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.

In Japan, major earthquakes are predicted to occur in the metropolitan area. In the time of such a disaster, communication systems will play an important role to transfer mitigation information such as instruction for people to move the evacuate area and for contractors to recover city functions. However, mitigation information may be unable to transfer smoothly, because of telecom infrastructure damage and conflicting information. Objective of this research is to clarify system requirements in order to build the mitigation network using wireless LAN systems. Use cases for network design are created based on reports and actions of public organizations when the great East Japan earthquake was happened. We propose the mitigation information network composed of three sub networks; the long-distance wireless LAN for connecting to the backup station in non-disaster area, the midrange wireless LAN for connecting between countermeasures offices, the information gathering and distribution network in disaster area. In order to decide specification of wireless systems and position of antenna, we measure throughput of 2.5GHz and 4.9GHz band between Shinjuku and Hachioji for the long-distance wireless LAN. Also we measure throughput of 4.9GHz band in Nishi-Shinjuku area, where is forest of tall buildings, for the information gathering and distribution network. The mitigation network will be built with these results.

Link aggregation bundles multiple physical links on a single virtual link, enabling very high-speed and large-capacity data communications. It also enables redundant communications. Several link aggregation methods have been proposed. These methods utilize transport layer link aggregation. In this paper, a new application level link aggregation is proposed and implemented on Android OS, which is one of the popular OSs for mobile devices such as smartphones and tablet PCs. The proposed application level link aggregation method is verified with use of an implemented terminal.

ABSTRACT Link aggregation bundles multiple physical links on a single virtual link, enabling very high‐speed and large‐capacity data communications. It also enables redundant communications. Several link aggregation methods have been proposed. These methods utilize transport/or lower layer link aggregation. In this paper, a new application‐level link aggregation is proposed and implemented on Android operating system (OS), which is one of the popular OSs for mobile devices such as smartphones and tablet PCs. The proposed application‐level link aggregation method is verified with use of an implemented terminal. Copyright © 2012 John Wiley & Sons, Ltd.

We study dynamic routing and wavelength assignment scheme when there are any available wavelengths on a route in the wavelength-routed networks. An optical wavelength path request is blocked when there are no available wavelengths over the selected route. In this paper, we present a new optical path establishment scheme for achieving low-blocking probability and shortening mean setup delay. It consists of two schemes. One is to start optical wavelength path establishment process from a source node on least hops route (LHR) when used wavelength is released. The other is to start it from a destination node on least load route (LLR) after reservation failure on LHR. We simulated two different topologies. It is shown the proposed scheme is better than existing schemes in both the topologies.

To support multicast over mobile IP networks, the IETF proposed two schemes, namely bi-directional tunneling (MIP-BT) and remote subscription (MIP-RS). MIP-BT provides mobility by establishing bi-directional tunnel from home agent to mobile node's care-of address. Although it does not require multicast tree reconstruction, it suffers from redundant routing that causes packet delivery delay and network bandwidth consumption. On the other hand, MIP-RS provides mobility by reconstructing multicast tree when mobile node enters a foreign network. Although MIP-RS provides shortest multicast routing path, it requires the reconstruction of entire multicast tree in case of source mobility and causes service disruption during the process of handover. To cope with those problems, we propose new source mobility scheme that enjoys the advantages of MIP-RS and provides seamless handover with the help of proxy router, which assists handover by swapping network addresses and conducting packet forwarding. We examine the deployment issues of the proposed scheme over the Internet and evaluate the proposed scheme from the viewpoint of routing distance and network bandwidth consumption through simulation experiments with various parameters, and then clarify the effectiveness and efficiency of the proposed scheme.

One of the main issues of mobile IPv6 is handover latency that causes service disruption time. Although plenty of proposals significantly reduce the service disruption time, they suffer from redundant routing that causes packet misordering and bandwidth consumption during the process of inter-domain handover. In this paper, we propose R-MIP, a routing-aware handover scheme for mobile IP, that minimizes the redundant routing during the process of inter-domain handover by utilizing forwarding routers. R-MIP consists of forwarding router discovery and proactive handover. We evaluate R-MIP in the view of packet misordering and bandwidth consumption, and clarify its efficiency. We also evaluate the impact of the forwarding router's capacity since routers have limited resources. By strategically locating forwarding routers, e.g. next to the router that has peering to another domain, the redundant routing caused by inter-domain handover will be efficiently suppressed.

One of the main issues of mobile IPv6 is handover latency that causes service disruption time. Although plenty of proposals significantly reduce the service disruption time, they suffer from redundant routing that causes packet misordering and excess bandwidth consumption. In this paper, we propose a new scheme that minimizes the redundant routing during the process of inter-domain handover by utilizing forwarding routers. Our proposed scheme consists of forwarding router discovery and proactive handover. Furthermore, we evaluate the proposed scheme in the view of packet misordering and bandwidth consumption, and clarify the effectiveness of the proposed scheme.

P2P content distribution networks are collecting interest to efficiently deliver rich contents such as audio and video. Stream interruption caused by relay peers dropping out of the P2P network is a problem in P2P live streaming systems. In this paper, we propose a P2P live streaming system with low stream interruption. In the proposed system, peers are connected to the peers with low drop-out probability and a wide and short P2P network is constructed. Also, multiple paths to the source is considered. We show the improvement in the interruption time by our algorithm through simulations.

