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The human blockage problem is an open issue in next- generation wireless access networks using millimeter-wave (mmWave) communications. A proactive base station (BS) handover system leveraging RGB and depth (RGB-D) cameras is proposed for solving the human blockage problem. RGB-D cameras observe mmWave communication ranges, and BS handover is conducted proactively before a human blockage causes serious...
A potential game based distributed channel selection scheme is proposed in this paper to mitigate the flow-in-the-middle (FIM) throughput starvation problem that frequently occurs in dense wireless local area networks (WLANs). The FIM throughput starvation occurs when neighbors of a given node are not within the carrier sense ranges of each other. Since they spatially reuse the channel and at least...
In this paper, an asymptotic analysis of the inversely proportional setting (IPS) of carrier sense threshold (CST) and transmission power in densely deployed wireless local area networks (WLANs) is presented. In densely deployed WLANs, CST adjustment is a crucial technology to enhance spatial channel reuse, but it can starve surrounding transmitters due to an asymmetric carrier sensing relationship...
Inversely proportional setting (IPS) of the transmission power and carrier sense threshold (CST) to a portion of access points/stations is discussed through numerical evaluation and experiments to examine coexistence with legacy devices. In densely deployed wireless local area networks (WLANs), tuning CST is a promising approach to facilitate spatial channel reuse. Particularly, IPS of the transmission...
This paper proposes a modified bat algorithm for optimal resource allocation scheme in closed access femtocell networks. Bat algorithm is a new nature-inspired metaheuristic algorithm which is inspired by the behaviour of bats echolocation. The main objective of the proposed algorithm is to select the best combination of resource blocks for femto users so as to minimize the co- and cross-tier interference...
In millimeter wave (mmWave) communications, when a pedestrian blocks the path of the line of sight (LOS) between a station (STA) and a base station (BS), the quality of communication sharply deteriorates. In order to cope with such human blockage, an RGB and depth (RGB-D) camera-assisted proactive handover scheme is proposed in this paper. The scheme uses images from an RGB-D camera to predict human...
Long propagation delay in wireless local area networks (WLANs) such as long distance WLANs and WLANs with radio-over-fiber (RoF) technology increases frame collisions. In particular, when a conventional WLAN coexists with the WLAN with long delay, the propagation delay causes serious throughput degradation and unfairness between the uplink and the downlink in the WLAN with long delay. In this paper,...
In-band full-duplex (IBFD) operation can potentially double the spectral efficiency of wireless networks. For IBFD operation, self-interference is a critical issue. In addition, in full-duplex cellular (FDC) networks, particularly when the cell size is small, inter-user interference would be another limiting factor for the performance. To overcome these issues, the scheduling scheme proposed in this...
Wireless local area network (WLAN) using millimeter wave (mmWave) communications is one of enabler of next generation wireless access networks since huge bandwidth is available in mmWave bands and it enables beyond Gbit/s communications. This paper experimentally evaluate the PHY rate and the throughput performance of off the shelf mmWave WLAN devices that are compatible with IEEE 802.11ad standard...
This paper proposes frame length optimization for wireless local area networks (WLANs) using an in-band full-duplex system that enables a WLAN access point and stations to transmit and receive frames at the same time on the same frequency channel. In in-band full-duplex WLANs, a primary sender which captures the channel transmits a frame to the intended receiver called a secondary sender and then...
This paper presents implementation of a reactive base station selection scheme for millimeter-wave (mmWave) communications. In mmWave communications, the frame loss rate increases and the throughput sharply decreases when a pedestrian blocks a line-of-sight (LOS) path. To alleviate this human blockage problem, base stations can be selected so as to maintain LOS paths on the basis of communication...
This paper investigates the achievable throughput of a multi-antenna two-hop relay link under hybrid full/half-duplex operation. The analysis is facilitated by realistic waveform simulations, which explicitly model all the essential circuit impairments occurring in the relay transceiver together with degrading channel estimation and self-interference cancellation. The obtained results indicate that...
This paper proposes an RGBD cameras-based wireless environment prediction and presents an implementation of a proactive traffic control system using the prediction results. In millimeter-wave and terahertz communications, frame loss rate increases and throughput is decreased tremendously when pedestrians block line-of-sight paths. Such serious human blockage does not occur in microwave communications...
This paper proposes a proactive base station selection system for millimeter-wave (mmWave) communications based on human blockage prediction using RGB and depth (RGB-D) cameras. In mmWave communications, the frame loss rate increases and the throughput sharply decreases if a pedestrian blocks a line-of-sight (LOS) path between a station and a base station.To address this human blockage problem, multiple...
Inserting attenuators between transceivers and antennas is proposed to improve spatial channel reuse in carrier sense multiple access with collision avoidance based WLANs. Using attenuators enables the access points or stations to decrease the powers of transmission signals and received signals, which equivalently results in the increase of the carrier sense threshold. Thus, the attenuation value...
This paper proposes a new CWmin control method called a virtual continuous CWmin control (VCCC) scheme. The key concept of this method is that it involves the use of small and large CWmin values probabilistically. The proposed scheme realizes the CWmin value as a nonnegative real number and solves the precise priority control problem. Moreover, we propose a theoretical analysis model for the proposed...
This paper presents a novel medium access control (MAC) mechanism for wireless local area network (WLAN) systems, called visual recognition based medium access control (VRMAC) mechanism. VRMAC exploits Wi-Fi and visible light communications techniques, using LEDs and a camera to facilitate collision-less medium access with low overhead. In VRMAC, stations (STAs) equipped with LEDs send medium-access...
As the demand for high-throughput communications in wireless LANs increases, the need for expanding channel bandwidth also increases. However, the use of wider band channels results in the decrease of the number of channels available. Therefore, if multiple access points (APs) are in proximity and the cells overlap, it is difficult for each AP to use an orthogonal channel, and competitions thus increase...
In this paper, a method for a multi-operator mobile relay node (RN) for cellular networks on a bus or train is proposed. The introduction of RNs enables an improvement in the spectral efficiency because an antenna with higher gain than that of user equipment (UE) can be installed in an RN. However, installing different RNs for different operators is not efficient because of the large amount of space...
In this paper, Pareto optimal multi-user transmission scheduling in a system comprising of one source, one relay, and two destinations is discussed. To achieve proportional fairness among users in multi-user case, a scheduling scheme for a hybrid of full- and half-duplex relaying (FHDR) is proposed in this paper, which extends a transmission scheduling for single-user hybrid FHDR. The optimization...
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