License assisted access(LAA) was proposed as a solution to the challenge of satisfying high throughput requirement in cellular network with limited licensed band. LAA uses long term evolution(LTE) carrier aggregation ...License assisted access(LAA) was proposed as a solution to the challenge of satisfying high throughput requirement in cellular network with limited licensed band. LAA uses long term evolution(LTE) carrier aggregation technique to combine licensed and unlicensed bands, specifically 5 GHz Wi Fi band, in order to achieve high data rates. However, LAA has several critical concerns for services provision on 5 GHz unlicensed band. In this article, an overview of the techniques concerning the coexistence of LTE and Wi Fi on the same unlicensed band is presented. We first present several general approaches including power control of LTE evolved Node B(e NB), carrier selection, LTE duty cycling, self clear to send(CTS) and request to send/CTS(RTS/CTS), and listen before talk(LBT). Then, we focus on LBT techniques for LAA-Wi Fi coexistence and discuss how LBT based coexistence solutions can dynamically respond to the variations in network load and ensure fair coexistence in a distributed manner. Based on the LBT mechanism, we also present a fairness-aware LAA-WiF i coexisting scheme with TXOP(transmitted in a single transmission opportunity) backoff for LAA e NB. Finally, the performances of various LBT solutions for LAA-Wi Fi coexistence are evaluated using Markov chain analytical model.展开更多
The growth of the wireless and mobile communication data traffic has brought severe challenges to the present telecommu- nication systems. To meet the ever-increasing mobile traffic demand in the next 5th generation ...The growth of the wireless and mobile communication data traffic has brought severe challenges to the present telecommu- nication systems. To meet the ever-increasing mobile traffic demand in the next 5th generation （SG） communication systems, deploying 5G in the unlicensed spectrum （SG-U）, has been regarded as a promising technology. The Third Generation Partnership Project （3GPP） has specified the standardization of the Li- censed Assisted Access （LAA） and its extension enhanced LAA （eLAA）, to opportunistically transmit in the unlicensed spectrum. The LAA/eLAA systems share unlicensed spectrum resource with other networks, e.g., the Wi-Fi systems. In this article, we analyze the coexistence between the eLAA and the Wi-Fi systems in the unlicensed spectrum. We firstly establish the system model where the eLAA coexists with the Wi-Fi systems. Then, we theoretically derive and figure out the unfairness in the multi-channel occupancy rate between the eLAA and the Wi-Fi systems. After that, we propose a weight based channel selection method to improve the fairness of the coexistence. The numerical results demonstrate that by avoiding contentions and declining collisions, our method not only enhances the fairness, but also improves the overall unlicensed spectrum usage rate.展开更多
Utilizing the unlicensed spectrum as supplementary is being studied to meet the increasingly growing demand of user equipment for rate,traffic and bandwidth,and thus to mitigate the current spectrum scarcity crisis.In...Utilizing the unlicensed spectrum as supplementary is being studied to meet the increasingly growing demand of user equipment for rate,traffic and bandwidth,and thus to mitigate the current spectrum scarcity crisis.In this paper,we investigate the uplink multi-user multiple-input multiple-output(UL MU-MIMO) technique to achieve multiplexing gain in unlicensed spectrum.We first define a new parameter called channel busy radio(CBR) which is related to the probability of occupying the unlicensed channel,and find that the failure to occupy the unlicensed channel leads to the performance degradation in unlicensed spectrum.Then,according to the user-specific CBR of the unlicensed channel,we propose a flexible scheduling scheme for UL MU-MIMO in unlicensed spectrum,and formulate an optimization problem for the optimal scheduled user number.Furthermore,an adaptive scheduling algorithm is proposed to decide the optimal number of the scheduled users efficiently.The simulation results show that,based on statistical channel condition in unlicensed spectrum,adjusting the number of the scheduled user flexibly can offset the degraded throughput and form an optimal MU-MIMO transmission.展开更多
<strong>Aim:</strong> To describe unlicensed personnel’s experience of digital signing lists via a smartphone application for the distribution of medication in municipal healthcare in Western Sweden.<s...<strong>Aim:</strong> To describe unlicensed personnel’s experience of digital signing lists via a smartphone application for the distribution of medication in municipal healthcare in Western Sweden.<strong> Design:</strong> A qualitative and quantitative design was used. <strong>Methods:</strong> The study included 48 unlicensed personnel, 28 of whom answered an open-ended questionnaire, while an additional 20 volunteered for individual interviews. The material was analysed by qualitative content analysis. <strong>Results:</strong> The results indicate that digital signing lists via a smartphone application are feasible, and efficient and facilitate the work. However, some aspects negatively affected the sense of security, meetings with patients and quality of care, such as an insufficient internet signal in some rural areas, difficulty remembering the password, as well as the change of focus from patient to smartphone. To improve quality of care and the meeting with the patient, it is crucial that the technology works and that unlicensed personnel develop technical skills.展开更多
