Search space design for control channel in wireless communication
Aspects of the present disclosure provide various flexible search space designs that can handle UEs with various capabilities and limitations. In some aspects of the disclosure, the downlink bandwidth may be divided into several self-contained sub-bands. Each sub-band may include one or more OFDM subcarriers or tones, and each UE may be configured to monitor one or more of the sub-bands for its downlink control channel. The sub-band is self-contained in such a way that each sub-band includes CCEs that are mapped to resource elements contained in the same sub-band. In some aspects of the disclosure, different sub-bands can be configured with the different transmission modes and pilot densities. The transmission mode, pilot density, and layer-ID may be determined as a function of each UE's search space.
1. A method of wireless communication operable at a scheduling entity,
comprising:
dividing a bandwidth into a plurality of sub-bands;
allocating a search space to each of a plurality of subordinate entities, wherein the search space comprises one or more control channel elements (CCEs) each mapped to one or more resource element groups (REGs) that are located in a same one of the plurality of sub-bands;
configuring at least two of the plurality of sub-bands to have respective sub-band configurations that are different in terms of reference signal configuration and pilot density configuration, wherein a first sub-band is configured as a broadcast-based control sub-band and a second sub-band is configured as a beamformed control sub-band;
transmitting a broadcast signal in the broadcast-based control sub-band;
transmitting a UE-specific signal in the beamformed control sub-band; and
transmitting one or more downlink control messages to the plurality of subordinate entities utilizing the one or more CCEs.
2. The method of claim 1 , further comprising:
mapping consecutive CCEs of the one or more CCEs to the REGs, wherein the REGs are distributed in frequency or consecutive in frequency.
3. The method of claim 1 , further comprising:
determining a pilot density as a function of the search space.
4. The method of claim 1 , further comprising:
determining a transmission mode as a function of the search space, wherein the transmission mode comprises at least one of single-layer mode, two-layer two-port space frequency block coding (SFBC) mode, multi-layer multiple-input and multiple-output (MIMO) mode, or multi-user MIMO mode.
5. The method of claim 4 , further comprising: determining a MIMO layer of a subordinate entity operating in the multi-user MIMO mode based on the search space of the subordinate entity.
6. The method of claim 1 , wherein a sub-band of the plurality of sub-bands is configured to have different configurations for a same subordinate entity in different transmission time intervals based on channel conditions.
7. A method of wireless communication operable at a subordinate entity, comprising:
receiving, from a scheduling entity, a sub-band configuration that indicates a plurality of sub-bands of a bandwidth, wherein at least two of the plurality of sub-bands have respective sub-band configurations that are different in terms of reference signal configuration and pilot density configuration, wherein a first sub-band is configured as a broadcast-based control sub-band and a second sub-band is configured as a beamformed control sub-band;
determining a search space comprising one or more control channel elements (CCEs), wherein each of the CCEs is mapped to one or more resource element groups (REGs) that are located in a same one of the plurality of sub-bands;
receiving a broadcast signal in the broadcast-based control sub-band;
receiving a UE-specific signal in the beamformed control sub-band; and
receiving one or more downlink control messages from the scheduling entity utilizing the one or more CCEs.
8. The method of claim 7 , wherein the one or more CCEs comprise:
consecutive CCEs that are mapped to the REGs that are distributed in frequency or consecutive in frequency.
9. The method of claim 7 , further comprising:
receiving user data in a Physical Downlink Shared Channel (PDSCH) utilizing one of the plurality of sub-bands.
10. The method of claim 7 , further comprising:
determining a pilot density as a function of the search space.
11. The method of claim 7 , further comprising:
determining a transmission mode as a function of the search space, wherein the transmission mode comprises at least one of single-layer mode, two-layer two-port space frequency block coding (SFBC) mode, multi-layer multiple-input and multiple-output (MIMO) mode, or multi-user MIMO mode.
12. The method of claim 11 , further comprising:
determining a MIMO layer when operating in the multi-user MIMO mode based on the search space of the subordinate entity.
