CN107018114A - A kind of SCMA code books blind estimating method - Google Patents
A kind of SCMA code books blind estimating method Download PDFInfo
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- CN107018114A CN107018114A CN201710137731.4A CN201710137731A CN107018114A CN 107018114 A CN107018114 A CN 107018114A CN 201710137731 A CN201710137731 A CN 201710137731A CN 107018114 A CN107018114 A CN 107018114A
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- Prior art keywords
- code book
- node
- message
- sent
- code
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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
-
- 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
Abstract
The invention discloses a kind of SCMA code books blind estimating method.This method is：1) usage factor figure represents SCMA resource impact situation, wherein, using each code book as a variable node, each resource block represents that the code book will take connected resource block and send data between code book and resource block as a function node comprising line；For each code book, one initial confidence level vector is set；2) user equipment (UE) first sends a preamble information before time/frequency source block is fixed as defined in LTE protocol sending the data of oneself；3) receiving terminal estimates whether each code book has user to use and using the number of users of the code book according to specifying the preamble information received in time/frequency source block and the factor graph to estimate code book service condition.The user data for the part that do not conflict can be successfully decoded in the case where there is code book conflict by the present invention.
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, more particularly to the estimation side during SCMA is accessed to code book service condition
Method.
Background technology
SCMA is a kind of new multiple access technique based on spread spectrum coding, and it combines low-density coding (LDS, Low
Density Signature) and multi-dimensional constellation diagram modulation, by selecting different code books, allow different users in anon-normal
Accessed in the case of friendship.Under same resources supplIes, SCMA technologies 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.
The research in the literature to SCMA technologies assumes receiving terminal to UE (User Equipment, Yong Hushe mostly 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 is calculated
Method) the transmission data of user are demodulated.If to UE code book Unknown Distribution, must use and combine code book detection
Multiple UE this not only adds the complexity of MPA algorithms, and can not be have selected same code book by JMPA (joint MPA) algorithm
Situation handled.
In actual system, UE number and the time for sending data are all unknown, therefore the mistake demodulated in SCMA
Which code book Cheng Zhong, have used, if has multiple UE to have selected same code book, and these information will be during demodulation
Estimated.
The content of the invention
For technical problem present in prior art, object of the present invention is to provide in a kind of SCMA schemes upper
The blind estimating method that row channel is detected to UE code book service condition.This method need UE send the data of oneself it
Before, a bit of determination information is first sent as lead code.The design of lead code does not have not special requirement, can use arbitrary
Bit stream is used as lead code.If the modulation system of transmitting terminal selection is not permanent envelope, can try one's best choosing when designing lead code
Select the big constellation point of energy.
Receiving terminal is estimated UE code book service condition using preamble information using MPA algorithms, that is, estimates every
Whether one code book has user to use, and the use of the number of users of this code book is how many.The estimated information of code book can be to follow-up
Decoding process is simplified, and the amount of calculation of decoding algorithm, but follow-up decoding side are reduced in the case where not reducing decoding performance
Case is not the core content of the present invention.The result that this method is estimated code book, can use same code to different users
This situation is detected that discovery code book as early as possible conflicts, and provides follow-up decoding foundation, but how to use the present invention's
Estimated result is not the core content of the present invention.
The alternative that SCMA technologies communicate as 5G, main application scenarios are mobile communication, and the present invention is follow-up
Example and illustrate be all on the premise of not particularly pointing out under the framework of LTE protocol carry out.Random in mobile communication connects
During entering, because base station is all unknown to UE situation, code book blind estimating method proposed by the present invention can be used to UE
Code book service condition estimated.To achieve these goals, the technical scheme is that：
1. in transmitting terminal, each UE is required for obtaining up synchronization according to the reference signal of down channel first, when having
When data will be sent, foregoing lead code is sent first fixing time/frequency source block as defined in agreement, oneself is then retransmited
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 row is according to estimating that the demand of accuracy rate is determined.
2. in receiving terminal, due to the characteristic of Stochastic accessing, receiver may receive multiple in specified time/frequency source block
UE sends the superposition of lead code, may be by MPA algorithms for each symbol received and the distribution situation of UE code books is entered
Row estimation, specific algorithm details will be described in detail later.
3. if the length of UE lead codes is a symbol, according to step 2, each symbol that receives can estimate one
The value of the confidence level of code book distribution situation, when the length of lead code is multiple symbols, can be folded multiple estimated results
Plus, to improve the degree of accuracy of code book estimation.
In the step 2, it is assumed that all UE to receiving terminal channel is all awgn channel, UE can be according to down channel
Reference signal adjusts transmission power, to ensure that the signal power for the signal arrival receiver that each UE is sent is roughly equal.
In the step 2, MPA algorithms according to actual UE deployment scenarios, can adjust the estimation range of code book.For example can be with
Limit each code book and at most have 2 UE selections, be at least no UE selections.
