• The Journal of the Convergence on Culture Technology
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• v.3 no.2
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• pp.43-48
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• 2017

5G will bring revolutionary development in mobile communication, and it is anticipated to have complete commercialization including mass adoption rate by 2020s. High number of smart devices including IoT, wearable devices, etc., which have high amount of data usage, will involve even higher data traffics. In addition, media dependency and demand is rapidly rising. These environmental aspects will necessity and sufficient condition for successful implementation of 5G mobile communication system. In this paper, global cooperation and competition for 5G technology leadership will be analyzed and summarized. Through this, proper solution to maintain competency of Korea in future will be proposed.

• Journal of Communications and Networks
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• v.7 no.4
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• pp.471-477
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• 2005

This paper proposes an efficient constraint-based optimization model for the design of 3G mobile networks, such as universal mobile telecommunications system (UMTS). The model concerns about finding a set of sites for locating radio network controllers (RNCs) from a set of pre-defined candidate sites, and at the same time optimally assigning node Bs to the selected RNCs. All these choices must satisfy a set of constraints and optimize an objective function. This problem is NP-hard and consequently cannot be practically solved by exact methods for real size networks. Thus, this paper proposes a hybrid search strategy for tackling this complex and combinatorial optimization problem. The proposed hybrid search strategy is composed of three phases: A constraint satisfaction method with an embedded problem-specific goal which guides the search for a good initial solution, an optimization phase using local search algorithms, such as tabu algorithm, and a post­optimization phase to improve solutions from the second phase by using a constraint optimization procedure. Computational results show that the proposed search strategy and the model are highly efficient. Optimal solutions are always obtained for small or medium sized problems. For large sized problems, the final results are on average within $5.77\%$ to $7.48\%$ of the lower bounds.

• Journal of Internet of Things and Convergence
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• v.5 no.2
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• pp.1-5
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• 2019

Looking at the surrounding environment in which we live, we are facing various situations in which new industries are emerging under the influence of ICT and at the same time, existing industries are combined with ICT technology. In addition, the network environment foretells a change from 4G to 5G. One of the things that is actively discussed during this 5G era is the smart factory. Faster transmission speeds are essential for the use of numerous data generated by various sensors used in smart factories. This study deals with smart factory technologies related to the 5G era. In addition to the various interpretations of smart factories, this study examined the situation and progress of smart factories in major countries around the world and described solutions.

• KIPS Transactions on Computer and Communication Systems
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• v.9 no.2
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• pp.31-36
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• 2020

The creation of the Defense Integrated Data Center(DIDC) has resulted in a reduction in manpower, operating costs, efficient and effective management of resources. However, it is difficult to effectively collect and manage the data of a large number of battlefields coming from equipments such as drones, robots, and IoT added to the fourth industrial revolution and the future battlefield. Therefore, we will propose the design of DIDC network system using NFV and SDN, which are emerging as the core technologies of 5G, a mobile communication technology. After analyzing the data sheet of each equipment, it is considered that by integrating the redundant functions, energy efficiency, resource utilization and effective network management will be possible.

• ETRI Journal
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• v.45 no.4
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• pp.615-626
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• 2023

Under limited transmission conditions, many factors affect the efficiency of video transmission. During the flight of an unmanned aerial vehicle (UAV), frequent network switching often occurs, and the channel transmission condition changes rapidly, resulting in low-video transmission efficiency. This paper presents an efficient video coding flow for UAVs working in the 5G nonstandalone network and proposes two bit controllers, including time and spatial bit controllers, in the flow. When the environment fluctuates significantly, the time bit controller adjusts the depth of the recursive codec to reduce the error propagation caused by excessive network inference. The spatial bit controller combines the spatial bit mask with the channel quality multiplier to adjust the bit allocation in space to allocate resources better and improve the efficiency of information carrying. In the spatial bit controller, a flexible mini graph is proposed to compute the channel quality multiplier. In this study, two bit controllers with end-to-end codec were combined, thereby constructing an efficient video coding flow. Many experiments have been performed in various environments. Concerning the multi-scale structural similarity index and peak signal-to-noise ratio, the performance of the coding flow is close to that of H.265 in the low bits per pixel area. With an increase in bits per pixel, the saturation bottleneck of the coding flow is at the same level as that of H.264.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.2
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• pp.243-248
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• 2012

In this paper we simulate the capacity of VOIP calls through WiFi network by computer simulations using OPNET modeler. The results show that sudden quality degradations occur on all VoIP calls when the number of call of an AP(Access Point) increases beyond a specific value. The reason of the quality degradation was turned out to be the queueing delay at the down link of AP. Under the IEEE 802.11b environments, the maximum number of VoIP calls of an AP maintaining the required voice quality (MOS > 2.5), was evaluated as 5, 12, and 27 when we use G.711, G.729a, and G.729a VAD codec, respectively.

