Showing papers by "Min-You Wu published in 2012"

A Survey on Multipacket Reception for Wireless Random Access Networks

Abstract: Multipacket reception (MPR) is the capability of simultaneous decoding of more than one packet from multiple concurrent transmissions. Continuous investigations on increasing the reception capability are giving new scientific contributions. In this paper, we provide an overview of MPR-related research work covering (1) the theoretically proved impacts and advantages of using MPR from a channel perspective to network capacity and throughput; (2) the various technologies that enable MPR from transmitter, transreceiver, and receiver perspectives; (3) previous work on protocol improvement to better exploit MPR. Indeed, MPR approaches have been applied in modern wireless mobile systems but the focus of this paper is to discuss MPR in random access wireless networks. Using MPR in such multihop environments calls for new adaptation on protocols, especially a cross-layer approach. To this end, we detail a scheduling method that targets full utilization of MPR capability.

Scheduling of connected autonomous vehicles on highway lanes

Abstract: With recent progress in vehicle autonomous driving and vehicular communication technologies, vehicle systems are developing towards fully connected and fully autonomous systems. This paper studies lane assignment strategies for connected autonomous vehicles in a highway scenario and their impact on the overall traffic efficiency and safety. We formulate a model of connected autonomous vehicles, which includes three features: traffic data available online, ultra-short reaction time, and cooperative driving. Based on this model, we propose a novel lane change maneuver Politely Change Lane (PCL), which achieves the tradeoff between traffic safety and efficiency. Its effectiveness is validated and evaluated by extensive simulations. The performance shows that PCL improves both safety and efficiency of the overall traffic, especially with heavy traffic.

Evaluation of Urban Vehicle Routing Algorithms

Abstract: In this paper, we focus on a typical CPS application, i.e., vehicle route navigation. Two fundamental problems are examined: 1) How different are various vehicle routing algorithms? 2) How valuable is real-time traffic information or historical traffic information in helping vehicle routing? Different from most previous works based on random walk model, we presented performance comparisons of four routing algorithms using real GPS sensory data from 4000 taxis. It shows that real-time traffic information could substantially improve the quality of vehicle path routing. Through our evaluation, we found that the paths selected by taxi drivers are usually not as good as expected. More importantly, utilizing real-time information could improve global transportation efficiency in terms of dispersing/managing traffic, which plays a key role in constructing an effective vehicular CPS.

Neighbor discovery algorithms in wireless networks using directional antennas

Abstract: Directional antennas provide great performance improvement for wireless networks, such as increased network capacity and reduced energy consumption. Nonetheless new media access and routing protocols are required to control the directional antenna system. One of the most important protocols is neighbor discovery, which is aiming at setting up links between nodes and their neighbors. In the past few years, a number of algorithms have been proposed for neighbor discovery with directional antennas. However, most of them cannot work efficiently when taking into account the collision case that more than one node exist in one directional beam. For practical considerations, we propose a new neighbor discovery algorithm to overcome this shortcoming. Moreover, we present a novel and practical mathematical model to analyze the performance of neighbor discovery algorithms considering collision effects. Numerical results clearly show our new algorithm always requires less time to discover the whole neighbors than previous ones. To the best of our knowledge, it is the first complete, practical analytical model that incorporates directional neighbor discovery algorithms.

A Metropolitan Taxi Mobility Model from Real GPS Traces

Abstract: The past few years have witnessed the growing interest in vehicular ad hoc networks (VANETs) and their potential applications for Internet of Things (IoT). Since the mobility model is crucial to simulation based researches of VANET, using a realistic mobility model can ensure the consistency between simulation results and real deployments. Although there are many mo- bility models characterizing the movement of mobile nodes, none of them consider the behavior of vehicles in a metropolitan scenario. In this paper, we present our study of extracting a mobility model for VANET from a large amount of real taxi GPS trace data. In order to capture charac- teristics of the urban vehicle network from microscopic to macroscopic aspects, we design three parameters and extract their values from the GPS trace data. Using this mobility model, we can generate the synthetic trace to simulate the movement of taxis in the urban area of a metropolis. The validation is carried through extensive comparisons between the synthetic trace and the real trace. The results show that our mobility model has a good approximation with the real scenario.