Currently,limited licensed frequency bands cannot meet the increasing demands for various wireless communication applications any more.It is necessary to extend wireless communication networks to unlicensed spectrum.I...Currently,limited licensed frequency bands cannot meet the increasing demands for various wireless communication applications any more.It is necessary to extend wireless communication networks to unlicensed spectrum.In this paper,we propose a new bargaining framework for unlicensed band access to achieve high spectrum efficiency,where one radio access technology(RAT)(such as macro cellular network)“competes”the unlicensed bands with multiple other RATs(such as small cellular networks or Wi-Fi)virtually.Considering that macro cell can share unlicensed frequencies with multiple small cells which are in the same coverage area for more freedom,we use bargaining game theory to fairly and effectively share the unlicensed spectrum between macro and multiple heterogeneous small cell networks,where bargaining loss and time dissipation loss for virtual“price”of unlicensed bands are mainly considered.In the oneto-many bargaining process,we also develop a multiple RAT alliance game strategy to reduce transmission loss in a joint manner.Simulation results show that the proposed unlicensed band sharing algorithm significantly improves the spectrum efficiency performance compared with the other practical schemes for heterogeneous networks.展开更多
基金supported in part by Joint Specialized Research Fund for the Doctoral Program of Higher Education (SRFDP) and Research Grants Council Earmarked Research Grants (RGC ERG) with Grant 20130142140002National Science Foundation of China with Grants 61531011 and 61471163Major Program of National Natural Science Foundation of Hubei in China with Grant 2016CFA009
文摘License assisted access(LAA) was proposed as a solution to the challenge of satisfying high throughput requirement in cellular network with limited licensed band. LAA uses long term evolution(LTE) carrier aggregation technique to combine licensed and unlicensed bands, specifically 5 GHz Wi Fi band, in order to achieve high data rates. However, LAA has several critical concerns for services provision on 5 GHz unlicensed band. In this article, an overview of the techniques concerning the coexistence of LTE and Wi Fi on the same unlicensed band is presented. We first present several general approaches including power control of LTE evolved Node B(e NB), carrier selection, LTE duty cycling, self clear to send(CTS) and request to send/CTS(RTS/CTS), and listen before talk(LBT). Then, we focus on LBT techniques for LAA-Wi Fi coexistence and discuss how LBT based coexistence solutions can dynamically respond to the variations in network load and ensure fair coexistence in a distributed manner. Based on the LBT mechanism, we also present a fairness-aware LAA-WiF i coexisting scheme with TXOP(transmitted in a single transmission opportunity) backoff for LAA e NB. Finally, the performances of various LBT solutions for LAA-Wi Fi coexistence are evaluated using Markov chain analytical model.
基金partly supported by the National Science and Technology Major Project(grant no.16510711600)the National Natural Science Foundation of China(grant no.61631013)partly supported by the National Natural Science Foundation of China(grant no.61401440)
文摘The growth of the wireless and mobile communication data traffic has brought severe challenges to the present telecommu- nication systems. To meet the ever-increasing mobile traffic demand in the next 5th generation （SG） communication systems, deploying 5G in the unlicensed spectrum （SG-U）, has been regarded as a promising technology. The Third Generation Partnership Project （3GPP） has specified the standardization of the Li- censed Assisted Access （LAA） and its extension enhanced LAA （eLAA）, to opportunistically transmit in the unlicensed spectrum. The LAA/eLAA systems share unlicensed spectrum resource with other networks, e.g., the Wi-Fi systems. In this article, we analyze the coexistence between the eLAA and the Wi-Fi systems in the unlicensed spectrum. We firstly establish the system model where the eLAA coexists with the Wi-Fi systems. Then, we theoretically derive and figure out the unfairness in the multi-channel occupancy rate between the eLAA and the Wi-Fi systems. After that, we propose a weight based channel selection method to improve the fairness of the coexistence. The numerical results demonstrate that by avoiding contentions and declining collisions, our method not only enhances the fairness, but also improves the overall unlicensed spectrum usage rate.
