SIGNAL TRANSMISSION METHOD AND APPARATUS

Abstract

A signal transmission method and apparatus, the method including generating a time domain Zadoff-Chu (ZC) sequence, generating a first frequency domain pilot sequence based on the time domain ZC sequence, obtaining a first frequency domain pilot signal by performing subcarrier mapping on the first frequency domain pilot sequence, obtaining a first time domain pilot signal by performing an inverse Fourier transform on the first frequency domain pilot signal, and sending the first time domain pilot signal, where a root q of the time domain ZC sequence satisfies a first constraint condition, and where the first constraint condition comprises an absolute value of q is less than or equal to a threshold, where the threshold is less than NZC−u, where NZC is a length of the time domain ZC sequence, and where u is a positive integer.

Description

TECHNICAL FIELD

This application relates to the field of communication technologies, and in particular, to a signal transmission method and an apparatus.

BACKGROUND

Integrated sensing and communication (ISAC) is widely considered as a key application scenario of next-generation wireless communication. Specifically, integrated sensing and communication means that a sent radio signal has both sensing and communication capabilities. Communication means that a sending end sends information to a receiving end. Sensing includes sensing a surrounding environment, a moving speed and a moving distance of an object, and the like.

A pilot signal is one of common signals in communication. How to implement ISAC by using the pilot signal and improve resource utilization is a problem to be resolved in this application.

SUMMARY

This application provides a signal transmission method and an apparatus, to generate a pilot signal in a chirp signal form, so as to implement ISAC by using the pilot signal, and improve resource utilization.

According to a first aspect, a signal transmission method is provided, including: generating a time domain Zadoff-Chu (ZC) sequence, generating a first frequency domain pilot sequence based on the time domain ZC sequence, performing subcarrier mapping on the first frequency domain pilot sequence to obtain a first frequency domain pilot signal, performing inverse Fourier transform on the first frequency domain pilot signal to obtain a first time domain pilot signal, and sending the first time domain pilot signal. A root q of the time domain ZC sequence satisfies a first constraint condition, and the first constraint condition includes: An absolute value of q is less than or equal to a threshold, the threshold is less than N_ZC−u, N_ZC is a length of the time domain ZC sequence, and u is a positive integer.

In this embodiment of this application, the time domain ZC sequence is generated (that is, a ZC sequence is generated in time domain), so that impact of a parameter (for example, the root q) of the ZC sequence on the first time domain pilot signal can be intuitively determined. This helps improve analog detection performance of the first time domain pilot signal (that is, the first time domain pilot signal can be as similar as possible to a chirp signal), so that ISAC can be further implemented by using the pilot signal, and resource utilization can be improved. In addition, a value of the root q of the ZC sequence (that is, the absolute value of q is less than or equal to the threshold) is constrained, so that the analog detection performance of the first time domain pilot signal can be improved (that is, a difference between the first time domain pilot signal and the chirp signal can be reduced).

Optionally, the first constraint condition includes: The absolute value of q is less than or equal to T_q, or the absolute value of q is a positive integer less than T_q, and T_q is a threshold, or absolute values of q are first M_q smallest values in a set of absolute values of optional q, and an absolute value of M_q^th optional q in the set is the threshold. Optional q and N_ZC are relatively prime.

Certainly, the foregoing two cases are merely examples, and an actual application is not limited thereto. Optionally, a value of T_q or M_q is related to at least one of a quantity N_d of subcarriers included in a transmission bandwidth, for example, a larger value of N_d indicates a larger value of T_q or M_q, a quantity N of subcarriers corresponding to the first frequency domain pilot signal, for example, a larger value of N indicates a larger value of T_q or M_q, and a maximum value T_z of a subcarrier mapping spacing z, for example, a larger value of T_z indicates a smaller value of T_q or M_q.

In this manner, parameter setting flexibility is improved while the analog detection performance of the first time domain pilot signal is ensured.

Optionally, the length N_ZC of the time domain ZC sequence satisfies a second constraint condition, and the second constraint condition includes:

$N_{\mathrm{ZC}}=N=\frac{N_d}{z};\mathrm{or}$ $N_{\mathrm{ZC}}=N=\frac{N_d}{z}-1;$

or

• • N_ZC is a maximum value in all possible values that are less than or equal to N and that enable a quantity of values of optional q to be {tilde over (M)}_q, where {tilde over (M)}_q is a positive integer, and

$N=\frac{N_d}{z};$

or

• • N_ZC is a maximum value in all possible values that are less than or equal to

$\frac{N_d}{z}$

and that enable a quantity of values of optional q to be {tilde over (M)}_q, where N_ZC=N, and {tilde over (M)}_q is a positive integer.

N is the quantity of subcarriers corresponding to the first frequency domain pilot signal, N_d is the quantity of subcarriers included in the transmission bandwidth, and z is the subcarrier mapping spacing.

In this manner, a value of the length N_ZC of the time domain ZC sequence is constrained, so that the analog detection performance of the first time domain pilot signal can be improved (that is, the difference between the first time domain pilot signal and the chirp signal can be reduced).

Optionally, the performing subcarrier mapping on the first frequency domain pilot sequence includes performing subcarrier mapping on the first frequency domain pilot sequence based on the subcarrier mapping spacing z.

z satisfies a third constraint condition, and the third constraint condition includes:

z is less than or equal to T_z, or z is a positive integer less than T_z.

Optionally, a value of T_z is related to at least one of the quantity N_d of subcarriers included in the transmission bandwidth, for example, a larger value of N_d indicates a larger value of T_z, and an absolute value of the root q of the time domain ZC sequence, for example, a larger value of q indicates a smaller value of T_z.

In this manner, parameter setting flexibility is improved while the analog detection performance of the first time domain pilot signal is ensured.

Optionally, the method may further include: receiving a second time domain pilot signal, where the second time domain pilot signal is a signal obtained by transmitting the first time domain pilot signal through a channel, and determining a distance and/or a speed of a target based on the first time domain pilot signal and the second time domain pilot signal.

In this manner, ranging, speed measurement, and the like are performed by using the pilot signal, to implement ISAC.

According to a second aspect, a signal transmission method is provided, including: generating a frequency domain ZC sequence, generating a second frequency domain pilot sequence based on the frequency domain ZC sequence, performing subcarrier mapping on the second frequency domain pilot sequence to obtain a second frequency domain pilot signal, performing inverse Fourier transform on the second frequency domain pilot signal to obtain a third time domain pilot signal, and sending the third time domain pilot signal. A root q of the frequency domain ZC sequence satisfies a fourth constraint condition, and the fourth constraint condition includes: An absolute value of q enables an absolute value of γ to be less than or equal to a threshold, γ and q satisfy: γq=δN_ZC−1, δ is an integer, the threshold is less than N_ZC−u, N_ZC is a length of the frequency domain ZC sequence, and u is a positive integer. γ is a root of a ZC sequence obtained by performing inverse Fourier transform on the frequency domain ZC sequence.

In this embodiment of this application, a ZC sequence is generated in frequency domain (that is, a ZC sequence is constructed in frequency domain), so that a Fourier transform step of converting a time domain signal into a frequency domain signal can be omitted, and signal processing efficiency can be improved. In addition, ISAC may also be implemented by generating the ZC sequence in frequency domain, and d₋₁ (a ZC sequence obtained by performing inverse Fourier transform on the frequency domain ZC sequence, that is, a time domain ZC sequence) is further constrained by constraining the root q of the frequency domain ZC sequence. This can improve analog detection performance of the third time domain pilot signal (that is, reduce a difference between the third time domain pilot signal and a chirp signal).

Optionally, when N_ZC=5, values of q, δ, and γ may be:

• • q=1, δ=0, and γ=−1; or
  • q=2, δ=1, and γ=2; or
  • q=3, δ=−1, and γ=−2; or
  • q=4, δ=1, and γ=1.

Certainly, the foregoing is merely examples herein, and N_ZC may have other values.

Optionally, the fourth constraint condition includes: q enables the absolute value of γ to be less than or equal to T_q, or q is an integer that enables the absolute value of γ to be less than T_q, and T_q is the threshold, or q are first M_q values that are in a set of optional q and that enable the absolute value of γ to be smallest, an absolute value of γ corresponding to M_q^th optional q is the threshold, and the absolute value of γ corresponding to M_q^th optional q in the set is the threshold. Optional q and N_ZC are relatively prime.

Certainly, the foregoing two cases are merely examples, and an actual application is not limited thereto.

Optionally, a value of T_q or M_q is related to at least one of a quantity N_d of subcarriers included in a transmission bandwidth, for example, a larger value of N_d indicates a larger value of T_q or M_q, a quantity N of subcarriers corresponding to the second frequency domain pilot signal, for example, a larger value of N indicates a larger value of T_q or M_q, and a maximum value T_z of a subcarrier mapping spacing z, for example, a larger value of T_z indicates a smaller value of T_q or M_q.

In this manner, parameter setting flexibility is improved while analog detection performance of the third time domain pilot signal is ensured.

