CN105939541B - The equivalent subcarrier distribution system and method for multi-user's time frequency coding diversity MT-CDMA - Google Patents

The equivalent subcarrier distribution system and method for multi-user's time frequency coding diversity MT-CDMA Download PDF

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CN105939541B
CN105939541B CN201610256975.XA CN201610256975A CN105939541B CN 105939541 B CN105939541 B CN 105939541B CN 201610256975 A CN201610256975 A CN 201610256975A CN 105939541 B CN105939541 B CN 105939541B
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user
subcarrier
equivalent
sub
equivalent subcarrier
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CN105939541A (en
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张晓光
王艳芬
孙彦景
王刚
翟文艳
霍羽
郭颖
李松
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China University of Mining and Technology CUMT
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/04—Wireless resource allocation
    • H04W72/044—Wireless resource allocation based on the type of the allocated resource
    • H04W72/0453—Resources in frequency domain, e.g. a carrier in FDMA
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2626—Arrangements specific to the transmitter only
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2626—Arrangements specific to the transmitter only
    • H04L27/2627—Modulators
    • H04L27/2628—Inverse Fourier transform modulators, e.g. inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators
    • H04L27/263—Inverse Fourier transform modulators, e.g. inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators modification of IFFT/IDFT modulator for performance improvement
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2649—Demodulators
    • H04L27/265—Fourier transform demodulators, e.g. fast Fourier transform [FFT] or discrete Fourier transform [DFT] demodulators
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/12—Wireless traffic scheduling
    • H04W72/121—Wireless traffic scheduling for groups of terminals or users

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Discrete Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Mathematical Physics (AREA)
  • Radio Transmission System (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

The invention discloses the equivalent subcarrier distribution system of multi-user's time frequency coding diversity MT-CDMA a kind of and methods.The system and method include: to obtain yield value of each user on each equivalent subcarrier in time frequency coding diversity MT-CDMA system in the channel yield value on each subcarrier according to each user；Each user is evaluated according to user data rate threshold value to need that several equivalent subcarriers is selected to transmit；Using block of sub-carriers diversity mode at equal intervals, there is similar transmission characteristic to ensure the subcarrier in each piecemeal on the whole；Regard each subcarrier piecemeal as an equivalent subcarrier, carries out equivalent subcarrier distribution according to Principle of infusing water.Advantage: this method considers the characteristics of each user rate differs greatly, and can satisfy the demand of multi-user's time frequency coding diversity MT-CDMA system different rates；The compatibility with existing multi-user MT-CDMA adaptive population system is maintained, the transformation of system can be readily achieved.

Description

The equivalent subcarrier distribution system and method for multi-user's time frequency coding diversity MT-CDMA
Technical field
The present invention relates to a kind of equivalent subcarrier distribution system and method, especially a kind of multi-user's time frequency coding diversity The equivalent subcarrier distribution system and method for MT-CDMA.
Background technique
In future mobile communication system, user is more and more for the business demand of high speed, the transmission of the data of high quality, The service how to provide high quality on limited radio frequency resources for more users just becomes more and more important.Patent ZL201310187393.7 provides a kind of time frequency coding diversity MT-CDMA system, which is not only able to utilize time frequency coding Diversity, and while not reducing system single user's data rate, more numbers of users can be accommodated, are before one kind has The solution on way.It, can be according to every for multi-user's time frequency coding diversity MT-CDMA system but in wireless channel The transmission rate of a user distributes one or more sub-block (equivalent subcarrier) to user, if be only randomly assigned, although Complexity is lower, but will lead to and some do not have enough power to carry the equivalent sub- load of any information bit in deep fades Wave, their user cannot be used by being assigned to those with very high probability, and the fading parameter of different user is in system It is completely self-contained, in the known integrated circuit it is a fact that, for the same transmitter, different user fading status experienced is different, if to The equivalent subcarrier that family uses carries out reasonable distribution, and transmission performance can be greatly improved.But consider different user to information source Rate requirement differs greatly, and different monitoring signal data rates needs several hundred bit/s to differ to tens Kbit/s, number words Sound signal data rate needs tens Kbit/s, and video signal data rate needs several hundred Kbit/s or a few Mbit/s or tens Mbit/s etc., therefore make for this time frequency coding diversity MT-CDMA system that patent ZL201310187393.7 is provided Algorithm is randomly assigned with traditional equivalent subcarrier, it is evident that has been unable to meet demand of the different user to source rate.
Summary of the invention
To overcome the shortcomings of that system above, the present invention provide the equivalent son of multi-user's time frequency coding diversity MT-CDMA a kind of Carrier assignment system and method.One or more equivalent sub- load can be distributed to user according to the transmission rate of each user Wave meets the needs of different user is to source rate, improves transmission performance.
