y protected. User-plane traffic (IP packets) is encrypted and can be integrity protected. User-plane integrity protection is a new feature (relative to LTE) that is useful for small-data transmissions, and particularly Octet 1 Octet 1 Octet 2 Octet N Octet 3 TMD PDU Octet 4 Octet 5 Octet 1 Octet 2 Octet N Octet 3 UMD PDU with 12-bit SN and so Octet 4 Octet 5 ACK_SN Octet 1 ACK_SN Octet 2 Octet N IRRRRRRR Octet 3 AMD PDU with 12-bit SN and so NACK_SN Octet 4 NACK_SN Octet 5 Octet 1 NACK_SN Octet 6 Octet 2 NACK_SN Octet 7 Octet 3 SOstart Octet 8 Octet 4 SOstart Octet 9 Octet 5 SOend Octet 10 Octet 6 SOend Octet 11 NACK range Octet 12 Octet N NACK_S SN Octet 13 AMD PDU with 18-bit SN with so NACK_SN Octet 14 STATUS RLC PDU with 12-bit SN Figure 2.14 Functional block diagram of the PDCP entities [11]. New Radio Access Layer 2/3 Aspects and System Operation 225 for constrained IoT devices. Data traffic including voice calls, Internet traffic, and text messages are protected using encryption. The device and the network mutually authenti- cate each other and use integrity-protected signaling. This setup makes nearly impossible for an unauthorized party to decrypt and read the information that is communicated over the air. Although integrity protection of user-plane data is supported in 5G networks, this feature is not used in E-UTRA-NR-DC (EN-DC) scenarios since LTE systems only pro- vide integrity protection of control-plane messages. When duplication is configured for a radio bearer by RRC, a secondary RLC entity is added to the radio bearer to handle the duplicated PDCP PDUs, where the logical chan- nels corresponding to the primary and the secondary RLC entities are referred to as the primary logical channel and the secondary logical channel, respectively. Therefore, the duplication function at PDCP sublayer consists of submitting the same PDCP PDUs twice, that is, to the primary RLC entity and to the secondary RLC entity. With two independent transmission paths, packet duplication would improve the transmission rel