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HomePlug AV 네트워크에서의 성능 향상을 위한 적응적 Contention Window 조절 방식
윤성국(Sung-Guk Yoon),윤정균(Jeongkyun Yun),김병승(Byungseung Kim),박세웅(Saewoong Bahk) 한국통신학회 2008 韓國通信學會論文誌 Vol.33 No.5B
HomePlug AV (HPAV)는 댁내에 깔려있는 전력선을 이용하여 데이터 전송뿐만 아니라 음향과 영상까지 전송을 목표로 HomePlug Alliance에서 제정한 표준이다. 이 표준은 TDMA와 CSMA/CA 기술을 혼합하여 사용하는 MAC 기술을 사용한다. HPAV의 CSMA/CA 프로토콜은 Contention Window (CW)와 Deferral Counter (DC)라는 두 가지 주요한 변수를 가지고 HPAV 네트워크를 제어한다. 본 논문에서는 CW와 DC가 성능에 미치는 영향을 여러 각도에서 조명하였고 이를 기반으로 HPAV MAC의 수율을 높이기 위한 적응적 CW 조절 방식을 제안한다. 여러 실험을 통해 얻은 결과 CW가 DC 보다 수율에 더 민감한 성질을 가지고 있어서 제안하는 방식은 DC는 표준에 정의된 기본값을 사용하고 CW만을 조정한다. 제안하는 방식은 네트워크가 과부하가 걸려있다면 CW를 두 배로 늘려주고 네트워크의 부하가 적으면 CW를 반으로 줄여주는 단순한 방식을 이용함으로 복잡도를 낮춰 구현이 가능하다는 장점이 있다. 모의실험과 수리분석을 통해 제안하는 방식이 여러 다양한 환경에서 좋은 성능을 보이는 것을 확인할 수 있다. HomePlug AV (HPAV) is the standard for distribution of Audio/Video content as well as data within the home by using the power line. It uses a hybrid access mechanism that combines TDMA with CSMA/CA for MAC technology. The CSMA/CA protocol in HPAV has two main control knobs that can be used for access control: contention window (CW) size and deferral counter (DC). In this paper, we extensively investigate the impacts of CW and DC on performance through simulations, and propose an adaptive mechanism that adjusts the CW size to enhance the throughput in HPAV MAC. We find that the CW size is more influential on performance than the DC. Therefore, to make controlling the network easier, our proposal uses a default value of DC and adjusts the CW size. Our scheme simply increases or decreases the CW size if the network is too busy or too idle, respectively. We compare the performance of our proposal with those of the standard and other competitive schemes in terms of throughput and fairness. Our simulation and analysis results show that our adaptive CW mechanism performs very well under various scenarios.
경요도적 절제술 후 방광 이행세포암의 재발에 관계하는 요소들
남기동,구봉식,윤성국,박병호,남경진,최종철,이기남,이영일,정덕환,Nam, Gi-Dong,Koo, Bong-Sik,Yoon, Sung-Guk,Park, Byeong-Ho,Nam, Gyeong-Jin,Choi, Jong-Cheol,Lee, Gi-Nam,Lee, Yeong-Il,Jeong, Deok-Hwan 대한영상의학회 1998 대한영상의학회지 Vol.38 No.4
Purpose: To evaluate factors related to the recurrence of TCC(transitional cell carcinoma) in the urinary bladder after transurethral resection of bladder tumor(TUR-BT). Materials and Methods : We retrospectively reviewed 54 patients in whom TCC (transitional cell carcinoma) after TUR-BT had been confirmed. Recurrence was evaluated by US, CT, cystoscopy and urine smear during the follow-up period of 6 months. The multiplicity, shape, size, and calcification of TCC, as revealed by radiologic studies, were evaluated retrospectively before TUR-BT. After TUR-BT, the histologic grade and pathologic stage of TCC were evaluated. Results : According to the multiplicity of TCC, the recurrence rate was 66.7% in the multiple type and 28.6% in the single type(p=0.039);according to shape, this rate was 61.5% in the sessile type and 29.3% in the pedunculated type(p=0.0505), and according to mass size, the rate was 41.7% in tumors more than 3cm in diameter and 35.7% in tumors less than 3cm(p=0.706). In the presence of calcification, the recurrence rate was 40.0% and in its absence, this rate was 36.7%(p=0.885). Pathologically, the higher the grade and stage of TCC, the higher the recurrence rate(respectively p=0.010 and 0.041). Conclusions : Radiologically, multiple and/or sessile type TCC had a higher recurrence rate than the single and/or pedunculated type. Pathologically, when the grade and stage of bladder tumor were higher, recurrence rates were higher.