Wireless sensor network is becoming more and more popular in recent years, but energy- constrained characteristic of sensor nodes is one of the critical issues that we must consider in system design. In this paper, a ...Wireless sensor network is becoming more and more popular in recent years, but energy- constrained characteristic of sensor nodes is one of the critical issues that we must consider in system design. In this paper, a cluster-based virtual VBLAST transmission scheme is proposed to achieve energy savings for energy-constrained wireless sensor networks. In the proposed scheme, instead of using cluster member as cooperative nodes, multiple cluster heads cooperate to form virtual antenna array so that V-BLAST based virtual MIMO transmission can be implemented. Based on the communication energy consumption model, a way to optimize the parameters for the scheme is given. In addition, detailed simulation is performed to evaluate the performance of the proposed scheme for both densely and sparsely deployed sensor networks. Theoretical analysis and simulation results verify the energy efficiency of the proposed scheme.展开更多
An interference alignment(IA)spectrum sharing method based on Rayleigh quotient is proposed for distributed multi-user multi-antenna cognitive radio(CR) networks.The interference from cognitive users(CUs)to the primar...An interference alignment(IA)spectrum sharing method based on Rayleigh quotient is proposed for distributed multi-user multi-antenna cognitive radio(CR) networks.The interference from cognitive users(CUs)to the primary(PR) system is constrained through the Rayleigh quotients of channel matrices to deal with the absence of PR users(PUs) in the IA process.As a result,the IA scheme can be applied in CR networks without harmful interference to PUs.Compared with existing IA based spectrum sharing methods,the proposed method is more general because of breaking the restriction that CUs can only transmit on the idle sub-channels of the PR system.Moreover,in comparison to other four spectrum sharing methods applicable in general scene,the proposed method leads to improved performance of achievable sum rate of the CR system as well as guarantees the transmission of PUs.展开更多
In a three-dimensional (3D) multiple- input multiple-output (MIMO) system, the base station can use both horizontal and vertical spaces, transmitting spatial beam to users more accurately. This system has caught t...In a three-dimensional (3D) multiple- input multiple-output (MIMO) system, the base station can use both horizontal and vertical spaces, transmitting spatial beam to users more accurately. This system has caught the attention of researchers in recent years. The existing research on the 3D MIMO technology is based on the assumption that the base station can acquire the ideal channel state information (CSI), which is not actually the case in real systems. Therefore, this paper introduces a limited feedback transmission scheme based on mobile station (MS) compensation in the 3D MIMO system. In this scheme, the vertical antenna gain of the 3D MIMO system compensation is assigned to the MS. Two CSI-RS ports are configured at the base station, omnidirectional CSI-RS port and partial CSI-RS port. The MS can calculate the horizontal CSI and the vertical beam gain according to omnidirectional CSI-RS port and partial CSI- RS port, respectively. Partial CSI-RS resources are used to calculate the channel after being weighted by the vertical beam vector, MS selects the optimal vertical precoding vector. Simulations show that compared with the reference strategy, the transmission scheme with limited feedback based on the MS compensation proposed in this article has more advantages. The average spectral efficiency of the system and the cell edge spectral efficiency can be greatly improved.展开更多
Massive MIMO systems have got extraordinary spectral efficiency using a large number of base station antennas,but it is in the challenge of pilot contamination using the aligned pilots.To address this issue,a selectiv...Massive MIMO systems have got extraordinary spectral efficiency using a large number of base station antennas,but it is in the challenge of pilot contamination using the aligned pilots.To address this issue,a selective transmission is proposed using time-shifted pilots with cell grouping,where the strong interfering users in downlink transmission cells are temporally stopped during the pilots transmission in uplink cells.Based on the spatial characteristics of physical channel models,the strong interfering users are selected to minimize the inter-cell interference and the cell grouping is designed to have less temporally stopped users within a smaller area.Furthermore,a Kalman estimator is proposed to reduce the unexpected effect of residual interferences in channel estimation,which exploits both the spatial-time correlation of channels and the share of the interference information.The numerical results show that our scheme significantly improves the channel estimation accuracy and the data rates.展开更多
