Existence Discovery Technology

Abstract

The present disclosure relates to techniques for performing presence discovery in wireless communications. A wireless device may monitor a wireless medium for a discovery signal. A candidate discovery signal may be detected. A frequency offset estimate consistency check may be performed on the candidate discovery signal. A peak-to-sidelobe ratio check may be performed on the candidate discovery signal. The wireless device may determine whether the candidate discovery signal is a false positive based at least in part on the frequency offset estimate consistency check and the peak-to-sidelobe ratio check.

Description

Technical Field

[0001] The present patent application relates to wireless communications, including techniques for performing presence discovery in wireless communication systems. Background Art

[0002] The use of wireless communication systems is growing rapidly. In addition, wireless communication technology has evolved from only voice communication to also include the transmission of data (such as the Internet and multimedia content).

[0003] Mobile electronic devices may take the form of smartphones or tablet computers that are commonly carried by users. Wearable devices (also referred to as accessory devices) are a newer form of mobile electronic devices, an example of which is a smart watch. In addition, low-cost, low-complexity wireless devices intended for static or dynamic deployment are also increasing rapidly as part of the development of the "Internet of Things". In other words, the complexity, capabilities, traffic patterns and other characteristics of the required devices are increasingly wide-ranging. In general, it is desirable to recognize and provide improved support for a wide range of required wireless communication characteristics. Therefore, improvements in the art are desired. Summary of the invention

[0004] Embodiments of systems, apparatus, and methods are presented herein for, inter alia, performing presence discovery in a wireless communication system.

[0005] As described above, there are an increasing number of use cases for different kinds of wireless devices with widely varying capabilities and usage expectations. While many wireless communication systems primarily utilize infrastructure mode types of communications, e.g., where one or more base stations and potentially supporting networks are used as intermediary devices between endpoint devices, one possible use case for wireless communications includes direct device-to-device communications. The present disclosure presents various techniques for supporting such communications, including features and techniques for performing device-to-device discovery communications using narrower bandwidth communication channels, as well as techniques that may be used more generally for discovery and / or other types of wireless communications.

[0006] According to the techniques described herein, the rate at which false alarms occur when performing discovery detection can be reduced, while having a relatively small impact on the rate at which actual discovery communications are detected. For example, one method of reducing the false alarm rate may include performing a frequency offset estimate consistency check when a candidate discovery signal is detected. It may be possible to use such a check to identify many false alarm candidates (e.g., which may be generated by interference or noise) because actual discovery communications may typically have a smaller frequency offset range relative to such false alarm candidates, and therefore, in at least some embodiments, candidate discovery signals with frequency offsets outside of this range may be reasonably classified as false alarms.

[0007] As another example, another method of reducing the false alarm rate may include performing a peak sidelobe ratio check when a candidate discovery signal is detected. In at least some embodiments, it may be possible to use such a check to identify many false alarm candidates because when there is actual discovery communication, it may typically have a relatively high peak sidelobe ratio, so that a candidate discovery signal with a peak sidelobe ratio below a certain threshold can be reasonably classified as a false alarm.

[0008] At least in some cases, such techniques can be used together, which can reduce false alarm rates to a greater extent than using either technique alone. Alternatively, such techniques can be used alone if desired. Reducing false alarm rates when using such techniques to detect discovery communications may be particularly beneficial for wireless communication scenarios where long-range power-constrained communications are desired, at least according to some embodiments.

[0009] In such cases, it may be further beneficial to increase the likelihood of successfully detecting actual discovery communications. Therefore, at least in some cases, techniques for possible methods of performing timing acquisition and / or frequency offset estimation are also described herein, which can improve the accuracy of discovery signal detection. As possible examples, these methods can include iteratively refining the timing acquisition estimate for the same set of signal samples, iteratively refining the frequency offset estimate for the same set of signal samples, and / or combining iteratively refining the timing acquisition estimate and iteratively refining the frequency offset estimate with each other.

[0010] The techniques described herein may be implemented in and / or used with a number of different types of devices, including, but not limited to, cellular telephones, tablet computers, accessories and / or wearable computing devices, drones, drone controllers, automobiles, and / or motor vehicles, portable media players, cellular base stations and other cellular network infrastructure equipment, servers, and any of a variety of other computing devices.

[0011] This summary 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 subject matter described in this invention in any way. Other features, aspects and advantages of the subject matter described herein will become apparent through the following detailed description, drawings and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] 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.

[0013] Figure 1 An example wireless communication system including an accessory device according to some embodiments is shown;

[0014] Figure 2 An example wireless communication system is shown in which two wireless devices can perform direct device-to-device communication according to some embodiments;

[0015] Figure 3 is a block diagram illustrating an example wireless device according to some embodiments;

[0016] Figure 4 is a block diagram illustrating an example base station according to some embodiments;

[0017] Figure 5 is a communication flow diagram illustrating an exemplary method for performing presence discovery in a wireless communication system according to some embodiments; and

[0018] Figure 6-Figure 8 illustrates possible aspects and features of an exemplary possible narrowband device-to-device communication framework according to some embodiments;

[0019] Fig. 9 is a flow chart illustrating aspects of an exemplary method for performing presence discovery according to some embodiments, wherein a frequency offset error consistency check and a peak-to-sidelobe ratio check are used to reduce false positives;

[0020] Fig.10 is a flow chart illustrating aspects of an exemplary method for performing iterative parameter estimation according to some embodiments;

[0021] Fig.11 is a flow chart illustrating aspects of an exemplary method for performing iterative time offset estimation according to some embodiments;

[0022] Fig.12 is a flow chart illustrating aspects of an exemplary method for performing iterative frequency offset estimation according to some embodiments; and

[0023] Fig.13 is a flow chart illustrating aspects of an exemplary method for performing iterative time and frequency offset estimation 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 are 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] Priority information

[0026] This application claims priority to U.S. Provisional Patent Application Serial No. 62 / 868,364, filed on June 28, 2019, entitled “PRESENCE DISCOVERY TECHNIQUES,” which is hereby incorporated by reference in its entirety as if fully set forth herein.

[0027] Acronyms

[0028] The following acronyms are used in this disclosure.

[0029] 3GPP: Third Generation Partnership Project

[0030] 3GPP2: Third Generation Partnership Project 2

[0031] GSM: Global System for Mobile Communications

[0032] UMTS: Universal Mobile Telecommunications System

[0033] LTE: Long Term Evolution

[0034] IoT: Internet of Things

[0035] NB: Narrow Band

[0036] D2D: Device to Device

[0037] OOC: Out of Coverage

[0038] the term

[0039] The following are definitions of terms used in this disclosure:

[0040] Memory medium - any of various types of non-transitory memory devices or storage devices. The term "memory medium" is intended to include installation media, for example, CD-ROM, floppy disk or tape device; 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 a combination 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.

[0041] 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.

[0042] 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".

[0043] 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.

[0044] User Equipment (UE) (or "UE device") - any of various types of computer systems or devices that are mobile or portable and that perform wireless communications. Examples of UE devices include mobile phones or smartphones (e.g., iPhones). TM , based on Android TM phones), tablets (e.g., iPad TM 、Samsung Galaxy TM ), 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, other handheld devices, cars and / or motor vehicles, unmanned aerial vehicles (UAVs) (e.g., remotely piloted aircraft), unmanned aerial vehicle controllers (UACs), etc. In general, the term "UE" or "UE device" can be broadly defined to include any electronic device, computing device, and / or telecommunication device (or a combination of these devices) that is convenient for a user to transport and capable of wireless communication.

[0045] Wireless Device—Any of various types of computer systems or devices that perform wireless communications. A wireless device may be portable (or mobile), or may be stationary or fixed at a certain location. A UE is an example of a wireless device.

[0046] Communication device - any of various types of computer systems or devices that perform communication, where the communication may be wired or wireless. A communication device may be portable (or mobile), or may be stationary or fixed at a location. A wireless device is an example of a communication device. A UE is another example of a communication device.

[0047] 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 communication system.

[0048] Link budget limited—includes the full range of its ordinary meaning and includes at least the characteristics of a wireless device (e.g., UE) that exhibits limited communication capabilities or limited power relative to a device that is not link budget limited or relative to a device for which a radio access technology (RAT) standard has been developed. A link budget limited wireless device may experience relatively limited receive capabilities and / or transmit capabilities, which may be due to one or more factors, such as device design, device size, battery size, antenna size or design, transmit power, receive power, current transmission medium conditions, and / or other factors. Such devices may be referred to herein as "link budget limited" (or "link budget constrained") devices. A device may be inherently link budget limited due to the size of the device, battery power, and / or transmit / receive power. For example, a smart watch that communicates with a base station via LTE or LTE-A may be inherently link budget limited due to its reduced transmit / receive power and / or antenna reduction. Wearable devices such as smart watches are generally link budget limited devices. Alternatively, a device may not be inherently link budget limited, e.g., may have sufficient size, battery power, and / or transmit / receive power for normal communication over LTE or LTE-A, but may be temporarily link budget limited due to current communication conditions, e.g., a smartphone at a cell edge, etc. It is noted that the term "link budget limited" includes or encompasses power limitations, and thus a link-limited device may be considered a link budget limited device.

[0049] Processing element (or processor) - refers to various elements or combinations of elements that are capable of performing functions in a device (e.g., a user equipment device or a cellular network device). A processing element may include, for example, a processor and associated memory, portions or circuits of individual processor cores, entire processor cores, separate processors, processor arrays, circuits such as ASICs (application specific integrated circuits), programmable hardware elements such as field programmable gate arrays (FPGAs), and any of the above combinations.

[0050] 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 checkboxes, 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.

