CN115174337A - OFDM waveform parameter self-adaption method based on limited Thompson sampling - Google Patents

OFDM waveform parameter self-adaption method based on limited Thompson sampling Download PDF

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CN115174337A
CN115174337A CN202211085190.2A CN202211085190A CN115174337A CN 115174337 A CN115174337 A CN 115174337A CN 202211085190 A CN202211085190 A CN 202211085190A CN 115174337 A CN115174337 A CN 115174337A
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sampling
waveform
transmission success
success probability
ofdm waveform
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CN115174337B (en
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熊俊
罗海鹏
刘潇然
魏急波
赵海涛
辜方林
刘兴光
靳增源
陈海涛
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National University of Defense Technology
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    • H04—ELECTRIC COMMUNICATION TECHNIQUE
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    • H04L27/00—Modulated-carrier systems
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
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Abstract

The application relates to an OFDM waveform parameter self-adaption method based on limited Thompson sampling. The method comprises the following steps: modeling the transmission success probability of the candidate OFDM waveform into a beta distribution according to a limited Thompson sampling algorithm, sampling the transmission success probability of the candidate waveform through the model and a sequential inverse sampling algorithm to obtain a transmission success probability sampling result meeting the waveform characteristic requirement, calculating according to the wave transmission success probability sampling result, selecting the waveform with the maximum average spectral efficiency for transmission, updating beta distribution parameters corresponding to the waveform with the maximum average spectral efficiency according to information fed back by a receiving terminal test, and finally obtaining the optimal waveform under the current channel through continuous trial and error convergence. By adopting the invention, when the channel quality information is unknown, the optimal OFDM waveform suitable for the current channel can be selected continuously and intelligently through channel interaction with the channel, thereby effectively solving the problem of selecting the optimal OFDM waveform in the actual wireless communication.

Description

OFDM waveform parameter self-adaption method based on limited Thompson sampling
Technical Field
The application relates to the technical field of communication, in particular to an OFDM waveform parameter self-adaption method based on limited Thompson sampling.
Background
An Orthogonal Frequency Division Multiplexing (OFDM) system is a wireless communication system that realizes high-rate transmission in a Frequency selective channel, but is affected by small-scale fading of a wireless channel, and Inter-Symbol Interference (ISI) and Inter-Carrier Interference (ICI) generated by multipath effect and doppler effect seriously affect decoding recovery of information bits at a receiving end. Therefore, in the OFDM, the influence caused by multipath delay is reduced by introducing Cyclic Prefix (CP), and enough CP can eliminate inter-symbol interference caused by multipath delay, or the influence caused by inter-carrier interference can be reduced by reducing the number of subcarriers and increasing the subcarrier spacing. The OFDM waveform with longer CP length and less number of subcarriers can certainly achieve more reliable transmission, but the spectrum efficiency is very low, and therefore, it is a significant task to select the optimal OFDM waveform for transmission according to different wireless channels.
The existing adaptive OFDM algorithm is mostly realized based on formula derivation, a closed expression between OFDM waveform parameters and transmission performance is given by assuming that channel quality information accords with certain specific distribution, and the optimal OFDM waveform parameters are given by simple dichotomy or differentiation. The method has the problems that on one hand, the method is only suitable for OFDM waveform self-adaptation under the assumption of a specific channel, and the problem of OFDM waveform selection in actual communication is difficult to solve; on the other hand, the performance of the algorithm depends on accurate channel estimation, and the performance of the algorithm is reduced due to channel estimation errors of a receiving end and time delay generated by returning a channel estimation result to a transmitting end.
Disclosure of Invention
In view of the foregoing, it is necessary to provide an OFDM waveform parameter adaptive method based on limited thompson sampling without depending on any channel assumption and channel estimation.
A method of OFDM waveform parameter adaptation based on limited thompson sampling, the method comprising:
the transmitting terminal constructs the transmission success probability of the candidate OFDM waveform into a transmission success probability model in the form of beta distribution according to a limited Thompson sampling algorithm;
sampling the transmission success probability of the candidate OFDM waveform according to a transmission success probability model and a sequential inverse sampling algorithm to obtain a transmission success probability sampling result meeting the waveform characteristic requirement;
calculating a transmission success probability sampling result to obtain the average spectrum efficiency of candidate OFDM waveforms, and selecting the candidate OFDM waveform with the maximum average spectrum efficiency to transmit a preset data packet to a receiving end;
the receiving end checks the received data packet through a cyclic redundancy check algorithm and sends a check result to the transmitting end;
and the transmitting end receives the check result, and repeatedly updates the beta distribution parameters corresponding to the candidate OFDM waveform with the maximum average spectral efficiency according to the check result until convergence to obtain the OFDM waveform with the maximum average spectral efficiency under the current channel.
In one embodiment, sampling the transmission success probability of the candidate OFDM waveform according to a transmission success probability model and a sequential inverse sampling algorithm to obtain a transmission success probability sampling result meeting the waveform characteristic requirement, includes:
calculating the transmission success probability model to obtain an accumulative distribution function of the transmission success probability model;
sampling the transmission success probability of the candidate OFDM waveforms according to a sequential inverse sampling algorithm to obtain a transmission success probability sampling random value;
and calculating according to the cumulative distribution function and the transmission success probability sampling random value to obtain a transmission success probability sampling result meeting the waveform characteristic requirement.
