This invention generally relates to wireless communications and more particularly to resource management of wireless communication links using relay devices.
Many wireless communication systems that employ several base stations that provide wireless service to user equipment (UE) devices enable sidelink communication between two or more UE devices where the UE devices can communicate directly with other UE devices. With sidelink communication, UE devices transmit data signals to each other over a communication link using the cellular resources instead of through a base station. Such Proximity Services (ProSe) communication is sometimes also referred to as device-to-device (D2D). In addition, one or more UE devices can be used as relay devices between a UE device and a destination where the relay device forwards data between a UE device and the destination. The destination may be a communication network or another UE device (destination UE device). Where the destination is the network, the relay functionality is typically referred to as UE-to-Network (U2N) relaying and the relay UE device establishes a communication path between the remote UE and a base station (gNB) or cell. In some situations, for example, the UE device may be out of the service area of the base station and the relay UE device provides a communication link routed from such an out-of-coverage (OoC) UE device through a relay UE device to the base station. Where the destination device another UE device (target UE device), the relaying functionality is typically referred to as UE-to-UE (U2U) relaying.
A remote user equipment (UE) device is restricted to same-cell relay UE device reselection if the communication link quality to the same-cell relay device is above a threshold and network access is available through a same-cell relay UE device. Where the communication link quality to the same-cell relay device is below the threshold, the source UE device performs unrestricted relay reselection that includes evaluating relay UE devices within coverage of one or more cells other than the serving cell of the UE device. The UE device served by a first cell receives a coverage indicator from a same-cell relay UE device served by the first cell where the coverage indicator at least indicates that the same-cell relay UE device is in coverage of the first cell. The source UE device determines a sidelink Reference Signal Received Power (SL-RSRP) level based on a relay sidelink reference signal received from the same-cell relay UE device. If the SL-RSRP level is above a threshold, the source UE device attempts to establish relay communication through the same-cell relay UE device and refrains from performing an unrestricted relay selection procedure that includes evaluating other relay UE devices in coverage of cells other than the first cell. Where an attempt to establish relay communication through the same cell relay UE device fails, the source UE device no longer refrains from performing the unrestricted relay selection procedure and evaluates a relay UE device in coverage of a second cell.
As discussed above, a relay UE device provides connectivity between a source UE device and a destination which can be another UE device (destination UE device) or a network. Where the destination is the network, the relay provides connectivity to a cell provided by a base station (gNB) of the network. The relayed connection between a source UE device and destination UE device is sometimes referred to as a UE to UE (U2U) relay connection. The relayed connection between a source UE device and a base station (gNB) is sometimes referred to as a UE to network (U2N) relay connection. In conventional systems where the relay connects to a base station (gNB), the relay UE device is required to meet certain criteria to function as a relay. For example, the relay UE device must be in coverage and have a cellular (Uu) communication link to the base station of sufficient quality in order to be available for relaying functions. For U2N relaying, therefore all candidate relay devices are assumed to be within coverage of the base station (gNB).
With U2U relaying, typically there is no such restriction and the relay UE device may be in coverage or OoC of the cell. The working principle of the two relaying mechanisms are different. Currently, in order for a source UE device and the relay UE device to discover each other as part of the relay selection and reselection procedure, Model A or Model B discovery procedure is used. With Model A discovery, either the remote UE or the relay UE may announce their presence with “I am here” and no response is expected. With Model B discovery, a request is made by announcing “Are you there?” The receiving device may respond to the request of its presence.
Conventional systems support the following two scenarios for Layer 2 (L2) U2N relay procedures: 1) the relay UE device and source UE device are in the same cell before remote connection via the relay UE device, and 2) before remote connection via a relay UE device, the relay UE device and the source UE device are in different cells. Regarding discovery in conventional systems, a source UE device in Radio Resource Control (RRC) states of RRC_CONNECTED, RRC_IDLE and RRC_INACTIVE is allowed to transmit discovery messages if the measured signal strength of the serving cell is lower than a configured threshold. In conventional systems, therefore, the source UE device is able to perform relay selection that includes evaluating relay UE device or other cells when the measured signal strength of its serving cell is lower than a configured threshold.
