Ultra reliable low latency connection support in radio access networks

CROSS-REFERENCE TO RELATED APPLICATIONS

0001This application claims the benefit of priority to U.S. Provisional Patent Applications U.S. Patent Application Ser. No. 62/402,710 entitled “Ultra Reliable Low Latency Connection Support in Radio Access Networks” filed Sep. 30, 2016, and U.S. Patent Application Ser. No. 62/443,152 entitled “Ultra Reliable Low Latency Connection Support in Radio Access Networks” filed Jan. 6, 2017, and U.S. Patent Application Ser. No. 62/469,708 entitled “Ultra Reliable Low Latency Connection Support in Radio Access Networks” filed Mar. 10, 2017 the contents of which are hereby incorporated by reference in their entirety.

TECHNICAL FIELD

0002This present invention relates to ultra-reliable and low latency connections in Radio Access Networks.

BACKGROUND

0003In a mobile communications network, a User Equipment (UE) connects to the network via the radio access network, and more specifically through a radio access link to a Radio Access Node, such as a NodeB, an evolved Node B (eNodeB) or other equivalent node including a gNodeB. Transmissions between the UE and a node in the network typically involve at least a wireless channel between a radio access node and the UE. Typically there are further wired connections between the radio access node and other nodes in the radio access network or a core network. Mobile networks have historically been designed to support the mobility of a UE (although mobility is not required in a UE). To maintain the connection between the UE and the network as the UE moves, handover procedures have been developed to allow a UE's session to be preserved as the radio access link moves between one access node and another. This process is known as a handover.

0004In developing handover procedures, the disruption of a connection with a UE as the UE is handed over from one eNodeB to another is expected. This has an impact on the reliability of a connection. A human operator using the mobile network for a voice call may not notice the disruption, but a data session for critical tasks may not be as forgiving.

0005The reliability of a connection is defined as a specified probability of successful transmission in a given time frame. For Ultra-Reliable Low Latency Connections (URLLC), a common reliability requirement is 1×10⁻⁵. This means that 99.999% of packets transmitted must be correctly received within the latency requirement. The latency requirement can vary based on the needs of the service. It has been noted that there are now use cases in which LTE based networks cannot provide connections that guarantee the latency required by real-time applications. In order to ensure reliability of the radio access channel, existing network designs, including the Long Term Evolution (LTE) standards promulgated by the Third Generation Partnership Project (3GPP), make use of error correcting mechanisms such as a Hybrid Automatic Repeat reQuest (HARQ). While HARQ and other similar mechanisms can provide a certain degree of reliability, the reliability may come at the cost of an increased latency. If the latency requirement is 1 ms or less, then HARQ and Automatic Repeat reQuest (ARQ) may not be suitable, as they can increase the latency of the transmission.

0006In order to provide both reliable and low latency connectivity, other techniques are required especially in mobility scenarios. In scenarios of high mobility or in ultradense deployments, the number of handovers that a UE may be subject to may further adversely impact the ability to meet the reliability and latency requirements.

0007Accordingly, there is a need for a system and method that at least partially addresses one or more limitations of the prior art.

0008This background information is provided to reveal information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.

SUMMARY

0009It is an object of the present invention to obviate or mitigate at least one disadvantage of the prior art.

0010According to one aspect, there is a method of performing packet duplication (PD) at a transmitter, comprising activating the PD at a Packet Data Convergence Protocol (PDCP) layer of the transmitter; and duplicating a PDCP PDU at the PDCP layer, wherein the duplicate PDCP PDUs are transmitted to two RLC entities.

0011According to one example, the activation of PD is applied in a dual-connectivity (DC)/multi-connectivity (MC) architecture or a carrier aggregation (CA) architecture. According to another, derivative example, the duplicate PDCP PDUs are assigned to different carriers. According to a 3^rdexample, derivative of the previous, a PD function at the PDCP layer is responsible for the duplicating. According to a 4^th, derivative on all previous, example the method further comprises deactivating the PD at the PDCP layer. According to a 5^th, derivative on all previous, example MAC control elements (MAC CEs) are conveyed between the transmitter and a receiver to trigger an activation or a deactivation of the PD. According to a 6th example, derivative on all previous, RRC signalling is received for configuring the PD. According to a 7^thexample, derivative on all previous, RRC signalling is received for activating or deactivating the PD.

0012According to another aspect there is a processing system for performing packet duplication (PD), comprising: a first unit, configured to activate the PD at a Packet Data Convergence Protocol (PDCP) layer of the processing system; and a second unit, configured to duplicate a PDCP PDU at the PDCP layer, wherein the duplicate PDCP PDUs are transmitted to two RLC entities.

0013According to one example the activation of PD is applied in a dual-connectivity (DC)/multi-connectivity (MC) architecture or a (CA) architecture. According to a derivative example the duplicate PDCP PDUs are assigned to different carriers. According to a further example derivative on those previous a second unit is a PD function at the PDCP layer responsible for the duplicating. A last example, derivative on the previous, includes a third unit, configured to deactivate the PD at the PDCP layer.

0014According to a third aspect there is a device, comprising: the processing system according to any derivation of the previous aspect, and a fourth unit, configured to convey MAC control elements (MAC CEs) to trigger an activation or a deactivation of the PD.

0015According to one example, the fourth unit is further configured to receive RRC signalling for configuring the PD. According to another example the fourth unit is further configured to receive RRC signalling for activating or deactivating the PD.

0016The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description, taken in conjunction with the accompanying drawings which description is by way of example only.

BRIEF DESCRIPTION OF THE DRAWINGS

0017For a more complete understanding of this disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts.

0018<figref idref="DRAWINGS">FIG. 1</figref> is an illustration of the timing issues resulting in the Handover interruption time of LTE networks according to an embodiment;

0019<figref idref="DRAWINGS">FIG. 2</figref> illustrates a logical view of the connection between a UE and a plurality of radio access nodes, according to an embodiment;

0020<figref idref="DRAWINGS">FIG. 3</figref> illustrates a method of handover, according to an embodiment;

0021<figref idref="DRAWINGS">FIG. 4</figref> illustrates a method of transmitting data over redundant links, according to an embodiment;

0022<figref idref="DRAWINGS">FIG. 5</figref> illustrates a method of transmitting data over redundant links, according to an embodiment;

0023<figref idref="DRAWINGS">FIG. 6</figref> illustrates a logical view of the connection between a UE and a plurality of radio access nodes, according to an embodiment;

0024<figref idref="DRAWINGS">FIG. 7</figref> illustrates a logical view of the connection between a UE and a plurality of radio access nodes, according to an embodiment;

0025<figref idref="DRAWINGS">FIG. 8</figref> illustrates the average Signal to Noise Ratio (SNR) from source Master gNB (MgNB) and target MgNB during handover, according to an embodiment.

0026<figref idref="DRAWINGS">FIG. 9</figref> illustrates a method of seamless handover procedure with RRC transmission diversity and data duplication towards the source and target nodes, according to an embodiment;

0027<figref idref="DRAWINGS">FIG. 10</figref> illustrates an NR MC/DC Architecture for supporting PD, according to an embodiment;

0028<figref idref="DRAWINGS">FIG. 11</figref> illustrates NR CA Architecture for supporting PD, according to an embodiment;

0029<figref idref="DRAWINGS">FIG. 12</figref> illustrates example message flows for a Network triggered LS/PD activation procedure, according to an embodiment;

0030<figref idref="DRAWINGS">FIG. 13</figref> illustrates example message flows for a UE triggered LS/PD activation procedure, according to an embodiment;

0031<figref idref="DRAWINGS">FIG. 14</figref> illustrates example Signalling flow for activating packet duplication, according to an embodiment;

0032<figref idref="DRAWINGS">FIG. 15</figref> illustrates example Signalling flow for deactivating packet duplication, according to an embodiment;

0033<figref idref="DRAWINGS">FIG. 16</figref> illustrates example Signalling flow for activating and deactivating packet duplication based on criteria sent to the UE through RRC signalling, according to an embodiment; and

0034<figref idref="DRAWINGS">FIG. 17</figref> is a block diagram of a processing system that may be used for implementing the various network functions and the methods and signaling as described herein.

DETAILED DESCRIPTION

0035In discussing the provision of a URLLC level of service, it should be understood that a number of different networking levels need to be considered. Network layer details, as well as service layer details need to be considered, as does the management of session connectivity. Although some of the details in each of these parts of an overall solution overlap, an attempt will be made to deal with the details of one level at a time. As a result, figures may be introduced and discussed, and then discussed again as they pertain to a differ layer in the solution.

0036As noted above, the manner in which handover is achieved in an LTE networking environment can result in delayed delivery (or dropped packets) during a handover procedure. A UE is connected to a single eNodeB at a time. Leading up to the handover process, the UE is transmitting data to a single eNodeB, and the network is transmitting data to that same source eNodeB. However, as the UE connects to the target eNodeB, data that was sent to the source eNodeB before the handover and which had not been delivered, is not immediately present at the target eNodeB for delivery. This, as noted above, is not likely to be apparent to a human operator either on a voice call, or even watching a video stream that has been buffered locally. However, real time processes, including real time video sessions and certain control processes are not likely to be as forgiving.

0037In order to reduce the probability of Radio Link Failure (RLF) during mobility, enhancements to the handover procedure can be provided. One way to achieve seamless handover is to ensure that there is at least one Radio Access Network (RAN) node connected to the UE at all times. Downlink (DL) data can be made available to the target RAN node before a handover of the radio link. For Uplink (UL) communication, the target RAN node should have the path to the core network setup before a handover of the radio link. This allows for both UL and DL communications to be supported during a handover of the source RAN node to the target RAN node, which reduces the probability of RLF.

