Methods for Timing Advance Management in HARQ ACK Disabled NB-IoT-NTN
A system and a method are provided for optimizing application of timing advance command (TAC) mechanism in a Narrow Band Internet of Things (NB-IoT) non-terrestrial network (NTN) system utilizes a timing advance (TA) estimation restriction duration. After one operation of a timing advance (TA) estimation resulting in issuing of an initial TAC, the gNB ignores the results of new TA estimations until specified X seconds after the initial TAC is sent. TA estimation restriction duration refers to the time duration between the initial TA estimation and X seconds after the initial TAC. The value of X is specified such that X represents the minimum duration starting from the transmission of the first TAC in which any received NPUSCH within this duration is not based on a new TAC. By applying the TA estimation restriction duration, multiple corrections of the same TA error are prevented.
1 . A method for optimizing application of timing advance command (TAC) mechanism in a Narrow Band Internet of Things (NB-IoT) non-terrestrial network (NTN) system, the method comprising the steps of:
receiving a first Downlink Control Information (DCI) NO at a user equipment (UE);
transmitting, by the UE to a next generation node B (gNB), a first Narrowband Physical Uplink Shared Channel (NPUSCH) transmission in response to the first DCI N0;
estimating, by the gNB, a first timing advance (TA) error associated with the received first NPUSCH transmission;
transmitting, by the gNB, a first TA command (TAC) to the UE to correct the first TA error associated with the received first NPUSCH transmission; and
applying, by the gNB, a specified TA estimation restriction duration following the receipt of the first NPUSCH;
wherein one of:
a) any subsequent NPUSCH received during the specified TA estimation restriction duration does not trigger an additional TAC; or
b) for a subsequent NPUSCH received during the specified TA estimation restriction duration,
i) estimating, by the gNB, a second timing advance (TA) error associated with the received subsequent NPUSCH transmission;
ii) calculating, by the gNB, a differential TA error between the first TA error and the second TA error; and
iii) transmitting, by the gNB, a second TA command (TAC) to the UE to correct the differential TA error.
2 . The method according to claim 1 , wherein the TA estimation restriction duration is the time duration between the estimating of the first TA error and specified X seconds after the first TAC.
3 . The method according to claim 2 , wherein the value of X is specified to be equal to or greater than the sum of RTT UE-gNB plus 12 milliseconds, RTT UE-gNB denoting the round trip time (RTT) between the UE and the gNB.
4 . The method according to claim 2 , wherein any subsequent NPUSCH received during the specified TA estimation restriction duration does not trigger an additional TAC.
5 . The method according to claim 3 , wherein any subsequent NPUSCH received during the specified TA estimation restriction duration does not trigger an additional TAC.
6 . The method according to claim 2 , wherein the gNB ignores results of any new TA error estimations associated with any subsequent NPUSCH until the specified X seconds have elapsed after the first TAC has been transmitted.
7 . The method according to claim 3 , wherein the gNB ignores results of any new TA error estimations associated with any subsequent NPUSCH until the specified X seconds have elapsed after the first TAC has been transmitted.
8 . The method according to claim 2 , wherein the value of X is specified to ensure any UL transmission received by the gNB after the specified TA estimation restriction duration is based on the first TAC.
9 . The method according to claim 3 , wherein the value of X is specified to ensure any UL transmission received by the gNB after the specified TA estimation restriction duration is based on the first TAC.
10 . The method according to claim 1 , wherein any subsequent NPUSCH received during the specified TA estimation restriction duration does not trigger an additional TAC.
11 . The method according to claim 10 , wherein the gNB ignores results of any new TA error estimations associated with any subsequent NPUSCH until specified X seconds have elapsed after the first TAC has been transmitted.
12 . The method according to claim 1 , wherein for the subsequent NPUSCH received during the specified TA estimation restriction duration,
i) estimating, by the gNB, the second timing advance (TA) error associated with the received subsequent NPUSCH transmission;
ii) calculating, by the gNB, the differential TA error between the first TA error and the second TA error; and
iii) transmitting, by the gNB, the second TA command (TAC) to the UE to correct the differential TA error.
13 . The method according to claim 12 , wherein the TA estimation restriction duration is the time duration between the estimating of the first TA error and specified X seconds after the first TAC.
14 . The method according to claim 13 , wherein the value of X is specified to ensure any UL transmission received by the gNB after the specified TA estimation restriction duration is based on the first TAC.
15 . The method according to claim 13 , wherein the value of X is specified to be equal to or greater than the sum of RTT UE-gNB plus 12 milliseconds, RTT UE-gNB denoting the round trip time (RTT) between the UE and the gNB.