• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.3
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• pp.1336-1356
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• 2017

The spectrum scarcity crisis has resulted in a shortage of resources for many emerging wireless services, and research on dynamic spectrum management has been used to solve this problem. Game theory can allocate resources to users in an economic way through market competition. In this paper, we propose a bidding game-based spectrum allocation mechanism in cognitive radio network. In our framework, primary networks provide heterogeneous wireless service and different numbers of channels, while secondary users have diverse bandwidth demands for transmission. Considering the features of traffic and QoS demands, we design a weighted interference graph-based grouping algorithm to divide users into several groups and construct the non-interference user-set in the first step. In the second step, we propose the dynamic bidding game-based spectrum allocation strategy; we analyze both buyer's and seller's revenue and determine the best allocation strategy. We also prove that our mechanism can achieve balanced pricing schema in competition. Theoretical and simulation results show that our strategy provides a feasible solution to improve spectrum utilization, can maximize overall utility and guarantee users' individual rationality.

• Journal of Communications and Networks
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• v.13 no.4
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• pp.367-376
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• 2011

In this paper, we propose self-organizing schemes for the initial configuration of the neighbor cell list (NCL), maintenance of the NCL, and physical cell identifier (PCI) allocation in heterogeneous networks such as long term evolution systems where lower transmission power nodes are additionally deployed in macrocell networks. Accurate NCL maintenance is required for efficient PCI allocation and for avoiding handover delay and redundantly increased system overhead. Proposed self-organizing schemes for the initial NCL configuration and PCI allocation are based on evolved universal terrestrial radio access network NodeB (eNB) scanning that measures reference signal to interference and noise ratio and reference symbol received power, respectively, transmitted from adjacent eNBs. On the other hand, the maintenance of the NCL is managed by adding or removing cells based on periodic user equipment measurements. We provide performance analysis of the proposed schemes under various scenarios in the respects of NCL detection probability, NCL false alarm rate, handover delay area ratio, PCI conflict ratio, etc.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.2
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• pp.550-565
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• 2018

Cognitive radio technology is still the key technology of future mobile communication systems. Previous studies have focused on improving spectrum utilization and less energy consumption. In this paper, we propose an Overhead Reduced Scheme (ORS) for green cooperative spectrum sensing. Compared to traditional cooperative sensing scheme, ORS scheme divides the sensing time into three time slots and selects the best multi-mode user to report decisions. In consideration of reporting channel deviation, we derive closed-form expressions for detection probability and false alarm probability of ORS scheme based on Rayleigh fading channel. Simulation results show that ORS scheme can improve the perception accuracy while reducing the perceived delay and energy consumption in the process of perception, so as to realize the green communication.

• Journal of electromagnetic engineering and science
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• v.14 no.4
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• pp.353-359
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• 2014

Recently, the use of mobile devices has increased, and mobile traffic is growing rapidly. In order to deal with such massive traffic, cognitive radio (CR) is applied to efficiently use limited-spectrum resources. However, there can be multiple communication systems trying to access the white space (unused spectrum), and inevitable interference may occur to cause mutual performance degradation. Therefore, understanding the effects of interference in CR-based systems is crucial to meaningful operations of these systems. In this paper, we consider a long-term evolution (LTE) system using additional spectra by accessing the TV white space, where low-power devices (LPDs) are licensed primary users, in addition to TV broadcasting service providers. We model such a heterogeneous system to analyze the co-existence problem and evaluate the interference effects of LPDs on LTE user equipment (UE) throughput. We then present methods to mitigate the interference effects of LPDs by 'de-selecting' some of the UEs to effectively increase the overall sector throughput of the CR-based LTE system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.4
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• pp.1837-1860
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• 2020

We propose a general framework for studying resource allocation problem and the tradeoff between spectral efficiency (SE) and energy efficiency (EE) for downlink traffic in power domain-non-orthogonal multiple access (PD-NOMA) and device to device (D2D) based heterogeneous cloud radio access networks (H-CRANs) under imperfect channel state information (CSI). The aim is jointly optimize radio remote head (RRH) selection, spectrum allocation and power control, which is formulated as a multi-objective optimization (MOO) problem that can be solved with weighted Tchebycheff method. We propose a low-complexity algorithm to solve user association, spectrum allocation and power coordination separately. We first compute the CSI for RRHs. Then we study allocating the cell users (CUs) and D2D groups to different subchannels by constructing a bipartite graph and Hungrarian algorithm. To solve the power control and EE-SE tradeoff problems, we decompose the target function into two subproblems. Then, we utilize successive convex program approach to lower the computational complexity. Moreover, we use Lagrangian method and KKT conditions to find the global optimum with low complexity, and get a fast convergence by subgradient method. Numerical simulation results demonstrate that by using PD-NOMA technique and H-CRAN with D2D communications, the system gets good EE-SE tradeoff performance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.3
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• pp.2178-2184
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• 2015

