Common search space (CSS) for paging of NB-IoT devices
A method performed by a user equipment (UE) in idle mode, for determining common search space (CSS) for NB-IoT paging is disclosed. The method comprises determining a set of periodic subframes as a Paging Occasion (PO) subframe pattern. The method further comprises monitoring a starting subframe of paging CSS for a Radio Network Temporary Identifier (RNTI). The starting subframe of paging CSS is determined as follows: a first subframe (SF 0 ) defined by the Paging Occasion subframe pattern, is used when SF 0 is determined to be a valid downlink subframe. A next valid downlink subframe after SF 0 is used when SF 0 is determined to be an invalid downlink subframe.
1. A method performed by a user equipment (UE) in idle mode, for determining common search space (CSS) for Narrowband Internet of Things (NB-IoT) paging, the method comprising:
monitoring a starting subframe of the CSS for a Radio Network Temporary Identifier (RNTI);
wherein the starting subframe of the CSS is determined as follows:
use a first subframe (SF 0 ), according to a Paging Occasion subframe table, when the first subframe is determined, based on a received bitmap, to be a valid downlink subframe; and
use a next valid downlink subframe after the first subframe when the first subframe is determined to be an invalid downlink subframe.
2. The method according to claim 1 , wherein the UE determines that a subframe is a valid downlink subframe if:
the subframe is indicated as a valid downlink subframe in a Narrowband System Information Block 1 (NB-SIB1); and
the subframe does not contain any of the following:
NB-IoT Primary Synchronization Sequence (NPSS);
NB-IoT Secondary Synchronization Sequence (NSSS);
NB-IoT Physical Broadcast Channel (NPBCH); and
NB-SIB1.
3. The method according to claim 1 , wherein the first subframe is indicated by the Paging Occasion subframe table to be a starting subframe of Narrowband Physical Data Control Channel (NPDCCH) repetitions.
4. The method according to claim 3 , wherein the CSS is defined only over valid downlink subframes, such that when the NPDCCH repetition overlaps with an invalid downlink subframe, the NPDCCH repetition is delayed until a next valid downlink subframe.
5. The method according to claim 1 , wherein the UE determines a subframe is a valid downlink subframe based on a valid subframe pattern received in a System Information Block (SIB) message broadcast by a network node.
6. The method according to claim 1 , wherein the UE determines a subframe is a valid downlink subframe based on a valid subframe pattern, the valid subframe pattern comprising subframes not occupied by known broadcast channels or broadcast signals.
7. The method according to claim 1 , wherein the UE determines a subframe is a valid downlink subframe based on a first valid subframe pattern and a second valid subframe pattern;
the first valid subframe pattern being a downlink subframe pattern received in a System Information Block (SIB) message broadcast by a network node; and
the second valid subframe pattern comprising subframes not occupied by known broadcast channels or broadcast signals.
8. A method, performed by a network node, for determining common search space (CSS) for Narrowband Internet of Things (NB-IoT) paging, the method comprising:
transmitting a paging message to a user equipment (UE), the paging message beginning with a starting subframe of the CSS;
wherein the starting subframe of the CSS is determined as follows:
use a first subframe (SF 0 ), according to a Paging Occasion subframe table, when the first subframe is determined, based on a received bitmap, to be a valid downlink subframe; and
use a next valid downlink subframe after the first subframe when the first subframe is determined to be an invalid downlink subframe.
9. The method according to claim 8 , further comprising:
indicating a downlink subframe as valid in a Narrowband System Information Block 1 (NB-SIB1); and
wherein the network node determines the subframe is a valid downlink subframe if the subframe does not contain any of the following:
NB-IoT Primary Synchronization Sequence (NPSS);
NB-IoT Secondary Synchronization Sequence (NSSS);
NB-IoT Physical Broadcast Channel (NPBCH); and
NB-SIB1.
10. The method according to claim 8 , wherein the first subframe is indicated by the Paging Occasion subframe table to be a starting subframe of Narrowband Physical Data Control Channel (NPDCCH) repetitions.
11. The method according to claim 10 , wherein the CSS is defined only over valid downlink subframes, such that when the NPDCCH repetition overlaps with an invalid downlink subframe, the NPDCCH repetition is delayed until a next valid downlink subframe.