In order to investigate the benefit of multiple-input multiple-output(MIMO) technique applying to the high altitude platform(HAP), a 2×2 MIMO statistical model, which can accurately describe the channel between H...In order to investigate the benefit of multiple-input multiple-output(MIMO) technique applying to the high altitude platform(HAP), a 2×2 MIMO statistical model, which can accurately describe the channel between HAP and high-speed train, is presented. And dual polarization diversity is particularly considered. Based on first-order three-state Markov chain, the single-input single-output(SISO) channel, a subset of the MIMO channel is first established. The ray tracing approach applied to the digital relief model(DRM) which covers the railway between Xi'an and Zhengzhou is used to obtain the state probability vector and matrix of the state transition probability. The proposed model considers both Doppler shift and temporal correlation, and the polarization correlation and spatial correlation statistical properties of large-scale fading and smallscale fading are analyzed. Moreover, useful numerical results on the MIMO HAP channel outage capacity are provided based on which, significant capacity gains with respect to the conventional SISO case are illustrated. Such statistical channel model can be applied to the future wireless communication system between HAP and high-speed train.展开更多
Wireless sensor network (WSN) requires robust and efficient communication protocols to minimise delay and save energy. The lifetime of WSN can be maximised by selecting proper medium access control (MAC) scheme de...Wireless sensor network (WSN) requires robust and efficient communication protocols to minimise delay and save energy. The lifetime of WSN can be maximised by selecting proper medium access control (MAC) scheme depending on the contention level of the network. The throughput of WSN however reduces due to channel fading effects even with the proper design of MAC protocol. Hence this paper proposes a new MAC scheme for enabling packet transmission using cooperative multi-input multi-output (MIMO) utilising space time codes(STC) such as space time block code (STBC), space time trellis code (STTC) to achieve higher energy savings and lower delay by allowing nodes to transmit and receive information jointly. The performance of the proposed MAC protocol is evaluated in terms of transmission error probability, energy consumption and delay. Simulation results show that the proposed cooperative MIMO MAC protocol provides reliable and efficient transmission by leveraging MIMO diversity gains.展开更多
In real multiple-input multiple-output (MIMO) systems, the perfect channel state information (CSI) may be costly or impossible to acquire. But the channel statistical information can be considered relatively stationar...In real multiple-input multiple-output (MIMO) systems, the perfect channel state information (CSI) may be costly or impossible to acquire. But the channel statistical information can be considered relatively stationary during long-term transmission. The statistical information can be obtained at the receiver and fed back to the transmitter and do not require frequent update. By exploiting channel mean and covariance information at the transmitter simultaneously, this paper investigates the optimal trans- mission strategy for spatially correlated MIMO channels. An upper bound of ergodic capacity is derived and taken as the per- formance criterion. Simulation results are also given to show the performance improvement of the optimal transmission strategy.展开更多
In this paper, we propose a coordinated pilot reuse(CPR) approach to reduce the pilot overhead for multi-cell massive multi-input multi-output transmission. Unlike the conventional multi-cell pilot reuse approach in w...In this paper, we propose a coordinated pilot reuse(CPR) approach to reduce the pilot overhead for multi-cell massive multi-input multi-output transmission. Unlike the conventional multi-cell pilot reuse approach in which pilots can only be reused among different cells, the proposed CPR approach allows pilots to be reused among both inter-cell and intra-cell user equipments, and thus, pilot overhead can be efficiently reduced. For spatially correlated Rayleigh fading channels, we first present a CPR-based channel estimation method and a low complexity pilot allocation algorithm. Because CPR might lead to additional pilot interference, we develop a statistically robust uplink receiver and downlink precoder that takes channel estimation errors into account. The proposed uplink receiver and downlink precoder are robust to channel state information inaccuracy, and thus, can guarantee a certain transmission performance. Monte-Carlo simulations illustrate the significant performance improvement in net spectral efficiency offered by the proposed CPR approach.展开更多
文摘Wireless sensor network is becoming more and more popular in recent years, but energy- constrained characteristic of sensor nodes is one of the critical issues that we must consider in system design. In this paper, a cluster-based virtual VBLAST transmission scheme is proposed to achieve energy savings for energy-constrained wireless sensor networks. In the proposed scheme, instead of using cluster member as cooperative nodes, multiple cluster heads cooperate to form virtual antenna array so that V-BLAST based virtual MIMO transmission can be implemented. Based on the communication energy consumption model, a way to optimize the parameters for the scheme is given. In addition, detailed simulation is performed to evaluate the performance of the proposed scheme for both densely and sparsely deployed sensor networks. Theoretical analysis and simulation results verify the energy efficiency of the proposed scheme.