Optionally, the length N_ZC of the frequency domain ZC sequence satisfies a fifth constraint condition, and the fifth constraint condition includes:

$N_{\mathrm{ZC}}=N=\frac{N_d}{z};\mathrm{or}$ $N_{\mathrm{ZC}}=N=\frac{N_d}{z}-1;$

or

• • N_ZC is a maximum value in all possible values that are less than or equal to N and that enable a quantity of values of optional q to be {tilde over (M)}_q, where {tilde over (M)}_q is a positive integer, and

$N=\frac{N_d}{z};$

or

• • N_ZC is a maximum value in all possible values that are less than or equal to

$\frac{N_d}{z}$

and that enable a quantity of values of optional q to be {tilde over (M)}_q, where N_ZC=N, and {tilde over (M)}_q is a positive integer.

N is the quantity of subcarriers corresponding to the second frequency domain pilot signal, N_d is the quantity of subcarriers included in the transmission bandwidth, and z is the subcarrier mapping spacing.

In this manner, a value of the length N_ZC of the frequency domain ZC sequence is constrained, so that the analog detection performance of the third time domain pilot signal can be improved (that is, the difference between the third time domain pilot signal and the chirp signal can be reduced).

Optionally, the performing subcarrier mapping on the second frequency domain pilot sequence includes: performing subcarrier mapping on the second frequency domain pilot sequence based on the subcarrier mapping spacing z, where z satisfies a sixth constraint condition, and the sixth constraint condition includes z is less than or equal to T_z, or z is a positive integer less than T_z, and T_z is the threshold.

In this manner, the subcarrier mapping spacing z is constrained, so that the analog detection performance of the third time domain pilot signal can be improved (that is, the difference between the third time domain pilot signal and the chirp signal can be reduced).

Optionally, a value of T_z is related to at least one of the quantity N_d of subcarriers included in the transmission bandwidth, for example, a larger value of N_d indicates a larger value of T_z, the root q of the frequency domain ZC sequence, and the absolute value of γ, for example, a larger value of γ indicates a smaller value of T_z.

In this manner, parameter setting flexibility is improved while the analog detection performance of the third time domain pilot signal is ensured.

Optionally, the method may further include: receiving a fourth time domain pilot signal, where the fourth time domain pilot signal is a signal obtained by transmitting the third time domain pilot signal through a channel, and determining a distance and/or a speed of a target based on the third time domain pilot signal and the fourth time domain pilot signal.

In this manner, ranging, speed measurement, and the like are performed by using the pilot signal, to implement ISAC.

According to a third aspect, a communication apparatus is provided. The apparatus includes a module, a unit, or a technical means configured to implement the method in any one of the first aspect or the optional implementations of the first aspect.

For example, the apparatus may include: a processing module, configured to: generate a time domain ZC sequence, generate a first frequency domain pilot sequence based on the time domain ZC sequence, perform subcarrier mapping on the first frequency domain pilot sequence to obtain a first frequency domain pilot signal, and perform inverse Fourier transform on the first frequency domain pilot signal to obtain a first time domain pilot signal, and a transceiver module, configured to send the first time domain pilot signal. A root q of the time domain ZC sequence satisfies a first constraint condition, and the first constraint condition includes: An absolute value of q is less than or equal to a threshold, the threshold is less than N_ZC−u, N_ZC is a length of the time domain ZC sequence, and u is a positive integer.

According to a fourth aspect, a communication apparatus is provided. The apparatus includes a module, a unit, or a technical means configured to implement the method in any one of the second aspect or the optional implementations of the second aspect.

For example, the apparatus may include: a processing module, configured to: generate a frequency domain ZC sequence, generate a second frequency domain pilot sequence based on the frequency domain ZC sequence, perform subcarrier mapping on the second frequency domain pilot sequence to obtain a second frequency domain pilot signal, and perform inverse Fourier transform on the second frequency domain pilot signal to obtain a third time domain pilot signal, and a transceiver module, configured to send the third time domain pilot signal. A root q of the frequency domain ZC sequence satisfies a fourth constraint condition, and the fourth constraint condition includes: An absolute value of q enables an absolute value of γ less than or equal to a threshold, γ and q satisfy: γq=δN_ZC−1, δ is an integer, the threshold is less than N_ZC−u, N_ZC is a length of the frequency domain ZC sequence, and u is a positive integer.

According to a fifth aspect, a communication apparatus is provided. The apparatus includes a processor and an interface circuit, the interface circuit is electrically coupled to the processor, and the processor performs, by using a logic circuit or by executing code instructions, the method according to any one of the first aspect or the optional implementations of the first aspect or the method according to any one of the second aspect or the optional implementations of the second aspect.

According to a sixth aspect, a computer-readable storage medium is provided. The storage medium stores a computer program or instructions, and when the computer program or the instructions are run, the method according to any one of the first aspect or the optional implementations of the first aspect is performed, or the method according to any one of the second aspect or the optional implementations of the second aspect is performed.

According to a seventh aspect, a computer program product is provided, including instructions. When the instructions are run on a computer, the method according to any one of the first aspect or the optional implementations of the first aspect is performed, or the method according to any one of the second aspect or the optional implementations of the second aspect is performed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a frequency difference between a reflected signal and a transmitted signal;

FIG. 2 is a diagram of subcarrier mapping;

FIG. 3A to FIG. 3C are diagrams of several scenarios to which embodiments of this application may be applied;

FIG. 4 is a flowchart of a signal transmission method according to an embodiment of this application;

FIG. 5 is a flowchart of another signal transmission method according to an embodiment of this application;

FIG. 6 is a diagram of a communication apparatus according to an embodiment of this application; and

FIG. 7 is a diagram of another communication apparatus according to an embodiment of this application.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The following describes in detail embodiments of this application with reference to accompanying drawings.

Technical solutions in embodiments of this application may be applied to various communication systems, for example, a 5th generation (5G) communication system, a 6th generation (6G) communication system, another future evolved system, other systems that use wireless communication, or the like.

In embodiments of this application, “at least one” means one or more, and “a plurality of” means two or more. “And/or” describes an association relationship between associated objects and represents that three relationships may exist. For example, A and/or B may represent the following cases: Only A exists, both A and B exist, and only B exists, where A and B may be singular or plural. In the text descriptions of this application, the character “/” indicates an “or” relationship between associated objects, and in a formula in this application, the character “/” indicates a “division” relationship between associated objects. “Including at least one of A, B, and C” may represent: including A, including B, including C, including A and B, including A and C, including B and C, and including A, B, and C.

It may be understood that various numbers in embodiments of this application are merely used for differentiation for ease of description, and are not used to limit the scope of embodiments of this application. Sequence numbers do not mean execution sequences. The execution sequences of processes are determined based on functions and internal logic of the processes.

Integrated sensing and communication (ISAC) is widely considered as a key application scenario of a next-generation wireless communication system (for example, a 6th generation (6G) communication system).

A radar is one of common sensing devices. A working principle of the radar is that a sending end sends a continuous signal (that is, a transmitted signal) whose frequency linearly increases with time, that is, a linear frequency modulated continuous wave (FMCW), which is also referred to as a chirp signal, as shown in FIG. 1. When the transmitted signal is reflected by an object, a reflected signal is formed, and is received by the sending end. Due to a delay on a propagation path, there is a frequency difference Δf between the reflected signal and the transmitted signal, and the frequency difference Δf is positively correlated with a propagation delay τ:

$\Delta f=R·\tau =\frac{\mathrm{BW}}{T}·\frac{2d}{c}.$

R is a frequency change rate of the continuous frequency modulated signal, a specific value of R is a ratio of a bandwidth (BW) of the continuous frequency modulated signal to a period T of the continuous frequency modulated signal, d is a distance between a target object (that is, an object that reflects a signal) and the sending end (that is, the radar), c=3·10⁸ m/s and is a propagation speed of an electromagnetic wave, BW is a bandwidth, and T is a frequency change period.

The radar performs frequency mixing on the received reflected signal and the transmitted signal to obtain the frequency difference Δf between the two signals, and may calculate a distance between the object and the sending end (which also is a receiving end of the reflected signal, that is, the radar) based on Δf.

Δf<<BW, that is, a sampling rate of an analog-to-digital converter (ADC) of a receiver does not need to be designed based on a requirement of the bandwidth BW of an entire signal, and only needs to be designed based on Δf. This greatly reduces the sampling rate of the ADC and reduces costs.

For example, if T=1 ms, and d=1 km,

$\Delta f=\frac{\mathrm{BW}}{T}·\frac{2d}{c}=\mathrm{BW}·\frac{2}{3}·{10}^2.$

$\frac{2}{3}·{10}^{-2}\ll 1.$

Therefore, an FMCW-based linear frequency modulation signal (chirp signal) is usually used in sensing.

A pilot signal (which may also be referred to as a preamble signal, a preamble, a pilot, or the like) is one of common signals in communication.

