• 전자공학회논문지A
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• 제32A권2호
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• pp.11-18
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• 1995

Error detection in ARQ(Automatic Repeat Request) protocols is very important in wireless data communication systems. The throughput efficiency of ARQ protocols can be improved by dynamically adapting the protocol packet length so that it approaches the optimum value for throuhput efficiency. In this paper, a simple and novel adaptive packet length allocation method is proposed which transmits the packets with variable length by dyanmically estimating the channel codition. The simulation results show that the average of throughput is improved by 315.4% in the stop-and-wait protocol, 41.4% in the go-back-N protocol and 155.9% in the selective repeat protocol respectively. And the throughput performances of adaptive packet length allocation method approximately approach the theoritically optimal throughput performances.

• Journal of the Optical Society of Korea
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• 제20권1호
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• pp.36-41
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• 2016

Visible Light Communication (VLC) using Light Emitting Diodes (LEDs) within the existing lighting infrastructure can reduce the implementation cost and may gain higher throughput than radio frequency (RF) or Infrared (IR) based wireless systems. Current indoor VLC systems may suffer from poor downlink resource allocation problems and small system throughput. To address these two issues, we propose an algorithm called a conflict graph scheduling (CGS) algorithm, including a conflict graph and a scheme that is based on the conflict graph. The conflict graph can ensure that users are able to transmit data without interference. The scheme considers the user fairness and system throughput, so that they both can get optimum values. Simulation results show that the proposed algorithm can guarantee significant improvement of system throughput under the premise of fairness.

• Journal of Communications and Networks
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• 제13권3호
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• pp.214-220
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• 2011

This paper attempts to address the effectiveness of physical-layer network coding (PNC) on the throughput improvement for multi-hop multicast in random wireless ad hoc networks (WAHNs). We prove that the per session throughput order with PNC is tightly bounded as ${\Theta}((n\sqrt{m}R(n))^{-1})$ if $m=(R^{-2}(n))$, where n is the total number of nodes, R(n) is the communication range, and m is the number of destinations for each multicast session. We also show that per-session throughput order with PNC is tight bounded as ${\Theta}(n^{-1})$, when $m={\Omega}(R^{-2}(n))$. The results of this paper imply that PNC cannot improve the throughput order of multicast in random WAHNs, which is different from the intuition that PNC may improve the throughput order as it allows simultaneous signal access and combination.

• 한국통신학회논문지
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• 제38B권1호
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• pp.26-33
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• 2013

저전력, 저가의 초소형 기지국인 펨토셀은 heterogeneous network 의 중요 구성 요소 중 하나이다. 그러나 펨토셀 설치에 따른 셀 구조의 변화는 셀 간 간섭과 signaling overhead 증가와 같은 기술적인 문제를 야기할 수 있다. 이와 같은 기술적인 문제의 해결 방법 중 하나는 펨토셀이 SON(Self-Organized Network)과 같은 기법을 이용하여 자율적으로 전송전력을 조절하는 것이다. 펨토셀은 전송전력 조절을 통해 시스템 throughput을 향상시키거나 overhead를 감소시킬 수 있다. 일반적으로 시스템 throughput을 최대화하기 위한 펨토셀 전송 전력과 시스템 overhead 감소를 위한 펨토셀 전송 전력은 일치하지 않는다. 따라서 본 연구에서는 펨토셀이 시스템 overhead를 감소시키는 동시에 시스템 throughput을 향상시키도록 전송 전력을 조절하는 방법을 제안한다. 모의실험을 통해 제안 기법이 throughput만을 최대화하는 기법에 비하여 시스템 overhead를 41% 감소시키는 것을 확인하였다. 또한 커버리지만을 최적화 하는 기법에 비하여 throughput이 63% 향상되는 것을 확인하였다.

