CN112398764B - Frequency offset estimation method and system combining DMRS (demodulation reference signal) and PTRS (packet transport RS) - Google Patents
Frequency offset estimation method and system combining DMRS (demodulation reference signal) and PTRS (packet transport RS) Download PDFInfo
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- H—ELECTRICITY
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- H04L2027/0024—Carrier regulation at the receiver end
- H04L2027/0026—Correction of carrier offset
Abstract
The invention relates to a frequency offset estimation method and system combining DMRS and PTRS. The method comprises the following steps: carrying out channel estimation on a resource unit bearing the PT-RS and a DMRS corresponding to a subcarrier where the PT-RS is located to obtain a channel estimation value of each reference signal; the reference signal is PT-RS or DMRS; calculating correlation values between adjacent reference signal symbols according to the channel estimation value of each reference signal; acquiring the space between adjacent reference signal symbols; the distance between adjacent reference signal symbols is the number of OFDM symbols spaced between the adjacent reference signal symbols; and estimating the frequency offset according to the correlation values between all adjacent reference signal symbols and the intervals between the adjacent reference signal symbols to obtain a frequency offset estimation result. The invention can improve the real-time property of frequency offset estimation and ensure the performance of a receiver.
Description
Technical Field
The invention relates to the field of communication engineering, in particular to a frequency offset estimation method and system combining DMRS and PTRS.
Background
A Physical Downlink Shared Channel (PDSCH) DMRS is used for demodulating Downlink Shared Channel data, and a DMRS design of a 5GNR (5th generation, New Radio) system fully considers decoding delay and mobility scenarios, so that the scheduling number of OFDM symbols corresponding to the DMRS is at least 1 and at most 4.
The phase noise is from a local oscillator in a transmitting end and/or a receiving end of a communication system, and can have a large influence on the transmission of a multi-carrier signal, and particularly, the influence of the phase noise is more serious in a high-frequency band (above 6 GHz). In order to remove the phase noise, a new air interface (new radio) of a fifth generation (5th generation) communication system specially introduces a reference signal, namely PT-RS, according to which a receiving end can estimate and compensate the phase noise.
The Phase Tracking Reference Signal (PT-RS) is a Reference Signal dedicated to the ue (user equipment), and can be regarded as an extension of a Demodulation Reference Signal (DMRS), the PT-RS always transmits with the DMRS, and the PT-RS and the DMRS have a close relationship, for example, transmit in the same scheduling bandwidth, use the same sequence, use the same precoding, use port association, and have a QCL (Quasi Co-Location) relationship. In addition, since the phase noise has the same frequency selectivity in the whole frequency band and has a strong random characteristic in time, the PT-RS has the characteristics of being sparse in the frequency domain and dense in the time domain in time-frequency resource allocation.
Existing frequency offset estimation methods are usually based on periodically transmitted signals, such as ssb (synchronization Signal and pbcbhblock), trs (tracking Reference Signal), because the transmission period configuration of these signals may not match the frequency offset change rate, the frequency offset estimation cannot keep up, further affecting the receiver performance. Therefore, PT-RS cross product frequency discrimination can be used for tracking the frequency deviation in real time, and the performance of the receiver is ensured. However, if there is only one OFDM symbol of PT-RS within the scheduled tti (transmission Time interval), cross product frequency discrimination cannot be used. Therefore, the invention adopts the combination of DMRS and PT-RS to carry out frequency offset estimation, ensures that at least two OFDM symbols are included, and further realizes cross product frequency discrimination.
Disclosure of Invention
The invention aims to provide a frequency offset estimation method and a frequency offset estimation system combining DMRS and PTRS, which improve the real-time performance of frequency offset estimation and ensure the performance of a receiver.