A ZC sequence may be used in an uplink pilot design. A full name of ZC is a “Zadoff-Chu” sequence, and is also referred to as a Chu sequence or a Frank-Zadoff-Chu (FZC) sequence, which is specifically:

$x_q\left(n\right)=e^{-\frac{j\pi \mathrm{qn}\left(n+c+2p\right)}{N}},$

where 0≤n<N.

q is a root of the ZC sequence, 0<q<N, q and N are relatively prime, c=N mod 2, p is an integer, and N is a length (whose value is a positive integer) of the ZC sequence.

In a typical ZC sequence, N a prime number, c=1, and p=0, that is,

$x_q\left(n\right)=e^{-\frac{j\pi qn\left(n+1\right)}{N}},$

where 0≤n<N.

It may be understood that, based on the ZC sequence, if −N<q<0 is allowed, and −q and N are relatively prime, the ZC sequence may also be written as:

$x_q\left(n\right)=e^{-\frac{j\pi qn\left(n+c+2p\right)}{N}},\mathrm{or}{x}_q\left(n\right)=e^{\frac{j\pi qn\left(n+c+2p\right)}{N}},$

where 0≤n<N.

0<q<N or −N<q<0, abs(q) and N are relatively prime, c=N mod 2, p is an integer, and N is a length (whose value is a positive integer) of the ZC sequence. abs(q) indicates a function for obtaining an absolute value of q.

When an uplink pilot is designed by using a ZC sequence, a ZC sequence may be generated in frequency domain:

$X_q\left(m\right)=e^{-\frac{j\pi \mathrm{qn}\left(m+1\right)}{N_{\mathrm{zc}}}},$

where 0≤m<N_ZC

N_ZC is a maximum prime number less than or equal to a quantity N of reference signals.

Then, the N reference signals are obtained through cyclic shift extension, that is, {tilde over (X)}(n)=X_q(n mod N_zc), where 0≤n<N.

Then, the N reference signals are inserted into corresponding reference signal subcarriers, for example, as shown in FIG. 2. It should be noted that, in FIG. 2, an example in which a transmission bandwidth is N_d subcarriers and a reference signal is sent every other subcarrier is used, that is,

$N=\frac{N_d}{2}.$

Certainly, FIG. 2 is merely an example, and an actual application is not limited thereto.

Then, a time domain signal is obtained through inverse Fourier transform (for example, inverse fast Fourier transform (IFFT) or inverse discrete Fourier transform (IDFT)), and the time domain signal is transmitted through an antenna.

N_ZC is a prime number. Therefore, when q is any integer between 1 and N_ZC−1, q and N_ZC are relatively prime. A specific value of q is related to parameters such as a cell identity document (ID), a user ID, and an ID configured by a base station.

However, the foregoing method for generating a pilot signal has at least one of the following disadvantages:

1. When performing receiving by using an analog chirp signal, a receiving end needs to use a time domain signal (for example, a slope of a frequency of the signal changes with time) that matches the transmitted signal. However, the foregoing method in which a pilot sequence is generated in frequency domain and then converted to time domain is not intuitive, and cannot directly determine a signal sent in time domain (for example, a slope of a frequency of the signal changes with time). Therefore, it is difficult for a receiver to process a received signal and learn how to select a parameter of a frequency domain pilot sequence (for example, a value of a root q of the frequency domain pilot sequence).

2. Because N is an even number in a cellular network system (for example, a long term evolution (LTE) network system and a new radio (NR) network system), and N_ZC<N, a time domain sequence (that is, a sequence obtained by performing IFFTH on {tilde over (X)}(n) of the frequency domain sequence {tilde over (X)}(n) is no longer a chirp signal due to cyclic shift extension. Consequently, a receive signal cannot be detected at the receiving end by using an analog chirp signal.

In view of at least the foregoing factors, the technical solutions in embodiments of this application are provided, to generate a pilot signal whose frequency linearly changes with time, so as to implement ISAC by using the pilot signal, and improve resource utilization.

For example, refer to FIG. 3A. Embodiments of this application may be applied to a system for communication between a satellite and a terminal, and the system includes a satellite and a terminal-type network element. The satellite provides a communication service for a terminal device, and the terminal device includes but is not limited to a device such as a smartphone, a smartwatch, or a tablet computer. The satellite transmits downlink data to the terminal, and the terminal transmits uplink data to the satellite.

For example, refer to FIG. 3B. Embodiments of this application may be applied to a system for communication between satellites. A conventional inter-satellite link communication system may be divided into two parts: an acquisition, tracking, and pointing (ATP) subsystem and a communication subsystem. The communication subsystem is responsible for inter-satellite information transmission, and is a main part of the inter-satellite communication system. The ATP subsystem is responsible for acquisition, pointing, and tracking between satellites. Acquisition means determining a direction of arrival of an incident signal, pointing means adjusting a transmit wave to aim at a receiving direction, and tracking means continuously adjusting pointing and acquisition in an entire communication process.

For example, refer to FIG. 3C. Embodiments of this application may be applied to a wireless communication system such as a cellular communication system or a wireless local area network communication system. In the cellular communication system, one network device may provide a service for a plurality of terminals, and one terminal may also communicate with a plurality of network devices. In the wireless local area network communication system, one access point may serve a plurality of terminals, and one terminal may also communicate with a plurality of access points.

The network device is an apparatus that is deployed in a radio access network or a wireless local area network and that provides a wireless communication function for the terminal device. The network device may include various forms of macro base stations, micro base stations (also referred to as small stations), relay stations, access points, and the like. In systems using different radio access technologies, names of the network device may be different. Alternatively, the network device may be a radio controller in a CRAN (Cloud Radio Access Network) scenario. Alternatively, the network device may be a base station device in a future 5G network or a network device in a future evolved PLMN network. The network device may alternatively be a wearable device or a vehicle-mounted device. The network device may alternatively be a transmission and reception point (TRP). The network device may alternatively be an access point (AP).

In addition, the terminal in this specification may also be referred to as a terminal device. The terminal may include various handheld devices, vehicle-mounted devices, wearable devices, or computing devices that have a wireless communication function, or other processing devices connected to a wireless modem. The terminal may be a mobile station (MS), a subscriber unit, a cellular phone, a smartphone, a wireless data card, a personal digital assistant (PDA for short) computer, a tablet computer, a wireless modem, a handheld device (handset), a laptop computer, a machine type communication (MTC) terminal, or the like.

It should be understood that the foregoing several communication systems are merely examples. In actual application, embodiments of this application may be further applied to other communication systems.

FIG. 4 is a flowchart of a signal transmission method according to an embodiment of this application. The method may be applied to any device (for example, a satellite, a base station, a terminal, or an access point) in any one of the foregoing communication systems. The method includes the following steps:

S401: Generate a time domain ZC sequence.

Specifically, a ZC sequence is constructed in time domain. In this specification, the ZC sequence constructed in time domain is referred to as the time domain ZC sequence.

For example, it is assumed that there are N reference signals, N is a positive integer, and N_ZC time domain ZC sequences are generated:

$x\left(n\right)=e^{-\frac{j\pi qn\left(n+c+2p\right)}{N_{\mathrm{zc}}}},$

where 0≤n<N_ZC.

q is a root of the ZC sequence, 0<q<N_ZC, q and N_ZC are relatively prime, N_ZC is a length of the ZC sequence, a value of N_ZC is a positive integer, c=N mod 2, p is an integer, and n is an index of the sequence x(n).

It may be understood that a quantity of sequences may also be referred to as a length of the sequence. For example, the length of the time domain ZC sequence is N_ZC. In an actual case, a signal is usually described by using a quantity, and a sequence is usually described by using a length.

Certainly, in actual application, the time domain ZC sequence may alternatively be

$x\left(n\right)=e^{\frac{j\pi qn\left(n+c+2p\right)}{N_{zc}}}.$

In this case, it is required that 0<−q<N_ZC, and −q and N_ZC are relatively prime. This is not limited in this application.

In either form, it satisfies: 0<abs(q)<N_ZC, and abs(q) and N_ZC are relatively prime. abs(q) represents obtaining an absolute value of q.

For ease of description, an example in which the time domain ZC sequence is

$x\left(n\right)=e^{-\frac{j\pi qn\left(n+c+2p\right)}{N_{zc}}}$

is used below.

S402: Generate a first frequency domain pilot sequence based on the time domain ZC sequence.

x(n) in step S401 is still used as an example, and generating of the first frequency domain pilot sequence based on the time domain ZC sequence may include the following steps:

Perform a cyclic shift on x(n):

{tilde over (x)}(n)=x(n+a) mod N), where 0≤n<N_ZC, n is an index of the sequence {tilde over (x)}(n), and a is a positive integer.

Perform Fourier transform on {tilde over (x)}(n) to obtain a frequency domain sequence, that is,

$X\left(k\right)=\sum _{n=0}^{N-1}{\tilde{x}\left(n\right)}_e^{\frac{-j2\pi \mathrm{kn}}{N_{zc}}},$

where 0≤k<N_ZC, and k is an index of the sequence X(k).