0038If the UE is at the edge of the service area of a source RAN node, initiating a handover to the target node too early may result in a RLF of the target node. Similarly, if a handover is initiated too late then a RLF may occur at the source node. In order to reduce the likelihood of packet loss or delay associated with the handover procedure and to reduce the probability of RLF, simultaneous communication with both the source and target RAN nodes can be provided for UEs near the edge.

0039The timing diagram of <figref idref="DRAWINGS">FIG. 1</figref> showing the difference in the handover procedure between L′I′E and a proposed new radio (NR) technology. In conventional techniques, as shown by the LTE <b>1</b> process, after the handover (HO) command <b>10</b> is issued, there is a handover interruption time. In this window, transmissions with the UE are interrupted, By allowing the UE to connect to a plurality of different access nodes, as illustrated in the NR <b>2</b> process, there is a period of time <b>45</b> in which the UE is connected to more than one access node. This ensures that there is no interruption time (and effectively replaces the interruption time with a period in which simultaneous transmission <b>45</b> can be provided.)

0040This redundant transmission provides resilience to the possibility of link failure. It can also reduce any delays that would have been attributable to buffering by either end of the connection until the end of the handover interruption.

0041In the handover scenario where duplicate packets from the UE are received at both the source and target nodes, the duplicates can be removed either i) at the PDCP function of the target MgNB or ii) at the upper layers. That is, packets arriving within a latency bound from the source MgNB to the target MgNB via Xn can be detected and removed by the PDCP function at the target MgNB. Packets that may potentially exceed the latency bound over the Xn are forwarded directly by both the source and target MgNB nodes to be detected and removed at the upper layers. It should be understood that MgNB refers to a master gNB.

0042In order to ensure seamless handover of the MgNB, a make-before-break handover procedure may be used. For URLLC use cases, the UE may establish connectivity to the target MgNB before releasing the RRC connection to the source MgNB to allow for packet duplication via both MgNBs during a mobility event.

0043During a normal handover of UE connectivity from the source MgNB to a target MgNB, the UE may have only one link available for communication (data and RRC signaling), since the UE is required to release the RRC connection of the source MgNB before it establishes a new RRC connection to the target MgNB. In this case, the target reliability cannot be satisfied with a single link. Hence, simultaneous transmission of data and RRC signaling with links towards both the source and target MgNB throughout the handover will ensure higher reliability.

0044According to an example, during the Simultaneous Transmission period <b>45</b> the UE is connected to more than one access node (e.g., Source gNB and the Target gNB). During the Simultaneous Transmission period <b>45</b>, the Data Transmissions from Target <b>31</b> includes duplicate packets to those carried during the Simultaneous Transmission period <b>45</b> by the Data Transmission from the Source <b>15</b>. In other words, during Simultaneous Transmission period <b>45</b>, the Data Transmissions from Target <b>31</b> is a redundant transmission to that of the Data Transmissions from Target <b>31</b>. To avoid interference the Data Transmissions from Target <b>31</b> utilizes a different channel (or equivalently a different carrier) than the Data Transmission from the Source <b>15</b>.

0045Again, according to an example, the handover interruption time can be a window <b>20</b>, and may persist until handover is complete <b>25</b>. The interruption window <b>20</b> may separate the Data Transmission from the Source signal <b>15</b> and the Data Transmissions from Target signal <b>30</b>. The UE may Establish RRC Connection to Target <b>40</b> during the Data Transmission from the Source signal <b>15</b>. The Data Transmissions from Target <b>31</b> may commence prior to the end of the Data Transmission from the Source <b>15</b>.

0046It should be appreciated that the examples have been discussed with reference to MgNB nodes, other suitably equipped network access nodes can also be used including a base station (for example a NodeB, an evolved Node B (eNodeB, or eNB), a next generation NodeB (sometimes referred to as a gNodeB or gNB), or a Base Band Unit (BBU) associated with one or more remote radio heads.

0047The benefits of using packet duplication also reveal benefits of using simultaneous radio connections during a handover. <figref idref="DRAWINGS">FIG. 8</figref> illustrates the average SNR <b>670</b> from the source MgNB and the target MgNB during a handover.

0048The dependant variable axis of the graph illustrated by <figref idref="DRAWINGS">FIG. 8</figref> is SNR and the independent variable axis of this graph is Time/Distance <b>675</b>. <figref idref="DRAWINGS">FIG. 8</figref> plots the “SNR to Source MgNB” <b>590</b> and “SNR to Target MgNB” <b>595</b> curves as well as the “Region where packet duplication is required” <b>650</b>. The Time/Distance to “Establish RRC Connection to Target MgNB” <b>655</b>, “Release RRC Connection to Source MgNB” <b>665</b>, and the Time/Distance when there should be “Simultaneous Radio Connections” <b>660</b> between the UE and a plurality of ANs is also illustrated in <figref idref="DRAWINGS">FIG. 8</figref>.

0049The conditions during handover are similar to the channel conditions for the scenarios that show a large gain for using packet duplication. During a handover of the source MgNB, the average delta SNR between the source MgNB and the target MgNB is small and the average SNR for the best link is typically low. It can be concluded that packet duplication can be used during handover using simultaneous radio connections with the source and target nodes. With packet duplication, the target reliability can be achieved with lower overall resource usage.

0050Multi-connectivity (MC), the ability of the network to support a plurality of different connection paths, can aid in satisfying the reliability requirement. By ensuring that a UE always has at least two paths to the CN, such as during a handover, there is a reduced probability that the UE connection will be dropped or interrupted. In the multi-connectivity scenario, the UE can be connected to multiple access nodes on the same carrier or on different carriers.

0051LTE provides rudimentary dual-connectivity (DC) functionality. To provide multi-connectivity, the network elements can be designed to extend this DC concept in LTE. The 3C architecture option defined by the 3GPP can be used, where there is one common PDCP entity.

0052In a MC scenario (which may include a DC scenario) a radio access node is designated as a primary radio access node. Data packets can be sent to a secondary RAN node (by the primary radio access node) over an Xn interface. Uplink packets may be received by any of the RAN nodes to which the UE is connected. Each of the secondary RAN nodes then sends the received packets to the primary RAN node over the Xn Interface.

0053<figref idref="DRAWINGS">FIG. 2</figref> illustrates a protocol stack of the NR, where gNB refers to an access node.

0054The primary gNB (gNB-1 <b>200</b>) acts as an anchor or MgNB for this connection. If a new gNB (gNB-2 <b>250</b>) is to be added, the primary gNB will create a new Xn link <b>112</b> to the additional gNB. The PDCP layer <b>106</b> in the Anchor node can be used to remove the duplicate packets that are received from the multiple RAN nodes communicating with the UE <b>100</b>. The UE can be permitted to move across multiple distributed RAN nodes connected to the same Anchor node without needing to re-establish the security association with the PDCP layer <b>106</b>. When the UE <b>100</b> moves out of a coverage area associated with the anchor RAN node, the UE can establish the security association with the PDCP function in the target RAN node. Alternatively, the core network can initiate the key exchange during the mobility event.

0055In order to ensure seamless handover of the Anchor node function from a first gNB to a second gNB, a make-before-break handover procedure can be used. The UE <b>100</b> can establish a radio connection with the target Anchor node before releasing the RRC connection of the source Anchor node. Therefore, the UE <b>100</b> will have two simultaneous radio connections during a mobility event with only one RRC connection to the source RAN node. An exemplary procedure using simultaneous radio connections is illustrated in <figref idref="DRAWINGS">FIG. 11</figref>. It should be understood that SgNB refers to a Secondary gNB.

0056In the handover procedure, when the condition for handover is satisfied, the source MgNB sends an RRC connection reconfiguration for establishing a radio bearer to the target MgNB. In this case, the UE maintains a radio connection and RRC connection with the source MgNB. After the RB to the target node is established, packet duplication can be used for both data and RRC signaling.

0057According to an example embodiment of the handover procedure of <figref idref="DRAWINGS">FIG. 2</figref>, the UE <b>100</b> is configured with two protocol stack entities <b>101</b>, <b>102</b> so that UE <b>100</b> can simultaneously communicate with two access points (e.g, gNB's <b>200</b>, <b>250</b>). UE protocol stack entity <b>101</b> includes NR-RLC entity <b>110</b>, NR-MAC entity <b>115</b>, and NR-PHY entity <b>120</b>. UE protocol stack entity <b>102</b> includes a NR-RLC entity <b>111</b>, NR-MAC entity <b>141</b>, and NR-PHY entity <b>142</b> Both UE protocol stacks <b>101</b>,<b>102</b> share a common NR-PDCP entity <b>105</b>. The primary gNB's (gNB-1 <b>200</b>) protocol stack entity <b>103</b> includes a NR-PDCP <b>106</b>, NR-RLC entity <b>114</b>, NR-MAC entity <b>115</b>, and NR-PHY <b>120</b> entity. The second gNB's (gNB-2 <b>250</b>) protocol stack entity <b>104</b> includes NR-RLC <b>113</b>, NR-MAC entity <b>115</b>, and NR-PHY entity <b>120</b>, but does not require its own PDCP entity. The gNB-2 <b>250</b> protocol stack entity <b>104</b> communicates with gNB-1 <b>200</b>'s NR-PDCP <b>105</b> via the Xn <b>112</b> interface. UE protocol stack entity <b>102</b> including NR-RLC entity <b>111</b>, NR-MAC entity <b>141</b> and NR-PHY entity <b>142</b> communicates with the primary gNB's (gNB-1 <b>200</b>) protocol stack entity <b>103</b> using a first radio channel <b>116</b>. UE protocol stack entity <b>101</b> including NR-RLC entity <b>110</b>, NR MAC entity <b>115</b> and NR-PHY entity <b>120</b> communicates with the secondary gNB's (gNB-2 <b>250</b>) protocol stack entity <b>104</b> using a second radio channel <b>117</b>.