[0051] Configured to - Various components may be described as being "configured to" perform one or more tasks. In such environments, "configured to" is a broad statement that generally means "having a structure" that performs one or more tasks during operation. Thus, even when the component is not currently performing the task, the component can be configured to perform the task (e.g., a set of electrical conductors can be configured to electrically connect a module to another module even when the two modules are not connected). In some environments, "configured to" can be a broad statement that generally means "having a circuit system that performs one or more tasks during operation." Thus, even when the component is not currently turned on, the component can be configured to perform the task. Typically, the circuitry that forms the structure corresponding to "configured to" may include hardware circuits.

[0052] For ease of description, various components may be described as performing one or more tasks. Such descriptions should be interpreted as including the phrase "configured to". The description of a component being configured to perform one or more tasks is expressly intended to not invoke the interpretation of the sixth paragraph of Section 112 of Title 35 of the United States Code on that component.

[0053] Figure 1-Figure 2 —Wireless communication system

[0054] Figure 1 An example of a wireless cellular communication system is illustrated. It should be noted that Figure 1 This represents one possibility among many, and the features of the present disclosure may be implemented by any of a variety of systems as desired.For example, the embodiments described herein may be implemented in any type of wireless device.

[0055] As shown, the exemplary wireless communication system includes a cellular base station 102 that communicates over a transmission medium with one or more wireless devices 106A, 106B, etc., and an accessory device 107. Wireless devices 106A, 106B, and 107 may be user equipment, which may be referred to herein as "user equipment" (UE) or UE devices.

[0056] Base station 102 may be a base transceiver station (BTS) or a cell site and may include hardware and / or software that implements wireless communication with UE devices 106A, 106B, and 107. If base station 102 is implemented in the context of LTE, it may be referred to as an "eNodeB" or "eNB". If base station 102 is implemented in the context of 5G NR, it may alternatively be referred to as a "gNodeB" or "gNB". Base station 102 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, as well as various possible networks). Therefore, base station 102 may facilitate communication between UE device 106 and UE device 107 and / or communication between UE device 106 / 107 and network 100. Also as used herein, with respect to UE, sometimes a base station may be considered to represent a network in consideration of uplink and downlink communications of the UE. Therefore, a UE that communicates with one or more base stations in a network may also be understood as a UE that communicates with a network.

[0057] In other embodiments, the base station 102 may be configured to provide communications via one or more other wireless technologies, such as an access point supporting one or more WLAN protocols, such as 802.11a, b, g, n, ac, ad and / or ax, or LTE in an unlicensed band (LAA).

[0058] The communication area (or coverage area) of the base station 102 may be referred to as a “cell.” The base station 102 and the UE 106 / 107 may be configured to communicate over a transmission medium using any of various radio access technologies (RATs) or wireless communication technologies, such as GSM, UMTS (WCDMA, TDS-CDMA), LTE, Advanced LTE (LTE-A), NR, HSPA, 3GPP2CDMA2000 (e.g., 1xRTT, 1xEV-DO, HRPD, eHRPD), Wi-Fi, etc.

[0059] Thus, base station 102 and other similar base stations (not shown) operating according to one or more cellular communication technologies can be provided as a cell network that can provide continuous or near-continuous overlapping service to UE devices 106A-N and UE device 107 and similar devices within a geographic area via one or more cellular communication technologies.

[0060] Note that, at least in some cases, UE device 106 / 107 may be capable of communicating using any of a variety of wireless communication technologies. For example, UE device 106 / 107 may be configured to communicate using one or more of GSM, UMTS, CDMA2000, LTE, LTE-A, NR, WLAN, Bluetooth, one or more global navigation satellite systems (GNSS, such as GPS or GLONASS), one and / or more mobile television broadcast standards (e.g., ATSC-M / H), etc. Other combinations of wireless communication technologies (including more than two wireless communication technologies) are also possible. Similarly, in some cases, UE device 106 / UE device 107 may be configured to communicate using only a single wireless communication technology.

[0061] UE 106A and UE 106B may include handheld devices such as smart phones or tablets, and / or may include any of various types of devices with cellular communication capabilities. For example, one or more of UE 106A and UE 106B may be wireless devices intended for static or dynamic deployment, such as home appliances, measurement devices, control devices, etc. UE 106B may be configured to communicate with UE device 107, which may be referred to as accessory device 107. Accessory device 107 may be any of various types of wireless devices, which may generally be wearable devices with a small form factor and limited battery, output power and / or communication capabilities relative to UE 106. As a common example, UE 106B may be a smart phone carried by a user, and accessory device 107 may be a smart watch worn by the same user. UE 106B and accessory device 107 may communicate using any of various short-range communication protocols, such as Bluetooth or Wi-Fi.

[0062] UE 106B may also be configured to communicate with UE 106A. For example, UE 106A and UE 106B may be able to perform direct device-to-device (D2D) communications. D2D communications may be supported by cellular base station 102 (e.g., BS 102 may facilitate discovery, as well as various possible forms of assistance), or may be performed in a manner that is not supported by BS 102. For example, according to at least some aspects of the present disclosure, UE 106A and UE 106B may be able to arrange and perform D2D communications (e.g., including discovery communications) even when out of coverage of BS 102 and other cellular base stations.

[0063] Figure 2 Example UE devices 106A, 106B are shown in D2D communication with each other. The UE devices 106A, 106B may be a mobile phone, tablet or any other type of handheld device, a smart watch or other wearable device, a media player, a computer, a laptop, an unmanned aerial vehicle (UAV), an unmanned aerial vehicle controller (UAC), a car, or virtually any type of wireless device.

[0064] UE 106A, 106B may include a device or integrated circuit called a cellular modem for facilitating cellular communications. The cellular modem may include one or more processors (processing elements) configured to execute program instructions stored in a memory and / or various hardware components described herein. UE 106A, 106B may perform any of the method implementation schemes described in the present invention by executing such stored instructions. Alternatively or in addition, UE 106A, 106B may include programmable hardware elements, such as FPGAs (field programmable gate arrays), integrated circuits, and / or any of various other possible hardware components configured to perform (e.g., individually or in combination) any of the method implementation schemes described herein or any part of any of the method implementation schemes described herein. The cellular modem described herein may be used in a UE device as defined herein, a wireless device as defined herein, or a communication device as defined herein. The cellular modem described herein may also be used in a base station or other similar network-side device.

[0065] UE 106A, 106B may include one or more antennas for communicating using one or more wireless communication protocols according to one or more RAT standards. In some embodiments, one or both of UE 106A or UE 106B may be configured to communicate using a single shared radio component. The shared radio 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 radio frequency (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.

[0066] Alternatively, UE 106A and / or UE 106B may include two or more radio components. For example, in some embodiments, UE 106A and / or UE 106B may include a separate transmission chain and / or reception chain (e.g., including separate antennas and other 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 106A and / or UE 106B may include a shared radio component for communicating using any of LTE or CDMA2000 1xRTT (or LTE or GSM), and a shared radio component for communicating using Wi-Fi and BLUETOOTH. TM Each of the independent radio components for communication. Other configurations are also possible.

[0067] Figure 3 —Block diagram of UE equipment

[0068] Figure 3One possible block diagram of a UE device, such as UE device 106 or UE device 107, is shown. As shown, UE device 106 / 107 may include a system on chip (SOC) 300, which may include parts for various purposes. For example, as shown, SOC 300 may include a processor 302 and a display circuit 304, the processor 302 may execute program instructions for UE device 106 / 107, and the display circuit 304 may perform graphics processing and provide display signals to a display 360. SOC 300 may also include motion sensing circuit 370, which may detect the motion of UE 106, for example, using any of a gyroscope, an accelerometer, and / or various other motion sensing components. Processor 302 may also be coupled to a memory management unit (MMU) 340, which may be configured to receive addresses from processor 302 and translate those addresses into locations in memory (e.g., memory 306, read-only memory (ROM) 350, flash memory 310) and / or other circuits or devices, such as display circuit 304, radio 330, I / F 320, and / or display 360. MMU 340 may be configured to perform memory protection and page table translation or setup. In some embodiments, MMU 340 may be included as part of processor 302.

[0069] As shown, the SOC 300 may be coupled to various other circuits of the UE 106 / 107. For example, the UE 106 / 107 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, a docking station, a charging station, etc.), a display 360, and wireless communication circuits 330 (e.g., for LTE, LTE-A, NR, CDMA2000, Bluetooth, Wi-Fi, NFC, GPS, etc.).

[0070] The UE device 106 / 107 may include at least one antenna and may include multiple antennas 335a and 335b for performing wireless communications with a base station and / or other devices in some embodiments. For example, the UE device 106 / 107 may use antennas 335a and 335b to perform wireless communications. As described above, the UE device 106 / 107 may be configured to use multiple wireless communication standards or radio access technologies (RATs) for wireless communications in some embodiments.

[0071] Wireless communication circuitry 330 may include Wi-Fi logic 332, cellular modem 334, and Bluetooth logic 336. Wi-Fi logic 332 is used to enable UE device 106 / 107 to perform Wi-Fi communications on an 802.11 network. Bluetooth logic 336 is used to enable UE device 106 / 107 to perform Bluetooth communications. Cellular modem 334 may be a lower power cellular modem capable of performing cellular communications according to one or more cellular communication technologies.

[0072] As described herein, UE 106 / 107 may include hardware components and software components for implementing embodiments of the present disclosure. The processor 302 of UE device 106 / UE device 107 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). In other embodiments, one or more processors 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). In addition, the processor 302 may be coupled to a processor such as a processor 106 / 107. Figure 3 The other components shown and / or may interoperate with other components to perform discovery detection according to various embodiments disclosed herein. The one or more processors 302 may also implement various other applications and / or end-user applications running on the UE 106. Alternatively or in addition, one or more components of the wireless communication circuit 330 (e.g., cellular modem 334) of the UE device 106 / 107 may be configured as a processor that executes program instructions stored on a memory medium (e.g., a non-transitory computer-readable memory medium), is configured as an FPGA (field programmable gate array) and / or uses a processor of a dedicated hardware component that may include an ASIC (application-specific integrated circuit) to implement part or all of the methods described herein.

