WO2024036563A1

WO2024036563A1 - An extensive system architecture to support multipath configuration

Info

Publication number: WO2024036563A1
Application number: PCT/CN2022/113322
Authority: WO
Inventors: Guan-Yu Lin; Xuelong Wang; Nathan Edward Tenny
Original assignee: Mediatek Inc.
Priority date: 2022-08-18
Filing date: 2022-08-18
Publication date: 2024-02-22

Abstract

Apparatus and methods are provided to support system architecture when multipath is configured for a remote UE, and how the remote UE configured with multipath to monito paging and acquire system information. In one novel aspect, when relay UE and remote UE are served by the same gNB, the direct and indirect path of a remote UE can be considered as a single or separate RRC connection. In one novel aspect, the PCell can be always the serving cell of the remote UE, can be configurable by the network, or can be the serving cell of the first established path. In one novel aspect, to monitor paging, the remote UE can monitor paging occasion by itself, relay on relay UE to monitor paging, or to determine whether to monitor paging according to where the PCell is, and whether relay and remote UE are served by the same gNB or not. For system information acquisition, a remote UE can receive or request system information by itself, or rely on relay UE to forward the system information, or determine whether to acquire by itself according to where the PCell is, whether relay and remote UE are served by the same gNB or not, and whether dedicated network configuration is provided.

Description

AN EXTENSIVE SYSTEM ARCHITECTURE TO SUPPORT MULTIPATH CONFIGURATION

TECHNICAL FIELD

The disclosed embodiments relate generally to wireless communication, and, more particularly, to introduce system architecture for supporting a remote UE configured with multipath.

BACKGROUND

L2 Relay and L3 relay

To extend network coverage, diverse relay technologies are developed. A relay node can be used to forward the packet/signal between the network node (e.g. the based station, the transmission and reception point (TRP) ) and the use equipment (UE) .

The relay node can be network vendor deployed infrastructure, such as LTE Relay node, or NR IAB (integrated access backhaul) node specified since 3GPP Rel-16. This kind of relay nodes are controlled by the network and probably be transparent to the UE.

Another kind of relay node could be a user deployed relay, e.g., using a user equipment as relay (UE relay) . This kind of relay node, compared to IAB, has a much more limited transmission/reception capability in forwarding traffic. However, its advantage is to support low-cost and dynamic/flexible deployment. Using a UE relay to extend network coverage is known as UE-to-NW relay.

In 3GPP context, a relay UE uses sidelink (SL, different from uplink and downlink) resource to communicate with a remote UE (or source UE, who is the source of traffic to be forwarded) . Therefore, in 3GPP, UE-to-NW relay is also known as SL relay.

To support sidelink relay, there are two kinds of UE-to-Network Relay architecture, i.e. Layer 2 relay (L2 relay) and Layer 3 relay (L3 relay) .

L3 based Sidelink Relay UE forwards data packet flow of the Remote UE as IP traffic as a general Router in data communication network. The IP traffic based forwarding is conducted in a best efforts way. For L3 UE-to-Network Relay, there exist both SLRBs over PC5 and Uu Radio Bearers to carry the QoS flows established between Remote UE and 5GC. L3 UE-to-Network Relay can support flow based mapping at SDAP layer when converting PC5 flow to Uu Flow, or vice versa, during traffic forwarding. Note that since L3 based Sidelink Relay UE works like an IP router, remote UE is transparent to the base station, i.e., the base station cannot know whether the traffic transmitted by a relay UE originates from this relay UE itself, or originates from a remote UE but is forwarded by this relay UE.

In contrast, in case of L2 based SL Relay, relaying is performed above RLC sublayer via Relay UE for both CP and UP between Remote UE and network. Uu SDAP/PDCP and RRC are terminated between Remote UE and gNB, while RLC, MAC and PHY are terminated in each link (i.e. the link between Remote UE and UE-to-Network Relay UE and the link between UE-to-Network Relay UE and the gNB) .

