International Journal of Space-Based and Situated Computing (9 papers in press)
Construction and Maintenance of k-Hop CDS in MANET with Two Classes of Mobile Terminals
by Eiichiro Kodama, Bhed Bahadur Bista, Jiahong Wang, Toyoo Takata
Abstract: Since mobile ad hoc networks (MANETs) do not have fixed or predefined infrastructures, nodes need to frequently flood control messages to discovery and maintain routes, which causes performance problems in traffic and energy consumption, contention, and collision. A general solution is to construct a virtual backbone as the basis of routing and broadcasting, and the Connected Dominating Set (CDS) has been widely used. This paper presents a distributed approach to constructing and maintaining a k-hop CDS in the MANET with two classes of nodes. A unique characteristic that differentiates the proposed approach from existing ones is that, any value can be specified for k, and a larger k contributes to a smaller CDS. If k is large enough, the resulting CDS will contain only a single node. Especially, the constructed CDS will be more robust, and will be little affected by the topology change of a MANET.
Keywords: Mobile ad hoc networks; Virtual backbone; k-hop connected dominating set; Distributed algorithms; Routing;.
MIMO host location optimisation in active access-point configuration algorithm for elastic WLAN system
by Sumon Kumar Debnath, Nobuo Funabiki, Mousumi Saha, Md. Selim Al Mamun, Wen-Chung Kao
Abstract: Recently, a wireless local-area networks (WLANs) has become prevailing around the world due to the low-cost and flexible Internet access by wireless communications between user hosts and access points (APs) in the network. Previously, we proposed the active AP configuration algorithm for the elastic WLAN system that dynamically optimises the network configuration by activating/deactivating APs and assigning the channels and associated hosts depending on network situations. However, it assumed that only single-input-single-output (SISO) links are used, although multiple-input-multiple-output (MIMO) links have become popular for fast communications. Currently, most commercial APs can use MIMO, while a subset of hosts can use it, referred as MIMO hosts in this paper. Then, by optimising the locations of MIMO hosts, the performance of the network is expected to be improved. In this paper, we present the MIMO host location optimisation as the extension of the active AP configuration algorithm. Through simulations in two network topologies using the WIMNET simulator, the throughput improvements by this proposal are confirmed.
Keywords: access-point configuration; algorithm; wireless local-area networks; WLANs; multiple-input-multiple-output MIMO; host location; optimisation.
Resource Management for Raft Consensus Protocol
by Takuro Nakagawa, Naohiro Hayashibara
Abstract: Protocols which solve agreement problems are essential building blocks for fault-tolerant distributed applications. Especially, many consensus protocols have been proposed in recent decades. Paxos is the most famous consensus protocol but it is difficult to understand and even more to implement. The recently proposed Raft consensus protocol is a leader based consensus protocol. It is a simple enough to understand itself. It consumes every resource in the system for achieving an agreement as well as other consensus protocols. Thus, there is a problem on resource and energy consumption when the system consists of thousands or millions of nodes. This paper proposes a resource management mechanism for Raft protocol in a large-scale systems or clusters. It is for an elastic Raft cluster by introducing the notion of suspended nodes. In this mechanism, a leader node arouses suspended nodes when some nodes failed. Then, we show the performance evaluation of the proposed protocol regarding the number of messages sent by nodes and the number of execution steps for consensus executions. We also show the message-efficiency and the cost for the resource management mechanism by comparing the proposed protocol with Raft protocol.
Keywords: Consensus; Raft; Resource management; Message efficient; Performance evaluation.
Recognition of a variety of activities considering smartphone positions
by Yuki Oguri, Shogo Matsuno, Minoru Ohyama
Abstract: We present a high-accuracy recognition method for various activities using smartphone sensors based on device positions. Many researchers have attempted to estimate various activities, particularly using sensors such as the built-in accelerometer of a smartphone. Considerable research has been conducted under conditions such as placing a smartphone in a trouser pocket; however, few have focused on the changing context and influence of the smartphone position. Herein, we present a method for recognizing seven types of activities considering three smartphone positions, and conducted two experiments to estimate each activity and identify the actual state under continuous movement at a university campus. The results indicate that the seven states can be classified with an average accuracy of 98.53% for three different smartphone positions. We also correctly identified these activities with 91.66% accuracy. Using our method, we can create practical services such as healthcare applications with a high degree of accuracy.
Keywords: smartphone; activity recognition; device position; accelerometer; barometer; support vector machine;.
Estimation System of Food Texture using Neural Network and Fuzzy Logic
by Shigeru Kato, Naoki Wada
Abstract: This paper discusses on a system which estimates food textures using hybrid model of neural network and fuzzy logic. The system consists of an equipment which obtains a load change and a sound signal while a sharp probe is stabbing a food, and a computer system which estimates numerical degrees of the food textures. Firstly, the neural network assumes numerical membership degrees of the food. The fuzzy logic infers a numerical degree of the food texture considering the estimated membership degrees. In the experiment, the validity of our proposed system is discussed. Finally future prospect is mentioned.