[0073] Figure 4 —Block diagram of a base station

[0074] Figure 4 An exemplary block diagram of a base station 102 according to some embodiments 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 or other circuit or device, 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).

[0075] The base station 102 may include at least one network port 470. Figure 1 and Figure 2 As described in , the network port 470 may be configured to couple to a telephone network and provide multiple devices, such as the UE devices 106 / 107 , with access to the telephone network.

[0076] The network port 470 (or an additional network port) may also be configured or alternatively configured to be coupled 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 UE devices 106 / 107. For example, the core network may include, for example, a mobility management entity (MME) for providing mobility management services, a serving gateway (SGW) and / or a packet data network gateway (PGW) for providing external data connections such as to the Internet, and the like. 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., between other UE devices served by the cellular service provider).

[0077] The base station 102 may include at least one antenna 434 and possibly multiple antennas. One or more antennas 434 may be configured to operate as a wireless transceiver and may be further configured to communicate with the UE device 106 / 107 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 communication standards, including but not limited to LTE, LTE-A, NR, GSM, UMTS, CDMA2000, Wi-Fi, etc.

[0078] Base station 102 may be configured to communicate wirelessly using multiple wireless communication standards. In some cases, base station 102 may include multiple radios that enable base station 102 to communicate according to multiple wireless communication technologies. For example, as one possibility, base station 102 may include an LTE radio for performing communications according to LTE and a Wi-Fi radio for performing communications according to Wi-Fi. In such cases, base station 102 may be capable of operating as both an LTE base station and a Wi-Fi access point. As another possibility, base station 102 may include a multimode radio component capable of performing communications according to any of multiple wireless communication technologies (e.g., LTE and NR, LTE and Wi-Fi, LTE and UMTS, LTE and CDMA2000, UMTS and GSM, etc.).

[0079] As further described later in the present invention, the base station 102 may include hardware and software components for implementing or supporting the implementation of the features described in the present invention. For example, although many of the features described herein relate to device-to-device communication that can be performed by a UE device without relying on an intervening base station, a cellular base station can be configured so that it can also perform device-to-device communication according to the features described herein. As another possibility, the BS 102 may help configure the UE 106 to perform device-to-device communication according to the features described herein, and / or the specific features described herein may be performed or not performed by the device at least in part based on whether there is a BS 102 providing cellular service within the device range. According to some embodiments, 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 combination with one or more of the other components 430, 432, 434, 440, 450, 460, and 470, the processor 404 of the base station 102 may be configured to implement or support some or all of the embodiments of the features described herein.

[0080] Figure 5 -Communication Flowchart

[0081] Figure 5 1 is a communication flow diagram illustrating a method for performing presence discovery in a wireless communication system according to some embodiments. In various embodiments, some of the illustrated method elements may be performed simultaneously in an order different from the order shown, may be replaced by other method elements, or may be omitted. Additional method elements may also be performed as needed.

[0082] Figure 5 Aspects of the method may be performed by a wireless device, such as in Figure 1-Figure 3 shown in and relative to Figure 1-Figure 3 The UE 106A-B or UE 107 described above can be implemented, or more generally, can be implemented in other devices in combination with any of the computer systems or devices shown in the above figures as needed. Figure 5 At least some elements of the method are described in terms of the use of communication technologies and / or features associated with LTE and / or 3GPP specification documents, but such description is not intended to limit the present disclosure and can be used in any suitable wireless communication system as needed. Figure 5 Aspects of the method. As shown, the method can be operated as follows.

[0083] In 502, the wireless device may monitor the wireless medium for discovery signals. For example, the wireless device may act as a potential discovery responder, attempting to determine whether any discovery signals are being transmitted to the wireless device by another wireless device acting as a discovery initiator in a device-to-device (D2D) wireless communication framework. According to at least some embodiments, the wireless medium may include one or more narrowband Internet of Things (NB-IoT) carriers, and / or may be any of a variety of other possible (e.g., narrowband) carriers.

[0084] According to some embodiments, the wireless device may monitor the wireless medium during a "discovery period" or "discovery window" defined within the wireless communication system framework. As one possibility, monitoring the wireless medium for discovery signals may include correlating signals received on the wireless medium with one or more known discovery preamble signals (e.g., as specified by the wireless communication system).

[0085] In 504, the wireless device may determine that a candidate discovery signal is detected. In some cases, the wireless device may determine that multiple candidate discovery signals are detected during a discovery period or discovery window in which the wireless device monitors the wireless medium for discovery signals. Determining that a candidate discovery signal is detected may be performed in any of a variety of possible ways. As one such possibility, the wireless device may determine that a candidate discovery signal is detected if correlating a signal received on the wireless medium with a known discovery preamble signal results in a correlation peak greater than a correlation peak threshold (e.g., for a particular set of signal samples).

[0086] In some embodiments, an iterative method may be used to perform frequency offset estimation and / or time offset estimation on the candidate discovery signal. According to at least some embodiments, such methods may improve the accuracy of candidate discovery signal detection.

[0087] For example, as a possible iterative method for performing frequency offset estimation, the wireless device may use a first number of neighboring samples (which may be a relatively small number of neighboring samples) to obtain a first frequency offset estimate for a candidate discovery signal, for example, at least as a possibility, the neighboring samples are selected to tolerate the maximum possible impairment caused by the target estimate in the original received signal and to achieve the maximum parameter estimation range in the original received signal. The first frequency offset estimate may be used to compensate the received signal, and the wireless device may determine a second number of neighboring samples for a second frequency offset estimate on the same signal. The second number of neighboring samples may be greater than the first number of neighboring samples, for example, to improve estimation accuracy. The wireless device may then use the second number of neighboring samples to obtain a second (e.g., refined) frequency offset estimate for the compensated candidate discovery signal. The wireless device may perform further iterations (e.g., further compensate the candidate discovery signal and increase the number of neighboring samples used to perform frequency offset estimation) as needed (or until the tunable range of the number of neighboring samples is reached), for example, to further improve estimation accuracy. In other words, the wireless device may obtain a frequency offset estimate for the candidate discovery signal and iteratively refine the frequency offset estimate, wherein at each iteration, the candidate discovery signal is compensated by the frequency offset estimate from the previous iteration and an increasing number of neighboring samples are used.

[0088] Similarly, as a possible iterative method of performing time offset estimation, the wireless device may use a first number of neighboring resource elements (which may be a relatively small number of neighboring resource elements) to obtain a first time offset estimate for a candidate discovery signal, for example, at least as a possibility, the neighboring samples are selected to tolerate the maximum possible impairment caused by the target estimate in the original received signal and to achieve the maximum parameter estimation range in the original received signal. The received signal may be compensated using the first time offset estimate, and the wireless device may determine a second number of neighboring resource elements for a second time offset estimate on the same signal. The second number of neighboring resource elements may be greater than the first number of neighboring resource elements, for example, to improve estimation accuracy. The wireless device may then use the second number of neighboring resource elements to obtain a second (e.g., refined) time offset estimate for the compensated candidate discovery signal. The wireless device may perform further iterations (e.g., further compensate the candidate discovery signal and increase the number of neighboring resource elements used to perform time offset estimation) as needed (or until the tunable range of the number of neighboring resource elements is reached), for example, to further improve estimation accuracy. In other words, the wireless device may obtain a time offset estimate for the candidate discovery signal and iteratively refine the time offset estimate, wherein at each iteration, the candidate discovery signal is compensated by the time offset estimate from the previous iteration and an increasing number of adjacent frequency resource elements are used.

[0089] As another possibility, a combined iterative time offset estimation and frequency offset estimation method may be used if desired. For example, the wireless device may perform coarse timing acquisition on the candidate discovery signal, and then perform coarse frequency offset estimation on the candidate discovery signal based on the coarse timing acquisition. As a further iteration, the wireless device may then perform fine timing acquisition on the candidate discovery signal based on the coarse frequency offset acquisition; and perform fine frequency offset estimation on the candidate discovery signal based on the fine timing acquisition. Thus, coarse timing acquisition, coarse frequency offset estimation, fine timing acquisition, and fine frequency offset estimation may be iteratively performed on the same set of signal samples of the candidate discovery signal, as well as possibly any desired number of further iterations of timing acquisition and frequency offset estimation.

[0090] According to at least some embodiments, such methods that may be capable of providing significantly improved estimation accuracy for a set of signal samples relative to non-iterative methods may be particularly useful in D2D discovery scenarios that may be performed over long distances between power-constrained devices (e.g., UEs). For example, in such scenarios, it may be the case that discovery transmissions are performed infrequently and at a relatively high power cost. Thus, techniques that may provide improved detection of individual discovery transmissions (including by providing more accurate time and / or frequency offset estimates), or that may at least reduce the number of discovery signal repetitions required to perform discovery, may beneficially reduce power costs to a transmitting device (e.g., a discovery initiator) and time delays for two peer entities to establish a D2D communication link.

[0091] It may also improve discovery performance in such long-range D2D communication scenarios (e.g., where noise and / or interference may co-occur) to provide techniques to reduce the number of instances where a wireless device determines that it has detected a discovery signal but the detected discovery signal is not an actual discovery signal. Thus, in some embodiments, a wireless device may additionally or alternatively implement one or more techniques that may reduce this "false positive" (or "false alarm") rate when performing discovery.