基金supported by National Natural Science Foundation of China under Grant 6120123361271262Fundamental Research Funds for the Central Universities (2013G1241114)
文摘An interference alignment(IA)spectrum sharing method based on Rayleigh quotient is proposed for distributed multi-user multi-antenna cognitive radio(CR) networks.The interference from cognitive users(CUs)to the primary(PR) system is constrained through the Rayleigh quotients of channel matrices to deal with the absence of PR users(PUs) in the IA process.As a result,the IA scheme can be applied in CR networks without harmful interference to PUs.Compared with existing IA based spectrum sharing methods,the proposed method is more general because of breaking the restriction that CUs can only transmit on the idle sub-channels of the PR system.Moreover,in comparison to other four spectrum sharing methods applicable in general scene,the proposed method leads to improved performance of achievable sum rate of the CR system as well as guarantees the transmission of PUs.
基金the National Natural Science Foundation of China Grants No.61302106,51274018,the National Science & Technology Pillar Program Grants No.2013BAK06B03 Natural Science Foundation of Hebei Province No.F2014502029 and the Fundamental Research Funds for the Central Universities Grants No.2014MS100
文摘In a three-dimensional (3D) multiple- input multiple-output (MIMO) system, the base station can use both horizontal and vertical spaces, transmitting spatial beam to users more accurately. This system has caught the attention of researchers in recent years. The existing research on the 3D MIMO technology is based on the assumption that the base station can acquire the ideal channel state information (CSI), which is not actually the case in real systems. Therefore, this paper introduces a limited feedback transmission scheme based on mobile station (MS) compensation in the 3D MIMO system. In this scheme, the vertical antenna gain of the 3D MIMO system compensation is assigned to the MS. Two CSI-RS ports are configured at the base station, omnidirectional CSI-RS port and partial CSI-RS port. The MS can calculate the horizontal CSI and the vertical beam gain according to omnidirectional CSI-RS port and partial CSI- RS port, respectively. Partial CSI-RS resources are used to calculate the channel after being weighted by the vertical beam vector, MS selects the optimal vertical precoding vector. Simulations show that compared with the reference strategy, the transmission scheme with limited feedback based on the MS compensation proposed in this article has more advantages. The average spectral efficiency of the system and the cell edge spectral efficiency can be greatly improved.
基金Supported by the Program for Excellent Talents in Beijing(No.2014000020124G040)National Natural Science Foundation of China(No.61372089,61571021)National Natural Science Foundation of Beijing(No.4132007,4132015,4132019)
文摘Massive MIMO systems have got extraordinary spectral efficiency using a large number of base station antennas,but it is in the challenge of pilot contamination using the aligned pilots.To address this issue,a selective transmission is proposed using time-shifted pilots with cell grouping,where the strong interfering users in downlink transmission cells are temporally stopped during the pilots transmission in uplink cells.Based on the spatial characteristics of physical channel models,the strong interfering users are selected to minimize the inter-cell interference and the cell grouping is designed to have less temporally stopped users within a smaller area.Furthermore,a Kalman estimator is proposed to reduce the unexpected effect of residual interferences in channel estimation,which exploits both the spatial-time correlation of channels and the share of the interference information.The numerical results show that our scheme significantly improves the channel estimation accuracy and the data rates.
