BACKGROUND

The following relates generally to wireless communications, and more specifically to channel state information (CSI) computation for effective isotropic radiated power (EIRP)-constrained transmissions.

Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include fourth generation (4G) systems such as Long Term Evolution (LTE) systems, LTE-Advanced (LTE-A) systems, or LTE-A Pro systems, and fifth generation (5G) systems which may be referred to as New Radio (NR) systems. These systems may employ technologies such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal frequency division multiple access (OFDMA), or discrete Fourier transform-spread-orthogonal frequency division multiplexing (DFT-S-OFDM). A wireless multiple-access communications system may include a number of base stations or network access nodes, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE).

In some wireless communications systems, such as those operating in a contention-based or other shared radio frequency spectrum band, wireless devices (e.g., UEs, base stations) may be limited by one or more transmission constraints. For instance, regulatory agencies (e.g., Federal Communications Commission (FCC)) may set a total power limit (e.g., EIRP limit), which may be based on whether the spectrum in use is unlicensed or licensed, whether the frequency band is in use, etc. Further, in some cases, in addition to the total power limit in unlicensed spectrum, wireless devices may be limited by an overall power spectral density (PSD) limit. In some cases, a UE may not be aware a base station is operating under EIRP constraints, which may impact channel quality reporting. Thus, efficient techniques for reporting channel quality, for example, based on EIRP constraints at the base station, may serve to optimize network performance.

SUMMARY

The described techniques relate to improved methods, systems, devices, or apparatuses that support channel state information (CSI) computation for effective isotropic radiated power (EIRP) constrained transmissions. Generally, the described techniques provide for different CSI measurement and reporting techniques based on an operating mode (i.e., standard mode, or EIRP-constrained mode) at the base station. In some examples, regulatory guidance may impose a total power limit, and/or a power spectral density (PSD) limit, which may be based in part on frequency band in use, unlicensed or licensed spectrum, etc. In some aspects, EIRP limits may be specified per unit bandwidth (e.g., 1 megahertz (MHz) bandwidth). In one example, assuming a user equipment (UE) allocation exceeds 1 MHz bandwidth (e.g., more than 1 resource block (RB) at 60 kilohertz (kHz) subcarrier spacing), EIRP limitations may be applied on a per RB basis. In some circumstances, for a particular UE computing and reporting CSI, EIRP constraints may be accounted for to improve reporting accuracy, as well as optimize uplink power. For instance, a UE may employ different modes of CSI reporting based on explicit signaling (e.g., Radio Resource Control (RRC)), or path loss measured at the UE.

In some cases, the base station may signal a scaling factor to account for a transmit power backoff in EIRP-constrained mode, reduce the scheduled modulation and coding scheme (MCS) (e.g., modulation depth), and increase the scheduled rank, modify the mapping scheme used for downlink (e.g., Physical Downlink Shared Channel (PDSCH), or NR-PDSCH) transmissions, provide an offset applicable for EIRP-constrained scenarios, or a combination thereof. In some other cases, the base station may switch to a different transmission scheme (e.g., space time block coding (STBC), or space frequency block coding (SFBC)). In some cases, the network or base station may introduce antenna port selection, for example, while utilizing a codebook based precoding scheme. For instance, the base station may select a subset of possible codebooks to specify for port selection when the number of antennas exceeds a threshold. That is, under EIRP constraints, the base station may only use a subset of antenna ports to compensate for the smaller scaling factor. In some cases, while operating in EIRP-constrained mode, the payload size may be calculated to be independent of the number of layers used. In such cases, the UE may utilize a combination of the number of layers used for transport block size (TBS) determination, and the number of actual transmission layers to compute/report CSI.

A method of wireless communications at a UE is described. The method may include receiving a downlink transmission from a base station over a wireless channel, selecting, based on the received downlink transmission, a CSI computation mode for the wireless channel, where the CSI computation mode is based on an EIRP constraint, measuring a set of one or more CSI reference signals (CSI-RSs) from the base station to obtain a CSI measurement, and transmitting a CSI report to the base station based on the selected CSI computation mode and the CSI measurement.

An apparatus for wireless communications at a UE is described. The apparatus may include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to receive a downlink transmission from a base station over a wireless channel, select, based on the received downlink transmission, a CSI computation mode for the wireless channel, where the CSI computation mode is based on an effective isotropic radiated power (EIRP) constraint, measure a set of one or more CSI-RSs from the base station to obtain a CSI measurement, and transmit a CSI report to the base station based on the selected CSI computation mode and the CSI measurement.

Another apparatus for wireless communications at a UE is described. The apparatus may include means for receiving a downlink transmission from a base station over a wireless channel, selecting, based on the received downlink transmission, a CSI computation mode for the wireless channel, where the CSI computation mode is based on an EIRP constraint, measuring a set of one or more CSI-RSs from the base station to obtain a CSI measurement, and transmitting a CSI report to the base station based on the selected CSI computation mode and the CSI measurement.

