Physical downlink control channel, PDCCH, search space design for fifth generation, 5G, and latency reduction
Techniques for xPDCCH (5G (Fifth Generation) Physical Downlink Control Channel) design are discussed. In various aspects, xPDCCH can be transmitted via one or more OFDM (Orthogonal Frequency Division Multiplexing) symbols, with each OFDM symbol comprising a xPDCCH search space. Each xPDCCH search space can have one or two distinct xPDCCH sets, with each xPDCCH set having a xCCE (5G Control Channel Element) starting position that can be based on one of several predetermined rules, and can depend on one or more factors.
1. An apparatus configured to be employed within a User Equipment (UE), comprising:
a memory; and
one or more processors configured to:
determine, for each of a plurality of orthogonal frequency division multiplexing (OFDM) symbols in a subframe, a distinct fifth generation (5G) physical downlink control channel (xPDCCH) search space in that OFDM symbol, wherein the distinct xPDCCH search space in each of the plurality of OFDM symbols is determined based on a predefined rule and includes a starting 5G control channel element (xCCE) position determined based on a hashing table, wherein the hashing table is initialized with constants that vary between distinct OFDM symbols of the plurality of OFDM symbols; and
perform blind decoding on the distinct xPDCCH search space in each of the plurality of OFDM symbols to decode one or more 5G downlink control information (xDCI) messages.
2. The apparatus of claim 1 , wherein the distinct xPDCCH search space in each of the plurality of OFDM symbols comprises common search space of the distinct xPDCCH search space and a UE-specific search space of the distinct xPDCCH search space.
3. The apparatus of claim 1 , wherein the distinct xPDCCH search space in each of the plurality of OFDM symbols comprises xCCEs.
4. The apparatus of claim 1 , wherein the plurality of OFDM symbols includes a first OFDM symbol and a second OFDM symbol, wherein the distinct xPDCCH search space in the first OFDM symbol comprises first xCCEs and the distinct xPDCCH search space in the second OFDM symbol comprises second xCCEs, wherein the starting xCCE position of the first xCCEs is distinct from the starting xCCE position of the second xCCEs.
5. The apparatus of claim 4 , wherein the first xCCEs are a first continuous set of xCCEs, and wherein the second xCCEs are a second continuous set of xCCEs.
6. The apparatus of claim 4 , wherein the first xCCEs comprise a first pair of distinct sets of xCCEs separated by one or more xCCEs, and wherein the second xCCEs comprises a second pair of distinct sets of xCCEs separated by at least one xCCE.
7. The apparatus of claim 4 , wherein the starting xCCE position of the first xCCEs and the starting xCCE position of the second xCCEs are both functions of an OFDM symbol index, the fixed offset, and a slot number within a radio frame comprising the subframe.
8. A non-transitory machine readable medium comprising instructions that, when executed, cause a User Equipment (UE) to:
receive a set of signals via each of one or more orthogonal frequency division multiplexing (OFDM) symbols in a subframe, wherein each of the one or more OFDM symbols comprises a distinct fifth generation (5G) physical downlink control channel (xPDCCH) search space, wherein each distinct xPDCCH search space comprises one or more distinct xPDCCH sets;
determine the distinct xPDCCH search space of each of the one or more OFDM symbols based on a predefined rule, wherein the predefined rule defines a 5G control channel element (xCCE) starting position for each distinct xPDCCH set, wherein the xCCE starting position for each distinct xPDCCH set is based at least in part on one or more of a cell radio network temporary identity (C-RNTI), a subframe index of the subframe, a symbol index of the OFDM symbol comprising that distinct xPDCCH set, or a xPDCCH set index of that xPDCCH set;
calculate the xCCE starting position for each distinct xPDCCH set based on a hashing table, wherein the hashing table is initialized with constants that vary between one or more of distinct OFDM symbols of the one or more OFDM symbols, or distinct xPDCCH sets within a given OFDM symbol of the one or more OFDM symbols; and
decode one or more 5G downlink control information (xDCI) messages via blind decoding on the distinct xPDCCH search space in each of the one or more OFDM symbols.
9. The machine readable medium of claim 8 , wherein each distinct xPDCCH search space comprises a single continuous xPDCCH set.
10. The machine readable medium of claim 8 , wherein each distinct xPDCCH search space comprises a pair of distinct xPDCCH sets separated by one or more xCCEs.
11. The machine readable medium of claim 8 , wherein the xCCE starting position for each distinct xPDCCH set is based at least in part on a slot number within a radio frame comprising the subframe, and one or more predefined constants.
12. The machine readable medium of claim 8 , wherein the one or more OFDM symbols comprise N xPDCCH sym OFDM symbols, and wherein the xCCE starting position for each distinct xPDCCH set is based at least in part on N xPDCCH sym .
13. The machine readable medium of claim 8 , wherein the xPDCCH search space of at least one of the one or more OFDM symbols comprises a shortened physical downlink control channel (S-PDCCH) search space.
14. The machine readable medium of claim 13 , wherein the xCCE starting position for the S-PDCCH search space is based at least in part on a shortened transmission time interval (S-TTI) index associated with the S-PDCCH search space.
15. The machine readable medium of claim 8 , wherein the one or more OFDM symbols comprises two or more OFDM symbols.
16. An apparatus configured to be employed within an Evolved NodeB (eNB), comprising:
a memory; and
one or more processors configured to:
determine a number of orthogonal frequency division multiplexing (OFDM) symbols for fifth generation (5G) physical downlink control channel (xPDCCH) in a subframe, wherein the number of OFDM symbols for xPDCCH in the subframe is N xPDCCH sym and has a value of two or more; and
map downlink control information (DCI) messages for one or more user equipments (UEs) to a distinct xPDCCH search space in each of the first N xPDCCH sym OFDM symbols of the subframe, wherein each distinct xPDCCH search space has a 5G control channel element (xCCE) starting position defined via a predefined rule, wherein the predefined rule is based at least in part on one or more of a cell radio network temporary identity (C-RNTI), a subframe index of the subframe, or a symbol index of the OFDM symbol, and wherein the xCCE starting position is determined based on a hashing table, wherein the hashing table is initialized with constants that vary between distinct OFDM symbols of the number of OFDM symbols.
17. The apparatus of claim 16 , wherein each xPDCCH search space comprises a common search space and one or more UE-specific search spaces.
18. The apparatus of claim 16 , wherein each xPDCCH search space comprises a pair of distinct xPDCCH sets separated by one or more xCCEs.
19. The apparatus of claim 16 , wherein each xPDCCH search space comprises a continuous set of xCCEs.
20. The apparatus of claim 16 , wherein the one or more processors are further configured to generate higher layer signaling that indicates the value of N xPDCCH sym , wherein the higher layer signaling comprises one of a 5G master information block (xMIB), a 5G system information block (xSIB), or radio resource control (RRC) signaling.
21. The apparatus of claim 16 , wherein the distinct xPDCCH search space in each of the N xPDCCH sym OFDM symbols has a distinct xCCE starting position.