TECHNICAL FIELD

The present application relates generally to the field of wireless communication networks, and more specifically to so-called integrated access backhaul (IAB) networks in which network nodes utilize wireless communications both to provide access to devices and to relay (e.g., “backhaul”) communications from devices and/or other nodes to a core network.

BACKGROUND

FIG. 1illustrates a high-level view of a fifth-generation (5G) cellular (e.g., wireless) network architecture, consisting of a Next Generation RAN (NG-RAN) and a 5G Core (5GC). The NG-RAN can include a set of gNodeB's (gNBs) connected to the 5GC via one or more NG interfaces, whereas the gNBs can be connected to each other via one or more Xn interfaces. Each of the gNBs can support frequency division duplexing (FDD), time division duplexing (TDD), or a combination thereof. The radio technology for the NG-RAN is often referred to as “New Radio” (NR).

The NG RAN logical nodes shown inFIG. 1(and described in TS 38.401 and TR 38.801) include a Central Unit (CU or gNB-CU) and one or more Distributed Units (DU or gNB-DU). The CU is a logical node that is a centralized unit that hosts high layer protocols and includes a number of gNB functions, including controlling the operation of DUs. A DU is a decentralized logical node that hosts lower layer protocols and can include, depending on the functional split option, various subsets of the gNB functions. (As used herein, the terms “central unit” and “centralized unit” are used interchangeably, and the terms “distributed unit” and “decentralized unit” are used interchangeability.) The gNB-CU connects to gNB-DUs over respective F1 logical interfaces. The gNB-CU and connected gNB-DUs are only visible to other gNBs and the 5GC as a gNB, e.g., the F1 interface is not visible beyond gNB-CU.

Furthermore, the F1 interface between the gNB-CU and gNB-DU is specified, or based on, the following general principles:F1 is an open interface;F1 supports the exchange of signalling information between respective endpoints, as well as data transmission to the respective endpoints;from a logical standpoint, F1 is a point-to-point interface between the endpoints (even in the absence of a physical direct connection between the endpoints);F1 supports control plane (CP) and user plane (UP) separation, such that a gNB-CU may be separated in CP and UP; F1 separates Radio Network Layer (RNL) and Transport Network Layer (TNL);F1 enables exchange of user-equipment (UE) associated information and non-UE associated information;F1 is defined to be future proof with respect to new requirements, services, and functions;A gNB terminates X2, Xn, NG and S1-U interfaces and, for the F1 interface between DU and CU, utilizes the F1 application part protocol (F1-AP) which is defined in 3GPP TS 38.473.

Furthermore, a CU can host protocols such as RRC and PDCP, while a DU can host protocols such as RLC, MAC and PHY. Other variants of protocol distributions between CU and DU can exist, however, such as hosting the RRC, PDCP and part of the RLC protocol in the CU (e.g., Automatic Retransmission Request (ARQ) function), while hosting the remaining parts of the RLC protocol in the DU, together with MAC and PHY. In some exemplary embodiments, the CU can host RRC and PDCP, where PDCP is assumed to handle both UP traffic and CP traffic. Nevertheless, other exemplary embodiments may utilize other protocol splits that by hosting certain protocols in the CU and certain others in the DU. Exemplary embodiments can also locate centralized control plane protocols (e.g., PDCP-C and RRC) in a different CU with respect to the centralized user plane protocols (e.g., PDCP-U).

It has also been agreed in 3GPP RAN3 Working Group (WG) to support a separation of the gNB-CU into a CU-CP function (including RRC and PDCP for signaling radio bearers) and CU-UP function (including PDCP for user plane). The CU-CP and CU-UP parts communicate with each other using the E1-AP protocol over the E1 interface.FIG. 2shows an exemplary gNB architecture based on the DU-CU split and the further separation between CU-CP and CU-UP.

In the gNB split CU-DU architecture, DC can be achieved by means of allowing a UE to connect to multiple DUs served by the same CU or by allowing a UE to connect to multiple DUs served by different CUs. As illustrated inFIG. 1, a gNB can include a gNB-CU connected to one or more gNB-DUs via respective F1 interfaces, all of which are described hereinafter in greater detail. In the NG-RAN architecture, however, a gNB-DU can be connected to only a single gNB-CU.

The NG-RAN is layered into a Radio Network Layer (RNL) and a Transport Network Layer (TNL). The NG-RAN architecture, i.e., the NG-RAN logical nodes and interfaces between them, is defined as part of the RNL. For each NG-RAN interface (NG, Xn, F1) the related TNL protocol and the functionality are specified. The TNL provides services for user plane transport and signaling transport. In NG-Flex configuration, each gNB is connected to all 5GC nodes within a pool area. The pool area is defined in 3GPP TS 23.501. If security protection for control plane and user plane data on TNL of NG-RAN interfaces has to be supported, NDS/IP (3GPP TS 33.401) shall be applied.