[0092] In 506, the wireless device may determine whether the candidate discovery signal is a false positive based on one or more checks or tests. One such possible check may include a frequency offset estimate consistency check. Another such possible check may include a peak-to-sidelobe ratio check.

[0093] According to some embodiments, the frequency offset estimate consistency check may include determining whether the estimated frequency offset of the candidate discovery signal exceeds a frequency offset threshold. In some cases, multiple frequency offset estimates of the candidate discovery signal may be obtained, for example, using different time lags. In such cases, if the relative difference between the different frequency offset estimates of the candidate discovery signal exceeds the relative frequency offset difference threshold, it may be determined that the candidate discovery signal has not passed the frequency offset estimate check, and if the relative difference between the different frequency offset estimates of the candidate discovery signal does not exceed the relative frequency offset difference threshold, it may be determined that the candidate discovery signal has passed the frequency offset estimate check. As another possibility, if any of the frequency offset estimates of the candidate discovery signal exceeds the absolute frequency offset threshold, it may be determined that the candidate discovery signal has not passed the frequency offset estimate check, and if none of the frequency offset estimates of the candidate discovery signal exceeds the absolute frequency offset threshold, it may be determined that the candidate discovery signal has passed the frequency offset estimate check.

[0094] According to some embodiments, the peak sidelobe ratio check includes determining whether the estimated peak sidelobe ratio of the candidate discovery signal exceeds a peak sidelobe ratio threshold. For example, the wireless device may calculate the peak sidelobe ratio of the candidate discovery signal, determine that the candidate discovery signal passes the peak sidelobe ratio check if the peak sidelobe ratio is greater than the peak sidelobe ratio threshold, and determine that the candidate discovery signal fails the peak sidelobe ratio check if the peak sidelobe ratio is less than the peak sidelobe ratio threshold.

[0095] As previously described, the frequency offset estimate consistency check and the peak sidelobe ratio check may be used alone or in combination (and may be used in combination with one or more other checks or tests as desired). As one possibility, if they are used in combination, if the candidate discovery signal does not pass the frequency offset estimate consistency check or the peak sidelobe ratio check, the wireless device may determine that the candidate discovery signal is a false positive, and if the candidate discovery signal passes both the frequency offset estimate consistency check and the peak sidelobe ratio check, it may be determined that the candidate discovery signal is an actual detected discovery signal. Other methods are also possible.

[0096] As previously mentioned, in some cases, the wireless device may detect multiple candidate discovery signals. In such scenarios, it may be the case that the wireless device determines whether each candidate discovery signal is a false alarm or an actual detected discovery signal in a similar manner, for example, by checking whether the candidate discovery signal passes a frequency offset estimation consistency check, a peak-to-sidelobe ratio check, and / or one or more other checks / tests, as needed.

[0097] In some embodiments, if the wireless device determines that the discovery signal is detected and is not a false alarm, the wireless device may determine that an actual discovery signal is detected. In such cases, the wireless device may respond to the discovery signal and / or otherwise proceed with further discovery signaling, for example, according to a discovery framework of the wireless communication system used by the wireless device. For example, among various possibilities, the discovery response transmission may include a response that helps the discovery initiator track the wireless device, and / or may include a connection request message.

[0098] Note that although Figure 5 The method is primarily directed to D2D communication between two wireless devices, but similar techniques may be used to establish and communicate based on any number of additional D2D connections between wireless devices, and / or more generally for other types of presence discovery communications. For example, a wireless device may utilize similar techniques to establish additional D2D connections with any number of wireless devices in parallel, and communicate with those wireless devices based on those additional D2D connections. Figure 5 At least some of the techniques described in the method may be used in other wireless communication contexts (e.g., in addition to or as an alternative to D2D communications). For example, a wireless device may benefit from utilizing an iterative approach for timing acquisition and / or frequency offset estimation in any of a variety of wireless communication systems, among various other possibilities.

[0099] Figure 6-Figure 13 and additional information

[0100] Provided Figure 6-Figure 13 and the following additional information, which illustrates the Figure 5 Further considerations and possible specific implementation details of the method are not intended to limit the present disclosure as a whole. Various variations and alternatives to the details provided below are possible and should be considered to fall within the scope of the present disclosure.

[0101] At least some existing wireless communication technologies include framework elements for device-to-device communication, also referred to as sidelink communication. For example, the 3GPP standards organization includes D2D / sidelink protocols such as Proximity Services (ProSe), for example, where in addition to synchronization signals transmitted in the central 6RBs of the system bandwidth, discovery pool resources, sidelink protocol channel allocations, and sidelink shared channel allocations can be located in various other (e.g., outer) RBs of the system bandwidth over time. Performing such sidelink communications in accordance with existing D2D protocols can cover relatively wideband operations, for example, covering at least 6RBs (e.g., 1.4MHz) and potentially up to 100RBs (e.g., 20MHz).

[0102] While such a potential wideband D2D framework may be useful in some cases, in at least some cases, a narrower deployment may be advantageous. For example, for the transmission power regime of many devices, the propagation characteristics used for narrowband communication may result in a greater range capacity than wider bandwidth communication. It should be noted that, at least in some instances, if a lower frequency communication band is used for narrowband D2D communication (e.g., as a possibility, 900 MHz unlicensed spectrum), the effective communication range can be further increased. As another possibility, some (e.g., lower complexity) devices may be configured to perform only narrowband communications (e.g., may have RF front-end limitations, and / or may have battery limitations that functionally limit the ability to perform wider bandwidth communications). As another possibility, some devices, even if capable of both wideband and narrowband communications, may preferably perform narrowband communications when possible, for example, if narrowband communications can reduce device power consumption.

[0103] Thus, at least according to some embodiments, narrowband (e.g., 180kHz) D2D communication systems may also or alternatively be used. According to some embodiments, such techniques may be used for situations when one or more of the communicating wireless devices are not within the communication range of a cellular base station (e.g., the devices may be OOC).

[0104] For example, such systems may be developed to provide long-range peer-to-peer (P2P) / D2D communications, e.g., in the absence of a wide area network (WAN) or WLAN radio connection, and support a variety of possible features. At least according to some embodiments, such systems may support the aforementioned Figure 5 Some or all of the features described.

[0105] According to some embodiments, such systems may operate in unlicensed low ISM bands, e.g., between 700 MHz and 1 GHz, for extended range purposes, and may use one or more carriers of approximately 200 kHz. Such systems may be designed to meet local spectrum regulatory requirements, such as channel duty cycle, operating frequency, hopping pattern, LBT, maximum transmit power, and occupied bandwidth.

[0106] As one possibility to provide a physical narrowband carrier for narrowband D2D communications, a NB-IoT carrier may be used. According to some embodiments, the NB-IoT carrier may be configured for use in a standalone deployment (e.g., in a repurposed GSM band), a guard band deployment (e.g., in a guard band frequency between LTE carriers), and an intra-band deployment (e.g., within an LTE carrier). Alternatively, the NB-IoT carrier may be used in an unlicensed band. In any of these possible deployment modes, the NB-IoT carrier may include a variety of key features. For example, according to some embodiments, among various possible features, the NB-IoT carrier may support flexible timelines for control and data channels; may support peak rates of approximately 20 kbps in the downlink and 60 kbps in the uplink; may use single-tone (e.g., 3.75 KHz and 15 KHz) and multi-tone (15 kHz) uplink modulation using pi / 2 binary phase shift keying or pi / 4 quadrature phase shift keying (quadrature phase shift keying may also be used in the downlink); may use a single antenna, half-duplex frequency division multiplexing; and / or may use a carrier bandwidth of 180 kHz per UE. A frequency hopping feature for D2D communications may be supported. In some cases, the NB-IoT carrier may provide a coverage enhancement feature for supporting up to 20 dB of coverage. Alternatively, any number of other physical narrowband carriers may be used in a narrowband D2D communication system.

[0107] Any of the various features may be included in a D2D system, including when operating in a regulated unlicensed spectrum, such as an unlicensed spectrum of 900 MHz. For example, frequency hopping (FHSS) may be used. The channel carrier frequencies may be separated by a minimum of 25 kHz, or the hopping channels may be separated by a 20 dB bandwidth, whichever is greater. If the 20 dB bandwidth is less than 250 kHz (for example, this may be the case if an NB-IoT carrier is used), the system may use at least 50 channels. In this case, the average dwell time on a particular channel may not exceed 400 ms (for example, duty cycle <= 2%) over a period of 20 seconds, and / or the transmission power may not be higher than 30 dBm. If the 20 dB bandwidth is 250 kHz or higher, the system may use at least 25 channels. In this case, the average dwell time may not exceed 400 ms (for example, duty cycle <= 4%) over a period of 10 seconds, and / or the transmission power may not be higher than 24 dBm. For example, the following table shows a possible set of specified characteristics for a possible D2D communication system, depending on the 20dB bandwidth of the hopping channel used:

[0108] BW Channel Number TX Power time Dwell time <250KHz >＝50 30dBm 400ms 20 seconds >250KHz >＝25 24dBm 400ms 10 seconds

[0109] Thus, as an exemplary possibility, if the 900MHz unlicensed band (US ISM 900, 902-918MHz) is used with a NB-IoT carrier (e.g., each with 200kHz, including guard bands), a combination of 80 frequencies may be configured. In another configuration, a combination of 130 frequencies covering 902-928MHz may be used. Other frequency combinations, e.g., with other numbers of available frequencies, are also possible. Various combinations of these frequencies may be configured as "scanning channels" and "paging channels" that may be used for discovery and / or other purposes, if desired.