For the examples herein, however, the source UE device is restricted from performing relay selection that includes evaluating relay UE devices in coverage of other cells when a measured signal strength of a same-cell relay UE device is above a threshold. The source UE device can perform an unrestricted relay selection procedure if a relay connection cannot be established through the same-cell rely UE device. In addition, some examples also restrict the source UE device transmitting discovery signals to select a different-cell relay UE device in coverage of a cell other than the serving cell of the source UE device based on the measured signal level of the serving cell. In addition to the conventional threshold where the source UE device is restricted from selecting any relay UE device if the serving cell measured signal level is above a threshold, the source UE device is restricted from selecting a different-cell relay UE device in coverage of a cell other the serving cell when the serving cell measured signal level is above a second threshold. The second threshold is lower than the conventional threshold (first threshold).
Although the techniques discussed herein may be applied to various types of systems and communication specifications, the devices of the example operate in accordance with at least one revision of a 3GPP New Radio (NR) V2X communication specification. The techniques discussed herein, therefore, may be adopted by one or more future revisions of communication specifications although the techniques may be applied to other communication specifications where sidelink or D2D is employed. More specifically the techniques may be applied to current and future releases of 3GPP NR specifications. For example, the techniques may also be applied to 3GPP NR (Rel-17).
For the example, the source UE device 102 is within coverage of the first cell 110 while being served by the first base station 108. The source UE device 102 determines that it is within coverage of the first cell 112. The source UE device 102 receives a coverage indicator 116, from the same-cell relay UE device 104, indicating that the same-cell relay UE device 104 is in-coverage of the first cell 110. The source UE device 102 determines that relay UE device 104 is in coverage of the same cell (first cell 110) providing service to the source UE device 102. For the examples herein, the source UE device 102 is determined to be in-coverage of a cell when it is camped on the cell where the source UE device 102 is in the RRC IDLE state or the RRC INACTIVE state with the cell, without connecting indirectly via a relay UE device. The source UE device 102, therefore, determines that it is in coverage of the first cell 112 if it is camped on the first cell 112. The source UE device evaluates the coverage indicator 116 and determines that the same-cell relay UE device 104 is within coverage of the same cell (first cell 110) that is providing service to the source UE device 102.
The source UE device measures a reference signal 118 transmitted by the same-cell relay UE device and determines whether the source UE device may execute and unrestricted relay selection procedure based on measured level of the reference signal 118. For the example, the measured SL-RSRP level is compared to the relay cell restriction threshold and, if the measured SL-RSRP level is below the relay cell restriction threshold, the source UE device 102 determines that an unrestricted relay selection procedure can be performed. Otherwise, the UE device determines that the relay selection procedure is restricted to same-cell UE devices. The unrestricted relay selection procedure includes evaluating relay UE devices (different-cell relay UE devices) in coverage of cells other than the cell (first cell 110) providing service to the source UE device 102, such as the different-cell relay UE device 106.
The source UE device 102 receives a coverage indicator 120 from the different-cell relay UE device 106 that indicates the different-cell relay UE device 106 is in coverage of the second cell 112. When the relay selection/reselection is unrestricted, the source UE device 102 receives and measures a SL reference signal 122 transmitted by the different-cell relay UE device 106. The source UE device 102 performs relay (re)selection based on SL-RSRP of the SL reference signal 122. In the interest of brevity and clarity, the example of
For the example of
When the UE device measures an RSRP level that is above the second threshold 212 but below the first threshold 210, such as when the UE device 102 is in the second location 202, the source UE device 102 is authorized to consider same-cell relay UE devices. Accordingly, the UE device 102 may transmit SL discovery signals for relay (re)selection but only evaluates same-cell relay UE devices. In some configurations and situations, the source UE device may consider different-cell relay UE devices but prioritizes same-cell relay UE devices. For example, if no same-cell relay UE device can be identified that is capable of providing communication link to the network at the required minimum quality level, the source UE device 102 may select a different-cell relay UE device or communicate directly with the base station 108.
