With promising applications in e-health and entertainment, wireless body area networks （WBANs） have attracted the interest of both academia and industry. If WBANs are densely deployed within a small area, serious pr...With promising applications in e-health and entertainment, wireless body area networks （WBANs） have attracted the interest of both academia and industry. If WBANs are densely deployed within a small area, serious problems may arise between the WBANs. In this paper, we discuss issues related to the coexistence of WBANs and investigate the main factors that cause inter-WBAN interference. We survey inter- WBAN interference mitigation strategies and track recent research developments. We also discuss unresolved issues related to inter-WBAN interference mitigation and propose fu- ture research directions.展开更多
To improve the anti-jamming and interference mitigation ability of the UAV-aided communication systems, this paper investigates the channel selection optimization problem in face of both internal mutual interference a...To improve the anti-jamming and interference mitigation ability of the UAV-aided communication systems, this paper investigates the channel selection optimization problem in face of both internal mutual interference and external malicious jamming. A cooperative anti-jamming and interference mitigation method based on local altruistic is proposed to optimize UAVs’ channel selection. Specifically, a Stackelberg game is modeled to formulate the confrontation relationship between UAVs and the jammer. A local altruistic game is modeled with each UAV considering the utilities of both itself and other UAVs. A distributed cooperative anti-jamming and interference mitigation algorithm is proposed to obtain the Stackelberg equilibrium. Finally, the convergence of the proposed algorithm and the impact of the transmission power on the system loss value are analyzed, and the anti-jamming performance of the proposed algorithm can be improved by around 64% compared with the existing algorithms.展开更多
Device to Device(D2D)communication is emerging as a new participant promising technology in 5G cellular networks to promote green energy networks.D2D communication can improve communication delays,spectral efficiency,...Device to Device(D2D)communication is emerging as a new participant promising technology in 5G cellular networks to promote green energy networks.D2D communication can improve communication delays,spectral efficiency,system capacity,data off-loading,and many other fruitful scenarios where D2D can be implemented.Nevertheless,induction of D2D communication in reuse mode with the conventional cellular network can cause severe interference issues,which can significantly degrade network performance.To reap all the benefits of induction of D2D communication with conventional cellular communication,it is imperative to minimize interference’s detrimental effects.Efficient power control can minimize the negative effects of interference and get benefits promised by D2D communication.In this work,we propose two power control schemes,Power Control Scheme 1(PCS 1)and Power Control Scheme 2(PCS 2),to minimize the interference and provide performance analysis.Simulation results observe improvements with PCS 1 and PCS 2 as compared to without using any power control scheme in terms of data rate in both uplink and downlink communication modes of Cellular User Equipment(CUE).展开更多
The field of Wireless Sensor Networks (WSNs) has revolutionized tremendously in the recent past with its major application in Wireless Body Area Networks (WBANs). This has in the same dimension attracted immense inter...The field of Wireless Sensor Networks (WSNs) has revolutionized tremendously in the recent past with its major application in Wireless Body Area Networks (WBANs). This has in the same dimension attracted immense interests from the researchers and technology providers. The operational modality of the WBANs is that a few sensor nodes are placed in or around the body and that they are meant to operate within a limited condition while providing high performance in terms of WBAN life time, high throughput, high data reliability, minimum or no delay and low power consumption. As most of the WBAN operates within the universal Industrial, Scientific and Medical (ISM) Narrow Band (NB) wireless band (2.4 Ghz) frequency band, this has posed a challenge in respect to inter, intra and co-channel interference especially in dense areas and high mobility scenarios. As well the body posture changes dynamically due to these mobility effects. In this paper, we propose a hybrid WBAN interference mitigation model based on Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) Contention Window (CW) approach and User Priority (UP) queues. Using Omnet++ simulation, a comparison to the IEEE 802.15.6 based WBAN protocol is presented under the standing, walking sitting and Lying postural mobility scenarios. The results show that the proposed hybrid model outperforms IEEE 802.15.6 based CSMA/CA protocol in areas of network throughput, bandwidth efficiency and network delay in these mobility postures.展开更多