If N=N_ZC, X(k), is the first frequency domain pilot sequence.

If N>N_ZC, X(k) is cyclically extended, so that a length of X(k) reaches N. If N<N_ZC, X(k) is truncated, and a length of X(k) reaches N. For example,

{tilde over (X)}(k)=X((k+b) mod N), where 0≤k<N, k is an index of the sequence {tilde over (X)}(k), and b is an integer.

Perform phase offset on {tilde over (X)}(n) to obtain the first frequency domain pilot sequence:

X(k)=X(k)e^jck, where 0≤k<N, k is an index of the sequence X(k), and c is a real number.

S403: Perform subcarrier mapping on the first frequency domain pilot sequence to obtain a first frequency domain pilot signal.

Specifically, the first frequency domain pilot sequence (for example, X(k)) is mapped to N subcarriers by using a mapping function. The mapping function is, for example, f(l), l∈ϕ, where 0≤f(l)<N.

It is assumed that a transmission bandwidth is N_d subcarriers, subcarrier mapping may be performed on the first frequency domain pilot sequence based on a subcarrier mapping spacing z, that is, one reference signal is placed on every z subcarriers. z is a positive integer that can be divisible by N_d. For example, when z=1, a reference signal is continuously placed on each subcarrier, and when z=2, one reference signal is placed on every two subcarriers. It can be learned that the quantity N of reference signals satisfies:

$N\le \frac{N_d}{z}.$

The reference signal includes but is not limited to one or more of a channel state information reference signal (CSI-RS), a sounding reference signal (SRS), a demodulation reference signal (DMRS), a phase tracking reference signal (PT-RS), a tracking reference signal (T-RS), or a positioning reference signal (PRS).

S404: Perform inverse Fourier transform on the first frequency domain pilot signal to obtain a first time domain pilot signal.

For example, L-point inverse Fourier transform (or Fourier transform with a length or a size of L) is performed, where L≥N, to obtain the first time domain pilot signal:

$r\left(n\right)=\sum _{l\in \Phi }W\left(l\right)·{\overline{x}\left(f\left(l\right)\right)}_e^{\frac{j2\pi }{L}nl}.$

r(n) is a digital discrete time domain signal, n is an integer, f(l) is an index of a X(k) sequence corresponding to an l^th subcarrier, ϕ is a set of reference signal subcarriers, and W(l) is a weighting coefficient on the l_th subcarrier.

S405: Send the first time domain pilot signal.

Optionally, a cyclic prefix (CP) may be further added to the first time domain pilot signal, and the first time domain pilot signal having the CP is sent.

It may be understood that, when the first time domain pilot signal is represented by using an analog continuous time domain signal, the first time domain pilot signal may also be represented as:

$r\left(t\right)=\sum _{l\in \Phi }W\left(l\right)·\overline{X}\left(f\left(l\right)\right)e^{j2\pi l\Delta ft}.$

Time t∈[T₀, T_end] (unit: second) is start time and end time of the signal, and Δf (unit: Hz) is a subcarrier width.

Values of a, b, c, and ϕ may be configured by a network device, or may be related to an identifier of a terminal device. Some possible values of f(l) are f(l)=l−l₀, ϕ={l₀, . . . , l₀+N−1}, where l₀ is an integer. When the first time domain pilot signal is represented by using an analog continuous time domain signal, l₀≥0. This is convenient to express an index of a subcarrier. When the first time domain pilot signal is represented by using a digital discrete time domain signal, because

$e^{\frac{\mathrm{j2}\pi }{L}\mathrm{nl}}=e^{\frac{j2\pi }{L}n\left(1+\mathrm{vL}\right)},$

where v is any integer, l₀ may be a negative integer, 0, or a positive integer. Generally, for convenience of digital signal processing, L is an even number, and the sequence X(k) is continuously mapped to a subcarrier interval

$[-\frac{L}{2},\frac{L}{2})\mathrm{or}(-\frac{L}{2},\frac{L}{2}].$

Therefore, the following constraints:

$l_0+N-1\le \frac{L}{2}\frac{L}{2}-1,\mathrm{and}{l}_0\ge -\frac{L}{2}\mathrm{or}-\frac{L}{2}+1$

may be further implemented.

In the foregoing solution, the ZC sequence is generated in time domain, so that impact of a parameter (for example, the root q and N_ZC) of the ZC sequence on the first time domain pilot signal can be intuitively determined. This helps improve analog detection performance of the first time domain pilot signal (that is, the first time domain pilot signal can be as similar as possible to a chirp signal), so that ISAC can be further implemented by using the pilot signal, and resource utilization can be improved.

For example, ISAC is implemented by using the pilot signal. After S405, a second time domain pilot signal may be further received, where the second time domain pilot signal is a signal obtained by transmitting the first time domain pilot signal through a channel, and a distance and/or a speed of a target are/is determined based on the first time domain pilot signal and the second time domain pilot signal. For example, the distance of the target is determined based on a frequency difference determined based on the first time domain pilot signal and the second time domain pilot signal.

It may be understood that a larger absolute value of the root (namely, q) of the time domain ZC sequence indicates a larger difference between an ideal chirp signal and finally obtained first time domain pilot signals r(n) and r(t). Consequently, performance of a receiver deteriorates. Therefore, in this embodiment of this application, a value range of q is constrained, to improve the analog detection performance of the first time domain pilot signal.

In a possible design, q satisfies a first constraint condition, and the first constraint condition includes: The absolute value of q is less than or equal to a threshold, the threshold is less than N_ZC−u, N_ZC is the length of the time domain ZC sequence, and u is a positive integer.

For example, the first constraint condition includes: The absolute value of q is less than or equal to T_q, or the absolute value of q is a positive integer less than T_q. Correspondingly, T_q is the threshold.

For example, absolute values of q are first M_q smallest values in a set of absolute values of optional q. Correspondingly, an absolute value of M_q^th optional q in the set is the threshold.

Optional q and N_ZC are relatively prime. For example, the set of the absolute values of optional q is a set including all possible absolute values of q that are relatively prime to N_ZC.

Certainly, the first constraint condition is not limited to the foregoing two examples.

During specific implementation, a value of T_q or M_q may be configured by a base station or agreed on between a sending device and a receiving device. This is not limited in this application.

Optionally, the value of T_q or M_q is related to at least one of the following:

(1) A quantity N_d of subcarriers included in a transmission bandwidth.

A larger value of N_d indicates less distortion caused by abs(q)>1. Therefore, a larger value of the absolute value of q can be tolerated. Therefore, a larger value of N_d indicates a larger value of T_q or M_q.

For example, N_d=n₁ corresponds to T_q=t₁, N_d=n₂ corresponds to T_q=t₂, and if n₁≤n₂, t₁≤t₂. Alternatively, N_d=n₁ corresponds to M_q=t₁, N_d=n₂ corresponds to M_q=t₂, and if n₁≤n₂, t₁≤t₂.

(2) A quantity N of subcarriers (that is, a quantity of reference signals) corresponding to the first frequency domain pilot signal.

A larger value of N indicates less distortion caused by abs(q)>1. Therefore, a larger value of the absolute value of q can be tolerated. Therefore, a larger value of N indicates a larger value of T_q or M_q.

For example, N=n₁ corresponds to T_q=t₁, N=n₂ corresponds to T_q=t₂, and if n₁≤n₂, t₁≤t₂. Alternatively, N=n₁ corresponds to M_q=t₁, N=n₂ corresponds to M_q=t₂, and if n₁≤n₂, t₁≤t₂.

(3) A maximum value T_z of the subcarrier mapping spacing z.

A smaller value of T_z indicates less distortion caused by abs(q)>1. Therefore, a larger value of the absolute value of q can be tolerated. Therefore, a larger value of T_z indicates a smaller value of T_q or M_q.

For example, T_q=q₁ corresponds to T_z=t₁, T_q=q₂ corresponds to T_z=t₂, and if t₁≤t₂, abs(q₁)≥abs(q₂). Alternatively, M_q=q₁ corresponds to T_z=t₁, M_q=q₂ corresponds to T_z=t₂, and if t₁≤t₂, abs(q₁)≥abs(q₂).

In this embodiment of this application, the value of the root q of the ZC sequence is constrained, so that the analog detection performance of the first time domain pilot signal can be improved (that is, the difference between the first time domain pilot signal and the chirp signal can be reduced), thereby helping implement ISAC by using the pilot signal, and improving resource utilization.

It may be understood that a larger difference between N and N_ZC while N_ZC is less than N indicates a larger difference between the chirp signal and the finally obtained first time domain pilot signals r(n) and r(t). Consequently, the performance of the receiver deteriorates. Therefore, in this embodiment of this application, a value of N_ZC may be further constrained, to improve the analog detection performance of the first time domain pilot signal.

In a possible design, the length N_ZC of the time domain ZC sequence satisfies a second constraint condition, and the second constraint condition may be any one of the following:

(1) N_ZC is a maximum prime number less than or equal to N, where

$N=\frac{N_d}{z}.$

Alternatively, this may be described as that N is a maximum prime number less than or equal to

$\frac{N_d}{z},$

where N_ZC=N. N_ZC and the absolute value of the root q of the time domain ZC sequence are relatively prime.

