TECHNICAL FIELD

[0001] This description relates to communications.

BACKGROUND

[0002] A communication system may be a facility that enables communication between two or more nodes or devices, such as fixed or mobile communication devices. Signals can be carried on wired or wireless carriers.

[0003] An example of a cellular communication system is an architecture that is being standardized by the 3 ^rd Generation Partnership Project (3 GPP). A recent development in this field is often referred to as the Long Term Evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology.

E-UTRA (evolved UMTS Terrestrial Radio Access) is the air interface of 3GPP's Long Term Evolution (LTE) upgrade path for mobile networks. In LTE, base stations or access points (APs), which are referred to as enhanced Node B (eNBs), provide wireless access within a coverage area or cell. In LTE, mobile devices, or mobile stations are referred to as user equipments (UE). LTE has included a number of improvements or developments.

[0004] 5G New Radio (NR) development is part of a continued mobile broadband evolution process to meet the requirements of 5G, similar to earlier evolution of 3G & 4G wireless networks. A goal of 5G is to provide significant improvement in wireless performance, which may include new levels of data rate, latency, reliability, and security. 5G NR may also scale to efficiently connect the massive Internet of Things (IoT), and may offer new types of mission-critical services. BSs in 5G/NR may be referred to as gNBs.

SUMMARY

[0005] According to an example embodiment, a method includes establishing, by a base station, a first connection that includes an uplink radio bearer between a first sidelink user device and the base station and a downlink radio bearer between the base station and a second sidelink user device; receiving, by a protocol entity of the base station via the uplink radio bearer, one or more protocol data units from the first sidelink user device; and transmitting, by the protocol entity of the base station via the downlink radio bearer, one or more of the received protocol data units to the second sidelink user device; and wherein the protocol entity of the base station is a common protocol entity that both tracks sequence numbers of the one or more protocol data units that are received by the protocol entity of the base station from the first sidelink user device via the uplink radio bearer and tracks sequence numbers of the one or more protocol data units that are transmitted by the protocol entity of the base station to the second sidelink user device via the downlink radio bearer.

[0006] According to an example embodiment, an apparatus includes at least one processor and at least one memory including computer instructions, when executed by the at least one processor, cause the apparatus to: establish, by a base station, a first connection that includes an uplink radio bearer between a first sidelink user device and the base station and a downlink radio bearer between the base station and a second sidelink user device; receive, by a protocol entity of the base station via the uplink radio bearer, one or more protocol data units from the first sidelink user device; and transmit, by the protocol entity of the base station via the downlink radio bearer, one or more of the received protocol data units to the second sidelink user device; and wherein the protocol entity of the base station is a common protocol entity that both tracks sequence numbers of the one or more protocol data units that are received by the protocol entity of the base station from the first sidelink user device via the uplink radio bearer and tracks sequence numbers of the one or more protocol data units that are transmitted by the protocol entity of the base station to the second sidelink user device via the downlink radio bearer.

[0007] According to an example embodiment, a computer program product includes a computer-readable storage medium and storing executable code that, when executed by at least one data processing apparatus, is configured to cause the at least one data processing apparatus to perform a method including: establishing, by a base station, a first connection that includes an uplink radio bearer between a first sidelink user device and the base station and a downlink radio bearer between the base station and a second sidelink user device; receiving, by a protocol entity of the base station via the uplink radio bearer, one or more protocol data units from the first sidelink user device; and transmiting, by the protocol entity of the base station via the downlink radio bearer, one or more of the received protocol data units to the second sidelink user device; and wherein the protocol entity of the base station is a common protocol entity that both tracks sequence numbers of the one or more protocol data units that are received by the protocol entity of the base station from the first sidelink user device via the uplink radio bearer and tracks sequence numbers of the one or more protocol data units that are transmitted by the protocol entity of the base station to the second sidelink user device via the downlink radio bearer.

[0008] According to an example embodiment, a method includes establishing, by a second sidelink user device, a first connection that includes a downlink bearer between a base station and the second sidelink user device; establishing, a second connection that includes a sidelink radio bearer between a first sidelink user device and the second sidelink user device; receiving, by the second sidelink user device from the first sidelink user device via the sidelink radio bearer, one or more protocol data units; and receiving, by the second sidelink user device from the base station via the downlink bearer, one or more protocol data unit; wherein a common set of sequence numbers are used for a set of protocol data units, for at least one of: 1) duplication of the set of protocol data units via both the sidelink bearer and the downlink bearer, or 2) spliting each protocol data unit of the set of protocol data units via either of the sidelink bearer and the downlink bearer.

[0009] According to an example embodiment, an apparatus includes at least one processor and at least one memory including computer instructions, when executed by the at least one processor, cause the apparatus to: establish, by a second sidelink user device, a first connection that includes a downlink bearer between a base station and the second sidelink user device; establish, a second connection that includes a sidelink radio bearer between a first sidelink user device and the second sidelink user device; receive, by the second sidelink user device from the first sidelink user device via the sidelink radio bearer, one or more protocol data units; and receive, by the second sidelink user device from the base station via the downlink bearer, one or more protocol data unit; wherein a common set of sequence numbers are used for a set of protocol data units, for at least one of: 1) duplication of the set of protocol data units via both the side link bearer and the downlink bearer, or 2) splitting each protocol data unit of the set of protocol data units via either of the sidelink bearer and the downlink bearer.

[0010] According to an example embodiment, a computer program product includes a computer-readable storage medium and storing executable code that, when executed by at least one data processing apparatus, is configured to cause the at least one data processing apparatus to perform a method including: establishing, by a second sidelink user device, a first connection that includes a downlink bearer between a base station and the second sidelink user device; establishing, a second connection that includes a sidelink radio bearer between a first sidelink user device and the second sidelink user device; receiving, by the second sidelink user device from the first sidelink user device via the sidelink radio bearer, one or more protocol data units; and receiving, by the second sidelink user device from the base station via the downlink bearer, one or more protocol data unit; wherein a common set of sequence numbers are used for a set of protocol data units, for at least one of: 1 ) duplication of the set of protocol data units via both the sidelink bearer and the downlink bearer, or 2) splitting each protocol data unit of the set of protocol data units via either of the sidelink bearer and the downlink bearer.

[0011] According to an example embodiment, a method includes establishing, by a second sidelink user device, a first connection that includes a downlink bearer between a base station and the second sidelink user device; establishing, a second connection that includes a sidelink radio bearer between a first sidelink user device and the second sidelink user device; receiving, by the second sidelink user device from the first sidelink user device via the sidelink radio bearer, one or more protocol data units; and receiving, by the second sidelink user device from the base station via the downlink bearer, one or more protocol data units; wherein a same sequence number is used for a protocol data unit that is both received by the second sidelink user device from the first sidelink user device via the sidelink radio bearer and received by the second sidelink user device from the base station via the downlink radio bearer.

[0012] According to an example embodiment, an apparatus includes at least one processor and at least one memory including computer instructions, when executed by the at least one processor, cause the apparatus to: establish, by a second sidelink user device, a first connection that includes a downlink bearer between a base station and the second sidelink user device; establish, a second connection that includes a sidelink radio bearer between a first sidelink user device and the second sidelink user device; receive, by the second sidelink user device from the first sidelink user device via the sidelink radio bearer, one or more protocol data units; and receive, by the second sidelink user device from the base station via the downlink bearer, one or more protocol data units; wherein a same sequence number is used for a protocol data unit that is both received by the second sidelink user device from the first sidelink user device via the sidelink radio bearer and received by the second sidelink user device from the base station via the downlink radio bearer.

[0013] According to an example embodiment, a computer program product includes a computer-readable storage medium and storing executable code that, when executed by at least one data processing apparatus, is configured to cause the at least one data processing apparatus to perform a method including: establishing, by a second sidelink user device, a first connection that includes a downlink bearer between a base station and the second sidelink user device; establishing, a second connection that includes a sidelink radio bearer between a first sidelink user device and the second sidelink user device; receiving, by the second sidelink user device from the first sidelink user device via the sidelink radio bearer, one or more protocol data units; and receiving, by the second sidelink user device from the base station via the downlink bearer, one or more protocol data units; wherein a same sequence number is used for a protocol data unit that is both received by the second sidelink user device from the first sidelink user device via the sidelink radio bearer and received by the second sidelink user device from the base station via the downlink radio bearer.

[0014] According to an example embodiment, a method includes establishing, by a base station, a first connection that includes an uplink radio bearer between a first sidelink user device and the base station and a downlink radio bearer between the base station and a second sidelink user device; receiving, by a protocol entity of the base station via the uplink radio bearer, one or more protocol data units from the first sidelink user device; and transmitting, by the protocol entity of the base station via the downlink radio bearer, one or more of the received protocol data units to the second sidelink user device; wherein a sidelink radio bearer is established between the first sidelink user device and the second sidelink user device; and wherein a common set of sequence numbers are used for a set of protocol data units, for at least one of: 1) duplication of the set of protocol data units via both the sidelink bearer and the downlink bearer, or 2) splitting each protocol data unit of the set of protocol data units via either of the sidelink bearer and the downlink bearer.

