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Báo cáo hóa học: " A review on synchronous CDMA systems: optimum overloaded codes, channel capacity, and power control"

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: A review on synchronous CDMA systems: optimum overloaded codes, channel capacity, and power control | Hosseini et al. EURASIP Journal on Wireless Communications and Networking 2011 2011 62 EURASIP Journal on . http jwcn.eurasipjournals.eom content 2011 1 62 Wireless Communications and Networking a SpringerOpen Journal RESEARCH Open Access A review on synchronous CDMA systems optimum overloaded codes channel capacity and power control Seyed Amirhossein Hosseini Omid Javidbakht Pedram Pad and Farrokh Marvasti Abstract This paper is a tutorial review on important issues related to code-division multiple-access CDMA systems such as channel capacity power control and optimum codes specifically we consider optimum overloaded codes that achieve errorless transmission in the absence of noise for the binary and nonbinary cases. A survey of lower and upper bounds for the sum channel capacity of such systems is given in the presence and absence of channel noise. The asymptotic results for the channel capacity are also investigated. The channel capacity errorless transmission codes and power estimation for near-far effects are also explored. The emphasis of this tutorial review is on the overloaded CDMA systems. Keywords Code Division Multiple Access CDMA Optimum codes channel capacity bounds near-far effects power control I Introduction code-division multiple access CDMA has been the most important multiple access technology for the 3rd generation GSM and American Cellular systems 1 . Optical CDMA systems have become an alternative multiple access for fiber optics and optical wireless systems 2-4 . In CDMA systems each user is assigned a unique code signature that consists of a number of chips. The signature length also called chip rate is defined as the number of chips in each signature code. Each user signature is multiplied by the respective data and the transmitted vectors are added up in the common channel. The resultant vector is then observed at the received user end. In order to decode the received signal the detector of the received user should know its own unique .