In this manner, values of optional q may be as many as possible.

$\begin{array}{cc}{N}_{\mathrm{ZC}}=N=\frac{N_d}{z}.& \left(2\right)\end{array}$

In this manner, distortion of the first time domain pilot signal can be as small as possible.

$\begin{array}{cc}{N}_{\mathrm{ZC}}=N=\frac{N_d}{z}-1.& \left(3\right)\end{array}$

Because

$\frac{N_d}{z}$

is usually an even number, in this manner, distortion caused by N_ZC can be minimized, and N_ZC is set to an odd number, so that values of optional q are as many as possible.

(4) N_ZC is a maximum value in all possible values that are less than or equal to N and that enable a quantity of values of optional q to be {tilde over (M)}_q, where {tilde over (M)}_q is a positive integer, and

$N=\frac{N_d}{z}.$

In this manner, the quantity of values of optional q may be {tilde over (M)}_q. A value of {tilde over (M)}_q may be configured by a base station or agreed on by a signal receiving party and a signal sending party. Optionally, {tilde over (M)}_q is equal to M_q.

(5) N_ZC is a maximum value in all possible values that are less than or equal to

$\frac{N_d}{z}$

and that enable a quantity of values of optional q to be {tilde over (M)}_q, where N_ZC=N, and {tilde over (M)}_q is a positive integer.

In this manner, the quantity of values of optional q may be {tilde over (M)}_q. A value of {tilde over (M)}_q may be configured by a base station or agreed on by a signal receiving party and a signal sending party. Optionally, {tilde over (M)}_q is equal to M_q.

In this embodiment of this application, a value of the length N_ZC of the ZC sequence is constrained, so that the analog detection performance of the first time domain pilot signal can be improved (that is, the difference between the first time domain pilot signal and the chirp signal can be reduced), thereby helping implement ISAC by using the pilot signal, and improving resource utilization.

It may be understood that a larger subcarrier mapping spacing (namely, z) indicates a larger difference between the ideal chirp signal and the finally obtained first time domain pilot signals r(n) and r(t). Consequently, the performance of the receiver deteriorates. Therefore, in this embodiment of this application, a value of z may be further constrained, to improve the analog detection performance of the first time domain pilot signal.

In a possible design, z satisfies a third constraint condition, and the third constraint condition may be any one of (1) z is less than or equal to T_z, and (2) z is a positive integer less than T_z

During specific implementation, a value of T_z may be configured by a base station or agreed on by a signal receiving party and a signal sending party.

Optionally, the value of T_z may be related to at least one of the following:

(1) The quantity N_d of subcarriers included in the transmission bandwidth.

A larger value of N_d indicates less distortion caused by T_z>1. Therefore, a larger value of T_z can be tolerated. Therefore, a larger value of N_d indicates a larger value of T_z.

For example, N_d=n₁ corresponds to T_z=t₁, N_d=n₂ corresponds to T_z=t₂, and if n₁≤n₂, t₁≤t₂.

(2) The absolute value of the root q of the time domain ZC sequence.

A smaller absolute value of q indicates less distortion caused by T_z>1. Therefore, a larger value of T_z can be tolerated. Therefore, a larger value of q indicates a smaller value of T_z.

For example, abs(q)=q₁ corresponds to T_z=t₁, abs(q)=q₂ corresponds to T_z=t₂, and if q_1≥92, t₁≤t₂.

In this embodiment of this application, the subcarrier mapping spacing z is constrained, so that the analog detection performance of the first time domain pilot signal can be improved (that is, the difference between the first time domain pilot signal and the chirp signal can be reduced), thereby helping implement ISAC by using the pilot signal, and improving resource utilization.

The foregoing describes a method for constructing the ZC sequence in time domain to generate the pilot signal, and the following describes a method for generating a ZC sequence in frequency domain to generate a pilot signal.

FIG. 5 is a flowchart of another signal transmission method according to an embodiment of this application. The method may be applied to any device (for example, a satellite, a base station, a terminal, or an access point) in any one of the foregoing communication systems. The method includes the following steps:

S501: Generate a frequency domain ZC sequence.

Specifically, a ZC sequence is constructed in frequency domain. In this specification, the ZC sequence constructed in frequency domain is referred to as the frequency domain ZC sequence.

For example, it is assumed that there are N reference signals, N is a positive integer, and N_ZC (N_ZC≤N) frequency domain ZC sequences (that is, a frequency domain ZC sequence with a length of N_ZC) are generated:

$X\left(k\right)=e^{-\frac{j\pi qk\left(k+c+2p\right)}{N_{\mathrm{ZC}}}},$

where 0≤k<N_ZC.

k is an index of the sequence X(k), q is a root of the ZC sequence, 0<q<N_ZC, q and N_ZC are relatively prime, N_ZC is a length of the ZC sequence, a value of N_ZC is a positive integer, c=N mod 2, and p is an integer.

Certainly, in actual application, the frequency domain ZC sequence may alternatively be

$X\left(k\right)=e^{\frac{j\pi qk\left(k+c+2p\right)}{N_{\mathrm{ZC}}}}.$

In this case, it is required that 0<−q<N_ZC, and −q and N_ZC are relatively prime. This is not limited in this application.

In either form, it satisfies: 0<abs(q)<N_ZC, and abs(q) and N_ZC are relatively prime. abs(q) represents obtaining an absolute value of q.

For ease of description, an example in which the frequency domain ZC sequence is

$X\left(k\right)=e^{-\frac{j\pi qk\left(k+c+2p\right)}{N_{\mathrm{ZC}}}}$

is used below.

S502: Generate a second frequency domain pilot sequence based on the frequency domain ZC sequence.

For example, if N_ZC<N, X(k) is cyclically extended to N, and if N_ZC>N, X(k) is truncated to N. For example,

{tilde over (X)}(k)=X(k+α)mod N) where 0≤j<N, k is an index of the {tilde over (X)}(k) sequence, and α is an integer.

Perform phase offset on {tilde over (X)}(k) to obtain the second frequency domain pilot sequence:

X(k)={tilde over (X)}(k)e^jβk, where 0≤k<N, k is an index of the sequence X(k), and β is a real number.

S503: Perform subcarrier mapping on the second frequency domain pilot sequence to obtain a second frequency domain pilot signal.

Specifically, the second frequency domain pilot sequence (for example, X(k)) is mapped to N subcarriers. It is assumed that a transmission bandwidth is N_d subcarriers, subcarrier mapping may be performed on the second frequency domain pilot sequence based on a subcarrier mapping spacing z. For this step, refer to S403. Details are not described herein again.

S504: Perform inverse Fourier transform on the second frequency domain pilot signal to obtain a third time domain pilot signal.

For example, L-point inverse Fourier transform is performed to obtain the third time domain pilot signal:

$r\left(n\right)=\sum _{l\in \Phi }W\left(l\right)•\stackrel{\_}{X}\left(f\left(l\right)\right)e^{\frac{j2\pi }{L}nl},$

where Φ is a set of reference signal subcarriers, n is an integer, f(l) is an index of a sequence X(k) corresponding to an l_th subcarrier, and W(l) is a weighting coefficient on the l_th subcarrier.

S505: Send the third time domain pilot signal.

Optionally, a CP may be further added to the third time domain pilot signal, and the third time domain pilot signal having the CP is sent.

Similarly, it may be understood that the third time domain pilot signal may also be represented by using an analog continuous time domain signal. For details, refer to related content of S405. Details are not described herein again.

In the foregoing solution, the ZC sequence is generated in frequency domain, steps are simple, and a step of performing Fourier transform to convert a time domain signal into a frequency domain signal is omitted, so that signal processing efficiency can be improved. In addition, ISAC may also be implemented by generating the ZC sequence in frequency domain. For example, after S505, ISAC may be further implemented by using a pilot signal as an example. After S505, a fourth time domain pilot signal may be further received, where the fourth time domain pilot signal is a signal obtained by transmitting the third time domain pilot signal through a channel, and a distance and/or a speed of a target are/is determined based on the third time domain pilot signal and the fourth time domain pilot signal. For example, the distance of the target is determined based on a frequency difference determined based on the third time domain pilot signal and the fourth time domain pilot signal.

In this embodiment of this application, a time domain sequence obtained by performing inverse Fourier transform on X(k) is:

$x\left(n\right)={\sum }_{k=0}^{N-1}X\left(k\right)e^{\frac{j2\pi kn}{N}}=A\underset{x_{\gamma }\left(n\right)}{\underbrace{e^{\frac{-j\pi \gamma n\left(n+\left(c+2p\right)\right)}{N}}}}{e}^{j\theta }.$

It can be learned that x(n) is obtained by multiplying a time domain ZC sequence x_γ(n) whose root is γ by a phase offset θ. A receiver may compensate for the phase offset without performance loss.

