WO2019097108A1

WO2019097108A1 - Multi-gnb pdcp duplication report for multi-connectivity in urllc scenarios

Info

Publication number: WO2019097108A1
Application number: PCT/FI2018/050711
Authority: WO
Inventors: Klaus Pedersen; Daniela Laselva; Nurul MAHMOOD
Original assignee: Nokia Technologies Oy
Priority date: 2017-11-16
Filing date: 2018-10-04
Publication date: 2019-05-23

Abstract

In accordance with example embodiments of the invention as disclosed herein there is at least a method and apparatus to perform receiving at a user equipment of a communication network an indication of at least one packet data unit that is to be received from at least one base station of a set of base stations of the communication network communicatively coupled to the user equipment; determining whether the at least one packet data unit to be received is a duplicate of at least one packet data unit already received by the user equipment; and based on determining that the at least one packet data unit is a duplicate packet data unit, informing at least one other base station of the communication network of the duplicate at least one packet data unit. Further, to perform determining that at least one packet data unit that is to be sent to a user equipment of a communication network is a duplicate at least one packet data unit already received by the user equipment; and based on determining that the at least one packet data unit to be sent to the user equipment is a duplicate packet data unit, informing the user equipment of the duplicate at least one packet data unit.

Description

MULTI-GNB PDCP DUPLICATION REPORT FOR MULTI-CONNECTIVITY IN

URLLC SCENARIOS

TECHNICAL FIELD:

The teachings in accordance with the exemplary embodiments of this invention relate generally to a signaling sequence design that allows detection and elimination of duplicate packets, such as radio link control, medium access control, and/or packet data convergence protocol packets to be communicated between network devices, and more specifically relate to novel signalling between network devices such as user equipment and a base station to allow detection and elimination of the communication of these duplicate packets between multi-connected network devices.

BACKGROUND:

This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.

Certain abbreviations that may be found in the description and/or in the Figures are herewith defined as follows:

5G NR: 5G New Radio

ACK: Acknowledgment

CA: Carrier Aggregation

DC: Dual Connectivity

DCI: Downlink Control Information

EN-DC: E-Utran-NR DC

HARQ: Hybrid Automatic Repeat Request

MAC: Medium Access Control

MC: Multi-connected

MgNB: Master g Node B

NE-DC: NR-E-Utran DC

PDCP: Packet Data Convergence Protocol

PDU: Packet Data Unit PHY: Physical

RAN Radio Access Network

RLC: Radio Link Controller

SgNB: Secondary g Node B

SN: Sequence Number

URLLC Ultra-Reliable Low Latency Communication

X2: X2 interface between two eNBs

Xn: Xn interface between two gNBs

Dual connectivity (DC), as standardized by 3 GPP in LTE Release 12/13, extends the LTE- Advanced Carrier Aggregation (CA) functionality to allow a user equipment (UE) to simultaneously receive/send data from / to two different eNBs via a master eNB (MeNB) and secondary eNB (SeNB). In dual connectivity (or multi-connectivity) situations user plane (PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminations are established by the base stations towards the UE. The base stations are interconnected with each other by means of the X2 interface, and also connected to the network by means of an S 1 interface. The S 1 interface supports a many-to-many relation between MMEs / Serving Gateways and eNBs. Further, in dual or multi-connectivity situations the PDCP layer in the RAN cloud would be responsible for duplicating the data across multiple cells.

However, issues with this data duplication across multiple cells in multi-connectivity situations includes that a device such as a UE communicatively coupled to more than one other network device will likely receive the same PDCP packets from more than one of these devices. Thus, a multi-connected environment a network device, such as a serving base station (i.e. PDCP anchor node), will send duplicates of PDCP packets it receives, to the other network devices or base stations also communicating with the UE in a multi-connected environment. This can result in at least increased overhead for internetworking between cells, increased signal processing delays, unnecessary network traffic/load, and/or additional interference, which the Applicant feels needs to be addressed.

The example embodiments of the invention work to overcome at least the issues described above.

SUMMARY:

In an example aspect of the invention, there is a method, such as performed by a user side apparatus, comprising: receiving at a user equipment of a communication network an indication of at least one packet data unit that is to be received from at least one base station of a set of base stations of the communication network communicatively coupled to the user equipment; determining whether the at least one packet data unit to be received is a duplicate of at least one packet data unit already received by the user equipment; and based on determining that the at least one packet data unit is a duplicate packet data unit, informing at least one other base station of the communication network of the duplicate at least one packet data unit.

A further example embodiment is a method comprising the method of the previous paragraph, wherein the at least one packet data unit is received in a transport block transmission, and wherein the transport block comprises a medium access control (MAC) packet data unit, wherein the medium access control packet data unit comprises a medium access control service data unit which includes one Packet Data Convergence Protocol service data unit, where there is receiving an indication from a base station of the set of base stations that the at least one packet data unit is a duplicate packet data unit, wherein the indication comprises a one bit duplication flag received in downlink control information by the user equipment prior to reception of the at least one packet data unit at the user equipment, and wherein one bit duplication flag is associated with a scheduled transmission time interval of the at least one packet.

A non-transitory computer-readable medium storing program code, the program code executed by at least one processor to perform at least the method as described in the paragraphs above.

In another example aspect of the invention, there is an apparatus, such as a user equipment side apparatus, comprising: at least one processor; and at least one memory including computer program code, where the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to at least: receive at a user equipment of a communication network an indication of at least one packet data unit that is to be received from at least one base station of a set of base stations of the communication network communicatively coupled to the user equipment; determine whether the at least one packet data unit to be received is a duplicate of at least one packet data unit already received by the user equipment; and based on determining that the at least one packet data unit is a duplicate packet data unit, inform at least one other base station of the communication network of the duplicate at least one packet data unit.

A further example embodiment is an apparatus comprising the apparatus of the previous paragraph, wherein the at least one packet data unit is received in a transport block transmission, and wherein the transport block comprises a medium access control packet data unit, wherein the medium access control packet data unit comprises a medium access control service data unit which includes one Packet Data Convergence Protocol service data unit, where there is receiving an indication from a base station of the set of base stations that the at least one packet data unit is a duplicate packet data unit, wherein the indication comprises a one bit duplication flag received in downlink control information by the user equipment prior to reception of the at least one packet data unit at the user equipment, and wherein one bit duplication flag is associated with a scheduled transmission time interval of the at least one packet.

