• 대한전자공학회논문지TC
• /
• 제44권9호
• /
• pp.17-24
• /
• 2007

본 논문에서는 멀티 홉 OFDMA 시스템에서 relay간 무선자원을 효율적으로 재사용하기 위한 방법으로 sub-cell reuse partitioning 기법을 제안한다. 셀 내에서 relay 들에 주파수 자원을 더 많이 재사용을 할수록 사용 가능한 자원이 늘어나 셀 용량을 증가시킬 수 있다. 하지만 이 경우 자원이 재사용되면서 동시에 발생되는 간섭이 많아져 Relay Station(RS) sub-cell edge에서 SINR 성능이 나빠질 수 있으며 결과적으로 fairness 성능을 나쁘게 만들 수 있다. 본 논문에서는 throughput 및 fairness 성능을 모두 좋게 만들기 위해 RS sub-cell을 내부와 외부로 나누어 내부에서는 재사용을 더 많이 하고, 외부에서는 재사용을 덜 적용하는 sub-cell reuse partitioning 기법을 제안하였다. 제안한 기법의 성능을 분석하기 위하여 모의실험을 구성하였다. Fairness 분석을 위하여 reuse partitioning과 함께 적용할 수 있는 스케줄링 알고리즘도 구현하였다. 도출된 성능 결과를 분석하여 sub-cell reuse partitioning 기법을 적용하여 throughput 성능과 fairness 성능을 함께 개선할 수 있음을 확인하였다. 특히, 스케줄링을 fairness 성능을 개선하는 방향으로 적용할 때, sub-cell reuse partitioning 기법을 적용하여 얻어지는 throughput 성능의 개선 효과가 더 크게 됨을 확인하였다.

• 한국멀티미디어학회논문지
• /
• 제16권5호
• /
• pp.601-609
• /
• 2013

One of the most serious factors constraining the next generation cellular mobile consumer communication systems will be the severe co-channel interference experienced at the cell edge. Such a capacity-degrading impairment combined with the limited available spectrum resource makes it essential to develop more spectrally efficient solutions to enhance the system performance and enrich the mobile user's application services. This paper proposes a unique hybrid method of frequency hopping (FH) and subcarrier-reuse-partitioning that can maximize the system capacity by efficiently utilizing the available spectrum while at the same time reduce the co-channel interference effect. The main feature of the proposed method is that it applies an optimal combination of different frequency reuse factors (FRF) and FH-subcarrier allocation patterns into the partitioned cell regions. From the simulation results, it is shown that the proposed method can achieve the optimum number of subcarrier subsets according to the frequency-reuse distance and results in better performance than the fixed FRF methods, for a given partitioning arrangement. The results are presented in the context of both blocking probability and BER performances. It will also be shown how the proposed scheme is well suited to FH-OFDMA based cellular systems aiming at low co-channel interference performance and optimized number of subcarriers.

• Journal of Communications and Networks
• /
• 제8권1호
• /
• pp.13-20
• /
• 2006

In cellular mobile communications, how to achieve optimum system capacity with limited frequency spectrum is one of the main research issues. Many dynamic channel assignment (DCA) schemes have been proposed and studied to allocate the channels more efficiently, thus, the capacity of cellular systems is improved. Reuse partitioning (RP) is another technique to achieve higher capacity by reducing the overall reuse distance. In this paper, we present a network-based DCA scheme with the implementation of RP technique, namely dynamic reuse partitioning with interference information (DRP-WI). The scheme aims to minimize the effect of assigned channels on the availability of channels for use in the interfering cells and to reduce their overall reuse distances. The performance of DRP-WI is measured in terms of blocking probability and system capacity. Simulation results have confirmed the effectiveness of DRP-WI scheme. Under both uniform and non-uniform traffic distributions, DRP-WI exhibits outstanding performance in improving the system capacity. It can provide about 100% capacity improvement as compared to conventional fixed channel assignment scheme with 70 system channels.

• 한국전자파학회논문지
• /
• 제18권5호
• /
• pp.465-470
• /
• 2007

멀티미디어 이동 통신에서 동일 채널 간섭은 시스템의 성능을 저하시키는 중요한 요인이다. 본 논문에서는 이러한 동일 채널 간섭을 억제하고 시스템의 성능을 최대화하기 위하여 주파수 재사용 구간을 사용한다. 먼저 수학적 모델링을 통하여 주파수 재사용 구간을 적용한 시스템에서의 동일 채널 간섭량을 분석한다. 이를 바탕으로 시스템 전송량을 최대화 시킬 수 있는 주파수 재사용 구간을 결정한다. 마지막으로 분석 결과와 모의 실험 결과를 통하여 주파수 재사용 구간을 적용한 시스템이 동일 채널 간섭량을 줄이며 시스템 전송량을 최대화 시킬 수 있음을 보인다. 실험 결과를 통하여 셀의 트레픽 로드에 따라서 재사용 구간이 $0.7{\sim}0.8$의 구간에서 시스템 전송량이 최대화 되며, 셀룰러 시스템 디자인 변수로 이와 같은 결과를 이용하면 시스템 전송량을 최대화 할 수 있다.

