• Journal of the Korea Institute of Military Science and Technology
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• v.24 no.1
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• pp.115-122
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• 2021

In this paper, we propose a dynamic slot allocation scheme to improve the slot utilization rate in tactical multi-hop networks in which the channel condition varies due to node movements. The proposed scheme takes advantage of the fact that nodes that are more than three hops apart can use the same slot simultaneously. The frame is divided into two parts: the control period and the data period. To know the available slot information within two-hop distance, the node exchanges a slot allocation information with one-hop neighbors during the control period. The node can get the information on idle slots that are not used within two-hop distance but assigned already to other nodes that are more than three-hop away. The identified idle slot can be used by the node, which increases the slot utilization rate. The performance analysis results of the proposed scheme show that it increases the slot utilization rate sufficiently despite the overhead of the control period in the multi-hop networks of the future soldier system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.9
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• pp.1117-1122
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• 2019

In this paper, a power allocation scheme is proposed to improve the fairness of user data rates in downlink non-orthogonal multiple access systems with one base station and two users. In particular, the power allocation scheme is presented to maximize the fairness of average user data rates assuming independent Rayleigh fading channels, where the fairness maximization is achieved when the average user data rates are equal. For the fairness evaluation, hence approximate expressions for the average user data rates and the average sum date rate of the proposed scheme are provided by using high signal-to-noise ratio approximation. Through simulation investigation, the derived approximate expressions for the average data rates are verified, and it is shown that the proposed scheme is superior to the conventional power allocation schemes in terms of the fairness of the average user data rates.

• Journal of Communications and Networks
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• v.14 no.4
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• pp.374-384
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• 2012

Utilizing artificial noise (AN) is a good means to guarantee security against eavesdropping in a multi-inputmulti-output system, where the AN is designed to lie in the null space of the legitimate receiver's channel direction information (CDI). However, imperfect CDI will lead to noise leakage at the legitimate receiver and cause significant loss in the achievable secrecy rate. In this paper, we consider a delayed feedback system, and investigate the impact of delayed CDI on security by using a transmit beamforming and AN scheme. By exploiting the Gauss-Markov fading spectrum to model the feedback delay, we derive a closed-form expression of the upper bound on the secrecy rate loss, where $N_t$ = 2. For a moderate number of antennas where $N_t$ > 2, two special cases, based on the first-order statistics of the noise leakage and large number theory, are explored to approximate the respective upper bounds. In addition, to maintain a constant signal-to-interferenceplus-noise ratio degradation, we analyze the corresponding delay constraint. Furthermore, based on the obtained closed-form expression of the lower bound on the achievable secrecy rate, we investigate an optimal power allocation strategy between the information signal and the AN. The analytical and numerical results obtained based on first-order statistics can be regarded as a good approximation of the capacity that can be achieved at the legitimate receiver with a certain number of antennas, $N_t$. In addition, for a given delay, we show that optimal power allocation is not sensitive to the number of antennas in a high signal-to-noise ratio regime. The simulation results further indicate that the achievable secrecy rate with optimal power allocation can be improved significantly as compared to that with fixed power allocation. In addition, as the delay increases, the ratio of power allocated to the AN should be decreased to reduce the secrecy rate degradation.

• Journal of Digital Convergence
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• v.10 no.8
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• pp.91-96
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• 2012

The purpose of this study is to examine the rationality for public organizations' cost allocation method through the case of special post offices. The proper use of allocation method is crucial to promote and nurture the public organization sector. On that note, this paper presents how to apply the proper estimation method. The cost allocation method is to split the total expense into appropriate services and departments. Using the basic expense rate and the standard depreciation rate and area at each post office, the total cost is calculated into the cost per person and area. As a result, the correct cost can be assigned through allocation per according service unit.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.4A
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• pp.344-350
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• 2007

Start after striking space key 2 times. Lately, a lot of researches have been done on the resource allocation for multiuser OFDM(Orthogonal Frequency Division Multiplexing) systems due to its spectral efficiency for high-rate multimedia data services. For multimedia services in which every user is guaranteed to have minimum required bit rate and bit error probability, it is critical to utilize the limited resources efficiently to improve the performance of the system. The introduced allocation method improves spectral efficiency to use the left subcarriers in Zhang's algorithm. By using this method, the system can provide services to more users constantly, except for a bit increasing complexity and memory for deciding the left subcarriers and reallocating the subcarriers.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.5
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• pp.691-708
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• 2010