0058It should be appreciated that, as an example, the second gNB's (gNB-2 <b>250</b>) protocol stack entity <b>104</b> can include a PDCP entity, but such a PDCP entity is disabled or not used in this example when another RAN node is acting as a master or anchor node. Accordingly, when the UE moves out of range from its anchor gNB (e.g., gNB-1 <b>200</b>), another gNB (e.g., gNB-2 <b>250</b>) is configured as the new anchor RAN node, activating its PDCP entity. It should also be appreciated that while only 1 secondary RAN node is illustrated in <figref idref="DRAWINGS">FIG. 2</figref>, there can be additional secondary access nodes.

0059Another example procedure is illustrated in <figref idref="DRAWINGS">FIG. 3</figref>, using simultaneous radio connections, according to an embodiment.

0060<figref idref="DRAWINGS">FIG. 3</figref> illustrates the handover procedure after the RRC connection and a path to transfer data between the UE <b>100</b> and the Source gNB <b>300</b> have been established (via the Establish RRC Connection <b>400</b> and the Data <b>405</b> signals). When the condition for handover is satisfied (via “Criteria for seamless handover satisfied” procedure <b>410</b>), the source gNB <b>300</b> sends an RRC connection reconfiguration for establishing a radio bearer (RB) to the target gNB (as illustrated by the “Secondary RRC connection request to target” <b>415</b> signal) to UE <b>100</b>. In some embodiments this activates packet duplication (PD) to ensure PDUs are not lost during handover. In this case, the UE <b>100</b> maintains a radio connection and RRC connection with the source gNB <b>300</b>. After the RB to the target node is established, as illustrated by the “Establish another RRC connection” signal <b>420</b> passed between the UE <b>100</b> and target gNB <b>340</b>, packet duplication can be used for both data and RRC signaling. In this embodiment, packet duplication includes transmitting duplicated packets between UE <b>100</b> and Source gNB <b>300</b> via “Data” signal <b>425</b> and between UE <b>100</b> and the Target gNB <b>340</b> via “Data” signal <b>430</b>.

0061When the condition for releasing the RRC connection with the source node is satisfied, the source node (and optionally the target node) sends an RRC connection reconfiguration command to complete the RRC connection to the target node. The radio link with the source node is maintained. Once the RRC connection is established to the target node the UE may detach the radio connection from the source node.

0062This is illustrated by the “Criteria for releasing source satisfied” process <b>435</b>. The “Detach Command” <b>440</b> sent from the Source gNB <b>300</b> to UE <b>100</b> causes UE <b>100</b> to execute the “Detach from source gNB” process <b>445</b>. In some embodiments this can trigger PD deactivation if PD is not required all the time for the session.

0063In some embodiments, the UE sends duplicate packets to a plurality of access nodes. Each of the access nodes send the received packets to the PDCP function of the primary access node (which may involve transmission over an Xn interface, or other such interface). In the DL direction, the PDCP function in the primary node generates duplicate packets and forwards the packets to the secondary node/nodes over an Xn interface. The UE removes any duplicate packets received.

0064The redundant transmission afforded by the redundant connection can further reduce the delay by eliminating the re-ordering delay in the RLC and PDCP layers. In embodiments of the URLLC in which ARQ and HARQ are not used, re-ordering at the RLC and PDCP layers may not be necessary. Similarly, the RLC re-ordering may not be necessary. Although one RLC entity may have missing PDUs, in a MC architecture, there is an increased likelihood that a PDU that would otherwise be missing will be received by at least one of the radio nodes. This results in a reduced probability of each RLC missing the same PDU. As noted, embodiments of the proposed invention may afford for the elimination, or reduction in the amount, of reordering necessary if ARQ and HARQ are not employed in the presence of multiple redundant packets.

0065<figref idref="DRAWINGS">FIG. 4</figref> illustrates an exemplary embodiment of a URLLC transmission. Duplicate UL packets in this embodiment are removed by the anchor RAN node, while the UE <b>100</b> removes duplicate DL packets. For UL transmission, the UE <b>100</b> transmits packets to each of a plurality of access. As a result, a single packet may be received by more than one access node. All received packets are forwarded by the plurality of received AN nodes to a single RAN node (the anchor RAN node gNB-1 <b>200</b>), typically over the Xn <b>112</b> interface as noted earlier. Only the anchor RAN node gNB-1 <b>200</b> needs to implement a PDCP function for this connection. The packets received by the anchor node (both over the air interface and over the Xn interface <b>112</b>) are forwarded to the PDCP function <b>106</b>. The PDCP function <b>106</b> of the Anchor node removes the duplicate packets resulting from the redundant connection. In DL transmissions, the PDCP function <b>105</b> in the UE <b>101</b> can be used to account for duplicate packets received as a result of the redundant transmissions from the plurality of access nodes. Each of the secondary access nodes receives packets for redundant transmission over the Xn interface <b>112</b> from the primary access node.

0066Accordingly PDCP included in gNB-1 <b>200</b> can duplicate packets and pass them to both gNB-2 <b>250</b> and UE <b>100</b> (illustrated by the “Duplicate packets and send to multiple AN nodes” process <b>470</b> and DL Data signals <b>475</b> and <b>480</b>). UE <b>100</b> also includes a PDCP <b>105</b> that executes the “Remove duplicate packets” process <b>485</b> to remove duplicated packets received from both gNB-1 <b>200</b> and gNB-2 <b>250</b>. Once again, in some embodiments, it does not matter whether it is the original PDU or the duplicate PDCP PDU which is removed (e.g., deleted).

0067According to one example of the embodiment of <figref idref="DRAWINGS">FIG. 4</figref>, the anchor RAN node is gNB-2 <b>250</b>). In an example of the same embodiment the UE <b>100</b> transmits packets to each of a plurality of access nodes as illustrated by the “Duplicate packets and send the multiple AN nodes” process <b>450</b> and UL Data signals <b>455</b> and <b>460</b>. Process <b>450</b>'s packet duplication includes producing a duplicated PDU (referred to as a duplicate PDCP PDU) is performed by <figref idref="DRAWINGS">FIG. 2</figref>'s NR-PDCP <b>105</b>. The duplicated packets from NR-PDCP <b>105</b> are transmitted simultaneously to gNB-1 <b>200</b> and gNB-2 <b>250</b> via the UE's two NR protocol stack entities <b>101</b>, <b>102</b> and more specifically the NR RLC <b>110</b>, <b>111</b>, NR MAC <b>115</b>, <b>141</b> and NR PHY <b>120</b>, <b>142</b> entities. Accordingly the PDCP layer <b>105</b> duplicates packets, and delivers an original PDCP PDU via a first RLC entity <b>110</b>, first MAC entity <b>115</b> and first PHY entity <b>120</b> and delivers a duplicate PDCP PDU via a second RLC entity <b>111</b>, second MAC entity <b>141</b> and second PHY entity <b>142</b>. For example, UE protocol stack entity <b>101</b> (includes NR-RLC entity <b>110</b>, NR MAC entity <b>115</b> and NR PHY entity <b>120</b>) transmits an original PDCP PDU via communication channel <b>117</b> to the gNB-2 <b>250</b>. Similarly, UE protocol stack entity <b>102</b> (includes a NR-RLC entity <b>111</b>, NR MAC entity <b>141</b> and NR PHY entity <b>142</b>) transmits a duplicate PDCP PDU to the gNB-1 <b>200</b> via communication channel <b>116</b>.

0068According to another example of the embodiment of <figref idref="DRAWINGS">FIG. 4</figref> the PDCP function <b>106</b> of the Anchor node removes the duplicate packets resulting from the redundant connection as illustrated by the “Remove duplicate packets” process <b>465</b>. In some embodiments, it does not matter whether it is the original PDU or the duplicate PDCP PDU which is removed (e.g., deleted).

0069Removing duplicate packets is illustrated by the “Remove duplicate packets” in example process <b>465</b>. In some embodiments, it does not matter whether it is the original PDU or the duplicate PDCP PDU which is removed (e.g., deleted).

0070It will be appreciated that the above proposed method and system can make use of simultaneous transmissions over a plurality of redundant links. This can be used to reduce the likelihood of RLF and increase the reliability of the connection. These redundant links can be created through a multi-connection architecture, of which a dual connection architecture can be understood as a special case. The PDCP function can be centered in the primary RAN node and the UE. Secondary RAN nodes can receive downlink packets from the primary RAN node over the Xn interface, and can provide received uplink packets to the primary RAN node over the Xn interface without applying PDCP functions. The PDCP functions can be used to detect and address duplicate packets

0071Issues related to provision of redundant connectivity as discussed above, from the perspective of the network layer, will now be discussed.