When the measured RSRP level to the base station is below the second relay restriction threshold 212, the source UE device 102 is authorized to select different-cell relay UE devices, such as the different-cell relay UE device 106 in the example. Therefore, the multiple thresholds allow management of resource and the prioritization of same-cell relay UE devices and different-cell relay UE devices.
In some situations, the techniques discussed with reference to
The controller 404 includes any combination of hardware, software, and/or firmware for executing the functions described herein as well as facilitating the overall functionality of the base station 400. An example of a suitable controller 404 includes code running on a microprocessor or processor arrangement connected to memory. The transmitter 406 includes electronics configured to transmit wireless signals. In some situations, the transmitter 406 may include multiple transmitters. The receiver 408 includes electronics configured to receive wireless signals. In some situations, the receiver 408 may include multiple receivers. The receiver 408 and transmitter 406 receive and transmit signals, respectively, through an antenna 410. The antenna 410 may include separate transmit and receive antennas. In some circumstances, the antenna 410 may include multiple transmit and receive antennas.
The transmitter 406 and receiver 408 in the example of
The transmitter 406 includes a modulator (not shown), and the receiver 408 includes a demodulator (not shown). The modulator modulates the signals to be transmitted as part of the downlink signals and can apply any one of a plurality of modulation orders. The demodulator demodulates any uplink signals received at the base station 400 in accordance with one of a plurality of modulation orders.
The base station 400 includes a communication interface 412 for transmitting and receiving messages with other base stations. The communication interface 412 may be connected to a backhaul or network enabling communication with other base stations. In some situations, the link between base stations may include at least some wireless portions. The communication interface 412, therefore, may include wireless communication functionality and may utilize some of the components of the transmitter 406 and/or receiver 408.
The UE device 500 includes at least a controller 502, a transmitter 504 and a receiver 506. The controller 502 includes any combination of hardware, software, and/or firmware for executing the functions described herein as well as facilitating the overall functionality of a communication device. An example of a suitable controller 502 includes code running on a microprocessor or processor arrangement connected to memory. The transmitter 504 includes electronics configured to transmit wireless signals. In some situations, the transmitter 504 may include multiple transmitters. The receiver 506 includes electronics configured to receive wireless signals. In some situations, the receiver 506 may include multiple receivers. The receiver 504 and transmitter 506 receive and transmit signals, respectively, through antenna 508. The antenna 508 may include separate transmit and receive antennas. In some circumstances, the antenna 508 may include multiple transmit and receive antennas.
The transmitter 504 and receiver 506 in the example of
The transmitter 506 includes a modulator (not shown), and the receiver 504 includes a demodulator (not shown). The modulator can apply any one of a plurality of modulation orders to modulate the signals to be transmitted as part of the uplink signals. The demodulator demodulates the downlink signals in accordance with one of a plurality of modulation orders.
At step 602, the source UE device 102 is camped on the first cell 110. The source UE device 103, therefore, is within coverage of the first cell 110 while being served by the first base station 108. For the examples herein, the source UE device 102 is determined to be in-coverage of a cell when it is camped on the cell where the source UE device 102 is in the RRC IDLE state or the RRC INACTIVE state with the cell, without connecting indirectly via a relay UE device.
At step 604, the source UE device 102 receives a coverage indicator 116, from the same-cell relay UE device 104, indicating that the same-cell relay UE device 104 is in-coverage of the first cell 110. The same-cell relay UE device 104 may send the coverage indicator 116 in a PC5 broadcast message, such as a sidelink discovery signal, or the coverage indicator 104 may be part of the MAC header, part of the upper layer message, or may be a field within the physical sidelink control channel (PSCCH). The coverage indicator 116 indicates that the same-cell relay UE device 104 is within coverage of the first cell 110 and may provide additional information in some situations. In the example, therefore, the coverage indicator 116 at least identifies the first cell 110 with a unique identifier, such as cell ID. The source UE device 102 determines that relay UE device 104 is in coverage of the same cell (first cell 110) providing service to the source UE device 102. In some situations, transmission of the coverage indicator can be omitted or may be part of other transmissions. For example, a U2N relay UE candidate may transmit discovery that includes the cell ID of the cell on which the U2N relay UE candidate is camped. Although a U2N relay UE device cannot send discovery unless the device is in coverage, a U2U relay may transmit discovery even when out of coverage. At step 606, the source UE device receives a reference signal from the same cell relay UE device 104 and measures the signal to determine the SL-RSRP level.