[0110] For example, Figure 6 One possible interval structure for a synchronization preamble based framework that can be used for D2D communication is shown. According to the interval structure shown, the overall timeline structure can be based on the UE local UTC time consisting of regular discovery intervals. Each discovery interval can have a predefined length (e.g., 720ms, or any other desired length) and can have a start time based on a public UE ID known system-wide (or at least group-wide). The hopping interval can have the same length as the discovery interval and can have a predefined offset from the discovery interval (e.g., 360ms, or any other desired offset).

[0111] As shown, the discovery interval may include three types of time resources: synchronization preamble, anchor preamble, and frequency hopping unit (which may include one or more resource units).

[0112] According to some embodiments, each synchronization preamble may have a predefined length (e.g., 50ms, or any other desired length) and may be a preamble for initial synchronization and data access of a new data session starting with a discovery interval (without pre-synchronization). In other words, the synchronization preamble may be transmitted by the UE at the start time of the discovery interval to start a new data session without pre-synchronization. For broadcast services, such as presence discovery, some common synchronization preambles may be predefined. The UE may also have its own dedicated synchronization preamble, which may hop at each hopping interval based on the UE ID and the UE local UTC time. For example, the synchronization preamble pool may be divided into a certain number of groups (e.g., each group is associated with a synchronization ID), wherein each group includes a certain number of synchronization sequences. Therefore, the public synchronization ID set may have several synchronization IDs for public use, and the dedicated synchronization ID set may therefore have the remaining synchronization IDs that can be used for each UE. In such cases, the UE synchronization preamble hopping performed at each hopping interval based on the UE ID and the UE local UTC time may be in the dedicated synchronization ID set associated with the UE. The frequency used to transmit the synchronization preamble may also be hopped at each hopping interval based on the UE ID and the UE local UTC time.

[0113] The synchronization preamble window can be used to receive a synchronization preamble transmitted by another UE. According to some embodiments, there may be multiple (e.g., 3 or another number) types of synchronization preamble windows. For example, a normal synchronization preamble window may be aligned with the beginning of a discovery interval, but with + / - normal drift space. As a possibility, the length of a normal synchronization preamble window may be equal to the synchronization preamble length plus twice the normal drift space. A long synchronization preamble window may be a synchronization preamble window aligned similarly to the length of the discovery interval plus twice the normal drift space. An extended synchronization preamble window may be a synchronization preamble window extended to multiple lengths of the discovery interval. For example, as a possibility, the length may be several multiples of the length of the discovery interval, which is equal to the number of days that the UE has been outside the GNSS coverage. Other values ​​are also possible.

[0114] The anchor preamble may be a reference signal used for synchronization tracking and data access. The anchor preamble may be transmitted at the start time of a scheduling interval to start a new data session with a UE that has already synchronized with it. According to some embodiments, the anchor preamble may be scrambled with a golden sequence based on the UE ID and the link ID. The sequence used for the anchor preamble may hop between a set of such sequences at each hopping interval, for example, based on the UE ID and the UE local UTC time. According to at least some embodiments, the anchor preamble may be scrambled with a golden sequence based on the UE ID and the link ID. Figure 6 The scheduling interval may be the shortest configured packet exchange session length between peer UEs. It may include multiple hopping units, each of which may include one or more resource units. A data packet may span one or more hopping units. A hopping unit may be a time unit for hopping in a hopping interval. A resource unit may be a resource allocation unit specified according to NB-IoT.

[0115] exist Figure 6 In an interval structure, frequency hopping may be used at specific intervals. According to some embodiments, a system deployed according to such a framework may include a certain number of frequency channels (e.g., as a possibility, 63, or any other desired number), which may be randomly reordered in each regular frequency hopping interval based on a common UE ID and local UTC time. It is noted that the scheduling interval may be shared by a clock master and a clock slave, so that the FH units in the scheduling interval may follow the FH sequence of the clock master, and the clock slave UE follows the timing and FH sequence of the clock master for transmission and reception. According to at least some embodiments, different scheduling intervals may have the same or different clock master and slave pairs.

[0116] Figure 7 Also shown according to some embodiments Figure 6Possible idle procedure aspects of such a framework are shown. As shown, a UE in idle mode may perform a periodic search for a relevant synchronization preamble in a normal synchronization preamble window in each discovery interval, e.g., to receive a synchronization preamble from a UE whose UTC time difference from the local UTC time is less than or equal to twice the normal drift space.

[0117] According to some embodiments, wireless devices participating in such D2D communication schemes may be assigned a physical layer (PHY) synchronization identifier (sync ID). The PHY sync ID may represent a set of dedicated preamble sequences associated with the wireless device. One or more common preamble sequences may also be configured, for example, to indicate certain public discovery messages. Thus, if a 7-bit PHY sync ID is used, 125 PHY sync IDs may be feasible, which represents 125 preamble groups. If 4 sequences are provided for each group, and 4 common sequences are provided, a total of 504 preamble sequences may be configured.

[0118] The synchronization preamble sequence may be used for initial symbol timing correction and carrier frequency offset (CFO) correction, as well as for synchronization preamble type detection (eg, if applicable) and PHY synchronization ID detection. Figure 8 Shows such as Figure 6 Sync preamble transmission within the sync preamble window of the discovery interval shown. A wireless device detecting a preamble during such a D2D period can determine whether the preamble is a common preamble or a preamble associated with its PHY sync ID (e.g., in which case the wireless device can further listen to one or more discovery messages) or a preamble associated with another PHY sync ID (e.g., in which case the wireless device can continue DRX for the remainder of the D2D period). Once the discovery process is completed between the two wireless devices, both the initiator UE and the receiver UE can be in a discovered state relative to each other, and the wireless devices can be able to perform D2D data communication.

[0119] Therefore, according to Figure 6In the communication framework of D2D communication systems, as well as in many other D2D communication systems, discovery technology can be an important part of the entire communication framework. The process of detecting whether a discovery initiator (DI) sends a unique preamble sequence at a discovery responder (DR) (e.g., during a discovery window) may be referred to as presence discovery detection (PDD). At least in some cases, the design metrics of PDD may include low false detection rates and low false alarm rates, such as to minimize system power usage. The presence of false alarms can typically be caused by interference and / or noise. Therefore, it may be useful to provide a method for minimizing the false alarm rate while maintaining a low false detection rate when performing PDD. Such methods may include methods based on performing frequency offset estimation consistency (FOEC) checks, methods based on performing peak sidelobe ratio (PSR) checks, and / or methods based on performing both FOEC checks and PSR checks.

[0120] In at least some embodiments, with respect to correctly detected discovery signals, the absolute frequency difference of the frequency offset estimate may be low enough for most cases that a threshold can be defined that excludes a significant portion of false positive instances while excluding a relatively small number of correctly detected discovery signals.

[0121] In addition, at least in some embodiments, for correct detection, frequency offset estimates from different methods (e.g., by selecting different time lags) may generally be consistent, while for false alarms, different frequency offset estimates may vary significantly. Therefore, one possible method of performing a FOEC check may include performing a default PDD for each input sample, and performing an additional PDD to obtain a different frequency estimate (e.g., with a different time lag) when a potential peak is detected. This process may be repeated until the current preamble search window ends. After the current preamble search window ends (or if necessary, while performing a search), the FOEC of each recorded potential peak may be checked. If one of the potential peaks passes the FOEC check (e.g., and possibly if one or more other checks are passed), a signal detection may be declared, while if no potential peak passes the FOEC check, no detection may be declared.

[0122] The FOEC check may be performed in any of a variety of ways. As one possibility, the relative difference between the different frequency offset estimates of the potential peak may be checked against a certain threshold, such that if the relative difference exceeds the threshold, FOEC failure may be declared. Otherwise, FOEC success may be declared. As another possibility, FOEC failure may be declared if one of the absolute frequency offset estimates exceeds a certain threshold. Otherwise, FOEC success may be declared. Note that as another possibility, it may be the case that only one potential peak is retained during the entire preamble search window, if desired.

[0123] As previously described herein, if desired, a peak-to-sidelobe ratio-based approach may also or alternatively be used to determine whether a potential peak may be a false alarm. Such an approach may be based on a design requirement that the discovery preamble signal has a strong autocorrelation characteristic such that a single peak will appear if the input to the PDD module includes the desired discovery signal. In contrast, in a pure interference scenario (e.g., where all peaks represent false alarms), it may be the case that multiple sidelobes appear at different times in the discovery signal search window.

[0124] Based on such observations, it may be possible to design the PSR check so that a list of candidate peaks (e.g., those with the highest PDD metrics) is maintained during the presence of a discovery signal search window. Alternatively, such a list may be constructed after the search window ends, for example, if intermediate results are stored. After the search window ends, the PSR of one or more of the strongest peaks may be checked to determine whether the PSR exceeds a certain threshold. If the PSR does exceed the threshold, success may be declared (e.g., relative to a PSR check). Otherwise, a PDD failure may be declared.

[0125] Since the FOEC-based method and the PSR-based method can exploit different signal characteristics, the combined method can also be used to further reduce the false alarm rate compared to using only one such method. Fig. 9 is a flow chart illustrating aspects of an exemplary such method for performing presence discovery in accordance with some embodiments, wherein frequency offset error consistency checks and peak-to-sidelobe ratio checks are used to reduce false positives.

