Method and apparatus for multi-user multiple input-multiple output (MU-MIMO) complexity reduction for frequency dispersive channels
A method and apparatus are disclosed to reduce MU-MIMO complexity in a receiver. In one embodiment, a method implemented in a network node includes determining a frequency dispersion of a channel for a wireless device (WD); and based at least in part on the determination of the frequency dispersion, determining at least one frequency spacing for at least one weight associated with the channel. In another embodiment, a method implemented in a WD includes transmitting a signal to the network node; and receiving an allocation of at least one time-frequency resource based at least in part on a determination of a frequency dispersion on the transmitted signal, the at least one time-frequency resource being shared between the WD and at least one other WD.
1 . A method implemented in a network node for multi-user multiple input multiple output (MU-MIMO), communications, the method comprising:
determining a measurement of frequency dispersion of a channel for a wireless device (WD);
determining at least one frequency spacing based on computing one or more weights associated with the channel for separating the WD and at least one other WD which share a same time-frequency resource, the one or more weights being computed at a higher rate in a frequency domain if the channel is more frequency dispersive such that the frequency distance between weight samples is smaller as compared to the one or more weights being computed at a slower rate in the frequency domain if the channel is less frequency dispersive such that the frequency distance between weight samples is greater;
allocating at least one shared time-frequency resource to the WD and the at least one other WD based in part on at least one of the frequency dispersion measurement and the at least one frequency spacing; and
determining a number of other spatially separate wireless devices, WDs, to co-schedule with the WD on the shared time-frequency resource based at least in part on whether the determined frequency dispersion measurement is less than a defined threshold.
2 . The method of claim 1 , wherein the determining the frequency dispersion comprises:
determining a channel estimate for the WD at each subcarrier within a frequency region.
3 . The method of claim 2 , wherein subcarriers within the frequency region are represented by indices and the indices are integer values.
4 . The method of claim 2 , wherein the frequency region is represented by an integer corresponding to a physical resource block index.
5 . The method of claim 1 , wherein the determining the frequency dispersion comprises:
determining a mean frequency dispersion value for a plurality of frequency dispersion measurements, the plurality of frequency dispersion measurements taken over at least one physical resource block and over at least one antenna stream and at least one beam stream.
6 . The method of claim 5 , wherein the one of the at least one antenna stream and the at least one beam stream used to determine the mean frequency dispersion value is selected based on whether the corresponding stream has a power that at least meets a predetermined threshold power value.
7 . The method of claim 5 , wherein a number of the at least one physical resource block used to determine the mean frequency dispersion value is a predetermined number.
8 . A network node for multi-user multiple input multiple output (MU-MIMO) communications, the network node comprising:
processing circuitry, the processing circuitry configured to cause the network node to:
determine a measurement of frequency dispersion of a channel for a wireless device (WD);
determine at least one frequency spacing based on computing one or more weights associated with the channel for separating the WD and at least one other WD which share a same time-frequency resource, the one or more weights being computed at a higher rate in a frequency domain if the channel is more frequency dispersive such that the frequency distance between weight samples is smaller as compared to the one or more weights being computed at a slower rate in the frequency domain if the channel is less frequency dispersive such that the frequency distance between weight samples is greater;
allocating at least one shared time-frequency resource to the WD and the at least one other WD based in part on at least one of the frequency dispersion measurement and the at least one frequency spacing; and
determine a number of other spatially separate wireless devices, WDs, to co-schedule with the WD on the shared time-frequency resource based at least in part on whether the determined frequency dispersion measurement is less than a defined threshold.
9 . The network node of claim 8 , wherein the processing circuitry is configured to determine the frequency dispersion by being configured to cause the network node to:
determine a mean frequency dispersion value for a plurality of frequency dispersion measurements, the plurality of frequency dispersion measurements taken over at least one physical resource block and for one of at least one antenna stream and at least one beam stream.
10 . The network node of claim 9 , wherein the one of the at least one antenna stream and the at least one beam stream used to determine the mean frequency dispersion value is selected based on whether the corresponding stream has a power that at least meets a predetermined threshold power value.
11 . The network node of claim 10 , wherein a number of the at least one physical resource block used to determine the mean frequency dispersion value is a predetermined number.