WIRELESS COMMUNICATIONS AND MOBILE COMPUTING Wirel. Commun. Mob. Comput. 2015; 15:203–214 Published online 14 November 2012 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/wcm.2325 RESEARCH ARTICLE Narrow-band interference suppression in wavelet packets based multicarrier multicode CDMA overlay system Maryam M. Akho-Zahieh and Nasser Abdellatif * Department of Electrical and Computer Engineering, Applied Science Private University, Amman 11931,Jordan ABSTRACT The wavelet packets based multicarrier (MC) multicode (MCD) code-division multiple-access (CDMA) transceiver consists of the MCD part, which ensures the transmission for high speed and flexible data rate; the MC part contributing to robustness to frequency-selective fading and flexibility for handling multiple data rates; and wavelet packets (WPs) modulation technique, which contributes to the mitigation of the interference problems. As WPs have lower sidelobes compared with sinusoidal carriers, this system is very effective in reducing the problem of inter-carrier interference. Of course, like any CDMA system, the system can suppress a given amount of interference. This paper considers an interference suppression scheme which will enhance the performance of the system. The receiver employs suppression filters to mitigate the effect of narrow-band jammer interference. The framework for the system and the performance evaluation are presented in terms of the bit error rate and the outage probability over a Nakagami fading channel. Also, we investigate how the performance is influenced by various parameters, such as the number of taps of the suppression filter and the ratio of narrow-band interference bandwidth to the spread-spectrum bandwidth. Finally, the performance of the system is compared with the performance of sinusoidal based MC/MCD-CDMA system denoted Sin-MC/MCD-CDMA. Copyright © 2012 John Wiley & Sons, Ltd. KEYWORDS suppression filter; wavelet packet; multicarrier; multicode; CDMA *Correspondence Nasser Abdellatif, Department of Electrical and Computer Engineering, Applied Science Private University, Amman 11931,Jordan. E-mail: nasser_abdellatif@asu.edu.jo; nasser.abdellatif@gmail.com 1. INTRODUCTION The multicarrier (MC) multicode (MCD) code-division multiple-access (CDMA) system achieves the advantages of both MC-CDMA and MCD-CDMA systems, which are (i) variable data rates without interference scaling and (ii) enhanced robustness to mitigating multipath fading. By combining the properties of MCD and MC techniques, a MC/MCD-CDMA system that uses wavelet packet (WP) as subcarrier is proposed in this paper. The system is denoted as WP-MC/MCD-CDMA. Previous studies [1,2] have shown that the problems posed by sinusoidal carriers can be solved by WPs. Unlike sinusoids, WPs have many attractive properties including: (1) Much lower sidelobes with negligible sidelobe energy leakage compared with sinusoid carriers. This property is effective in suppressing inter-carrier interference (ICI) and multiple-access interference. (2) Naturally orthogonal and well localized in both time and frequency domains, which relaxes the require- ment of frequency or time guard between different user signals. In fact, orthogonality is maintained for overlapped WPs in both time and frequency domains. This is an advantage of using WPs to model communication channels that are character- ized not only by frequency selectivity but also by time variation. The WP-MC/MCD-CDMA [1] uses WP as subcarrier instead of sinusoidal function, because of that, it could mitigate the problem of ICI associated with using sinusoidal carrier and suppress interferences caused by multipath fading. Various schemes of MC-CDMA systems have been proposed in recent years, and they can be Copyright © 2012 John Wiley & Sons, Ltd. 203