locust jumping was proposed, and its kinematic characteris- tics were analyzed. A series of experiments were conducted to observe locust morphology and jumping process. According to classic mechanics, the jumping process analysis was conducted to build the relationship of the locust jumping parameters. The take-offphase was divided into four stages in detail. Based on the biological observation and kinematics analysis, a mechanical model was proposed to simulate locust jumping. The forces of the flexible-rigid hopping mechanism at each stage were ana- lyzed. The kinematic analysis using pseudo-rigid-body model was described by D-H method. It is confirmed that the proposed bionic mechanism has the similar performance as the locust hind leg in hopping. Moreover, the jumping angle which decides the jumping process was discussed, and its relation with other parameters was established. A calculation case analysis corroborated the method. The results of this paper show that the proposed bionic mechanism which is inspired by the locust hind limb has an excellent kinematics performance, which can provide a foundation for design and motion planning of the hopping robot.
基金National Natural Science Foundation of China (No. 61901230, 61801445 and 91738201)Key pre-research project for civil space technology: Research project on VHTS communication technology (No. B0106)。
文摘Beam hopping technology provides a foundation for the flexible allocation and efficient utilization of satellite resources,which is considered as a key technology for the next generation of high throughput satellite systems.To alleviate the contradiction between resource utilization and co-frequency interference in beam hopping technology,this paper firstly studies dynamic clustering to balance traffic between clusters and proposes cluster hopping pool optimization method to avoid inter-cluster interference.Then based on the optimization results,a novel joint beam hopping and precoding algorithm is provided to combine resource allocation and intra-cluster interference suppression,which can make efficient utilization of system resources and achieve reliable and near-optimal transmission capacity.The simulation results show that,compared with traditional methods,the proposed algorithms can dynamically adjust to balance demand traffic between clusters and meet the service requirements of each beam,also eliminate the co-channel interference to improve the performance of satellite network.
基金National Natural Science Foundation of China under Grant No. 60973141Natural Science Foundation of Tianjin under Grant No. 09JCYBJ00300Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant No. 20100031110030
文摘End hopping is an active and effective technology for defending against adversaries in the network warfare.Synchronization is a key technology of end hopping.However,the common synchronization methods are insufficient for end hopping.Based on timestamp synchronization,this paper proposes a novel method of Distributed Timestamp Synchronization(DTS)to improve the capacity of synchronization.DTS uses a list of timestamp servers which are located all over the Internet to synchronize timestamp,and a list of clock offsets to adjust the synchronized timestamp.DTS can overcome the main deficiencies(request overwhelming and boundary failure)of timestamp synchronization.Experiments show that DTS is a feasible synchronization technology for end hopping.
基金the Natural Science Foundation of China under Grant 61801319Sichuan Science and Technology Program under Grant 2020JDJQ0061+1 种基金the Education Agency Project of Sichuan Province under Grant 18ZB0419the Sichuan University of Science and Engineering Talent Introduction Project under Grant 2020RC33。
文摘Satellite mobile system and space-airground integrated network have a prominent superiority in global coverage which plays a critical role in remote and non-land regions, as well as emergency communications. However, due to the gradual angle attenuations of the satellite antennas, it is difficult to achieve full frequency multiplex among different beams as terrestrial 5G network. Multi-color frequency reuse is widely adopted in both academic and industry. Beam hopping scheme has attracted the attention of researchers recently due to the allocation flexibility. In this paper, we focus on analyzing the performance benefits of beam hopping compared with multi-color frequency reuse scheme in non-uniform user and traffic distributions in satellite system. Aerial networks are also introduced to form a space-airground integrated network for coverage enhancement,and the capacity improvement is analyzed. Besides,additional improved techniques are provided to make comprehensive analysis and comparisons. Theoretical analysis and simulation results indicate that the beam hopping scheme has a prominent superiority in the system capacity compared with the traditional multicolor frequency reuse scheme in both satellite mobile system and future space-air-ground integrated network.
基金the National Natural Science Foundation of China (No.90604035 and 60572142)the Program for New Century Excellent Talents in University (NCET) (No.NECT-05-0795).
文摘In this paper,a property of Frequency Hopping (FH) sequence set with No Hit Zone (NHZ) is analyzed. Based on matrix transform and mapping methods,respectively,two classes of NHZ FH sequences are presented. These NHZ FH sequences have good Hamming auto-correlation and Hamming cross-correlation properties. FH Code-Division Multiple Access (FH-CDMA) communication systems employing such NHZ FH sequences will eliminate multiple-access interference if the maximum time delay is shorter than the length of the NHZ.
基金supported by the National Natural Science Foundation of China(No.61501496)
文摘Attacking time-sensitive targets has rigid demands for the timeliness and reliability of information transmission, while typical Media Access Control（MAC） designed for this application works well only in very light-load scenarios; as a consequence, the performances of system throughput and channel utilization are degraded. For this problem, a feedback-retransmission based asynchronous FRequency hopping Media Access（FRMA） control protocol is proposed. Burst communication, asynchronous Frequency Hopping（FH）, channel coding, and feedback retransmission are utilized in FRMA. With the mechanism of asynchronous FH, immediate packet transmission and multi-packet reception can be realized, and thus the timeliness is improved.Furthermore, reliability can be achieved via channel coding and feedback retransmission. With theories of queuing theory, Markov model, packets collision model, and discrete Laplace transformation, the formulas of packet success probability, system throughput, average packet end-to-end delay, and delay distribution are obtained. The approximation accuracy of theoretical derivation is verified by experimental results. Within a light-load network, the proposed FRMA has the ability of millisecond delay and 99% reliability as well as outperforms the non-feedback-retransmission based asynchronous frequency hopping media access control protocol.
