tailieunhanh - Báo cáo hóa học: " Research Article MAP Channel-Estimation-Based PIC Receiver for Downlink MC-CDMA Systems"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Research Article MAP Channel-Estimation-Based PIC Receiver for Downlink MC-CDMA Systems | Hindawi Publishing Corporation EURASIP Journal on Wireless Communications and Networking Volume 2008 Article ID 570624 9 pages doi 2008 570624 Research Article MAP Channel-Estimation-Based PIC Receiver for Downlink MC-CDMA Systems Hakan Dogan 1 Erdal Panayirci 2 Hakan A. Cirpan 1 and Bernard H. Fleury3 1 Department of Electrical and Electronics Engineering Istanbul University Avcilar 34850 Istanbul Turkey 2 Department of Electronics Enginering KadirHas University Cibali 34083 Istanbul Turkey 3 Section Navigation and Communications Department of Electronic Systems Aalborg University Fredrik Bajers Vej 7A3 DK-9000 Aalborg Denmark and The Telecommunications Research Center Donau City Strasse 1 1220 Vienna ftw. Austria Correspondence should be addressed to Hakan Dogan hdogan@ Received 15 May 2007 Revised 10 September 2007 Accepted 2 October 2007 Recommended by Arne Svensson We propose a joint MAP channel estimation and data detection technique based on the expectation maximization EM method with paralel interference cancelation PIC for downlink multicarrier MC code division multiple access CDMA systems in the presence of frequency selective channels. The quality of multiple access interference MAI which can be improved by using channel estimation and data estimation of all active users affects considerably the performance of PIC detector. Therefore data and channel estimation performance obtained in the initial stage has a significant relationship with the performance of PIC. So obviously it is necessary to make excellent joint data and channel estimation for initialization of PIC detector. The EM algorithm derived estimates the complex channel parameters of each subcarrier iteratively and generates the soft information representing the data a posterior probabilities. The soft information is then employed in a PIC module to detect the symbols efficiently. Moreover the MAP-EM approach considers the channel variations as random processes and .