The technical problems to be solved by the invention include: the equivalent subcarrier point of multi-user's time frequency coding diversity MT-CDMA Match system and method；
Equivalent subcarrier distribution system: including transmitter and receiver system；The transmitter terminal: multi-user data First to enter equivalent subcarrier self-adjusted block module, after converting by equivalent subcarrier gains algorithm, user can be connect The serial number for the equivalent subcarrier received feeds back to transmitting terminal, and transmitting terminal carries out equivalent subcarrier according to the information and user rate of feedback Distribution determines to distribute suitable one or several equivalent subcarriers to each user；The user data of each sub-block (frame) later Bit is of a size of NcThe Walsh+PN spread spectrum code character matrix time-frequency two-dimensional of × K extends, N in formulacFor the subcarrier in each piecemeal Number, K is spread code length, then by IFFT, parallel-serial conversion plus cyclic prefix, is finally launched from antenna；When to certain For a user, the performance of all equivalent subcarriers cannot all receive, then the request of the user is rejected；
The receiver end: after reception signal, it is necessary first to remove cyclic prefix, carry out serioparallel exchange and FFT becomes After alternatively, spread spectrum code character sequence is adjusted into de-correlation block and carries out two dimension despreading detection, is distinguished in different low correlators Different user on block, transmitting terminal pilot signal transmitted will be estimated on all subcarriers so that user carries out channel in practical communication Meter carries out adaptive demodulation to the user for occupying multiple equivalent subcarriers, finally extracts the data information output of each user.
Equivalent sub-carrier wave distribution method:
According to total carrier number and total number of users, and spread spectrum code length, the frame structure of time-frequency two-dimensional extension is determined, it is also just true in this way Determined the sub-carrier number in each equivalent block of sub-carriers, then using block of sub-carriers diversity mode at equal intervals, generate user etc. Subcarrier gains are imitated, the serial number that user will be appreciated by equivalent subcarrier feeds back to transmitting terminal, and transmitting terminal is according to the letter of feedback Breath carries out equivalent subcarrier distribution；Evaluated according to data rate threshold value each user need to select several equivalent subcarriers come It is transmitted；Finally equivalent subcarrier distribution, for some user, all equivalent subcarriers are carried out according to Principle of infusing water Performance cannot all receive, then the request of the user is rejected.
The block of sub-carriers diversity mode at equal intervals: consider several subcarriers adjacent, within correlation bandwidth With very high correlation and transmission characteristic, they are divided into different piecemeals, it is ensured that the son in each piecemeal carries Wave has similar transmission characteristic on the whole, according to optimum allocation as a result, different piecemeals will have approximately equal bit total Number, such result is by close to optimal allocation result, and progress is at equal intervals after block of sub-carriers diversity, by each subcarrier piecemeal Regard an equivalent subcarrier as to carry out adaptive equivalent subcarrier distribution, to improve the performance of system.
Each user data rate requires may be different, therefore each user adaptively occupies one or more equivalent sons Carrier wave can push away to obtain each IFFT/ by the sub-carrier number of user's transmission rate, the modulation system of use and each equivalent subcarrier FFT period (Ts) in the data volume that needs to transmit.
The equivalent subcarrier gains of the generation user: transmitting terminal will lead to first when carrying out the distribution of equivalent subcarrier Cross the gain information composition U × N matrix H of U user that pilot signal is estimated on each subcarrier
Wherein, N indicates total number of sub-carriers, hu,nGain of u-th of user on n-th of subcarrier is indicated, since time-frequency is compiled Code diversity MT-CDMA system is divided into B piecemeal, and the sub-carrier number on each piecemeal is Nc=N/B, therefore each user exists here Gain information on each equivalent subcarrier can be obtained by the gain information on each subcarrier in each piecemeal.Overloading The modulation system of wavelength-division group can be determined by the average value of all subcarrier gains in each grouping, because of time frequency coding diversity MT-CDMA system and multicarrier grouping system have similarity, so calculating equivalent subcarrier in this reference method of arithmetical average Gain.Arithmetic mean of instantaneous value scheme (AM, Arithmetic Mean gain) takes all subcarrier gains in subcarrier piecemeal Equivalent gain of the average value as the piecemeal, i.e.,
Wherein, b=1,2 ... B, n=1,2 ... Nc, B is piecemeal sum, NcFor the sub-carrier number in each piecemeal, B=here Nc.It determines that user selects the number of equivalent subcarrier: by matrix H, calculating each user on each equivalent subcarrier according to formula (2) Gain information, form U × B matrix G
Wherein: U indicates total number of users,hthIt is the channel gain amplitude door that can be easily accepted by a user Limit value.
