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Resource allocation for multicast services in multicarrier wireless communications
Changho Suh,Jeonghoon Mo IEEE 2008 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.7 No.1
<P>We consider a multicast resource allocation problem for the downlink in OFDM-based wireless cellular network systems. In a conventional multicast system, to accommodate users with bad channel conditions, the transmission is based on the worst case user. We show that such a multicast system saturates the capacity when the number of users increases in fading environments. We exploit the multicarrier nature of OFDM and advances in coding techniques such as MDC (multiple description coding), in which arbitrary combinations of layers can be decoded at the receiver. Different MDC layers are carried over different subcarriers and users with good channels receive data from more subcarriers than users with poor channel conditions. We present an optimal subcarrier/bit allocation method requiring full search of possible candidates. To reduce the complexity, we propose a two-step suboptimum algorithm by separating subcarrier allocation and bit loading. Numerical results show that the proposed heuristics significantly outperform the conventional multicast transmission scheme. The difference between optimum and heuristic solutions is less than 5%.</P>
Suh, Changho,Tan, Vincent Y. F.,Zhao, Renbo Institute of Electrical and Electronics Engineers 2017 IEEE Transactions on Information Theory Vol. No.
<P>We study the top-K ranking problem where the goal is to recover the set of top-K ranked items out of a large collection of items based on partially revealed preferences. We consider an adversarial crowdsourced setting where there are two population sets, and pairwise comparison samples drawn from one of the populations follow the standard Bradley-Terry-Luce model (i.e., the chance of item i beating item j is proportional to the relative score of item i to item j), while in the other population, the corresponding chance is inversely proportional to the relative score. When the relative size of the two populations is known, we characterize the minimax limit on the sample size required (up to a constant) for reliably identifying the top-K items, and demonstrate how it scales with the relative size. Moreover, by leveraging a tensor decomposition method for disambiguating mixture distributions, we extend our result to the more realistic scenario, in which the relative population size is unknown, thus establishing an upper bound on the fundamental limit of the sample size for recovering the top-K set.</P>
Two-Way Interference Channel Capacity: How to Have the Cake and Eat It Too
Suh, Changho,Cho, Jaewoong,Tse, David IEEE 2018 IEEE transactions on information theory Vol.64 No.6
<P>Two-way communication is prevalent and its fundamental limits are first studied in the point-to-point setting by Shannon. One natural extension is a two-way interference channel (IC) with four independent messages: two associated with each direction of communication. In this paper, we explore a deterministic two-way IC, which captures the key properties of the wireless Gaussian channel. Our main contribution lies in the complete capacity region characterization of the two-way IC (with respect to the forward and backward sum-rate pair) via a new achievable scheme and a new converse. One surprising consequence of this result is that not only we can get an interaction gain over the one-way non-feedback capacities, we can sometimes <I>get all the way to perfect feedback capacities in both directions simultaneously</I>. In addition, our novel outer bound characterizes channel regimes in which interaction has no bearing on capacity.</P>
Computation in Multicast Networks: Function Alignment and Converse Theorems
Changho Suh,Goela, Naveen,Gastpar, Michael Institute of Electrical and Electronics Engineers 2016 IEEE Transactions on Information Theory Vol. No.
<P>The classical problem in a network coding theory considers communication over multicast networks. Multiple transmitters send independent messages to multiple receivers that decode the same set of messages. In this paper, computation over multicast networks is considered: each receiver decodes an identical function of the original messages. For a countably infinite class of two-transmitter two-receiver single-hop linear deterministic networks, the computation capacity is characterized for a linear function (modulo-2 sum) of Bernoulli sources. A new upper bound is derived that is tighter than cut-set-based and genie-aided bounds. A matching inner bound is established via the development of a network decomposition theorem, which identifies elementary parallel subnetworks that can constitute an original network without loss of optimality. The decomposition theorem provides a conceptually simple proof of achievability that generalizes to L-transmitter L-receiver networks.</P>
Suh Munshik(서문식),Oh Changho(오창호) 한국산업경영학회 2006 한국산업경영학회 발표논문집 Vol.1 No.-
This study delves deeper into the possibilities of service personnel"s intrinsic elements influence customer"s recovery satisfaction as psychological instruments for identifying latent profiles to service marketing stimuli in the context of service failure. Specifically, the application of service personnel"s psychological approach is extended by considering the inclusion of variables emphasizing the customer-contact employee"s attitude of mind in severe service failure. This study also sheds light on the HRM strategies that have been adopted in service recovery to amplify service providers" performance levels.<BR> In addition, most of current service recovery studies focus on the relationship between satisfaction and other constructs, such as loyalty and service quality. Yet, there is a paucity of research addressing the factors that lead to a customer building long-term relationship. Consequently, very little is known about relationship dissolution between recovery satisfaction and psychological variables.
호텔서비스제공자의 셀프리더십이 서비스회복과 직무만족 및 서비스품질에 미치는 영향
서문식(Suh munshik),오창호(Oh changho),전홍대(Jeon hongdae) 한국산업경영학회 2006 경영연구 Vol.21 No.2
본 연구는 서비스실패상황에서 현장종업원의 내재적요소라 할 수 있는 셀프리더십이 서비스회복, 직무만족 그리고 호텔의 서비스품질 향상에 미치는 중요한 영향을 실증 조사하였다. 특급호텔 현장종업원을 대상으로 한 구조방정식 분석 결과 제시한 6개의 가설적 관계가 통계적으로 모두 유의한 것으로 나타났다. 본 연구에서 제안한 가설적 모델은 완전히 만족스러운 정도는 아니지만 적어도 수용 가능한 수준의 모델 적합도를 지니고 있는 것으로 나타났다. 마지막으로 직무만족과 서비스회복은 셀프리더십과 서비스품질간을 매개하는 것으로 나타났다. 이러한 분석결과를 통해서 서비스조직이 서비스품질향상을 위해 서비스제공자의 행동적 측면만을 강조하기 보다는 직업에 대한 투철한 가치관을 형성시키고 심리적 요인들을 강화시킬 수 있는 셀프리더십에 관심을 기울여야 함을 이해할 수 있다. 그리고 셀프리더십과 이론적으로 그리고 실무적으로 그 중요성이 더해가는 서비스회복과의 유의한 관계를 새롭게 이해할 수 있었다. This study investigated the effects of hotel service provider"s intrinsic factor(self-leadership) on service recovery, job satisfaction and service quality. The model was tested with a sample of hotel service providers by using structural equation modeling. The findings supported the effects of self-leadership and all structural path coefficients were significant. Further, job satisfaction and service recovery fully mediated the effects of self-leadership on service quality. The results of the present study demonstrate that service organizations need to focus on employee"s intrinsic factors such as self-leadership and self-efficacy. Thus, it provides new insights into the relationships among self-leadership, service recovery, job satisfaction and service quality. In sum, theocratical and practical implications on the self-leadership are proposed.