A Non-Cooperative Game on Distributed Dynamic Channel Selection for Multichannel Cognitive Radio Networks

Jo Woon Chong(정조운),Hyundong Shin(신현동) 한국통신학회 2009 한국통신학회 학술대회논문집 Vol.2009 No.11

An Adaptive WLAN Interference Mitigation Scheme for ZigBee Sensor Networks

Chong, Jo Woon,Cho, Chae Ho,Hwang, Ho Young,Sung, Dan Keun Taylor & Francis 2015 INTERNATIONAL JOURNAL OF DISTRIBUTED SENSOR NETWOR Vol.2015 No.-

Statistical multiplexing-based hybrid FH-OFDMA system for OFDM-based UWB indoor radio access networks

Chong, Jo Woon,Jung, Bang Chul,Sung, Dan Keun IEEE 2006 IEEE transactions on microwave theory and techniqu Vol.54 No.4

We propose a statistical multiplexing-based hybrid frequency-hopping orthogonal frequency-division multiple-access (HFH-OFDMA) system to increase the downlink user capacity of orthogonal frequency-division multiplexing (OFDM)-based ultra-wideband (UWB) indoor radio access networks (RANs). The downlink user capacity is here defined as the maximum allowable number of users served with a given data rate in a piconet. Statistical multiplexing, as noted by Walrand and Varaiya in 2000, is a method in which multiple users with intermittent transmissions efficiently share a link. The adoption of a statistical multiplexing concept enables the HFH-OFDMA system to accommodate many more users than the conventional FH-OFDMA system can. In OFDM-based UWB indoor RANs, the downlink user capacity of the HFH-OFDMA system is limited by either the total number of available subcarriers in a piconet (resource-limited) or the FCC UWB emission limit (power-limited). We analyze the downlink user capacity of the proposed HFH-OFDMA system in both single-piconet and multipiconet environments. In the single-piconet environment, the proposed HFH-OFDMA system which operates in 3.168-3.696-GHz band accommodates 256 users with a data rate of 532.5 kb/s in an OFDM-based UWB indoor RAN, while the proposed HFH-OFDMA system in the multipiconet environment, under the same conditions of the single-piconet environment, accommodates 110 users with a data rate of 532.5 kb/s.

Cross-Layer Performance Analysis for CSMA/CA Protocols: Impact of Imperfect Sensing

Jo Woon Chong,Dan Keun Sung,Youngchul Sung IEEE 2010 IEEE Transactions on Vehicular Technology VT Vol.59 No.3

<P>In this paper, the performance of carrier-sense multiple access (CSMA)/collision-avoidance (CA) protocols in the presence of carrier-sensing errors is analyzed. Two types of carrier-sensing errors, i.e., false alarm and miss-detection, are considered, and their impact on the system performance is analyzed using a new CSMA/CA model based on a Markov chain capturing the sensing error at the physical layer. The system throughput and delay as functions of the sensing error probabilities, as well as other CSMA/CA parameters, are obtained, and their sensitivity with respect to a key physical-layer parameter, i.e., the sensing threshold, is analyzed for commonly used energy detectors or matched filters. It is shown that the throughput and delay sensitivity heavily depends on the ratio of the contention window size W to the frame length L, and the throughput is sensitive to the design of the sensing threshold when the ratio W/L is either small or large. The result provides guidelines about how to operate CSMA/CA considering imperfect sensing at the physical layer.</P>

RawPEACH: Multiband CSMA/CA-Based Cognitive Radio Networks

Chong, Jo-Woon,Sung, Young-Chul,Sung, Dan-Keun The Korea Institute of Information and Commucation 2009 Journal of communications and networks Vol.11 No.2

A new medium access control (MAC) scheme embedding physical channels into multiband carrier sense multiple access/collision avoidance (CSMA/CA) networks is proposed to provide strict quality of service (QoS) guarantee to high priority users. In the proposed scheme, two priority classes of users, primary and secondary users, are supported. For primary users physical channels are provided to ensure strict QoS, whereas secondary users are provided with best-effort service using CSMA/CA modified for multiband operation. The performance of the proposed MAC scheme is investigated using a new multiband CSMA/CA Markov chain model capturing the primary user activity and the operation of secondary users in multiple bands. The throughput of secondary users is obtained as a function of the primary user activity and other CSMA/CA parameters. It is shown that the new MAC scheme yields larger throughput than the conventional single-band CSMA/CA when both schemes use the same bandwidth.

