The quantitative effects of inaccurate uplink spatial signature observations on downlink signal to interference ratio

We have found that at least 20% of the time, variations of up to 50% relative angle change in the uplink spatial signature (SS) may produce insignificant degradation (less than 2 dB) in SIR at the mobile regardless of the downlink beamforming method. Although the pseudoinverse spatial signature downlink beamforming method is the most sensitive to the uplink SS relative angle change, its superior absolute performance allows it to withstand relative angle change of up to 60% and still produce a better downlink SIR than the other downlink methods.