• Journal of KIISE:Information Networking
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• v.29 no.5
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• pp.466-472
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• 2002

We investigate the load sharing problem between the umbrella cell and the overlaid tells in hierarchical cell structure. A load sharing strategy is proposed and its performance is evaluated by simulation when it is used for transmission of the mobile Internet traffic using the High Speed Downlink Packet Access scheme. The results show that, with the proposed strategy, the microcell backs well the overlaid picocells up, especially when a specific picocell cluster suffers unusual heavy load condition. By using the strategy, we can reduce the installation cost, otherwise needed for increasing the system capacity of every picocell cluster to cope with the unusual heavy load.

• Journal of Advanced Navigation Technology
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• v.9 no.2
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• pp.93-102
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• 2005

This paper presents an interface configuration between Access Point(AP) and Radio Over Fiber (ROF) transceiver for the wireless internet system. The wireless internet could provides 60km/h mobility and 50Mbps IP based data services for each mobile terminal. Thus, cost effective cell infrastructure is inevitably required. This paper suggests an interface configuration between AP and passive integrated picocell(PIP) involving ROF links. Nonlinear characteristics of ROF link using a typical FP transceiver are measured for wireless internet applications.

• ETRI Journal
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• v.28 no.3
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• pp.282-290
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• 2006

In vertically overlaid cellular systems, a temporary traffic concentration can occur in a hot-spot area, and this adversely affects overall system capacity. In this paper, we develop an adaptive hot-spot operating scheme (AHOS) to mitigate the negative effects from the nonuniform distribution of user location and the variation in the mixture of QoS requirements in orthogonal frequency division multiple access downlink systems. Here, the base station in a macrocell can control the operation of picocells within the cell, and turns them on or off according to the system overload estimation function. In order to determine whether the set of picocells is turned on or off, we define an AHOS gain index that describes the number of subcarriers saved to the macrocell by turning a specific picocell on. For initiating the picocell OFF procedure, we utilize the changes in traffic concentration and co-channel interference to the neighboring cells. According to computer simulation, the AHOS has been proved to have maximize system throughput while maintaining a very low QoS outage probability under various system scenarios in both a single-cell and multi-cell environments.

• Journal of Information Technology Applications and Management
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• v.14 no.4
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• pp.1-16
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• 2007

In the microcell- or picocell-based system the frequent movements of the mobile bring about excessive traffics into the networks. A mobile location estimation mechanism can facilitate both efficient resource allocation and better QoS provisioning through handoff optimization. Existing location estimation schemes consider only LOS model and have poor performance in presence of multi-path and shadowing. In this paper we study a novel scheme which can increase estimation accuracy by considering NLOS environment and other multiple decision parameters than the received signal strength.

• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1709-1712
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• 2002

In the microcell- or picocell-based system the frequent movements of the mobile bring about excessive traffics into the networks. A mobile location estimation mechanism can facilitate both efficient resource allocation and better QoS provisioning through handoff optimization. Existing location estimation schemes consider only LOS model and have poor performance in presence of multi- path and shadowing. In this paper we study a novel scheme which can increase estimation accuracy by considering NLOS environment

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.8
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• pp.39-44
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• 2013

Long Term Evolution (LTE) - Advanced has developed Heterogeneous Network (HetNet) that consists of a mix of macrocells and low-power nodes such as picocells to improve the system performance. Also, to encourage data offloading in HetNet, Cell Range Expansion (CRE) have been introduced. In this paper, we propose a cell selection scheme based on Signal to Interference plus Noise Ratio (SINR) for optimal offloading effect. And we manage the interference for user located in cell range expanded region using Almost Blank Subframe (ABS) with flexible ABS ratio to improve the spectrum efficiency in time domain. Simulation results show that proposed scheme can improve spectrum efficiency of macrocell and picocell user. Eventually, proposed scheme can imporve overall user performance.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.4
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• pp.30-44
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• 2003

In the microcell-or picocell-based system the frequent movements of mobiles bring about excessive traffics into the networks. A mobile location estimation mechanism can facilitate both efficient resource allocation and better QoS provisioning through handoff optimization. Existing location estimation schemes consider only LOS model and have poor performance in presence of multi-path and shadowing. In this paper we study novel schemes which can increase estimation accuracy by considering NLOS environment and other multiple decision parameters than the received signal strength.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.2
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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.

• Journal of the Korea Society for Simulation
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• v.10 no.4
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• pp.11-20
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• 2001

In the IMT-2000 networks, the model of micro/pico cell is suggested for transmission of multimedia service. Hence, the efficient method is required for processing of mobile calls in micro/pico cell. In the central urban area, mobile calls may be dynamically increased because of many mobile users. And microcel]/picocell size has small size, handover calls will be more increased. Therefore, many of mobile calls is occurred at a cell in the central urban area, so channel requests for these calls will be increased in the call. In this paper, we propose a scheme, FTC(Fault Tolerant Channel allocation) which is the channel management method for hard handover and new call in a mobile cell of central urban area. When available channels in the cell are consumed, the FTC investigates channel states of neighbor cells in the RNC(Radio Network Controller) or BSC (Base Station Center), and provide available channel for mobile call. The ]no scheme is analyzed and compared with existing channel management method by simulation.

• Journal of Internet Computing and Services
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• v.6 no.5
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• pp.167-175
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• 2005

In the microcell or picocell-based system the frequent movements of mobiles bring about excessive traffics Into the networks. A mobile location estimation mechanism can facilitate both efficient resource allocation and better QoS provisioning through handoff optimization. Existing location estimation schemes consider only LOS model and have poor performance in presence of multi-path and shadowing. In this paper we study multi-criteria decision making which can increase estimation accuracy by considering other multiple decision parameters than the received signal strength.