Patent Description:
Multi-antenna systems employ a number of antennas or antenna arrays to enable a higher reliability, a higher throughput, or both, by providing a transmission diversity gain, a spatial multiplexing gain and/or a beamforming gain. As one of multi-antenna techniques, beamforming focuses energy of signal transmission and/or reception into a targeted direction, leading to significant improvements in signal strengths received by communication devices. As a result, a system-wide spectrum efficiency can be achieved, especially when combined with proper scheduling of multiple terminal devices.

For the New Radio (NR) operating in millimeter wave (mmW) bands, due to high free space loss, high-gain directional beams may be beneficial to signal transmissions, including control signals, such as System Information and Synchronization Blocks (SSBs) and Channel State Information - Reference Signals (CSI-RSs), and data signals.

Different beamforming schemes, e.g., different beam vectors, may be desired for different types or purposes of signals to achieve a tradeoff between e.g., a beam sweeping efficiency and a beamforming gain. For example, a wide beam may have a high efficiency and a low latency in beam sweeping, but may have a low beamforming gain and thus a low signal quality, or vice versa.

There is thus a need for a beam vector design that can provide a high flexibility in selection of beam vectors for different types or purposes of signals.

A paper entitled "<NPL>) discloses joint multi-beam training and codebook design for indoor high-throughput transmissions under limited training steps.

It is an object of the present disclosure to provide a method and a network device for beam vector selection, capable of providing a high flexibility in selection of beam vectors for different types or purposes of signals in an efficient manner.

This object is achieved by the subject-matter of the independent claims. Preferred embodiments of the invention are set forth in the dependent claims.

According to a first aspect of the present disclosure, a method in a network device is provided. The method includes: determining a number, N, of sets of beam vectors by: creating a first set of beam vectors orthogonal to each other; and determining an n-th set of beam vectors each obtained by linear combination of two or more beam vectors from the (n-<NUM>)-th set of beam vectors, where N and n are integers and N≥n><NUM>. The method further includes: selecting, from one or more of the N sets, a plurality of beam vectors for beamforming of a radio signal.

In an embodiment, the beam vectors in the first set can be eigen vectors spanning a Hilbert space.

In an embodiment, the first set of beam vectors can be created based on a Discrete Fourier Transform (DFT) based matrix.

In an embodiment, the DFT based matrix can be: <MAT> where w = e-2πi/K, K is a number of beam vectors in the first set and i is an imaginary unit, and each column of W is one beam vector of the first set.

In an embodiment, each beam vector in the n-th set can be obtained by linear combination of two or more adjacent beam vectors from the (n-<NUM>)-th set of beam vectors.

In an embodiment, the plurality of beam vectors can be selected for beamforming of the radio signal for transmission to a terminal device based on an Angle of Arrival (AOA) of another radio signal from the terminal device.

In an embodiment, the first set of beam vectors can be created based on a random matrix.

In an embodiment, the first set of beam vectors can be created by: generating a random matrix X, where X is a K*K matrix; calculating R=XHX, where XH is a Hermitian conjugate of X; and calculating an eigen decomposition of R as R=QHDQ. Each column of Q is one beam vector of the first set.

In an embodiment, the first set of beam vectors can be created based on a channel matrix.

In an embodiment, the first set of beam vectors can be created by: obtaining a channel matrix Hm for each of a number, M, of terminal devices, where Hm is a Tm x TA matrix for an m-th terminal device out of the M terminal devices, m is an integer and M≥m><NUM>, TA is a number of antennas at the network device and TA=K, and Tm is a number of antennas at the m-th terminal device; calculating Rm= HmHHm, where Hm H is a Hermitian conjugate of Hm; calculating a covariance of Rm over the M terminal devices as R=E(Rm), where E() denotes mathematical expectation; and calculating an eigen decomposition of R as R=QHDQ. Each column of Q is one beam vector of the first set.

The plurality of beam vectors are selected based on one or more of: a maximum allowable number of beams for a full spatial coverage sweeping or repetition of the radio signal during a period of time to cover a serving area, a targeted transmission or reception beamforming gain for the radio signal, or an allowable latency and/or a maximum period for a successful transmission or reception of the radio signal above a predetermined probability.