Call admission control (CAC) is essential for the QoS guarantee communications. VoIP services require QoS guarantee in the existing telephony services. This paper proposes a new CAC scheme for VoIP to achieve an efficient use of network resources by adopting a dynamic routing and a routing history table. This scheme chooses the better route out of the two candidate routes where the admission conditions are satisfied. Two candidate routes are randomly chosen from all the available candidate routes. The routing history table memorizes the resulting routing information for the fixed time interval for the succeeding calls. Within the fixed time interval, the succeeding calls are assigned to the same route. After the fixed time interval, the memorized routing information is cleared, and the call admission control algorithm starts again from the beginning. It is confirmed by simulations that the proposed scheme achieves better performance than the existing CAC with alternate routing scheme.

The demand to access multimedia data such as live video is increasing due to the spread of broadband access network. However, the Internet only provides the so called best-effort service. The network condition of the Internet shows fluctuation. Delivering video without any control causes degradation of the final video quality. To avoid such degradation, we must control video traffic to adapt to the fluctuating available bandwidth. In this paper, we propose a technique to find the available bandwidth for end-to-end stream connections over the Internet. We claim that the correlation coefficient of the network delay of an end-to-end stream is closely related to the bottleneck-link load for the end-to-end stream connection. We show and prove the relationship through analysis and simulations.

The demand to access multimedia data such as live video is increasing due to the spread of broadband access network. However, the Internet only provides so called best-effort service. The network condition of the Internet shows fluctuation. Delivering video without any control causes degradation of the final video quality. In this paper we propose a stream-rate control algorithm RC/sup 3/ that uses correlation of network delay to evaluate available bandwidth. We show performance of RC/sup 3/ derived from simulations.

The present issue of the IEEE Journal on Selected Areas in Communications provides a forum in which suppliers of telecommunications services and suppliers of telecommunications equipment can come together with the academic and research communities to meet the quality needs of end users. Papers cover the areas of understanding and communicating customer needs, tools and techniques for managing quality and evolving survivability, reliability, and security needs.>

This paper focuses on how transmission error performance can be evaluated by parameters such as errored seconds (ES) and severely errored seconds (SES), under in-service conditions. Currently, attention is being paid to In-Service Monitoring (ISM) as an effective measurement technique for the error performance in digital networks. So the paper, first of all, overviews error performance parameters and shows the concept of ISM. It next discusses estimation methods for the error performance of digital channels by using information on anomaly and defect events in transmission systems. Furthermore, the paper refers to the potential usage of ISM for service quality estimation and performance assurance.>

Demand for high-speed wide-band telecommunication services is rapidly growing due to the remarkable progress in office, factory, and laboratory automation. These services are expected to be first introduced in leased circuits and then extended, to high-speed switched services. This paper presents the users' demands for such high-speed services and the NTT design concepts for the high-speed digital data transmission system (HDDTS) in NTT to provide such high-speed leased circuit service. The ISDN user-network interface is adopted. The basic high-speed pointto-point transmission service started in October 1984, and enhanced leased circuit service involving multiplexed interfaces and muitipoint circuits will be introduced in the fall of 1985.

In the future information society, various kinds of services will be required in offices, factories, homes, and communities. Fiber optic broad-band systems will play the most important role in the integrated services networks that will provide such services. This paper reviews field trials of fiber optic broad-band systems in Japan, focusing on subscriber loop system technology.

Future subscriber loops will provide various services including broad-band video. Fiber optic technology is the key for introducing these services. The Electrical Communication Laboratories (ECL) of Nippon Telegraph and Telephone Public Corporation (NTT) have been promoting research and development on basic technology of fiber optic subscriber loops, and studying the ways to use fiber optic subscriber loops for new services. As one of the programs, a field trial of fiber optic subscriber loops was planned and conducted in the Yokosuka area from April 1980 until May 1981. This paper first describes fiber optic transmission technologies for subscriber loops. Then, the system configuration and experimental results of the Yokosuka field trial are presented.

This paper investigates the effects of speckle noise on analog video transmission systems using semiconductor laser diodes. The system linearity degradation due to speckle noise is examined using different fiber types. Then this paper proposes a new modulation technique employing a superimposed pulse scheme to reduce speckle noise. It is experimentally confirmed that the proposed modulation method is effective in reducing speckle noise. Based on the above investigations, analog video transmission experiments are performed using single-mode fibers, step-index multimode fibers, and graded-index multimode fibers in the 0.8 and 1.3 μm wavelength regions. The results of the transmission tests have confirmed the feasibility of analog video transmission using semiconductor laser diodes.

Experimental investigation was carried out on nonlinear video distortions of differential gain and differential phase in various optical transmitters using laser diode structures having a single transverse mode operation. It was observed that the measured nonlinearity of laser diodes was comparable to that of a typical LED. A simple linearizing technique for improving the nonlinearity, using an emphasis principle, is proposed and was experimentally examined, yielding promising results.