Multiple antenna wireless communication systems: limits to capacity growth

We present a general multiple path scattering model for multiple transmit, multiple receive wireless systems. The model is generated using physical modelling of the scatterers surrounding transmit and the receive arrays. The condition of the resulting multiple-input multiple-output (MIMO) transfer matrix is then examined. A key parameter η which determines the channel condition is identified. This parameter depends on the local scatter geometries, the separation of arrays, and the wavelength of the transmitted signal. We show that there exists a critical value for this parameter at which the channel condition changes sharply. The implication is that the promised linear growth in channel capacity may not eventuate if the separation of the transmit and receive arrays is large (≈10× or 20× at 2 GHz) compared with the distance from array elements to local scatterers. Monte-Carlo simulations are used to demonstrate these claims.