Cross cell beam persistence in a massive multiple-input, multiple output (MIMO) environment
In wireless operating environments, wireless user devices are often within the coverage area of multiple base stations. The base station providing the best uplink for the user device may be different than the base station providing the best downlink for the user device. Systems and techniques for asymmetric uplink and downlink communications for a user device are provided. In embodiments, the user device initially synchronizes with a base station. Both the uplink and downlink are initially served by this base station. A determination is then made whether to handoff the downlink for the user device to another base station. When a determination is indicated, the downlink is handed off to the second base station. Thereafter, periodic measurements are made. The determinations whether to handoff the uplink and downlink for the user device are made independently.
1. A user device supporting cross cell beam persistence comprising:
a transmitter configured to transmit over an uplink for the user device;
a receiver configured to receive over a downlink for the user device; and
a cross cell beam persistence determination module configured to select a first base station to service the uplink for the user device and to select a second base station, different from the first base station, to service the downlink for the user device based on the second base station increasing a number of antennas at the second base station used to service the downlink for the user device,
wherein a downlink region defined by the downlink for the user device is extended into an uplink region defined by the uplink for the user device as the user device moves into the uplink region to maintain the downlink for the user device.
2. The user device of claim 1 , further comprising:
a measurement module configured to obtain downlink measurements for a set of base stations within range of the user device.
3. The user device of claim 2 , wherein the cross cell beam persistence module is further configured to select the second base station to service the downlink for the user device based on the downlink measurements obtained by the measurement module.
4. The user device of claim 1 , wherein the second base station is a massive multiple input multiple output (MIMO) base station.
5. The user device of claim 2 , wherein the cross cell persistence module is further configured to select the second base station from the set of base stations based on the number of antennas used by base stations in the set of base stations to transmit downlink signals and a beam forming gain of the base stations in the set of base stations.
6. The user device of claim 5 , wherein the cross cell persistence module is further configured to select the second base station from the set of base stations based on a load on base stations in the set of base stations.
7. The user device of claim 2 , wherein the cross cell persistence determination module is further configured to negotiate with a base station in the set of base stations during the selection of the second base station.
8. The user device of claim 1 , wherein the cross cell beam persistence determination module is further configured to select the first base station to service the uplink for the user device and to select the second base station, different from the first base station, to service the downlink for the user device in accordance with a periodic selection scheme.
9. The user device of claim 1 , wherein the cross cell beam persistence determination module is further configured to send a sounding reference signal to base stations in the set of base stations.
10. A method for performing cross cell beam persistence in a user device, comprising:
synchronizing with a first base station, wherein the first base station services both an uplink and a downlink for the user device;
determining whether to handoff the uplink for the user device from the first base station to a second base station based on uplink measurements for base stations in a set of base stations within range of the user device;
initiating handoff of the uplink to the second base station when a handoff of the uplink is indicated by the determining; and
determining whether to handoff the downlink for the user device from the first base station to a third base station based on whether the first base station will increase a number of antennas at the first base station used to service the downlink for the user device,
wherein a downlink region defined by the downlink for the user device is extended into an uplink region defined by the uplink for the user device as the user device moves into the uplink region to maintain the downlink for the user device.
11. The method of claim 10 , wherein the first base station is a massive multiple input, multiple output (MIMO) base station.
12. The method of claim 10 , further comprising;
performing downlink measurements for base stations in the set of base stations within range of the user device; and
initiating handoff of the downlink to the third base station when a handoff of the downlink is indicated by the determining whether to handoff the downlink for the user device from the first base station to the third base station.
13. The method of claim 12 , wherein the second base station and the third base station are the same base station.
14. The method of claim 12 , wherein determining whether to handoff the downlink further comprises determining whether to handoff the downlink for the user device from the first base station to the third base station based on the number of antennas used by base stations in the set of base stations to transmit downlink signals.
15. The method of claim 12 , wherein determining whether to handoff the downlink further comprises determining whether to handoff the downlink for the user device from the first base station to the third base station based on a load on base stations in the set of base stations.
16. The method of claim 10 , further comprising:
periodically repeating the determining to handoff the uplink and initiating steps.
17. The method of claim 10 , wherein the first base station is a massive MIMO base station.
18. A method for performing cross cell beam persistence in a network element, comprising:
receiving uplink measurements for base stations in a set of base stations within range of a first base station that services both an uplink and a downlink for a user device; and
handing off the uplink for the user device from the first base station to a second base station based on the uplink measurements for the base stations in the set of base stations;
maintaining the downlink for the user device from the first base station based on the first base station increasing a number of antennas at the first base station used to service the downlink for the user device;
wherein a downlink region defined by the downlink for the user device is extended into an uplink region defined by the uplink for the user device as the user device moves into the uplink region to maintain the downlink for the user device.
19. The method of claim 18 , wherein the first base station is a massive multiple input, multiple output (MIMO) base station.
20. The method of claim 19 , wherein the downlink region is extended into the uplink region using beam forming.