Joint beamforming weights and IQ data scaling approach for improved fronthaul

1 . A method performed by a baseband unit, BBU, for scaling beamforming weights, BFWs, to assist a Radio Unit, RU, with beamforming, the method comprising:

obtaining a plurality of frequency-domain BFWs for beamforming of a number of downlink data streams in frequency-domain to be transmitted to at least one wireless device via a plurality of antennas;

scaling the plurality of frequency-domain BFWs based on at least one scaling factor;

compressing the plurality of scaled frequency-domain BFWs;

transmitting, to the RU, the plurality of scaled frequency-domain BFWs that have been compressed;

based on the at least one scaling factor used to scale the frequency-domain BFWs, determining at least one user plane scaling factor for frequency-domain user plane In-phase/Quadrature, IQ, data;

scaling the frequency-domain user plane IQ data based on the at least one user plane scaling factor;

transmitting the scaled frequency-domain user plane IQ data to the RU.

2 . A method by a radio unit, RU, for performing beamforming based on frequency-domain beamforming weights, BFWs, scaled by a baseband unit, BBU, the method comprising:

receiving, from the BBU, a plurality of scaled frequency-domain BFWs for beamforming of a number of downlink data streams in the frequency domain to be transmitted to at least one wireless device, wherein the plurality of scaled frequency-domain BFWs are compressed;

decompressing the plurality of scaled frequency-domain BFWs;

receiving, from the BBU, scaled frequency-domain user plane In-phase/Quadrature, IQ, data for the number of downlink data streams, the scaled frequency-domain user plane IQ data being scaled based on at least one user plane scaling factor, and wherein the at least one user plane scaling factor compensates for at least one scaling factor used to scale the frequency-domain BFWs by the BBU; and

conducting beamforming on the number of downlink data streams in the frequency domain based on the plurality of scaled frequency-domain BFWs and the scaled frequency-domain user plane IQ data.

3 . A baseband unit, BBU, for scaling beamforming weights, BFWs, to assist a Radio Unit, RU, with beamforming, the BBU adapted to:

obtain a plurality of frequency-domain BFWs for beamforming of a number of downlink data streams in frequency-domain to be transmitted to at least one wireless device via a plurality of antennas;

scale the plurality of frequency-domain BFWs based on at least one scaling factor;

compress the plurality of scaled frequency-domain BFWs;

transmit, to the RU, the plurality of scaled frequency-domain BFWs that have been compressed;

based on the at least one scaling factor used to scale the frequency-domain BFWs, determine at least one user plane scaling factor for frequency-domain user plane In-phase/Quadrature, IQ, data;

scale the frequency-domain user plane IQ data based on the at least one user plane scaling factor;

transmit the scaled frequency-domain user plane IQ data to the RU.

4 . The BBU of claim 3 , wherein the at least one user plane scaling factor is determined to compensate for the at least one scaling factor used to scale the plurality of frequency-domain BFWs.

5 . The BBU of claim 3 , wherein the at least one user plane scaling factor comprises a plurality of user plane scaling factors.

6 . The BBU of claim 5 , wherein:

each of the plurality of user plane scaling factors is associated with a particular one of a plurality of layers, and

the frequency-domain user plane IQ data comprises I and Q values for each one of the plurality of layers.

7 . The BBU of claim 6 , wherein:

each of the plurality of user plane scaling factors is associated with a particular one of a plurality of spatial streams.

8 . The BBU of claim 6 , wherein each of the plurality of user plane scaling factors is associated with a subcarrier and/or subcarrier group.

9 . The BBU of claim 3 , wherein the user plane IQ data comprises a plurality of frequency-domain user-layer signals.

10 . The BBU of claim 3 , wherein when compressing the plurality of scaled frequency-domain BFWs the BBU is adapted to compress the plurality of scaled frequency-domain BFWs to a predefined fixed-point data format with fewer bits than an original number of bits representing the scaled frequency-domain BFWs.

11 . The BBU of claim 3 , wherein the at least one scaling factor used for scaling the frequency-domain BFWs increases an accuracy of the frequency-domain BFWs after quantization.

12 . The BBU of claim 3 , wherein the frequency-domain user plane IQ data is sent to the RU in at least one user plane message.

13 . The BBU of claim 3 , wherein the scaled frequency-domain BFWs are sent to the RU in at least one control plane message.

14 . The BBU of claim 3 , wherein the BBU is adapted to send scheduling information for the frequency-domain user plane IQ data in at least one control plane message.

15 . The BBU of claim 3 , wherein the BBU and the RU are associated with a distributed network node.

16 . A radio unit, RU, for performing beamforming based on frequency-domain beamforming weights, BFWs, scaled by a baseband unit, BBU, the RU adapted to:

receive, from a baseband unit, BBU, a plurality of scaled frequency-domain BFWs for beamforming of a number of downlink data streams in frequency domain to be transmitted to at least one wireless device, wherein the plurality of scaled frequency-domain BFWs are compressed; and

decompress the plurality of scaled frequency-domain BFWs;

receive, from the BBU, scaled frequency-domain user plane In-phase/Quadrature, IQ, data for the number of downlink data streams, the scaled user plane IQ data being scaled based on at least one user plane scaling factor, and wherein the at least one user plane scaling factor compensates for at least one scaling factor used to scale the BFWs by the BBU; and

conduct beamforming on the number of downlink data streams in the frequency domain based on the plurality of scaled frequency-domain BFWs and the scaled frequency-domain user plane IQ data.

17 . The RU of claim 16 , wherein the at least one user plane scaling factor comprises a plurality of user plane scaling factors.

18 . The RU of claim 17 , wherein:

each of the plurality of user plane scaling factors is associated with a particular one of a plurality of layers, and

the frequency-domain user plane IQ data comprises I and Q values for each one of the plurality of layers.

19 . The RU of claim 17 , wherein: each of the user plane scaling factors is associated with a particular one of a plurality of spatial streams.

20 . The RU of claim 18 , wherein each of the user plane scaling factors is associated with a subcarrier and/or subcarrier group.

21 . The RU of claim 16 , wherein the scaled frequency domain user plane IQ data comprises a plurality of frequency-domain user-layer signals.

22 . The RU of claim 16 , wherein the plurality of frequency domain BFWs are compressed to a predefined fixed-point data format with fewer bits than the original number of bits representing the scaled frequency-domain BFWs.

23 . The RU of claim 16 , wherein the at least one scaling factor used for scaling the plurality of frequency-domain BFWs increases an accuracy of the plurality of frequency domain BFWs after quantization by the BBU.

24 . The RU of claim 16 , wherein the scaled frequency domain user plane IQ data is received by the RU in at least one user plane message.

25 . The RU of claim 16 , wherein the plurality of scaled frequency-domain BFWs is received by the RU in at least one control plane message.

26 . The RU of claim 16 , further adapted to receive scheduling information for the frequency-domain user plane IQ data in at least one control plane message.