13. The method of claim 7 , wherein a sub-band of the plurality of sub-bands is configured to have different configurations for a same subordinate entity in different transmission time intervals based on channel conditions.
14. A scheduling entity configured for wireless communication comprising:
a communication interface configured to communicate with a plurality of subordinate entities;
a memory storing executable code; and
a processor operatively coupled to the communication interface and the memory,
wherein the processor is configured by the executable code to:
divide a bandwidth into a plurality of sub-bands;
allocate a search space to each of the plurality of subordinate entities, wherein the search space comprises one or more control channel elements (CCEs) each mapped to one or more resource element groups (REGs) that are located in a same one of the plurality of sub-bands;
configure at least two of the plurality of sub-bands to have respective sub-band configurations that are different in terms of reference signal configuration and pilot density configuration, wherein a first sub-band is configured as a broadcast-based control sub-band and a second sub-band is configured as a beamformed control sub-band;
transmit a broadcast signal, utilizing the communication interface, in the broadcast-based control sub-band;
transmit a UE-specific signal, utilizing the communication interface, in the beamformed control sub-band; and
transmit one or more downlink control messages, utilizing the communication interface, to the plurality of subordinate entities utilizing the one or more CCEs.
15. The scheduling entity of claim 14 , wherein the processor is further configured to:
map consecutive CCEs of the one or more CCEs to the REGs, wherein the REGs are distributed in frequency or consecutive in frequency.
16. The scheduling entity of claim 14 , wherein the processor is further configured to:
determine a pilot density as a function of the search space.
17. The scheduling entity of claim 14 , wherein the processor is further configured to:
determine a transmission mode as a function of the search space, wherein the transmission mode comprises at least one of single-layer mode, two-layer two-port space frequency block coding (SFBC) mode, multi-layer multiple-input and multiple-output (MIMO) mode, or multi-user MIMO mode.
18. The scheduling entity of claim 17 , wherein the processor is further configured to:
determine a MIMO layer of a subordinate entity operating in the multi-user MIMO mode based on the search space of the subordinate entity.
19. A subordinate entity configured for wireless communication comprising:
a communication interface configured to communicate with a scheduling entity;
a memory storing executable code; and
a processor operatively coupled to the communication interface and the memory,
wherein the processor is configured by the executable code to:
receive a sub-band configuration that indicates a plurality of sub-bands of a bandwidth, wherein at least two of the plurality of sub-bands have respective sub-band configurations that are different in terms of reference signal configuration and pilot density configuration, wherein a first sub-band is configured as a broadcast-based control sub-band and a second sub-band is configured as a beamformed control sub-band;
determine a search space comprising one or more control channel elements (CCEs), wherein each of the CCEs is mapped to one or more resource element groups (REGs) that are located in a same one of the plurality of sub-bands;
receive a broadcast signal, utilizing the communication interface, in the broadcast-based control sub-band;
receive a UE-specific signal, utilizing the communication interface, in the beamformed control sub-band; and
receive one or more downlink control messages, utilizing the communication interface, from the scheduling entity utilizing the one or more CCEs.
20. The subordinate entity of claim 19 , wherein the one or more CCEs comprise:
consecutive CCEs that are mapped to the REGs that are distributed in frequency or consecutive in frequency.
21. The subordinate entity of claim 19 , wherein the processor is further configured to:
receive user data in a Physical Downlink Shared Channel (PDSCH) utilizing one of the plurality of sub-bands.
22. The subordinate entity of claim 19 , wherein the processor is further configured to:
determine a pilot density as a function of the search space.
23. The subordinate entity of claim 19 , wherein the processor is further configured to:
determine a transmission mode as a function of the search space, wherein the transmission mode comprises at least one of single-layer mode, two-layer two-port space frequency block coding (SFBC) mode, multi-layer multiple-input and multiple-output (MIMO) mode, or multi-user MIMO mode.
24. The subordinate entity of claim 23 , wherein the processor is further configured to:
determine a MIMO layer when operating in the multi-user MIMO mode based on the search space of the subordinate entity.