CDMA is a multiple access technique, which is based on spread spectrum modulation scheme. It allows a multiple users to access the channel simultaneously, with each user's data being multiplied by a unique and orthogonal pseudo-random code sequence. Spread spectrum, as the name suggests, modulates the narrow band data and spreads it over a much wider bandwidth, thus transmitted data has a very low power spectral density. Moreover the inherent interference rejection capability of CDMA makes it suited to radio frequency environment. CDMA is interference limited, due to the multiple access interference of multiple users. Although orthogonal codes could result in no multiple access interference (MAI), in flat fading channels, the orthogonality will not be guaranteed in frequency selective fading channels because of interchip interference, which will cause MAI and degrade the system performance. One approach to suppress the effect of inter-chip interference in frequency selective fading channels is the combination of CDMA and multi-carrier modulation, such as OFDM that can achieve high spectral efficiency because the spectrum of successive sub-carriers is allowed. The combined CDMA system with OFDM is mainly categorized into MC/DS-CDMA and MCCDMA.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.