Two efficient and low complexity multiuser scheduling algorithms are proposed for the uplink multi- ple-input multiple-output systems in this paper. Conventionally, the exhaustive search algorithm （ESA） can give the...Two efficient and low complexity multiuser scheduling algorithms are proposed for the uplink multi- ple-input multiple-output systems in this paper. Conventionally, the exhaustive search algorithm （ESA） can give the optimal performance; however, it is complexity prohibitive for practical implementation. Aiming at re- ducing the complexity while keeping the achievable sum rate performance, two heuristic algorithms are proposed for the multiuser scheduling problems： the improved genetic algorithm and simplified norm-based greedy algo- rithm. Moreover, we also consider the heterogeneity scenario where a modified grouping-based user selection al- gorithm is given to guarantee the user＇ s fairness. Specifically, the asymptotic behavior of the norm-based greed- y algorithm is given when each user is equipped with one antenna. Numerical examples demonstrate the superi- ority of our proposed schedulin~ and ~rouoin~ algorithms.展开更多
This paper presents a new Wireless Power Transfer(WPT)approach by aligning the phases of a group of spatially distributed Radio Frequency(RF)transmitters(TX)at the target receiver(RX)device.Our approach can transfer e...This paper presents a new Wireless Power Transfer(WPT)approach by aligning the phases of a group of spatially distributed Radio Frequency(RF)transmitters(TX)at the target receiver(RX)device.Our approach can transfer energy over tens of meters and even to targets blocked by obstacles.Compared to popular beamforming based WPTs,our approach leads to a drastically different energy density distribution:the energy density at the target receiver is much higher than the energy density at other locations.Due to this unique energy distribution pattern,our approach offers a safer WPT solution,which can be potentially scaled up to ship a higher level of energy over longer distances.Specifically,we model the energy density distribution and prove that our proposed system can create a high energy peak exactly at the target receiver.Then we conduct detailed simulation studies to investigate how the actual energy distribution is impacted by various important system parameters,including number/topology of transmitters,transmitter antenna directionality,the distance between receiver and transmitters,and environmental multipath.Finally,we build an actual prototype with 17 N210 and 4 B210 Universal Software Radio Peripheral(USRP)nodes,through which we validate the salient features and performance promises of the proposed system.展开更多
Industrial control systems （ICSs） are widely used in critical infrastructures, making them popular targets for attacks to cause catastrophic physical damage. As one of the most critical components in ICSs, the progr...Industrial control systems （ICSs） are widely used in critical infrastructures, making them popular targets for attacks to cause catastrophic physical damage. As one of the most critical components in ICSs, the programmable logic controller （PLC） controls the actuators directly. A PLC executing a malicious program can cause significant property loss or even casualties. The number of attacks targeted at PLCs has increased noticeably over the last few years, exposing the vulnerability of the PLC and the importance of PLC protection. Unfortunately, PLCs cannot be protected by traditional intrusion detection systems or antivirus software. Thus, an effective method for PLC protection is yet to be designed. Motivated by these concerns, we propose a non-invasive power- based anomaly detection scheme for PLCs. The basic idea is to detect malicious software execution in a PLC through analyzing its power consumption, which is measured by inserting a shunt resistor in series with the CPU in a PLC while it is executing instructions. To analyze the power measurements, we extract a discriminative feature set from the power trace, and then train a long short-term memory （LSTM） neural network with the features of normal samples to predict the next time step of a normal sample. Finally, an abnormal sample is identified through comparing the predicted sample and the actual sample. The advantages of our method are that it requires no software modification on the original system and is able to detect unknown attacks effectively. The method is evaluated on a lab testbed, and for a trojan attack whose difference from the normal program is around 0.63%, the detection accuracy reaches 99.83%.展开更多
To suppress the side-band interferences caused by multiband orthogonal frequency division multiplexing （MB-OFDM）-based cognitive radio systems, a mathematical expression of the side-band signal is derived. Based on ...To suppress the side-band interferences caused by multiband orthogonal frequency division multiplexing （MB-OFDM）-based cognitive radio systems, a mathematical expression of the side-band signal is derived. Based on this expression, the constraints among the transmitted symbols, which help to suppress the interferences, are obtained. Combined with the constraints, a type of block Turbo code modulation scheme is proposed. In the modulation scheme, the side-band interferences are attenuated quickly. Compared with other techniques, in this scheme, the interference suppression is implemented more easily and sufficiently. Simultaneously, the bit error rate （BER） performance can be improved. Theoretical analyses and simulation results show that it is highly applicable for MB-OFDM-based cognitive radio systems to suffer from Rayleigh fading.展开更多
In this paper we consider interference-aware uplink transmission schemes for multicell multiple-input multiple-output （MIMO） system. Unlike conventional transmission schemes without considering the interference prob...In this paper we consider interference-aware uplink transmission schemes for multicell multiple-input multiple-output （MIMO） system. Unlike conventional transmission schemes without considering the interference probably caused to other cell, we jointly optimize the transceiver beamforming vectors to maximize the desired signals while removing the intercell interference. Specifically, for a two-cell system where each transmitter is equipped with two antennas, we derive the closed-form expression for the transmit scheme called coordinated beamforming （CBF） via generalized-eigen analysis. Moreover, when asymmetric interference is considered, we give a balancing beamforming （BBF） scheme where the interfering transmitter is to strike a compromise between maximizing the desired signal and minimizing the generated interference. Simulation results show that both schemes perform better than conventional schemes under different scenarios.展开更多
基金Sponsored by the Technology Specific Project(Grant No. 2010ZX03002-003-01)
文摘Two efficient and low complexity multiuser scheduling algorithms are proposed for the uplink multi- ple-input multiple-output systems in this paper. Conventionally, the exhaustive search algorithm （ESA） can give the optimal performance; however, it is complexity prohibitive for practical implementation. Aiming at re- ducing the complexity while keeping the achievable sum rate performance, two heuristic algorithms are proposed for the multiuser scheduling problems： the improved genetic algorithm and simplified norm-based greedy algo- rithm. Moreover, we also consider the heterogeneity scenario where a modified grouping-based user selection al- gorithm is given to guarantee the user＇ s fairness. Specifically, the asymptotic behavior of the norm-based greed- y algorithm is given when each user is equipped with one antenna. Numerical examples demonstrate the superi- ority of our proposed schedulin~ and ~rouoin~ algorithms.
