TECHNICAL FIELD

Embodiments of this application relate to the field of communications technologies, and in particular, to signal transmission in a wireless communications system.

BACKGROUND

With increasing communication requirements, a next generation wireless communications network (for example, 5th generation mobile communication (5th generation, 5G)) with an operating frequency band of at least 6 GHz can provide an ultrafast data communication service. In a frequency range of at least 6 GHz, frequency bands available for the next generation wireless communications network include frequency bands of 28 GHz, 39 GHz, 60 GHz, 73 GHz, and the like. A high frequency communications system of at least 6 GHz has significant characteristics such as large bandwidth and a highly integrated antenna array, thereby easily achieving a relatively high throughput. In addition, compared with an existing wireless communications network, the high frequency communications system is subject to severer intermediate radio frequency distortion, especially impact caused by phase noise (PHN) or a phase offset. In addition, a Doppler effect and a carrier frequency offset (CFO) have greater impact on performance of the high frequency communications system as a location of a frequency band becomes higher. A common characteristic of the phase noise, the Doppler effect, and the CFO is that a phase error or a phase offset is caused when the high frequency communications system receives data, consequently the high frequency communications system is degraded in performance or even cannot work.

It is proposed that in the next generation wireless communications system, a phase tracking reference signal (PTRS) or a phase compensation reference signal is used to estimate a common phase error (CPE). Because phase offsets or rotations on all carriers of a same multicarrier symbol are the same, the accuracy of CPE estimation depends on a quantity of PTRSs in frequency domain. How to design a PTRS is an urgent problem to be resolved.

An existing technology is to set an association relationship between a frequency domain density of a PTRS and scheduled bandwidth. For example, the association relationship between the frequency domain density of the PTRS and the scheduled bandwidth is set as shown in Table 1.

TABLE 1Scheduled bandwidthFrequency domain density of a PTRS0 ≤ NRB< NRB1Skipping setting a PTRSNRB1≤ NRB< NRB2FD1NRB2≤ NRB< NRB3FD2NRB3≤ NRB< NRB4FD3NRB4≤ NRB< NRB5FD4NRB5≤ NRBFD5

NRBrepresents a current scheduled bandwidth whose unit is a resource block (RB); NRBirepresents bandwidth thresholds corresponding to different frequency domain densities; FD1, FD2, . . . , and FD5are frequency domain densities; if FD1=1, it indicates that each resource block is mapped to one PTRS; and by analogy, if FD2=1/2, it indicates that every two resource blocks are mapped to one PTRS. A transmit end and a receive end each can determine a current frequency domain density of a PTRS based on scheduled bandwidth.

According to the association relationship in Table 1, larger scheduled bandwidth indicates a smaller frequency domain density of the PTRS, to be specific, FD1>FD2> . . . >FD5. However, when a value of the scheduled bandwidth is equal to a threshold or is close to a threshold, a quantity of PTRSs jumps. For example, if 4≤NRB<8, one PTRS is set for each RB, if 8≤NRB<32, one PTRS is set for every two RBs, and if NRB≥32, one PTRS is set for every four RBs. Therefore, scheduled bandwidth of 6 RBs corresponds to 6 PTRSs, scheduled bandwidth of 8 RBs corresponds to 4 PTRSs, scheduled bandwidth of 30 RBs corresponds to 15 PTRSs, and scheduled bandwidth of 32 RBs corresponds to 8 PTRSs. In other words, when the value of the scheduled bandwidth is close to the threshold, an increase in the scheduled bandwidth leads to a decrease in the quantity of PTRSs, so that the accuracy of the CPE estimation cannot be ensured. Because of the jump, a decrease in the scheduled bandwidth leads to an increase in the quantity of PTRSs, so that spectral efficiency is reduced.

Another existing technology is to set an association relationship between a quantity of PTRSs in frequency domain and scheduled bandwidth. For example, the association relationship between the quantity of PTRSs in frequency domain and the scheduled bandwidth is set as shown in Table 2.

TABLE 2Scheduled bandwidthFrequency domain density of a PTRS0 ≤ NRB< NRB11 or L1/NRBNRB1≤ NRB< NRB2L2/NRBNRB2≤ NRB< NRB3L3/NRB. . .. . .NRB5≤ NRBLN/NRB

According to the solution in Table 2, when the quantity of PTRSs in frequency domain corresponding to each interval is fixed, it can be ensured that the quantity of PTRSs remains unchanged or is increased as the scheduled bandwidth is increased.

