CN109302740B - Frequency synchronization method, AP (access point) equipment, server and system - Google Patents

Frequency synchronization method, AP (access point) equipment, server and system Download PDF

Info

Publication number
CN109302740B
CN109302740B CN201811246529.6A CN201811246529A CN109302740B CN 109302740 B CN109302740 B CN 109302740B CN 201811246529 A CN201811246529 A CN 201811246529A CN 109302740 B CN109302740 B CN 109302740B
Authority
CN
China
Prior art keywords
transmitting
receiving
antenna
antennas
frequency deviation
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN201811246529.6A
Other languages
Chinese (zh)
Other versions
CN109302740A (en
Inventor
张学彦
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ruijie Networks Co Ltd
Original Assignee
Ruijie Networks Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ruijie Networks Co Ltd filed Critical Ruijie Networks Co Ltd
Priority to CN201811246529.6A priority Critical patent/CN109302740B/en
Publication of CN109302740A publication Critical patent/CN109302740A/en
Application granted granted Critical
Publication of CN109302740B publication Critical patent/CN109302740B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W56/00—Synchronisation arrangements
    • H04W56/0035—Synchronisation arrangements detecting errors in frequency or phase
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0014—Carrier regulation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0014—Carrier regulation
    • H04L2027/0018—Arrangements at the transmitter end
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0014—Carrier regulation
    • H04L2027/0024—Carrier regulation at the receiver end
    • H04L2027/0026—Correction of carrier offset

Abstract

The embodiment of the invention provides a frequency synchronization method, AP (access point) equipment, a server and an MIMO (multiple input multiple output) system. The method comprises the following steps: each receiving and transmitting antenna in the wireless access point sequentially transmits a transmitting training frame containing a leader sequence to other receiving and transmitting antennas; calculating estimated frequency deviation between the transceiving antenna and other transceiving antennas by other transceiving antennas in the wireless access point according to the received receiving training frame corresponding to each transceiving antenna; the receiving and transmitting antenna sends the estimated frequency deviation between other receiving and transmitting antennas to a server in the MIMO system, so that the server determines a frequency deviation matrix according to the estimated frequency deviation and determines the relative frequency deviation of each receiving and transmitting antenna according to the frequency deviation matrix; each transmitting and receiving antenna compensates the transmitting frequency of the transmitting and receiving antenna according to the relative frequency deviation. The invention reduces the frequency deviation influence caused by different crystal oscillators at the transmitting end, and improves the system performance of a distributed antenna cooperation scene.

