A nonlinear dynamic system for spread spectrum code acquisition

Abstract

Nonlinear differential equations and iterated maps can perform any computation. Sometimes, the most difficult part of performing a useful computation, however, is writing the program. Furthermore, in practice, we often need to build special purpose computing hardware suited to run a particular program. Nonlinear dynamics provides a novel and useful language for constructing "algorithms" and "computer architectures." We apply the language of nonlinear dynamics to solve a fast coding problem which has previously been implemented by a Digital Signal Processor chip in digital wireless receivers. We eventually hope to produce a novel physical system which exhibits the nonlinear dynamics we require, thereby creating one of the first nonlinear dynamic systems engineered to perform a practical computation. This system, called an Analog Feedback Shift Register (AFSR), should be a faster, more reliable, less expensive, and lower power Spread Spectrum (SS) code acquisition system for wireless receivers. A prohibitive factor in creating ubiquitous short range, digital radio transceivers is the difficulty and expense of creating a mechanism for locking onto the incoming Spread Spectrum code sequence. AFSR is also potentially useful in other applications where low cost, low power channel sharing or addressing is required, for example in wireless auto-identification tags.