In an embodiment, the radio signal may be a System Information and Synchronization Signal Block (SSB), a Channel State Information - Reference Signal (CSI-RS) or a reference or payload signal for multi-layer or multi-user transmission.

In an embodiment, the plurality of beam vectors can be selected from the n<NUM>-th set when the radio signal is the SSB, or from the n<NUM>-th set when the radio signal is the CSI-RS, or from the n<NUM>-th set when the radio signal is the reference or payload signal for multi-layer or multi-user transmission, wherein n<NUM>, n<NUM> and n<NUM> are integers and N≥n<NUM>≥n<NUM>≥n<NUM>≥<NUM>.

According to a second aspect of the present disclosure, a network device is provided. The network device includes a transceiver, a processor and a memory. The memory stores instructions executable by the processor whereby the network device is operative to perform the method according to the above first aspect.

According to a third aspect of the present disclosure, a computer readable storage medium is provided. The computer readable storage medium has computer program instructions stored thereon. The computer program instructions, when executed by a processor in a network device, cause the router to perform the method according to the above first aspect.

With the embodiments of the present disclosure, a hierarchical design of beam vectors is introduced. An elementary (i.e., the first) set of beam vectors orthogonal to each other is created and the n-th set of beam vectors is determined such that each beam vector in the n-th set is obtained by linear combination of two or more beam vectors from the (n-<NUM>)-th set of beam vectors. Then, a plurality of beam vectors can be selected from one or more sets for beamforming of a radio signal. Such hierarchical design is highly flexible and efficient in selection of beam vectors for different types or purposes of signals, so as to achieve a desired tradeoff between e.g., a beam sweeping efficiency and a beamforming gain.

The above and other objects, features and advantages will be more apparent from the following description of embodiments with reference to the figures, in which:.

As used herein, the term "wireless communication network" refers to a network following any suitable communication standards, such as NR, LTE-Advanced (LTE-A), LTE, Wideband Code Division Multiple Access (WCDMA), High-Speed Packet Access (HSPA), and so on. Furthermore, the communications between a terminal device and a network device in the wireless communication network may be performed according to any suitable generation communication protocols, including, but not limited to, Global System for Mobile Communications (GSM), Universal Mobile Telecommunications System (UMTS), Long Term Evolution (LTE), and/or other suitable <NUM> (the first generation), <NUM> (the second generation), <NUM>, <NUM>, <NUM> (the third generation), <NUM> (the fourth generation), <NUM>, <NUM> (the fifth generation) communication protocols, wireless local area network (WLAN) standards, such as the IEEE <NUM> standards; and/or any other appropriate wireless communication standard, such as the Worldwide Interoperability for Microwave Access (WiMax), Bluetooth, and/or ZigBee standards, and/or any other protocols either currently known or to be developed in the future.

The term "network device" refers to a device in a wireless communication network via which a terminal device accesses the network and receives services therefrom. The network device refers to a base station (BS), an access point (AP), or any other suitable device in the wireless communication network. The BS may be, for example, a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), or (next) generation NodeB (gNB), a Remote Radio Unit (RRU), a radio header (RH), a remote radio head (RRH), a relay, a low power node such as a femto, a pico, and so forth. Yet further examples of the network device may include multi-standard radio (MSR) radio equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs), base transceiver stations (BTSs), transmission points, transmission nodes. More generally, however, the network device may represent any suitable device (or group of devices) capable, configured, arranged, and/or operable to enable and/or provide a terminal device access to the wireless communication network or to provide some service to a terminal device that has accessed the wireless communication network.

The term "network node" refers to a device connected to a network node such as a BS or an AP, e.g., via any appropriate network. For example, the network node may refer to a cloud server, a cloud computing node or any other node capable of data processing, computing and/or communicating information with one or more network devices.