An adaptation layer over RLC layer is supported in Uu to perform bearer mapping and it can be also placed over PC5 to perform bearer mapping at sidelink. The adaptation layer between the Relay UE and gNB is able to differentiate between bearers (SRBs, DRBs) of a particular Remote UE. Within a Uu DRB, different Remote UEs and different bearers of the Remote UE can be indicated by additional information included in adaptation layer header. Unlike in L3 relay, in L2 relay the base station is aware of each remote UE, and thus before the relay UE starts to forward normal data traffic, the end-to-end connection between a remote UE and the base station should be established first. After establishing the RRC connection via SL relay, the remote UE can then forward data traffic based on the established bearers and the forwarding/router information carried in adaptation layer.

Relay selection

In 3GPP R17, sidelink relay is supported to enable network coverage extension. To extend network coverage, there are RSRP (received signal strength xxx) criteria to determine whether a UE can serve as a relay UE or a remote UE.

To be specific, in 3GPP R17 spec for SL relay, it is specified that a remote UE should have the measured Uu RSRP below a RSRP threshold (threshHighRemote) . This means a UE can request for help traffic forwarding only when the UE has a very bad Uu RSRP. Besides, a UE can serve as a relay UE only when its Uu RSRP is above a RSRP threshold (threshLowRelay) . This means a UE can help other UE to forward traffic only when the UE has good Uu link quality. In addition, a UE can be a relay UE only when its Uu RSRP is below another RSRP threshold (known as threshHighRelay) , which is used to prevent cell-center UE from being a relay. Otherwise, if a relay UE is in very cell center, and a remote UE is in cell edge, the remote UE would transmit with a very large power to communicate with the cell center UE and thus cause much interference to its neighboring UE. Finally, there is a sidelink RSRP threshold (sl-RSRP-Thresh) used to measure the sidleink quality between the remote UE and the relay UE. If the SL RSRP is below the threshold, the sidelink towards the relay is considered too bad to support satisfactory relay performance.

When a UE satisfies the remote UE criteria (Uu RSRP below threshHighRemote) , it is up to UE implementation to perform cell reselection or relay selection.

Single path relay and multipath relay

Note that in 3GPP R17, only single path UE-to-NW relay is supported. That is, a UE can select one of direct path (i.e. directly connect to a gNB via Uu link) or indirect path (i.e. connect to the gNB via traffic forwarding of a relay UE) , but not both. Besides, 3GPP R17 only support single-hop UE-to-NW relay. Support of multi-hop UE-to-NW relay is left to future releases.

To further extend the UE-to-NW relay, we can consider multi-hop and multi-path aspects. Multi-hop relay, obviously, can help to eliminate deep coverage hole. In contrast, multipath relay allows multiple traffic forwarding paths from the source to destination, which definitely increase the transmission reliability and may be also beneficial to remote UE throughput.

SUMMARY

Methods are provided to support system architecture when multipath is configured for a remote UE.

In one novel aspect, it is proposed how to model the two paths of a remote UE, when the remote UE and the selected relay UE are configured with (1) same gNB and same serving cell, (2) same gNB but different serving cells, and (3) different gNBs.

In one novel aspect, it is proposed how a remote UE determine PCell when multipath is configured.

In one novel aspect, it is proposed how a remote UE monitor paging message, when multipath is configured and a relay UE can help forward paging message.

In one novel aspect, it is proposed how a remote UE receives system information, when multipath is configured and a relay UE can help forward system information.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 illustrate the topology of a remote UE configured with multiple paths, wherein the relay UE and remote UE select serving cells of the same gNB.

Figure 2 illustrate the topology of a remote UE configured with multiple paths, wherein the relay UE and remote UE select serving cells of different gNBs.

Figure 3 shows a remote UE configured with two indirect paths, and the two relay UE select serving cells belonging to the same gNB.

Figure 4 shows a remote UE configured with two indirect paths, and the two relay UE select serving cells belonging to different gNBs.

DETAILED DESCRIPTION

Reference will now be made in detail to some embodiments of the invention, examples of which are illustrated in the accompanying drawings.

In the following description, we use dual-path as examples to explain our inventions. But notice that our ideas are not limited to dual path but can be generalized to multipath scenarios wherein the number of paths between remote UE and gNB are equal to or more than 2.

