Certain aspects of the present disclosure provide techniques for wireless communications by a user equipment (UE). The UE detects at least one of a first type of reference signal (RS) or a second type of RS within an active bandwidth part (BWP). The UE then derives uplink (UL) transmission timing and corresponding accuracy requirement, based on which type of RS was detected. The UE then transmits UL signals based on the derived UL transmission timing and the corresponding accuracy requirement.

Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a base station may transmit, and a user equipment (UE) may receive, initial timing advance information in a msg2 communication of a four-step random access channel procedure based at least in part on a subcarrier spacing in a cell associated with the base station. The UE may transmit, and the base station may receive, a msg3 communication with an initial timing advance that is based at least in part on the initial timing advance information. The base station may transmit, and the UE may receive, updated timing advance information resolving a timing advance wrap-around between the UE and the base station based at least in part on the base station detecting the msg3 communication. Numerous other aspects are provided.

Certain aspects of the present disclosure provide techniques for over-the-air synchronization of integrated access and backhaul communications. An example method that may be performed by a network entity includes receiving, from a first wireless node, an indication of a value of a timing adjustment factor associated with a communication between the first wireless node and a second wireless node and communicating with the first wireless node or the second wireless node based on the value of the timing adjustment factor.

A method and apparatus for performing a random access (RACH) procedure is disclosed. In one embodiment, a method performed by a wireless communication node, includes: performing a plurality of random access (RACH) procedures with a wireless communication device on a first frequency resource set and a second frequency resource set, wherein the plurality of RACH procedures each comprises: receiving a first message on a first frequency resource from the wireless communication device, wherein the first frequency resource is selected from the first frequency resource set; transmitting a second message on a second frequency resource to the wireless communication device within a pre-determined time window, wherein the second frequency resource is selected from the second frequency resource set; receiving a third message on the first frequency resource from the wireless communication device; and transmitting a fourth message on the second frequency resource to the wireless communication device.

Methods and apparatuses are described for wireless communications. Cells may be grouped into a plurality of cell groups. A wireless device may transmit a plurality of preambles. The wireless device may also transmit a packet using a transmission power that is based on a power ramp-up of the preambles.

Methods and apparatuses are described for wireless communications. Cells may be grouped into a plurality of cell groups. A time adjustment may be determined and applied to uplink transmission timing of a cell group. A transmission timing difference between a first cell group and a second cell group may be determined. If the transmission timing difference exceeding a threshold, one or more devices may stop transmitting uplink signals via one or more secondary cells and/or may stop applying the timing adjustment for a cell group.

The present disclosure describes a communication method, including: sending, by a user equipment (UE), a request message to a micro network node, so that the micro network node sends an indication message to a macro network node; receiving an uplink resource sent according to the indication message by the macro network node; and sending uplink signaling or uplink data to the macro network node according to the uplink resource. The present disclosure further describes a corresponding device and system. The micro network node participates in accessing the user equipment (UE) to a network so that a UE can rapidly access the network and reduce access delay.

A cooperative wireless system using a multicast protocol to facilitate coordinating coherent addition and subtraction of wireless signaling or other beams originating from a plurality of antenna units at a target location is contemplated. The system may utilize multicast-based regulation and distribution of transmission control parameters necessary for the antenna units to synchronize the wireless signaling in a manner sufficient to enable the coherent addition and subtraction thereof at the target location.

A Node-B sends a polling message to a wireless transmit/receive unit (WTRU). The WTRU sends an uplink synchronization burst in response to the polling message without contention. The Node-B estimates an uplink timing shift based on the synchronization burst and sends an uplink timing adjustment command to the WTRU. The WTRU then adjusts uplink timing based on the uplink timing adjustment command. Alternatively, the Node-B may send a scheduling message for uplink synchronization to the WTRU. The WTRU may send a synchronization burst based on the scheduling message. Alternatively, the WTRU may perform contention-based uplink synchronization after receiving a synchronization request from the Node-B. The WTRU may enter an idle state instead of performing a handover to a new cell when the WTRU moves to the new cell. A discontinuous reception (DRX) interval for the WTRU may be set based on activity of the WTRU.

Systems, methods, apparatuses, and computer program products for an uplink timing synchronization recovery process for RACH-less handover are provided. One method includes detecting, by a network node, that at least one uplink transmission has not been successfully received from a user equipment. The method may also include transmitting a physical downlink control channel (PDCCH) order to the user equipment for re-initiating random access procedure (RACH) in order to become uplink synchronized.