• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.6A
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• pp.445-457
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• 2009

Recently, there are growing interests in femto-cell for providing indoor users with various broadband multimedia services more efficiently. The technical issues regarding femto-cell such as interference management, self-organization, and resource allocation are now being intensively studied and investigated by researchers worldwide. In this paper, two novel schemes of neighboring cell list(NCL) management are proposed for the IEEE 802.16e system where a macro-cell and huge number of femto-cells coexist. The proposed schemes, named MS location-based neighboring cell list management and BS type-based neighboring cell list management, enable a mobile station(MS) to perform fast scanning and efficient handover by means of preselecting the candidate target femto-cells with high possibility for handover. The simulation result shows that the proposed schemes improve the MS's handover-related performance in terms of scanning power and scanning time compared with the conventional managements scheme of IEEE 802.16e system.

• Journal of Internet Computing and Services
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• v.23 no.5
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• pp.25-31
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• 2022

In ultra dense networks (UDNs), macro user equipments (MUEs) have significant interference from small-cell access points (SAPs) since a number of SAPs are deployed in the coverage of macro base stations of 5G mobile communication systems. In this paper, we propose a dynamic channel assignment scheme to increase the performance of MUEs for the uplink of UDNs even though the number of SAPs is increased. The target of the proposed dynamic channel assignment scheme is that the signal-to-interference and noise ratio (SINR) of MUEs is above a given SINR threshold assigning different subchannels to SUEs from those of MUEs. Simulation results show that the proposed dynamic channel assignment scheme outperforms others in terms of the mean MUE capacity even though the mean SUE capacity is decreased a little lower.

• Journal of Internet Computing and Services
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• v.22 no.6
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• pp.9-15
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• 2021

In ultra-dense heterogeneous networks, the amount of interference from small-cell base stations(SBS) to macro-cell user equipments (MUEs) increases significantly as the number of SBSs increases and it causes the MUEs to decrease the signal-to-interference and noise ratio(SINR) and system capacity. In this paper, we propose a small-cell based cooperative multi-point(CoMP) communication scheme that can guarantee the performance of MUEs even when the number of SBSs increases. In the proposed scheme, MUEs first find SBSs that give signal strength equal to or greater than a given SINR threshold and then they are served by different numbers of the selected SBSs using CoMP to improve the performance of MUEs. Simulation results show that the proposed small-cell based CoMP scheme outperforms other interference management or CoMP schemes in terms of the SINR and system capacity of MUEs.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.8A
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• pp.648-660
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• 2012

The low-power, low-cost femtocell network has been proposed not only to alleviate traffic load to the macro base station (eNB) but also to cover the indoor coverage hole problem. However, in the dense femtocell environment where many femtocells are deployed to cover the whole large office building, performance of such femtocell environment can be deteriorated due to severe co-channel interference problem between the eNB and femtocells and among neighboring femtocells. In particular, a macro UE(mUE) located within femtocell coverage may experience severe co-channel interference from surrounding femtocells. Therefore, In this paper, we propose a novel power control schemes to mitigate interference to a mUE under such dense LTE femtocell environment. With proposed femtocell power control schemes, performance of the mUE can be greatly improved in terms of the outage probability and the SINR while maintaining satisfying femtocell performance. Simulation based performance study shows that the proposed power control scheme is able to enhance mUE performance more than 30% than the conventional dense femtocell in terms of the two performance metrics.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.5C
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• pp.344-354
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• 2005

In this paper, we proposed a new lifting architecture for JPEG2000 and implemented to ASIC. We proposed a new cell to execute unit calculation of lifting using the property of lifting which is the repetitious arithmetic with same structure, and then recomposed the whole lifting by expanding it. After the operational sequence of lifting arithmetic was analyzed in detail and the causality was imposed for implementation to hardware, the unit cell was optimized. A new lifting kernel was organized by expanding simply the unit cell, and a lifting processor was implemented for Motion JPEG2000 using it. The implemented lifting kernel can accommodate the tile size of $1024{\times}1024$, and support both lossy compression using the (9,7) filter and lossless compression using (5,3) filter. Also, it has the same output rate as input rate, and can continuously output the wavelet coefficients of 4 types(LL, LH, HL, HH) at the same time. The implemented lifting processor completed a course of ASIC using $0.35{\mu}m$ CMOS library of SAMSUNG. It occupied about 90,000 gates, and stably operated in about 150MHz though difference from the used macro cell for the multiplier. Finally, the improved operated in about 150MHz though difference from the used macro cell for the multiplier. Finally, the performance can be identified in comparison with the previous researches and commercial IPs.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.7C
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• pp.647-657
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• 2005