Models for multipath configuration (PCell configuration, CA/DC model, paging monitoring, and system information acquisition)

The system architecture to support multipath depends on the relay topology. Considering a remote UE configured with two paths and single-hop relay, four possible network topologies are shown in Figure 1, 2, 3, and 4.

Figure 1 shows a remote UE configured with a direct path and an indirect path, and both remote UE and remote UE select serving cells belonging to the same gNB. In this topology, the system model may also depend on whether relay UE and remote UE select the same or different serving cells of the same gNB.

Figure 2 shows a remote UE configured with a direct path and an indirect path, and both remote UE and remote UE select serving cells belonging to different gNBs.

Figure 3 shows a remote UE configured with two indirect paths, and the two relay UE select serving cells belonging to the same gNB. In this topology, the system model may also depend on whether relay UE and remote UE select the same or different serving cells of the same gNB.

In this invention, the description is mainly for topologies of Figure 1 and 2, but note that the design idea can be extended to topologies in Figure 3 and 4 easily.

PCell configuration

In multipath configuration, remote and relay UE may select different cells for their Uu link (

e.g. cell

1 and 2 respectively) . A question is whether UE should consider cell 1 or cell 2 as its PCell.

In one embodiment, the remote UE always consider PCell in its direct Uu link. The advantage is that, using direct link for control signaling transmission may reduce signaling latency and have better reliability. In this case, if a UE originally has a relay path, and it adds the direct path later, the network would need to reconfigure the PCell, if relay UE and remote UE are linked to different serving cells.

In one embodiment, whether the PCell is on remote’s Uu link or relay’s Uu link is up to network configuration. This embodiment allows remote’s Uu link as SCell, and thus we can reuse existing SCell activation approach (e.g. dormant BWP) to save remote UE power.

In one embodiment, remote UE treats the first established path as the PCell. If the UE starts with the indirect path, the gNB can add the direct path as an SCell, and vice versa. This embodiment may be the simplest alternative in terms of spec impact, and it gives the flexibility of network determination without the need to add special signalling and procedures for switching which path is the PCell.

CA/DC model

For multipath, a question is how the two paths interact with each other, or, the corresponding protocol stacks.

In one embodiment, if remote and relay are connected to the same gNB, we may consider it with multi-CC model. In the multi-CC model, when considering a remote UE with a direct link and an indirect link, the remote UE maintain (at least) a UL carrier (in its Uu link) and a SL carrier (for communicating with relay UE) . The two paths, from remote UE perspective, belongs to the same RRC connection, because the two paths terminate at the same gNB, and for both paths remote UE use the same (unique) C-RNTI.

In one embodiment, if remote and relay are connected to the same gNB, and we model it as multi-CC model, we can then use MAC CE like signaling to control the (de) activation of each path. For example, we can generalize the definition of CC in SCell (de) activation MAC CE as per path, so that gNB can use the modified MAC CE to make an indirect path enter activated/deactivated/dormant state. For another example, we can define a new MAC CE format to control the activated/deactivated/dormant state of each indirect paths, separate from legacy SCell.

In one embodiment, if remote and relay are connected to the same gNB, we may consider it as multi-connection model. In the so-called multi-connection model, the remote UE maintain separate RRC connections for the two paths. The gNB may assign different C-RNTI for the remote UE to manage the two paths separately.

In one embodiment, if remote and relay UE are connected to different gNBs, remote UE apply DC (dual connectivity) model to handle the two paths. That is, similar to legacy DC, remote UE consider the two paths with separate RRC/RLC/MAC layer. Received traffic from the two paths (for downlink) may be merged in PDCP layer, and transmitted traffic may be split in PDCP layer. There may be a split bearer configured so that the remote UE can transmit/receive traffic to/from different gNBs.

Paging monitoring

One discussion point to support multipath is about paging monitoring. In R17 single-hop single-path relay, a RRC IDLE/INACTIVE remote UE needs not monitor paging byitself. The relay UE may monitor paging occasion for the remote UE, or the relay UE would receive and forward the paging notification when receiving dedicated RRC message from the gNB.