• 한국통신학회논문지
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• 제34권9B호
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• pp.876-882
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• 2009

본 논문에서는 relay 기반 OFDMA 시스템에서 cell throughput 향상을 위한 Base Station (BS)과 Relay Station (RS)의 sub-cell 커버리지 조절 기법을 제안하였다. Relay 시스템에서는 BS-RS 링크에서 무선 자원을 추가로 소비하기 때문에, 이를 고려하지 않고 sub-cell 커버리지를 설정하면, 자원 사용량이 증가하여 throughput이 저하될 수 있기 때문에 자원 소모를 고려한 sub-cell 커버리지 설정이 필요하다. 이 때, 설정된 sub-cell 커버리지를 고정하여 운용할 수도 있지만, 트래픽 상황의 변화에 따라서 커버리지를 효과적으로 조절해주면, throughput 성능을 더욱 향상시킬 수 있다. 본 연구에서는 MS가 이동할 때에, 멀티홉 전송에 따른 relay link에서의 자원의 소모와 자원 재사용 정도를 함께 고려하여 sub-cell 커버리지를 조절하는 기법을 제안하고 분석하였다. 제안하는 커버리지 조절 기법에서는 BS와 RS로부터의 수신 SINR 값 비율로 threshold 값을 정하고 이를 이용하여 sub-cell 경계를 설정하였다. 그리고 트래픽의 변화에 따라 멀티홉에서의 자원의 소모와 자원 재사용을 고려한 effective transmitted bits per subchannel을 이용하여 sub-cell 경계를 적응적으로 조절하였다. 성능 분석을 위해 이 경우 cell throughput을 도출하였다. 제안하는 커버리지 조절 기법을 적용할 때, 고정하여 운용하는 경우에 비해, cell throughput이 향상되는 것을 확인하고, 정량적으로 분석하였다.

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

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권2호
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• pp.668-685
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• 2019

Provision of higher throughput without sacrificing consistency guarantees in replication systems is a critical problem. In this paper, we propose a novel approach called Bidirectional Chain Replication (BCR) to improve throughput in traditional Chain Replication (CR) through better utilization of computing and communication resources of the chain. Unlike CR where the whole replicated data store is treated as a single unit, in BCR the replicated shared data at each server in the chain is split into two disjoint Logical Partitions ($LP_1$, $LP_2$). This forms two chains running concurrently on the same hardware in two opposite directions; the first chain ($CR_1$) exclusively manipulates data objects in $LP_1$, while the second chain ($CR_2$) exclusively manipulates data objects in $LP_2$, therefore, conflict is avoided and concurrency is guaranteed. The simultaneous employment of these two chains results in better utilization of hardware in the sense that the two chains can evenly share the workload, hence, throughput can be improved without sacrificing consistency. Experimental results showed an improvement of approximately 85% in throughput of BCR over CR.

• Journal of Multimedia Information System
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• 제3권4호
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• pp.149-154
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• 2016

Wireless mesh networks (WMNs) are used for metropolitan area network that requires high network throughput for handling many users. TDMA-based access is a common solution for this problem and several scheduling methods have been proposed. However, existing heuristic methods have room for improvement at network throughput although they are low complexity. In this paper, we propose a novel divided scheduling method based on structural characteristics in order to improve network throughput in WMNs. It separately schedules neighbor links of gateways and that of the other links by different scheduling algorithms. Simulation-based evaluations show that our proposal improves up to 14% of network throughput compared with conventional scheduling algorithm script.

• Journal of Communications and Networks
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• 제12권1호
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• pp.43-51
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• 2010

IEEE 802.11 defines distributed coordination function (DCF), which is characterized by CSMA/CA and binary exponential backoff (BEB) algorithm. Most modifications on DCF so far have focused on updating of the contention window (CW) size depending on the outcome of own frame transmission without considering freezing periods experienced in the backoff interval. We propose two simple but novel schemes which effectively utilize the number of freezing periods sensed during the current backoff interval. The proposed schemes can be applied to DCF and its family, such as double increment double decrement (DIDD). Saturation throughput of the proposed schemes is analyzed by means of Bianchi's Markovian model. Computer simulation validates the accuracy of the analysis. Numerical results based on IEEE 802.11b show that up to about 20% improvement of saturation throughput can be achieved by combining the proposed scheme with conventional schemes when applied to the basic access procedure.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2007년도 하계종합학술대회 논문집
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• pp.97-98
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• 2007

In this paper, we investigate the throughput capacity of a multi-hop relay network with cognitive radio (CR) enabled relay stations (RS). We suggested a TDMA/FDMA based frame structure where RSs dynamically select unused channels to communicate with the base station (BS) using CR techniques to analyze the throughput capacity. We developed the throughput capacity model for the proposed system based on utilization factor. The analytical results based on those equations show significant improvement in throughput capacity for CR enabled multi-hop relay system.