• Journal of Electrical Engineering and information Science
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• v.3 no.3
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• pp.402-407
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• 1998

In this paper, an outage probability in the presence of Rayligh faded cochannel interference and Gaussian noise for cellular mobile telephone system is described. Our result is a computational formula that can be applied with or without Gaussian noise in Rayleigh faded cochannel interferences. Without Gaussian noise, the situation degenerates to usual case of the cochannel interferences. The result can be applied also in the presence of Gaussian noise with or without cochannel interference.

• Journal of electromagnetic engineering and science
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• v.12 no.2
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• pp.142-147
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• 2012

In this paper, we propose a novel protocol called Cooperative Multi-hop transmission using Incremental Relaying (CMIR). We evaluate the performance of the CMIR protocol by deriving expressions for the average end-to-end outage probability and the average number of transmissions. Monte Carlo simulations are presented to verify the accuracy of the theoretical analyses.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.2A
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• pp.91-98
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• 2009

This paper provides new exact-closed form expressions for average SER and average BER as well as outage probability for M-PSK signaling with selection combining over independent but non-identically distributed Rayleigh fading paths. The validity of these expressions is verified by the Monte-Carlo simulations. All of numerical results are in excellent agreement with simulation results.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.5
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• pp.122-129
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• 2009

In this paper, we have proposed the QoS (quality of services) control scheme which can adjust data transfer rates of the session participants in response to their radio channel conditions under the time-varying propagation radio environment. The outage probability is selected as the performance index in order to compare the performance of the proposed scheme with the conventional QoS control scheme. The outage probability of the single and multiple paths is mathematically derived here and its numerical results are investigated. The results show that the significant performance improvement can be obtained compared with the conventional scheme and also the diversity gain can improve the radio link outage as the degrees of the multipath diversity increases. Therefore the overall performance improvement in terms of the QoS of the outage probability can be significantly be achieved by applying the proposed scheme.

• Journal of Communications and Networks
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• v.12 no.6
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• pp.616-623
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• 2010

In this paper, exact closed-form expressions for outage probability and bit error probability (BEP) are presented for multi-hop decode-and-forward (DF) relaying schemes in conjunction with cooperative diversity, in which selection combining technique is employed at each node. We have shown that the proposed protocol offers remarkable diversity advantage over direct transmission as well as the conventional DF relaying schemes with the same combining technique. We then investigate the system performance when different diversity schemes are employed. It has been observed that the system performance loss due to selection combining relative to maximal ratio combining is not significant. Simulations are performed to confirm our theoretical analysis.

• Journal of information and communication convergence engineering
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• v.9 no.6
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• pp.641-646
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• 2011

In this paper, we investigate a power control problem which is very critical in underlay-based spectrum sharing systems. Although an underlay-based spectrum sharing system is more efficient compared to an overlay-based spectrum sharing system in terms of spectral utilization, some practical problems obstruct its commercialization. One of them is a real-time-based power adaptation of secondary transmitters. In the underlay-based spectrum sharing system, it is essential to adapt secondary user's transmit power to interference channel states to secure primary users' communication. Thus, we propose a practical power control scheme for secondary transmitters. The feedback overhead of our proposed scheme is insignificant because it requires one-bit signaling, while the optimal power control scheme requires the perfect information of channel states. In addition, the proposed scheme is robust to feedback delay. We compare the performance of the optimal and proposed schemes in terms of primary user's outage probability and secondary user's throughput. Our simulation results show that the proposed scheme is almost optimal in terms of both primary user's outage probability and secondary user's throughput when the secondary user's transmit power is low. As the secondary user's transmit power increases, the primary user's outage probability of the proposed scheme is degraded compared with the optimal scheme while the secondary user's throughput still approaches that of the optimal scheme. If the feedback delay is considered, however, the proposed scheme approaches the optimal scheme in terms of both the primary user's outage probability and secondary user's throughput regardless of the secondary user's transmit power.

• Journal of IKEEE
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• v.13 no.4
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• pp.75-81
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• 2009

The cellular system in the next generation decreases the range of transmission of a signal as well as increases the rate of transmission adapting the method of multi-hop relaying with the relay. However, the fact of decreasing the range of transmission with the method of multi-hop relaying means increasing interferential amount in the outer cell; therefore, the deployment of the relay can affect to the function of the cellular system. In this thesis, the deployment of the relay is determined for the maximum rate of transmission, based on the transmission power of the relay and the variation of interferential amount. The condition to determine the deployment of the relay is analyzed with the mathematical model; in addition, its performance is verified through the result of a simulation. Based on the analysis of this thesis, the established deployment and transmission power of the relay to minimize the average outage probability exist. Furthermore, the relay contributes to enlargement of capacity of cells, decreasing the average outage probability in the situation of less severe interference between cells with reuse of frequency. However, the relay should be restrained in use in the situation of severe interference between cells due to the fact that the outage probability of inter-cells can be increased.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.5B
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• pp.338-347
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• 2012

In this paper, we propose the cooperative transmission scheme (CTS) for system throughput maximization in OFDMA based enterprise femtocell networks. In our scheme, the user equipment (UE) can receive the desired signal from serving femtocell BS (fBS) as well as an adjacent fBS. Thus, UE achieves an improved signal to interference plus and noise ratio (SINR) by the synchronized two signals. The performances of this strategy consider not only the call-level quality of service (QoS) but also the packet-level QoS. We first measure the call blocking probability and utilization for the downlink resources for various offered load in femtocell. Based on that, the outage probability and effective throughput of the system are simulated. Simulation results show that the proposed scheme can reduce the outage probability for enterprise femtocell compared with conventional systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.12
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• pp.771-773
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• 2014

Dual-polarization antenna system has been being researched for wireless communications under short range line-of-sight channel environments. In this paper, probability density function of signal-to-interference-ratio(SIR) for the dual-polarization antenna system is derived, and SIR outage is analyzed. It is shown that the upper bound capacity of a dual-polarization antenna system without polarization alignment is 4.5324 bps/hz.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.2
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• pp.369-371
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• 2015

In this letter, we analyze the outage performance of the signal-to-noise ratio (SNR)-based selective relaying in a relay network, where the relay terminal may retransmit the received signal or remain silent based on the received SNR of the link from the source to the relay. For the proposed relaying scheme, we derive the exact outage probability.