Tetsuo Tsujioka

Collaborative movement of rescue robots for reliable and effective networking in disaster area

We investigated a collaboration scheme for rescue robots for reliable and effective operation of rescue systems using robots. The investigation focused on the collaborative movement of robots to maintain their wireless network. We propose classifying the robots into search robots and relay robots and using a behavior algorithm for their collaborative movement. According to the algorithm, search robots explore the disaster area and search for victims, whereas relay robots act as relay terminals within the network. Each robot classifies itself autonomously and repeatedly as the system operation progresses. We evaluated the performance of the victim detection system (a rescue system introduced in our previous paper) based on the proposed scheme by computer simulation. Its performance was improved compared with the case where every robot walked randomly in the disaster area and no classification occurred

Coordination of Rescue Robots for Real-Time Exploration Over Disaster Areas

A coordination procedure is proposed for a multi-robot rescue system that performs real-time exploration over disaster areas. Real-time exploration means that every robot exploring the area always has a communication path to human operators standing by a monitor station and that the communication path is configured by ad hoc wireless networking. The proposed system procedure consists of the autonomous classification of robots into search and relay types and behavior algorithms for each class of robot. Search robots explore the areas and relay robots act as relay terminals between search robots and monitor station. The rule of the classification and the behavior algorithm refer to the forwarding table of each robot constructed for ad hoc networking. Computer simulations are executed with the decision-theoretic approach as the exploration strategy of search robots.

Integrated operations of multi-robot rescue system with ad hoc networking

Integrated operations of a multi-robot rescue system are investigated. The system consists of a base station (BS) and autonomous mobile robots. A wireless ad hoc network connects all of them. Mobile robots coordinatedly explore a disaster area to detect victims and send their information to operators at the BS. Three related subjects are reviewed in this paper. First, autonomous chain network formations by rescue robots are investigated. The chain networks are essential for reconnaissance into distant spaces in disaster areas. Second, wireless QoS networks for multi-robot systems are investigated. This QoS scheme reserves the transmission bandwidth when a robot sends wideband signals to the BS through the chain network. Finally, wireless power supply networks for multi-robot systems are investigated. This scheme alleviates the problem of power source exhaustion of each robot and improves the reliability of multi-robot rescue systems.

Multiple-Length Variable-Weight Optical Orthogonal Codes for Supporting Multirate Multimedia Services in Optical CDMA Networks

Future optical code division multiple access (CDMA) networks should be designed for multirate and fully integrated multimedia services. In the conventional schemes, multilength optical orthogonal codes (OOCs) are designed to support multirate systems, while variable-weight OOCs are designed to support differentiated quality of service (QoS) for multimedia applications. In this paper, a novel class of optical signature codes; multiple-length variable-weight optical orthogonal codes (MLVW-OOC) is proposed for supporting multirate and integrated multimedia services in optical CDMA networks. The proposed MLVW-OOC has features that are easy to construct variable-weight codes and expanded to multiple-length codes. A construction method for designing MLVW-OOCs up to three levels of codes is discussed. The designed MLVW-OOCs can support differentiated requirements on data rates and QoS for several types of services in the networks. A code analysis for obtaining the value of cross-correlation constraints or multiple access interference (MAI) computation for several levels of codes is also suggested. The cross-correlation constraints of the proposed codes are better than the conventional codes such as multilength OOCs. Finally, the bit error probability performance of the two-level MLVW-OOC is evaluated analytically. The results show that the proposed MLVW-OOC can provide differentiated bit error probability performances for several combinations of data rates and QoS.

Design of strict variable-weight optical orthogonal codes for differentiated quality of service in optical CDMA networks

Variable-weight optical orthogonal codes (VW-OOCs) are one of the alternative designs for providing differentiated quality of service (QoS) at the physical level in optical CDMA (OCDMA) systems. In this paper, we address two novel designs for strict VW-OOCs which can guarantee the code correlation value of one. The proposed strict VW-OOCs enable many types of data transmission to be supported over OCDMA networks. Two algorithms for new codes are presented, where a number of codewords and a number of different code weights can be selected. The designs of strict VW-OOCs with several different code weights are discussed. An evaluation method for the new codes is presented; this considers intervals used for all codewords in each code set and offers a comparison with those of conventional codes. The correlation constraints of the proposed codes, based on the used intervals, are more strict than for some conventional codes. In addition, the bit error probability performance of the proposed codes in an OCDMA network with a triplet-service is evaluated analytically. Results show that the proposed codes can allow the differentiated QoS to support multi-service in OCDMA networks.