The term "terminal device" refers to any end device that can access a wireless communication network and receive services therefrom. By way of example and not limitation, the terminal device refers to a mobile terminal, user equipment (UE), or other suitable devices. The UE may be, for example, a Subscriber Station (SS), a Portable Subscriber Station, a Mobile Station (MS), or an Access Terminal (AT). The terminal device may include, but not limited to, portable computers, desktop computers, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones, tablets, personal digital assistants (PDAs), wearable terminal devices, vehicle-mounted wireless terminal devices, wireless endpoints, mobile stations, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), USB dongles, smart devices, wireless customerpremises equipment (CPE) and the like. In the following description, the terms "terminal device", "terminal", "user equipment" and "UE" may be used interchangeably. As one example, a terminal device may represent a UE configured for communication in accordance with one or more communication standards promulgated by the 3rd Generation Partnership Project (3GPP), such as 3GPP's GSM, UMTS, LTE, and/or <NUM> standards. As used herein, a "user equipment" or "UE" may not necessarily have a "user" in the sense of a human user who owns and/or operates the relevant device. In some embodiments, a terminal device may be configured to transmit and/or receive information without direct human interaction. For instance, a terminal device may be designed to transmit information to a network on a predetermined schedule, when triggered by an internal or external event, or in response to requests from the wireless communication network. Instead, a UE may represent a device that is intended for sale to, or operation by, a human user but that may not initially be associated with a specific human user.

The terminal device may support device-to-device (D2D) communication, for example by implementing a 3GPP standard for sidelink communication, and may in this case be referred to as a D2D communication device.

As yet another example, in an Internet of Things (IOT) scenario, a terminal device may represent a machine or other device that performs monitoring and/or measurements, and transmits the results of such monitoring and/or measurements to another terminal device and/or network equipment. The terminal device may in this case be a machine-to-machine (M2M) device, which may in a 3GPP context be referred to as a machine-type communication (MTC) device. As one particular example, the terminal device may be a UE implementing the 3GPP narrow band internet of things (NB-IoT) standard. Particular examples of such machines or devices are sensors, metering devices such as power meters, industrial machinery, or home or personal appliances, for example refrigerators, televisions, personal wearables such as watches etc. In other scenarios, a terminal device may represent a vehicle or other equipment that is capable of monitoring and/or reporting on its operational status or other functions associated with its operation.

As used herein, a downlink transmission refers to a transmission from a network device to a terminal device, and an uplink transmission refers to a transmission in an opposite direction.

<FIG> is a flowchart illustrating a method <NUM> for beam vector selection according to an embodiment of the present disclosure. The method <NUM> can be performed at a network device, e.g., an eNB or gNB.

At block <NUM>, a number, N, of sets of beam vectors are determined as follows, where N is an integer larger than <NUM>.

In the block <NUM>, first of all, a first set (also referred to as "elementary set" hereinafter) of beam vectors orthogonal to each other is created. Here, the beam vectors in the elementary set can be eigen vectors spanning a Hilbert space. Using eigen vectors spanning a Hilbert space is particularly advantageous as a Hilbert space is "complete" mathematically.

For example, let p denote the number of antennas for beamforming at the network device, q denote the number of beam vectors in the elementary set, and Vj, j=<NUM>, <NUM>,. , q, denote a beam vector in the elementary set. For simplicity, it is assumed that p=q in the following.

In an example, the elementary set can be created based on a Discrete Fourier Transform (DFT) based matrix. For example, the DFT based matrix can be: <MAT> where w = e-<NUM>πi/K, K is a number of beam vectors in the first set and i is an imaginary unit, and each column of W is one beam vector of the elementary set, i.e., W = [V<NUM>,V<NUM> ·····, VK].

Alternatively, the elementary set can be created based on a random matrix. In particular, the elementary set can be created by: generating a random matrix X, where X is a K*K matrix; calculating R=XHX, where XH is a Hermitian conjugate of X; and calculating an eigen decomposition of R as R=QHDQ. In this case, each column of Q is one beam vector of the elementary set, i.e., Q = [V<NUM>,V<NUM> ·····, VK]. Here, D is a diagonal matrix.

Alternatively, the elementary set can be created based on a channel matrix. In particular, the elementary set can be created by: obtaining a channel matrix Hm for each of a number, M, of terminal devices, where Hm is a Tm x TA matrix for an m-th terminal device out of the M terminal devices, m is an integer and M≥m><NUM>, TA is a number of antennas at the network device and TA=K, and Tm is a number of antennas at the m-th terminal device; calculating Rm= HmHHm, where Hm H is a Hermitian conjugate of Hm; calculating a covariance of Rm over the M terminal devices as R=E(Rm), where E() denotes mathematical expectation; and calculating an eigen decomposition of R as R=QHDQ. In this case, each column of Q is one beam vector of the elementary set, i.e., Q = [V<NUM>,V<NUM> ·····, VK]. Here, D is a diagonal matrix.

