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Comments on “Near-Body Shadowing Analysis at 60 GHz”
Kim, Donggu,Lee, Hoojin,Kang, Joonhyuk Institute of Electrical and Electronics Engineers 2017 IEEE transactions on antennas and propagation Vol.65 No.6
<P>In a recent paper, Mavridis et al. proposed a statistical diffraction model to characterize the channel near the human body (i.e., near-body zone) at 60 GHz in an indoor communication environment. Specifically, they demonstrated that the near-body zone has been separated into the front and back regions, and both regions can be theoretically modeled by a two-wave with diffuse power (TWDP) distribution, the statistical properties of which are described by two parameters <TEX>$K$</TEX> and <TEX>$\Delta $</TEX> defined as <disp-formula> <TEX>\begin{equation*} K=\frac {V_{1}^{2}+V_{2}^{2}}{2\sigma ^{2}} \end{equation*}</TEX></disp-formula> and <disp-formula> <TEX>\begin{equation*} \Delta =\frac {2V_{1}V_{2}}{V_{1}^{2}+V_{2}^{2}}, \end{equation*}</TEX></disp-formula> which represent the ratio of the total specular power to the diffused power and the relative power level of the two specular components, respectively, where <TEX>$V_{1}$</TEX> and <TEX>$V_{2}$</TEX> denote the magnitudes of the two specular components, and <TEX>$2\sigma ^{2}$</TEX> represents the average power of the diffused components.</P>
Cooperation Strategies for Partly Wireless C-RAN
Kim, Donggu,Yang, Yanpeng,Sung, Ki Won,Kang, Joonhyuk IEEE 2018 IEEE COMMUNICATIONS LETTERS Vol.22 No.6
<P>This letter presents a variant of cloud radio access network (C-RAN) architecture, which we term partly wireless C-RAN (PW-CRAN). It is characterized by extra radio nodes connected through the existing remote radio heads. Because of the newly connected nodes and the consequent additional delay, the operation of PW-CRAN requires different approaches compared with that of the typical C-RAN. Specifically, the effect of delayed channel state information on the suitability of network cooperation should be identified. To tackle this problem, we introduce two representative cooperation strategies and evaluate the performance with regard to the delay via simulations. Numerical results suggest that it is better to exclude the extra nodes from cooperation if they incur excess delay. Furthermore, whether the delay is deemed excessive depends on the interference environment. Hence, we provide quantified guidelines on the cooperation strategy of PW-CRAN.</P>
Impact of Two-Ray Fading on the Error Rate Performance of Binary Signals with MRC Diversity
Donggu Kim(김동구),Hoojin Lee(이후진) 대한전자공학회 2018 전자공학회논문지 Vol.55 No.6
통신 시스템에서 최악의 페이딩이라고 알려진 two-ray (TR) 페이딩의 영향을 효과적으로 분석하기 위해, 본 논문에서는 일반적인 binary 변조 방식을 채택한 시스템의 정확한 비트 오류율 (bit error rate)에 대한 포괄적이고 통합적인 닫힌 형태의 수식을 유도한다. 또한, maximal ratio combining (MRC) 다이버시티 기법을 채택한 시스템에서의 정확한 비트 오류율 수식도 함께 구한다. 추가적으로 high signal-to-noise ratio (SNR) 영역에서의 통합적인 닫힌 형태의 점근적 비트 오류율 수식 유도를 통해 TR 페이딩이 통신 시스템에 미치는 영향 및 가장 대표적인 페이딩 모델인 Rayleigh 페이딩 채널 환경과 비교했을 때의 상대적인 SNR 성능 열화에 대해서 보다 효과적으로 분석할 수 있게 된다. 후반부에는 다양한 수치 해석 결과를 제시하여 본 논문에서 유도된 여러 수식들의 정확성을 입증한다. Aiming at effectively evaluate the impact of well-known worst-case fading (i.e., two-ray (TR) fading), this paper derives a generic unified exact bit error rate (BER) expression for general binary signals, which can be used to obtain the respective more concise closed-form formula of each binary signaling. Moreover, the exact BER formulas for the binary signals with maximal ratio combining (MRC) diversity are also derived. Focusing on the high signal-to-noise ratio (SNR) regime, the unified asymptotic closed-form BER expression is established, which enables us to obtain more intuitive insights into the achievable error rate performance. Based on the derived asymptotic expression, we further investigate the asymptotic SNR performance losses of TR fading with respect to Rayleigh fading. Some numerical results are presented to verify the concurrence between our derived exact and asymptotic BER expressions, and validate the theoretically derived asymptotic SNR performance losses.