基金partly supported by the NSFC International Cooperation and Exchange Program(Grant No.61461136001)partly supported by the Shanghai Rising-Star Program(grant no.17QA1403800)+2 种基金the NSFC International Cooperation and Exchange Program(Grant No.61461136004)partly supported by the ESEC project of Tekes and the National Natural Science Foundation of China(Grant No.61401440)partly supported by the NSFC International Cooperation and Exchange Program(Grant No.61461136003)
文摘Utilizing the unlicensed spectrum as supplementary is being studied to meet the increasingly growing demand of user equipment for rate,traffic and bandwidth,and thus to mitigate the current spectrum scarcity crisis.In this paper,we investigate the uplink multi-user multiple-input multiple-output(UL MU-MIMO) technique to achieve multiplexing gain in unlicensed spectrum.We first define a new parameter called channel busy radio(CBR) which is related to the probability of occupying the unlicensed channel,and find that the failure to occupy the unlicensed channel leads to the performance degradation in unlicensed spectrum.Then,according to the user-specific CBR of the unlicensed channel,we propose a flexible scheduling scheme for UL MU-MIMO in unlicensed spectrum,and formulate an optimization problem for the optimal scheduled user number.Furthermore,an adaptive scheduling algorithm is proposed to decide the optimal number of the scheduled users efficiently.The simulation results show that,based on statistical channel condition in unlicensed spectrum,adjusting the number of the scheduled user flexibly can offset the degraded throughput and form an optimal MU-MIMO transmission.
文摘<strong>Aim:</strong> To describe unlicensed personnel’s experience of digital signing lists via a smartphone application for the distribution of medication in municipal healthcare in Western Sweden.<strong> Design:</strong> A qualitative and quantitative design was used. <strong>Methods:</strong> The study included 48 unlicensed personnel, 28 of whom answered an open-ended questionnaire, while an additional 20 volunteered for individual interviews. The material was analysed by qualitative content analysis. <strong>Results:</strong> The results indicate that digital signing lists via a smartphone application are feasible, and efficient and facilitate the work. However, some aspects negatively affected the sense of security, meetings with patients and quality of care, such as an insufficient internet signal in some rural areas, difficulty remembering the password, as well as the change of focus from patient to smartphone. To improve quality of care and the meeting with the patient, it is crucial that the technology works and that unlicensed personnel develop technical skills.
基金the National Natural Science Foundation of China under Grant 61871433,61828103in part by the Research Platform of South China Normal University and Foshan
文摘Currently,limited licensed frequency bands cannot meet the increasing demands for various wireless communication applications any more.It is necessary to extend wireless communication networks to unlicensed spectrum.In this paper,we propose a new bargaining framework for unlicensed band access to achieve high spectrum efficiency,where one radio access technology(RAT)(such as macro cellular network)“competes”the unlicensed bands with multiple other RATs(such as small cellular networks or Wi-Fi)virtually.Considering that macro cell can share unlicensed frequencies with multiple small cells which are in the same coverage area for more freedom,we use bargaining game theory to fairly and effectively share the unlicensed spectrum between macro and multiple heterogeneous small cell networks,where bargaining loss and time dissipation loss for virtual“price”of unlicensed bands are mainly considered.In the oneto-many bargaining process,we also develop a multiple RAT alliance game strategy to reduce transmission loss in a joint manner.Simulation results show that the proposed unlicensed band sharing algorithm significantly improves the spectrum efficiency performance compared with the other practical schemes for heterogeneous networks.