In one embodiment, sampling the transmission success probability of the candidate OFDM waveform according to a sequential inverse sampling algorithm to obtain a transmission success probability sampling random value includes:
sampling the transmission success probability of the candidate OFDM waveforms according to a sequential inverse sampling algorithmiA candidate OFDM waveform obtained in the range
Figure 493951DEST_PATH_IMAGE001
Inner sampled random value
Figure 437637DEST_PATH_IMAGE002
Wherein, in the step (A),
Figure 996794DEST_PATH_IMAGE003
which represents the lower bound of the random value,
Figure 709535DEST_PATH_IMAGE004
which represents the upper bound of the random value,
Figure 430366DEST_PATH_IMAGE005
representing waveform samples longer than the cyclic prefix length of the current candidate OFDM waveform to be sampled,
Figure 861348DEST_PATH_IMAGE006
representing waveform sampling results that are fewer than the number of subcarriers of the current candidate OFDM waveform to be sampled,
Figure 224196DEST_PATH_IMAGE007
the function of the cumulative distribution is represented,
Figure 558488DEST_PATH_IMAGE008
and
Figure 450220DEST_PATH_IMAGE009
is shown asiAnd parameters of the beta distribution corresponding to the transmission success probability of the candidate OFDM waveforms.
In one embodiment, the calculating according to the cumulative distribution function and the transmission success probability sampling random value to obtain the transmission success probability sampling result meeting the requirement of the waveform characteristics comprises:
when the cumulative distribution function is equal to the random value of the transmission success probability sampling, the transmission success probability sampling result meeting the waveform characteristic requirement is obtained and expressed as
Figure 368498DEST_PATH_IMAGE010
Wherein, the first and the second end of the pipe are connected with each other,
Figure 269458DEST_PATH_IMAGE011
denotes the firstiThe probability of success of the transmission is sampled as a result,
Figure 691212DEST_PATH_IMAGE012
representing the inverse of the cumulative distribution function.
In one embodiment, the waveform characteristic requirement is determined according to the cyclic prefix length and the subcarrier number of the candidate OFDM waveform, and the cyclic prefix length and the subcarrier number are determined according to an adaptive algorithm, wherein the subcarriers of the candidate OFDM waveform have the same coding mode.
In one embodiment, determining the waveform characteristic requirement according to the cyclic prefix length and the number of subcarriers of the candidate OFDM waveform comprises:
the requirements for determining the characteristics of the waveform according to the cyclic prefix length and the subcarrier number of the candidate OFDM waveform are
Figure 19425DEST_PATH_IMAGE013
Wherein, in the step (A),
Figure 159419DEST_PATH_IMAGE015
is shown asjThe result of the sampling of the probability of success of the transmission,
Figure 67332DEST_PATH_IMAGE016
is shown asiThe cyclic prefix length of a candidate OFDM waveform,
Figure 609172DEST_PATH_IMAGE017
is shown asjThe cyclic prefix length of a candidate OFDM waveform,
Figure 609751DEST_PATH_IMAGE018
is shown asiThe number of sub-carriers of a number of candidate OFDM waveforms,
Figure 237042DEST_PATH_IMAGE019
is shown asjThe number of subcarriers of a candidate OFDM waveform.
In one embodiment, the calculating the sampling result of the transmission success probability to obtain the average spectrum efficiency of the candidate OFDM waveforms, and selecting the candidate OFDM waveform with the largest average spectrum efficiency to transmit the preset data packet to the receiving end includes:
calculating the transmission success probability sampling result to obtain the average spectrum efficiency of the transmission success probability sampling result, which is expressed as
Figure 745384DEST_PATH_IMAGE020
Figure 141730DEST_PATH_IMAGE021
Wherein, the first and the second end of the pipe are connected with each other,
Figure 811746DEST_PATH_IMAGE022
which represents the average spectral efficiency of the spectrum,
Figure 129594DEST_PATH_IMAGE023
which is indicative of the efficiency of the spectrum,
Figure 707206DEST_PATH_IMAGE024
representing the number of bits loaded in the candidate OFDM waveform,
Figure 223638DEST_PATH_IMAGE025
representing a predicted transmission success probability based on the transmission success probability sampling results,
Figure 566020DEST_PATH_IMAGE027
the duration of the symbol is represented by,
Figure 371165DEST_PATH_IMAGE028
which represents the sampling interval between the first and second samples,
Figure 955730DEST_PATH_IMAGE029
which is indicative of the bandwidth of the signal,
Figure 326669DEST_PATH_IMAGE030
representing the number of subcarriers of the candidate OFDM waveform,
Figure 338487DEST_PATH_IMAGE031
representing a cyclic prefix length of the candidate OFDM waveform;
and selecting the candidate OFDM waveform with the maximum average spectrum efficiency to transmit a preset data packet to a receiving end.
In one embodiment, the receiving end checks the received data packet through a cyclic redundancy check algorithm, and sends the check result to the transmitting end, including:
the receiving end checks the received data through a cyclic redundancy check algorithm, and if the check is successful, the receiving end feeds back the confirmation receiving information to the transmitting end; and if the verification fails, feeding back negative confirmation receiving information to the transmitting end.