It is possible different to consider that each user data rate requires, therefore each user can should adaptively occupy 1 Or Nu(Nu≤ B) a equivalent subcarrier, by the subcarrier of user's transmission rate, the modulation system of use and each equivalent subcarrier Number can push away to obtain each IFFT/FFT period (Ts) in the data volume that needs to transmit, it is assumed that number of modulation levels M, each equivalent sub- load Wave has subcarrier NcA, it is R that some user, which requires transmission rate,u(bit/s), when
At this point, this transmission rate is RuUser should occupy NuA equivalent subcarrier.
The equivalent subcarrier of the Principle of infusing water distributes: generating U × B rank matrix F by G
Wherein, each element of matrix F is
Wherein fu,bThe weight of u-th of user occupancy, b-th of equivalent subcarrier is described, if fu,b=1/m is indicated u-th User has m equivalent subcarriers that can distribute, and b-th of equivalent subcarrier is only one of them.
The sum of each column element of matrix F is S={ s1,s2,…sB, i.e.,
sbThe sum of the weight of b-th of equivalent subcarrier of all user occupancies is described, in order to reduce same equivalent subcarrier Interference between the user of upper distribution, here according to Principle of infusing water, by constantly adjusting each equivalent subcarrier of user occupancy Weight makes sb(b=1,2 ... B) constantly level off to its mean value, that is, meet
min{max(sb)-min(sb)} (8)
Introduce vector C={ c1,c2…cB, cbWhether adjustable it is used as b-th of equivalent subcarrier in assigning process It is beautiful, be defined as
The detailed process of the equivalent Subcarrier Allocation Algorithm are as follows:
(1) the fading information H according to user on each subcarrier initializes matrix F, vector S and C；
(2) element s is found out in vector Sb, meet sb=min { sb|sb∈S∩cb≠ 0 }, b=1,2 ... B；
(3) f is found out in the b column of matrix F firstu,b=max { fu,b|fu,b≠0,fu,b≠ 1 }, u=1,2 ... U；So After make fu,b=1；IfGo to (4)；IfGo to (5).
(4) it finds out Indicate fu,i≠0,fu,i≠ 1 equivalent subcarrier i collection It closes, makes fu,i=1；
1. if still had after iteration B-1 times hereinIllustrate that user is rejected, goes to (5)；
2. ifBack to (4)；
3. ifIt enables on u-th of userFu,i=0, go to (5).
By step (3)~(4), matrix F is updated.
(5) vector S and C are recalculated according still further to formula (7) and (9).If C ≠ 0, (2) step is returned to, if C=0, knot Beam.
After algorithm operation is completed, the u row of matrix F has Nu(Nu≤ B) a element value is 1, other is 0, is shown u-th User is assigned to NuOn a equivalent subcarrier, equivalent sub- load that the position of 1 place rectangular array of element, as user are assigned Wave, sbIndicate the number of users of b-th of equivalent subcarrier of occupancy.
The utility model has the advantages that due to using above-mentioned distribution system and method, it is first determined each equivalent subcarrier (sub-block) In sub-carrier number Nc；Subcarrier piecemeal is carried out using block of sub-carriers diversity mode at equal intervals, is conducive to allocation result close to most It is excellent；Generate user equivalent subcarrier gains after, evaluated according to data rate threshold value each user need to select it is several Equivalent subcarrier is transmitted；Reasonable distribution finally has been carried out to equivalent subcarrier according to Principle of infusing water, has realized this hair Bright purpose.
Advantage: the equivalent subcarrier distribution system and method consider the characteristics of each user rate differs greatly, can Meets the needs of multi-user's time frequency coding diversity MT-CDMA system different rates；It maintains with existing multi-user MT-CDMA certainly The compatibility for adapting to resource allocation system, can be readily achieved the transformation of system.It is not only able to the transmission according to each user Rate distributes one or more equivalent subcarrier to user, and can satisfy demand of the different user to source rate, together Shi Gaishan transmission performance.
Detailed description of the invention
Fig. 1 show multi-user's time frequency coding diversity MT-CDMA system self-adaption resource allocation system block diagram.
The equivalent subcarrier that Fig. 2 is multi-user's time frequency coding diversity MT-CDMA distributes transmitter and receiver structure chart.
Fig. 3 a is all subchannels of present invention block of sub-carriers diversity mode figure at equal intervals.
Fig. 3 b is present invention interval subchannel piecemeal block of sub-carriers diversity mode figure at equal intervals.
Fig. 4 is that the equivalent subcarrier of multi-user is randomly assigned to compare with the bit error rate performance of equivalent subcarrier self-adjusted block Figure.