In Orthogonal Frequency Division Multiple Access (OFDMA) systems, such as Long Term Evolution (LTE) and so on, the resources used by each user are orthogonal, and the OFDMA systems performances are mainly affected by ...In Orthogonal Frequency Division Multiple Access (OFDMA) systems, such as Long Term Evolution (LTE) and so on, the resources used by each user are orthogonal, and the OFDMA systems performances are mainly affected by the inter-cell interference. Therefore, the inter-cell interference mitigation technology becomes a hotspot. The objective of interference mitigation technologies used in OFDMA systems are to increase cell-edge throughput and average cell throughput. In this paper, the Resource Block Planning (BRBP) based scheme is proposed to mitigate the inter-cell interference and improve the cell-edge throughput. Comparison between the simulation results of BRBP and Round Robin (RR) illustrates that the enhanced performance of BRBP.展开更多
An interference mitigation for acquisition method,based on both energy center and spectrum symmetry detection,has been proposed as a possible solution to the problem of signal acquisition susceptibility to continuous-...An interference mitigation for acquisition method,based on both energy center and spectrum symmetry detection,has been proposed as a possible solution to the problem of signal acquisition susceptibility to continuous-wave interference(CWI)in unified carrier telemetry,tracking,and command(TT&C)systems.With subcarrier modulation index as a priori condition,the existence of CWI is determined by comparing the energy center with the symmetric center.In the presence of interference,the interference frequency point is assumed and culled;sequentially,the spectral symmetry is used to verify whether the signal acquisition is realized.Theoretical analysis,simulations,and experimental results demonstrate that the method can realize the acquisition of the main carrier target signal with an interference-to-signal ratio of 31 dB,which represents an improvement over the existing continuous-wave interference mitigation for acquisition methods.展开更多
Millimeter-wave communications are suitable for application to massive multiple-input multiple-output systems in order to satisfy the ever-growing data traffic demands of the next-generation wireless communication.How...Millimeter-wave communications are suitable for application to massive multiple-input multiple-output systems in order to satisfy the ever-growing data traffic demands of the next-generation wireless communication.However,their practical deployment is hindered by the high cost of complex hardware,such as radio frequency(RF)chains.To this end,operation in the beamspace domain,through beam selection,is a viable solution.Generally,the conventional beam selection schemes focus on the feedback and exhaustive search techniques.In addition,since the same beam in the beamspace may be assigned to a different user,conventional beam selection schemes suffer serious multi-user interference.In addition,some RF chains may be wasted,since they do not contribute to the sum-rate performance.Thus,a fingerprint-based beam selection scheme is proposed to solve these problems.The proposed scheme conducts offline group-based fingerprint database construction and online beam selection to mitigate multi-user interference.In the offline phase,the contributing users with the same best beam are grouped.After grouping,a fingerprint database is created for each group.In the online phase,beam selection is performed for purposes of interference mitigation using the information contained in the group-based fingerprint database.The simulation results confirm that the proposed beam selection scheme can achieve a signal-to-interference-plus-noise ratio and sum-rate performance which is close to those of a fully digital system,and having much higher energy efficiency.展开更多
This paper investigates the performance of the W band millimeter wave (mmWave) backhaul network proposed by our EU TWEETHER project. We focus on the downlink transmission of the mmWave backhaul network, in which each ...This paper investigates the performance of the W band millimeter wave (mmWave) backhaul network proposed by our EU TWEETHER project. We focus on the downlink transmission of the mmWave backhaul network, in which each of the hubs serves a cluster of base stations (BSs). In the considered backhaul network, available frequency resources are first allocated to the downlink links with the consideration of fairness issue. In order to mitigate interference in the mmWave backhaul network, each hub operates the proposed algorithm, namely cooperation and power adaptation (CPA). Our simulation results show that, the backhaul network with mmWave capabilities can achieve a significant better throughput performance than the sub-6 GHz ultra high frequency (UHF) backhaul network. Furthermore, our simulations also reveal that the proposed CPA algorithm can efficiently combat interference in the backhaul network.展开更多
As the most sensitive single-dish radio telescope,the Five-hundred Aperture Spherical radio Telescope(FAST)is very susceptive to radio frequency interference(RFI)from active radio services.Moreover,due to the rapid de...As the most sensitive single-dish radio telescope,the Five-hundred Aperture Spherical radio Telescope(FAST)is very susceptive to radio frequency interference(RFI)from active radio services.Moreover,due to the rapid development of space applications and research,satellite interference has become one of the main RFI sources for FAST,particularly at the L band.Therefore,we have developed several measures to mitigate satellite RFI.On the one hand,an antenna with 4.5-meter diameter has been constructed and installed at the FAST site to detect the satellite interference in the frequency band between 1 to 5 GHz.Meanwhile,we have developed a satellite RFI database based on the FAST sky coverage,the observing frequency bands,and known satellite systems.By combining the satellite RFI monitoring antenna and the database,we have established a satellite RFI mitigation system.With this system,we can not only track satellites to collect their characteristics and update the database but also help the observer to program the observing plan by predicting satellite interference.During the practical observation of FAST at the L band,the feasibility of this system to mitigate satellite RFI has been proved.In particular,the system effectively avoids strong satellite interference from entering the main beam of the telescope and causing receiver saturation.展开更多
