Downlink control channel transmissions

1. An apparatus of a user equipment (UE) operable to identify downlink control channel candidates for receiving downlink control information, the apparatus comprising:

one or more processors configured to:

decode a downlink control information (DCI) format received from an eNodeB, the DCI format indicating a set of resource blocks (RBs) in one or more subframes allocated for reception or transmission of data or control information in a shortened transmission time interval (S-TTI);

identify a subset of resource elements (REs) within the set of RBs in the one or more subframes, wherein the subset of REs correspond to shortened physical downlink control channel (S-PDCCH) candidates in the S-TTI of the one or more subframes; and

attempt to decode the S-PDCCH candidates in the S-TTI of the one or more subframes, wherein S-PDCCH candidates that are successfully decoded cause the UE to identify the downlink control information; and

memory configured to store the identified downlink control information.

2. The apparatus of claim 1 , further comprising a transceiver configured to:

receive the DCI format from the eNodeB; and

receive the downlink control information from the eNodeB.

3. The apparatus of claim 1 , wherein the DCI format includes:

time-frequency radio resource assignment information; and

one or more of a modulation and coding rate, a S-PDCCH control size or a reference signal (RS) type.

4. The apparatus of claim 1 , wherein the DCI format is received on a legacy PDCCH region, and downlink control resources used for the DCI format are identified by: a dedicated radio network temporary identifier (RNTI) value assigned by higher layers, or a predefined value in a 1-bit information element (IE) field in the DCI format.

5. The apparatus of claim 1 , wherein the one or more processors are further configured to:

determine, at the UE, a starting orthogonal frequency division multiplexing (OFDM) symbol and a number of OFDM symbols in one or more subframes used for an S-PDCCH transmission from the eNodeB;

identify a group of REs in the OFDM symbols to form one or more shortened resource element groups (S-REGs), wherein the group of REs in the OFDM symbol corresponds to the subset of REs within the set of RBs in the one or more subframes;

identify one or more S-TTI control channel elements (S-CCEs) from the one or more S-REGs; and

aggregate the one or more S-CCEs, wherein the S-PDCCH transmission is received from the eNodeB using the one or more aggregated S-CCEs.

6. The apparatus of claim 5 , wherein:

the starting OFDM symbol used for the S-PDCCH transmission from the eNodeB is determined based on a number of OFDM symbols in the S-TTI or configured via higher layer signaling; and

the number of OFDM symbols used for the S-PDCCH transmission from the eNodeB is: signaled by the DCI format, or configured via higher layer signaling, or defined in a Third Generation Partnership Project (3GPP) Long-Term Evolution (LTE) specification, or dependent on a UE-specific S-TTI length that is configured by higher layers.

7. The apparatus of claim 5 , wherein:

the S-CCE includes three S-REGs, and each S-REG includes all REs except REs carrying a demodulation reference signal (DMRS) within one physical resource block (PRB) in one OFDM symbol in an increasing order of frequency; or

the S-CCE includes two S-REGs, and each S-REG includes all REs except REs carrying a DMRS within one PRB in two consecutive OFDM symbols; or

the S-CCE includes six S-REGs, and each S-REG includes six REs.

8. The apparatus of claim 7 , wherein:

one S-REG includes REs k within one OFDM symbol with k=k 0 +0, k 0 +1, . . . , k 0 +5, wherein k 0 is a first RE in frequency index in a PRB; or

one S-REG includes REs k within one OFDM symbol with k=k 0 +6, k 0 +7, . . . , k 0 +11,; or

one S-REG includes even REs k within one OFDM symbol with k=k 0 +0, k 0 +2, . . . , k 0 +10; or

one S-REG includes odd REs k within one OFDM symbol with k=k 0 +1, k 0 +7, . . . , k 0 +11.

9. The apparatus of claim 5 , wherein the one or more processors are further configured to map a block of encoded DCI symbols to REs in the one or more S-REGs, wherein the REs are not utilized for a cell-specific reference signal (CRS), zero power (ZP) channel state information reference signal (CSI-RS) or nonzero power (NZP) CSI-RS.

