Cell-free network is a promising architecture with numerous merits in energy efficiency and macro diversity,which is easy and flexible to integrate with other communication technologies.However,its current network top...Cell-free network is a promising architecture with numerous merits in energy efficiency and macro diversity,which is easy and flexible to integrate with other communication technologies.However,its current network topology where access points(APs)are connected to a central processing unit(CPU)to jointly serve the users,causes huge burden to the fronthaul network.To deal with this problem,in this paper,we first combine thoughts in user-centric(UC)network where users are served by selected subset of APs.Then,we propose a successful transmission probability(STP)based AP clustering scheme to reduce the fronthaul capacity requirement(FCR).By using stochastic geometry and proper approximation methods,the approximated STP calculation expression is derived.Numerical simulations demonstrate that the obtained STP expression can provide a tight approximation compared to Monte Carlo simulation results under different system parameters while keeping the computation tractable.Furthermore,the relationship between the FCR and the STP threshold is formulated as a clustering optimization problem,which gives insights on clustering design in UC-CF network systems.We show by simulation results that the proposed scheme requires less fronthaul capacity than the original CF approach while ensuring the STP performance.展开更多
In ultra-dense networks(UDN),multiple association can be regarded as a user-centric pattern in which a user can be served by multiple base stations(BSs).The data rate and quality of service can be improved.However,BSs...In ultra-dense networks(UDN),multiple association can be regarded as a user-centric pattern in which a user can be served by multiple base stations(BSs).The data rate and quality of service can be improved.However,BSs in user-centric paradigm are required to serve more users due to this multiple association scheme.The improvement of system performance may be limited by the improving load of BSs.In this letter,we develope an analytical framework for the load distribution of BSs in heterogeneous user-centric UDN.Based on open loop power control(OLPC),a user-centric scheme is considered in which the clustered serving BSs can provide given signal to interference plus noise ratio(SINR)for any typical user.As for any BS in different tiers,by leveraging stochastic geometry,we derive the Probability Mass Function(PMF)of the number of the served users,the Cumulative Distribution Function(CDF)of total power consumption,and the CDF bounds of downlink sum data rate.The accuracy of the theoretical analysis is validated by numerical simulations,and the effect the system parameters on the load of BSs is also presented.展开更多
Network densification is a promising solution to fulfill network capacity requirement and transmission rate for beyond 5G and 6G wireless communications.Ultra-dense network(UDN)integrates heterogeneous network resourc...Network densification is a promising solution to fulfill network capacity requirement and transmission rate for beyond 5G and 6G wireless communications.Ultra-dense network(UDN)integrates heterogeneous network resources and coordinates technologies on quality of service controlling,to provide users with flexible service.However,dense deployment reduces coverage radius of the cell,resulting in an increase on handover frequency,which makes a serious impact on service continuity.In this paper,we propose a proactive selection method for dynamic access points grouping(DAPGing)in accordance with“user-centric”philosophy,which selects target Access Points(AP)and reduces handover times to ensure communication continuity.This method includes two criteria:1)the user’s sojourn time,which is determined by analyzing the AP coverage area;2)neighbor relationship between APs,which is determined by coverage area and signal strength characteristics between neighboring APs.Therefore,candidate APs become the proactive selected ones to update the AP group.Stochastic geometry is used to build system model and performance metrics are analyzed,including AP group coverage probability and average update frequency.Experimental analysis shows that the proposed proactive selection method brings similar coverage probability to traditional handover method,while average update frequency is reduced more than 20%selection criteria.展开更多
The mobile data traffic has been exponentially growing during the last several decades.This was enabled by the densification of the network infrastructure in terms of increased cell density(i.e.,Ultra-Dense Network(UD...The mobile data traffic has been exponentially growing during the last several decades.This was enabled by the densification of the network infrastructure in terms of increased cell density(i.e.,Ultra-Dense Network(UDN))and/or the increased number of active antennas per Access Point(AP)(i.e.,massive Multiple-Input Multiple-Output(mMIMO)).However,neither UDN nor mMIMO will meet the increasing demand for the data rate of the Sixth Generation(6G)wireless communications due to the inter-cell interference and large quality-of-service variations.Cell-Free(CF)mMIMO,which combines the best aspects of UDN and mMIMO,is viewed as a key solution to this issue.In such systems,each User Equipment(UE)is served by a preferred set of surrounding APs cooperatively.In this paper,we provide a survey of the state-of-the-art literature on CF mMIMO.As a starting point,the significance and the basic properties of CF mMIMO are highlighted.We then present the canonical framework to discuss the essential details(i.e.,transmission procedure and mathematical system model).Next,we provide a deep look at the resource allocation and signal processing problems related to CF mMIMO and survey the up-to-date schemes and algorithms.After that,we discuss the practical issues in implementing CF mMIMO and point out the potential future directions.Finally,we conclude this paper with a summary of the key lessons learned in this field.展开更多
Fully coordinated Cell-Free(CF)networks can alleviate the Inter-Cell Interference(ICI)for the cell-edge users in cellular networks.Due to the complex topology of the association between the Access Points(APs)and the u...Fully coordinated Cell-Free(CF)networks can alleviate the Inter-Cell Interference(ICI)for the cell-edge users in cellular networks.Due to the complex topology of the association between the Access Points(APs)and the users in CF networks,it is challenging to deploy CF networks in practical scenarios.In order to make CF networks feasible,we introduce User-Centric(UC)networks enabling each user served by a limited number of APs.As a low-cost and energy-efficient technology,Reconfigurable Intelligent Surface(RIS)can be embedded in UC networks to further improve the system performance.First,we provide a brief survey on the prior works in UC networks for clear comprehension.Then,we formulate a Spectral Efficiency(SE)maximization problem for RIS-enhanced UC networks.For solving the non-convex problem,we divide it into three subproblems and propose a joint optimization framework for optimizing AP-user association,active beamforming of multiple antennas at the APs,and the passive beamforming of the RIS.Besides,a channel gain based association method coupled with the design of RIS is proposed to construct a dynamic and efficient association.The subproblems about optimizing active and passive beamforming are solved with the fractional programming.Simulation results show that the proposed joint optimization framework for RIS-enhanced UC networks can obtain good SE compared with other benchmark schemes.展开更多