Description

Frequency synchronization method, AP (access point) equipment, server and system
Technical Field
The embodiment of the invention relates to the technical field of wireless communication, in particular to a frequency synchronization method, AP (access point) equipment, a server and an MIMO (multiple input multiple output) system.
Background
The Multiple Input Multiple Output (MIMO) technique can improve the system channel capacity by Multiple times without increasing the spectrum resources and the antenna transmission power, and thus is widely applied to wireless communication systems. The method for placing multiple antennas from the base station end of the wireless communication system applying the MIMO technology can be divided into two categories: one is localized MIMO and the other is distributed MIMO. The centralized MIMO means that a plurality of antennas are arranged to form an antenna array coverage cell, and all the antennas are centralized at the position of a base station; distributed MIMO refers to that multiple antennas of a base station are dispersed in a coverage cell, and there is no limitation of spatial location.
For MIMO systems, the most important factor related to their channel capacity is the correlation of the fading of the channel of each antenna. Due to the fact that the distributed MIMO antenna is far away, channel fading formed between different antennas and users can be regarded as completely uncorrelated under most conditions, and channel capacity is large. In addition, the distributed MIMO system has certain advantages in the aspects of cell edge coverage, multi-user co-frequency transmission and the like. While distributed MIMO systems have advantages over centralized MIMO systems, they are also accompanied by more complex system architectures and a series of technical problems.
When the distributed MIMO is used for cooperatively transmitting signals, because the crystal oscillators adopted by all transmitting antennas are different, a plurality of different frequency offsets exist at the receiving antennas, and the estimation and compensation of the frequency offsets are difficult. The conventional frequency offset algorithm can only process one frequency offset, one frequency at the transmitting end and one frequency at the receiving end, and then estimate and compensate the frequency deviation between the two. However, for the distributed MIMO system, since the antennas are different sources, there are several different frequencies, and signals with different frequencies are mixed together during cooperative transmission, the conventional frequency offset compensation algorithm cannot compensate the mixed frequency offset differently.
When the frequency offset of the received signal cannot be properly compensated, the constellation diagram of the received signal generates angle rotation, and signal constellation diagram diffusion occurs at the same time, so that the receiving performance is influenced.
Disclosure of Invention
Aiming at the defects in the prior art, the embodiment of the invention provides a frequency synchronization method, AP equipment, a server and an MIMO system.
In a first aspect, an embodiment of the present invention provides a frequency synchronization method for a distributed MIMO system, including:
each transceiving antenna M in a wireless access pointiTo other receiving and transmitting antennas M in turnjSending a sending training frame S containing a leader sequence, wherein i is not equal to j and i, j belongs to [1, m ∈]M is the total number of the receiving and transmitting antennas in the wireless access point;
other transceiving antennas M in the wireless access pointjAccording to each receiving-transmitting antenna M receivediCorresponding received training frame S'iCalculating said transmitting/receiving antenna MiWith said other transceiving antenna MjEstimated frequency deviation Δ F therebetweeni→j；
From said estimated frequency deviation Δ Fi→jDetermining a frequency offset matrix Hm*mAnd according to the frequency offset matrix Hm*mDetermining each of said transceiving antennas MiRelative frequency deviation epsilon ofi；
Each of the transmitting and receiving antennas MiAccording to the relative frequency deviation epsiloniAccording to said relative frequency deviation epsiloniFor the transmitting and receiving antenna MiIs compensated for.
As in the above method, optionally, each transceiving antenna M in the wireless access pointiTo other receiving and transmitting antennas M in turnjTransmitting a transmission training frame S including a preamble sequence, comprising:
each transceiving antenna M in a wireless access pointiAdjusting a standard long training sequence in a wireless communication protocol according to formula (1), and determining a modified long training sequence:
BABAB + p ABAB formula (1)
Wherein BABAB is a standard long training sequence specified by a communication protocol, ABAB is a sequence except a guard interval B in the standard long training sequence, and p is a positive integer;
determining a sending training frame S containing a leader sequence according to the modified long training sequence;
each of the transmitting and receiving antennas MiTo other receiving and transmitting antennas M in turnjAnd sending the sending training frame S.
As mentioned above, optionally, the other transceiving antennas MjAccording to each receiving-transmitting antenna M receivediCorresponding received training frame S'iCalculating said transmitting/receiving antenna MiWith said other transceiving antenna MjEstimated frequency deviation Δ F therebetweeni→jThe method comprises the following steps:
the other transceiving antenna MjFrom each transceiver antenna MiCorresponding received training frame S'iMiddle-intercepting first frequency offset estimation signal
Figure GDA0002783565620000031
And after D sampling points are spaced, receiving a training frame S'iIntermediate-intercept second frequency offset estimation signal
Figure GDA0002783565620000032
Wherein the content of the first and second substances,
Figure GDA0002783565620000033
and
Figure GDA0002783565620000034
the lengths of the N-type carbon nanotubes are all N;
estimating the first frequency offset signal according to equation (3)
Figure GDA0002783565620000035
And the second frequency offset estimation signal
Figure GDA0002783565620000036
Performing correlation operation to determine the first frequency offset estimation signal
Figure GDA0002783565620000037
And the second frequency offset estimation signal
Figure GDA0002783565620000038
Signal phase difference phi ofi：
Figure GDA0002783565620000039
Calculating the transceiving antenna M according to formula (4)iWith said other transceiving antenna MjEstimated frequency deviation Δ F therebetweeni→j
Figure GDA00027835656200000310
Wherein phase (phi)i) For the signal phase difference phiiT is the duration of a single sampling point, and D is the sampling interval;
Figure GDA00027835656200000311
estimating a signal for the second frequency offset
Figure GDA00027835656200000312
The conjugate value of (c).
In a second aspect, another embodiment of the present invention provides a frequency synchronization method for a distributed MIMO system, including:
receiving each transceiving antenna M in wireless access pointiOther transmitting and receiving antennas M for transmissionjAnd the transmitting/receiving antenna MiEstimated frequency deviation Δ F therebetweenj→iWhere i ≠ j and i, j ∈ [1, m ∈]M is the total number of the receiving and transmitting antennas in the wireless access point;
from said estimated frequency deviation Δ Fj→iDetermining a frequency offset matrix Hm*m；
According to the frequency offset matrix Hm*mDetermining each of said transceiving antennas MiRelative frequency deviation epsilon ofi；
Deviation of the relative frequency epsiloniTo each of said transceiving antennas MiFor the receiving and transmitting antenna MiAccording to the relative frequency deviation epsiloniFor the transmitting and receiving antenna MiIs compensated for.
As with the method above, optionally, the frequency deviation Δ F is estimated based on the estimatej→iDetermining a frequency offset matrix Hm*mThe method comprises the following steps:
determining the frequency offset matrix H according to equation (5)m*m：
Figure GDA0002783565620000041
Wherein, Δ Fi→j＝ΔFj→i＝0,i＝j&i,j∈[1,m]。
As above, optionally, the frequency offset matrix H is based on the frequency offset matrix Hm*mDetermining each of said transceiving antennas MiRelative frequency deviation epsilon ofiThe method comprises the following steps:
calculating the transceiving antenna M according to equation (6)iRelative frequency offset matrix F':
Figure GDA0002783565620000042
wherein the content of the first and second substances,
Figure GDA0002783565620000043
Fifor transmitting and receiving antennas MiThe carrier frequency of (a);
calculating each of the transceiving antennas M according to the formula (7)iRelative frequency deviation epsilon ofi：
εi＝Fi-F1Formula (7)
Wherein i belongs to [1, m ].
As with the method described above, optionally, the equation (6) is determined according to the following steps:
least square function after frequency deviation compensation
Figure GDA0002783565620000051
To FiCalculating the partial derivative and determining the partial derivative function
Figure GDA0002783565620000052
Let the partial derivative function equal to 0, then
Figure GDA0002783565620000053
The above equation is developed to determine the constraint equation:
Figure GDA0002783565620000054
determining the formula (6) according to formula (8):
Figure GDA0002783565620000055
wherein the content of the first and second substances,
Figure GDA0002783565620000056
in a third aspect, an embodiment of the present invention provides a wireless access point AP device, including:
multiple transmitting/receiving antennas MiReceiving and transmitting antenna MjAnd processing means, where i ≠ j and i, j ∈ [1, m ∈ j]M is the total number of the receiving and transmitting antennas in the wireless access point equipment;
the transmitting and receiving antenna MiFor sequentially transmitting to other transceiving antennas MjSending a sending training frame S containing a leader sequence;
the transmitting and receiving antenna MjFor each transceiving antenna M receivediCorresponding received training frame S'iCalculating said transmitting/receiving antenna MiWith each other transceiving antenna MjEstimated frequency deviation Δ F therebetweeni→j；
The processing device is used for estimating the frequency deviation delta F according to the frequency deviationj→iDetermining a frequency offset matrix Hm*mAnd according to the frequency offset matrix Hm*mDetermining each of said transceiving antennas MiRelative frequency deviation epsilon ofi；
The transmitting and receiving antenna MiAnd also for determining the relative frequency deviation epsiloniFor the transmitting and receiving antenna MiIs compensated for.
As above AP device, optionally, the transceiving antenna MiThe method is specifically used for:
adjusting a standard long training sequence in a wireless communication protocol according to formula (1), and determining a modified long training sequence:
BABAB + p ABAB formula (1)
Wherein BABAB is a standard long training sequence specified by a communication protocol, ABAB is a sequence except a guard interval B in the standard long training sequence, and p is a positive integer;
determining a sending training frame S containing a leader sequence according to the modified long training sequence;
to other receiving and transmitting antennas M in turnjAnd sending the sending training frame S.
As the AP device, optionally, the other transceiving antenna MjParticularly for：
From each transceiver antenna MiCorresponding received training frame S'iMiddle-intercepting first frequency offset estimation signal
Figure GDA0002783565620000061
And after D sampling points are spaced, receiving a training frame S'iIntermediate-intercept second frequency offset estimation signal
Figure GDA0002783565620000062
Wherein the content of the first and second substances,
Figure GDA0002783565620000063
and
Figure GDA0002783565620000064
the lengths of the N-type carbon nanotubes are all N;
estimating the first frequency offset signal according to equation (3)
Figure GDA0002783565620000065
And the second frequency offset estimation signal
Figure GDA0002783565620000066
Performing correlation operation to determine the first frequency offset estimation signal
Figure GDA0002783565620000067
And the second frequency offset estimation signal
Figure GDA0002783565620000068
Signal phase difference phi ofi：
Figure GDA0002783565620000071
Calculating the transceiving antenna M according to formula (4)iWith each other transceiving antenna MjEstimated frequency deviation Δ F therebetweeni→j
Figure GDA0002783565620000072
Wherein phase (phi)i) For the signal phase difference phiiT is the duration of a single sampling point, and D is the sampling interval;
Figure GDA0002783565620000073
estimating a signal for the second frequency offset
Figure GDA0002783565620000074
The conjugate value of (c).
In a fourth aspect, an embodiment of the present invention provides a server, including:
a receiving module for receiving each transmitting/receiving antenna M in the wireless access pointiOther transmitting and receiving antennas M for transmissionjAnd the transmitting/receiving antenna MiEstimated frequency deviation Δ F therebetweenj→iWhere i ≠ j and i, j ∈ [1, m ∈]M is the total number of the receiving and transmitting antennas in the wireless access point;
a sorting module for sorting out the estimated frequency deviation Δ Fj→iDetermining a frequency offset matrix Hm*m；
A relative frequency offset determining module for determining the frequency offset matrix H according to the frequency offset matrixm*mDetermining each of said transceiving antennas MiRelative frequency deviation epsilon ofi；
A transmission module for transmitting the relative frequency deviation epsiloniTo each of said transceiving antennas MiFor the receiving and transmitting antenna MiAccording to the relative frequency deviation epsiloniFor the transmitting and receiving antenna MiIs compensated for.
Optionally, the above server, the sorting module is specifically configured to:
determining the frequency offset matrix H according to equation (5)m*m：
Figure GDA0002783565620000075
Wherein, Δ Fi→j＝ΔFj→i＝0,i＝j&i,j∈[1,m]。
Optionally, the relative frequency offset determining module is specifically configured to:
calculating the transceiving antenna M according to equation (6)iRelative frequency offset matrix F':
Figure GDA0002783565620000081
wherein the content of the first and second substances,
Figure GDA0002783565620000082
Fifor transmitting and receiving antennas MiThe carrier frequency of (a);
calculating each of the transceiving antennas M according to the formula (7)iRelative frequency deviation epsilon ofi：
εi＝Fi-F1Formula (7)
Wherein i belongs to [1, m ].
In a fifth aspect, an embodiment of the present invention provides a MIMO system, including: a wireless access point AP device as described above and a server as described above.
