Earticle

Since mobile traffic has been growing recently, the deployment of indoor small cells has become an attractive solution to enhance coverage. However, the increasing density of cells makes inter-cell interference more considerable. In this paper, we propose a max-throughput Interference Avoidance (MTIA) centralized algorithm to improve the system’s throughput. Based on signaling and reports, a central controller connected to each base station can properly turn off base stations that may induce a relatively strong interference, and thus increase SINR. We implemented the MTIA algorithm in an LTE TDD network simulation and showed that MTIA effectively reduces inter-cell interference and improves the system’s throughput.

이 논문에서는 백스케터 통신에서 악의적인 간섭이 존재할 때, 게임이론을 적용하여 간섭으로부터 회피하고 통신의 성능 최적화를통한 성능 분석에 관한 내용을 다룬다. 백스케터 통신을 원신호원을 반사하여, 백스케터 신호를 전송하기 때문에 악의적인 간섭에취약하게 된다. 이를 해결하기 위해 리더-펄로워 관계인 스텔켈베르그 게임이론을 적용하며, 라그랑지안 승수 방법을 통해 최적화를수행한다. 또한, 네쉬 게임이론과 스텔켈베르그 두 가지 게임이론을 백스케터 통신에 적용하고 적용된 게임이론에 따른 백스케터통신의 간섭 회피 성능을 비교 분석을 수행한다. 본 논문의 시뮬레이션을 통해 스텔켈베르그 게임이론이 악의적인 간섭 회피에서더 나은 성능을 보임을 증명하고, 백스케터의 통신 최적의 성능과 스텔켈베르그 게임 균형을 확인한다.

In this paper, we study an interference avoidance scenario in the presence of a interferer which can rapidly observe the transmit power of backscatter communications and effectively interrupt backscatter signals. We consider a power control with a sub-channel allocation to avoid interference attacks and a power-splitting ratio for backscattering and RF energy harvesting in sensors. We formulate the problem based on a Stackelberg game theory and compute the optimal transmit power, power-splitting ratio, and sub-channel allocation parameter to maximize a utility function against the interferer. We propose the utility maximization using Lagrangian dual decomposition for the backscatter communications and the interferer to prove the existence of the Stackelberg equilibrium. Numerical results show that the proposed algorithms effectively maximize the utility, compared to that of the algorithm based on the Nash game, so as to overcome a malicious interference in backscatter communications

Tool interference is one of the most critical problems in machining die cavities and punches. When machining concave or convex regions of cavities with large radius tool in rough cutting, the tool easily overcuts or undercuts the portions of the surface, which result in machining inaccuracy. So the generation of interference-free tool path must be required for more efficient rough cutting. In this paper, we present a method for modeling die cavities which consist of simple surface or analytic compoyund surfaces and present an algorithm for checking and removing the tool interference occurred in machining the die cavities. Using these algorithms, we can represent a die cavity, and check the interfer- ence regions, and then remove these interferences. Especially we focus on the side interference in the sides of analytic elements and base surface boundary.

In this paper, we propose a resource allocation and Tx power control scheme, called resource allocation and power control (RAPC) in an LTE-Advanced device-to-device (D2D) network. In the proposed scheme, the macro base station (mBS) and D2D senders (D2DSs) service macro user equipment (mUEs) and D2D receivers (D2DRs) use the different frequency bands and Tx power chosen as D2D links’ locations in inner and outer zones to reduce interference substantially. We analyze and compare the proposed scheme and random resource allocation (RRA) scheme with fractional frequency reuse (FFR) systems in terms of the system throughput for DL and outage probability according to the number of D2D user’s (D2DR) traffic density. Simulation results show that the RAPC scheme has better performance than the random resource allocation (RRA) scheme performance in terms of the system throughput and outage probability for mUEs and D2DRs.

Advances in MEMS (Micro Electro Mechanical Systems), microprocessor, and wireless technologies, have accelerated deployment of network-capable computing devices attached to various objects over the world. These devices should be small in size and have a characteristic of extremely low power consumption. Therefore, in 2004, IEEE 802.15.4 has been established as a global standard for LR-WPANs. After that, the phenomenal popularity of this standard has also led to indiscreet deployment of other WPANs. Therefore, LR-WPANs can suffer from collision by other WPAN devices. In order to solve collision problem in IEEE 802.15.4, in this paper we introduce a novel channel scheduling scheme which is an adaptive method with fast recovery. The proposed scheme can minimize the possibility of beacon collisions by efficiently managing the multiple available channels in a hybrid manner combining proactive and reactive methods.