In one embodiment, the receiving, by the transmitting end, the verification result, and repeatedly updating the beta distribution parameter corresponding to the candidate OFDM waveform with the maximum average spectral efficiency according to the verification result until the OFDM waveform with the maximum average spectral efficiency in the current channel is obtained includes:
when the transmitting terminal receives the confirmed receiving information, the Beta distribution parameters corresponding to the candidate OFDM waveform with the maximum average spectrum efficiency are subjected to the confirmed receiving information
Figure 162087DEST_PATH_IMAGE032
Updating the parameters;
when the transmitting terminal receives the negative confirmation receiving information, the beta distribution parameters corresponding to the candidate OFDM waveform with the maximum average spectrum efficiency are selected according to the negative confirmation receiving information
Figure 815922DEST_PATH_IMAGE033
Updating the parameters;
by pairs
Figure 41367DEST_PATH_IMAGE034
Parameters and
Figure 427349DEST_PATH_IMAGE035
and repeatedly updating the parameters until the OFDM waveform with the maximum average spectrum efficiency under the current channel is obtained.
According to the OFDM waveform parameter self-adaption method based on limited Thompson sampling, the transmission success probability of multiple candidate OFDM waveforms is modeled into a transmission success probability model in a form of beta distribution, the transmission success probability of the candidate OFDM waveforms is sampled according to the transmission success probability model and a sequential inverse sampling algorithm before each transmission, the transmission success probability sampling result meeting the waveform characteristic requirement is obtained, the transmission success probability sampling result is calculated and compared, the candidate OFDM waveform with the maximum average spectral efficiency is selected to transmit a preset data packet to a receiving end, then the beta distribution parameter corresponding to the candidate OFDM waveform with the maximum average spectral efficiency is updated according to the testing result fed back after the receiving end carries out cyclic redundancy check, and finally the OFDM waveform with the maximum average spectral efficiency under the current channel is converged through continuous trial errors. Compared with the prior art, the method provided by the invention overcomes the dependence of the traditional adaptive OFDM waveform algorithm on accurate channel modeling and channel estimation, and effectively solves the problem of selecting the optimal OFDM waveform in actual wireless communication by continuously and intelligently selecting the optimal OFDM waveform suitable for the current channel through channel interaction with the channel under the condition of not knowing channel quality information.
Drawings
Fig. 1 is a schematic flowchart of an OFDM waveform parameter adaptive method based on limited thompson sampling in an embodiment;
fig. 2 is a schematic diagram of a wireless communication system implemented according to the method of the present invention;
FIG. 3 is a graph comparing the average reward performance obtained by the method of the present invention and the classical Thompson sampling algorithm over 100 time steps of transmission in one embodiment;
fig. 4 is a graph comparing the average reward performance obtained by the method of the present invention and the classical thompson sampling algorithm within 1000 time steps of transmission in one embodiment.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of and not restrictive on the broad application.
In one embodiment, as shown in fig. 1, there is provided an OFDM waveform parameter adaptive method based on limited thompson sampling, including the following steps:
and step 102, the transmitting terminal constructs the transmission success probability of the candidate OFDM waveform into a transmission success probability model in the form of beta distribution according to the limited Thompson sampling algorithm.
Specifically, for the secondiCandidate OFDM waveform
Figure 269403DEST_PATH_IMAGE036
According to the limited Thompson sampling algorithm
Figure 697235DEST_PATH_IMAGE037
Is constructed as a transmission success probability model in the form of a beta distribution, expressed as
Figure 777187DEST_PATH_IMAGE038
Wherein
Figure 396387DEST_PATH_IMAGE039
Which indicates the probability of success of the transmission,
Figure 397841DEST_PATH_IMAGE040
and
Figure 127900DEST_PATH_IMAGE041
two shape parameters representing a beta distribution; after modeling, all beta distribution parameters need to be initialized to
Figure 62358DEST_PATH_IMAGE042
，
Figure 118038DEST_PATH_IMAGE043
The beta distribution is then equivalent to a uniform distribution.
It is to be understood that the probability of success of transmission of a candidate OFDM waveform refers to the use of an OFDM waveform
Figure 403526DEST_PATH_IMAGE044
And transmitting, and feeding back the probability of confirming the receiving information (ACK) by the receiving end.
And 104, sampling the transmission success probability of the candidate OFDM waveform according to the transmission success probability model and the sequential inverse sampling algorithm to obtain a transmission success probability sampling result meeting the waveform characteristic requirement.
It can be understood that, the sequential inverse sampling algorithm is to perform inverse sampling on all candidate OFDM waveforms in a sequence from a large robustness to a small robustness to obtain a transmission success probability sampling result meeting the waveform characteristic requirement, where the waveform characteristic requirement is determined by the cyclic prefix length and the number of subcarriers of the candidate OFDM waveforms, and the transmission success probability sampling result meeting the waveform characteristic requirement is that the longer the CP length is, the smaller the number of subcarriers under a fixed bandwidth is, that is, the larger the subcarrier interval is, the stronger the robustness of the candidate OFDM waveform is, and the higher the transmission success probability obtained by sampling is.