Then, an n-th set of beam vectors is determined, with each beam vector in the n-th set being obtained by linear combination of two or more beam vectors from the (n-<NUM>)-th set of beam vectors, where n is an integer and N≥n><NUM>.

For example, let <MAT>, c=<NUM>, <NUM>,. , Cn, denote a beam vector in the n-th set: <MAT> where Cn is the number of beam vectors in the n-th set, Vck ∈ Vc which is a subset of the elementary set {V<NUM>,V<NUM> ·····, VK} and contains beam vectors used for constituting <MAT> which is a subset of the (n-<NUM>)-th set <MAT> and contains beam vectors used for constituting <MAT> (n><NUM>), snc is the number of vectors in Vc (n=<NUM>) or <MAT> (n><NUM>), <MAT> is a factor for amplitude normalization, and <MAT> is a linear combination coefficient.

As an example, each beam vector in the n-th set can be obtained by linear combination of two or more adjacent or non-adjacent beam vectors from the (n-<NUM>)-th set of beam vectors, e.g., when the elementary set is created according to Equation (<NUM>). For example, according to Equation (<NUM>), when N=<NUM>, K=<NUM>, C<NUM>=<NUM>, C<NUM>=<NUM>, C<NUM>=<NUM>, <MAT> can be obtained by linear combination of V<NUM> and V<NUM>, <MAT> can be obtained by linear combination of V<NUM> and V<NUM>, <MAT> can be obtained by linear combination of V<NUM> and V<NUM>, <MAT> can be obtained by linear combination of V<NUM> and V<NUM>, <MAT> can be obtained by linear combination of V<NUM> and V<NUM>, <MAT> can be obtained by linear combination of <MAT> and <MAT> can be obtained by linear combination of <MAT> and <MAT>, and <MAT> can be obtained by linear combination of <MAT> and <MAT>.

It is to be noted here that each beam vector in the n-th set is not necessarily to be obtained by linear combination of the same number of beam vectors from the (n-<NUM>)-th set of beam vectors. That is, in Equation (<NUM>), for a given value of n, snc may vary for different values of c.

At block <NUM>, a plurality of beam vectors are selected from one or more of the N sets for beamforming of a radio signal.

For example, the plurality of beam vectors can be selected for beamforming of the radio signal for transmission to a terminal device based on an Angle of Arrival (AOA) of another radio signal from the terminal device, e.g., when the elementary set is created according to Equation (<NUM>). For a uniformly spaced linear array of antenna elements, the elementary set created according to Equation (<NUM>) is particularly advantageous in that it can indicate an actual angular sweeping of beams (azimuth, or elevation, depending on the array bore sight directions). Therefore, such elementary set is especially suitable to transmission schemes based on the AoA type of angular parameters. This feature can be exploited when a gNB is to track a Line of Sight (LoS) terminal device while it is moving. Such elementary set corresponds to increasing angles of the beams, and the ordering of the beam vectors is useful for gradually tracking the moving terminal device easily, e.g., by gradually increasing or decreasing the angle. Hence, according to AoAs of signals from the terminal device, beam vectors having increasing or decreasing indices can be selected for efficient searching or smooth tracking of the terminal device.

In an example, in the block <NUM>, the plurality of beam vectors can be selected based on a maximum allowable number of beams for a full spatial coverage sweeping or repetition of the radio signal during a period of time to cover a serving area. For example, 3GPP defines that, for frequency bands < <NUM>, a maximum number of SSB sweeping beams should be smaller than or equal to <NUM>; while for mmWave bands, up to <NUM> SSB beams can be supported. In practice, a gNB can flexibly configure different numbers of SSB beams. If the configured number of SSB beams is small, beam vectors in a high-level set (i.e., having a large n value), i.e., "wide" beams, can be used to cover an entire serving area. Additionally or alternatively, the plurality of beam vectors can be selected based on a targeted transmission or reception beamforming gain for the radio signal, and/or an allowable latency and/or a maximum period for a successful transmission or reception of the radio signal above a predetermined probability. For example, beam vectors in a high-level set (i.e., having a large n value), i.e., "wide" beams, typically provide high efficiency, low latency, but low beamforming gain; while beam vectors in a low-level set (i.e., having a small n value), i.e., "narrow" beams, typically provide low efficiency, high latency, but high beamforming gain. The selection in the block <NUM> can be made based on a desired tradeoff among these factors.