According to the frequency synchronization method of the distributed MIMO system, each transmitting and receiving antenna at the transmitting end sequentially transmits and receives training frames containing leader sequences transmitted by other transmitting and receiving antennas, estimated frequency deviation among the transmitting and receiving antennas is estimated, relative frequency deviation of each transmitting and receiving antenna is determined according to the estimated frequency deviation, frequency compensation is carried out on each transmitting and receiving antenna according to the relative frequency deviation, frequency deviation influence caused by different crystal oscillators is reduced at the transmitting end, the transmitting frequency of each distributed antenna is synchronized, and system performance of a distributed antenna cooperation scene is improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and those skilled in the art can also obtain other drawings according to the drawings without creative efforts.
Fig. 1 is a schematic flow chart of a frequency synchronization method of a distributed MIMO system according to an embodiment of the present invention;
fig. 2 is a schematic topological connection diagram of a distributed MIMO system according to an embodiment of the present invention;
FIG. 3 is a diagram illustrating a preamble structure in the 802.11 protocol;
fig. 4 is a schematic flowchart of a frequency synchronization method for a distributed MIMO system according to another embodiment of the present invention;
fig. 5 is a schematic structural diagram of a wireless access point AP device according to an embodiment of the present invention;
fig. 6 is a schematic structural diagram of a server according to an embodiment of the present invention;
fig. 7 is a schematic structural diagram of a MIMO system according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, 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 some, but not all, embodiments of the present invention. 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.
Fig. 1 is a schematic flow chart of a frequency synchronization method of a distributed MIMO system according to an embodiment of the present invention, as shown in fig. 1, the method includes:
step S11, each transmitting/receiving antenna M in the wireless access pointiTo other receiving and transmitting antennas M in turnjSending a sending training frame S containing a leader sequence, wherein i is not equal to j and i, j belongs to [1, m ∈]M is the total number of the receiving and transmitting antennas in the wireless access point;
specifically, when the distributed MIMO collaboratively transmits signals, because the crystal oscillators adopted by the transmitting antennas are different, a plurality of different frequency offsets exist at the receiving antennas, which brings difficulty to the estimation and compensation of the frequency offsets. For this problem, the conventional frequency offset estimation compensation algorithm is not applicable. When the frequency offset of the received signal cannot be properly compensated, the constellation diagram of the received signal generates angle rotation, and signal constellation diagram diffusion occurs at the same time, so that the receiving performance is influenced. Taking the 802.11 protocol as an example, the frequency deviation of each antenna of the distributed MIMO system in the protocol exceeds 200Hz, which results in significant performance degradation.
Fig. 2 is a schematic diagram of a topological connection of a distributed MIMO system according to an embodiment of the present invention, and as shown in fig. 2, assuming that all access points AP and stations STA in the MIMO system use a single antenna, the AP1-APm transmits signals, and the STA1-STAm receives signals. In the distributed MIMO system, because the crystal oscillators adopted by the transmitting antennas are different, a plurality of different frequency offsets exist at the receiving antennas, so that the frequency offset influence caused by the different crystal oscillators can be reduced at the transmitting end in order to improve the quality of the signals cooperatively transmitted by the distributed MIMO system, the transmitting frequencies of the distributed antennas are synchronized, and the effectiveness of the frequency offset estimation compensation algorithm of the conventional terminal is ensured.
When the frequency of the distributed MIMO system needs to be synchronized, in order to avoid using terminal equipment for feedback, the relative frequency offset of each receiving and transmitting antenna can be calculated at the side of the wireless access point AP, each receiving and transmitting antenna in the AP is respectively used as a transmitting end and a receiving end, training frames are sent to other receiving and transmitting antennas in the base station, so that the estimated frequency offset of each receiving and transmitting antenna is obtained, the relative frequency offset of each receiving and transmitting antenna is calculated, the relative frequency offset is compensated when a signal is transmitted, namely, the terminal equipment is not required to be matched, the offset of each AP end is synchronized, and the transmission frequency synchronization is realized at the transmitting end.
Specifically, the wireless access point AP of the MIMO system includes M transceiving antennas, denoted as M1,…,Mi,…,Mj,…,MmWhere i ≠ j and i, j ∈ [1, m ∈]And m is more than 1. Transceiver antenna M1,…,Mi,…,Mj,…,MmTransmitting the transmission training frame S containing the leader sequence in sequence when one of the receiving and transmitting antennas MiTransmitting a training frame SOther transmitting and receiving antenna MjThe training frame is received. It should be noted that when the transmitting/receiving antenna M is usedjTransmitting training frame S, transmitting-receiving antenna MiThen is the transmitting-receiving antenna MjCorresponding other transceiving antennas for receiving the transceiving antenna MjA transmitted training frame S.
Step S12, the other transmitting/receiving antenna MjAccording to each receiving-transmitting antenna M receivediCorresponding received training frame S'iCalculating said transmitting/receiving antenna MiWith each other transceiving antenna MjEstimated frequency deviation Δ F therebetweeni→j；
Specifically, due to different frequency offsets between the transceiving antennas, the receiving training frames of different transceiving antennas are different and are denoted as S 'for convenience of distinguishing'iDenotes the reception of the ith transmitting-receiving antenna MiThe received signal of (1). When receiving and transmitting antenna M1When transmitting the transmission training frame S containing the leader sequence, other receiving and transmitting antennas MjAcquiring received training frame S'1Other transmitting and receiving antennas M, since the transmitted and received signals are knownjMay be based on received training frame S'1Estimating the transmitting/receiving antenna M1With each other transceiving antenna MjEstimated frequency deviation Δ F therebetween1→j(ii) a Then, the transmitting/receiving antenna M2Transmitting a transmit training frame S containing a preamble sequence, other transmit-receive antennas MjFrom received training frame S'2Estimating the transmitting/receiving antenna M2With each other transceiving antenna MjEstimated frequency deviation Δ F therebetween2→jBy analogy, each transmitting-receiving antenna MiTo other receiving and transmitting antennas M in turnjTransmitting training frame S, other transmitting-receiving antenna MjFrom received training frame S'iEstimating the transmitting/receiving antenna MiWith each other transceiving antenna MjEstimated frequency deviation Δ F therebetweeni→j. Accordingly, when the transmitting/receiving antenna MjTransmitting and receiving antenna M when transmitting training frame S containing leading sequenceiCalculating transceiver antenna MjAnd a transmitting/receiving antenna MiEstimated frequency deviation Δ F therebetweenj→i. In the ideal case, the transmitting and receiving antenna MiAnd a transmitting/receiving antenna MjEstimated frequency deviation Δ F therebetweeni→jAnd a transmitting/receiving antenna MjAnd a transmitting/receiving antenna MiEstimated frequency deviation Δ F therebetweenj→iAre opposite numbers.
Step S13, estimating the frequency deviation delta F according to the frequency deviationi→jDetermining a frequency offset matrix Hm*mAnd according to the frequency offset matrix Hm*mDetermining each of said transceiving antennas MiRelative frequency deviation epsilon ofi；
Specifically, the AP transmits and receives signals according to each transmitting and receiving antenna MiWith other transmitting-receiving antennas MjEstimated frequency deviation Δ F therebetweeni→jAnd each other transceiving antenna MjAnd a transmitting/receiving antenna MiEstimated frequency deviation Δ F therebetweenj→iDetermining a frequency offset matrix Hm*mIn which H ism*mAnd m rows and m columns of matrix elements, wherein each matrix element is the estimated frequency deviation.
AP then according to Hm*mCalculating each transmit-receive antenna MiRelative frequency deviation epsilon ofiI.e. one of the transmitting and receiving antennas MjIs fixed, calculates other transmitting and receiving antennas MiAnd a transmitting/receiving antenna MjRelative frequency deviation epsilon ofiThus, only the other transmitting/receiving antenna M needs to be adjustediThe transmitting frequencies of these transmitting and receiving antennas are compared with the transmitting and receiving antenna MjAnd synchronization can be realized, so that the transmission frequency synchronization of all the transmitting and receiving antennas in the whole AP can be realized.
Furthermore, each transceiving antenna M in the APiOther transmitting and receiving antennas M can also be usedjAnd a transmitting/receiving antenna MiEstimated frequency deviation Δ F therebetweenj→iSending to a server in the MIMO system, calculating by the server each transmit-receive antenna MiRelative frequency deviation epsilon ofi. In particular, the server receiving transmit receive antenna M in the MIMO systemiWith other transmitting-receiving antennas MjEstimated frequency deviation Δ F therebetweeni→jThen, the server in the MIMO system receives the estimated frequency deviation Δ Fj→i(ΔFi→j) Determining a frequency offset matrix Hm*mIn which H ism*mMatrix element comprising m rows and m columnsEach matrix element is an estimated frequency offset, and when the receiving and transmitting antennas are the same, the corresponding estimated frequency offset is 0, i.e. Δ Fi→j＝ΔFj→i＝0,i＝j&i,j∈[1,m]If an estimated frequency offset is not received, the frequency offset is set to 0.
For a distributed MIMO system, since antennas are different sources, there are several different transmission frequencies, signals of different frequencies will be mixed together during cooperative transmission, and a conventional frequency offset compensation algorithm cannot distinguish and compensate frequency offsets mixed together. One feasible way is to synchronize the antenna frequency of the transmitting end during signal transmission, so that the mixed signal can be regarded as only one frequency, and the server can adjust according to the frequency H for the convenience of frequency compensationm*mCalculating each transmit-receive antenna MiRelative frequency deviation epsilon ofiI.e. one of the transmitting and receiving antennas MjIs fixed, calculates other transmitting and receiving antennas MiAnd a transmitting/receiving antenna MjRelative frequency deviation epsilon ofiThus, only the other transmitting/receiving antenna M needs to be adjustediThe transmitting frequencies of these transmitting and receiving antennas are compared with the transmitting and receiving antenna MjAnd synchronization can be realized, so that the transmission frequency synchronization of all the transmitting and receiving antennas in the whole AP can be realized. The server then transmits each transmitting-receiving antenna MiRelative frequency deviation epsilon ofiTo the transmitting/receiving antenna Mi。
Step S14, each of the transceiving antennas MiAccording to the relative frequency deviation epsiloniFor the transmitting and receiving antenna MiIs compensated for.
In particular, each transceiving antenna MiAccording to relative frequency deviation epsiloniCompensating the own transmitting frequency and correcting the transmitting-receiving antenna MiThe local oscillation frequency configuration of the AP achieves the purpose of synchronizing the frequency of each receiving and transmitting antenna in the AP.
Furthermore, if the relative frequency deviation is obtained by server processing, the transmitting/receiving antenna MiReceiving the relative frequency deviation epsilon sent by the serveriThen, based on the relative frequency deviation epsiloniFor the transmitting and receiving antenna MiCompensating the transmitting frequency of the transmitting and receiving antenna M, and correcting the transmitting and receiving antenna MiThe local oscillation frequency configuration of the AP achieves the purpose of synchronizing the frequency of each receiving and transmitting antenna in the AP.
According to the frequency synchronization method of the distributed MIMO system, each transmitting and receiving antenna at the transmitting end sequentially transmits and receives training frames containing leader sequences transmitted by other transmitting and receiving antennas, estimated frequency deviation among the transmitting and receiving antennas is estimated, relative frequency deviation of each transmitting and receiving antenna is determined according to the estimated frequency deviation, frequency compensation is carried out on each transmitting and receiving antenna according to the relative frequency deviation, frequency deviation influence caused by different crystal oscillators is reduced at the transmitting end, the transmitting frequency of each distributed antenna is synchronized, and system performance of a distributed antenna cooperation scene is improved.
On the basis of the above embodiments, further, each transceiving antenna M in the wireless access pointiTo other receiving and transmitting antennas M in turnjTransmitting a transmission training frame S including a preamble sequence, comprising:
each transceiving antenna M in a wireless access pointiAdjusting a standard long training sequence in a wireless communication protocol according to formula (1), and determining a modified long training sequence:
BABAB + p ABAB formula (1)
Wherein BABAB is a standard long training sequence specified by a communication protocol, ABAB is a sequence except a guard interval B in the standard long training sequence, and p is a positive integer;
determining a sending training frame S containing a leader sequence according to the modified long training sequence;
each of the transmitting and receiving antennas MiTo other receiving and transmitting antennas M in turnjAnd sending the sending training frame S.
Specifically, fig. 3 is a schematic diagram of a preamble sequence structure in an 802.11 protocol, as shown in fig. 3, a preamble sequence defined in the 802.11 protocol includes a Short Training Sequence (STF) and a Long Training sequence (LTF), the preamble sequence includes 10 Short Training symbols T1 to T10, 2 Long Training symbols T1 and T2, and a guard interval GI2 and 2 Long Training symbols T1 and T2 form a standard Long Training sequence LTF10 Short Training symbols for performing automatic gain control at a receiving end, timing acquisition, and coarse synchronization of frequency; the 2 long training symbols are used for channel estimation at the receiving end and fine synchronization of the system frequency. In LTF, T1 is a copy of T2, and AB denotes the sequence corresponding to T1, a is the first half sequence in T1, and B is the second half sequence in T1, since the guard interval GI2 is a copy of the second half sequence in T2, i.e., the sequence corresponding to guard interval GI2 is B, the structure of the standard long training sequence can be written as BABAB.
