CN107018114B - A kind of SCMA code book blind estimating method - Google Patents
A kind of SCMA code book blind estimating method Download PDFInfo
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- CN107018114B CN107018114B CN201710137731.4A CN201710137731A CN107018114B CN 107018114 B CN107018114 B CN 107018114B CN 201710137731 A CN201710137731 A CN 201710137731A CN 107018114 B CN107018114 B CN 107018114B
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- code book
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
- H04L1/0045—Arrangements at the receiver end
- H04L1/0055—MAP-decoding
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
- H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
- H04L27/38—Demodulator circuits; Receiver circuits
Abstract
The invention discloses a kind of SCMA code book blind estimating methods.The method include the steps that 1) usage factor figure indicates the resource impact situation of SCMA, wherein, using each code book as a variable node, each resource block indicates that the code book will occupy resource block connected to it and send data comprising line between code book and resource block as a function node；For each code book, one initial confidence level vector is set；2) user equipment (UE) is fixed as defined in the LTE protocol before time/frequency source block sends the data of oneself, first sends a preamble information；3) code book service condition is estimated according to the preamble information and the factor graph that receive in specified time/frequency source block in receiving end, estimates whether each code book has user to use and use the number of users of the code book.The present invention user data for the part that do not conflict can be successfully decoded there are code book conflict.
Description
Technical field
The invention belongs to digital communicating field, be related to a kind of SCMA (Sparse Code Multiple Access, it is sparse
Encode multiple access access) code book blind estimating method, in particular to the estimation side of code book service condition during SCMA is accessed
Method.
Background technique
SCMA is a kind of novel multiple access technique based on spread spectrum coding, it combines low-density coding (LDS, Low
Density Signature) and multi-dimensional constellation diagram modulation, by selecting different code book, allow different users it is non-just
It is accessed in the case of friendship.Under same resources supplIes, SCMA technology can support more users to connect, and even more than pass
The spreading ratio of system CDMA technology, therefore have good prospect in the Internet of Things application for needing magnanimity to connect.
Assume receiving end to UE (User Equipment, Yong Hushe mostly the research of SCMA technology in the literature at present
It is standby) distribution situation of code book is it is known that then using the MPA of suboptimum, (Message Passing Algorithm, message transmission are calculated
Method) the transmission data of user are demodulated.If must use to the code book Unknown Distribution of UE and combine code book detection
JMPA (joint MPA) algorithm, this not only adds the complexities of MPA algorithm, and can not select same code book to multiple UE
The case where handled.
In actual system, the number of UE and the time for sending data are all unknown, therefore in the mistake of SCMA demodulation
Which code book Cheng Zhong has used, if has multiple UE to select the same code book, these information will be during demodulation
Estimated.
Summary of the invention
For the technical problems in the prior art, the object of the present invention is to provide in a kind of SCMA scheme upper
The blind estimating method that row channel detects the code book service condition of UE.This method need UE send oneself data it
Before, a bit of determining information is first sent as lead code.There is no special requirements for the design of lead code, can be used arbitrary
Bit stream is as lead code.If the modulation system of transmitting terminal selection is not permanent envelope, can be selected as far as possible when designing lead code
Select the big constellation point of energy.
Receiving end is estimated using preamble information using code book service condition of the MPA algorithm to UE, that is, estimates every
Whether one code book has user's use, and the number of users using this code book is how many.The estimated information of code book can be to subsequent
Decoding process is simplified, and the calculation amount of decoding algorithm, but subsequent decoding side are reduced in the case where not reducing decoding performance
Case is not core of the invention content.This method to code book estimated as a result, can be to different users using same code
This case where, is detected, discovery code book conflict as early as possible, and provides foundation to subsequent decoding, but how using of the invention
Estimated result is not core of the invention content.
The alternative that SCMA technology is communicated as 5G, main application scenarios are mobile communication, and the present invention is subsequent
Example and explanation be all to be carried out under the frame of LTE protocol under the premise of not particularly pointing out.In connecing at random for mobile communication
During entering, due to the case where base station is to UE be all it is unknown, code book blind estimating method proposed by the present invention can be used to UE
Code book service condition estimated.To achieve the goals above, the technical scheme is that
1. in transmitting terminal, each UE requires the synchronization for obtaining uplink according to the reference signal of down channel first, when having
When data will be sent, time/frequency source block is fixed as defined in the agreement and sends lead code above-mentioned first, then retransmits oneself
Data.The preamble content of transmission can be any known array, sequence length most it is short be a symbol length, lead code sequence
The length of column is determined according to the demand to estimation accuracy rate.
2., due to the characteristic of random access, receiver may will receive multiple in specified time/frequency source block in receiving end
UE sends the superposition of lead code, for each symbol received may be by MPA algorithm to the distribution situation of UE code book into
Row estimation, specific algorithm details will be described in detail later.
3. if, according to step 2, each reception symbol can estimate one the length of UE lead code is a symbol
The value of the confidence level of code book distribution situation can fold multiple estimated results when the length of lead code is multiple symbols
Add, the accuracy of Lai Tigao code book estimation.
