Hierarchical Location Service Research Articles

A hierarchical location service architecture for VANET with aggregated location update

For Vehicular Ad-Hoc Network (VANET) location services, scalability toward the extensive network scale and high mobility of vehicles is a key issue. Furthermore, minimization of signaling overhead is another important issue for emerging applications such as IoV (Internet of vehicles) which require frequent and continuous collection of location information. Some of the VANET location service mechanisms solely rely on per-vehicle server assignment and location updates, and thus, impose heavy server maintenance complexity and/or signaling overhead. On the other hand, there exist mechanisms that perform aggregated location updates based on hierarchical architecture. The legacy mechanisms with aggregated location update, though, either suffer lack of service reliability or cannot take full advantage of the location update aggregation in reducing the location update overhead. Accordingly, we propose a dynamic Mobile Group-based Location Service (MoGLS), a scalable VANET location service, which is robust to the mobility in terms of both reliability and overhead. MoGLS is based on a hierarchical structure of servers. The lower level is composed of dynamic groups of vehicles with similar trajectories, and one of the vehicles in each group takes the role of lower level location server. Higher level is comprised of the unit areas with an infrastructure-based fixed server. For the location update from the lower to the higher level server, aggregation of information is applied. By the leverage of characteristics that lower level servers move together with their member vehicles, mechanisms to prevent the deterioration of service reliability due to aggregated location update are proposed while taking full advantage of the aggregated location update in reducing the signaling overhead. MoGLS includes dynamic group management, location update and discovery, and a group merge algorithm for the optimal group formation. Through the performance comparisons via simulation, it is shown that MoGLS provides satisfactory service reliability with smaller signaling overhead compared to the existing hierarchical VANET location service mechanisms with aggregated location update. Furthermore, the performance of MoGLS is shown to be more stable toward the increase of density and speed of vehicles.

Location service implementation in vehicular networks by nodes clustering in urban environments

Position based protocols, such as routing protocols, require a location service to find the position of destination nodes. In other words, a source node requests the location of the destination from the location service, and then the service starts to search for the destination node and returns its location to the source node. In this paper, a Cluster Based Location Service (CBLS) for Vehicular Ad-hoc networks (VANETS) is proposed. CBLS divides the vehicles into clusters according to their speed, distance and neighboring parameters. A node in each cluster, cluster head, collects the other nodes position information and passes it to a main server in a hierarchical manner. In the proposed service, instead of fixed antennas, the vehicles antennas are used, so the services scalability and efficiency grow and capital cost decreases. The performance evaluation of the proposed service shows it outperforms the traditional (without clustering) hierarchical location services in terms of query delay and success rate.

무선 센서 네트워크에서 이동 싱크 그룹을 위한 위치 서비스와 데이터 전송 프로토콜

본 논문은 센서 노드들의 에너지 소비를 줄이고 소스로부터 이동 싱크 그룹까지 데이터를 전달하기 위한 새로운 위치 서비스와 위치 기반 라우팅을 제안한다. 기존 방안들과는 다르게, 제안 방안은 그룹 영역 대신 싱크 그룹을 대표하는 리더 싱크 위치 정보를 사용한다. 그래서, 제안 방안은 소스와 리더 싱크 간의 위치 서비스와 위치 기반 라우팅을 위한 상위 계층과 리더 싱크와 멤버 싱크들 간의 위치 서비스와 라우팅을 위한 하위 계층으로 이루어진 계층적 위치 서비스와 위치 기반 라우팅을 사용한다. 각각의 상위와 하위 계층의 위치 서비스와 위치 기반 라우팅은 플러딩을 사용하지 않기 때문에 제안 방안은 센서 노드들의 에너지 소비를 줄일 수 있다. 다양한 시뮬레이션 결과는 제안 방안이 기존 방안보다 우수함을 증명한다. In this paper, we propose a new location service and location-based routing for data dissemination from a source to a mobile group sink in less energy consumption of the sensor node. Unlike the existing protocols, the proposed protocol uses a leader sink instead of a group area as the location information to represent a mobile sink group. The proposed protocol also uses grid leaders on virtual grid structure to support sink mobility in location service. By using a leader sink as a representative and grid leaders for mobility supporting, the proposed protocol can exploit an efficient hierarchical location service and data dissemination method without using flooding. Accordingly, the proposed protocol carries out upper layer location services and data dissemination between a leader sink and a source and lower layer location services and data dissemination between the leader sink and member sinks. Simulation results demonstrate that the proposed protocol achieves energy-efficiency.