Design of Reconfigurable Multiweight Wavelength-Time Optical Codes for Secure Multimedia Optical CDMA Networks

Multiweight optical codes are one of the alternative designs for differentiated quality-of-service (QoS) in multimedia optical CDMA (OCDMA) networks. In this paper, we address the design of reconfigurable multiweight wavelength-time optical codes that lead to secure multimedia transmission in OCDMA networks. The proposed multiweight wavelength-time optical codes are constructed based on quasigroups (QGs) for wavelength hopping and one-dimensional multiweight optical orthogonal codes (MWOOCs) for time spreading, then called QG/MWOOCs. Both QGs and MWOOCs are randomly generated by computer search. As a result, the proposed QG/MWOOCs have many different code set groups which differ in both time and wavelengths positions. Furthermore, a secure network is suggested by employing reconfigurable encoders/decoders array waveguide gratings (AWGs)-based, which allow the users to change their codewords patterns to protect against eavesdropping. Finally, the degree of security which may provide by the proposed scheme is analyzed. The results show that the proposed scheme offers both differentiated QoS and differentiated quality-of-security (QoSec) in multimedia OCDMA networks.

Development of a real-time vital data collection system from players during a football game

In order to plan effective training menus and avoid injuries and diseases, vital signs monitoring for athletes during training and game is essential, where a key issue is how to collect vital data reliably and in real-time from many people spread in a large field. To realize such a real-time vital data monitoring system, we developed prototype wireless vital sensor nodes, and conducted twice field experiments to evaluate the packet success rate (PSR), where we put the sensor nodes to the waists of 22 players and collected packets from all of them during a football game. In this paper, we present the detail of the real-time vital data collection system composed of the prototype sensor nodes and data collection nodes, and discuss the experimental results in terms of PSR and diversity gain.

Autonomous chain network formation by multi-robot rescue system with ad hoc networking

The autonomous chain network formation by multi-robot rescue system is investigated. Chain networks connecting a base station and rescue robots are essential to reconnoiter distant spaces in disaster areas. The chains must be formed to assure communications among them and must be transformed if the target of exploration changes. These formations must be executed by autonomous movements of robots from reliable viewpoints in rescue operations. As the basis of their movements, we adopt autonomous classification of robots into search robots and relay robots. They act according to the behavior algorithms of each class of robot to form chain network threading the path to the distant spaces. The rule of the classification and the behavior algorithm refer forwarding table of each robot constructed for ad hoc networking. The results of simulations show that chain networks are formed and transformed by rescue robots appropriately for their reconnaissance to distant spaces even though three spaces exist beyond different corridors stemming from the safety zone where base station is established.

OPN02-1: Multiple-Length Variable-Weight Optical Orthogonal Codes for Multi-Rate Multi-Quality Optical CDMA Systems

A new class of optical signature codes; multiple-length variable-weight optical orthogonal codes (MLVW-OOC) is proposed for multi-rate multi-quality optical CDMA systems. The proposed codes are more flexible in codelength and codeweight with low correlation properties to accommodate many different types of services and many different levels of data rates in the systems. The code analysis for obtaining the exact value of maximum cross-correlation function or multiple-access interference (MAI) computation for several levels of codes is also suggested. Finally, the bit error probability performance of the proposed codes for two-level (i.e., two different lengths and weights) is evaluated analytically in this paper. The result shows that the proposed MLVW-OOC can provide differentiated performance for several combinations of rates and qualities.

Clinical tests and evaluations of a Wireless ECG sensor for realization of ubiquitous health care systems

This paper introduces the concept of an online medical diagnosis system for ubiquitous health care using a wireless ECG sensor. To confirm the feasibility ofthe system, we conducted clinical tests by 67 subjects with a wireless ECG sensor and a Holter ECG monitor simultaneously for comparison purpose. We made five types of evaluations such as analyses on data loss rate, burst data loss length, ECG waveforms comparison, normalized cross-correlation and heart rate variability (HRV) by RR50. The results show that, as long as the sensed data are successfully received at a receiver, the wireless ECG sensor has a comparable performance with the Holter ECG monitor.