In the step 2, it is assumed that the channel of all UE to receiving end is all awgn channel, and UE can be according to down channel
Reference signal adjusts transmission power, to guarantee that the signal power of signal arrival receiver of each UE transmission is roughly equal.
In the step 2, MPA algorithm can adjust the estimation range of code book according to practical UE deployment scenario.Such as it can be with
It limits each code book and at most has 2 UE selections, be at least no UE selection.
The demodulation of SCMA is divided into two parts by SCMA code book distribution situation algorithm for estimating proposed by the present invention: code book is estimated
Meter and code word demodulation.The invention mainly relates to the parts of code book estimation, and individually carrying out estimation to code book service condition is to reduce
The cost of spectrum efficiency obtains the simplification of decoding algorithm, and can reduce to a certain extent due to code book conflict caused by
The bit error rate rises.
Compared with prior art, the positive effect of the present invention are as follows:
1. proposing a kind of new code book usable condition algorithm for estimating.
2. the user data for the part that do not conflict can be successfully decoded there are code book conflict.
Detailed description of the invention
Fig. 1 is flow chart of the method for the present invention；
Fig. 2 is the factor graph for the SCMA scheme that present example uses；
Fig. 3 is the planisphere that present example uses；
(a) it is No. 0 planisphere, (b) is No. 1 planisphere, (c) is No. 2 planispheres；
The case where Fig. 4 is present example difference code book selection planisphere figure；
Fig. 5 is the relational graph of preamble length and estimation accuracy rate.
Specific embodiment
Process of the invention carries out algorithm for estimating described in the invention as shown in Figure 1, below in conjunction with an example
Clear, complete description.It is understood that described example is only a part of example of the invention, rather than all
Embodiment.Based on the embodiments of the present invention, those skilled in the art are obtained without making creative work
Every other embodiment, shall fall within the protection scope of the present invention.
The preset condition of this example is as follows:
Factor graph can be used to indicate in the resource impact situation of 1.SCMA.As shown in Fig. 2, one shares 6 code books, occupy
4 resource blocks.Fig. 2 is a factor graph, and code book (circular node) is variable node, and resource block (square nodes) is function section
Point.Indicate that this code book will occupy this resource block and send data comprising line between code book node and resource block.What Fig. 2 was indicated
The each code book of factor graph sends data on 2 resource blocks, and each resource block includes the data investigation of 3 code books.
2.UE is modulated using lead code of the QPSK scheme to transmission, and a symbol includes two binary digits, is not being had
In the case where having code book conflict, according to the structure of factor graph, each resource block is up to the superposition of 3 QPSK symbols.
3. assuming that be up to 2 users select same code book
In condition 1 described above, the decoding unit of each SCMA is 4 reception symbols, the case where no code book conflicts
The transmission data of lower at most corresponding 6 users.
In condition 2 described above, the planisphere that UE is used will do it rotation appropriate, so that be superimposed on resource block
The rotation angle of QPSK symbol is different.Fig. 3 is 3 planispheres used in this example, and No. 1 and No. 2 planispheres are respectively to 0
Number planisphere has rotated π/6 and π/3.Fig. 4 illustrates the planisphere situation that each code book is selected in coding.Above code book node
Two numbers show the planisphere serial number that this code book uses on different resource block, and the number below resource node is
Planisphere serial number used in three symbols that may be superimposed on this node.The sequence of serial number and resource node and code in figure
Putting in order for this node is identical.
Now according to symbol and factor graph is received, specific code book is estimated that MPA algorithm description is as follows:
Corresponding 6 variable nodes of 1.6 code book nodes, corresponding 4 function nodes of 4 reception symbols.
2. initial confidence level vector assume all code book selections be all it is equiprobable, i.e., for each code book, all may be used
It can be there are three types of situation: being selected without UE；There is 1 UE selection；There are 2 UE selections.The probability of initial situation each case is all 1/
3。
3. being indicated by for example following formula of the message that function node is sent to variable node
For the message transmitted in factor graph along the side bi-directional of factor graph, the content of transmitting is variable node difference value
Probability.In the case of in this example, this probability is the vector of one 3 dimensionRespectively represent this variable node (i.e. corresponding code book) without UE selection,
There is 1 probability UE selection and there are 2 UE to select.Footnote k in formula indicates corresponding k-th of variable node, and footnote n represents the
N function node.
Above in formulaIt represents for k-th of variable node Vk(i.e. k-th of code book), in the l times iteration
When there is i UE to select this code book probability.This probability is by n-th of function node FnIt is sent to k-th of variable section
Point VkMessage, it is according to from addition to VkOther be connected to function node FnVariable node VjThe message sended overCalculating is got.Calculation method is exactly the part of formula right side of the equal sign, it is calculated according to complete general formula in n node
The value of upper k variable is qkiWhen, other nodes all may situation probability superposition.WhereinRepresentative function
Node FnOn the symbol R that receivesnThe data vector sent out with each case (is usedIndicate) between Euclidean distance.Multiply
Method part will be connected to this function node F to allnOther variable nodes VjIt is traversed, and summing part will be to institute
There is the combination of the value condition (i.e. code book selection situation) of these nodes to be traversed.
