Language：English   Publisher：Japan Society for Simulation Technology  

<p>Information floating (IF) is an invisible infrastructure in which mobile nodes can receive information that seems to be floating in a designated area. IF is realized by successively transferring information from a mobile node to other nodes in an epidemic manner with wireless direct communication in designated areas. IF has many potential applications, such as advertisements for local communities, specific communication for disasters, alert systems for pedestrians and vehicles, and so on. To design alert systems on a road, some articles theoretically analyze the mean lifetime of the floating in a one-dimensional street. In past researches, however, identical traffic volume and velocity were assumed in all the lanes. The difference in traffic volume between lanes and the correlation between traffic volume and velocity were omitted for simplicity. In this paper, we recognize the importance of these two factors and reveal their effects on the mean lifetime of IF with a new theoretical method. In it, we consider not only the effects of the above two factors but also the complicated features of IF that were ignored in previous methods.</p>

DOI： 10.15748/jasse.3.97

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

Information floating delivers information to mobile nodes in specific areas without meaningless spreading of information by permitting mobile nodes to directly transfer information to other nodes by wireless links in designated areas called transmittable areas. In this paper, we assume that mobile nodes change direction at intersections after receiving such information as warnings and local advertisements and that an information source remains in some place away from the transmittable area and continuously broadcasts information. We analyze performance of information floating under these assumptions to explore effects of the behavior changes of mobile nodes, decision deadline of the behavior change, and existence of a fixed source on information floating. We theoretically analyze the probability that a node cannot receive information and also derive the size of each transmittable area so that this probability is close to desired values.

DOI： 10.1587/transfun.E99.A.1529

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Other Link： http://dblp.uni-trier.de/db/journals/ieicet/ieicet99a.html#journals/ieicet/NakanoM16

Language：English   Publisher：Japan Society for Simulation Technology  

<p>During large-scale disasters, some regions can become isolated from critical information exchanges due to problems with communication infrastructures. In this paper, we consider information exchange among isolated shelters in such cases using epidemic transmission, which distributes information without infrastructure by direct communication between nodes and their movements. As mobile nodes for epidemic transmission, we consider transport vehicles that are leaving a distribution center to deliver relief goods to shelters. These transport vehicles receive information from the shelters and distribute it to other shelters together with the relief goods. As a result, information is shared by the shelter. Suppose that transport vehicles move along different traveling paths and exchange information at the distribution center. Transport vehicles can also get new information from other transport vehicles while they wait for new relief goods to arrive at the distribution center. Transport vehicles might be able to receive more new information by waiting for a longer time, although such additional waiting time causes a greater delay of the delivery of relief goods. In this paper, we consider the relation between relief goods delivery and information sharing by transport vehicles with epidemic transmission and analyze how the additional waiting time affects the delay of relief goods and the time needed for information sharing by computer simulation.</p>

DOI： 10.15748/jasse.3.114

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Language：Japanese   Publisher：Japan Society for Simulation Technology  

&amp;nbsp;&amp;nbsp;Epidemic transmission can distribute information over the service area by direct wireless communication between mobile nodes and mobility of the mobile nodes. By using epidemic transmission repeatedly, we can send information to mobile nodes entering a specific area. This is called Information Floating (IF). In this paper, we consider IF to distribute an advertisement to guide customers to a target place (shopping place). The purpose of advertisement delivery is to deliver an advertisement to mobile nodes before they arrive at the target place and to guide mobile nodes to the target place. We divide a service area into some small areas, and consider how to decide the areas where the advertisement is virtually floated. To do this, we use probe data such as traffic volume entering each small area. We consider three methods to decide the areas for IF, and evaluate these methods by computer simulation. Two of the three methods use probe data. In computer simulation, we consider uniform and non-uniform traffic distributions, and small and large traffic volumes to assume various situations. We show effective methods in the various situations.&lt;br&gt;

DOI： 10.11308/tjsst.7.85

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

Delay Tolerant Network (DTN) has been emerged to support the network connectivity of the disruptive networks. A variety of routing methods have been proposed to reduce the latency for message delivery. PROPHET was proposed as a probabilistic routing that utilizes history of encounters and transitivity of nodes, which is computed as contact probability. While PROPHET improves the performance of DTN due to contact probability, contact probability is just one parameter reflecting the mobility pattern of nodes, and further study on utilizing contacting information of mobility pattern is still an important problem. Hence, in this paper, we try to improve routing for DIN by using a novel metric other than contact probability as mobility information. We propose the routing protocol to use mean residual contact time that describes the contact period for a given pair of nodes. The simulation results show that using the mean residual contact time can improve the performance of routing protocols for DTN. In addition, we also show in what situations the proposed method provides more efficient data delivery service. We characterize these situations using a parameter called Variation Metric.

