TECHNICAL FIELD

This application relates to the communications field, and more specifically, to a reference signal transmission method and a device.

BACKGROUND

In an existing communications system, when a sending device sends data to a receiving device, due to impact of a radio channel and impact of a non-ideal factor, such as a transmission delay, a carrier frequency offset, a sampling clock offset, and a crystal oscillator frequency drift caused by a temperature, data received by the receiving device is distorted compared with the data sent by the sending device. To enable the receiving device to recover the original data from the distorted data, it is necessary to know channel information and information about the non-ideal factor to compensate for the distortion of the received data. In the existing communications system, the information is generally obtained in a manner in which the sending device sends, to the receiving device, a signal that is learned by both the sending device and the receiving device in advance. The signal is referred to as a reference signal or a pilot.

A plurality of reference signals with different functions are defined in an existing wireless communications system. For example, a narrowband reference signal (NRS) and a narrowband positioning reference signal (NPRS) are defined in a narrowband internet of things (NB-IoT) system. A cell-specific reference signal (CRS), a terminal-device-specific reference signal associated with a physical downlink shared channel (PDSCH), a positioning reference signal (PRS), a channel state information-reference signal (CSI-RS), and the like are defined in a long term evolution (LTE) system. A demodulation reference signal (DMRS), a CSI-RS, a phase tracking reference signal (PTRS), and the like for different physical channels are defined in a new radio (NR) system. These reference signals are generated based on a pseudo-random sequence.

FIG.1shows three mapping patterns of the NPRS in one subframe. In view of in-band deployment, antenna port quantities, being 1, 2 and 4, for a physical broadcast channel (PBCH) correspond to two different mapping patterns. It can be learned fromFIG.1that, for mapping patterns in three scenarios, in one OFDM symbol, the NPRS has only six different frequency position offset modes, and a frequency shift is determined according to NIDNPRSmod 6. However, the NB-IoT system supports a maximum of 4096 cell identifiers NIDNPRS. Therefore, for the receiving device, at a same moment, frequency offset positions of NPRSs received from two sending devices may be the same.

For two intra-frequency cells, for example, a cell 1 and a cell 2, the cell 1 generates and sends an NPRS in any manner shown inFIG.1, the cell 2 also generates and sends an NPRS in a manner the same as that of the cell 1, and frequency offset positions of the NPRSs of the cell 1 and the cell 2 are the same. If the cell 1 is a target cell and the cell 2 is an interfering cell, the NPRS sent by the cell 2 causes interference to the NPRS sent by the cell 1. For the cell 1, NPRS sequences in any two radio frames are the same. For the cell 2, NPRS sequences in any two radio frames are also the same.

In an enhanced coverage scenario, the NPRSs of the cell 1 and the cell 2 are sent in a plurality of consecutive radio frames. After receiving the NPRS sent by the cell 1 (the target cell), the receiving device processes the NPRSs in the radio frames and then performs in-phase combination on the NPRSs in the radio frames, and also performs in-phase combination on the received NPRS of the cell 2 (the interfering cell). Consequently, an increase in interference power is caused.

For the foregoing reference signals of other types, the foregoing problem also exists when reference signals in a plurality of radio frames are combined.

SUMMARY

This application provides a reference signal transmission method to improve inter-cell interference randomization performance.

According to a first aspect, a reference signal sequence transmission method is provided. The method includes: generating a reference signal sequence based on a frame number of a radio frame; mapping at least a part of reference signals in the reference signal sequence to a resource position that corresponds to the radio frame and that is used to transmit the at least a part of reference signals; and sending the at least a part of reference signals at the resource position or sending an orthogonal reference signal at the resource position, where the orthogonal reference signal is obtained by multiplying the at least a part of reference signals by a preset orthogonal code.

In the foregoing method, when the reference signal sequence is generated, the reference signal sequence is generated based on the frame number of the radio frame, so that reference signal sequences in any two radio frames in an interfering cell are different. Therefore, interference caused by a reference signal of the interfering cell to a reference signal of a target cell can be reduced.

Specifically, when a receiving device receives, from the target cell, reference signals in a plurality of radio frames in the target cell, the receiving device needs to perform combination processing on the reference signals of the target cell. When receiving the reference signals of the target cell, the receiving device usually also receives, from the interfering cell, reference signals in a plurality of radio frames in the interfering cell. Correspondingly, the receiving device performs combination processing on the received reference signals, and the combination processing also includes combination processing on the reference signals of the interfering cell. For combining, by the receiving device, the reference signals in the plurality of radio frames in the target cell, because a manner of generating the reference signals of the target cell is known to the receiving device, the receiving device may generate the reference signals in the receiving device, the combination is combination performed after the receiving device processes, in each radio frame, the received reference signals of the target cell and the reference signals generated in the receiving device. Therefore, the combination does not cause these reference signals of the target cell to be canceled by each other. For combining, by the receiving device, the reference signals in the plurality of radio frames in the interfering cell, because the reference signal sequences in any two radio frames in the interfering cell are different, and the reference signals of the interfering cell are unknown to the receiving device, these reference signals of the interfering cell may be canceled by each other as much as possible, so that interference caused by the reference signal of the interfering cell to the reference signal of the target cell can be reduced.