0072In a system that allows MC/DC, a UE will connect to a RAN node, for service. As the UE moves, it may connect to a second RAN node. The first RAN node will be considered the source RAN node. As the UE approaches a second RAN node (referred to as a target RAN node), it can connect to the target RAN node, while still communicating with the current serving (source) RAN node. To reduce the delay associated with handover at least one of the following requirements should be addressed: <ul id="ul0001" list-style="none"><li id="ul0001-0001" num="0000"><ul id="ul0002" list-style="none"><li id="ul0002-0001" num="0073">The target RAN node may be provided context information about the UE (and its connections) before the UE establishes a connection to the target RAN node. This allows for a reduction in the handover delay that would otherwise be caused by the UE needing to establish context information with the target RAN node;</li><li id="ul0002-0002" num="0074">Connections to the core network (CN) for both UL and DL traffic may be established by the target RAN in advance of (or no later than the time of) establishing the connection with the UE;</li><li id="ul0002-0003" num="0075">Downlink traffic destined for the UE, may be made available to both the current serving RAN node and the target RAN node.</li></ul></li></ul>

0076While the above factors can reduce the likelihood of packet delay or connection loss with the UE, it should also be understood that other factors can contribute to the reliability required for a URLLC connection. Such factors can include a requirement for redundant links, both radio links and links in the network infrastructure. Such redundant links may be provided using different RAN nodes, some of which may employ a different Radio Access Technology (RAT). In cases, the redundant connection can make use of the above described DC/MC architecture. This can allow for UL and DL transmissions using a plurality of different transmit/receive points. Another factor can include support for a seamless handover. Seamless handover support in the network can help to ensure that the UE has access to a connection to the network with limited or no interruption of service during a transition from one radio link to another. Seamless handovers can also aid in ensuring that packets are neither lost nor delayed when switching from one radio access link to another.

0077Multi-connectivity can be used to help in satisfying reliability requirements by ensuring that a UE always has at least two paths to the CN. In the multi-connectivity scenario, the UE can be connected to multiple access nodes on the same carrier or on different carriers. In some cases, different access nodes can be using different RATs (e.g. LTE and NR). Dual connectivity can make use of different generations of radio access links (e.g. an LTE or HSPA) connection along with a next generation radio access technology (e.g. 5G RAT) which may make use of different frequency connections (e.g. sub 6 GHz or millimeter wave connections). For example, different frequency connections may be used to support Multi-RAT.

0078Multi-connectivity can be enabled through an extension of the existing DC concept in LTE. The 3C architecture option can be used, where there is one common PDCP entity, for example the gNB-1 <b>200</b> as illustrated in <figref idref="DRAWINGS">FIG. 2</figref>. Because initial deployments of a next generation (such as a so-called 5G network) may not have uniform coverage, connectivity through multiple RATs (e.g. NR and LTE) allows for early support of a URLLC service without needing to wait for a deployment that covers a full geographic area. The transmission of data across multiple RATs should take into account the different interworking deployment options. For example, a next generation radio technology (NR) may operate in standalone mode or it may be supported by an LTE node. A node from either generation can be used as the anchor node. In the multi-RAT case, the serving RAN nodes can contain transmission and reception points (TRPs) from both RATs.

0079As shown in <figref idref="DRAWINGS">FIG. 5</figref>, a UE <b>350</b> can communicate with a next generation Node B (gNodeB, or gNB), over an interface indicated as NR-Uu <b>137</b>, which is an analog to the Uu <b>127</b> interface to an LTE eNB. An Xn interface <b>112</b> is used to connect the primary RAN node (gNB <b>200</b>) to a secondary RAN node (eNB <b>370</b>). Similar to the discussion above with respect to <figref idref="DRAWINGS">FIG. 2</figref>, the Xn interface allows for downlink traffic to be pushed to the target RAN node, and for UL traffic received by the target RAN node to be pushed to the primary RAN node. PDCP functions can be implemented at the UE and the primary RAN node (here illustrated as the gNB <b>200</b>). Those skilled in the art will appreciate that further secondary nodes can be connected, each having an Xn interface to the primary RAN node.

0080The PDCP layer <b>105</b> in the primary/anchor RAN node can be relied upon to remove duplicate UL packets received from the UE <b>350</b> over the plurality of radio links. The UE <b>350</b> can move through the combined service areas of the plurality of target RAN nodes each connected to the same Anchor node. In some embodiments, the connection can be shifted between the connected RAN nodes without needing to re-establish the security association with the PDCP layer. When the UE moves out of coverage of the anchor RAN node the UE can establish the security association with the PDCP function in the target RAN node. Alternatively, the core network can initiate the key exchange during the mobility event.

0081UE <b>350</b> uses two layer stacks when connected simultaneously to both NR RANs and LTE RANs. The layer stack used by UE <b>350</b> to connect with the LTE RAN eNB <b>370</b> includes a RLC <b>125</b>, MAC <b>130</b>, and PHY <b>135</b> layers. This ability to simultaneous connect to two different Radio Access Technologies (RATs) enables support for multiple Radio Access Technologies (multi-RAT). The layer stack used by UE <b>350</b> to connect with NR RAN gNB <b>200</b> includes NR-RLC <b>110</b>, NR-MAC <b>115</b>, and NR-PHY <b>120</b> layers. Both of these layer stacks in this embodiment share a NR-PDCP <b>105</b> layer. gNB <b>200</b> in this embodiment's layer stack includes NR-PDCP <b>106</b>, NR-RLC <b>114</b>, NR-MAC <b>143</b>, and NR-PHY <b>144</b> layers. eNB <b>270</b> in this embodiment's layer stack includes RLC <b>156</b>, MAC <b>157</b>, and PHY <b>158</b> layers.

0082UL and DL transmissions in a URLLC scenario are illustrated in <figref idref="DRAWINGS">FIG. 6</figref>. As can be seen, the UE sends duplicate packets to a plurality of access nodes. Each of the access nodes send the received packets to the PDCP function of the primary access node (which may involve transmission over an Xn interface, or other such interface). In the DL direction, the PDCP function in the primary node generates intentional duplicate packets by forwarding packets to the secondary node/nodes over an Xn interface. The UE removes any duplicate packets received.

0083<figref idref="DRAWINGS">FIG. 6</figref> illustrates an embodiment where the UE <b>100</b> connects to an LTE eNB <b>320</b> as well as gNB <b>310</b> and Anchor node <b>330</b> to illustrate the UE's ability to be connected simultaneously to both NR RANs and LTE RANs. Thus <figref idref="DRAWINGS">FIG. 6</figref> illustrates an embodiment that allows simultaneous connection to two different Radio Access Technologies (RATs), although it should be appreciated that this is an example of multiple Radio Access Technologies (multi-RAT). UE <b>100</b> duplicates packets and sends them to both the gNB <b>310</b> and eNB <b>320</b> via the “Duplicate packets and send to multiple AN nodes” process <b>490</b> and “UL Data” signals <b>495</b> and <b>500</b>. Each of the access nodes send the received packets to the PDCP function of the Anchor node <b>330</b> (which may involve transmission over an Xn interface, or other such interface). Accordingly, gNB <b>310</b> then passes this data to Anchor <b>330</b> via the “UL Data” <b>505</b> signal, which can be via an Xn interface It should be appreciated that in some embodiments, gNB <b>310</b> can act as the anchor node, in which case signal <b>505</b> represents internal signalling between entities. eNB <b>320</b> also passes the same data to Anchor <b>330</b> via the “UL Data” <b>510</b> signal (which can be an Xn Interface). Anchor <b>330</b> includes a PDCP function configured to remove duplicate UL packets it receives by executing the “Remove duplicate packets” <b>515</b> process. Anchor <b>330</b> also duplicates DL packets and sends them to both the eNB <b>320</b> and gNB <b>310</b> via the “Duplicate packets and send to multiple AN nodes” <b>520</b> process and “DL Data” <b>525</b> and <b>530</b> signals, which can be via an Xn interface) eNB <b>320</b> sends DL data it receives from Anchor <b>330</b> to UE <b>100</b> via “DL Data” <b>540</b> signal. gNB <b>310</b> also sends DL data it receives from Anchor <b>330</b> to UE <b>100</b> via “DL Data” <b>535</b>. UE <b>100</b> removes duplicate DL data it receives from eNB <b>320</b> and gNB <b>310</b> by executing the “Remove duplicate packets” process <b>545</b>.

0084In order to ensure seamless handover of the Anchor node responsibilities, a make-before-break handover procedure can be used. The UE can establish a radio connection with the target Anchor node before releasing the RRC connection of the source Anchor node. Therefore, the UE will have two simultaneous radio connections during a mobility event, but there is one RRC connection with the source node. The handover procedure using simultaneous radio connections is illustrated in <figref idref="DRAWINGS">FIG. 9</figref>.

0085In the handover procedure, when the condition for handover is satisfied, the source MgNB <b>360</b> sends an RRC connection reconfiguration for establishing a radio bearer to the target MgNB. In this case, the UE <b>100</b> maintains a radio connection and RRC connection with the source MgNB <b>360</b>. After the RB to the target node <b>365</b> is established, packet duplication can be used for both data and RRC signaling.

0086When the condition for releasing the RRC connection with the source node is satisfied, the source node (and optionally the target node) sends an RRC connection reconfiguration command to complete the RRC connection to the target node. The radio link with the source node is maintained. Once the RRC connection is established to the target node the UE may detach the radio connection from the source node.

0087The redundant links, used in the above described method and system, can be achieved through the use of MC (of which DC can be viewed as a special case). In such a configuration, the RAN nodes can be configured to use a common PDCP entity. The PDCP function for the transmitting RAN nodes can support packet duplication for a multi-connectivity architecture. The PDCP functions at the primary RAN node and at the UE can be assigned responsibility for handling packet duplication. During mobility, the UE can be provided with a plurality of simultaneous radio connections to both source and target RAN nodes to allow for reduction in the likelihood of service interruption in handovers. In this case, the UE maintains a single RRC connection.

