USER EQUIPMENT LOCALIZATION IN CENTRALIZED OR CLOUD RADIO ACCESS NETWORK
The present disclosure describes techniques of user equipment localization in centralized or cloud radio access networks (C-RANs). In the UE localization techniques of the present disclosure, a base station (gNB) configures a plurality of radio units (RUs) serving a cell to transmit one or more downlink signals using various time and/or frequency resources to user equipment (UEs) of the cell. The UEs use the one or more downlink signals to measure quality of downlink channels between the UEs and the plurality of RUs and reports the measured qualities in uplink using one or more CSI reports. The gNB then selects one or more RUs from the plurality of RUs for each UE based on the received CSI reports. Finally, the gNB transmits downlink data towards the UEs and receives uplink data from the UEs using their respective RUs.
1 . A method performed using a system comprising: at least one baseband unit to perform at least some baseband processing; and a plurality of radio units to wirelessly communicate with a plurality of user equipment via a respective set of one or more antennas, wherein the at least one baseband unit and the plurality of radio units are communicatively coupled with each other, the method comprising:
grouping the plurality of radio units into one or more groups, each group comprising at least one radio unit;
for each group:
configuring each radio unit of the group to transmit a different downlink signal to a user equipment at a unique time instance within a predefined time interval, wherein the transmissions of the different downlink signals for one group are repeated in a same sequential manner for another group at time instances distinct from the unique time instances, and wherein a time duration between two consecutive downlink signal transmissions within a group and across the one or more groups is same; and
receiving a measurement report comprising signal strength measurements of the different downlink signals at the end of the predefined time interval; and
selecting one or more radio units from the plurality of radio units for serving the user equipment based on the received measurement reports.
2 . The method of claim 1 , further comprising:
comparing the signal strength measurements of the downlink signals with a predefined threshold value; and
selecting the one or more radio units from the plurality of radio units for serving the user equipment based on a result of the comparison.
3 . The method of claim 1 , wherein configuring each radio unit of the group to transmit a different downlink signal comprises configuring each radio unit of the group to transmit a wideband downlink signal to the user equipment.
4 . The method of claim 1 , wherein the different downlink signals comprise Channel State Information Reference Signals (CSI-RSs).
5 . The method of claim 1 , wherein each of the plurality of radio units is configured to serve a same cell.
6 . A method performed using a system comprising: at least one baseband unit to perform at least some baseband processing; and a plurality of radio units to wirelessly communicate with a plurality of user equipment via a respective set of one or more antennas, wherein the at least one baseband unit and the plurality of radio units are communicatively coupled with each other, the method comprising:
(a) partitioning available downlink bandwidth into a plurality of sub-bands;
(b) grouping the plurality of radio units into one or more groups, wherein each group comprises at least one radio unit, and wherein a number of the at least one radio unit in each group is less than or equal to a number of the plurality of sub-bands;
(c) at a first-time instance, performing the following for each group:
configuring each radio unit of the group to transmit a same downlink signal to a user equipment in a unique sub-band of the plurality of sub-bands, wherein a downlink signal transmitted from at least one radio unit of one group is different from a downlink signal transmitted from at least one radio unit of another group;
(d) receiving a measurement report comprising sub-band level signal strength measurements of the downlink signal transmissions from the plurality of radio units after the first-time instance; and
(e) selecting one or more radio units from the plurality of radio units for serving the user equipment based on the received measurement report.
7 . The method of claim 6 , further comprising:
comparing the sub-band level signal strength measurements of the downlink signal transmissions with a predefined threshold value; and
selecting the one or more radio units from the plurality of radio units for serving the user equipment based on a result of the comparison.
8 . The method of claim 6 , further comprising:
repeating steps (c)-(d) at subsequent time instances, wherein for each subsequent time instance, each of the at least one radio unit of the group transmits the downlink signal to the user equipment in a sub-band which is different from the unique sub-bands previously used by the radio unit, and wherein a number of different time instances at which the downlink signals are transmitted is equal to the number of the plurality of sub-bands.
9 . The method of claim 8 , further comprising:
determining an average signal strength for each radio unit based on the sub-band level signal strength measurements of each radio unit across the plurality of sub-bands; and
selecting one or more radio units from the plurality of radio units for serving the user equipment based on the average signal strengths.
10 . The method of claim 9 , further comprising:
comparing the average signal strengths for each radio unit with a predefined threshold value; and
selecting the one or more radio units from the plurality of radio units for serving the user equipment based on a result of the comparison.
11 . The method of claim 6 , wherein the different downlink signals comprise Channel State Information Reference Signals (CSI-RSs).
12 . The method of claim 6 , wherein each of the one or more groups comprises distinct radio units.
13 . The method of claim 6 , wherein each of the plurality of radio units is configured to serve a same cell.
14 . A system comprising:
at least one baseband unit to perform at least some baseband processing; and
a plurality of radio units to wirelessly communicate with a plurality of user equipment via a respective set of one or more antennas, wherein the at least one baseband unit and the plurality of radio units are communicatively coupled with each other,
wherein the system is configured to:
group the plurality of radio units into one or more groups, each group comprising at least one radio unit;
for each group:
configure each radio unit of the group to transmit a different downlink signal to a user equipment at a unique time instance within a predefined time interval, wherein the transmissions of the different downlink signals for one group are repeated in a same sequential manner for another group at time instances distinct from the unique time instances, and wherein a time duration between two consecutive downlink signal transmissions within a group and across the one or more groups is same; and
receive a measurement report comprising signal strength measurements of the different downlink signals at the end of the predefined time interval; and
select one or more radio units from the plurality of radio units for serving the user equipment based on the received measurement reports.
15 . The system of claim 14 , further configured to:
compare the signal strength measurements of the downlink signals with a predefined threshold value; and
select the one or more radio units from the plurality of radio units for serving the user equipment based on a result of the comparison.
16 . The system of claim 14 , wherein to configure each radio unit of the group to transmit a different downlink signal, the system is configured to:
configure each radio unit of the group to transmit a wideband downlink signal to the user equipment.
17 . The system of claim 14 , wherein the different downlink signals comprise Channel State Information Reference Signals (CSI-RSs).
18 . The system of claim 14 , wherein each of the one or more groups comprises distinct radio units.
19 . The system of claim 14 , wherein each of the plurality of radio units is configured to serve a same cell.
20 . The system of claim 14 , wherein the at least one baseband unit comprises at least one distributed unit.