CN105897318B - The self-adaptive modulation method of the extensive mimo system of multi-user based on ZF receivers - Google Patents

The self-adaptive modulation method of the extensive mimo system of multi-user based on ZF receivers Download PDF

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CN105897318B
CN105897318B CN201610205444.8A CN201610205444A CN105897318B CN 105897318 B CN105897318 B CN 105897318B CN 201610205444 A CN201610205444 A CN 201610205444A CN 105897318 B CN105897318 B CN 105897318B
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base station
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adaptive modulation
receivers
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CN105897318A (en
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钟财军
周月浩
张朝阳
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Zhejiang University ZJU
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H04B7/0452—Multi-user MIMO systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
    • H04B7/0619—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal using feedback from receiving side
    • H04B7/0652—Feedback error handling
    • H04B7/0656—Feedback error handling at the transmitter, e.g. error detection at base station
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • H04L25/0204—Channel estimation of multiple channels

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Power Engineering (AREA)
  • Mobile Radio Communication Systems (AREA)
  • Radio Transmission System (AREA)

Abstract

The present invention relates to a kind of self-adaptive modulation methods of the extensive mimo system of the multi-user based on ZF receivers, include the following steps：1) K user is respectively to Base Transmitter pilot frequency sequence；The base station has M root antennas；2) base station is according to the pilot signal Y of reception, estimates that large-scale decline factor beta to the channel state information G of base station, and is fed back to user by each user；3) user k is according to the large-scale decline factor beta of acquisitionkCalculate approximate Signal to Interference plus Noise RatioAnd based on approximate Signal to Interference plus Noise RatioImplement Adaptive Modulation, the modulation system or transmission power of adjustment transmitting signal, wherein k=1,2 ..., K；4) after base station receives the transmitting signal of K user, machine testing is received using ZF.The self-adaptive modulation method not only reduces feedback information of the base station to user, next reduces computation complexity.