In order to achieve the purpose, the invention provides the following scheme:
a frequency offset estimation method combining DMRS and PTRS comprises the following steps:
carrying out channel estimation on a resource unit bearing the PT-RS and a DMRS corresponding to a subcarrier where the PT-RS is located to obtain a channel estimation value of each reference signal; the reference signal is PT-RS or DMRS;
calculating correlation values between adjacent reference signal symbols according to the channel estimation value of each reference signal; the reference signal symbol is a PTRS symbol or a DMRS symbol, the PTRS symbol is an OFDM symbol where PT-RS is located, and the DMRS symbol is an OFDM symbol where DMRS is located; the number of PTRS symbols is greater than or equal to 1;
acquiring the space between adjacent reference signal symbols; the distance between adjacent reference signal symbols is the number of OFDM symbols spaced between the adjacent reference signal symbols;
and estimating the frequency offset according to the correlation values between all adjacent reference signal symbols and the intervals between the adjacent reference signal symbols to obtain a frequency offset estimation result.
Optionally, the performing channel estimation on the resource element bearing the PT-RS and the DMRS corresponding to the subcarrier where the PT-RS is located to obtain a channel estimation value of each reference signal specifically includes:
using LS channel estimation method, using formula
Performing channel estimation on the reference signals to obtain a channel estimation value of each reference signal; in the formula, Hr,k,iThe channel estimation value of an r receiving antenna corresponding to a k subcarrier of an ith reference signal symbol; r is the number of the receiving antenna, and k is the number of the subcarrier; y isr,k,iDenotes the received signal of the r-th receiving antenna corresponding to the k-th subcarrier of the ith reference signal symbol, sk,iA reference signal sequence carried by a k subcarrier representing an ith reference signal symbol; (s)k,i)*Is s isk,iConjugation of (1); | | non-woven hair2Representing a complex modulo squaring operation.
Optionally, the calculating a correlation value between adjacent reference signal symbols according to the channel estimation value of each reference signal specifically includes:
using formulas
Calculating correlation values between adjacent reference signal symbols; wherein, Corri,i+1Represents a correlation value between an ith reference signal symbol and an (i + 1) th reference signal symbol; hr,k,iThe channel estimation value of an r receiving antenna corresponding to a k subcarrier of an ith reference signal symbol; hr,k,i+1The channel estimation value of an r-th receiving antenna corresponding to a k-th subcarrier of an i + 1-th reference signal symbol; r is the number of the receiving antenna, and r is 0,1, …, RxNum-1; k is the number of the subcarrier, and k is 0,1, …, N-1; conj () denotes a complex conjugating operation.
Optionally, the estimating the frequency offset according to the correlation values between all adjacent reference signal symbols and the intervals between adjacent reference signal symbols to obtain a frequency offset estimation result specifically includes:
using formulas
Estimating the frequency offset; in the formula, FOE is a frequency deviation estimated value; corri,i+1Represents a correlation value between an ith reference signal symbol and an (i + 1) th reference signal symbol; l isi,i+1Represents the spacing between the ith reference signal symbol and the (i + 1) th reference signal symbol; i is 1,2, …, M-1, M is the number of reference signal symbols; angle () represents a complex angle-finding operation; t isofdm-SymRepresenting the time duration of one OFDM symbol.
A DMRS and PTRS combined frequency offset estimation system, comprising:
the channel estimation module is used for carrying out channel estimation on the resource unit bearing the PT-RS and the DMRS corresponding to the subcarrier where the PT-RS is located to obtain a channel estimation value of each reference signal; the reference signal is PT-RS or DMRS;
a correlation value calculation module, configured to calculate a correlation value between adjacent reference signal symbols according to the channel estimation value of each reference signal; the reference signal symbol is a PTRS symbol or a DMRS symbol, the PTRS symbol is an OFDM symbol where PT-RS is located, and the DMRS symbol is an OFDM symbol where DMRS is located; the number of PTRS symbols is greater than or equal to 1;
the distance acquisition module is used for acquiring the distance between adjacent reference signal symbols; the distance between adjacent reference signal symbols is the number of OFDM symbols spaced between the adjacent reference signal symbols;
and the frequency offset estimation module is used for estimating the frequency offset according to the correlation values between all adjacent reference signal symbols and the intervals between the adjacent reference signal symbols to obtain a frequency offset estimation result.
