BACKGROUND

The following relates generally to wireless communication and more specifically to determining and indicating a range of beam correspondence between wireless nodes.

Wireless communication 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 multiple-access systems 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 code-division multiple access (CDMA) systems, time-division multiple access (TDMA) systems, frequency-division multiple access (FDMA) systems, and orthogonal frequency-division multiple access (OFDMA) systems.

By way of example, a wireless multiple-access communication system may include a number of base stations, each simultaneously supporting communication with multiple communication devices, otherwise known as user equipments (UEs). A base station may communicate with UEs on downlink (DL) channels (e.g., for transmissions from a base station to a UE) and uplink (UL) channels (e.g., for transmissions from a UE to a base station).

Wireless communication systems may operate in millimeter wave (mmW) frequency ranges, e.g., 28 GHz, 40 GHz, 60 GHz, etc. Wireless communication at these frequencies may be associated with increased signal attenuation (e.g., path loss), which may be influenced by various factors, such as temperature, barometric pressure, diffraction, etc. As a result, signal processing techniques, such as beamforming, may be used to coherently combine energy and overcome the path losses at these frequencies. Due to the increased amount of path loss in mmW communication systems, transmissions from the base station and/or the UE may be beamformed.

Wireless communication between two wireless nodes, e.g., between a base station and a UE, may use beams or beamformed signals for transmission and/or reception. A base station may transmit beamformed signals on DL beams associated with the base station. A UE may receive a signal on one or more DL beams associated with the UE. The DL beam associated with the base station and the DL beam associated with the UE used for DL communication between the base station and the UE constitute a DL beam pair. Similarly, a UE may transmit beamformed signals on UL beams associated with the UE. A base station may receive a signal on one or more UL beams associated with the base station. The UL beam associated with the UE and the UL beam associated with the base station used for UL communication between the UE and the base station constitute an UL beam pair. In some instances, the DL beam pair and the UL beam pair may be the same (e.g., may represent the same beam pairs). In other instances, differences may exist between a DL beam pair and an UL beam pair.

SUMMARY

Some examples of wireless communication systems support determining and indicating a range of beam correspondence (e.g., a level of beam reciprocity) between wireless nodes. For example, a downlink (DL) transmission, via one or more beams, from a transmitting wireless node (e.g., evolved nodeB (eNB)) may be used to identify a corresponding DL reception beam for a receiving wireless node (e.g., user equipment (UE)). The DL transmission beam and DL reception beam may be identified as a beam pair for the wireless nodes (e.g., a DL beam pair). A level of correspondence may be determined for one or both of the wireless nodes.

For example, a level of correspondence may be determined between a DL transmission beam and an uplink (UL) reception beam of a first wireless node (e.g., a transmitting wireless node) when communicating with a second wireless node (e.g., a receiving wireless node). Similarly, a level of correspondence may be determined between a DL reception beam and an UL transmission beam of the second wireless node when communicating with the first wireless node. Once a wireless node determines a level of correspondence between a transmit and receive beam, these beams may be used to communicate with other wireless nodes. A level of correspondence may be indicated such that, for example, the DL beam training information (e.g., beam pair) may be used to identify a beam pair for UL communication.

A method of wireless communication is described. The method may include exchanging one or more signals between a first wireless node and a second wireless node and determining, at the first wireless node and based at least in part on the one or more signals, a range of correspondence between at least one of a transmit beam of the first wireless node and a receive beam of the first wireless node.

An apparatus for wireless communication is described. The apparatus may include means for exchanging one or more signals between a first wireless node and a second wireless node and means for determining, at the first wireless node and based at least in part on the one or more signals, a range of correspondence between at least one of a transmit beam of the first wireless node and a receive beam of the first wireless node.

Another apparatus for wireless communication 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 operable to cause the processor to exchange one or more signals between a first wireless node and a second wireless node and determine, at the first wireless node and based at least in part on the one or more signals, a range of correspondence between at least one of a transmit beam of the first wireless node and a receive beam of the first wireless node.