And 106, calculating the transmission success probability sampling result to obtain the average spectral efficiency of the candidate OFDM waveforms, and selecting the candidate OFDM waveform with the maximum average spectral efficiency to transmit the preset data packet to the receiving end.
It will be appreciated that the average spectral efficiency may be considered as the desired reward, subject to channel multipath delay and doppler shift, with different OFDM waveforms having different success probabilities of transmission, with a higher probability of success in selecting the sampled OFDM waveform that is the most desirable reward for data transmission.
And step 108, the receiving end checks the received data packet through a cyclic redundancy check algorithm, and sends a check result to the transmitting end.
It can be understood that the receiving end checks the received data packet through a cyclic redundancy check algorithm, and if the receiving end successfully recovers the data packet, the receiving end feeds back Acknowledgement (ACK) to the transmitting end, otherwise, feeds back negative NACK to the transmitting end.
And step 110, the transmitting end receives the check result, and repeatedly updates the beta distribution parameters corresponding to the candidate OFDM waveform with the maximum average spectral efficiency according to the check result until convergence to obtain the OFDM waveform with the maximum average spectral efficiency under the current channel.
It can be understood that the transmitting end repeatedly updates the beta distribution parameters corresponding to the sampled OFDM waveform with the maximum average spectral efficiency according to the ACK/NACK fed back by the receiving end, gradually converges to the OFDM waveform with the highest expected reward under the current channel in the interaction process with the channel, can solve the problem of selecting the optimal OFDM waveform in the actual wireless communication, and has good performance in the unknown time-varying channel with limited feedback.
The OFDM waveform parameter self-adaption method based on limited Thompson sampling models transmission success probability of multiple candidate OFDM waveforms into a transmission success probability model in a form of beta distribution, samples the transmission success probability of the candidate OFDM waveforms according to the transmission success probability model and a sequential inverse sampling algorithm before each transmission to obtain a transmission success probability sampling result meeting the waveform characteristic requirement, calculates and compares the transmission success probability sampling result, selects the candidate OFDM waveform with the maximum average spectral efficiency to transmit a preset data packet to a receiving end, updates the beta distribution parameter corresponding to the candidate OFDM waveform with the maximum average spectral efficiency according to a test result fed back after cyclic redundancy check is carried out by the receiving end, and finally converges to the OFDM waveform with the maximum average spectral efficiency under the current channel through continuous trial and error. Compared with the prior art, the method provided by the invention overcomes the dependence of the traditional adaptive OFDM waveform algorithm on accurate channel modeling and channel estimation, and effectively solves the problem of selecting the optimal OFDM waveform in actual wireless communication by continuously and intelligently selecting the optimal OFDM waveform suitable for the current channel through channel interaction with the channel under the condition of not knowing channel quality information.
In one embodiment, sampling the candidate OFDM waveform according to a transmission success probability model and a sequential inverse sampling algorithm to obtain a preliminary sampling result includes:
for transmission success probability model
Figure 874959DEST_PATH_IMAGE045
Calculating to obtain the cumulative distribution function of the transmission success probability model as
Figure 929502DEST_PATH_IMAGE046
；
Sampling the transmission success probability of the candidate OFDM waveforms according to a sequential inverse sampling algorithmiA candidate OFDM waveform obtained in the range
Figure 657549DEST_PATH_IMAGE047
Inner sampled random value
Figure 164754DEST_PATH_IMAGE048
Wherein, in the step (A),
Figure 439878DEST_PATH_IMAGE049
which represents the lower bound of the random value,
Figure 614507DEST_PATH_IMAGE050
which represents the upper bound of the random value,
Figure 480832DEST_PATH_IMAGE051
representing waveform samples longer than the cyclic prefix length of the current candidate OFDM waveform to be sampled,
Figure 6491DEST_PATH_IMAGE053
representing a waveform sampling result that is less than the number of subcarriers of the current candidate OFDM waveform to be sampled,
Figure 616464DEST_PATH_IMAGE055
and
Figure 848862DEST_PATH_IMAGE056
is shown asiParameters of beta distribution corresponding to the probability of successful transmission of the candidate OFDM waveforms;
calculating according to the cumulative distribution function and the random value of the transmission success probability sampling, and obtaining the sampling result of the transmission success probability meeting the waveform characteristic requirement when the cumulative distribution function is equal to the random value of the transmission success probability sampling, wherein the sampling result is expressed as
Figure 886088DEST_PATH_IMAGE057
Wherein the content of the first and second substances,
Figure 633464DEST_PATH_IMAGE058
indicating the ith transmission success probability sample result,
Figure 825891DEST_PATH_IMAGE059
representing the inverse of the cumulative distribution function.
It can be understood that, in the sequential inverse sampling method, by using the relationship between the candidate OFDM waveforms, the OFDM waveform with the stronger robustness is considered to be the OFDM waveform with the longer CP length and the smaller number of subcarriers, and should be sampled to obtain the higher probability of successful transmission of the data packet, so that only the sampling result meeting the requirement of the waveform characteristics is recorded. The sequential inverse sampling algorithm utilizes the knowledge of the wireless communication theory, the OFDM waveform with higher robustness obtained by sampling can be predicted to obtain higher transmission success probability, and the convergence can be faster by reducing unreasonable sampling results.