Radio Frequency Interference(RFI)mitigation is essential for supporting the science output of Five-hundred-meter Aperture Spherical radio Telescope(FAST)due to its high sensitivity.In order to protect FAST from RFI,an...Radio Frequency Interference(RFI)mitigation is essential for supporting the science output of Five-hundred-meter Aperture Spherical radio Telescope(FAST)due to its high sensitivity.In order to protect FAST from RFI,an Electromagnetic Compatibility(EMC)study has been carried out and the operation of a Radio Quiet Zone(RQZ)is ongoing.RFI measurements of the telescope instruments and monitoring of the active radio services outside the site have revealed the radiation properties of the RFI sources.Based on the measurement results and theoretical analysis,various EMC methods have been implemented for the telescope to decrease the RFIs.Meanwhile,the main RFI sources in the FAST RQZ,such as mobile stations,broadcast stations and navigation instruments,have been identified,and the technical measures have been adopted to protect the quiet radio environment around the site.The early science outputs of FAST have demonstrated the efficiency of RFI mitigation methods.展开更多
In order to meet the demands for high transmission rates and high service quality in broadband wireless communication systems, orthogonal frequency division multiplexing （OFDM） has been adopted in some standards. Ho...In order to meet the demands for high transmission rates and high service quality in broadband wireless communication systems, orthogonal frequency division multiplexing （OFDM） has been adopted in some standards. However, the inter-block interference （IBI） and inter-carrier interference （ICI） in an OFDM system affect the performance. To mitigate IBI and ICI, some pre-processing approaches have been proposed based on full channel state information （CSI）, which improved the system performance. A pre-processing filter based on partial CSI at the transmitter is designed and investigated. The filter coefficient is given by the optimization processing, the symbol error rate （SER） is tested, and the computation complexity of the proposed scheme is analyzed. Computer simulation results show that the proposed pre-processing filter can effectively mitigate IBI and ICI and the performance can be improved. Compared with pre-processing approaches at the transmitter based on full CSI, the proposed scheme has high spectral efficiency, limited CSI feedback and low computation complexity.展开更多
High complexity and high latency are key problems for multiuser detection （MUD） to be applied to a mobile station in cellular networks. To tackle these problems, an interleave division multiple access （IDMA） based...High complexity and high latency are key problems for multiuser detection （MUD） to be applied to a mobile station in cellular networks. To tackle these problems, an interleave division multiple access （IDMA） based multiple access scheme, grouped spread IDMA （GSIDMA）, is proposed. In a GSIDMA system, lower complexity and latency for mobile stations can be achieved by appropriately dividing active users into different groups. The system model of GSIDMA is constructed and followed by analysing on its system capacity, complexity and latency, and bit error rate （BER） performance. The extrinsic information transfer （EXIT） chart is used to analyze the convergence behavior of the iteration process. The grouping method and interleavers-reuse issue for GSIDMA are also discussed preliminarily. The analyses and simulation results indicate that the complexity and latency of the proposed scheme are much lower than those of IDMA, whereas its BER performance is close to the latter. The properties of low complexity and low latency make it more feasible for the practical implementation.展开更多
By examining the two neighboring Haihe Bridges with semi-and full-closed bridge decks,the aerodynamic interference between the two decks on the vortex-induced vibration(VIV)and the corresponding aerodynamic mitigation...By examining the two neighboring Haihe Bridges with semi-and full-closed bridge decks,the aerodynamic interference between the two decks on the vortex-induced vibration(VIV)and the corresponding aerodynamic mitigation measures are investigated via a series of wind tunnel tests with a spring-suspended sectional model aided with computational fluid dynamics(CFD)method.The results show that the VIV responses of both bridges can be significantly affected by the aerodynamic interference and that the extent of the influence varies with the shapes of the windward and leeward decks.The VIV amplitudes of the windward bridge are often fairly close to those of the single bridge.However,those of the leeward bridge are magnified substantially by aerodynamic interference if the same structural and aerodynamic configurations are adopted for the two bridges.Otherwise,the VIV responses are not significantly increased and may even be reduced by the aerodynamic interference if different configurations are employed for the two bridges.Furthermore,an effective combined measure of adding wind barriers and sharpening the wind fairing noses of the two box decks is presented for mitigating both the vertical and torsional VIV responses of the windward and leeward bridges.展开更多
