• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.12
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• pp.3154-3164
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• 1996

A major concern in a cellular mobile communication system is how to efficiently utilize the limited amount of frequencies. Various channel assignment methods and traffic sharing schemes have been proposed to improve system performance. However, these approaches suffer from complicated software and hardware requirements due to increased amount of traffic control In this paper, we propose a new method for improving system performance by controlling the powers of the set-up and voice channels of each cell site. We first show that the average number of blocked calls in a system is minimized when the traffic reates are made identical for all cell sites in a system. This result, together with the relationship between the channel powers and the service area, is used to determine the appropriate channel powers of each cell site. We also determine the upper limit on the channel power of each cell site considering co-channel interference and numerically show that the proposed method is effective in reducing the number of blocked calls without an excessive increase in the amount of system control.

• Proceedings of the KIEE Conference
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• 2002.07d
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• pp.2559-2561
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• 2002

This paper presents a systematic method of probing channel characteristics and communication reliabilities of home PLC (power line communication) network applied to the Internet accessed control of home appliances. The effects of the three performance deterioating factors, i.e., additive noise, channel attenuation, and intersymbol interference, can be systematically measured by applying the channel probing waveform in the frequency range from 100kHz to 450kHz. The agreement between the derived probability of bit error and the measured probability of bit error supports the validity of the proposed approach of probing home power line channel characteristics. The experimental results performed with the constructed test-bed applying the proposed channel probing method also support the feasibility of commercially deploying the PLC modem installed home appliances and their services for the Internet accessed home automation.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.46 no.4
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• pp.87-93
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• 2009

Wireless mesh networks (WMNs) are emerging technologies that provide ubiquitous environments and wireless broadband access. The aggregate capacity of WMNs can be improved by minimizing the effect of channel interference. The IEEE 802.11b/g standard which is mainly used for the network interface technology in WMNs provides 3 multiple channels. We must consider the channel scanning delay and the channel dependency problem to effectively assign channels in like these multi-channel WMNs. This paper proposes a cluster-based channel assignment (CB-CA) algorithm for multi-channel WMNs to solve such problems. The CB-CA does not perform the channel scanning and the channel switching through assigning co-channel to the inter-cluster head (CH) links. In the CB-CA, the communication between the CH and cluster member (CM) nodes uses a channel has no effect on channels being used by the inter-CH links. Therefore, the CB-CA can minimize the interference within multi-channel environments. Our simulation results show that CB-CA can improve the performance of WMNs.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.2B
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• pp.87-96
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• 2012

In this paper, we consider a 2-hop relay system where both the relay and destination nodes suffer from the arbitrary number of co-channel interferers. More specifically, assuming that the relay and access channels as well as interference channels are all subject to Rayleigh fading, we derive an exact closed-form expression for outage probability of the amplify-and-forward (AF) relay system, and furthermore compute its upper and lower bounds. Based on these bounds, we derive the upper and lower bounds on the average bit error rate (BER) of the AF relay system. We also confirm the accuracy of our derivation by investigating the performance gap between the performance bounds under consideration and simulation results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.2 s.93
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• pp.182-188
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• 2005

This paper presents an efficient technique for interference suppression in IEEE 802.11b WLAN systems. A linearly constrained adaptive array processor which may improve reception performance of WLAN device by reducing co-channel interference signal and multipath effects effectively was proposed. A spatial smoothing method is used to prevent cancellation of a desired signal in a coherent environment and also integral nulling method is employed to improve the array performance in indoor environment. It was shown that the integral nulling approach performed best while the spatial smoothing method performed better than linearly constrained array processing. The performance of the WLAN system may be improved by the proposed methods which reduce co-channel, coherent, and WPAN interferences effectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.8A
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• pp.733-738
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• 2002