In an optional implementation, the foregoing resource position may be one or more resource elements (RE) on one symbol, and the one or more REs may be distributed in at least one resource block (resource block, RB) or distributed in a plurality of RBs.

In an optional implementation, the one or more REs may alternatively be distributed in at least one or more resource units. Any resource unit in the one or more resource units may be a resource unit including one or more time units in time domain and one or more frequency domain units in frequency domain, or any resource unit may be a resource unit including one or more neighboring frequency domain units in frequency domain. The time domain unit may be a symbol, a slot, a subframe, a radio frame, a superframe, or the like. The frequency domain unit may be a subcarrier, a carrier, a frequency band, or the like. Different time domain units may be consecutive or discrete, and different frequency domain units may be consecutive or discrete.

In an optional implementation, the foregoing symbol includes but is not limited to an orthogonal frequency division multiplexing (OFDM) symbol, a sparse code multiple access (SCMA) symbol, a filtered orthogonal frequency division multiplexing (F-OFDM) symbol, or a non-orthogonal multiple access (NOMA) symbol. A type of the symbol may be specifically determined based on an actual situation.

In an optional implementation, the generating a reference signal sequence based on a frame number of a radio frame includes: generating a pseudo-random sequence; and generating the reference signal sequence based on at least a part of sequences in the pseudo-random sequence, where an index of the at least a part of sequences corresponds to the frame number of the radio frame.

At least a part of reference signals are selected from the pseudo-random sequence based on the frame number of the radio frame, and the reference signal sequence is generated based on the at least a part of reference signals, so that the at least a part of reference signals selected from the pseudo-random sequence based on radio frames with different frame numbers are different. In this way, reference signal sequences in any two radio frames in each cell are different, so that when the receiving device performs in-phase combination on the received reference signal sequences in the plurality of radio frames, interference caused by the reference signal of the interfering cell to the reference signal of the target cell is reduced.

In an optional implementation, the reference signal sequence rl,ns(m) meets the following formula

rl,ns(m)=12⁢(1-2·c⁡(2⁢m+L))+j⁢12⁢(1-2·c⁡(2⁢m+1+L)),m=0,1,…,NRE·NRB-1⁢L=2⁢NRE·NRB·nf,
where

nfis the frame number of the radio frame, NRBis a quantity of resource blocks (RBs), NREis a quantity of resource elements REs, nsis an index of any slot in the radio frame, and l is an index of any symbol in the slot; and c(2m+L) and c(2m+1+L) are the at least a part of sequences in the pseudo-random sequence generated based on an initialization seed, (2m+L) and (2m+1+L) are indexes of the at least a part of sequences, and the initialization seed is determined based on at least one of ns, l, an index of any subframe in the radio frame, a cell identifier, a radio network temporary identifier (radio network temporary identity, RNTI), an identifier of a cyclic prefix (cyclic prefix, CP), a reference signal identifier, a channel identifier, a subcarrier identifier, and a carrier identifier.

In an optional implementation, the generating a reference signal sequence based on a frame number of a radio frame includes: performing a modulo operation on the frame number of the radio frame based on a preset value K, where K is a positive integer; and generating the reference signal sequence based on a value resulting from the frame number of the radio frame mod K.

The reference signal sequence is generated based on the value resulting from the frame number of the radio frame mod K, so that reference signal sequences in radio frames in which any two values resulting from performing a modulo operation by using the preset value K are different in each cell are different. Therefore, when the receiving device performs in-phase combination on the received reference signal sequences in the plurality of radio frames, interference caused by the reference signal of the interfering cell to the reference signal of the target cell is reduced.

In an optional implementation, the generating a reference signal sequence based on a frame number of a radio frame includes: generating a pseudo-random sequence; and generating the reference signal sequence based on at least a part of sequences in the pseudo-random sequence, where an index of the at least a part of sequences corresponds to a value resulting from the frame number of the radio frame mod K.