In the 802.11 protocol, an LTF with a length of 8us is used for frequency offset estimation, but the design is used for frequency synchronization of a transmitting end and a receiving end, and for multi-antenna cooperative synchronization, the accuracy of the frequency offset estimation method is not enough to meet the requirement. Based on the statistical principle, the estimation accuracy can be improved by increasing the number of phase measurement samples, and the estimation accuracy is improved by increasing the frequency offset estimation field.
In order to reuse the original transceiving system as much as possible, the basic structure of the preamble sequence is maintained, the LTFs in the preamble sequence are adjusted as follows, and the modified long training sequence is determined:
BABAB + p ABAB formula (1)
Wherein p is a positive integer and is a newly added frequency offset estimation field, ABAB is a sequence except for a guard interval B in a standard long training sequence, that is, ABAB is a sequence corresponding to two long training symbols T1+ T2, so that the original long training sequence is adjusted, data of T1+ T2 is increased by p times, and the original preamble sequence is extended, because in the 802.11 protocol, BABAB is 160 points, a total of 8us, that is, one a or B is 32 points, and the length is 1.6us, if BABAB +10 ABAB, 45 a or B is 45 x 1.6us 72us, and the total length of the preamble sequence is 72+8 x 80 us.
Then, the transmitting/receiving antenna MiThe original standard long training sequence in the training frame is adjusted into a modified field training sequence, and the training frame S is sent in sequence.
In actual tests, the precision within 15Hz can be achieved when p is 8, and most of synchronization requirements can be basically met; in order to keep the lengths of the preamble symbols consistent and avoid the influence of symbol misalignment, p may be 10 in practical applications.
Currently, a common MIMO system is mainly centralized MIMO. Distributed MIMO is in the development stage and is gradually put into commercial use. CoMP (Coordinated Multiple Points, Coordinated multi-point) techniques such as LTE-a are typical distributed MIMO applications. CoMP transmission refers to a plurality of geographically separated transmission points, and is coordinated to participate in data transmission for one terminal or jointly receive data transmitted by one terminal, and the plurality of transmission points participating in the coordination generally refer to base stations of different cells. CoMP technology places an edge user on the same frequency of several base stations, which serve the user at the same time, to improve the coverage performance of the edge user. By adopting CoMP, the inter-cell interference can be reduced, and the spectrum efficiency of cell edge users can be improved. When a terminal moves from a cell a to a cell B, the associated base station needs to be switched, so-called roaming; in this process, when the terminal is located at the boundary of two cells, signals on both sides are mixed together and may interfere with each other. If two cells can cooperatively transmit signals, the phenomenon of signal interference does not occur, and an important premise for cooperative transmission is that the transmission frequencies of the two cells are synchronized. Therefore, the frequency synchronization method provided by the embodiment of the invention can also effectively solve the problem of cell roaming switching.
The frequency synchronization method of the distributed MIMO system provided by the embodiment of the invention completes the frame of self calibration of the carrier frequency deviation of the antenna in the transmitting terminal, and provides a frequency deviation estimation precision improvement method on the basis of the 802.11 protocol, and the mutual frequency deviation can be obtained through simple interaction of all the antennas, so that the transmitting frequency of all the distributed antennas is synchronized, and the system performance of a distributed antenna cooperation scene is improved. In addition, the embodiment of the invention can enlarge the coverage area of the antenna, reduce the interference of the edge of the cell and effectively solve the problem of cell roaming switching by the same frequency transmission of the distributed antennas.
In addition to the above embodiments, the other transceiving antennas MjAccording to each receiving-transmitting antenna M receivediCorresponding received training frame S'iCalculating said transmitting/receiving antenna MiWith each other transceiving antenna MjEstimated frequency deviation Δ F therebetweeni→jThe method comprises the following steps:
the other transceiving antenna MjFrom each transceiver antenna MiCorresponding received training frame S'iMiddle-intercepting first frequency offset estimation signal
Figure GDA0002783565620000141
And after D sampling points are spaced, receiving a training frame S'iIntermediate-intercept second frequency offset estimation signal
Figure GDA0002783565620000142
Wherein the content of the first and second substances,
Figure GDA0002783565620000143
and
Figure GDA0002783565620000144
the lengths of the N-type carbon nanotubes are all N;
estimating the first frequency offset signal according to equation (3)
Figure GDA0002783565620000145
And the second frequency offset estimation signal
Figure GDA0002783565620000146
Performing correlation operation to determine the first frequency offset estimation signal
Figure GDA0002783565620000147
And the second frequency offset estimation signal
Figure GDA0002783565620000148
Signal phase difference phi ofi：
Figure GDA0002783565620000151
Calculating the transceiving antenna M according to formula (4)iWith each other transceiving antenna MjEstimated frequency ofRate deviation Δ Fi→j
Figure GDA0002783565620000152
Wherein phase (phi)i) For the signal phase difference phiiT is the duration of a single sampling point, and D is the sampling interval;
Figure GDA0002783565620000153
estimating a signal for the second frequency offset
Figure GDA0002783565620000154
The conjugate value of (c).
In particular, for any one transceiving antenna MjReceiving and transmitting antenna MiThe transmitted training frame is:
Figure GDA0002783565620000155
wherein, S'iFor receiving training frames, S is a transmitted training frame, and alpha is a transmitting-receiving antenna MiAnd a transmitting/receiving antenna MjFrequency deviation therebetween, also denoted as Δ Fi→jT is the duration of the signal,
Figure GDA0002783565620000156
is the initial phase.
Thereafter, other transmit-receive antennas receive training frame S'iMiddle-intercepted frequency offset estimation signal with length of N
Figure GDA0002783565620000157
Recording as a first frequency offset estimation signal, delaying D sampling points, and intercepting the frequency offset estimation signal with the length of N
Figure GDA0002783565620000158
Recording as a second frequency offset estimation signal, wherein 2N + D does not exceed the length of the preamble training sequence, N is a positive integer, and in practical application, D is a delay intentionally made for generating a phase difference and is acquired after the delay is required to be ensuredSample(s)
Figure GDA0002783565620000159
Following the original
Figure GDA00027835656200001510
Is consistent, so D may be a multiple of 64 points. For example, for 72us of BABABABABAB long training sequence, 320 points are cut from the starting position
Figure GDA00027835656200001511
Namely, it is
Figure GDA00027835656200001512
The corresponding long training sequence is BABABABABA, and 320 points are taken after 64 points are delayed
Figure GDA00027835656200001513
Then
Figure GDA00027835656200001514
The corresponding long training sequence is also BABABABABA. Although it is used for
Figure GDA00027835656200001515
As with the original data, but due to the effect of the frequency offset,
Figure GDA00027835656200001516
the phases are different and thus can be varied according to
Figure GDA00027835656200001517
And
Figure GDA00027835656200001518
the frequency deviation is calculated.
Specifically, a signal is estimated for a first frequency offset
Figure GDA00027835656200001519
And a second frequency offset estimation signal
Figure GDA00027835656200001520
Performing correlation operation and summation to calculate a first frequency offset estimation signal
Figure GDA00027835656200001521
And a second frequency offset estimation signal
Figure GDA00027835656200001522
Signal phase difference phi ofi：
Figure GDA00027835656200001523
Wherein E is the summed and accumulated amplitude, t is the duration of 1 sample point, 2 pi · α · D · t is the phase deviation of the delayed D sample points,
Figure GDA00027835656200001524
estimating a signal for a second frequency offset
Figure GDA00027835656200001525
Can further calculate the transceiving antenna M according to the formula (4)iWith other transmitting-receiving antennas MjEstimated frequency deviation Δ F therebetweeni→j：
Figure GDA0002783565620000161
Wherein phase (phi)i) For the signal phase difference phiiSo that m-1 deltaf can be calculated for each transmit-receive antennai→j。
In practical applications, the AP may determine the frequency offset matrix H according to equation (5)m*m：
Figure GDA0002783565620000162
Wherein, Δ Fi→j＝ΔFj→i＝0,i＝j&i,j∈[1,m]。
The AP then calculates the transmit receive antenna M according to equation (6)iPhase ofFor the frequency offset matrix F':
Figure GDA0002783565620000163
wherein the content of the first and second substances,
Figure GDA0002783565620000164
Fifor transmitting and receiving antennas MiThe carrier frequency of (a);
finally, the AP calculates each of the transceiving antennas M according to the formula (7)iRelative frequency deviation epsilon ofi：
εi＝Fi-F1Formula (7)
Wherein i belongs to [1, m ].
The frequency synchronization method of the distributed MIMO system provided by the embodiment of the invention completes the frame of self calibration of the carrier frequency deviation of the antenna in the transmitting terminal, and provides a frequency deviation estimation precision improvement method on the basis of the 802.11 protocol, and the mutual frequency deviation can be obtained through simple interaction of all the antennas, so that the transmitting frequency of all the distributed antennas is synchronized, and the system performance of a distributed antenna cooperation scene is improved.
Fig. 4 is a schematic flow chart of a frequency synchronization method of a distributed MIMO system according to another embodiment of the present invention, as shown in fig. 4, the method includes:
step S41, receiving each transmitting-receiving antenna M in the wireless access pointiOther transmitting and receiving antennas M for transmissionjAnd the transmitting/receiving antenna MiEstimated frequency deviation Δ F therebetweenj→iWhere i ≠ j and i, j ∈ [1, m ∈]M is the total number of the receiving and transmitting antennas in the wireless access point;
specifically, the receiving and transmitting antenna in the wireless access point AP of the MIMO system is M1,…,Mi,…,Mj,…,MmTransmitting the transmission training frame S containing the leader sequence in sequence when one of the receiving and transmitting antennas MiOther transmit-receive antennas M during transmission of the training frame SjThe training frame is received. It should be noted that when the transmitting/receiving antenna M is usedjWhen the training frame S is transmitted,transceiver antenna MiThen is the transmitting-receiving antenna MjCorresponding other transceiving antennas for receiving the transceiving antenna MjA transmitted training frame S. Each transceiver antenna MiTo other receiving and transmitting antennas M in turnjTransmitting training frame S, other transmitting-receiving antenna MjFrom received training frame S'iEstimating the transmitting/receiving antenna MiWith each other transceiving antenna MjEstimated frequency deviation Δ F therebetweeni→j。
Receiving of each transmitting/receiving antenna M by server in MIMO systemiOther transmitting and receiving antennas M for transmissionjAnd a transmitting/receiving antenna MiEstimated frequency deviation Δ F therebetweenj→iCorrespondingly, the server in the MIMO system also receives the transmitting and receiving antenna MiWith other transmitting-receiving antennas MjEstimated frequency deviation Δ F therebetweeni→j。
Step S42, estimating the frequency deviation delta F according to the frequency deviationj→iDetermining a frequency offset matrix Hm*m；
In particular, the server estimates the frequency deviation Δ F from the receptionj→i(ΔFi→j) Determining a frequency offset matrix Hm*mIn which H ism*mMatrix elements comprising m rows and m columns, each matrix element being an estimated frequency offset, which corresponds to an estimated frequency offset of 0, i.e. Δ F, when the receiving and transmitting antennas are identicali→j＝ΔFj→i＝0,i＝j&i,j∈[1,m]If an estimated frequency offset is not received, the frequency offset is set to 0.
Step S43, according to the frequency offset matrix Hm*mDetermining each of said transceiving antennas MiRelative frequency deviation epsilon ofi；
Specifically, for a distributed MIMO system, since antennas are different sources, there are several different transmission frequencies, signals of different frequencies will be mixed together during cooperative transmission, and a conventional frequency offset compensation algorithm cannot distinguish and compensate frequency offsets mixed together. One possible way is to synchronize the antenna frequency of the transmitting end during signal transmission, so that the mixed signal can be regarded as having only one frequency, and to facilitate frequency compensationFor compensation adjustment, the server can be according to Hm*mCalculating each transmit-receive antenna MiRelative frequency deviation epsilon ofiI.e. one of the transmitting and receiving antennas MjIs fixed, calculates other transmitting and receiving antennas MiAnd a transmitting/receiving antenna MjRelative frequency deviation epsilon ofiThus, only the other transmitting/receiving antenna M needs to be adjustediThe transmitting frequencies of these transmitting and receiving antennas are compared with the transmitting and receiving antenna MjAnd synchronization can be realized, so that the transmission frequency synchronization of all the transmitting and receiving antennas in the whole AP can be realized.
Step S44, deviation epsilon of the relative frequencyiTo each of said transceiving antennas MiFor the receiving and transmitting antenna MiAccording to the relative frequency deviation epsiloniFor the transmitting and receiving antenna MiIs compensated for.
In particular, the server will transmit each transceiving antenna MiRelative frequency deviation epsilon ofiTo the transmitting/receiving antenna Mi. Transceiver antenna MiReceiving the relative frequency deviation epsilon sent by the serveriThen, based on the relative frequency deviation epsiloniFor the transmitting and receiving antenna MiCompensating the transmitting frequency of the transmitting and receiving antenna M, and correcting the transmitting and receiving antenna MiThe local oscillation frequency configuration of the AP achieves the purpose of synchronizing the frequency of each receiving and transmitting antenna in the AP.