Mobile barrier coverage for dynamic objects in wireless sensor networks

Abstract: This paper studies mobile barrier coverage (MBC) surrounding dynamic objects. In the real world, several dynamic objects can benefit from MBC. For example, marching troop can detect any adversary intrusion without blind spot by MBC. However, conventional works only focused on barrier coverage for static objects, which fail when the objects start to move. Issues to address these dynamic-object scenarios, we propose the problem of mobile barrier coverage for dynamic objects. The most challenge is how to effectively maintain MBC when the motion of objects are unpredictable. We propose a fully distributed algorithm for mobile sensor nodes to cooperatively move and maintain the high-quality barrier coverage. The extensive simulations based on large-scale trace data demonstrate the efficiency and efficacy of the proposed algorithm.

On optimal service directory selection in urban vehicular networks

Abstract: This paper studies the Delay Bounded Service Discovery Protocol (DB-SDP) problem in Urban Vehicular Ad-hoc Networks (VANETs). Services and resources on the vehicles must be discovered before they become available to the whole network. In distributed Service Discovery Protocols (SDPs), Service Directories (SDs) are selected to store the service description for other vehicles. Selecting SDs is difficult because VANETs has the disruptive nature which incurs a significant delay, whereas the users may have QoS requirements that the query for some certain service must be answered within some delay bound. We study the problem of optimal SD selection that minimizes the number of the SDs under such delay bound requirement. We theoretically prove that such SD selection problem is NP-complete even when the future positions of the vehicles are known as a priori. To solve the DB-SDP without the prior knowledge of future traces, we theoretically and empirically analyze the number of vehicles covered by the set of SDs within a delay bound. We find the number of covered vehicles exhibits some strong regularity. Regarding this regularity, we develop a heuristic iterative algorithm for the optimal SD selection. We conduct extensive trace driven simulations based on real vehicular GPS data and the results show that with high probability, our algorithm can select SD sets 50% smaller than those selected by alternative algorithms.

Eagle eye: A dual-radio architecture in delay tolerant networks

Abstract: In most delay tolerant network (DTN) applications, mobile nodes utilize WiFi radios to obtain local information and transmit data. One bottleneck on DTN delivery performance is the short communication range of the WiFi radio. Rather than designing efficient protocols on WiFi based DTN, we propose a novel dual-radio architecture by adding a long-range low-bitrate eagle eye (EE) radio on every node. This EE radio can “see” real-time movement information of nodes in a significantly large range, and so much early scheduling can be done with this radio when compared with WiFi which is still in charge of data transmissions. Benefiting from this cooperative dual radios architecture, we design distributed EE routing protocol for minimizing delivery delay in DTNs. Through our prototype implementation with 7 EE devices and simulations based on real trace data of 4000 taxis in Shanghai, we show that the proposed architecture is able to achieve as low as 40% of the average delay with traditional DTNs.

On Capacity of Wireless Networks Using Practical Directional Antennas

Abstract: Capacity is one fundamental problem in wireless Ad hoc networks. Deploying directional antennas to wireless networks can reduce interference among concurrent transmissions and increase spatial reuse, while the technology of multi-channel can separate concurrent transmissions. Therefore, combining these two technologies into one wireless network is capable of great improvement on the network capacity. Recent studies proposed a multi-channel network architecture that equips each wireless node with multiple directional antennas, which is called MC-MDA network. The capacity in MC-MDA network is derived under arbitrary and random placements. However, they only used a simplified directional antenna model. For approaching the more accurate capacity in real scenario, we consider a hybrid antenna model, which takes the effect of side lobe into account. We derive the capacity upper-bounds of MC-MDA networks in arbitrary and random network with the hybrid model to find the effect of side lobe. We show that the network capacity is closely related to the ratio of the radiuses of side lobe to main lobe. The capacity decreases when the ratio increases. Moreover, we compare the network capacity of MC-MDA using the simplified antenna model with our results.