Performance Evaluation of W-CDMA Systems with Filtered Gold Sequences Ken Umeno †‡ and Sheng-hung Shih ‡ †Communications Research Laboratory 4-2-1 Nukui-Kitamachi, Koganei, Tokyo 184-8795 Japan ‡Japan Science and Technology Corporation 4F Sanshin Bldg. ,Shibuya, Shibuya-ku Tokyo 150-0002 Japan E-mail: †umeno@crl.go.jp, ‡{chaosken,luckystone}@idele.com Abstract －The third generation (3G) systems are designed for multimedia communication: with them person-to-person communication can be enhanced with high quality images and video, and access to information and services on public and private networks will be enhanced by the higher data rates and new flexible communication capabilities of 3G. W-CDMA (Wideband Code Division Multiple Access) technology has emerged as the most widely adopted 3G air interface. It’s already deployed as commercial products in Japan. In this paper, we proposed a digital filter – LSF (Lebesgue Spectrum Filter) that can be used for optimizing scrambling code to suppress interference in W-CDMA system. Simulation results show the LSF can increase the capacity of W-CDMA system. Index Terms － Chaos, W-CDMA, Digital Filter, Lebesgue spectrum 1. Introduction The third generation (3G) systems are designed for multimedia communication: with them person-to-person communication can be enhanced with high quality images and video, and access to information and services on public and private networks will be enhanced by the higher data rates and new flexible communication capabilities of 3G. W-CDMA (Wideband Code Division Multiple Access) is the main third generation air interface inn the world. W-CDMA has been already commercially operated in Japan and will be deployed in Europe and Asia. A complex-valued scrambling code is used in W-CDMA for separating terminals and base stations. This paper is focus on improving the correlation characteristic of scrambling code so that the BER can be decreased. From this viewpoint, a digital filter called LSF (Lebesgue Spectrum Filter) has been developed and will be proved it has capability to optimize the scrambling codes and increase the capacity of W-CDMA system. This paper is organized as follows. In section 2 the overview of W-CDMA system will be described. Then, the theory of LSF (Lebesgue Spectrum Filter) will be detailed in section 3. In section 4, simulation result will be shown and discussed. Finally, conclusions will be drawn in section 5. 2. Overview of W-CDMA system W-CDMA technology has emerged as the most widely adopted third generation air interface. Its specification has been created and optimized in 3GPP (the 3 rd Generation Partnership Project), which is the joint standardization project of the standardization bodies from Europe, Japan, the USA and China. In Japan, W-CDMA system is commercially operated from Oct. 2001. Table 1 lists the main features of W-CDMA system. [1,2,3] Carrier spacing 5MHz Chip rate 3.84Mcps Power control frequency 1500Hz, both uplink and downlink Base station synchronization Not needed Multiple access method DS-CDMA Frame length 10ms Multirate concept Variable spreading factor and multicode Table 1. Main W-CDMA features The data generated at higher layer is carried over the air with transport channels, which are mapped in the physical layer to different physical channels. The way different transport channels are mapped to different physical channels is shown in Fig.1. In addition to channel spreading, part of the process in W-CDMA system is the scrambling operation. This is needed to separate terminals or base stations from each other. Scrambling is used on the top of spreading, so it does not change the signal bandwidth but only makes the signals from different sources separable from each other. Fig. 2 shows the relation of the chip rate in the channel to spreading and scrambling in W-CDMA.