基金sponsored by National Natural Science Foundation of China (No.91538104,No.91438205)China Postdoctoral Science Foundation (No.2011M500664)
文摘In order to investigate the benefit of multiple-input multiple-output(MIMO) technique applying to the high altitude platform(HAP), a 2×2 MIMO statistical model, which can accurately describe the channel between HAP and high-speed train, is presented. And dual polarization diversity is particularly considered. Based on first-order three-state Markov chain, the single-input single-output(SISO) channel, a subset of the MIMO channel is first established. The ray tracing approach applied to the digital relief model(DRM) which covers the railway between Xi'an and Zhengzhou is used to obtain the state probability vector and matrix of the state transition probability. The proposed model considers both Doppler shift and temporal correlation, and the polarization correlation and spatial correlation statistical properties of large-scale fading and smallscale fading are analyzed. Moreover, useful numerical results on the MIMO HAP channel outage capacity are provided based on which, significant capacity gains with respect to the conventional SISO case are illustrated. Such statistical channel model can be applied to the future wireless communication system between HAP and high-speed train.
文摘Wireless sensor network (WSN) requires robust and efficient communication protocols to minimise delay and save energy. The lifetime of WSN can be maximised by selecting proper medium access control (MAC) scheme depending on the contention level of the network. The throughput of WSN however reduces due to channel fading effects even with the proper design of MAC protocol. Hence this paper proposes a new MAC scheme for enabling packet transmission using cooperative multi-input multi-output (MIMO) utilising space time codes(STC) such as space time block code (STBC), space time trellis code (STTC) to achieve higher energy savings and lower delay by allowing nodes to transmit and receive information jointly. The performance of the proposed MAC protocol is evaluated in terms of transmission error probability, energy consumption and delay. Simulation results show that the proposed cooperative MIMO MAC protocol provides reliable and efficient transmission by leveraging MIMO diversity gains.
文摘In real multiple-input multiple-output (MIMO) systems, the perfect channel state information (CSI) may be costly or impossible to acquire. But the channel statistical information can be considered relatively stationary during long-term transmission. The statistical information can be obtained at the receiver and fed back to the transmitter and do not require frequent update. By exploiting channel mean and covariance information at the transmitter simultaneously, this paper investigates the optimal trans- mission strategy for spatially correlated MIMO channels. An upper bound of ergodic capacity is derived and taken as the per- formance criterion. Simulation results are also given to show the performance improvement of the optimal transmission strategy.
基金supported by the National Natural Science Foundation of China(Grant Nos.6147111361320106003&61201171)+3 种基金the National Hi-Tech Research and Development Program of China("863"Project)(Grant Nos.2015AA01A701&2014AA01A704)the National Science and Technology Major Project of China(Grant No.2014ZX03003006-003)the Program for Jiangsu Innovation TeamYOU Li was supported in part by the China Scholarship Council(CSC)
文摘In this paper, we propose a coordinated pilot reuse(CPR) approach to reduce the pilot overhead for multi-cell massive multi-input multi-output transmission. Unlike the conventional multi-cell pilot reuse approach in which pilots can only be reused among different cells, the proposed CPR approach allows pilots to be reused among both inter-cell and intra-cell user equipments, and thus, pilot overhead can be efficiently reduced. For spatially correlated Rayleigh fading channels, we first present a CPR-based channel estimation method and a low complexity pilot allocation algorithm. Because CPR might lead to additional pilot interference, we develop a statistically robust uplink receiver and downlink precoder that takes channel estimation errors into account. The proposed uplink receiver and downlink precoder are robust to channel state information inaccuracy, and thus, can guarantee a certain transmission performance. Monte-Carlo simulations illustrate the significant performance improvement in net spectral efficiency offered by the proposed CPR approach.