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Park, Yosub,Heo, Jihaeng,Hong, Daesik IEEE 2017 IEEE communications letters Vol.21 No.8
<P>This letter analyzes a spectral efficiency (SE) performance reflecting heterogeneous channel estimation (CE) capabilities across user equipment (UE) in ultra-dense small cell networks. Specifically, we derive asymptotic and approximated SE performances considering different kinds of CE capabilities. The analysis and simulation results lead us to some new intuitions as follows. First, the heterogeneity of CE capabilities across UEs has a great effect on SE performance in ultra-dense networks. Second, as the cell density increases, SE performance is asymptotically converged to its limit point when heterogeneous CE capabilities are considered, whereas the SE logarithmically increases in the perfect CE case.</P>
Resource Size Control for Reliability Improvement in Cellular-Based V2V Communication
Park, Yosub,Kim, Taehyung,Hong, Daesik IEEE 2019 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY Vol.68 No.1
<P>In vehicle-to-vehicle (V2V) communication, link reliability has been regarded as an important performance metric, especially for safety-critical broadcast services. In this paper, we analyze the link reliability of the centralized mode (Mode 3) for long-term evolution (LTE)-based V2V (LTE-V2V) from the PHY/MAC perspectives. Moreover, we derive the statistical distribution of the interference distance and interference to noise ratio (INR) for LTE-V2V. Based on this analytical framework, we propose a resource size control (RSC) method for improving link reliability. The proposed RSC adapts the resource size according to the macroscopic network parameters such as vehicle density, communication range, and message size. Numerical results show that the proposed method improves link reliability compared with the fixed resource size setting in a highway scenario. Moreover, it is observed that larger-sized resources are preferred when the vehicle density decreases, the message size increases, or the communication range decreases.</P>
Jeong, Jinkyo,Park, Yosub,Weon, Sungwoo,Kim, Jintae,Choi, Sooyong,Hong, Daesik IEEE 2018 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.17 No.10
<P>This paper proposes a new generalized frequency division multiplexing (GFDM) system that eliminates the effects of intrinsic interference and makes it possible to insert a pilot for channel estimation without interference. We express inter-subsymbol interference (ISI) and inter-carrier interference (ICI), which represent the intrinsic interference in GFDM systems, in a matrix form. The proposed GFDM system can remove the ISI through pre-processing and post-processing, which are done by eigendecomposition. We analytically derive the sufficient condition for the ICI removal. In this way, the proposed GFDM system is able to eliminate the effects of both the ISI and ICI. Furthermore, we investigate the prototype filter structures of the proposed GFDM system transformed by pre-processing and post-processing. We verify that the changed prototype filter structures are able to insert pilot symbols that are orthogonal to data symbols. Hence, the pilot symbols for channel estimation can be clearly observed. Simulation results demonstrate that the proposed system has better BER performance than conventional GFDM systems when the channel estimation process is considered.</P>
A New Filter-Bank Multicarrier System: The Linearly Processed FBMC System
Kim, Jintae,Park, Yosub,Weon, Sungwoo,Jeong, Jinkyo,Choi, Sooyong,Hong, Daesik IEEE 2018 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.17 No.7
<P>In this paper, we propose a linearly processed filter-bank multicarrier (LP-FBMC) system which employs faster than Nyquist signaling to remove residual intrinsic interferences. We represent the FBMC transceiver in a matrix form and then apply singular value decomposition-based linear transformation in order to convert the overlapped FBMC data into parallel independent interference-free data. This interference-free characteristic of the proposed LP-FBMC system enables the use of conventional multiple antenna configurations. Performance evaluations show that out-of-band emission performance of the proposed LP-FBMC system is superior to those of conventional quadrature amplitude-based FBMC (FBMC-QAM) and orthogonal frequency division multiplexing systems. Furthermore, the proposed LP-FBMC system outperforms the conventional FBMC-QAM in terms of bit error rate performance when high order modulation is employed under time-varying channel and multiuser uplink environment.</P>
Aligned Reverse Frame Structure for Interference Mitigation in Dynamic TDD Systems
Lee, Kwonjong,Park, Yosub,Na, Minsoo,Wang, Hanho,Hong, Daesik IEEE 2017 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.16 No.10
<P>The dynamic time division duplex (TDD) system has been proposed as a way to meet today's asymmetrically and dynamically changing traffic demand. However, this approach causes cross-link interference, because neighboring base stations and user elements transmit in opposite directions. In this paper, we investigate and analyze the characteristics of cross-link interference in dynamic TDD systems. Based on this observation, we propose an aligned reverse frame structure to utilize and cancel the cross-link interference. Mathematical analysis and numerical results verify that the proposed scheme achieves performance enhancement in terms of capacity compared with conventional dynamic TDD systems.</P>
Time Spread-Windowed OFDM for Spectral Efficiency Improvement
Kim, Hyejin,Jung, Insik,Park, Yosub,Chung, Wonsuk,Choi, Sooyong,Hong, Daesik IEEE 2018 IEEE wireless communications letters Vol.7 No.5
<P>This letter proposes a new orthogonal frequency division multiplexing (OFDM)-based waveform, called time spread-windowed OFDM (TS-W-OFDM). TS-W-OFDM applies a windowing procedure to improve spectral efficiency and a time spreading method to create a block signal structure. Numerical results show that TS-W-OFDM has higher spectral efficiency and nearly same error rate compared to the conventional cyclic prefix-OFDM, windowed-OFDM (W-OFDM), weighted overlap and add-based OFDM (WOLA-OFDM), and filtered-OFDM (F-OFDM). In addition, they also show that TS-W-OFDM has lower complexity than W-OFDM, WOLA-OFDM, and F-OFDM.</P>