In another example aspect of the invention, there is an apparatus, such as a user equipment side apparatus, comprising: means for receiving at a user equipment of a communication network an indication of at least one packet data unit that is to be received from at least one base station of a set of base stations of the communication network communicatively coupled to the user equipment; means for determining whether the at least one packet data unit to be received is a duplicate of at least one packet data unit already received by the user equipment; and means, based on determining that the at least one packet data unit is a duplicate packet data unit, for informing at least one other base station of the communication network of the duplicate at least one packet data unit.

In an example aspect of the invention, there is a method, such as a method that may be performed by a network side apparatus, comprising determining that at least one packet data unit that is to be sent to a user equipment of a communication network is a duplicate at least one packet data unit already received by the user equipment; and based on determining that the at least one packet data unit to be sent to the user equipment is a duplicate packet data unit, informing the user equipment of the duplicate at least one packet data unit. A further example embodiment is a method comprising the method of the previous paragraph, wherein the at least one packet data unit comprises a radio link controller, a multiple access channel, and a Packet Data Convergence Protocol packet data unit, wherein there is receiving from the user equipment a“new ACK report” indicating a duplicate reporting set comprising one or more network devices associated with a sent duplicated packet data unit, wherein the informing is using an indication flag sent to the user equipment identifying that the at least one packet data unit to be sent is a duplicate, wherein the indication flag comprises a one bit duplication flag sent in downlink control information to the user equipment prior to reception of the at least one packet data unit by the user equipment, wherein the one bit duplication flag is associated with a scheduled transmission time interval of the at least one packet data unit, wherein the one bit duplication flag is applicable to only radio bearers that are at least one of configured for multi- connectivity and mapped to certain quality of service class identifiers, wherein the downlink control information is identifying a packet data convergence protocol window to be conducted for the user equipment in which the duplicate at least one packet data unit is to be sent to the user equipment, wherein there is for a case the at least one packet data convergence protocol packet data unit to be sent to a user equipment comprises at least one packet data convergence protocol packet data unit belonging to radio bearers configured for the multi-connectivity, the one bit duplication flag applies to all of the at least one packet data convergence protocol packet data unit, wherein the at least one packet data unit comprises at least one packet data convergence protocol packet data unit, and for a case the at least one packet data convergence protocol packet data unit to be sent to a user equipment comprises at least one packet data convergence protocol packet data unit belonging to radio bearers configured for the multi-connectivity, the at least one packet data convergence protocol packet data unit are to be sent in a same transmission, wherein there is in response to the informing, receiving from the user equipment a packet data convergence protocol status report comprising an acknowledgement to at least one other base station, wherein the at least one other base station is not a base station that sent the duplicate at least one packet data unit, wherein the acknowledgment is indicating the duplicate at least one packet data unit, wherein the acknowledgment causes the at least one other base station to flush any packet data convergence protocol packets that are associated with the indicated duplicate packet data unit and that are buffered at a packet data convergence protocol layer of the at least one other base station.

A non-transitory computer-readable medium storing program code, the program code executed by at least one processor to perform at least the method as described in the paragraphs above. In another example aspect of the invention, there is an apparatus, such as a network side apparatus, comprising: at least one processor; and at least one memory including computer program code, where the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to at least: determine that at least one packet data unit that is to be sent to a user equipment of a communication network is a duplicate at least one packet data unit already received by the user equipment; and based on determining that the at least one packet data unit to be sent to the user equipment is a duplicate packet data unit, inform the user equipment of the duplicate at least one packet data unit.

A further example embodiment is an apparatus comprising the apparatus of the previous paragraph, wherein the at least one packet data unit comprises a radio link controller, a multiple access channel, and a Packet Data Convergence Protocol packet data unit, wherein there is receiving from the user equipment a“new ACK report” indicating a duplicate reporting set comprising one or more network devices associated with a sent duplicated packet data unit, wherein the informing is using an indication flag sent to the user equipment identifying that the at least one packet data unit to be sent is a duplicate, wherein the indication flag comprises a one bit duplication flag sent in downlink control information to the user equipment prior to reception of the at least one packet data unit by the user equipment, wherein the one bit duplication flag is associated with a scheduled transmission time interval of the at least one packet data unit, wherein the one bit duplication flag is applicable to only radio bearers that are at least one of configured for multi-connectivity and mapped to certain quality of service class identifiers, wherein the downlink control information is identifying a packet data convergence protocol window to be conducted for the user equipment in which the duplicate at least one packet data unit is to be sent to the user equipment, wherein there is for a case the at least one packet data convergence protocol packet data unit to be sent to a user equipment comprises at least one packet data convergence protocol packet data unit belonging to radio bearers configured for the multi connectivity, the one bit duplication flag applies to all of the at least one packet data convergence protocol packet data unit, wherein the at least one packet data unit comprises at least one packet data convergence protocol packet data unit, and for a case the at least one packet data convergence protocol packet data unit to be sent to a user equipment comprises at least one packet data convergence protocol packet data unit belonging to radio bearers configured for the multi-connectivity, the at least one packet data convergence protocol packet data unit are to be sent in a same transmission, wherein there is in response to the informing, receiving from the user equipment a packet data convergence protocol status report comprising an acknowledgement to at least one other base station, wherein the at least one other base station is not a base station that sent the duplicate at least one packet data unit, wherein the acknowledgment is indicating the duplicate at least one packet data unit, wherein the acknowledgment causes the at least one other base station to flush any packet data convergence protocol packets that are associated with the indicated duplicate packet data unit and that are buffered at a packet data convergence protocol layer of the at least one other base station.

In an example aspect of the invention, there is an apparatus, such as network side apparatus, comprising means for determining that at least one packet data unit that is to be sent to a user equipment of a communication network is a duplicate at least one packet data unit already received by the user equipment; and means, based on determining that the at least one packet data unit to be sent to the user equipment is a duplicate packet data unit, for informing the user equipment of the duplicate at least one packet data unit.

BRIEF DESCRIPTION OF THE DRAWINGS:

The foregoing and other aspects of embodiments of this invention are made more evident in the following Detailed Description, when read in conjunction with the attached Drawing Figures, wherein:

Figure 1 shows multi-connectivity for data duplication in accordance with the example embodiments;

Figure 2 shows a high level block diagram of various devices used in carrying out various aspects of the invention;

Figure 3 shows a non- limiting example of a proposed PDCP status report to prepare/report when the UE is configured in duplication mode;

Figure 4 shows an implementation schematic of the proposed changes in accordance with the example embodiments; and

Figure 5A and 5B each show a method in accordance with example embodiments of the invention which may be performed by an apparatus.

