• Journal of information and communication convergence engineering
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• 제16권2호
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• pp.72-77
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• 2018

This paper presents a novel channel capacity maximization method for a distorted $2{\times}2$ line-of-sight (LOS) multiple-input multiple-output (MIMO) link. A LOS MIMO link may be distorted by the influence of environmental factors such that the channel capacity of the LOS MIMO link may be degraded. By using the proposed method, the channel capacity of a distorted $2{\times}2$ LOS MIMO link can be the same as that of the ideal $2{\times}2$ LOS MIMO link. The proposed method employs an additional receiver antenna to maximize the channel capacity. In contrast to a $3{\times}2$ LOS MIMO link, a receiver circuit for a third receiving antenna is not necessary. Hence, the receiver for the proposed method is much simpler than that for a $3{\times}2$ LOS MIMO link. We determine the optimal position of the additional receiver antenna analytically. Simulation results show that the channel capacity can approach the ideal using the proposed method.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(1)
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• pp.117-120
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• 2000

This paper discusses solutions for forward link power allocation based on 3GPP(FDD) standardization reports and which meet the required Eb/No of forward link channels. In addition, the forward link user capacity in a mixed service environment. Cell coverage is induced from the user capacity solutions using the urban propagation model. In an urban macrocell environment, the forward link user capacity turns out to be roughly 29 and 3, respectively, for voice and data service (144 kbps) at a distance of 1 km, and in an urban microcell environment, the user capacity turns out to be Toughly 14, 4, and 2, respectively, for voice and two data services (144 kbps, 384 kbps) when the cell radius is 0.2 km.

• 한국통신학회논문지
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• 제26권11B호
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• pp.1534-1539
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• 2001

In this paper, effects of soft handoff region on the reverse link capacity of a DS-CDMA cellular system are investigated. The reverse link capacity of a CDMA cellular system is calculated at a given soft handoff region ratio (SHRR) and path loss model. The results show that the reverse link capacity increases by 1 ∼ 4 channels according to the soft handoff region ratio and the path loss model. However, in the case of the path loss model having a large attenuation exponent ($\mu$ = 5) and a small shadowing standard deviation ( $\sigma$ = 6 dB), the reverse link capacity is no more increased by increasing SHRR.

• 한국전자파학회논문지
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• 제21권10호
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• pp.1194-1199
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• 2010

본 논문에서는 빔 성형(beamforming) 기술을 사용하는 릴레이 기반 셀룰러 네트웍에서, 순방향 링크 채널 상태에 대한 제한된 피드백 정보를 이용하여, 동시에 전송되는 송신기과 수신기 사이의 직접 링크(direct link)와 중계기(relay station)와 수신기 사이의 중계 링크(relaying link) 간의 간섭을 효과적으로 억제하는 간섭 회피(interference avoidance) 빔 성형 기술을 제안한다. 이를 위해 송신기는 빔 성형을 사용하여 한정된 공간으로만 직접링크 신호 전력을 전송하고, 송신기의 간섭 전력이 도달하지 않는 공간 영역에 위치한 릴레이들의 relaying을 허용함으로써, 효과적으로 직접 링크와 중계 링크간 간섭을 억제할 수 있는 충돌 회피(collision avoidance) 스케줄링 기술을 제안한다. 시뮬레이션을 통해 제안하는 간섭 회피 빔 성형 기술이 중계 링크의 전송 용량을 보장하면서 동시에 전송되는 직접 링크 전송 용량을 최대화 할 수 있음을 보인다.

