Physical downlink control channel design for narrow band internet of things
Narrowband downlink control channel (NB-PDCCH) design for Narrowband Internet of Thing (IoT) devices is proposed. In one novel aspect, NB-PDCCH spans both first and second slots in the region of legacy physical downlink shared channel (PDSCH). A plurality of physical resource blocks (PRBs) is allocated for NB-PDCCH transmission that carry downlink control information (DCI). Furthermore, each NB-IoT device can be configured with n PRB PRB pairs for NB-PDCCH transmission (e.g., n PRB =1, 2, 4, or 8), and an NB-PDCCH transmission time interval (TTI) is composed by n PRB subframes. An NB-PDCCH is encoded and occupies multiple narrowband control channel elements (NCCEs) based on aggregation level. In a preferred embodiment, each PRB pair for NB-PDCCH occupies two NCCEs.
1. A method comprising:
receiving a control signal by a user equipment (UE) to determine received physical resource blocks (PRBs) that carry downlink control information;
determining a set of candidate narrowband physical downlink control channels (NB-PDCCHs) within the PRBs, wherein each NB-PDCCH is associated with a set of narrowband control channel elements (NCCEs) for NB-PDCCH transmission;
collecting a plurality of resource elements (REs) for each NCCE, wherein each NCCE consists of a number of REs based on an NCCE to RE de-mapping rule, wherein one PRB is allocated for one NB-PDCCH having two NCCEs, wherein a first NCCE of the PRB is mapped to REs belonging to a first plurality of contiguous subcarriers of the PRB, and wherein a second NCCE of the PRB is mapped to REs belonging to a second plurality of contiguous subcarriers of the PRB; and
decoding the downlink control information that are mapped to the collected REs.
2. The method of claim 1 , wherein the collected REs for each NCCE are physically contiguous REs excluding REs allocated for NB-PDCCH demodulation reference signal transmission within a block of physically contiguous radio resources.
3. The method of claim 2 , wherein the NB-PDCCH demodulation reference signal is a cell specific reference signal (CRS).
4. The method of claim 1 , wherein the UE decodes the downlink control information in a single NCCE per NB-PDCCH transmission.
5. The method of claim 1 , wherein the UE decodes the downlink control information in a plurality of NCCEs per NB-PDCCH transmission.
6. The method of claim 1 , wherein the control signal defines a UE search space for the PRBs that carry the downlink control information.
7. A user equipment (UE) comprising:
a receiver that receives a control signal to determine received physical resource blocks (PRBs) that carry downlink control information in a cellular network;
a controller that determines a set of candidate narrowband physical downlink control channels (NB-PDCCHs) within the PRBs, wherein each NB-PDCCH is associated with a set of narrowband control channel elements (NCCEs) for NB-PDCCH transmission;
a collector that collects a plurality of resource elements (REs) for each NCCE, wherein each NCCE consists of a number of REs based on an NCCE to RE de-mapping rule, wherein one PRB is allocated for one NB-PDCCH having two NCCEs, wherein a first NCCE of the PRB is mapped to REs belonging to a first plurality of contiguous subcarriers of the PRB, and wherein a second NCCE of the PRB is mapped to REs belonging to a second plurality of contiguous subcarriers of the PRB; and
a decoder that decodes the downlink control information that are mapped to the collected REs.
8. The UE of claim 7 , wherein the collected REs for each NCCE are physically contiguous REs excluding REs allocated for NB-PDCCH demodulation reference signal transmission within a block of physically contiguous radio resources.
9. The UE of claim 8 , wherein the NB-PDCCH demodulation reference signal is a cell specific reference signal (CRS).
10. The UE of claim 7 , wherein the UE decodes the downlink control information in a single NCCE per NB-PDCCH transmission.
11. The UE of claim 7 , wherein the UE decodes the downlink control information in a plurality of NCCEs per NB-PDCCH transmission.
12. The UE of claim 7 , wherein the control signal defines a UE search space for the PRBs that carry the downlink control information.
13. A method comprising:
transmitting a control signal from a communication device, wherein a set of physical resource blocks (PRBs) is allocated to carry downlink control information (DCI);
determining a set of candidate narrowband physical downlink control channels (NB-PDCCHs) within the PRBs, wherein each NB-PDCCH is associated with a set of narrowband control channel elements (NCCEs) to potentially carry the DCI;
mapping a plurality of resource elements (REs) to each NCCE based on an RE to NCCE mapping rule, wherein one PRB is allocated for one NB-PDCCH having two NCCEs, wherein a first NCCE of the PRB is mapped to REs belonging to a first plurality of contiguous subcarriers of the PRB, and wherein a second NCCE of the PRB is mapped to REs belonging to a second plurality of contiguous subcarriers of the PRB; and
encoding the DCI over the set of NCCEs to be transmitted to a UE if the DCI is intended for the UE.
14. The method of claim 13 , wherein the downlink control information is carried in a single NCCE per NB-PDCCH transmission.
15. The method of claim 13 , wherein the downlink control information is carried in a plurality of NCCEs per NB-PDCCH transmission.
16. The method of claim 13 , wherein the control signal defines a UE search space for the PRBs that carry the downlink control information.
17. The method of claim 16 , wherein the UE search space is defined by an aggregation level of NCCEs per NB-PDCCH, a repetition number for NB-PDCCH transmission time interval (TTI) repetition, and a number of candidate NB-PDCCHs.