Poster Session : PS 0712 ; Rheumatology ; Acute Myocarditis in Patients with Systemic Lupus Erythematosus: Experience from Affi liated Hospitals of Catholic University of Korea

( In Woon Baek ),( Ki Jo Kim ),( Yune Jung Park ),( Chong Hyeon Yoon ),( Wan Uk Kim ),( Chul Soo Cho ) 대한내과학회 2014 대한내과학회 추계학술발표논문집 Vol.2014 No.1

Background: To determine the factors associated with occurrence of acute myocarditis (AMC) and its outcomes in patients with systemic lupus erythematosus (SLE). Methods: This was a retrospective study of hospitalized SLE patients with AMC from 2002 to 2014 at Catholic University affi liated hospitals. A diagnosis of AMC was made on the basis of clinical fi ndings, electrocardiographic changes, elevated cardiac enzymes levels and echocardiographic abnormalities. Eighty-six SLE patients who showed no echocardiographic evidence of myocarditis were enrolled as a control group. The clinical and laboratory data from each patient were collected from the charts and compared between 2 groups. Results: During these periods, 22 SLE patients were identifi ed to have AMC (male 3, female 19). Patients with AMC, as compared with those without, were found to be associated with shorter disease duration and higher frequency of smoking (P<0. 005, P<0. 05, respectively). Moreover, they showed signifi cantly higher SLE disease activity index score (P<0. 001) and C-reactive protein levels (P<0. 001), but lower complement levels (C3, C4 and CH50, all P<0. 005). Interestingly, antiphospholipid syndrome (APS) was more prevalent in patients with AMC compared with those without (P<0. 01). In multivariate analysis, shorter disease duration, smoking and presence of APS wereindependent factors associated with AMC in SLE patients. All patients with AMC received high-dose corticosteroid and 2 of them received intravenous cyclophosphamide; 17 patients completely recovered, but 5 died. Conclusions: AMC patients are more likely to have high disease activity and its occurrence is associated with shorter disease duration, smoking, and presence of APS.

Poster Session : PS 0711 ; Rheumatology ; Causal Link Between Thrombocytopenia and Poor Prognosis in Patients with Systemic Lupus Erythematosus

( Ki Jo Kim ),( In Woon Baek ),( Chong Hyeon Yoon ),( Wan Uk Kim ),( Chul Soo Cho ) 대한내과학회 2014 대한내과학회 추계학술발표논문집 Vol.2014 No.1

Background: Thrombocytopenia is a common hematologic manifestation of systemic lupus erythematosus (SLE) and forecasts an unfavorable outcome for SLE. The aim of this study is to investigate the causes of thrombocytopenia and their frequency in SLE patients and to fi nd out the clinical evidence linking lupus-associated thrombocytopenia and poor prognosis. Methods: The charts of 393 patients with SLE from a single tertiary center between 1988 and 2012 were reviewed. Thrombocytopenia was defined as a platelet count <100,000/ L and clinical and serologic characteristic of the study subjects were analyzed with a focus on the incidence and associations of thrombocytopenia. Results: Thrombocytopenia of 318 events was found in 154 patients and the most common causes are thrombocytopenia during fiare-up (135, 42. 5%) and isolated thrombocytopenia (105, 33%). Patients with thrombocytopenia had more pulmonary hypertension, hemolytic anemia, and neuropsychiatric involvement and received higher dose of glucocorticoid. Infection and arterial thrombosis occurred more commonly and progression rate to end-stage renal disease was higher in patients with thrombocytopenia. Positive rate of anti-histone antibody and lupus anticoagulant was also higher in patients with thrombocytopenia. During follow-up, patients with thrombocytopenia had higher cumulative organ damage and showed signifi cantly reduced survival rate. By multivariate analysis, thrombocytopenia (HR 4. 958, 95% CI 1. 231-19. 969, P = 0. 024), infection (HR 9. 293, 95% CI 2. 222-38. 869, P = 0. 002) and cumulative dose of glucocorticoid (HR 14. 993, 95% CI 3. 232-69. 545, P = 0. 001) were independent predictors of mortality. Conclusions: Thrombocytopenia is closely linked with critical manifestations affecting the disease outcome and functions as an independent predictor for mortality.