The root q of the frequency domain ZC sequence X(k) and a root γ of the time domain ZC sequence x_γ(n) satisfy: γq=δN_ZC−1, where δ is a positive integer, and examples of values of δ are shown in Table 1.

TABLE 1
NZC = 5
q	δ	γ
1	0	−1
2	1	2
3	−1	−2
4	1	1

It may be understood that a larger absolute value of the root (namely, γ) of the time domain ZC sequence indicates a larger difference between the third time domain pilot signal and an ideal chirp signal. Consequently, performance of the receiver deteriorates. However, there is a correspondence (namely, γq=δN_ZC−1) between the root q of the frequency domain ZC sequence X(k) and the root γ of the time domain ZC sequence x_γ(n). Therefore, in this embodiment of this application, a value range of q may be constrained to constrain γ, to improve analog detection performance of the third time domain pilot signal.

In a possible design, the root q of the frequency domain ZC sequence satisfies a fourth constraint condition, and the fourth constraint condition includes: The absolute value of q enables an absolute value of γ to be less than or equal to a threshold, γ and q satisfy: γq=δN_ZC−1, δ is an integer, the threshold is less than N_ZC−u, N_ZC is a length of the frequency domain ZC sequence, and u is a positive integer.

For example, the fourth constraint condition includes: q enables the absolute value of γ to be less than or equal to T_q, or q is an integer that enables the absolute value of γ to be less than T_q, and T_q is the threshold.

For example, the fourth constraint condition includes: q are first M_q values that are in a set of optional q and that enable the absolute value of γ to be smallest, an absolute value of γ corresponding to M_q^th optional q is the threshold, and the absolute value of γ corresponding to M_q^th optional q in the set is the threshold. Optional q and N_ZC are relatively prime.

Optional q and N_ZC are relatively prime. For example, the set of the absolute values of optional q is a set including all possible absolute values of q that are relatively prime to N_ZC.

Certainly, the fourth constraint condition is not limited to the foregoing two examples.

During specific implementation, a value of T_q or M_q may be configured by a base station or agreed on between a sending device and a receiving device. This is not limited in this application.

Optionally, the value of T_q or M_q is related to at least one of the following.

(1) A quantity N_d of subcarriers included in a transmission bandwidth.

A larger value of N_d indicates less distortion caused by abs(γ)>1. Therefore, a larger absolute value of γ can be tolerated. Therefore, a larger value of N_d indicates a larger value of T_q or M_q.

For example, N_d=n₁ corresponds to T_q=t₁, N_d=n₂ corresponds to T_q=t₂, and if n₁≤n₂, t₁≤t₂. Alternatively, N_d=n₁ corresponds to M_q=t₁, N_d=n₂ corresponds to M_q=t₂, and if n₁≤n₂, t₁≤t₂.

(2) A quantity N of subcarriers corresponding to the second frequency domain pilot signal.

A larger value of N indicates less distortion caused by abs(γ)>1. Therefore, a larger absolute value of γ can be tolerated. Therefore, a larger value of N indicates a larger value of T_q or M_q.

For example, N=n₁ corresponds to T_q=t₁, N=n₂ corresponds to T_q=t₂, and if n₁≤n₂, t₁≤t₂. Alternatively, N=n₁ corresponds to M_q=t₁, N=n₂ corresponds to M_q=t₂, and if n₁≤n₂, t₁≤t₂.

(3) A maximum value T_z of a subcarrier mapping spacing z.

A smaller value of T_z indicates less distortion caused by abs(γ)>1. Therefore, a larger absolute value of γ can be tolerated. Therefore, a larger value of T_z indicates a smaller value of T_q or M_q.

For example, T_q=q₁ corresponds to T_z=t₁, T_q=q₂ corresponds to T_z=t₂, q=q₁ corresponds to γ=d₁, and q=q₂ corresponds to γ=d₂. If t₁≤t₂, abs(d₁)≥abs(d₂). Alternatively, M_q=q₁ corresponds to T_z=t₁, M_q=q₂ corresponds to T_z=t₂, and if t₁≤t₂, abs(d₁)≥abs(d₂).

In this embodiment of this application, the root γ of the time domain ZC sequence may be constrained by constraining the value of the root q of the frequency domain ZC sequence, so that the analog detection performance of the third time domain pilot signal can be improved (that is, the difference between the third time domain pilot signal and the chirp signal can be reduced), thereby helping implement ISAC by using the pilot signal, and improving resource utilization.

It may be understood that a larger difference between N and N_ZC while N_ZC is less than N indicates a larger difference between the finally obtained third time domain pilot signal and the chirp signal. Consequently, the performance of the receiver deteriorates. Therefore, in this embodiment of this application, a value of N_ZC may be further constrained, to improve the analog detection performance of the third time domain pilot signal.

In a possible design, the length N_ZC of the time domain ZC sequence satisfies a fifth constraint condition, and the fifth constraint condition may be any one of the following.

(1) N_ZC is a maximum prime number less than or equal to N, where

$N=\frac{N_d}{z}.$

Alternatively, this may be described as that N is a maximum prime number less than or equal to

$\frac{N_d}{z},$

where N_ZC=N. N_ZC and the absolute value of the root q of the time domain ZC sequence are relatively prime.

In this manner, values of optional q may be as many as possible.

$\begin{array}{cc}{N}_{\mathrm{ZC}}=N=\frac{N_d}{z}.& \left(2\right)\end{array}$

In this manner, distortion of the third time domain pilot signal can be as small as possible.

$\begin{array}{cc}{N}_{\mathrm{ZC}}=N=\frac{N_d}{z}-1.& \left(3\right)\end{array}$

Because

$\frac{N_d}{z}$

is usually an even number, in this manner, distortion caused by N_ZC can be minimized, and N_ZC is set to an odd number, so that values of optional q are as many as possible.

(4) N_ZC is a maximum value in all possible values that are less than or equal to N and that enable a quantity of values of optional q to be {tilde over (M)}_q, where {tilde over (M)}_q is a positive integer, and

$N=\frac{N_d}{z}.$

In this manner, the quantity of values of optional q may be {tilde over (M)}_q. A value of {tilde over (M)}_q may be configured by a base station or agreed on by a signal receiving party and a signal sending party. Optionally, {tilde over (M)}_q is equal to M_q.

(5) N_ZC is a maximum value in all possible values that are less than or equal to

$\frac{N_d}{z}$

and that enable a quantity of values of optional q to be {tilde over (M)}_q, where N_ZC=N, and {tilde over (M)}_q is a positive integer.

In this manner, the quantity of values of optional q may be {tilde over (M)}_q. A value of {tilde over (M)}_q may be configured by a base station or agreed on by a signal receiving party and a signal sending party. Optionally, {tilde over (M)}_q is equal to M_q.

In this embodiment of this application, the value of the length N_ZC of the ZC sequence is constrained, so that the analog detection performance of the third time domain pilot signal can be improved (that is, the difference between the third time domain pilot signal and the chirp signal can be reduced), thereby helping implement ISAC by using the pilot signal, and improving resource utilization.

It may be understood that a larger subcarrier mapping spacing (namely, z) indicates a larger difference between the finally obtained third time domain pilot signal and the ideal chirp signal. Consequently, the performance of the receiver deteriorates. Therefore, in this embodiment of this application, a value of z may be further constrained, to improve the analog detection performance of the third time domain pilot signal.

In a possible design, z satisfies a sixth constraint condition, and the sixth constraint condition may be any one of the following (1) z is less than or equal to T_z, and (2) z is a positive integer less than T_z.

During specific implementation, a value of T_z may be configured by a base station or agreed on by a signal receiving party and a signal sending party.

Optionally, the value of T_z may be related to at least one of the following.

(1) The quantity N_d of subcarriers included in the transmission bandwidth.

A larger value of N_d indicates less distortion caused by T_z>1. Therefore, a larger value of T_z can be tolerated. Therefore, a larger value of N_d indicates a larger value of T_z.

For example, N_d=n₁ corresponds to T_z=t₁, N_d=n₂ corresponds to T_z=t₂, and if n₁≤n₂, t₁≤t₂.

(2) The root q of the frequency domain ZC sequence.

A smaller absolute value of q indicates less distortion caused by T_z>1. Therefore, a larger value of T_z can be tolerated. Therefore, a larger value of q indicates a smaller value of T_z.

For example, abs(q)=q₁ corresponds to T_z=t₁, abs(q)=q₂ corresponds to T_z=t₂, and if q₁≥q₂, t₁≤t₂.

(3) The absolute value of the root γ of the time domain ZC sequence.

A smaller value of γ indicates less distortion caused by T_z>1. Therefore, a larger value of T_z can be tolerated. Therefore, a larger value of γ indicates a smaller value of T_z.

For example, q=q₁ corresponds to γ=d₁, T₂=t₁, q=q₂ corresponds to γ=d₂, T₂=t₂, and if abs(d₁)≥abs(d₂), t₁≤t₂.