DETAIFED DESCRIPTION:

In this invention, we propose a sequence design that will be able to allow detection and elimination of duplicate PDCP packets to be communicated between network devices such as user equipment and a base station.

5G NR is expected to see the extension of DC to consider more than two cells, i.e., toward multi connectivity, although in Rel-l5 the number of cells is still restricted to 2. Moreover, it is being proposed as a potential solution for Ultra Reliable Fow Fatency Communication (URFFC) application, in order to boost data robustness and reliability. URFFC support is an important new feature brought by 5G, with a potential to support a vast set of applications that rely on mission- critical links. The example embodiments of the invention are aimed at improving the operation of multi- connected (MC) downlink for URLLC and HRLC (High Reliability Low Latency) applications in 5G NR (i.e., NR DC) as well as in NR-LTE DC (i.e., EN-DC, NE-DC).

NR dual connectivity operation with data duplication in the downlink direction is schematically presented in Figure 1. As shown in Figure 1 there is an MgNB (Master g Node B) 170 and a SgNB (Secondary g Node B) 180. Further, as shown in Figure 1 a UE 110 is multi-connected to the MgNB 170 (PDCP Anchor node) and the SgNB 180 (PDCP Duplicating node) for dual connectivity operations. Further, as shown in Figure 1 the duplicate PDCP packets 160 are communicated between the MgNB 170 and the SgNB 180. As shown in Figure 1 these operations can be performed at a PDCP layer in a gNB such as a gNB anchor node. In addition, as shown in Figure 1 the duplicate PDCP packets can be transmitted to the UE 110 via the links 140 and 150 as shown in Figure 1. The example embodiments of the invention work to perform detection, reporting, and elimination of these duplicate PDCP packets to be communicated between multi- connected network devices such as shown in Figure 1.

The gNB, which is in control of the PDCP duplication is called the PDCP anchor node, whereas any other gNB serving the duplicated PDCP packet for a given UE is termed as the PDCP duplicating node. After packets arrive at the PDCP-anchor gNB, duplicate packets are dynamically forwarded to the PDCP duplicating gNB node(s), such as over an Xn interface. The same data packet (i.e., PDCP PDU with a given sequence number, SN) is then independently transmitted over to the same UE through the multiple different links (the anchor gNB and the duplicating gNBs). The set of gNBs transmitting the duplicated packet is termed herein as the duplication set.

The MAC-layer HARQ ACK signalling for each PHY transmission is sent to the transmitting gNB i.e., the transmission from the anchor gNB is acknowledged by the UE to the anchor gNB, and that ACK will provide the indication that the PDCP PDUs mapped to the transmission where successfully received. This is under the assumption that URFFC will be configured with RFC UM (Unacknowledged Mode) and therefore no RFC ACKs (RFC status reports) are available as indication of successful delivery to the upper layer (i.e., PDCP).

Similarly, the transmission from the duplicating gNB is acknowledged from the UE to that particular gNB. It should be noted that the duplicating gNB will provide the indication of successful delivery to the anchor gNB by means of flow control (i.e., data status delivery procedure over Xn). Due to the stochastic nature of wireless systems, PDCP packets do not always arrive at the UE in sequential order. For example, a packet with a later sequence number may be successfully received while a packet with a lower sequence number is undergoing (HARQ) retransmissions. There is a PDCP level reordering mechanism at the receiving end PDCP layer to handle such out of sequence packet arrival. The basic principle is that the receiving UE waits for a certain window, according to the re-ordering timer, to receive PDCP packets (PDCP receive window) before forwarding the packets in the window to the upper layers in order to accord time for any possible out-of-sequence packets to arrive.

When a PDCP packet (with a given sequence number - SN) is received successfully by a UE from any leg (i.e. any of the connection through a node within the duplication set), any later copy of that SN received at the UE through other legs in the duplication set is discarded at the PDCP layer. Discarding successfully received PDCP packets at the UE is inefficient since it results in unnecessary transmissions in the network, leading to unnecessary network traffic/load in the affected cells and additional interference in the neighbour cells.

A PDCP packet, already successfully received at the UE, could be either buffered at the PDCP layer of the other duplicating network nodes such as a base station, eNB, or gNB, or already processed by the lower layers of those nodes, undergoing PHY transmissions/retransmissions. Example embodiments of the invention are aimed at allowing a successfully received PDCP packet at the UE to be‘flushed’ (i.e. eliminated) from the PDCP layer of the duplicating node.

In principle, since the same data packet is being transmitted from at least two different gNBs, the transmission of any packet copy should be stopped as soon as it is successfully received at the UE. However, under present 3 GPP specifications there are no mechanisms agreed yet to signal successful receipt of duplicate data packet to network devices, such as duplicating gNBs, other than the anchor gNB (thanks to flow control mechanisms). In other words, unless that duplicating is indicated to different network devices and associated transmissions or re-transmissions of the duplicate packets that were already successfully received at the UE are stopped, then the duplicated packets will still be transmitted again to the UE from other gNBs or eNBs in the duplication set.

The example embodiments of the invention work to address at least these problems by providing a mechanism to let the UE signal successful receipt of a duplicated data packet to multiple gNBs in the duplication set. Before describing the example embodiments of the invention in further detail, reference is made to Figure 2 for illustrating a simplified block diagram of various electronic devices that are suitable for use in practicing the example embodiments of this invention. Figure 2 shows a block diagram of one possible and non-limiting exemplary system in which the example embodiments of the invention may be practiced. In Figure 2, a user equipment (UE) 110 is in wireless communication with a wireless network 100. A UE is a wireless, typically mobile device that can access a wireless network. The UE 110 includes one or more processors 120, one or more memories 125, and one or more transceivers 130 interconnected through one or more buses 127. Each of the one or more transceivers 130 includes a receiver Rx, 132 and a transmitter Tx 133. The one or more buses 127 may be address, data, or control buses, and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, fiber optics or other optical communication equipment, and the like. The one or more transceivers 130 are connected to one or more antennas 128. The one or more transceivers 130 have multi-connectivity configurations and communicate over the wireless network 100 or any other network. The one or more memories 125 include computer program code 123. The UE 110 may include a duplicate D/R module 140-1 which is configured to perform the example embodiments of the invention including duplicate packet data unit detection and reporting (D/R) as described herein. The duplicate D/R module 140-1, the acronym D/R referring to PDCP detection and reporting as in accordance with the example embodiments as disclosed herein, can comprise one of or both parts 140-1 and/or duplicate D/R processor 140-2, which may be implemented in a number of ways. The duplicate D/R module 140- 1 may be implemented in hardware, such as being implemented as part of the one or more processors 120. The duplicate D/R module 140-1 may be implemented also as an integrated circuit or through other hardware such as a programmable gate array. In another example, the duplicate D/R module 140-1 may be implemented as duplicate D/R processor 140-2, which is implemented as computer program code 123 and is executed by the one or more processors 120. For instance, the one or more memories 125 and the computer program code 123 may be configured, with the one or more processors 120, to cause the user equipment 1 10 to perform one or more of the operations as described herein. The UE 110 communicates with gNB 170 and the gNB 180 via a wireless link 111.