In one embodiment, the cyclic prefix length and the number of subcarriers are determined according to the candidate OFDM waveformThe target determines the waveform characteristic requirements expressed as
Figure 709533DEST_PATH_IMAGE060
Wherein, in the process,
Figure 386502DEST_PATH_IMAGE061
denotes the firstjThe result of the sampling of the probability of success of the transmission,
Figure 355595DEST_PATH_IMAGE062
denotes the firstiThe cyclic prefix length of each of the candidate OFDM waveforms,
Figure 572950DEST_PATH_IMAGE063
denotes the firstjThe cyclic prefix length of each of the candidate OFDM waveforms,
Figure 576678DEST_PATH_IMAGE064
denotes the firstiThe number of sub-carriers of a number of candidate OFDM waveforms,
Figure 955707DEST_PATH_IMAGE065
denotes the firstjThe number of subcarriers of each candidate OFDM waveform is recorded as the sampling result of all transmission success probability meeting the waveform characteristic requirement
Figure 412096DEST_PATH_IMAGE066
，IRepresents the total number of sampling results;
and determining the length of the cyclic prefix and the number of subcarriers according to an adaptive algorithm, wherein the subcarriers of the candidate OFDM waveforms have the same coding mode.
It can be understood that the influence caused by multipath delay can be reduced by introducing the cyclic prefix, the inter-symbol interference caused by multipath delay can be eliminated by enough cyclic prefix, the influence caused by inter-carrier interference can be reduced by reducing the number of subcarriers and increasing the interval of subcarriers, and the OFDM waveform with longer cyclic prefix length and less number of subcarriers can realize more reliable transmission.
In one embodiment, the calculating the transmission success probability sampling result to obtain an average spectral efficiency of the candidate OFDM waveforms, and selecting the candidate OFDM waveform with the maximum average spectral efficiency to transmit the preset data packet to the receiving end includes:
calculating the transmission success probability sampling result to obtain the average spectrum efficiency of the transmission success probability sampling result, which is expressed as
Figure 370825DEST_PATH_IMAGE067
Figure 229059DEST_PATH_IMAGE068
Wherein the content of the first and second substances,
Figure 811613DEST_PATH_IMAGE069
which represents the average spectral efficiency of the spectrum,
Figure 755298DEST_PATH_IMAGE070
which is indicative of the efficiency of the spectrum,
Figure 252138DEST_PATH_IMAGE071
representing the number of bits loaded in the candidate OFDM waveform,
Figure 964879DEST_PATH_IMAGE072
representing a predicted transmission success probability based on the transmission success probability sampling results,
Figure 951290DEST_PATH_IMAGE073
the duration of the symbol is represented by,
Figure 647851DEST_PATH_IMAGE074
which represents the interval of sampling,
Figure 745120DEST_PATH_IMAGE075
which is indicative of the bandwidth of the signal,
Figure 515629DEST_PATH_IMAGE076
sub-carriers representing candidate OFDM waveformsThe number of the first and second groups is,
Figure 672941DEST_PATH_IMAGE077
a cyclic prefix length representing a candidate OFDM waveform;
and selecting the candidate OFDM waveform with the maximum average spectrum efficiency to transmit a preset data packet to a receiving end.
It can be understood that the candidate OFDM waveform with the largest average spectrum efficiency is selected as a carrier of a data packet for transmission, a specific transmission mode between the transmitting end and the receiving end is an automatic repeat request mechanism, and the data packet transmission is performed on the basis of unreliable service according to the two mechanisms of acknowledgement and timeout used by the automatic repeat request mechanism (ARQ), so as to realize reliable communication between the transmitting end and the receiving end.
In one embodiment, the receiving end checks the received data packet through a cyclic redundancy check algorithm, and sends the check result to the transmitting end, including:
the receiving end checks the received data packet through a cyclic redundancy check algorithm, if the check is successful, the receiving end feeds back ACK if the receiving end successfully recovers the data packet, and the ACK is marked as transmission feedback
Figure 856798DEST_PATH_IMAGE078
(ii) a If the check fails, feeding back NACK to the transmitting end, and recording as transmission feedback
Figure 993644DEST_PATH_IMAGE079
。
In one embodiment, the receiving, by the transmitting end, the verification result, and repeatedly updating the beta distribution parameter corresponding to the candidate OFDM waveform with the maximum average spectral efficiency according to the verification result until the OFDM waveform with the maximum average spectral efficiency in the current channel is obtained includes:
when the transmitting terminal receives the confirmed receiving information, the Beta distribution parameters corresponding to the candidate OFDM waveform with the maximum average spectrum efficiency are subjected to the confirmed receiving information
Figure 884239DEST_PATH_IMAGE080
Updating of parametersAfter the
Figure 212452DEST_PATH_IMAGE081
Parameter is
Figure 352447DEST_PATH_IMAGE082
；
When the transmitting terminal receives the negative confirmation receiving information, the beta distribution parameters corresponding to the candidate OFDM waveform with the maximum average spectrum efficiency are selected according to the negative confirmation receiving information
Figure 322677DEST_PATH_IMAGE083
Updating of parameters, updated
Figure 864516DEST_PATH_IMAGE084
Parameter is
Figure 566893DEST_PATH_IMAGE085
；
By pairs
Figure 459763DEST_PATH_IMAGE086
Parameters and
Figure 436946DEST_PATH_IMAGE087
the parameters are repeatedly updated, and the updated beta distribution is expressed as
Figure 98872DEST_PATH_IMAGE088
And obtaining the OFDM waveform with the maximum average spectrum efficiency under the current channel until convergence.