DOI： 10.1587/transinf.E95.D.451

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Other Link： http://dblp.uni-trier.de/db/journals/ieicet/ieicet95d.html#journals/ieicet/KimNMSP12

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WORLD SCIENTIFIC PUBL CO PTE LTD  

In ad hoc networks, the analysis of connectivity performance is crucial. The waiting time to deliver message M from source S to destination D is a measure of connectivity that reflects the effects of mobility, and some approximate methods have been proposed to theoretically analyze the mean waiting time in one-dimensional ad hoc networks that consist of mobile nodes moving along a street. In this paper, we extend these approximate methods to analyze the mean waiting time in two-dimensional networks with a lattice structure with various flows of mobile nodes. We discuss how the mean waiting times behave in such complicated street networks and how to approximate two kinds of mean waiting times. We show that our approximate methods can successfully compute the mean waiting times for even traffic patterns and roughly estimate them for uneven traffic patterns in two-dimensional lattice networks. In these analyses, we consider two shadowing models to investigate how shadowing affects the waiting time. We also discuss the effect of different positions of S on the mean waiting time.

DOI： 10.1142/S0218126610007006

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

Analysis of waiting time to deliver a message M from a source S to a destination D is deeply related to connectivity analysis, which is an important issue in fundamental studies of mobile multi-hop networks. In [1], we compared the mean waiting times of two methods to deliver M with the mean value of the minimum waiting time. The mean minimum waiting time was obtained by computer simulation because theoretical analysis of this mean is not easy, although another two methods were analyzed theoretically. In this paper, we propose an approximate method to theoretically analyze the mean minimum waiting time in a one-dimensional street network, and show that this method gives a good approximation of the mean minimum waiting time. Also, we consider shadowing and change of directions of mobile nodes at intersections as negative factors arising in two-dimensional street networks. We extend the above method to compute the mean minimum waiting time considering these factors, and discuss how the mean minimum waiting time is affected by these factors.

DOI： 10.1587/transfun.E92.A.2236

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Other Link： http://dblp.uni-trier.de/db/journals/ieicet/ieicet92a.html#journals/ieicet/NakanoMOSS09

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

In multi-hop wireless networks, since source and destination nodes usually have some candidate paths between them, communication quality depends on the selection of a path from these candidates. For network design, characterizing the best path is important. To do this, in [1], [2], we used expected transmission count (ETX) as a metric of communication quality and showed that the best path for ETX is modeled by a path that consists of links whose lengths are close to each other in static one-dimensional multi-hop networks with a condition that the ETX function of a link is a convex monotonically increasing function. By using the results of this characterization, a minimum route ETX can be approximately computed in a one-dimensional random network. However, other metrics fail to satisfy the above condition, like medium time metric (MTM). In this paper, we use MTM as a metric of communication quality and show that we cannot directly apply the results of [1], [2] to the characterization of the best path for MTM and the computation of minimum route MTM. In this paper, we characterize the path that minimizes route MTM in a different manner from [1], [2] and propose a new approximate method suitable for the computation of minimum route MTM.

DOI： 10.1587/transfun.E92.A.2227

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Other Link： http://dblp.uni-trier.de/db/journals/ieicet/ieicet92a.html#journals/ieicet/MiyakitaNSS09

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

In multi-hop Wireless networks. communication quality depends oil the selection of it path between Source and destination nodes from several candidate paths. Exploring low path selection affects communication quality is important to characterize the best path. To do this. in [1]. We used expected transmission count (ETX) as it metric of communication quality and theoretically characterized minimum route ETX, which is the ETX of the best path, in it static one-dimensional random multi-hop network. In this paper. we characterize minimum route ETX in static two-dimensional multi-hop networks. We give the exact formula of minimum route ETX in it two-dimensional network. assuming that nodes are located with lattice structure and that the ETX function satisfies three conditions for simplifying analysis. This formula can be Used as all upper bound of minimum route ETX Without two of the three conditions. We show that this upper bound is Close to minimum route ETX by comparing it with simulation results. Before deriving the formula, We also give the formula for a one-dimensional network where nodes are located at constant intervals. We also Show that minimum route ETX in the lattice network is close to that in it two-dimensional random network if the node density is large. based on a comparison between the numerical and simulation results.

