Hybrid Multi-Synchronization Signals for Wideband NR Carriers

Abstract

The present invention is entitled "Hybrid Multi-Sync Signal for Wideband NR Carriers". The present disclosure relates to a technique for a base station (BS) to configure a default synchronization signal (SS) and a supplementary synchronization signal (SS) at a sub-band bandwidth in a wireless communication system. The supplementary SS may be configured in response to determining that the BS uses a single narrowband radio frequency chain for wireless communication with a UE. The BS may configure the supplementary SS to be close in frequency to a PDCCH search space currently used by the UE. The default SS may be configured to support initial access and may have a shorter periodicity, while the supplementary SS may be configured to not support initial access and may have a longer periodicity. The BS may additionally or alternatively configure a tracking reference signal (RS), wherein the tracking RS is configured on demand based on a current network load of the BS. The tracking RS may be configured with a sub-band bandwidth, wherein the sub-band bandwidth is selected based on a bandwidth allocated to active UEs for wireless communication with the BS.

Description

[0001] This application is a divisional application of the PCT application entering the Chinese national phase, with an international filing date of April 20, 2018, a national application number of 201880026198.7, and an invention name of “Method and apparatus for performing hybrid multi-synchronous signals for broadband NR carriers”. Technical Field

[0002] The present application relates to wireless communications, including techniques for hybrid multi-synchronous signals for performing wireless communications. Background Art

[0003] The use of wireless communication systems is growing rapidly. In addition, there are a number of different wireless communication technologies and standards. Some examples of wireless communication standards include GSM, UMTS (e.g., associated with WCDMA or TD-SCDMA air interfaces), LTE, Advanced LTE (LTE-A), HSPA, 3GPP2 CDMA2000 (e.g., 1xRTT, 1xEV-DO, HRPD, eHRPD), IEEE 802.11 (WLAN or Wi-Fi), IEEE 802.16 (WiMAX), Bluetooth, etc. Many such wireless communication standards provide for the use of known signals (e.g., pilot signals or reference signals) for a variety of purposes (such as synchronization, measurement, equalization, control, etc.). Summary of the invention

[0004] Embodiments of methods of configuring default and supplementary synchronization ("sync") signals, in particular in a cellular communication system, and devices configured to implement the methods are presented herein.

[0005] In some embodiments, a base station (BS) may configure a default synchronization signal (SS) within a carrier bandwidth. The BS may determine whether a user equipment device (UE) in wireless communication with the BS uses a single narrowband radio frequency (RF) chain for wireless communication with the BS. In response to determining that the UE uses a single narrowband RF chain for wireless communication with the BS, the BS may configure a supplementary SS within the carrier bandwidth.

[0006] In some embodiments, the supplemental SS is configured to be close in frequency to a PDCCH search space currently used by the UE, wherein the supplemental SS and the PDCCH search space can be simultaneously monitored by the narrowband RF chain of the UE.

[0007] In some embodiments, the default SS and the supplementary SS repeat periodically, and the supplementary SS has a larger period than the default SS. In some embodiments, the default SS supports initial access, while the supplementary SS does not support initial access.

[0008] In some implementations, each of the default SS and the supplemental SS is configured with a sub-band resolution.

[0009] In some embodiments, a base station (BS) configures a tracking reference signal (RS) on demand based on the current network load of the BS. In some embodiments, the tracking RS can be configured with a sub-band bandwidth, where the sub-band bandwidth is selected based on the bandwidth allocated to active user equipment devices (UEs) for wireless communication with the BS.

[0010] In some embodiments, the tracking RS is configured to have a duration selected based on the current DRX setting.

[0011] In other embodiments, a user equipment device (UE) is configured with a first sub-band radio frequency (RF) chain to monitor a PDCCH search space. The UE may be further configured with a second sub-band RF chain, wherein the second sub-band RF chain may be configured to be periodically turned on to monitor a synchronization signal.

[0012] It should be noted that the techniques described herein may be implemented in and / or used with a number of different types of devices, including but not limited to base stations, access points, cellular telephones, portable media players, tablet computers, wearable devices, and various other computing devices.

[0013] This disclosure is intended to provide a brief overview of some of the topics described in this document. Therefore, it should be understood that the above features are only examples and should not be interpreted as narrowing the scope or essence of the topics described herein in any way. Other features, aspects and advantages of the topics described herein will become apparent through the following detailed description, drawings and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] A better understanding of the present subject matter may be obtained when the following detailed description of the embodiments is considered in conjunction with the following drawings, in which:

[0015] Figure 1 illustrates an exemplary (and simplified) wireless communication system according to some embodiments;

[0016] Figure 2 A base station ("BS", or "eNodeB" or "eNB" in the LTE context) communicating with a user equipment ("UE") device is shown according to some embodiments;

[0017] Figure 3 shows an exemplary block diagram of a UE according to some embodiments;

[0018] Figure 4illustrates an exemplary block diagram of a BS according to some embodiments;

[0019] Figure 5 Various allocations of sub-band radio frequency (RF) chains for BSs and UEs are shown according to various embodiments;

[0020] Figure 6 A first UE configured with an RF chain spanning the entire carrier bandwidth (BW) and a second UE configured with two sub-band RF chains are shown according to various embodiments;

[0021] Figure 7 illustrates a default synchronization signal and a supplemental synchronization signal configured within a carrier bandwidth according to some embodiments;

[0022] Figure 8 is a flow chart illustrating a method for configuring a default synchronization signal and a supplemental synchronization signal within a carrier bandwidth according to some embodiments; and

[0023] Fig. 9 is a flow chart illustrating a method for retuning a narrowband RF chain to monitor for a supplemental synchronization signal according to some embodiments.

