• 한국멀티미디어학회논문지
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• 제15권12호
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• pp.1456-1463
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• 2012

In this paper, we study the ON/OFF control policy of base stations in two-tier heterogeneous cellular networks to minimize the total power consumption of the system. Using heterogeneous cellular networks is a potential approach of providing higher throughput and coverage compared to conventional networks with only macrocell deployment, but in fact heterogeneous cellular networks often operates regardless of total power consumption, which is a very important issue of modern cellular networks. We propose a policy that controls the activation/deactivation of base stations in heterogeneous cellular networks to minimize total power consumption. Under this policy, the total power consumed can be significantly reduced when the traffic is low while the QoS requirement is satisfied.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권2호
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• pp.462-483
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• 2016

The research on optimization of cellular network's energy efficiency (EE) towards environmental and economic sustainability has attracted increasing attention recently. In this survey, we discuss the opportunities, trends and challenges of this challenging topic. Two major contributions are presented namely 1) survey of proposed energy efficiency metrics; 2) survey of proposed energy efficient solutions. We provide a broad overview of the state of-the-art energy efficient methods covering base station (BS) hardware design, network planning and deployment, and network management and operation stages. In order to further understand how EE is assessed and improved through the heterogeneous network (HetNet), BS's energy-awareness and several typical HetNet deployment scenarios such as macrocell-microcell and macrocell-picocell are presented. The analysis of different HetNet deployment scenarios gives insights towards a successful deployment of energy efficient cellular networks.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권3호
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• pp.1074-1086
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• 2015

We Relay-assisted cellular network architecture has been developed to cover cell-edge users and to improve capacity. However, the deployment of relay stations (RSs) in cellular networks may increase the total energy consumption. Though energy efficiency has become a major concern in cellular networks, little work has studied the energy efficiency of relay-assisted cellular networks by sleep scheduling. In this paper, a distributed base stations (BSs) sleep scheduling scheme in relay-assisted cellular networks is proposed. The goal is to maximize the energy efficiency under the spectral efficiency constraint. Firstly, whether the BSs should be sleeping or active is determined by the traffic profile. Then, the transmission powers of the active BSs are optimized within the game-theoretic framework, by using an interior-point method, so as to maximize the energy efficiency. Simulation results demonstrate that the effectiveness of the proposed scheme is superior to that turning on all the BSs without sleep scheduling.

• 한국정보통신학회논문지
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• 제20권10호
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• pp.1873-1880
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• 2016

셀룰러 네트워크를 운용하는데 드는 에너지의 대부분은 기지국에 의해서 소비되므로 에너지 효율적인 셀룰러 네트워크를 위하여 기지국의 송신 전력을 줄이는 것이 필요하다. 본 논문에서는 셀룰러 네트워크의 에너지 효율을 향상시키기 위한 목적으로 플로킹(flocking) 모델에 기반한 분산 송신전력제어 알고리즘을 제안한다. 새 무리에서 각각의 새가 자신의 속도를 인접한 이웃 새들의 평균 속도로 맞춰 날아가는 것과 같이, 제안 방안에서는 각 셀의 단말의전송률이 인접 셀의 같은 채널을 사용하는 단말의 평균 전송률과 같도록 서빙 기지국의 송신 전력을 제어한다. 모의실험 결과 제안한 분산 송신전력제어 알고리즘은 플로킹 모델과 같은 수렴 속성을 가지며, 셀 간 간섭이 증가함에 따라 낮은 아웃티지 확률을 유지하면서도 기지국의 전력 소모를 효과적으로 줄일 수 있음을 보여준다. 이를 통하여 제안 방안은 기지국 수가 20개 이상일 때 셀룰러 네트워크의 에너지 효율을 기존 방식 대비 두 배 이상 향상시킨다.

• 인터넷정보학회논문지
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• 제19권2호
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• pp.9-15
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• 2018

This paper proposes an energy efficient adaptive relay station ON/OFF scheme with different frequency reuse factors (FRFs) to enhance the system throughput and reduce the transmission energy consumption for the transparent mode of 2-hop cellular relay networks (CRNs) based on orthogonal frequency division multiple access and time division duplex. In the proposed scheme, the base station turns on or off the relay stations (RSs) when they are overutilized and undertuilized based on the traffic density of the cell coverage, respectively. Through the simulation results, we show that the proposed scheme outperforms the conventional CRN in terms of the energy consumption with the same system throughput. Further, in order to increase the system throughput with low energy consumption, the best way is FRF 1 when the number of operating RSs is up to 4 and FRF 2 otherwise.

