Apparatus and methods are provided for initial access in the multi-beam operation. In one novel aspect, the UE receives multiple response messages and selects one message as the response message. In one embodiment, the UE selects a subset of a configured UL resources, transmits a first message, wherein the first message is transmitted one or more times on each of the selected set of UL resources, receives one or more first-message-response messages from the BS, and selects one response message, wherein the selected response message indicates a corresponding BS RX resource, which is used by the UE for subsequent communication with the BS. In one embodiment, the selection of UL resources is at least based on transmitting spatial characteristics of the BS, the UE or both, which indicates whether the BS/UE is reciprocal, partial reciprocal or non-reciprocal.