However, this solution also brings about a problem of nonuniform PTRS mapping because when the quantity of PTRSs is fixed, LN/NRBmay not be an integer. In the prior art, Formula (1) is used to determine a number i of an RB in which a PTRS is mapped to an OFDM symbol.

i=⌊l⁢PL⌋+k,l=0,1,…⁢,L-1Formula⁢⁢(1)

P represents a quantity of scheduled RBs, that is, NRB; L represents a quantity of PTRSs; and k is an offset value that may be set to 0 or 1.FIG. 1is a schematic diagram of mapping a fixed quantity of PTRSs to a plurality of types of scheduled bandwidth. If 8 PTRSs are mapped to RBs whose quantities are 9 to 16 and k=0, the RBs to which the PTRSs are mapped are shown inFIG. 1. It can be learned that the RBs to which the PTRSs are mapped are nonuniform. In other words, spacings between adjacent RBs to which the PTRSs are mapped are different. Because the PTRS mapping is nonuniform, it may become more difficult to deal with a collision between a PTRS and another reference signal (reference signal, RS) or channel.

SUMMARY

This application provides an information transmission method and apparatus, to configure a PTRS properly.

According to an aspect of this application, an information transmission solution is provided, including: determining, by a transmit end device, a time domain density of a phase tracking reference signal PTRS; determining a frequency domain density of the PTRS; mapping the PTRS to an orthogonal frequency division multiplexing OFDM symbol based on the time domain density, the frequency domain density, and/or a frequency domain offset; and sending a signal that includes the OFDM symbol to which the PTRS is mapped.

In a design, the frequency domain density of the PTRS may be determined based on available bandwidth, and then the PTRS is mapped. Because the PTRS is mapped based on the available bandwidth instead of scheduled bandwidth, no PTRS is mapped to collided bandwidth, thereby effectively avoiding a collision between the PTRS and another signal.

In another design, the frequency domain density of the PTRS may be determined based on index information of a scheduled resource block RB or an available resource block RB or a quantity of scheduled or available RBs. In this design, a quantity of PTRSs can be prevented from jumping when a value of scheduled bandwidth is close to a threshold, both accuracy of common phase error estimation and spectral efficiency are taken into consideration, and the PTRSs can be uniformly mapped in the scheduled or available bandwidth, thereby properly configuring the PTRSs.

The method further includes: receiving, by a receive end device, one or more orthogonal frequency division multiplexing OFDM symbols; and determining the phase tracking reference signal PTRS mapped to the one or more OFDM symbols. The determining the PTRS includes: determining the time domain density of the phase tracking reference signal PTRS; and determining the frequency domain density of the phase tracking reference signal PTRS based on the available bandwidth, or determining the frequency domain density of the phase tracking reference signal PTRS based on the scheduled or available resource block RB. The receive end device can accurately and efficiently obtain a received signal on the PTRS based on the time domain density and the frequency domain density of the PTRS, thereby improving the efficiency of receiving the PTRS signal.

In a possible implementation, the determining a time domain density of a PTRS includes: determining the time domain density of the PTRS based on a modulation and coding scheme MCS. In this implementation, when the time domain density of the PTRS is determined, symbols to which PTRSs are mapped are determined.

In another possible implementation, the determining the frequency domain density of the PTRS based on index information of a scheduled RB or an available RB or a quantity of scheduled or available RBs includes: dividing the scheduled or available RB into at least one RB index interval, where each RB index interval corresponds to a frequency domain density of the PTRS. In this implementation, the scheduled or available RB is divided into one or more RB index intervals, and RB index intervals may correspond to different frequency domain densities of the PTRS, so that PTRSs can be distributed uniformly in frequency domain.

In still another possible implementation, each RB index interval corresponds to one frequency domain offset, and the frequency domain offset is a remainder between a set offset and the frequency domain density of the PTRS corresponding to each RB index interval. In this implementation, a frequency domain offset is obtained by using a REM operation, and the PTRS is mapped based on the frequency domain offset in each RB index interval, so that the PTRSs can be distributed uniformly in frequency domain.

In yet another possible implementation, each RB index interval corresponds to one frequency domain offset, and the frequency domain offset corresponding to each RB index interval is a preset value, or at least one frequency domain offset and the at least one RB index interval constitute a correspondence list.

In still yet another possible implementation, the index information of the scheduled or available RB is a serial number obtained after numbers of scheduled virtual RBs are sorted, or the index information of the scheduled or available RB is a serial number obtained after numbers of the scheduled physical RBs are sorted. In this implementation, an index of the RB is a relative RB number, so that the index of the scheduled or available RB is a number in order.