0088According to an example, the procedure may begin after the RCC connection has been established (“Establish RRC Connection” <b>400</b> and “Data” <b>405</b> signals) between UE <b>100</b> and Source MgNB <b>360</b>. It should be appreciated that the procedure for handover, packet duplication, and releasing the source, according to the embodiment illustrated in <figref idref="DRAWINGS">FIG. 9</figref>, is an alternative to the embodiment illustrated in <figref idref="DRAWINGS">FIG. 3</figref>.

0089According to further example, there is a “Criteria for seamless handover satisfied” process <b>410</b> optionally provided for satisfaction of the handover condition. The destination of the RRC connection reconfiguration for establishing a radio bearer may be the UE <b>100</b> via the “RRC Connection Reconfig. (establish RB only) signal <b>550</b>. The target node <b>365</b> may be established via the “Establish Radio Bearer” <b>555</b> signal. For packet duplication, data may be transmitted between UE <b>100</b> and Source MgNB <b>360</b> via “Data” <b>560</b> signal and between UE <b>100</b> and Target MgNB <b>365</b> via “Data” <b>565</b> signal.

0090Again, by example, the condition for releasing the RRC connection with the source node may be satisfied via the “Criteria for releasing source satisfied” procedure <b>570</b>). The source node may signal this via the “RRC Conn. Reconfig. (complete the RRC connection to target)” signal <b>575</b> and target node via the “Complete RRC Connection to Target MgNB” <b>580</b> signal. The UE may detach the radio connection from the source node via the “Detach from source MgNB” process.

0091<figref idref="DRAWINGS">FIG. 7</figref> illustrates an embodiment in which a Radio Access Node <b>602</b> is shown operating as a secondary node <b>605</b> to a primary node <b>600</b>, and also operating as a primary node <b>610</b>. to another secondary node <b>615</b> As will be understood, each primary node can have a plurality of secondary nodes, and such a structure as illustrated in <figref idref="DRAWINGS">FIG. 7</figref> allows for a tree-like structure in modeling the relationship between nodes.

0092In order to achieve better resource utilization and improve spectral efficiency when supporting packet duplication (PD), the various diversity techniques supported in LTE and 5G (new radio (NR)) architectures can be exploited and enhanced. These architectural techniques include: <ul id="ul0003" list-style="none"><li id="ul0003-0001" num="0000"><ul id="ul0004" list-style="none"><li id="ul0004-0001" num="0093">Multi-connectivity/Dual-connectivity (MC/DC): Mode of operation where the UE is able to access radio resources provided by at least two different network access nodes (e.g. Master and Secondary gNBs) which are connected via a non-ideal backhaul (i.e. Xn interface). In an example, the network access nodes can be Master and Secondary gNBs of the same or different Radio Access Technologies (RATs).</li><li id="ul0004-0002" num="0094">Carrier Aggregation (CA): Mode of operation where multiple component carriers (CCs) can be used together in both frequency division duplex (FDD) and time division duplex (TDD) transmission modes to achieve high data rates. In this architecture, multiple small cells can be configured with different carriers. The small cells are connected to the macro cell with ideal backhaul.</li></ul></li></ul>

0095Enhancements that can be made to the MC/DC and CA architectures to support PD techniques will be discussed below.

0096First, enhancements that can be made to the MC/DC architectures to support PD techniques will be discussed, according to various embodiments. The MC/DC architecture includes the master and secondary gNBs (MgNB <b>600</b>, <b>610</b> and SgNB <b>605</b>, <b>615</b>) connected via the Xn interfaces <b>250</b>, <b>112</b>. While the MgNB <b>600</b> hosts the full RAN protocol stack (composed of the PDCP <b>105</b>, RLC <b>114</b>, MAC <b>143</b> and PHY <b>144</b> layers), the SgNB <b>615</b> hosts only the lower layers (i.e. RLC <b>125</b>, MAC <b>130</b> and PHY <b>135</b>). Also each MgNB can support multiple links/cells, consisting of a Primary Cell (PCell) and a number of Secondary Cells (SCells). Collectively, the cells/links controlled by the MgNB form the Macro Cell Group (MCG). The SgNB, in turn, supports and controls the Secondary Cell Group (SCG) including a Primary-Small Cell (PSCell) and a number of SCells.

0097It should be appreciated that Primary RAN node <b>600</b> supports an Xn interface <b>250</b> to communicate with Secondary RAN node <b>605</b>. The Secondary RAN node <b>605</b> hosts the lower layers which include NR-RLC <b>145</b>, NR-MAC <b>150</b> and NR PHY <b>155</b>. Pseudo Primary RAN node <b>610</b> hosts the full RAN protocol stack including NR-PDCP <b>625</b> along with the lower layers which include NR-RLC <b>145</b>, NR-MAC <b>150</b> and NR PHY <b>155</b>. It is noted that in the embodiment illustrated the lower layers which include NR-RLC <b>145</b>, NR-MAC <b>150</b> and NR PHY <b>155</b> are shared between Pseudo Primary RAN node <b>610</b> and the Secondary RAN node <b>605</b>, but it should be appreciated that separate RLC, MAC and PHY entities could be used.

0098The RRC entity <b>700</b> hosted at the MgNB <b>362</b>, will be responsible for configuring all the protocol layers of both the MgNB <b>362</b> and SgNB <b>367</b> as shown in <figref idref="DRAWINGS">FIG. 10</figref>. <figref idref="DRAWINGS">FIG. 10</figref> illustrates an example NR MC/DC Architecture for supporting PD, according to an embodiment. For supporting PD, a goal is to configure and assign each duplicate protocol data unit (PDU) to a different set of links/cells in the MgNB <b>362</b> and SgNBs <b>367</b> to realize maximum diversity. In another embodiment, the MC/DC Architecture can include other RATs. For example, it may include NR in combination with LTE or eLTE.

0099In such an MC/DC architecture, the PDCP <b>706</b> entity at the transmitter hosts a new Packet Duplication (PD) function which duplicates the PDCP PDUs. Each instance of the duplicate PDUs may carry the same PDCP sequence number (SN). At the receiver, the PDCP entity hosts a PD removal function which may perform combining of the received PDCP PDUs (e.g. using a bit level soft combining technique).

0100The radio bearer to logical channel mapping between PDCP and RLC can be configured to be one-to-one such that further duplication is not necessary at the RLC <b>711</b> layer. The RLC may be configured (by RRC <b>700</b>) to operate in either the unacknowledged mode (UM) or the transparent mode (TM) mode when PD at PDCP is activated.

0101In each access node (i.e. MgNB <b>362</b> and SgNB <b>367</b>) in MC/DC, the logical channels at the MAC <b>705</b> layer may be mapped to a transport channel associated with a different link/cell/carrier. In this case, the mapping between each logical channel to transport channel is also configured to one-to-one. There can be a common scheduler/multiplexer at the upper MAC (U-MAC <b>705</b>) layer that can perform cross-carrier scheduling of the MAC PDUs or transport blocks (TBs) across different link/cell/carrier. In the lower MAC (L-MAC <b>710</b>) layer, each link can in turn be handled by its own HARQ process that can be configured to support a certain maximum number of re-transmissions (e.g. 1 re-transmission per HARQ process). This allows the HARQ processes (for each link) to operate independently of each other.

0102At the PHY <b>715</b> layer, each transport channel can be handled by its own PHY <b>715</b> entity, enabling different number of physical resource blocks (PRBs) and modulation and coding schemes (MCS) to be configurable in both downlink (DL) and Uplink (UL) transmissions.

0103Enhancements that can be made to the CA architecture to support PD techniques will be discussed, according to various embodiments. <figref idref="DRAWINGS">FIG. 11</figref> illustrates an example NR CA Architecture for supporting PD, according to an embodiment. The CA architecture includes a standalone access node which can include a full RAN protocol stack with the capability to support transmissions over multiple CCs. The CCs, in turn, can include a Primary Cell (PCell) and a number of Secondary Cells (SCells). For supporting PD, each duplicate packet can be assigned to a different CC. Also in CA, the duplication function can be hosted either at the PDCP entity or the MAC entity.

0104In the case when PD is performed at PDCP <b>706</b>, a similar operation can be implemented as described above with respect to the MC/DC architecture. In some embodiments, if PD is performed at the MAC <b>705</b> layer each received MAC service data unit (SDU) (from the RLC <b>711</b>) can be duplicated into multiple MAC PDUs (i.e. multiple transport blocks (TBs) of the same size). Here, in contrast to the case of duplicating at the PDCP, the mapping between each logical channel to transport channel is 1-to-many. Accordingly the RRC <b>700</b> can configure the MAC layer to ensure that each transport channel is mapped to a different CC.

0105At the U-MAC <b>705</b>, there can be a common scheduler/multiplexer which can perform cross-carrier scheduling of the MAC PDUs between different CCs. There can also be a common HARQ entity that can function across different CCs while supporting a common HARQ buffer. At the L-MAC <b>710</b>, each CC can be associated with its own HARQ process, which may be configured to handle a certain maximum number of re-transmissions. The received data in each HARQ process can be stored in the common buffer managed by the common HARQ entity. The HARQ ACK/NACK feedback in each HARQ process can be controlled from the common HARQ entity. At the receiver, soft combining technique can be used to perform combining of the received packets across different HARQ processes at the common HARQ entity. Additionally, soft combining at the receiver removes the duplicates and the resulting PDU is forwarded to the upper layers (i.e. RLC <b>711</b> and PDCP <b>706</b>).

0106The following table is a Summary of Architectural Impacts for supporting PD, according to embodiments.