The gNB 170 (NR/5G Node B or possibly an evolved NB) is a base station such as a secondary node base station (e.g., for NR or LTE long term evolution) that communicates with devices such as gNB 180 and UE 110 of Figure 2. The gNB 170 provides access to wireless devices such as the UE 110 to the wireless network 100. The gNB 170 includes one or more processors 152, one or more memories 155, one or more network interfaces (N/W I/F(s)) 161, and one or more transceivers 160 interconnected through one or more buses 157. Each of the one or more transceivers 160 includes a receiver Rx 162 and a transmitter Tx 163. The one or more transceivers 160 are connected to one or more antennas 158. The one or more memories 155 include computer program code 153. The gNB 170 includes a duplicate D/R module 150-1 which is configured to perform example embodiments of the invention as described herein. The duplicate D/R module 150-1 can comprise one of or both parts 150-1 and/or duplicate D/R processor 150- 2, which may be implemented in a number of ways. The duplicate D/R module 150-1 may be implemented in hardware, such as being implemented as part of the one or more processors 152. The duplicate D/R module 150-1 may be implemented also as an integrated circuit or through other hardware such as a programmable gate array. In another example, the duplicate D/R module 150-1 may be implemented as duplicate D/R processor 150-2, which is implemented as computer program code 153 and is executed by the one or more processors 152. For instance, the one or more memories 155 and the computer program code 153 are configured to cause, with the one or more processors 152, the gNB 170 to perform one or more of the operations as described herein. The one or more network interfaces 161 and 191 and the one or more transceivers 160 that have multi-connectivity configurations and communicate over the wireless network 100 or any other network. Such communication can be between the gNB 170, the gNB 180, and the UE 110 via the links 176 and 111. In addition, two or more gNB 170 may communicate with another gNB or eNB using, e.g., links 176. The links 176 may be wired or wireless or both and may implement, e.g., an X2 interface. Further the links 176 may be through other network devices such as, but not limited to an NCE/MME/SGW device such as the NCE/MME/SGW 190 of Figure 2.

The gNB 180 (NR/5G Node B or possibly an evolved NB) is a base station such as a master node base station (e.g., for NR or LTE long term evolution) that communicates with devices such as the gNB 170 and/or UE 110 and/or the wireless network 100. The gNB 180 includes one or more processors 182, one or more memories 195, one or more network interfaces (N/W I/F(s)) 191, and one or more transceivers 190 interconnected through one or more buses 187. Each of the one or more transceivers 190 includes a receiver Rx 192 and a transmitter Tx 183. The one or more transceivers 190 are connected to one or more antennas 185. The one or more transceivers 190 have multi-connectivity configurations and communicate over the wireless network 100 or any other network. The one or more memories 195 include computer program code 193. The gNB 180 also includes a duplicate D/R processor 199 which is configured to perform example embodiments of the invention as described herein. The duplicate D/R processor 199 may be implemented in hardware as duplicate D/R module 180-1, such as being implemented as part of the one or more processors 182. The duplicate D/R module 180- 1 may be implemented also as an integrated circuit or through other hardware such as a programmable gate array. In another example, the duplicate D/R module 180-1 may be implemented as the duplicate D/R processor 199, which is implemented as computer program code 193 and is executed by the one or more processors 182. For instance, the one or more memories 155 and the computer program code 153 are configured to cause, with the one or more processors 182, the gNB 180 to perform one or more of the operations as described herein. The one or more network interfaces 181 communicate over a network such as via the links 176. Two or more gNB 170 or gNB 180 may communicate with another gNB and/or eNB or any other device using, e.g., links 176. The links 176 maybe wired or wireless or both and may implement, e.g., an X2 interface. Further, as stated above the links 176 may be through other network devices such as, but not limited to an NCE/MME/SGW device such as the NCE/MME/SGW 190 of Figure 2.

The one or more buses 157 and 187 may be address, data, or control buses, and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, fiber optics or other optical communication equipment, wireless channels, and the like. For example, the one or more transceivers 160 and/or 190 may be implemented as a remote radio head (RRH) 203 and/or 205, with the other elements of the gNB 170 being physically in a different location from the RRH, and the one or more buses 157 could be implemented in part as fiber optic cable to connect the other elements of the gNB 170 to a RRH.

It is noted that description herein indicates that“cells” perform functions, but it should be clear that the gNB that forms the cell will perform the functions. The cell makes up part of a gNB. That is, there can be multiple cells per gNB.

The wireless network 100 may include a network control element (NCE) 190 that may include MME (Mobility Management Entity)/SGW (Serving Gateway) functionality, and which provides connectivity with a further network, such as a telephone network and/or a data communications network (e.g., the Internet). The gNB 170 is coupled via a link 131 to the NCE 190. The gNB 180 is coupled via a link 200 to the NCE 190. Further, the gNB 180 is coupled via links 176 to the gNB 170. The links 131, 176, and/or 200 may be implemented as, e.g., an Sl interface.

The NCE 190 includes one or more processors 175, one or more memories 171, and one or more network interfaces (N/W I/F(s)) 197, interconnected through one or more buses coupled with the link 185. The one or more memories 171 include computer program code 173. The one or more memories 171 and the computer program code 173 are configured to, with the one or more processors 175, cause the NCE 190 to perform one or more operations which may be needed to support the operations in accordance with the example embodiments of the invention. The wireless network 100 may implement network virtualization, which is the process of combining hardware and software network resources and network functionality into a single, software-based administrative entity, a virtual network. Network virtualization involves platform virtualization, often combined with resource virtualization. Network virtualization is categorized as either external, combining many networks, or parts of networks, into a virtual unit, or internal, providing network-like functionality to software containers on a single system. Note that the virtualized entities that result from the network virtualization are still implemented, at some level, using hardware such as processors 152, 182, or 175 and memories 155, 195, and 171, and also such virtualized entities create technical effects.