10. The apparatus of claim 5 , wherein:

a S-CCE number (n) corresponds to S-REGs in N S-REG S-CCE consecutive physical resource block (PRB) indices starting from a PRB N RB (0) +n×N S-REG S-CCE , where N RB (0) is a starting PRB within an allocated S-TTI PRB sets and N S-REG S-CCE represents a number of S-REGs per S-CCE; or

a S-CCE number (n) corresponds to S-REGs in a PRB numbered with N RB (0) +n+j×┌N RB S /N S-REG S-CCE ┐, where j=0, . . . , N S-REG S-CCE −1, and N RB S is a total number of RBs for an allocated S-TTI PRB set; or

a S-CCE number (n) corresponds to S-REGs numbered (n mod N S-REG RB )+jN S-REG RB in a PRB index (k+n×N S-REG S-CCE /N S-REG RB +N RB (0) ); where k=0, 1, . . . , N S-REG S-CCE /N S-REG RB −1, and N S-REG RB is a total number of S-REGs within a single RB; or

a S-CCE number (n) corresponds to S-REGs numbered (n mod N S-REG RB ) in PRB indices N RB (0) +n+l×┌N RB S /N S-REG S-CCE ┐, where l=0, 1, . . . , N S-REG S-CCE −1.

11. The apparatus of claim 10 , wherein:

S-CCEs corresponding to a S-PDCCH candidate m of a search space at aggregation level L is given by: L{m mod └N S CCE,k /L┘}+i, wherein i=0, . . . , L−1, m−0, 1, . . . M (L) −1, and M (L) is a number of S-PDCCH candidates to monitor at aggregation level L; or

S-CCEs corresponding to a S-PDCCH candidate m of an S-PDCCH specific search space SS k (L) is given by: L{(Y k +m)mod └N S-CCE,k /L┘}+i, wherein i=0, . . . , L−1, m=0, 1, . . . M (L) is and M (L) is a number of S-PDCCH candidates to monitor at aggregation level L in an S-TTI RB set, and Y k is defined by: Y k =(A·Y k-1 ) mod D, wherein Y −1 =n RNTI ≠0, A−39827, D−65537, and k is an S-TTI index within the one or more subframes, wherein N S-CCE,k is a number of S-CCEs in a control region of the S-PDCCH in S-TTI k.

12. The apparatus of claim 1 , wherein a number of aggregation levels (L) and a number of S-PDCCH candidates to monitor at a given aggregation level L is configured via higher layer signaling for the UE or dynamically configured by the DCI format transmitted to the UE in the one or more subframes.

13. The apparatus of claim 1 , wherein:

a DCI format used to schedule a shortened physical downlink shared channel (S-PDSCH) and a shortened physical uplink shared channel (S-PUSCH) in the S-TTI in the one or more subframes is received on a legacy PDCCH region, and legacy PDCCH candidates are determined based on a dedicated cell radio network temporary identifier (C-RNTI) assigned by higher layers; or

a DCI format used to schedule the S-PDSCH and the S-PUSCH in the S-TTI in the one or more subframes is received over the S-PDCCH.

14. The apparatus of claim 1 , wherein:

a DCI format used to schedule a shortened physical downlink shared channel (S-PDSCH) and a shortened physical uplink shared channel (S-PUSCH) in the S-TTI in the one or more subframes is received on a legacy PDCCH region when the UE is configured with a cell-specific reference signal (CRS) for S-PDCCH demodulation; or

a DCI format used to schedule the S-PDSCH and the S-PUSCH in the S-TTI in the one or more subframes is received over the S-PDCCH when the UE is not configured with CRS for S-PDCCH demodulation.

15. The apparatus of claim 1 , wherein:

a number of information bits in a DCI format used for a shortened physical downlink shared channel (S-PDSCH) is equal to a number of information bits in a DCI format used for shortened physical uplink shared channel (S-PUSCH) scheduling in a single S-TTI; and

a DCI format used for the S-PDSCH and the DCI format used for the S-PUSCH scheduling are distinguished using a 1-bit flag information element (IE) that is included in each of the DCI format used for the S-PDSCH and the DCI format used for the S-PUSCH scheduling.

16. An apparatus of an eNodeB operable to provide downlink control information, the apparatus comprising:

memory; and

one or more processors configured to:

encode a downlink control information (DCI) format for transmission to a user equipment (UE), the DCI format indicating a set of resource blocks (RBs) one or more subframes allocated for reception or transmission of data or control information in a shortened transmission time interval (S-TTI); and

encode the downlink control information for transmission to the UE, wherein a subset of resource elements (REs) within the set of RBs in the one or more subframes corresponds to shortened physical downlink control channel (S-PDCCH) candidates in the S-TTI of the one or more subframes, and the S-PDCCH candidates in the S-TTI of the one or more subframes correspond to the downlink control information.

