Tracking reference signals for new radio

1. A user equipment (UE) in a mobile communication network to communicate with a base station (BS), the UE comprising:

a memory; and

processing circuitry, coupled with the memory, the processing circuitry configured to:

cause coarse time and frequency synchronization information, obtained from primary and secondary synchronization signals (PSS/SSS), to be stored in the memory;

decode, based on the coarse time and frequency synchronization information stored in the memory, a physical broadcast channel to obtain a first system information;

acquire, based on the first system information, a second system information;

cause transmission of a physical random access channel (PRACH), based on the first and second system information, to trigger a transmission of a first tracking reference signal (TRS) by the BS; and

receive a second TRS from the BS associated with a paging message, the second TRS sent independent from the transmission of the PRACH, wherein the second TRS for the paging message is received in a same system bandwidth over which the first and second system information is received, or in a configurable cell-specific bandwidth or a UE specific bandwidth.

2. The UE of claim 1 , wherein the first system information is to be included in a master information block (MIB) and the second system information is to be included in one or more system information blocks (SIBs).

3. The UE of claim 1 , wherein the first system information is minimum system information (MSI) and the second system information is remaining minimum system information (RMSI) or other system information (OSI).

4. The UE of claim 1 , wherein the processing circuitry is further configured to:

obtain downlink control information (DCI) carried by a physical downlink control channel (PDCCH), to schedule physical downlink shared channel (PDSCH) that is to carry the system information; and

perform fine time synchronization and fine frequency synchronization based on the transmission of the first TRS by the BS.

5. The UE of claim 1 , wherein the processing circuitry is further configured to:

identify the first TRS from the BS; and

perform, based on the first TRS, fine time and frequency synchronization with the BS, wherein the fine time and frequency synchronization is more accurate than the coarse time and frequency synchronization information.

6. The UE of claim 5 , wherein the processing circuitry is further configured to:

estimate, based on the first TRS, a set of quasi-co-location (QCL) parameters of a channel between the BS and the UE.

7. The UE of claim 1 , wherein the first and second system information and the first TRS are to be received over a same bandwidth.

8. The UE of claim 7 , wherein the same bandwidth comprises a same number of physical resource blocks (PRBs) over which the PSS/SSS are transmitted when the BS is in an energy-savings mode.

9. The UE of claim 1 , wherein the processing circuitry is further configured to:

determine, based on the first and second system information, a configuration of cell-specific bandwidth over which the first TRS is to be received.

10. The UE of claim 1 , wherein the first and second system information is to be received over a first bandwidth and the first TRS is to be received over a second bandwidth that is larger than the first bandwidth.

11. The UE of claim 1 , wherein the first TRS is received over a UE-specific bandwidth configured by radio resource control (RRC) signaling after RRC connection setup.

12. The UE of claim 1 , wherein the transmission of the PRACH is to trigger periodic transmissions of the first TRS by the BS.

13. The UE of claim 1 , wherein the first TRS is received in a downlink slot in a time division duplex (TDD) system, and wherein the downlink slot is defined by a mathematical formula, or by interleaved orthogonal frequency-division multiple Access (OFDMA) signal structure.

14. The UE of claim 1 , wherein the processing circuitry is further configured to:

determine, based on the first and second system information, a configuration of a bandwidth over which the first TRS is to be received.

15. A non-transitory computer-readable medium comprising instructions to cause a base station (BS), upon execution of the instructions by one or more processors, to:

transmit, by primary and secondary synchronization signals (PSS/SSS), coarse time and frequency synchronization information to a user equipment (UE);

transmit a first system information and a second system information to the UE;

receive a physical random access channel (PRACH) from the UE to trigger a transmission of a first tracking reference signal (TRS) to the UE;

transmit the first TRS to the UE; and

transmit a second TRS to the UE associated with a paging message, wherein the second TRS is triggered in response to the paging message arriving in a buffer of the BS and is sent independent from the reception of the PRACH, and wherein the second TRS for the paging message is transmitted in a same system bandwidth over which the first and second system information is transmitted, or in a configurable cell-specific bandwidth or a UE specific bandwidth.

16. The non-transitory computer-readable medium of claim 15 , wherein the first TRS is transmitted periodically after receiving the PRACH from the UE.

17. A method, comprising:

obtaining, by a user equipment (UE) and from primary and secondary synchronization signals (PSS/SSS), coarse time and frequency synchronization information;

decoding, by the UE and based on the coarse time and frequency synchronization information, a physical broadcast channel to obtain a master system information (MSI);

acquiring, by the UE and based on the MSI, one or more remaining minimum system information (RMSI) or other system information (OSI);

causing, by the UE, transmission of a physical random access channel (PRACH), based on the MSI and the one or more RMSI and OSIs, to trigger a transmission of a first tracking reference signal (TRS) by a base station (BS); and

receiving a second TRS from the BS associated with a paging message, the second TRS sent independent from the transmission of the PRACH, wherein the second TRS for the paging message is received periodically in a fixed specified narrowband bandwidth.

18. The method of claim 17 , further comprising:

performing fine time synchronization and fine frequency synchronization based on the transmission of the first TRS by the BS.