Kuong-Ho Chen

CHIRON: An energy-efficient chain-based hierarchical routing protocol in wireless sensor networks

Due to the power restriction of sensor nodes, efficient routing, in wireless sensor networks, is a critical approach to saving nodes energy and thus prolonging the network lifetime. Even the chain-based routing is one of significant routing mechanisms, several common flaws, such as data propagation delay and redundant transmission, are associated. In this paper, we propose an energy efficient Chain-Based Hierarchical Routing Protocol, named as CHIRON, to alleviate such deficiencies. Based on the BeamStar concept [9], the main idea of CHIRON is to split the sensing field into a number of smaller areas, so that it can create multiple shorter chains to reduce the data transmission delay and redundant path, and therefore effectively conserve the node energy and prolong the network lifetime. Simulation results show that, in contrast to Enhanced PEGASIS and PEGASIS protocols, the proposed CHIRON can achieve about 15% and 168% improvements on average data propagation delay, 30% and 65% improvements on redundant transmission path, respectively. By these contributions, the network lifetime can also be extended to about 14%∼7% and 50%∼23%, under various small and large simulation areas, respectively.

HarpiaGrid: A Geography-Aware Grid-based Routing Protocol for Vehicular Ad Hoc Networks

Vehicular Ad Hoc Network (VANET) is a research field attracting growing attention. Current routing protocols in VANETs usually use route discovery to forward data packets to the destination. In addition, if vehicle density is low in the network, there might not be vehicles available to deliver the packet. This paper proposes HarpiaGrid, a geography-aware grid-based routing protocol for VANETs. The protocol uses map data to generate a shortest transmission grid route, effectively trades route discovery communication overhead with insignificant computation time. By restricting packets in grid sequences rather than blindly greedy search and making use of route cache approach, HarpiaGrid reduces many unnecessary transmissions, thus greatly improving routing efficiency. Moreover, in the route maintenance, this work proposes a local recovery scheme and uses backtracking techniques to generate a new grid forwarding route, providing superior fault-tolerance capability. Experiments were conducted, and the results demonstrated that the proposed scheme is indeed more efficient than other protocols.

HarpiaGrid: A Reliable Grid-based Routing Protocol for Vehicular Ad Hoc Networks

Vehicular ad hoc network (VANET) is a research field attracting growing attention. Current routing protocols in VANET usually use geographic information to forward data packets to the destination. Since geographic routing is stateless, during routing forwarding, route recovery processes would be continuously initiated if any topology hole exists, resulting in serious performance degradation. In addition, if vehicle density is low in the network, there might not be vehicles available to deliver the packet. This paper proposes HarpiaGrid, a reliable grid-based routing protocol for VANETs. The protocol utilizes in-car navigators to produce geographically logical routing paths, effectively trades route discovery network overhead with insignificant computation time. In addition, by taking advantage of the information provided by gridded geographic data, transmissions are made more efficient. Moreover, in the route maintenance, a fault-tolerance procedure is designed to avoid dead paths. Simulations were conducted, and the results demonstrated that the proposed scheme is indeed more efficient and reliable than other protocols.

A seamless and reliable distributed network file system utilizing webspace

A distributed file system integrates the storage devices on the network and stores files on remote file servers so that clients can access them through Internet anytime and anywhere. However, to ensure the reliability and security of critical data, the maintenance cost is usually high. Some researches propose solutions to use Webspace as storage. These are efficient for individual users or small enterprises. However, these solutions have three drawbacks: 1) they support only single specific Webspace, 2) they can not ensure data confidentiality, and 3) they can not ensure data reliability. This paper introduces a distributed file system, the general file system (GFS), which integrates the advantage of distributed file system and the convenience of Webspace. GFS also integrates several heterogeneous spaces and promises the reliability and security. Besides, for users, it is easy to operate GFS through the interface provided by the virtual file system. At the end, the experiments result shows that GFS outperform than other solutions using Webspace.

A Scalable and Reliable Multicast Routing Protocol for Ad-hoc Wireless Networks

Multicasting is an essential service for ad-hoc wireless networks. In a multicasting environment with multiple senders, receivers or meeting members, traditional multicast routing protocols must pay great overhead for multiple multicast sessions. This work presents a scalable and reliable multicasting protocol for ad-hoc wireless networks. A virtual backbone is used as a shared structure for multiple sessions. A clustering scheme is used to reduce the routing path length. A novel scheme is developed to effectively multicast packets using forwarding gates. Furthermore, a lost packet recovery scheme is developed for reliable packet transmission. This scheme can be used to improve the reliability of traditional non-acknowledged multicasting approach. Experiments were conducted to evaluate the proposed multicasting scheme and the results demonstrate that our scheme outperforms other schemes in terms of packet delivery ratio, packet delivery time, control overhead, multicast efficiency, and cost effect. Furthermore, our approach is stable for networks with high mobility and the lost packet recovery scheme is cost-effective.

