TECHNICAL FIELD

The present disclosure relates generally to a system and method for digital communications, and, in particular embodiments, to a system and method for communications system training.

BACKGROUND

Antenna element to element channel estimation in a communication system with large numbers of antennas is prohibitive in terms of computational resources and communications overhead, such as in a massive multiple input multiple output (MIMO) communication system with tens or hundreds or more antennas. The amount of computation and communications required to support antenna element to element channel estimation is compounded in deployments that are highly dynamic in nature, when the channel estimation has to be performed with high frequency to meet the constantly changing environment and to accommodate dynamic traffic changes.

Therefore, there is a need for systems and methods that support communications system training that do not require excessive amounts of computational resources and communications overhead and still can achieve a same level of, or even improved, performance, such as throughput performance, for example.

SUMMARY

Example embodiments provide a system and method for communications system training.

In accordance with an example embodiment, a computer implemented method for operating a communications device is provided. The method includes receiving, by the communications device from one or more access nodes, a first transmission including a first signal on one or more resources associated with signal reception, deriving, by the communications device, a receive filter in accordance with the received first transmission, deriving, by the communications device, a transmit filter in accordance with the receive filter, precoding, by the communications device, a second signal with the transmit filter, thereby producing a second transmission, and transmitting, by the communications device to the one or more access nodes, the second transmission.

Optionally, in any of the preceding embodiments, an embodiment wherein the first transmission comprises the first signal transmitted on one or more first transmission ports, and wherein each first transmission port corresponds to a transmission layer, and a first number of transmission layers of the first transmission corresponds to a first transmission rankfirst transmission rank.

Optionally, in any of the preceding embodiments, an embodiment wherein the first transmission comprises the first signal transmitted on one or more first transmission ports, with each first transmission port corresponds to a transmission layer, and wherein the transmit filter is a weighted version of the receive filter weighted by weights associated with each of the transmission layers.

Optionally, in any of the preceding embodiments, an embodiment wherein the second transmission is transmitted on one or more second transmission ports, and wherein the first number of transmission layers of the first transmission and a second number of transmission layers of the second transmission are the same.

Optionally, in any of the preceding embodiments, an embodiment wherein the one or more first transmission ports of the first transmission and one or more second transmission ports of the second transmission have a one-to-one mapping.

Optionally, in any of the preceding embodiments, an embodiment wherein the resources associated with signal reception comprise at least one of non-zero-power (NZP) channel state information reference signal (CSI-RS) resources configured for channel and interference measurement, NZP CSI-RS resources configured for channel measurement, demodulation reference signal (DMRS) resources, or physical downlink shared channel (PDSCH) resources.

Optionally, in any of the preceding embodiments, an embodiment wherein the communications device further receives interference on resources associated with interference transmission, and wherein deriving the receive filter further comprising deriving, by the communications device, the receive filter in accordance with the received first transmission and the received interference.

Optionally, in any of the preceding embodiments, an embodiment wherein the resources associated with interference transmission comprise at least one of NZP CSI-RS resources configured for channel and interference measurement, NZP CSI-RS resources configured for channel measurement, NZP CSI-RS resources configured for interference measurement, zero-power (ZP) CSI-RS resources configured for interference measurement, CSI interference measurement resources, DMRS resources, or PDSCH resources.

Optionally, in any of the preceding embodiments, an embodiment wherein the communications device derives the receive filter in accordance with the received first transmission and the received interference on resources associated with signal reception and interference transmission that are partially overlapped or completely overlapped.

Optionally, in any of the preceding embodiments, an embodiment further comprising sending, by the communications device to the one or more access nodes, feedback information based on the received first transmission and the received interference.

Optionally, in any of the preceding embodiments, an embodiment further comprising repeating, by the communications device, the receiving, the deriving the receive filter, the deriving the transmit filter, the precoding, and the transmitting until an end criterion is met.

Optionally, in any of the preceding embodiments, an embodiment wherein the end criterion comprises at least one of a signal plus interference to noise ratio (SINR) meeting a threshold, or the communications device receiving an instruction to stop training.

Optionally, in any of the preceding embodiments, an embodiment wherein the second transmission is one of a sounding reference signal (SRS) transmission or a DMRS transmission.

Optionally, in any of the preceding embodiments, an embodiment wherein the transmit filter and the receive filter are equivalent.

Optionally, in any of the preceding embodiments, an embodiment wherein the transmit filter and the receive filter are at least one of conjugate transposed versions of each other, conjugated versions of each other, scaled versions of each other, normalized versions of each other, or are identical to each other.

Optionally, in any of the preceding embodiments, an embodiment wherein the receive filter is derived in accordance with a minimum mean square error (MMSE) combiner.

Optionally, in any of the preceding embodiments, an embodiment further comprising sending, by the communications device to the one or more access nodes prior to receiving the first transmission, a precoded SRS or a non-precoded SRS.

Optionally, in any of the preceding embodiments, an embodiment wherein the communications device transmits the SRS with the same filter used for a reception of a periodic CSI-RS or a semi-persistent CSI-RS, and for a reception of interference.

Optionally, in any of the preceding embodiments, an embodiment wherein the first and second transmissions occur over one or more subbands, and wherein the receive filter and the transmit filter are separately derived for each subband.

Optionally, in any of the preceding embodiments, an embodiment wherein the transmit filter comprises a multi-antenna precoder, and wherein the receive filter comprises a multi-antenna combiner.