SCMA demodulation divide into two parts by SCMA code books 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 part of code book estimation, it is with reduction that estimation is individually carried out to code book service condition
The cost of spectrum efficiency obtains the simplification of decoding algorithm, it is possible to reduce to a certain extent due to caused by code book conflict
The bit error rate rises.
Compared with prior art, the positive effect of the present invention is：
1. propose a kind of new code book usable condition algorithm for estimating.
2. in the case where there is code book conflict, the user data for the part that do not conflict can be successfully decoded.
Brief description of the drawings
Fig. 1 is flow chart of the method for the present invention；
Fig. 2 is the factor graph for the SCMA schemes that present example is used；
Fig. 3 is the planisphere that present example is used；
(a) it is No. 0 planisphere, (b) is No. 1 planisphere, (c) is No. 2 planispheres；
Fig. 4 is the situation map of the different codebook selecting planispheres of present example；
Fig. 5 is the graph of a relation of preamble length and estimation accuracy rate.
Embodiment
The flow of the present invention to algorithm for estimating described in the invention as shown in figure 1, below in conjunction with an example, carry out
Clear, complete description.It is understood that described example is only a part of example of the present invention, rather than all
Embodiment.Based on the embodiment in the present invention, those skilled in the art are obtained under the premise of creative work is not made
Every other embodiment, belong to the scope of protection of the invention.
The preparatory condition of this example is as follows：
1.SCMA resource impact situation can be represented with usage factor figure.As shown in Fig. 2 one has 6 code books, take
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.Represent that this code book will take this resource block and send data comprising line between code book node and resource block.What Fig. 2 was represented
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 QPSK schemes to the lead code of transmission, and a symbol includes two binary digits, is not having
In the case of having code book conflict, according to the structure of factor graph, each resource block is up to the superposition of 3 QPSK symbols.
3. assume that be up to 2 users select same code book
In condition 1 described above, each SCMA decoding unit is 4 reception symbols, in situation about conflicting without code book
The transmission data of 6 users of lower at most correspondence.
In condition 2 described above, the planisphere that UE is used can carry out appropriate rotation so that be superimposed on resource block
The anglec of rotation of QPSK symbols is different.Fig. 3 is 3 planispheres used in this example, and No. 1 and No. 2 planispheres are respectively to 0
Number planisphere have 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 numerals indicate the planisphere sequence number that this code book is used on different resource block, and the numeral below resource node is
May planisphere sequence number used in three symbols of superposition on this node.The order and resource node and code of sequence number 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 arthmetic statements are as follows：
1.6 code book node 6 variable nodes of correspondence, 4 receive symbol 4 function nodes of correspondence.
2. initial confidence level vector assumes that all codebook selectings are all equiprobable, i.e., for each code book, all may be used
There can be three kinds of situations：There is no UE selections；There is 1 UE selection；There are 2 UE selections.The probability of initial situation each case is all 1/
3。
3. by function node the message of variable node such as following formula is sent to represent
Side bi-directional of the message transmitted in factor graph along factor graph, the content of transmission is the different values of variable node
Probability.In the case of in this example, this probability is the vector of a 3-dimensional
This variable node (i.e. corresponding code book) is represented respectively, and the probability of 2 UE selections is selected, there is 1 UE selection and had without UE.
Footnote k in formula represents k-th of variable node of correspondence, and footnote n represents n-th of function node.
Above in formulaRepresent for k-th of variable node Vk(i.e. k-th code book), in the l times iteration
When there is i UE to have selected the probability of this code book.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 except VkOther be connected to function node FnVariable node VjThe message sended overCalculate and.Computational methods are exactly the part on the right of formula equal sign, and it is calculated in n nodes according to complete general formula
The value of upper k variables is qkiWhen, other nodes all may situation probability superposition.WhereinRepresentative function section
Point FnOn the symbol R that receivesnThe data vector sent out with each case (is usedRepresent) between Euclidean distance.Multiplication
Part will be connected to this function node F to allnOther variable nodes VjTraveled through, and part of summing will be to all
The combination of the value condition (i.e. codebook selecting situation) of these nodes is traveled through.
If calculated in log-domain, and utilize Jacobian formula log (ea+eb) ≈ max (a, b), it is possible to upper
The simplified formula in face is：
4. by variable node the message of function node such as following formula is sent to represent
It is similar with step 3, the message of function node is sent to from variable nodeEqually it is taking for variable node
It is worth probability vector.It summarizes the message (i.e. probability) that other function nodes are sended 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 can be reduced to addition：
5. the content of iterative process repeat step 3 and step 4, the highest iterations until reaching agreement.
6. obtaining final probability value finally according to the message received on variable node, the maximum use of probable value is chosen
Amount is exported as the result of this algorithm.The result finally obtained is 6 n dimensional vector ns, and each element is represented in each code book
On the number of users that includes.