At step 608, the source UE device determines whether the measured SL-RSRP is greater than the relay cell restriction threshold. If the measured SL-RSRP is not greater than the relay cell restriction threshold, the method continues at step 610, Otherwise, the method proceeds to step 612.
At step 610, the source UE device 102 performs an unrestricted relay selection procedure where different-cell relay UE devices can be evaluated and considered for relay (re)selection. For example, the different-cell relay UE device 106 can be identified during discovery and determined to be within the second cell 112 based on received coverage indicator. The source UE device 102 evaluates RSRP levels and other criteria in accordance with relay reselection to determine whether to select the different-cell relay UE device 106. For the example, a different-cell relay UE device is selected only when a measured SL-RSRP level of the different-cell relay UE device is greater than a measured SL-RSRP level of a same-cell relay UE device. Therefore, where there is no different-cell relay UE device having a SL-RSRP level greater than the SL-RSRP level of a same-cell relay UE device, communication may continue through the same-cell relay UE device even if the SL-RSRP of the same-cell relay UE device is not greater than the relay cell restriction threshold.
At step 612, the source UE device attempts a relay connection to the network through the same-cell relay UE device 104.
At step 614, it is determined whether the relay connection was successful. Examples of reasons that the relay connection through the relay UE device 104 may not be successful include traffic congestion in the serving cell, access barring, rejection of the establishment request or the establishment cannot be originated. If the relay connection is successful, the method proceeds to step 616 where the communication continues through the same-cell relay UE device 104. Otherwise, the method continues at step 610 where the source UE device 102 performs the unrestricted relay (re)selection.
At step 702, the source UE device 102 is camped on the first cell 110. The source UE device 103, therefore, is within coverage of the first cell 110 while being served by the first base station 108. For the examples herein, the source UE device 102 is determined to be in-coverage of a cell when it is camped on the cell where the source UE device 102 is in the RRC IDLE state or the RRC INACTIVE state with the cell, without connecting indirectly via a relay UE device.
At step 704, the RSRP level of the serving cell is measured. For the example, the source UE device 102 receives and measures a reference signal transmitted by the serving cell, such as a reference signal transmitted by the first base station 108 in the first cell 110.
At step 706, the source UE device determines whether the measured serving cell RSRP level is greater than a first serving cell restriction threshold. If the measured RSRP is greater than the first serving cell restriction threshold, the method continues at step 708 where the source UE device connects to the network directly through the first cell 110 provided by the first base station 108. Otherwise, the method proceeds to step 710.
At step 710, the source UE device determines whether the measured serving cell RSRP level is greater than a second serving cell restriction threshold. The second serving cell restriction threshold is less than the first serving cell restriction threshold. If the measured RSRP is not greater than the second serving cell restriction threshold, the method continues at step 712. Otherwise, the method continues at step 714.
At step 712, the source UE device 102 performs an unrestricted relay selection procedure where different-cell relay UE devices can be evaluated and considered for relay (re)selection. For example, the different-cell relay UE device 106 can be identified during discovery and determined to be within the second cell 112 based on received coverage indicator. The source UE device 102 evaluates SL-RSRP levels and other criteria in accordance with relay reselection to determine whether to select the different-cell relay UE device 106. For the example, a different-cell relay UE device is selected only when a measured SL-RSRP level of the different-cell relay UE device is greater than a measured SL-RSRP level of a same-cell relay UE device. Therefore, communication may continue through the same-cell relay UE device even if the SL-RSRP of the same-cell relay UE device is not greater than the relay cell restriction threshold when no different-cell relay UE device has a SL-RSRP level greater than the SL-RSRP level of a same-cell relay UE device.
At step 714, the source UE device attempts a relay connection to the network through the same-cell relay UE device 104.