According to another aspect of this application, an information transmission solution is provided, including: uniformly configuring, by a transmit end device, phase tracking reference signals PTRSs, and mapping the PTRSs to an OFDM symbol; and receiving, by a receive end device, an orthogonal frequency division multiplexing OFDM symbol to which the PTRSs are mapped, and obtaining a received signal on the PTRS, where the PTRS is mapped to the OFDM symbol based on a time domain density, a frequency domain density, and/or a frequency domain offset, and the frequency domain density is determined based on index information of a scheduled or available resource block RB or a quantity of scheduled or available RBs. In this implementation, because the transmit end device uniformly configures the PTRS, the receive end device can accurately and efficiently obtain a received signal on the PTRS, thereby improving the efficiency of receiving the PTRS signal.

In a possible implementation, after the obtaining a received signal on the PTRS, the method further includes: estimating a common phase error based on the received signal on the PTRS. In this implementation, the transmit end device properly configures the PTRS, so that the received signal on the PTRS can be used to accurately estimate the common phase error.

In a possible design, the available bandwidth is a part other than (not including) preoccupied bandwidth in the scheduled bandwidth, or the available bandwidth is a part other than (not including) reserved bandwidth in the scheduled bandwidth, or the available bandwidth is a part other than (not including) preoccupied bandwidth and reserved bandwidth in the scheduled bandwidth.

In a possible design, available bandwidth can be respectively calculated on those symbols to which the PTRSs are mapped. For example, if the time domain density of the PTRS is 1/2, a possible result is that the PTRSs are respectively mapped to symbols 1, 3, 5, 7, and . . . , and the available bandwidth of the symbols 1, 3, 5, 7, and . . . is respectively calculated.

In another possible design, the downlink signal includes one or more of the following: a synchronization block SS block, a physical downlink control channel PDCCH, an enhanced physical downlink control channel EPDCCH, a physical broadcast channel PBCH, a primary synchronization signal PSS, a secondary synchronization signal SSS, a demodulation reference signal DMRS, or a channel state information-reference signal CSI-RS.

In another possible design, the uplink signal is one or more of the following: a physical uplink control channel PUCCH, a demodulation reference signal DMRS, and a sounding reference signal SRS.

Optionally, a table is preconfigured or prestored, and the table records information about a mapping relationship between available bandwidth and a frequency domain density or a quantity of PTRSs in frequency domain.

In a possible design, the transmit end device and/or the receive end device may store a correspondence list.

The list includes at least one RB index interval and at least one frequency domain density of the PTRS, and the RB index interval and the frequency domain density of the PTRS are in a one-to-one correspondence; or

the list includes at least one RB quantity interval and at least one frequency domain density of the PTRS, and the RB quantity interval and the frequency domain density of the PTRS are in a one-to-one correspondence; or

the list includes at least one RB index interval, at least one frequency domain density of the PTRS, and at least one frequency domain offset, and the RB index interval, the frequency domain density of the PTRS, and the frequency domain offset are in a one-to-one correspondence; or

the list includes at least one RB quantity interval, at least one frequency domain density of the PTRS, and at least one frequency domain offset, and the RB quantity interval, the frequency domain density of the PTRS, and the frequency domain offset are in a one-to-one correspondence.

In another possible design, when the available bandwidth is lower than a preset threshold, the frequency domain density of the PTRS is 0 or the quantity of the PTRSs in frequency domain is 0.

When the available bandwidth is lower than a preset threshold, the PTRS does not need to be mapped because when the available bandwidth is lower than a preset threshold, if the PTRS is mapped, spectral efficiency decreases. Therefore, skipping mapping the PTRS is a better option.

The transmit end device (network device) may send one or more of the following to the terminal device: information used to indicate current MCS index information, information used to indicate scheduled bandwidth, information used to indicate preoccupied bandwidth, and information used to indicate reserved bandwidth.

According to still another aspect of this application, a communication solution is provided, including: determining, by a transmit end device, a time domain density of a phase tracking reference signal PTRS; determining a quantity L of PTRSs mapped in frequency domain; determining a frequency domain RB number i of L PTRSs on NRBresource blocks RBs according to the following formula:

i=1⁢⁢⌊NRBL⌋+k1,1=0,1,…⁢,L-1;k1=0,1,…⁢,NRB-L*⁢⌊NRBL⌋,
where k1is an offset, and k1is an integer; mapping the PTRS to an OFDM symbol based on the time domain density and the frequency domain RB number of the PTRS; and sending the OFDM symbol to which the PTRS is mapped; and receiving, by a receive end device, an orthogonal frequency division multiplexing OFDM symbol to which the phase tracking reference signal PTRS is mapped, and obtaining a received signal on the PTRS. According to the PTRS configuration in this communication solution, both accuracy of common phase error estimation and spectral efficiency are taken into consideration, and the PTRSs can be uniformly mapped in the scheduled or available bandwidth, thereby properly configuring the PTRSs. The receive end device can accurately and efficiently obtain a received signal on the PTRS, thereby improving the efficiency of receiving the PTRS signal.