[0126] As shown, in 902, the method may include checking whether the current search window is over. If not, then in 904, the method may include performing PDD for each input sample. In 906, it may be determined whether a potential peak is detected, such as whether the current PDD value is greater than a potential peak threshold. If a potential peak is detected, then in 908, another PDD may be performed for the potential peak to obtain one or more different frequency offset estimates (e.g., with different time lags). In addition, in 910, it may be determined whether the current PDD value is greater than the value of the candidate peak in the candidate peak list. If so, then in 912, the peak candidate list may be updated to include the current candidate peak (e.g., including any additional frequency offset estimates obtained for the candidate peak). These steps may be repeated until the search window ends. Once the search window ends, in 914, a PSR check may be performed for each potential peak recorded, or a PSR check may be performed for the peak with the maximum PDD value in the recorded peak, or a PSR check may be performed for a portion of the potential peaks recorded. In 916, it may be determined whether each candidate peak for which a PSR check is performed passes the PSR check. If no candidate peak passes the PSR check, then in 924, it may be determined that no discovery synchronization signal is detected. If at least one candidate peak passes the PSR check, then in 918, a FOEC check may be performed on the candidate peaks that pass the PSR check. In 920, it may be determined whether each candidate peak for which the FOEC check is performed passes the FOEC check. If no candidate peak passes the FOEC check, then in 924, it may be determined that no discovery synchronization signal is detected. In 922, if the candidate peak passes the FOEC check as well as the PSR check, detection may be declared.

[0127] In at least some cases, PDD performance can be significantly improved by using such false alarm reduction techniques.

[0128] In wireless communication systems, parameter estimation can play an important role. The accuracy of such estimation can directly affect the achievable key performance indicators (KPIs), such as data throughput. Therefore, according to some embodiments, iterative parameter estimation methods that can improve the accuracy of parameter estimation can be used herein, for example, in combination with other techniques described herein or independently (for example, compared to non-iterative methods). Such methods can be used for any scenario in iterative time offset estimation, iterative frequency offset estimation, combined iterative time offset and iterative frequency offset estimation and / or various other parameter estimation scenarios.

[0129] Fig.10It is a flowchart illustrating various aspects of an exemplary method for performing iterative parameter estimation according to some embodiments. In order to estimate parameters (e.g., frequency offset, time offset), the received signal that can be damaged by the estimated parameters together with noise and / or interference can be analyzed. During the received signal analysis, considerations such as possible signal damage caused by one or more target estimated parameters, the scope of one or more estimated parameters, and the achievable accuracy of parameter estimation can be used to select some control parameters for the estimator. For different control parameter values, there may usually be a compromise in these considerations.

[0130] according to Fig.10 In a method of, in 1002, an initial control parameter selection may be performed. The initial control parameter selection may include selecting a set of control parameters to tolerate the maximum possible impairment caused by the target estimation in the original received signal and to achieve the maximum parameter estimation range in the original received signal. In 1004, parameter estimation may be performed using the selected control parameters. In 1006, the received signal may be compensated by the estimated parameters from the previous iteration. In 1008, the next iteration may be started, wherein the control parameters may be fine-tuned, for example, by adjusting the control parameters to tolerate the maximum possible impairment within the compensated received signal and to achieve the maximum parameter estimation range within the compensated received signal. In 1010, parameter estimation may be performed using the fine-tuned control parameters. In 1012, it may be determined whether one or more additional iterations are needed or desired. If so, the method may return to step 1006. If not, the iterative parameter estimation may be completed. As one possibility, the iteration may continue until a certain threshold of estimation accuracy is reached or the tunable range of the control parameters is reached. In at least some embodiments, control parameter refinement may be configured to achieve better estimation accuracy at each iteration, for example because the required estimation range and maximum impairment caused by the target parameter may be significantly reduced after compensating the signal by the parameter estimation of the previous iteration.

[0131] Fig.11 is a flow chart illustrating aspects of an exemplary method for performing iterative parameter estimation according to some embodiments, wherein the estimated parameter is a time offset. In some embodiments, the time offset estimation may be performed in the frequency domain during a data communication session. To eliminate noise / interference effects, adjacent frequency resource elements may be averaged prior to differential coherent combining for time offset estimation. Thus, the number of adjacent frequency resource elements (N) may be re ) can be used as a control parameter. This parameter can affect the estimator so that N re Larger values ​​of may provide more accurate estimates by allowing more noise / interference rejection, but may also reduce the achievable estimate range. Additionally, the average signal strength may decrease during the averaging period, for example due to different phases caused by time offsets.

[0132] according to Fig.11 In the method, in 1102, the initial N may be selected, for example, based on the maximum time offset in the reference signal (if available). re In 1104, the selected N re The time offset estimation is performed by using the value of N. In 1106, the reference signal may be compensated by the estimated time offset from the previous iteration, for example, via a phase rotation in the frequency domain. In 1108, N may be used, for example, to re The amount selected based on the residual time offset due to delay spread and the maximum tuning range may be increased. At 1110, the increased N re The time offset estimation is performed using the value. In 1112, it can be determined whether one or more additional iterations are needed or desired. If so, the method can return to step 1106. If not, the iterative time offset estimation can be completed. As one possibility, the iteration can continue until a certain threshold of estimation accuracy is reached or N is reached. re The adjustable range.

[0133] Fig.12 is a flow chart illustrating aspects of an exemplary method for performing iterative parameter estimation according to some embodiments, wherein the estimated parameter is a frequency offset. In some embodiments, the frequency offset estimation may be performed in the time domain during initial synchronization. To eliminate noise / interference effects, adjacent samples may be averaged before differentially coherently combining the averaged samples. Thus, the number of adjacent samples (N) smp ) can be used as a control parameter. This parameter can affect the estimator so that N smp Larger values ​​of may provide more accurate estimates by allowing more noise / interference suppression, but may also reduce the achievable estimation range. Additionally, the average signal strength may decrease during averaging, for example due to different phase rotations in different samples caused by frequency offset.

[0134] according to Fig.12 In the method, in 1202, the initial N may be selected based on, for example, the maximum frequency offset in the received signal. smp In 1204, the selected N smp The frequency offset estimation may be performed by using the value of N. In 1206, the reference signal may be compensated by the estimated frequency offset from the previous iteration, for example, via linear phase rotation. In 1208, N may be used, for example, to smp The amount selected based on the residual frequency offset determined by the channel coherence time and the maximum tuning range may be increased. At 1210, the increased N smpThe frequency offset estimation is performed using the value. In 1212, it may be determined whether one or more additional iterations are needed or desired. If so, the method may return to step 1206. If not, the iterative frequency offset estimation may be completed. As one possibility, the iterations may continue until a certain threshold of estimation accuracy is reached or N is reached. smp The adjustable range.

[0135] Therefore, at least according to some embodiments, the use of such an iterative method can allow for more accurate parameter estimation for a given set of signal samples. For example, at least in some cases, when such a method is used for frequency offset estimation, the residual frequency error can be significantly reduced after the second iteration compared to after the first iteration.

[0136] Furthermore, in at least some embodiments, an iterative approach may be utilized to perform combined timing and frequency estimation. Fig.13 is a flow chart illustrating aspects of such an exemplary method for performing iterative time and frequency offset estimation according to some embodiments. Fig.13 In the method of , in 1302, a coarse timing acquisition with a small coherent combining length (e.g., due to taking into account the possible worst frequency offset of the signal) can be performed on the received signal. In 1304, it can be determined whether the coarse timing acquisition leads to a possible correct timing candidate. If not, the method can return to step 1302. If so, the method can proceed to 1306, where the timing candidate can be added to the timing database. Proceeding to step 1308, a coarse frequency offset estimation can be performed based on the current coarse timing assumption. In 1310, the received signal can be compensated based on the current coarse frequency and time offset assumptions. In 1312, a fine timing acquisition can be performed based on the frequency compensated signal, for example, with a larger coherent combining length. In 1314, a fine frequency offset estimation can be performed based on the refined timing estimate. The timing database can be updated with the refined timing and frequency offset estimates, and the method can return to step 1302 for further timing candidate detection.

[0137] As previously described, at least in some cases, such iterative methods for performing parameter estimation can provide improved accuracy relative to non-iterative methods. Although in some cases, even with non-iterative methods, parameter estimates can be refined (e.g., using different signals over time), it is particularly beneficial to obtain such improved accuracy on a single set of signal samples in the case of more limited availability of the signal to which parameter estimation is to be performed. For example, as previously described, at least according to some embodiments, when performing discovery communications or other communications between power-limited (e.g., UE) devices over a relatively long range, the improvement of parameter estimation at each instance of signal reception may be particularly beneficial for, for example, improving the possibility of correctly detecting discovery signals and / or reducing the need for transmission repetitions that may occur at high power costs and / or may increase connection setup delays. In addition, at least according to some embodiments, it may be desirable to improve parameter estimation accuracy by using such iterative methods even in the case of easier acquisition of synchronization signals, reference signals, and / or other signals to which parameter estimation is to be performed.

[0138] In the following, further exemplary embodiments are provided.

[0139] A set of embodiments may include a method comprising: by a first wireless device: monitoring a wireless medium for a discovery signal; determining that a candidate discovery signal has been detected; performing a frequency offset estimate consistency check on the candidate discovery signal; performing a peak sidelobe ratio check on the candidate discovery signal; and determining whether the candidate discovery signal is a false alarm based at least in part on the frequency offset estimate consistency check and the peak sidelobe ratio check.

[0140] According to some embodiments, the frequency offset estimate consistency check includes determining whether the estimated frequency offset of the candidate discovery signal exceeds a frequency offset threshold.

[0141] According to some embodiments, the peak sidelobe ratio check includes determining whether an estimated peak sidelobe ratio of the candidate discovery signal exceeds a peak sidelobe ratio threshold.

[0142] According to some embodiments, the method also includes: if the candidate discovery signal fails to pass the frequency offset estimation consistency check or the peak sidelobe ratio check, determining that the candidate discovery signal is a false alarm; if the candidate discovery signal passes both the frequency offset estimation consistency check and the peak sidelobe ratio check, determining that the candidate discovery signal is an actually detected discovery signal.

[0143] According to some embodiments, the method also includes: obtaining a frequency offset estimate for the candidate discovery signal; and iteratively refining the frequency offset estimate for the candidate discovery signal, wherein at each iteration, the candidate discovery signal is compensated by the frequency offset estimate from the previous iteration and an increased number of adjacent time samples are used.

