Data-record size requirements for adaptive space-time DS-CDMA signal detection

We investigate the data-record size requirements of sample-matrix-inversion-based minimum-variance-distortionless response and maximum-signal-to-interference-plus-noise-ratio adaptive algorithms to meet a given performance objective in joint space-time signal-detection problems for direct-sequence code-division multiple-access systems. We derive closed-form expressions that provide the data-record size that is necessary to achieve a given performance confidence level in a neighborhood of the optimal performance point, as well as expressions that identify the performance level that can be reached for a given data-record size. This is done by using close approximations of the involved probability density functions. The practical significance of the derived expressions lies in the fact that the expressions are functions of the number of antenna elements, the number of multipaths, and the system spreading gain only, while they depend neither on the ideal input covariance matrix, which is not known in most realistic applications, nor on the exact ideal performance value.