Wen-Hwa Liao

A TDMA-based bandwidth reservation protocol for QoS routing in a wireless mobile ad hoc network

This paper considers the bandwidth reservation problem in a mobile ad hoc network (MANET) to support QoS (quality-of-service) routing. We approach this problem by assuming a common channel shared by all hosts under a TDMA (time division multiple access) channel model. Existing solutions have addressed this problem by assuming a stronger multi-antenna model, where the bandwidth of a link is independent of the transmitting/receiving activities of its neighboring links, or a less strong CDMA-over-TDMA channel model, where the use of a time slot on a link is only dependent on the status of its one-hop neighboring links. While more practical and less costly, using a TDMA model needs to face the challenge of radio interference problems. In this paper, we propose a new protocol that can reserve routes by addressing both the hidden-terminal and exposed-terminal problems. The protocol can conduct accurate bandwidth calculation while performing route discovery. Simulation results are presented to verify how this new protocol performs.

A Multi-path QoS Routing Protocol in a Wireless Mobile ad Hoc Network

A mobile ad hoc network (MANET) is one consisting of a set of mobile hosts capable of communicating with each other without the assistance of base stations. This paper considers the QoS (qualityof-service) routing problem in a MANET. We propose an on-demand protocol for searching for a multi-path QoS route from a source host to a destination host in a MANET, where a multi-path is a network with a source and a sink satisfying certain bandwidth requirement. Existing works all try to find a uni-path to the destination. The basic idea is to distribute a number of tickets from the source, which can be further partitioned into sub-tickets to search for a satisfactory multi-path. Through simulations, we justify that the value of our multi-path protocol is on its flexibility: (i) when the network bandwidth is very limited, it can offer a higher success rate to find a satisfactory QoS route than those protocols which try to find a uni-path, and (ii) when the network bandwidth is sufficient, it can perform almost the same as those protocols which try to find a uni-path (in both routing overhead and success rate).

Data aggregation in wireless sensor networks using ant colony algorithm

Data aggregation is important in energy constraint wireless sensor networks which exploits correlated sensing data and aggregates at the intermediate nodes to reduce the number of messages exchanged network. This paper considers the problem of constructing data aggregation tree in a wireless sensor network for a group of source nodes to send sensory data to a single sink node. The ant colony system provides a natural and intrinsic way of exploring search space in determining data aggregation. Moreover, we propose an ant colony algorithm for data aggregation in wireless sensor networks. Every ant will explore all possible paths from the source node to the sink node. The data aggregation tree is constructed by the accumulated pheromone. Simulations have shown that our algorithm can reduce significant energy costs.

A sensor deployment approach using glowworm swarm optimization algorithm in wireless sensor networks

A wireless sensor network is composed of a large number of sensor nodes that are densely deployed in a sensing environment. The effectiveness of the wireless sensor networks depends to a large extent on the coverage provided by the sensor deployment scheme. In this paper, we present a sensor deployment scheme based on glowworm swarm optimization (GSO) to enhance the coverage after an initial random deployment of the sensors. Each sensor node is considered as individual glowworms emitting a luminant substance called luciferin and the intensity of the luciferin is dependent on the distance between the sensor node and its neighboring sensors. A sensor node is attracted towards its neighbors having lower intensity of luciferin and decides to move towards one of them. In this way, the coverage of the sensing field is maximized as the sensor nodes tend to move towards the region having lower sensor density. Simulation results show that our GSO-based sensor deployment approach can provide high coverage with limited movement of the sensor nodes.

SF-MAC: A Spatially Fair MAC Protocol for Underwater Acoustic Sensor Networks

Underwater acoustic sensor networks (UWSN) have attracted a lot of attention recently. The long propagation delay of acoustic signals in UWSN causes spatial-temporal uncertainty making spatial fairness in UWSN a challenging problem. Time of arrival of the packets depends on both the sending time and the distance between the transmitter and the receiver. Hence, it is difficult to avoid collision and guarantee the fairness of transmission in underwater environment. In this paper, we propose a spatially fair multiple access control (SF-MAC) protocol called SF-MAC in UWSN. The SF-MAC can avoid collision by postponing the clear-to-send frame equal to period of request-to-send (RTS) contention period. The receiver collects RTSs from all the contenders during the RTS contention period and calculates the potential sending time of each of contender. It determines the earliest transmitter with a probability rule that compares with the first RTS. In case of multiple contenders, the SF-MAC can maintain a more exact order of transmission to achieve fairness of transmission. Finally, we present a comprehensive performance study via simulations. The results show that SF-MAC can perform better than existing MAC schemes (such as MACA, MACA-U, and T-Lohi) in terms of the spatial fairness and network throughput.