When multipath is configured, there are several possible embodiments.

In one embodiment, if remote UE and relay UE selects the same gNB and the same serving cell, the remote UE relies on relay UE to forward the paging notification.

In one embodiment, if remote UE and relay UE selects the same gNB and the same serving cell, the remote UE monitor paging message by itself.

In one embodiment, if remote UE and relay UE select the same gNB but different serving cells, the remote UE still relies on relay UE to forward the paging notification. That is, as long as remote UE and relay UE select the same gNB, we reuse legacy paging procedure for SL relay. For example, it’s assumed that the gNB would transmit paging message of the remote UE to the relay UE via dedicated RRC signaling.

In one embodiment, if remote UE and relay UE select the same gNB but different serving cells, whether remote UE monitor its own paging occasion depends on whether the PCell is located. If PCell is configured in relay direct Uu link, relay monitor paging for remote. If PCell is configured in remote direct Uu link, remote monitor paging occasion by itself.

In one embodiment, if remote UE and relay UE select different gNBs, remote UE monitor its paging occasion for the direct link, and relay UE help forward the paging message from the gNB of the indirect path.

In one embodiment, if remote UE and relay UE select different gNBs, remote UE needs not monitor paging for direct path. If the gNB in the direct path wants to page the remote UE, the paging message is redirected to the gNB of the indirect path, and then forward to the remote UE via relay UE.

In one embodiment, if remote UE and relay UE select different gNBs, remote UE needs to monitor paging for direct path, and relay UE needs not help forwarding paging message. If the gNB in the indirect path wants to page the remote UE, the paging message is redirected to the gNB of the direct path.

System information acquisition

In legacy 3GPP R17 sidelink relay (single-path relay) , relay UE would acquire system information for remote UE, which is useful when remote UE is out of Uu coverage. When a remote UE is configured with multipath, several embodiments as described below are possible.

In one embodiment, if remote UE and relay UE selects the same gNB and the same serving cell, and this serving cell is PCell, the remote UE relies on relay UE to acquire and forward the desired system information. That is, the remote UE does not or is not requested to monitor the broadcasted system information of the PCell.

In one embodiment, if remote UE and relay UE selects the same gNB and the same serving cell, and this serving cell is PCell, the remote UE monitor system information by itself.

In one embodiment, if remote UE and relay UE selects the same gNB and the same serving cell, and this serving cell is PCell, whether remote UE acquire system information by itself or by relay forwarding depends on the type of system information. For example, for those system information related to latency critical services or functions, remote UE can be configured to acquire it and monitor the change via direct Uu link.

In one embodiment, if remote UE and relay UE selects the same gNB and the same serving cell, and this serving cell is PCell, remote is allowed to simultaneously acquire system information via direct Uu link and request system information from the relay UE via indirect path.

In one embodiment, if remote UE and relay UE selects the same gNB and the same serving cell, and this serving cell is PCell, network may configure remote UE to acquire system information via different ways (only via direct path, only via indirect path, via either direct or indirect path, or via both direct and indirect paths) for different types/categories of system information (or SIBs, system information blocks) .

In one embodiment, if remote UE and relay UE select the same gNB but different serving cells, whether remote UE acquire its system information via direct Uu link depends on whether the PCell is located. If PCell is configured in relay direct Uu link, relay provide system information of the PCell to remote. If PCell is configured in remote direct Uu link, remote acquire system information via direct remote Uu link.

In one embodiment, if remote UE and relay UE select the same gNB but different serving cells, and if PCell is configured in remote direct Uu link, the remote UE still relay on relay UE to forward the system information. That is, the remote UE does not monitor it selected serving cell (PCell) . Instead, when its PCell has system information update, the PCell use dedicated signaling, via direct or indirect oath, to provide the remote UE with updated system information or to notify remote UE which system information (of interest) is changed.

In one embodiment, if remote UE and relay UE select different gNB, remote UE acquire system information from the PCell of the direct link, while relay UE help forward the system information from the gNB of the indirect path.

