• Journal of KIISE:Information Networking
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• v.37 no.4
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• pp.294-300
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• 2010

In this paper, We analysis of effective coverage extension for Tri-sector cellular systems using Multi-hop Relay based on IEEE802.16j system. In the proposed international standard of IEEE 802.16j MMR (Mobile Multi-hop Relay) use of the omni-directional antenna, 3-sector and 6-sector antenna is considered to Base Station and Relay Station. Omni-directional antenna service can offer as all directions but a throughput decreases due to the signal interference of near Relay Stations. In the directional antenna, cause of an interference with the base station which it arranges an antenna so that a beam can have the direct and does with neighbor Base Station and Relay Station can be reduced interference, therefore the effective throughput is higher than the omni-directional antenna system. But, In case of Base Station and Relay Station use the directional antenna, the efficiency which the directional antenna has the Co-channel interference due to in the different cell by the channel reuse is decreased. In this study, we propose the structure of arranging the Base Station and Relay Station having the directional antenna in the NBTC, WBTC antenna in a multi-tier. It compared and analyzed with the mode that the multi-hop Relay Station has the omni-directional antenna, Relay Station are used the NBTC antenna and the WBTC antenna system also, We analyze a relation between the performance degradation and the cell coverage extension which it follows because the number of hop in the multi-hop Relay Station.

• Journal of Internet Computing and Services
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• v.24 no.1
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• pp.1-7
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• 2023

Recently, the technology of device-to-device(D2D) communication has been receiving big attention to improve the system performance since the amount of high quality/large capacity data traffic from smart phones and various devices of Internet of Things increase rapidly in 5G/6G based next generation cellular networks. However, even though the system performance of macro cells increase by reusing the frequency, the performance of macro user equipments(MUEs) decrease because of the strong interference from D2D user equipments(DUEs). Therefore, this paper proposes a dynamic channel management(DCM) scheme for DUEs to guarantee the performance of MUEs as the number of DUEs increases in next generation downlink cellular networks. In the proposed D2D DCM scheme, macro base stations dynamically assign subchannels to DUEs based on the interference information and signal to interference and noise ratio(SINR) of MUEs. Simulation results show that the proposed D2D DCM scheme outperforms other schemes in terms of the mean MUE capacity as the threshold of the SINR of MUEs incareases.

• International Journal of Computer Science & Network Security
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• v.23 no.4
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• pp.55-68
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• 2023

In recent years, the Television White Space (TVWS) has attracted the interest of many researchers due to its propagation characteristics obtainable between 470MHz and 790MHz spectrum bands. The plenty of unused channels in the TV spectrum allows the secondary users (SUs) to use the channels for broadband services especially in rural areas. However, when the number of SUs increases in the TVWS wireless network the aggregate interference also increases. Aggregate interferences are the combined harmful interferences that can include both co-channel and adjacent interferences. The aggregate interference on the side of Primary Users (PUs) has been extensively scrutinized. Therefore, resource allocation (power and spectrum) is crucial when designing the TVWS network to avoid interferences from Secondary Users (SUs) to PUs and among SUs themselves. This paper proposes a model to improve the resource allocation for reducing the aggregate interface among SUs for broadband services in rural areas. The proposed model uses joint power and spectrum hybrid Firefly algorithm (FA), Genetic algorithm (GA), and Particle Swarm Optimization algorithm (PSO) which is considered the Co-channel interference (CCI) and Adjacent Channel Interference (ACI). The algorithm is integrated with the admission control algorithm so that; there is a possibility to remove some of the SUs in the TVWS network whenever the SINR threshold for SUs and PU are not met. We considered the infeasible system whereby all SUs and PU may not be supported simultaneously. Therefore, we proposed a joint spectrum and power allocation with an admission control algorithm whose better complexity and performance than the ones which have been proposed in the existing algorithms in the literature. The performance of the proposed algorithm is compared using the metrics such as sum throughput, PU SINR, algorithm running time and SU SINR less than threshold and the results show that the PSOFAGA with ELGR admission control algorithm has best performance compared to GA, PSO, FA, and FAGAPSO algorithms.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.10
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• pp.2053-2063
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• 1994

Recently, there has been much interest in the terrestrial broadcasting of the HDTV signal. However, in the Simulcast where the NTSC and HDTV signal are transmitted using the same channel, the cochannel interference occurs which degrade the transmission performance. Recently, the GA(Grand Alliance) proposed the cochannel interference rejection system which use comb filter. However, this method shows poor performance for the NTSC carrier variation [7]. In this paper we propose a novel NTSC cochannel interference rejection system which shows improved performance for the NTSC carrier variation. In the proposed scheme, the adaptive notch filter is employed along with adaptive channel equalizer. In this paper, we also present some analytical results on the NTSC rejection performance of the GA and proposed scheme. Computer simulation results reveal that the proposed scheme outperforms order outperforms order of 10 in the BER(bit error rate) sense for the normal condition.