[0015] According to an example embodiment, an apparatus includes at least one processor and at least one memory including computer instructions, when executed by the at least one processor, cause the apparatus to: establish, by a base station, a first connection that includes an uplink radio bearer between a first sidelink user device and the base station and a downlink radio bearer between the base station and a second sidelink user device; receive, by a protocol entity of the base station via the uplink radio bearer, one or more protocol data units from the first sidelink user device; and transmit, by the protocol entity of the base station via the downlink radio bearer, one or more of the received protocol data units to the second sidelink user device; wherein a sidelink radio bearer is established between the first sidelink user device and the second sidelink user device; and wherein a common set of sequence numbers are used for a set of protocol data units, for at least one of: 1) duplication of the set of protocol data units via both the sidelink bearer and the downlink bearer, or 2) splitting each protocol data unit of the set of protocol data units via either of the sidelink bearer and the downlink bearer.

[0016] According to an example embodiment, a computer program product includes a computer-readable storage medium and storing executable code that, when executed by at least one data processing apparatus, is configured to cause the at least one data processing apparatus to perform a method including: establishing, by a base station, a first connection that includes an uplink radio bearer between a first sidelink user device and the base station and a downlink radio bearer between the base station and a second sidelink user device; receiving, by a protocol entity of the base station via the uplink radio bearer, one or more protocol data units from the first sidelink user device; and transmitting, by the protocol entity of the base station via the downlink radio bearer, one or more of the received protocol data units to the second sidelink user device; wherein a sidelink radio bearer is established between the first sidelink user device and the second sidelink user device; and wherein a common set of sequence numbers are used for a set of protocol data units, for at least one of: 1 ) duplication of the set of protocol data units via both the sidelink bearer and the downlink bearer, or 2) splitting each protocol data unit of the set of protocol data units via either of the sidelink bearer and the downlink bearer.

[0017] According to an example embodiment, a method includes establishing, by a base station, a first connection that includes an uplink radio bearer between a first sidelink user device and the base station and a downlink radio bearer between the base station and a second sidelink user device; receiving, by a protocol entity of the base station via the uplink radio bearer, one or more protocol data units from the first sidelink user device; and transmitting, by the protocol entity of the base station via the downlink radio bearer, one or more of the received protocol data units to the second sidelink user device; wherein a sidelink radio bearer is established between the first sidelink user device and the second sidelink user device; and wherein a same sequence number is used for a protocol data unit that is both: 1 ) transmitted by the first sidelink user device to the second sidelink user device via the sidelink radio bearer, and 2) transmitted by the base station to the second sidelink user device via the downlink radio bearer.

[0018] According to an example embodiment, an apparatus includes at least one processor and at least one memory including computer instructions, when executed by the at least one processor, cause the apparatus to: establish, by a base station, a first connection that includes an uplink radio bearer between a first sidelink user device and the base station and a downlink radio bearer between the base station and a second sidelink user device; receive, by a protocol entity of the base station via the uplink radio bearer, one or more protocol data units from the first sidelink user device; and transmit, by the protocol entity of the base station via the downlink radio bearer, one or more of the received protocol data units to the second sidelink user device; wherein a sidelink radio bearer is established between the first sidelink user device and the second sidelink user device; and wherein a same sequence number is used for a protocol data unit that is both: 1) transmitted by the first sidelink user device to the second sidelink user device via the sidelink radio bearer, and 2) transmitted by the base station to the second sidelink user device via the downlink radio bearer.

[0019] According to an example embodiment, a computer program product includes a computer-readable storage medium and storing executable code that, when executed by at least one data processing apparatus, is configured to cause the at least one data processing apparatus to perform a method including: establishing, by a base station, a first connection that includes an uplink radio bearer between a first sidelink user device and the base station and a downlink radio bearer between the base station and a second sidelink user device; receiving, by a protocol entity of the base station via the uplink radio bearer, one or more protocol data units from the first sidelink user device; and transmiting, by the protocol entity of the base station via the downlink radio bearer, one or more of the received protocol data units to the second sidelink user device; wherein a sidelink radio bearer is established between the first sidelink user device and the second sidelink user device; and wherein a same sequence number is used for a protocol data unit that is both: 1) transmitted by the first sidelink user device to the second sidelink user device via the sidelink radio bearer, and 2) transmitted by the base station to the second sidelink user device via the downlink radio bearer.

[0020] The details of one or more examples of embodiments are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG. 1 is a block diagram of a wireless network according to an example embodiment.

[0022] FIG. 2 is a diagram of a network according to an example embodiment.

[0023] FIG. 3 is a diagram illustrating a network according to another example embodiment.

[0024] FIG. 4 is a diagram illustration operation of a network according to an example embodiment.

[0025] FIG. 5 is a flow chart illustrating operation of a base station according to an example embodiment.

[0026] FIG. 6 is a flow chart illustrating operation of a user device according to an example embodiment.

[0027] FIG. 7 is a flow chart illustrating operation of a user device according to an example embodiment.

[0028] FIG. 8 is a flow chart illustrating operation of a base station according to another example embodiment.

[0029] FIG. 9 is a flow chart illustrating operation of a base station according to another example embodiment.

[0030] FIG. 10 is a block diagram of a node or wireless station (e.g., base station/ access point, relay node or mobile station/user device) according to an example embodiment.

DETAILED DESCRIPTION

[0031] FIG. 1 is a block diagram of a wireless network 130 according to an example embodiment. In the wireless network 130 of FIG. 1 , user devices 131, 132, 133 and 135, which may also be referred to as mobile stations (MSs) or user equipment (UEs), may be connected (and in communication) with a base station (BS) 134, which may also be referred to as an access point (AP), an enhanced Node B (eNB), a gNB, or a network node. At least part of the functionalities of an access point (AP), base station (BS) or (e)Node B (eNB) or gNB may be also be carried out by any node, server or host which may be operably coupled to a transceiver, such as a remote radio head. BS (or AP) 134 provides wireless coverage within a cell 136, including to user devices 131 , 132, 133 and 135. Although only four user devices are shown as being connected or attached to BS 134, any number of user devices may be provided. BS 134 is also connected to a core network 150 via a Sl interface 151. This is merely one simple example of a wireless network, and others may be used.

[0032] In addition, two UEs may directly communicate via a sidelink (SL) connection, which may also be referred to as a device-to-device (D2D) connection. [0033] A user device (user terminal, user equipment (UE) or mobile station) may refer to a portable computing device that includes wireless mobile communication devices operating with or without a subscriber identification module (SIM), including, but not limited to, the following types of devices: a mobile station (MS), a mobile phone, a cell phone, a smartphone, a personal digital assistant (PDA), a handset, a device using a wireless modem (alarm or measurement device, etc.), a laptop and/or touch screen computer, a tablet, a phablet, a game console, a notebook, and a multimedia device, as examples. It should be appreciated that a user device may also be a nearly exclusive uplink only device, of which an example is a camera or video camera loading images or video clips to a network.

[0034] In LTE (as an example), core network 150 may be referred to as

Evolved Packet Core (EPC), which may include a mobility management entity (MME) which may handle or assist with mobility/handover of user devices between BSs, one or more gateways that may forward data and control signals between the BSs and packet data networks or the Internet, and other control functions or blocks.

[0035] In addition, by way of illustrative example, the various example

embodiments or techniques described herein may be applied to various types of user devices or data service types, or may apply to user devices that may have multiple applications running thereon that may be of different data service types. New Radio (5G) development may support a number of different applications or a number of different data service types, such as for example: machine type communications (MTC), enhanced machine type communication (eMTC), Internet of Things (IoT), and/or narrowband IoT user devices, enhanced mobile broadband (eMBB), wireless relaying including self- backhauling, D2D (device-to-device) communications, and ultra-reliable and low-latency communications (ETRLLC). Scenarios may cover both traditional licensed band

operation as well as unlicensed band operation.

[0036] IoT may refer to an ever-growing group of objects that may have

Internet or network connectivity, so that these objects may send information to and receive information from other network devices. For example, many sensor type applications or devices may monitor a physical condition or a status, and may send a report to a server or other network device, e.g., when an event occurs. Machine Type Communications (MTC, or Machine to Machine communications) may, for example, be characterized by fully automatic data generation, exchange, processing and actuation among intelligent machines, with or without intervention of humans. Enhanced mobile broadband (eMBB) may support much higher data rates than currently available in LTE.

[0037] Ultra-reliable and low-latency communications (URLLC) is a new data service type, or new usage scenario, which may be supported for New Radio (5G) systems. This enables emerging new applications and services, such as industrial automations, autonomous driving, vehicular safety, e-health services, and so on. 3GPP targets in providing connectivity with reliability corresponding to block error rate (BLER) of 10 ⁵ and up to 1 ms U-Plane (user/data plane) latency, by way of illustrative example. Thus, for example, URLLC user devices/UEs may require a significantly lower block error rate than other types of user devices/UEs as well as low latency (with or without requirement for simultaneous high reliability)

[0038] The various example embodiments may be applied to a wide variety of wireless technologies or wireless networks, such as LTE, LTE-A, 5G, cmWave, and/or mmWave band networks, IoT, MTC, eMTC, eMBB, URLLC, etc., or any other wireless network or wireless technology. These example networks, technologies or data service types are provided only as illustrative examples.