DOI： 10.1587/transcom.E92.B.745

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Other Link： http://dblp.uni-trier.de/db/journals/ieicet/ieicet92b.html#journals/ieicet/MiyakitaNMSS09

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

In multi-hop wireless networks, communication quality depends on the route from a source to a destination. In this paper, we consider a one-dimensional multi-hop wireless network where nodes are distributed randomly and theoretically analyze the relation between communication quality and routing policy using a measure called the Expected Transmission Count (ETX), which is the predicted number of data transmissions required to send a packet over that link, including retransmissions. First, we theoretically analyze the mean length of links, the mean number of hops, and the mean route ETX, which is the sum of the ETXs of all links in a route, of Longest Path Routing (LPR), and Shortest Path Routing (SPR). Second, we propose Adjustable Routing (AR), an approximation to Optimum Routing (OR), which minimizes route ETX. We theoretically compute the above characteristic values of AR. We also theoretically compute a lower bound of the mean route ETX of OR. We compare LPR, SPR, and OR using the results of analyses and show differences between these algorithms in the route ETX.

DOI： 10.1093/ietcom/e91-b.8.2533

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

In mobile multi-hop networks, a source node S and a destination node D sometimes encounter a situation where there is no multi-hop path between them when a message M, destined for D, arrives at S. In this situation, we cannot send M from S to D immediately; however, we can deliver M to D after waiting some time with the help of two capabilities of mobility. One of the capabilities is to construct a connected multi-hop path by changing the topology of the network during the waiting time (Capability 1), and the other is to move M closer to D during the waiting time (Capability 2). In this paper, we consider three methods to deliver M from S to D by using these capabilities in different ways. Method 1 uses Capability I and sends M from S to D after waiting until a connected multi-hop path appears between S and D. Method 2 uses Capability 2 and delivers M to D by allowing a mobile node to carry M from S to D. Method 3 is a combination of Methods 1 and 2 and minimizes the waiting time. We evaluate and compare these three methods in terms of the mean waiting time, from the time when M arrives at S to the time when D starts receiving M, as a new approach to connectivity evaluation. We consider a one-dimensional mobile multi-hop network consisting of mobile nodes flowing in opposite directions along a street. First, we derive some approximate equations and propose an estimation method to compute the mean waiting time of Method 1. Second, we theoretically analyze the mean waiting time of Method 2, and compute a lower bound of that of Method 3. By comparing the three methods under the same assumptions using results of the analyses and some simulation results, we show relations between the mean waiting times of these methods and show how Capabilities 1 and 2 differently affect the mean waiting time.

DOI： 10.1093/ietcom/e91-b.6.1874

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：日本シミュレーション学会  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Recently, Electric Vehicle (EV) is considered as one of important technologies of smart grid; however, there are some problems for spreading EVs. One of these problems is that charging the battery of an EV needs a longer time than refueling of gasoline vehicles. To overcome these problems, for example, some local governments in Japan started projects in which restaurants and shops rent outlets for charging EV of their customers while doing something such as eating or shopping. Under such projects, if an EV driver knows information on chargers such as the locations of chargers and the mean waiting times for using chargers, the driver may be able to reduce the time spent only for charging (pure waiting time). In this paper, we theoretically analyze the mean of the pure waiting time in cases where drivers know and do not know the above information. From the numerical results, we discuss what information is important to reduce the pure waiting time.

DOI： 10.1109/ISADS.2015.50

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Recently, Electric Vehicle (EV) is considered as an important technology; however, there are some problems for spreading EVs. One of these problems is that charging the battery of an EV needs a longer time than refueling of gasoline vehicles. To overcome these problems, for example, some local governments in Japan started projects in which restaurants and shops rent outlets for charging EV of their customers during eating or shopping. On the other hand, other local government in Japan has developed a system to reserve chargers by sharing information on usage of chargers. In this paper, we consider the above service to rent outlets during eating or shopping, and discuss how methods to reserve chargers affect the waiting time for charging EVs.

