Reference signal for wireless communication systems
Aspects of this disclosure relate transmitting and/or receiving reference symbols. A first reference symbol includes a symbol and a cyclically shifted portion of the symbol, where the cyclically shifted portion has cyclic shift length. A second reference symbol includes a cyclically shifted version of the first reference symbol that is cyclically shifted relative to the first reference symbol by the cyclic shift length. The first and second reference symbols are transmitted consecutively from at least one antenna.
1. A method of transmitting reference symbols, the method comprising:
generating a first reference symbol comprising a symbol and a cyclically shifted portion of the symbol, the cyclically shifted portion having a cyclic shift length;
generating a second reference symbol, wherein the second reference symbol comprises a cyclically shifted version of the first reference symbol that is cyclically shifted relative to the first reference symbol by the cyclic shift length; and
transmitting, via at least one antenna, the first and second reference symbols consecutively.
2. The method of claim 1 , wherein the cyclically shifted portion is a cyclic prefix, and the symbol follows the cyclic prefix in the first reference symbol.
3. The method of claim 1 , wherein a frame offset between uplink symbols and downlink symbols is greater than the cyclic shift length.
4. The method of claim 1 , wherein said generating the second reference symbol comprises applying a frequency domain (FD) phase ramp to at least the symbol of the first reference symbol.
5. The method of claim 1 , wherein said generating the first reference symbol comprises adding the cyclically shifted portion in a time domain.
6. The method of claim 1 , wherein said generating the first reference symbol comprises applying weighted overlap and add roll off.
7. The method of claim 1 , further comprising applying phase ramping to the first and second reference symbols to pre-compensate for at least a frame offset between uplink symbols and downlink symbols.
8. The method of claim 7 , wherein said applying phase ramping also pre-compensates for an additional offset.
9. The method of claim 7 , wherein said applying phase ramping also pre-compensates for a New Radio standard specified phase rotation.
10. The method of claim 1 , wherein said transmitting comprises a time domain duplex (TDD) transmission.
11. The method of claim 1 , wherein the first and second reference symbols are orthogonal frequency division multiplexing (OFDM) symbols.
12. The method of claim 1 , wherein the first and second reference symbols include at least one of Discrete Fourier Transform-spread Orthogonal Frequency Division Multiple Access symbols, Interleaved-Frequency Division Multiple Access symbols, or other time domain waveform symbols.
13. The method of claim 1 , wherein the first reference symbol is generated based on at least one of Gold sequence or Zadoff-Chu sequence.
14. A system for transmitting reference symbols, the system comprising:
at least one antenna;
a base band unit; and
a radio frequency processing unit in communication with the base band unit;
wherein the base band unit and radio frequency processing unit are together configured to:
generate a first reference symbol comprising a symbol and a cyclically shifted portion of the symbol, the cyclically shifted portion having a cyclic shift length;
generate a second reference symbol, wherein the second reference symbol comprises a cyclically shifted version of the first reference symbol that is cyclically shifted relative to the first reference symbol by the cyclic shift length; and
cause the first and second reference symbols to be consecutively transmitted from the at least one antenna.
15. The system of claim 14 , wherein the radio frequency processing unit comprises a remote radio unit.
16. The system of claim 14 , wherein the radio frequency processing unit comprises fronthaul circuitry.
17. The system of claim 14 , wherein a frame offset between uplink symbols and downlink symbols is greater than the cyclic shift length.
18. The system of claim 14 , wherein the first and second reference symbols are transmitted as part of a time domain duplex (TDD) transmission.
19. The system of claim 14 , wherein the base band unit comprises a phase ramping block configured to apply phase ramping to the symbol, and wherein the second reference symbol is generated based on an output signal from the phase ramping block.
20. The system of claim 14 , wherein the radio frequency processing unit is configured to perform an inverse Fast Fourier Transform on a frequency domain version of the symbol provided by the base band unit, and to add the cyclically shifted portion to the first reference symbol.
21. Non-transitory, computer-readable storage comprising computer-executable instructions, wherein the computer-executable instructions, when executed by a base band unit, cause a method to be performed, the method comprising:
generating a first reference symbol comprising a symbol and a cyclically shifted portion of the symbol, the cyclically shifted portion having a cyclic shift length;
generating a second reference symbol, wherein the second reference symbol comprises a cyclically shifted version of the first reference symbol that is cyclically shifted relative to the first reference symbol by the cyclic shift length; and
transmitting, via at least one antenna, the first and second reference symbols consecutively.