Resource allocation (RA) in multi-cell OFDMA systems is very important for maximizing system throughput. Although sub-channel RA is optimal in terms of system throughput, more interest is given to chunk-based RA to simplify RA algorithms and minimize required signalling. In this paper, we propose a fairness-aware chunk-based RA algorithm for the downlink transmission of multi-cell OFDMA system with fractional frequency reuse (FFR) adoption. Simulation results reveal that our proposed algorithm outperforms two reference algorithms in the literature in terms of some system metrics such as average spectral efficiency (SE), users’ fairness and cell-edge users’ rates.

View full abstract

In previous study, a monitoring system of removing intravenous drip (IV) needles by RFID is suggested and evaluated. When patients removed their IV needles, this system alerts the accidents to nurses. This paper tries to improve this system by use of improved antennas in order to reduce false-positive. For our proposed system, a tag antenna and a reader antenna are designed. In addition, characteristics of these antennas are calculated. Moreover, our proposed system is evaluated by use of a fabricated antennas and an examinee. From the results, this paper shows a stable monitoring system of removing IV needle.

View full abstract

We propose a low false alarm attackers detection in the IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL) by considering timing inconstancy between rank measurements. In the proposed scheme, each node sends the latest rank broadcasted to neighbor nodes instead of its current rank to a sink so as to avoid the rank mismatch due to timing inconstancy. We also introduce the timestamp for reporting rank measurements to decrease the false alarm due to packet loss. Simulation results show that the proposed scheme reduces the false alarm rate.

View full abstract

The effect of various installation positions of a frame wire installed in a photovoltaic (PV) power generation system on radiation noise from the DC side of such a system is investigated in the frequency range from 150 kHz to 30 MHz. First, a PV measurement model with two PV panels is proposed. The radiation noise from this model is compared with that from a simulation model. Good agreement between the measured and simulation results is obtained. Then, the radiation noise from this model with various installation positions of the frame wire is investigated. When the frame wire is installed along power lines, the radiation noise is suppressed at low frequencies where the phases of the currents of the power lines and the frame wire are reverse. Furthermore, the radiation noise increases at low frequencies when the frame wire is vertically installed between the corner of the PV panels and the ground plane. This increase is caused by the loop formed by the PV panels, power lines and the frame wire.

View full abstract

We propose a method to measure the packet processing time (PPT) of remote hosts that use network interface cards (NICs) with interrupt coalescence (IC). The model is based on sending a pair of probe packets. The proposed method first detects whether the host under test uses IC and then measures PPT. The presented experimental evaluation under 100- and 1000-Mb/s transmission speeds shows that the proposed method consistently measures PPT with high efficacy.

View full abstract

Mobile terminal stations utilizing wireless local area network (WLAN) devices have recently increased. Hence, packet collisions due to interfering signals have become an important issue. WLANs detect collisions when the acknowledgment (ACK) frame is not returned. This considerably reduces the WLAN transmission efficiency. This paper proposes a retransmission control scheme utilizing multiple input multiple output (MIMO) transmission, in which collisions may be detected during signal transmission. We evaluated and analyzed the effectiveness of the proposed scheme through computer simulations and theoretical analysis. The theoretical analysis agree with the computer simulation results, indicating the efficiency and reliability of our proposed scheme.

View full abstract

Channel interference in wireless local area networks (LANs) has become an unavoidable problem in home networks (HNWs) with the widespread use of smartphones and tablets. In addition, streaming video over WiFi has become popular on HNWs. However, channel interference in streaming traffic continues longer than that in other data traffic and deteriorates the quality of communications of all other devices using the same channel. Therefore, this paper proposes a new WiFi concierge system that visualizes the conditions of WiFi channels by using new methods of estimating channel congestion and detecting streaming traffic to avoid channels where interference has occurred due to streaming traffic. Furthermore, monitoring experiments were conducted in several apartments to test and investigate the validity of the proposed system. As a result, we concluded that the proposed system could recommend better channels to its users.

View full abstract

We propose a downlink transmission timing shift in the centralized radio access network architecture that advances the downlink transmission timing in order to improve the frame efficiency for time-division duplex radio access network with the optical transmission line. We evaluate the frame efficiency of the proposed downlink transmission timing shift with numerical simulation.

View full abstract

This letter proposes a frequency cooperative automatic repeat request (ARQ) scheme for multi-band WLAN where 60 GHz band is used for high-speed transmissions in combination with 2.4/5 GHz bands for maintaining connectivity in the presence of severe shadowing in 60 GHz band. The proposed scheme switches between 60 GHz and 2.4/5 GHz based on monitoring ACK reception and received SNR, where ACK frame is transmitted by 2.4/5 GHz for reliable retransmission. Simulation results show that the proposed ARQ scheme is less susceptible to severe shadowing caused by human activities than conventional non-cooperative ARQ schemes using only either 60 GHz or 2.4/5 GHz.

View full abstract