• 한국통신학회논문지
• /
• 제34권9B호
• /
• pp.892-899
• /
• 2009

주파수 분할 재사용 기법은 셀룰러 시스템의 성능을 향상시키기 위한 기술이다. 주파수 분할 재사용 기반시스템에 대한 기존 연구에서는 호의 발생과 채널 선택 과정을 설명하고 있지 않다. 따라서 본 논문에서는 단말의 채널 선택 과정을 설명하고 주파수 분할 재사용 기반 시스템의 성능을 분석한다. 성능은 채널 사용률과 호 차단 확률로 나타낸다. 본 논문의 결과는 차후 주파수 분할 재사용 기반 시스템의 성능 분석에 추가되어 실제적인 시스템의 성능 분석을 가능하게 할 것이다.

• 한국정보처리학회논문지
• /
• 제7권2호
• /
• pp.437-445
• /
• 2000

마이크로셀룰러 네트워크에서 재사용 분할 시스템은 고속 단말의 핸드오프 증가로 시스템 성능이 저하되는 단점을 갖는다. 따라서 본 논문에서는 마이크로셀을 이용한 재사용 분할 시스템의 성능을 개선하기 위하여 내부셀과 외부셀의 트래픽 분포 비율에 따라 고속과 저속 단말의 자원을 관리하는 핸드오프 알고리즘을 제안한다. 또한 고속과 저속 단말의 성능을 분석하고 컴퓨터 시뮬레션을 통해서 핸드오프 확률, 호 절단 확률에 대하여 RPS와 비교 평가한다.

• 한국통신학회논문지
• /
• 제40권3호
• /
• pp.559-567
• /
• 2015

This paper focuses on evaluating the performance of a cellular network using power control based frequency reuse partitioning (FRP) in downlink (DL). In our work, in order to have the realistic environment, the spectral efficiency of the system is evaluated through traffic analysis, which most of the previous works did not consider. To further decrease the cell edge user's outage, the concept of power ratio is introduced and applied to the DL FRP based cellular network. In considering network topology, we first divide the cell coverage area into two regions, the inner and outer regions. We then allocate different sub-bands in the inner and outer regions of each cell. In the analysis, for each zone ratio, the performance of FRP system is evaluated for the given number of power ratios. We consider performance metrics such as call blocking probability, channel utilization, outage probability and effective throughput. The simulation results show that there is a significant improvement in the outage experienced by outer UEs with power control scheme compared to that with no power control scheme and an increase in overall system throughput.

• Nuclear Engineering and Technology
• /
• 제50권7호
• /
• pp.1060-1067
• /
• 2018

A feasibility of reusing option of spent nuclear fuel in a fusion-fission hybrid system without partitioning was checked as an alternative option of pyro-processing with critical reactor system. Neutronic study was performed with MCNP 6.1 for this option, direct reuse of spent PWR fuel (DRUP). Various options with DRUP fuel were compared with the reference design concept; transmutation purpose blanket with (U-TRU)Zr fuel loading connected with pyro-processing. Performance parameters to be compared are transmutation performance of transuranic (TRU) nuclides, required fusion power and tritium breeding ratio (TBR). When blanket part is loaded only with DRUP, initial $k_{eff}$ level becomes too low to maintain a practical subcritical system, increasing the required fusion power. In this case, production rate of TRU nuclides exceeds the incineration rate. Design optimization is done for combining DRUP fuel with (U-TRU)Zr fuel. Reactivity swing is reduced to about 2447 pcm through fissile breeding compared to (U-TRU)Zr fuel option. Therefore, a required fusion power is reduced and tritium breeding performance is improved. However, transmutation performance with TRU nuclides especially $^{241}Am$ is degraded because of softening effect of spectrum. It is known that partitioning and transmutation should be accompanied with fusion-fission hybrid system for the effective transmutation of TRU.

• 한국통신학회논문지
• /
• 제37권8B호
• /
• pp.677-686
• /
• 2012

In the presence of a high power cellular network, picocells are added to a Macro-cell layout aiming to enhance total system throughput from cell-splitting. While because of the different transmission power between macrocell and picocell, and co-channel interference challenges between the existing macrocell and the new low power node-picocell, these problems result in no substantive improvement to total system effective throughput. Some works have investigated on these problems. Pico Cell Range Expansion (CRE) technique tries to employ some methods (such as adding a bias for Pico cell RSRP) to drive to offload some UEs to camp on picocells. In this work, we propose two solution schemes (including cell selection method, channel allocation and serving process) and combine new adaptive frequency partitioning reuse scheme to improve the total system throughput. In the simulation, we evaluate the performances of heterogeneous networks for downlink transmission in terms of channel utilization per cell (pico and macro), call blocking probability, outage probability and effective throughput. The simulation results show that the call blocking probability and outage probability are reduced remarkably and the throughput is increased effectively.

• International Journal of Computer Science & Network Security
• /
• 제22권4호
• /
• pp.292-298
• /
• 2022

Femtocell networks can be a potential method for increasing the capacity of LTE networks, especially in indoor areas. However, unplanned deployment of femtocells results in co-tier interference and cross-tier interference problems. The interference reduces the advantages of implementing femtocell networks to a certain extent. The notion of Fractional Frequency Reuse (FFR) is proposed in order to reduce the impact of interference on the system's performance. In this paper, a dynamic approach for efficiently partitioning the spectrum is suggested. The goal is to enhance the capacity of femtocells, which will improve the performance of the system. The suggested strategy allocates less resources to the macrocell portion of the network, which has a greater number of femtocells deployed to maximize the utilization of available resources for femtocell users. The spectrum division would be dynamic. The proposed strategy is evaluated through a simulation using MATLAB tool. In conclusion, the results showed that the proposed scheme has the potential to boost the system's capacity.