• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제12권4호
• /
• pp.1471-1488
• /
• 2018

Interference mitigation is a significant issue in the cognitive heterogeneous networks, this paper studied how to reduce the interference to macrocell users (MU) and improve system throughput. Establish the interference model with imperfect spectrum sensing by analyzing the source of interference complexity. Based on the user topology, the optimize problem was built to maximize the downlink throughput under given interference constraint and the total power constraint. We decompose the resource allocation problem into subcarrier allocation and power allocation. In the subcarrier assignment step, the allocated number of subcarriers satisfies the requirement of the femtocell users (FU).Then, we designed the power allocation algorithm based on the Lagrange multiplier method and the improved water filling method. Simulation results and performance analyses show that the proposed algorithm causes less interference to MU than the algorithm without considering imperfect spectrum sensing, and the system achieves better throughput performance.

• Journal of electromagnetic engineering and science
• /
• 제10권3호
• /
• pp.99-103
• /
• 2010

Motivated by recent works on spectrum-sharing systems, this paper investigates the effects of transmit diversity on the peak interference power limited cognitive radio(CR) networks. In particular, we derive the ergodic and outage capacities of a spectrum-sharing system with multiple transmit-antennas. To derive the capacities, peak interference power constraint is imposed to protect the primary receiver. In a CR transmitter and receiver pair with multiple antennas at the transmitter side, the allowable transmit power is distributed over the transmit-antennas to achieve transmit diversity at the receiver. We investigate the effect of this power distribution when a peak interference power constraint is imposed to protect the primary receiver. We show that the transmit diversity does not improve the ergodic capacity compared to the single-antenna system. On the other hand, the transmit diversity significantly improves the outage capacity. For example, two transmit-antennas improve the outage capacity 10 times compared to the single-antenna with a 0 dB interference constraint.

• 한국통신학회논문지
• /
• 제35권11A호
• /
• pp.1038-1044
• /
• 2010

무선 통신 환경에서 간섭은 성능을 악화 시키는 요소이다. Han-Kobayashi 방식은 간섭의 영향을 줄이기 위해서 전송하는 신호를 개인신호와 공용신호로 분리하여 전송하고 수신기에서는 간섭 사용자의 공용신호를 제거하므로써 부분적으로 간섭을 제거한다. 본 논문에서는 개인신호만 전송할 때에 필요한 신호대 잡음비를 이용하여, 개인신호와 공용신호에 최적으로 전력을 할당하는 간단한 방법을 제안한다. 시뮬레이션을 통해서 제안하는 전력 할당 방법이 전수조사를 통한 기법의 성능에 근접함을 확인한다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제9권11호
• /
• pp.4331-4346
• /
• 2015

The femtocell network, which is designed for low power transmission and consists of consumer installed small base stations, coexists with macrocells to exploit spatial reuse gain. For its realization, cross-tier interference mitigation is an important issue. To solve this problem, we propose a joint access and power control scheme that requires limited information exchange between the femto and macro networks. Our objective is to maximize the network throughput while satisfying each user's quality of service (QoS) requirement. To accomplish this, we first introduce two distributed interference detection schemes, i.e., the femto base station and macro user equipment based schemes. Then, the proposed scheme dynamically adjusts the transmission power and makes a decision on the access mode of each femto base station. Through extensive simulations, we show that the proposed scheme outperforms earlier works in terms of the throughput and outage probability.

• 한국광학회지
• /
• 제13권6호
• /
• pp.479-485
• /
• 2002

다중모드간섭을 이용한 임의 분배 비율의 광전력 분배기에 대한 벡터 해석법을 제시한다 광전력 분배는 집적 광학의 기초가 되는 부분이며 특히 광전력 비율을 임의로 조절할 수 있다면 많은 응용분야에 유용할 것이다. 본 벡터 해석법은 기존의 다중모드간섭 현상에 대한 해석적 결과를 도식화함으로써 임의 분배 비율의 다중모드간섭 광전력 분배기 설계를 보다 쉽게 할 수 있다는 장점을 가지고 있다.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2003년도 통신소사이어티 추계학술대회논문집
• /
• pp.195-199
• /
• 2003

BEE 802.11 Wireless LAN protocol uses fixed transmission power. It does not consider a power control mechanism based on the distance between the transmitter and the receiver in order to improve overall channel utilization. In home environment, where stations generally lie around an AP, the AP is subject to use transmission power more than it needs. And wireless LAN stations may require different minimal desired received power. If there are many adjacent BSSs in densely populated WLAN area, they might cause RF interference to one another. In this paper we focus on the improvement of aggregate utilization by mitigating RF interference among BSSs. We show that RF interference by APs can be reduced by controlling transmission power using Link Margin information. The reduced interference will then lead to the increased aggregate throughput which is efficient resource utilization.