基金The National Natural Science Foundation of China(No.61531009,No.61471108)The National Major Projects of China(No.2016ZX03001009)。
文摘This paper deals with the follower jamming(FJ)resistance for the frequency hopping(FH)communication system over additive white Gaussian noise(AWGN)channel.Conventional FH systems are susceptible to be jammed by FJ,and multi-pattern frequency hopping(MPFH)has good resistance to FJ.To further improve the FJ rejection capability of MPFH,we propose a wide gap multi-pattern frequency hopping(WGMPFH)scheme.WGMPFH uses channels to represent messages,and the data channel and complementary channel are hopping on orthogonal frequency slots according to wide gap FH patterns.The transmitted signal lures FJ to aim at the data channel and the complementary channel is away from FJ by adopting wide gap frequency patterns.FJ does not affect the complementary channel but increases the signal energy in the data channel,thus the effect of FJ is reduced.Its bit error rate(BER)is derived under FJ and the effects of three FJ parameters(tracking success probability,jamming duration ratio and jamming bandwidth ratio)on the BER performance of WGMPFH are investigated versus the co nventional FH/BFSK and MPFH system.Numerical and simulation results show that when under the worst-case FJ,the proposed WGMPFH outperforms the MPFH by about 1-3 dB and outperforms the conventional FH/BFSK by more than 4 dB.The proposed WGMPFH shows superior jamming rejection performance under FJ especially in severe signal-to-jamming ratio(SJR).
基金supported by the National Key Research and Development Program of China 2021YFB2900504, 2020YFB1807900。
文摘Low earth orbit(LEO) satellite communications can provide ubiquitous and reliable services,making it an essential part of the Internet of Everything network. Beam hopping(BH) is an emerging technology for effectively addressing the issue of low resource utilization caused by the non-uniform spatio-temporal distribution of traffic demands. However, how to allocate multi-dimensional resources in a timely and efficient way for the highly dynamic LEO satellite systems remains a challenge. This paper proposes a joint beam scheduling and power optimization beam hopping(JBSPO-BH) algorithm considering the differences in the geographic distribution of sink nodes. The JBSPO-BH algorithm decouples the original problem into two sub-problems. The beam scheduling problem is modelled as a potential game,and the Nash equilibrium(NE) point is obtained as the beam scheduling strategy. Moreover, the penalty function interior point method is applied to optimize the power allocation. Simulation results show that the JBSPO-BH algorithm has low time complexity and fast convergence and achieves better performance both in throughput and fairness. Compared with greedybased BH, greedy-based BH with the power optimization, round-robin BH, Max-SINR BH and satellite resource allocation algorithm, the throughput of the proposed algorithm is improved by 44.99%, 20.79%,156.06%, 15.39% and 8.17%, respectively.
基金Supported by National Natural Science Foundation of China (No.60676053)
文摘A novel frequency hopping(FH) sequences generator based on advanced encryption standard(AES) iterated block cipher is proposed for FH communication systems.The analysis shows that the FH sequences based on AES algorithm have good performance in uniformity, correlation, complexity and security.A high-speed, low-power and low-cost ASIC of FH sequences generator is implemented by optimizing the structure of S-Box and MixColumns of AES algorithm, proposing a hierarchical power management strategy, and applying ...
基金the National Natural Science Foundation of China under Grant 61371125
文摘Based on the anti-jamming performance of differential frequency hopping(DFH)systems in Additive White Gaussian Noise(AWGN)channel,Fountain code is introduced to the DFH systems as the outer error correcting code in this paper to investigate the improvements against partial-band jamming over AWGN channel.The performance of Fountain coded DFH is theoretically analyzed and numerically simulated.The total frequency of hopping in the simulation is 16,and results show that,on one hand,when exact jamming state information(JSI)is available,and the number of jamming frequency is n=16,the bit error rate(BER)of 10~3 is achieved with the signal to interference ratio(SIR)approximately 7.5 dB over AWGN channel,and the performance improves about 1-1.5dB compared with the no-coded system.When the number of jamming frequency is n=2,the performance increases 15-17dB.On the other hand,when JSI is unavailable,a joint JSI estimation and decoding algorithm is proposed.The BER of 103 is achieved with jamming-frequency n 16,SIR=8dB and signal noise ratio(SNR)10dB over AWGN channel.It's proved that this algorithm provides robust anti-jamming pertbrmance even without JSI.The anti-jamming performance of Fountain coded DFH systems is obviously superior to no-coded DFH systems.
基金supported by the Doctor Sustention Foundation of Telecommunication Engineering Institute,Air Force Engineering University (No.KDYBSJJ08605)the Key Laboratory Foundation of National Defense Science and Technology (No.9140c860302)
文摘In order to achieve fast synchronization of the modulation hopping system, a synchronization scheme called short code to guide long code is adopted, and the initial synchronization hops and service hops are designed in detail.According to the system requirements for short code in the properties of time-varying, safety and balance, an algorithm to design wide-gap chaos short code based on TOD is proposed.Synchronization performance analysis shows that the algorithm has good performance, the initial synchronization time and the later entering network synchronization time are short, additionally, maximum synchronization time difference and synchronization maintaining time are long, all of which meet the needs of normal communications, and further verify the synchronization scheme feasible.