Optionally, the channel estimation module specifically includes:
an LS channel estimation unit for adopting LS channel estimation method and using formula
Performing channel estimation on the reference signals to obtain a channel estimation value of each reference signal; in the formula, Hr,k,iThe channel estimation value of an r receiving antenna corresponding to a k subcarrier of an ith reference signal symbol; r is the number of the receiving antenna, and k is the number of the subcarrier; y isr,k,iDenotes the received signal of the r-th receiving antenna corresponding to the k-th subcarrier of the ith reference signal symbol, sk,iA reference signal sequence carried by a k subcarrier representing an ith reference signal symbol; (s)k,i)*Is s isk,iConjugation of (1); | | non-woven hair2Representing a complex modulo squaring operation.
Optionally, the correlation value calculating module specifically includes:
a correlation value calculation unit for using a formula
Calculating correlation values between adjacent reference signal symbols; wherein, Corri,i+1Represents a correlation value between an ith reference signal symbol and an (i + 1) th reference signal symbol; hr,k,iThe channel estimation value of an r receiving antenna corresponding to a k subcarrier of an ith reference signal symbol; hr,k,i+1The r-th subcarrier corresponding to the k-th subcarrier of the (i + 1) -th reference signal symbolReceiving channel estimation values of antennas; r is the number of the receiving antenna, and r is 0,1, …, RxNum-1; k is the number of the subcarrier, and k is 0,1, …, N-1; conj () denotes a complex conjugating operation.
Optionally, the frequency offset estimation module specifically includes:
a frequency offset estimation unit for using the formula
Estimating the frequency offset; in the formula, FOE is a frequency deviation estimated value; corri,i+1Represents a correlation value between an ith reference signal symbol and an (i + 1) th reference signal symbol; l isi,i+1Represents the spacing between the ith reference signal symbol and the (i + 1) th reference signal symbol; i is 1,2, …, M-1, M is the number of reference signal symbols; angle () represents a complex angle-finding operation; t isofdm-SymRepresenting the time duration of one OFDM symbol.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the invention combines DMRS and PTRS to carry out frequency offset estimation, the period of PT-RS is matched with the frequency offset change rate, and meanwhile, when the number of PTRS symbols is 1, cross product frequency discrimination can be carried out by combining DMRS symbols together, thus breaking through the limitation of frequency offset estimation on PTRS symbols. Therefore, the frequency offset can be tracked in real time, the real-time performance and the accuracy of frequency offset estimation are improved, and the performance of a receiver is further ensured.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
FIG. 1 is a schematic flow chart of a frequency offset estimation method combining DMRS and PTRS according to the present invention;
FIG. 2 is a schematic structural diagram of a frequency offset estimation system combining DMRS and PTRS according to the present invention;
fig. 3 is a diagram illustrating a PT-RS configuration according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
The phase noise has the same frequency selectivity on the whole frequency band and has stronger random characteristics in time, so that the PT-RS has the characteristics of sparseness in a frequency domain and denseness in a time domain in time frequency resource allocation. Frequency domain density of PT-RS using KPT-RSIs represented by KPT-RSE {2,4}, representing KPT-RSConfiguring a PT-RS subcarrier by one RB (resource Block), wherein the time domain density is LPT-RSIs represented by LPT-RSE {1,2,4}, represents LPT-RSOne PT-RS symbol is configured for one OFDM symbol.
