Downlink control information (DCI) design for low cost devices
Certain aspects of the present disclosure relate to techniques for reducing the decoding complexity for low cost devices (e.g., low cost UEs). One technique may include simplifying the PDCCH format. This may include generating a compact DCI format for transmitting DCI to a low cost device. The compact DCI format may correspond to at least one standard DCI format used by a regular UE and may comprise a reduced number of bits when compared to the standard DCI format. Another technique may include reducing the number of blind decodes. This technique may include selecting a set of resources for transmitting DCI from a limited set of decoding candidates, such that a receiving low cost device need only perform blind decodes for the limited set of decoding candidates.
1. A method for wireless communications, comprising:
generating downlink control information (DCI) according to a compact DCI format used for at least one of uplink (UL) or downlink (DL) communications by a first device of a first type, wherein the compact DCI format corresponds to at least one standard DCI format used by a second device of a second type and comprises a reduced number of bits when compared to the at least one standard DCI format; and
transmitting the DCI according to the compact DCI format, wherein the DCI comprises DCI for a limited set of resource allocation possibilities and lacks a bit allocated for a frequency hopping flag.
2. The method of claim 1 , wherein the first device of the first type comprises reduced processing capability when compared to the second device of the second type.
3. The method of claim 1 , wherein the first device comprises a low cost User Equipment (UE).
4. The method of claim 1 , wherein generating the DCI comprises generating the DCI without bits allocated for resource allocation information, wherein the DCI allocates resources for one user at a time.
5. The method of claim 1 , wherein:
generating the DCI comprises generating the DCI for a limited set of Hybrid Automatic Repeat Request (HARQ) processes, and
the DCI lacks an indication of a HARQ process.
6. The method of claim 1 , wherein generating the DCI comprises generating the DCI without a bit allocated for differentiating between DCI formats 1A and 0, wherein the DCI formats 1A and 0 have different sizes.
7. The method of claim 1 , wherein:
generating the DCI comprises generating a reduced length cyclic redundancy check (CRC) for the DCI, and
generating the reduced length CRC comprises generating a CRC of a first length and truncating the CRC of the first length to generate the reduced length CRC.
8. The method of claim 1 , wherein generating the DCI comprises at least one of:
generating the DCI without bits allocated for redundancy version (RV), or
generating the DCI without bits allocated for sounding reference signal (SRS) request.
9. The method of claim 1 , wherein:
the DCI comprises DCI for a limited modulation and coding scheme (MCS), and
the limited MCS comprises Quadrature Phase Shift Keying (QPSK) with a limited set of transport block sizes.
10. The method of claim 1 , wherein generating the DCI comprises at least one of:
generating the DCI with reduced bit-width for transmitter power control (TPC); or
generating the DCI with reduced bit-width for demodulation deference signal (DM-RS).
11. The method of claim 1 , wherein the DCI lacks a bit allocated for a multi-cluster flag, or the DCI lacks a bit allocated for Virtual Resource Block assignment.
12. The method of claim 1 , further comprising:
determining whether periodic channel state information (CSI) is supported;
keeping aperiodic CSI if periodic CSI is not supported based on the determination; and
removing aperiodic CSI if periodic CSI is supported based on the determination.
13. The method of claim 1 , wherein the DCI lacks a bit allocated for downlink assignment index (DAI) or UL assignment index, wherein a one to one mapping is maintained between DL subframe and UL subframe for each UE.
14. The method of claim 1 , further comprising:
selecting a set of resources for transmitting the DCI from a limited set of decoding candidates; and
transmitting the DCI using the set of resources, such that a receiving UE need only perform blind decodes for the limited set of decoding candidates.
15. A method for wireless communications by a first device of a first type, comprising:
receiving downlink control information (DCI) according to a compact DCI format used for at least one of uplink (UL) or downlink (DL) communications, wherein the compact DCI format corresponds to at least one standard DCI format used by a second device of a second type and comprises a reduced number of bits when compared to the at least one standard DCI format; and
processing the received DCI according to the compact DCI format, wherein the received DCI comprises DCI for a limited set of resource allocation possibilities and lacks a bit allocated for a frequency hopping flag.
16. The method of claim 15 , wherein the first device of the first type comprises reduced processing capability when compared to the second device of the second type.
17. The method of claim 15 , wherein the first device comprises a low cost user equipment (UE).
18. The method of claim 15 , wherein the DCI lacks bits allocated for resource allocation information, and wherein the DCI allocates resources for one user at a time.
19. The method of claim 15 , wherein:
the DCI comprises DCI for a limited set of hybrid automatic repeat request (HARQ) processes, and
the DCI lacks an indication of a HARQ process.
20. The method of claim 15 , wherein the DCI lacks a bit allocated for differentiating between DCI formats 1A and 0, wherein the DCI formats 1A and 0 have different sizes.
21. The method of claim 15 , wherein:
the DCI comprises a reduced length cyclic redundancy check (CRC) for the DCI, and
the reduced length CRC comprises a CRC generated by generating a CRC of a first length and truncating the CRC of the first length to generate the reduced length CRC.
