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다중안테나를 고려한 직교 주파수 분할 다중 접속 방식의 역방향 부호화 성능 검증
조한규,홍대식 대한전자공학회 2007 電子工學會論文誌-TC (Telecommunications) Vol.44 No.4
In this paper, link-level performance of a OFDMA technique, which has been considered as a standard for 802.16, 802.20, 3G-LTE, WiMax, and WiBro, is evaluated for next-generation wireless communication systems. While many researches have focused on uncoded forward-link performances, this paper provides a coded performance of a reverse-link OFDMA system. Performance degradation due to time offset among reverse-link users and frequency offset during FFT process is investigated. Transmitter and receiver antenna diversity techniques are used to overcome performance degradation. Performance of a OFDMA system is compared with a CDMA system in terms of FER and throughput to emphasize the advantage of OFDMA system for a reverse-link. Finally, under given specification, Eb/No required to achieve the maximum throughput of a reverse-link is proposed considering various coded rates and antenna permutations. 본고 에서는 802.16, 802.20 및 3G-LTE, WiMax, 그리고, WiBro와 같은 차세대 이동통신 시스템의 규격으로 고려되고 있는직교 주파수 분할 다중 접속 방식 (orthogonal frequency division multiple access; OFDMA)의 물리 계층 성능을 검증한다. 대부분의 연구 결과가 순방향 성능 향상에 집중되어 있기에 상대적으로 미약한 역방향을 고려하며, 많은 연구 결과가 부호화를 고려하지 않은 것에 비해 본 연구에서는 LDPC (low-density parity check) 부호화를 고려한다. 역방향의 경우 다양한 사용자간의 시간 동기 오차, 그리고, FFT (fast Fourier transform) 시 주파수 동기 오차가 존재하므로, 이를 고려한 성능 열화를 살펴본다. 다양한 성능 열화 요인을 갖는 역방향 링크의 성능 향상을 위하여, 송수신 안테나 다이버시티에 의한 성능 향상을 살펴본다. 또한, 동일한 성능 열화 요인 하에서 코드 분할 다중 접속 방식 (code division multiple access; CDMA)과의 프레임 오율 (frame error rate; FER) 및 throughput 비교를 통해 역방향 OFDMA 시스템의 장점을 부각하며, 최종적으로 다양한 부호화율 및 안테나 조합을 고려한 역방향 OFDMA시스템의 최대 throughput 달성을 위한 요구 Eb/No를 제안한다.
조한규,박정제,전시영,김진평,안성기,임종범,송민성 대한이비인후과학회 2007 대한이비인후과학회지 두경부외과학 Vol.50 No.9
Background and Objectives:Laryngeal trauma ocurs uncomonly, but when it does, it can cause acute airway obstruction and ases the outcome of the treatment. Materials and Method:We analyzed the medical records of 32 patients with acute laryngeal trauma from 1992 to 2006, retrospectively. Results:The most comon cause of injury was traffic accident. Voice change was the most common symptom. Vocal cord palsy in patients with redistributed in minor injury was improved in all of the group that re-ceived conservative management. If there are significant endolaryngeal laceration or arytenoid disruption, which can occur with major trauma, consideration should be given to placing an endolaryngeal stent. But there was no diference in improvement rates betwen those receiving treatment with stent and those without stent. Thus, consider severity, treatment with stent is likely to yield to significant benefit. Conclusion:Vocal cord palsy in patients with redistributed in minor trauma may be managed conservatively. We conclude that patients with major trauma of endolaryngeal mucosa should use a stent in their treatment. (Korean J Otorhi -nolaryngol-Head Neck Surg 2007 ;50 :800-6)
Otologic Manifestation in IgG4-Related Systemic Disease
조한규,이윤종,정진행,구자원 대한이비인후과학회 2011 Clinical and Experimental Otorhinolaryngology Vol.4 No.1
IgG4-related systemic disease, including autoimmune pancreatitis, is a multi-organ disorder characterized by elevated serum immunoglobulin G4 (IgG4) concentration and IgG4-positive plasma cell infiltration. We report a case of a 66-years-old woman with IgG4-related hearing disorder, presenting with fluctuating mixed hearing loss with middle ear effusion. The serum IgG4 level was elevated and pathological examination revealed dense infiltration of IgG4-positive lymphocyte in the renal parenchyma, lung tissue and lacrimal gland. With intravenous methylprednisolone at a dose of 60 mg daily, improvement of hearing loss were observed. No recurrence was observed for 6 months with mainternance of prednisolone and methotrexate.