Fig. 1 is a flowchart illustrating a frequency offset estimation method combining DMRS and PTRS according to the present invention. As shown in fig. 1, the frequency offset estimation method combining DMRS and PTRS of the present invention includes the following steps:
step 100: and performing channel estimation on the resource unit bearing the PT-RS and the DMRS corresponding to the subcarrier where the PT-RS is located to obtain a channel estimation value of each reference signal. Aiming at the condition that the number of PTRS symbols is more than or equal to 1 (the PTRS symbols are OFDM symbols where PT-RS is located), especially aiming at the condition that the number of the PTRS symbols is equal to 1, the invention adopts an LS (least square) channel estimation method to obtain the frequency domain response of each reference signal, namely the frequency domain response of all resource units bearing the PT-RS and the frequency domain response of the DMRS corresponding to the subcarrier where the PT-RS is located, and the formula is as follows:
in the formula, Hr,k,iThe channel estimation value of an r receiving antenna corresponding to a k subcarrier of an ith reference signal symbol; r is the number of the receiving antenna, namely the antenna index; k is the number of the subcarrier, namely the subcarrier index; i is the OFDM symbol index of the reference signal symbol, i.e. represents the ith reference signal symbol; y isr,k,iDenotes the received signal of the r-th receiving antenna corresponding to the k-th subcarrier of the ith reference signal symbol, sk,iA reference signal sequence carried by a k subcarrier representing an ith reference signal symbol; (s)k,i)*Is s isk,iConjugation of (1); | | non-woven hair2Representing a complex modulo squaring operation. The reference signal of the invention is PT-RS or DMRS, the corresponding reference signal symbol is PTRS symbol or DMRS symbol, PTRS symbol is OFDM symbol where PT-RS locates, DMRS symbol is OFDM symbol where DMRS locates. Since there may be only 1 PTRS symbol, reference signal symbols adjacent to the PTRS symbol may be DMRS symbols, and when there are a plurality of PTRS symbols, reference signal symbols adjacent to the PTRS symbol may be PTRS symbols and may also be DMRS symbols.
Step 200: and calculating correlation values between adjacent reference signal symbols according to the channel estimation value of each reference signal. Specifically, the correlation value calculation formula is as follows:
in the formula, Corri,i+1Represents a correlation value between an ith reference signal symbol and an (i + 1) th reference signal symbol; hr,k,iThe channel estimation value of an r receiving antenna corresponding to a k subcarrier of an ith reference signal symbol; hr,k,i+1The channel estimation value of an r-th receiving antenna corresponding to a k-th subcarrier of an i + 1-th reference signal symbol; r is the number of the receiving antenna, and r is 0,1, …, RxNum-1; k is the number of the subcarrier, k is 0,1,…, N-1; conj () denotes a complex conjugating operation.
When calculating the correlation value of the adjacent reference signal symbols, the invention obtains the correlation value between the whole adjacent reference signal symbols by dimension summation of the number of receiving antennas and the number of subcarriers.
Step 300: the spacing between adjacent reference signal symbols is obtained. The spacing between adjacent reference signal symbols is the number of OFDM symbols spaced between adjacent reference signal symbols. The number of receiving antennas is RxNum, namely r belongs to {0, 1.. RxNum-1}, and the number of PT-RS subcarriers in a Physical Downlink Shared Channel (PDSCH) calling bandwidth is N, namely k belongs to {0, 1.. N-1 }; the total number of PTRS symbols and DMRS symbols, namely the number of reference signal symbols is M, namely i belongs to {1, 2.. M }, and the distances between adjacent reference signal symbols are { L } respectively1,2,L2,3,...LM-1,MIn which L is1,2Indicating the spacing between the 1 st and 2 nd reference signal symbols, i.e. the number of OFDM intervals, and so on, LM-1,MIndicating the number of OFDM symbols spaced between the M-1 th and mth reference signal symbols.
Step 400: and estimating the frequency offset according to the correlation values between all adjacent reference signal symbols and the intervals between the adjacent reference signal symbols to obtain a frequency offset estimation result. Specifically, an angle is calculated from correlation values of adjacent reference signal symbols, and then the calculated angle is divided by a time interval of the adjacent reference signal symbols (the interval includes a constant multiple of 2 x pi), so as to obtain a frequency offset estimation value; then, averaging the frequency offset estimation values obtained by the multiple groups of adjacent reference signal symbols to obtain a final FOE value, wherein the specific formula is as follows:
in the formula, FOE is a frequency deviation estimated value; corri,i+1Represents a correlation value between an ith reference signal symbol and an (i + 1) th reference signal symbol; angle () represents a complex angle-finding operation; t isofdm-SymRepresents the time duration of one OFDM symbol; l isi,i+1And M is the number of the reference signal symbols.