It can be understood through
Figure 270352DEST_PATH_IMAGE089
Parameters and
Figure 588201DEST_PATH_IMAGE090
the parameters are repeatedly updated, the average spectrum efficiency of each transmission gradually tends to be stable along with the transmission of the data packet, and the OFDM waveform with the maximum average spectrum efficiency obtained by sampling before each transmission gradually converges to the current signalThe optimum waveform under the track.
In a specific embodiment, the parameters of the candidate OFDM waveforms include 3 CP lengths and 3 seed carrier numbers, and 9 candidate OFDM waveforms are formed, and specific simulation parameters thereof are shown in table 1.
TABLE 1 simulation parameters
Figure 369075DEST_PATH_IMAGE091
For 9 candidate OFDM waveforms, the specific steps of obtaining the OFDM waveform with the maximum average spectrum efficiency under the current channel by the OFDM waveform parameter adaptive method based on the limited Thompson sampling are as follows:
(1) By using
Figure 151087DEST_PATH_IMAGE092
Representing optional candidate OFDM waveforms, modeling the transmission success probability of each OFDM waveform as a beta distribution
Figure 992004DEST_PATH_IMAGE093
(ii) a Initialization
Figure 593886DEST_PATH_IMAGE094
、
Figure 381714DEST_PATH_IMAGE095
(ii) a Initializing transmit packet quantity records
Figure 752652DEST_PATH_IMAGE096
。
（2）
Figure 764470DEST_PATH_IMAGE097
。
(3) For all OFDM waveforms, performing inverse sampling according to an inverse sampling algorithm from the robustness to the robustness in a descending order, and specifically performing the following operations: for wave form
Figure 588070DEST_PATH_IMAGE098
The data packet is transmitted intoThe power probability conforms to the beta distribution
Figure 743370DEST_PATH_IMAGE099
First, generate
Figure 968815DEST_PATH_IMAGE100
Random number of inner
Figure 354797DEST_PATH_IMAGE101
Then obtaining a sampling result as
Figure 931272DEST_PATH_IMAGE102
. In the above-described operation of the process,
Figure 123219DEST_PATH_IMAGE103
represents the lower bound of the random number value and satisfies
Figure 203170DEST_PATH_IMAGE104
，
Figure 25633DEST_PATH_IMAGE105
The random number value is shown to be upper bound and satisfies
Figure 823824DEST_PATH_IMAGE106
，
Figure 288304DEST_PATH_IMAGE107
Representing waveform samples longer than the cyclic prefix length of the current waveform to be sampled,
Figure 753920DEST_PATH_IMAGE108
representing waveform sampling results that are fewer than the number of subcarriers of the current waveform to be sampled. According to the above operation, the sequential sampling can be satisfied
Figure 45487DEST_PATH_IMAGE109
All required transmission success probability sampling results are
Figure 65395DEST_PATH_IMAGE110
。
(4) And calculating the average spectrum efficiency which is expected to be obtained by using each waveform to transmit the data packet according to the sampling result:
Figure 802407DEST_PATH_IMAGE111
the candidate OFDM waveform with the maximum expected reward is compared to
Figure 122530DEST_PATH_IMAGE112
And transmits a data packet using the waveform, wherein,
Figure 817953DEST_PATH_IMAGE113
is shown as
Figure 590737DEST_PATH_IMAGE114
The OFDM waveform selected for each time step,
Figure 865861DEST_PATH_IMAGE115
indicates that the selection result is the first
Figure 774911DEST_PATH_IMAGE116
A candidate OFDM waveform.
(5) The receiving end feeds back ACK or NACK after checking, and the transmitting end transmits the feedback according to the current time step
Figure 172394DEST_PATH_IMAGE117
Updating corresponding candidate OFDM waveforms
Figure 166895DEST_PATH_IMAGE118
The updated beta distribution is
Figure 245710DEST_PATH_IMAGE119
(6) Repeating the steps (2) to (5) until
Figure 776310DEST_PATH_IMAGE120
。
(7) And (4) repeating the steps (1) to (6) to perform 100 Monte Carlo simulations, and calculating to obtain the average reward of each time step, wherein the average reward of each time step is the average value of the rewards obtained by the 100 Monte Carlo simulations at the time step.
In a specific embodiment, as shown in fig. 2, a wireless communication system implemented based on the method of the present invention is also presented. The method comprises the steps that signal bit data sent by a transmitting end of a communication system are subjected to convolutional coding to obtain coded bits, the coded bits are mapped into constellation symbols according to an orthogonal amplitude modulation (M-QAM) method, the modulated constellation symbols are OFDM symbols according to inverse Fourier transform (IFFT), a CP is added in front of each OFDM symbol according to an adaptive algorithm, the OFDM waveform with the maximum average spectral efficiency under the current channel is selected according to the OFDM waveform parameter adaptive method based on limited Thompson sampling, and reliable data communication at two ends is achieved by the communication system through an automatic request retransmission mechanism in data transmission. The receiving end of the communication system receives transmission data, processes OFDM symbols through de-CP and Fourier transform, obtains information bits through carrying out quadrature amplitude demodulation and Viterbi decoding on the OFDM symbols in sequence and successfully recovering, finally verifies the recovered information bits through a cyclic redundancy check algorithm, and feeds back ACK/NACK information indicating whether the current data packet is successfully transmitted to the receiving end to complete data communication. Each subcarrier in the communication system uses the same modulation and coding mode, and the selection of the CP length and the number of the subcarriers in the system is realized based on an adaptive algorithm.
