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The IEEE 802.16 standard for wireless metropolitan area networks (WMANs) is defined to meet the need for wide-range broadband wireless access at low cost. The objective of this paper is to study how to exploit spectral reuse in resource allocation in an IEEE 802.16 mesh network, which includes routing tree construction (RTC), bandwidth allocation, time-slot assignment, and bandwidth guarantee of real-time flows. The proposed spectral reuse framework covers bandwidth allocation at the application layer, RTC and resource sharing at the medium access control (MAC) layer, and channel reuse at the physical layer. To the best of our knowledge, this is the first paper that formally quantifies spectral reuse in IEEE 802.16 mesh networks and exploits spectral efficiency under an integrated framework. Simulation results show that the proposed schemes significantly improve the throughput of IEEE 802.16 mesh networks.

This paper proposes a group-based emergency guiding system for mobile users using smartphones, called Go FAST, which can model the spatiotemporal mobility of indoor people. A dedicated path can be determined to provide the shortest evacuation time for each group of nearby people. The Go FAST system considers the corridor capacities and lengths, exit capacities, concurrent motion, distribution of indoor people, and dedicated escape path to accurately estimate the evacuation time for each group. Based on the estimated evacuation time, the evacuation load can evenly distributed among exits to minimize the total evacuation time. Go FAST can alleviate the congestion of all corridors and exits to reduce the total evacuation time as much as possible. An Android-based prototype with iBeacon indoor localization is implemented to verify the feasibility of our Go FAST system. Simulation results show that Go FAST outperforms existing schemes and can achieve the shortest evacuation time for group-based emergency guiding.

In this paper, we design an augmented reality based social networking system, called SocialYou, for mobile users using smartphones. The SocialYou system only needs a single-finger action that drags the icon of social networking websites to the target face on the screen of a smartphone. The target user webpage in a specific social networking website can be immediately displayed in the social media App or built-in web browser. Through SocialYou, mobile users do not need to know the target identifier in advance. In addition, mobile users do not need to input identifier information by themselves. Furthermore, mobile users can select a specific target among multiple candidates from the camera of a smartphone. SocialYou reveals an innovative user interface for social networking between mobile users. We have implemented an Android-based SocialYou system that outperforms existing methods in experimental results.

In this paper, we propose a video-based metropolitan positioning system (V-MPS) for providing centimeter-grade localization in vehicular networks. The V-MPS system integrates vehicular networks with installed roadside/intersection cameras to provide positioning information to vehicles on the road. V-MPS can estimate the precise position of a vehicle and detect the located lane for each vehicle. To the best of our knowledge, V-MPS is the first positioning system which provides the following features: 1) it achieves the centimeter-grade positioning accuracy for vehicular networks that can detect the located lanes of vehicles, 2) it employs existing roadside/intersection cameras that can keep additional construction cost low, and 3) it establishes an innovative infrastructure for applications of next-generation Intelligent Transportation System (ITS) that can make lane-level traffic control, collision avoidance, and vehicle navigation possible. With vehicular networks, the estimated positions can be broadcast to nearby vehicles. With roadside/intersection cameras, the lane positions of vehicles can be detected even if GPS is not accurate enough to provide lane-level localization. In addition, the traffic condition can be continually monitored to optimize driving efficiency for next-generation ITS. This paper demonstrates our current prototype.

Safety applications in vehicular networks have been popular research topics in recent years, such as forward collision warning, emergency braking warning and intersection collision warning systems. The basic safety message broadcast from each car transmits the position, car speed and car heading information. Neighbouring cars receiving this information can decide if there is any danger within the next second. However, the safety application message has positioning accuracy and time-critical problems. Accurate positioning of the car provides a more effective warning to the driver. Moreover, the reliable and efficient delivery of safety information needs to be improved when the penetration rate increases. Hence, this paper proposes a cooperative emergency braking warning system to solve the above problems. This is a system that integrates a camera sensor to construct the state of neighbourhood cars in order to solve the first problem. It then proposes to reduce the repeat and derivable information between the broadcast messages in order to solve the second problem. The proposed system has been implemented to provide a safer driving environment.

On-line analytical processing (OLAP) provides analysis of multi-dimensional data stored in a database and achieves great success in many applications such as sales, marketing, financial data analysis. OLAP operation is a dominant part of data analysis especially when addressing a large amount of data. With the emergence of the MapReduce paradigm and cloud technology, OLAP operation can be processed on big data that resides in scalable, distributed storage. However, current MapReduce implementations of OLAP operation processing have a major performance drawback caused by improper processing procedure. This is crucial when dimension or dependent attributes are large, which is a common case for most data warehouses hold nowadays. To solve this issue, this paper proposes a methodology to accelerate the performance of OLAP operation processing on big data. We have conducted the experiments on the basic algebra of OLAP operation with different data sizes to demonstrate the effectiveness of our system.

This paper considers the location-tracking problem in PCS networks. Solutions to this problem in fact highly depend on the mobility patterns of mobile subscribers [ACM DIAL-M (1999) 72]. In the literature, many works have assumed a simple random walk model, where mobile subscribers always stay in a roaming state and can move in any direction with equal probability. In this paper, we propose a new Stop-or-Move Mobility (SMM) model, which is characterized by the following features: 'transition between stop and move', 'infrequent transition', 'memory of roaming direction', and 'oblivious in different moves'. Based on this mobility model, a static and an adaptive location-tracking Scheme are developed. The schemes only need to keep very little information for each user. Analyses and simulations are provided, which show that the proposed schemes are quite prospective.