17. The apparatus of claim 16 , wherein the DCI format includes:

time-frequency radio resource assignment information; and

one or more of a modulation and coding rate, a S-PDCCH control size or a reference signal (RS) type.

18. The apparatus of claim 16 , wherein the DCI format is transmitted on a legacy PDCCH region, and downlink control resources used for the DCI format are identified by: a dedicated radio network temporary identifier (RNTI) value assigned by higher layers, or a predefined value in a 1-bit information element (IE) field in the DCI format.

19. The apparatus of claim 16 , wherein a number of aggregation levels (L) and a number of S-PDCCH candidates for monitoring at a given aggregation level L is configured via higher layer signaling to the UE or dynamically configured by the DCI format transmitted to the UE in the one or more subframes.

20. At least one non-transitory machine readable storage medium having instructions embodied thereon for identifying downlink control channel candidates at a user equipment (UE) for receiving downlink control information from an eNodeB, the instructions when executed by one or more processors of the UE perform the following:

decoding, at the UE, a downlink control information (DCI) format received from an eNodeB, the DCI format indicating a set of resource blocks (RBs) in one or more subframes allocated for reception or transmission of data or control information in a shortened transmission time interval (S-TTI);

identifying, at the UE, a subset of resource elements (REs) within the set of RBs in the one or more subframes, and the subset of REs correspond to shortened physical downlink control channel (S-PDCCH) candidates in the S-TTI of the one or more subframes; and

attempting, at the UE, to decode the S-PDCCH candidates in the S-TTI of the one or more subframes, wherein S-PDCCH candidates that are successfully decoded cause the UE to identify the downlink control information.

21. The at least one non-transitory machine readable storage medium of claim 20 , further comprising instructions when executed perform the following:

determining, at the UE, a starting orthogonal frequency division multiplexing (OFDM) symbol and a number of OFDM symbols in the one or more subframes used for an S-PDCCH transmission from the eNodeB;

identifying a group of REs in the OFDM symbols to form one or more shortened resource element groups (S-REGs), wherein the group of REs in the OFDM symbol corresponds to the subset of REs within the set of RBs in the one or more subframes;

identifying one or more S-TTI control channel elements (S-CCEs) from the one or more S-REGs; and

aggregating the one or more S-CCEs, wherein the S-PDCCH transmission is received from the eNodeB using the one or more aggregated S-CCEs.

22. The at least one non-transitory machine readable storage medium of claim 21 , wherein:

the starting OFDM symbol used for the S-PDCCH transmission from the eNodeB is determined based on a number of OFDM symbols in the S-TTI or configured via higher layer signaling; and

the number of OFDM symbols used for the S-PDCCH transmission from the eNodeB is signaled by the DCI format or configured via higher layer signaling, and the number of OFDM symbols depends on a UE-specific S-TTI length.

23. The at least one non-transitory machine readable storage medium of claim 21 , wherein:

the S-CCE includes three S-REGs, and each S-REG includes all REs except REs carrying a demodulation reference signal (DMRS) within one physical resource block (PRB) in one OFDM symbol in an increasing order of frequency; or

the S-CCE includes two S-REGs, and each S-REG includes all REs except REs carrying a DMRS within one PRB in two consecutive OFDM symbols; or

the S-CCE includes six S-REGs, and each S-REG includes six REs.

24. The at least one non-transitory machine readable storage medium of claim 23 , wherein:

one S-REG includes REs k within one OFDM symbol with k=k 0 +0, k 0 +1, . . . , k 0 +5, wherein k 0 is a first RE in frequency index in a PRB; or

one S-REG includes REs k within one OFDM symbol with k=k 0 +6, k 0 +7, . . . , k 0 +11; or

one S-REG includes even REs k within one OFDM symbol with k=k 0 +0, k 0 +2, . . . , k 0 +10; or

one S-REG includes odd REs k within one OFDM symbol with k=k 0 +1, k 0 +7, . . . , k 0 +11.