Specific embodiment
The equivalent subcarrier distribution system and method for multi-user's time frequency coding diversity MT-CDMA；
The equivalent subcarrier distribution system: including transmitter and receiver system；The transmitter terminal: multi-purpose User data will first enter equivalent subcarrier self-adjusted block module, and after being converted by equivalent subcarrier gains algorithm, user will The serial number of the equivalent subcarrier of acceptable feeds back to transmitting terminal, and transmitting terminal carries out equivalent according to the information and user rate of feedback Subcarrier distribution determines to distribute suitable one or several equivalent subcarriers to each user；The use of each sub-block (frame) later User data bit is of a size of NcThe Walsh+PN spread spectrum code character matrix time-frequency two-dimensional extension of × K, then turns by IFFT and string It changes, add cyclic prefix, finally launch from antenna；For some user, the performance of all equivalent subcarriers is not It can receive, then the request of the user is rejected；
The receiver end: after reception signal, it is necessary first to remove cyclic prefix, carry out serioparallel exchange and FFT becomes After alternatively, spread spectrum code character sequence is adjusted into de-correlation block and carries out two dimension despreading detection, is distinguished in different low correlators Different user on block, transmitting terminal pilot signal transmitted will be estimated on all subcarriers so that user carries out channel in practical communication Meter carries out adaptive demodulation to the user for occupying multiple equivalent subcarriers, finally extracts the data information output of each user.
Equivalent sub-carrier wave distribution method:
According to total carrier number and total number of users, and spread spectrum code length, the frame structure of time-frequency two-dimensional extension is determined, it is also just true in this way Determined the sub-carrier number in each equivalent block of sub-carriers, then using block of sub-carriers diversity mode at equal intervals, generate user etc. Subcarrier gains are imitated, the serial number that user will be appreciated by equivalent subcarrier feeds back to transmitting terminal, and transmitting terminal is according to the letter of feedback Breath carries out equivalent subcarrier distribution；
Each user is evaluated according to data rate threshold value to need that several equivalent subcarriers is selected to transmit；Finally Equivalent subcarrier distribution is carried out according to Principle of infusing water, for some user, the performance of all equivalent subcarriers cannot all be connect By then the request of the user is rejected.
For analysis system model, definition available subcarrier number is N, and total number of users of system is U, by all subcarriers and User is divided into B sub-block, and N/B=Nc, NcFor integer, the number of each sub-block sub-carriers, the maximum that system can accommodate are indicated Number of users is U=BK, and K is spread code length, and the maximum number of user that each sub-block can accommodate is U/B=K, and defines one group of ruler Very little is NcThe Walsh+PN spreading code matrix w of × KkAs each sub-block spreading code, each sub-block constitutes an equivalent sub- load Wave.
According to total carrier number N and total number of users U, and spread spectrum code length K, the frame structure of time-frequency two-dimensional extension is determined, determine every Sub-carrier number N in a equivalent subcarrier (sub-block)c；Then consider the mode of subcarrier piecemeal, principle is desirable to each equivalent The yield value of subcarrier is conducive to allocation result close to optimal, presses block of sub-carriers diversity mode at equal intervals here closer to better； Next, generate user equivalent subcarrier gains, need the channel yield value according to each user on each subcarrier come Obtain yield value of each user on each equivalent subcarrier in time frequency coding diversity MT-CDMA system；Next, according to Data rate threshold value to evaluate each user needs that several equivalent subcarriers is selected to transmit；Finally according to Principle of infusing water Carry out equivalent subcarrier distribution.
The block of sub-carriers diversity mode at equal intervals considers several subcarriers adjacent, within correlation bandwidth With very high correlation and transmission characteristic, they are divided into different piecemeals, it is ensured that the son in each piecemeal carries Wave has similar transmission characteristic on the whole, according to optimum allocation as a result, different piecemeals will have approximately equal bit total Number, such result is by close to optimal allocation result, and progress is at equal intervals after block of sub-carriers diversity, by each subcarrier piecemeal Regard an equivalent subcarrier as to carry out adaptive equivalent subcarrier distribution, to improve the performance of system.
Each user data rate requires may be different, therefore each user adaptively occupies one or more equivalent sons Carrier wave can push away to obtain each IFFT/ by the sub-carrier number of user's transmission rate, the modulation system of use and each equivalent subcarrier FFT period (Ts) in the data volume that needs to transmit.
The equivalent subcarrier gains of the generation user: transmitting terminal will lead to first when carrying out the distribution of equivalent subcarrier Cross the gain information composition U × N matrix H of U user that pilot signal is estimated on each subcarrier
Wherein hu,nGain of u-th of user on n-th of subcarrier is indicated, due to time frequency coding diversity MT-CDMA system It is divided into B piecemeal, the sub-carrier number on each piecemeal is Nc=N/B, thus here each user on each equivalent subcarrier Gain information can be obtained by the gain information on each subcarrier in each piecemeal.The modulation system of multicarrier grouping It can be determined by the average value of all subcarrier gains in each grouping, because of time frequency coding diversity MT-CDMA system and overloading Wave grouping system has similarity, so calculating equivalent subcarrier gains in this reference method of arithmetical average.Arithmetic mean of instantaneous value side Case (AM, Arithmetic Mean gain) is to take the average value of all subcarrier gains in subcarrier piecemeal as the piecemeal Equivalent gain, i.e.,
Wherein, b=1,2 ... B, n=1,2 ... Nc, B is piecemeal sum, NcFor the sub-carrier number in each piecemeal, B=here Nc.It determines that user selects the number of equivalent subcarrier: by matrix H, calculating each user on each equivalent subcarrier according to formula (2) Gain information, form U × B matrix G
Wherein:hthIt is the channel gain amplitude threshold that can be easily accepted by a user.