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For wide popularization of Electric Vehicles (EVs), there are many problems to be overcome. One of the problems is that charging the battery of an EV needs a much longer time than refueling of gasoline vehicles. Efficient and wide deployment of charging stations is also an important problem. To overcome these problems, some local governments in Japan started projects to develop a system in which customers visiting commercial facilities charge batteries of EV during doing something at the commercial facilities (i.e. shopping, eating). In this system, a customer does not feel being kept waiting while doing something, and as a result, the system can virtually reduce a customer&#039;s time spent only for charging. In this paper, we consider efficient location of battery chargers to commercial facilities in this system. To do this, we propose some location methods considering popularity of the facilities, and evaluate performance of the proposed methods.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Japan Society for Simulation Technology  

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This paper considers a network problem in charging infrastructure for electric vehicles (EVs). It generally takes a longer time to charge the empty battery of an EV than refueling of gasoline vehicles. It is not easy to actually reduce the waiting time for charging. However, if charging is done during shopping or eating, the charging time is no longer the waiting time. Of course, we may sometimes have to wait a longer time to charge batteries than shopping time to prevent running out of the batteries during the next drive. This means that we have a trade off between the extra waiting time and possibility to run out of battery. In this paper, we theoretically consider properties of this trade off and theoretically analyze characteristics of the extra waiting time needed to guarantee that an EV does not run out of battery in a drive. We discuss effects of some factors such as density of charging stations, the number of outlets in each station, the number of waiting cars, and so on. © 2011 IEEE.

DOI： 10.1109/SGMS.2011.6089020

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DOI： 10.1109/ictc.2010.5674826

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In multi-hop wireless networks, we often encounter a situation where there are some candidate paths between source node S and destination node D, and have to choose a path from the candidates. Although ordinary routing protocols select paths with minimum hops, QoS (Quality of Service) routing protocols evaluate paths using measures of QoS, such as expected transmission count (ETX). In multi-hop wireless networks with QoS routing, it is an important issue to identify and characterize the best path from the viewpoint of network design. To do this, in [1], we proposed an approximate method to theoretically compute minimum route ETX in static one-dimensional random multihop wireless networks, and in [2], we theoretically identified the best path and gave an exact formula to compute minimum route ETX in static lattice multi-hop wireless networks. In this paper, we propose a new approximate method to theoretically analyze minimum route ETX in a two-dimensional random network. In this method, we extend the approximate method proposed in [1] to be used for two-dimensional random networks. We show this approximate method well describes minimum route ETX by comparing the numerical results of the theoretical methods and simulation results. ©2009 IEEE.

DOI： 10.1109/ISCIT.2009.5341111

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Abstract Delay Tolerant Networks (DTNs)are networks that enable us to exchange information by tolerating a long delay time. DTNs can be applied to various purposes such as disaster communication, regional information dissemination and so on. In wireless DTNs, we have to diffuse copies of information among mobile nodes to deliver information to destination. Information tends to reach destination more easily if more copies are spread over the network. At the same time, however, many unnecessary exchanges of copies of information cause waste of battery of mobile nodes and unnecessary traffic among the network. Hence, it is necessary to control diffusion of copies of information by reducing exchanges of copies between mobile nodes. In this report, we virtually define small regions in the service area, and assume that a database stores location information of mobile nodes and a log of communi- cation of each node. The database system gives statistical information on exchange of flows of copies in each small region and that between a pair of small regions. Based on the information, we restrict information exchange in small regions that are not so necessary to diffuse information. We show the effectiveness of the proposed method by computer simulation in lattice road networks.

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Delay Tolerant Networks (DTNs)are networks that enable us to exchange information by tolerating a long delay time. DTNs can be applied to various purposes such as disaster communication, regional information dissemination and so on. In this report, we consider to apply DTNs to regional spreading and automatic collection of electronic free papers. As a related work, a model of barter exchange generating the currency, which is called Yasutomi&#039;s model, is proposed. In this report, we try to apply this model to the above spreading and collection of electronic free papers. We propose an information-exchange method that utilizes the view vector, which is introduced in Yasutomi&#039;s model, and show that the view vector accelerate the spreading of new electronic paper and the collection of 01d electronic paper. In addition, we propose another method to make the above method more effective and evaluate this method.