• ETRI Journal
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• v.38 no.6
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• pp.1064-1073
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• 2016

An adaptive speech streaming method to improve the perceived speech quality of a software-based multipoint control unit (SW-based MCU) over IP networks is proposed. First, the proposed method predicts whether the speech packet to be transmitted is lost. To this end, the proposed method learns the pattern of packet losses in the IP network, and then predicts the loss of the packet to be transmitted over that IP network. The proposed method classifies the speech signal into different classes of silence, unvoiced, speech onset, or voiced frame. Based on the results of packet loss prediction and speech classification, the proposed method determines the proper amount and bitrate of redundant speech data (RSD) that are sent with primary speech data (PSD) in order to assist the speech decoder to restore the speech signals of lost packets. Specifically, when a packet is predicted to be lost, the amount and bitrate of the RSD must be increased through a reduction in the bitrate of the PSD. The effectiveness of the proposed method for learning the packet loss pattern and assigning a different speech coding rate is then demonstrated using a support vector machine and adaptive multirate-narrowband, respectively. The results show that as compared with conventional methods that restore lost speech signals, the proposed method remarkably improves the perceived speech quality of an SW-based MCU under various packet loss conditions in an IP network.

• Korean Journal of Food Science and Technology
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• v.34 no.5
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• pp.830-834
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• 2002

본 연구는 동적 전단진동(dynamic shear oscillation) 측정방법을 이용하여 농도가 젤라틴의 동적 레올로지 특성에 미치는 영향에 대하여 관찰하였다. $5^{\circ}C$에서의 젤라틴의 저장 탄성률(storage modulus, G#)과 손실 탄성률(loss modulus, G@)은 농도가 증가함에 따라 증가하는 경향을 보였다. 0.9%를 제외한 모든 농도(2.0-4.9%)에서 젤라틴의 G#은 G@보다 매우 높은 값을 나타냈으며, G#과 G@이 ${\omega}$ 의존성이 없는 true 겔과 같은 거동을 나타냈다. 젤라틴의 농도와 K#(G#에 대한 절편)와의 관계에서는 높은 결정계수$(R^2=0.99)$를 보여주면서 좋은 상관관계를 나타냈다. 여러 온도범위$(-5,\;0,\;5,\;10^{\circ}C)$에서 각 온도별로 측정된 K#값은 $-5^{\circ}C(59.5Pa)\;>\;0^{\circ}C(4.09Pa)\;>\;5^{\circ}C(1.41Pa)\;>\;10^{\circ}C(0.35Pa)$의 순으로 가장 낮은 온도에서 K#값이 가장 높은 것으로 나타났다. 또한 냉각과정에서 최종냉각온도인 $5^{\circ}C$에서 측정된 젤라틴의 최대 G#수치는 4.9%(2399Pa)>4.1%(1744Pa)>3.0%(1159Pa)>2.0%(519.3Pa)>0.9%(3.15Pa)의 순으로 높은 농도에서 높게 나타났다. Aging 10시간 동안 젤라틴 겔의 구조형성은 겉보기 first-order kinetics로부터 겉보기 구조형성 속도상수(K)를 결정함으로써 파악될 수 있다. 젤라틴의 농도가 증가함에 따라 K값은 증가하였으며, 농도와 K값과의 관계는 높은 결정계수$(R^2)$를 나타내면서 좋은 상관관계를 보여주었다(Fig. 7). 10시간 aging 후 G#은주파수$({\omega})$ 의존성이 없이 독립적인 것으로 나타났다. 따라서 이들 젤라틴 겔은 aging하는 동안에 탄성이 점점 강해지고 10시간 후에는 가교결합의 밀도가 증가하여 강한 탄성을 가진 고무질 망상구조(rubber network)를 형성했음을 알 수 있다.

• Journal of Internet Computing and Services
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• v.24 no.5
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• pp.1-7
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• 2023

This paper proposes a small cell resource partitioning allocation method to solve interference to machine type communication devices (MTCD) and improve performance in 5G heterogeneous networks (HetNet) where macro base station (MBS) and many small cell base stations (SBS) are overlaid. In the 5G HetNet, since various types of MTCDs generate data traffic, the load on the MBS increases. Therefore, in order to reduce the MBS load, a cell range expansion (CRE) method is applied in which a bias value is added to the received signal strength from the SBS and MTCDs satisfying the condition is connected to the SBS. More MTCDs connecting to the SBS through the CRE will reduce the load on the MBS, but performance of MTCDs will degrade due to interference, so a method to solve this problem is needed. The proposed small cell resource partitioning allocation method allocates resources with less interference from the MBS to mitigate interference of MTCDs newly added in the SBS with CRE, and improve the overall MTCD performace using separating resources according to the performance of existing MTCDs in the SBS. Through simulation results, the proposed small cell resource partitioning allocation method shows performance improvement of 21% and 126% in MTCDs capacity connected to MBS and SBS respectively, compared to the existing resource allocation methods.

• Journal of Internet Computing and Services
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• v.20 no.3
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• pp.13-24
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• 2019

The key concept of NOMA among 5G network technologies is to set the power allocation coefficient for each node. In this study, we implemented the algorithm that calculates the uplink/downlink power allocation coefficients which is the key concept of NOMA technology through analysis of minimum SNR required for successful decoding at the receiver, based on Full Duplex NOMA relay system. The performance comparison between the proposed algorithm and the existing power allocation methods is performed and the performance is confirmed in terms of ergodic sum capacity and outage probability.