Quasi co-location framework for beam reception in single frequency networks

Abstract

The invention relates to a quasi-co-location framework for beam reception in a single frequency network. User equipment (UE) operation in a single frequency network (SFN) is disclosed. The UE may receive one or more transmission configuration indication (TCI) states corresponding to one or more downlink resources; receiving a demodulation reference signal (DMRS), wherein the DMRS is quasi-co-located (QCL) with one or more channel state information reference signals (CSI-RS) from the plurality of cells of the SFN and quasi-co-located (QCL) information is included in the one or more TCIs; and determining a time and a frequency offset corresponding to each of the plurality of cells based on the CSI-RS.

Description

[0001] This application is a divisional application of the invention patent application with application date of May 15, 2020, application number 202080100855.5, and invention name “Quasi-co-site framework for beam reception in single frequency networks”. Technical Field

[0002] The present disclosure relates to wireless communications, and more particularly, to a quasi co-location framework for beamforming in a single frequency network. Background Art

[0003] A single frequency network (SFN) may refer to a wireless network in which multiple cells transmit the same signal on the same channel at the same time. SFN may use beamforming, which is an antenna technique for transmitting directional signals. In this type of scenario, downlink reception at a user equipment (UE) may include combining beams from multiple transmission points. Therefore, the UE may have to track time and frequency offsets from multiple cells. Summary of the invention

[0004] Some exemplary embodiments relate to a method performed by a user equipment (UE). The method includes receiving one or more transmission configuration indication (TCI) states corresponding to one or more downlink resources; receiving a demodulation reference signal (DMRS), wherein the DMRS is quasi-co-located (QCL) with one or more channel state information reference signals (CSI-RS) from multiple cells of a single frequency network (SFN) and quasi-co-located (QCL) information is included in the one or more TCIs; and determining a time and frequency offset corresponding to each of the multiple cells based on the CSI-RS.

[0005] Other exemplary embodiments relate to a user equipment (UE) having a transceiver and a processor. The transceiver is configured to connect to multiple cells of a single frequency network (SFN). The processor is configured to receive one or more transmission configuration indication (TCI) states corresponding to one or more downlink resources; receive a demodulation reference signal (DMRS), wherein the DMRS is quasi-co-located (QCL) with one or more channel state information reference signals (CSI-RS) from the multiple cells of the SFN and quasi-co-located (QCL) information is included in the one or more TCIs; and determine a time and frequency offset corresponding to each of the multiple cells based on the CSI-RS.

[0006] Other exemplary embodiments relate to a method performed by a user equipment (UE). The method includes receiving one or more transmission configuration indication (TCI) states corresponding to one or more downlink resources; receiving a demodulation reference signal (DMRS), wherein the DMRS is quasi-co-located (QCL) with a channel state information reference signal (CSI-RS), the CSI-RS is quasi-co-located with multiple system synchronization blocks (SSBs) of multiple cells from a single frequency network (SFN), and quasi-co-located (QCL) information is included in the one or more TCIs; and determining a time and frequency offset corresponding to each of the multiple cells based on the CSI-RS and at least one of the SSBs.

[0007] Additional exemplary embodiments relate to a user equipment (UE) having a transceiver and a processor. The transceiver is configured to connect to multiple cells of a single frequency network (SFN). The processor is configured to receive one or more transmission configuration indication (TCI) states corresponding to one or more downlink resources; receive a demodulation reference signal (DMRS), wherein the DMRS is quasi-co-located (QCL) with a channel state information reference signal (CSI-RS), the CSI-RS is quasi-co-located with multiple system synchronization blocks (SSBs) from the multiple cells of the SFN, and quasi-co-located (QCL) information is included in the one or more TCIs; and determine a time and frequency offset corresponding to each of the multiple cells based on the CSI-RS and at least one of the SSBs. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 Exemplary network arrangements are shown according to various exemplary embodiments.

[0009] Figure 2 An exemplary user equipment (UE) is shown in accordance with various exemplary embodiments.

[0010] Figure 3 An exemplary quasi co-located (QCL) framework is shown, in which a demodulation reference signal (DMRS) is quasi co-located with one or more tracking reference signals (TRS), and each TRS is quasi co-located with a system synchronization block (SSB).

