Uplink timing maintenance for communication paths including multiple legs involving a relay entity
A method and apparatus are provided, in which a service link path delay relative to a first leg of a communication path of a communication between the user equipment and a network entity via a relay entity is estimated ( 602 ), where the first leg corresponds to a portion of the communication path between the user equipment and the relay entity. A feeder link path delay relative to a second leg of the communication path is determined ( 604 ), where the second leg corresponds to a portion of the communication path between the relay entity and the network entity, based upon at least a received signaling indication. A timing advance value is calculated ( 606 ), based upon the service link path delay and the feeder link path delay. An uplink transmission timing of the user equipment is adjusted ( 608 ), based upon the calculated timing advance value.
1 . A user equipment (UE) for wireless communication, comprising:
at least one memory; and
at least one processor coupled with the at least one memory and configured to cause the UE to:
estimate a service link path delay relative to a first leg of a communication path of a communication between the UE and a network entity via a relay entity, wherein the first leg corresponds to a portion of the communication path between the user equipment and the relay entity;
determine a feeder link path delay relative to a second leg of the communication path based at least in part on a signaling indication received from the network entity, wherein the second leg corresponds to a portion of the communication path between the relay entity and the network entity;
calculate a timing advance value based on the service link path delay and the feeder link path delay, wherein the timing advance value is two times a sum of the service link path delay and the feeder link path delay; and
adjust an uplink transmission timing of the UE communicating with the network entity via the relay entity based on the calculated timing advance value.
2 . The UE of claim 1 , wherein to estimate the service link path delay relative to the first leg of the communication path, the at least one processor is configured to cause the UE to determine a distance between an identified position of the UE and a position of the relay entity, and calculate the service link path delay based on an expected rate that a communication signal traverses an amount of space associated with the determined distance.
3 . The UE of claim 2 , wherein the at least one processor is configured to cause the UE to predict the position of the relay entity based on signaling information provided by the relay entity.
4 . The UE of claim 1 , wherein the relay entity is a space based satellite in orbit around Earth, wherein the space based satellite has a relative movement that follows a predefined predictable pattern.
5 . The UE of claim 1 , wherein the at least one processor is configured to cause the UE to:
initiate a timer having a predetermined duration based on initially estimating the service link path delay relative to the first leg of the communication path; and
estimate a new service link path delay based on expiration of the predetermined duration of the timer.
6 . The UE of claim 1 , wherein the determine the feeder link path delay relative to the second leg of the communication path is based on a calculated elapsed amount of time between a first point in time that a signal between the relay entity and the network entity is transmitted, and a second point in time that a response to the transmitted signal is received.
7 . The UE of claim 1 , wherein the at least one processor is configured to cause the UE to:
initiate a timer having a predetermined duration based on initially determining the feeder link path delay relative to the second leg of the communication path based on at least the received signaling indication; and
request an update as another received signaling indication based on expiration of the predetermined duration of the timer.
8 . The UE of claim 7 , wherein the another received signaling indication is triggered by a random access procedure.
9 . The UE of claim 7 , wherein the another received signaling indication includes a trigger to send system information for acquisition of an offset value associated with the feeder link path delay.
10 . The UE of claim 7 , wherein the received signaling indication is a timing advance command indicating a relative timing difference.
11 . The UE of claim 10 , wherein the timer is restarted in response to receiving the timing advance command indicating the relative timing difference.
12 . A method performed by a user equipment (UE), the method comprising:
estimating a service link path delay relative to a first leg of a communication path of a communication between the UE and a network entity via a relay entity, wherein the first leg corresponds to a portion of the communication path between the user equipment and the relay entity;
determining a feeder link path delay relative to a second leg of the communication path based at least in part on a signaling indication received from the network entity, wherein the second leg corresponds to a portion of the communication path between the relay entity and the network entity;
calculating a timing advance value based on the service link path delay and the feeder link path delay, wherein the timing advance value is two times a sum of the service link path delay and the feeder link path delay; and
adjusting an uplink transmission timing of the UE communicating with the network entity via the relay entity based on the calculated timing advance value.
13 . A network entity for wireless communication, comprising:
at least one memory; and
at least one processor coupled with the at least one memory and configured to cause the network entity to:
determine a feeder link path delay of a feeder link path between the network entity and a relay entity, via which the network entity communicates with a user equipment (UE);
transmit, to the UE via the relay entity, a signaling indication associated with the determined feeder link path delay; and
receive, from the UE, an uplink transmission, wherein a timing of the uplink transmission has been advanced based on a timing advance value calculated based on the feeder link path delay and a service link path delay associated with a service link path between the UE and the relay entity, wherein the timing advance value is two times a sum of the service link path delay and the feeder link path delay, and wherein the timing of the uplink transmission corresponds with a timing of a network downlink transmission.
14 . A method performed by a network entity, the method comprising:
determining a feeder link path delay of a feeder link path between the network entity and a relay entity, via which the network entity communicates with a user equipment (UE);
transmitting, to the UE via the relay entity, a signaling indication associated with the determined feeder link path delay; and
receiving, from the UE, an uplink transmission, wherein a timing of the uplink transmission has been advanced based on a timing advance value calculated based on the feeder link path delay and a service link path delay associated with a service link path between the UE and the relay entity, wherein the timing advance value is two times a sum of the service link path delay and the feeder link path delay, and wherein the timing of the uplink transmission corresponds with a timing of a network downlink transmission.
15 . The method of claim 12 , wherein to estimate the service link path delay relative to the first leg of the communication path, the method further comprising:
determining a distance between an identified position of the UE and a position of the relay entity, and calculating the service link path delay based on an expected rate that a communication signal traverses an amount of space associated with the determined distance.
16 . The method of claim 15 , further comprising:
predicting the position of the relay entity based on signaling information provided by the relay entity.
17 . The method of claim 12 , wherein the relay entity is a space based satellite in orbit around Earth, where in the space based satellite has a relative movement that follows a predefined predictable pattern.
18 . The method of claim 12 , further comprising:
initiating a timer having a predetermined duration based on initially estimating the service link path delay relative to the first leg of the communication path; and
estimating a new service link path delay based on expiration of the predetermined duration of the timer.
19 . The method of claim 12 , wherein the determining the feeder link path delay relative to the second leg of the communication path is based on a calculated elapsed amount of time between a first point in time that a signal between the relay entity and the network entity is transmitted, and a second point in time that a response to the transmitted signal is received.
20 . The method of claim 12 , further comprising:
initiating a timer having a predetermined duration based on initially determining the feeder link path delay relative to the second leg of the communication path based on at least the received signaling indication; and
requesting an update as another received signaling indication based on expiration of the predetermined duration of the timer.