Description

The self-adaptive modulation method of the extensive mimo system of multi-user based on ZF receivers
Technical field
The present invention relates to fields of communication technology, and in particular to a kind of extensive mimo system of multi-user based on ZF receivers Self-adaptive modulation method.
Background technology
In order to meet the wireless data service demand of continuous development, as the big rule that can be obviously improved system spectral efficiency Mould MIMO technology gradually obtains more and more concerns.Traditional mimo system refers in transmitting terminal and receiving terminal respectively using more A transmitting antenna and reception antenna make signal pass through the mutiple antennas transmission of transmitting terminal and receiving terminal and receive, so as to improve logical Believe quality.The number of antennas of base station end is amplified to more than 100 by extensive mimo system, even more.When base station end is equipped with big rule When mould aerial array, the accidental channel vector between user and base station becomes progressive orthogonal；The influence of multipath fading coefficient is put down ?；The interference between user can be eliminated by simple signal processing technology.Therefore, extensive mimo system becomes in 5G Core technology.
On the other hand, Adaptive Modulation and Coding (AMC) technology be confrontation wireless channel decline, lifting system capacity it is effective Means.In AMC technologies, channel state information (CSI) that transmitting terminal is fed back according to receiving terminal be adaptively adjusted transmission power, Modulation coding scheme etc. improves communication quality to overcome the time-varying characteristics of channel.Note that channel state information packet here Include multipath fading and large-scale decline.
How in the extensive mimo system of multi-user, effectively apply Adaptive Modulation and Coding technology undoubtedly with important Value.Traditional Adaptive Modulation and Coding technology requires transmitting terminal to be based on instantaneous channel state information and carries out Adaptive Transmission, However, for extensive mimo system, it is extremely difficult to obtain instantaneous channel state information in user terminal；Meanwhile it is traditional How Adaptive Modulation and Coding technology it is also great be applied to the extensive mimo system of multi-user mainly for single user system Challenge.
Existing adaptive modulation coding method has：(1) the quick self-adapted modulation technique based on transient channel variation (FAM)；(2) it is based on averageSlow adaptive modulation technology (SAM).After analyzing existing method, find：Method (1) need a large amount of feedback overhead to adapt to continually changing multipath fading coefficient；Method (2) largely reduces instead Expense is presented, but the threshold value under various modulation systems is difficult to calculate, current research is concentrated mainly on single user MRC diversity receptions In system.
To sum up, the present invention proposes a kind of relatively easy, and suitable for the adaptive of the extensive mimo system of multi-user Modulator approach.
Invention content
It is an object of the invention to the limitation for existing adaptive modulation coding method, provide it is a kind of it is practical can The self-adaptive modulation method of the capable extensive mimo system of the multi-user based on ZF receivers.
In order to solve the above technical problems, technical solution provided by the present invention is：
A kind of self-adaptive modulation method of the extensive mimo system of multi-user based on ZF receivers, includes the following steps：
1) K user is respectively to Base Transmitter pilot frequency sequence；The base station has M root antennas；
2) base station is according to the pilot signal Y of reception, estimate each user to base station channel state information G, and by big ruler Degree fading coefficients β feeds back to user；
3) user k is according to the large-scale decline factor beta of acquisitionkCalculate approximate Signal to Interference plus Noise RatioAnd it is dry based on approximate letter It makes an uproar ratioImplement Adaptive Modulation, the modulation system or transmission power of adjustment transmitting signal, wherein k=1,2 ..., K；
4) after base station receives the transmitting signal of K user, machine testing is received using ZF.
In user to before Base Transmitter signal, the pilot signal that base station is first sent according to user estimates each in cell The large-scale decline coefficient of user, and this is fed back into user.Under the restrictive condition of desired bit error rate (BER), user k Using base station feedback information, approximate Signal to Interference plus Noise Ratio is calculatedThe modulation methods of dynamic adjustment transmitting signal Formula or transmission power, the channel capacity of lifting system.Secondly, in order to keep the channel between user mutually orthogonal, user is eliminated Between interference, base station using ZF detect.This method can be used for Multi User Adaptive Modulation system, while utilize extensive day The advantage of linear system system, can implement Adaptive Modulation just with large-scale decline channel.
Pilot signal Y=G φ, φ are the matrixes being made of the pilot frequency sequence that K length is τ in the step 2).Multiply With pilot frequency sequence φK×τConjugate transposition, accurately estimate all users to base station channel state information G ∈ CM×K(including it is big Scale declines and multipath fading).When tending to be infinite due to antenna number M, the influence of multipath fading can be averaged, so Large-scale decline coefficient can basisEstimation obtains.
Channel state information G=[g in the step 2)1,g2…gK]；WhereinWherein k= 1,2,…,K；gkChannel vectors of the expression user k to base station；hkMultipath fading coefficients of the expression user k to base station；βkIt indicates User k to base station large-scale decline coefficient,Wherein dkK-th of user is indicated to the distance of base station, γ is decaying Index, zkIndicate a lognormal stochastic variable.
The hkIt is the circle symmetric complex random distribution that 0 variance is 1 to obey mean value；The βkIt declines including geometry It is fallen with shade；The zkIt is a lognormal stochastic variable, i.e. 10log10(zk) obey zero-mean, standard deviation σshadow Gaussian Profile, under different scenes, standard deviation sigmashadowThere is different value ranges.
Approximate Signal to Interference plus Noise Ratio in the step 3)Wherein puIndicate that user emits the work(of signal Rate, M indicate the antenna amount that base station has, βkLarge-scale decline coefficients of the expression user k to base station.
Due to each user instantaneous SINR can by the combined effect of multipath fading coefficient and large-scale decline coefficient, So the SINR of user kkIt can be expressed as：
Wherein H=[h1,h2,···,hK]∈CM×K。
According to traditional adaptive modulation coding method, user must quickly and accurately obtain instantaneous SINR, come Capture the variation of decline.So instantaneous SINR once changes, base station will be fed back to user, and adjustment user sends The modulation system of signal.However in extensive mimo system, with the increase of antenna number M, multipath fading is rapid " hard Change " (i.e. the influence of multipath fading can be averaged).Therefore it can be obtained according to the law of large numbers：
SoTo obtain the final product
It can thus be seen that in extensive mimo system, when base station is detected using ZF, the approximate Signal to Interference plus Noise Ratio of userIt is only related with the large-scale decline coefficient of oneself, it is unrelated with multipath fading coefficient.
