The present disclosure relates to 5th Generation (5G) New Radio (NR) non-terrestrial network (NTN) operation, and relates more particularly to monitoring the downlink control signal in Narrow-Band Internet-of-Things (NB-IoT) for NTN.
NB-IoT physical downlink control channel (NPDCCH) is used to carry Downlink Control Information (DCI). Some examples of information contained in DCI include uplink (UL) grant information and downlink (DL) scheduling information.
In legacy (traditional) terrestrial networks (TNs), an example of which is illustrated in
Therefore, there is a need to optimize and update the DL monitoring restriction for the UE in IoT NTN networks to improve UE performance.
According to an example embodiment of the present disclosure, a method of optimizing the monitoring time window conditions or restrictions of NPDCCH for NBIOT-NTN is provided, which optimization enables UE to reduce power consumption by no longer requiring monitoring of NPDCCH for a dispensable duration.
According to an example embodiment of the present disclosure, the changes that need to be made for NPDCCH monitoring restriction are provided for the case where UE does not need to monitor incoming DL signal which is transmitted by the gNB/eNB in response to UL transmissions.
For an example scenario involving NB-IoT Physical Uplink Shared Channel (NPUSCH) with the same hybrid automatic repeat request (HARQ) process when 2 HARQs are configured, if an NB-IoT UE is configured with higher layer parameter twoHARQ-ProcessesConfig., and if the UE has an NPUSCH transmission ending in subframe n, then at least one of: 1) the UE is not required to receive transmissions in the Type B half-duplex guard periods for FDD; and 2) the UE is not expected to receive an NPDCCH with DCI format N0/N1 for the same HARQ process ID as the NPUSCH transmission in any subframe starting from subframe n+1−nTAUE to subframe n+3+Kmac, where nTAUE=ceil(NTA,UE-specific).
For an example scenario relating to monitoring restrictions involving subframe after NPUSCH processing, if the UE is not using higher layer parameter edt-Parameters or if the UE is using higher layer parameter edt-Parameters and 0≤IMCS≤2, (IMCS is the modulation and coding scheme field read from the DCI), then: if the NB-IoT UE has a NPUSCH transmission ending in subframe n, the UE is not required to monitor NPDCCH in any subframe starting from subframe n+1−nTAUE to subframe n+3+Kmac, where nTAUEceil(NTA,UE-specific).
For an example scenario relates to monitoring restrictions involving subframe after NPUSCH carrying Message 3 (Msg3), if the NB-IoT UE has an NPUSCH transmission for Msg3 ending in subframe n′with transport block size TBSMsg3, whereas if maximum transport block size TBSMsg3,max for Msg3 would have been selected the NPUSCH transmission would have ended in subframe n, the UE is not required to monitor NPDCCH in any subframe starting from subframe n′+1−nTAUE to subframe n+3+Kmac, where nTAUE=ceil(NTA,UE-specific).
For an example scenario relating to Narrowband Physical Random-Access Channel (NPRACH) for scheduling request (SR) involved in a long NPRACH transmission, for an NB-IoT UE configured with higher layer parameter sr-WithoutHARQ-ACK-Config, if the transmission of a narrowband random access preamble for SR ends on subframe n, then: in case of frame structure type 1 with NPRACH format 0 and 1 when the number of NPRACH repetitions is greater than or equal to 64, or NPRACH format 2 when the number of NPRACH repetitions is greater than or equal to 16, the UE is not required to monitor NPDCCH UE-specific search space from subframe n−nTAUE to subframe n+40+Kmac, where nTAUE=ceil(NTA,UE-specific).
For an example scenario relating to Narrowband Physical Random-Access Channel (NPRACH) for scheduling request (SR) involved in a short NPRACH transmission, for an NB-IoT UE configured with higher layer parameter sr-WithoutHARQ-ACK-Config, unless the transmission of a narrowband random access preamble for SR ends on subframe n, the UE is not required to monitor NPDCCH UE-specific search space from subframe n−nTAUE to subframe n+3+Kmac, where nTAUE=ceil(NTA,UE-specific).
