FIRST NETWORK NODE, SECOND NETWORK NODE, CENTRAL NETWORK NODE AND METHODS PERFORMED THEREBY FOR HANDLING DATA

A method by a first network node for handling data. The first network node operates in a communications network. The first network node applies a Kalman filter of a first type to a first aggregation of a first set of measurements (yl) collected via a first plurality of antenna elements, and a first set of filtered data (ŝ0) received from a second network node, using a first covariance matrix (P0). The applying of the Kalman filter () outputs a second set of filtered data (ŝ), and a second covariance matrix (P). The first network node then sends, in uplink, the second set of filtered data (ŝ) and the second covariance matrix (P) to one of: another network node subsequently adjacent to the first network node towards a central network node, and the central network node.