HCBLS: A Hierarchical Cluster-Based Location Service in Urban Environment

Vehicle location information is central to many location-based services and applications in VANETs. Tracking vehicles positions and maintaining an accurate up-to-date view of the entire network are not easy due to the high mobility of vehicles and consequently rapid topology changes. The design of a scalable, accurate, and efficient location service is still a very challenging issue. In this paper, we propose a lightweight hierarchical cluster-based location service in city environments (HCBLS). HCBLS integrates a logical clustering based on the city digital map and consequently does not involve extra signaling overhead. An advanced location update aggregation at different levels of the assumed hierarchy is adopted to maintain up-to-date and accurate location information. Simulation results show that HCBLS achieves much better performances than the Efficient Map-Based Location Service (EMBLS) and any regular (non-cluster-based) updating scheme. HCBLS increases the success rate by around 10%, improves the overview of the network by more than 30%, lowers the location update and query costs by more than 7 times, lowers the message delivery latency by around 3 times, and presents around 4 times better localization accuracy.

Joint routing and location-based service in VANETs

Geographic routing protocols use location information when they need to route packets. In the meantime, location information are maintained by location-based services provided by network nodes in a distributed manner. Routing and location services are very related but are used separately. Therefore, the overhead of the location-based service is not considered when we evaluate the geographic routing overhead. Our aim is to combine routing protocols with location-based services in order to reduce communication establishment latency and routing overhead.Our main contribution is to reduce the location overhead. Thus, we propose two combinations: (1) a geographic routing protocol with GLS called Hybrid Routing and Grid Location Service (HRGLS) and (2) a geographic routing protocol with HLS denoted Hybrid Routing and Hierarchical Location Service (HRHLS), where instead of launching an exact position request, we send the packet to the old destination position and when the packet is approaching the former position, we request the exact one.The complexity of the location query cost in both proposed schemes is O(logN), while it is O(N) in the case of HLS and GLS. Simulation results also confirm the complexity analysis and show promising results in terms of latency, packet delivery ratio and control message overhead.

Location Update Improvement Using Fuzzy Logic Optimization in Location Based Routing Protocols in MANET

Several position-based routing protocols have been developed for mobile ad hoc networks. Many of these protocols assume that a location service is available which provides location information on the nodes in the network. This paper introduces a new schema in management of mobile nodes location in mobile ad hoc networks. Fuzzy logic optimization is applied to a better management of location update operation in hierarchical location services. Update management overhead is decreased without significant loss of query success probability. One-hop-chain-technique is used for Auto compensation. A new composed method can update mobile nodes location when the nodes cross a grid boundary. The proposed method uses a dynamic grid area that ?solves the ping-pong problem between grids. Simulation results show that these methods are effective. The algorithms are distributed and can keep scalability in the scenario of increasing nodes density?. The described solutions are not limited to a special network grid ordering, and can be used in every hierarchical ordering like GLS if the ordering can be mappable on these methods.

Hierarchical Location Service with Prediction in Mobile Ad-Hoc Networks

Position-based routing protocols take advantage of location information to perform a stateless and efficient routing. To enable position-based routing, a node must be able to discover the location of the messages' destination node. This task is typically accomplished by a location service. Recently, several location service protocols have been developed for ad hoc networks. In this paper we propose a novel location service called PHLS: Predictive Hierarchical Location Service. In PHLS, the entire network is partitioned into a hierarchy of smaller and smaller regions. For each node, one node in each-level region of the hierarchy is chosen as its local location server. When the network initializes or when a node attaches the network, nodes contact their local location server with their current location information (ie. position and velocity). Then, they only need to update their location server when they move away from their current region. Finally, nodes query their location servers and get the exact or predicted location of destination nodes.

A cross-layer framework for position-based routing and medium access control in heterogeneous mobile ad hoc networks

Many Mobile Ad Hoc Networks (MANETs) are composed of nodes with heterogeneous communication capabilities in terms of transmission power, data rate, battery life, reliability, etc. Heterogeneous MANETS (H-MANETs) often encounter problems in both Medium Access Control (MAC) and routing layers due to link asymmetry. But meanwhile, H-MANETs have many advantages including: scalability, robustness, and connectivity. In this paper we present a two-layer approach which spans the MAC and network layers for H-MANETs to minimize the problems caused by link asymmetry and exploit the advantages of H-MANETs simultaneously. At the network layer, we design a hierarchical Location service (LS) protocol and a node density adaptive position-based routing protocol. At the MAC layer we propose a new MAC protocol which uses two communication channels and closely ties in with the network layer to solve the MAC problems caused by link asymmetry. We evaluate our approach using both probabilistic analysis and simulations.