[0144] According to some embodiments, the method also includes: obtaining a time offset estimate for the candidate discovery signal; and iteratively refining the time offset estimate for the candidate discovery signal, wherein at each iteration, the candidate discovery signal is compensated by the time offset estimate from the previous iteration and an increased number of adjacent frequency resource elements are used.

[0145] According to some embodiments, the candidate discovery signal includes a device-to-device (D2D) discovery signal, wherein monitoring the wireless medium for the discovery signal further includes associating a signal received on the wireless medium with one or more known D2D discovery preamble signals; wherein determining that a candidate discovery signal has been detected further includes determining that associating the signal received on the wireless medium with the one or more known D2D discovery preamble signals results in a correlation peak greater than a correlation peak threshold.

[0146] Another group of embodiments may include an apparatus comprising: a processor configured to cause a wireless device to: monitor a wireless medium for a discovery signal; determine that a candidate discovery signal has been detected; perform a frequency offset estimate consistency check on the candidate discovery signal; and determine whether the candidate discovery signal is a false alarm based at least in part on the frequency offset estimate consistency check.

[0147] According to some embodiments, in order to perform a frequency offset estimation consistency check, the processor is further configured to enable the wireless device to: use different time lags to obtain multiple frequency offset estimates of a candidate discovery signal; if the relative difference between different frequency offset estimates exceeds a relative frequency offset difference threshold, determine that the candidate discovery signal has not passed the frequency offset estimation check; and if the relative difference between different frequency offset estimates does not exceed the relative frequency offset difference threshold, determine that the candidate discovery signal has passed the frequency offset estimation check.

[0148] According to some embodiments, in order to perform a frequency offset estimate consistency check, the processor is further configured to enable the wireless device to: obtain multiple frequency offset estimates of the candidate discovery signal using different time lags; determine that the candidate discovery signal has not passed the frequency offset estimate check if any of the frequency offset estimates of the candidate discovery signal exceeds an absolute frequency offset threshold; and determine that the candidate discovery signal has passed the frequency offset estimate check if none of the frequency offset estimates of the candidate discovery signal exceeds the absolute frequency offset threshold.

[0149] According to some embodiments, the processor is further configured to cause the wireless device to: perform a peak sidelobe ratio check on the candidate discovery signal; and further determine whether the candidate discovery signal is a false alarm based at least in part on the peak sidelobe ratio check of the candidate discovery signal.

[0150] According to some embodiments, in order to perform a peak sidelobe ratio check, the processor is further configured to cause the wireless device to: calculate the peak sidelobe ratio of the candidate discovery signal; if the peak sidelobe ratio is greater than a peak sidelobe ratio threshold, determine that the candidate discovery signal passes the peak sidelobe ratio check; and if the peak sidelobe ratio is less than the peak sidelobe ratio threshold, determine that the candidate discovery signal fails the peak sidelobe ratio check.

[0151] According to some embodiments, the processing element is further configured to cause the wireless device to: use a first number of adjacent samples to obtain a first frequency offset estimate for a candidate discovery signal; use the first frequency offset estimate to compensate the candidate discovery signal; determine a second number of adjacent samples to be used for a second frequency offset estimate, wherein the second number of adjacent samples is greater than the first number of adjacent samples; and use the second number of adjacent samples to obtain a compensated second frequency offset estimate for the candidate discovery signal.

[0152] According to some embodiments, the processor is further configured to cause the wireless device to: use a first number of adjacent frequency resource elements to obtain a first time offset estimate for a candidate discovery signal; use the first time offset estimate to compensate the candidate discovery signal; determine a second number of adjacent frequency resource elements to be used for a second time offset estimate, wherein the second number of adjacent frequency resource elements is greater than the first number of adjacent frequency resource elements; and use the second number of adjacent frequency resource elements to obtain a compensated second time offset estimate for the candidate discovery signal.

[0153] Another set of embodiments may include a wireless device comprising: an antenna; a radio component operably coupled to the antenna; and a processor operably coupled to the radio component; wherein the wireless device is configured to: monitor a wireless medium for a discovery signal; determine that a candidate discovery signal is detected; perform a coarse timing acquisition on the candidate discovery signal; perform a coarse frequency offset estimation on the candidate discovery signal based on the coarse timing acquisition; perform a fine timing acquisition on the candidate discovery signal based on the coarse frequency offset acquisition; and perform a fine frequency offset estimation on the candidate discovery signal based on the fine timing acquisition.

[0154] According to some embodiments, coarse timing acquisition, coarse frequency offset estimation, fine timing acquisition, and fine frequency offset estimation are iteratively performed on the same set of signal samples.

[0155] According to some embodiments, the wireless device is further configured to: perform a frequency offset estimate consistency check on the candidate discovery signal; and determine whether the candidate discovery signal is a false alarm based at least in part on the frequency offset estimate consistency check.

[0156] According to some embodiments, the wireless device is further configured to: perform a peak sidelobe ratio check on the candidate discovery signal; and determine whether the candidate discovery signal is a false alarm based at least in part on the peak sidelobe ratio check.

[0157] According to some embodiments, the wireless device is further configured to: determine that multiple candidate discovery signals are detected; and for each of the multiple candidate discovery signals, iteratively perform coarse timing acquisition, coarse frequency offset estimation, fine timing acquisition and fine frequency offset estimation on the same set of signal samples.

[0158] According to some embodiments, the wireless device is further configured to: determine that multiple candidate discovery signals are detected; perform one or more of a frequency offset estimate consistency check or a peak sidelobe ratio check on each of the multiple candidate discovery signals; and determine whether each of the candidate discovery signals is a false alarm based at least in part on one or more of the frequency offset estimate consistency check or the peak sidelobe ratio check.

[0159] Yet another example embodiment may include a method, comprising: performing, by a wireless device: any or all of the foregoing examples.

[0160] Another exemplary embodiment may include a wireless device comprising: an antenna; a radio component coupled to the antenna; and a processing element operably coupled to the radio component, wherein the device is configured to implement any or all of the foregoing examples.

[0161] Another example embodiment may include an apparatus comprising: a processing element configured to cause a wireless device to implement any or all of the foregoing examples.

[0162] Another exemplary set of embodiments may include a non-transitory computer-accessible storage medium including program instructions that, when executed at a device, cause the device to implement any or all portions of any of the foregoing examples.

[0163] Another exemplary set of embodiments may include a computer program comprising instructions for performing any or all of any of the foregoing examples.

[0164] Another exemplary set of embodiments may include an apparatus including means for performing any or all of the elements of any of the preceding examples.

[0165] 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.

[0166] In addition to the exemplary embodiments described above, more 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.

[0167] 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 of the method embodiments described herein or any combination of such subsets.

[0168] In some embodiments, a device (e.g., UE 106 or 107) 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 method implementations described herein or any combination of such subsets). The device may be implemented in any of various forms.

[0169] 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 method for wireless communication, comprising: monitoring the wireless medium for discovery signals; determining that a candidate discovery signal is detected; Obtaining a frequency offset estimate of the candidate discovery signal; iteratively refining the frequency offset estimate of the candidate discovery signal, wherein at each iteration the candidate discovery signal is compensated by the frequency offset estimate from a previous iteration and an increasing number of adjacent time samples are used; performing a frequency offset estimation consistency check on the candidate discovery signal; performing a peak sidelobe ratio check on the candidate discovery signal; as well as A determination is made whether the candidate discovery signal is a false positive based at least in part on the frequency offset estimate consistency check and the peak-to-sidelobe ratio check.

2. The method according to claim 1, The frequency offset estimation consistency check includes determining whether the estimated frequency offset of the candidate discovery signal exceeds a frequency offset threshold.

3. The method according to claim 1, The peak sidelobe ratio check includes determining whether an estimated peak sidelobe ratio of the candidate discovery signal exceeds a peak sidelobe ratio threshold.

4. The method according to claim 1, wherein the method further comprises: If the candidate discovery signal fails the frequency offset estimation consistency check or the peak-to-sidelobe ratio check, determining that the candidate discovery signal is a false alarm; as well as If the candidate discovery signal passes both the frequency offset estimation consistency check and the peak-to-sidelobe ratio check, it is determined that the candidate discovery signal is an actually detected discovery signal.

5. The method according to claim 1, wherein the method further comprises: Obtaining a time offset estimate of the candidate discovery signal; as well as iteratively refining the time offset estimate of the candidate discovery signal, Wherein at each iteration, the candidate discovery signal is compensated by the time offset estimate from a previous iteration and an increasing number of adjacent frequency resource elements are used.

6. The method according to claim 1, The candidate discovery signal comprises a device-to-device (D2D) discovery signal, wherein monitoring the wireless medium for discovery signals further comprises correlating signals received on the wireless medium with one or more known D2D discovery preamble signals; Wherein determining that a candidate discovery signal is detected further comprises determining that correlating a signal received over the wireless medium with the one or more known D2D discovery preamble signals results in a correlation peak value greater than a correlation peak threshold value.

7. An apparatus for wireless communication, comprising: A processor configured to cause the wireless device to: monitoring the wireless medium for discovery signals; determining that a candidate discovery signal is detected; Performing a frequency offset estimation consistency check on the candidate discovery signal includes: obtaining a plurality of frequency offset estimates of the candidate discovery signal using different time lags, If the relative difference between different frequency offset estimates exceeds a relative frequency offset difference threshold, determining that the candidate discovery signal fails the frequency offset estimate consistency check, and If the relative difference between different frequency offset estimates does not exceed the relative frequency offset difference threshold, determining that the candidate discovery signal passes the frequency offset estimate consistency check; as well as A determination is made whether the candidate discovery signal is a false positive based at least in part on the frequency offset estimate consistency check.