In accordance with an example embodiment, computer implemented method for operating an access node in a training mode is provided. The method includes precoding, by the access node, a first signal with a transmit filter, thereby producing a first transmission, transmitting, by the access node to a communications device, the first transmission, receiving, by the access node from the communications device, a second transmission including second signal on resources associated with signal reception, deriving, by the access node, a receive filter in accordance with the received second transmission, and deriving, by the access node, the transmit filter in accordance with the receive filter.

Optionally, in any of the preceding embodiments, an embodiment further comprising repeating, by the access node, the precoding, the transmitting, the receiving, the deriving the receive filter, and the deriving the transmit filter until an end criterion is met.

Optionally, in any of the preceding embodiments, an embodiment wherein the end criterion comprises a SINR meeting a threshold.

Optionally, in any of the preceding embodiments, an embodiment further comprising receiving, by the access node from the communications device, feedback information, and wherein deriving the receive filter is in accordance with the feedback information.

Optionally, in any of the preceding embodiments, an embodiment wherein the first transmission is transmitted over a plurality of transmission layers, and wherein the method further comprises reducing, by the access node, a first transmission rankfirst transmission rank when a SINR of at least one transmission layer is below a threshold, and signaling, by the access node to the communications device, the reduced first transmission rankfirst transmission rank.

Optionally, in any of the preceding embodiments, an embodiment further comprising sending, by the access node to the communications device, an instruction to stop operating in the training mode.

Optionally, in any of the preceding embodiments, an embodiment wherein deriving the receive filter comprises adjusting the receive filter to maximize a SINR of a communications system including the communications device and the access node.

Optionally, in any of the preceding embodiments, an embodiment further comprising receiving, by the access node from the communications device prior to precoding the first signal, a SRS or a non-precoded SRS.

Optionally, in any of the preceding embodiments, an embodiment wherein the transmit filter is selected in accordance with the SRS or the non-precoded SRS.

Optionally, in any of the preceding embodiments, an embodiment further comprising, prior to precoding the first signal, sending, by the access node to the communications device, a trigger initiating operating in the training mode.

Optionally, in any of the preceding embodiments, an embodiment wherein the first transmission is transmitted on one or more first transmission ports, wherein the second transmission comprises the second signal transmitted on one or more second transmission ports, and wherein the one or more first transmission ports of the first transmission and the one or more second transmission ports of the second transmission have a one-to-one mapping.

In accordance with an example embodiment, a communications device is provided. The communications device includes a memory storage comprising instructions, and one or more processors in communication with the memory storage. The one or more processors execute the instructions to receive, from one or more access nodes, a first transmission including a first signal on one or more resources associated with signal reception, derive a receive filter in accordance with the received first transmission, derive a transmit filter in accordance with the receive filter, precode a second signal with the transmit filter, thereby producing a second transmission, and transmit, to the one or more access nodes, the second transmission.

Optionally, in any of the preceding embodiments, an embodiment wherein interference is received on resources associated with interference transmission, and wherein the one or more processors further execute the instructions to derive the receive filter in accordance with the received first transmission and the received interference.

Optionally, in any of the preceding embodiments, an embodiment wherein the one or more processors further execute the instructions to send, to the one or more access nodes, feedback information based on the received first transmission and the received interference.

Optionally, in any of the preceding embodiments, an embodiment wherein the one or more processors further execute the instructions to repeat receiving the first transmission, deriving the receive filter, deriving the transmit filter, precoding the second signal, and transmitting the second transmission until an end criterion is met.

Optionally, in any of the preceding embodiments, an embodiment wherein the one or more processors further execute the instructions to send, to the one or more access nodes prior to receiving the first transmission, a precoded SRS or a non-precoded SRS.

In accordance with an example embodiment, an access node is provided. The access node includes a memory storage comprising instructions, and one or more processors in communication with the memory storage. The one or more processors execute the instructions to precode a first signal with a transmit filter, thereby producing a first transmission, transmit, to a communications device, the first transmission, receive, from the communications device, a second transmission including second signal on resources associated with signal reception, derive a receive filter in accordance with the received second transmission, and derive the transmit filter in accordance with the receive filter.

Optionally, in any of the preceding embodiments, an embodiment wherein the one or more processors further execute the instructions to repeat precoding the first signal, transmitting the first transmission, receiving the second transmission, deriving the receive filter, and deriving the transmit filter until an end criterion is met.

Optionally, in any of the preceding embodiments, an embodiment wherein the one or more processors further execute the instructions to receive, from the communications device, feedback information, and wherein the receive filter is derived in accordance with the feedback information.

Optionally, in any of the preceding embodiments, an embodiment wherein the first transmission is transmitted over a plurality of transmission layers, and wherein the one or more processors further execute the instructions to reduce a first transmission rank when a SINR of at least one transmission layer is below a threshold, and signal, to the communications device, the reduced first transmission rank.

Optionally, in any of the preceding embodiments, an embodiment wherein the one or more processors further execute the instructions to send, to the communications device, an instruction to stop operating in a training mode.

Optionally, in any of the preceding embodiments, an embodiment wherein the one or more processors further execute the instructions to receive, from the communications device prior to precoding the first signal, a SRS or a non-precoded SRS.

Optionally, in any of the preceding embodiments, an embodiment wherein the one or more processors further execute the instructions to send, to the communications device prior to precoding the first signal, a trigger initiating operating in a training mode.

Practice of the foregoing embodiments enables a distributed low complexity training procedure that scales well in communications systems with large numbers of antennas. The low complexity allows the training to occur with high frequency to more accurately capture the nature of dynamic operating environments.