In this paper, we proposed a new lifting architecture for JPEG2000 and implemented to ASIC. We proposed a new cell to execute unit calculation of lifting using the property of lifting which is the repetitious arithmetic with same structure, and then recomposed the whole lifting by expanding it. After the operational sequence of lifting arithmetic was analyzed in detail and the causality was imposed for implementation to hardware, the unit cell was optimized. A new lifting kernel was organized by expanding simply the unit cell, and a lifting processor was implemented for Motion JPEG2000 using it. The implemented lifting kernel can accommodate the tile size of 1024$\times$1024, and support both lossy compression using the (9,7) filter and lossless compression using (5,3) filter. Also, it has the same output rate as input rate, and can continuously output the wavelet coefficients of 4 types(LL, LH, HL, HH) at the same time. The implemented lifting processor completed a course of ASIC using 0.35$\mu$m CMOS library of SAMSUNG. It occupied about 90,000 gates, and stably operated in about 150MHz though difference from the used macro cell for the multiplier. Finally, the improved operated in about 150MHz though difference from the used macro cell for the multiplier. Finally, the performance can be identified in comparison with the previous researches and commercial IPs.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.10
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• pp.1517-1524
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• 2022

In this paper, we consider a heterogeneous network (HetNet) consisting of one macro base station and multiple small base stations, and assume the coordinated multi-point transmission between the base stations. In addition, we assume that the channel between the base station and the user consists of path loss and Rayleigh fading. Under these assumptions, we present the energy efficiency (EE) achievable by the user for a given base station and we formulate an optimization problem of dynamic cell selection and transmit power allocation to maximize the total EE of the HetNet. In this paper, we propose an unsupervised deep learning method to solve the optimization problem. The proposed deep learning-based scheme can provide high EE while having low complexity compared to the conventional iterative convergence methods. Through the simulation, we show that the proposed dynamic cell selection scheme provides higher EE performance than the maximum signal-to-interference-plus-noise ratio scheme and the Lagrangian dual decomposition scheme, and the proposed transmit power allocation scheme provides the similar performance to the trust region interior point method which can achieve the maximum EE.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.4A
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• pp.291-301
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• 2009

In this paper, the effect of ISI(Inter-Symbol Interference) and ICI(Inter-Carrier Interference) due to time difference of arrival on OFDMA-based mobile multi-hop relay (MMR) systems is analyzed. Analyses are performed for the ISI caused by the previous OFDMA symbol transmitted from neighboring macro or relay cell as well as the ISI caused by the next OFDMA symbol transmitted from neighboring macro or relay cell. Then, an effective SINR(Signal to Interference plus Noise Ratio) estimation method and a path selection method considering time difference of arrival are proposed to minimize the effect of ISI and ICI. It is shown by simulation that the performance degradation caused by time difference of arrival can be significantly mitigated when the proposed path selection method is applied to the uplink of OFDMA-based MMR systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.11
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• pp.771-778
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• 2014

We propose Femto-cell power control scheme in HeNet with Game Theory. The Femto-cell which provide high quality with low power is issued by many benefits, however there is a bunch of interferences when many Femto-cells use overlapped bandwidth with Macro-cell. We defined base station of cellular networks and mobile users as players of Game Theory, and configured interference effect among each other as power utility function. Futhermore, we showed enhanced overall system performance, lower power usage and interference decrease by using optimal power.

• KIPS Transactions on Computer and Communication Systems
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• v.10 no.8
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• pp.215-222
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• 2021

In order to alleviate the limited resource problem and interference problem in cellular networks, the dual connectivity technology has been introduced with the cooperation of small cell base stations. In this paper, we design a new efficient and fair resource allocation scheme for the dual connectivity technology. Based on two different bargaining solutions - Generalizing Tempered Aspiration bargaining solution and Gupta and Livne bargaining solution, we develop a two-stage radio resource allocation method. At the first stage, radio resource is divided into two groups, such as real-time and non-real-time data services, by using the Generalizing Tempered Aspiration bargaining solution. At the second stage, the minimum request processing speeds for users in both groups are guaranteed by using the Gupta and Livne bargaining solution. These two-step approach can allocate the 5G radio resource sequentially while maximizing the network system performance. Finally, the performance evaluation confirms that the proposed scheme can get a better performance than other existing protocols in terms of overall system throughput, fairness, and communication failure rate according to an increase in service requests.