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Recently, Electric Vehicle (EV) is considered as an important technology;however, there are some problems for spreading EVs. One of these problems is that charging the battery of an EV needs a longer time than refueling of gasoline vehicles. To overcome these problems, for example, some local governments in Japan started projects in which restaurants and shops rent outlets for charging EV of their customers during eating or shopping. On the other hand, other local government in Japan has developed a system to efficiently reserve chargers by sharing information on usage of chargers. In this paper, we consider the above service to rent outlets during eating or shopping, and discuss how methods to reserve chargers affect the waiting time for charging EVs.

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Recently, Electric Vehicle (EV) is considered as an important technology; however, there are some problems for spreading EVs. One of these problems is that charging the battery of an EV needs a longer time than refueling of gasoline vehicles. Deployment of charging stations is also a problem. To overcome these problems, for example, some local governments in Japan started projects in which restaurants and shops rent outlets for charging EV of their customers during eating or shopping. Under such projects, if an EV driver knows information on chargers such as the locations of chargers and the mean waiting time for using chargers, the driver may be able to reduce the time spent only for charging. In this report, we theoretically analyze the mean of the time spent only for charging in cases where drivers know and do not know the above information. From the numerical results, we discuss what information is important to reduce the time spent only for charging.

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When a large-scale disaster occurs, communication infrastructures can be disabled, and some regions can be isolated from each other from a viewpoint of information exchange. In this case, it is important to ensure a way to exchange information between these isolated regions. To do this, it is known that an epidemic transmission, in which mobile nodes deliver information by itself, is effective. By using an epidemic transmission, we can confirm the safety of the family in other regions although the delay time for delivery may be increased. In this report, we consider a situation where communication infrastructure between some places of refuge are completely disabled. We consider information delivery to such places of refuge by vehicles for transporting relief goods and using epidemic transmission. We analyze the relation between efficiency of transportation of relief goods and spreading of information by computer simulation.

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In the simulation for evaluating mobile multi-hop wireless networks, we often use a method of observing network conditions for every At seconds, where At is a positive constant. For such a method, to realize high accuracy of the simulation, we have to use small At; however, small At also causes an increase of the runtime of the simulation. To cope with this problem, we proposed a new simulation method, where we observe network conditions only when a link between two nodes becomes connected or disconnected, and showed that this method can improve the efficiency of the simulation. However, in a situation where the density of nodes is significantly low or significantly high, the above method does not work so efficiently due to an increase of unnecessary observations. In this report, we propose improved versions of the above method, which ignore clearly unnecessary observations, and show that the proposed methods make the simulation more efficient.

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Electric Vehicle (EV) is considered as an important technology, and has been studied widely. For charging a battery of an EV, we can use quick chargers at charging stations; however, quick chargers have not spread sufficiently. Furthermore, a quick charger needs a longer time than refueling of gasoline vehicles. On the other hand, we can use a household wall outlet to charge a battery of EV; however, it needs a much longer charging time, and we cannot use every outlet. To overcome this problem, Niigata and Kanagawa prefectures started projects in which restaurants and shops rent outlets for charging EV of their customers during eating or shopping. We call a network consisting of such shops with outlets a charging network. In the charging network, we can choose the length of charging time and the frequency of charging. This means that we may choose an efficient way of charging. In this report, we theoretically consider how long we should charge the EV at each shop to increase the probability that an EV can reach the destination before the battery is dead while decreasing the time length of charging. Furthermore, we theoretically consider how much we should charge the EV at each shop. We also consider effects of some factors such as the number of outlets and the number of waiting cars.

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In multi-hop wireless networks, the positions of nodes are generally random, and the transmission range of each node is finite. Therefore, the source and destination nodes do not always have a multi-hop path between them. Hence, an analysis of the connectivity is important. In this paper, we derive an approximate formula of the probability that there is at least one path between the source and destination nodes x away from each other in a two-dimensional random network. First, we consider the form of the function of this probability with respect to x. Next, we observe the relation between four constants in this function and the density of nodes by using computer simulation and find the functions that fit the simulation results. From these results, we finally derive the approximate formula of the connectivity.

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Event date： 2010.3

Language：Japanese  

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Event date： 2010.1

Language：Japanese  

In multi-hop wireless networks, the source and destination nodes usually have some candidate paths between them, and the path quality depends on the selection of a multi-hop path from these candidates. Therefore, it is important to choose a path with high quality. To evaluate the quality of the network, it is also important to clarify the relation between network topology, path selection, and communication quality. To do this, in [1], we used expected transmission count (ETX) as a metric of path quality, characterized the best path, which maximizes the communication quality, and proposed a theoretical method to compute the route ETX of the best path in a one-dimensional random network. In this paper, we extend the method in [1] to two-dimensional networks and characterize the best path for ETX in a two-dimensional random network. Based on this characterization, we theoretically and approximately analyze the route ETX of the best path in a two-dimensional random network.