[0024] Although the features described herein are susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and described in detail herein. However, it should be understood that the drawings and detailed description thereof are not intended to limit this document to the specific forms disclosed, but on the contrary, the purpose is to cover all modifications, equivalents and alternatives that fall within the spirit and scope of the subject matter as defined by the appended claims. DETAILED DESCRIPTION

[0025] the term

[0026] The following is a glossary of terms used in this disclosure:

[0027] Memory medium - any of various types of non-transitory memory devices or storage devices. The term "memory medium" is intended to include installation media, such as CD-ROM, floppy disk or tape devices; computer system memory or random access memory such as DRAM, DDR RAM, SRAM, EDO RAM, Rambus RAM, etc.; non-volatile memory such as flash memory, magnetic media, for example, hard disk drive or optical storage device; registers or other similar types of memory elements, etc. The memory medium may also include other types of non-transitory memory or combinations thereof. In addition, the memory medium may be located in the first computer system executing the program, or may be located in a different second computer system connected to the first computer system via a network such as the Internet. In the latter case, the second computer system may provide program instructions to the first computer for execution. The term "memory medium" may include two or more memory media that may reside in different locations in different computer systems connected, for example, via a network. The memory medium may store program instructions (e.g., expressed as a computer program) that may be executed by one or more processors.

[0028] Carrier Medium—storage media as described above, and physical transmission media such as a bus, network, and / or other physical transmission media that transport signals such as electrical, electromagnetic or digital signals.

[0029] Programmable hardware element - includes various hardware devices that include multiple programmable function blocks connected via programmable interconnects. Examples include FPGA (field programmable gate array), PLD (programmable logic device), FPOA (field programmable object array), and CPLD (complex PLD). Programmable function blocks can vary from fine-grained (combinational logic unit or lookup table) to coarse-grained (arithmetic logic unit or processor core). Programmable hardware elements may also be referred to as "configurable logic units".

[0030] Computer System - Any of various types of computing or processing systems, including a personal computer system (PC), a mainframe computer system, a workstation, a network appliance, an Internet appliance, a personal digital assistant (PDA), a television system, a grid computing system, or other devices or combinations of devices. In general, the term "computer system" can be broadly defined to encompass any device (or combination of devices) having at least one processor that executes instructions from a memory medium.

[0031] User Equipment (UE) (or "UE device") - any of various types of computer system devices that are mobile or portable and perform wireless communications. Examples of UE devices include mobile phones or smart phones (e.g., iPhone TM , based on Android TMphones), portable gaming devices (e.g., Nintendo DS TM , PlayStation Portable TM 、Gameboy Advance TM , iPhone TM ), laptops, wearable devices (e.g., smart watches, smart glasses), PDAs, portable Internet devices, music players, data storage devices or other handheld devices, etc. In general, the term "UE" or "UE device" can be broadly defined to cover any electronic device, computing device and / or telecommunication device (or combination of devices) that can be easily transmitted by a user and capable of wireless communication.

[0032] Base Station - The term "base station" has the full breadth of its ordinary meaning and includes at least a wireless communication station that is installed at a fixed location and used to communicate as part of a wireless telephone system or radio system.

[0033] Processing Element - refers to various elements or combinations of elements. Processing elements include, for example, circuits such as ASICs (application specific integrated circuits), portions or circuits of individual processor cores, entire processor cores, individual processors, programmable hardware devices such as field programmable gate arrays (FPGAs), and / or larger portions of systems including multiple processors.

[0034] Channel - a medium used to transmit information from a sender (transmitter) to a receiver. It should be noted that since the characteristics of the term "channel" may vary according to different wireless protocols, the term "channel" used herein may be considered to be used in a manner that conforms to the standards of the type of device to which the term is used. In some standards, the channel width may be variable (e.g., depending on device capabilities, frequency band conditions, etc.). For example, LTE may support scalable channel bandwidths of 1.4 MHz to 20 MHz. In contrast, a WLAN channel may be 22 MHz wide, while a Bluetooth channel may be 1 MHz wide. Other protocols and standards may include different definitions of channels. In addition, some standards may define and use multiple types of channels, such as different channels for uplink or downlink and / or different channels for different purposes such as data, control information, etc.

[0035] Frequency band—The term “frequency band” has the full breadth of its ordinary meaning and includes at least a segment of the spectrum (eg, radio frequency spectrum) in which channels are used or set aside for the same purpose.

[0036] Automatic—refers to an action or operation performed by a computer system (e.g., software executed by a computer system) or a device (e.g., a circuit, a programmable hardware element, an ASIC, etc.) without the need for user input to directly specify or perform the action or operation. Thus, the term "automatic" is in contrast to a user manually performing or specifying an action, where the user provides input to directly perform the action. An automatic process may be initiated by input provided by a user, but subsequent actions performed "automatically" are not specified by the user, i.e., are not performed "manually," where the user specifies each action to be performed. For example, a user filling out an electronic form by selecting each field and providing input specifying information (e.g., by typing in information, selecting check boxes, radio selections, etc.) is manually filling out the form, even though the computer system must update the form in response to the user action. The form may be automatically filled out by a computer system, where the computer system (e.g., software executed on the computer system) analyzes the fields of the form and fills out the form without any user input specifying the answers to the fields. As indicated above, a user may invoke automatic filling out of a form, but not participate in the actual filling out of the form (e.g., the user does not manually specify the answers to the fields but rather they are automatically completed). This specification provides various examples of operations that are automatically performed in response to actions taken by a user.

[0037] Figure 1 and Figure 2 —Communications system

[0038] Figure 1 An exemplary (and simplified) wireless communication system according to one embodiment is shown. Note that Figure 1 The system is only one example of a possible system, and the embodiments may be implemented in any of a variety of systems as desired.