0000<tables id="TABLE-US-00001" num="00001"><table frame="none" colsep="0" rowsep="0"><tgroup align="left" colsep="0" rowsep="0" cols="3"><colspec colname="offset" colwidth="28pt" align="left" /><colspec colname="1" colwidth="91pt" align="left" /><colspec colname="2" colwidth="98pt" align="left" /><thead><row><entry /><entry namest="offset" nameend="2" align="center" rowsep="1" /></row><row><entry /><entry>Impacts in CA to</entry><entry>Impacts in MC/DC</entry></row><row><entry /><entry>support PD</entry><entry>to support PD</entry></row><row><entry /><entry namest="offset" nameend="2" align="center" rowsep="1" /></row></thead><tbody valign="top"><row><entry /></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="3"><colspec colname="1" colwidth="28pt" align="left" /><colspec colname="2" colwidth="91pt" align="left" /><colspec colname="3" colwidth="98pt" align="left" /><tbody valign="top"><row><entry>RRC</entry><entry>RRC may configure the CCs</entry><entry>RRC may configure MgNB</entry></row><row><entry /><entry>for packet duplication. The</entry><entry>and SgNBs for PD. The</entry></row><row><entry /><entry>SCells are added/removed</entry><entry>SgNBs are added/removed</entry></row><row><entry /><entry>based on (UL control</entry><entry>based on UCI and/or</entry></row><row><entry /><entry>information (UCI).</entry><entry>neighbour cell measurements.</entry></row><row><entry>PDCP</entry><entry>No impact unless packet</entry><entry>Consists of new PD function</entry></row><row><entry /><entry>duplication is performed at</entry><entry>which is responsible for</entry></row><row><entry /><entry>PDCP. If PD is performed at</entry><entry>duplicating PDCP PDUs at</entry></row><row><entry /><entry>PDCP then a new PD</entry><entry>Tx and removing received</entry></row><row><entry /><entry>function is required.</entry><entry>duplicate PDUs (via a</entry></row><row><entry /><entry /><entry>combining technique) at Rx</entry></row><row><entry>RLC</entry><entry>No impact. ARQ is</entry><entry>No impact. ARQ is configured</entry></row><row><entry /><entry>configured in UM or TM</entry><entry>in UM or TM mode by default</entry></row><row><entry /><entry>mode by default at both</entry><entry>at both MgNB and SgNB</entry></row><row><entry /><entry>MgNB and SgNB</entry></row><row><entry>MAC</entry><entry>Consist of common U-MAC</entry><entry>In DL, a common</entry></row><row><entry /><entry>(scheduler, HARQ entity)</entry><entry>scheduler/multiplexer may</entry></row><row><entry /><entry>and multiple L-MAC (for</entry><entry>perform cross-carrier</entry></row><row><entry /><entry>each CC). In DL, common</entry><entry>scheduling of the MAC SDUs</entry></row><row><entry /><entry>scheduler performs</entry><entry>received from upper layers.</entry></row><row><entry /><entry>duplication of the MAC</entry><entry>Each MAC PDUs are assigned</entry></row><row><entry /><entry>SDUs received from upper</entry><entry>to different CCs (PDSCH).</entry></row><row><entry /><entry>layers. Each duplicated</entry><entry>In the receiver, the PDU</entry></row><row><entry /><entry>PDU is assigned to different</entry><entry>from different CCs (PUSCH)</entry></row><row><entry /><entry>CCs. In the receiver, the</entry><entry>need not be combined. HARQ</entry></row><row><entry /><entry>PDUs from different CCs</entry><entry>process in each CC may</entry></row><row><entry /><entry>are soft combined. Each CC</entry><entry>support retransmissions</entry></row><row><entry /><entry>may allow re-transmission</entry><entry>but cross CC-HARQ</entry></row><row><entry /><entry>for HARQ. A common</entry><entry>management of HARQ is</entry></row><row><entry /><entry>HARQ entity may manage</entry><entry>not required.</entry></row><row><entry /><entry>all CC-HARQ processes.</entry></row><row><entry /><entry>For UL Tx, the UE is</entry></row><row><entry /><entry>assigned multiple UL</entry></row><row><entry /><entry>grants on different CCs</entry></row><row><entry /><entry>for PD. The receiver in</entry></row><row><entry /><entry>the gNB may perform soft</entry></row><row><entry /><entry>combining across CCs.</entry></row><row><entry>PHY</entry><entry>No impact</entry><entry>No impact</entry></row><row><entry namest="1" nameend="3" align="center" rowsep="1" /></row></tbody></tgroup></table></tables>

0107Triggering techniques to support Packet Duplication will now be discussed according to various embodiments.

0108In the initial access procedure (i.e. RRC Connection Establishment procedure) the UE is able to provide its capability information to the PCell (i.e. MgNB) indicating the number of CCs and Tx/Rx chains (for accessing SgNBs) it can support. The UE may specifically indicate its preference for Inter-band CA configuration and the reliability requirement to support URLLC.

0109Based on specified capability, the RRC entity configures the PCell and a number of SCells in the MCG for supporting URLLC transmissions. Optionally, the RRC may also configure a set of SCGs, consisting of PSCell and SCells in the SgNBs, as part of the RRC Connection Reconfiguration procedure. In the case when the PSCell in the SgNB is configured, the configuration parameters are transmitted from the MgNB via RRC containers (as part of SgNB Addition/Change request procedure) over the Xn interface. New SgNBs can be added to the existing SCG set and existing SgNBs can be either updated or released via the RRC Connection Reconfiguration procedure in the case when the UE is mobile. After the initial access procedure, the following options can be applied as a triggering mechanism to activate/deactivate the PD mode.

0110Triggering for packet duplication and link selection will now be discussed according to various embodiments.

0111As an alternative to PD, Link Selection (LS) techniques according to embodiments can achieve reliability by selecting and provisioning the best available transmission link based on fast channel measurements. This is based on the assumption that there exists a coverage region in the network with highly favorable channel conditions (e.g. High SNR with line of sight (LOS), low load) where transmitting over a single best link is sufficient to satisfy the URLLC requirements. Outside of this region PD approaches as discussed herein are used to satisfy URLLC requirements.

0112In this regard, a triggering mechanism can be applied to toggle between LS and PD modes based on a selection criterion which can be implemented either at the network or UE as described below.

0113First, a network triggered approach will be discussed according to embodiments. An example network triggered LS/PD activation procedure is illustrated in <figref idref="DRAWINGS">FIG. 12</figref>, according to an embodiment. In the network triggered approach, the MgNB <b>370</b> initially activates the PCell and deactivates the SCells among the set of links/CCs configured by the RRC. The activation/deactivation status of the links/CCs can be conveyed to the UE <b>100</b> via the MAC control elements (MAC CEs). Note that in the case of MC/DC, the set of links utilized for PD may include those from both the MGC (MgNB) and SGC (SgNB).

0114The MgNB <b>370</b> may also request the channel quality information (CQI) reports from UE <b>100</b> on all activated links/CCs via a DL control information (DCI) signal. The UE <b>100</b> transmits the CQI reports via the UCI. If PDCP/RLC data buffer is non-empty, the UE <b>100</b> may also transmit the Scheduling Request (SR) on the UCI.

0115Based on the channel measurements and the overall load information, the MgNB <b>370</b> may use a triggering criterion to determine the best transmission mode for the UE <b>100</b>. That is, the selection of LS or PD is performed by selecting the best k CCs (or links) out of the n available CCs, where when k=1 LS is selected and when k>1 PD is selected. As an example, the steps involved in the triggering criteria can be listed as follows: <ul id="ul0005" list-style="none"><li id="ul0005-0001" num="0000"><ul id="ul0006" list-style="none"><li id="ul0006-0001" num="0116">i) If the CQI and the resources available on the best link is sufficient to meet the reliability requirement, the MgNB <b>370</b> selects the LS mode</li><li id="ul0006-0002" num="0117">ii) If the CQI and the resources available on the best link are not sufficient to meet the reliability requirement then the MgNB <b>370</b> considers the second best link for selecting the PD mode. The second best link should satisfy the following criteria: i) the CQI of the second best link is above a CQI_threshold, ii) the delta_CQI of the best link and the second best link is below a delta_threshold and iii) the resources available on the second best link is above a resource_threshold.</li><li id="ul0006-0003" num="0118">iii) If the two best links are not sufficient to meet the reliability requirement then the MgNB <b>370</b> also considers the third best link. The third best link should also satisfy the above requirements for CQI_threshold, delta_threshold and resource threshold.</li><li id="ul0006-0004" num="0119">iv) This procedure is repeated until the reliability requirement is satisfied or there are no more links (cells/carriers).</li></ul></li></ul>

0120In the case when LS is selected, the MgNB <b>370</b> selects one activated link/CC and sends a DCI, to assign DL resources or to grant UL resources for a single transmission.

0121If PD is selected, the MgNB <b>370</b> selects multiple activated links/CCs and sends a DCI for each of the selected link/CC. A new DCI format may be used to indicate that the UL grant is used for PD. The new packet duplication field may be a single bit to identify which grants are used for PD.

0122Alternatively, the packet duplication field may be a sequence number, which identifies the grants that are used for specific PD transmissions.

0123In another embodiment, a single UL grant can be sent to the UE, which indicates the cells/carriers to use for PD.

0124Based on the selected mode the MgNB allocates resources on the activated link(s)/CC(s) and indicates the resource configuration (e.g. PRBs, MCS, antenna ports) to the UE in the DCI. The MgNB may also provide UL grants and activates the semi-persistent scheduling (SPS) configuration via the DCI.