It is possible different to consider that each user data rate requires, therefore each user can should adaptively occupy 1 Or Nu(Nu≤ B) a equivalent subcarrier, by the subcarrier of user's transmission rate, the modulation system of use and each equivalent subcarrier Number can push away to obtain each IFFT/FFT period (Ts) in the data volume that needs to transmit, it is assumed that number of modulation levels M, each equivalent sub- load Wave has subcarrier NcA, it is R that some user, which requires transmission rate,u(bit/s), when
At this point, this transmission rate is RuUser should occupy NuA equivalent subcarrier.
The equivalent subcarrier of the Principle of infusing water distributes: generating U × B rank matrix F by G
Wherein, each element of matrix F is
Wherein fu,bThe weight of u-th of user occupancy, b-th of equivalent subcarrier is described, if fu,b=1/m is indicated u-th User has m equivalent subcarriers that can distribute, and b-th of equivalent subcarrier is only one of them.
The sum of each column element of matrix F is S={ s1,s2,…sB, i.e.,
sbThe sum of the weight of b-th of equivalent subcarrier of all user occupancies is described, in order to reduce same equivalent subcarrier Interference between the user of upper distribution, here according to Principle of infusing water, by constantly adjusting each equivalent subcarrier of user occupancy Weight makes sb(b=1,2 ... B) constantly level off to its mean value, that is, meet
min{max(sb)-min(sb)} (8)
Introduce vector C={ c1,c2…cB, cbWhether adjustable it is used as b-th of equivalent subcarrier in assigning process It is beautiful, be defined as
The detailed process of the equivalent Subcarrier Allocation Algorithm are as follows:
(1) the fading information H according to user on each subcarrier initializes matrix F, vector S and C；
(2) element s is found out in vector Sb, meet sb=min { sb|sb∈S∩cb≠ 0 }, b=1,2 ... B；
(3) f is found out in the b column of matrix F firstu,b=max { fu,b|fu,b≠0,fu,b≠ 1 }, u=1,2 ... U；So After make fu,b=1；IfGo to (4)；IfGo to (5).
(4) it finds out Indicate fu,i≠0,fu,i≠ 1 equivalent subcarrier i collection It closes, makes fu,i=1；
1. if still had after iteration B-1 times hereinIllustrate that user is rejected, goes to (5)；
2. ifBack to (4)；
3. ifIt enables on u-th of userFu,i=0, go to (5).
By step (3)~(4), matrix F is updated.
(5) vector S and C are recalculated according still further to formula (7) and (9).If C ≠ 0, (2) step is returned to, if C=0, knot Beam；
After algorithm operation is completed, the u row of matrix F has Nu(Nu≤ B) a element value is 1, other is 0, is shown u-th User is assigned to NuOn a equivalent subcarrier, equivalent sub- load that the position of 1 place rectangular array of element, as user are assigned Wave, sbIndicate the number of users of b-th of equivalent subcarrier of occupancy.
Fig. 1 show multi-user's time frequency coding diversity MT-CDMA adaptive population system block diagram.Transmitter terminal is more User data will first enter equivalent subcarrier self-adjusted block module, according to the result and user rate of the estimation of each subscriber channel Suitable one or several equivalent subcarriers are distributed to each user, then, for needing the user of multiple equivalent subcarriers, root According to the channel gain situation for each equivalent subcarrier that it is occupied, single user adaptive bit and power allocation is carried out, i.e., adaptively Modulation, modulated data carry out time-frequency two-dimensional extension, low correlation module, IFFT transformation, parallel-serial conversion plus CP as unit of frame Enter mine Dense Multipath Channels afterwards；After receiving end receives signal, CP, serioparallel exchange, FFT transform and decorrelation are first passed around Module, then adjustment spread spectrum code character sequence carries out two dimension despreading detection, carries out to the user for occupying multiple equivalent subcarriers adaptive It should demodulate, finally extract the data information output of each user.