Based on the above scheme, the present invention further provides a frequency offset estimation system combining DMRS and PTRS, and fig. 2 is a schematic structural diagram of the frequency offset estimation system combining DMRS and PTRS according to the present invention. As shown in fig. 2, the frequency offset estimation system combining DMRS and PTRS of the present invention includes:
the channel estimation module 201 is configured to perform channel estimation on the resource element bearing the PT-RS and the DMRS corresponding to the subcarrier where the PT-RS is located, to obtain a channel estimation value of each reference signal. The reference signal is PT-RS or DMRS, and specifically, the channel estimation module 201 includes: an LS channel estimation unit for adopting LS channel estimation method and using formula
Performing channel estimation on each reference signal to obtain a channel estimation value of each reference signal; in the formula, Hr,k,iThe channel estimation value of an r receiving antenna corresponding to a k subcarrier of an ith reference signal symbol; the reference signal symbols are OFDM symbols where PT-RS are located, and the number of the reference signal symbols is not less than 2; r is the number of the receiving antenna, and k is the number of the subcarrier; y isr,k,iDenotes the received signal of the r-th receiving antenna corresponding to the k-th subcarrier of the ith reference signal symbol, sk,iA PT-RS sequence carried by a k sub-carrier representing an ith reference signal symbol; (s)k,i)*Is s isk,iConjugation of (1); | | non-woven hair2Representing a complex modulo squaring operation.
A correlation value calculating module 202, configured to calculate a correlation value between adjacent reference signal symbols according to the channel estimation value of the resource unit in which each PT-RS is located. The reference signal symbol is a PTRS symbol or a DMRS symbol, the PTRS symbol is an OFDM symbol where PT-RS is located, and the DMRS symbol is an OFDM symbol where DMRS is located; the number of PTRS symbols is greater than or equal to 1. Specifically, the correlation value calculation module 202 includes: a correlation value calculation unit for using a formula
Calculating correlation values between adjacent reference signal symbols; wherein, Corri,i+1Represents a correlation value between an ith reference signal symbol and an (i + 1) th reference signal symbol; hr,k,iThe channel estimation value of an r receiving antenna corresponding to a k subcarrier of an ith reference signal symbol; hr,k,i+1The channel estimation value of an r-th receiving antenna corresponding to a k-th subcarrier of an i + 1-th reference signal symbol; r is the number of the receiving antenna, and r is 0,1, …, RxNum-1; k is the number of the subcarrier, and k is 0,1, …, N-1; conj () denotes a complex conjugating operation.
A space obtaining module 203, configured to obtain a space between adjacent reference signal symbols; the spacing between adjacent reference signal symbols is the number of OFDM symbols spaced between adjacent reference signal symbols.
And the frequency offset estimation module 204 is configured to estimate a frequency offset according to correlation values between all adjacent reference signal symbols and intervals between adjacent reference signal symbols, so as to obtain a frequency offset estimation result. Specifically, the frequency offset estimation module includes: a frequency offset estimation unit for using the formula
Estimating the frequency offset; in the formula, FOE is a frequency deviation estimated value; corri,i+1Represents a correlation value between an ith reference signal symbol and an (i + 1) th reference signal symbol; l isi,i+1Represents the spacing between the ith reference signal symbol and the (i + 1) th reference signal symbol; i is 1,2, …, M-1, M is the number of reference signal symbols; angle () represents a complex angle-finding operation; t isofdm-SymRepresenting the time duration of one OFDM symbol.
The following provides a specific example to further illustrate the invention.