A non-transitory computer-readable medium storing code for wireless communications at a UE is described. The code may include instructions executable by a processor to receive a downlink transmission from a base station over a wireless channel, select, based on the received downlink transmission, a CSI computation mode for the wireless channel, where the CSI computation mode is based on an EIRP constraint, measure a set of one or more CSI-RSs from the base station to obtain a CSI measurement, and transmit a CSI report to the base station based on the selected CSI computation mode and the CSI measurement.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, receiving the downlink transmission from the base station may include operations, features, means, or instructions for receiving in the downlink transmission an indication of the CSI computation mode, where selecting the CSI computation mode may be further based on the indication of the CSI computation mode.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, receiving the downlink transmission from the base station may include operations, features, means, or instructions for receiving in the downlink transmission an indication of the CSI computation mode, where selecting the CSI computation mode may be further based on the indication of the CSI computation mode.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining a pathloss of the downlink transmission, where selecting the CSI computation mode may be further based on the pathloss of the downlink transmission.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for scaling the CSI measurement based on the selected CSI computation mode, where the CSI report may be based on the scaled CSI measurement.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving a scaling factor for the selected CSI computation mode from the base station, where the CSI measurement may be scaled using the received scaling factor.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for identifying a precoder of the base station, the precoder based on a number of antenna ports in use by the base station, where the number of antenna ports in use by the base station may be fewer than a total number of antenna ports of the base station and using the precoder to receive one or more of: the downlink transmission or a second downlink transmission.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining a transport block size based on a rank of the downlink transmission and using the determined transport block size to receive one or more of: the downlink transmission or a second downlink transmission.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving from the base station a first rank parameter associated with a transport block size and a second rank parameter indicating a transmission rank, determining the transport block size based on the received rank parameter and using the determined transport block size and the indicated transmission rank to receive one or more of: the downlink transmission or a second downlink transmission.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving from the base station a transport block size scaling factor, determining a transport block size based on the transport block size scaling factor and using the determined transport block size to receive one or more of: the downlink transmission or a second downlink transmission.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for using, based on the CSI computation mode, STBC/SFBC to receive one or more of: the downlink transmission or a second downlink transmission.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, one or more of the downlink transmission or a second downlink transmission may include operations, features, means, or instructions for mapping different portions of a code block of the data transmission to different transmit layers, mapping the different transmit layers to frequency and time resources and using the mapping of the different portions of the code block and the different transmit layers to receive the transport block.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for adjusting a measured pathloss of the base station based on the base station operating according to the EIRP constraint and setting an uplink power for a random access procedure with the base station based on the scaling.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving an offset parameter from the base station, where adjusting the measured pathloss may be based on the received offset parameter.

A method of wireless communications is described. The method may include selecting a CSI computation mode for a wireless channel based on an EIRP constraint at the base station, performing a downlink transmission to a UE over the wireless channel, the downlink transmission indicating the CSI computation mode for the wireless channel, transmitting a set of one or more CSI-RSs over the wireless channel in accordance with the EIRP constraint, and receiving from the UE a CSI report based on the selected CSI computation mode and the transmitted set of CSI-RSs.

An apparatus for wireless communications is described. The apparatus may include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to select a CSI computation mode for a wireless channel based on an EIRP constraint at the base station, perform a downlink transmission to a UE over the wireless channel, the downlink transmission indicating the CSI computation mode for the wireless channel, transmit a set of one or more CSI-RSs over the wireless channel in accordance with the EIRP constraint, and receive from the UE a CSI report based on the selected CSI computation mode and the transmitted set of CSI-RSs.

Another apparatus for wireless communications is described. The apparatus may include means for selecting a CSI computation mode for a wireless channel based on an EIRP constraint at the base station, performing a downlink transmission to a UE over the wireless channel, the downlink transmission indicating the CSI computation mode for the wireless channel, transmitting a set of one or more CSI-RSs over the wireless channel in accordance with the EIRP constraint, and receiving from the UE a CSI report based on the selected CSI computation mode and the transmitted set of CSI-RSs.

A non-transitory computer-readable medium storing code for wireless communications is described. The code may include instructions executable by a processor to select a CSI computation mode for a wireless channel based on an EIRP constraint at the base station, perform a downlink transmission to a UE over the wireless channel, the downlink transmission indicating the CSI computation mode for the wireless channel, transmit a set of one or more CSI-RSs over the wireless channel in accordance with the EIRP constraint, and receive from the UE a CSI report based on the selected CSI computation mode and the transmitted set of CSI-RSs.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for generating an indication of the CSI computation mode, where the downlink transmission includes the indication of the CSI computation mode.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting the scaling factor to the UE.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for identifying a precoder of the base station, the precoder based at least in on part on a number of antenna ports in use by the base station, where the number of antenna ports in use by the base station may be fewer than a total number of base station antenna ports.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining a transport block size based on a rank of the downlink transmission and using the determined transport block size to transmit one or more of: the downlink transmission or a second downlink transmission.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining a transport block size, transmitting to the UE a first rank parameter associated with the determined transport block size and a second rank parameter indicating a transmission rank and using the determined transport block size and the indicated transmission rank to transmit one or more of: the downlink transmission or a second downlink transmission.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining a transport block size, transmitting to the UE a transport block size scaling factor based on the determined transport block size and using the determined transport block size to transmit one or more of: the downlink transmission or a second downlink transmission.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for using, based on the CSI computation mode, STBC/SFBC to transmit one or more of: the downlink transmission or a second downlink transmission.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, one or more of the downlink transmission or a second downlink transmission may include operations, features, means, or instructions for mapping different portions of a code block of the transport block to different transmit layers, mapping the different transmit layers to frequency and time resources and using the mapping of the different portions of the code block and the different transmit layers to transmit the transport block.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting a pathloss offset parameter to the UE based on the EIRP constraint.