According to the frequency synchronization method of the distributed MIMO system, each transmitting and receiving antenna at the transmitting end sequentially transmits and receives training frames containing leader sequences transmitted by other transmitting and receiving antennas, estimated frequency deviation among the transmitting and receiving antennas is estimated, relative frequency deviation of each transmitting and receiving antenna is determined according to the estimated frequency deviation, frequency compensation is carried out on each transmitting and receiving antenna according to the relative frequency deviation, frequency deviation influence caused by different crystal oscillators is reduced at the transmitting end, the transmitting frequency of each distributed antenna is synchronized, and system performance of a distributed antenna cooperation scene is improved.
On the basis of the above embodiment, further, the frequency deviation Δ F is estimated according to the estimationj→iDetermining a frequency offset matrix Hm*mThe method comprises the following steps:
determining the frequency offset according to equation (5)Matrix Hm*m：
Figure GDA0002783565620000191
Wherein, Δ Fi→j＝ΔFj→i＝0,i＝j&i,j∈[1,m]。
In particular, the server receives each transmitting-receiving antenna MiOther transmitting and receiving antennas M for transmissionjAnd a transmitting/receiving antenna MiEstimated frequency deviation Δ F therebetweenj→iThereafter, a frequency offset matrix of m is determined according to equation (5), wherein:
Figure GDA0002783565620000192
and, in the frequency offset matrix Hm*mWhen i is j, Δ Fi→j＝ΔFj→i＝0。
Then, the server is based on the frequency offset matrix Hm*mCan determine each transceiving antenna MiRelative frequency deviation epsilon ofi。
According to the frequency synchronization method of the distributed MIMO system, each receiving and transmitting antenna at the transmitting end sequentially sends and receives training frames containing leader sequences sent by other receiving and transmitting antennas, estimates the estimated frequency deviation among the receiving and transmitting antennas, determines the frequency offset matrix, determines the relative frequency deviation of each receiving and transmitting antenna according to the frequency offset matrix, performs frequency compensation on each receiving and transmitting antenna according to the relative frequency deviation, reduces the frequency offset influence caused by different crystal oscillators at the transmitting end, synchronizes the transmitting frequency of each distributed antenna, and further improves the system performance of a distributed antenna cooperation scene.
On the basis of the foregoing embodiments, further, the frequency offset matrix H is obtained according to the frequency offset matrix Hm*mDetermining each of said transceiving antennas MiRelative frequency deviation epsilon ofiThe method comprises the following steps:
calculating the transceiving antenna M according to equation (6)iRelative frequency offset matrix F'：
Figure GDA0002783565620000201
Wherein the content of the first and second substances,
Figure GDA0002783565620000202
Fifor transmitting and receiving antennas MiThe carrier frequency of (a);
calculating each of the transceiving antennas M according to the formula (7)iRelative frequency deviation epsilon ofi：
εi＝Fi-F1Formula (7)
Wherein i belongs to [1, m ].
In particular, let the matrix
Figure GDA0002783565620000203
Matrix array
Figure GDA0002783565620000204
Matrix array
Figure GDA0002783565620000205
The matrix equation M × F ═ G can be obtained, where F isiFor transmitting and receiving antennas MiBecause the matrix M is not full, the matrix equation M × F 'cannot be directly solved, and because the equation of no influence on what value is taken in the first column of the matrix M is true, the matrix M can be converted into the matrix M' by arbitrarily taking the value in the first column, so that the matrix M 'is full, for example, the first column of the matrix M' is all the number 1.
Then, a relative frequency offset matrix F ' is calculated from M ' × F ' ═ G. For example, according to the formula F '═ (M')-1*M′*F′＝(M′)-1G calculates a relative frequency offset matrix F ', or according to the formula F ' ((2M ')T*(2M′))-1*(2M′)TG, solving a relative frequency offset matrix F', which is actually solving each transmit-receive antenna MiRelative to the transmitting and receiving antenna M1Of frequency deviation epsiloniWherein, epsiloniIs a phase ofFor the elements of the frequency offset matrix F ∈i＝Fi-F1. Thus, each transmitting/receiving antenna MiAccording to epsiloniAdjusting the transmitting antenna to the transceiving antenna M1And synchronizing, so that the transmitting frequencies of the transmitting antennas of the transmitting end are synchronized. The method achieves the synchronous precision of +/-30 Hz in the real machine test, and the precision can be further improved if a higher phase noise design index is adopted.
The frequency synchronization method of the distributed MIMO system provided by the embodiment of the invention comprises the steps of sequentially sending and receiving training frames containing leader sequences sent by other transceiving antennas at each transceiving antenna of a transmitting terminal, estimating the estimated frequency deviation among the transceiving antennas, determining the relative frequency deviation of each transceiving antenna according to a frequency offset matrix, and carrying out frequency compensation on each transceiving antenna according to the relative frequency deviation.
On the basis of the above embodiments, further, the formula (6) is determined according to the following steps:
least square function after frequency deviation compensation
Figure GDA0002783565620000211
To FiCalculating the partial derivative and determining the partial derivative function
Figure GDA0002783565620000212
Let the partial derivative function equal to 0, then
Figure GDA0002783565620000213
The above equation is developed to determine the constraint equation:
Figure GDA0002783565620000221
determining the formula (6) according to formula (8):
Figure GDA0002783565620000222
wherein the content of the first and second substances,
Figure GDA0002783565620000223
in particular, for any two transceiving antennas MiAnd a transmitting/receiving antenna MjAntenna M for transmitting and receivingiAnd its transmitting-receiving antenna MjEstimated frequency deviation Δ F therebetweeni→jCan be expressed as: Δ Fi→j＝Fj-Fi+Ei→jWherein F isiFor transmitting and receiving antennas MiOf the transmission frequency, FjFor transmitting and receiving antennas MjOf the transmission frequency, Ei→jAnd ideally, the frequency offset estimation error is 0. Aiming at the phenomenon of inconsistent multi-antenna frequency offset estimation in measurement, the method can be converted into a solution optimization problem, and a target function is constructed according to the least square principle:
Figure GDA0002783565620000224
then to FiCalculating the partial derivative and determining the partial derivative function
Figure GDA0002783565620000231
Let the partial derivative function equal to 0, then have
Figure GDA0002783565620000232
The above formula is expanded to obtain a constraint equation
Figure GDA0002783565620000233
Is expressed as formula (8) and has
Figure GDA0002783565620000234
Therefore, the above equation can be subtracted from both sides of the equation of equation (8) to obtain:
Figure GDA0002783565620000235
after finishing, formula (6) can be obtained:
Figure GDA0002783565620000241
and finally, correcting the local oscillation frequency configuration of each receiving and transmitting antenna according to the value of the F' to achieve the aim of synchronizing the frequency of each receiving and transmitting antenna.
The frequency synchronization method of the distributed MIMO system provided by the embodiment of the invention comprises the steps of sequentially sending and receiving training frames containing leader sequences sent by other transceiving antennas at each transceiving antenna at a transmitting end, estimating the estimated frequency deviation among the transceiving antennas, determining the relative frequency deviation of each transceiving antenna according to a frequency offset matrix, and carrying out frequency compensation on each transceiving antenna according to the relative frequency deviation, thereby providing a method for processing the inconsistency of the estimation errors of multiple antennas.
Fig. 5 is a schematic structural diagram of an AP device of a wireless access point according to an embodiment of the present invention, and as shown in fig. 5, the AP device includes: multiple transmitting/receiving antennas M i51. Transceiver antenna M j52 and processing means 53, wherein i ≠ j and i, j ∈ [1, m ∈ j]And m is the total number of the transmitting and receiving antennas in the AP equipment, wherein:
the transmitting and receiving antenna M i51 for sequentially transmitting to other transmitting/receiving antennas M j52 transmitting a transmission training frame S containing a leader sequence; the transmitting and receiving antenna M j52 for receiving each transceiving antenna M i51 corresponding received training frame S'iCalculating said transmitting/receiving antenna M i51 and each of the other transmit-receive antennas MjEstimated frequency deviation Δ F between 52i→j(ii) a The processing device is used for estimating the frequency deviation delta F according to the frequency deviationj→iDetermining a frequency offset matrix Hm*mAnd according to the frequency offset matrix Hm*mDetermining each of said transceiving antennas MiRelative frequency deviation epsilon ofi；
The transmitting and receiving antenna M i51 are also arranged to, depending on said relative frequency deviation epsiloniFor the transmitting and receiving antenna M i51 are compensated.
Specifically, the wireless access point AP of the MIMO system includes M transceiving antennas, denoted as M1,…,Mi,…,Mj,…,MmWhere i ≠ j and i, j ∈ [1, m ∈]And m is more than 1. Transceiver antenna M1,…,Mi,…,Mj,…,MmTransmitting the transmission training frame S containing the leader sequence in sequence when one of the receiving and transmitting antennas M i51 transmitting training frame S, other transmitting and receiving antenna MjThe training frame is received 52. It should be noted that when the transmitting/receiving antenna M is usedj52 transmit training frame S, transmit-receive antenna M i51 is the transmitting/receiving antenna M j52 other transceiver antenna for receiving the transceiver antenna M j52 transmitted training frame S. Each transceiver antenna M i51 to other transmitting and receiving antennas M in turn j52 transmit training frame S, other transmit-receive antennas Mj52 from received training frame S'iEstimating the transmitting/receiving antenna M i51 and each of the other transmit-receive antennas MjEstimated frequency deviation Δ F between 52i→j. The processing means 53 are based on the estimated frequency deviation deltafj→iDetermining a frequency offset matrix Hm*mIn which H ism*mMatrix elements with m rows and m columns, each matrix element being an estimated frequency deviation, and according to the frequency deviation matrix Hm*mDetermining each transmitting/receiving antenna MiRelative frequency deviation epsilon ofi. Furthermore, each transceiving antenna M i51 other transmitting and receiving antennas M can be usedj52 and a transmitting/receiving antenna M i51 of the estimated frequency deviation deltafj→iSending to a server in the MIMO system, after which the server in the MIMO system receives the estimated frequency deviation Δ Fj→i(ΔFi→j) Determining a frequency offset matrix Hm*mIn which H ism*mMatrix elements comprising m rows and m columns, each matrix element being an estimated frequency offset, which corresponds to an estimated frequency offset of 0, i.e. Δ F, when the receiving and transmitting antennas are identicali→j＝ΔFj→i＝0,i＝j&i,j∈[1,m]If an estimated frequency offset is not received, the frequency offset is set to 0. Transceiver antenna M i51 receiving the relative frequency deviation epsilon sent by the serveriThen, based on the relative frequency deviation epsiloniFor the transmitting and receiving antenna M i51, and correcting the transmitting/receiving antenna M i51, the purpose of synchronizing the frequency of each transmitting and receiving antenna in the AP is achieved. The apparatus provided in the embodiment of the present invention is configured to implement the method, and its functions specifically refer to the method embodiment, which is not described herein again.
According to the AP equipment provided by the embodiment of the invention, each transmitting and receiving antenna sequentially transmits and receives training frames containing leader sequences transmitted by other transmitting and receiving antennas at the transmitting end, the estimated frequency deviation among the transmitting and receiving antennas is estimated, the relative frequency deviation of each transmitting and receiving antenna is determined according to the estimated frequency deviation, the frequency compensation is carried out on each transmitting and receiving antenna according to the relative frequency deviation, the frequency deviation influence caused by different crystal oscillators is reduced at the transmitting end, the transmitting frequency of each distributed antenna is synchronized, and the system performance of a distributed antenna cooperation scene is improved.
On the basis of the above embodiments, further, the transceiving antenna MiThe method is specifically used for:
adjusting a standard long training sequence in a wireless communication protocol according to formula (1), and determining a modified long training sequence:
BABAB + p ABAB formula (1)
Wherein BABAB is a standard long training sequence specified by a communication protocol, ABAB is a sequence except a guard interval B in the standard long training sequence, and p is a positive integer;
determining a sending training frame S containing a leader sequence according to the modified long training sequence;
to other receiving and transmitting antennas M in turnjAnd sending the sending training frame S.
Specifically, in order to reuse the original transceiving system as much as possible, the basic structure of the preamble sequence is maintained, and the LTFs in the preamble sequence are adjusted as follows to determine the modified long training sequence:
BABAB + p ABAB formula (1)
Wherein p is a positive integer, and is a newly added frequency offset estimation field, that is, an original long training sequence is adjusted, p times of T1+ T2 data (ABAB) are added, and an original preamble sequence is extended, because in the 802.11 protocol, BABAB is 160 points, 8us in total, that is, one a or B is 32 points, and the length is 1.6us, if BABAB +10 ABAB, 45 a or B, that is, 45 x 1.6us 72us, and the total length of the preamble sequence is 72+ 8us 80 us.
Then, the transmitting/receiving antenna MiThe original standard long training sequence in the training frame is adjusted into a modified field training sequence, and the training frame S is sent in sequence.
In actual tests, the precision within 15Hz can be achieved when p is 8, and most of synchronization requirements can be basically met; in order to keep the lengths of the preamble symbols consistent and avoid the influence of symbol misalignment, p may be 10 in practical applications. The apparatus provided in the embodiment of the present invention is configured to implement the method, and its functions specifically refer to the method embodiment, which is not described herein again.