The equivalent subcarrier that Fig. 2 is multi-user's time frequency coding diversity MT-CDMA distributes transmitter and receiver structure.It is sending out Penetrate generator terminal: user estimates the channel gain of all subcarriers, and after being converted by equivalent subcarrier gains algorithm, user can be with The serial number of the equivalent subcarrier received feeds back to transmitting terminal, and transmitting terminal carries out equivalent subcarrier distribution according to the information of feedback, it The bits of user data of each sub-block (frame) is of a size of N afterwardscThe Walsh+PN spread spectrum code character matrix time-frequency two-dimensional extension of × K, Then by IFFT, parallel-serial conversion plus CP, finally launch from antenna, if for some user, all equivalent sons The performance of carrier wave cannot all receive, then the request of the user is rejected；In receiver end, remove CP, serioparallel exchange, FFT it Afterwards, two dimension despreading detection is carried out, the different user in different low related sub-blocks is distinguished, transmitting terminal will be in practical communication Pilot signal transmitted is on all subcarriers so as to user's progress channel estimation.
Fig. 3 is block of sub-carriers diversity mode at equal intervals.By time frequency coding diversity MT-CDMA system model it is found that using etc. It is spaced block of sub-carriers diversity mode, is because several subcarriers adjacent, within correlation bandwidth have very high correlation Property and transmission characteristic, they are divided into different piecemeals, it is ensured that the subcarrier in each piecemeal has phase on the whole Close transmission characteristic, according to optimum allocation as a result, different piecemeals will have approximately equal total number of bits, such result will Close to optimal allocation result, progress is at equal intervals after block of sub-carriers diversity, so that it may regard each subcarrier piecemeal as one Equivalent subcarrier distributes to carry out adaptive equivalent subcarrier, to improve the performance of system.
Fig. 4 is that the equivalent subcarrier of multi-user is randomly assigned to compare with the bit error rate performance of equivalent subcarrier self-adjusted block. As seen from the figure, the bit error rate performance of equivalent subcarrier self-adjusted block system proposed by the present invention is better than being randomly assigned system, when Average error rate is 2 × 10-5When, the present invention can provide the snr gains of about 6.5dB.
Emulation experiment
Simulating, verifying has been carried out to method of the invention below.
(1) number of users maximum difference counts on single equivalent subcarrier
The present invention makes s by constantly adjusting the weight of each equivalent subcarrier of user occupancyb(b=1,2 ... B) constantly Leveling off to its mean value (meets min { max (sb)-min(sb)), to reduce between the user distributed on same equivalent subcarrier Interference.Defined variable D1:
D1After indicating that equivalent subcarrier is assigned every time, possessing the most sum of number of users, to possess number of users least equivalent Number of users difference between subcarrier (wherein this numerical value is smaller, and co-channel interference is smaller).At number of users U=40,80,100, often A user selects an equivalent subcarrier, and equivalent sub-carrier number B=8, the channel gain amplitude threshold that can be easily accepted by a user is still It is so hth=1 and hth=1.2,1000 emulation statistics is carried out, table 1 is obtained:
When each user of table 1 selects an equivalent subcarrier, D11000 average statisticals
The data result of table 1 shows when each user distribution one for multi-user's time frequency coding diversity MT-CDMA system It is either single with can have increase tendency by the increase of the received channel gain amplitude threshold of user when equivalent subcarrier Number of users difference or difference variation tendency on equivalent subcarrier prove that co-channel interference of the present invention is smaller.
When number of users is U=40,80,100, it is assumed that wherein the 30th to the 40th needs 3 block of sub-carriers transmission, etc. Sub-carrier number B=8 is imitated, the channel gain amplitude threshold that can be easily accepted by a user still is hth=1 and hth=1.2, it carries out 1000 times Emulation statistics, obtains table 2:
When 2 certain user of table selects multiple equivalent subcarriers, D11000 average statisticals
The data result for comparing Tables 1 and 2 shows each user when multi-user's time frequency coding diversity MT-CDMA system When subcarrier equivalent according to rate requirement distribution more than one, the number of users difference on single equivalent subcarrier is than each user One equivalent subcarrier situation of distribution is increased slightly, but difference still has the characteristics that disperse co-channel interference less than 2.
(2) probability statistics that user service cannot be satisfied
{ h in the present inventionu,b, b=1,2 ... B }, b-th of equivalent subcarrier is not received general for u-th of user RateFor
The probability that then u-th of user service cannot be satisfied is approximately
If there is U user requires to service simultaneously, UP (P=P is averagely had1) a user cannot be satisfied.The present invention In equivalent sub-carrier number B=8, number of users U=40,80 and 100, wherein the 30th to the 40th needs the transmission of 3 block of sub-carriers, The channel gain amplitude threshold h that can be easily accepted by a userthWhen=1,1000 emulation statistics is carried out, table 3 is obtained:
The number of users that 3 service request of table cannot be satisfied
The theoretical value of system and simulation value are almost the same it can be seen from 3 data of table, the service request of most users Be it is satisfiable, the probability that user is refused is about 0.55%.The present invention is according to the different rates demand of different user, each User needs the equivalent sub-carrier number N occupiedu(Nu>=1) different, the service of u-th of user is only in NuOn a equivalent subcarrier Channel gain be greater than threshold value can just be satisfied.
