On generalized covariance-based velocity estimation

We look at the problem of how a moving receiver (mobile station) estimates its own velocity from the autocovariance of functions of the quadrature components of the received signal. In cellular systems, this information-bearing signal conveying voice, data, or both and transmitted from a base station is well characterized as a narrow-band Gaussian random process specified by Clarke´s (1968) model. The need for such estimation arises, for example, in the design of handoff algorithms for microcellular systems. We consider here the performance of estimators based on two classes of functions: the integral-power sum of the quadrature components G_1,n(t)=r_iⁿ(t)+r_qⁿ (t) and integral powers of the complex envelope G_2,n(t)=[r_i²(t)+r_q² (t)]^n/2, n∈Z⁺, respectively. A particular case of this approach for n=2 was first considered by Sampath and Holtzman (1993) and subsequently by Austin and Stuber (1994). For each of the two classes of functions, we derive the optimal (in a defined sense) estimator and show that all estimators based on G_2,n (t) have identical performance and are generally inferior to those based on G_1,n(t). We also study the implications of Aulin´s model (1979) when used to evaluate the performance of estimators based on the integral-power sum of the quadrature components. Last, using a proposed analytical model, we analyze the effect of the scattering distribution on the performance of the estimators, corroborating some previous results obtained by Austin and Stuber by simulation