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Bai Y.,Beihang University | Bai Y.,Dissemination in Communication Networks Laboratory | Huang J.,Michigan State University
IEICE Transactions on Communications | Year: 2010

Data query is one of the most important issues in wireless ad hoc networks, since the ultimate goal of these networks is to support efficient data sharing among wireless nodes. In this paper, we study the issue of data query for delay-sensitive applications in dense wireless ad hoc networks. We focus our attention on step-by-step expanding ring-based data query, which provides an upper bound on query delay to any expanding ring based query strategies. Two replication strategies including Index Replication (IR) and Data Replication (DR) are considered, to improve the delay performance of data query. We analyze the probabilistic behavior of query delay for both DR and IR by theoretical methods, and develop analytical models to approximate the minimum number of replicas required for both query strategies if an application-specified delay bound is imposed. Our work is validated through extensive simulations. Copyright © 2010. Source

Yizhou H.,Beijing University of Posts and Telecommunications | Yizhou H.,Dissemination in Communication Networks Laboratory | Gaofeng C.,Beijing University of Posts and Telecommunications | Pengxu L.,Beijing University of Posts and Telecommunications | And 2 more authors.
Journal of China Universities of Posts and Telecommunications | Year: 2015

Because of the integration of long term evolution (LTE) technology and mobile satellite communication systems, uplink access technology for LTE-based geo-stationary earth orbit (GEO) satellite has become a popular research topic for satellite system. In order to solve the problem of unreasonable design for physical random access channel (PRACH) signal structure and reduce the effect of time uncertainty, this paper proposes a novel random access preamble based on time pre-compensation (TPC) for LTE-Satellite (LTE-S) system. In this scheme, by applying the method of non-linear least squares, the user terminal (UT) can use the receiving power to estimate the communication round trip delay (RTD) and based on the transmission delay of the beam center and the satellite, RTD can be compensated before transmission. Therefore, the preamble length and duration can be reduced without related to the maximum of RTD. In order to verify the performance of the scheme, the MATLAB is used to build a test system. The simulation results show that the proposed preamble satisfies the requirements of LTE-S system, and the better performance than previous researches is obtained. © 2015 The Journal of China Universities of Posts and Telecommunications. Source

Feng T.,University of Electronic Science and Technology of China | Zhang X.,University of Electronic Science and Technology of China | Tang W.,University of Electronic Science and Technology of China | Wang J.,University of Electronic Science and Technology of China | Guo Y.,Dissemination in Communication Networks Laboratory
2014 Australasian Telecommunication Networks and Applications Conference, ATNAC 2014 | Year: 2015

Cooperative relaying technology has been proved to be one of the most promising techniques to improve the throughput of CR networks. In this paper, cognitive relay networks with amplify-and-forward (AF) protocol in a spectrumsharing scenario have been considered. Compared with previous studies, we further consider the transmit power constraint on secondary source node (SS). Namely, we impose both transmit power constraint and interference power constraint on SS and secondary relay node (SR). As well we obtain the exact outage probability which works as the performance measurement of CR networks. To analyze the influential factors for system performance, the closed form expression of outage probability needs to be derived. However, it is mathematical intractable. Hence, an approximate approach is adopted as a solution. Finally, Monte-Carlo simulations are conducted to verify the accuracy of our approximation, the error sources of our analytical results are discussed as well. © 2014 IEEE. Source

Bai Y.-B.,Beihang University | Bai Y.-B.,Dissemination in Communication Networks Laboratory | Zhu X.,Beihang University | Shao X.,Institute for Infocomm Research | Yang W.-T.,Beihang University
Mobile Networks and Applications | Year: 2012

Mobile Ad Hoc Networks (MANETs) have inherently dynamic topologies and heterogeneous network environments. Due to the distributed, multi-hop nature of these networks, as well as limited network resource, wireless capacity and random mobility of nodes, Quality of Service (QoS) provisioning faces severe challenges, especially in multicast scenarios. Resource admission control is one of the most effective methods for resource utilization and QoS guaranteed. In this paper, we combine resource admission control technologies and intelligent methods, propose a fuzzy decision-based resource admission control mechanism for MANETs (FAST), which can fast respond to dynamic topology changes and unstable link status. FAST also supports multicast and destination heterogeneity. Users can choose multiple evaluation parameters with different weights of services in fuzzy decision. Simulation results have proved the efficiency of the mechanism. © Springer Science+Business Media, LLC 2012. Source

Sun Z.,Harbin Engineering University | Sun Z.,Dissemination in Communication Networks Laboratory | Ning X.,Harbin Engineering University | Hu J.,Harbin Engineering University | Wang X.,Harbin Engineering University
2014 International Conference on Mechatronics, Electronic, Industrial and Control Engineering, MEIC 2014 | Year: 2014

In order to increase bandwidth efficiency of band limited communication system, a new multi-band digital modulation scheme based on Quaternary Carrier Orthogonal Sinusoidal Non-linear Chirp Keying (QCO-SNCK) is proposed. Firstly, by analyzing the orthogonality of SNCK modulated waveform samples, 4 mutually orthogonal waveform samples are selected as a set of new orthogonal subcarriers. Secondly, by using coherent demodulation method in the receiver, the quaternary wireless digital communication system has been achieved. Then the MATLAB software simulation platform is built to analysis the performance of the QCO-SNCK system. Theoretical and simulation results show that: when the communication channel bandwidth is limited, the bandwidth efficiency of QCO-SNCK system is 2 times wider than that of SNCK. Compared with Quadrature Phase Shift Keying (QPSK), the bandwidth efficiency of QCO-SNCK system has adjustable performance and higher flexibility. In addition, QCO-SNCK system has a strong ability of resisting Doppler frequency shift (DFS) which can be applied to wireless communication system with high rate mobile communication terminals. © 2014. The authors - Published by Atlantis Press. Source

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