At least a part of reference signals are selected from the pseudo-random sequence based on the value resulting from the frame number of the radio frame mod K, and the reference signal sequence is generated based on the at least a part of reference signals, so that the at least a part of reference signals selected from the pseudo-random sequence based on different values resulting from performing a modulo operation by using K are different, and further, reference signal sequences in radio frames in which any two values resulting from performing a modulo operation by using the preset value K are different in each cell are different. Therefore, when the receiving device performs in-phase combination on the received reference signal sequences in the plurality of radio frames, interference caused by the reference signal of the interfering cell to the reference signal of the target cell is reduced.

In an optional implementation, the reference signal sequence rl,ns(m) meets the following formula:

rl,ns(m)=12⁢(1-2·c⁡(2⁢m+L))+j⁢12⁢(1-2·c⁡(2⁢m+1+L)),m=0,1,…,NRE·NRB-1⁢L=2⁢NRE·NRB·(nf⁢mod⁢K),
where nfis the frame number of the radio frame, NRBis a quantity of resource blocks, NREis a quantity of resource elements REs, nsis an index of any slot in the radio frame, and l is an index of any symbol in the slot; and c(2m+L) and c(2m+1+L) are the at least a part of sequences in the pseudo-random sequence generated based on an initialization seed, (2m+L) and (2m+1+L) are indexes of the at least a part of sequences, nrfmod K is the value resulting from the frame number of the radio frame mod K, and the initialization seed is determined based on at least one of ns, l, an index of any subframe in the radio frame, a cell identifier, a radio network temporary identifier RNTI, an identifier of a cyclic prefix CP, a reference signal identifier, a channel identifier, a subcarrier identifier, and a carrier identifier.

In an optional implementation, the generating a reference signal sequence based on a frame number of a radio frame includes: generating a pseudo-random sequence based on the frame number of the radio frame; and generating the reference signal sequence based on the pseudo-random sequence.

The pseudo-random sequence is generated based on the frame number of the radio frame, and the reference signal sequence is generated based on the pseudo-random sequence, so that reference signal sequences in any two radio frames in each cell are different. Therefore, when the receiving device performs in-phase combination on the received reference signal sequences in the plurality of radio frames, interference caused by the reference signal of the interfering cell to the reference signal of the target cell is reduced.

In an optional implementation, the generating a pseudo-random sequence based on the frame number of the radio frame includes: determining an initialization seed of the pseudo-random sequence based on a first parameter set, where the first parameter set includes the frame number of the radio frame or a value resulting from the frame number of the radio frame mod K, and K is a positive integer; and generating the pseudo-random sequence based on the initialization seed.

The initialization seed of the pseudo-random sequence is generated based on the frame number of the radio frame or the value resulting from the frame number of the radio frame mod K. Then, the pseudo-random sequence is generated based on the initialization seed to make randomized sequences generated based on frame numbers of different radio frames different, or to make pseudo-random sequences generated based on different values resulting from the frame number of the radio frame mod K different, and finally, to make reference signal sequences generated based on the frame numbers of different radio frames or different values resulting from the frame number of the radio frame mod K different. Therefore, when the receiving device performs in-phase combination on the received reference signal sequences in the plurality of radio frames, interference caused by the reference signal of the interfering cell to the reference signal of the target cell is reduced.

In an optional implementation, the reference signal sequence rl,ns(m) meets the following formula:

rl,ns(m)=12⁢(1-2·c⁡(2⁢m+L))+j⁢12⁢(1-2·c⁡(2⁢m+1+L)),m=0,1,…,NRE·NRB-1⁢L=2⁢NRE·NRB·(Nsymb·ns+l),
where NRBis a quantity of resource blocks RBs, NREis a quantity of resource elements REs, Nsymbis a quantity of symbols in any slot, nsis an index of any slot in the radio frame, and l is an index of any symbol in the slot; and c(2m+L) and c(2m+1+L) are at least a part of sequences in the pseudo-random sequence generated based on the initialization seed.

In an optional implementation, the first parameter set further includes at least one of an index of any subframe in the radio frame, a cell identifier, a radio network temporary identifier RNTI, an identifier of a cyclic prefix CP, a reference signal identifier, a channel identifier, a subcarrier identifier, and a carrier identifier.

In an optional implementation, the pseudo-random sequence is a Gold sequence.

According to a second aspect, a reference signal transmission method is provided. The method includes: generating a reference signal sequence; determining a first index set based on a frame number of a radio frame, where the first index set is used to indicate at least a part of reference signals in the reference signal sequence; mapping the at least a part of reference signals to a resource position that corresponds to the radio frame and that is used to transmit the at least a part of reference signals; and sending the at least a part of reference signals at the resource position or sending an orthogonal reference signal at the resource position, where the orthogonal reference signal is obtained by multiplying the at least a part of reference signals by a preset orthogonal code.