[0011] Figure 4 An exemplary QCL framework is shown in which the DMRS is quasi-co-located with a single TRS, and the TRS is quasi-co-located with one or more SSBs. DETAILED DESCRIPTION

[0012] The exemplary embodiments may be further understood with reference to the following description and associated drawings, wherein like elements have the same reference numerals.The exemplary embodiments relate to downlink reception at a user equipment (UE) operating in a single frequency network (SFN) utilizing beamforming.

[0013] The exemplary embodiments are described with respect to UE. However, reference to UE is provided for illustration purposes only. The exemplary embodiments may be used with any electronic component that can establish a connection with a network and is configured with hardware, software and / or firmware for exchanging information and data with the network. Therefore, UE described herein is used to represent any electronic component.

[0014] The exemplary embodiments are also described with reference to beamforming. Those of ordinary skill in the art will appreciate that beamforming is an antenna technique for transmitting or receiving directional signals. From the perspective of a transmission point (e.g., a cell), beamforming may refer to propagating a directional signal. Throughout the specification, beamformed signals may be referred to as beams. Beams may be generated by having multiple antenna elements radiate the same signal. Increasing the number of antenna elements radiating a signal reduces the width of the radiation pattern and increases the gain. The exemplary embodiments relate to a UE receiving beams from multiple cells.

[0015] In addition, the exemplary embodiments are described with reference to a 5G New Radio (NR) cellular network. However, reference to a 5G NR network is provided for illustration purposes only. The exemplary embodiments may be used with any network that implements beamforming of the same signal from multiple transmission points. Thus, a 5G NR network as described herein may represent any network that includes functionality associated with beamforming.

[0016] The 5G NR network may use the SFN mode. SFN may refer to a wireless network in which two or more cells transmit the same signal on the same frequency channel at the same time. SFN deployment may be used for coverage areas where UEs are expected to exhibit high-speed mobility. For example, SFN deployment may be used for high-speed train (HST) systems. SFN provides performance benefits for UEs on HST systems because it can reduce switching opportunities and increase system robustness. However, the exemplary embodiments are not limited to the context of HST systems and may be applicable to any coverage area utilizing the SFN mode.

[0017] For SFN mode, downlink reception at the UE can be based on combined beams from multiple cells. From the UE's perspective, the presence of different SFN cells can be transparent. However, the beams from each cell can have different characteristics. For example, the synchronization signal blocks (SSBs) associated with each cell can be different. With respect to time and frequency offsets, the UE tracks the SSBs and the corresponding tracking reference signals (TRS).

[0018] The demodulation reference signal (DMRS) of the physical downlink control channel (PDCCH) or the physical downlink shared channel (PDSCH) can be quasi co-located (QCL) with the TRS. The TRS can also be quasi co-located with one SSB. The UE can use any of these concepts for time and frequency offset tracking. An exemplary embodiment is directed to defining a quasi co-located (QCL) framework for DMRS or PDCCH / PDSCH to facilitate tracking of time and frequency offsets from multiple SFN cells.

[0019] Figure 1 A network arrangement 100 according to various exemplary embodiments is shown. The network arrangement 100 includes a UE 110. Those skilled in the art will appreciate that the UE 110 may be any type of electronic component configured to communicate via a network, such as a mobile phone, a tablet computer, a smart phone, a tablet phone, an embedded device, a wearable device, a Cat-M device, a Cat-M1 device, an MTC device, an eMTC device, other types of Internet of Things (IoT) devices, etc. A practical network arrangement may include any number of UEs used by any number of users. Therefore, the example of a single UE 110 is provided for illustration purposes only.

[0020] UE 110 may communicate with one or more networks. In the example of network arrangement 100, the network with which UE 110 may wirelessly communicate is a 5G New Radio (NR) radio access network (5G NR-RAN) 120. However, UE 110 may also communicate with other types of networks (e.g., LTE, legacy, wireless local area network (WLAN), etc.), and UE 110 may also communicate with a network via a wired connection. Therefore, UE 110 may include a 5G NR chipset to communicate with 5G NR-RAN 120.

