Masako Shinohara

Data Replication Considering Power Consumption in Ad Hoc Networks

In mobile ad hoc networks, a mobile host holding data items frequently accessed by other hosts needs to transmit them many times and consumes more power than other hosts. In this paper, we propose replica allocation methods for not only improving data availability but also balancing the power consumption among mobile hosts. In these methods, each mobile host replicates data items taking into account their access frequencies, the numbers of their replicas, and the hosts remaining battery power. We present simulation results to evaluate the performance of our proposed methods.

A Message Processing Method for Top-k Query for Traffic Reduction in Ad Hoc Networks

In ad hoc networks, to acquire only necessary data items, it is effective that each mobile node retrieves data items using a top-k query, in which data items are ordered by the score of a particular attribute, and the query-issuing mobile node acquires data items with the k highest scores. In this paper, we propose a message processing method for a top-k query for reducing traffic and keeping the accuracy of the query result, i.e., guaranteeing that data items with the k highest scores in the entire network are acquired. When a mobile node transmits query and reply messages, our method can be used to reduce candidates of data items included in the top-k result to prevent unnecessary data transmissions. Moreover, if a mobile node detects a disconnection of a radio link, it searches for an alternative path to transmit the reply message to the query-issuing node. We present simulation results to evaluate the performance of our proposed method.

Replica allocation considering power consumption in mobile ad hoc networks

In ad hoc networks, it is effective that each mobile host creates replicas of data items held by other hosts for improving data accessibility. However, a mobile host holding data items frequently accessed by other hosts needs to transmit them many times and consumes more power than other hosts. In this paper, we propose a replica allocation method for not only improving data accessibility but also balancing the power consumption among mobile hosts. In this method, each mobile host replicates data items considering their access frequencies, the numbers of their replicas, and the remaining amount of its battery. We present simulation results to evaluate the performance of our proposed method

A Top-k Query Method by Estimating Score Distribution in Mobile Ad Hoc Networks

In mobile ad hoc networks (MANETs), to acquire only necessary data items, it is effective that each mobile node retrieves data items using a top-k query, in which data items are ordered by the score of a particular attribute and the query-issuing mobile node acquires data items with k highest scores. In this paper, we propose a query processing method for top-k query for reducing traffic and also keeping high accuracy of the query result. In this method, each mobile node constructs a histogram from the scores of its holding data items and estimates the distribution of scores of all data items and k-th score in the entire network. This histogram is attached with query messages and replies so that other mobile nodes can estimate the score distribution and k-th score more accurately. When transmitting a reply, each mobile node sends back only data items whose scores that are larger than the estimated k-th score to reduce traffic as much as possible. We also present simulation results to evaluate the performance of our proposed method.

A data access method considering power consumption in ad hoc networks

In ad hoc networks, it is effective that each mobile host creates replicas of data items held by other mobile hosts for improving data accessibility. When a mobile host requests a data item (replica) held by another mobile host, it usually uses the shortest path for the data transmission. In this case, mobile hosts at the center of the network relay many data items and consume much power. In this paper, we propose a data access method to balance the power consumption among mobile hosts. This method selects a path between the request issuing host and the requested data holder considering the path length and the remaining amount of batteries of mobile hosts along the path. We present simulation results to evaluate the performance of our proposed method.

Consistency Management among Replicas Using a Quorum System in Ad Hoc Networks

Data replication is effective for improving data availability in ad hoc networks. In an environment where data updates occur, replicas of a data item may be inconsistent. To solve this problem, quorum based consistency management is a promising approach. To reduce communication overhead, it is better to make the number of mobile hosts in each quorum small. In this paper, we propose a consistency management method that constructs quorums with fewer mobile hosts.

Quorum-based consistency management among replicas in ad hoc networks with data update

In this paper, we propose a consistency management method that constructs quorums with a small number of mobile hosts in ad hoc networks. In this method, when a mobile host discovers paths to other mobile hosts that construct quorums, it restricts the propagation area of query packets. As a result, this method can reduce the communication overhead while keeping the strict consistency among replicas.

Quorum-Based Consistency Management for Data Replication in Mobile Ad Hoc Networks

In this paper, we propose a consistency management method that constructs quorums with fewer nodes. In our method, assuming that the area where nodes exist is divided into several regions, each quorum is constructed based on the locations of the regions. As a result, the proposed methods can reduce the communication overhead while keeping the strict consistency among replicas.

A Data Dissemination Method for Information Sharing Based on Inter-Vehicle Communication

In an Intelligent Transport System (ITS), information sharing based on inter-vehicle communication is effective for improving data availability. In this paper, we propose a data dissemination method for sharing data items among vehicles, which increases the opportunity for vehicles to acquire more fresh data items that users request. In our proposed method, vehicles are grouped according to their locations, and movement directions are estimated from their route information. Then, data items that are more likely to be accessed in the near future are disseminated between two groups. We also present simulation results to evaluate the performance of our proposed method.

A Data Transmission Method Using Multicast in Mobile Ad Hoc Networks

In mobile ad hoc networks, when a mobile host receives a data request from another host, the host usually transmits the requested data item by unicast. However, if mobile hosts hold data items that are frequently requested by others, they have to transmit the data items many times and consume a large amount of power. In this paper, we propose a data transmission method for not only maintaining data availability but also reducing traffic for data access. In our proposed method, each mobile host sends a data request attached with the deadline to receive the requested data item by the determined time. Moreover, each mobile host collects multiple requests for data items and transmits the requested data items by multicast, and thus, reduces data traffic. We also show the results of simulation experiments regarding the performance of our proposed method.