[0039] As noted, according to an example embodiment, two UEs may directly communicate via a sidelink (SL) connection, which may also be referred to as a device- to-device (D2D) connection. For example, a SL connection between two UEs may be used by UEs to communicate with each other, e.g., either instead of a Uu (BS-UE) connection, or in addition to a Uu (BS-UE) connection.

[0040] Some of use cases that may benefit from D2D/SL communication may also require high reliability or high data rate communication. Thus, in some example cases, a D2D link/SL (sidelink) alone may be not able to meet the requirements of a UE or application, e.g., such as in a complex or demanding environment of IoT. For instance, two UEs, provided in two moving vehicles or cars, may be communicating via SL connection. In this case, for example, SL performance (for the DL or D2D connection between the two UEs) may be heavily degraded if a large truck momentarily is present in middle of (or between) the two vehicles/cars, thus temporarily blocking the signal between the two UEs communicating via SL, thus at least temporarily negatively impacting SL performance in terms of reliability and/or data rate. Or, in another illustrative example, two robots (each having a UE) may be communicating via SL (D2D) connection/communication, and the two robots/machines that communicate via SL may move further away and/or may become blocked by another machine, which may decrease or negatively impact the SL performance, e.g., in terms of reliability and/or data rate. SL communication may also allow offloading of traffic from BS/network.

[0041] According to an example embodiment, two UEs may be configured to communicate via two parallel connections. LIG. 2 is a diagram of a network 200 according to an example embodiment. As shown in LIG. 2, UE 212 and UE 214 may be connected (and communicate) via a first or primary connection, e.g., a sidelink (SL) connection 220, which may include a sidelink (SL) radio bearer (SLRB) 222. Because the UEs 212 and 214 communicate via a sidelink (SL) connection 220 and/or SL radio bearer 222, the UEs 212 and 214 may be considered to be SL UEs 212 and 214. Also, according to an illustrative example, UEs 212 and 214 may be considered to be a TX (transmit) SL UE 212 and a RX (receive) SL UE 214, respectively, because (in this example shown in LIG. 2), TX SL UE 212 transmits data to RX SL UE 214 (also, a transmission in the opposite direction may also be provided, which is not shown in LIG. 2). Also, BS 134 may be in communication with (and/or connected to) SL UEs 212 and 214. Thus, for example, TX (transmit) SL UE 212 may be in communication with RX (receive) SL UE 214 via BS 134. Lor example, a secondary connection 224 may include uplink secondary Uu radio bearer (UL SURB) 226 from TX SL UE 212 to BS 134, and a downlink secondary Uu radio bearer (DL SURB) 228 from BS 134 to RX SL UE 214, where a Uu radio bearer may refer to a radio (or wireless) bearer provided between a UE and a BS.

[0042] Note, that, by way of illustrative example, only one direction of transmission paths are shown in LIG. 2 (e.g., a primary or sidelink connection for a SL transmission from TX SL UE 212 directly to RX SL UE 214, and also a secondary connection for a transmission from TX SL UE 212 to RX SL UE 214 via BS 134).

However, it should be understood that communication between UEs 212 and 214 may be bidirectional. Thus, connections and/or radio bearers may also be provided to allow transmission in the opposite direction, e.g., for transmission from RX SL UE 214 directly to TX SL UE 212 via a separate SLRB (not shown), as well as additional UL bearer (also not shown) to allow transmission from UE 2l4 to BS 2lO and an additional DL bearer to allow transmission from BS 134 to UE 212, respectively.

[0043] Thus, as noted with reference to FIG. 2, two connections or

communication paths may be provided to allow TX SL UE 212 to transmit data or signals to RX SL UE 21 , including 1) a first connection (e.g., a primary connection, including or provided via a SLRB 222) may be provided as a SL connection 220 between TX SL UE 212, e.g., to allow SL communication from TX DL UE 212 to RX SL UE 214, and 2) a second (e.g., secondary) connection 224 may also be provided to allow communication from TX SL UE 212 to RX SL UE 214 via BS 134 (e.g., via UL SURB 226 and DL SURB 228).

[0044] According to an example embodiment, these two connections or communication paths may allow for one or more of: 1) duplication (e.g., where each protocol data unit (PDU) may be transmitted by TX SL UE 212 via both primary connection 220 and secondary connection 224), or 2) split transmission (e.g., where each PDU is transmitted via either of, but typically not both of, primary connection 220 and secondary connection 224). In an illustrative example embodiment, duplication may be used to increase reliability and/or reduce latency (e.g., if a PDU transmission fails along one connection or communication path, the PDU may still be successfully transmitted via the other connection or communication path), while split transmission may be used to increase data rate and/or data throughput (e.g., use of two different connections or communication paths to improve data rate or data throughput), for example.

[0045] According to an example embodiment, as noted above, two UEs may be configured to communicate via two parallel connections, including both 1) a sidelink (SL) connection (e.g., as a primary connection) and a BS-UE connection (e.g., as a secondary connection). The SL connection between the SL UEs may be provided via (or may include) a SL radio bearer (SLRB). The BS-UE connection may be provided via (or may include) an uplink (UL) secondary Uu radio bearer (UL SURB) from a TX SL UE to a BS, and then a DL SURB from the BS to a RX (receive) SL UE. A Uu interface may refer to the radio interface between a BS and UE.

[0046] In an example embodiment, with respect to duplication of transmission from the TX SL UE 212, the SL connection 220 may be considered to be a primary connection between SL UEs 212 and 214, with the connection 224 via BS 134 to be a secondary connection. For example, the primary connection may be used to transmit all PDUs/packets, while the secondary connection may be used to transmit and/or receive either all PDETs/packets, or only those PDETs/packets that have not been received by RX SL UE 214. Thus, as a primary connection (for example) the SL connection 220 may be used to transmit PDUs, and the RX SL UE 214 may receive and decode PDUs via the secondary connection 224 that were not or have not been received via the primary connection. In a first example embodiment, the SL connection may be a primary connection and the connection via the BS 134 may be a secondary connection. While in a second example embodiment, the connection via the BS 134 (including UL SURB 226 and DL SURB 228) may be a primary connection, and the SL connection (including SL radio bearer 222) may be a secondary connection.

[0047] As shown in FIG. 2, TX SL UE 212 includes a protocol stack, including a Packet Data Convergence Protocol (PDCP) entity 216A. Similarly RX SL UE 214 includes a protocol stack including a PDCP entity 216B. PDCP entities 216A and 216B are peer protocol entities that cooperate (and/or communicate) to perform PDCP services and functions/PDCP services and functions, which may include, e.g., one or more of (or even all):

[0048] 1) Header compression and decompression for user plane data (e.g., using Robust Header compression(ROHC)) wherein the PDCP entity may compress and decompress headers for one or more lower layer headers/PDUs, such as for headers for Radio Link Control (RLC) entity, Media Access Control (MAC) entity, and/or Physical (PHY) entity);

[0049] 2) Performing security functions for user plane data (user data) and control plane data (control signals/control signaling), including ciphering/deciphering (encryption and decryption of data/SDUs);

[0050] 3) Tracking of PDU sequence numbers for the transfer of user plane data and control plane data between PDCP entities, including one or more of: transmission and reception of data between PDCP entities, providing (adding or including) sequence numbers for packets or PDUs, checking PDCP sequence numbers on received PDCP PDUs, determining which packets have been transmitted or not and/or which packets have been received or not received (e.g., based on PDCP sequence numbers and/or feedback (such as ACK/NACKs or a reception status report (RSR)) from a receiving PDCP entity), sending ACK (Acknowledgements to acknowledge receipt of a PDU) or NACKs (negative ACK, to indicate that a PDU has not been received); duplicate PDU detection, PDCP SDU (service data unit) discard (e.g., timer based PDCP SDU discard and/or discard of duplicate PDUs), retransmission of PDCP SDUs (service data units); and

[0051] 4) Additional functions related to PDCP data processing, including: duplication of PDCP PDUs (e.g., where duplication of data is required), providing in- order delivery of data/packets to upper layer(s), and duplicate detection (e.g.,

discarding/dropping duplicate data packets/SDUs, such as where upper layer requires in- order delivery), PDCP PDU (protocol data unit) routing (e.g., in case of split bearers).

[0052] Thus, for example, the PDCP entity 216A (for TX SL UE 212) and

PDCP entity 216B (for RX SL UE 214) may perform one or more (or even all) PDCP services/functions, such as one or more of header compression/decompression, security functions (ciphering/deciphering), tracking of PDU sequence numbers for the transfer of user plane data and control plane data between PDCP entities, and/or one or more additional functions related to PDCP data processing. Thus, the PDCP entities 216A and 216B may be considered as full or complete PDCP entities, for example.