Implementing Adaptive Modulation and Coding in the step 3) refers to：
1) under the restrictive condition of desired bit error rate, the threshold value of SINR under different modulating mode is obtained
2) when the approximate Signal to Interference plus Noise Ratio of user kIt falls in regionInterior, then user k is usedCorresponding modulation system.
The different modulating mode refers to：BPSK, QPSK, 8-PSK, 16-QAM, 32-QAM and 64QAM.
The detection method of ZF receivers is in the step 4)：After base station receives the transmitting signal of K user, according to The channel state information G of estimation calculates ZF linearity tests matrix W=(GHG)-1GH, then handle the transmitting signal received.
Compared with the existing technology, beneficial effects of the present invention are embodied in：
(1) reduce feedback information：According to the approximate Signal to Interference plus Noise Ratio of each userIt carries out adaptive The SINR of modulating-coding, user is only related to large-scale decline coefficient, and the coherence time of large-scale decline coefficient is much larger than small The coherence time of scale fading coefficients reduces feedback information of the base station to user.
(2) computation complexity is reduced：In the Adaptive Modulation and Coding based on instantaneous SINR, base station needs to calculate every A user includes the SINR of large-scale decline coefficient and multipath fading coefficient, including matrix inversion operation；However big Scale mimo system, based on approximate Signal to Interference plus Noise RatioAdaptive Modulation and Coding, base station is only needed to user Large-scale decline coefficient is fed back, calculating matrix is not needed and inverts.
Description of the drawings
Fig. 1 is application scenarios schematic diagram of the present invention；
Fig. 2 is that the present invention is based on the flows of the self-adaptive modulation method of the extensive mimo system of the multi-user of ZF receivers Figure；
Fig. 3 is the Adaptive Modulation (LAM) of the extensive mimo system of multi-user based on ZF receivers and biography in the present invention The analogous diagram that the average spectral efficiency (ase) of Adaptive Modulation (FAM) of the system based on instantaneous SINR compares.
Specific implementation mode
The present invention is further described with reference to embodiment and attached drawing.
As shown in Figure 1, in the extensive mimo system of multi-user, base station is with large-scale antenna array, antenna number M has in cell K user, each user to be equipped with single antenna.By the feedback information of base station, user is according to only and large scale The relevant approximate Signal to Interference plus Noise Ratio of fading coefficientsCarry out Adaptive Modulation.
As shown in Fig. 2, the self-adaptive modulation method of the extensive mimo system of multi-user based on ZF receivers, including it is as follows Step：
1) K user is respectively to Base Transmitter pilot frequency sequence；The base station has M root antennas；
2) base station is according to the pilot signal Y of reception, estimate each user to base station channel state information G, and by big ruler Degree fading coefficients β feeds back to user；
The extensive mimo system of the multi-user works under the pattern of TDD, and base station can leading by uplink The Y estimations of frequency signal obtain good channel state information G.
Pilot signal Y=G φ, φ are the matrixes being made of the pilot frequency sequence that K length is τ in the step 2).Multiply With pilot frequency sequence φK×τConjugate transposition, accurately estimate all users to base station channel state information G ∈ CM×K(including it is big Scale declines and multipath fading).When tending to be infinite due to antenna number M, the influence of multipath fading can be averaged, so Large-scale decline coefficient can basisEstimation obtains.
Channel state information G=[g in the step 2)1,g2…gK]；WhereinWherein k= 1,2,…,K；gkChannel vectors of the expression user k to base station；hkIndicate that user k to the multipath fading coefficient of base station, is obeyed equal Value is the circle symmetric complex random distribution that 0 variance is 1；βkIndicate user k to the large-scale decline coefficient of base station, including geometry Decline and shade are fallen,Wherein dkK-th of user is indicated to the distance of base station, γ is damped expoential, zkIndicate one Lognormal stochastic variable, i.e. 10log10(zk) obey zero-mean, standard deviation σshadowGaussian Profile, in different scenes Under, standard deviation sigmashadowThere is different value ranges.
3) user k is according to the large-scale decline factor beta of acquisitionkCalculate approximate Signal to Interference plus Noise RatioAnd it is dry based on approximate letter It makes an uproar ratioImplement Adaptive Modulation, the modulation system or transmission power of adjustment transmitting signal, wherein k=1,2 ..., K；
Approximate Signal to Interference plus Noise Ratio in the step 3)Wherein puIndicate that user emits the work(of signal Rate, M indicate the antenna amount that base station has, βkLarge-scale decline coefficients of the expression user k to base station.
Approximate Signal to Interference plus Noise RatioIt can be obtained by following formula, since the instantaneous SINR of each user can be by The combined effect of multipath fading coefficient and large-scale decline coefficient, so the SINR of user kkIt can be expressed as：
Wherein H=[h1,h2,…,hK]∈CM×K。
According to traditional adaptive modulation coding method, user must quickly and accurately obtain instantaneous SINR, come Capture the variation of decline.So instantaneous SINR once changes, base station will be fed back to user, and adjustment user sends The modulation system of signal.However in extensive mimo system, with the increase of antenna number M, multipath fading is rapid " hard Change " (i.e. the influence of multipath fading can be averaged).Therefore it can be obtained according to the law of large numbers：
SoTo obtain the final product
It can thus be seen that in extensive mimo system, when base station is detected using ZF, the approximate Signal to Interference plus Noise Ratio of userIt is only related with the large-scale decline coefficient of oneself, it is unrelated with multipath fading coefficient.
Implementing Adaptive Modulation and Coding in the step 3) refers to：Under the restrictive condition of desired bit error rate, obtain The threshold value of SINR under to different modulating modeThe different modulating mode refers to：BPSK,QPSK,8-PSK,16- QAM, 32-QAM and 64QAM.When the approximate Signal to Interference plus Noise Ratio of user kIt falls in regionIt is interior, then it uses Family k may be usedCorresponding modulation system.
4) after base station receives the transmitting signal of K user, machine testing is received using ZF.
In order to keep the channel between user mutually orthogonal, the interference between user is eliminated, base station is detected using ZF.Described The detection method of ZF receivers is in step 4)：After base station receives the transmitting signal of K user, according to the channel status of estimation Information G calculates ZF linearity tests matrix W=(GHG)-1GH, then handle the transmitting signal received.
Fig. 3 is the Adaptive Modulation (LAM) of the extensive mimo system of multi-user based on ZF receivers, and wink is based on tradition When SINR Adaptive Modulation (FAM), the average spectral efficiency (ase) in antenna for base station number M=32 and 128 is compared, The increase with antenna for base station number can be obtained, the performance of LAM is closer to FAM.Moreover, as antenna for base station number is into one Step increases, and LAM has the advantage for reducing feedback information and reducing computation complexity relative to FAM.

