US 12,244,378 B2
Methods, baseband unit system and radio unit of a distributed base station having cascade-coupled radio units
Yezi Huang, Täby (SE); Chenguang Lu, Sollentuna (SE); and Miguel Berg, Sollentuna (SE)
Assigned to Telefonaktiebolaget LM Ericsson (publ), Stockholm (SE)
Appl. No. 18/277,638
Filed by Telefonaktiebolaget LM Ericsson (publ), Stockholm (SE)
PCT Filed Apr. 1, 2021, PCT No. PCT/SE2021/050302
§ 371(c)(1), (2) Date Aug. 17, 2023,
PCT Pub. No. WO2022/211690, PCT Pub. Date Oct. 6, 2022.
Prior Publication US 2024/0187061 A1, Jun. 6, 2024
Int. Cl. H04B 7/06 (2006.01); H04B 7/024 (2017.01); H04B 7/0452 (2017.01)
CPC H04B 7/0617 (2013.01) [H04B 7/024 (2013.01); H04B 7/0452 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A method performed by a first radio unit, RU, of a distributed base station system, the first RU comprising N1 antennas, the distributed base station system further comprising a Baseband Unit, BBU, connected to the first RU over a fronthaul link and a second RU connected to the first RU over an RU link, the second RU comprising N2 antennas, the method comprising:
obtaining first uplink signals yin frequency domain as received at the N1 antennas from a number of UEs, the first uplink signals y1 comprising K user-layer signals in frequency domain overlaid with interference signals and noise;
obtaining a first channel estimate Ĥ1 of wireless communication channels H1 in frequency domain between the number of UEs and the N1 antennas;
determining a first part of beamforming weights, BFW, for the first RU based on the first channel estimate Ĥ1 and on reference signals received at the N1 antennas together with the first uplink signals, the first part of BFW being used to reduce the N1 first uplink signals to K+M first intermediate signals y1, where K+M is lower than N1;
determining the K+M first intermediate signals y1 based on the N1 first uplink signals y1 and on the first part of the BFW for the first RU;
determining a first part of intermediate BFW C1 for interference cancellation at the BBU based on the first channel estimate Ĥ1 and on the reference signals received at the N1 antennas together with the first uplink signals,
receiving, from the second RU, K+M second intermediate signals y2, the second intermediate signals being determined by the second RU based on second uplink signals y2 in frequency domain as received at the N2 antennas of the second RU from the number of UEs and on a first part of BFW for the second RU determined by the second RU based on a second channel estimate Ĥ2 of wireless communication channels H2 in frequency domain between the number UEs and the N2 antennas and on reference signals received at the N2 antennas together with the second uplink signals, the first part of BFW of the second RU being used to reduce the N2 second uplink signals to the K+M second intermediate signals y2, where K+M is lower than N2;
receiving, from the second RU, a second part of intermediate BFW C2 for interference cancellation, determined by the second RU based on the second channel estimate Ĥ2 and on the reference signals received at the N2 antennas together with the second uplink signals;
combining the first intermediate signals y1and the second intermediate signals y2 into combined intermediate signals y1+y2;
combining the first part of intermediate BFW C1 and the second part of intermediate BFW C2 into combined intermediate BFW C1+C2, and
sending, to the BBU over the fronthaul link, the combined intermediate signals y1+y2 and the combined intermediate BFW C1+C2.