[0053] According to an example embodiment, BS 134 may also include a

PDCP entity 210 for performing one or more PDCP services or functions. In an example embodiment, BS 134 may include a reduced common PDCP 210, e.g., in which PDCP 210 may: 1) may perform PDCP functions or services for both: A) PDCP PDUs/data that are received by the BS 134 from the TX SL UE 212 via UL SURB 226, and B)

PDCP PDUs/data that are transmitted from BS 134 to RX DL UE 214 via DL SURB 228. In this manner, the PDCP entity 210 may be considered to be a combined PDCP entity because PDCP entity 210 may combine (or may perform both) PDCP services or functions related to both receiving data from PDCP entity 216 A of TX DL UE 212 and sending/transmitting data to PDCP entity 216B of RX DL UE 214.

[0054] Furthermore, the reduced common PDCP entity 210 may, at least in some cases, be a reduced (or limited) PDCP entity because it may include (or may perform) only a portion or subset of the PDCP services or functions that may typically be performed or provided by a PDCP entity. For example, with respect to the secondary connection 224 (via UL SURB 226 and DL SURB 228), the PDCP entity 210 (of BS 134) may perform only a portion or subset of the PDCP services or functions, as there may be some PDCP services or functions performed by PDCP entities 216A and 216B that are not performed by PDCP entity 210. In an illustrative example, PDCP entity 210 may perform only: 3) tracking of PDU sequence numbers for the transfer of user plane data and control plane data between PDCP entities, including one or more of:

transmission and reception of data between PDCP entities, providing (adding or including) sequence numbers for packets or PDUs, checking PDCP sequence numbers on received PDCP PDUs, determining which packets have been transmitted or not and/or which packets have been received or not received (e.g., based on PDCP sequence numbers and/or feedback (such as ACK/NACKs or a reception status report (RSR)) from a receiving PDCP entity), sending ACK (Acknowledgements to acknowledge receipt of a PDU) or NACKs (negative ACK, to indicate that a PDU has not been received);

duplicate PDU detection, PDCP SDU (service data unit)/PDU discard (e.g., timer based PDCP SDU discard and/or discard of duplicate PDUs), retransmission of PDCP SDUs (service data units)/PDUs.

[0055] Also, in an illustrative example embodiment, the reduced common

PDCP entity 210 may not (necessarily) perform one or more of: 1) header

compression/decompression, 2) security functions (ciphering/deciphering), and/or 4) one or more additional functions related to PDCP data processing. This may be because, for example, the PDCP entities at the beginning (PDCP 216A) and the end (PDCP 216B) of the secondary connection 224 may perform these PDCP services of one or more of: 1) header compression/decompression, 2) security functions (ciphering/deciphering), and/or 4) one or more additional functions related to PDCP data processing, and it may be unnecessary for PDCP entity 210 (e.g., operating as an intermediate node or relay node in this example for connection 224) to repeat these PDCP services, for example, for the secondary connection 224. However, reduced common PDCP entity 210 of BS 134 may be expected to perform some (or at least some) very basic functions related to the tracking of PDU sequence numbers for the transfer (delivery) of user plane data and/or control plane data between PDCP entities (e.g., to receive PDCP data from PDCP entity 216A, and to send/transmit PDCP data to PDCP entity 216B). Thus, in at least some example embodiments, PDCP entity 210 may be a reduced common PDCP entity, for example.

[0056] Alternatively, a full or complete (or mostly complete) PDCP entity may be used at BS 134 to receive and forward data between PDCP entity 216A and PDCP entity 216B, for example. Also, in another example embodiment, rather than a common (or single) PDCP entity, PDCP entity 210 may be provided as multiple (or separate) PDCP entities, each PDCP entity for handling either receiving PDCP data or transmitting PDCP data.

[0057] Also, according to an example embodiment, PDCP 216B and/or RX SL

UE 214 may send a reception status report (RSR) 230 to PDCP 210 and/or BS 134. The RSR 230, for example, may identify one or more PDUs (e.g., PDCP PDUs) that have been received by the RX SL UE 214 (e.g., regardless whether the received PDU was received via primary or side link connection 220 or via secondary connection 224), and/or may identify one or more PDUs that have not been received by RX SL UE 214 (e.g.., where there is a missing PDU or a gap in received PDUs). The reduced common PDCP 210 and/or BS 134 may receive the RSR 230, and may then transmit one or more PDUs based on the received RSR 230, e.g., by transmitting a missing or omitted PDU (e.g., for duplication and/split transmission) and/or BS 134 may drop or discard a PDU that has been reported in the RSR as being received by the RS SL UE 214, for example. In an example embodiment, even for duplication, at least in some cases, the BS 134 and/or reduced common PDCP 210 may discard or drop a PDU that was indicated as being received by the RX SL UE 214 or PDCP entity 216B (e.g., presumably such received PDU may have been received by RX SL UE 214 via SL RB 222, and thus, there is no longer a need to send a duplicate of such PDU from BS 134).

[0058] In addition, TX SL UE 212 may send a SL buffer status report (BSR)

(e.g., to indicate data or an amount of data for transmission via the sidelink connection 220 or SL bearer 222) and/or a SURB buffer status report (SURB BSR) (e.g., to indicate an amount of data that is in a buffer for transmission to RX SL UE via UL SURB 226). However, according to an example embodiment, sending two different buffer status reports may be inefficient, e.g., such as in the case where the primary connection 220 and secondary connection 224 may be provided for data duplication or split transmission. For example, in the case of data duplication, the PDUs/data in the data buffer of TX SL UE 212 will (presumably) be expected to be transmitted via both primary connection 220 and secondary connection 224 (at least for some or many PDUs/data in the buffer). Thus, in some cases, it may be redundant for TX SL UE 212 to send both the SLR BSR and a SURB BSR.

[0059] Thus, according to an example embodiment, as shown in FIG. 2, TX SL

UE 212 may transmit (and BS 134 may receive) a common BSR 232 that

identifies/indicates a status of a data buffer (e.g., an amount of data in the data buffer, type of data, priority of the data, ...) of the TX SL UE 212 for both transmission via the SL RB 222 to the RX SL UE 214 and for transmission via the UL SURB 226 to BS 134. In response to receiving the common BSR, the BS may allocate: 1) a first set of time- frequency resources for the TX SL UE 212 to transmit one or more PDUs via the SL RB 222 to RX DL UE 214, and a second set of time-frequency resources for the TX SL UE 212 to transmit one or more PDUs via the UL SURB 226 to BS 134. Thus, in the case of duplication, the combined (or common) BSR 232 may indicate a UE buffer status, e.g., which may indicate an amount of data to be transmitted via both SL RB and SURBs. Similarly, in case of data splitting (split transmission), a combined BSR may similarly reveal or indicate information about the amount of data to be split among the two connections (e.g., half of indicated data in the buffer to be transmitted via each of the two connections).

[0060] FIG. 3 is a diagram illustrating a network according to another example embodiment. For example, the network of FIG. 3 may be considered an example embodiment of a more detailed illustration of the network 200 shown in FIG. 2. The same reference numerals in FIGs. 2 and 3 refer to the same entities. TX SL UE 212 includes a PDCP entity 216A, and RLC/MAC/PHY protocol stack 312 for UL SURB 226, and a RLC/MAC/PHY protocol stack 314 for SL RB 222. Thus, PDCP entity 216A may either split or duplicate PDUs or data for transmission, depending on the

transmission mode as either split transmission or duplication, respectively. For duplication, a copy of each PDU or data may be transmitted (or duplicated for transmission) via both RLC/MAC/PHY protocol stack 312 to UL SURB 226 and RLC/MAC/PHY protocol stack 314 to SL RB 222.

[0061] Similarly, as shown in FIG. 3, RX SL UE 214 may include a PDCP entity 216B, e.g., which may receive data/PDUs via both a RLC/MAC/PHY protocol stack 320 that is connected to SL RB 222, and a RLC/MAC/PHY protocol stack 322 that is connected to SL SURB 228, for example.

[0062] Also, as shown in FIG. 3, BS 134 may include a reduced common PDCP entity 210. PDCP entity 210 may be connected to a RLC/MAC/PHY protocol stack 316, which is connected to receive data from UL SURB 226, and a RLC/MAC/PHY protocol stack 318, which is connected to transmit data via DL SURB 228. Further example details of various example embodiments will now be described.

[0063] Example embodiments may relate to operation of a secondary Uu (BS-

UE) connection, which may assist a primary SL transmission. According to an example embodiment, a SL (D2D) connection 220 is established as the primary connection for e2e (end-to-end) communication between devices (UEs), such as between UEs 212 and2l4 (FIG. 2). In addition, a secondary connection via base station (BS) 134 may also be established for the same e2e communication, i.e., the UL transmission from one communication device/UE may be mapped to the DL transmission of other devices so that the e2e (end-to-end) communication is routed via BS 134. Considering that there is a full radio protocol stack from PHY to PDCP (e.g., at each of SL UEs 212 and 2l4) over the primary SL connection 220, the secondary Uu connection 224 (via BS 134) may not need to fully support or include all radio protocol layers or protocol services, e.g., which may reduce the processing power and delay over the secondary Uu connection 224 for simplification and better performance.