[0021] The 5G NR-RAN 120 may be part of a cellular network that may be deployed by a cellular provider such as Verizon, AT&T, Sprint, T-Mobile, etc. The network 120 may include, for example, base stations (NodeB, eNodeB, HeNB, eNBS, gNB, gNodeB, macrocell base stations, microcell base stations, small cell base stations, femtocell base stations, etc.) configured to send and receive traffic from UEs equipped with appropriate cellular chipsets.

[0022] The base station (e.g., gNB 120A, gNB 120B) may include one or more communication interfaces to exchange data and / or information with the camped UE, the corresponding RAN, the cellular core network 130, the Internet 140, etc. It will be appreciated by those skilled in the art that any association process may be performed for the UE 110 to connect to the 5G NR-RAN 120. For example, as described above, the 5G NR-RAN 120 may be associated with a specific cellular service provider, where the UE 110 and / or its user has agreement and credential information (e.g., stored on a SIM card). Upon detecting the presence of the 5G NR-RAN 120, the UE 110 may transmit the corresponding credential information in order to associate with the 5G NR-RAN 120. More specifically, the UE 110 may be associated with a specific cell (e.g., gNB 120A of the 5G NR-RAN 120).

[0023] As described above, the exemplary embodiments relate to SFN. In this example, 5G NR-RAN 120 may use gNB 120A and gNB 120B to provide SFN functionality. That is, gNB 120A and gNB 120B may be configured to transmit the same signal to UE 110 at the same time.

[0024] In addition to the network 120, the network arrangement 100 includes a cellular core network 130, the Internet 140, an IP multimedia subsystem (IMS) 150, and a network service backbone 160. The cellular core network 130 can be viewed as an interconnected collection of components that manage the operation and traffic of the cellular network. The cellular core network 130 also manages the traffic flowing between the cellular network and the Internet 140. The IMS 150 can be generally described as an architecture for delivering multimedia services to the UE 110 using the IP protocol. The IMS 150 can communicate with the cellular core network 130 and the Internet 140 to provide multimedia services to the UE 110. The network service backbone 160 communicates directly or indirectly with the Internet 140 and the cellular core network 130. The network service backbone 160 can be generally described as a set of components (e.g., servers, network storage arrangements, etc.) that implement a set of services that can be used to extend the functionality of the UE 110 to communicate with various networks.

[0025] Figure 2 An exemplary user equipment (UE) 110 is shown in accordance with various exemplary embodiments. Figure 1UE 110 is described with reference to a network arrangement 100 of FIG. UE 110 may represent any electronic device and may include a processor 205, a memory arrangement 210, a display device 215, an input / output (I / O) device 220, a transceiver 225, and other components 230. Other components 230 may include, for example, a SIM card, an audio input device, an audio output device, a battery providing a limited power source, a data acquisition device, a port for electrically connecting UE 110 to other electronic devices, and the like.

[0026] Processor 205 may be configured to execute multiple engines of UE 110. For example, the engines may include SFN reception engine 235. SFN reception engine 235 may perform various operations related to receiving and combining beams from multiple cells (e.g., gNB 120A and gNB 120B).

[0027] The above-described engine as an application (e.g., program) executed by the processor 205 is merely exemplary. The functions associated with the engine may also be represented as an independent combined component of the UE 110, or may be a modular component coupled to the UE 110, for example, an integrated circuit with or without firmware. For example, an integrated circuit may include an input circuit for receiving a signal and a processing circuit for processing the signal and other information. The engine may also be embodied as an application or multiple separate applications. In addition, in some UEs, the functionality described for the processor 205 is shared between two or more processors such as a baseband processor and an application processor. The exemplary embodiments may be implemented in any of these or other configurations of the UE.

[0028] The memory arrangement 210 may be a hardware component configured to store data related to operations performed by the UE 110. The display device 215 may be a hardware component configured to display data to a user, and the I / O device 220 may be a hardware component that enables user input. The display device 215 and the I / O device 1120 may be separate components or may be integrated together (such as a touch screen). The transceiver 225 may be a hardware component configured to establish a connection with the 5G NR-RAN 120 and any other suitable type of wireless network. Thus, the transceiver 225 may operate on a variety of different frequencies or channels (e.g., a set of continuous frequencies).

