INITIAL ACCESS IN HIGH FREQUENCY WIRELESS SYSTEMS
Methods, devices and systems are provided for performing a random access (RA) procedure. A wireless transmit/receive unit (WTRU) may be configured to receive RA resource sets, where each of the RA resource sets is associated with a node-B directional beam, select an RA resource set from among the RA resource sets, and initiate an RA procedure based on the selected RA resource set. The RA procedure may include selecting multiple preambles which include a preamble for each resource of a plurality of resources corresponding to the selected RA resource set. The WTRU may be configured to sequentially transmit the selected multiple preambles in sequential RA transmissions, and may be configured to receive, from a node-B, in response to the RA transmissions, at least one RA response (RAR), where each of the received at least one RAR corresponds to one of the transmitted multiple preambles.
1 . A method for use in a wireless transmit/receive unit (WTRU), the method comprising:
receiving, from a base station (BS), a plurality of beam reference signals (BRSs) associated with a plurality of random access (RA) resource sets, wherein each BRS is associated with a RA resource set of the plurality of RA resource sets;
determining, based on a measurement of at least one BRS of the plurality of BRSs, a respective RA resource set, wherein the determined RA resource set includes a plurality of RA resources;
transmitting, using a first resource of the plurality of RA resources in the determined RA resource set, to the BS, a first preamble;
transmitting, using a second resource of the plurality of RA resources in the determined RA resource set, to the BS, a second preamble; and
receiving, from the BS, a random access response (RAR), in response to the first preamble and or the second preamble.