[0064] Thus, for example, a SL connection 220 may be used as a primary connection for an e2e (end-to-end) service between two or more UEs (e.g., between UEs 212 and 214) and a cellular (e.g., NR or 5G or LTE) link routed through a BS 134 may be used as a secondary connection 220 for the same e2e service, which may include a secondary Uu RB (SURB), or SURBs, to assist the primary SL RB 222 for duplication or split transmission. [0065] Thus, for example, a network may include two connections (or separate transmission paths between UEs). For example, a network may include, e.g.: a primary connection 220 that includes a SL radio bearer (SL RB 222) between two SL UEs, e.g., from a TX SL UE 212 to a RX SL UE 214. RX SL UE 214 may monitor a SL resource pool configured by BS 134 to receive data transmitted via SL RB 222. Or, a resource may be preconfigured for out of coverage. Also, TX SL UE 212 may obtain or receive a resource allocation provided by BS or may autonomously select the resources from configured resource pool. Then TX SL UE 212 may transmit SL scheduling assignment indicating MCS and resources used, and destination UE ID, where RX SL UE 214 may use the destination UE ID to determine that this data is for it. The network may also include a secondary (e.g., Uu) connection, e.g., where two SURBs are used (UL SURB 226 from TX SL UE 212 to BS 134, and DL SURB 228 from BS 134 to RX SL UE 214). The secondary or Uu connection via UL SURB 226 and DL SURB 228 creates or provides an alternative data path between the two SL UEs.

[0066] According to an example embodiment, an e2e (end-to-end) PDCP protocol communication may be established between UE 212 and UE 214, where a SL connection 220 may operate as a primary connection; and BS 134 may be used as a relay node for a secondary (e.g., Uu) connection, wherein a PDCP entity 210 at the BS 134 allows tracking of PDU SNs for the transfer of data/PDUs via the secondary or Uu connection 224.

[0067] According to an example embodiment, a SURB (e.g., UL SURB 226 and/or DL SURB 228 via BS 134) may have one or more of the following characteristics: SURB may not be configured with full radio protocol stack, as the primary SL

connection or RB has the full protocol stack up to PDCP for e2e traffic transmission. The SURB may be configured to have full MAC and RLC functionalities and the reduced PDCP functionalities. The reduced PDCP entity configured to the SURB is mainly used to record the transmission/reception status of the primary SL PDCP entity based on SL PDCP PDU SN (sequence number) in order to facilitate data transmission and to avoid unnecessary duplication transmission as well as to speed up split transmission over SURB. Also, a SURB may not have a corresponding backhaul bearer (Sl tunnel) to map on, as compared to regular RB over Uu. Instead, the UL SURB 226 of the primary SL connection’s transmitting device (UE 212) will be routed to the DL SURB 228 of receiving device(s) (e.g., UE 214) of the same primary SL connection 220. Herein, the UL SURB 226 may be unicast RB while the DL SURB 228 may be either unicast or multicast RB depending on, for example, whether the primary SL connection 220 is for one-to-one communication or one-to-many communication.

[0068] In a common situation a radio bearer may be provided between a UE and a BS, and a Sl backhaul bearer is provided to reach CN (core network). However, in an example embodiment, there may be a UL radio bearer (UL SURB 226), and UL data will not be routed to CN, but is routed to DL SURB 228 to SL RX UE 214. Lor example, if the involved SL UEs (e.g., UEs 212 and 214) are subscribed to the different PLMN (public land mobile networks), the support of SURB may also implicitly or explicitly indicate the multi-PLMN support wherein at least one of the serving PLMNs of the TX SL UE 212 or Rx SL UE 214 of primary SL connection 220 allows for RAN level access for UE from other PLMN for SURB. Because there can be more than one RX UE receiving from the same TX UE, it may be preferable to prioritize the serving RAN (radio access network (e.g., including BS 134) of the TX UE to support SURB.

[0069] One example case is where TX SL UE 212 and RX SL UE 214 may be connected to or camping on same cell or same BS. But a more complicated case may arise where UE 212 and UE 214 may be connected to or camping on two different cells or BSs, and these two BSs may communicate via X2/Xn connection to make it look like one BS, from UE perspective.

[0070] When UL SURB 226 and DL SURB 228 are configured, the common reduced PDCP entity 210 for UL and DL SURBs (226, 228) are established in BS 134. This common reduced PDCP entity 210 of BS 134 may represent or provide both: 1) the RX (receive) PDCP entity of UL SURB 226 that receives PDCP PDUs from the primary TX SL UE 212, and 2) the TX (transmit) PDCP entity of DL SURB 228 that transmits PDCP PDUs of the primary SL connection from BS 134 to the RX SL UE 214.

[0071] In case DL SURB 228 is configured for unicast transmission, the reduced PDCP entity 210 cooperates with the primary SL’s RX UE PDCP entity 216B based on the reported PDCP PDU SN in order to skip or speed up the transmission of received PDCP PDU of the primary SL over DL SURB 228 (e.g., by skipping or omitting the transmission of a PDU that has already been received by SL RX UE 214). To support this, the SL PDCP entity 216B of the primary SL’s RX UE 214 is triggered to transmit the PDCP PDU Reception Status Report (PDCP RSR) - indicates PDCP PDU SNs received, regardless whether a PDU was received via SL RB 222 or via SURB(s) 226 and 228, and thus no need to send/resend the indicated SNs via DL SURB 228 any PDU SN that has already been received. Also, another RSR case may be where RSR from RX SL UE 214 may indicate a missing PDU SN(s) to BS PDCP 210, e.g., indicating that lst and 3rd SNs were received (e.g., where 2 ^nd PDU SN is missing or not yet received by RX SL UE 214), and then BS 134 may apply or use a higher priority (e.g., apply priority resources, so that BS 134 may schedule missing SN as soon as possible) for DL SURB 228 to transmit the missing PDU to RX SL UE 214.

[0072] By way of illustrative example(s), the transmission of the PDCP RSR

(reception status report that is transmitted from the RX SL UE 214 to the BS 134) may be triggered by one or more of (as examples):

[0073] (i) when the gap (or difference) between a SN of a latest received PDCP

PDU from SL RB 222 and a SN of a latest received PDCP PDU from DL SURB 228 is larger than a configured threshold (note: this trigger may typically be used for duplication transmission). An example threshold may be 4 PDUs, and a SL RB transmission may be ahead of SURB transmission, e.g., because SL RB 222 is only 1 hop, SURB is 2 hops, and for example, a SL RB 222 transmission may be 4 PDUs ahead, and thus, these 4 PDUs do not need to be transmitted by BS 134 via DL SURB 228, and can be deleted/discarded (and not transmitted) by BS 134 and not sent via DL SURB 228; and/or

[0074] (ii) when a missing PDCP PDU is identified by PDCP entity 216B of

RX SL UE 214 (note, this trigger may be applied, for example, based on either duplication and/or split transmission), which may cause the BS 134 to prioritize (e.g., allocate resources for immediate or quick transmission) allocation of DL SURB resources to transmit the missing PDU; and/or

[0075] (iii) periodically (where RSR may be sent every X seconds, or every X subframes or slots, etc.).

[0076] The PDCP RSR (reception status report from RX SL UE 214) may, for example, indicate either the last in-sequence received PDCP PDU or a missing PDCP PDU(s) of the SL reception (for SL RB 222). Based on the received PDCP RSR, the reduced PDCP entity 210 at the serving BS 134 may omit or skip transmission of (not transmit) one or more PDUs that have already been received by RX SL UE 214, but have not been transmitted from the BS 134 over DL SURB 228, e.g., in case of duplication. If the missing PDCP PDU is reported by the PDCP RSR and the reported missing PDCP PDU(s) is in the reduced PDCP entity buffer, the BS 134 may determine to temporarily increase the scheduling priority of the DL SURB 228 to speed up (e.g., reduce transmission delay or latency, which may include prioritizing resources for) the transmission of the missing PDCP PDU from the BS 134 to RX SL UE 214.

[0077] Also, according to an example embodiment, PDU SNs in UL SURB 228 may be same as PDU SNs in DL SURB 228 (e.g., a PDU that is received by BS 134 via UL SURB 226 may have a same SN as the same PDU that is sent/forwarded by BS 134 via DL SURB 228). Also, for example, PDU SNs for SL RB 222 may be (or may use) the same PDU SNs as the UL SURB 226, for same or duplicate PDUs that are transmitted on both SL RB 222 and UL SURB 226. Thus, for example, a same PDU SN may be used for a PDU that is transmitted on (or duplicated on) SL RB 222, UL SURB 226 and/or DL SURB 228. This may simplify operation of the SURB and/or PDCP entity 210 of BS 134, since TX SL UE 212, PDCP entity 210 of BS 134 and/or RX SL UE 214 may use a same (or common) PDU SN(s) for same or duplicate PDUs, so that no PDU SN conversion is necessary between different radio bearers, for example.