文摘This paper presents a new Wireless Power Transfer(WPT)approach by aligning the phases of a group of spatially distributed Radio Frequency(RF)transmitters(TX)at the target receiver(RX)device.Our approach can transfer energy over tens of meters and even to targets blocked by obstacles.Compared to popular beamforming based WPTs,our approach leads to a drastically different energy density distribution:the energy density at the target receiver is much higher than the energy density at other locations.Due to this unique energy distribution pattern,our approach offers a safer WPT solution,which can be potentially scaled up to ship a higher level of energy over longer distances.Specifically,we model the energy density distribution and prove that our proposed system can create a high energy peak exactly at the target receiver.Then we conduct detailed simulation studies to investigate how the actual energy distribution is impacted by various important system parameters,including number/topology of transmitters,transmitter antenna directionality,the distance between receiver and transmitters,and environmental multipath.Finally,we build an actual prototype with 17 N210 and 4 B210 Universal Software Radio Peripheral(USRP)nodes,through which we validate the salient features and performance promises of the proposed system.
基金Project supported by the National Basic Research Program(973)of China(No.2015AA050202)
文摘Industrial control systems （ICSs） are widely used in critical infrastructures, making them popular targets for attacks to cause catastrophic physical damage. As one of the most critical components in ICSs, the programmable logic controller （PLC） controls the actuators directly. A PLC executing a malicious program can cause significant property loss or even casualties. The number of attacks targeted at PLCs has increased noticeably over the last few years, exposing the vulnerability of the PLC and the importance of PLC protection. Unfortunately, PLCs cannot be protected by traditional intrusion detection systems or antivirus software. Thus, an effective method for PLC protection is yet to be designed. Motivated by these concerns, we propose a non-invasive power- based anomaly detection scheme for PLCs. The basic idea is to detect malicious software execution in a PLC through analyzing its power consumption, which is measured by inserting a shunt resistor in series with the CPU in a PLC while it is executing instructions. To analyze the power measurements, we extract a discriminative feature set from the power trace, and then train a long short-term memory （LSTM） neural network with the features of normal samples to predict the next time step of a normal sample. Finally, an abnormal sample is identified through comparing the predicted sample and the actual sample. The advantages of our method are that it requires no software modification on the original system and is able to detect unknown attacks effectively. The method is evaluated on a lab testbed, and for a trojan attack whose difference from the normal program is around 0.63%, the detection accuracy reaches 99.83%.
基金supported by the National Natural Science Foundation of China(60432040,60772021)the Research Fund forthe Doctoral Program of Higher Education(20060013008)University IT Research Center Project(INHA UWB-ITRC),Korea,and the Project iCHIP financed by Italian Ministry of Foreign Affairs,the Innovation Fund for Graduate Student of Bupt,China
文摘To suppress the side-band interferences caused by multiband orthogonal frequency division multiplexing （MB-OFDM）-based cognitive radio systems, a mathematical expression of the side-band signal is derived. Based on this expression, the constraints among the transmitted symbols, which help to suppress the interferences, are obtained. Combined with the constraints, a type of block Turbo code modulation scheme is proposed. In the modulation scheme, the side-band interferences are attenuated quickly. Compared with other techniques, in this scheme, the interference suppression is implemented more easily and sufficiently. Simultaneously, the bit error rate （BER） performance can be improved. Theoretical analyses and simulation results show that it is highly applicable for MB-OFDM-based cognitive radio systems to suffer from Rayleigh fading.
基金supported by Chinese Important National Science and Technology Specific Project (2010ZX03002-003-01)
文摘In this paper we consider interference-aware uplink transmission schemes for multicell multiple-input multiple-output （MIMO） system. Unlike conventional transmission schemes without considering the interference probably caused to other cell, we jointly optimize the transceiver beamforming vectors to maximize the desired signals while removing the intercell interference. Specifically, for a two-cell system where each transmitter is equipped with two antennas, we derive the closed-form expression for the transmit scheme called coordinated beamforming （CBF） via generalized-eigen analysis. Moreover, when asymmetric interference is considered, we give a balancing beamforming （BBF） scheme where the interfering transmitter is to strike a compromise between maximizing the desired signal and minimizing the generated interference. Simulation results show that both schemes perform better than conventional schemes under different scenarios.