Inter-cell interference (ICI) is a major problem in heterogeneous networks, such as two-tier femtocell (FC) networks, because it leads to poor cell-edge throughput and system capacity. Dynamic ICI coordination (ICIC) schemes, which do not require prior frequency planning, must be employed for interference avoidance in such networks. In contrast to existing dynamic ICIC schemes that focus on homogeneous network scenarios, we propose a novel semi-distributed dynamic ICIC scheme to mitigate interference in heterogeneous network scenarios. With the goal of maximizing the utility of individual users, two separate algorithms, namely the FC base station (FBS)-level algorithm and FC management system (FMS)-level algorithm, are employed to restrict resource usage by dominant interference-creating cells. The distributed functionality of the FBS-level algorithm and low computational complexity of the FMS-level algorithm are the main advantages of the proposed scheme. Simulation results demonstrate improvement in cell-edge performance with no impact on system capacity or user fairness, which confirms the effectiveness of the proposed scheme compared to static and semi-static ICIC schemes.

Co-channel interference between macro-femtocell networks is an unresolved problem, due to the frequency reuse phenomenon. To mitigate such interference, a secondary femtocell must acquire channel-state knowledge about a co-channel macrocell user and accordingly condition the maximum transmit power of femtocell user. This paper proposes a pilot-based spectrum sensing (PSS) algorithm for overlaid femtocell networks to sense the presence of a macrocell user over a channel of interest. The PSS algorithm senses the pilot tones in the received signal through the power level and the correlation metric comparisons between the received signal and the local reference pilots. On ensuring the existence of a co-channel macrocell user, the maximum transmit power of the corresponding femtocell user is optimized so as to avoid interference. Time and frequency offsets are carefully handled in our proposal. Simulation results show that the PSS algorithm outperforms existing sensing techniques, even at poor received signal quality. It requires less sensing time and provides better detection probability over existing techniques.

When we assign frequency resources to a new radio service, the existing services need not to be interfered with by the new service. Therefore, when we make a frequency assignment, a guard band is necessary to separate adjacent frequency bands so that both can transmit simultaneously without interfering with each other. In this paper, we propose an efficient frequency guard band decision rule for avoiding interference between radio services. The guard band is established based on the probability of interference in the previously arranged scenario. The interference probability is calculated using the spectrum engineering advanced Monte Carlo(MC) analysis tool(SEAMCAT). After applying the proposed algorithm to set up the frequency guard band, we can decide on the guard band appropriately because the result satisfies the predefined criterion.

Unmanned Surface Vessels (USV) may interfere with ships in the same lane during navigation and may be affected by ships that actively collide or intercept the USV. Evidently, the latter poses a greater threat than the former. This paper proposes the concept of active and inactive interference. It is necessary for the USV to accurately classify the vessels' intentions to conduct a suitable collision avoidance strategy. However, the existing research on collision avoidance of USV focuses on avoiding moving obstacles and rarely considers the interference intention of dynamic obstacles for USV when choosing collision avoidance strategies. This paper proposes an algorithm to recognize the interference intention of ships by combining visual classification with a Support Vector Machine (SVM). First, a Convolutional Neural Network (CNN) is proposed to distinguish the merchant ship from a high-performance ship that actively interferes with the USV with high probability. A high-dimensional feature dataset was designed to illustrate the navigation characteristics of an obstacle, and Principal Component Analysis (PCA) was then employed to reduce the dimensionality of the dataset for obstacle classification. A modified SVM is presented to classify obstacles into active and inactive interference intention categories. Moreover, an escape algorithm based on an improved artificial potential field method is proposed for vessels with active interference. The simulation and experimental results clearly show that the USV can successfully identify the interference intention of obstacles and adopt a specific collision avoidance strategy for obstacles with active interference intentions. Using this algorithm, the USV can safely avoid obstacles with different interference intentions.

이기종 비면허 기기들이 동일한 주파수 대역을 공동 사용하기 위해서는 주파수 간섭 회피 기법이 필요하다. 본 논문에서는 이기종 비면허 대역 공동 사용의 대표적인 예로서 2.4 GHz ISM 대역에서 동작하는 WLAN과 WPAN 간의 주파수 간섭을 MAC 계층에서 분석하였다. 분석 결과, WPAN의 성능이 WLAN의 간섭으로 인하여 크게 저하되는 것을 시뮬레이션과 실험을 통해 확인하였다. 이러한 주파수 간섭을 회피하기 위한 방법으로 WPAN 시스템을 위한 채널 변경 기법을 새롭게 제안하였다. 실험을 통하여 제안한 채널 변경 기법이 고정된 채널을 사용하는 기존의 방법에 비하여 주파수 간섭의 영향을 회피할 수 있음을 확인하였다.

In order for heterogeneous unlicensed devices to co-exist on the same frequency band, the frequency interference avoidance mechanism is necessary. In this paper, a frequency interference between WLAN and WPAN systems that operate at 2.4 GHz ISM band was analyzed in the MAC layer. We observed that WPAN systems suffer from severe interference from WLAN systems. To avoid this interference problem, we propose a new channel shift algorithm for WPAN systems. We showed that the proposed channel shift algorithm is better than the traditional WPAN system which uses a fixed channel in terms of throughput.