25. The at least one non-transitory machine readable storage medium of claim 21 , further comprising instructions when executed perform the following: mapping a block of encoded DCI symbols to REs in the one or more S-REGs, wherein the REs are not utilized for a cell-specific reference signal (CRS), zero power (ZP) channel state information reference signal (CSI-RS) or nonzero power (NZP) CSI-RS.

26. The at least one non-transitory machine readable storage medium of claim 21 , wherein:

a S-CCE number (n) corresponds to S-REGs in N S-REG S-CCE consecutive physical resource block (PRB) indices starting from a PRB N RB (0) |n×N S REG S CCE , where N RB (0) is a starting PRB within an allocated S-TTI PRB sets and N S-REG S-CCE represents a number of S-REGs per S-CCE; or

a S-CCE number (n) corresponds to S-REGs in a PRB numbered with N RB (0) +n+j×┌N RB S /N S-REG S-CCE ┐, where j=0, . . . , N S-REG S-CCE −1, and N RB S is a total number of RBs for an allocated S-TTI PRB set; or

a S-CCE number (n) corresponds to S-REGs numbered (n mod N S-REG RB )+jN S-REG RB in a PRB index (k+n×N S-REG S-CCE /N S-REG RB +N RB (0) ); where k=0, 1, . . . , N S-REG S-CCE /N S-REG RB −1, and N S-REG RB is a total number of S-REGs within a single RB; or

a S-CCE number (n) corresponds to S-REGs numbered (n mod N S-REG RB ) in PRB indices N RB (0) +n+l×┌N RB S /N S-REG S-CCE ┐, where l=0, 1, . . . , N S-REG S-CCE −1.

27. The at least one non-transitory machine readable storage medium of claim 26 , wherein:

S-CCEs corresponding to a S-PDCCH candidate m of a search space at aggregation level L is given by: L{m mod └N S-CCE,k /L┘}+i, wherein i−0, . . . , L−1, m−0, 1, . . . M (L) −1, and M (L) is a number of S-PDCCH candidates to monitor at aggregation level L; or

S-CCEs corresponding to a S-PDCCH candidate m of an S-PDCCH specific search space SS k (L) is given by: L{(Y k +m)mod └N S-CCE,k /L┘}+i, wherein i=0, . . . , L−1, m=0, 1, . . . M (L) is and M (L) is a number of S-PDCCH candidates to monitor at aggregation level L in an S-TTI RB set, and Y k is defined by: Y k =(A·Y k-1 ) mod D, wherein Y −1 =n RNTI ≠0, A−39827, D−65537, and k is an S-TTI index within the one or more subframes, wherein N S-CCE,k is a number of S-CCEs in a control region of the S-PDCCH in S-TTI k.

28. The at least one non-transitory machine readable storage medium of claim 20 , wherein:

a DCI format used to schedule a shortened physical downlink shared channel (S-PDSCH) and a shortened physical uplink shared channel (S-PUSCH) in the S-TTI in the one or more subframes is received on a legacy PDCCH region, and legacy PDCCH candidates are determined based on a dedicated cell radio network temporary identifier (C-RNTI) assigned by higher layers; or

a DCI format used to schedule the S-PDSCH and the S-PUSCH in the S-TTI in the one or more subframes is received over the S-PDCCH in the S-TTI in the one or more subframes based on higher layers.

29. The at least one non-transitory machine readable storage medium of claim 20 , wherein:

a DCI format used to schedule a shortened physical downlink shared channel (S-PDSCH) and a shortened physical uplink shared channel (S-PUSCH) in the S-TTI in the one or more subframes is received on a legacy PDCCH region when the UE is configured with a cell-specific reference signal (CRS) for S-PDCCH demodulation; or

a DCI format used to schedule the S-PDSCH and the S-PUSCH in the S-TTI in the one or more subframes is received over the S-PDCCH when the UE is not configured with CRS for S-PDCCH demodulation.

30. The at least one non-transitory machine readable storage medium of claim 20 , wherein:

a number of information bits in a DCI format used for a shortened physical downlink shared channel (S-PDSCH) is equal to a number of information bits in a DCI format used for shortened physical uplink shared channel (S-PUSCH) scheduling in a single S-TTI; and

a DCI format used for the S-PDSCH and the DCI format used for the S-PUSCH scheduling are distinguished using a 1-bit flag information element (IE) that is included in each of the DCI format used for the S-PDSCH and the DCI format used for the S-PUSCH scheduling.