[0039] As shown, the exemplary wireless communication system includes a base station 102A, which communicates with one or more user equipment 106A, user equipment 106B, etc. to user equipment 106N through a transmission medium. Each of the user equipments may be referred to as a "user device (UE)" in this document. Therefore, the user equipment 106 is referred to as a UE or UE device.

[0040] Base station 102A may be a base transceiver station (BTS) or a cell site and may include hardware to enable wireless communications with UEs 106A to 106N. Base station 102A may also be equipped to communicate with network 100 (e.g., a core network of a cellular service provider, a telecommunications network such as a public switched telephone network (PSTN), and / or the Internet, among other possibilities). Thus, base station 102A may facilitate communications between user devices and / or between user devices and network 100.

[0041] The communication area (or coverage area) of a base station may be referred to as a “cell.” The base station 102A and the UE 106 may be configured to communicate via a transmission medium using any of a variety of radio access technologies (RATs), which are also referred to as wireless communication technologies or telecommunication standards, such as GSM, UMTS (WCDMA, TD-SCDMA), LTE, Advanced LTE (LTE-A), HSPA, 3GPP2 CDMA2000 (e.g., 1xRTT, 1xEV-DO, HRPD, eHRPD), Wi-Fi, WiMAX, New Radio (NR), etc.

[0042] Base station 102A and other similar base stations (such as base stations 102B...102N) operating according to the same or different cellular communication standards can therefore be provided as a network of cells that can provide continuous or nearly continuous overlapping service to UE 106A-N and similar devices over a wide geographic area via one or more cellular communication standards.

[0043] Therefore, although the base station 102A may be Figure 1 UEs 106A-N shown in FIG. 1 provide a "serving cell", but each UE 106 may also be able to receive signals from (and possibly be within communication range of) one or more other cells (which may be provided by base stations 102B-N and / or any other base stations), which may be referred to as "neighboring cells". Such cells may also be able to facilitate communications between user devices and / or between user devices and network 100. Such cells may include "macro" cells, "micro" cells, "pico" cells, and / or cells of any various other granularity of service area size. For example, in Figure 1 The base stations 102A-B shown in FIG. 1 may be macro cells, while the base station 102N may be a micro cell. Other configurations are also possible.

[0044] It should be noted that the UE 106 may be capable of communicating using multiple wireless communication standards. For example, in addition to at least one cellular communication protocol (e.g., GSM, UMTS (WCDMA, TD-SCDMA), LTE, LTE-A, HSPA, 3GPP2 CDMA2000 (e.g., 1xRTT, 1xEV-DO, HRPD, eHRPD), etc.), NR, the UE 106 may be configured to communicate using wireless networking (e.g., Wi-Fi) and / or peer-to-peer wireless communication protocols (e.g., BT, Wi-Fi peers, etc.). If desired, the UE 106 may also or alternatively be configured to communicate using one or more global navigation satellite systems (GNSS, such as GPS or GLONASS), one or more mobile television broadcast standards (e.g., ATSC-M / H or DVB-H), and / or any other wireless communication protocols. Other combinations of wireless communication standards (including more than two wireless communication standards) are also possible.

[0045] Figure 2 A user device 106 (e.g., one of devices 106A to 106N) is shown communicating with a base station 102 (e.g., one of base stations 102A to 102N) according to one embodiment. UE 106 may be a device with cellular communication capabilities, such as a mobile phone, a handheld device, a wearable device, a computer or tablet, or substantially any type of wireless device.

[0046] UE 106 may include a processor configured to execute program instructions stored in a memory. UE 106 may perform any of the method implementations described herein by executing such stored instructions. Alternatively or in addition, UE 106 may include a programmable hardware element, such as an FPGA (field programmable gate array) configured to perform any of the method implementations described herein or any part of any of the method implementations described herein.

[0047] UE 106 may include one or more antennas for communicating using one or more wireless communication protocols or technologies. In one embodiment, UE 106 may be configured to communicate using CDMA2000 (1xRTT / 1xEV-DO / HRPD / eHRPD) or LTE using a single shared radio component and / or any one of GSM or LTE using a single shared radio component. The shared radio component may be coupled to a single antenna, or may be coupled to multiple antennas (e.g., for MIMO) for performing wireless communications. Typically, the radio component may include any combination of a baseband processor, an analog RF signal processing circuit (e.g., including filters, mixers, oscillators, amplifiers, etc.), or a digital processing circuit (e.g., for digital modulation and other digital processing). Similarly, the radio component may use the aforementioned hardware to implement one or more receive chains and transmit chains. For example, UE 106 may share one or more portions of a receive chain and / or transmit chain between multiple wireless communication technologies such as those discussed above.

[0048] In some embodiments, UE 106 may include independent (and possibly multiple) transmission chains and / or reception chains (e.g., including independent RF and / or digital radio components) for each wireless communication protocol configured to communicate with it. As another possibility, UE 106 may include one or more radio components shared between multiple wireless communication protocols, and one or more radio components used uniquely by a single wireless communication protocol. For example, UE 106 may include a shared radio component for communicating using any of LTE, 1xRTT, and NR (or LTE or GSM), and an independent radio component for communicating using each of Wi-Fi and Bluetooth. Other configurations are also possible.

[0049] Figure 3 —Exemplary block diagram of UE

[0050] Figure 3An exemplary block diagram of a UE 106 according to one embodiment is shown. As shown, the UE 106 may include a system on a chip (SOC) 300, which may include parts for various purposes. For example, as shown, the SOC 300 may include a processor 302 that can execute program instructions for the UE 106, and a display circuit 304 that can perform graphics processing and provide display signals to a display 360. The processor 302 may also be coupled to a memory management unit (MMU) 340 (the MMU may be configured to receive addresses from the processor 302 and convert those addresses into locations in a memory (e.g., a memory 306, a read-only memory (ROM) 350, a NAND flash memory 310), and / or coupled to other circuits or devices (such as a display circuit 304, a wireless communication circuit 330, a connector I / F 320, and / or a display 360). The MMU 340 may be configured to perform memory protection and page table conversion or setup. In some embodiments, the MMU 340 may be included as part of the processor 302.