[0078] To improve the power consumption of RX SL UE 214, the RX SL UE

214 may omit receiving and/or decoding data via DL SURB 228 if no missing PDCP PDU has been identified even though DL SURB is used to transmit the duplicated data. Thus, because SL connection may be a primary connection, and Uu connection (via BS 134) may be secondary connection, the RX SL UE 214 may, for example, receive and/or decode data via the DL SURB 228 only if RX SL UE 214 identifies a PDU SN was not received (and thus the RX SL UE 214 should attempt to receive such missing PDU via the DL SURB 228 of the secondary connection 224). On the other hand, if RX SL UE 214 receives a PDU via SL RB 222, then the RX SL UE 214 may skip or not receive this PDU via DL SURB 228, e.g., to improve power consumption of the RX SL UE 214, for example. [0079] Also, according to an example embodiment, single or combined buffer status report (BSR) may be reported by TX SL UE 212 for both SL RB 222 and UL SURB 226. Thus, a UE 212 may report only one BSR for both UL SURB 228 and SL RB 222, as there may be no need to have separate SL BSR (buffer status report) and a SURB BSR. Also, to allow for RX SL UE 214 to use the DL SURB 228 of secondary connection to receive a missing PDU (e.g., which was not received via SL RB 222), a BS 134 may advantageously allocate the SL resources earlier than (or before) UL resources for UL SURB, to make sure the UE always transmits a PDU via SL RB 222 before transmitting the same PDU via UL SURB 226 to BS 134 (where BS 134 may typically forward such PDU to RX SL UE 214). This may allow the RX SL UE 214 to determine whether the resources allocated for the DL SURB 228 should be monitored (e.g., if there is a missing PDU) in order to obtain a missing PDU (a PDU not yet received by RX SL UE 214). In this example, the RX SL UE 214 may detect and receive the data/PDU via DL SURB 228(of secondary connection 224), e.g., when (such as only when) RX SL UE 214 was unable to receive the same PDU via SL RB 222 (or primary connection). Or, the RX SL UE 214 may detect a missing PDU, and then monitors resources assigned (allocated) to DL SURB 228 to receive the missing PDU until RX SL UE 214 receives the missing PDU. Thus, in an example embodiment, a SL connection 220 (and SL RB 222) may be used as primary, and then when a missing PDU is detected by RX SL UE 214, the RX SL UE 214 may then spend time/energy to monitor DL SURB 228 to receive missing PDU. So the SL transmission of data may, for example, be performed by TX SL UE 212 before transmission of same data in UL SURB 226 to BS 134. In UE

autonomous resource allocation, for UL SURB transmission to BS, there may be, for example, a 4 TTI (transmission time interval) delay between UL grant received by TX UE, and the UE TX UL data. If TX SL UE 212 has not yet transmitted the same PDU, then the TX SL UE 212 should transmit via SL connection 220 the same data in less than 4 TTIs, so that SL transmission of the PDU would occur before transmission of that PDU via UL SURB (could be transmitted via same TTI, or earlier TTI as UL SURB TX for example.). This enhancement can be applied for both options of DL unicast and broadcast/multicast transmissions. To ensure that the RX SL UE does not miss any useful duplication transmission from DL SURB 228, TX SL UE 212 should select SL resources to transmit the PDCP PDU over the primary SL connection, e.g., no later than the scheduled UL transmission on UL SURB 226 for the same PDCP PDU if the primary SL connection 220 is configured to use UE autonomous resource allocation mode. If the primary SL connection 220 is configured to use the BS scheduled resource allocation mode, the BS scheduling can allocate SL resources in the subframes earlier than that allocated for UL SURB, for example.

[0080] Lor duplication transmission via the primary SL RB 222 and SURB

(226, 228), if the primary SL RB 222 is configured to use the BS scheduled resource allocation, the SL RB and corresponding UL SURB may share the same BSR (buffer status report). That is, the UL-BSR on SURB can be skipped and the BS 134 may allocate the UL resources for SURB based on the received SL-BSR of the primary SL or vice versa. TX SL UE 212 may send a (combined) BSR to BS 134 for both SL RB 222 and UL SURB 226. If SL RB 222 is BS scheduled, then transmission is scheduled by BS 134, then this informs BS how much data is buffered at TX SL UE 212, and BS can schedule SL RB 222 and UL SURB 226. BS 134 may, for example, schedule resources for SL RB 222 transmissions before resources for UL SURB 226 transmissions. This common BSR for SL RB 222 and UL SURB 226 may be also applied for the split transmission and BS 134 may determine how to split the transmission of reported buffered data between SL RB 222 and UL SURB 226.

[0081] According to an example embodiment, a common reduced PDCP entity

210 may be configured for BS 134, instead of the full independent PDCP entity for UL SURB 226 and DL SURB 228. The e2e SL PDCP entity (PDCP entities 216A, 216B) may include or provide a full functionality of PDCP, e.g., such as ciphering, header compression, reordering and duplication detection etc. Therefore, these functions are not needed in the reduced PDCP entity 210 of SURB in the BS 134. The SL PDCP PDU format may be used by the reduced PDCP entity 210 in the BS 134 to identify the SN. Thus, in an example embodiment, PDCP entity 210 at BS 134 may be merely forwarding data, and tracking and/or checking SNs of PDUs to assist in data transmission or delivery between TX SL UE 212 and RX SL UE 214 via BS 134. Lor example, the other PDCP functions may be handled at the SL UEs 212, 214.

[0082] According to an example embodiment, there may be a SDU Type field in SL PDCP PDU header. If SURB is configured for either duplication or split data of primary SL RB, the SL PDCP entity 216A may be configured to determine duplication or split based on the SDU type field indication. For instance, the SDUs with type“PC5 signaling” may be duplicated to the SURB while the SDUs with type“IP” or“non- IP” may be split to the SURB. The SURB in the BS 134 may also use SDU type field to identify whether it is duplicated or split data and then process the data differently. Thus, under duplication, each PDU transmitted over SL RB 222 may be duplicated and also transmitted over secondary (Uu) connection 220 (SURBs 226, 228). In another example embodiment, PDCP entity 216A may duplicate only certain SDUs types for transmission over SURB, such as control SDUs or PC5 signaling, and not data SDUs, for example.

[0083] FIG. 4 is a diagram illustration operation of a network according to an example embodiment. As shown in FIG. 4, a TX SL UE 212, a RX SL UE 214, and a BS 134 are in communication. At 410, a primary SL connection 220 (e.g., including a SL RB 222) may be established between TX SL UE 212 and RX SL UE 214. At 412, a SURB establishment request (412) is sent by TX SL UE 212 to BS 134 e.g., to request establishment of UL SURB 226 and DL SURB 228. At 414 and 416, a SURB establishment (reduced PDCP configuration) (414) is received by the TX SL UE 212 from the BS 134, and received by RX SL UE 214 from BS 134, including one or more SURB configuration parameters, e.g., RLC, MAC and PHY (physical layer) related configurations for the UL SURB 226 and DL SURB 228, for example. At 418, BS 134 establishes a common reduced (and/or virtual) PDCP entity 210 for SURB (226, 228) for UE 212 and UE 214. At 420, TX SL UE 212 may transmit a common SL RB/UL SURB buffer status report (BSR) for both SL RB and UL SURB, e.g., which may indicate a status of a data buffer for transmission via both SL RB and UL SURB. At 422, TX SL UE 212 may transmit data over a primary (SL) connection 220 and SL RB 222 to RX SL UE 214. At 424, TX SL UE 212 may transmit duplicated data (e.g., duplicate PDU(s)) via UL SURB 226 to BS 134.

[0084] At 426, RX SL UE 214 may detect a trigger to send the PDCP RSR to

BS 134, such as: (i) when a gap (or difference) between a SN of a latest received PDCP PDU from SL RB 222 and a SN of a latest received PDCP PDU from DL SURB 228 is larger than a configured threshold; and/or (ii) when a missing PDCP PDU is identified by PDCP entity 216B of RX SL UE 214; and/or (iii) periodically.

[0085] At 428, in response to detecting the trigger condition, the RX SL UE 214 sends the reception status report (RSR) to BS 134. At 430, the BS 134 may determine whether to skip (or omit transmission and discard) a transmission of a received PDCP PDU(s) based on reported SN in RSR. For example, if a PDU was indicated in RSR as already received by RX SL UE 214, then the BS 134 may determine that this received PDU may be omitted or skipped, and discarded. But, at 432, another PDU that was indicated in RSR as not received may be transmitted (a duplicate is transmitted by BS 134 via DL SURB 228 to RX SL UE 214).

[0086] Embodiment 1 : FIG. 5 is a flow chart illustrating operation of a base station according to an example embodiment. Operation 510 includes establishing, by a base station, a first connection that includes an uplink radio bearer between a first sidelink user device and the base station and a downlink radio bearer between the base station and a second sidelink user device. Operation 520 includes receiving, by a protocol entity of the base station via the uplink radio bearer, one or more protocol data units from the first sidelink user device. And, operation 530 includes transmiting, by the protocol entity of the base station via the downlink radio bearer, one or more of the received protocol data units to the second sidelink user device. For operation 540, the protocol entity of the base station is a common protocol entity that both tracks sequence numbers of the one or more protocol data units that are received by the protocol entity of the base station from the first sidelink user device via the uplink radio bearer and tracks sequence numbers of the one or more protocol data units that are transmitted by the protocol entity of the base station to the second sidelink user device via the downlink radio bearer.