Further, the beam vectors can be selected for different signals or purposes and/or at different phases, which may have different desired tradeoffs among the above factors. For example, the radio signal may include an SSB, a CSI-RS or a reference or payload signal for multi-layer or multi-user transmission. Accordingly, the plurality of beam vectors can be selected from the n<NUM>-th set when the radio signal is the SSB, or from the n<NUM>-th set when the radio signal is the CSI-RS, or from the n<NUM>-th set when the radio signal is the reference or payload signal for multi-layer or multi-user transmission, where n<NUM>, n<NUM> and n<NUM> are integers and N≥n<NUM>≥n<NUM>≥n<NUM>≥<NUM>. For example, in a synchronization phase, the SSB may use wider beams for higher efficiency and lower latency. In a data transmission phase, the CSI-RS may use narrower beams than the SSB, while the signal for multi-layer or multi-user transmission may use even narrower beams (e.g., those in the elementary set) for higher beamforming gains and thus higher signal qualities.

Correspondingly to the method <NUM> as described above, a network device is provided. <FIG> is a block diagram of a network device <NUM> according to an embodiment of the present disclosure.

As shown in <FIG>, the network device <NUM> includes a determining unit <NUM> configured to determine a number, N, of sets of beam vectors by: creating a first set of beam vectors orthogonal to each other; and determining an n-th set of beam vectors each obtained by linear combination of two or more beam vectors from the (n-<NUM>)-th set of beam vectors, where N and n are integers and N≥n><NUM>. The network device <NUM> further includes a selecting unit <NUM> configured to select, from one or more of the N sets, a plurality of beam vectors for beamforming of a radio signal.

In an embodiment, the DFT based matrix can be the matrix shown in the above Equation (<NUM>).

In an embodiment, the selecting unit <NUM> can be configured to select the plurality of beam vectors for beamforming of the radio signal for transmission to a terminal device based on an Angle of Arrival (AOA) of another radio signal from the terminal device.

In an embodiment, the selecting unit <NUM> can be configured to select the plurality of beam vectors based on one or more of: a maximum allowable number of beams for a full spatial coverage sweeping or repetition of the radio signal during a period of time to cover a serving area, a targeted transmission or reception beamforming gain for the radio signal, or an allowable latency and/or a maximum period for a successful transmission or reception of the radio signal above a predetermined probability.

In an embodiment, the selecting unit <NUM> can be configured to select the plurality of beam vectors from the n<NUM>-th set when the radio signal is the SSB, or from the n<NUM>-th set when the radio signal is the CSI-RS, or from the n<NUM>-th set when the radio signal is the reference or payload signal for multi-layer or multi-user transmission, wherein n<NUM>, n<NUM> and n<NUM> are integers and N≥n<NUM>≥n<NUM>≥n<NUM>≥<NUM>.

The determining unit <NUM> and the selecting unit <NUM> can be implemented as a pure hardware solution or as a combination of software and hardware, e.g., by one or more of: a processor or a micro-processor and adequate software and memory for storing of the software, a Programmable Logic Device (PLD) or other electronic component(s) or processing circuitry configured to perform the actions described above, and illustrated, e.g., in <FIG>.

<FIG> is a block diagram of a network device <NUM> according to another embodiment of the present disclosure.

The network device <NUM> includes a transceiver <NUM>, a processor <NUM> and a memory <NUM>. The memory <NUM> contains instructions executable by the processor <NUM> whereby the network device <NUM> is operative to perform the actions, e.g., of the procedure described earlier in conjunction with <FIG>. Particularly, the memory <NUM> contains instructions executable by the processor <NUM> whereby the network device <NUM> is operative to: determine a number, N, of sets of beam vectors by: creating a first set of beam vectors orthogonal to each other; and determining an n-th set of beam vectors each obtained by linear combination of two or more beam vectors from the (n-<NUM>)-th set of beam vectors, where N and n are integers and N≥n><NUM>; and select, from one or more of the N sets, a plurality of beam vectors for beamforming of a radio signal.