(3) bit error rate performance
The equivalent sub-carrier wave distribution method of multi-user's time frequency coding diversity MT-CDMA system of the present invention, is not simple Each user is evenly distributed on each equivalent subcarrier by ground, but allows each user to only use according to Principle of infusing water and come to it Say the good equivalent subcarrier of gain.
It is extended to 100ms with maximum delay, multipath number is Lp=5 analog wireless channels, and assume each user each Gain h on subcarrieru,n, n=1, the mutually indepedent Rayleigh distributed of 2 ... N.The total sub-carrier number of system is N=64, equivalent son Carrier number is B=8, bandwidth 20MHz, carrier frequency 2.4GHz, modulation system QPSK, a length of 120 (Walsh of spreading code 15), number of users U=40 can be received wherein the 30th to the 40th needs 3 block of sub-carriers transmission by user by long 8, PN long Channel gain amplitude threshold hth=1, using Matlab software carry out system emulation, more equivalent subcarrier be randomly assigned and The bit error rate performance of equivalent subcarrier self-adjusted block.
The equivalent subcarrier of multi-user is randomly assigned to compare with the bit error rate performance of equivalent subcarrier self-adjusted block such as Fig. 4 institute Show, as seen from the figure, the bit error rate performance of equivalent subcarrier self-adjusted block system proposed by the present invention is better than being randomly assigned system, When average error rate is 2 × 10-5When, the present invention can provide the snr gains of about 6.5dB.

Claims (3)

1. a kind of equivalent sub-carrier wave distribution method of multi-user's time frequency coding diversity MT-CDMA system, the MT-CDMA system Including transmitter terminal and receiver end；
The transmitter terminal: multi-user data will first enter equivalent subcarrier self-adjusted block module, pass through equivalent subcarrier After gain algorithm conversion, the serial number that user will be appreciated by equivalent subcarrier feeds back to transmitting terminal, and transmitting terminal is according to feedback Information and user rate carry out equivalent subcarrier distribution, determine to distribute suitable one or several equivalent sub- loads to each user Wave；The bits of user data of each frame sub-block is of a size of N latercThe Walsh+PN spread spectrum code character matrix time-frequency two-dimensional of × K expands Exhibition is finally launched from antenna then by IFFT, parallel-serial conversion plus cyclic prefix；For some user, institute Having the performance of equivalent subcarrier cannot all receive, then the request of the user is rejected；
The receiver end: after receiving signal, it is necessary first to remove cyclic prefix, carry out serioparallel exchange and FFT transform it Afterwards, spread spectrum code character sequence is adjusted into de-correlation block and carry out two dimension despreading detection, distinguish in different low related sub-blocks Different user, transmitting terminal will carry out channel estimation on all subcarriers so as to user by pilot signal transmitted in practical communication, Adaptive demodulation is carried out to the user for occupying multiple equivalent subcarriers, finally extracts the data information output of each user；
Equivalent sub-carrier wave distribution method: according to total carrier number and total number of users, and spread spectrum code length, the frame of time-frequency two-dimensional extension is determined Structure has also determined that the sub-carrier number in each equivalent block of sub-carriers in this way, then using block of sub-carriers diversity side at equal intervals Formula generates the equivalent subcarrier gains of user, and the serial number that user will be appreciated by equivalent subcarrier feeds back to transmitting terminal, sends End carries out equivalent subcarrier distribution according to the information of feedback；Evaluated according to data rate threshold value each user need to select it is several A equivalent subcarrier is transmitted；Finally equivalent subcarrier distribution, for some user, institute are carried out according to Principle of infusing water Having the performance of equivalent subcarrier cannot all receive, then the request of the user is rejected；
The block of sub-carriers diversity mode at equal intervals: consider that several subcarriers adjacent, within correlation bandwidth have They are divided into different piecemeals by very high correlation and transmission characteristic, it is ensured that the subcarrier in each piecemeal is whole There is similar transmission characteristic on body, according to optimum allocation as a result, different piecemeals will have approximately equal total number of bits, this The result of sample will be regarded each subcarrier piecemeal as after carrying out block of sub-carriers diversity at equal intervals close to optimal allocation result One equivalent subcarrier distributes to carry out adaptive equivalent subcarrier, to improve the performance of system；
Each user data rate requires may be different, therefore each user adaptively occupies one or more equivalent subcarriers, It can be pushed away to obtain each IFFT/FFT weeks by the sub-carrier number of user's transmission rate, the modulation system of use and each equivalent subcarrier Phase TsThe interior data volume for needing to transmit；
It is characterized in that: the equivalent subcarrier gains of the generation user: transmitting terminal is when carrying out the distribution of equivalent subcarrier, first Gain information of the U user estimated by pilot signal on each subcarrier is formed into U × N matrix H
Wherein, N indicates total number of sub-carriers, hu,nGain of u-th of user on n-th of subcarrier is indicated, due to time frequency coding point Collection MT-CDMA system is divided into B piecemeal, and the sub-carrier number on each piecemeal is Nc=N/B, thus here each user each Gain information on equivalent subcarrier can be obtained by the gain information on each subcarrier in each piecemeal；Overloading wavelength-division The modulation system of group can be determined by the average value of all subcarrier gains in each grouping, because of time frequency coding diversity MT- Cdma system and multicarrier grouping system have similarity, increase so calculating equivalent subcarrier in this reference method of arithmetical average Benefit；Arithmetic mean of instantaneous value scheme is to take the average value of all subcarrier gains in subcarrier piecemeal as the equivalent gain of the piecemeal, I.e.