Densification via the deployment of more and more base stations (e.g., macro or micro base stations) is one of the mechanisms that can be employed to satisfy the increasing demand for bandwidth and/or capacity in mobile networks, which is mainly driven by the increasing use of video streaming services. Due to the availability of more spectrum in the millimeter wave (mmw) band, deploying small cells that operate in this band is an attractive deployment option for these purposes. However, the normal approach of connecting the small cells to the operator's backhaul network with optical fiber can end up being very expensive and impractical. Employing wireless links for connecting the small cells to the operator's network is a cheaper and more practical alternative. One such approach is an integrated access backhaul (IAB) network where the operator can utilize part of the radio resources for the backhaul link.

Integrated Access and Backhaul (IAB) has been studied earlier in 3GPP in the scope of Long Term Evolution (LTE) Rel-10. In that work, an architecture was adopted where a Relay Node (RN) has the functionality of an LTE eNB and UE modem. The RN is connected to a donor eNB which has a S1/X2 proxy functionality hiding the RN from the rest of the network. That architecture enabled the Donor eNB to also be aware of the UEs behind the RN and hide any UE mobility between Donor eNB and Relay Node(2) on the same Donor eNB from the CN. During the Rel-10 study, other architectures were also considered including, e.g., where the RNs are more transparent to the Donor gNB and allocated a separate stand-alone P/S-GW node.

For 5G/NR, similar options utilizing IAB can also be considered. One difference compared to LTE is the gNB-CU/DU split described above, which separates time critical RLC/MAC/PHY protocols from less time critical RRC/PDCP protocols. It is anticipated that a similar split could also be applied for the IAB case. Other IAB-related differences anticipated in NR as compared to LTE are the support of multiple hops and the support of redundant paths.

Nevertheless, the NG-RAN split CU/DU architecture exemplified byFIG. 1creates certain difficulties for IAB. For example, the potential for gNBs to connect through multiple RNs can create certain difficulties due to the cascading of the gNB-CU functionalities within those RNs.

SUMMARY

Accordingly, exemplary embodiments of the present disclosure address shortcomings in NG-RAN split DU/CU architectures that are arranged in an IAB configuration, thereby enabling the otherwise-advantageous deployment of IAB solutions. Such exemplary embodiments can include methods and/or procedures for reducing Packet Data Convergence Protocol (PDCP) processing performed in a node of a multi-hop, IAB network. For example, the exemplary methods and/or procedures can be performed by various network nodes in an IAB network (or components thereof), including gNB-CUs, intermediate IAB nodes, and IAB access nodes.

The exemplary methods and/or procedures can include receiving a configuration that includes a first characteristic associated with at least one of the following: the node and data packets received by the node. In some embodiments, the received configuration can also include an indication of whether to enable or to disable a first PDCP processing operation based on the first characteristic. In some embodiments, the received configuration can also include a second characteristic associated with at least one of the following: the node and data packets received by the node.

The exemplary methods and/or procedures can also include receiving a data packet having one or more packet characteristics, and determining if there is a match between the one or more packet characteristics and the first characteristic. The exemplary method and/or procedure can include enabling or disabling the first PDCP processing operation on the data packet based on the result of the determination. In some embodiments, the enabling or disabling can include enabling the first PDCP processing operation if the one or more packet characteristics match the first characteristic, and disabling the first PDCP processing operation if the one or more packet characteristics do not match the first characteristic. In some embodiments, enabling or disabling of the first PDCP processing operation can be further based on the indication and/or the second characteristic.

In some exemplary embodiments, the first PDCP processing operation can include one or more of encryption, decryption, integrity protection, and integrity verification of PDCP messages. In some exemplary embodiments, the first PDCP processing operation can include either the pair of encryption and integrity protection, or the pair of decryption and integrity verification. In such case, each operation of the pair can be enabled or disabled independently of the other operation of the pair.

In some exemplary embodiments, disabling the first PDCP processing operation can include performing at least one of a null ciphering algorithm and a null integrity protection algorithm. In some exemplary embodiments, the first characteristic can include a first data transmission protocol and, optionally, a second data transmission protocol. In some exemplary embodiments, the first characteristic can include a hop count threshold. In some exemplary embodiments, the first characteristic can include identities of one or more radio bearers used to carry data packets. In some embodiments, the first characteristic can include identification of first and second partitions of a GPRS Tunneling Protocol Tunnel Endpoint ID (GTP TEID) space. In some embodiments, the first characteristic can include a plurality of addresses associated with one or more user equipment, UEs, served by the IAB network.

Exemplary embodiments also include network nodes (e.g., gNB-CU, intermediate IAB nodes, IAB access nodes, or components thereof) configured and/or arranged to perform operations corresponding to various exemplary methods and/or procedures described herein. Other exemplary embodiments include non-transitory, computer-readable media storing computer-executable instructions embodying operations corresponding to various exemplary methods and/or procedures described herein.