[0029] In a first aspect, exemplary embodiments are directed to implementing a QCL framework for a DMRS quasi-co-located with one or more TRSs to facilitate tracking of time and frequency offsets from multiple cells.

[0030] Figure 3An exemplary QCL framework is shown in which a DMRS is quasi-co-located with one or more TRSs, and each TRS is quasi-co-located with an SSB. For example, consider a scenario in which gNB 120A and gNB 120B operate in SFN mode and serve UE 110. In this example, gNB 120A transmits a first SSB 305, and gNB 120B transmits a second SSB 310.

[0031] Each SSB is quasi-co-located with the corresponding TRS. Figure 3 As shown, SSB 305 is quasi-co-located with TRS 315, and SSB 310 is quasi-co-located with TRS 320. Each TRS is also quasi-co-located with the same DMRS. Figure 3 As shown, both TRS 315 and TRS 320 are quasi-co-located with the same DMRS 325. The exemplary embodiments are not limited to DMRS, Figure 3 The QCL framework shown in may also be applicable to any type of information and / or data transmitted on the PDCCH, PDSCH, or any other suitable type of downlink channel.

[0032] The following exemplary embodiments relate to implementing Figure 3 , to facilitate tracking of time and frequency offsets from multiple cells (e.g., gNB 120A, gNB 120B). Although the following examples are described with respect to two cells, those skilled in the art will understand how the exemplary concepts described herein may be applicable to scenarios involving more than two cells.

[0033] The network may transmit a transmission configuration indication (TCI) for a control resource set (CORESET) or a PDSCH to UE 110. The TCI may indicate to UE 110 the QCL relationship between antenna ports for downlink communication.

[0034] QCL information may be included, such as, but not limited to, cell ID, bandwidth part (BWP) ID, reference signal list, serving cell index, QCL type (e.g., type A, type B, type C, type D), and maxNrofReferenceSignalforQCL indication which may be based on UE capability information. Cells of the network may be configured with multiple (CSI-RS) resources of the same QCL type. The QCL type may indicate one or more QCL parameters, including, but not limited to, Doppler shift, Doppler spread, average delay, delay spread, etc.

[0035] Multiple TCI states may be configured as a CORESET or activated for a PDSCH. For a CORESET, a cell may use a medium access control (MAC) control element (CE) to indicate multiple TCI states. The DMRS port corresponding to the PDCCH in the CORESET may be quasi-co-located based on a combination of reference signals in the indicated TCI state. For the PDSCH, a cell may use a MAC CE to activate multiple TCI states corresponding to a TCI code point in the downlink control information (DCI). The TCI state for PDSCH reception may be indicated by the DCI. In addition, the DMRS port of the PDSCH may be quasi-co-located based on a combination of reference signals indicated by the TCI state. In some embodiments, when more than one TCI state is indicated, the gNB may configure whether the DMRS port of the PDSCH is quasi-co-located with the reference signal in the indicated TCI state, or whether different DMRS ports of the PDSCH are quasi-co-located with reference signals in different indicated TCI states. This configuration may be based on RRC signaling, MAC CE, or DCI.

[0036] In some embodiments, when QCL type D is not configured in the TCI state, the multiple TCI states mentioned above may be applicable. Alternatively, if multiple QCL type D are indicated in the TCI state, the UE 110 may follow the TCI state with the lowest or highest ID. Alternatively, when applicable, the QCL type D indicated by the TCI state may be the same.

[0037] When the DMRS of the PDCCH is quasi-co-located with multiple CSI-RS, which CSI-RS can be used for radio link monitoring (RLM) or beam failure detection (BFD) may depend on the UE 110 implementation. In one embodiment, the UE 110 may select a CSI-RS based on the resource ID to perform RLM or BFD for the CORESET. In this example, the highest or lowest resource ID may be selected. However, in actual operation scenarios, any resource ID may be selected for any appropriate reason.

[0038] In another embodiment, UE 110 may select a CSI-RS based on periodicity and resource ID to perform RLM or BFD for a CORESET. UE 110 may select a CSI-RS with the lowest periodicity. If the periodicity is the same for multiple CSI-RSs, UE 110 may select a CSI-RS with the lowest resource ID.