8. The apparatus of claim 7, wherein to perform the frequency offset estimate consistency check, the processor is further configured to cause the wireless device to: determining that the candidate discovery signal fails the frequency offset estimate consistency check if any of the frequency offset estimates for the candidate discovery signal exceeds an absolute frequency offset threshold; and If none of the frequency offset estimates of the candidate discovery signal exceeds the absolute frequency offset threshold, it is determined that the candidate discovery signal passes the frequency offset estimate consistency check.

9. The apparatus of claim 7, wherein the processor is further configured to cause the wireless device to: performing a peak-to-sidelobe ratio check on the candidate discovery signal; and A determination is further made whether the candidate discovery signal is a false positive based at least in part on the peak sidelobe ratio check of the candidate discovery signal.

10. The apparatus of claim 9, wherein to perform the peak sidelobe ratio check, the processor is further configured to cause the wireless device to: Calculating a peak sidelobe ratio of the candidate discovery signal; If the peak sidelobe ratio is greater than a peak sidelobe ratio threshold, determining that the candidate discovery signal passes the peak sidelobe ratio check; and If the peak sidelobe ratio is less than the peak sidelobe ratio threshold, it is determined that the candidate discovery signal fails the peak sidelobe ratio check.

11. The apparatus of claim 7, wherein the processor is further configured to cause the wireless device to: Obtaining a first frequency offset estimate for the candidate discovery signal using a first number of adjacent samples; compensating the candidate discovery signal using the first frequency offset estimate; determining a second number of adjacent samples to be used for a second frequency offset estimate, wherein the second number of adjacent samples is greater than the first number of adjacent samples; and The second number of adjacent samples is used to obtain the second frequency offset estimate of the compensated candidate discovery signal.

12. The apparatus of claim 7, wherein the processor is further configured to cause the wireless device to: Obtaining a first time offset estimate for the candidate discovery signal using a first number of adjacent frequency resource elements; compensating the candidate discovery signal using the first time offset estimate; determining a second number of adjacent frequency resource elements to be used for a second time offset estimation, wherein the second number of adjacent frequency resource elements is greater than the first number of adjacent frequency resource elements; and The second time offset estimate of the compensated candidate discovery signal is obtained using the second number of adjacent frequency resource elements.

13. A wireless device comprising: antenna; a radio operably coupled to the antenna; as well as a processor operatively coupled to the radio; The wireless device is configured to: monitoring the wireless medium for discovery signals; determining that a candidate discovery signal is detected; Performing a frequency offset estimation consistency check on the candidate discovery signal includes: obtaining a plurality of frequency offset estimates of the candidate discovery signal using different time lags, determining that the candidate discovery signal fails the frequency offset estimate consistency check if any of the frequency offset estimates for the candidate discovery signal exceeds an absolute frequency offset threshold, and determining that the candidate discovery signal passes the frequency offset estimate consistency check if none of the frequency offset estimates of the candidate discovery signal exceeds the absolute frequency offset threshold; as well as A determination is made whether the candidate discovery signal is a false positive based at least in part on the frequency offset estimate consistency check.

14. The wireless device of claim 13, wherein the wireless device is further configured to: If the relative difference between different frequency offset estimates exceeds a relative frequency offset difference threshold, determining that the candidate discovery signal fails the frequency offset estimate consistency check; and If the relative difference between different frequency offset estimates does not exceed the relative frequency offset difference threshold, it is determined that the candidate discovery signal passes the frequency offset estimate consistency check.

15. The wireless device of claim 13, wherein the wireless device is further configured to: performing a peak-to-sidelobe ratio check on the candidate discovery signal; and A determination is further made whether the candidate discovery signal is a false positive based at least in part on the peak sidelobe ratio check of the candidate discovery signal.

16. The wireless device of claim 15, wherein the wireless device is further configured to: Calculating a peak sidelobe ratio of the candidate discovery signal; If the peak sidelobe ratio is greater than a peak sidelobe ratio threshold, determining that the candidate discovery signal passes the peak sidelobe ratio check; and If the peak sidelobe ratio is less than the peak sidelobe ratio threshold, it is determined that the candidate discovery signal fails the peak sidelobe ratio check.

17. The wireless device of claim 13, wherein the wireless device is further configured to: Obtaining a first frequency offset estimate for the candidate discovery signal using a first number of adjacent samples; compensating the candidate discovery signal using the first frequency offset estimate; determining a second number of adjacent samples to be used for a second frequency offset estimate, wherein the second number of adjacent samples is greater than the first number of adjacent samples; and The second number of adjacent samples is used to obtain the second frequency offset estimate of the compensated candidate discovery signal.

18. The wireless device of claim 13, wherein the wireless device is further configured to: Obtaining a first time offset estimate for the candidate discovery signal using a first number of adjacent frequency resource elements; compensating the candidate discovery signal using the first time offset estimate; determining a second number of adjacent frequency resource elements to be used for a second time offset estimation, wherein the second number of adjacent frequency resource elements is greater than the first number of adjacent frequency resource elements; and The second time offset estimate of the compensated candidate discovery signal is obtained using the second number of adjacent frequency resource elements.

19. A wireless device comprising: antenna; a radio operably coupled to the antenna; as well as a processor operatively coupled to the radio; The wireless device is configured to perform the method according to any one of claims 1-6.

20. A non-transitory computer-readable storage medium comprising instructions stored thereon, which, when executed by a processor of a wireless device, cause the wireless device to perform the method according to any one of claims 1-6.

21. A computer program product comprising instructions which, when executed by a processor of a wireless device, cause the wireless device to perform the method according to any one of claims 1-6.

22. A method for wireless communication, comprising the following operations: monitoring the wireless medium for discovery signals; determining that a candidate discovery signal is detected; Performing a frequency offset estimation consistency check on the candidate discovery signal includes: obtaining a plurality of frequency offset estimates of the candidate discovery signal using different time lags, If the relative difference between different frequency offset estimates exceeds a relative frequency offset difference threshold, determining that the candidate discovery signal fails the frequency offset estimate consistency check, and If the relative difference between different frequency offset estimates does not exceed the relative frequency offset difference threshold, determining that the candidate discovery signal passes the frequency offset estimate consistency check; as well as A determination is made whether the candidate discovery signal is a false positive based at least in part on the frequency offset estimate consistency check.

23. The method of claim 22, wherein the operation of performing the frequency offset estimate consistency check further comprises: determining that the candidate discovery signal fails the frequency offset estimate consistency check if any of the frequency offset estimates of the candidate discovery signal exceeds an absolute frequency offset threshold; as well as If none of the frequency offset estimates of the candidate discovery signal exceeds the absolute frequency offset threshold, it is determined that the candidate discovery signal passes the frequency offset estimate consistency check.

24. A non-transitory computer-readable storage medium comprising instructions stored thereon, which, when executed by a processor of a wireless device, cause the wireless device to perform the method according to any one of claims 22-23.

25. A computer program product comprising instructions which, when executed by a processor of a wireless device, cause the wireless device to perform the method according to any one of claims 22-23.

26. A method for wireless communication, comprising the following operations: monitoring the wireless medium for discovery signals; determining that a candidate discovery signal is detected; Performing a frequency offset estimation consistency check on the candidate discovery signal includes: obtaining a plurality of frequency offset estimates of the candidate discovery signal using different time lags, determining that the candidate discovery signal fails the frequency offset estimate consistency check if any of the frequency offset estimates for the candidate discovery signal exceeds an absolute frequency offset threshold, and determining that the candidate discovery signal passes the frequency offset estimate consistency check if none of the frequency offset estimates of the candidate discovery signal exceeds the absolute frequency offset threshold; as well as A determination is made whether the candidate discovery signal is a false positive based at least in part on the frequency offset estimate consistency check.

27. The method according to claim 26, further comprising the following operations: performing a peak-to-sidelobe ratio check on the candidate discovery signal; and A determination is further made based at least in part on the peak-to-sidelobe ratio check whether the candidate discovery signal is a false positive.

28. The method according to claim 27, further comprising the following operations: Calculating a peak sidelobe ratio of the candidate discovery signal; If the peak sidelobe ratio is greater than a peak sidelobe ratio threshold, determining that the candidate discovery signal passes the peak sidelobe ratio check; and If the peak sidelobe ratio is less than the peak sidelobe ratio threshold, it is determined that the candidate discovery signal fails the peak sidelobe ratio check.

29. The method according to claim 26, further comprising the following operations: Obtaining a first frequency offset estimate for the candidate discovery signal using a first number of adjacent samples; compensating the candidate discovery signal using the first frequency offset estimate; determining a second number of adjacent samples to be used for a second frequency offset estimate, wherein the second number of adjacent samples is greater than the first number of adjacent samples; as well as The second number of adjacent samples is used to obtain the second frequency offset estimate of the compensated candidate discovery signal.

30. The method according to claim 26, further comprising the following operations: Obtaining a first time offset estimate for the candidate discovery signal using a first number of adjacent frequency resource elements; compensating the candidate discovery signal using the first time offset estimate; determining a second number of adjacent frequency resource elements to be used for a second time offset estimation, wherein the second number of adjacent frequency resource elements is greater than the first number of adjacent frequency resource elements; and The second time offset estimate of the compensated candidate discovery signal is obtained using the second number of adjacent frequency resource elements.

31. A non-transitory computer-readable storage medium comprising instructions stored thereon, which, when executed by a processor of a wireless device, cause the wireless device to perform the method according to any one of claims 26-30.

32. A computer program product comprising instructions which, when executed by a processor of a wireless device, cause the wireless device to perform the method according to any one of claims 26-30.

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