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Iterative Demodulation and Decoding of Uplink Multiuser M-ary FSK Using OFDMA Mapping
Jinho Choi,Jeongseok Ha IEEE 2013 IEEE COMMUNICATIONS LETTERS Vol.17 No.9
<P>In this paper, we study iterative demodulation and decoding (IDD) for a multiuser system where users employ M-ary frequency shift keying to transmit their signals to a base station (BS). Since joint multiuser detection requires a prohibitively high computational complexity, we propose a suboptimal low-complexity detection method that can take into account extrinsic bit information, which is well-suited to IDD. Under a certain condition, its complexity grows linearly with the number of users.</P>
Compressive Channel Division Multiple Access for MTC Under Frequency-Selective Fading
Jinho Choi,Nam Yul Yu Institute of Electrical and Electronics Engineers 2017 IEEE Transactions on Communications Vol. No.
<P>In this paper, we study random access for machine-type communications based on a multiple access scheme that exploits different channel state information (CSI) from active devices under frequency-selective fading, which is called channel division multiple access (ChDMA). In ChDMA, in order to use a low-complexity compressive sensing (CS) algorithm for multiuser detection (MUD) with a high transmission rate, we propose to use index modulation. Since the CSI is used as a signature for MUD, the CSI estimation becomes crucial. For the CSI estimation, pilot transmission can be considered where each active device randomly chooses a pilot from a set of pre-determined pilots. Since the CSI estimation suffers from pilot collision in this case, we propose multiple pilot transmissions and show that a low probability of collision can be achieved. A CS-based approach is derived not only to estimate the CSI, but also to detect randomly selected multiple pilot signals by exploiting the sparsity of active devices over frequency-selective fading channels.</P>
A preliminary study on whether M&A information is useful to predict promising industries
Jinho Choi,Sunghun Chung,Yong Sik Chang 한국정보기술학회 2019 Proceedings of The International Workshop on Futur Vol.2018 No.1
Companies are struggling in diversifying and growing their current businesses due to lack of information on diversification and low level of capabilities for the future commercialization. In this study, we suggest a comprehensive framework that explores the new business opportunities for the growth of firms in the future. We first theoretically examine whether all M&A transactions are related to promising areas or not. Secondly, we analyze the trends of global M&As in terms of its frequency and transactional value for the last 15 years. Lastly, we conduct the association analysis to identify the degree of M&A connections between industry areas.
A Cholesky Factorization Based Approach for Blind FIR Channel Identification
Jinho Choi,Cheng-Chew Lim IEEE 2008 IEEE transactions on signal processing Vol.56 No.4
<P>For blind channel identification, various techniques, including transmitter-induced cyclostationarity based approaches, have been proposed in literature. To induce cyclostationarity at the transmitter, zero padding to every symbol packet can be considered. Some subspace methods are proposed for the channel estimation by exploiting the induced cyclostationarity. Due to zero padding, the covariance matrix of received signal vectors can have a special structure. Utilizing this structure, we can estimate channel impulse responses through factorization. In this correspondence, we propose a factorization based approach to estimate channel impulse responses. In general, the proposed factorization based approach can work with a small number of samples and becomes much more computationally efficient than the subspace method when the length of packets is long.</P>