1. A method for use in a wireless transmit/receive unit (WTRU), the method comprising:
receiving, by the WTRU from a first base station, a configuration message which includes correspondence information regarding a plurality of beam reference signals, wherein the correspondence information includes information regarding designation of at least one set of physical random access channel (PRACH) resources for each of the plurality of beam reference signals; measuring, by the WTRU, the plurality of beam reference signals, transmitted from a second base station; selecting, by the WTRU, a beam reference signal from among the plurality of measured beam references signals; determining, by the WTRU, a set of PRACH resources for the selected beam reference signal based on the information regarding designation of at least one set of PRACH resources for each of the plurality of measured beam reference signals included in the correspondence information; and transmitting, by the WTRU to the second base station, a PRACH transmission using at least one PRACH resource of the determined set of PRACH resources.
2. The method of claim 1, wherein the configuration message is at least one of a broadcast message or a radio resource control (RRC) message.
3. The method of claim 1, wherein the plurality of beam reference signals are channel state information reference signals (CSI-RSs).
4. The method of claim 3, wherein the CSI-RSs are derived from pseudo-random sequences.
5. The method of claim 4, wherein the CSI-RSs are code division multiplexed (CDM) using Walsh sequences.
6. The method of claim 1, wherein the correspondence information regarding the plurality of measured beam reference signals includes a plurality of measurement configurations.
7. The method of claim 1, wherein the determined set of PRACH resources includes at least one PRACH preamble and wherein the PRACH transmission is a PRACH preamble in the determined set of PRACH resources.
8. The method of claim 1, wherein the WTRU selects the beam reference signal based on a determination that a measured beam reference signal power is better than a threshold on at least one beam reference signal.
9. The method of claim 1, wherein the plurality of beam reference signals is a plurality of 3-D beam reference signals.
10. The method of claim 1, further comprising:
determining, by the WTRU, the PRACH transmission based on the received correspondence information.
11. A wireless transmit/receive unit (WTRU) for determining resources, the WTRU comprising:
a transceiver; and a processor, operatively coupled to the transceiver; wherein:
the transceiver is configured to receive from a first base station, a configuration message which includes correspondence information regarding a plurality of beam reference signals, wherein the correspondence information includes information regarding designation of at least one set of physical random access channel (PRACH) resources for each of the plurality of beam reference signals;
the processor is configured to measure the plurality of beam reference signals, transmitted from a second base station;
the processor is configured to select a beam reference signal from among the plurality of measured beam references signals;
the processor is configured to determine a set of PRACH resources for the selected beam reference signal based on the information regarding designation of at least one set of PRACH resources for each of the plurality of measured beam reference signals included in the correspondence information; and
the transceiver is configured to transmit to the second base station, a PRACH transmission using at least one PRACH resource of the determined set of PRACH resources.
12. The WTRU of claim 11, wherein the configuration message is at least one of a broadcast message or a radio resource control (RRC) message.
13. The WTRU of claim 11, wherein the plurality of beam reference signals are channel state information reference signals (CSI-RSs).
14. The WTRU of claim 13, wherein the CSI-RSs are derived from pseudo-random sequences.
15. The WTRU of claim 14, wherein the CSI-RSs are code division multiplexed (CDM) using Walsh sequences.
16. The WTRU of claim 11, wherein the correspondence information regarding the plurality of measured beam reference signals includes a plurality of measurement configurations.
17. The WTRU of claim 11, wherein the determined set of PRACH resources includes at least one PRACH preamble and wherein the PRACH transmission is a PRACH preamble in the determined set of PRACH resources.
18. The WTRU of claim 11, wherein the WTRU selects the beam reference signal based on a determination that a measured beam reference signal power is better than a threshold on at least one beam reference signal.
19. The WTRU of claim 11, wherein the plurality of beam reference signals is a plurality of 3-D beam reference signals.
20. The WTRU of claim 11, wherein the processor is further configured to determine the PRACH transmission based on the received correspondence information.