12. The method according to claim 8 , wherein the network node transmits a valid downlink subframe pattern in a System Information Block (SIB) message broadcast to the UE.
13. A user equipment (UE) configured for determining common search space (CSS) for Narrowband Internet of Things (NB-IoT) paging while operating in idle mode, the UE comprising:
processing circuitry configured to:
monitor a starting subframe of the CSS for a Radio Network Temporary Identifier (RNTI);
wherein the starting subframe of the CSS is determined as follows:
use a first subframe (SF 0 ), according to a Paging Occasion subframe table, when the first subframe is determined, based on a received bitmap, to be a valid downlink subframe; and
use a next valid downlink subframe after the first subframe when the first subframe is determined to be an invalid downlink subframe.
14. The UE according to claim 13 , wherein the processing circuitry is configured to determine a subframe is a valid downlink subframe if:
the subframe is indicated as a valid downlink subframe in a Narrowband System Information Block 1 (NB-SIB1); and
the subframe does not contain any of the following:
NB-IoT Primary Synchronization Sequence (NPSS);
NB-IoT Secondary Synchronization Sequence (NSSS);
NB-IoT Physical Broadcast Channel (NPBCH); and
NB-SIB1.
15. The UE according to claim 13 , wherein the first subframe is indicated by the Paging Occasion subframe table to be a starting subframe of Narrowband Physical Data Control Channel (NPDCCH) repetitions.
16. The UE according to claim 15 , wherein the CSS is defined only over valid downlink subframes, such that when the NPDCCH repetition overlaps with an invalid downlink subframe, the NPDCCH repetition is delayed until a next valid downlink subframe.
17. The UE according to claim 13 , wherein the processing circuitry is configured to determine a subframe is a valid downlink subframe based on a valid subframe pattern received in a System Information Block (SIB) message broadcast by a network node.
18. The UE according to claim 13 , wherein the processing circuitry is configured to determine a subframe is a valid downlink subframe based on a valid subframe pattern, the valid subframe pattern comprising subframes not occupied by known broadcast channels or broadcast signals.
19. The UE according to claim 13 , wherein the processing circuitry is configured to determine a subframe is a valid downlink subframe based on a first valid subframe pattern and a second valid subframe pattern;
the first valid subframe pattern being a downlink subframe pattern received in a System Information Block (SIB) message broadcast by a network node; and
the second valid subframe pattern comprising subframes not occupied by known broadcast channels or broadcast signals.
20. A network node configured for determining common search space (CSS) for Narrowband Internet of Things (NB-IoT) paging, the network node comprising:
processing circuitry configured to:
transmit a paging message to a user equipment (UE), the paging message beginning with a starting subframe of the CSS;
wherein the starting subframe of the CSS is determined as follows:
use a first subframe (SF 0 ), according to a Paging Occasion subframe table, when the first subframe is determined, based on a received bitmap, to be a valid downlink subframe; and
use a next valid downlink subframe after the first subframe when the first subframe is determined to be an invalid downlink subframe.
21. The network node according to claim 20 , wherein the processing circuitry is further configured to:
determine a subframe is a valid downlink subframe if the subframe does not contain any of the following:
NB-IoT Primary Synchronization Sequence (NPSS);
NB-IoT Secondary Synchronization Sequence (NSSS);
NB-IoT Physical Broadcast Channel (NPBCH); and
NB-SIB1; and
indicate the subframe as a valid downlink subframe in System Information Block 1 (SIB1).
22. The network node according to claim 20 , wherein the first subframe is indicated by the Paging Occasion subframe table to be a starting subframe of Narrowband Physical Data Control Channel (NPDCCH) repetitions.
23. The network node according to claim 22 , wherein the CSS is defined only over valid downlink subframes, such that when the NPDCCH repetition overlaps with an invalid downlink subframe, the NPDCCH repetition is delayed until a next valid downlink subframe.
24. The network node according to claim 20 , wherein the processing circuitry is further configured to transmit a valid subframe pattern in a System Information Block (SIB) message broadcast to the UE.