• Journal of Communications and Networks
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• 제17권5호
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• pp.506-516
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• 2015

Wireless sensor networks (WSNs) are generally comprised of densely deployed sensor nodes, which results in highly redundant sensor data transmissions and energy waste. Since the sensor nodes depend on batteries for energy, previous studies have focused on designing energy-efficient medium access control (MAC) protocols to extend the network lifetime. However, the energy-efficient protocols induce an extra end-to-end delay, and therefore recent increase in focus on WSNs has led to timely and reliable communication protocols for mission-critical applications. In this paper, we propose an energy efficient and delay guaranteeing node scheduling scheme inspired by biological systems, which have gained considerable attention as a computing and problem solving technique.With the identification of analogies between cellular signaling systems and WSN systems, we formulate a new mathematical model that considers the networking challenges of WSNs. The proposed bio-inspired algorithm determines the state of the sensor node, as required by each application and as determined by the local environmental conditions and the states of the adjacent nodes. A control analysis shows that the proposed bio-inspired scheme guarantees the system stability by controlling the parameters of each node. Simulation results also indicate that the proposed scheme provides significant energy savings, as well as reliable delay guarantees by controlling the states of the sensor nodes.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권3호
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• pp.446-458
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• 2013

Recently, energy-efficient cellular transmission has received considerable research attention to improve the energy efficiency of wireless communication. In this paper, we consider a cellular network consisting of one base station (BS) and multiple user terminals and explore the network coding for enhancing the energy efficiency of cellular downlink transmission from BS to users. We propose the network coded cellular transmission scheme and conduct its energy consumption analysis with target outage probability and data rate requirements in Rayleigh fading environments. Then, the energy efficiency in Bits-per-Joule is further defined and analyzed to evaluate the number of bits delivered per Joule of energy cost. Numerical results show that the network coded cellular transmission significantly outperforms the traditional cellular transmission in terms of energy efficiency, implying that given a Joule of energy cost, the network coded cellular transmission scheme can deliver more bits than the traditional cellular transmission.

• 한국통신학회논문지
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• 제41권10호
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• pp.1186-1189
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• 2016

셀룰러 단말의 에너지 효율을 높이기 위하여 플로킹(flocking) 모델을 기반으로 상향링크 송신전력 제어 알고리즘을 제안한다. 플로킹 모델에서 각각의 새가 주변 새들의 평균 속도로 자신의 속도를 맞추어 나가는 것처럼, 각 셀의 단말은 주변 셀 동일 채널 단말들의 상향링크 전송률의 평균값과 자신의 상향링크 전송률이 같도록 송신 파워를 분산적으로 제어한다. 모의실험 결과 제안한 상향링크 송신전력제어 방법은 낮은 아웃티지 확률을 유지하면서 단말의 전력소비를 효과적으로 낮추어 단말의 에너지 효율을 향상시킨다.

• 한국멀티미디어학회:학술대회논문집
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• 한국멀티미디어학회 2012년도 춘계학술발표대회논문집
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• pp.158-159
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• 2012

Heterogeneous cellular networks can provide high throughput and coverage compare to conventional networks of only macrocell deployment, however it operates regardless of total power consumption, which is a very important issue of modern cellular networks. We propose a policy that control the on/off state of base stations in heterogeneous networks according daily traffic profile. Under this policy, the total power consumed can be significantly reduced when the traffic is low while preserving QoS requirement.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권10호
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• pp.3921-3944
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• 2015

Currently Energy-Saving (ES) methods in cellular networks could be improved, as compensation method for irregular Base Station (BS) deployment is not effective, most regional ES algorithm is complex, and performance decline caused by ES action is not evaluated well. To resolve above issues, a low-complexity energy efficient BS cooperation mechanism for Long Time Evolution (LTE) networks is proposed. The mechanism firstly models the ES optimization problem with coverage, resource, power and Quality of Service (QoS) constraints. To resolve the problem with low complexity, it is decomposed into two sub-problems: BS Mode Determination (BMD) problem and User Association Optimization (UAO) problem. To resolve BMD, regional dynamic multi-stage algorithms with BS cooperation pair taking account of load and geographic topology is analyzed. And then a distributed heuristic algorithm guaranteeing user QoS is adopted to resolve UAO. The mechanism is simulated under four LTE scenarios. Comparing to other algorithms, results show that the mechanism can obtain better energy efficiency with acceptable coverage, throughput, and QoS performance.