In connection with
In the following sections, the proposed changes for optimizing the NPDCCH monitoring restrictions are discussed for various scenarios. UE-specific TA will be used by UE in connected mode before UL transmission. nTAUE is the UE-specific TA in the unit of subframes, and nTAUE=ceil(NTA,UE-specific) in msec (any floating value will be converted to upper integer value, e.g., ceil(3.23)=4). The estimate of UE to eNB/gNB (base station) round trip time (RTT) is equal to the sum of UE's TTA and Kmac, where UE's TTA is represented by the following formula:
T
TA=(NTA,UE-specific+NTA,common+NTA,offset)×Ts
In the above formula, the various variables are defined as follows:
a) NTA is timing offset between uplink and downlink radio frames at the UE, expressed in units of Ts. NTA works in the same way as legacy terrestrial networks. It is part of closed-loop uplink timing correction procedure. The amount of timing advance is being estimated by the eNB and the value is being communicated to UE in timing advance command.
b) NTA,UE-specific is UE-self-estimated TA to pre-compensate for the service link delay between the UE and the satellite. It is computed by the UE based on satellite-ephemeris-related higher-layers parameters if configured, otherwise NTA,UE-specific=0.
c) NTA,common is network-controlled (or network-specified) common TA, and may include any timing offset considered necessary by the network (e.g., feeder link delay). It is derived from the higher-layer parameters TACommon, TACommonDrift, and TACommonDriftVariation if configured, otherwise NTA,common=0. These parameters are given to the UE in SIB31-NB.
d) NTA, offset is Fixed timing advance offset, expressed in units of Ts. For frame structure type 1, NTA,offset=0.
e) Ts is basic unit of time expressed in millisecond (msec). Therefore, the granularity of TTA is 1 Ts, i.e., 1 msec.
In the present disclosure, several example optimization changes (relative to existing configuration restrictions in Terrestrial Network) are provided, e.g., to 3GPP TS36.213 version 16.6, to accommodate the impact of UE-eNB RTT.
This example scenario involves NB-IoT Physical Uplink Shared Channel (NPUSCH) with the same hybrid automatic repeat request (HARQ) process when 2 HARQs are configured. As a point of reference, the existing configuration restrictions (e.g., 3GPP TS36.213 version 16.6) in a Terrestrial Network (TN) provide that, if an NB-IoT UE is configured with higher layer parameter twoHARQ-ProcessesConfig., and if the UE has an NPUSCH transmission ending in subframe n, then: 1) the UE is not required to receive transmissions in the Type B half-duplex guard periods for frequency division duplex (FDD); and 2) the UE is not expected to receive an NB-IoT Physical Downlink Control Channel (NPDCCH) with downlink control information (DCI) format N0/N1 for the same HARQ process ID as the NPUSCH transmission in any subframe starting from subframe n+1 to subframe n+3.
In contrast, for NTN, the UE DL Acknowledgement (ACK)/Negative Acknowledgement (NACK) monitoring restrictions are modified for this example scenario. The HARQ-ACK timing in response to NPUSCH transmission is n+4+Kmac. The DL subframe n+3+Kmac corresponds to the subframe immediately before HARQ-ACK. Also, it should be noted that the DL subframe n+1−nTAUE starts immediately after UL subframe n. Therefore, the below-described changes need to be applied to the existing specifications, e.g., to 3GPP TS36.213 version 16.6, to properly accommodate the RTT between the UE and eNB. If an NB-IoT UE is configured with higher layer parameter twoHARQ-ProcessesConfig., and if the UE has an NPUSCH transmission ending in subframe n, then at least one of: 1) the UE is not required to receive transmissions in the Type B half-duplex guard periods for FDD; and 2) the UE is not expected to receive an NPDCCH with DCI format N0/N1 for the same HARQ process ID as the NPUSCH transmission in any subframe starting from subframe n+1−nTAUE to subframe n+3+Kmac, where nTAUE=ceil(NTA,UE-specific).
This example scenario relates to monitoring restrictions involving subframe after NPUSCH processing. As a point of reference, the existing configuration restrictions (e.g., 3GPP TS36.213 version 16.6) in a Terrestrial Network (TN) provide that, if the UE is not using higher layer parameter edt-Parameters or if the UE is using higher layer parameter edt-Parameters and 0≤IMCS≤2 , (IMCS is the modulation and coding scheme field read from the DCI), then: if the NB-IoT UE has a NPUSCH transmission ending in subframe n , the UE is not required to monitor NPDCCH in any subframe starting from subframe n+1 to subframe n+3.
In contrast, for NTN, the UE DL monitoring restrictions are modified for this example scenario, i.e., the below-described changes need to be applied to the existing specifications, e.g., to 3GPP TS36.213 version 16.6, to properly accommodate the RTT between the UE and eNB. If the UE is not using higher layer parameter edt-Parameters or if the UE is using higher layer parameter edt-Parameters and 0≤IMCS≤2, (IMCS is the modulation and coding scheme field read from the DCI), then: if the NB-IoT UE has a NPUSCH transmission ending in subframe n , the UE is not required to monitor NPDCCH in any subframe starting from subframe n+1−nTAUE to subframe n+3+Kmac, where nTAUE=ceil(NTA,UE-specific).