0125In the UL, the UE transmits the data on Physical UL shared channel (PUSCH) while continuing to report the CQI on all activated CCs (on Physical UL control channel (PUCCH)). Subsequent transmissions may include the Buffer Status report (BSR) on the MAC CE.

0126In the DL, the data is transmitted on the scheduled links(s)/CC(s) on Physical DL shared channel (PDSCH).

0127The MgNB may update the configured link/CC set which can be indicated to the UE via the RRC Connection Reconfiguration procedure

0128As an example, during the process, UE <b>100</b> and MgNB <b>370</b> exchange “RRC Connection Re-establishment” information via signal <b>375</b>, “UE Capability Information” via signal <b>380</b>, and “RRC Connection Reconfiguration (Pcell and Scell Configuration)” via signal <b>385</b>.

0129The triggering criteria may be exemplified by “Criteria for LS/PD trigger” process <b>395</b>. During this process UE <b>100</b> and MgNB <b>370</b> exchange “LS/PD Trigger (MAC CE)” information via signal <b>800</b>, “UL Grants (PDCCH)” via signal <b>805</b>, and “URLLC data and UCI (PUCCH, PUSCH)” via signal <b>810</b>.

0130According to an example, reports of the process may be communicated on the Physical UL control channel (PUCCH) via the “UCI (CQI of configured CCs)” signal <b>390</b>.

0131According to a further example, the DCI may be sent via “URRLC data and DCI (PDSCH, PDCCH)” signal <b>815</b>.

0132A UE triggered approach will now be discussed according to embodiments. An example UE triggered LS/PD activation procedure is illustrated in <figref idref="DRAWINGS">FIG. 13</figref>, according to an embodiment. Similar to the network triggered case, in the UE <b>100</b> triggered case the MgNB <b>370</b> activates a set of links/CCs for the UE <b>100</b> to perform channel measurements. All links/CCs, except for PCell, are initially set to be in the default deactivated state.

0000However, in contrast to the network triggered case, the MgNB may pre-allocate certain resources on the configured links while still retaining the links in deactivated state. The MgNB may also provide resource configuration (e.g. PRBs, range of potential MCS) along with the UL grants via the DCI. In addition, the UL grant for each link may contain a validity timer, indicating the duration in which the resources in the corresponding links are valid and reserved for the UE

0133Based on availability of data in the PDCP/RLC buffer and the measured channel conditions, UE may apply a criterion to determine the trigger for selecting the PD mode. As an example, the steps involved in the triggering criteria for LS/PD are listed as follows: <ul id="ul0007" list-style="none"><li id="ul0007-0001" num="0000"><ul id="ul0008" list-style="none"><li id="ul0008-0001" num="0134">i) If the CQI of the best link is sufficient to meet the reliability requirement, the UE selects the LS mode</li><li id="ul0008-0002" num="0135">ii) If the CQI of the best link is not sufficient to meet the reliability requirement then the UE considers the second best link for selecting the PD mode. The second best link should satisfy the following criteria: i) the CQI of the second best link is above a CQI_threshold, ii) the delta_CQI of the best link and the second best link is below a delta_threshold.</li><li id="ul0008-0003" num="0136">iii) If the two best links are not sufficient to meet the reliability requirement then the UE also considers the third best link. The third best link should also satisfy the above requirements for CQI_threshold and delta_threshold.</li><li id="ul0008-0004" num="0137">iv) This procedure is repeated until the reliability requirement is satisfied or there are no more links (cells/carriers).</li></ul></li></ul>

0138In the UL, the UE <b>100</b> transmits data on the PUSCH. In the DL, the data is transmitted on the scheduled links (cells/CCs) on PDSCH.

0139Additionally, it should be possible for the MgNB to overrule the UE-triggered selection capability dynamically by sending an indicator in the PDCCH to limit the use of the grant free resources to the primary cell/carrier. This indicator can be a single bit to indicate whether or not the UE uses PD on the grant free resources on the different cells/carriers. The PD indicator can be signaled either dynamically or semi-statically.

0140Alternatively, there can be a PD indicator for the grant free resources on each cell/carrier. The UE can only use the grant free resources on the cells/carriers where the PD indicator is set.

0141In another embodiment, RRC signaling can be used to configure PD on the grant free resources on multiple cells/carriers.

0142Signalling for Packet Duplication will now be discussed, according to embodiments. The criteria for activating and deactivating packet duplication depend on the DL and UL channel conditions as well as on the loading in the different cells/carriers. In both DC/MC and CA architectures, the MgNB (PCell) makes the decision on whether or not to activate packet duplication for the UE.

0143Once packet duplication is activated, the MgNB can dynamically decide how many links (cells) are used for both DL and UL transmission to satisfy the required reliability. The UE may receive one or more DL assignments or UL grants for the transmission of a packet.

0144The number of links that are used for UL and DL may be different. This is because the loading in the UL can DL can be significantly different.

0145The network may also provide the UE with criteria to determine when to use packet duplication, while the UE is configured for packet duplication. This allows the UE to decide when to use packet duplication.

0146Pre-allocation described above conforms with the grant-free technique where resources are pre-allocated for the UEs without going through the dynamic scheduling procedure involving scheduling request (SR) sent by the UE and subsequent resource allocation. By way of example, MgNB <b>370</b> informs UE <b>100</b> of the UL grant via the “UL Grants for pre-allocated resources on configured CCs (PDCCH)” signal <b>805</b>. During this process, MgNB <b>370</b> and UE <b>100</b> also exchange “RRC Connection Re-establishment” information via signal <b>375</b>, “UE Capability Information” via signal <b>380</b>, and “RRC Connection Reconfiguration (Pcell and Scell Configuration)” via signal <b>385</b>.

0147According to example implementations, the trigger criterion may be satisfied by the “Criteria for LS/PD trigger” process <b>395</b>). Further, the data may be transmitted in UL by via “URLLC data (PUSCH), MAC CE (PS/PD Trigger), UCI (CQI reports)” signal <b>820</b> and by “URLLC data and DCI (PDSCH, PDCCH)” signal <b>815</b> in DL.

0148<figref idref="DRAWINGS">FIG. 14</figref> illustrates an example Signalling flow for activating packet duplication, according to embodiments. In this procedure, new cells/carriers can be added for the UE <b>100</b> based on the UE's measurement reports. The serving MgNB can use link selection to determine the best cell/carrier to send the packets. If the criteria for activating packet duplication (PD) <b>865</b> are satisfied then the serving MgNB <b>370</b> sends an RRC connection Reconfiguration message <b>870</b> to active the PD mode. Once the UE <b>100</b> sends the RRC Reconfiguration Complete message <b>875</b>, the packet duplication mode can be activated. This means the UE can receive multiple DL assignment messages and multiple UL grants for the same URLLC packet. Use of the link selection may be via Data <b>855</b> passed between UE <b>100</b> and MgNB <b>370</b> and Data <b>860</b> passed between UE <b>100</b> and SgNB <b>830</b>.

0149UE <b>100</b> signals MgNB <b>370</b> of the DL Measurements (SgNB) <b>835</b>, MgNB <b>370</b> and SgNB <b>830</b> exchange “Add PScell” information <b>840</b>, and MgNB <b>370</b> transmits RRC Connection Reconfig (add SgNB) message <b>845</b>. A radio bearer <b>850</b> is also established between UE <b>100</b> and SgNB <b>830</b>. Once PD has been configured for a Data Radio Bearer (DRB), MAC <b>100</b> control elements to activate or deactivate PD. Duplicated packets are sent between UE <b>100</b> and MgNB <b>370</b> via Data <b>560</b> and between UE <b>100</b> and SgNB <b>830</b> via Data <b>565</b>.

0150<figref idref="DRAWINGS">FIG. 15</figref> illustrates example Signalling flow for deactivating packet duplication, according to embodiments. In this procedure, if the UE <b>100</b> is in PD mode, the serving MgNB <b>370</b> evaluates the criteria for deactivating PD based on the UE's channel measurements and on the loading in the cells/carriers. If the PD criteria are satisfied, the MgNB <b>370</b> sends an RRC Connection Reconfiguration message <b>871</b> to deactivate the PD mode. Once the UE <b>100</b> sends the RRC Reconfiguration Complete message <b>876</b>, the PD mode can be disabled and the serving MgNB can use link selection to transmit the packets.

0151The link selection process involves sharing Data <b>855</b> between UE <b>100</b> and MgNB <b>370</b> and Data <b>860</b> between UE <b>100</b> and SgNB <b>830</b>. According to an example, duplicated packets flow between UE <b>100</b> and MgNB <b>370</b> via signal <b>560</b> and between UE <b>100</b> and SgNB <b>830</b> via signal <b>565</b>. Evaluation of the criteria for deactivating PD may be via process <b>866</b>. Channel measurements may be received from UE <b>100</b> by MgNB <b>370</b> via “DL Measurements (SgNB)” signal <b>835</b>).

0152In some scenarios, the MgNB can provide the UE with criteria to activate/deactivate packet duplication. The UE evaluates the criteria to determine when to use packet duplication. <figref idref="DRAWINGS">FIG. 16</figref> illustrates example Signalling flow for activating and deactivating packet duplication based on criteria sent to the UE <b>100</b> through RRC signalling, according to embodiments. In this procedure, the MgNB <b>370</b> sends an RRC Connection Reconfiguration message <b>873</b> to configure the UE <b>100</b> with the PD activation criteria. In this case, the UE <b>100</b> is also configured with resources that can be used for packet duplication (e.g. grant free resources on multiple cells/carriers).

0153In some embodiments, the same signalling for activating/deactivating packet duplication can be applied in both DC/MC and CA architectures.