The AP equipment provided by the embodiment of the invention completes the frame of self calibration of the frequency deviation of the antenna carrier frequency in the transmitting terminal, and provides a frequency deviation estimation precision improvement method on the basis of the 802.11 protocol, and the mutual frequency deviation can be obtained through simple interaction of all the antennas, so that the transmitting frequency of all the distributed antennas is synchronous, and the system performance of a distributed antenna cooperation scene is improved. In addition, the embodiment of the invention can enlarge the coverage area of the antenna, reduce the interference of the edge of the cell and effectively solve the problem of cell roaming switching by the same frequency transmission of the distributed antennas.
In addition to the above embodiments, the other transceiving antennas MjThe method is specifically used for:
from each transceiver antenna MiCorresponding received training frame S'iMiddle-intercepting first frequency offset estimation signal
Figure GDA0002783565620000271
And after D sampling points are spaced, receiving a training frame S'iMiddle interceptionSecond frequency offset estimation signal
Figure GDA0002783565620000272
Wherein the content of the first and second substances,
Figure GDA0002783565620000273
and
Figure GDA0002783565620000274
the lengths of the N-type carbon nanotubes are all N;
estimating the first frequency offset signal according to equation (3)
Figure GDA0002783565620000275
And the second frequency offset estimation signal
Figure GDA0002783565620000276
Performing correlation operation to determine the first frequency offset estimation signal
Figure GDA0002783565620000277
And the second frequency offset estimation signal
Figure GDA0002783565620000278
Signal phase difference phi ofi：
Figure GDA0002783565620000279
Calculating the transceiving antenna M according to formula (4)iWith each other transceiving antenna MjEstimated frequency deviation Δ F therebetweeni→j
Figure GDA00027835656200002710
Wherein phase (phi)i) For the signal phase difference phiiT is the duration of a single sampling point, and D is the sampling interval;
Figure GDA00027835656200002711
estimating a signal for the second frequency offset
Figure GDA00027835656200002712
The conjugate value of (c).
Specifically, the other transceiving antennas receive training frame S'iMiddle-intercepted frequency offset estimation signal with length of N
Figure GDA00027835656200002713
Recording as a first frequency offset estimation signal, delaying D sampling points, and intercepting the frequency offset estimation signal with the length of N
Figure GDA00027835656200002714
Recording as a second frequency deviation estimation signal, and estimating the first frequency deviation
Figure GDA00027835656200002715
And a second frequency offset estimation signal
Figure GDA00027835656200002716
Performing correlation operation and summation to calculate a first frequency offset estimation signal
Figure GDA00027835656200002717
And a second frequency offset estimation signal
Figure GDA00027835656200002718
Signal phase difference phi ofi：
Figure GDA00027835656200002719
Wherein E is the magnitude of the summation accumulation,
Figure GDA00027835656200002720
estimating a signal for a second frequency offset
Figure GDA00027835656200002722
The conjugate value of (c). t being 1 sample pointThe duration, 2 pi · α · D · t is the phase deviation of the delayed D sampling points, and the transceiver antenna M can be calculated according to the formula (4)iWith other transmitting-receiving antennas MjEstimated frequency deviation Δ F therebetweeni→j：
Figure GDA00027835656200002721
Wherein phase (phi)i) For the signal phase difference phiiSo that m-1 deltaf can be calculated for each transmit-receive antennai→j. The apparatus provided in the embodiment of the present invention is configured to implement the method, and its functions specifically refer to the method embodiment, which is not described herein again.
The AP equipment provided by the embodiment of the invention completes the frame of self calibration of the frequency deviation of the antenna carrier frequency in the transmitting terminal, and provides a frequency deviation estimation precision improvement method on the basis of the 802.11 protocol, and the mutual frequency deviation can be obtained through simple interaction of all the antennas, so that the transmitting frequency of all the distributed antennas is synchronous, and the system performance of a distributed antenna cooperation scene is improved.
Fig. 6 is a schematic structural diagram of a server according to an embodiment of the present invention, and as shown in fig. 6, the server includes: a receiving module 61, a sorting module 62, a relative frequency offset determining module 63 and a sending module 64, wherein:
the receiving module 61 is used for receiving each transceiving antenna M in the wireless access pointiTransmitting other receiving and transmitting antenna MjAnd the transmitting/receiving antenna MiEstimated frequency deviation Δ F therebetweenj→iWhere i ≠ j and i, j ∈ [1, m ∈]M is the total number of the receiving and transmitting antennas in the wireless access point; the sorting module 62 is configured to determine the estimated frequency deviation Δ Fj→iDetermining a frequency offset matrix Hm*m(ii) a The relative frequency offset determining module 63 is configured to determine the frequency offset matrix H according to the frequency offset matrix Hm*mDetermining each of said transceiving antennas MiRelative frequency deviation epsilon ofi(ii) a A sending module 64 for sending the relative frequency deviation epsiloniTo each of said transceiving antennas MiFor the receiving and transmitting antenna MiAccording to the relative frequency deviation epsiloniTo what is calledThe transmitting and receiving antenna MiIs compensated for.
Specifically, the receiving and transmitting antenna in the wireless access point AP of the MIMO system is M1,…,Mi,…,Mj,…,MmTransmitting the transmission training frame S containing the leader sequence in sequence when one of the receiving and transmitting antennas MiOther transmit-receive antennas M during transmission of the training frame SjThe training frame is received. It should be noted that when the transmitting/receiving antenna M is usedjTransmitting training frame S, transmitting-receiving antenna MiThen is the transmitting-receiving antenna MjCorresponding other transceiving antennas for receiving the transceiving antenna MjA transmitted training frame S. Each transceiver antenna MiTo other receiving and transmitting antennas M in turnjTransmitting training frame S, other transmitting-receiving antenna MjFrom received training frame S'iEstimating the transmitting/receiving antenna MiWith each other transceiving antenna MjEstimated frequency deviation Δ F therebetweeni→j。
The receiving module 61 receives each transmitting/receiving antenna MiOther transmitting and receiving antennas M for transmissionjAnd a transmitting/receiving antenna MiEstimated frequency deviation Δ F therebetweenj→iThe unscrambling module 62 estimates the frequency deviation Δ F based on the received frequency offsetj→i(ΔFi→j) Determining a frequency offset matrix Hm*mIn which H ism*mMatrix elements comprising m rows and m columns, each matrix element being an estimated frequency offset, which corresponds to an estimated frequency offset of 0, i.e. Δ F, when the receiving and transmitting antennas are identicali→j＝ΔFj→i＝0,i＝j&i,j∈[1,m]If an estimated frequency offset is not received, the frequency offset is set to 0. The relative frequency offset determining module 63 determines the frequency offset according to Hm*mCalculating each transmit-receive antenna MiRelative frequency deviation epsilon ofiI.e. one of the transmitting and receiving antennas MjIs fixed, calculates other transmitting and receiving antennas MiAnd a transmitting/receiving antenna MjRelative frequency deviation epsilon ofi. The transmitting module 64 transmits each transmitting/receiving antenna MiRelative frequency deviation epsilon ofiTo the transmitting/receiving antenna Mi. Transceiver antenna MiReceiving the relative frequency deviation epsilon sent by the serveriThen, based on the relative frequency deviation epsiloniFor the transmitting and receiving antenna MiCompensating the transmitting frequency of the transmitting and receiving antenna M, and correcting the transmitting and receiving antenna MiThe local oscillation frequency configuration of the AP achieves the purpose of synchronizing the frequency of each receiving and transmitting antenna in the AP. The apparatus provided in the embodiment of the present invention is configured to implement the method, and its functions specifically refer to the method embodiment, which is not described herein again.
According to the server provided by the embodiment of the invention, each transmitting and receiving antenna sequentially transmits and receives training frames containing leader sequences sent by other transmitting and receiving antennas at the transmitting end, the estimated frequency deviation among the transmitting and receiving antennas is estimated, the relative frequency deviation of each transmitting and receiving antenna is determined according to the estimated frequency deviation, the frequency compensation is carried out on each transmitting and receiving antenna according to the relative frequency deviation, the frequency deviation influence caused by different crystal oscillators is reduced at the transmitting end, the transmitting frequency of each distributed antenna is synchronized, and the system performance of a distributed antenna cooperation scene is improved.
On the basis of the foregoing embodiment, further, the sorting module is specifically configured to:
determining the frequency offset matrix H according to equation (5)m*m：
Figure GDA0002783565620000291
Wherein, Δ Fi→j＝ΔFj→i＝0,i＝j&i,j∈[1,m]。
Specifically, the sorting module determines an m x m frequency offset matrix according to formula (5), wherein:
Figure GDA0002783565620000301
and, in the frequency offset matrix Hm*mWhen i is j, Δ Fi→j＝ΔFj→i0. The apparatus provided in the embodiment of the present invention is configured to implement the method, and its functions specifically refer to the method embodiment, which is not described herein again.
According to the server provided by the embodiment of the invention, each transmitting and receiving antenna at the transmitting end sequentially transmits and receives training frames containing leader sequences transmitted by other transmitting and receiving antennas, estimates the estimated frequency deviation among the transmitting and receiving antennas, determines the frequency deviation matrix, determines the relative frequency deviation of each transmitting and receiving antenna according to the frequency deviation matrix, performs frequency compensation on each transmitting and receiving antenna according to the relative frequency deviation, reduces the frequency deviation influence caused by different crystal oscillators at the transmitting end, synchronizes the transmitting frequency of each distributed antenna, and further improves the system performance of a distributed antenna cooperation scene.
On the basis of the foregoing embodiments, further, the relative frequency offset determining module is specifically configured to:
calculating the transceiving antenna M according to equation (6)iRelative frequency offset matrix F':
Figure GDA0002783565620000302
wherein the content of the first and second substances,
Figure GDA0002783565620000311
Fifor transmitting and receiving antennas MiThe carrier frequency of (a);
calculating each of the transceiving antennas M according to the formula (7)iRelative frequency deviation epsilon ofi：
εi＝Fi-F1Formula (7)
Wherein i belongs to [1, m ].
In particular, the relative frequency offset determination module order matrix
Figure GDA0002783565620000312
Matrix array
Figure GDA0002783565620000313
Matrix array
Figure GDA0002783565620000314
The matrix equation M × F ═ G can be obtained, where F isiFor transmitting and receiving antennas MiSince the matrix M is not of full rank, and thereforeThe matrix equation M × F 'cannot be directly solved, and since the equation is established regardless of what value is taken in the first column of the matrix M, the matrix M may be converted into the matrix M' by arbitrarily taking a value in the first column, so that the matrix M 'is full rank, for example, the first column of the matrix M' is all the number 1.
Then, a relative frequency offset matrix F ' is calculated from M ' × F ' ═ G. For example, according to the formula F '═ (M')-1*M′*F′＝(M′)-1G calculates a relative frequency offset matrix F ', or according to the formula F ' ((2M ')T*(2M′))-1*(2M′)TG, solving a relative frequency offset matrix F', which is actually solving each transmit-receive antenna MiRelative to the transmitting and receiving antenna M1Of frequency deviation epsiloniWherein, epsiloniIs an element of a relative frequency offset matrix Fi＝Fi-F1. The apparatus provided in the embodiment of the present invention is configured to implement the method, and its functions specifically refer to the method embodiment, which is not described herein again.
According to the server provided by the embodiment of the invention, each transmitting and receiving antenna sequentially transmits and receives training frames containing leader sequences sent by other transmitting and receiving antennas at the transmitting end, the estimation frequency deviation among the transmitting and receiving antennas is estimated, the relative frequency deviation of each transmitting and receiving antenna is determined according to the frequency offset matrix, and the frequency compensation is carried out on each transmitting and receiving antenna according to the relative frequency deviation.
Fig. 7 is a schematic structural diagram of a MIMO system according to an embodiment of the present invention, where as shown in fig. 7, the MIMO system includes: the functions of the AP device 71 in the MIMO system specifically refer to the AP device embodiment, and the functions of the server 72 in the MIMO system specifically refer to the server embodiment, which are not described herein again.
Those of ordinary skill in the art will understand that: all or part of the steps for realizing the method embodiments can be completed by hardware related to program instructions, the program can be stored in a computer readable storage medium, and the program executes the steps comprising the method embodiments when executed; and the aforementioned storage medium includes: various media that can store program codes, such as ROM, RAM, magnetic or optical disks.
The above-described embodiments of the apparatuses and the like are merely illustrative, wherein the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.
Finally, it should be noted that: the above embodiments are only used for illustrating the technical solutions of the embodiments of the present invention, and are not limited thereto; although embodiments of the present invention have been described in detail with reference to the foregoing embodiments, those skilled in the art will understand that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims (14)