Association of Anemic Hypoxia and Increased Pulmonary Artery Systolic Pressure in Patients With Systemic Lupus Erythematosus : Anemic Hypoxia With PAH in SLE

Kim, Ki-Jo,Baek, In-Woon,Yoon, Chong-Hyeon,Kim, Wan-Uk,Cho, Chul-Soo Wiley (John WileySons) 2015 Arthritis care & research Vol.67 No.12

스포츠 마사지의 무드변화에 대한 효과

김완조,김종희,김석련,윤기운 대한스포츠의학회 1994 대한스포츠의학회지 Vol.12 No.1

The purpose of the present investigation was to assess the relationship between sports massage and positive mood enhancement. Subjects were the student in physical education. Experimental conditions were rest, massage and recovery 30min after performing maximal exercise with short duration, In massage treatment condition a cetified massage therapist gave a 15-min warm-up massage. All subjects completed the profile of mood states Results indicated that massage condition produced positive mood enhancement with significant decreases in tension and total mood distribution while maintaining high levels of vigor, which is representative mental health. Practical applications o the use of massage both before and after competition and exercise are discussed.

Intervehicle Communication: Cox-Fox Modeling

Youngmin Jeong,Jo Woon Chong,Hyundong Shin,Win, M. Z. IEEE 2013 IEEE journal on selected areas in communications Vol.31 No.9

<P>Safety message dissemination in a vehicular ad-hoc network (VANET) requires vehicle-to-vehicle (V2V) communication with low latency and high reliability. The dynamics of vehicle passing and queueing as well as high mobility create distinctive propagation characteristics of wireless medium and inevitable uncertainty in space-time patterns of the vehicle density on a road. It is therefore of great importance to account for random vehicle locations in V2V communication. In this paper, we characterize intervehicle communication in a random field of vehicles, where a beacon or head vehicle (transmitter) broadcasts safety or warning messages to neighboring client vehicles (receivers) randomly located in a cluster on the road. To account for a doubly stochastic property of the VANET, we first model vehicle's random locations as a stationary Cox process with Fox's H-distributed random intensity (vehicle concentration) and derive the distributional functions of the lth nearest client's distance from the beacon in such a Fox Cox field of vehicles. We then consolidate this spatial randomness of receiving vehicles into a path loss model and develop a triply-composite Fox channel model that combines key wireless propagation effects such as the distance-dependent path loss, large-scale fading (shadowing), and small-scale fading (multipath fading). In Fox channel modeling, each constituent propagation effect is described as Fox's H-variate, culminating again in Fox's H-variate for the received power or equivalently the instantaneous signal-to-noise ratio at the lth nearest client vehicle. Due to versatility of Fox's H-functions, this stochastic channel model can encompass a variety of well-established or generalized statistical propagation models used in wireless communication; be well-fitted to measurement data in diverse propagation environments by varying parameters; and facilitate a unifying analysis for fundamental physical-layer performances, such as error probability and channel capacity, using again the language of Fox's H-functions. This work serves to develop a unifying framework to characterize V2V communication in a doubly stochastic VANET by averaging both the small- and large-scale fading effects as well as the (random) distance-dependent path losses.</P>