Yasuhisa Takizawa

Tree-Based Routing Protocol for Cognitive Wireless Access Networks

A cognitive wireless network is mostly deployed as wireless access network to optimize the utilization efficiency of radio resource by using multiple wireless systems. In such deployment, the network topology based on a tree structure can be efficiently and quickly constructed among the cognitive terminals (CT) by using the cognitive base station (CBS) as a root, to support the multihop communication. However, the original tree-based routing (TBR) protocol is designed to handle a single wireless system such as IEEE802.11a or lib, and thus can not be applied to the cognitive networks configured with multiple wireless systems, which may have the different bandwidths and transmission ranges. To solve this problem, we propose in this paper an efficient and practical protocol, called cognitive tree-based routing (CTBR) protocol, which extends and significantly enhances the ability of the known TBR protocol to enable it to support multiple wireless systems such as IEEE802.11g and IEEE802.11j. Simulation results reveal that our proposed CTBR protocol that utilizes the cognitive-aware link metric to select a route with the best end-to-end metric and an interface with the least local load for any source-destination pair, achieves much higher performance than the utilization of normal metric associated with the hop count.

Traffic Control for Cognitive Wireless Networks Composed of IEEE802.11 and IEEE802.16

In emerging wireless communication environments, a variety of wireless systems will coexist using a variety of applications. On the other hand, concern is increasing that the growing use of wireless systems will exhaust finite radio resources. Cognitive radio, which aims to optimize the utilization efficiency of radio resources by combining multiple wireless systems, has been proposed as a solution to this problem. In a cognitive wireless network composed of nodes equipped with multiple wireless systems, we have proposed a traffic control method that decreases delay and increases throughput by using wireless link aggregation. In this paper, our proposed method is presented, and its performance is shown through evaluation with IEEE802.11 and IEEE802.16.

Packet Allocation for Efficient Use of Multiple Wireless Links in Cognitive Radio Networks

Recently, the use of wireless systems as cellular phones, PHS, Wi-Fi, and WiMAX has been expanding. Meanwhile the resources of wireless radio systems are finite. Therefore, there is concern about exhausting these resources due to their expanded growth. The cognitive radio networks have been proposed to resolve this problem. We previously proposed cognitive radio network system architecture, which includes a novel intermediate communication layer, the Cognitive Convergence Layer (CCL). To efficiently use the capability of each wireless interface, CCL must opportunely allocate input traffic to wireless interfaces. In this paper, we propose the Resource Time Sharing Algorithm (RTSA), which is a new packet allocation algorithm for high performance bandwidth aggregation. We have conducted extensive simulations to evaluate the RTSA performance in two different scenarios. As a result of comparisons with other traditional methods, we can show that RTSA achieves higher aggregated throughput and packet delay performance.

Self-Organizing Location Estimation Method Using Received Signal Strength

The location information of ubiquitous objects is one of the key issues for context-aware systems. Therefore, several positioning systems to obtain precise location information have been researched. However, they have scalability and flexibility problems because they need completely configured space with a large number of sensors. To avoid the problems, we proposed a self-organizing location estimation method that uses ad hoc networks and Self-Organizing Maps and needs no prepared space with a large number of sensors. But, as in other similar precise localization methods, the proposed method needs advanced distance measurements unavailable to conventional wireless communication systems. In this paper, the self-organizing location estimation methods modification for distance measurement that uses received signal strength available to conventional wireless communication systems but which fluctuates uncertainly, is described and location estimation accuracy with the modified method is shown.

Cloud-based Self-Organizing Localization for wireless sensor networks in mixture environments of LOS and NLOS

Wireless sensor networks (WSNs) are an essential technology for Internet of Things (IoT) and Machine-to-Machime (M2M), which attempt to accommodate physical things on the Internet. WSNs are presumably applied in environments where a diverse space contains obstacles. In radio propagation, the space is the mixture space of Line-of-Sight (LOS) and Non-Line-of-Sight (NLOS), and the WSN topology is anisotropic. We previously proposed a Self-Organizing Localization (SOL), which is a localization applied to Self-Organizing Maps. A SOL is capable of estimating accurate node location with only neighbor topology information. However, it suffers from the following two issues: misestimation occasionally occurs in the LOS/NLOS mixture space and the amount of inter-node communication increases owing to the iteration exchanges of node locations between nodes. In this paper, we propose a cloud computing-based SOL that solves the above issues.

Node localization for sensor networks using Self-Organizing Maps

The localization of sensor node is one of the key issues for sensor network systems. Therefore, several localization systems to obtain precise location information have been researched. However, they need completely configured space using a large number of anchor nodes of which location are well known, and are not suitable for sensor networks. To avoid the problems, we proposed the node localization method based on Self-Organizing Maps and needs no prepared space with a large number of anchor nodes. But, as in other similar precise localization methods, the proposed method needs advanced distance measurements unavailable in conventional sensor node systems. In this paper, the modification of the self-organizing localization for distance measurement that uses received signal strength available in conventional sensor node systems is described and its location estimation accuracy is shown.

Packet distribution for complex wireless access route using IEEE802.11/802.16 and its field trial

The diversification of wireless communication usage has been proceeding rapidly with the diffusion of cellular phones, WiFi and WiMAX. In the emerging wireless communication environments, diverse wireless systems coexist. On the other hand, there is increasing concern that the growing use of wireless systems will exhaust the finite wireless resources. To solve this problem, we aim to optimize the utilization of wireless resources by combining communications among multiple wireless interfaces. In this paper, we propose a packet distribution for complex access route combining IEEE802.11/802.16 wireless links in parallel and tandem, and show its performance in field trial. The proposed method improves delay and throughput in the network by taking full advantages of wireless media diversity.

Traffic control for communications using multiple IEEE802.11 wireless interfaces

The diversification of wireless communication usage has been proceeding rapidly with the diffusion of cellular phones and WiFi. In the emerging wireless communication environments, various wireless systems coexist and various applications can be simultaneously used. On the other hand, there is increasing concern that the growing use of wireless systems will exhaust the finite wireless resources. Cognitive radio has been proposed as a solution to this problem. Cognitive radio aims to optimize the utilization of wireless resources by combining communications among multiple wireless interfaces. In this paper, we propose a traffic control for communications using multiple IEEE802.11 wireless interfaces. The proposed method optimizes the utilization efficiency of an IEEE802.11 wireless cell based on cell cost, which shows the load of the cell and then improves delay and throughput in the network.

Self-Organizing Localization for Wireless Sensor Networks based on RSSI

The localization of sensor nodes is one of the key issues for sensor network systems. Therefore, to obtain precise location information, several localization systems have been researched. However, they need an arranged space using a large number of anchor ...

Self-Organizing Location Estimation Method using Ad-hoc Networks

Several positioning systems to obtain precise location information have been researched. However, they have scalability and flexibility problems because they need completely configured space with a large number of sensors. To avoid the problems, we have proposed a self-organizing location estimation method that uses ad hoc networks and Self- Organizing Maps and needs no prepared space with a large number of sensors. In this paper and our demonstration, the proposed method and its characteristic are presented.