Methods of segmentation and concatenation for new radio user plane are proposed. For high speed data traffic, all PDCP PDUs are segmented into fixed-length segments at RLC layer. The MAC layer can then concatenate these segments based on real time uplink grants. Under this mechanism, segmentation related header fields can be pre-computed since they are not dependent on the uplink grant process. For low data rate with small packet size traffic, a solution of PDCP layer concatenation is proposed to reduce protocol overhead. Multiple PDCP SDUs are concatenated into a single PDCP PDU. The level of PDCP concatenation is configured by the base station or implemented by the UE.