In this embodiment of this application, the subcarrier mapping spacing z is constrained, so that the analog detection performance of the third time domain pilot signal can be improved (that is, the difference between the third time domain pilot signal and the chirp signal can be reduced), thereby helping implement ISAC by using the pilot signal, and improving resource utilization.

Based on a same technical idea, an embodiment of this application provides a communication apparatus 600. The apparatus 600 may be, for example, a satellite, a base station, a terminal, an access point, or a chip inside a satellite, a base station, a terminal, or an access point. The apparatus 600 includes corresponding modules, units, or means for performing the method steps in the embodiment shown in FIG. 4 or FIG. 5. The functions, units, or means may be implemented by software, may be implemented by hardware, or may be implemented by hardware executing corresponding software.

For example, refer to FIG. 6. The apparatus 600 may include a processing module 601 and a transceiver module 602.

When the apparatus 600 is configured to implement the method in the embodiment shown in FIG. 4, the processing module 601 is configured to: generate a time domain ZC sequence, generate a first frequency domain pilot sequence based on the time domain ZC sequence, perform subcarrier mapping on the first frequency domain pilot sequence to obtain a first frequency domain pilot signal, and perform inverse Fourier transform on the first frequency domain pilot signal to obtain a first time domain pilot signal, and the transceiver module 602 is configured to send the first time domain pilot signal. A root q of the time domain ZC sequence satisfies a first constraint condition, and the first constraint condition includes: An absolute value of q is less than or equal to a threshold, the threshold is less than N_ZC−u, N_ZC is a length of the time domain ZC sequence, and u is a positive integer.

When the apparatus 600 is configured to implement the method in the embodiment shown in FIG. 5, the processing module 601 is configured to generate a frequency domain ZC sequence, generate a second frequency domain pilot sequence based on the frequency domain ZC sequence, perform subcarrier mapping on the second frequency domain pilot sequence to obtain a second frequency domain pilot signal, and perform inverse Fourier transform on the second frequency domain pilot signal to obtain a third time domain pilot signal, and the transceiver module 602 is configured to send the third time domain pilot signal. A root q of the frequency domain ZC sequence satisfies a fourth constraint condition, and the fourth constraint condition includes: An absolute value of q enables an absolute value of γ to be less than or equal to a threshold, γ and q satisfy: γq=δN_ZC−1, δ is an integer, the threshold is less than N_ZC−u, N_ZC is a length of the frequency domain ZC sequence, and u is a positive integer.

It should be understood that all related content of the steps in the foregoing method embodiment may be referenced to function descriptions of corresponding functional modules. Details are not described herein again.

Based on a same technical idea, refer to FIG. 7. An embodiment of this application further provides a communication apparatus 700, including at least one processor 701 and a communication interface 703 that is communicatively connected to the at least one processor 701, where the at least one processor 701 executes instructions stored in the memory 702, to enable the apparatus to perform, by using the communication interface 703, the method steps performed by the network device in the embodiment shown in FIG. 5.

Optionally, the memory 702 is located outside the apparatus 700.

Optionally, the apparatus 700 includes the memory 702, the memory 702 is connected to the at least one processor 701, and the memory 702 stores instructions that can be executed by the at least one processor 701. In FIG. 7, a dashed line indicates that the memory 702 is optional for the apparatus 700.

The processor 701 and the memory 702 may be coupled through an interface circuit, or may be integrated together. This is not limited herein.

A specific connection medium between the processor 701, the memory 702, and the communication interface 703 is not limited in this embodiment of this application. In this embodiment of this application, the processor 701, the memory 702, and the communication interface 703 are connected through a bus 704 in FIG. 7. The bus is represented by using a bold line in FIG. 7. A connection manner between other components is merely an example for description, and is not limited thereto. The bus may be classified into an address bus, a data bus, a control bus, and the like. For ease of representation, only one bold line is used for representation in FIG. 7, but this does not mean that there is only one bus or only one type of bus.

A specific connection medium between the processor 701, the memory 702, and the communication interface 703 is not limited in this embodiment of this application. In this embodiment of this application, the processor 701, the memory 702, and the communication interface 703 are connected through a bus 704 in FIG. 7. The bus is represented by using a bold line in FIG. 7. A connection manner between other components is merely an example for description, and is not limited thereto. The bus may be classified into an address bus, a data bus, a control bus, and the like. For ease of representation, only one bold line is used for representation in FIG. 7, but this does not mean that there is only one bus or only one type of bus.

It should be understood that the processor mentioned in this embodiment of this application may be implemented by using hardware or by software. When the processor is implemented by using hardware, the processor may be a logic circuit, an integrated circuit, or the like. When the processor is implemented by using software, the processor may be a general-purpose processor, and is implemented by reading software code stored in the memory.

For example, the processor may be a central processing unit (CPU), or may be another general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA) or another programmable logic device, a discrete gate or a transistor logic device, a discrete hardware component, or the like. The general-purpose processor may be a microprocessor, or the processor may be any conventional processor or the like.

It should be understood that the memory mentioned in this embodiment of this application may be a volatile memory or a non-volatile memory, or may include both a volatile memory and a non-volatile memory. The non-volatile memory may be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory. The volatile memory may be a random access memory (RAM), used as an external cache. By way of example and not limitation, RAMs in many forms may be used, for example, a static random access memory (SRAM), a dynamic random access memory (DRAM), a synchronous dynamic random access memory (SDRAM), a double data rate synchronous dynamic random access memory (DDR SDRAM), an enhanced synchronous dynamic random access memory (ESDRAM), a synchlink dynamic random access memory (SLDRAM), and a direct rambus random access memory (DR RAM).

It should be noted that when the processor is a general-purpose processor, a DSP, an ASIC, an FPGA or another programmable logic device, a discrete gate or a transistor logic device, or a discrete hardware component, the memory (storage module) may be integrated into the processor.

It should be noted that the memory described in this specification aims to include but is not limited to these memories and any memory of another proper type.

Based on a same technical idea, an embodiment of this application further provides a computer-readable storage medium, including a program or instructions. When the program or the instructions are run on a computer, the method shown in FIG. 4 or FIG. 5 is performed.

Based on a same technical idea, an embodiment of this application further provides a computer program product, including instructions. When the instructions are run on a computer, the method shown in FIG. 4 or FIG. 5 is performed.

All related content of the steps in the foregoing method embodiment may be referenced to function descriptions of corresponding functional modules. Details are not described herein again.

A person skilled in the art should understand that embodiments of this application may be provided as a method, a system, or a computer program product. Therefore, this application may use a form of hardware only embodiments, software only embodiments, or embodiments with a combination of software and hardware. In addition, this application may use a form of a computer program product that is implemented on one or more computer-usable storage media (including but not limited to a disk memory, a CD-ROM, an optical memory, and the like) that include computer-usable program code.

This application is described with reference to the flowcharts and/or block diagrams of the method, the device (or system), and the computer program product according to this application. It should be understood that computer program instructions may be used to implement each process and/or each block in the flowcharts and/or the block diagrams and a combination of a process and/or a block in the flowcharts and/or the block diagrams. These computer program instructions may be provided for a general-purpose computer, a dedicated computer, an embedded processor, or a processor of any other programmable data processing device to generate a machine, so that the instructions executed by a computer or a processor of any other programmable data processing device generate an apparatus for implementing a specific function in one or more processes in the flowcharts and/or in one or more blocks in the block diagrams.

These computer program instructions may be stored in a computer-readable memory that can instruct the computer or any other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory generate an artifact that includes an instruction apparatus. The instruction apparatus implements a specific function in one or more processes in the flowcharts and/or in one or more blocks in the block diagrams.

The computer program instructions may alternatively be loaded onto a computer or another programmable data processing device, so that a series of operations and steps are performed on the computer or the another programmable device, so that computer-implemented processing is generated. Therefore, the instructions executed on the computer or the another programmable device provide steps for implementing a specific function in one or more procedures in the flowcharts and/or in one or more blocks in the block diagrams.

It is clear that a person skilled in the art can make various modifications and variations to this application without departing from the protection scope of this application. This application is intended to cover these modifications and variations of this application provided that they fall within the scope of protection defined by the following claims and their equivalent technologies.

Claims

1. A signal transmission method, comprising: generating a time domain Zadoff-Chu (ZC) sequence;generating a first frequency domain pilot sequence based on the time domain ZC sequence;obtaining a first frequency domain pilot signal by performing subcarrier mapping on the first frequency domain pilot sequence;obtaining a first time domain pilot signal by performing an inverse Fourier transform on the first frequency domain pilot signal; andsending the first time domain pilot signal, wherein a root q of the time domain ZC sequence satisfies a first constraint condition, and wherein the first constraint condition comprises an absolute value of q is less than or equal to a threshold, wherein the threshold is less than NZC−u, wherein NZC is a length of the time domain ZC sequence, and wherein u is a positive integer.