Claims

A method for a remote UE to determine the protocol architecture and the PCell when multipath is configured.
The mentioned of claim 1, wherein when remote and relay are connected to the same gNB, the remote UE is considered with a single RRC connection to the network.
The mentioned of claim 1, wherein when remote and relay are connected to the same gNB, the remote UE is considered with a separate RRC connections for different (e.g. direct paths and indirect path) paths separately.
The mentioned of claim 1, wherein when remote and relay are connected to different gNB, the remote UE is considered with a separate RRC connections for different (e.g. direct paths and indirect path) paths separately.
The mentioned of claim 1, wherein the PCell is the serving cell of remote UE’s Uu link.
The mentioned of claim 1, wherein the PCell of a remote UE is configured by the network, and can be updated by the network via RRC message.
The mentioned of claim 1, wherein the PCell of a remote UE is the serving cell of the first path. That is, if the first path of a remote UE is a direct path, the PCell is the NR serving cell of the remote UE; otherwise, the PCell is the NR serving cell of the serving relay UE.
A method for a remote UE to perform paging monitoring when multipath is configured.
The method of claim 8, wherein if remote UE and relay UE selects the same gNB and the same serving cell, relay UE monitor paging for the remote UE.
The method of claim 8, wherein if remote UE and relay UE selects the same gNB and the same serving cell, remote UE monitor its own paging occasion and relay UE does not help monitor paging for the remote UE.
The method of claim 8, if remote UE and relay UE select the same gNB but different serving cells, the remote UE still relies on relay UE to forward the paging notification.
The method of claim 8, if remote UE and relay UE select the same gNB but different serving cells, whether remote UE monitor its own paging occasion depends on whether the PCell is located. If PCell is configured in relay direct Uu link, relay monitor paging for remote. If PCell is configured in remote direct Uu link, remote monitor paging occasion by itself.
The method of claim 8, if remote UE and relay UE select different gNBs, remote UE monitor its paging occasion for the direct link, and relay UE help forward the paging message from the gNB of the indirect path.
The method of claim 8, if remote UE and relay UE select different gNBs, remote UE needs not monitor paging for direct path, and rely on relay UE to forward the paging message/notification
The method of claim 8, if remote UE and relay UE select different gNBs, remote UE is required to monitor paging for direct path, and relay UE need not monitor paging occasion and/or forward the paging message/notification for the remote UE.
A method for a remote UE to acquire system information when multipath is configured.
The method of claim 16, wherein if remote UE and relay UE selects the same gNB and the same serving cell, and this serving cell is PCell, the remote UE relies on relay UE to acquire and forward the desired system information.
The method of claim 16, wherein if remote UE and relay UE selects the same gNB and the same serving cell, and this serving cell is PCell, the remote UE monitor system information by itself.
The method of claim 16, wherein if remote UE and relay UE selects the same gNB and the same serving cell, and this serving cell is PCell, whether remote UE acquire system information by itself or by relay forwarding depends on the type of system information.
The method of claim 16, wherein if remote UE and relay UE selects the same gNB and the same serving cell, and this serving cell is PCell, remote is allowed to simultaneously acquire system information via direct Uu link and request system information from the relay UE via indirect path.
The method of claim 16, wherein if remote UE and relay UE selects the same gNB and the same serving cell, and this serving cell is PCell, network may configure remote UE to acquire system information via different ways (only via direct path, only via indirect path, via either direct or indirect path, or via both direct and indirect paths) for different types/categories of system information (or SIBs, system information blocks) .
The method of claim 16, wherein if remote UE and relay UE select the same gNB but different serving cells, whether remote UE acquire its system information via direct Uu link depends on whether the PCell is located. If PCell is configured in relay direct Uu link, relay provide system information of the PCell to remote. If PCell is configured in remote direct Uu link, remote acquire system information via direct remote Uu link.
The method of claim 16, wherein if remote UE and relay UE select the same gNB but different serving cells, the remote UE rely on relay UE to forward system information of PCell, even if PCell is configured in remote direct Uu link.
The method of claim 16, wherein if remote UE and relay UE select different gNBs, remote UE acquire system information from the PCell of the direct link, while relay UE help forward the system information from the gNB of the indirect path.