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Event date： 2010

Language：English  

In multi-hop wireless networks, if we know the packet reception rates of all links in the network, we can find the path with the minimum energy consumption. However, to obtain the packet reception rates with high accuracy, we need a number of exchanges of probe packets. Also, the energy consumption along a path depends on a routing method. In this paper, we consider three routing methods and evaluate the relation between the number of broadcasts of probe packets and the total energy consumption along the paths selected by these methods. © 2010 IEEE.

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Event date： 2009.9

Language：Japanese  

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Event date： 2009.6

Language：Japanese  

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Event date： 2009.3

Language：Japanese  

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Event date： 2008.10

Language：Japanese  

In mobile multi-hop networks, messages are delivered in various manners. We can send a massage M after constructing a multi-hop path between a source node S and a destination node D (Method 1). We can make a mobile node to deliver M to D by allowing a mobile node to carry M from S to D (Method 2). We can also use a combination of Methods 1 and 2 (Method 3). The mean waiting time for arrival of M at D can be used as a measure of capability of flow of mobile nodes to deliver messages. In this report, we use the mean waiting time to evaluate capability of flow of mobile nodes to deliver messages, and theoretically analyze the mean waiting time of Method 3. We propose a method to theoretically analyze the mean waiting time in a one-dimensional street network. Also, we consider a two-dimensional street network and propose methods to compute the mean waiting time considering effects of shadowing and change of direction at intersections. We show numerical results and evaluate these methods.

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Event date： 2008.10

Language：Japanese  

In multi-hop wireless networks, the source and destination nodes usually have some candidate paths between them, and the path quality depends on the selection of a multi-hop path from these candidates. Therefore, it is important to choose a path with high quality. To evaluate the quality of the network, it is also important to clarify the relation between network topology, path selection, and communication quality. To do this, in [1], we used expected transmission count (ETX) as a metric of path quality, characterized the best path, which maximizes the communication quality, and proposed a theoretical method to compute the route ETX in a one-dimensional random network. In this paper, we use medium time metric (MTM) as a metric of path quality and characterize the best path in a one-dimensional random network. We characterize the path that minimizes route MTM by comparing MTMs of routes selected based on two different policies with minimum route MTM.

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Event date： 2008.6

Language：Japanese  

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Event date： 2008.2

Language：Japanese  

In multi-hop wireless networks, the source and destination nodes usually have some candidate paths between them, and the path quality depends on the selection of a multi-hop path from these candidates. Therefore, it is important to choose a high quality path. In this paper, we use ETX (Expected Transmission Count) as a metric of path quailty and theoretically analyze the ETX of the best path, which maximized the communication quality, in a lattice network. We approximately analyzed the ETX of the best path in a one-dimensional network where nodes are randomly distributed, and exaclty analyzed the ETX of the best path in a one-dimensional network where nodes are located at constant intervals. In this paper, we extend the latter result to a two-dimensional network and exactly analyze the ETX of the best path in the two-dimensional network where nodes are located with lattice structure.

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Event date： 2007.11

Language：Japanese  

In multi-hop wireless networks, the source and destination nodes usually have some candidate paths between them, and the path quality depends on the selection of a multi-hop path from these candidates. Therefore, it is important to choose a high quality path. Also, the theoretical analysis of the relation between the selection of a path and the quality of the path is important to evaluate the performance of networks. In this paper, we use ETX (expected transmission count) as a metric of path quality and analyze the ETX of the best path, which maximizes the communication quality. We approximately analyzed the ETX of the best path in a one-dimensional network where nodes are randomly distributed because the exact analysis is difficult in such a network. Then in this paper, we derive two theorems to exactly analyze the ETX of the best path in the network where nodes are located at constant intervals. Theorem 1 gives ETX of the best k-hop path, which maximizes the communication quality in all k-hop paths. Theorem 2 limits the number of hops of the best path to at most two candidates. We compute the ETX of the best path using Theorems 1 and 2, and compare a path which minimizes the length of each link and another path which minimizes the number of hops with the best path in the ETX.

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Event date： 2007.6

Language：Japanese  

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