Reciprocal channel sounding reference signal multiplexing
Systems and techniques are disclosed to enhance the efficiency of available bandwidth between UEs and base stations. A UE transmits a sounding reference signal (SRS) to the base station. The base station characterizes the uplink channel based on the SRS received and, using reciprocity, applies the channel characterization for the downlink channel. As part of applying the channel information, the base station forms the beam to the UE based on the uplink channel information obtained from the SRS. The UE may include an array of antennas, each UE transmitting a different SRS that the base station receives and uses to characterize the downlink. Multiple UEs (or a single UE with multiple antennas) transmit SRS at the same time and frequency allocation (non-orthogonal), but with each sending its own unique SRS. Further, multiple UEs (or a single UE with multiple antennas) may send their SRS at unique time/frequency allocations (orthogonal).
1. A method for communicating with a base station, comprising:
determining, by a user equipment (UE), each one of multiple narrowband sounding reference signals (SRSs) based on a bandwidth capability of the UE being narrower than a system bandwidth of a channel;
transmitting, from the UE, each one of the multiple narrowband SRSs at a different frequency sub-band during one subframe; and
receiving, by the UE from the base station, a beamformed downlink communication based on information obtained from each one of the multiple narrow band SRSs corresponding to each of the different frequency sub-bands, wherein the beamformed downlink communication based on information obtained from each one of the multiple narrowband SRSs corresponding to each of the different frequency sub-bands comprises a beamformed downlink communication having a bandwidth greater than the width of each of the frequency sub-bands, wherein the different frequency sub-bands cover a portion of an entire bandwidth of the system bandwidth of the channel, wherein a number of different frequency sub-bands is selected based on a threshold for channel reciprocity.
2. The method of claim 1 , wherein the different frequency sub-bands cover an entire bandwidth of the system bandwidth of the channel.
3. The method of claim 1 , wherein transmitting each one of the multiple narrowband SRSs at a different frequency sub-band during one subframe comprises transmitting each one of the multiple narrowband SRSs during a different time resource of the one subframe.
4. A user equipment (UE), comprising:
a processor configured to determine each one of multiple narrowband sounding reference signals (SRSs) based on a bandwidth capability of the UE being narrower than a system bandwidth of a channel; and
a transceiver configured to:
transmit each one of the multiple narrowband SRSs at a different frequency sub-band during one subframe; and
receive from a base station a beamformed downlink communication based on information obtained from each one of the multiple narrowband SRSs corresponding to each of the different frequency sub-bands, wherein the beamformed downlink communication based on information obtained from each one of the multiple narrowband SRSs corresponding to each of the different frequency sub-bands comprises a beamformed downlink communication having a bandwidth greater than the width of each of the frequency sub-bands, wherein the different frequency sub-bands cover a portion of an entire bandwidth of the system bandwidth of the channel, wherein a number of different frequency sub-bands is selected based on a threshold for channel reciprocity.
5. The user equipment of claim 4 , wherein the different frequency sub-bands cover an entire bandwidth of the system bandwidth of the channel.
6. The user equipment of claim 5 , wherein transmitting each one of the multiple narrowband SRSs at a different frequency sub-band during one subframe comprises transmitting each one of the multiple narrowband SRSs during a different time resource of the one subframe.