Wherein, U indicates total number of users, b=1,2 ... B, n=1,2 ... Nc, B is piecemeal sum, NcFor the subcarrier in each piecemeal It counts, here B=Nc；
It determines that user selects the number of equivalent subcarrier: by matrix H, calculating each user in each equivalent sub- load according to formula (2) Gain information on wave forms U × B matrix G
Wherein:hthIt is the channel gain amplitude threshold that can be easily accepted by a user；
It is possible different to consider that each user data rate requires, therefore each user can should adaptively occupy 1 or Nu, A equivalent subcarrier, wherein Nu≤ B, by the subcarrier of user's transmission rate, the modulation system of use and each equivalent subcarrier Number can push away to obtain each IFFT/FFT cycle TsThe interior data volume for needing to transmit, it is assumed that number of modulation levels M, each equivalent subcarrier There is subcarrier NcA, it is R that some user, which requires transmission rate,uBit/s, when
At this point, this transmission rate is RuUser should occupy NuA equivalent subcarrier.
2. the equivalent sub-carrier wave distribution method of multi-user's time frequency coding diversity MT-CDMA system according to claim 1, It is characterized in: U × B rank matrix F the equivalent subcarrier distribution of the Principle of infusing water: is generated by G
Wherein, each element of matrix F is
Wherein fu,bThe weight of u-th of user occupancy, b-th of equivalent subcarrier is described, if fu,b=1/m indicates u-th of user There are m equivalent subcarriers that can distribute, and b-th of equivalent subcarrier is only one of them；
The sum of each column element of matrix F is S={ s1,s2,…sB, i.e.,
sbThe sum of the weight of b-th of equivalent subcarrier of all user occupancies is described, is distributed on same equivalent subcarrier to reduce User between interference, here according to Principle of infusing water, the weight by constantly adjusting each equivalent subcarrier of user occupancy makes Obtain sbConstantly level off to its mean value, wherein b=1,2 ... B meet
min{max(sb)-min(sb)} (8)
Introduce vector C={ c1,c2…cB, cbIt is used as the whether adjustable mark of b-th of equivalent subcarrier in assigning process Will is defined as
3. the equivalent sub-carrier wave distribution method of multi-user's time frequency coding diversity MT-CDMA system according to claim 2, It is characterized in: the algorithm of equivalent subcarrier distribution, specific steps are as follows:
Step (1), the fading information H according to user on each subcarrier initialize matrix F, vector S and C；
Step (2) finds out element s in vector Sb, meet sb=min { sb|sb∈S∩cb≠ 0 }, b=1,2 ... B；
Step (3) finds out f in the b column of matrix F firstu,b=max { fu,b|fu,b≠0,fu,b≠ 1 }, u=1,2 ... U；So After make fu,b=1；IfGo to step (4)；IfGo to step (5)；
Step (4) is found out Indicate fu,i≠0,fu,i≠ 1 equivalent subcarrier i collection It closes, makes fu,i=1；
1. if still had after iteration B-1 times hereinIllustrate that user is rejected, goes to step (5)；
2. ifBack to step (4)；
3. ifIt enables on u-th of userFu,i=0, go to step (5)；
By step (3)~step (4), matrix F is updated；
Step (5) recalculates vector S and C according still further to formula (7) and (9)；If C ≠ 0, return to step (2), if C=0, knot Beam；
After algorithm operation is completed, the u row of matrix F has Nu, Nu≤ B element value is 1, and other is 0, shows u-th of user's quilt It is assigned to NuOn a equivalent subcarrier, the equivalent subcarrier that the position of 1 place rectangular array of element, as user are assigned, sbIt indicates Occupy the number of users of b-th of equivalent subcarrier.
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