Jae‐Min Lee

This paper evaluates the outage probability of cognitive relay networks with cooperation between secondary users based on the underlay approach, while adhering to the interference constraint on the primary user, i.e., the limited amount of interference which the primary user can tolerate. A relay selection criterion, suitable for cognitive relay networks, is provided, and using it, we derive the outage probability. It is shown that the outage probability of cognitive relay networks is higher tha

Full-duplex (FD) radio has been introduced for bidirectional communications on the same temporal and spectral resources so as to maximize spectral efficiency. In this paper, motivated by the recent advances in FD radios, we provide a foundation for HDHNs, composed of multi-tier networks with a mixture of APs, operating either in bidirectional FD mode or downlink HD mode. Specifically, we characterize the network interference from FD-mode cells, and derive the HDHN throughput by accounting for AP

This paper analyzes spectrum sharing between multiple systems. The efficiency of spectrum sharing is determined primarily by interference, which is a function of the spatial densities of the transmitters in systems dependent on the chosen spectrum sharing method. One method is underlay, which allows all systems to concurrently use the whole spectrum, and the other is overlay, in which a system only utilizes its own assigned spectrum. We define the spectrum-sharing transmission capacity (S-TC) as

This paper considers the problem of efficient usage of subcarriers in downlink orthogonal frequency-division multiple access (OFDMA) multi-hop cellular networks. Multi-hop transmission can either save or waste subcarriers depending on quality of service (QoS) requirements, interference from other cells, and the location of a given mobile station (MS). Preventing unnecessary usage of multi-hop transmission requires the use of a transmission mode selection (TMS) scheme, and we propose two types of

This paper analyzes large-scale networks that share the spectrum with interference cancellation (IC). The efficiency of spectrum sharing is determined primarily by interference, which in turn depends on the spatial densities, the interference cancellation method, and the spectrum sharing method, i.e., underlay or overlay. By assuming the Poisson distribution for transmitters, equal transmission power in the same system, and an interference-limited environment, this paper finds the performance ga

Secrecy is essential for a variety of emerging wireless applications where distributed confidential information is communicated in a multilevel network from sources to destinations. Network secrecy can be accomplished by exploiting the intrinsic properties of multilevel wireless networks (MWN). This paper introduces the concept of distributed network secrecy (DNS) and develops a framework for the design and analysis of secure, reliable, and efficient MWNs. Our framework accounts for node spatial

The location tracking of a mobile station is required to support the location-based services and the radio resource management. The improved location tracking algorithm which uses the Kalman filter with the velocity renovation process is proposed. The velocity renovation process consists of a velocity estimator and a direction finder. By this process, the proposed algorithm can use accurately estimated velocity in the location estimation. The proposed algorithm reduces more than 66% of the locat

In the forthcoming 6G wireless networks, the explosive growth in the number of human-type devices and machine-type devices will result in the network densification including both end-device (ED) densification and base station (BS) densification. Owing to the unique features of the network densification, not only new challenging problems would be introduced, but also the techniques, used in conventional networks, would no longer be effective. In this article, the features of network densification

Wireless mobile social networks have been introduced to consider characteristics of mobile user's behaviors for network configuration. The device-to-device (D2D) communication is to increase the network spectral efficiency by allowing users to communicate directly with the corresponding destinations. This paper develops a framework for the design of reliable D2D communication provided wireless mobile social network (D2D-MSN), and introduces a D2D- MSN throughput as a new measurement of the spect

A critical problem in open-spectrum communications is fairness with respect to the coexistence of heterogeneous systems with different resource units and traffic models. In addition, the sensing performances of different systems can also lead to unfair resource utilization between systems. To address this problem, we derive a continuous-time Markov chain model to show the effect of sensing performance on system coexistence. The analysis derived from this model is then used as the basis for a sen

The efficiency of spectrum sharing can be improved by interference suppression and/or cancellation. This paper analyzes the performance of spectrum sharing networks with interference cancellation (IC) based on the spectrum-sharing transmission capacity (S-TC), defined as the number of successful transmissions per unit area while guaranteeing all target outage probabilities of spectrum-sharing systems. The effectiveness of IC can be characterized by the coefficient of cancellation (CoC) and a spe

1997년 외환위기 전 한국경제는 심각한 구조적 문제가 있었지만 그것이 외환위기의 원인은 아니었다. 외환위기는 정부의 유동성 부족, 즉 한국 정부가 단기외채에 비해 외화준비금을 너무 적게 가지고 있었기 때문에 일어난 것이다. 그런 관점에서 보면 IMF와 미국이 요구한 외환위기의 해결책은 유효하지 않았고 매우 불공정했다. 그럼에도 불구하고 한국의 朝野는 국내의 구조적 문제를 개혁하는 데 이용한다는 목적으로 IMF와 미국의 요구를 적극 수용하였다. 그 결과 기업과 금융기관의 경영 건전성과 투명성이 향상되는 등 개혁의 성과를 거두었지만, 그 과정에서 외국인이 국내투자에서 거둔 차익이 한국인이 대외투자에서 거둔 차익을 초과하는 액수가 3,000여억달러에 달하였다. 외환위기 후 나타난 투자 및 고용 부진, 소득 분배 악화, 총요소생산성 증가 부진, 재정 건전성 악화 등도 외환위기 후 급속한 구조조정을 하면서 필요한 다른 개혁이 따라주지 못해서 일어난 것으로 외환위기의 처리과정과 관련이 있다.

이 논문은 기업 이윤율에 대한 노동조합의 영향이 1980년대 권위주의 시기, 민주화 이후 경제위기 전까지 시기, 위기 후 시기에 있어서 기업 규모에 따라 어떻게 나타나고 있는지를 분석한다. 권위주의 시기 대기업에서는노동조합이 이윤율을 낮추는 효과는 없는 반면 여타기업에서는 이윤율을낮추는 효과가 있었다. 민주화 이후 위기 전까지의 시기에 두 그룹 모두에서 노동조합이 이윤율을 낮추는 효과가 있었다. 위기 후에는 대기업에서는노동조합이 여전히 이윤율을 낮추고 있지만, 여타기업에서 노동조합은 이윤율을 낮추는 힘을 잃어버렸다. 위기 후 시기를 권위주의 시기와 비교해 보면 대기업에서는 노동조합이 이윤율을 낮추는 힘이 더 강한 반면, 여타기업에서는 더 약해졌다.

This paper presents a new framework to evaluate the performance of wireless networks with intrinsic secrecy. Specifically, we put forth the notion of secure node packing (SNP), defined as the number of legitimate users capable of transmitting data with secrecy using stochastic geometry. Transmission with secrecy means a legitimate receiver can decode transmitted data (reliability) while its corresponding eavesdropper cannot decode (secrecy). The SNP is derived for two cases of secure transmissio

In this paper, a resource management for fixed relay stations (FRS) with the limited capability is considered in down-link OFDMA multi-hop cellular networks. All of MSs which want to use a FRS in multi-hop transmission can not be supported when the capability of the FRS is insufficient. Hence, the multi-hop user admission (MUA) is required to determine the admitted MSs to use the FRS because the gain obtained from multi-hop transmission is different to each MS. The problem of MUA is formulated t