Euisin Lee

Vehicular cloud networking: architecture and design principles

Over the past several decades, VANET has been a core networking technology to provide safety and comfort to drivers in vehicular environments. Emerging applications and services, however, require major changes to its underlying computing and networking models, which demand new network planning for VANET. This article especially examines how VANET evolves with two emerging paradigms: vehicular cloud computing and information-centric networking. VCC brings the mobile cloud model to vehicular networks and thus changes the way of network service provisioning, whereas ICN changes the notion of data routing and dissemination. We envision a new vehicular networking system, vehicular cloud networking, on top of them. This article scrutinizes its architecture and operations, and discusses its design principles.

Elastic routing: a novel geographic routing for mobile sinks in wireless sensor networks

Geographic routing has been considered as an efficient, simple and scalable routing protocol for wireless sensor networks, since it exploits pure location information instead of global topology information to route data packets towards a static sink. Recently, a number of research works have shown that mobile sinks can achieve high energy efficiency and load balance than static ones. In order to receive data packets continuously, a mobile sink must update its location to the source frequently. However, frequent location updates of mobile sinks may lead to both rapid energy consumption of the sensor nodes and increased collisions in wireless transmissions. The authors propose a novel geographic routing for mobile sinks to address this issue. The proposed scheme takes advantage of wireless broadcast transmission nature of wireless sensor nodes. When a sink moves, the new location information is propagated along the reverse geographic routing path to the source during data delivery. Analysis and simulation results indicate that elastic routing is superior to other protocols in terms of control overhead, data delivery delay and energy consumption.

Mobile Geocasting to Support Mobile Sink Groups in Wireless Sensor Networks

Traditionally, geocasting has been known as the appropriate scheme for providing effective data dissemination from a source to all nodes in a geographically restricted region. However, since the geocasting typically assumes the restricted region is stationary, it is hard to directly adopt the traditional geocasting in order to offer effective data delivery to mobile sink groups that have geographically collective mobility. Hence, this letter proposes a novel geocasting, called M-Geocasting (Mobile Geocasting). M-Geocasting provides the representative location information of a sink group to sources. The location information contains information with respect to a restricted region in which all member sinks of the group exist. A source disseminates data to the closest node in the region; then, the node restrictedly floods the data only within the region. Also, to support local movement of member sinks toward out of scope of the region, some nodes on boundary of the region maintain the data and offer it to member sinks out of scope of the region.

Energy-Efficient Data Dissemination Protocol for Detouring Routing Holes in Wireless Sensor Networks

Void areas (holes) as an inevitable phenomenon exist in geographic routing of wireless sensor networks, because the unpredictable and harsh nature application environment or uneven energy consumption. Most of the existing schemes for the issue tend to construct a static detour path to bypass a hole. The static detour path may lead to uneven energy consumption of the nodes on the perimeter of the hole; thus it may enlarge the hole. At the same time, traffic would concentrate on the peripheral node of the hole; thus the nodes on the perimeter of the hole tend to be depleted quickly. In previous work, we have proposed a hole geometric model to reduce the energy consumption and packet collisions of the nodes on the hole boundary. This scheme, however, still has the static detour path problem. Therefore, we extend the previous work by constructing a dynamic detour path hole geometric model for wireless sensor networks in this paper. The location of hole detour anchor is dynamically shifted according to Gaussian function, just generating dynamic hole detour paths.

Sink Location Service for Geographic Routing in Wireless Sensor Networks

Geographic routing has been considered as an efficient, simple, and scalable routing protocol for wireless sensor networks since it exploits pure location information instead of global topology information to route data packets. Geographic routing requires the sources nodes to be aware of the location of the sinks. How can source nodes get sinks locations with low overhead is a difficult issue in wireless sensor networks. In this paper, we propose a Sink Location Service for geographic routing in wireless Sensor Networks. In this scheme, a source node and a sink node send sink location announcement and query messages along two paths respectively by geographic routing. The node located on the crossing point of the two paths informs the source about the sink location. Then the source can send data packet to the sink by geographic routing. How to guarantee that these two paths have at least one crossing point in any irregular profile of sensor network is the challenge of this paper. Simulation results show that our protocol is significantly superior to other protocols in terms of energy consumption and control overhead.

Data gathering mechanism with local sink in geographic routing for wireless sensor networks

Most existing geographic routing protocols on sensor networks concentrates on finding ways to guarantee data forwarding from the source to the destination, and not many protocols have been done on gathering and aggregating data of sources in a local and adjacent region. However, data generated from the sources in the region are often redundant and highly correlated. Accordingly, gathering and aggregating data from the region in the sensor networks is important and necessary to save the energy and wireless resources of sensor nodes. We introduce the concept of a local sink to address this issue in geographic routing. The local sink is a sensor node in the region, in which the sensor node is temporarily selected by a global sink for gathering and aggregating data from sources in the region and delivering the aggregated data to the global sink. We next design a Single Local Sink Model for determining optimal location of single local sink. Because the buffer size of a local sink is limited and the deadline of data is constrained, single local sink is capable of carrying out many sources in a large-scale local and adjacent region. Hence, we also extend the Single Local Sink Model to a Multiple Local Sinks Model. We next propose a data gathering mechanism that gathers data in the region through the local sink and delivers the aggregated data to the global sink. Simulation results show that the proposed mechanism is more efficient in terms of the energy consumption, the data delivery ratio, and the deadline miss ratio than the existing mechanisms.