The embodiment is based on a 5G NR system, DMRS configured by the 5G NR system occupies OFDM symbols with indexes of 2 and 7, and the basic configuration of PT-RS associated with the DMRS is KPT-RS＝2，LPT-RSThe specific mapping is shown in fig. 3, where one column indicates one OFDM symbol and RB indicates a resource block, where 2 is the sameComprising 4 resource blocks. As can be seen from fig. 3, the number of OFDM symbols occupied by PT-RS is 5, i.e. the number of PTRS symbols is 5; the number of OFDM symbols occupied by the DMRS is 2, that is, the number of DMRS symbols is 2, and then the total number of reference signal symbols is M-5 + 2-7. And the interval between adjacent reference signal symbols is { L1,2,L2,3,L3,4,L4,5,L5,6, L 6,72,2,1,2, 2. In this embodiment, the bandwidth of PDSCH scheduling is 20RB, and then the number N of PT-RS subcarriers is 10. The number of receiving antennas is RxNum 2, then, the process of calculating the frequency offset estimation FOE is:
(1) using LS channel estimation, a channel estimate for each reference signal is obtained:
wherein, yr,k,lRepresents the received signal of the l PT-RS symbol, the k subcarrier and the r receiving antenna, sk,lRepresents the ith PT-RS symbol, the PT-RS sequence carried by the kth subcarrier,(s)k,l)*Is sk,lThe conjugation, | | | non-woven counting phosphor2Representing the complex modulo square.
(2) Calculating a correlation value:
(3) the FOE estimate is:
the embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.
Claims (6)
1. A frequency offset estimation method combining DMRS and PTRS is characterized by comprising the following steps:
carrying out channel estimation on a resource unit bearing the PT-RS and a DMRS corresponding to a subcarrier where the PT-RS is located to obtain a channel estimation value of each reference signal; the reference signal is PT-RS or DMRS;
calculating correlation values between adjacent reference signal symbols according to the channel estimation value of each reference signal; the reference signal symbol is a PTRS symbol or a DMRS symbol, the PTRS symbol is an OFDM symbol where PT-RS is located, and the DMRS symbol is an OFDM symbol where DMRS is located; the number of PTRS symbols is greater than or equal to 1;
acquiring the space between adjacent reference signal symbols; the distance between adjacent reference signal symbols is the number of OFDM symbols spaced between the adjacent reference signal symbols;
using a formula according to correlation values between all adjacent reference signal symbols and distances between adjacent reference signal symbols
Estimating the frequency offset to obtain a frequency offset estimation result; in the formula, FOE is a frequency deviation estimated value; corri,i+1Represents a correlation value between an ith reference signal symbol and an (i + 1) th reference signal symbol; l isi,i+1Represents the spacing between the ith reference signal symbol and the (i + 1) th reference signal symbol; i is 1,2, …, M-1, M is the number of reference signal symbols; angle () represents a complex angle-finding operation; t isofdm-SymRepresenting the time duration of one OFDM symbol.
2. The method for estimating frequency offset in conjunction with DMRS and PTRS according to claim 1, wherein the performing channel estimation on the resource element carrying PT-RS and the DMRS corresponding to the subcarrier where PT-RS is located to obtain the channel estimation value of each reference signal specifically comprises:
using LS channel estimation method, using formula
Performing channel estimation on the reference signals to obtain a channel estimation value of each reference signal; in the formula, Hr,k,iThe channel estimation value of an r receiving antenna corresponding to a k subcarrier of an ith reference signal symbol; r is the number of the receiving antenna, and k is the number of the subcarrier; y isr,k,iDenotes the received signal of the r-th receiving antenna corresponding to the k-th subcarrier of the ith reference signal symbol, sk,iA reference signal sequence carried by a k subcarrier representing an ith reference signal symbol; (s)k,i)*Is s isk,iConjugation of (1); | | non-woven hair2Representing a complex modulo squaring operation.