• 한국통신학회:학술대회논문집
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• 한국통신학회 1983년도 추계학술발표회논문집
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• pp.108-111
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• 1983

This paper presents a new method for the optimum capacity assignment in store-and-forward communication networks under a total fixed-capacity constraints. Any two link capacities needed in this method can have the desirable quantites and then other capacities can be obtained from the fixed two link capacities. When the minimum and the maximum capacities that are the quantites of the conventional method are fixed, the total average time delay from the new method is almost the same as that from the conventional method. And when the minimum capacity is fixed, the new method gives smaller average time delay.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 ITC-CSCC -1
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• pp.125-128
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• 2000

In this paper, we derive forward link Erlang capacity reflecting both outage probability and blocking probability of each traffic type in mixed traffics environment. We firstly determine the number of available virtual trunks of the forward link from a circuit switching perspective. Then, capacity sharing model and generalized Erlang model are employed to derive joint Erlang capacity of various traffics types.

• 한국통신학회논문지
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• 제25권4A호
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• pp.481-488
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• 2000

The demands for mobile communication service are growing rapidly. In heavily populated areas, cell split is unavoidable to increase the capacity of the cellular system. Cell splitting makes a cellular system to have mixed cell sizes. For cell planning, it is necessary to analyze the reverse link capacity of a CDMA cellular system with mixed cell sizes. In this paper, we propose a method to calculate the reverse link capacity of a CDMA cellular system with mixed cell sizes. When a macro cell is split into three micro cells, as an example, we calculate the reverse link capacities for the three micro cells and the neighboring macro cells. The results show that as the radius of a micro cell decreases, the reverse link capacity of the micro cell increases, while those of the neighboring macro cells decrease.

• 한국ITS학회 논문지
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• 제11권1호
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• pp.105-111
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• 2012

본 연구에서는 정보통신기술을 활용한 미래전 개념인 네트워크 중심전 수행에 있어서 가장 보편적으로 쓰이고 있는 Link-16의 기술적 요소들을 물리계층, 데이터링크 계층, 응용계층 (전술메시지교환) 측면에서 검토하고 작전운용 측면에서 Link-16 만의 장점과 한계점을 도출해 보기로 한다. 또한 Link-16의 타임슬롯 구조, NPG 개념, 멀티네팅 개념을 기반으로 주요 작전을 수행하는 데 있어서 Link-16이 갖는 통신용량이 과연 충분한지 정량적 분석을 수행한다. 이러한 연구결과는 향후 Link-16의 국내도입에 있어서 타당성 검토를 위한 기초자료로 활용될 수 있을 것이다.

• ETRI Journal
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• 제40권3호
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• pp.330-336
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• 2018

Free-space optical (FSO) systems have attracted much attention from both research and application perspectives owing to their many benefits, such as license-free operation, low-cost, and high data rates. This paper investigates the ergodic capacity of FSO systems, which is an important metric of system performance. The stochastic temporary laser-beam blockage, pointing errors, and atmospheric turbulence are simultaneously considered. The results illustrate that the link blockage causes a decreased ergodic capacity. We show that to maximize the ergodic capacity, there is an optimal value of the laser-beam radius at the waist, which largely depends on pointing errors; however, it is independent of the atmospheric turbulence and the probability of link blockage.

• Journal of Communications and Networks
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• 제10권2호
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• pp.175-185
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• 2008

In this paper, we investigate the effect of cooperative and selection relaying schemes on multiuser diversity in downlink cellular systems with fixed relay stations (RSs). Each mobile station (MS) is either directly connected to a base station (BS) and/or connected to a relay station. We first derive closed-form solutions or upper-bound of the ergodic and outage capacities of four different downlink data relaying schemes: A direct scheme, a relay scheme, a selection scheme, and a cooperative scheme. The selection scheme selects the best access link between the BS and an MS. For all schemes, the capacity of the BS-RS link is assumed to be always larger than that of RS-MS link. Half-duplex channel use and repetition based relaying schemes are assumed for relaying operations. We also analyze the system capacity in a multiuser diversity environment in which a maximum signal-to-noise ratio (SNR) scheduler is used at a base station. The result shows that the selection scheme outperforms the other three schemes in terms of link ergodic capacity, link outage capacity, and system ergodic capacity. Furthermore, our results show that cooperative and selection diversity techniques limit the performance gain that could have been achieved by the multiuser diversity technique.