User equipment-designed demodulation reference signal pattern book

1. A user equipment (UE) to design a demodulation reference signal (DMRS) pattern book defining a set of DMRS patterns associated with a downlink channel of a long term evolution (LTE) wireless network, the UE comprising:

a receiver to receive a reference signal carried in a downlink subframe, the reference signal indicating wireless channel characteristics; and

circuitry operatively coupled to the receiver, the circuitry configured to:

perform channel and noise variance estimation based on the wireless channel characteristics indicated by the received reference signal;

obtain estimates of multipath-time delay and Doppler spreads;

derive channel coherence time and coherence bandwidth based on the obtained estimates of multipath-time delay and Doppler spreads; and

prepare a DMRS pattern book as a function of the noise variance estimation, the channel coherence time, and the coherence bandwidth.

2. The UE of claim 1 , in which the received reference signal comprises a cell-specific reference signal (CRS), and in which the circuitry is further configured to perform the channel and noise variance estimation based on channel characteristics indicated by the CRS reference signal.

3. The UE of claim 1 , in which the received reference signal comprises a channel state information reference signal (CSI-RS), and in which the circuitry is further configured to perform the channel and noise variance estimation based on channel characteristics indicated by the CSI-RS reference signal.

4. The UE of claim 1 , in which the wireless channel characteristics include frequency-selective fading channel characteristics having multiple bandwidth parts, each of different ones of the multiple bandwidth parts having a corresponding coherence time and coherence bandwidth, and the DMRS pattern book including DMRS patterns optimized for the different ones of the multiple bandwidth parts based on the corresponding coherence time and coherence bandwidth.

5. The UE of claim 1 , in which the DMRS pattern book includes a DMRS pattern that occurs once for each of multiple consecutive subframes.

6. The UE of claim 1 , in which the DMRS pattern book includes a DMRS pattern having a density of subcarriers that is based on a frequency domain variability of the wireless channel characteristics.

7. The UE of claim 1 , in which the DMRS pattern book is a frequency-dependent DMRS pattern book including DMRS patterns designed for the entire available bandwidth or a portion of the bandwidth.

8. The UE of claim 7 , in which the frequency-dependent DMRS pattern book is associated with information identifying the portions of the bandwidth that correspond to different ones of the DMRS patterns.

9. A user equipment (UE) configured to monitor a wireless communication channel and signal to an evolved node B (eNB) information defining a set of demodulation reference signal (DMRS) patterns, the UE comprising:

a receiver configured to receive known signals from the eNB, the known signals being modified by transmission through the wireless communication channel from the eNB to the UE;

a transmitter; and

circuitry operationally coupled to the receiver and transmitter, the circuitry configured to:

determine conditions of the wireless channel based on the received known signals;

design the set of DMRS patterns dynamically based on the conditions of the wireless communication channel; and

cause the transmitter to transmit to the eNB the information defining the set of DMRS patterns, wherein radio resource control (RRC) signaling is used to signal to the eNB the information defining the set of DMRS patterns, and wherein the RRC signaling provides information defining whether a DMRS pattern of the set of DMRS patterns is to be repeated for multiple physical resource blocks.

10. The UE of claim 9 , in which the RRC signaling provides a total number of DMRS patterns of the set of DMRS patterns.

11. The UE of claim 9 , in which the set of DMRS patterns identifies resource element (RE) indexes of a DMRS pattern in one or more associated physical resource blocks.

12. The UE of claim 9 , in which the information defining the set of DMRS patterns includes a periodicity of DMRS resource element (RE) locations in frequency or time domains.

13. The UE of claim 12 , in which, in the frequency domain, the DMRS RE locations are allocated periodically among physical resource blocks.

14. The UE of claim 12 , in which, for the time domain, the DMRS RE locations are allocated periodically among subframes.

15. An evolved node b (eNB) configured to select, and transmit to a user equipment (UE), a demodulation reference signal (DMRS), the eNB comprising:

a receiver configured to wirelessly communicate with the UE and receive from it a UE-designed DMRS pattern book;

a transmitter configured to transmit a DMRS during a physical downlink shared channel (PDSCH) transmission; and

circuitry configured to:

select between a DMRS pattern of the UE-designed DMRS pattern book and a pre-defined DMRS pattern, the pre-defined DMRS pattern being not defined by the UE and having been previously specified on the eNB and the UE;

indicate the selected DMRS pattern to the UE; and

cause the transmitter to transmit the DMRS during the PDSCH transmission.

16. The eNB of claim 15 , in which the circuitry is further configured to use radio resource control (RRC) signaling to inform the UE which DMRS pattern is to be used for the PDSCH transmission.

17. The eNB of claim 15 , in which the circuitry indicates the selected DMRS pattern on a subframe basis for the PDSCH transmission.

18. The eNB of claim 15 , in which the circuitry is further configured to provide downlink control information in a physical downlink control channel (PDCCH) transmission to indicate the selected DMRS pattern.

19. The eNB of claim 18 , in which the selected DMRS pattern has an associated index value, the associated index value being transmitted in the PDCCH transmission to indicate the selected DMRS pattern.

20. A user equipment (UE) configured to monitor a wireless communication channel and signal to an evolved node B (eNB) information defining a set of demodulation reference signal (DMRS) patterns, the UE comprising:

a receiver configured to receive known signals from the eNB, the known signals being modified by transmission through the wireless communication channel from the eNB to the UE;

a transmitter; and

circuitry operationally coupled to the receiver and transmitter, the circuitry configured to:

determine conditions of the wireless channel based on the received known signals;

design the set of DMRS patterns dynamically based on the conditions of the wireless communication channel; and

cause the transmitter to transmit to the eNB the information defining the set of DMRS patterns, wherein the information defining the set of DMRS patterns includes a periodicity of DMRS resource element (RE) locations in frequency or time domains.

21. The UE of claim 20 , in which the circuitry is further configured to use radio resource control (RRC) signaling to signal to the eNB the information defining the set of DMRS patterns.

22. The UE of claim 21 , in which the RRC signaling provides a total number of DMRS patterns of the set of DMRS patterns.

23. The UE of claim 21 , in which the RRC signaling provides information defining whether a DMRS pattern of the set of DMRS patterns is to be repeated for multiple physical resource blocks.

24. The UE of claim 20 , in which the set of DMRS patterns identifies resource element (RE) indexes of a DMRS pattern in one or more associated physical resource blocks.

25. The UE of claim 20 , in which, in the frequency domain, the DMRS RE locations are allocated periodically among physical resource blocks.

26. The UE of claim 20 , in which, for the time domain, the DMRS RE locations are allocated periodically among subframes.