Wi Fi网络下的视频多播传输问题是目前的研究热点,针对当前视频多播传输方案使得处于区域边界处的用户享受到的服务质量较低、可靠性差这一不足,提出一种基于多访问点(AP)协作的视频多播可靠传输方案。通过在多个AP间展开协作,每个AP可...Wi Fi网络下的视频多播传输问题是目前的研究热点,针对当前视频多播传输方案使得处于区域边界处的用户享受到的服务质量较低、可靠性差这一不足,提出一种基于多访问点(AP)协作的视频多播可靠传输方案。通过在多个AP间展开协作,每个AP可传输完全不同或部分不同的FEC编码报文,多播接收器利用空间和时间分集来提升性能。此外,我们还提出一种支持FEC码率自适应的资源分配算法,有效地提高了有限无线资源的利用率和视频质量。最后,通过全面的仿真实验评估了本文算法的有效性,与传统的单AP点多播算法相比,本文算法使用户满意率提升了37.1%。展开更多
Background:The use of mobile phone significantly improved the outcomes of tobacco cessation.However,its feasibility and acceptability were unclear in the Chinese population.This study was to explore the feasibility of...Background:The use of mobile phone significantly improved the outcomes of tobacco cessation.However,its feasibility and acceptability were unclear in the Chinese population.This study was to explore the feasibility of using Wi-Fi access points(APs)as a platform to provide smoking cessation help at 17 airports and 38 railway stations across China.Methods:This study was divided into two stages:platform development and population survey.In the first stage,a survey platform was developed and incorporated into Wi-Fi service at airports and railway stations,which could provide survey content as a pop-up window when participants tried to access the Wi-Fi service.In the second stage,a population survey was conducted to explore the intention to receive tobacco cessation support.Results:A total of 20,199 users participated and 13,628 users submitted the survey,with a response rate of 67.47%.The smoking rate was 30.9%.A total of 86.58%of smoking participants and 2.44%of non-smoking participants wished to receive tobacco cessation support,respectively.The multivariate analysis showed intention to receive support did not differ in age,gender,and heaviness of smoking(P>0.05).Conclusion:Providing tobacco cessation support via Wi-Fi APs is feasible and efficient,and smokers have high intention to receive tobacco cessation support.It is suggested hospitals,academia,information technology industries,and government agencies must work together to provide tobacco cessation support via mHealth.展开更多
Wireless node localization is one of the key technologies for wireless sensor networks. Outdoor localization can use GPS, AGPS (Assisted Global Positioning System) [6], but in buildings like supermarkets and undergrou...Wireless node localization is one of the key technologies for wireless sensor networks. Outdoor localization can use GPS, AGPS (Assisted Global Positioning System) [6], but in buildings like supermarkets and underground parking, the accuracy of GPS and even AGPS will be greatly reduced. Since Indoor localization requests higher accuracy, using GPS or AGPS for indoor localization is not feasible in the current view. RSSI-based trilateral localization algorithm, due to its low cost, no additional hardware support, and easy-understanding, it becomes the mainstream localization algorithm in wireless sensor networks. With the development of wireless sensor networks and smart devices, the number of WIFI access point in these buildings is increasing, as long as a mobile smart device can detect three or three more known WIFI hotspots’ positions, it would be relatively easy to realize self-localization (Usually WIFI access points locations are fixed). The key problem is that the RSSI value is relatively vulnerable to the influence of the physical environment, causing large calculation error in RSSI-based localization algorithm. The paper proposes an improved RSSI-based algorithm, the experimental results show that compared with original RSSI-based localization algorithms the algorithm improves the localization accuracy and reduces the deviation.展开更多
为了进一步提升基于RSS(received signal strength)的WiFi室内定位算法的精度和可靠度,本文对比研究了基于标准差(standard deviation,STD)的AP(access points)选取算法和基于信号丢失率(signal loss rate,SLR)的AP选取算法,并提出了新...为了进一步提升基于RSS(received signal strength)的WiFi室内定位算法的精度和可靠度,本文对比研究了基于标准差(standard deviation,STD)的AP(access points)选取算法和基于信号丢失率(signal loss rate,SLR)的AP选取算法,并提出了新的基于STD和SLR融合的AP选取算法。实验结果表明,基于STD的AP选取算法定位精度受到AP子集个数的影响,当子集个数大于6并继续增加时,定位精度变化不再明显;基于SLR的AP选取算法耗时最少;新的基于STD和SLR融合的AP选取算法定位耗时略大于融合前的两种AP选取算法,但其定位精度和可靠性明显优于其他两种AP选取算法。展开更多
基金supported by a grant from the National Key Research and Development Program of China(Project No.2017YFC1309400).
文摘Background:The use of mobile phone significantly improved the outcomes of tobacco cessation.However,its feasibility and acceptability were unclear in the Chinese population.This study was to explore the feasibility of using Wi-Fi access points(APs)as a platform to provide smoking cessation help at 17 airports and 38 railway stations across China.Methods:This study was divided into two stages:platform development and population survey.In the first stage,a survey platform was developed and incorporated into Wi-Fi service at airports and railway stations,which could provide survey content as a pop-up window when participants tried to access the Wi-Fi service.In the second stage,a population survey was conducted to explore the intention to receive tobacco cessation support.Results:A total of 20,199 users participated and 13,628 users submitted the survey,with a response rate of 67.47%.The smoking rate was 30.9%.A total of 86.58%of smoking participants and 2.44%of non-smoking participants wished to receive tobacco cessation support,respectively.The multivariate analysis showed intention to receive support did not differ in age,gender,and heaviness of smoking(P>0.05).Conclusion:Providing tobacco cessation support via Wi-Fi APs is feasible and efficient,and smokers have high intention to receive tobacco cessation support.It is suggested hospitals,academia,information technology industries,and government agencies must work together to provide tobacco cessation support via mHealth.
文摘Wireless node localization is one of the key technologies for wireless sensor networks. Outdoor localization can use GPS, AGPS (Assisted Global Positioning System) [6], but in buildings like supermarkets and underground parking, the accuracy of GPS and even AGPS will be greatly reduced. Since Indoor localization requests higher accuracy, using GPS or AGPS for indoor localization is not feasible in the current view. RSSI-based trilateral localization algorithm, due to its low cost, no additional hardware support, and easy-understanding, it becomes the mainstream localization algorithm in wireless sensor networks. With the development of wireless sensor networks and smart devices, the number of WIFI access point in these buildings is increasing, as long as a mobile smart device can detect three or three more known WIFI hotspots’ positions, it would be relatively easy to realize self-localization (Usually WIFI access points locations are fixed). The key problem is that the RSSI value is relatively vulnerable to the influence of the physical environment, causing large calculation error in RSSI-based localization algorithm. The paper proposes an improved RSSI-based algorithm, the experimental results show that compared with original RSSI-based localization algorithms the algorithm improves the localization accuracy and reduces the deviation.
文摘为了进一步提升基于RSS(received signal strength)的WiFi室内定位算法的精度和可靠度,本文对比研究了基于标准差(standard deviation,STD)的AP(access points)选取算法和基于信号丢失率(signal loss rate,SLR)的AP选取算法,并提出了新的基于STD和SLR融合的AP选取算法。实验结果表明,基于STD的AP选取算法定位精度受到AP子集个数的影响,当子集个数大于6并继续增加时,定位精度变化不再明显;基于SLR的AP选取算法耗时最少;新的基于STD和SLR融合的AP选取算法定位耗时略大于融合前的两种AP选取算法,但其定位精度和可靠性明显优于其他两种AP选取算法。