[0051] As shown, SOC 300 may be coupled to various other circuits of UE 106. For example, UE 106 may include various types of memory (e.g., including NAND flash memory 310), a connector interface 320 (e.g., for coupling to a computer system, taskbar, charging station), a display 360, and wireless communication circuitry (e.g., radio components) 330 (e.g., for LTE, Wi-Fi, GPS, etc.).

[0052] The UE device 106 may include at least one antenna (and in various possibilities, multiple antennas, e.g., for MIMO and / or for implementing different wireless communication technologies) for performing wireless communications with base stations and / or other devices. For example, the UE device 106 may perform wireless communications using antenna 335. As mentioned above, in some embodiments, the UE 106 may be configured to perform wireless communications using multiple wireless communication standards.

[0053] As described further subsequently herein, the UE 106 may include features for implementing features related to the use of dedicated measurement / synchronization subframes in a cellular communication system (such as, in particular, those described herein with reference to Figure 6The processor 302 of the UE device 106 may be configured to implement some or all of the methods described herein, for example, by executing program instructions stored on a memory medium (e.g., a non-transitory computer-readable memory medium). In other embodiments, the processor 302 may be configured as a programmable hardware element such as an FPGA (field programmable gate array), or as an ASIC (application-specific integrated circuit). Alternatively (or in addition), in combination with one or more of the other components 300, 304, 306, 310, 320, 330, 335, 340, 350, 360, the processor 302 of the UE device 106 may be configured to implement some or all of the features described herein, such as those described herein with reference to Figure 6 Especially described features.

[0054] Figure 4 —Exemplary block diagram of a base station

[0055] Figure 4 An exemplary block diagram of a base station 102 according to one embodiment is shown. Note that Figure 4 The base station of is only one example of a possible base station. As shown, the base station 102 may include a processor 404 that may execute program instructions for the base station 102. The processor 404 may also be coupled to a memory management unit (MMU) 440 (which may be configured to receive addresses from the processor 404 and convert these addresses to locations in memory (e.g., memory 460 and read-only memory (ROM) 450)) or to other circuits or devices.

[0056] Base station 102 may include at least one network port 470. Network port 470 may be configured to couple to a telephone network and provide access to the telephone network described above. Figure 1 and Figure 2 Multiple devices of the telephone network described in, such as UE device 106.

[0057] The network port 470 (or an additional network port) may be further configured or alternatively configured to couple to a cellular network, such as a core network of a cellular service provider. The core network may provide mobility-related services and / or other services to multiple devices, such as the UE device 106. In some cases, the network port 470 may be coupled to a telephone network via the core network, and / or the core network may provide a telephone network (e.g., in other UE devices served by the cellular service provider).

[0058] The base station 102 may include at least one antenna 434 and possibly multiple antennas. The antenna 434 may be configured to operate as a wireless transceiver and may be further configured to communicate with the UE device 106 via the radio component 430. The antenna 434 communicates with the radio component 430 via a communication chain 432. The communication chain 432 may be a receive chain, a transmit chain, or both. The radio component 430 may be configured to communicate via various wireless telecommunication standards, including but not limited to NR, LTE, LTE-A, UMTS, CDMA2000, Wi-Fi, etc.

[0059] BS 102 may be configured to perform wireless communications using multiple wireless communication standards. In some cases, base station 102 may include multiple radio components that enable base station 102 to communicate according to multiple wireless communication technologies. For example, as one possibility, base station 102 may include an NR radio component for performing communications according to NR and a Wi-Fi radio component for performing communications according to Wi-Fi. In such cases, base station 102 may be able to operate as both an NR base station and a Wi-Fi access point. As another possibility, base station 102 may include a multi-mode radio component capable of performing communications according to any of a variety of wireless communication technologies (e.g., NR and Wi-Fi; NR and LTE; LTE and CDMA2000; UMTS and GSM, etc.).

[0060] As described further subsequently herein, BS 102 may include features for implementing features related to the use of hybrid multi-synchronization signals for wideband carriers in cellular communication systems (such as those described in particular herein with reference to Figure 6 and Figure 7 The processor 404 of the base station 102 may be configured to implement part or all of the methods described herein, for example, by executing program instructions stored on a memory medium (e.g., a non-transitory computer-readable memory medium). Alternatively, the processor 404 may be configured as a programmable hardware element such as an FPGA (field programmable gate array), or as an ASIC (application-specific integrated circuit), or a combination thereof. Alternatively (or in addition), in conjunction with one or more of the other components 430, 432, 434, 440, 450, 460, 470, the processor 404 of the BS 102 may be configured to implement part or all of the features described herein, such as, in particular, those described herein with reference to Figure 6 and Figure 7 The characteristics described.

[0061] Multiple RF chains

[0062] It is expected that the new radio (NR) may support a wider carrier bandwidth than LTE. For example, due to the backward compatibility requirements of LTE Release 8 UEs, LTE has component carriers (CCs) with bandwidths up to 20 mHz. In addition, in LTE, the UE typically needs to monitor the entire bandwidth of the CC in order to communicate with the BS, because the UE needs to be able to access access information, scheduling information, payload information, etc. distributed across the entire bandwidth of the CC.

