Channel estimation applique for multiple antenna wireless communications

Abstract

Multiple antenna wireless communication systems require accurate knowledge of the transfer function between all paths. This invention discloses a system wherein a test signal generator at a transmitter station and a facsimile generator at a receiver station go through an acquisition and tracking process which aligns the two signals, removing errors in the time base of generation, the frequency offset of generation and the time of arrival, so that a logical processor can compute the frequency transfer function of propagation pathways between the multiple input and multiple output antennas. In turn, these channel measurements are used in an adaptive, concurrently sent communication signal. The frequency transfer functions are conveyed back to the transmit end via a control channel permitting an adaptivity function at the transmit end to influence subsequent selection of communication parameters, among which are typically transmitted data rate, selection of modulation, selection of forward error correcting coding, and selection of frequency band for transmission. The same measurement is conveyed to an adaptivity function at the receive end for use in the communications receiver to select signal combining variables such as gain control, and equalization of amplitude and phase, versus frequency. An alternate embodiment invention of this type is described which is additionally useful for mobile multiple antenna communications channels. Another variation embodiment is described for pure propagation measurements only, absent conveyance of end-user information.