If calculated in log-domain, and utilize Jacobian formula log (ea+eb) ≈ max (a, b), so that it may upper
The simplified formula in face are as follows:
4. being indicated by for example following formula of the message that variable node is sent to function node
It is similar with step 3, the message of function node is sent to from variable nodeIt is equally taking for variable node
It is worth probability vector.It summarizes the message (i.e. probability) that other function nodes send over, but due to being independent event respectively, because
This final result is obtained by these probability multiplications.If equally calculated in log-domain, multiplication be can simplify as addition:
5. iterative process repeats the content of step 3 and step 4, the highest the number of iterations until reaching agreement.
6. finally obtaining final probability value according to the message received on variable node, the maximum use of probability value is chosen
Amount is exported as the result of this algorithm.The final result is 6 n dimensional vector ns, and each element is represented in each code book
On include number of users.
Fig. 5 is the performance curve obtained by emulation.The condition of emulation is the factor graph according to Fig. 1, it is assumed that has 7 users
Data are sent simultaneously, and one of code book there are 2 UE selections, remaining code book all only has 1 UE to select, three in simulation result
Curve distribution represents detection when preamble length is 2,4 and 6 bit lengths under the conditions of different signal-to-noise ratio
Error probability.The MPA algorithm used when emulation uses log-domain and is calculated, and highest the number of iterations is set as 5.Using pair
The error probability that number field method obtains is slightly above the method in non-logarithmic domain, but simulation velocity increases significantly.
The up channel in a kind of SCMA system provided by the present invention is described above by embodiment to use code book
The estimation method of situation, it will be understood by those of skill in the art that in the range for not departing from essence of the invention, it can be to this hair
It is bright to make certain deformation or modification；Preparation method is also not necessarily limited to the content disclosed in embodiment.
Claims (7)
1. a kind of SCMA code book blind estimating method, the steps include:
1) usage factor figure indicates the resource impact situation of SCMA, wherein using each code book as a variable node, each resource
Block indicates that the code book will occupy resource block connected to it and send comprising line between code book and resource block as a function node
Data；For each code book, one initial confidence level vector is set；
2) user equipment (UE) is fixed as defined in the LTE protocol before time/frequency source block sends the data of oneself, and it is leading first to send one
Code information；
3) receiving end carries out code book service condition according to the preamble information and the factor graph that receive in specified time/frequency source block
Estimation, estimates whether each code book has user to use and use the number of users of the code book；Wherein calculated using code book estimation MPA
Method estimates code book service condition, specifically: 31) calculate the message that variable node is sent to by function node, Yi Jiyou
Variable node is sent to the message of function node；32) highest the number of iterations of the step 31) until reaching agreement is repeated；33) basis
The message received on variable node obtains final probability value, chooses the maximum number of users of probability value as code book and uses feelings
The estimated result of condition.
2. method described in claim 1, which is characterized in that utilize formulaIt calculates by n-th of function node FnIt is sent to k-th of variable node
VkMessageWherein, qkiFor i-th of value of the code book on k node,For the l times iteration Shi Congqi
It is connected to function node FnVariable node VjIt is sent to function node FnMessage,Representative function node FnOn
The symbol R receivednWith data vector estimated by each caseBetween Euclidean distance, qjmFor on j node
M-th of value.
3. method according to claim 2, it is characterised in that utilize formula log (ea+eb) ≈ max (a, b) is right Abbreviation is carried out, the formula obtained after abbreviation is utilized Calculate the message that variable node is sent to by function node.
4. method according to claim 2, which is characterized in that utilize formulaIt calculates by becoming
Amount node is sent to the message of function nodeWherein,To be connected to change from other when the l times iteration
Measure node VkFunction node FjIt is sent to variable node VkMessage.
5. method as claimed in claim 4, which is characterized in that utilize formula log (ea+eb) ≈ max (a, b) is to formulaAbbreviation is carried out, the formula obtained after abbreviation is utilized
Calculate the message that function node is sent to by variable node.
6. method as claimed in claim 1 to 5, which is characterized in that the sequence length of the preamble information is most short to be
The length of one symbol.
7. method as claimed in claim 6, which is characterized in that be modulated using lead code of the QPSK scheme to transmission, often
One symbol includes two binary digits.
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| CN201710137731.4A CN107018114B (en) | 2017-03-09 | 2017-03-09 | A kind of SCMA code book blind estimating method |
| PCT/CN2017/114303 WO2018161654A1 (en) | 2017-03-09 | 2017-12-01 | Scma codebook blind estimation method |
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| CN112565153B (en) * | 2020-11-30 | 2023-06-09 | 沈阳理工大学 | SCMA multi-user codebook design method based on rotation mapping |
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| US20160254937A1 (en) * | 2015-02-27 | 2016-09-01 | Huawei Technologies Co., Ltd | Low complexity scma/lds detection systems and methods |
| CN107018114B (en) * | 2017-03-09 | 2019-09-06 | 北京大学 | A kind of SCMA code book blind estimating method |
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