International Journal of Space-Based and Situated Computing (4 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;.