Enterprise architecture (EA) efforts focus on business, technology, data, and application architecture, and their integration. However, less attention has been given to one of the most critical EA elements, i.e., user...Enterprise architecture (EA) efforts focus on business, technology, data, and application architecture, and their integration. However, less attention has been given to one of the most critical EA elements, i.e., users (EA audiences). As a result, existing EA management systems (EAMS) have become old, large, content-centric document-repositories that are unable to provide meaningful information of use to the enterprise users and aligned with their needs and functional scope. We argue that a semantic technology based mechanism focusing on enterprise information and user-centricity has the potential to solve this problem. In this context, we present a novel ontology-based strategy named the user-centric semantics-oriented EA (U-SEA) model. Based on this model, we have developed a user-centric semantics-oriented enterprise architecture management (U-SEAM) system. Our approach is generic enough to be used in a wide variety of user-centric EAM applications. The results obtained show computational feasibility to integrate and govern enterprise information and to reduce complexity with respect to interoperability between enterprise information and users.展开更多
As agricultural machines become more complex, it is increasingly critical that special attention be directed to the design of the user interface to ensure that the operator will have an adequate understanding of the s...As agricultural machines become more complex, it is increasingly critical that special attention be directed to the design of the user interface to ensure that the operator will have an adequate understanding of the status of the machine at all times. A user-centred design focus was employed to develop two conceptual designs (UCD1 & UCD2) for a user interface for an agricultural air seeder. The two concepts were compared against an existing user interface (baseline condition) using the metrics of situation awareness (Situation Awareness Global Assessment Technique), mental workload (Integrated Workload Scale), reaction time, and subjective feedback. There were no statistically significant differences among the three user interfaces based on the metric of situation awareness;however, UCD2 was deemed to be significantly better than either UCD1 or the baseline interface on the basis of mental workload, reaction time and subjective feedback. The research has demonstrated that a user-centred design focus will generate a better user interface for an agricultural machine.展开更多
This article describes a user-centred method used to design innovative pattern recognition software for technical paper documents. This kind of software can make some errors of interpretation. It will therefore be imp...This article describes a user-centred method used to design innovative pattern recognition software for technical paper documents. This kind of software can make some errors of interpretation. It will therefore be important that human operators are able to identify and correct these mistakes. The identification of errors is a difficult task because operators need to establish co-reference between the initial document and it interpretation. Moreover, users must be able to checks the interpretation without forgetting any area. This task requires the interface is easy to use. The experiments showed that the sequential display of interpretation is the most effective and that the interruptions by user reduce task duration. Moreover, queries by the system may improve error detection. This paper summarizes the main results of the research conducted in the context of this design for enhance the interface, and describes the specifications to which it gave rise.展开更多
5G sets an ambitious goal of increasing the capacity per area of current 4G network by 1000 fold. Due to the high splitting gain of dense small cells, ultra dense network(UDN) is widely considered as a key component i...5G sets an ambitious goal of increasing the capacity per area of current 4G network by 1000 fold. Due to the high splitting gain of dense small cells, ultra dense network(UDN) is widely considered as a key component in achieving this goal. In this paper, we outline the main challenges that come with dense cell deployment, including interference, mobility, power consumption and backhaul. Technologies designed to tackle these challenges in long term evolution system(LTE) and their deficiencies in UDN context are also analyzed. To combat these challenges more efficiently, a series of technologies are introduced along with some of our initial research results. Moreover, the trends of user-centric and peer-to-peer design in UDN are also elaborated.展开更多
文摘Cell-free network is a promising architecture with numerous merits in energy efficiency and macro diversity,which is easy and flexible to integrate with other communication technologies.However,its current network topology where access points(APs)are connected to a central processing unit(CPU)to jointly serve the users,causes huge burden to the fronthaul network.To deal with this problem,in this paper,we first combine thoughts in user-centric(UC)network where users are served by selected subset of APs.Then,we propose a successful transmission probability(STP)based AP clustering scheme to reduce the fronthaul capacity requirement(FCR).By using stochastic geometry and proper approximation methods,the approximated STP calculation expression is derived.Numerical simulations demonstrate that the obtained STP expression can provide a tight approximation compared to Monte Carlo simulation results under different system parameters while keeping the computation tractable.Furthermore,the relationship between the FCR and the STP threshold is formulated as a clustering optimization problem,which gives insights on clustering design in UC-CF network systems.We show by simulation results that the proposed scheme requires less fronthaul capacity than the original CF approach while ensuring the STP performance.
