Youiti Kado

A hybrid centralized routing protocol for 802.11s WMNs

Wireless mesh networks (WMNs) are being widely accepted as a critical wireless access solution for various applications. Due to minimal mobility in mesh nodes, a backbone topology can be effectively maintained in WMN using a proactive routing protocol. In IEEE 802.11s standard, a tree-based routing (TBR) protocol is adopted as a viable proactive routing protocol for a WMN with user traffic flowing to/from a wired network through a root (i.e., a mesh portal). However, the performance of the TBR protocol degrades rapidly as the user traffic becomes dominated by intra-mesh traffic. The reason is that the routing path through the root even for intra-mesh traffic unnecessarily overloads the root. Furthermore, the TBR performance becomes more severe when the network size of WMN is large, which could lead to the huge amount of intra-mesh traffic towards the root. To overcome these problems, we propose a new routing mechanism, root driven routing (RDR) protocol, for the root to quickly determine the best-metric route for any source-destination pair of intra-mesh traffic. For inter-mesh traffic, the original TBR protocol is employed. Thus, the hybrid centralized routing protocol that combines TBR and RDR and is adaptive to all traffic scenarios. Our simulation results reveal that the proposed RDR protocol outperforms the TBR protocol with much lower average end-to-end delay and much higher packet delivery ratio for intra-mesh traffic. The simulation results also provide some insight into the right tradeoff between the TBR protocol and the RDR protocol to achieve the best performance of the hybrid centralized routing protocol for WMNs.

Hybrid Indoor Location Estimation System Using Image Processing and WiFi Strength

Recently, the service of cellular phone which is dependent on the location is spreading widely. Various techniques are suggested for the location estimation in indoor, however, indoor location estimation techniques have many subjects with a cost and an aspect of the accuracy. To deal with these subjects, we propose a quite new hybrid indoor location estimation method for paying attention to a smart phone with built-in wifi and camera. The proposal method is able to realized both highly accuracy of indoor location estimation and low cost by using the two-dimensional marker, wifi base stations, and the radio wave strength of adhoc communications. Verified by using simulation was able to demonstrate the effectiveness.

An efficient power supply system using phase control in 2D communication

The two-dimensional (2D) communication is a novel physical form of communication that utilizes the surface as a communication medium to provide data communication and power supply services to the devices placed on top of it. In the previous works, we have developed 2D communication systems that allow the devices to simultaneously perform both data and power transmission wherever it is placed on the 2D sheet. Instead of spreading the microwave thoroughly in the thin 2D sheet, we can also concentrate it only on the place where the device is put, by adjusting the phase of the multiple input signals. To largely strengthen the efficiency of power supply in the 2D communication, in this paper, we build up an efficient power supply system by using phase control to converge the microwave on a specific area in the 2D sheet, and evaluate its performance by measuring the output power over the developed 2D communication system.

Using game theory for power and rate control in wireless ad hoc networks

To attain an optimum network performance, a game theory approach is the best tools that may be used to model the interaction among independent devices in order to design the state-of-the-art communication protocol for wireless ad hoc networks, which are characterized by the complexity of mobility and traffic models, the dynamic topology, and the unpredictability of link quality. In this paper, we describe how various interactions in wireless ad hoc networks can be modeled as a game. To be more specific, we use a game-theoretic approach to specify how to efficiently use locally transmit power and assign optimally the transmission rate. The criterion of optimality is the stability of the underlying communications protocols, carrying out our proposed joint power and rate control scheme. By computer simulations, we investigate the performance of proposed scheme assuming the wireless ad hoc environment and show our simulation results in terms of utility, goodput, and power consumption.

High-accuracy positioning using phase difference of electrode array for two-dimensional communication sensor network (2DCSN)

The two-dimensional communication sensor network (2DCSN) is a novel physical form of communication that utilizes the surface as a communication medium to provide both data and power transmission services to the devices placed atop it. To enable 2DCSN to detect the position of sensor devices on the 2D communication sheet, we develop a simple and highly accurate position identifying method that maps phase differences measured at electrode array corresponding to a pilot signal sent by sensor device. We evaluate our proposed method by performing actual position measurement on a 30 cm × 30 cm area, where the phase differences are measured by eight array electrodes corresponding to 2.44GHz pilot signal. The experiment results reveal that our method can detect position at resolution of 2.5 cm square grid perfectly.

