Abstract

this paper is to provide an overview of these techniques. An excellent review of those methods developed prior to 1988 can be found in a survey paper authored by Milstein [12]. Thus, although we will review all of the methods that have been proposed, we will treat these earlier methods only briefly, and we will focus instead on those that have been developed more recently. It should also be noted that much of the work in this area has been motivated by the application of spread spectrum as an anti-jamming signaling method for military use; however it is equally applicable to the problem of NBI in cellular CDMA. Current research makes a more conscious effort to incorporate methodologies that allow for performance improvements when considering the spread signal as a CDMA signal, as we will discuss later. We begin, in the following section, with a brief review of NBI mitigation techniques based on the linear signal processing regimes of adaptive linear transversal filtering, and Fourier-domain filtering. These methods represent the original approaches to this problem, and they are quite well developed. Most of this paper, on the other hand, will be concerned with recently developed model-based techniques that employ non-standard signal processing methods to enhance the interference rejection capabilities in CDMA systems beyond those of standard methods. In particular, in the second section we consider techniques based on nonlinear filtering [15] in which the spread spectrum CDMA signal (which is digital) is modeled as a non-Gaussian noise in the interference suppression process. Further, in the third section we consider the situation in which the NBI is also a digital communications signal. In this situation, multiuser detection techniques [16] can be used to give quite ...

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