In a possible implementation, the RB number is a serial number obtained after numbers of scheduled virtual RBs are sorted, or the RB number is a serial number obtained after numbers of the scheduled physical RBs are sorted. In this implementation, an index of the RB is a relative RB number, so that the index of the scheduled or available RB is a number in order.

In another possible implementation, frequency domain resource element RE number IndexREof L PTRSs on NRBresource blocks can be determined according to the following formula:

IndexRE=1*⁢⌊NRB⁢*⁢12L⁢*⁢IDMRS⌋⁢*⁢IDMRS+k2⁢*⁢IDMRS,1=0,1,…⁢,L-1,
where IDMRSis a frequency domain spacing of a demodulation reference signal DMRS; and k2is an offset of the RE, and

k2=0,1,…⁢,NRB⁢*⁢12IDMRS-L*⁢⌊NRB⁢*⁢12L⁢*⁢IDMRS⌋.
In this implementation, the PTRS is mapped at an RE level, and a mapping location of the PTRS is related to a DMRS location of a DMRS port associated with the PTRS.

According to yet another aspect of this application, a communications apparatus is further provided. The communications apparatus may be used as a transmit end device or a receive end device to implement any one of the foregoing communication solutions. For example, the communications apparatus may be a chip (for example, a baseband chip, or a communications chip) or a device (for example, a network device, a base station, a baseband processing board, or a terminal device). The foregoing methods can be implemented by software, by hardware, or by hardware executing corresponding software.

In a possible implementation, a structure of the communications apparatus includes a processor and a memory. The processor is configured to support the apparatus in performing a corresponding function in the foregoing communication method. The memory is configured to be coupled to the processor, and the memory stores a program (instruction) and/or data required by the apparatus. Optionally, the communications apparatus may further include a communications interface configured to support communication between the apparatus and another network element.

In another possible implementation, the communications apparatus may include a processing unit and a transceiver unit. The transceiver unit is configured to implement a sending/receiving function, and the processing unit is configured to implement the foregoing processing functions. For example, the processing unit is configured to determine a time domain density of a phase tracking reference signal PTRS. The processing unit is further configured to determine a frequency domain density of a PTRS. The communications apparatus may further include a storage unit, and the storage unit is configured to implement the foregoing saving/storage function, for example, storing a correspondence list or another required program (instruction) and data. The processing unit can be implemented by using one or more processors, and the storage unit can be implemented by using one or more processors. The transceiver unit may be a transceiver circuit (an input/output circuit), a communications interface, or a transceiver.

For example, when the communications apparatus is a chip, the transceiver unit may be an input/output circuit or a communications interface. When the communications apparatus is a base station or a terminal, the transceiver unit may be a transceiver (may also be referred to as a transceiver).

In a possible implementation, the processing unit may be configured to determine a time domain density of a PTRS based on a modulation and coding scheme MCS.

In a possible implementation, the processing unit may be configured to divide a scheduled RB or an available RB into at least one RB index interval, and each RB index interval corresponds to a frequency domain density of the PTRS.

In a possible implementation, each RB index interval corresponds to one frequency domain offset, and the frequency domain offset is a remainder between a set offset and the frequency domain density of the PTRS corresponding to each RB index interval.

In a possible implementation, each RB index interval corresponds to one frequency domain offset, and the frequency domain offset corresponding to each RB index interval is a preset value, or at least one frequency domain offset and the at least one RB index interval constitute a correspondence list.

In a possible implementation, the index information of the scheduled or available RB is a serial number obtained after numbers of scheduled virtual RBs are sorted, or the index information of the scheduled or available RB is a serial number obtained after numbers of the scheduled physical RBs are sorted.

In a possible implementation, the processing unit is further configured to estimate a common phase error based on the received signal on the PTRS.

In a possible implementation, the processing unit is configured to determine a quantity L of the PTRSs mapped in frequency domain.

In a possible implementation, the processing unit is configured to determine a frequency domain resource element RE number IndexREof L PTRSs.

According to still yet another aspect of this application, a wireless communications system is provided, including the transmit end device and the receive end device.

According to a further aspect of this application, a computer readable storage medium is provided. The computer readable storage medium stores an instruction. When the instruction is run on a computer, the computer performs the method in the foregoing aspects.

According to a still further aspect of this application, a computer program product including an instruction is provided. When the instruction is run on a computer, the computer performs the methods in the foregoing aspects.