Keywords: food texture; neural network; fuzzy logic;.
Both the Single user and Multi user MIMO System Design with Individual Transmit Power Constraint and Improper Constellation
by Raja Muthalagu
Abstract: This work address the problem of designing joint optimum transceiver forrnboth single-user (SU) and Multi-user (MU) multiple-input multiple-output system.rnMost of the previous works on both SU and MU MIMO system, joint precoder andrndecoder designs are based on the total transmit power constraint (TTPC) with properrnmodulation techniques. On the other hand, in practice, individual transmit powerrnconstraint (ITPC) is more realistic as the power at each antenna at the transmitterrnis restricted independently by the linearity of the power amplifier. In this work, arnminimum total mean squared error (TMSE) design is formulated as a nonconvexrnoptimization problem under equal power allocation (EPA) and the power constraintrnthat jointly meets both EPA and TTPC (i.e ITPC). The closed-form optimum linearrnprecoder and decoder for single-user multiple-input multiple-output (SU-MIMO)rnsystems with an improper modulation are determined by solving this nonconvexrnoptimization problem. It considers both the perfect and imperfect channel state informationrn(CSI) is available at both the transmitter and receiver. The simulationrnresults show the performance improvement of the proposed work over conventionalrnwork in terms of bit error rate (BER).
Keywords: Multiple-input multiple-output (MIMO); Total mean squared error (TMSE); Channel state information (CSI).
Resource Propagation Algorithm considering Predicates to Complement Knowledge Bases in Linked Data
by Toshitaka Maki, Kazuki Takahashi, Toshihiko Wakahara, Akihisa Kodate, Noboru Sonehara
Abstract: Linked Data are directed graph data with descriptive labels using Uniform Resource Identifiers (URI) and based on Resource Description Framework (RDF). Linked Data which are published as Open Data on the Web are called Linked Open Data (LOD). LOD is popular as a technology for constructing the Semantic Web because it can create a knowledge base by linking various resources. However, a large amount of the Linked Data does not have sufficient links since resources defined by URI type are scarce. Therefore, this paper presents a new Resource Propagation Algorithm (RPA) which predicts links between resources in the Linked Data, and complements the knowledge bases by considering predicates in the RDF structure. The presented experiment demonstrate that the RPA was able to complement semantic links between resources considering each predicate.
Keywords: open data; linked data; RDF; graph; predicate; link prediction.
A Throughput Estimation Model under Two-Link Concurrent Communications with Partially Overlapping Channels and Its Application to Channel Assignment in IEEE 802.11n WLAN
by Ismael Munene Kwenga, Nobuo Funabiki, Minoru Kuribayashi, Rahardhita Widyatra Sudibyo, Wen-Chung Kao
Abstract: Currently, the IEEE 802.11n wireless local-area network (WLAN) has been deployed world-wide due to exibility and low costs. A key challenge in the WLAN deployment is to provide high data-rate under strong interferences due to the limited frequency channels. In WLAN, the adjacent channels are partially overlapped with each other, called partially overlapping channels (POCs). Then, the optimal POC assignment to the access-points (APs) in WLAN using the mathematical model is important to improve the performance, particularly for usage of the channel bonding. In this paper, we propose the throughput estimation model extension for concurrent communications of two IEEE 802.11n links under interferences using POCs and the channel bonding, from extensive measurement results under a variety of conditions. Then, based on this model, we present the channel assignment extension in the active AP configuration algorithm for the elastic WLAN system, which dynamically optimizes the topology depending on network conditions. For the evaluation, we verify the model accuracy through comparing estimated throughputs with measured ones under various conditions. On top of that, we confirm throughput improvements by adopting POCs from using merely orthogonal
channels (OCs) in simulations and experiments in several topologies.
Keywords: WLAN; access point; IEEE 802.11n; partially overlapping channel; throughput estimation model; channel assignment.
Special Issue on: Advanced Technologies for Next-Generation Communications and Networked Applications
Introduction to content centric network architectures replacing traditional location centric network
by Tetsuya Shigeyasu
Abstract: Nowadays, Internet has became most important infrastructure used by the population over the 38.8 billion.rnThe Internet is the inseparable from our daily life. The Internet based on such location centric communication, however, may induces high risk of networkrncongestion and network service down due to network traffic dominated by contents delivery and multimedia applications. rnThen, the concept of CCN (Content Centric Network) or ICN (Information Centric Network) has been attracting the attention to resolve the problems under the location based network architecture.rnThis paper explains the overview of the overview of network architectures based on CCN concept in order to help researchers developing well suited next-generation CCN based network architectures.
Keywords: content centric network; host centric network; in-network caching; caching algorithm.