Claims (5)

1. a kind of self-adaptive modulation method of the extensive mimo system of multi-user based on ZF receivers, which is characterized in that including Following steps：
1) K user is respectively to Base Transmitter pilot frequency sequence；The base station has M root antennas；
2) base station is according to the pilot signal Y of reception, estimates that each user to the channel state information G of base station, and large scale is declined Fall factor betakFeed back to user k；
Channel state information G=[g in the step 2)1,g2···gK]；
WhereinWherein k=1,2, K；M indicates antenna for base station quantity；C indicates complex field；gk Channel vectors of the expression user k to base station；hkMultipath fading coefficients of the expression user k to base station；βkIndicate user k to base station Large-scale decline coefficient,Wherein dkK-th of user is indicated to the distance of base station, γ is damped expoential, zkIt indicates One lognormal stochastic variable；
3) user k is according to the large-scale decline factor beta of acquisitionkCalculate approximate Signal to Interference plus Noise RatioAnd based on approximate Signal to Interference plus Noise RatioImplementation Adaptive Modulation, the modulation system or transmission power of adjustment transmitting signal, wherein k=1,2, K；
Approximate Signal to Interference plus Noise Ratio in the step 3)Wherein puIndicate that user emits the power of signal, M tables Show the antenna amount that base station has, βkLarge-scale decline coefficients of the expression user k to base station；
4) after base station receives the transmitting signal of K user, machine testing is received using ZF.
2. the self-adaptive modulation method of the extensive mimo system of the multi-user according to claim 1 based on ZF receivers, It is characterized in that, pilot signal Y=G φ, φ are the matrixes being made of the pilot frequency sequence that K length is τ in the step 2).
3. the self-adaptive modulation method of the extensive mimo system of the multi-user according to claim 2 based on ZF receivers, It is characterized in that, implementation Adaptive Modulation refers in the step 3)：
1) under the restrictive condition of desired bit error rate, the threshold value of SINR under different modulating mode is obtainedWherein N tables Show maximum modulation exponent number；
2) when the approximate Signal to Interference plus Noise Ratio of user kIt falls in regionInterior, then user k is usedIt is right The modulation system answered.
4. the self-adaptive modulation method of the extensive mimo system of the multi-user according to claim 3 based on ZF receivers, It is characterized in that, the different modulating mode refers to：BPSK, QPSK, 8-PSK, 16-QAM, 32-QAM and 64QAM.
5. the self-adaptive modulation method of the extensive mimo system of the multi-user according to claim 1 based on ZF receivers, It is characterized in that, the detection method of ZF receivers is in the step 4)：After base station receives the transmitting signal of K user, According to the channel state information G of estimation, ZF linearity tests matrix W=(G is calculatedHG)-1GH, then handle the transmitting received Signal.
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CN104378150A (en) * 2014-10-29 2015-02-25 郑州大学 Power distribution method for minimizing symbol error rate in distributed MIMO system

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