In order to further verify the beneficial effects of the OFDM waveform parameter adaptive method based on limited thompson sampling proposed by the present invention, under the simulation parameters shown in table 1, the average reward obtained by 100 monte carlo simulations within 100 time steps of the method proposed by the present invention and the classical Thompson Sampling (TS) algorithm is compared, wherein only one data packet is transmitted in one time step, and the comparison result is shown in fig. 3. The average reward shows that the method well realizes the selection of the self-adaptive OFDM waveform without knowing an accurate channel model and channel estimation, and compared with the simple application of classical Thompson sampling to the self-adaptive OFDM waveform, the algorithm effectively utilizes the relation among the OFDM waveforms, has faster convergence and can obtain higher average reward in the earlier stage of the algorithm.
Further, under the simulation parameters shown in table 1, the average reward obtained by 100 monte carlo simulations in 1000 time steps of the method provided by the invention and the classic Thompson Sampling (TS) algorithm are compared, and the comparison result is shown in fig. 4, so that after the two algorithms are converged, the average reward performance obtained by each transmission is equivalent, and the provided algorithm not only accelerates the convergence speed of the algorithm, but also does not bring about the performance reduction after the convergence of the algorithm.
It should be understood that, although the steps in the flowchart of fig. 1 are shown in order as indicated by the arrows, the steps are not necessarily performed in order as indicated by the arrows. The steps are not performed in the exact order shown and described, and may be performed in other orders, unless explicitly stated otherwise. Moreover, at least some of the steps in fig. 1 may include multiple sub-steps or multiple stages that are not necessarily performed at the same time, but may be performed at different times, and the order of performing the sub-steps or stages is not necessarily sequential, but may be performed alternately or alternately with other steps or at least some of the sub-steps or stages of other steps.
All possible combinations of the technical features in the above embodiments may not be described for the sake of brevity, but should be considered as being within the scope of the present disclosure as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims (9)

1. An OFDM waveform parameter adaptive method based on limited Thompson sampling, which is characterized by comprising the following steps:
the transmitting end constructs the transmission success probability of the candidate OFDM waveform into a transmission success probability model in the form of beta distribution according to a limited Thompson sampling algorithm;
sampling the transmission success probability of the candidate OFDM waveform according to the transmission success probability model and the sequential inverse sampling algorithm to obtain a transmission success probability sampling result meeting the waveform characteristic requirement;
calculating the transmission success probability sampling result to obtain the average spectrum efficiency of the candidate OFDM waveforms, and selecting the candidate OFDM waveform with the maximum average spectrum efficiency to transmit a preset data packet to a receiving end;
the receiving end checks the received data packet through a cyclic redundancy check algorithm and sends a check result to the transmitting end;
and the transmitting end receives the check result, and repeatedly updates the beta distribution parameters corresponding to the candidate OFDM waveform with the maximum average spectral efficiency according to the check result until convergence to obtain the OFDM waveform with the maximum average spectral efficiency under the current channel.
2. The method of claim 1, wherein sampling the transmission success probability of the candidate OFDM waveform according to the transmission success probability model and a sequential inverse sampling algorithm to obtain a transmission success probability sampling result meeting the waveform characteristic requirement, comprises:
calculating the transmission success probability model to obtain an accumulative distribution function of the transmission success probability model;
sampling the transmission success probability of the candidate OFDM waveforms according to the sequential inverse sampling algorithm to obtain a transmission success probability sampling random value;
and calculating according to the cumulative distribution function and the transmission success probability sampling random value to obtain a transmission success probability sampling result meeting the waveform characteristic requirement.
3. The method of claim 2, wherein sampling the probability of transmission success of the candidate OFDM waveform according to the sequential inverse sampling algorithm to obtain a random value of transmission success probability sampling comprises:
sampling the transmission success probability of the candidate OFDM waveforms according to the sequential inverse sampling algorithmiA candidate OFDM waveform obtained in the range
Figure 833798DEST_PATH_IMAGE001
Inner sampled random value
Figure 282097DEST_PATH_IMAGE002
Wherein, in the step (A),
Figure 327413DEST_PATH_IMAGE003
which represents the lower bound of the random value,
Figure 253781DEST_PATH_IMAGE004
which represents the upper bound of the random value,
Figure 100776DEST_PATH_IMAGE005
representing waveform sampling results longer than the cyclic prefix length of the current candidate OFDM waveform to be sampled,
Figure 454397DEST_PATH_IMAGE006
representing a waveform sampling result that is less than the number of subcarriers of the current candidate OFDM waveform to be sampled,
Figure 252589DEST_PATH_IMAGE007
the function of the cumulative distribution is represented,
Figure 982647DEST_PATH_IMAGE008
and
Figure 182685DEST_PATH_IMAGE009
represents the firstiAnd parameters of the beta distribution corresponding to the transmission success probability of the candidate OFDM waveforms.
