Using time division duplexing systems in frequency division duplexing networks
Described herein are technologies that utilize full duplex gateway terminals in satellite networks with half duplex user equipment. The disclosed scheduling technologies incorporate the knowledge of the propagation delay between a gateway terminal and each UE in communication with the gateway terminal. Based on this propagation delay, a scheduler can allocate DL and UL time slots in a scheduling frame in a way that avoids allocating overlapping DL and UL time slots at each UE.
1. A method for scheduling time slots in a frame for a gateway terminal and a plurality of user equipment (UE) in a communications system, the method comprising:
determining a propagation delay between the gateway terminal and each UE of the plurality of UE;
determining, for each UE of the plurality of UE, one or more conflicting time slots at the UE based on the propagation delay between the gateway terminal and the UE, a conflicting time slot being a time slot in which the UE is scheduled to simultaneously transmit and receive;
populating a gateway schedule subject to a constraint to avoid conflicting time slots at each UE of the plurality of UE by:
generating a plurality of potential gateway schedules that avoid conflicting time slots at each UE of the plurality of UE; and
selecting as the gateway schedule a potential gateway schedule from the plurality of potential gateway schedules that improves network utilization relative to unselected potential gateway schedules of the plurality of potential gateway schedules; and
communicating a schedule that corresponds to the gateway schedule to each UE of the plurality of UE.
2. The method of claim 1 , wherein the schedule that corresponds to the gateway schedule for a particular UE includes a schedule with downlink time slots delayed in time relative to the gateway schedule, the delay in time equal to the propagation time associated with the particular UE, and with uplink time slots advanced in time relative to the gateway schedule, the advance in time equal to the propagation time associated with the particular UE.
3. The method of claim 1 , wherein populating the gateway schedule includes, for each UE of the plurality of UE, allocating a plurality of downlink time slots.
4. The method of claim 3 , wherein populating the gateway schedule further includes, for each UE of the plurality of UE, identifying one or more uplink slots that violate the constraint to avoid conflicting time slots due at least in part to the one or more uplink slots overlapping in time with one or more of the plurality of downlink time slots.
5. The method of claim 1 , wherein populating the gateway schedule includes, for each UE of the plurality of UE, allocating a plurality of uplink time slots.
6. The method of claim 5 , wherein populating the gateway schedule further includes, for each UE of the plurality of UE, identifying one or more downlink slots that violate the constraint to avoid conflicting time slots due at least in part to the one or more downlink slots overlapping in time with one or more of the plurality of uplink time slots.
7. The method of claim 1 , wherein the propagation delay of a particular UE changes.
8. The method of claim 7 , wherein the gateway schedule is updated responsive to a change in the propagation delay of the particular UE.
9. The method of claim 7 , wherein the propagation delay of the particular UE varies over time.
10. A scheduler in a communications system that includes a gateway terminal and a plurality of user equipment (UE), the scheduler comprising:
a data store configured to store computer executable instructions for scheduling downlink and uplink time slots of a frame in the communications system; and
a processor in communication with the data store, the processor configured to execute the computer executable instructions to perform the following:
determine a propagation delay between the gateway terminal and each UE of the plurality of UE;
determine, for each UE of the plurality of UE, one or more conflicting time slots at the UE based on the propagation delay between the gateway terminal and the UE, a conflicting time slot being a time slot in which the UE is scheduled to simultaneously transmit and receive;
populate a gateway schedule subject to a constraint to avoid conflicting time slots at each UE of the plurality of UE by:
generate a plurality of potential gateway schedules that avoid conflicting time slots at each UE of the plurality of UE; and
select as the gateway schedule a potential gateway schedule from the plurality of potential gateway schedules that improves network utilization relative to unselected potential gateway schedules of the plurality of potential gateway schedules; and
communicate a schedule that corresponds to the gateway schedule to each UE of the plurality of UE.
11. The scheduler of claim 10 , wherein the scheduler is incorporated into the gateway terminal of the communications system.