The computer readable memories 125, 155, 171, and 195 may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The computer readable memories 125, 155, 171, and 195 may be means for performing storage functions. The processors 125, 155, 171, and 195 may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on a multi-core processor architecture, as non-limiting examples. The processors 120, 152, 175, and 182 may be means for performing functions, such as controlling the UE 110, gNB 170, gNB 180, and other functions as described herein.

In general, the various embodiments of the user equipment 110 can include, but are not limited to, cellular telephones such as smart phones, tablets, personal digital assistants (PDAs) having wireless communication capabilities, portable computers having wireless communication capabilities, image capture devices such as digital cameras having wireless communication capabilities, gaming devices having wireless communication capabilities, music storage and playback appliances having wireless communication capabilities, Internet appliances permitting wireless Internet access and browsing, tablets with wireless communication capabilities, as well as portable units or terminals that incorporate combinations of such functions.

The example embodiments of the invention work to solve at least the problems as described above. In accordance with an example embodiment of the invention there is at least a method and apparatus to allow a user equipment (UE) to indicate successful receipt of a duplicated data packet (i.e., PDCP PDU SN) to multiple gNBs in an efficient manner. The example embodiments of the invention include two key elements. Firstly, a mechanism is proposed for the network to signal to the UE that a data packet is duplicated and may be transmitted from a certain set of gNBs defined as the“duplication set”. Secondly, a proposal for the UE to transmit a novel“duplication status report” to any node in the duplication set to indicate that certain PDCP PDUs have been successfully received, is put forth.

Mechanism to signal that a data packet is duplicated

In order for an UE to signal acknowledgements of successful reception of packets which are duplicated at the network side, to multiple gNBs while minimizing the associated signaling, it has to know two pieces of key information, namely i) for which packets to send such multi-gNB ACK, and ii) which gNBs to send this ACK to.

The latter (ίί) information about the gNBs in the duplication set can be semi-statically preconfigured during the DC configuration (i.e., via RRC), and hence need not be signaled dynamically at per-TTI granularity. For the former (/), we propose to include a one-bit flag in the PDCCH DCI (scheduling grant) to allow indication of whether a certain transport block include a PDCP packet that is duplicated, i.e. the packet has been duplicated and may be received via one or more nodes in the duplication set.

The proposed one-bit duplication flag can provide the indication on a per transmission time internal (TTI) granularity, and on whether the PDCP PDUs packets included in this physical transport block transmission (i.e., associated to the PDCCH DCI in the given TTI) are duplicated.

The TTI is a parameter in digital telecommunication networks related to encapsulation of data from higher layers into frames for transmission on the radio link layer. TTI refers to the duration of a transmission on the radio link layer. The TTI refers to the time-domain length of the transmission of the data blocks passed from the higher network layers to the radio link layer. For 5G NR, the TTI size can equal one mini-slot, one slot, or multiple slots using slot aggregation with a data transmission scheduled to span one or multiple slots. Further, the transport block that is sent during one TTI can take different sizes, depending on how many physical resource blocks (PRBs) and the modulation and coding scheme (MCS) used. Hence, data made available for the MAC (from the PDCP/RLC layers) can be scheduled on different numbers of PRBs depending on the data size and supported MCS for the UE. In accordance with the example embodiments this TTI information can be used to identify a physical transmission in which duplicate PDCP packets may occur. Further, it should be noticed that in the same physical transmission, multiple PDCP PDUs could be multiplexed, such as with MAC-level multiplexing. For example, the MAC layer for a given UE may multiplex in the same physical transmission one or more PDCP PDUs from one or more radio bearers of the UE. In a general case, some of those PDCP PDUs may have been duplicated, some may have not. Specific rules can be implemented to help the UE to interpret correctly the one-bit duplication flag and identify how to apply it to an entire set of PDCP PDUs received within one transmission. These rules include (as non- limiting examples):

A) The one-bit duplication flag is applicable only to any radio bearer configured with DC/MC/duplication and/or mapped to certain QCIs, for example 5QI, meant for reliable services. A duplication set indicated by this flag can be semi-statically configured or pre-configured, e.g. via RRC; and

B) If a physical transmission includes more than one PDCP PDU belonging to radio bearer(s) configured with duplication, the one-bit duplication flag present in the PDCCH DCI should be applied to all of the included PDCP PDUs within that physical transmission.

In accordance with the example embodiments the rules above could be provided to the UE such as by means of RRC configuration or be pre-known / pre-specified, or predetermined by the UE. It should be noted that in accordance with an example embodiment the one-bit duplication flag enables a reduction in“ACKs” signaling, and is given in the context of dynamic scheduling rather than semi-persistent scheduling.

Mechanism to transmit ACKs to multiple gNBs

Once a UE successfully decodes a packet (i.e. transport block) that is duplicated, it can identify the gNBs in the duplication set and transmit an acknowledgment to all the gNBs in duplication set. Upon receiving such an ACK, the gNBs in the duplication set will be able to flush any un transmitted packets from their PDCP buffer matching the acknowledged packet identifiers, thereby freeing resources.

The PDCP-level duplication status report indicates which PDCP PDUs have been successfully received at the UE from any node in the duplication set for multi-connectivity communications. For the sake of optimizing the signaling, the report can be constructed specifically for a given node, to include for a node n only those“ACKs” regarding the packets provided by other nodes, i.e., not including the successful receptions of the packets sent by the node n target of the indication, since those“ACKs” can be inferred by these lower layer acknowledgments (e.g. HARQ ACKs). As a consequence of the UE indication, each node in the duplication set will be able to flush the PDCP PDUs included in the duplication status report if buffered at the PDCP layer.

A non- limiting example of the proposed PDCP duplication status report is shown in Figure 3. As shown in Figure 3 there is a sample status report to prepare/report when the UE is configured in duplication mode. This sample status report includes a PDU type 30 field, a PDU SN (sequence number) field, and an Oct (Octet) n indicator 34. Wherein N is an integer.

