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 (SF0) defined by the Paging Occasion subframe pattern, is used when SF0 is determined to be a valid downlink subframe. A next valid downlink subframe after SF0 is used when SF0 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:
determining a set of subframes as a Paging Occasion (PO) subframe pattern;
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 (SF0), according to the Paging Occasion subframe pattern, when the first subframe is determined 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 Paging Occasion subframe pattern is determined according to a subframe pattern table.
4. The method according to claim 1 , wherein the first subframe is indicated by the Paging Occasion subframe pattern to be a starting subframe of Narrowband Physical Data Control Channel (NPDCCH) repetitions.
5. The method according to claim 4 , 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.
6. 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.
7. 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.
8. 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.
9. A method, performed by a network node, for determining common search space (CSS) for Narrowband Internet of Things (NB-IoT) paging, the method comprising:
determining a set of subframes as a Paging Occasion (PO) subframe pattern;
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 (SF0), according to the Paging Occasion subframe pattern, when the first subframe is determined 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.
10. The method according to claim 9 , 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.
11. The method according to claim 9 , wherein the Paging Occasion subframe pattern is determined according to a subframe pattern table.
12. The method according to claim 9 , wherein the first subframe is indicated by the Paging Occasion subframe pattern to be a starting subframe of Narrowband Physical Data Control Channel (NPDCCH) repetitions.
13. The method according to claim 12 , 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.
14. The method according to claim 9 , wherein the network node transmits a valid downlink subframe pattern in a System Information Block (SIB) message broadcast to the UE.
15. 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:
determine a set of subframes as a Paging Occasion (PO) subframe pattern;
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 (SF0), according to the Paging Occasion subframe pattern, when the first subframe is determined 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.
16. The UE according to claim 15 , 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.
17. The UE according to claim 15 , wherein the Paging Occasion subframe pattern is determined according to a subframe pattern table.
18. The UE according to claim 15 , wherein the first subframe is indicated by the Paging Occasion subframe pattern to be a starting subframe of Narrowband Physical Data Control Channel (NPDCCH) repetitions.
19. The UE according to claim 18 , 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.
20. The UE according to claim 15 , 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.
21. The UE according to claim 15 , 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.
22. The UE according to claim 15 , 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.
23. 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:
determine a set of subframes as a Paging Occasion (PO) subframe pattern;
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 (SF0), according to the Paging Occasion subframe pattern, when the first subframe is determined 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.
24. The network node according to claim 23 , 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).
25. The network node according to claim 23 , wherein the Paging Occasion subframe pattern is determined according to a subframe pattern table.
26. The network node according to claim 23 , wherein the first subframe is indicated by the Paging Occasion subframe pattern to be a starting subframe of Narrowband Physical Data Control Channel (NPDCCH) repetitions.
27. The network node according to claim 26 , 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.
28. The network node according to claim 23 , wherein the processing circuitry is further configured to transmit a valid subframe pattern in a System Information Block (SIB) message broadcast to the UE.