12. The scheduler of claim 10 , wherein the schedule that corresponds to the gateway schedule for a particular UE includes a schedule with downlink time slots delayed in time relative to the gateway schedule, the delay in time equal to the propagation time associated with the particular UE, and with uplink time slots advanced in time relative to the gateway schedule, the advance in time equal to the propagation time associated with the particular UE.
13. The scheduler of claim 10 , wherein populating the gateway schedule includes, for each UE of the plurality of UE, allocating a plurality of downlink time slots.
14. The scheduler of claim 13 , wherein populating the gateway schedule further includes, for each UE of the plurality of UE, identifying one or more uplink slots that violate the constraint to avoid conflicting time slots due at least in part to the one or more uplink slots overlapping in time with one or more of the plurality of downlink time slots.
15. The scheduler of claim 10 , wherein the propagation delay of a particular UE changes.
16. The scheduler of claim 15 , wherein the gateway schedule is updated responsive to a change in the propagation delay of the particular UE.
17. The scheduler of claim 15 , wherein the propagation delay of the particular UE varies over time.
18. A communications system comprising:
a plurality of user equipment (UE) configured for half duplex operation;
a gateway terminal configured for full duplex operation, the gateway terminal configured to communicate with each UE of the plurality of UE; and
a scheduler in communication with the gateway terminal, the scheduler configured to schedule time slots of a frame in the communications system by performing the following:
determine a propagation delay between the gateway terminal and each UE of the plurality of UE;
determine, for each UE of the plurality of UE, one or more conflicting time slots at the UE based on the propagation delay between the gateway terminal and the UE, a conflicting time slot being a time slot in which the UE is scheduled to simultaneously transmit and receive;
populate a gateway schedule subject to a constraint to avoid conflicting time slots at each UE of the plurality of UE by:
generate a plurality of potential gateway schedules that avoid conflicting time slots at each UE of the plurality of UE; and
select as the gateway schedule a potential gateway schedule from the plurality of potential gateway schedules that improves network utilization relative to unselected potential gateway schedules of the plurality of potential gateway schedules; and
communicate a schedule that corresponds to the gateway schedule to each UE of the plurality of UE.
19. The communications system of claim 18 , wherein the scheduler is incorporated into the gateway terminal of the communications system.
20. The communications system of claim 18 , wherein the schedule that corresponds to the gateway schedule for a particular UE includes a schedule with downlink time slots delayed in time relative to the gateway schedule, the delay in time equal to the propagation time associated with the particular UE, and with uplink time slots advanced in time relative to the gateway schedule, the advance in time equal to the propagation time associated with the particular UE.
21. The communications system of claim 18 , wherein populating the gateway schedule includes, for each UE of the plurality of UE, allocating a plurality of downlink time slots.
22. The communications system of claim 21 , wherein populating the gateway schedule further includes, for each UE of the plurality of UE, identifying one or more uplink slots that violate the constraint to avoid conflicting time slots due at least in part to the one or more uplink slots overlapping in time with one or more of the plurality of downlink time slots.
23. The communications system of claim 18 , wherein populating the gateway schedule includes, for each UE of the plurality of UE, allocating a plurality of uplink time slots.
24. The communications system of claim 23 , wherein populating the gateway schedule further includes, for each UE of the plurality of UE, identifying one or more downlink slots that violate the constraint to avoid conflicting time slots due at least in part to the one or more downlink slots overlapping in time with one or more of the plurality of uplink time slots.
25. The communications system of claim 18 , wherein the propagation delay of a particular UE changes.
26. The communications system of claim 25 , wherein the gateway schedule is updated responsive to a change in the propagation delay of the particular UE.
27. The communications system of claim 25 , wherein the propagation delay of the particular UE varies over time.
28. The communications system of claim 18 , wherein at least one UE of the plurality of UE has a propagation delay that is greater than or equal to a duration of one time slot in the gateway schedule.
29. The communications system of claim 28 , wherein at least one UE of the plurality of UE has a propagation delay that is greater than or equal to a duration of two consecutive time slots in the gateway schedule.