3. The method for frequency offset estimation based on a combination of DMRS and PTRS as claimed in claim 1, wherein the calculating the correlation values between adjacent reference signal symbols according to the channel estimation value of each reference signal specifically comprises:
using formulas
Calculating correlation values between adjacent reference signal symbols; wherein, Corri,i+1Represents a correlation value between an ith reference signal symbol and an (i + 1) th reference signal symbol; hr,k,iThe channel estimation value of an r receiving antenna corresponding to a k subcarrier of an ith reference signal symbol; hr,k,i+1The channel estimation value of an r-th receiving antenna corresponding to a k-th subcarrier of an i + 1-th reference signal symbol; r is the number of the receiving antenna, and r is 0,1, …, RxNum-1; k is the number of the sub-carriers,k is 0,1, …, N-1; conj () denotes a complex conjugating operation.
4. A frequency offset estimation system combining DMRS and PTRS, comprising:
the channel estimation module is used for carrying out channel estimation on the resource unit bearing the PT-RS and the DMRS corresponding to the subcarrier where the PT-RS is located to obtain a channel estimation value of each reference signal; the reference signal is PT-RS or DMRS;
a correlation value calculation module, configured to calculate a correlation value between adjacent reference signal symbols according to the channel estimation value of each reference signal; the reference signal symbol is a PTRS symbol or a DMRS symbol, the PTRS symbol is an OFDM symbol where PT-RS is located, and the DMRS symbol is an OFDM symbol where DMRS is located; the number of PTRS symbols is greater than or equal to 1;
the distance acquisition module is used for acquiring the distance between adjacent reference signal symbols; the distance between adjacent reference signal symbols is the number of OFDM symbols spaced between the adjacent reference signal symbols;
the frequency offset estimation module is used for estimating frequency offset according to correlation values between all adjacent reference signal symbols and intervals between the adjacent reference signal symbols to obtain a frequency offset estimation result; the frequency offset estimation module specifically includes:
a frequency offset estimation unit for using the formula
Estimating the frequency offset; in the formula, FOE is a frequency deviation estimated value; corri,i+1Represents a correlation value between an ith reference signal symbol and an (i + 1) th reference signal symbol; l isi,i+1Represents the spacing between the ith reference signal symbol and the (i + 1) th reference signal symbol; i is 1,2, …, M-1, M is the number of reference signal symbols; angle () represents a complex angle-finding operation; t isofdm-SymRepresenting the time duration of one OFDM symbol.
5. The system for frequency offset estimation combining DMRS and PTRS of claim 4, wherein the channel estimation module specifically comprises:
an LS channel estimation unit for adopting LS channel estimation method and using formula
Performing channel estimation on the reference signals to obtain a channel estimation value of each reference signal; in the formula, Hr,k,iThe channel estimation value of an r receiving antenna corresponding to a k subcarrier of an ith reference signal symbol; r is the number of the receiving antenna, and k is the number of the subcarrier; y isr,k,iDenotes the received signal of the r-th receiving antenna corresponding to the k-th subcarrier of the ith reference signal symbol, sk,iA reference signal sequence carried by a k subcarrier representing an ith reference signal symbol; (s)k,i)*Is s isk,iConjugation of (1); | | non-woven hair2Representing a complex modulo squaring operation.
6. The system for frequency offset estimation combining DMRS and PTRS of claim 4, wherein the correlation value calculation module specifically comprises:
a correlation value calculation unit for using a formula
Calculating correlation values between adjacent reference signal symbols; wherein, Corri,i+1Represents a correlation value between an ith reference signal symbol and an (i + 1) th reference signal symbol; hr,k,iThe channel estimation value of an r receiving antenna corresponding to a k subcarrier of an ith reference signal symbol; hr,k,i+1The channel estimation value of an r-th receiving antenna corresponding to a k-th subcarrier of an i + 1-th reference signal symbol; r is the number of the receiving antenna, and r is 0,1, …, RxNum-1; k is the number of the subcarrier, and k is 0,1, …, N-1; conj () denotes a complex conjugating operation.
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