A Communication Architecture to Reflect User Mobility Issue in Wireless Sensor Fields

Typical sensor networks consist of users, sinks, and a number of sensor nodes. The traditional architecture usually assumes that there is a legacy network between users and sinks. However, practical users like firefighters and soldiers move around sensor fields and they might not have any direct communication through legacy networks. In other words, sensor networks are the only communication channel between users and sinks in practical sensor fields. Now there are no researches with respect to architecture to support the user mobility. Thus it is necessary to deliberate a new architecture for such the issue. In this paper, a novel communication architecture was presented where a user operates around an infrastructureless sensor field. A new networking model was then proposed, named dynamic sink model, to support user mobility on the novel architecture. In the model a sink is temporarily selected among generic sensor nodes by a user when the user wants to get information from a sensor network. The chosen sink gathers data from sensor nodes for interested tasks and propagates collected information to the user via the sensor network. The performance of the dynamic sink model on the novel architecture was evaluated and explored with regard to average delay, delivery ratio, and network lifetime compared with the common static sink network model on typical communication architecture.

Communication model and protocol based on multiple static sinks for supporting mobile users in wireless sensor networks

Typical communication model of wireless sensor networks consists of users, sinks, and a number of sensor nodes. The users are remote from wireless sensor networks and they gather data from the sinks via legacy networks. However, in practical sensor network applications, there are two types of users: traditional remote users and mobile users such as fire-fighters and soldiers. The mobile users may move around sensor fields and they communicate with the sinks only via the sensor networks in order to gather data like location information of victims in disaster areas. In this paper, in order to effectively support both the remote users and the mobile users, we propose a novel communication model relying on the typical sensor network model. In the model, multiple static sinks connect with legacy networks and divide a sensor field into the number of the multiple sinks. Through sharing queries and data via the legacy networks, the multiple static sinks provide high throughput through distributed data gathering and low latency through short-hops data delivery. Multiple static sinks deliver the aggregated data to the remote users via the legacy networks. In case of the mobile users, when a mobile user moves around, it receives the aggregated data from the nearest static sink. Simulation results show that the proposed model is more efficient in terms of energy consumption, data delivery ratio, and delay than the existing models.

Communication Scheme to Support Sink Mobility in Multi-hop Clustered Wireless Sensor Networks

In wireless sensor networks, the studies that support sink mobility without global position information exploit a Backbone-based Virtual Infrastructure (BVI) to avoid the routing structure construction per each mobile sink by full network flooding. The BVI approach typically considers one-hop clusters and a backbone structure-based tree configured by the cluster heads (CHs). For data dissemination to a mobile sink, the head of the cluster where the mobile sink exists registers the backbone structure on behalf of the sink, and then source nodes generate the data to their CHs via the tree. Finally, the CHs deliver the data to the mobile sink. However, the one-hop cluster makes the tree organized by too many CHs so that it causes large location registration overhead according to movement of the sink. Moreover, the data delivery via the tree with a large number of CHs might lead to data delivery from source nodes to the sink though detour paths due to always delivering data via the tree. Namely, although the source nodes exist at nearest clusters from the cluster attached by the sink, if they are located in different branch of the tree, the data should be delivered via detour paths on the tree. Therefore, we propose a novel BVI-based communication protocol to support sink mobility without global position information. To reduce the number of CHs, we consider multi-hop clusters. Also, to avoid the location registration of a mobile sink to the whole CHs, we uses a rendezvous CH on which queries of the mobile sink and reporting data of a source node meet. However, such a manner also has data detour problem that the source node sends data packets to the mobile sink via the rendezvous CH. Thus, we present a scheme to find a path with fewer hop-counts between CHs where the source node and the mobile sink are located in. Simulation results show that the proposed protocol is superior to the existing protocols in terms of the control overhead and the data delivery hop counts.

Novel service protocol for supporting remote and mobile users in wireless sensor networks with multiple static sinks

A wireless sensor network typically consists of users, a sink, and a number of sensor nodes. The users may be remotely connected to a wireless sensor network and via legacy networks such as Internet or Satellite the remote users obtain data collected by the sink that is statically located at a border of the wireless sensor network. However, in practical sensor network applications, there might be two types of users: the traditional remote users and mobile users such as firefighters and soldiers. The mobile users may move around sensor fields and they communicate with the static sink only via the wireless sensor networks in order to obtain data like location information of victims in disaster areas. For supporting the mobile users, existing studies consider temporary structures. However, the temporary structures are constructed per each mobile user or each source nodes so that it causes large energy consumption of sensor nodes. Moreover, since some of them establish the source-based structure, sinks in them cannot gather collective information like mean temperature and object detection. In this paper, to effectively support both the remote users and the mobile users, we propose a novel service protocol relying on the typical wireless sensor network. In the protocol, multiple static sinks connect with legacy networks and divide a sensor field into the number of the multiple sinks. Through sharing queries and data via the legacy networks, the multiple static sinks provide high throughput through distributed data gathering and low latency through short-hops data delivery. Multiple static sinks deliver the aggregated data to the remote users via the legacy networks. In case of the mobile users, when a mobile user moves around, it receives the aggregated data from the nearest static sink. Simulation results show that the proposed protocol is more efficient in terms of energy consumption, data delivery ratio, and delay than the existing protocols.