In a different embodiment, assistance information is utilized to determine whether 64QAM should be used for sidelink communications between UE1 and UE2. The BS or UE obtains UE assistance information and performs transmission parameters related configuration or adjustment according to the information. For example, the BS or UE may determine whether the UE uses 64QAM on sidelink communications based on the information.

The UE assistance information includes at least one of the following: speed of UE1 and/or UE2, acceleration of UE1 and/or UE2, movement direction of UE1 and/or UE2, sidelink measurement information of the sidelink communication, MCS information, retransmission times, and transmission resource information. The sidelink measurement information includes at least one of the following: SL RSRP measurement results, SL RSRQ measurement results, SL RSSI measurement results, SL CSI (channel state information), which contains at least CQI (Channel Quality Indicator) index information.

In one embodiment, UE1 and/or UE2 transmit its own UE assistance information to the BS, and the BS configures or adjusts transmission parameters for UE1 and/or UE2 according to the received UE assistance information. Optionally, UE1 and/or UE2 may send UE assistance information to the BS via PUCCH (Physical Uplink Control Channel) or MAC CE or RRC dedicated signaling.