Efficient power transmission system using phase-conjugation of multiple inputs for 2D communication

The two-dimensional (2D) communication is a novel physical form of communication that utilizes the surface as a communication medium to provide both data and power transmission services. To efficiently transmit a relatively-large amount of electric power (several watts), we have developed a 2D communication system that concentrates the electric power on a specific spot by using phase control of multiple inputs. However, to find the optimal phases of the multiple inputs making the microwave converge on a specific spot in the 2D sheet, the prior knowledge of the devices position, and/or the pre-experiment measuring the output power, are needed. In wireless communication area, it is know that the retrodirective array scheme can efficiently transmit the power in a self-phasing manner, which uses the pilot signals sent by the devices. In this paper, we apply the retrodirective array scheme to the 2D communication system, and propose a power transmission scheme using the phase-conjugation of multiple inputs. To confirm the effectiveness of the proposal scheme, we evaluate its performance by computer simulation and realistic measurement. Both results show that the proposal scheme can achieve the retrodirectivity over the 2D communication system.

A Study of Wireless Mesh Network Routing Protocols for Push-to-Talk Traffic

Wireless mesh networks (WMNs) are becoming well-known as a new broadband Internet access technology through multihop transmission nowadays. With the tremendous popularity of the group communication, such as Push-to-Talk service, the need to deliver the traffic of push-to-talk over WMNs is becoming important. Since the push-to-talk traffic over WMNs is delay-sensitive traffic, a proactive routing protocol that keep routes continuously updated is ideally best-suited protocol. Among the proactive routing protocols, a tree-based routing (TBR) protocol is a viable routing protocol for WMNs because traffic that is directed to/from a wired network can be well-handled via a portal (a root). However, the performance of TBR protocol can be degraded rapidly when the number of group talking increases, which also leads to the intra-mesh traffics increases in the network. To mitigate this problem, we proposed a centralized tree-based routing protocol, which enables the root to provide the best metric route for intra-mesh traffics. In other words, the proposed protocol can disperse the intra-mesh traffics around the root when an overwhelming traffic volume occurred. Our simulation studies reveal that the proposed protocol outperforms both AODV and TBR protocols in terms of packet delivery ratio, average end-to-end delay, and data throughput as the number of active users becomes larger.

Digital scope on communication sheet for media interaction

This paper introduces an interface platform to visualize location-specific media on lightweight displays that are placed and moved over a two dimensional map. The position of each display in the 2D space is dynamically sensed. The media data are transmitted to the detected display accordingly via a newly invented communication sheet underneath the map. Users can move the display on the sheet to magnify and explore interesting spots or items, while the contents received are image and video at different levels of detail. The platform is multi-user oriented, power efficient, and capable of performing multi-channel wide bandwidth transmission. As a physical medium, the communication sheet provides a large 2D space for interaction that a flat screen and touch panel cannot achieve. We have done experiments on the designed platform for verifying its effectiveness in education and exposition. These experiments have demonstrated its promising features in multimedia presentation.

Power provision scheme considering shadowing effect for two-dimensional communication systems

Two-dimensional communication system (2DCS) is a novel communication system which utilizes surface of sheet as communication medium. 2DCS provides wireless power supply as well as safely and high-speed data transmission to sensor devices. However, how to suppress the standing wave effect to a minimum is still an open issue for 2DCS. In this study, we explore how the power distribution on sheet medium changes by the location of input coupler, and then compose a scheme of the power provision with multiple single or compound couplers where shadowing effect is considered to suppress the standing wave effect. Through simulation experiments, we evaluate the performance of proposed scheme to improve the power provision efficiency over 2DCS.

Deployment and experimental verification for data communication in heterogeneous wireless networks

With the growing interest in various wireless networks, the need for seamless connection and interoperability of heterogeneous wireless networks is becoming increasingly important. In this research, we focus on deploying the heterogeneous wireless networks, which consists of Wi-Fi networks and ZigBee networks. In heterogeneous wireless networks, data communication between pair of a sensor node and a mesh node is essential, meaning that the sensor node may receive data from the Wi-Fi device, and vice versa. We conduct some experiments to test and verify the interoperability issues, i.e., the coexistence radio interference and addressing of the heterogeneous wireless networks. We also investigate the effect of background traffic on the performance of heterogeneous wireless networks. The results reveal that both round-trip delay and packet loss increase as the background traffic increases.