[0039] In further embodiments, UE 110 may select CSI-RS to perform RLM or BFD based on all configured CSI-RS resources. RLM / BFD execution may be determined by the type (e.g., minimum, maximum, average, assumed, etc.) of block error rate (BLER) in the CSI-RS resources. However, it is not required that the exemplary QCL framework has TCI for PDCCH, and there may be scenarios where this type of TCI is not configured for PDCCH.

[0040] In a second aspect, exemplary embodiments are directed to implementing a QCL framework for a TRS quasi-co-located with one or more SSBs to facilitate tracking of time and frequency offsets from multiple cells. Figure 4 An exemplary QCL framework is shown in which the DMRS is quasi-co-located with a single TRS and the TRS is quasi-co-located with one or more SSBs. For example, consider a scenario in which gNB 120A and gNB 120B operate in SFN mode and serve UE 110. In this example, gNB 120A transmits a first SSB 405 and gNB 120B transmits a second SSB 410.

[0041] Each SSB is quasi-co-located with the corresponding TRS. Figure 4 As shown, both SSB 405 and SSB 410 are quasi-co-located with TRS 415. TRS is also quasi-co-located with DMRS. Figure 4 As shown, TRS 415 is quasi-co-located with DMRS 420. The exemplary embodiment is not limited to DMRS. Figure 4 The QCL framework shown in may also be applicable to any type of information and / or data transmitted on the PDCCH, PDSCH, or any other suitable type of downlink channel.

[0042] The following exemplary embodiments relate to implementing Figure 4 , to facilitate tracking of time and frequency offsets from multiple cells (e.g., gNB 120A, gNB 120B). Although the following examples are described with respect to two cells, those skilled in the art will understand how the exemplary concepts described herein may be applicable to scenarios involving more than two cells.

[0043] The network may transmit (TCI) for a control resource set (CORESET) or PDSCH to UE 110. TCI may indicate to UE 110 the QCL relationship between antenna ports used for downlink communication.

[0044] QCL information may be included, such as but not limited to cell ID, bwp ID, reference signal list, serving cell index, QCL type (e.g., type A, type B, type C, type D), and maxNrofReferenceSignalforQCL indication which may be based on UE capability information. A cell of the network may be configured with multiple SSB resources of the same QCL type. The QCL type may indicate one or more QCL parameters, including but not limited to Doppler shift, Doppler spread, average delay, delay spread, etc.

[0045] Multiple TCI states can be configured for CSI-RS. CSI-RS can be quasi-co-located based on a combination of reference signals in the indicated TCI states. For periodic CSI-RS, multiple TCI states can be configured by radio resource control (RRC) signaling for each CSI-RS resource. For semi-persistent CSI-RS, multiple TCI states can be configured by MAC CE for each CSI-RS resource. For aperiodic CSI-RS, each trigger state in the DCI can correspond to multiple TCI states. When QCL type D is not configured in the TCI state, multiple TCI states may be applicable. Alternatively, if multiple QCL type Ds are indicated in the TCI state, UE 110 may follow the TCI state with the lowest or highest ID.

[0046] To facilitate automatic gain control (AGC), UE 110 may be aware of the transmit power offset between the SSB and TRS and between the TRS and PDSCH. The power offset between the TRS and the SSB may be configured by a layer 1 (L1) parameter Pc_ss. If multiple SSBs are configured in the TCI state of the TRS, the SSBs may be based on the same transmit power. In other embodiments, if the SSBs are based on different transmit powers, Pc_ss is based on the minimum or maximum or average transmit power among the quasi-co-located SSBs.

[0047] Regardless of which QCL framework is utilized, when UE 110 is configured with multiple serving cells and multiple reference signals are configured as QCL sources with the same parameters, there are several cross-carrier indication options that can be utilized. In one embodiment, the reference signal may be from the same serving cell as the target downlink signal. In another embodiment, the reference signal may be from the same serving cell (same or different than the target downlink signal). In another embodiment, the reference signal may be from different serving cells. In another embodiment, the reference signals may be allowed to have the same bandwidth in the same serving cell so that UE 110 can easily combine them.

