HYBRID INTERFERENCE CANCELLATION RECEIVER FOR DS-CDMA SYSTEMS L.Nithyanandan and P.Dananjayan Department of Electronics and Communication Engineering Pondicherry college of Engineering Pondicherry – 605014 Email- pdananjayan@hotmail.com ABSTRACT In a CDMA system, the performance of channel matched filter receivers are limited by the presence of multi-user interference. Hence receivers must be capable of suppressing these interferences. Interference suppression or interference cancellation works by subtracting the interfering users from the received signal, thus allowing an improved error rate for the user of interest. In this paper a hybrid interference cancellation receiver is designed by combining the successive and parallel interference cancellation algorithms, so that the advantages of both the schemes are utilized effectively. The hybrid interference cancellation scheme results in a simple, faster and reliable receiver. With the help of simulations, it is shown that this hybrid approach outperforms the other multi-user detection schemes. 1. INTRODUCTION One of the fastest growing technologies in the recent past is the Wireless personal communication technology. The most widely available media for commercial wireless personal communication is the Cellular mobile telephony. The goal of personal communication Services (PCS) industry is to expand the capabilities of the current second generation cellular system to provide enhanced services like wireless facsimile, e-mail, wireless video services, bank transactions etc. While there is still some distance to cover before reaching this point, many developing PCS technologies are key in achieving ultimate third generation goals. These technologies include adaptive antenna arrays (smart antennas), adaptive equalization, speech coding, propagation prediction, and advanced signal processing techniques for mitigating interference effects. The first radio systems were designed to transmit and receive information on a single frequency or channel but are usually very inefficient in terms of traffic throughput. In contrast, the multiple access wireless system allows the sharing of available channels by various users with a well defined method to access these channels. Out of the multiple access schemes available like TDMA, FDMA and CDMA ITU-T has identified CDMA 2000 as the wireless access standard for third generation wireless communication due to its advantages. The most challenging part in any of these kinds of wireless technologies is that of the receivers. The receiver design decides the size, weight and cost of a mobile unit. Hence a receiver should be of petite size, with a reduction of weight and yet at an affordable cost. At the same time, the receiver should be efficient and must perform well under all circumstances. A novel hybrid interference cancellation receiver has been proposed and the performance is analyzed in this paper. 2. CDMA RECEIVER The change from a single user environment to a multiuser environment necessarily entails a modification in receiver design if high performance is to