[0063] In contrast, it is expected (e.g., from 3GPP RAN1) that NR specifications will support up to 400Mhz on each CC in Rel. 15. (RAN1#88). Due to cost / transmission requirements, it may be challenging for some UEs to cover the entire wideband carrier in NR with a single RF chain. Figure 5 Four potential RF chain allocations for BS and UE according to various embodiments are shown. As shown, Case 1 shows that both the BS and UE have a single RF chain covering the entire channel bandwidth (BW). Case 2 shows a case where the UE has a single RF chain to cover the entire channel BW, and the BS has two RF chains (RF chain A and RF chain B) that each cover half of the total channel BW. Case 3 shows a complementary case, where the BS uses a single RF chain to monitor the entire channel BW, and the UE uses two RF chains (RF chain X and RF chain Y) that each monitor half of the channel BW. Finally, Case 4 shows a case where both the BS and UE use two RF chains, each of which monitors half of the channel BW. As needed, there may also be other possibilities, namely having a larger number of RF chains.

[0064] In addition, some UEs / devices may include only one RF chain (e.g., a narrowband RF chain) that is narrower than the CC bandwidth. In other words, NR may support functionality in which the UE does not monitor the entire bandwidth of the CC. For example, if the carrier bandwidth is 400Mhz, some UEs may include only a single RF chain with a bandwidth of 100Mhz, so that they are unable to monitor the entire channel bandwidth. In some embodiments, the UE may be configured to have an RF chain that is adjustable to alternatively monitor the entire component carrier bandwidth or a bandwidth that is less than the component carrier bandwidth. For example, the RF chain may adjust its monitorable bandwidth based on current communication requirements, and may be configured to act as a narrowband RF chain (e.g., to reduce power consumption). Throughout this disclosure, a "narrowband RF chain" may be considered to refer to any RF chain that is configured to monitor a bandwidth that is less than the entire CC bandwidth associated with communications with a base station.

[0065] In LTE carrier aggregation (CA), each component carrier has its own synchronization signal (SS) and broadcast signal (called physical broadcast channel, or PBCH). Typically, in LTE, the RF chain of a UE is sufficient to cover a CC, and often even the entire frequency band. The UE can simultaneously monitor the SS, PBCH, and all scheduling information in the physical downlink control channel (PDCCH).

[0066] In NR carrier aggregation, the CC bandwidth can be wider than the UE bandwidth. In other words, the UE can operate using a sub-band radio frequency (RF) chain. Depending on the network (NW) load, in some embodiments, the gNB may need to configure the UE to a different sub-band (i.e., to a different part of the CC bandwidth) to monitor the PDCCH in order to distribute the load.

[0067] In these implementations, the problem arises of how the NB UE reads the SS / PBCH while still monitoring the PDCCH search space. Various implementations that address this problem are discussed below.

[0068] Figure 6 -UE with multiple NB RF chains

[0069] In some embodiments, such as Figure 6 As shown, the UE can be configured to have multiple RF chains. For example, the UE can use the first RF chain (UE 2RF_1) to monitor its configured PDCCH search space. It can periodically turn on the second RF chain (UE 2RF_2) to monitor SS / PBCH. For example, among other possibilities, the second RF chain can be periodically used for tracking, measurement, or radio link monitoring. Since the UE may only need to monitor SS / PBCH occasionally, the second RF chain can be turned off when not in use to avoid unnecessary battery consumption. In contrast, in some embodiments, the first RF chain can be configured to remain turned on while monitoring the PDCCH search space. As shown, UE 1 has a single RF chain with a bandwidth covering the entire carrier BW. Therefore, the UE may not need to configure a second RF chain.

[0070] Figure 7 -UE with one NB RF chain

[0071] Figure 7 Another embodiment using hybrid multi-synchronization signals (multiple SSs) is shown. In this embodiment, the BS can configure supplementary SSs so that the UE can use a single sub-band RF chain to cover both SS and PDCCH search space.

[0072] As shown, the first UE has a single RF chain (UE 1RF) that spans the entire bandwidth of the CC. However, the second UE has a single RF chain (UE 2RF_1) with limited bandwidth that can only monitor a portion of the entire carrier bandwidth.

[0073] In this embodiment, the BS may configure a default SS within the carrier bandwidth, which may be used by the first UE with a wideband RF chain. Alternatively or in addition, the default SS may be configured by a similar Figure 6 UE 2 in the UE is used, the UE is configured with multiple sub-band RF chains ( Figure 7 ). The default SS may support initial access. In other words, when the UE wakes up and attempts an initial connection with the BS, the default SS may be configured to be usable by the UE. The default SS may be configured to be repeated periodically with a short period (e.g., 10 ms or another period) so that the UE attempting to connect to the BS will not have to wait for a long time to receive the default SS.

[0074] While the default SS may be sufficient to serve the first UE with a wideband RF chain, the second UE with a single narrowband RF chain may not be able to monitor the default SS and the PDCCH search space simultaneously. In this case, it may be desirable for the BS to determine whether the UE device that is wirelessly communicating with the BS is using a single narrowband RF chain. For example, in some embodiments, the BS may receive a communication specifying the hardware configuration or current settings of the UE from the UE. Alternatively, the BS may determine that the UE is using a single narrowband RF chain based on other characteristics of the communication received from the UE. In response to determining that the UE is wirelessly communicating with the BS using a single narrowband RF chain, the BS may configure a supplementary SS within the carrier bandwidth (e.g., the supplementary SS may be configured dynamically or semi-statically). In some embodiments, the supplementary SS may be selectively and / or dynamically configured based on need (e.g., based on the current load of the narrowband UE with a single RF chain). In some embodiments, where (in frequency) and when to configure the supplementary SS may be selected based on the characteristics of the UE (e.g., based on the UE's use of a single narrowband RF chain, based on the location of its allocated PDCCH search space, etc.).