This example scenario relates to monitoring restrictions involving subframe after NPUSCH carrying Message 3 (Msg3). As a point of reference, the existing configuration restrictions (e.g., 3GPP TS36.213 version 16.6) in a Terrestrial Network (TN) provide that, if the NB-IoT UE has an NPUSCH transmission for Msg3 ending in subframe n′with transport block size TBSMsg3, whereas if maximum transport block size TBSMsg3,max for Msg3 would have been selected the NPUSCH transmission would have ended in subframe n, the UE is not required to monitor NPDCCH in any subframe starting from subframe n′+1 to subframe n+3.
In contrast, for NTN, the UE DL monitoring restrictions are modified for this example scenario, i.e., the below-described changes need to be applied to the existing specifications, e.g., to 3GPP TS36.213 version 16.6, to properly accommodate the RTT between the UE and eNB. If the NB-IoT UE has an NPUSCH transmission for Msg3 ending in subframe n′with transport block size TBSMsg3, whereas if maximum transport block size TBSMsg3,max for Msg3 would have been selected the NPUSCH transmission would have ended in subframe n, the UE is not required to monitor NPDCCH in any subframe starting from subframe n′+1−nTAUE to subframe n+3+Kmac, where nTAUE=ceil(NTA,UE-specific).
This example scenario relates to Narrowband Physical Random-Access Channel (NPRACH) for scheduling request (SR) involved in long NPRACH transmission. As a point of reference, the existing configuration restrictions (e.g., 3GPP TS36.213 version 16.6) in a Terrestrial Network (TN) provide that, for an NB-IoT UE configured with higher layer parameter sr-WithoutHARQ-ACK-Config, if the transmission of a narrowband random access preamble for SR ends on subframe n, then: in case of frame structure type 1 with NPRACH format 0 and 1 when the number of NPRACH repetitions is greater than or equal to 64, or NPRACH format 2 when the number of NPRACH repetitions is greater than or equal to 16, the UE is not required to monitor NPDCCH UE-specific search space from subframe n to subframe n+40.
In contrast, for NTN, the UE DL monitoring restrictions are modified for this example scenario, i.e., the below-described changes need to be applied to the existing specifications, e.g., to 3GPP TS36.213 version 16.6, to properly accommodate the RTT between the UE and eNB. For an NB-IoT UE configured with higher layer parameter sr-WithoutHARQ-ACK-Config, if the transmission of a narrowband random access preamble for SR ends on subframe n, then: in case of frame structure type 1 with NPRACH format 0 and 1 when the number of NPRACH repetitions is greater than or equal to 64, or NPRACH format 2 when the number of NPRACH repetitions is greater than or equal to 16, the UE is not required to monitor NPDCCH UE-specific search space from subframe n−nTAUE to subframe n+40+Kmac, where nTAUE=ceil(NTA,UE-specific).
This example scenario relates to Narrowband Physical Random-Access Channel (NPRACH) for scheduling request (SR) involved in short NPRACH transmission. As a point of reference, the existing configuration restrictions (e.g., 3GPP TS36.213 version 16.6) in a Terrestrial Network (TN) provide that, for an NB-IoT UE configured with higher layer parameter sr-WithoutHARQ-ACK-Config, unless the transmission of a narrowband random access preamble for SR ends on subframe n, the UE is not required to monitor NPDCCH UE-specific search space from subframe n to subframe n+3.
In contrast, for NTN, the UE DL monitoring restrictions are modified for this example scenario, i.e., the below-described changes need to be applied to the existing specifications, e.g., to 3GPP TS36.213 version 16.6, to properly accommodate the RTT between the UE and eNB. For an NB-IoT UE configured with higher layer parameter sr-WithoutHARQ-ACK-Config, unless the transmission of a narrowband random access preamble for SR ends on subframe n, the UE is not required to monitor NPDCCH UE-specific search space from subframe n−nTAUE to subframe n+3+Kmac, where nTAUE=ceil(NTA,UE-specific).
According to the example embodiments of the present disclosure, impact of Kmac timing is taken into consideration for optimizing the monitoring window for DL reception at UE. The disclosed example embodiments of system optimization will help UEs reduce power consumption as UEs will not be required to monitor for DL signal for a longer duration.
Although the example embodiments of the present disclosure have been described in the context of NB-IoT for NTN operation, the present disclosure is equally applicable to 5G NR NTN operation, e.g., LTE Machine Type Communication (LTE-M) technology, and .
Number | Date | Country | Kind |
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202121051977 | Nov 2021 | IN | national |