Space-time measurement of indoor radio propagation

Most existing techniques for indoor radio propagation measurement do not re solve the angles from which signal components arrive at the receiving anten na. Knowledge of the angle-of-arrival is required for evaluation of evolvin g systems that employ smart antenna technology to provide features such as geolocation, interference cancellation, and space division multiplexing. Th is paper presents a novel technique for the joint measurement of the angles , times and complex amplitudes of discrete path arrivals in an indoor propa gation environment. A data acquisition system, based upon a vector network analyzer and multichannel antenna array is described, together with its use to collect channel measurement matrices. The inherent error sources presen t in these measurement matrices are investigated using a compact indoor ane choic range. Two signal processing algorithms are presented whereby the cha nnel parameters may be estimated from raw measurements. In the first approa ch, an optimum beamformer is derived which compensates for systematic error s in the data acquisition system. This approach features very low computati onal complexity, and delivers modest resolution of path components. The sec ond algorithm is based upon the maximum likelihood criterion, using the mea sured calibration matrices as space-time basis functions. This algorithm pr ovides super-resolution of all path parameters, at the cost of increased co mputation. Several example measurements are given, and future directions of our research are indicated.