[0087] Embodiment 2: According to an example embodiment of embodiment

1 , wherein a second connection that includes a sidelink radio bearer is established between the first sidelink user device and the second sidelink user device.

[0088] Embodiment 3: According to an example embodiment of any of embodiments 1-2, wherein the protocol entity of the base station is a common Packet Data Convergence Protocol (PDCP) entity.

[0089] Embodiment 4: According to an example embodiment of any of embodiments 1-3, and further comprising receiving, by the protocol entity of the base station from the second sidelink user device, a reception status report that either identifies one or more protocol data units that have been received by the second sidelink user device or identifies one or more protocol data units that have not been received by the second sidelink user device; wherein the transmitting, by the protocol entity of the base station via the downlink radio bearer comprises: transmitting, by the protocol entity of the base station via the downlink radio bearer based on the reception status report, one or more of the received protocol data units to the second sidelink user device.

[0090] Embodiment 5: According to an example embodiment of any of embodiments 1-4, wherein a second connection is provided between the first sidelink user device and the second sidelink user device via a sidelink radio bearer.

[0091] Embodiment 6: According to an example embodiment of any of embodiments 1-5, and further comprising receiving, by the base station from the first sidelink user device, a common buffer status report that identifies a status of a data buffer of the first sidelink user device for transmission via the sidelink radio bearer to the second sidelink user device and for transmission via the uplink radio bearer to the base station; allocating a first set of resources for the first sidelink user device to transmit one or more protocol data units via the sidelink radio bearer to the second sidelink user device; and allocating a second set of resources for the first sidelink user device to transmit one or more protocol data units to the base station via the uplink radio bearer.

[0092] Embodiment 7: According to an example embodiment of any of embodiments 1 -6 wherein a same sequence number is used for a protocol data unit that is both received by the base station via the uplink radio bearer from the first sidelink user device and then transmitted by the base station via the downlink radio bearer to the second sidelink user device.

[0093] Embodiment 8: According to an example embodiment of any of embodiments 1-7, wherein a same sequence number is used for a protocol data unit that is both received by the base station via the uplink radio bearer from the first sidelink user device and transmitted by the first sidelink user device to the second sidelink user device via a sidelink radio bearer.

[0094] Embodiment 9: According to an example embodiment of any of embodiments 4-8 , wherein the receiving, by the base station from the second sidelink user device, a reception status report comprises receiving a reception status report indicating that a first protocol data unit has been received by the second sidelink user device and that a second protocol data unit is missing or has not been received by the second sidelink user device; wherein the transmitting comprises omitting or skipping, by the base station, a transmission of the first protocol data unit that has already been received by the second sidelink user device, and transmitting, by the base station to the second sidelink user device, the second protocol data unit that is missing or has not been received by the second sidelink user device.

[0095] Embodiment 10: According to an example embodiment of any of embodiments 1-9, wherein the base station comprises: a first base station connected to the first sidelink user device; and a second base station connected to the second sidelink user device, wherein a base-station-to-base station connection is provided between the first base station and the second base station.

[0096] Embodiment 11 : According to an example embodiment of any of embodiments 2-10, wherein the second connection between the first sidelink user device and the second sidelink user device is a primary connection; and wherein the first connection is a secondary connection, wherein the base station transmits a duplicate protocol data unit via the downlink radio bearer of the secondary connection to the second sidelink user device for one or more of the protocol data units transmitted via the primary connection.

[0097] Embodiment 12: An apparatus comprising means for performing a method of any of embodiments 1-11.

[0098] Embodiment 13: An apparatus comprising at least one processor and at least one memory including computer instructions that, when executed by the at least one processor, cause the apparatus to perform a method of any of embodiments 1-12.

[0099] Embodiment 14: An apparatus comprising a computer program product including a non-transitory computer-readable storage medium and storing executable code that, when executed by at least one data processing apparatus, is configured to cause the at least one data processing apparatus to perform a method of any of embodiments 1- 1 1. [00100] Embodiment 15: An apparatus comprising at least one processor and at least one memory including computer instructions that, when executed by the at least one processor, cause the apparatus to: establish, by a base station, a first connection that includes an uplink radio bearer between a first side link user device and the base station and a downlink radio bearer between the base station and a second sidelink user device; receive, by a protocol entity of the base station via the uplink radio bearer, one or more protocol data units from the first sidelink user device; and transmit, by the protocol entity of the base station via the downlink radio bearer, one or more of the received protocol data units to the second sidelink user device; wherein the protocol entity of the base station is a common protocol entity that both tracks sequence numbers of the one or more protocol data units that are received by the protocol entity of the base station from the first sidelink user device via the uplink radio bearer and tracks sequence numbers of the one or more protocol data units that are transmitted by the protocol entity of the base station to the second sidelink user device via the downlink radio bearer.

[00101] Embodiment 16: FIG. 6 is a flow chart illustrating operation of a user device according to an example embodiment. Operation 610 includes establishing, by a second sidelink user device, a first connection that includes a downlink bearer between a base station and the second sidelink user device. Operation 620 includes establishing, a second connection that includes a sidelink radio bearer between a first sidelink user device and the second sidelink user device. Operation 630 includes receiving, by the second sidelink user device from the first sidelink user device via the sidelink radio bearer, one or more protocol data units. Operation 640 includes receiving, by the second sidelink user device from the base station via the downlink bearer, one or more protocol data unit. For operation 650, a common set of sequence numbers are used for a set of protocol data units, for at least one of: 1 ) duplication of the set of protocol data units via both the sidelink bearer and the downlink bearer, or 2) splitting each protocol data unit of the set of protocol data units via either of the sidelink bearer and the downlink bearer.

[00102] Embodiment 17: FIG. 7 is a flow chart illustrating operation of a user device according to an example embodiment. Operation 710 includes establishing, by a second sidelink user device, a first connection that includes a downlink bearer between a base station and the second sidelink user device. Operation 720 includes establishing, a second connection that includes a sidelink radio bearer between a first sidelink user device and the second sidelink user device. Operation 730 includes receiving, by the second sidelink user device from the first sidelink user device via the sidelink radio bearer, one or more protocol data units. Operation 740 includes receiving, by the second sidelink user device from the base station via the downlink bearer, one or more protocol data unit. For operation 750, a same sequence number is used for a protocol data unit that is both received by the second sidelink user device from the first sidelink user device via the sidelink radio bearer and received by the second sidelink user device from the base station via the downlink radio bearer.

[00103] Embodiment 18: According to an example embodiment of embodiment 17, and further comprising: sending, by the second sidelink user device to the base station, a reception status report that indicates either one or more protocol data units that have been received by the second sidelink user device or one or more protocol data units that have not been received by the second sidelink user device.

[00104] Embodiment 19: According to an example embodiment of any of embodiments 17-18, and further comprising: receiving, by the second sidelink user device from the base station via the downlink radio bearer, one or more protocol data units that have not yet been received by the second sidelink user device.

[00105] Embodiment 20: According to an example embodiment of any of embodiments 17-19, wherein the second connection is a primary connection for receiving protocol data units by the second sidelink user device from the first sidelink user device, and the first connection is a secondary connection for receiving protocol data units by the second sidelink user device.

[00106] Embodiment 21 : According to an example embodiment of any of embodiments 17-20, wherein the sending the reception status report is performed in response to one or more of the following: determining, by the second sidelink user device, that a gap between a sequence number of a latest received protocol data unit received by the second sidelink user device from the first sidelink user device via the sidelink radio bearer and a sequence number of a latest received protocol data unit received by the second sidelink user device from the base station via the downlink radio bearer is greater than a threshold; determining, by the second sidelink user device, that a protocol data unit is missing or has not been received from the first sidelink user device via the sidelink radio bearer; and periodically, or at a periodic time interval.

[00107] Embodiment 22: An apparatus comprising means for performing a method of any of embodiments 16-21.

[00108] Embodiment 23: An apparatus comprising at least one processor and at least one memory including computer instructions that, when executed by the at least one processor, cause the apparatus to perform a method of any of embodiments 16-21.

[00109] Embodiment 24: An apparatus comprising a computer program product including a non-transitory computer-readable storage medium and storing executable code that, when executed by at least one data processing apparatus, is configured to cause the at least one data processing apparatus to perform a method of any of embodiments 16-21.

[00110] Embodiment 25: An apparatus comprising at least one processor and at least one memory including computer instructions that, when executed by the at least one processor, cause the apparatus to: establish, by a second sidelink user device, a first connection that includes a downlink bearer between a base station and the second sidelink user device; establish, a second connection that includes a sidelink radio bearer between a first sidelink user device and the second sidelink user device; receive, by the second sidelink user device from the first sidelink user device via the sidelink radio bearer, one or more protocol data units; and receive, by the second sidelink user device from the base station via the downlink bearer, one or more protocol data unit; wherein a same sequence number is used for a protocol data unit that is both received by the second sidelink user device from the first sidelink user device via the sidelink radio bearer and received by the second sidelink user device from the base station via the downlink radio bearer.