[0048] For uplink communications, if a TCI state with multiple downlink reference signals as QCL sources is configured for uplink transmission, the UE 110 can derive the uplink power control path loss based on the downlink reference signal. In some embodiments, the path loss can be derived based on a reference signal in the TCI state. The reference signal can be selected based on the resource ID (e.g., the highest ID, the lowest ID, or any other appropriate basis). Alternatively, the reference signal can be selected based on the periodicity and the resource ID. For example, the UE 110 can select the reference signal with the lowest periodicity. If the periodicity is the same for the reference signal, the UE 110 can select the reference signal with the lowest resource ID.

[0049] In other embodiments, the path loss may be derived based on all reference signals in the TCI state. In one example, the path loss may be equal to the transmission power minus the average received power of each reference signal. In another example, the path loss may be equal to the transmission power minus the maximum received power in each reference signal. In another example, the path loss may be equal to the transmission power minus the minimum received power in each reference signal.

[0050] Those skilled in the art will appreciate that the exemplary embodiments described above may be implemented with any suitable software configuration or hardware configuration or combination thereof. Exemplary hardware platforms for implementing the exemplary embodiments may include, for example, Intel x86-based platforms with compatible operating systems, Windows OS, Mac platforms and MAC OS, mobile devices with operating systems such as iOS, Android, etc. The exemplary embodiments of the above methods may be embodied as a program comprising lines of code stored on a non-transitory computer-readable storage medium, which, when compiled, may be executed on a processor or microprocessor.

[0051] Although this patent application describes various combinations of various embodiments each having different features, those skilled in the art will understand that any feature of an embodiment may be combined with features of other embodiments in any manner not publicly denied or with features that are not functionally or logically inconsistent with the operation or function of the device of the embodiments disclosed in the present invention.

[0052] It is understood that the use of personally identifiable information should be subject to privacy policies and practices that are generally recognized to meet or exceed industry or government requirements for maintaining user privacy. Specifically, personally identifiable information data should be managed and processed to minimize the risk of unintentional or unauthorized access or use, and the nature of the authorized use should be clearly stated to users.

[0053] It will be apparent to those skilled in the art that various modifications may be made to the present disclosure without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure is intended to cover modifications and variations of the present disclosure, provided that these modifications and variations are within the scope of the appended claims and their equivalents.

Claims

1. An apparatus comprising a processing circuit, the processing circuit being configured to: Based on signaling from the network, processing a medium access control element MAC CE containing a transmission configuration indication TCI state corresponding to a physical downlink control channel PDCCH resource; and The PDCCH resource is monitored based on the TCI status.

2. The apparatus according to claim 1, wherein the MAC CE further includes an indication of a serving cell to which the MAC CE applies.

3. The apparatus according to claim 1, wherein the MAC CE further includes an indication of a control resource set CORESET to which the TCI state applies.

4. The apparatus of claim 3, wherein the MAC CE comprises a plurality of TCI states associated with the CORESET.

5. An apparatus comprising a processing circuit, the processing circuit being configured to: generating a medium access control element MAC CE for transmission to a user equipment UE, wherein the MAC CE includes a transmission configuration indication TCI state corresponding to a physical downlink control channel PDCCH resource; and A reference signal is generated for transmission to the UE via the PDCCH resource.

6. The apparatus of claim 5, wherein the MAC CE further includes an indication of a serving cell to which the MAC CE applies.

7. The apparatus according to claim 5, wherein the MAC CE further includes an indication of a control resource set CORESET to which the TCI state applies.

8. The apparatus of claim 7, wherein the MAC CE comprises a plurality of TCI states associated with the CORESET.

9. A user equipment UE, comprising: a transceiver configured to communicate with a network; as well as a processor communicatively coupled to the transceiver and configured to: Based on signaling from the network, processing a medium access control element MAC CE containing a transmission configuration indication TCI state corresponding to a physical downlink control channel PDCCH resource; and The PDCCH resource is monitored based on the TCI status.

10. The UE according to claim 9, wherein the MAC CE further includes an indication of a serving cell to which the MAC CE applies.

11. The UE according to claim 9, wherein the MAC CE further includes an indication of a control resource set CORESET to which the TCI state applies.

12. The UE of claim 11, wherein the MAC CE includes a plurality of TCI states associated with the CORESET.

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