In the two-tier femtocell network, a central macroceU is underlaid with a large number of shorter range femtocell hotspots, which is preferably in the universal frequency reuse mode. This kind of new network architect...In the two-tier femtocell network, a central macroceU is underlaid with a large number of shorter range femtocell hotspots, which is preferably in the universal frequency reuse mode. This kind of new network architecture brings about urgent challenges to the schemes of interference management and the radio resource allocation. Motivated by these challenges, three contributions are made in this paper： 1） A novel joint subchannel and power allocation problem for orthogonal frequency division multiple access （OFDMA） downlink based femtocells is formulated on the premise of minimizing radiated interference of every Femto base station. 2） The pseudo-handover based scheduling information exchange method is proposed to exchange the co-tier and cross-tier information, and thus avoid the collision interference. 3） An iterative scheme of power control and subchannel is proposed to solve the formulated problem in contribution 1）, which is an NP-complete problem. Through simulations and comparisons with four other schemes, better performance in reducing interference and improving the spectrum efficiency is achieved by the proposed scheme.展开更多
Mobile data traffic is going through an explosive growth recently as mobile smart devices become more and more ubiquitous, causing huge pressure on cellular network. Taking advantage of its low cost and easy-to-deploy...Mobile data traffic is going through an explosive growth recently as mobile smart devices become more and more ubiquitous, causing huge pressure on cellular network. Taking advantage of its low cost and easy-to-deploy feature, wireless local-area networks（WLAN） becomes increasingly popular to offload data streams from cellular network, followed by higher and higher density of its deployment. However, the high density of WLAN will cause more interference, which results in degradation of its performance. Therefore, in order to enhance the performance of the network, we aim to minimize the interference caused by high density of WLAN. In this paper, we propose a novel power control scheme to achieve the above aim. We use the quality of experience（QoE） evaluation to coordinate the power of each access point（AP） and finally realize the optimization of the entire network. According to the simulation results, our scheme improves the performance of the network significantly in many aspects, including throughput and QoE.展开更多
In this paper,a double-effect DNN-based Digital Back-Propagation(DBP)scheme is proposed and studied to achieve the Integrated Communication and Sensing(ICS)ability,which can not only realize nonlinear damage mitigatio...In this paper,a double-effect DNN-based Digital Back-Propagation(DBP)scheme is proposed and studied to achieve the Integrated Communication and Sensing(ICS)ability,which can not only realize nonlinear damage mitigation but also monitor the optical power and dispersion profile over multi-span links.The link status information can be extracted by the characteristics of the learned optical fiber parameters without any other measuring instruments.The efficiency and feasibility of this method have been investigated in different fiber link conditions,including various launch power,transmission distance,and the location and the amount of the abnormal losses.A good monitoring performance can be obtained while the launch optical power is 2 dBm which does not affect the normal operation of the optical communication system and the step size of DBP is 20 km which can provide a better distance resolution.This scheme successfully detects the location of single or multiple optical attenuators in long-distance multi-span fiber links,including different abnormal losses of 2 dB,4 dB,and 6 dB in 360 km and serval combinations of abnormal losses of(1 dB,5 dB),(3 dB,3 dB),(5 dB,1 dB)in 360 km and 760 km.Meanwhile,the transfer relationship of the estimated coefficient values with different step sizes is further investigated to reduce the complexity of the fiber nonlinear damage compensation.These results provide an attractive approach for precisely sensing the optical fiber link status information and making correct strategies timely to ensure optical communication system operations.展开更多
基金supported by the National Natural Science Foundation of China under Grant No.61202406the USTC Grand Master Professor Funds under Grant No.ZC9850290097
文摘With promising applications in e-health and entertainment, wireless body area networks （WBANs） have attracted the interest of both academia and industry. If WBANs are densely deployed within a small area, serious problems may arise between the WBANs. In this paper, we discuss issues related to the coexistence of WBANs and investigate the main factors that cause inter-WBAN interference. We survey inter- WBAN interference mitigation strategies and track recent research developments. We also discuss unresolved issues related to inter-WBAN interference mitigation and propose fu- ture research directions.