Ant colony optimization based sensor deployment protocol for wireless sensor networks

Research highlights? We consider the problem of sensor deployment to achieve complete coverage of the service region and maximize the lifetime of the network. ? We model the deployment problem as the multiple knapsack problem. ? Based on ACO algorithm, we proposed a deployment scheme to prolong the network lifetime, while ensuring complete coverage of the service region. Sensor deployment is one of the most important issues in wireless sensor networks, because an efficient deployment scheme can reduce the deployment cost and enhance the detection capability of the wireless sensor networks. In addition, it can enhance the quality of monitoring in wireless sensor networks by increasing the coverage area. Ant colony optimization (ACO) algorithm provides a natural and intrinsic way of exploration of search space for multiple knapsack problem (MKP). In this work, we consider the problem of sensor deployment to achieve complete coverage of the service region and maximize the lifetime of the network. We model the deployment problem as the multiple knapsack problem. Based on ACO algorithm, we proposed a deployment scheme to prolong the network lifetime, while ensuring complete coverage of the service region. The simulations show that our algorithm can prolong the lifetime of the network.

A Multi-Path QoS Routing Protocol in a Wireless Mobile Ad Hoc Network

A mobile ad hoc network (MANET) is one composed of a set of mobile hosts capable of communicating with each other without the assistance of base stations. This paper considers the QoS (quality-of-service) routing problem in a MANET, which is important for many real-time multimedia applications. We propose an on-demand protocol for searching for a multi-path QoS route from a source host to a destination host in a MANET, where a multi-path is a network with a source and a sink satisfying certain bandwidth requirement. Existing works all try to find a uni-path to the destination. The basic idea is to distribute a number of tickets from the source, which can be further partitioned into subtickets to search for a satisfactory multi-path. Through simulations, we justify that the value of our multi-path protocol is in its flexibility: (i) when the network bandwidth is very limited, it can offer a higher success rate to find a satisfactory QoS route than those protocols which try to find a uni-path, and (ii) when the network bandwidth is sufficient, it can perform almost the same as those protocols which try to find a uni-path (in both routing overhead and success rate).

A grid-based dynamic load balancing approach for data-centric storage in wireless sensor networks

In many data-centric storage techniques, each event corresponds to a hashing location by event type. However, most of them fail to deal with storage memory space due to high percentage of the load is assigned to a relatively small portion of the sensor nodes. Hence, these nodes may fail to deal with the storage of the sensor nodes effectively. To solve the problem, we propose a grid-based dynamic load balancing approach for data-centric storage in sensor networks that relies on two schemes: (1) a cover-up scheme to deal with a problem of a storage node whose memory space is depleted. This scheme can adjust the number of storage nodes dynamically; (2) the multi-threshold levels to achieve load balancing in each grid and all nodes get load balancing. Simulations have shown that our scheme can enhance the quality of data and avoid hotspot of the storage while there are a vast number of the events in a sensor network.

Peer to Peer Botnet Detection Using Data Mining Scheme

Botnet was composed of the virus-infected computers severely threaten the security of internet. Hackers, firstly, implanted virus in targeted computers, which were then commanded and controlled by them via the internet to operate distributed denial of services (DDoS), steal confidential information, distribute junk mails and other malicious acts. By imitating P2P software, P2P botnet used multiple main controller to avoid single point of failure, and failed various misuse detecting technologies together with encryption technologies. Differentiating from the normal network behavior, P2P botnet sets up numerous sessions without consuming bandwidth substantially, causing itself exposed to the anomaly detection technology. The data mining scheme was tested in real internet to prove its capability of discovering the host of P2P botnet. Crucially, the research applied the original dissimilarity of P2P botnet differing from normal internet behaviors as parameters of data mining, which were then clustered and distinguished to obtain reliable results with acceptable accuracy.

On avoiding RTS collisions for IEEE 802.11-based wireless ad hoc networks

The paper proposes an RCA (RTS collision avoidance) MAC protocol to reduce RTS collisions for IEEE 802.11-based mobile ad hoc networks (MANETs). RTS/CTS exchanging is used for the resolution of the hidden terminal problem. However, the paper shows that, even the backoff counters of two stations are different, RTS frames are also collided to each other due to the hidden terminal problem. The situation would be getting worse in high traffic load or in a dense network. RTS collisions not only result in the following CTS or ACK collisions, but also induce false blocking problem, even dead locks of transmissions. To address the above problems, an RCA MAC protocol is proposed to reduce RTS collisions. The RCA protocol utilizes a narrow band, called the tone channel, to announce the RTS transmission in advance in order to preclude the RTS transmissions of two-hop neighbors. To reduce the channel and hardware overhead, an improvement to the RCA protocol is also devised, which only uses a single channel and one transceiver to reduce RTS collisions. The RCA protocol provides a type of fast collision detection and decreases the probability of RTS collisions, which is benefit for RTS/CTS exchange scheme. Meanwhile, the RCA protocol can reduce the retransmission cost and have lower control overhead than that of IEEE 802.11 DCF. In addition, simulation results verify the advantages of the RCA protocol in comparison with IEEE 802.11 DCF.