• International Journal of Computer Science & Network Security
• /
• 제22권4호
• /
• pp.223-228
• /
• 2022

Femtocells are being incorporated into heterogeneous networks in order to increase the network capacity. However, intensive deployment of femtocells results in undesired interference, which lowers the system's performance. Controlling the femtocell transmission power is one of of the aspects that can be addressed in order to mitigate the negative effects of the interference. It may also be utilized to facilitate the auto-configuration of the network's conductance, if necessary. This paper proposes the use of an auto-configuration technique for transmission power. The suggested technique is based on the transmission power of macrocells and the coverage provided by femtocells. The simulation findings show that the network's capacity has increased, and the amount of interference has decreased.

• 대한전자공학회논문지TC
• /
• 제49권8호
• /
• pp.77-83
• /
• 2012

본 논문에서는 주파수 공유 시스템의 구 채널 환경(outdated channel environment)에서 일차 사용자(primary user)에 의한 간섭이 존재할 때 이차 사용자(secondary user)의 평균값 기반 전력 할당 기법의 성능을 분석하고, 평가한다. 일차 사용자의 신호가 이차 사용자의 수신단에서 간섭으로 작용할 때, 이차 사용자의 에르고딕 용량(ergodic capacity)의 상한값을 분석하고, 이를 기반으로 일차 사용자에 의한 간섭이 이차 사용자의 성능 저하에 어느 정도 영향을 끼치는지 고찰한다. 모의 실험을 통해 간섭에 의한 이차 사용자의 성능 저하 정도를 보이고, 일차 사용자에 의한 간섭이 커질수록, 평균값 기반 전력 할당 기법의 용량이 구 채널 정보 기반 전력 할당 기법의 용량보다 좋아지는 영역이 작아지는 것을 보여준다.

• 한국통신학회논문지
• /
• 제29권2A호
• /
• pp.166-173
• /
• 2004

위성 통신 시스템은 지상국과 위성에서 고출력의 비선형 HPA(high power amplifiers)를 사용하게 된다. 그러므로 HPA의 비선형성이 통신 시스템에 미치는 영향을 고려하는 것이 중요하다. 본 연구는 비선형성 HPA에 의한 전력 스펙트럼 밀도 변화와 IBO(input back-off)에 따라 신호의 왜곡과 하모닉 성분의 크기 변화를 구한다. 그리고 BPSK 위성 통신 시스템에서, HPA에 의한 인접 채널 간섭(ACI : adjacent channel interference) 및 외부 재밍 간섭 등에 의한 동일채널 간섭(CCI : co-channel interference)를 고려하여 성능분석을 한다. 일정한 uplink SNR(signal to noise power ratio), uplink SIR(signal to co-channel interference power ratio), downlink SIR인 상황에서, 인접 채널 간섭의 크기에 따른 BER 성능 변화를 구한다. 위성에만 비선형 HPA가 있을 경우는, 비선형에 의한 인접 채널 간섭의 크기에 따라 성능에 많은 차이가 있음을 확인하였다. 그리고 지상국과 위성에서 모두 비선형 왜곡이 있을 때, CCI와 인접 채널 간섭에 의하여 더욱 성능이 저하된다.

• 한국전기전자재료학회논문지
• /
• 제23권8호
• /
• pp.645-650
• /
• 2010

The continuous increase demand for electric power leads to the additional construction of transmission facilities, but it is not easy to acquire right-of-way for transmission facilities. Therefor, there is a need for compact tower that can be built on a narrow right-of-way the compact tower with polymer insulation arm is a solution. It can be upgrading conventional 154 kV transmission line voltages to 345 kV levels. However transmission voltage is increasing, environment interference (corona noise, radio interference, etc.) will occur gradually. This environment interference is depending on the electrical clearances of tower and configuration of conductors. Therefore the analysis of the factors of environmental interference is necessary in order to upgrading transmission voltage. This paper presents the design factor of a compact tower to meet the environmental interference standard.