22. The method of claim 15 , wherein the DCI lacks at least one of:
bits allocated for redundancy version (RV), or
bits allocated for sounding reference signal (SRS) request.
23. The method of claim 15 , wherein:
the DCI comprises DCI for a limited modulation and coding scheme (MCS), and
the limited MCS comprises Quadrature Phase Shift Keying (QPSK) with a limited set of transport block sizes.
24. The method of claim 15 , wherein the DCI comprises at least one of:
DCI with reduced bit-width for transmitter power control (TPC), or
DCI with reduced bit-width for demodulation reference signal (DM-RS).
25. The method of claim 15 , wherein the DCI lacks a bit allocated for multi-cluster flag, or the DCI lacks a bit allocated for Virtual Resource Block assignment.
26. The method of claim 15 , wherein the DCI comprises:
DCI with aperiodic channel state information (CSI) if periodic CSI is not supported, and
DCI without aperiodic CSI if periodic CSI is supported.
27. The method of claim 15 , wherein the DCI lacks a bit allocated for downlink assignment index (DAI) or UL assignment index, wherein a one to one mapping is maintained between DL subframe and UL subframe for each UE.
28. The method of claim 15 , wherein:
the DCI is transmitted using a set of resources selected from a limited set of decoding candidates; and
the method further comprises performing blind decodes for the limited set of decoding candidates to detect a downlink control channel containing the DCI.
29. An apparatus for wireless communications, comprising:
at least one processor;
memory coupled with the at least one processor, the memory storing instructions executable by the at least one processor to cause the apparatus to:
generate downlink control information (DCI) according to a compact DCI format used for least one of uplink (UL) or downlink (DL) communications by a first device of a first type, wherein the compact DCI format corresponds to at least one standard DCI format used by a second device of a second type and comprises a reduced number of bits when compared to the at least one standard DCI format; and
transmit the DCI according to the compact DCI format, wherein the DCI comprises DCI for a limited set of resource allocation possibilities and lacks a bit allocated for a frequency hopping flag.
30. An apparatus for wireless communications by a first device of a first type, comprising:
at least one processor;
memory coupled with the at least one processor, the memory storing instructions executable by the at least one processor to cause the apparatus to:
instructions stored in the memory and executable by the at least one processor to cause the apparatus to:
receive downlink control information (DCI) according to a compact DCI format used for at least one of uplink (UL) or downlink (DL) communications, wherein the compact DCI format corresponds to at least one standard DCI format used by a second device of a second type and comprises a reduced number of bits when compared to the at least one standard DCI format; and
process the received DCI according to the compact DCI format, wherein the received DCI comprises DCI for a limited set of resource allocation possibilities and lacks a bit allocated for a frequency hopping flag.
31. An apparatus for wireless communication comprising:
means for generating downlink control information (DCI) according to a compact DCI format used for least one of uplink (UL) or downlink (DL) communications by a first device of a first type, wherein the compact DCI format corresponds to at least one standard DCI format used by a second device of a second type and comprises a reduced number of bits when compared to the at least one standard DCI format; and
means for transmitting the DCI according to the compact DCI format, wherein the DCI comprises DCI for a limited set of resource allocation possibilities and lacks a bit allocated for a frequency hopping flag.
32. An apparatus for wireless communications by a first device of a first type, comprising:
means for receiving downlink control information (DCI) according to a compact DCI format used for at least one of uplink (UL) or downlink (DL) communications, wherein the compact DCI format corresponds to at least one standard DCI format used by a second device of a second type and comprises a reduced number of bits when compared to the at least one standard DCI format; and
means for processing the received DCI according to the compact DCI format, wherein the received DCI comprises DCI for a limited set of resource allocation possibilities and lacks a bit allocated for a frequency hopping flag.
33. A non-transitory computer readable medium storing computer executable code thereon for wireless communication comprising code for:
generating downlink control information (DCI) according to a compact DCI format used for least one of uplink (UL) or downlink (DL) communications by a first device of a first type, wherein the compact DCI format corresponds to at least one standard DCI format used by a second device of a second type and comprises a reduced number of bits when compared to the at least one standard DCI format; and
transmitting the DCI according to the compact DCI format, wherein the DCI comprises DCI for a limited set of resource allocation possibilities and lacks a bit allocated for a frequency hopping flag.
34. A non-transitory computer readable medium storing computer executable code thereon for wireless communication by a first device of a first type comprising code for:
receiving downlink control information (DCI) according to a compact DCI format used for at least one of uplink (UL) or downlink (DL) communications, wherein the compact DCI format corresponds to at least one standard DCI format used by a second device of a second type and comprises a reduced number of bits when compared to the at least one standard DCI format; and
processing the received DCI according to the compact DCI format, wherein the received DCI comprises DCI for a limited set of resource allocation possibilities and lacks a bit allocated for a frequency hopping flag.