Figure 4 depicts the implementation of example embodiments of the invention. Figure 4 demonstrates the concepts of a duplication flag to indicate that a packet is duplicated, and the PDCP duplication status report to the gNBs in the duplication set which did not transmit the successfully delivered SNs. As shown in Figure 4 there is the MgNB (Master g Node B) 170 (PDCP Anchor node) and the SgNB (Secondary g Node B) 180, each of which are connected to the other and connected to the UE 110. As shown in Figure 4 after the MgNB 170 receives PDCP packets 410 from the Core Network, the MgNB sends as a duplicated packet at least some of these PDCP packets to the SgNB 180 as duplicated packets 160. As shown in Figure 4 these packets are sent to the UE 110 by both the MgNB 170 and the SgNB 180, thus the UE 1 10 is receiving duplicate PDCP packets. In this example the SgNB can be considered part of a duplication set as it is sending the same packets again to the UE 110 (i.e. duplicate packets). The MgNB 170 also send the UE 110 an indication of the duplicate PDCP packets. This indication can include a Duplication flag 450 as shown in Figure 4. In accordance with the example embodiments of the invention the UE 110 uses the indication from the network to identify the physical transmission with duplicate PDCP packets to prepare the duplication status report 430 which identifies what are the PDCP PDUs that have been successfully received at the UE from any of the node in the duplication set, and sends it to either the MgNB 170 and/or the SgNB 180. Further, the status report can be sent to eNBs or gNBs in the duplication set other than the transmitting eNB or gNB. Then based on the status report from the UE 110 the MgNB 170 and/or the SgNB discard any duplicate PDCP packets 470 and 480, respectively, which may be buffered at these devices. In accordance with the example embodiments this discarding can happen at a PDCP layer or another layer of the base stations. As a note this example is not limiting and the operations in accordance with the example embodiments may differ and/or be in a different order.

Figure 5 A illustrates operations which may be performed by a device such as, but not limited to, a device such as the UE 110 as in Figure 2. As shown in step 510 there is receiving at a user equipment of a communication network an indication of at least one packet data unit that is to be received from at least one base station of a set of base stations of the communication network communicatively coupled to the user equipment; as shown in step 520 of Figure 5A there is determining whether the at least one packet data unit to be received is a duplicate of at least one packet data unit already received by the user equipment; then as shown in step 530 of Figure 5A there is, based on determining that the at least one packet data unit is a duplicate packet data unit, informing at least one other base station of the communication network of the duplicate at least one packet data unit.

In accordance with the example embodiments as described in the paragraph above, the at least one packet data unit is received in a transport block transmission, and wherein the transport block comprises a medium access control packet data unit.

In accordance with the example embodiments as described in the paragraphs above, the medium access control packet data unit comprises a medium access control service data unit which includes one PDCP service data unit.

In accordance with the example embodiments as described in the paragraphs above, there is receiving an indication from a base station of the set of base stations that the at least one packet data unit is a duplicate packet data unit.

In accordance with the example embodiments as described in the paragraphs above, the indication comprises a one bit duplication flag received in downlink control information by the user equipment prior to reception of the at least one packet data unit at the user equipment.

In accordance with the example embodiments as described in the paragraphs above, the one bit duplication flag is associated with a scheduled transmission time interval of the at least one packet.

A non-transitory computer-readable medium (Memory(ies) 125 of Figure 2) storing program code (Computer Program Code 123 and/or Duplicate D/R Module 140-1 of Figure 2), the program code executed by at least one processor (Processor(s) 120 and/or Duplicate D/R processor 140-2 of Figure 2) to perform the operations as at least described in the paragraphs above.

In accordance with an example embodiment of the invention as described above there is an apparatus comprising: means for receiving (transceivers 130 and Rx 132 as in Figure 2) at a user equipment (UE 110 as in Figure 2) of a communication network (Network 100 as in Figure 2) an indication of at least one packet data unit that is to be received from at least one base station of a set of base stations of the communication network communicatively coupled to the user equipment; means for determining (Computer Program Code 123 and/or Duplicate D/R Module 140-1; and at least one processor (Processor(s) 120 and/or Duplicate D/R processor 140-2 of Figure 2) whether the at least one packet data unit to be received is a duplicate of at least one packet data unit already received by the user equipment; and means, based on determining that the at least one packet data unit is a duplicate packet data unit, for informing (transceivers 130 and Tx 133 as in Figure 2) at least one other base station (gNB 170 and/or gNB 180 as in Figure 2) of the communication network of the duplicate at least one packet data unit.

In the example aspect of the invention according to the paragraphs above, wherein at least the means for receiving, determining, and informing comprises a non-transitory computer readable medium [Memory(ies) 125 of Figure 2] encoded with a computer program [Computer Program Code 123 and/or Duplicate D/R Module 140-1 of Figure 2] executable by at least one processor [Processor(s) 120 and/or Duplicate D/R processor 140-2 of Figure 2]

Figure 5B illustrates operations which may be performed by a device such as, but not limited to, a device such as the gNB 170 and/or gNB 180 as in Figure 2. As shown in step 550 there is determining that at least one packet data unit that is to be sent to a user equipment of a communication network is a duplicate at least one packet data unit already received by the user equipment; then as shown in step 560 of Figure 5B there is, based on determining that the at least one packet data unit to be sent to the user equipment is a duplicate packet data unit, informing the user equipment of the duplicate at least one packet data unit.

In accordance with the example embodiments as described in the paragraph above, the at least one packet data unit comprises a radio link controller, a multiple access channel, and a Packet Data Convergence Protocol packet data unit.

In accordance with the example embodiments as described in the paragraphs above, there is receiving from the user equipment a“new ACK report” indicating a duplicate reporting set comprising one or more network devices associated with a sent duplicated packet data unit.

In accordance with the example embodiments as described in the paragraphs above, the informing is using an indication flag sent to the user equipment identifying that the at least one packet data unit to be sent is a duplicate. In accordance with the example embodiments as described in the paragraphs above, the indication flag comprises a one bit duplication flag sent in downlink control information to the user equipment prior to reception of the at least one packet data unit by the user equipment.

In accordance with the example embodiments as described in the paragraphs above, the one bit duplication flag is associated with a scheduled transmission time interval of the at least one packet data unit.

In accordance with the example embodiments as described in the paragraphs above, the one bit duplication flag is applicable to only radio bearers that are at least one of configured for multi connectivity and mapped to certain quality of service class identifiers.

In accordance with the example embodiments as described in the paragraphs above, the downlink control information is identifying a packet data convergence protocol window to be conducted for the user equipment in which the duplicate at least one packet data unit is to be sent to the user equipment.

In accordance with the example embodiments as described in the paragraphs above, there is for a case the at least one packet data convergence protocol packet data unit to be sent to a user equipment comprises at least one packet data convergence protocol packet data unit belonging to radio bearers configured for the multi-connectivity, the one bit duplication flag applies to all of the at least one packet data convergence protocol packet data unit.

In accordance with the example embodiments as described in the paragraphs above, the at least one packet data unit comprises at least one packet data convergence protocol packet data unit, and for a case the at least one packet data convergence protocol packet data unit to be sent to a user equipment comprises at least one packet data convergence protocol packet data unit belonging to radio bearers configured for the multi-connectivity, the at least one packet data convergence protocol packet data unit are to be sent in a same transmission.