1. A frequency synchronization method of a distributed MIMO system is characterized by comprising the following steps:
each transceiving antenna M in a wireless access pointiTo other receiving and transmitting antennas M in turnjSending a sending training frame S containing a leader sequence, wherein i is not equal to j and i, j belongs to [1, m ∈]M is the total number of the receiving and transmitting antennas in the wireless access point;
other transceiving antennas M in the wireless access pointjAccording to each receiving-transmitting antenna M receivediCorresponding received training frame S'iCalculating said transmitting/receiving antenna MiAnd the placeThe other transmitting/receiving antenna MjEstimated frequency deviation Δ F therebetweeni→j；
From said estimated frequency deviation Δ Fi→jDetermining a frequency offset matrix Hm*mAnd according to the frequency offset matrix Hm*mDetermining each of said transceiving antennas MiRelative frequency deviation epsilon ofi；
Each of the transmitting and receiving antennas MiAccording to the relative frequency deviation epsiloniAccording to said relative frequency deviation epsiloniFor the transmitting and receiving antenna MiIs compensated for.
2. Method according to claim 1, characterized in that each transceiving antenna M in said wireless access pointiTo other receiving and transmitting antennas M in turnjTransmitting a transmission training frame S including a preamble sequence, comprising:
each transceiving antenna M in a wireless access pointiAdjusting a standard long training sequence in a wireless communication protocol according to formula (1), and determining a modified long training sequence:
BABAB + p ABAB formula (1)
Wherein BABAB is a standard long training sequence specified by a communication protocol, ABAB is a sequence except a guard interval B in the standard long training sequence, and p is a positive integer;
determining a sending training frame S containing a leader sequence according to the modified long training sequence;
each of the transmitting and receiving antennas MiTo other receiving and transmitting antennas M in turnjAnd sending the sending training frame S.
3. Method according to claim 2, characterized in that said other transceiving antennas MjAccording to each receiving-transmitting antenna M receivediCorresponding received training frame S'iCalculating said transmitting/receiving antenna MiWith said other transceiving antenna MjEstimated frequency deviation Δ F therebetweeni→jThe method comprises the following steps:
the other transceiving antenna MjFrom each transceiver antenna MiCorresponding received training frame S'iMiddle-intercepting first frequency offset estimation signal
Figure FDA0002783565610000011
And after D sampling points are spaced, receiving a training frame S'iIntermediate-intercept second frequency offset estimation signal
Figure FDA0002783565610000012
Wherein the content of the first and second substances,
Figure FDA0002783565610000013
and
Figure FDA0002783565610000014
the lengths of the N-type carbon nanotubes are all N;
estimating the first frequency offset signal according to equation (3)
Figure FDA0002783565610000021
And the second frequency offset estimation signal
Figure FDA0002783565610000022
Performing correlation operation to determine the first frequency offset estimation signal
Figure FDA0002783565610000023
And the second frequency offset estimation signal
Figure FDA0002783565610000024
Signal phase difference phi ofi：
Figure FDA0002783565610000025
Calculating the transceiving antenna M according to formula (4)iWith said other transceiving antenna MjEstimated frequency deviation Δ F therebetweeni→j
Figure FDA0002783565610000026
Wherein phase (phi)i) For the signal phase difference phiiT is the duration of a single sampling point, and D is the sampling interval;
Figure FDA0002783565610000027
estimating a signal for the second frequency offset
Figure FDA0002783565610000028
The conjugate value of (c).
4. A frequency synchronization method of a distributed MIMO system is characterized by comprising the following steps:
receiving each transceiving antenna M in wireless access pointiOther transmitting and receiving antennas M for transmissionjAnd the transmitting/receiving antenna MiEstimated frequency deviation Δ F therebetweenj→iWhere i ≠ j and i, j ∈ [1, m ∈]M is the total number of the receiving and transmitting antennas in the wireless access point;
from said estimated frequency deviation Δ Fj→iDetermining a frequency offset matrix Hm*m；
According to the frequency offset matrix Hm*mDetermining each of said transceiving antennas MiRelative frequency deviation epsilon ofi；
Deviation of the relative frequency epsiloniTo each of said transceiving antennas MiFor the receiving and transmitting antenna MiAccording to the relative frequency deviation epsiloniFor the transmitting and receiving antenna MiIs compensated for.
5. Method according to claim 4, characterized in that said frequency deviation Δ F is estimated from said estimatesj→iDetermining a frequency offset matrix Hm*mThe method comprises the following steps:
determining the frequency offset matrix H according to equation (5)m*m：
Figure FDA0002783565610000031
Wherein, Δ Fi→j＝ΔFj→i＝0,i＝j&i,j∈[1,m]。
6. The method of claim 5, wherein the frequency offset matrix H is based on the frequency offset matrixm*mDetermining each of said transceiving antennas MiRelative frequency deviation epsilon ofiThe method comprises the following steps:
calculating the transceiving antenna M according to equation (6)iRelative frequency offset matrix F':
Figure FDA0002783565610000032
wherein the content of the first and second substances,
Figure FDA0002783565610000033
Fifor transmitting and receiving antennas MiThe carrier frequency of (a);
calculating each of the transceiving antennas M according to the formula (7)iRelative frequency deviation epsilon ofi：
εi＝Fi-F1Formula (7)
Wherein i belongs to [1, m ].
7. The method of claim 6, wherein the formula (6) is determined according to the following steps:
least square function after frequency deviation compensation
Figure FDA0002783565610000041
To FiCalculating the partial derivative and determining the partial derivative function
Figure FDA0002783565610000042
Let the partial derivative function equal to 0, then
Figure FDA0002783565610000043
Equation (1);
expanding equation (1) above, a constraint equation is determined:
Figure FDA0002783565610000044
determining the formula (6) according to formula (8):
Figure FDA0002783565610000045
wherein the content of the first and second substances,
Figure FDA0002783565610000051
8. a wireless access point, AP, device, comprising:
multiple transmitting/receiving antennas MiReceiving and transmitting antenna MjAnd processing means, where i ≠ j and i, j ∈ [1, m ∈ j]M is the total number of the receiving and transmitting antennas in the wireless access point equipment;
the transmitting and receiving antenna MiFor sequentially transmitting to other transceiving antennas MjSending a sending training frame S containing a leader sequence;
the transmitting and receiving antenna MjFor each transceiving antenna M receivediCorresponding received training frame S'iCalculating said transmitting/receiving antenna MiWith each other transceiving antenna MjEstimated frequency deviation Δ F therebetweeni→j；
The processing device is used for estimating the frequency deviation delta F according to the frequency deviationj→iDetermining a frequency offset matrix Hm*mAnd according to the frequency offset matrix Hm*mDetermining each of said transceiving antennas MiRelative frequency deviation epsilon ofi；
The transmitting and receiving antenna MiAnd also for determining the relative frequency deviation epsiloniFor the transmitting and receiving antenna MiIs compensated for.
9. AP device according to claim 8, characterised in that said transceiving antenna MiThe method is specifically used for:
adjusting a standard long training sequence in a wireless communication protocol according to formula (1), and determining a modified long training sequence:
BABAB + p ABAB formula (1)
Wherein BABAB is a standard long training sequence specified by a communication protocol, ABAB is a sequence except a guard interval B in the standard long training sequence, and p is a positive integer;
determining a sending training frame S containing a leader sequence according to the modified long training sequence;
to other receiving and transmitting antennas M in turnjAnd sending the sending training frame S.
10. The AP device according to claim 9, wherein the other transceiving antenna MjThe method is specifically used for:
from each transceiver antenna MiCorresponding received training frame S'iMiddle-intercepting first frequency offset estimation signal
Figure FDA0002783565610000061
And after D sampling points are spaced, receiving a training frame S'iIntermediate-intercept second frequency offset estimation signal
Figure FDA0002783565610000062
Wherein the content of the first and second substances,
Figure FDA0002783565610000063
and
Figure FDA0002783565610000064
the lengths of the N-type carbon nanotubes are all N;
estimating the first frequency offset signal according to equation (3)
Figure FDA0002783565610000065
And the second frequency offset estimation signal
Figure FDA0002783565610000066
Performing correlation operation to determine the first frequency offset estimation signal
Figure FDA0002783565610000067
And the second frequency offset estimation signal
Figure FDA0002783565610000068
Signal phase difference phi ofi：
Figure FDA0002783565610000069
Calculating the transceiving antenna M according to formula (4)iWith each other transceiving antenna MjEstimated frequency deviation Δ F therebetweeni→j
Figure FDA00027835656100000610
Wherein phase (phi)i) For the signal phase difference phiiT is the duration of a single sampling point, and D is the sampling interval;
Figure FDA00027835656100000611
estimating a signal for the second frequency offset
Figure FDA00027835656100000612
The conjugate value of (c).
11. A server, comprising:
a receiving module for receiving each transmitting/receiving antenna M in the wireless access pointiOther transmitting and receiving antennas M for transmissionjAnd the transmitting/receiving antenna MiEstimated frequency deviation Δ F therebetweenj→iWhere i ≠ j and i, j ∈ [1, m ∈]M is the total number of the receiving and transmitting antennas in the wireless access point;
a sorting module for sorting out the estimated frequency deviation Δ Fj→iDetermining a frequency offset matrix Hm*m；
A relative frequency offset determining module for determining the frequency offset matrix H according to the frequency offset matrixm*mDetermining each of said transceiving antennas MiRelative frequency deviation epsilon ofi；
A transmission module for transmitting the relative frequency deviation epsiloniTo each of said transceiving antennas MiFor the receiving and transmitting antenna MiAccording to the relative frequency deviation epsiloniFor the transmitting and receiving antenna MiIs compensated for.
12. The server according to claim 11, wherein the sorting module is specifically configured to:
determining the frequency offset matrix H according to equation (5)m*m：
Figure FDA0002783565610000071
Wherein, Δ Fi→j＝ΔFj→i＝0,i＝j&i,j∈[1,m]。
13. The server according to claim 12, wherein the relative frequency offset determining module is specifically configured to:
calculating the transceiving antenna M according to equation (6)iRelative frequency offset matrix F':
Figure FDA0002783565610000072
wherein the content of the first and second substances,
Figure FDA0002783565610000073
Fifor transmitting and receiving antennas MiThe carrier frequency of (a);
calculating each of the transceiving antennas M according to the formula (7)iRelative frequency deviation epsilon ofi：
εi＝Fi-F1Formula (7)
Wherein i belongs to [1, m ].
14. A multiple-input multiple-output, MIMO, system comprising: wireless access point, AP, device according to any of claims 8 to 10 and server according to any of claims 11 to 13.
CN201811246529.6A 2018-10-25 2018-10-25 Frequency synchronization method, AP (access point) equipment, server and system Active CN109302740B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN201811246529.6A CN109302740B (en) 2018-10-25 2018-10-25 Frequency synchronization method, AP (access point) equipment, server and system