基金supported by National Natural Science Foundation of China (No. 61971161)Foundation of Science and Technology on Communication Networks Laboratory (No.6142104190410)Heilongjiang Touyan Team(No. HITTY20190009)
文摘In ultra-dense networks(UDN),multiple association can be regarded as a user-centric pattern in which a user can be served by multiple base stations(BSs).The data rate and quality of service can be improved.However,BSs in user-centric paradigm are required to serve more users due to this multiple association scheme.The improvement of system performance may be limited by the improving load of BSs.In this letter,we develope an analytical framework for the load distribution of BSs in heterogeneous user-centric UDN.Based on open loop power control(OLPC),a user-centric scheme is considered in which the clustered serving BSs can provide given signal to interference plus noise ratio(SINR)for any typical user.As for any BS in different tiers,by leveraging stochastic geometry,we derive the Probability Mass Function(PMF)of the number of the served users,the Cumulative Distribution Function(CDF)of total power consumption,and the CDF bounds of downlink sum data rate.The accuracy of the theoretical analysis is validated by numerical simulations,and the effect the system parameters on the load of BSs is also presented.
基金This work was supported by the National Natural Science Foundation of China(NSFC)under Grant 61931005.
文摘Network densification is a promising solution to fulfill network capacity requirement and transmission rate for beyond 5G and 6G wireless communications.Ultra-dense network(UDN)integrates heterogeneous network resources and coordinates technologies on quality of service controlling,to provide users with flexible service.However,dense deployment reduces coverage radius of the cell,resulting in an increase on handover frequency,which makes a serious impact on service continuity.In this paper,we propose a proactive selection method for dynamic access points grouping(DAPGing)in accordance with“user-centric”philosophy,which selects target Access Points(AP)and reduces handover times to ensure communication continuity.This method includes two criteria:1)the user’s sojourn time,which is determined by analyzing the AP coverage area;2)neighbor relationship between APs,which is determined by coverage area and signal strength characteristics between neighboring APs.Therefore,candidate APs become the proactive selected ones to update the AP group.Stochastic geometry is used to build system model and performance metrics are analyzed,including AP group coverage probability and average update frequency.Experimental analysis shows that the proposed proactive selection method brings similar coverage probability to traditional handover method,while average update frequency is reduced more than 20%selection criteria.
基金This work was supported in part by National Key R&D Program of China under Grant 2020YFB1807201in part by National Natural Science Foundation of China under Grants 61971027,U1834210,and 61961130391+2 种基金in part by Beijing Natural Science Foundation under Grant L202013in part by Frontiers Science Center for Smart High-speed Railway System under Grant 2020JBZD005in part by the Royal Society Newton Advanced Fellowship under Grant NA191006.E.Björnson was supported by the Grant 2019-05068 from the Swedish Research Council.
文摘The mobile data traffic has been exponentially growing during the last several decades.This was enabled by the densification of the network infrastructure in terms of increased cell density(i.e.,Ultra-Dense Network(UDN))and/or the increased number of active antennas per Access Point(AP)(i.e.,massive Multiple-Input Multiple-Output(mMIMO)).However,neither UDN nor mMIMO will meet the increasing demand for the data rate of the Sixth Generation(6G)wireless communications due to the inter-cell interference and large quality-of-service variations.Cell-Free(CF)mMIMO,which combines the best aspects of UDN and mMIMO,is viewed as a key solution to this issue.In such systems,each User Equipment(UE)is served by a preferred set of surrounding APs cooperatively.In this paper,we provide a survey of the state-of-the-art literature on CF mMIMO.As a starting point,the significance and the basic properties of CF mMIMO are highlighted.We then present the canonical framework to discuss the essential details(i.e.,transmission procedure and mathematical system model).Next,we provide a deep look at the resource allocation and signal processing problems related to CF mMIMO and survey the up-to-date schemes and algorithms.After that,we discuss the practical issues in implementing CF mMIMO and point out the potential future directions.Finally,we conclude this paper with a summary of the key lessons learned in this field.
基金supported by the project funded by the China Postdoctoral Science Foundation(No.2022M710534)the National Natural Science Foundation of Chongqing,China(No.CSTB2022NSCQ-MSX0327)+2 种基金the National Natural Science Foundation of China(Nos.61901066 and 62271092)the State Key Laboratory of Integrated Services Networks(No.ISN22-17)the Opening Fund of State Key Laboratory of Millimeter Waves(No.K202228).
文摘Fully coordinated Cell-Free(CF)networks can alleviate the Inter-Cell Interference(ICI)for the cell-edge users in cellular networks.Due to the complex topology of the association between the Access Points(APs)and the users in CF networks,it is challenging to deploy CF networks in practical scenarios.In order to make CF networks feasible,we introduce User-Centric(UC)networks enabling each user served by a limited number of APs.As a low-cost and energy-efficient technology,Reconfigurable Intelligent Surface(RIS)can be embedded in UC networks to further improve the system performance.First,we provide a brief survey on the prior works in UC networks for clear comprehension.Then,we formulate a Spectral Efficiency(SE)maximization problem for RIS-enhanced UC networks.For solving the non-convex problem,we divide it into three subproblems and propose a joint optimization framework for optimizing AP-user association,active beamforming of multiple antennas at the APs,and the passive beamforming of the RIS.Besides,a channel gain based association method coupled with the design of RIS is proposed to construct a dynamic and efficient association.The subproblems about optimizing active and passive beamforming are solved with the fractional programming.Simulation results show that the proposed joint optimization framework for RIS-enhanced UC networks can obtain good SE compared with other benchmark schemes.
文摘Enterprise architecture (EA) efforts focus on business, technology, data, and application architecture, and their integration. However, less attention has been given to one of the most critical EA elements, i.e., users (EA audiences). As a result, existing EA management systems (EAMS) have become old, large, content-centric document-repositories that are unable to provide meaningful information of use to the enterprise users and aligned with their needs and functional scope. We argue that a semantic technology based mechanism focusing on enterprise information and user-centricity has the potential to solve this problem. In this context, we present a novel ontology-based strategy named the user-centric semantics-oriented EA (U-SEA) model. Based on this model, we have developed a user-centric semantics-oriented enterprise architecture management (U-SEAM) system. Our approach is generic enough to be used in a wide variety of user-centric EAM applications. The results obtained show computational feasibility to integrate and govern enterprise information and to reduce complexity with respect to interoperability between enterprise information and users.
文摘As agricultural machines become more complex, it is increasingly critical that special attention be directed to the design of the user interface to ensure that the operator will have an adequate understanding of the status of the machine at all times. A user-centred design focus was employed to develop two conceptual designs (UCD1 & UCD2) for a user interface for an agricultural air seeder. The two concepts were compared against an existing user interface (baseline condition) using the metrics of situation awareness (Situation Awareness Global Assessment Technique), mental workload (Integrated Workload Scale), reaction time, and subjective feedback. There were no statistically significant differences among the three user interfaces based on the metric of situation awareness;however, UCD2 was deemed to be significantly better than either UCD1 or the baseline interface on the basis of mental workload, reaction time and subjective feedback. The research has demonstrated that a user-centred design focus will generate a better user interface for an agricultural machine.
文摘This article describes a user-centred method used to design innovative pattern recognition software for technical paper documents. This kind of software can make some errors of interpretation. It will therefore be important that human operators are able to identify and correct these mistakes. The identification of errors is a difficult task because operators need to establish co-reference between the initial document and it interpretation. Moreover, users must be able to checks the interpretation without forgetting any area. This task requires the interface is easy to use. The experiments showed that the sequential display of interpretation is the most effective and that the interruptions by user reduce task duration. Moreover, queries by the system may improve error detection. This paper summarizes the main results of the research conducted in the context of this design for enhance the interface, and describes the specifications to which it gave rise.
文摘5G sets an ambitious goal of increasing the capacity per area of current 4G network by 1000 fold. Due to the high splitting gain of dense small cells, ultra dense network(UDN) is widely considered as a key component in achieving this goal. In this paper, we outline the main challenges that come with dense cell deployment, including interference, mobility, power consumption and backhaul. Technologies designed to tackle these challenges in long term evolution system(LTE) and their deficiencies in UDN context are also analyzed. To combat these challenges more efficiently, a series of technologies are introduced along with some of our initial research results. Moreover, the trends of user-centric and peer-to-peer design in UDN are also elaborated.