2. The method according to claim 1, wherein the first constraint condition comprises: the absolute value of q is less than or equal to Tq, or the absolute value of q is a positive integer less than Tq, and Tq is the threshold; orabsolute values of q are first Mq smallest values in a set of absolute values of optional q, and an absolute value of Mqth optional q in the set is the threshold, wherein optional q and NZC are relatively prime.

3. The method according to claim 2, wherein a value of Tq or Mq is related to at least one of: a quantity Nd of subcarriers comprised in a transmission bandwidth; ora quantity N of subcarriers corresponding to the first frequency domain pilot signal; ora maximum value Tz of a subcarrier mapping spacing z.

4. The method according to claim 3, wherein at least one of: an increasing value of Nd indicates an increasing value of Tq or Mq; oran increasing value of N indicates an increasing value of Tq or Mq; oran increasing value of Tz indicates a decreasing value of Tq or Mq.

5. The method according to claim 1, wherein the length NZC of the time domain ZC sequence satisfies a second constraint condition, and wherein the second constraint condition comprises:

6. The method according to claim 1, wherein the performing subcarrier mapping on the first frequency domain pilot sequence comprises: performing subcarrier mapping on the first frequency domain pilot sequence based on the subcarrier mapping spacing z; andwherein z satisfies a third constraint condition, and the third constraint condition comprises z being less than or equal to Tz, or z being a positive integer less than Tz.

7. The method according to claim 6, wherein a value of Tz is related to at least one of: the quantity Nd of subcarriers comprised in the transmission bandwidth; orthe absolute value of the root q of the time domain ZC sequence.

8. The method according to claim 7, wherein at least one of an increasing value of Nd indicates an increasing value of Tz; ora an increasing of q indicates a decreasing value of Tz.

9. The method according to claim 1, further comprising: receiving a second time domain pilot signal, wherein the second time domain pilot signal is a signal obtained by transmitting the first time domain pilot signal through a channel; anddetermining at least one of a distance or a speed of a target based on the first time domain pilot signal and the second time domain pilot signal.

10. A signal transmission method, comprising: generating a frequency domain Zadoff-Chu (ZC) sequence;generating a second frequency domain pilot sequence based on the frequency domain ZC sequence;obtaining a second frequency domain pilot signal by performing subcarrier mapping on the second frequency domain pilot sequence;obtaining a third time domain pilot signal by performing inverse Fourier transform on the second frequency domain pilot signal; andsending the third time domain pilot signal, wherein a root q of the frequency domain ZC sequence satisfies a fourth constraint condition, and wherein the fourth constraint condition comprises at least one of an absolute value of q enabling an absolute value of γ to be less than or equal to a threshold, wherein γ and q satisfy: γq=δNZC−1, wherein δ is an integer, wherein the threshold is less than NZC−u, wherein NZC is a length of the frequency domain ZC sequence, and wherein u is a positive integer.

11. The method according to claim 10, wherein γ is a root of a ZC sequence obtained by performing inverse Fourier transform on the frequency domain ZC sequence.

12. The method according to claim 10, wherein the fourth constraint condition comprises: q enables the absolute value of γ to be less than or equal to Tq, or q is an integer that enables the absolute value of γ to be less than Tq, and Tq is the threshold; orq are first Mq values that are in a set of optional q and that enable the absolute value of γ to be smallest, wherein an absolute value of γ corresponding to Mqth optional q is the threshold, and wherein the absolute value of γ corresponding to Mqth optional q in the set is the threshold, and wherein optional q and NZC are relatively prime.

13. The method according to claim 12, wherein a value of Tq or Mq is related to at least one of: a quantity Nd of subcarriers comprised in a transmission bandwidth;a quantity N of subcarriers corresponding to the second frequency domain pilot signal; anda maximum value Tz of a subcarrier mapping spacing z.

14. The method according to claim 13, wherein an increasing value of Nd indicates an increasing value of Tq or Mq; oran increasing value of N indicates an increasing value of Tq or Mq; oran increasing value of Tz indicates a decreasing value of Tq or Mq.

15. The method according to claim 10, wherein the length NZC of the frequency domain ZC sequence satisfies a fifth constraint condition; and wherein the fifth constraint condition comprises:

16. The method according to claim 11, wherein the performing subcarrier mapping on the second frequency domain pilot sequence comprises: performing subcarrier mapping on the second frequency domain pilot sequence based on the subcarrier mapping spacing z;wherein z satisfies a sixth constraint condition; andwherein the sixth constraint condition comprises: z is less than or equal to Tz, or z is a positive integer less than Tz, and Tz is the threshold.

17. The method according to claim 16, wherein a value of Tz is related to at least one of: the quantity Nd of subcarriers comprised in the transmission bandwidth;the root q of the frequency domain ZC sequence; oran absolute value of d−1.

18. The method according to claim 17, wherein an increasing value of Nd indicates an increasing value of Tz; oran increasing value of γ indicates a decreasing value of Tz.

19. The method according to claim 10, wherein the method further comprises: receiving a fourth time domain pilot signal, wherein the fourth time domain pilot signal is a signal obtained by transmitting the third time domain pilot signal through a channel; anddetermining at least one of a distance or a speed of a target based on the third time domain pilot signal and the fourth time domain pilot signal.

20. A communication apparatus, comprising: a transceiver;one or more processors; andat least one non-transitory computer readable memory connected to the one or more processors and including computer program code, wherein the at least one non-transitory computer readable memory and the computer program code are configured, with the one or more processors, to cause the communication apparatus to at least:generate a time domain Zadoff-Chu (ZC) sequence;generate a first frequency domain pilot sequence based on the time domain ZC sequence;obtain a first frequency domain pilot signal by performing subcarrier mapping on the first frequency domain pilot sequence;obtain a first time domain pilot signal by performing inverse Fourier transform on the first frequency domain pilot signal; andcause the transceiver to send the first time domain pilot signal;wherein a root q of the time domain ZC sequence satisfies a first constraint condition, and wherein the first constraint condition comprises an absolute value of q is less than or equal to a threshold, wherein the threshold is less than NZC−u, wherein NZC is a length of the time domain ZC sequence, and wherein u is a positive integer.

21. The apparatus according to claim 20, wherein the length NZC of the time domain ZC sequence satisfies a second constraint condition, and wherein the second constraint condition comprises:

22. The apparatus according to claim 20, wherein the at least one non-transitory computer readable memory and the computer program code are configured, with the one or more processors, to further cause the communication apparatus to perform subcarrier mapping on the first frequency domain pilot sequence based on the subcarrier mapping spacing z; wherein z satisfies a third constraint condition, and wherein the third constraint condition comprises:z is less than or equal to Tz, or z is a positive integer less than Tz.

23. The apparatus according to claim 20, wherein the at least one non-transitory computer readable memory and the computer program code are configured, with the one or more processors, further cause the communication apparatus to: receive, through the transceiver module, a second time domain pilot signal, wherein the second time domain pilot signal is a signal obtained by transmitting the first time domain pilot signal through a channel; anddetermine at least one of a distance or a speed of a target based on the first time domain pilot signal and the second time domain pilot signal.

24. A communication apparatus, comprising: a transceiver;one or more processors; andat least one non-transitory computer readable memory connected to the one or more processors and including computer program code, wherein the at least one non-transitory computer readable memory and the computer program code are configured, with the one or more processors, to cause the communication apparatus to at least: generate a frequency domain Zadoff-Chu (ZC) sequence;generate a second frequency domain pilot sequence based on the frequency domain ZC sequence;obtain a second frequency domain pilot signal by performing subcarrier mapping on the second frequency domain pilot sequence;obtain a third time domain pilot signal by performing inverse Fourier transform on the second frequency domain pilot signal; andcause the transceiver to send the third time domain pilot signal wherein a root q of the frequency domain ZC sequence satisfies a fourth constraint condition, and wherein the fourth constraint condition comprises an absolute value of q enables an absolute value of γ to be less than or equal to a threshold, wherein γ and q satisfy: γq=δNZC−1, wherein δ is an integer, wherein the threshold is less than NZC−u, wherein NZC is a length of the frequency domain ZC sequence, and wherein u is a positive integer.

25. The apparatus according to claim 24, wherein the length NZC of the frequency domain ZC sequence satisfies a fifth constraint condition; and wherein the fifth constraint condition comprises:

26. The apparatus according to claim 24, wherein the at least one non-transitory computer readable memory and the computer program code are configured, with the one or more processors, further cause the communication apparatus to perform subcarrier mapping on the second frequency domain pilot sequence based on the subcarrier mapping spacing z, wherein z satisfies a sixth constraint condition, and wherein the sixth constraint condition comprises: z is less than or equal to Tz, or z is a positive integer less than Tz, and Tz is the threshold.

27. The apparatus according to claim 24, at least one non-transitory computer readable memory and the computer program code are configured, with the one or more processors, further cause the communication apparatus to receive a fourth time domain pilot signal, wherein the fourth time domain pilot signal is a signal obtained by transmitting the third time domain pilot signal through a channel; anddetermine at least one of a distance or a speed of a target based on the third time domain pilot signal and the fourth time domain pilot signal.