Zero Cross-correlation Zone (ZCZ) code has a good performance in Multi-user CDMA system to get low correlation zone and reject co-channel interference. In this paper, we do analysis of spreading code design to obtain this kind of property of correlations with a complex spreading scheme and denote their effective performance for mobile communication system. In addition, a Jacket polyphase sequence is an example to show the improved performance and regular properties effective performance for mobile communication system. In addition, a Jacket polyphase sequence is as an example to show the improved performance and regular properties.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.9B
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• pp.1608-1615
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• 1999

In this study, we investigate the inter cell interference of LMDS(Local multipoint Distribution Service) system cell in LMDS system design process. There are several interference sources in LMDS system but we consider co-channel adjacent interference, cross-polarization interference, tx/rx interworking interference as three major factors. As the summation of each interference, C/N is keep 19 dB in 2km range but decreased gradually over 2km. Based on theoretical results, we process the experimental test and get results that C/I=20 dB have to be maintained to transmit the data successfully under rain fall attenuation condition. This experiential results are similar to the theoretical analysis results we examined.

• International Journal of Computer Science & Network Security
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• v.22 no.4
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• pp.367-373
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• 2022

Femtocells have recently been recognized for their potential to boost network capacity, improve end-user QoS and throughput, and do so at a cheap cost and with ease of implementation. The use of femtocells in indoor environments, such as residential buildings with neighboring homes, is becoming more popular. Femtocells are subject to interference from other femtocells, and the unwanted effects of interference are amplified when femtocells are deployed in close proximity to one another. As a consequence, the network's overall performance is degraded to a significant degree. One of the strategies that is thought to be effective in reducing the impact of interference is altering the transmission power of the femtocells. In this paper, a dynamic downlink transmission power of femtocells is suggested. In accordance with the observed cost function unit, each femtocell automatically changes its transmission power. If a femtocell causes too much interference for its neighbors, its transmission power level will be limited by that interference's rate. A simulation experiment is conducted to validate the effectiveness of the suggested system when compared with other schemes. When compared to previous schemes, which are addressed in this study, the numerical results show that the proposed strategy could provide more capacity while also ideally mitigating the influence of interference among co-channel deployed femtocells.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.5
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• pp.83-89
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• 2016

In this paper, we apply the complementation principle of five prime substances to reduce the phase interference. The transmitter and receiver match the concepts of co-operative and conflict to the direct and indirect signals. The result shows we investigate the proposed network topology such as 5 prime substances (5 user networks). The key observation is that optimal symmetric degree of freedom (DoF) can be achieved for 5 user network with different channel coherence times by adaptively selecting the interference alignment scheme via controlling the alignment feasibility of the transmitted signals. Theoretical results demonstrate the effectiveness of the proposed 5 user networks are well matched to the wireless mobile channel environment to achieve the symmetric DoF for different channel coherence times which ensures that the proposed networks are applicable for dense wireless network applications. Modulo 3 functionality in 5 user network topology makes it easier for the transmitter cooperation to achieve the DoF of 2/3 with the help of the interference alignment schemes.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.5
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• pp.55-62
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• 2019

In this paper, we consider K-user multiple-input multiple-output (MIMO) interference channel and present a transceiver design for simultaneous wireless information and power transfer (SWIPT) systems. In addition, we consider a SWIPT system where an information decoding receiver and an energy harvesting receiver are co-located at the same receiver. In the proposed scheme, signal-to-leakage plus noise ratio (SLNR) is used as a cost function and a transceiver is designed to satisfy the threshold of the harvested energy. More specifically, transmitter precoding vector, receiver filter vector, and power spitting factor are simultaneously designed to maximize SLNR with a constraint on the harvested energy. Through computer simulation, we compare the signal-to-interference plus noise ratio (SINR) performance of the proposed and conventional schemes. When a special condition among the number of transmit antennas, receive antennas, and users is satisfied, the proposed scheme showed better SINR performance than the conventional scheme at low signal-to-noise ratio (SNR) range. Also, when the condition is not satisfied, the proposed scheme showed better performance than the conventional scheme at all SNR range.