Fig. 5 is by emulating the performance curve obtained.The condition of emulation is the factor graph according to Fig. 1, it is assumed that have 7 users
Data are sent simultaneously, and one of code book there are 2 UE selections, and remaining code book all only has three in 1 UE selection, simulation result
Curve distribution represents the detection under the conditions of different signal to noise ratio when preamble length is 2,4 and 6 bit lengths
Error probability.The MPA algorithms used during emulation employ log-domain and calculated, and highest iterations is set as 5.Using pair
The error probability that number field method is obtained is slightly above the method in non-logarithmic domain, but simulation velocity increases significantly.
The up channel in a kind of SCMA systems provided by the present invention is described above by embodiment to use code book
The method of estimation of situation, it will be understood by those of skill in the art that in the scope for not departing from essence of the invention, can be to this hair
It is bright to make certain deformation or modification；Its preparation method is also not necessarily limited to the content disclosed in embodiment.
Claims (8)
1. a kind of SCMA code books blind estimating method, its step is：
1) usage factor figure represents SCMA resource impact situation, wherein, it regard each code book as a variable node, each resource
Block represents that the code book will take connected resource block and send between code book and resource block as a function node comprising line
Data；For each code book, one initial confidence level vector is set；
2) that one is sent before time/frequency source block is fixed as defined in LTE protocol sending the data of oneself, first is leading for user equipment (UE)
Code information；
3) preamble information that receiving terminal is received according to specifying in time/frequency source block and the factor graph are carried out to code book service condition
Estimation, estimates whether each code book has user to use and using the number of users of the code book.
2. the method as described in claim 1, it is characterised in that step 3) be using the implementation method of MPA algorithms：
21) calculate and the message of function node is sent to by variable node, and be sent to by variable node the message of function node；
22) repeat step 21) until reaching the highest iterations of agreement；
23) final probability value is obtained according to the message received on variable node, the maximum number of users of probable value is chosen and makees
For the estimated result of code book service condition.
3. the method described in claim 2, it is characterised in that utilize formula
Calculate the message that function node is sent to by variable nodeWherein,From other during for the l times iteration
It is connected to function node FnVariable node VjIt is sent to function node FnMessage,Representative function node FnOn connect
The symbol R receivednWith the data vector estimated by each caseBetween Euclidean distance；FnTo be sent to variable node
VkN-th of function node of message.
4. method as claimed in claim 3, it is characterised in that utilize formula Abbreviation is carried out, the formula obtained after abbreviation is utilized
Calculate the message that function node is sent to by variable node.
5. method as claimed in claim 3, it is characterised in that utilize formulaCalculate by becoming
Amount node is sent to the message of function nodeWherein,During for the l times iteration change is connected to from other
Measure node VkFunction node FjIt is sent to variable node VkMessage.
6. method as claimed in claim 5, it is characterised in that utilize formulaTo formulaAbbreviation is carried out, the formula obtained after abbreviation is utilized
Calculate the message that function node is sent to by variable node.
7. the method as described in claim 1 to 6 is any, it is characterised in that the sequence length of the preamble information is most short to be
The length of one symbol.
8. method as claimed in claim 7, it is characterised in that be modulated using QPSK schemes to the lead code of transmission, often
One symbol includes two binary digits.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| 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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| Application Number | Priority Date | Filing Date | Title |
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| CN201710137731.4A CN107018114B (en) | 2017-03-09 | 2017-03-09 | A kind of SCMA code book blind estimating method |
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| CN107018114A true CN107018114A (en) | 2017-08-04 |
| CN107018114B CN107018114B (en) | 2019-09-06 |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2018161654A1 (en) * | 2017-03-09 | 2018-09-13 | 北京大学 | Scma codebook blind estimation method |
| CN112565153A (en) * | 2020-11-30 | 2021-03-26 | 沈阳理工大学 | SCMA multi-user codebook design method based on rotation mapping |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20160254937A1 (en) * | 2015-02-27 | 2016-09-01 | Huawei Technologies Co., Ltd | Low complexity scma/lds detection systems and methods |
| CN106330207A (en) * | 2016-08-22 | 2017-01-11 | 电子科技大学 | Joint detection and decoding algorithm based on Turbo-SCMA system |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| 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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2017
- 2017-03-09 CN CN201710137731.4A patent/CN107018114B/en not_active Expired - Fee Related
- 2017-12-01 WO PCT/CN2017/114303 patent/WO2018161654A1/en active Application Filing
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20160254937A1 (en) * | 2015-02-27 | 2016-09-01 | Huawei Technologies Co., Ltd | Low complexity scma/lds detection systems and methods |
| CN106330207A (en) * | 2016-08-22 | 2017-01-11 | 电子科技大学 | Joint detection and decoding algorithm based on Turbo-SCMA system |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2018161654A1 (en) * | 2017-03-09 | 2018-09-13 | 北京大学 | Scma codebook blind estimation method |
| CN112565153A (en) * | 2020-11-30 | 2021-03-26 | 沈阳理工大学 | SCMA multi-user codebook design method based on rotation mapping |
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| Publication number | Publication date |
|---|---|
| WO2018161654A1 (en) | 2018-09-13 |
| CN107018114B (en) | 2019-09-06 |
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Granted publication date: 20190906 |