NimbleTransit: Public Transportation Transit Planning Using Semantic Service Composition Schemes

Advanced traveler information systems (ATIS) aim at collecting and disseminating helpful information to travelers. Among them there are systems providing public transit information as well as path planning services, called advanced public transportation systems (APTS). However, most modern APTSs maintained their own individual transportation service information in a non-sharable fashion, thus planning paths for large scope is difficult since there is no information exchanging methods for existing APTS. In addition, existing researches usually employ shortest path algorithms, and did not take advantages of other semantic information such as geographic locations, service information, etc., thus usually are not scalable well for large scope trip planning. This work proposes a semantic-based APTS framework for transit planning, where semantic Web-based service interfaces are specified for information exchanging, making it possible to integrate and organize heterogeneous data from various APTS and transportation enterprises. In addition, a semantic-based trip-planning scheme is designed to be used in NimbleTransit, where service information is aggregated in advance using semantic knowledge. Semantic service composition is then used to construct the path. A system prototype is implemented, and the results showed that the proposed scheme is indeed more effective and scalable than existing schemes.

TALONet: A power-efficient grid-based congestion avoidance scheme using multi-detouring technique in Wireless Sensor Networks

Traffic congestion avoidance is a critical issue associated with data routing in Wireless Sensor Networks (WSNs). Previous researches employ either traffic or resource control strategies as solutions. In this paper, we propose an energy-efficient grid-based traffic congestion avoidance scheme in WSNs, termed as TALONet. With our mechanism, the approaches applied to avoid congestion have three folds: 1) we use two different transmission power levels to alleviate the link-level congestion (LLC); 2) we also employ an effective buffer management approach to avoid node-level congestion (NLC); and 3) based on virtual grid frameworks, a multi-path detouring technique is used to increase the channel capacity for the congested traffic flows. Extensive simulation results show that our proposed TALONet scheme is superior to other existing protocols. Comparing to TARA [11], Backpressure, and naïve (without congestion control) schemes, the improvement on the number of dropped packets can be achieved to about 45%, 51%, and 80%, respectively.

CRINet: A secure and fault-tolerant data collection scheme using 3-way forwarding and group key management in wireless sensor networks

A critical security threat in a WSN is the compromising of sensor nodes. Not only can attackers use such vulnerability to eavesdrop on the dataflow, but could also inject bogus information into the network. However, most current secure data collection methods trade fault-tolerant ability for end-to-end protection, thus with poor performance. This work proposes CRINet, a secure and fault-tolerant data collection scheme with group key management mechanism. To achieve high reliability, sensing data would be transferred to the sink through multi-path. EBS is applied in CRINet for group key management in order to reduce re-key efforts. Simulation results demonstrate that CRINet scheme is superior in terms of data confidentiality and availability.

ZERO-conflict: a grouping-based approach for automatic generation of IPSec/VPN security policies

IPSec/VPN management is a complicated challenge, since IPSec functions correctly only if its security policies satisfy all administrated requirements. Computer-generated security policies tend to conflict with each other, which would causes network congestion or creates security vulnerability. Thus conflict resolving has become an issue. In this paper, a method to automatically generate policies is proposed. Instead of performing complicated conflict-checking procedures as most existing works do, the proposed Zero-Conflict algorithm is able to predict and avoid conflict in advance by using requirement groups and cut points techniques. Since policies are established without the need to perform backward conflict check, thus yielding a significantly less time-complexity, which is O(nlogn). Experimental results show that it maintains a satisfactorily minimal numbers of generated tunnels.

PyraNet: an efficient and reliable pyramidal wireless sensor network

In comparison to randomly deployed WSNs (Wireless Sensor Networks), pre-configured WSNs are superior in network performance for many aspects, including end-to-end delay time, data delivery ratio, and energy consumption. Several topologies concerning with pre-configured WSNs, such as grid, hexagonal, or de Bruijn, were proposed in past studies. The common flaws among them are that, the number of neighbors a node could have is so scarce as to significantly affect their fault-tolerance capabilities, and a longer network diameter often introduces a considerable transmission delay. In this paper, we thus propose an efficient and reliable network architecture, named as PyraNet, for pre-configured WSNs. In PyraNet, sensor nodes are first deployed as a pyramidal shape, and then a hypercube address allocation scheme is employed for its routing. Simulation results show that, for large-scale faulty networks, the proposed integrated architecture can achieve about 6%~14% improvement on data delivery ratio, compared to existing architectures. In addition, the energy consumption can also be reduced by 27%~61%, and thus effectively prolongs the network lifetime.