At step 716, it is determined whether the relay connection was successful. Examples of reasons that the relay connection through the relay UE device 104 may not be successful include traffic congestion in the serving cell, access barring, rejection of the establishment request or the establishment cannot be originated. If the relay connection is successful, the method proceeds to step 718 where the communication continues through the same-cell relay UE device 104. Otherwise, the method continues at step 712 where the source UE device 102 performs the unrestricted relay (re)selection.
At step 802, the source UE device 102 is camped on the first cell 110. The source UE device 103, therefore, is within coverage of the first cell 110 while being served by the first base station 108. For the examples herein, the source UE device 102 is determined to be in-coverage of a cell when it is camped on the cell where the source UE device 102 is in the RRC IDLE state or the RRC INACTIVE state with the cell, without connecting indirectly via a relay UE device.
At step 804, the RSRP level of the serving cell is measured. For the example, the source UE device 102 receives and measures a reference signal transmitted by the serving cell, such as a reference signal transited by the first base station 108 in the first cell 110.
At step 806, the source UE device determines whether the measured serving cell RSRP level is greater than a first serving cell restriction threshold. If the measured RSRP is greater than the first serving cell restriction threshold, the method continues at step 808 where the source UE device connects to the network directly through the first cell 110 provided by the first base station 108. Otherwise, the method proceeds to step 810.
At step 810, the source UE device determines whether the measured serving cell RSRP level is greater than a second serving cell restriction threshold. The second serving cell restriction threshold is less than the first serving cell restriction threshold. If the measured RSRP is not greater than the second serving cell restriction threshold, the method continues at step 812. Otherwise, the method continues at step 814.
At step 812, the source UE device 102 performs an unrestricted relay selection procedure where different-cell relay UE devices can be evaluated and considered for relay (re)selection. For example, the different-cell relay UE device 106 can be identified during discovery and determined to be within the second cell 112 based on received coverage indicator. The source UE device 102 evaluates SL-RSRP levels and other criteria in accordance with relay reselection to determine whether to select the different-cell relay UE device 106. For the example, a different-cell relay UE device is selected only when a measured SL-RSRP level of the different-cell relay UE device is greater than a measured SL-RSRP level of a same-cell relay UE device. Therefore, communication may continue through the same-cell relay UE device even if the SL-RSRP of the same-cell relay UE device is not greater than the relay cell restriction threshold where no different cell rely UE device has a SL-RSRP level greater than the SL-RRP level of a same-cell relay UE device.
At step 814, the source UE device receives a reference signal from the same cell relay UE device 104 and measures the signal to determine the SL-RSRP level.
At step 816, the source UE device determines whether the measured SL-RSRP is greater than the relay cell restriction threshold. If the measured SL-RSRP is not greater than the relay cell restriction threshold, the method continues at step 812. Otherwise, the method proceeds to step 818.
At step 818, the source UE device attempts a relay connection to the network through the same-cell relay UE device 104.
At step 820, it is determined whether the relay connection was successful. Examples of reasons that the relay connection through the relay UE device 104 may not be successful include traffic congestion in the serving cell, access barring, rejection of the establishment request or the establishment cannot be originated. If the relay connection is successful, the method proceeds to step 822 where the communication continues through the same-cell relay UE device 104. Otherwise, the method continues at step 812 where the source UE device 102 performs the unrestricted relay (re)selection.
Clearly, other embodiments and modifications of this invention will occur readily to those of ordinary skill in the art in view of these teachings. The above description is illustrative and not restrictive. This invention is to be limited only by the following claims, which include all such embodiments and modifications when viewed in conjunction with the above specification and accompanying drawings. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalents.
The present application claims the benefit of priority to Provisional Application No. 63/169,592 entitled “Discovery Resource for Relaying”, docket number TPRO 00359 US, filed Apr. 1, 2021, assigned to the assignee hereof and hereby expressly incorporated by reference in its entirety.
Filing Document | Filing Date | Country | Kind |
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PCT/US2022/021684 | 3/24/2022 | WO |
Number | Date | Country | |
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63169592 | Apr 2021 | US |