4. The method of claim 2, wherein calculating according to the cumulative distribution function and the transmission success probability sampling random value to obtain a transmission success probability sampling result meeting the waveform characteristic requirement comprises:
when the cumulative distribution function is equal to the random value of the transmission success probability sampling, a transmission success probability sampling result meeting the waveform characteristic requirement is obtained and expressed as
Figure 441628DEST_PATH_IMAGE010
Wherein the content of the first and second substances,
Figure 727115DEST_PATH_IMAGE011
is shown asiProbability of transmission success sampling results for a candidate OFDM waveform,
Figure 729707DEST_PATH_IMAGE012
an inverse function representing the cumulative distribution function.
5. The method of claim 4, wherein the waveform characterization requirements are determined according to a cyclic prefix length and a number of subcarriers of the candidate OFDM waveform, and wherein the cyclic prefix length and the number of subcarriers are determined according to an adaptive algorithm, wherein the subcarriers of the candidate OFDM waveform have the same coding scheme.
6. The method of claim 5, wherein determining the waveform characterization requirement based on a cyclic prefix length and a number of subcarriers of the candidate OFDM waveform comprises:
determining the characteristic requirement of the waveform according to the cyclic prefix length and the subcarrier number of the candidate OFDM waveform
Figure 784250DEST_PATH_IMAGE013
Wherein, in the step (A),
Figure 246718DEST_PATH_IMAGE014
denotes the firstjThe probability of success of the transmission is sampled as a result,
Figure 19502DEST_PATH_IMAGE015
denotes the firstiThe cyclic prefix length of a candidate OFDM waveform,
Figure 825784DEST_PATH_IMAGE016
is shown asjThe cyclic prefix length of a candidate OFDM waveform,
Figure 413DEST_PATH_IMAGE017
is shown asiThe number of subcarriers of a number of candidate OFDM waveforms,
Figure 601159DEST_PATH_IMAGE018
is shown asjThe number of subcarriers of a candidate OFDM waveform.
7. The method of claim 1, wherein calculating the transmission success probability sampling result to obtain an average spectral efficiency of the candidate OFDM waveforms, and selecting the candidate OFDM waveform with the maximum average spectral efficiency to transmit a preset data packet to a receiving end comprises:
calculating the transmission success probability sampling result to obtain the average spectrum efficiency of the transmission success probability sampling result, which is expressed as
Figure 861239DEST_PATH_IMAGE019
Figure 471212DEST_PATH_IMAGE020
Wherein the content of the first and second substances,
Figure 500348DEST_PATH_IMAGE021
which represents the average spectral efficiency of the spectrum,
Figure 537574DEST_PATH_IMAGE022
which is indicative of the efficiency of the spectrum,
Figure 520835DEST_PATH_IMAGE023
representing the number of bits loaded in the candidate OFDM waveform,
Figure 934499DEST_PATH_IMAGE024
representing a predicted transmission success probability derived from the transmission success probability sampling result,
Figure 552562DEST_PATH_IMAGE025
the duration of the symbol is represented by,
Figure 26269DEST_PATH_IMAGE026
which represents the interval of sampling,
Figure 729783DEST_PATH_IMAGE027
which is indicative of the bandwidth of the signal,
Figure 681558DEST_PATH_IMAGE028
representing the number of subcarriers of the candidate OFDM waveform,
Figure 419707DEST_PATH_IMAGE029
representing a cyclic prefix length of the candidate OFDM waveform;
and selecting the candidate OFDM waveform with the maximum average spectrum efficiency to transmit a preset data packet to a receiving end.
8. The method of claim 1, wherein a receiving end checks the received data packet by a cyclic redundancy check algorithm, and sends the check result to a transmitting end, comprising:
the receiving end checks the received data through a cyclic redundancy check algorithm, and if the check is successful, the receiving end feeds back the confirmation receiving information to the transmitting end; and if the verification fails, feeding back negative confirmation receiving information to the transmitting end.
9. The method of claim 8, wherein the transmitting end receives the check result, and repeatedly updates the beta distribution parameters corresponding to the candidate OFDM waveform with the maximum average spectral efficiency according to the check result until obtaining the OFDM waveform with the maximum average spectral efficiency under the current channel, comprising:
when the transmitting terminal receives the receiving confirmation information, according to the receiving confirmation information, the beta distribution parameters corresponding to the candidate OFDM waveform with the maximum average spectrum efficiency
Figure 64315DEST_PATH_IMAGE030
Updating the parameters;
when the transmitting terminal receives the negative confirmation receiving information, the beta distribution parameters corresponding to the candidate OFDM waveform with the maximum average spectrum efficiency are obtained according to the negative confirmation receiving information
Figure 520704DEST_PATH_IMAGE031
Updating parameters;
by aligning the
Figure 10592DEST_PATH_IMAGE032
Parameters and
Figure 928930DEST_PATH_IMAGE033
the parameters are repeatedly updated until the average frequency under the current channel is obtainedThe most spectrally efficient OFDM waveform.
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