[00111] Embodiment 26: FIG. 8 is a flow chart illustrating operation of a base station according to another example embodiment. Operation 810 includes establishing, by a base station, a first connection that includes an uplink radio bearer between a first sidelink user device and the base station and a downlink radio bearer between the base station and a second sidelink user device. Operation 820 includes receiving, by a protocol entity of the base station via the uplink radio bearer, one or more protocol data units from the first sidelink user device. Operation 830 includes transmitting, by the protocol entity of the base station via the downlink radio bearer, one or more of the received protocol data units to the second sidelink user device. For operation 840, a sidelink radio bearer is established between the first sidelink user device and the second sidelink user device. And for operation 850, a common set of sequence numbers are used for a set of protocol data units, for at least one of: 1) duplication of the set of protocol data units via both the sidelink bearer and the downlink bearer, or 2) splitting each protocol data unit of the set of protocol data units via either of the sidelink bearer and the downlink bearer.

[00112] Embodiment 27: FIG. 9 is a flow chart illustrating operation of a base station according to another example embodiment. Operation 910 includes establishing, by a base station, a first connection that includes an uplink radio bearer between a first sidelink user device and the base station and a downlink radio bearer between the base station and a second sidelink user device. Operation 920 includes receiving, by a protocol entity of the base station via the uplink radio bearer, one or more protocol data units from the first sidelink user device. Operation 930 includes transmitting, by the protocol entity of the base station via the downlink radio bearer, one or more of the received protocol data units to the second sidelink user device. For operation 940, a sidelink radio bearer is established between the first sidelink user device and the second sidelink user device. And, for operation 950, a same sequence number is used for a protocol data unit that is both: 1) transmitted by the first sidelink user device to the second sidelink user device via the sidelink radio bearer, and 2) transmitted by the base station to the second sidelink user device via the downlink radio bearer.

[00113] FIG. 10 is a block diagram of a wireless station (e.g., AP, BS, relay node, eNB/gNB, UE or user device) 1000 according to an example embodiment. The wireless station 1000 may include, for example, one or two RF (radio frequency) or wireless transceivers 1002A, 1002B, where each wireless transceiver includes a transmitter to transmit signals and a receiver to receive signals. The wireless station also includes a processor or control unit/entity (controller) 1004 to execute instructions or software and control transmission and receptions of signals, and a memory 1006 to store data and/or instructions. [00114] Processor 1004 may also make decisions or determinations, generate frames, packets or messages for transmission, decode received frames or messages for further processing, and other tasks or functions described herein. Processor 1004, which may be a baseband processor, for example, may generate messages, packets, frames or other signals for transmission via wireless transceiver 1002 (1002A or 1002B). Processor 1004 may control transmission of signals or messages over a wireless network, and may control the reception of signals or messages, etc., via a wireless network (e.g., after being down-converted by wireless transceiver 1002, for example). Processor 1004 may be programmable and capable of executing software or other instructions stored in memory or on other computer media to perform the various tasks and functions described above, such as one or more of the tasks or methods described above. Processor 1004 may be (or may include), for example, hardware, programmable logic, a programmable processor that executes software or firmware, and/or any combination of these. Using other terminology, processor 1004 and transceiver 1002 together may be considered as a wireless transmitter/receiver system, for example.

[00115] In addition, referring to FIG. 7, a controller (or processor) 1008 may execute software and instructions, and may provide overall control for the station 1000, and may provide control for other systems not shown in FIG. 10, such as controlling input/output devices (e.g., display, keypad), and/or may execute software for one or more applications that may be provided on wireless station 1000, such as, for example, an email program, audio/video applications, a word processor, a Voice over IP application, or other application or software.

[00116] In addition, a storage medium may be provided that includes stored instructions, which when executed by a controller or processor may result in the processor 1004, or other controller or processor, performing one or more of the functions or tasks described above.

[00117] According to another example embodiment, RF or wireless transceiver(s) 1002A/1002B may receive signals or data and/or transmit or send signals or data.

Processor 1004 (and possibly transceivers 1002A/1002B) may control the RF or wireless transceiver 1002A or 1002B to receive, send, broadcast or transmit signals or data.

[00118] The embodiments are not, however, restricted to the system that is given as an example, but a person skilled in the art may apply the solution to other

communication systems. Another example of a suitable communications system is the 5G concept. It is assumed that network architecture in 5G will be quite similar to that of the LTE-advanced. 5G is likely to use multiple input - multiple output (MIMO) antennas, many more base stations or nodes than the LTE (a so-called small cell concept), including macro sites operating in co-operation with smaller stations and perhaps also employing a variety of radio technologies for better coverage and enhanced data rates.

[00119] It should be appreciated that future networks may utilise network functions virtualization (NFV) which is a network architecture concept that proposes virtualizing network node functions into“building blocks” or entities that may be operationally connected or linked together to provide services. A virtualized network function (VNF) may comprise one or more virtual machines running computer program codes using standard or general type servers instead of customized hardware. Cloud computing or data storage may also be utilized. In radio communications this may mean node operations may be carried out, at least partly, in a server, host or node operationally coupled to a remote radio head. It is also possible that node operations may be distributed among a plurality of servers, nodes or hosts. It should also be understood that the distribution of labour between core network operations and base station operations may differ from that of the LTE or even be non-existent.

[00120] Embodiments of the various techniques described herein may be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations of them. Embodiments may implemented as a computer program product, i.e., a computer program tangibly embodied in an information carrier, e.g., in a machine-readable storage device or in a propagated signal, for execution by, or to control the operation of, a data processing apparatus, e.g., a programmable processor, a computer, or multiple computers. Embodiments may also be provided on a computer readable medium or computer readable storage medium, which may be a non-transitory medium. Embodiments of the various techniques may also include embodiments provided via transitory signals or media, and/or programs and/or software embodiments that are downloadable via the Internet or other network(s), either wired networks and/or wireless networks. In addition, embodiments may be provided via machine type communications (MTC), and also via an Internet of Things (IOT).

[00121] The computer program may be in source code form, object code form, or in some intermediate form, and it may be stored in some sort of carrier, distribution medium, or computer readable medium, which may be any entity or device capable of carrying the program. Such carriers include a record medium, computer memory, read only memory, photoelectrical and/or electrical carrier signal, telecommunications signal, and software distribution package, for example. Depending on the processing power needed, the computer program may be executed in a single electronic digital computer or it may be distributed amongst a number of computers.

[00122] Furthermore, embodiments of the various techniques described herein may use a cyber-physical system (CPS) (a system of collaborating computational elements controlling physical entities). CPS may enable the embodiment and

exploitation of massive amounts of interconnected ICT devices (sensors, actuators, processors microcontrollers, ...) embedded in physical objects at different locations. Mobile cyber physical systems, in which the physical system in question has inherent mobility, are a subcategory of cyber-physical systems. Examples of mobile physical systems include mobile robotics and electronics transported by humans or animals.

The rise in popularity of smartphones has increased interest in the area of mobile cyber physical systems. Therefore, various embodiments of techniques described herein may be provided via one or more of these technologies.

[00123] A computer program, such as the computer program(s) described above, can be written in any form of programming language, including compiled or interpreted languages, and can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit or part of it suitable for use in a computing environment. A computer program can be deployed to be executed on one computer or on multiple computers at one site or distributed across multiple sites and interconnected by a communication network.

[00124] Method steps may be performed by one or more programmable processors executing a computer program or computer program portions to perform functions by operating on input data and generating output. Method steps also may be performed by, and an apparatus may be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application-specific integrated circuit).

[00125] Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer, chip or chipset. Generally, a processor will receive instructions and data from a read-only memory or a random access memory or both. Elements of a computer may include at least one processor for executing instructions and one or more memory devices for storing instructions and data.

Generally, a computer also may include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto-optical disks, or optical disks. Information carriers suitable for embodying computer program instructions and data include all forms of non-volatile memory, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks. The processor and the memory may be supplemented by, or incorporated in, special purpose logic circuitry.

[00126] To provide for interaction with a user, embodiments may be

implemented on a computer having a display device, e.g., a cathode ray tube (CRT) or liquid crystal display (LCD) monitor, for displaying information to the user and a user interface, such as a keyboard and a pointing device, e.g., a mouse or a trackball, by which the user can provide input to the computer. Other kinds of devices can be used to provide for interaction with a user as well; for example, feedback provided to the user can be any form of sensory feedback, e.g., visual feedback, auditory feedback, or tactile feedback; and input from the user can be received in any form, including acoustic, speech, or tactile input.

[00127] Embodiments may be implemented in a computing system that includes a back-end component, e.g., as a data server, or that includes a middleware component, e.g., an application server, or that includes a front-end component, e.g., a client computer having a graphical user interface or a Web browser through which a user can interact with an embodiment, or any combination of such back-end, middleware, or front-end components. Components may be interconnected by any form or medium of digital data communication, e.g., a communication network. Examples of communication networks include a local area network (LAN) and a wide area network (WAN), e.g., the Internet.

[00128] While certain features of the described embodiments have been illustrated as described herein, many modifications, substitutions, changes and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the various embodiments.