基金supported in part by the National Natural Science Foundation of China (No.62271253,61901523,62001381)Fundamental Research Funds for the Central Universities (No.NS2023018)+2 种基金the National Aerospace Science Foundation of China under Grant 2023Z021052002the open research fund of National Mobile Communications Research Laboratory,Southeast University (No.2023D09)Postgraduate Research & Practice Innovation Program of NUAA (No.xcxjh20220402)。
文摘To improve the anti-jamming and interference mitigation ability of the UAV-aided communication systems, this paper investigates the channel selection optimization problem in face of both internal mutual interference and external malicious jamming. A cooperative anti-jamming and interference mitigation method based on local altruistic is proposed to optimize UAVs’ channel selection. Specifically, a Stackelberg game is modeled to formulate the confrontation relationship between UAVs and the jammer. A local altruistic game is modeled with each UAV considering the utilities of both itself and other UAVs. A distributed cooperative anti-jamming and interference mitigation algorithm is proposed to obtain the Stackelberg equilibrium. Finally, the convergence of the proposed algorithm and the impact of the transmission power on the system loss value are analyzed, and the anti-jamming performance of the proposed algorithm can be improved by around 64% compared with the existing algorithms.
基金supporting this work by Grant Code:19-ENG-1-01-0015.
文摘Device to Device(D2D)communication is emerging as a new participant promising technology in 5G cellular networks to promote green energy networks.D2D communication can improve communication delays,spectral efficiency,system capacity,data off-loading,and many other fruitful scenarios where D2D can be implemented.Nevertheless,induction of D2D communication in reuse mode with the conventional cellular network can cause severe interference issues,which can significantly degrade network performance.To reap all the benefits of induction of D2D communication with conventional cellular communication,it is imperative to minimize interference’s detrimental effects.Efficient power control can minimize the negative effects of interference and get benefits promised by D2D communication.In this work,we propose two power control schemes,Power Control Scheme 1(PCS 1)and Power Control Scheme 2(PCS 2),to minimize the interference and provide performance analysis.Simulation results observe improvements with PCS 1 and PCS 2 as compared to without using any power control scheme in terms of data rate in both uplink and downlink communication modes of Cellular User Equipment(CUE).
文摘The field of Wireless Sensor Networks (WSNs) has revolutionized tremendously in the recent past with its major application in Wireless Body Area Networks (WBANs). This has in the same dimension attracted immense interests from the researchers and technology providers. The operational modality of the WBANs is that a few sensor nodes are placed in or around the body and that they are meant to operate within a limited condition while providing high performance in terms of WBAN life time, high throughput, high data reliability, minimum or no delay and low power consumption. As most of the WBAN operates within the universal Industrial, Scientific and Medical (ISM) Narrow Band (NB) wireless band (2.4 Ghz) frequency band, this has posed a challenge in respect to inter, intra and co-channel interference especially in dense areas and high mobility scenarios. As well the body posture changes dynamically due to these mobility effects. In this paper, we propose a hybrid WBAN interference mitigation model based on Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) Contention Window (CW) approach and User Priority (UP) queues. Using Omnet++ simulation, a comparison to the IEEE 802.15.6 based WBAN protocol is presented under the standing, walking sitting and Lying postural mobility scenarios. The results show that the proposed hybrid model outperforms IEEE 802.15.6 based CSMA/CA protocol in areas of network throughput, bandwidth efficiency and network delay in these mobility postures.
文摘In Orthogonal Frequency Division Multiple Access (OFDMA) systems, such as Long Term Evolution (LTE) and so on, the resources used by each user are orthogonal, and the OFDMA systems performances are mainly affected by the inter-cell interference. Therefore, the inter-cell interference mitigation technology becomes a hotspot. The objective of interference mitigation technologies used in OFDMA systems are to increase cell-edge throughput and average cell throughput. In this paper, the Resource Block Planning (BRBP) based scheme is proposed to mitigate the inter-cell interference and improve the cell-edge throughput. Comparison between the simulation results of BRBP and Round Robin (RR) illustrates that the enhanced performance of BRBP.
基金Supported by the National Natural Science Foundation of China(61401026)
文摘An interference mitigation for acquisition method,based on both energy center and spectrum symmetry detection,has been proposed as a possible solution to the problem of signal acquisition susceptibility to continuous-wave interference(CWI)in unified carrier telemetry,tracking,and command(TT&C)systems.With subcarrier modulation index as a priori condition,the existence of CWI is determined by comparing the energy center with the symmetric center.In the presence of interference,the interference frequency point is assumed and culled;sequentially,the spectral symmetry is used to verify whether the signal acquisition is realized.Theoretical analysis,simulations,and experimental results demonstrate that the method can realize the acquisition of the main carrier target signal with an interference-to-signal ratio of 31 dB,which represents an improvement over the existing continuous-wave interference mitigation for acquisition methods.
基金The Ministry of Science and ICT(MSIT),Korea,under the Information Technology Research Center(ITRC)support program(IITP-2020-2016-0-00314)supervised by the Institute for Information&communications Technology Planning&Evaluation(IITP)was supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT:Ministry of Science and ICT)(2018R1A2B6002255 and 2020R1I1A1A01073948).
文摘Millimeter-wave communications are suitable for application to massive multiple-input multiple-output systems in order to satisfy the ever-growing data traffic demands of the next-generation wireless communication.However,their practical deployment is hindered by the high cost of complex hardware,such as radio frequency(RF)chains.To this end,operation in the beamspace domain,through beam selection,is a viable solution.Generally,the conventional beam selection schemes focus on the feedback and exhaustive search techniques.In addition,since the same beam in the beamspace may be assigned to a different user,conventional beam selection schemes suffer serious multi-user interference.In addition,some RF chains may be wasted,since they do not contribute to the sum-rate performance.Thus,a fingerprint-based beam selection scheme is proposed to solve these problems.The proposed scheme conducts offline group-based fingerprint database construction and online beam selection to mitigate multi-user interference.In the offline phase,the contributing users with the same best beam are grouped.After grouping,a fingerprint database is created for each group.In the online phase,beam selection is performed for purposes of interference mitigation using the information contained in the group-based fingerprint database.The simulation results confirm that the proposed beam selection scheme can achieve a signal-to-interference-plus-noise ratio and sum-rate performance which is close to those of a fully digital system,and having much higher energy efficiency.
文摘This paper investigates the performance of the W band millimeter wave (mmWave) backhaul network proposed by our EU TWEETHER project. We focus on the downlink transmission of the mmWave backhaul network, in which each of the hubs serves a cluster of base stations (BSs). In the considered backhaul network, available frequency resources are first allocated to the downlink links with the consideration of fairness issue. In order to mitigate interference in the mmWave backhaul network, each hub operates the proposed algorithm, namely cooperation and power adaptation (CPA). Our simulation results show that, the backhaul network with mmWave capabilities can achieve a significant better throughput performance than the sub-6 GHz ultra high frequency (UHF) backhaul network. Furthermore, our simulations also reveal that the proposed CPA algorithm can efficiently combat interference in the backhaul network.