An index of a reference signal that needs to be sent to a receiving device is determined in the generated reference signal sequence based on the frame number of the radio frame, so that indexes of reference signals that need to be sent to the receiving device and that are determined in the reference signal sequence based on different frame numbers of radio frames are different. In this way, reference signals in radio frames that have different frame numbers and that are sent to the receiving device are different, so that when the receiving device performs in-phase combination on received reference signal sequences in a plurality of radio frames, interference caused by a reference signal of an interfering cell to a reference signal of a target cell is reduced.

In an optional implementation, the determining a first index set based on a frame number of a radio frame includes: performing a modulo operation on the frame number of the radio frame based on a preset value K, where K is a positive integer; and determining the first index set based on a value resulting from the frame number of the radio frame mod K.

The index of the reference signal that needs to be sent to the receiving device is determined in the generated reference signal sequence based on the value resulting from the frame number of the radio frame mod K, so that indexes of reference signals that need to be sent to the receiving device and that are determined in the reference signal sequence based on different values resulting from the frame number of the radio frame mod K are different. In this way, reference signals that are sent to the receiving device and that are in radio frames in which different values result from the frame number of the radio frame mod K are different, so that when the receiving device performs in-phase combination on the received reference signal sequences in the plurality of radio frames, interference caused by the reference signal of the interfering cell to the reference signal of the target cell is reduced.

According to a third aspect, a reference signal transmission method is provided. The method includes: generating, by a receiving device, a reference signal sequence; determining, by the receiving device, a resource position, where the resource position is a resource position that corresponds to a radio frame and that is used to transmit at least a part of reference signals; and receiving, by the receiving device at the resource position, the at least a part of reference signals sent by a sending device, or receiving, by the receiving device at the resource position, an orthogonal reference signal, where the orthogonal reference signal is obtained by multiplying the at least a part of reference signals by a preset orthogonal code.

According to a fourth aspect, a communications apparatus is provided. The communications apparatus is configured to perform the reference signal transmission method according to any one of the first aspect or the possible implementations of the first aspect. Specifically, the communications apparatus may include modules configured to perform the reference signal transmission method according to any one of the first aspect or the possible implementations of the first aspect.

In an optional implementation, the communications apparatus is further configured to perform the reference signal transmission method according to any one of the second aspect or the possible implementations of the second aspect. Specifically, the communications apparatus may include modules configured to perform the reference signal transmission method according to any one of the second aspect or the possible implementations of the second aspect.

According to a fifth aspect, a communications apparatus is provided. The communications apparatus is configured to perform the reference signal transmission method according to any one of the third aspect or the possible implementations of the third aspect. Specifically, the communications apparatus may include modules configured to perform the reference signal transmission method according to any one of the third aspect or the possible implementations of the third aspect.

According to a sixth aspect, a communications device is provided. The communications device includes a processor and a memory, and the processor is configured to invoke a program stored in the memory, to perform the reference signal transmission method according to any one of the first aspect or the possible implementations of the first aspect.

In an optional implementation, the communications device is further configured to perform the reference signal transmission method according to any one of the second aspect or the possible implementations of the second aspect.

According to a seventh aspect, a communications device is provided. The communications device includes a processor and a memory, and the processor is configured to invoke a program stored in the memory, to perform the reference signal transmission method according to any one of the third aspect or the possible implementations of the third aspect.

According to an eighth aspect, a computer-readable storage medium is provided. The computer-readable storage medium stores a computer program, and when the program is executed by a processor, the method according to any one of the first aspect or the possible implementations of the first aspect is implemented.

In an optional implementation, the computer-readable storage medium is further configured to perform the reference signal transmission method according to any one of the second aspect or the possible implementations of the second aspect.

According to a ninth aspect, a computer-readable storage medium is provided. The computer-readable storage medium stores a computer program, and when the program is executed by a processor, the method according to any one of the third aspect or the possible implementations of the third aspect is implemented.

According to a tenth aspect, a computer program product is provided. The computer program product includes computer program code. When the computer program code is run by a processing unit or a processor of a communications device, the communications device is enabled to perform the method according to the first aspect.

In an optional implementation, when the computer program code is run by the processing unit or the processor of the communications device, the communications device is enabled to perform the method according to the second aspect.

According to an eleventh aspect, a computer program product is provided. The computer program product includes computer program code. When the computer program code is run by a processing unit or a processor of a communications device, the communications device is enabled to perform the method according to the third aspect.

According to a twelfth aspect, a chip system is provided. The chip system includes a processor, configured to support a communications device in implementing the method according to the first aspect.

In an optional implementation, the processor is further configured to support the communications device in implementing the method according to the second aspect.

According to a thirteenth aspect, a chip system is provided. The chip system includes a processor, configured to support a communications device in implementing the method according to the third aspect.