본 논문에서는 매크로기지국과 펨토기지국의 간섭을 회피하는 방법인 자원대체 간섭회피기법을 제안한다. 이 기법은 펨토셀 영역의 여유로운 자원을 할당받은 후에, 이기종망 간의 발생할 수 있는 충돌을 미리 검사하고 충돌이 예상되면 충돌가능자원을 회피하고 여유로운 자원으로 대체하여 통신을 한다. 본 기법을 적용하면 하향링크 및 상향링크에서 이기종망 간의 직교주파수를 적용하면서 발생할 수 있는 지연을 최소화 할 수가 있으며, 이기종망 간에서 주파수를 분할하여 통신을 하는 SFR 기법과 비교하여, 자원의 효율성을 높일 수가 있다.

Free-form surfaces arise in shipbuilding, automotive and aerospace industries. Specially compound free-form surfaces so do. Machining complicated products consist of compound surface, it is very important to avold and remove tool interferences. By the way, in compound surfaces the tool interference can occur not only in the tool path direction but also in the other direction. A new tool interference detection and correction using tool interference conditions is suggested to identify and correct the tool interference in compound surfaces.

Compound surface modeling is widely used for die cavities and punches. A compound surface is defined in 3-D space by specifying the topological relationship of several anlytic surface elements and a sculptured surface. A constructive solid gemonetry scheme is employed to model the analytic compound surface. the desired compound surface can be accomplished by specifying topological reationship in terms of boolean relations between pimitives and the sculptured surfaces. Additionally, a method is presented for checking and avoiding the tool interference occuued in machining the compound surface. Using this method. the interference of concave, convex, and side region can be checked easily and avoided rpapidly.

금형 제작에는 금형의 형상을 모델링 하는 모델링 기법과 이 모델링 정보로부터 공구의 경고계획, 황삭, 정삭, 잔삭가공과 가공조건등의 여러 가지 고려해야 하는 사항이 많이 있다. 근래에 들어 금형은 그 기능적인 측면뿐 아니라 미적 감각까지 만족시키는 심미안적인 측면이 많이 고려되고 있으며 CAD/CAM 소프트웨어, CNC, 머시닝 센터등릉 이용한 기술 집약적인 생 산체제로 변화하는 실정이며 금형의 생산성 향상 및 납기단축에 중점을 두고 있다. 본 연구에서는 이러한 공구간섭의 배경 을 바탕으로 하여 해석적 복합곡면에서 간섭이 발생하는 부위를 솔리드 모델링 기법을 응용하여 빠르게간섭역을 찾고 찾아진 간섭역에서의 공구간섭 현상을 검사하고 제거하고자 한다. 이러한 방법은 공구간섭검사에 필요한 계산시간을 단축하고 소요 되는 기억용량의 소모를 줄일 수 있으며 나아가 실시간 가공에도 적용할 수 있으리라 본다.

This paper presenta new method for tool interference acoidance using rectanguar approximation in NC machining of scuptured surface. The procedure of algorithm for approximation of sculptured surface to rectangular surface is described. Using this algorithm, we can check concave, convex, and side interference region and avoid these interferenes.

When machining a die cavity, many machining conditions must be considered. Especially when using a NC machine, The tool interference is a improtant problem. In this paper, we consider the tool interference of free-formed surfaces and analytic compound surfaces which having free_formed base and many primitives and present a method checking the tool interference regions and avoiding them

무선 통신 기반의 ESL(Electronic Shelf Label) 시스템은 일회용 종이 낭비를 줄이고 노동력 감소 및 실시간 정보 업데이트가 가능하다. 하지만 많은 수의 ESL 모듈이 설치된 환경은 ISM(Industry-Science-Medical) 대역의 RF(Radio frequency) 통신으로부터 간섭에 노출되어 있다. 본 논문에서는 ISM 대역을 사용하는 ESL 시스템의 혼잡을 회피하기 위하여 가시광 통신 기반 ESL 시스템을 제안한다. 제안하는 시스템은 관리자 서버로부터 입력된 상품 정보 및 ID를 ESL Tag로 전송하며, ESL Tag는 ID를 확인하여 해당 상품 정보를 표시한다. 실험을 통해 가시광 통신을 이용한 ESL 시스템이 가능함을 확인하였다.

The electronic shelf label(ESL) system based on wireless communication can reduce waste of disposable paper, reduce labor force and update real time information. However, the environment in which a large number of ESL modules are installed is exposed to interference from radio frequency(RF) communications in the Industry-Science-Medical(ISM) band. In this paper, we propose an ESL system based on visible light communication to avoid congestion of ESL system using ISM band. In the proposed system, the goods information and ID transmitted from the administrator server are transmitted in the ESL Tag, and the ESL Tag identifies the ID and displays the product information. Experiments show that ESL system using visible light communication is possible.