Hierarchical location service for wireless sensor networks with mobile sinks

AbstractIn wireless sensor networks (WSNs), a mobile sink can help eliminate the hotspot effect in the vicinity of the sink, which can balance the traffic load in the network and thus improve the network performance. Location‐based routing is an effective routing paradigm for supporting sink mobility in WSNs with mobile sinks (mWSNs). To support efficient location‐based routing, scalable location service must be provided to advertise the location information of mobile sinks in an mWSN. In this paper, we propose a new hierarchical location service for supporting location‐based routing in mWSNs. The proposed location service divides an mWSN into a grid structure and exploits the characteristics of static sensors and mobile sinks in selecting location servers. It can build, maintain, and update the grid‐spaced network structure via a simple hashing function. To reduce the location update cost, a hierarchy structure is built by choosing a subset of location servers in the network to store the location information of mobile sinks. The simulation results show that the proposed location service can significantly reduce the communication overhead caused by sink mobility while maintaining high routing performance, and scales well in terms of network size and sink number. Copyright © 2009 John Wiley & Sons, Ltd.

Balancing the tradeoffs between scalability and availability in mobile ad hoc networks with a flat hashing-based location service

In this paper, we propose FSLS (Flat-based Some-for-some Location Service), a new location service for ad hoc mobile networks. The location service is based on the hash-based sets system that can offer a high location information availability. The network area is divided into non-overlapping zones. A node identifier is mapped to a set of home zones, each of which contains a unique location server, which makes FSLS works as a some-for-some approach. Using cross-layer design, the service can tolerate server mobility and server failures, and last for a long time period. We analyze FSLS and six other existing location services. The theoretical analysis as well as simulation results show that FSLS offers a good trade-off between location availability and scalability. It comes second after a quorum-based location service in terms of location availability and it is the closest competitor to a hierarchical location service in terms of scalability.

Two scalable location service protocols for wireless ad hoc networks

We present two location service protocols, viz., the hierarchical location service protocol and the on-demand location service protocol, to track the position of mobile nodes in a wireless ad hoc network. The hierarchical location service uses a location-based hierarchy to maintain the location of nodes in the network, whereas the on-demand location service uses a unicast-based network probing, unlike flooding, to obtain the position of a node on-demand. In the unicast-based network probing, a location query for a node is unicast to nodes that are closer to a few fixed positions in the network. For a given network size, the number of such positions remains constant. Both the location service protocols use a heuristic greedy forwarding protocol, called the angular routing protocol, to circumvent dead ends, and to route packets beyond one hop. We use a theoretical framework to show that both the location service protocols are asymptotically scalable with respect to the number of nodes in the network. Further, we present results from an extensive simulation study comparing the performance of the proposed on-demand location service protocol with LAR1 and a combination of GPSR-GLS. Simulations show that the on-demand location service along with angular routing protocol outperforms the LAR1 and GPSR-GLS protocol in terms of control overhead, percentage of packets delivered, and average hop count, for various network scenarios.

Hierarchical location service for mobile ad-hoc networks

Position-based routing has proven to be a scalable and efficient way for packet routing in mobile ad-hoc networks. To enable position-based routing, a node must be able to discover the location of the node it wants to communicate with. This task is typically accomplished by a location service. In this paper, we propose a novel location service called HLS (Hierarchical Location Service). HLS divides the area covered by the network into a hierarchy of regions. The top level region covers the complete network. A region is subdivided into several regions of the next lower level until the lowest level is reached. We call a lowest level region a cell. For a given node A, one specific cell is selected on each level of the hierarchy by means of hash function. As A changes its position it transmits position updates to these responsible cells. If another node wants to determine the position of A it uses the same hash function to determine the cells that may hold information about the position of A. It then proceeds to query the nodes in these cells in the order of the hierarchy until it receives a reply containing the current position of A. Because of its hierarchical approach HLS is highly scalable and particularly well suited for networks where communication partners tend to be close to each other. Due to the inherent scaling limitations of ad-hoc networks it is very likely that most ad hoc networks will display this property. Furthermore HLS is very robust to node mobility and node failures since it uses regions to select location servers and not a chain of mobile nodes as it is the case, e.g., for the well known Grid Location Service (GLS). We demonstrate these traits by providing extensive simulation data on the behaviour of HLS in a wide range of scenarios and by using GLS as a benchmark.