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Recently, unmanned aerial vehicles (UAVs) have been employed to provide wireless communication services, which promotes the emergence of promising UAV-assisted heteroge-neous networks (UHetNets). However, due to the ever-increasing amount of data traffic and diverse wireless service demands of mobile users, it is challenging to efficiently allocate limited secure bandwidth for safe communication. To tackle this problem, in this paper, we propose a game theoretical secure bandwidth allocation scheme in UHetNets. Specifically, we first design a UAV-assisted bandwidth allocation framework, where each UAV as a flying base station reuses the secure spectrum to enhance the utilization rate of wireless resource. To allocate the restricted secure band-width, we further introduce the utility functions of both UAVs and mobile users, based on the real-time bandwidth capacity of each UAV and the demand of each mobile user. Stackelberg game is then utilized to model the dynamic interactions between UAVs and mobile users. Afterwards, we devise a gradient descent based optimal decision searching algorithm to achieve the Stackelberg equilibrium. The simulation results, at last, show the effectiveness of the proposed scheme to improve the utilities of both mobile users and UAVs.

A Virtual Output Queuing (VOQ) input buffer type switch provided with a buffer in each input port is proposed in this paper as an input buffer type switch that avoids Head-of-Line (HoL) blocking. A scheduling algorithm for a multiple VOQ input buffer type switch is also proposed. As a representative algorithm we use a Two-Dimensional Round Robin (2DRR) scheduling algorithm that achieves low-delay and has iSLIP to avoid starvation as well as high fairness between ports. This paper also proposes a layered scheduling algorithm for a VOQ input buffer type switch with an objective of fairness between ports and switching with lower delay. The frequency of packets not being output is reduced regardless of whether an output port is empty by using up patterns of all I/O pairs in N input N output switches. The N input N output switching is divided into smaller units. Fairness between the units is achieved by successively shifting the order of priority of each unit that will be switched. Simulations were used to evaluate the effectiveness of the proposed scheduling algorithm. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(6): 43–52, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20313

Rate control for multicasting is required for multipoint distribution of video over the Internet. In this paper, we focus on the video image quality during playback and propose layered multicast rate control using error correcting codes. First, we identify the severe degradation problem in the playback quality of the transmitted video due to packet losses resulting from congestion when transmitting high-quality video using conventional techniques. To address this problem, we propose a method adopting the parity generated by the error correcting code in addition to the rate control in order to maintain the video image quality. We perform a simulation to show that the proposed method enables rate control that prevents the degradation in quality caused by congestion. Furthermore, we find the optimum block size of the error correcting code with respect to the control latency, and quantitatively evaluate the packet loss ratio and transmission efficiency with respect to the system scale and the transmission efficiency with respect to the layer increment ratio. We also develop a layer coding technique and study the optimum error correcting code in real-time processing by the software and its implementability. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(5): 29–41, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10156

When UBR (Unspecified Bit Rate) service is used on an ATM network, cells are discarded in congestion and imperfect packets are generated that consume network resources in a wasteful manner. As a remedy, the EPD (Early Packet Discard) control is proposed, in which the cells are discarded on a packet basis in congestion by providing a threshold to the input buffer. However, with EDP control, there is a possibility that the EOP (End Of Packet) cell in AAL5 may be discarded. Thus, two successive packets become invalid. For this reason, the TT-EPD (Two Threshold-EPD) that prevents discarding of the EOP cell has been proposed. This scheme sets two threshold values (TH1 and TH2) and the fixed TH1 works similarly to EPD control. TH2 carries out dynamic control and secures the input region for the EOP cell in the buffer. In this scheme, the amount of buffer between TH1 and TH2 decreases and there is an increase in the number of acceptance failures in which the cells composing a packet initially accepted are discarded by TH2. In this paper, a method that keeps the amount of buffer between TH1 and TH2 constant to reduce the acceptance missing packets is proposed. The effectiveness of the proposed scheme is demonstrated by simulation. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(8): 50– 57, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10039

Uneven traffics may too much concentrate on specific nodes and the path requests will be blocked at these nodes in wavelength division multiplexing (WDM). This paper proposes a new load-balancing method applying link-cost adjustment based on betweenness centrality in WDM networks with wavelength converters. It is clarified that the proposed method drastically reduces a blocking probability as compared with that of the existing OSPF.