[0075] In this embodiment, as shown, the BS may be configured to transmit the supplementary SS along with the PBCH, and the BS may also be configured to transmit a PDCCH search space dedicated to the second UE (UE2) at a nearby frequency, so that the limited bandwidth supported by the RF chain of the second UE can monitor both the supplementary SS / PBCH and the UE2 PDCCH search space. The first UE (UE1) (whose RF chain is capable of monitoring the entire carrier BW) may be able to monitor the default SS / PBCH as well as the UE1 PDCCH search space with its single wideband RF chain. In other embodiments, the supplementary SS may be transmitted separately from the PBCH.

[0076] In some embodiments, the supplementary SS may be configured to reduce the associated downlink (DL) overhead. For example, the supplementary SS may be configured at a sub-band resolution (e.g., 100Mhz) and may be configured only when needed. In some embodiments, the supplementary SS may be configured to not support initial access and may have a sparser periodicity than the primary (default) SS that may support initial access. For example, the default SS may be configured to have a periodicity of 20ms (or some other periodicity), while the supplementary SS may be configured to have a periodicity of 100ms (or some other periodicity longer than the default SS periodicity). In some embodiments, each carrier may only need one default SS that supports initial access.

[0077] When the UE initially attempts to connect to the network, it may be expected that the UE will quickly synchronize with the network to begin communication. In this case, the UE may monitor the default SS, which repeats more frequently due to its shorter periodicity. However, once the UE is synchronized, the UE no longer needs to monitor the synchronization signal (e.g., the default SS) frequently, in which case the UE may monitor the less frequent supplementary SS, thereby saving battery life and reducing unnecessary network load. In some embodiments, the network may notify the UE of the location of the supplementary SS in time and / or frequency after initial synchronization using the default SS. For example, the BS may transmit a notification specifying the periodicity and measurement window of the supplementary SS to the UE. Another beneficial effect is that the network load of the control channel used to provide services to various UEs can be distributed in the supplementary SS throughout the bandwidth of the CC. Typically, the network can configure the supplementary SS on demand or as needed to avoid unnecessary use of network resources.

[0078] In some embodiments, the UE may need to periodically resynchronize with the network. Without the supplementary SS, the UE may have to periodically re-tune to a frequency that can monitor the default SS. This may take additional time and cause undesirable delays, and the UE may also miss payload data from the PDCCH search space when it is detuned to the default SS. The presence of the supplementary SS alleviates these problems by allowing the UE to monitor both the supplementary SS and the PDCCH search space with a single short bandwidth RF chain.

[0079] In some embodiments, the periodicity of the supplementary SS and the measurement window may be notified to the UE, for example, by the base station. According to various embodiments, the supplementary SS may be sent with or without the PBCH. For embodiments where the supplementary SS is not sent with the PBCH and, for example, the network needs to update the master information block (MIB), the network may request the UE to tune to the default SS to read the PBCH.

[0080] In some embodiments, multiple supplementary SSs may be configured for each of the plurality of UEs. For example, a supplementary SS may be configured on demand for each of the plurality of UEs, wherein each supplementary SS is activated only when the UE needs to access the supplementary SS.

[0081] Figure 8 - Supplement SS base station configuration

[0082] Figure 8 is a flow chart describing a method for a base station to configure a supplementary SS. Figure 8 The steps shown in FIG. 1 present reference to some embodiments according to the present invention. Figure 7 A high-level description of the method described. Some of the method elements shown may be performed concurrently in an order different from the order shown, or may be omitted. Additional method elements may also be performed as needed. As shown, the method may operate as follows.

[0083] At 802, the base station may configure a default SS within a carrier bandwidth. The base station may initialize communication with the UE by transmitting the default SS to the UE.

[0084] At 804, the base station may determine that the UE is using a single narrowband radio frequency chain. The base station may make this determination based on a notification message received from the UE or based on characteristics of other communications received from the UE (e.g., based on physical characteristics of a transmission received from the UE indicating that the transmission is a narrowband transmission).

[0085] At 806, the base station may configure a supplemental SS within the carrier bandwidth. As described in more detail above, the supplemental SS may be configured to be close in frequency to the PDCCH search space currently used by the UE. The base station may transmit a supplemental synchronization signal according to the configuration.

[0086] Fig. 9 -Supplement SS UE usage

[0087] Fig. 9 is a flow chart describing a method for a UE to use a supplementary SS. Fig. 9 The steps shown in FIG. 1 present reference to some embodiments according to the present invention. Figure 7 A high-level description of the method described. Some of the method elements shown may be performed concurrently in an order different from the order shown, or may be omitted. Additional method elements may also be performed as needed. As shown, the method may operate as follows.

[0088] At 902, the UE may initialize communication with a base station (BS) by receiving a default SS via a narrowband RF link. The default SS may be received within a carrier bandwidth.

[0089] At 904, the UE may (optionally) transmit a notification to the base station that the UE is using a single narrowband RF chain. Alternatively, in some embodiments, the base station may infer that the UE is using a single narrowband RF chain based on physical characteristics of payload transmissions from the UE. In these embodiments, the UE may not need to send a notification to the base station explicitly indicating that the UE is using a single narrowband RF chain.

[0090] At 906, the UE may re-tune the narrowband RF chain to monitor the supplemental SS. The UE may receive a notification from the BS specifying a periodicity and a measurement window associated with the supplemental SS. The UE may then receive the supplemental SS via the re-tuned narrowband RF chain.

[0091] NR Tracking Reference Signal

[0092] In order to perform time and frequency tracking, cellular communication networks usually use sufficiently dense and frequent pilots or reference signals (RS). For example, in LTE, a cell-specific reference signal (CRS) may be used with a bandwidth (e.g., 20 mHz) covering the entire bandwidth of a component carrier, and it is usually repeated every time slot (i.e., every 0.5 ms).