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN201811246529.6A CN109302740B (en) 2018-10-25 2018-10-25 Frequency synchronization method, AP (access point) equipment, server and system

Publications (2)

Publication Number Publication Date
CN109302740A CN109302740A (en) 2019-02-01
CN109302740B true CN109302740B (en) 2021-04-20

Family

ID=65158605

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201811246529.6A Active CN109302740B (en) 2018-10-25 2018-10-25 Frequency synchronization method, AP (access point) equipment, server and system

Country Status (1)

Country Link
CN (1) CN109302740B (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2023179837A1 (en) * 2022-03-21 2023-09-28 Telefonaktiebolaget Lm Ericsson (Publ) Synchronization for d-mimo

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112491751B (en) * 2019-09-12 2022-07-29 华为技术有限公司 Method, station and access point for uplink multi-station channel estimation

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2013075278A1 (en) * 2011-11-21 2013-05-30 中兴通讯股份有限公司 Frequency offset estimation and channel estimation method and system
CN106452531A (en) * 2016-10-27 2017-02-22 西安交通大学 A large-scale-MIMO based multi-user uplink frequency synchronization method

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7889819B2 (en) * 2002-10-04 2011-02-15 Apurva Mody Methods and systems for sampling frequency offset detection, correction and control for MIMO OFDM systems

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2013075278A1 (en) * 2011-11-21 2013-05-30 中兴通讯股份有限公司 Frequency offset estimation and channel estimation method and system
CN106452531A (en) * 2016-10-27 2017-02-22 西安交通大学 A large-scale-MIMO based multi-user uplink frequency synchronization method

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
Candidateds for estimating carrier frequency offset in MIMO systems;Tran Ngoc Dung etc;《IEEE》;20090731;全文 *
Frequency synchronization in MIMO systems;Kai deng;《IEEE》;20120731;全文 *
MIMO OFDM系统中的同步技术研究;邓凯;《CNKI》;20041220;第1-63页 *
Parameter estimation for MIMO systems with multiple frequency offsets;Wei dong etc;《IEEE》;20080731;全文 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2023179837A1 (en) * 2022-03-21 2023-09-28 Telefonaktiebolaget Lm Ericsson (Publ) Synchronization for d-mimo

Also Published As

Publication number Publication date
CN109302740A (en) 2019-02-01

Similar Documents

Publication Publication Date Title
US10230436B2 (en) Methods for channel information acquisition, signal detection and transmission in multi-user wireless communication systems
US5867478A (en) Synchronous coherent orthogonal frequency division multiplexing system, method, software and device
EP3267645B1 (en) Methods and devices for time and frequency offset estimation
US20090323515A1 (en) Ofdm transmittter and ofdm receiver
Rogalin et al. Hardware-impairment compensation for enabling distributed large-scale MIMO
US8478203B2 (en) Phase synchronization of base stations via mobile feedback in multipoint broadcasting
US20140211779A1 (en) Scalable synchronization for distributed multiuser mimo
US8867570B2 (en) Methods of transmitting pilot tones and data in spatial multiplexing transmission
US20130157602A1 (en) Method and System for Reducing the Complexity of Multi-Frequency Hypothesis Testing Using an Iterative Approach
TW201929444A (en) Multi-antenna system and percoding method thereof
CN109302740B (en) Frequency synchronization method, AP (access point) equipment, server and system
US10454664B2 (en) Phase synchronization and channel reciprocity calibration of antennas via terminal feedback
Cassiau et al. Time and frequency synchronization for CoMP with FBMC
Zhu et al. Double-sequence frequency synchronization for wideband millimeter-wave systems with few-bit ADCs
WO2010130101A1 (en) Method, device and system for channel pre-coding
CN108174439B (en) Multi-base station system and channel correction method thereof
Morelli et al. Estimation of residual carrier and sampling frequency offsets in OFDM-SDMA uplink transmissions
US11171696B2 (en) Distributed MIMO long training field method and system
US20180159670A1 (en) Multi-cell system and channel calibration method thereof
TWI641281B (en) Multi-cell system and channel calibration method thereof
US11057782B2 (en) Multi-cell coordination system and channel calibration method thereof
WO2019034252A1 (en) Techniques for determining localization of a mobile device
Iwelski et al. Feedback generation for CoMP transmission in unsynchronized networks with timing offset
WO2023216085A1 (en) Phase compensation for channel state information
Nikitopoulos et al. FASTER: Fine and accurate synchronization for large distributed MIMO wireless networks

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant