Joint Head Selection and Airtime Allocation for Data Dissemination in Mobile Social Networks

Mobile social networks (MSNs) enable people with similar interests to interact without Internet access. By forming a temporary group, users can disseminate their data to other interested users in proximity with short-range communication technologies. However, due to user mobility, airtime available for users in the same group to disseminate data is limited. In addition, for practical consideration, a star network topology among users in the group is expected. For the former, unfair airtime allocation among the users will undermine their willingness to participate in MSNs. For the latter, a group head is required to connect other users. These two problems have to be properly addressed to enable real implementation and adoption of MSNs. To this aim, we propose a Nash bargaining-based joint head selection and airtime allocation scheme for data dissemination within the group. Specifically, the bargaining game of joint head selection and airtime allocation is first formulated. Then, Nash bargaining solution (NBS) based optimization problems are proposed for a homogeneous case and a more general heterogeneous case. For both cases, the existence of solution to the optimization problem is proved, which guarantees Pareto optimality and proportional fairness. Next, an algorithm, allowing distributed implementation, for join head selection and airtime allocation is introduced. Finally, numerical results are presented to evaluate the performance, validate intuitions and derive insights of the proposed scheme

The improved separation method of coherent sources with two measurement surfaces based on statistically optimized near-field acoustical holography

A technique for separating coherent sources measured by two parallel arrays is proposed. The two measurement surfaces located in the opposite directions of the coherent sources. Similar to separate the aim source from background noise, this method can separate the single source from coherent sources, which makes the sound field information of single source in complex environment more accurate. Such improved separation method based on statistically optimized near-field acoustical holography, according to the sound pressure relationship between measurement surfaces and reconstruction surfaces to separate the sources, reduces the measurement data and obtains higher precision of reconstruction. The present paper uses the improved separation method to obtain the single source results from numerical simulations, gives the relative reconstruction errors with frequency from 100 Hz to 1400 Hz, and practical measurement

Fair Airtime Allocation for Content Dissemination in WiFi-Direct-Based Mobile Social Networks

The vast penetration of smart mobile devices provides a unique opportunity to make mobile social networking pervasive by leveraging the feature of short-range wireless communication technologies (e.g. WiFi Direct). In this paper, we study local content dissemination in WiFi-Direct-based mobile social networks (MSNs). We propose a simple GO-coordinated dissemination strategy, as WiFi Direct does not originally support content dissemination. Due to mobility and the short transmission range, the duration of nodes in contact tends to be limited and consequently they compete for the limited airtime to disseminate their own data. Therefore, fair allocation of the limited airtime among the nodes is required. We focus on fairness in content dissemination rate, which is a key application-layer metric, rather than fairness in throughput or airtime and formulate the allocation problem as a generalized Nash bargaining game wherein the nodes bargain for a share of the limited airtime. The game is proved to have a unique optimal solution, and an algorithm with low complexity is designed to find the optimal solution. Furthermore, we propose a detailed scheduling approach to implement the optimal solution. We also present numerical results to evaluate the Nash bargaining based allocation and scheduling

Performance evaluation of WiFi Direct for data dissemination in mobile social networks

WiFi Direct is a recent device-to-device communication technology standardized by the WiFi Alliance. Its increasing availability on popular mobile systems (e.g. Android) presents a unique opportunity for developers to implement mobile social networks (MSNs), a new paradigm that facilitates data dissemination without Internet access by leveraging human mobility and short-range communication technologies. Since WiFi Direct is not originally designed for such applications, it is significant to learn its performance in practice. In this paper, we investigate goodput and fairness of WiFi Direct for data dissemination in MSNs. To this end, we develop an MSN application and conduct three sets of experiments on a testbed comprising several Android devices. Experimental results show that the data loads and mobility of nodes greatly impact the goodput and fairness

Joint head selection and airtime allocation for data dissemination in mobile social networks

By forming a temporary group, users in mobile social networks (MSNs) can disseminate data to others in proximity with short-range communication technologies. However, due to user mobility, airtime available for users in the same group to disseminate data is limited. In addition, for practical consideration, a star network topology among users in the group is expected. For the former, unfair airtime allocation among the users will undermine their willingness to participate in MSNs. For the latter, a group head is required to connect other users. These two problems have to be properly addressed to enable real implementation and adoption of MSNs. To this aim, we propose a joint head selection and airtime allocation scheme for data dissemination within the group using Nash bargaining theory. Specifically, we consider two cases in terms of user preference on the data to be disseminated: a homogeneous case and a heterogeneous case. For each case, a Nash bargaining solution (NBS) based optimization problem is proposed. The existence of optimal solutions to the optimization problems is proved, which guarantees Pareto optimality and proportional fairness. Next, an algorithm that allows distributed implementation is introduced. Finally, numerical results are presented to evaluate the performance, validate intuitions and derive insights of the proposed scheme

Mobile social networks: Design requirements, architecture, and state-of-the-art technology

Mobile social networks (MSNs) are new systems for people to share content, communicate, and interact. Such networks combine social computing and mobile networking techniques to help in community detection, information dissemination, privacy preservation, etc. In this paper, we summarize the characteristics of MSNs and outline several requirements that should be taken into consideration during its design. A functional reference architecture of MSNs is introduced, and the building blocks of MSNs are described. We classify the literature falling under MSNs according to the building blocks of the architecture, and provide a detailed survey of MSNs. Finally, we present a discussion on the possible future development of MSNs

Development and evaluation of a portable and soft 3D-printed cast for laparoscopic choledochojejunostomy model in surgical training

Abstract Background Laparoscopic choledochojejunostomy (LCJ) is an essential basic skill for biliary surgeons. Therefore, we established a convenient and effective LCJ 3D printing model to evaluate whether the model could simulate the actual operation situation and determine its effectiveness and validity in surgical training. Methods A 3D printing dry laboratory model was established to simulate LCJ. The face and content validity of the model were evaluated by six experienced biliary surgeons based on 5-point Likert scale questionnaires. A total of 15 surgeons with different levels of experience performed LCJ on the model and evaluated the structural validity of the model using the objective structured assessment of technical skills (OSATS). Simultaneously, the operation time of each surgery was also recorded. A study was also performed to further evaluate the learning curve of residents. Results The operating space score of the model was 4.83 ± 0.41 points. The impression score of bile duct and intestinal canal was 4.33 ± 0.52 and 4.17 ± 0.41 points, respectively. The tactile sensation score of bile duct suture and intestinal canal suture was 4.00 ± 0.63 and 3.83 ± 0.41points, respectively. The OSATS score for model operation in the attending group was 29.20 ± 0.45 points, which was significantly higher than that in the fellow group (26.80 ± 1.10, P = 0.007) and the resident group (19.80 ± 1.30, P < 0.001). In addition, there was a statistical difference in operation time among surgeons of different experience levels (P < 0.05). Residents could significantly improve the surgical score and shorten the time of LCJ through repeated training. Conclusions The 3D printing LCJ model can simulate the real operation scenes and distinguish surgeons with different levels of experience. The model is expected to be one of the training methods for biliary tract surgery in the future

Distributed resource allocation in cloud-based wireless multimedia social networks

With the rapid penetration of mobile devices, more users prefer to watch multimedia live-streaming via their mobile terminals. Quality of service provision is normally a critical challenge in such multimedia sharing environments. In this article, we propose a new cloud-based WMSN to efficiently deal with multimedia sharing and distribution. We first motivate the use of cloud computing and social contexts in sharing live streaming. Then our WMSN architecture is presented with the description of the different components of the network. After that, we focus on distributed resource management and formulate the bandwidth allocation problem in a gametheoretical framework that is further implemented in a distributed manner. In addition, we note the potential selfish behavior of mobile users for resource competition and propose a cheat-proof mechanism to motivate mobile users to share bandwidth. Illustrative results demonstrate the best responses of different users in the game equilibrium as well as the effectiveness of the proposed cheating avoidance scheme. 1986-2012 IEEE.Scopus2-s2.0-8490501514