基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB23000000)the National Key Research and Development Program(No.2019YFB1312704)+2 种基金the National Natural Science Foundation of China(Program No.U1831128)the International Partnership Program of Chinese Academy of Sciences(Program No.114A11KYSB20160008)supported by the National Development and Reform Commission,the Key Laboratory of FAST of CAS。
文摘As the most sensitive single-dish radio telescope,the Five-hundred Aperture Spherical radio Telescope(FAST)is very susceptive to radio frequency interference(RFI)from active radio services.Moreover,due to the rapid development of space applications and research,satellite interference has become one of the main RFI sources for FAST,particularly at the L band.Therefore,we have developed several measures to mitigate satellite RFI.On the one hand,an antenna with 4.5-meter diameter has been constructed and installed at the FAST site to detect the satellite interference in the frequency band between 1 to 5 GHz.Meanwhile,we have developed a satellite RFI database based on the FAST sky coverage,the observing frequency bands,and known satellite systems.By combining the satellite RFI monitoring antenna and the database,we have established a satellite RFI mitigation system.With this system,we can not only track satellites to collect their characteristics and update the database but also help the observer to program the observing plan by predicting satellite interference.During the practical observation of FAST at the L band,the feasibility of this system to mitigate satellite RFI has been proved.In particular,the system effectively avoids strong satellite interference from entering the main beam of the telescope and causing receiver saturation.
基金supported by the National Development and Reform Commission,and the Key Laboratory of FAST of CAS
文摘Radio Frequency Interference(RFI)mitigation is essential for supporting the science output of Five-hundred-meter Aperture Spherical radio Telescope(FAST)due to its high sensitivity.In order to protect FAST from RFI,an Electromagnetic Compatibility(EMC)study has been carried out and the operation of a Radio Quiet Zone(RQZ)is ongoing.RFI measurements of the telescope instruments and monitoring of the active radio services outside the site have revealed the radiation properties of the RFI sources.Based on the measurement results and theoretical analysis,various EMC methods have been implemented for the telescope to decrease the RFIs.Meanwhile,the main RFI sources in the FAST RQZ,such as mobile stations,broadcast stations and navigation instruments,have been identified,and the technical measures have been adopted to protect the quiet radio environment around the site.The early science outputs of FAST have demonstrated the efficiency of RFI mitigation methods.
基金supported by the National Natural Science Foundation of China(60902045)the National High-Tech Research and Developmeent Program of China(863 Program)(2011AA01A105)
文摘In order to meet the demands for high transmission rates and high service quality in broadband wireless communication systems, orthogonal frequency division multiplexing （OFDM） has been adopted in some standards. However, the inter-block interference （IBI） and inter-carrier interference （ICI） in an OFDM system affect the performance. To mitigate IBI and ICI, some pre-processing approaches have been proposed based on full channel state information （CSI）, which improved the system performance. A pre-processing filter based on partial CSI at the transmitter is designed and investigated. The filter coefficient is given by the optimization processing, the symbol error rate （SER） is tested, and the computation complexity of the proposed scheme is analyzed. Computer simulation results show that the proposed pre-processing filter can effectively mitigate IBI and ICI and the performance can be improved. Compared with pre-processing approaches at the transmitter based on full CSI, the proposed scheme has high spectral efficiency, limited CSI feedback and low computation complexity.
基金supported by the National Natural Science Foundation of China (61171180)the National Basic Resaearch Program (923 Program) (2007CB31(0606))the Natural Sientific Research Innovation Foundation in Harbin Institute of Technology (HIT. NSRIF20011117)
文摘High complexity and high latency are key problems for multiuser detection （MUD） to be applied to a mobile station in cellular networks. To tackle these problems, an interleave division multiple access （IDMA） based multiple access scheme, grouped spread IDMA （GSIDMA）, is proposed. In a GSIDMA system, lower complexity and latency for mobile stations can be achieved by appropriately dividing active users into different groups. The system model of GSIDMA is constructed and followed by analysing on its system capacity, complexity and latency, and bit error rate （BER） performance. The extrinsic information transfer （EXIT） chart is used to analyze the convergence behavior of the iteration process. The grouping method and interleavers-reuse issue for GSIDMA are also discussed preliminarily. The analyses and simulation results indicate that the complexity and latency of the proposed scheme are much lower than those of IDMA, whereas its BER performance is close to the latter. The properties of low complexity and low latency make it more feasible for the practical implementation.
基金The work was supported by the Ministry of Science and Technology of China through the Fundamental Research Fund for State Key Laboratories(Grant No.SLDRCE08-A-02)the National Nature Science Foundation of China(Grant No.50978204).