In accordance with the example embodiments as described in the paragraphs above, there is, in response to the informing, receiving from the user equipment a packet data convergence protocol status report comprising an acknowledgement to at least one other base station, wherein the at least one other base station is not a base station that sent the duplicate at least one packet data unit, wherein the acknowledgment is indicating the duplicate at least one packet data unit. In accordance with the example embodiments as described in the paragraphs above, the acknowledgment causes the at least one other base station to flush any packet data convergence protocol packets that are associated with the indicated duplicate packet data unit and that are buffered at a packet data convergence protocol layer of the at least one other base station.

A non-transitory computer-readable medium (Memory(ies) 155 and/or Memory(ies) 195 of Figure 2) storing program code (Computer Program Code 153 and/or Computer Program Code 193), the program code executed by at least one processor (Duplicate D/R Module 150-1 and/or Duplicate D/R Module 180-1; and Processor(s) 152 and/or Processors 182 and/or Duplicate D/R processor 150-2 and/or Duplicate D/R processor 199 of Figure 2of Figure 2) to perform the operations as at least described in the paragraphs above.

In accordance with an example embodiment of the invention as described above there is an apparatus comprising: means for determining (Computer Program Code 133 and/or Computer Program Code 193; Duplicate D/R Module 150-1 and/or Duplicate D/R Module 180-1; and Processor(s) 152 and/or Processors 182 and/or Duplicate D/R processor 150-2 and/or Duplicate D/R processor 199 of Figure 2) that at least one packet data unit that is going to be sent to a user equipment (UE 110 as in Figure 2) of a communication network (Network 100 as in Figure 2) is a duplicate at least one packet data unit already received by the user equipment; and means, based on determining that the at least one packet data unit to be sent to the user equipment is a duplicate packet data unit, for informing (transceivers 160 and/or transceivers 190; and tx 163 and/or Tx 183 as in Figure 2) the user equipment of the duplicate at least one packet data unit.

In the example aspect of the invention according to the paragraphs above, wherein at least the means for determining and informing comprises a non-transitory computer readable medium [Memory(ies) 155 and/or Memory(ies) 195 as in Figure 2) encoded with a computer program [Computer Program Code 153 and/or Computer Program Code 193; and Duplicate D/R Module 150-1 and/or Duplicate D/R Module 180-1 of Figure 2] executable by at least one processor [Processor(s) 152 and/or Processors 182; and Duplicate D/R processor 150-2 and/or Duplicate D/R processor 199 of Figure 2]

Benefits of a method in accordance with the example embodiments include at least:

o Reducing unnecessary transmission from the multiple gNBs;

o Freeing network resources which then can be allocated elsewhere; o Reducing network interference by minimizing unnecessary transmission;

o Consequently improving the reliability of URLLC transmissions; and o Improving the overall network capacity and energy efficiency.

It is noted that any reference herein to 5G or LTE communications technologies and/or any reference to network devices such as, but not limited to, a gNB (i.e., base station) are non limiting. The example embodiments of the invention can be applied in addition to other legacy or newer communications technologies implemented by different types of devices.

The memories as described herein may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The data processors as described herein may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on a multi-core processor architecture, as non-limiting examples.

In general, the various embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto. While various aspects of the invention may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

Embodiments of the inventions may be practiced in various components such as integrated circuit modules. The design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.

The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. All of the embodiments described in this Detailed Description are exemplary embodiments provided to enable persons skilled in the art to make or use the invention and not to limit the scope of the invention which is defined by the claims. The foregoing description has provided by way of exemplary and non-limiting examples a full and informative description of the best method and apparatus presently contemplated by the inventors for carrying out the invention. However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings and the appended claims. However, all such and similar modifications of the teachings of this invention will still fall within the scope of this invention.

It should be noted that the terms "connected," "coupled," or any variant thereof, mean any connection or coupling, either direct or indirect, between two or more elements, and may encompass the presence of one or more intermediate elements between two elements that are "connected" or "coupled" together. The coupling or connection between the elements can be physical, logical, or a combination thereof. As employed herein two elements may be considered to be "connected" or "coupled" together by the use of one or more wires, cables and/or printed electrical connections, as well as by the use of electromagnetic energy, such as electromagnetic energy having wavelengths in the radio frequency region, the microwave region and the optical (both visible and invisible) region, as several non-limiting and non-exhaustive examples.

Furthermore, some of the features of the preferred embodiments of this invention could be used to advantage without the corresponding use of other features. As such, the foregoing description should be considered as merely illustrative of the principles of the invention, and not in limitation thereof.

Claims

1. A method, comprising:

receiving, at a user equipment of a communication network, an indication of at least one packet data unit that is to be received from at least one base station of a set of base stations of the communication network communicatively coupled to the user equipment;

determining whether the at least one packet data unit to be received is a duplicate of at least one packet data unit already received by the user equipment; and

based on determining that the at least one packet data unit is a duplicate packet data unit, informing at least one other base station of the communication network of the duplicate at least one packet data unit.

2. The method according to claim 1, wherein the at least one packet data unit is received in a transport block transmission, and wherein the transport block comprises a medium access control packet data unit.

3. The method according to any one of claims 1 or 2, wherein the medium access control packet data unit comprises a medium access control service data unit which includes one Packet Data Convergence Protocol service data unit.

4. The method according to any one of claims 1 or 2, comprising:

receiving an indication from a base station of the set of base stations that the at least one packet data unit is a duplicate packet data unit.

5. The method according to any one of the preceding claims, wherein the indication comprises a one bit duplication flag received in downlink control information by the user equipment prior to reception of the at least one packet data unit at the user equipment.

6. The method according to claim 5, wherein one bit duplication flag is associated with a scheduled transmission time interval of the at least one data packet.

7. An apparatus, comprising:

means for receiving, at a user equipment of a communication network, an indication of at least one packet data unit that is to be received from at least one base station of a set of base stations of the communication network communicatively coupled to the user equipment; means for determining whether the at least one packet data unit to be received is a duplicate of at least one packet data unit already received by the user equipment; and

means, based on determining that the at least one packet data unit is a duplicate packet data unit, for informing at least one other base station of the communication network of the duplicate at least one packet data unit.

8. The apparatus according to claim 7, wherein the at least one packet data unit is received in a transport block transmission, and wherein the transport block comprises a medium access control packet data unit.

