Code acquisition in a class of time-varying channels

Abstract

This paper presents a model for the code acquisition in a time-varying channel and evaluates the associated acquisition time statistics. We first use a finite-state Markov chain to represent the time-varying channel. Each channel state can have either a frequency-selective or a frequency-nonselective fading characteristic. This model is an unconstrained model as it does not take into account two time-parameters. The first time-parameters the "time unit" for the Markov channel, which has to be determined by the channel Doppler spread or its fading rate. The second time-parameter has to do with the detection structure. Incorporating the constraints imposed by these two time-parameters we discuss modifications of the unconstrained model, derive related statistics (e.g., probability distribution function or characteristic function) of the acquisition time and then provide numerical examples of the acquisition time performance.