A non-transitory computer readable medium for wireless communication is described. The non-transitory computer-readable medium may include instructions operable to cause a processor to exchange one or more signals between a first wireless node and a second wireless node and determine, at the first wireless node and based at least in part on the one or more signals, a range of correspondence between at least one of a transmit beam of the first wireless node and a receive beam of the first wireless node.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the range of correspondence includes full correspondence, partial correspondence, or no correspondence. Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for determining a range of correspondence between a transmit beam of the second wireless node and a receive beam of the second wireless node.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, exchanging one or more signals between the first wireless node and the second wireless node includes receiving, from the second wireless node, a signal indicating a range of calibration values associated with a transmit path and a receive path of the second wireless node. Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for using the range of calibration values to determine a range of correspondence between a transmit beam of the second wireless node and a receive beam of the second wireless node.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the range of calibration values includes at least one of a range of amplitude error of antenna weights, a range of phase error of antenna weights, or combinations thereof. In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the range of calibration values includes at least a difference between amplitude error of antenna weights associated with the transmit path and the receive path, a difference between phase error of antenna weights associated with the transmit path and the receive path, or combinations thereof.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, exchanging one or more signals between the first wireless node and the second wireless node includes receiving, from the second wireless node, a signal indicating a downlink quality of a transmission on a downlink beam pair that includes the transmit beam of the first wireless node and a receive beam of the second wireless node. Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for determining, at the first wireless node, an uplink quality of a transmission on an uplink beam pair that includes a transmit beam of the second wireless node and the receive beam of the first wireless node.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the first wireless node and the second wireless node may apply a similar beam shape for the transmit beam and the receive beam. In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the similar beam shape indicates that the transmit beam and the receive beam use a same set of antenna elements, or beam widths, or point to a same direction, or a combination thereof. Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for using the downlink quality and the uplink quality to determine the range of correspondence between the transmit beam of the second wireless node and the receive beam of the second wireless node.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, receiving the signal indicating the downlink quality includes receiving an indication of at least one of a reference signal received power (RSRP), or a reference signal received quality (RSRQ), or a signal-to-noise ratio (SNR), or a signal-to-interference-plus-noise ratio (SINR), or a channel quality indicator (CQI), or a received signal strength indicator (RSSI), or a combination thereof of the transmission on the downlink beam pair. In some examples of the method, apparatus, and non-transitory computer-readable medium described above, determining the uplink quality includes determining at least one of an RSRP, or an RSRQ, or an SNR, or an SINR, or a CQI or an RSSI, or a combination thereof of the transmission on the uplink beam pair.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the transmit beam of the first wireless node may be associated with a higher quality than other transmit beams of the first wireless node and the receive beam of the first wireless node may be associated with a higher quality than other receive beams of the first wireless node. In some examples of the method, apparatus, and non-transitory computer-readable medium described above, determining the range of correspondence includes determining a difference between indices of the transmit beam of the first wireless node and the receive beam of the first wireless node.

Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for determining an uncertainty region for beam mapping based on the determined difference. In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the range of correspondence corresponds to a breadth of the uncertainty region. Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for determining a difference between indices of a receive beam of the second wireless node and a transmit beam of the second wireless node.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, exchanging one or more signals includes receiving, from the second wireless node, an indication of a range of correspondence between a transmit beam of the second wireless node and a receive beam of the second wireless node. In some examples of the method, apparatus, and non-transitory computer-readable medium described above, receiving the indication of the range of correspondence between the transmit beam of the second wireless node and the receive beam of the second wireless node includes receiving the indication in a physical broadcast channel (PBCH), an extended physical broadcast channel (ePBCH), a random access channel (RACH) message, a physical downlink control channel (PDCCH), a physical uplink control channel (PUCCH), a physical uplink shared channel (PUSCH), a radio resource control (RRC) message, a master information block (MIB), or a system information block (SIB).

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, receiving the indication of the range of correspondence between the transmit beam of the second wireless node and the receive beam of the second wireless node includes receiving the indication as part of a handover procedure. In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the handover procedure is either a backward handover procedure or a forward handover procedure.

Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for determining a range of a beam sweep to be performed based at least in part on the range of correspondence and on a triggering event. In some examples of the method, apparatus, and non-transitory computer-readable medium described above, a range of a beam sweep to be performed for each of multiple simultaneous communication links may be different.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the triggering event includes awaking in connected mode from a discontinuous reception (DRX) cycle whose duration exceeds a threshold. In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the triggering event includes a changing of a transmission or reception subarray. In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the triggering event includes identifying that a temperature of either the first wireless node or the second wireless node has changed in excess of a threshold.

