Scalable Estimation Ring

1. A base station for a wireless network that performs calibration of an antenna array to remove distortion incurred by a plurality of transmit paths in the base station, the antenna array including a plurality of sub-arrays each connected to a corresponding one of the plurality of transmit paths, the base station comprising: a feedback receiver configured to receive a combined radio frequency feedback signal and output a combined feedback signal, the combined radio frequency feedback signal being a summation of a plurality of output signals of the plurality of transmit paths in response to a plurality of input signals; and a scalable estimation ring configured to estimate impulse responses of the plurality of transmit paths based on the combined feedback signal in a distributed manner, the scalable estimation ring comprising a plurality of scalable estimation ring coordinated processing components each operating to estimate the impulse response of a corresponding one of the plurality of transmit paths.

2. The base station of claim 1 wherein each transmit path of the plurality of transmit paths comprises a transmit chain, a feeder having a first end connected to an output of the transmit chain and a second end, and a coupler configured to connect the second end of the feeder to a corresponding one of the plurality of sub-arrays.

3. The base station of claim 2 wherein the transmit chains of the plurality of transmit paths are implemented in a single radio unit.

4. The base station of claim 2 wherein the transmit chains of the plurality of transmit paths are implemented in different radio units.

5. The base station of claim 2 wherein the transmit chains of at least two of the plurality of transmit paths are implemented in different radio units.

6. The base station of claim 1 wherein, in order to estimate the impulse responses of the plurality of transmit paths, for an initial iteration of the scalable estimation ring, each scalable estimation ring coordinated processing component of the plurality of scalable estimation ring coordinated processing components in the scalable estimation ring is configured to: receive a feedback signal for the scalable estimation ring coordinated processing component; compute an initial estimate of the impulse response of a corresponding transmit path of the plurality of transmit paths based on the feedback signal for the scalable estimation ring coordinated processing component; remove a contribution of the corresponding transmit path from the feedback signal for the scalable estimation ring coordinated processing component based on the initial estimate of the impulse response of the corresponding transmit path to thereby provide a feedback signal for a next scalable estimation ring coordinated processing component in the scalable estimation ring; and output the feedback signal for the next scalable estimation ring coordinated processing component in the scalable estimation ring.

7. The base station of claim 6 wherein: for a first scalable estimation ring coordinated processing component in the scalable estimation ring, the feedback signal for the initial iteration is the combined feedback signal from the feedback receiver; and for each additional scalable estimation ring coordinated processing component in the scalable estimation ring, the feedback signal for the initial iteration is the feedback signal output by a preceding scalable estimation ring coordinated processing component in the scalable estimation ring for the initial iteration.

8. The base station of claim 7 wherein, in order to estimate the impulse responses of the plurality of transmit paths, for a second iteration of the scalable estimation ring, each scalable estimation ring coordinated processing component of the plurality of scalable estimation ring coordinated processing components in the scalable estimation ring is configured to: receive a new feedback signal output by a preceding scalable estimation ring coordinated processing component in the scalable estimation ring; add the contribution of the corresponding transmit path removed in the initial iteration of the scalable estimation ring into the new feedback signal to thereby provide a modified new feedback signal; compute a new estimate of the impulse response of the corresponding transmit path based on the modified new feedback signal; remove a contribution of the corresponding transmit path from the modified new feedback signal based on the new estimate of the impulse response of the corresponding transmit path to thereby provide a new feedback signal for the next scalable estimation ring coordinated processing component in the scalable estimation ring; and output the new feedback signal for the next scalable estimation ring coordinated processing component in the scalable estimation ring.