Method for control channel detection in wideband operation

1. A method for control channel transmission in wideband operation containing a plurality of subbands performed in a base station (BS), comprising the steps of:

configuring at least one search space group (SSG) containing at least two different search space sets;

configuring at least one control resource set (CORESET) confined within one subband (SB1) among the plurality of subbands;

associating said at least one SSG with said at least one CORESET, the associated CORESET becoming a reference CORESET;

associating the reference CORESET and at least one frequency shifted CORESET of the reference CORESET confined within at least another subband (SB2, SB3) among the plurality of subbands, with said at least two different search space sets; the reference CORESET and the at least one frequency shifted CORESET sharing a same CORESET index (CORESET_ID 1);

performing a listen before talk (LBT) procedure over each subband of the plurality of subbands to detect available subbands;

transmitting, within available subbands, a control channel within the reference CORESET and the at least one frequency shifted CORESET.

2. The method for control channel transmission of claim 1 , wherein the at least one frequency shifted CORESET is also time shifted and wherein the reference CORESET and the at least one frequency and time shifted CORESET shares the same CORESET index (CORESET_ID 1).

3. The method for control channel transmission of claim 1 , wherein each search space set of the SSG configures monitoring occasion with a slot periodicity defining monitoring slots and at least one time location defining at least one monitoring starting time within said monitoring slots.

4. The method for control channel transmission of claim 3 , wherein during the search space set configuration, an explicit indication of the CORESET frequency shift is provided.

5. The method for control channel transmission of claim 3 , wherein during the search space set configuration, an implicit indication of the CORESET frequency shift is provided using a pre-defined index ordering of the different search space sets within said at least one search space group.

6. The method for control channel transmission of claim 1 , further comprising the step of:

either configuring, when more than one subband is available, a restriction to one available subband containing the configured reference CORESET or one frequency shifted CORESET of the reference CORESET associated with the configured at least one search space group;

or configuring, when more than one subband is available, a restriction to at least one of the configured reference CORESET or one frequency shifted CORESET of the reference CORESET associated with the configured at least one search space group.

7. The method for control channel transmission of claim 1 , wherein the CORESET are based on a control-channel element (CCE) index and a valid search space set is defined as a search space set which corresponding CORESET is in an available subband, the method further comprising the step of:

configuring, when the total number of CCE of the corresponding CORESET of valid search space sets exceeds a pre-defined threshold, to switch off some CCE from being monitored.

8. The method for control channel transmission of claim 1 , further comprising the step of:

signalling the available subbands via an explicit indication within a control signal (GC-PDCCH).

9. The method for control channel transmission of claim 1 , further comprising the steps of:

signalling the available subbands via an implicit indication through a transmission of a pre-known signal (DMRS).

10. A method for control channel detection m wideband operation containing a plurality of subbands, performed in a user equipment (UE), comprising the steps of:

monitoring at least one search space group associated with a reference control resource set (CORESET) confined in one subband among the plurality of subbands and containing at least two search space sets, by:

monitoring, within said one subband, one search space set of the search space group (SSG) containing the reference CORESET and

monitoring, within at least another subband, the at least another search space set of the SSG containing at least one frequency shifted CORESET of the reference CORESET confined m the at least another subband among the plurality of subbands;

the reference CORESET and the at least one frequency shifted CORESET sharing a same CORESET index (CORESET ID 1):

ignoring search space sets within unavailable subbands among the plurality of subbands after a listen before talk procedure has been performed by a base station over each subband of the wideband: and

detecting a control channel within the reference CORESET or the at least one frequency shifted CORESET.

11. The method for control channel detection of claim 10 , wherein the at least one frequency shifted CORESET is also time shifted and wherein the reference CORESET and the at least one frequency and time shifted CORESET shares the same CORESET index (CORESET_ID 1).

12. The method for control channel detection of claim 10 , wherein each search space set of the SSG configures monitoring occasion with a slot periodicity defining monitoring slots and at least one time location defining at least one monitoring starting time within said monitoring slots.

13. The method for control channel detection of claim 12 , further comprising a step of:

detecting an explicit indication of the CORESET frequency shift.

14. The method for control channel detection of claim 12 , further comprising a step of:

detecting an implicit indication of the CORESET frequency shift using a pre-defined index ordering of the different search space sets within said at least search space group.

15. The method for control channel detection of claim 10 , wherein a valid search space set is defined as a search space set which corresponding CORESET is in an available subband, the method comprising the step of:

selecting one SSG containing at least one valid search space set,

wherein the selected SSG contains multiple valid search space sets, the method comprising the step of:

either selecting one valid search space set from the valid search space sets;

or selecting at least two of the valid search space sets.

16. The method for control channel detection of claim 15 , comprising the step of:

detecting the selected valid search space set(s) either through an explicit indication in the RRC configuration or through an implicit indication of a pre-defined CCE index value.

17. The method for control channel detection of claim 15 , wherein the base station configures a number of control channel candidates within each search space set of the SSG, the method comprising the step of:

selecting, within the valid search spaces, only search spaces which have monitoring occasion in a current slot, if the number of control channel candidates exceeds a pre-defined maximum number within each valid search space set.

18. The method for control channel detection of claim 15 , wherein the base station configures a number of control channel candidates within each search space set of the SSG and wherein the CORESET are based on a control-channel element (CCE) index, the method comprising the step of:

selecting the CCEs within each of the corresponding CORESET to the valid search spaces having monitoring occasion in a current slot, if the number of non-overlapped CCEs exceeds a pre-defined maximum number.

19. The method for control channel detection of claim 17 , wherein the number of control channel candidates within each search space set is based on at least one aggregation level of control channel elements, the method comprising the step of:

further selecting search spaces set by removing a largest aggregation level value and its corresponding control channel candidates for each search space set with more than one aggregation level value.

20. The method for control channel detection of claim 17 , comprising the step of:

further reducing the number of control channel candidates by picking only one valid search space with a number of control channel candidates lower than a pre-defined maximum number of candidates or by dividing the number of candidates for each search space by an integer value.