In an embodiment, the DFT based matrix can be the matrix as shown in the above Equation (<NUM>).

In an embodiment, the plurality of beam vectors can be selected based on one or more of: a maximum allowable number of beams for a full spatial coverage sweeping or repetition of the radio signal during a period of time to cover a serving area, a targeted transmission or reception beamforming gain for the radio signal, or an allowable latency and/or a maximum period for a successful transmission or reception of the radio signal above a predetermined probability.

The present disclosure also provides at least one computer program product in the form of a non-volatile or volatile memory, e.g., a non-transitory computer readable storage medium, an Electrically Erasable Programmable Read-Only Memory (EEPROM), a flash memory and a hard drive. The computer program product includes a computer program. The computer program includes: code/computer readable instructions, which when executed by the processor <NUM> causes the network device <NUM> to perform the actions, e.g., of the procedure described earlier in conjunction with <FIG>.

The computer program product may be configured as a computer program code structured in computer program modules. The computer program modules could essentially perform the actions of the flow illustrated in <FIG>.

The processor may be a single CPU (Central processing unit), but could also comprise two or more processing units. For example, the processor may include general purpose microprocessors; instruction set processors and/or related chips sets and/or special purpose microprocessors such as Application Specific Integrated Circuit (ASICs). The processor may also comprise board memory for caching purposes. The computer program may be carried by a computer program product connected to the processor. The computer program product may comprise a non-transitory computer readable storage medium on which the computer program is stored. For example, the computer program product may be a flash memory, a Randomaccess memory (RAM), a Read-Only Memory (ROM), or an EEPROM, and the computer program modules described above could in alternative embodiments be distributed on different computer program products in the form of memories.

With reference to <FIG>, in accordance with an embodiment, a communication system includes a telecommunication network <NUM>, such as a 3GPP-type cellular network, which comprises an access network <NUM>, such as a radio access network, and a core network <NUM>. The access network <NUM> comprises a plurality of base stations 412a, 412b, 412c, such as NBs, eNBs, gNBs or other types of wireless access points, each defining a corresponding coverage area 413a, 413b, 413c. Each base station 412a, 412b, 412c is connectable to the core network <NUM> over a wired or wireless connection <NUM>. A first user equipment (UE) <NUM> located in coverage area 413c is configured to wirelessly connect to, or be paged by, the corresponding base station 412c.

The intermediate network <NUM> may be one of, or a combination of more than one of, a public, private or hosted network; the intermediate network <NUM>, if any, may be a backbone network or the Internet; in particular, the intermediate network <NUM> may comprise two or more subnetworks (not shown).

It is noted that the host computer <NUM>, base station <NUM> and UE <NUM> illustrated in <FIG> may be identical to the host computer <NUM>, one of the base stations 412a, 412b, 412c and one of the UEs <NUM>, <NUM> of <FIG>, respectively.

The wireless connection <NUM> between the UE <NUM> and the base station <NUM> is in accordance with the teachings of the embodiments described throughout this disclosure. One or more of the various embodiments improve the performance of OTT services provided to the UE <NUM> using the OTT connection <NUM>, in which the wireless connection <NUM> forms the last segment. More precisely, the teachings of these embodiments may improve data rate and/or latency and thereby provide benefits such as reduced user waiting time.

Claim 1:
A method (<NUM>) in a device, comprising:
determining (<NUM>) a number, N, of sets of beam vectors by:
creating a first set of beam vectors orthogonal to each other; and
determining an n-th set of beam vectors each obtained by linear combination of two or more beam vectors from the (n-<NUM>)-th set of beam vectors, where N and n are integers and N≥n><NUM>; and
selecting (<NUM>), from one or more of the N sets, a plurality of beam vectors for beamforming of a radio signal,
wherein said method is characterized in that the device is a network device and in that said selecting (<NUM>) is based on one or more of:
a maximum allowable number of beams for a full spatial coverage sweeping or repetition of the radio signal during a period of time to cover a serving area,
a targeted transmission or reception beamforming gain for the radio signal, or
an allowable latency and/or a maximum period for a successful transmission or reception of the radio signal above a predetermined probability.