[0093] To preserve network power, NR may not support "LTE-type" cell-specific reference signals, which are "dense" in both time and frequency domains and span the entire channel bandwidth. In addition, NR synchronization signals may have a default periodicity of 20ms (based on current RAN1 protocols), which is slower than LTE's SS periodicity of 10ms. Specifically, during peak data rates, a periodicity of 20ms may not be frequent enough for tracking RS.

[0094] It may be desirable that NR employ some type of reference signal for tracking purposes. Specifically, when transmitting with high spectral efficiency, it may be desirable to have a reference signal with high requirements for time / frequency accuracy. In some embodiments, the tracking RS will be a narrowband tracking RS. In some embodiments, as explained in further detail below, the tracking RS may be a periodic tracking RS optionally deployed on a sub-band basis.

[0095] On-demand tracking reference signal

[0096] In some embodiments, the tracking RS may be configured by the network. The tracking RS may have sufficient bandwidth in the frequency domain to achieve time tracking resolution. Alternatively or in addition, in some embodiments, the tracking RS may have sufficient density in the time domain to achieve frequency tracking range and / or resolution.

[0097] In some embodiments, the tracking RS may be configured on demand (semi-statically or dynamically) by the network to save power. For example, in some embodiments, the tracking RS may be turned on and off on each sub-band or each carrier based on the current network load. In some embodiments, the bandwidth of the tracking RS may be configured based on the RF chain bandwidth of the UE. For example, if all active UEs are configured and / or allocated within a 50Mhz sub-band, the tracking RS may only require up to 50Mhz in bandwidth. In some embodiments, the duration of the tracking RS may be configured based on the current DRX setting. For example, the network may only need to configure the tracking RS during the DRX on period and during a few time slots before the DRX on period.

[0098] The following numbered paragraphs describe additional embodiments of the invention.

[0099] In some embodiments, a base station (BS) configures a tracking reference signal (RS), wherein the tracking RS is configured on demand based on a current network load of the BS.

[0100] In some embodiments, the tracking RS may be configured with a sub-band bandwidth, where the sub-band bandwidth is selected based on a bandwidth allocated to active user equipment devices (UEs) in wireless communication with the BS.

[0101] In some implementations, the duration of tracking the RS is selected based on the current DRX setting.

[0102] In some embodiments, the tracking RS is configured to become active at periodic intervals.

[0103] In some embodiments, a user equipment device (UE) is configured with a first sub-band radio frequency (RF) chain to monitor a PDCCH search space. The UE device may also be configured with a second sub-band RF chain, wherein the second sub-band RF chain is configured to be periodically turned on to monitor a synchronization signal.

[0104] The embodiments of the present disclosure may be implemented in any of a variety of forms. For example, some embodiments may be implemented as computer-implemented methods, computer-readable storage media, or computer systems. Other embodiments may be implemented using one or more custom-designed hardware devices such as ASICs. Other embodiments may be implemented using one or more programmable hardware elements such as FPGAs.

[0105] In some embodiments, a non-transitory computer-readable storage medium may be configured such that it stores program instructions and / or data, wherein if the program instructions are executed by a computer system, the computer system is caused to perform a method, such as any one of the method embodiments described herein, or any combination of the method embodiments described herein, or any subset of any method embodiments described herein, or any combination of such subsets.

[0106] In some embodiments, a device (e.g., UE 106) may be configured to include a processor (or a group of processors) and a memory medium, wherein the memory medium stores program instructions, wherein the processor is configured to read and execute the program instructions from the memory medium, wherein the program instructions are executable to implement any of the various method implementations described herein (or any combination of the method implementations described herein, or any subset of any of the method implementations described herein, or any combination of such subsets). The device may be implemented in any of various forms.

[0107] Although the above embodiments have been described in considerable detail, numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to encompass all such variations and modifications.

Claims

1. A user equipment (UE), comprising: a radio component comprising an antenna configured for wireless communication; a processor operatively coupled to the radio; The UE is configured as follows: initializing communication with a base station (BS) by receiving a default synchronization signal (SS) configured by the base station via a radio frequency (RF) chain, the RF chain configured to monitor a first bandwidth that is less than a component carrier bandwidth used in the communication, wherein the default SS is configured within the first bandwidth; After initializing communication with the BS, a configuration is received for monitoring a second bandwidth that is smaller than the component carrier bandwidth and does not intersect with the first bandwidth, wherein within the second bandwidth, the UE monitors a supplementary SS via the RF chain, wherein the supplementary SS is configured to be close in frequency to a physical downlink control channel (PDCCH) search space so that the UE can monitor both the supplementary SS and the PDCCH via the RF chain.

2. The UE according to claim 1, wherein the UE is further configured to: A notification is transmitted to the BS that the UE is wirelessly communicating with the BS using the RF chain, the RF chain being configured to monitor a bandwidth less than a component carrier bandwidth used in the communication, wherein the monitoring of the supplemental SS via the RF chain is performed after transmitting the notification. 3 . The UE of claim 1 , wherein the default SS and the supplementary SS are repeated periodically, and wherein the supplementary SS has a longer repetition period than the default SS. The UE of claim 1 , wherein the default SS supports initial access, and wherein the supplementary SS does not support initial access. The UE of claim 1 , wherein each of the default SS and the supplementary SS is configured with a sub-band resolution.

6. The UE according to claim 1, wherein the UE is further configured to: A notification is received from the BS specifying a periodicity and a measurement window associated with the supplemental SS.

7. The UE according to claim 1, wherein the UE is further configured to: The supplemental SS is received together with a physical broadcast channel (PBCH).

