Masanori Nozaki

A wireless ad-hoc community network with reconfigurable topology architecture

A concept for a wireless ad-hoc community network (WACNet) is proposed with reconfigurable topology architecture with the aim of supporting the data communications among an unpredetermined group of people gathered temporarily within a specific confined area. In this architecture, the wireless network topology is controlled corresponding to changes in a networks distributed traffic, which is both unpredictable and uneven and corresponding to the logical topology so as to achieve efficient utilization of the network resources over radio frequencies. This paper describes the concept, system configuration, control method and the effects of this network in addition to presenting experimental results for a trial system which implemented the fundamental functions of this network by employing wireless LANs and PCs.

A Sensor Network Protocol for Automatic Meter Reading in an Apartment Building

A wireless sensor network for automatic meter reading needs to satisfy two contradicting requirements, i.e., long lifetime and prompt detection and notification of emergency. We propose a sensor network protocol for this purpose, in which sensor nodes operate on a low duty cycle while the latency of transmission is guaranteed to be less than a certain bound. In this protocol, each node is assigned a time slot in which it receives messages from other nodes. To accomplish slot assignment where nodes further from a BS are assigned earlier time slots for a packet to be transmitted to the BS in one cycle, we propose a slot assignment function with which a node can determine its own slot in a distributed way. We explore several slot assignment functions to find one which gives low and homogeneous contention over a grid network. The simulation results show that our protocol performs well close to the optimal case.

A Low-Overhead Handling Scheme of STA Association Information for IEEE 802.11s

A wireless mesh network has much attention for various applications such as home networks or hot spot services, and its standardization is now progressing at the IEEE 802.11s task group. One of the most important issues of the wireless mesh network is how to handle the association information of huge number of legacy user stations (STAs). In this paper, we propose a low-overhead handling scheme of the STA association information in order to solve this issue. In the proposed scheme, we introduce an on-demand approach to handle the STA association information. We also evaluate the overhead of the proposed scheme, and clarify its superiority.

A reconfigurable topology scheme for a wireless ad-hoc community network

This paper discusses a reconfigurable wireless network topology scheme for the purpose of adapting flexibly to unpredictably variable and unevenly distributed traffic and also utilizing network resources efficiently over radio frequencies, for application to a wireless ad-hoc community network. This paper presents the principle, control method and effects for the scheme and shows the experimental results of trial systems in which the fundamental functions of the scheme have been implemented.

Parent node discovery time reduction algorithm for low-power wireless sensor networks

In multi-hop wireless sensor networks (WSNs) consisting of intermittent operating nodes, increases the processing time in the parent node discovery phase is an important issue because in the conventional parent node discovery method, the joining node chooses a parent node from among all its neighboring nodes. In the proposed scheme, if a neighboring node satisfies the parent selection condition (e.g. having a minimum packet loss rate) for the joining node, it informs the joining node before the other nodes that do not satisfy the condition, allowing the joining node to choose it as a parent node first. In the scheme, neighboring nodes change the timing with which they reply in an autonomous distributed manner by a parameter defined in the scheme. To determine the relationship between the parameter and the processing time spent in the parent node discovery phase, we measured the processing time with wireless units, also in the environment where the hidden node problem happens. The results show that the processing time increases due to a collision caused by the hidden node problem when the parameter is quite small. The processing time also increases due to delay of first reply from a neighboring node when the parameter is quite large. However, the processing time reduces in the middle range of the parameter and the range is wide. Therefore, the proposed scheme can be applied to WSNs such that the number of the hidden nodes and the neighboring nodes cannot be determined precisely.