With the development of wireless network technologies, mobile users may use various networks easily and expect more advanced services. On the other hand, it may bring on some problems with network resource management that should lead the service provider to improve the current service quality and manage the network resource efficiently. This paper proposes the optimized radio resource management (RRM) scheme that integrates the Grey Relational Analysis (GRA) and game theory. The first applies the GRA to determine the Grey Relation Coefficient (GRC) factors that represent the network preference, and the network provider then selects the requested service that provide maximum payoff through Nash Equilibrium. Six requested services that have one application service among four different types of service classes were considered and the game was played repeatedly. In WiMAX, WLAN 1 and WLAN 2 game, the maximum payoff of each players was 93, 90.6 and 92.8 respectively. The experimental results show that every requested service can be selected by the network provider. Consequently, the proposed radio resource management mechanism is more effective in heterogeneous wireless networks.

• Journal of KIISE:Information Networking
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• v.36 no.3
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• pp.163-172
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• 2009

Various terminals equipped with multiple interfaces may receive services from wireless networks when they pass through the overlaid heterogeneous networks, and thus the vertical handovers across the wireless networks increases, which will become a big problem in the network resource management. This problem can be efficiently solved by common radio resource management (CRRM). In this paper, we propose two operation algorithms based on network selection jointly with vertical handover as the key CRRM strategies. When a new user tries to get services, the CRRM can choose the best target network according to the proposed Integrated Network Selection Algorithm. When the network cannot satisfy the request from the new users, the proposed Integrated Vertical Handover Algorithm moves existing users to neighborhood networks to accommodate new users. The performance of the proposed algorithms has been validated through extensive simulations.

• Journal of Broadcast Engineering
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• v.12 no.6
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• pp.542-554
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• 2007

Seamless streaming of multimedia content via heterogeneous networks to viewers using a variety of devices has been a desire for many multimedia services, for which the multimedia contents should be adapted to usage environments such as network characteristics, terminal capabilities, and user preferences. Scalability in video coding is one of attractive features to meet dynamically changing requirements of heterogeneous networks. Currently a new scalable video coding (SVC) is standardizing in the Joint Video Team (JVT) of the ISO/IEC Moving Picture Experts Group (MPEG) and the ITU-T Video Coding Experts Group (VCEG), which will be released as Extension 3 of H.264/MPEG-4 AVC. In this paper, we introduce new technologies of SVC and evaluate performance of it especially regarding on overhead bit-rate and coding efficiency to support spatial, temporal, and quality scalability.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.7
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• pp.1546-1553
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• 2015

In cognitive radio technology, the overall capacity of communications systems can be improved without allocating additional bands by allowing secondary system to utilize the band when a primary system who has right to use the band does not utilize it. Therefore, spectrum sensing to determine the existence of primary system is utmost important in the cognitive radio technology. In this work, we consider a novel cooperative spectrum sensing in cognitive cellular systems. Especially, we consider the case in which heterogeneous primary systems coexist, i.e., heterogenous transmission power and sensing requirement of primary system, such that only portion of users in cognitive cellular systems are able to detect the primary system. In this case, we propose new cooperative spectrum sensing with multiple sensing stages to properly detect the existence of primary systems in this kind of situations. Moreover, we analyze the performance of conventional cooperative spectrum sensing schemes such as OR-rule, AND-rule and MAJORITY-rule under the existence of heterogeneous primary systems. Finally, we investigate the performance of the proposed scheme through computer based simulations and show that the existence of primary systems can be determined accurately by using our proposed scheme.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.15 no.3
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• pp.192-199
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• 2015

Heterogeneous cellular networks are gaining momentum in industry and the research community, and are attracting the attention of standard bodies such as 3GPP LTE and IEEE 802.16j, whose objectives are to increase the capacity and coverage of cellular networks. In this article, we provide an overview of expansion strategies, optimal locations of base stations with different characteristics, and radio-planning models.