CAJ | 학술논문

信道间干扰是无线局域网在标准制定和实用中较重要的问题,如使用OFDM技术的高速率无线局域网标准802.11a,工作在国家信息基础设施频段5 GHz(许多国家无需频段许可),因此,可能出现多个用户使用相同子载波连接接入点.该类系统中,选用最大似然法进行参数估计是最优的,但计算复杂度大;选用次优但低复杂度的期望极大法作参数估计更具实用价值.在多用户使用同一载波接入时,实际仿真证实了期望极大算法可有效地抵抗信道间干扰.
신도간간우시무선국역망재표준제정화실용중교중요적문제,여사용OFDM기술적고속솔무선국역망표준802.11a,공작재국가신식기출설시빈단5 GHz(허다국가무수빈단허가),인차,가능출현다개용호사용상동자재파련접접입점.해류계통중,선용최대사연법진행삼수고계시최우적,단계산복잡도대;선용차우단저복잡도적기망겁대법작삼수고계경구실용개치.재다용호사용동일재파접입시,실제방진증실료기망겁대산법가유효지저항신도간간우.
Co-channel Interference (CCI) is an important issue in the design and deployment of WLANs because 802.11a uses Orthogonal Frequency Division Multiplexing (OFDM) and the spectrum allocated in the 5 GHz band is unlicensed. Therefore two or more adjacent users, connecting to different access points, could be using the same subcarriers. Though the estimation of unknown parameters using the maximum-likelihood (ML) is optimal, it is highly complex and could be analytically intractable. The expectation-maximization (EM)algorithm is a sub-optimal technique estimates the parameters in an iterative manner. This work investigates the application of EM to estimate desired user's signal in an OFDM system with CCI.