An important issue of supporting multi-users with diverse quality-of-service (QoS) requirements over wireless networks is how to optimize the systematic scheduling by intelligently utilizing the available network resource while, at the same time, to meet each communication service QoS requirement. In this work, we study the problem of a variety of communication services over multi-media heterogeneous cognitive OFDM system. We first divide the communication services into two parts. Multimedia applications such as broadband voice transmission and real-time video streaming are very delay-sensitive (DS) and need guaranteed throughput. On the other side, services like file transmission and email service are relatively delay tolerant (DT) so varying-rate transmission is acceptable. Then, we formulate the scheduling as a convex optimization problem, and propose low complexity distributed solutions by jointly considering channel assignment, bit allocation, and power allocation. Unlike prior works that do not care computational complexity. Furthermore, we propose the FAASA (Fairness Assured Adaptive Sub-carrier Allocation) algorithm for both DS and DT users, which is a dynamic sub-carrier allocation algorithm in order to maximize throughput while taking into account fairness. We provide extensive simulation results which demonstrate the effectiveness of our proposed schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4A
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• pp.337-344
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• 2011

In this paper, a multiple-input and multiple-output (MIMO) spatial multiplexing (SM) relay system is studied in a bit error rate (BER) sense, where every node is deployed with multiple antennas. In order to efficiently use the limited power resource, it is essential to optimally allocate the power to nodes and antennas. In this context, the power allocation (PA) algorithm based on minimum BER (MBER) for a MIMO SM relay system is proposed, which is derived by direct minimization of the average BER, and divided into inter-node and inter-antenna PA algorithm. The proposed scheme outperforms the conventional equal power allocation (EPA) algorithm without extra power consumption.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.1
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• pp.16-33
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• 2019

In this paper, a full-duplex NOMA relaying based underlay device-to-device (D2D) communication scheme is proposed, in which D2D transmitter assists cellular downlink transmission as a full-duplex relay. Specifically, D2D transmitter receives signals from base station and transmits the superposition signals to D2D receiver and cellular user in NOMA scheme simultaneously. Furthermore, we investigate the power allocation under the proposed scheme, aiming to maximize D2D link's achievable transmit rate under cellular link's transmit rate constraint and total power constraint. To tackle the power allocation problem, we first propose a power allocation method based on linear fractional programming. In addition, we derive closed-form expressions of the optimal transmit power for base station and D2D transmitter. Simulation results show that the performance of two solutions matches well and the proposed full-duplex NOMA relaying based underlay D2D communication scheme outperforms existing full-duplex relaying based D2D communication scheme.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2006.11a
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• pp.513-524
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• 2006

The ammunition allocation problem is a Multi-objective optimization(MOO) problem, maximizing fill-rate of multiple user troops and minimizing transportation time. Recent studies attempted to solve this problem by the prior preference articulation approach such as goal programming. They require that all the preference information of decision makers(DM) should be extracted prior to solving the problem. However, the prior preference information is difficult to implement properly in a rapidly changing state of war. Moreover they have some limitations such as heavy cognitive effort required to DM. This paper proposes a new ammunition allocation model based on more reasonable assumptions and uses an interactive MOO method to the ammunition allocation problem to overcome the limitations mentioned above. In particular, this article uses the GDF procedure, one of the well-known interactive optimization methods in the MOO liter-ature, in solving the ammunition allocation problem.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.7
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• pp.2350-2364
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• 2014

This paper addresses the problem of resource allocation in amplify-and-forward (AF) relayed OFDM based cognitive radio networks (CRNs). The purpose of resource allocation is to maximize the overall throughput, while satisfying the constraints on the individual power and the interference induced to the primary users (PUs). Additionally, different from the conventional resource allocation problem, the rate-guarantee constraints of the subcarriers are considered. We formulate the problem as a mixed integer programming task and adopt the dual decomposition technique to obtain an asymptotically optimal power allocation, subcarrier pairing and relay selection. Moreover, we further design a suboptimal algorithm that sacrifices little on performance but could significantly reduce computational complexity. Numerical simulation results confirm the optimality of the proposed algorithms and demonstrate the impact of the different constraints.