8. An apparatus configured to be included in a user equipment device (UE), the apparatus comprising: Memory; as well as a processor in communication with the memory, wherein the memory stores program instructions executable by the processor to cause the UE to: initializing communication with a base station (BS) by receiving a default synchronization signal (SS) configured by the base station via a radio frequency (RF) chain, the RF chain configured to monitor a first bandwidth that is less than a component carrier bandwidth used in the communication, wherein the default SS is configured within the first bandwidth; After initializing communication with the BS, a configuration is received for monitoring a second bandwidth that is smaller than the component carrier bandwidth and does not intersect with the first bandwidth, wherein within the second bandwidth, the UE monitors a supplementary SS via the RF chain, wherein the supplementary SS is configured to be close in frequency to a physical downlink control channel (PDCCH) search space so that the UE can monitor both the supplementary SS and the PDCCH via the RF chain.

9. The apparatus of claim 8, wherein the program instructions are further executable by the processor to cause the UE to: A notification is transmitted to the BS that the UE is wirelessly communicating with the BS using the RF chain, the RF chain being configured to monitor a bandwidth less than the component carrier bandwidth, wherein the supplemental SS is monitored via the RF chain after the transmission of the notification. 10 . The apparatus of claim 8 , wherein the default SS and the supplementary SS are repeated periodically, and wherein the supplementary SS has a different repetition period from that of the default SS.

11. The apparatus of claim 8, wherein the default SS supports initial access, and wherein the supplementary SS does not support initial access.

12. The apparatus of claim 8, wherein the program instructions are further executable by the processor to cause the UE to: A notification is received from the BS specifying a periodicity and a measurement window associated with the supplemental SS. 13 . The apparatus of claim 8 , wherein each of the default SS and the supplementary SS is configured with a sub-band resolution.

14. A method for wireless communication, comprising: By Base Station (BS): configuring a default synchronization signal (SS) within a first bandwidth that is smaller than a component carrier bandwidth used in communication with the BS for initializing the communication with the BS; determining whether a user equipment device (UE) in wireless communication with the BS uses a single radio frequency (RF) chain to communicate wirelessly with the BS; In response to determining that the UE uses a single RF chain for wireless communication with the BS, a supplementary SS is configured within a second bandwidth that is smaller than the component carrier bandwidth and disjoint with the first bandwidth, wherein the supplementary SS is configured to be close in frequency to a physical downlink control channel (PDCCH) search space so that the UE can monitor both the supplementary SS and the PDCCH via the RF chain. 15 . The method of claim 14 , wherein the default SS and the supplementary SS are repeated periodically, and wherein the supplementary SS has a different repetition period from that of the default SS.

16. The method of claim 14, wherein the default SS supports initial access, and wherein the supplementary SS does not support initial access. 17 . The method of claim 14 , wherein each of the default SS and the supplementary SS is configured with a sub-band resolution.

18. The method according to claim 14, further comprising: A notification is transmitted to the UE specifying a periodicity and a measurement window associated with the supplemental SS.

19. The method according to claim 14, further comprising: The supplementary SS is transmitted together with a physical broadcast channel (PBCH).

20. The method according to claim 14, Wherein determining whether the UE is using a single RF chain for wireless communication with the BS includes receiving a notification from the UE that the UE is using the single RF chain for wireless communication with the BS, the single RF chain being configured to monitor a bandwidth less than the component carrier bandwidth.

21. A method for wireless communication, comprising: By User Equipment (UE): initializing communication with a base station (BS) by receiving a default synchronization signal (SS) configured by the base station via a radio frequency (RF) chain, the RF chain configured to monitor a first bandwidth that is less than a component carrier bandwidth used in the communication, wherein the default SS is configured within the first bandwidth; as well as After initializing communication with the BS, a configuration is received for monitoring a second bandwidth that is smaller than the component carrier bandwidth and does not intersect with the first bandwidth, wherein within the second bandwidth, the UE monitors a supplementary SS via the RF chain, wherein the supplementary SS is configured to be close in frequency to a physical downlink control channel (PDCCH) search space so that the UE can monitor both the supplementary SS and the PDCCH via the RF chain.

22. The method according to claim 21, further comprising: A notification is transmitted to the BS that the UE is wirelessly communicating with the BS using the RF chain, the RF chain being configured to monitor a bandwidth less than a component carrier bandwidth used in the communication, wherein the monitoring of the supplemental SS via the RF chain is performed after transmitting the notification.

23. The method of claim 21, wherein the default SS and the supplementary SS are repeated periodically, and wherein the supplementary SS has a longer repetition period than the default SS.

24. The method of claim 21, wherein the default SS supports initial access, and wherein the supplementary SS does not support initial access.

25. The method of claim 21, wherein each of the default SS and the supplementary SS is configured with a sub-band resolution.

26. The method of claim 21, further comprising: A notification is received from the BS specifying a periodicity and a measurement window associated with the supplemental SS.

27. The method of claim 21, further comprising: The supplemental SS is received together with a physical broadcast channel (PBCH).

28. A computer readable storage medium comprising a computer program which, when executed by a processor of a user equipment device (UE), causes the processor to perform the method according to any one of claims 21 to 27.

29. A computer program product comprising program instructions which, when executed by a processor of a user equipment device (UE), cause the processor to perform the method according to any one of claims 21 to 27.

30. A base station, comprising: a radio component comprising an antenna configured for wireless communication; a processor operatively coupled to the radio; The base station is configured to perform the method according to any one of claims 14 to 20.

31. A base station, comprising: Memory; and A processor in communication with the memory, wherein the memory stores program instructions executable by the processor to cause the base station to perform the method according to any one of claims 14 to 20.

32. A computer-readable storage medium comprising a computer program which, when executed by a processor of a base station, causes the processor to perform the method according to any one of claims 14 to 20.

33. A computer program product comprising program instructions which, when executed by a processor of a base station, cause the processor to perform the method according to any one of claims 14 to 20.

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