0154In some embodiments, RRC signalling can be used to configure the packet duplication mode for the UE.

0155In some embodiments, the criteria for activating and deactivating packet duplication can depend on the DL and UL channel conditions as well as loading in the cell.

0156In some embodiments, the decision to use packet duplication for UL and DL can be determined independently.

0157In some embodiments, the decision to use packet duplication, while the UE is in packet duplication mode, can be made by the network. In other words, even if the UE is in packet duplication mode, the network can override the decision.

0158In some embodiments, the network may provide the UE with criteria to determine when to activate/deactivate packet duplication. The UE uses the criteria to make the decision on when to use packet duplication.

0159It should be appreciated that the methods described above can be implemented by controllers in the various devices (e.g., UE <b>100</b>, MgNB <b>370</b>, SgNB <b>830</b>, etc.). Accordingly, various embodiments include a controller including a processor and machine readable instructions which when executed by the processor cause the device to implement the above described methods and signaling.

0160Some of the Embodiments listed may be considered examples of the criteria for activating PD <b>880</b> and the criteria for deactivating PD <b>885</b>.

0161According to an example, UE <b>100</b> informs MgNB <b>370</b> that it has completed this configuration via the RRC Reconfig Complete message <b>875</b>. Once the UE determines the criteria for activating PD (based on criteria provided in the RRC signaling) is satisfied <b>880</b>, the UE switches into PD mode. At which point, duplicated packets flow between UE <b>100</b> and MgNB <b>370</b> via Data <b>560</b> and between UE <b>100</b> and SgNB <b>830</b> via Data <b>565</b>. Once the UE determines the criteria for deactivating PD (based on criteria provided in RRC signalling) is satisfied <b>885</b>, the UE deactivates PD mode. At which point link selection “Data” is passed between UE <b>100</b> and MgNB <b>370</b> via signal <b>855</b> and UE <b>100</b> and SgNB <b>830</b> via signal <b>860</b>.

0162<figref idref="DRAWINGS">FIG. 17</figref> is a block diagram of a processing system <b>1001</b> that may be used for implementing the various network functions and the methods and signaling as described above, according to embodiments. As shown in <figref idref="DRAWINGS">FIG. 17</figref>, processing system <b>1001</b> includes a processor <b>1010</b>, working memory <b>1020</b>, non-transitory storage <b>1030</b>, network interface, I/O interface <b>1040</b>, and depending on the node type, a transceiver <b>1060</b>, all of which are communicatively coupled via bi-directional bus <b>1070</b>.

0163According to certain embodiments, all of the depicted elements may be utilized, or only a subset of the elements. Further, the processing system <b>1001</b> may contain multiple instances of certain elements, such as multiple processors, memories, or transceivers. Also, elements of processing system <b>1001</b> may be directly coupled to other components without the bi-directional bus.

0164The memory may include any type of non-transitory memory such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous DRAM (SDRAM), read-only memory (ROM), any combination of such, or the like. The mass storage element may include any type of non-transitory storage device, such as a solid state drive, hard disk drive, a magnetic disk drive, an optical disk drive, USB drive, or any computer program product configured to store data and machine executable program code. According to certain embodiments, the memory or mass storage have recorded thereon statements and instructions executable by the processor for performing the aforementioned functions and steps. The processing system <b>1001</b> can be used to implement a UE or host which executes the various network and UE functions described herein. In an example, the host herein may be a RAN node.

0165Through the descriptions of the preceding embodiments, the present disclosure may be implemented by using hardware only or by using software and a necessary universal hardware platform. Based on such understandings, the technical solution of the present disclosure may be embodied in the form of a software product. The software product may be stored in a non-volatile or non-transitory storage medium, which can include the device memory as described above, or stored in removable memory such as compact disk read-only memory (CD-ROM), flash memory, or a removable hard disk. The software product includes a number of instructions that enable a computer device (computer, server, or network device) to execute the methods provided in the embodiments of the present disclosure. For example, such an execution may correspond to a simulation of the logical operations as described herein. The software product may additionally or alternatively include number of instructions that enable a computer device to execute operations for configuring or programming a digital logic apparatus in accordance with embodiments of the present disclosure.

0166Further embodiments of the present invention are provided in the following. It should be noted that the numbering used in the following section does not necessarily need to comply with the numbering used in the previous sections.

Embodiment 1

0167A method of handover of a User Equipment (UE) in a radio access network, for execution by a source radio access node having a first Radio Resource Control (RRC) connection to the UE, the method comprising:

0168determining that criteria for a seamless handover of the UE to a target radio access node have been satisfied;

0169transmitting to the UE an instruction to establish a second radio connection between the UE and the target radio access node while maintaining the radio and RRC connection with the source radio access node;

0170receiving, in response to the instruction to the UE to establish a radio connection, an indication that the second radio connection to the target radio access node has been established; and

0171transmitting to the UE an RRC connection reconfiguration command to move the RRC connection from the source RAN node to the target RAN node.

Embodiment 2

0172The method of embodiment 1 wherein the step of determining that criteria for a seamless handover have been satisfied includes receiving measurement reports from the UE.

Embodiment 3

0173The method of any preceding embodiment wherein the step of transmitting to the UE an instruction to establish a second radio connection includes transmitting an instruction to establish a second radio connection in parallel to the first radio connection that support the RRC connection.

Embodiment 4

0174The method of any preceding embodiment further including the step of transmitting data to the UE after transmitting to the UE the instruction to establish as second radio connection.

Embodiment 5

0175The method of any of embodiments 1 to 3 further including the step of transmitting data to the UE after receiving an indication that the second radio connection has been established.

Embodiment 6

0176A method of handover of a User Equipment from a first radio access node, with which a first Radio Resource Control (RRC) connection has been established, to a second radio access node in a radio access network, the method comprising:

0177transmitting to the first radio access node a signal measurement report indicative of the ability to connect to the second radio access node;

0178in response to receipt of an instruction from the first radio access node, establishing a second radio connection with the second radio access node;

0179transmitting data to, or receiving data from, the first and second radio access nodes;

0180and releasing the first RRC connection.

Embodiment 7

0181The method of embodiment 6 wherein the data transmitted to or received from the first and second radio access nodes is the same.

Embodiment 8

0182The method of any of embodiments 1 to 5 further comprising transmitting to the UE a detach command instructing the UE to release the first RRC connection.

Embodiment 9

0183The method of embodiment 8 wherein transmitting to the UE a detach command is subsequent to transmitting to the UE an RRC connection reconfiguration command.

Embodiment 10

0184Architectures as described.

Embodiment 11

0185A method of applying the same signalling for activating/deactivating packet duplication in both DC/MC and CA architectures.

Embodiment 12

0186A method of RRC signalling used to configure the packet duplication mode for the UE.

Embodiment 13

0187A method for activating and deactivating packet duplication utilizing criteria dependent on the DL and UL channel conditions as well as loading in the cell.

Embodiment 14

0188The method of embodiment 13 wherein the decision to use packet duplication for UL and DL can be determined independently.

Embodiment 15

0189A method of deciding to implement packet duplication determined by a UE.

Embodiment 16

0190The method of embodiment 15 wherein the UE receives criteria to determine when to activate/deactivate packet duplication from a network node.

Embodiment 17

0191A method of deciding to implement packet duplication determined by a network node.

Embodiment 18

0192The method of embodiment 17 wherein the network node can instruct a UE in packet duplication mode to change modes.

Embodiment 19

0193A method of handover of a User Equipment (UE) in a radio access network, for execution by a source radio access node having a first Radio Resource Control (RRC) connection to the UE, the method comprising:

0194receiving measurement reports from the UE;

0195transmitting to the UE an instruction to establish a second radio connection between the UE and a target radio access node while maintaining the radio and RRC connection with the source radio access node;

0196receiving, in response to the instruction to the UE to establish a radio connection, an indication that the second radio connection to the target radio access node has been established; and

0197transmitting to the UE an RRC connection reconfiguration command to move the RRC connection from the source RAN node to the target RAN node.

Embodiment 20

0198A method of a receiver, comprising:

0199activating the PD at a PDCP layer of the receiver; and

0200removing duplicate PDCP PDUs at the PDCP layer, wherein the duplicate PDCP PDUs are received from two RLC entities.

Embodiment 21

0201The method of claim <b>1</b>, the activation of PD is applied in a dual-connectivity (DC)/multi-connectivity (MC) architecture or a CA architecture.

Embodiment 22

0202The method of claim <b>20</b> or <b>21</b>, further comprising: deactivating the PD at the PDCP layer.

Embodiment 23

0203The method of any of claims <b>20</b>-<b>22</b>, MAC control elements (MAC CEs) may be conveyed between the receiver and a transmitter to trigger an activation or a deactivation of the PD.

Embodiment 24

0204The method of any of claims <b>20</b>-<b>23</b>, further comprising: transmitting RRC signalling for configuring the PD at a transmitter of the PDCP PDUs.

Embodiment 25

0205The method of any of claims <b>20</b>-<b>24</b>, further comprising: transmitting RRC signalling for activating or deactivating the PD at a transmitter of the PDCP PDUs.

Embodiment 26

0206The method of any of claims <b>20</b>-<b>25</b>, wherein a PD removal function at the PDCP layer performs combining of the received PDCP PDUs.

0207Although the present disclosure has been described with reference to specific features and embodiments thereof, it is evident that various modifications and combinations can be made thereto without departing from the disclosure. The specification and drawings are, accordingly, to be regarded simply as an illustration of examples of an invention defined by the appended claims, and are contemplated to cover any and all modifications, variations, combinations or equivalents that fall within the scope of the present disclosure.