• Journal of Satellite, Information and Communications
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• v.12 no.4
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• pp.100-105
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• 2017

In this paper, we study an interference avoidance scenario in the presence of a interferer which can rapidly observe the transmit power of backscatter communications and effectively interrupt backscatter signals. We consider a power control with a sub-channel allocation to avoid interference attacks and a power-splitting ratio for backscattering and RF energy harvesting in sensors. We formulate the problem based on a Stackelberg game theory and compute the optimal transmit power, power-splitting ratio, and sub-channel allocation parameter to maximize a utility function against the interferer. We propose the utility maximization using Lagrangian dual decomposition for the backscatter communications and the interferer to prove the existence of the Stackelberg equilibrium. Numerical results show that the proposed algorithms effectively maximize the utility, compared to that of the algorithm based on the Nash game, so as to overcome a malicious interference in backscatter communications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.1
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• pp.28-35
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• 2014

In this paper, we propose a SSD(simultaneous single band duplex) system with turbo equalizer for full-duplex over harsh ISI(inter symbol interference) channel. The proposed system uses RF(radio frequency) cancellation and digital cancellation to cancel self-interference caused by simultaneous single band duplex communication. Also, using turbo equalizer, the proposed system equalizes signal after digital cancellation. In this paper, we design SSD system with turbo equalizer. And then we evaluate BER(bit error rate) performance of the proposed system comparison with SSD system with adaptive equalizer. We use simulink program to confirm BER performance of the proposed system. The simulation results shows that the proposed system equalizes received signal effectively over harsh ISI channel and BER performance of the proposed system is better than BER performance of SSD system with adaptive equalizer.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.1
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• pp.44-57
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• 2013

In this paper, we propose a femtocell searching technique which can prevent a macrocell UE(user equipment) from losing synchronism to its serving macrocell near closed access femtocells in co-channel deployment due to the leakage of femtocell signals by using a CS(Common Signal). The CS, commonly transmitted by femtocells in a macrocell at the same time, enables the macrocell UEs to be kept synchronized with their serving macrocells since the CINR(Carrier to Interference and Noise Ratio) of base stations in macrocell can be kept high even near closed access femtocells. Also, the CS is designed in such a way that a macrocell UE can recognize the existence of femtocell by using the metric CSCINR(Common Signal Carrier to Interference and Ratio) measured with CS. In addition, the proposed femtocell searching technique can reduce the frequency of femtocell searching trial by using the metric on mobility of a macrocell UE defined in this paper, and the reduction of the frequency of handover trial can be also expected as a byproduct.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.6
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• pp.135-141
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• 2011

Analog medias are converting to digital with the development of the digital communications. The Korean radio broadcasting services yet on analog and the research for the digital radio is progressing. The digital conversion of radio broadcasting has already progressed in foreign countries because of the technical limitation of analog broadcasting(The radio-frequency efficiency is poor). DAB is one of the digital radio mode, it doesn't use on AM/FM band and uses on T-DMB frequency band. So, it has an advantage of being able to broadcast with the existing radio without interference at once. On the other hand, it has the potential to cause interference to existing T-DMB broadcasting. In this paper, we propose an efficient DAB channel allocation method for digital radio on T-DMB frequency band. This paper allocates the DAB channel without interference to existing T-DMB broadcasting and proves the proposed method through simulations for the interference analysis.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.11
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• pp.87-92
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• 2005

This paper analyzes the performance for an improved multistage parallel interference cancellation (PIC) technique with a reverse-link synchronous transmission technique (RLSTT) for DS-CDMA system in a frequency-selective Rayleigh fading channel with an imperfect power control scheme. The performance degradation due to power control error (PCE), which is approximated by a log-normally distributed random variable, is estimated as a function of the standard deviation of the PCE. The uncoded bit error performance is evaluated in order to estimate the system capacity. Comparing with the conventional one-stage PIC system, we show achievable gain around $60\%$ by the RLSTT even in the presence of PCE. We conclude that the capacity can be further improved via RLSTT, which alleviates the detrimental effects of the PCE

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.12
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• pp.10-19
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• 2001

In this paper, we propose an effective but simple multi-rate parallel interference canceller(PIC) for the international mobile telecommunications-2000(IMT-2000) 3rd generation partnership project (3GPP) system. For effective multi-rate processing, we define the basic block as one symbol period of the dedicated physical control channel(DPCCH) having the lowest data rate and common to all users. Then, decision and interference cancellation are performed at every basic block. For an asynchronous channel, we propose an advance removal scheme that removes in advance multiple access interference(MAI) due to the next blockof other users with shorter delay. Introducing a pipeline structure at a sample base, we can implement efficiently the PIC using the advance removal scheme with a minimum hardware and no extra computations. Through computer simulations, we analyze the bit error rate(BER) performance of the proposed PIC with respect to signal-to-noise ratio(SNR) and the number of users.