9. The apparatus according to any one of claims 7 or 8, wherein the medium access control packet data unit comprises a medium access control service data unit which includes one Packet Data Convergence Protocol service data unit.

10. The apparatus according to any one of claims 7 or 8, comprising:

means for receiving an indication from a base station of the set of base stations that the at least one packet data unit is a duplicate packet data unit.

11. The apparatus according to any one of the preceding claims, wherein the indication comprises a one bit duplication flag received in downlink control information by the user equipment prior to reception of the at least one packet data unit at the user equipment.

12. The apparatus according to claim 11 , wherein one bit duplication flag is associated with a scheduled transmission time interval of the at least one data packet.

13. A method, comprising :

determining that at least one packet data unit that is to be sent to a user equipment of a communication network is a duplicate at least one packet data unit already received by the user equipment; and

based on determining that the at least one packet data unit to be sent to the user equipment is a duplicate packet data unit, informing the user equipment of the duplicate at least one packet data unit.

14. The method according to claim 13, wherein the at least one packet data unit comprises a radio link controller, a multiple access channel, and at least one packet data convergence protocol packet data unit.

15. The method according to any one of claims 13 or 14, comprising:

receiving from the user equipment a“new ACK report” indicating a duplicate reporting set comprising one or more network devices associated with a sent duplicated packet data unit.

16. The method according to any one of claims 13 or 14, wherein the informing is using an indication flag sent to the user equipment identifying that the at least one packet data unit to be sent is a duplicate packet data unit.

17. The method according to claim 16, wherein the indication flag comprises a one bit duplication flag sent in downlink control information to the user equipment prior to reception of the at least one packet data unit by the user equipment.

18. The method according to claim 17, wherein the one bit duplication flag is associated with a scheduled transmission time interval of the at least one packet data unit.

19. The method according to claim 17, wherein the one bit duplication flag is applicable to only radio bearers that are at least one of configured for multi-connectivity and mapped to certain quality of service class identifiers.

20. The method according to claim 17, wherein the downlink control information is identifying a packet data convergence protocol window to be conducted for the user equipment in which the duplicate at least one packet data unit is to be sent to the user equipment.

21. The method according to claim 19, wherein there is for a case the at least one packet data convergence protocol packet data unit to be sent to a user equipment comprises at least one packet data convergence protocol packet data unit belonging to radio bearers configured for the multi-connectivity, the one bit duplication flag applies to all of the at least one packet data convergence protocol packet data unit.

22. The method according to claim 19, wherein the at least one packet data unit comprises at least one packet data convergence protocol packet data unit, and for a case the at least one packet data convergence protocol packet data unit to be sent to a user equipment comprises at least one packet data convergence protocol packet data unit belonging to radio bearers configured for the multi-connectivity, the at least one packet data convergence protocol packet data unit are to be sent in a same transmission.

23. The method according to any one of the preceding claims, comprising:

in response to the informing, receiving from the user equipment a packet data convergence protocol status report comprising an acknowledgement to at least one other base station, wherein the at least one other base station is not a base station that sent the duplicate at least one packet data unit, wherein the acknowledgment is indicating the duplicate at least one packet data unit.

24. The method according to claim 23, wherein the acknowledgment causes the at least one other base station to flush any packet data convergence protocol packets that are associated with the indicated duplicate packet data unit and that are buffered at a packet data convergence protocol layer of the at least one other base station.

25. An apparatus, comprising:

means for determining that at least one packet data unit that is to be sent to a user equipment of a communication network is a duplicate at least one packet data unit already received by the user equipment; and

means, based on determining that the at least one packet data unit to be sent to the user equipment is a duplicate packet data unit, for informing the user equipment of the duplicate at least one packet data unit.

26. The apparatus according to claim 25, wherein the at least one packet data unit comprises a radio link controller, a multiple access channel, and at least one packet data convergence protocol packet data unit.

27. The apparatus according to any one of claims 25 or 26, comprising:

means for receiving from the user equipment a“new ACK report” indicating a duplicate reporting set comprising one or more network devices associated with a sent duplicated packet data unit.

28. The apparatus according to any one of claims 25 or 26, wherein the informing is using an indication flag sent to the user equipment identifying that the at least one packet data unit to be sent is a duplicate packet data unit.

29. The apparatus according to claim 28, wherein the indication flag comprises a one bit duplication flag sent in downlink control information to the user equipment prior to reception of the at least one packet data unit by the user equipment.

30. The apparatus according to claim 29, wherein the one bit duplication flag is associated with a scheduled transmission time interval of the at least one packet data unit.

31. The apparatus according to claim 29, wherein the one bit duplication flag is applicable to only radio bearers that are at least one of configured for multi-connectivity and mapped to certain quality of service class identifiers.

32. The apparatus according to claim 29, wherein the downlink control information is identifying a packet data convergence protocol window to be conducted for the user equipment in which the duplicate at least one packet data unit is to be sent to the user equipment.

33. The apparatus according to claim 31 , wherein there is for a case the at least one packet data convergence protocol packet data unit to be sent to a user equipment comprises at least one packet data convergence protocol packet data unit belonging to radio bearers configured for the multi-connectivity, the one bit duplication flag applies to all of the at least one packet data convergence protocol packet data unit.

34. The apparatus according to claim 31, wherein the at least one packet data unit comprises at least one packet data convergence protocol packet data unit, and for a case the at least one packet data convergence protocol packet data unit to be sent to a user equipment comprises at least one packet data convergence protocol packet data unit belonging to radio bearers configured for the multi-connectivity, the at least one packet data convergence protocol packet data unit are to be sent in a same transmission.

35. The apparatus according to any one of the preceding claims, comprising:

means, in response to the informing, for receiving from the user equipment a packet data convergence protocol status report comprising an acknowledgement to at least one other base station, wherein the at least one other base station is not a base station that sent the duplicate at least one packet data unit, wherein the acknowledgment is indicating the duplicate at least one packet data unit.

36. The apparatus according to claim 35, wherein the acknowledgment causes the at least one other base station to flush any packet data convergence protocol packets that are associated with the indicated duplicate packet data unit and that are buffered at a packet data convergence protocol layer of the at least one other base station.

37. A communication system comprising the apparatus in accordance with any one of the claims 7 to 12 and the apparatus in accordance with any one of the claims 25 to 36.

38. A computer program comprising program code for executing the method according to any of claims 1 to 6 or claims 13 to 24.

39. The computer program according to claim 38, wherein the computer program is a computer program product comprising a computer-readable medium bearing computer program code embodied therein for use with a computer.