In this paper, we design an augmented reality based file transfer system called ShareAR. The ShareAR system only needs a single-finger action that drags the file icon to the target face on the screen of a mobile device. The dragged file can be transmitted to the target receiver who gets the file immediately as her/his mobile device is on-line or receives the file later after connecting to the Internet. Through ShareAR, users do not need to know the target account in advance. In addition, users do not need to input account information by themselves. Furthermore, users can select a specific target among multiple candidates from the camera of a mobile device. ShareAR reveals an innovative user interface to transfer files between mobile devices. We have implemented an Android-based ShareAR system that outperforms existing schemes in experimental results.

The IEEE 802.16 standard is designed to meet the need of metropolitan-area broadband wireless access. This work studies two collision-resolution requesting schemes for best-effort (BE) traffics in IEEE 802.16 networks. One is the exponential backoff scheme defined in the standard and the other is a piggyback mechanism enhanced by single-frame backoff, called the Request Piggyback (RPB) scheme. We analyze and compare their performance in terms of the request success probability and the packet delivery delay under Poisson traffic. The results show that the RPB scheme outperforms the exponential backoff scheme and can reduce request collision.

This paper proposes a load-balancing framework for emergency guiding based on wireless sensor networks. We design a load-balancing guiding scheme and derive an analytical model in order to reduce the total evacuation time of indoor people. The guiding scheme can provide the fastest path to an exit for people based on the evacuation time estimated by the analytical model. This is the first distributed solution which takes the corridor capacity and length, exit capacity, concurrent move, and people distribution into consideration for estimating evacuation time and planning escape paths. Through the proposed framework, the congestion of certain corridors and exits can be released to significantly reduce the total evacuation time. Analytical and simulation results show that our approach outperforms existing works, which can prevent people from following the local optimal guiding direction with the longer evacuation time in total. We also implement a prototype, called Load-balancing Emergency Guiding System (LEGS), which can compare evacuation time and guiding directions of existing schemes and ours under different people distribution.

The Eco-Sign system is a traffic light control system for minimizing greenhouse gases emitted by idling vehicles at intersections. Eco-Sign provides the following features: (i) it can notify vehicles to turn on/off their engines based on expected waiting time for green lights at intersections, (ii) it can dynamically adjust traffic light timing to minimize the number of vehicles stopping at an intersection based on vehicle arrival and departure rates, and (iii) it is a fully distributed system in the sense that each intersection can learn its local traffic condition and optimize its traffic sign setting to prevent congestions and thus traffic jams. Eco-Sign thus demonstrates a new traffic light control system for environmental protection.

The Vehicular Surveillance and Sensing System (VS3) is a 3G-based mobile device for car security applications. On the car side, it consists of a CO 2 sensor, a camera module, a 3G module, and a microprocessor. On the user side, only a 3G mobile phone is needed. VS3 provides the following features: (i) it can be triggered by events detected on car, (ii) events can be abnormal air quality or potential burglary, and (iii) it supports text or multimedia interaction with users. Application scenarios include detecting an abnormal CO 2 level or potential car burglary, which triggers VS3 to transmit SMS, MMS, or interactive video call to the vehicle owner, who can then monitor the car situation in return. VS3 thus demonstrates a new car security and burglarproof prototype.

The IEEE 802.16 standard for wireless metropolitan area networks (WMAN) has been created to meet the need of wide-range broadband wireless access at low cost. The objective of this paper is to study how to exploit spectral reuse in an IEEE 802.16 mesh network through timeslot allocation, bandwidth adaptation, hierarchical scheduling, and routing. To the best of our knowledge, this is the first work which formally quantifies spectral reuse in IEEE 802.16 mesh networks and which exploits spectral efficiency under an integrated framework. Simulation results show that the proposed spectral reuse scheduling and load-aware routing significantly enhance the network throughput performance in IEEE 802.16 mesh networks.

Summary Most methods of file transfer between mobile devices have to take considerable time to obtain and input target identifiers. To speed up file sharing of mobile devices, an intelligent file transfer framework is designed based on mobile cloud computing. Only single-finger action is performed in the proposed framework, which just drags the file to the target face on the touchscreen of a mobile device. The dragged file can be transmitted to the target receiver who can either get the file immediately as her/his mobile device is online or receive the file later after connecting to the Internet. Our framework provides the following features: (i) users do not need to know the target identifier in advance; (ii) users do not need to input identity information by themselves; and (iii) users can select a specific target among multiple candidates from the camera of a mobile device. The intelligent file transfer framework reveals an efficient architecture and innovative user interfaces to transfer files between mobile devices, which can significantly reduce the complexity and difficulty of file sharing. An Android-based prototype is implemented to verify the feasibility and superiority of our framework. Experimental results show that our approach outperforms existing schemes and can save large amounts of time in file sharing for mobile users. Copyright © 2015 John Wiley & Sons, Ltd.

This paper considers the location tracking problem in PCS networks. How a solution to this problem performs in fact highly, depends on the mobility patterns of users. In this paper we propose a new traveling salesman mobility (TSM) model, in the hope of catching the mobility patterns of a large group of users. The TSM model is characterized by features of "stop-or-move", "infrequent transition" "memory of roaming direction", and "oblivious in different moves". Then a location tracking strategy based on this TSM model is developed. The scheme only needs to keep very little information for each user. Analyses and simulations are provided, which show that the strategy is very prospective.