文摘By examining the two neighboring Haihe Bridges with semi-and full-closed bridge decks,the aerodynamic interference between the two decks on the vortex-induced vibration(VIV)and the corresponding aerodynamic mitigation measures are investigated via a series of wind tunnel tests with a spring-suspended sectional model aided with computational fluid dynamics(CFD)method.The results show that the VIV responses of both bridges can be significantly affected by the aerodynamic interference and that the extent of the influence varies with the shapes of the windward and leeward decks.The VIV amplitudes of the windward bridge are often fairly close to those of the single bridge.However,those of the leeward bridge are magnified substantially by aerodynamic interference if the same structural and aerodynamic configurations are adopted for the two bridges.Otherwise,the VIV responses are not significantly increased and may even be reduced by the aerodynamic interference if different configurations are employed for the two bridges.Furthermore,an effective combined measure of adding wind barriers and sharpening the wind fairing noses of the two box decks is presented for mitigating both the vertical and torsional VIV responses of the windward and leeward bridges.
基金supported by International Cooperation and Exchanges Project (2010DFA11060)the National Natural Science Foundation of China (60872048)
文摘In the two-tier femtocell network, a central macroceU is underlaid with a large number of shorter range femtocell hotspots, which is preferably in the universal frequency reuse mode. This kind of new network architecture brings about urgent challenges to the schemes of interference management and the radio resource allocation. Motivated by these challenges, three contributions are made in this paper： 1） A novel joint subchannel and power allocation problem for orthogonal frequency division multiple access （OFDMA） downlink based femtocells is formulated on the premise of minimizing radiated interference of every Femto base station. 2） The pseudo-handover based scheduling information exchange method is proposed to exchange the co-tier and cross-tier information, and thus avoid the collision interference. 3） An iterative scheme of power control and subchannel is proposed to solve the formulated problem in contribution 1）, which is an NP-complete problem. Through simulations and comparisons with four other schemes, better performance in reducing interference and improving the spectrum efficiency is achieved by the proposed scheme.
基金supported by the WLAN Achievement Transformation based on SDN of Beijing Municipal Commission of Education (201501001)
文摘Mobile data traffic is going through an explosive growth recently as mobile smart devices become more and more ubiquitous, causing huge pressure on cellular network. Taking advantage of its low cost and easy-to-deploy feature, wireless local-area networks（WLAN） becomes increasingly popular to offload data streams from cellular network, followed by higher and higher density of its deployment. However, the high density of WLAN will cause more interference, which results in degradation of its performance. Therefore, in order to enhance the performance of the network, we aim to minimize the interference caused by high density of WLAN. In this paper, we propose a novel power control scheme to achieve the above aim. We use the quality of experience（QoE） evaluation to coordinate the power of each access point（AP） and finally realize the optimization of the entire network. According to the simulation results, our scheme improves the performance of the network significantly in many aspects, including throughput and QoE.
基金supported by the National Key Research and Development Program of China (2019YFB1803905)the National Natural Science Foundation of China (No.62171022)+2 种基金Beijing Natural Science Foundation (4222009)Guangdong Basic and Applied Basic Research Foundation (2021B1515120057)the Scientific and Technological Innovation Foundation of Shunde Graduate School,USTB (No.BK19AF005)。
文摘In this paper,a double-effect DNN-based Digital Back-Propagation(DBP)scheme is proposed and studied to achieve the Integrated Communication and Sensing(ICS)ability,which can not only realize nonlinear damage mitigation but also monitor the optical power and dispersion profile over multi-span links.The link status information can be extracted by the characteristics of the learned optical fiber parameters without any other measuring instruments.The efficiency and feasibility of this method have been investigated in different fiber link conditions,including various launch power,transmission distance,and the location and the amount of the abnormal losses.A good monitoring performance can be obtained while the launch optical power is 2 dBm which does not affect the normal operation of the optical communication system and the step size of DBP is 20 km which can provide a better distance resolution.This scheme successfully detects the location of single or multiple optical attenuators in long-distance multi-span fiber links,including different abnormal losses of 2 dB,4 dB,and 6 dB in 360 km and serval combinations of abnormal losses of(1 dB,5 dB),(3 dB,3 dB),(5 dB,1 dB)in 360 km and 760 km.Meanwhile,the transfer relationship of the estimated coefficient values with different step sizes is further investigated to reduce the complexity of the fiber nonlinear damage compensation.These results provide an attractive approach for precisely sensing the optical fiber link status information and making correct strategies timely to ensure optical communication system operations.
