CN105897318A - Adaptive modulation method of multi-user large-scale MIMO system based on ZF receiver - Google Patents

Adaptive modulation method of multi-user large-scale MIMO system based on ZF receiver Download PDF

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CN105897318A
CN105897318A CN201610205444.8A CN201610205444A CN105897318A CN 105897318 A CN105897318 A CN 105897318A CN 201610205444 A CN201610205444 A CN 201610205444A CN 105897318 A CN105897318 A CN 105897318A
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user
base station
adaptive modulation
receiver
signal
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CN105897318B (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 invention relates to an adaptive modulation method of a multi-user large-scale MIMO system based on a ZF receiver, comprising the following steps: (1) K users transmit pilot sequences to a base station, wherein the base station has M antennas; (2) the base station estimates the channel state information G from each user to the base station according to a received pilot signal Y, and feeds a large-scale fading coefficient Beta back to the users; (3) a user k calculates the approximate signal to interference plus noise ratio SINR(k) according to the acquired large-scale fading coefficient Beta(k), and implements adaptive modulation based on the approximate SINR(k) to adjust the modulation mode or transmitting power of transmitted signals, wherein k=1, 2,...,K; and (4) the base station receives the transmitted signals of the K users, and then uses a ZF receiver to detect the signals. Through the adaptive modulation method, the feedback information from the base station to the users is reduced, and the calculation complexity is reduced.

Description

The self-adaptive modulation method of the extensive mimo system of multi-user based on ZF receiver
Technical field
The present invention relates to communication technical field, be specifically related to a kind of multi-user based on ZF receiver extensive The self-adaptive modulation method of mimo system.
Background technology
In order to meet the wireless data service demand of development, as being obviously improved system spectrum effect The extensive MIMO technology of rate gradually obtains increasing concern.Traditional mimo system refers to Transmitting terminal and receiving terminal use multiple transmitting antenna and reception antenna respectively, make signal pass through transmitting terminal and connect Multiple antenna transmission of receiving end and reception, thus improve communication quality.Extensive mimo system is by base station The number of antennas of end is amplified to more than 100, the most.When base station end is equipped with large-scale antenna array, Accidental channel vector between user and base station becomes progressive orthogonal；The impact of multipath fading coefficient is averaged； The interference between user just can be eliminated by simple signal processing technology.Therefore, extensive MIMO System becomes the core technology in 5G.
On the other hand, Adaptive Modulation and Coding (AMC) technology is antagonism wireless channel decline, promotes system The effective means of system capacity.In AMC technology, the channel condition information that transmitting terminal feeds back according to receiving terminal (CSI) it is adaptively adjusted transmitting power, modulation coding mode etc., thus overcomes the time-varying characteristics of channel, Improve communication quality.Noting, channel condition information here includes multipath fading and large scale decline.
How in the extensive mimo system of multi-user, effectively application self-adapting modulation coding techniques without Doubt and there is important value.Traditional Adaptive Modulation and Coding technology requires that transmitting terminal is based on transient channel shape State information carries out Adaptive Transmission, but, for extensive mimo system, obtain at user side Instantaneous channel state information is extremely difficult；Meanwhile, traditional Adaptive Modulation and Coding technology is mainly for list How custom system, be applied to the extensive mimo system of multi-user the most extremely challenging.
Existing adaptive modulation coding method has: the quick self-adapted tune that (1) changes based on transient channel Technology processed (FAM)；(2) based on averagelySlow adaptive modulation technology (SAM).To existing Methods analyst after, find: method (1) needs substantial amounts of feedback overhead to adapt to the little chi being continually changing Degree fading coefficients；Method (2) reduces feedback overhead largely, but the threshold under various modulation system Value is difficult to calculate, and current research is concentrated mainly in the system of single user MRC diversity reception.
To sum up, the present invention proposes a kind of relatively easy, and is applicable to multi-user extensive MIMO system The self-adaptive modulation method of system.
Summary of the invention
Present invention aims to the limitation of existing adaptive modulation coding method, it is provided that a kind of The self-adaptive modulation method of the more practicable extensive mimo system of multi-user based on ZF receiver.
For solving above-mentioned technical problem, technical scheme provided by the present invention is:
A kind of self-adaptive modulation method of the extensive mimo system of multi-user based on ZF receiver, bag Include following steps:
1) K user is respectively to Base Transmitter pilot frequency sequence；Described base station has M root antenna；
2) base station is according to pilot signal Y received, and estimates each user channel condition information G to base station, And large scale fading coefficients β is fed back to user；
3) user k is according to large scale fading coefficients β obtainedkCalculate approximation Signal to Interference plus Noise RatioAnd based on Approximation Signal to Interference plus Noise RatioImplement Adaptive Modulation, adjust and launch the modulation system of signal or launch merit Rate, wherein k=1,2 ..., K；
4), after base station receives the transmitting signal of K user, the detection of ZF receiver is used.
User before Base Transmitter signal, the pilot signal that base station first sends according to user, estimate little The large scale fading coefficients of each user in district, and this is fed back to user.In desired bit error rate (BER) under restrictive condition, user k utilizes base station feedback information, is calculated approximation Signal to Interference plus Noise RatioDynamically adjust and launch the modulation system of signal or launch power, promote the letter of system Road capacity.Secondly, in order to make the channel between user mutually orthogonal, eliminate the interference between user, base The employing ZF that stands detects.The method may be used for Multi User Adaptive Modulation system, utilizes extensive sky simultaneously The advantage of wire system, can implement Adaptive Modulation just with large scale fading channel.
Described step 2) in pilot signal Y=G φ, φ be to be made up of the pilot frequency sequence of K a length of τ Matrix.It is multiplied by pilot frequency sequence φK×τConjugate transpose, accurately estimate all users channel shape to base station State information G ∈ CM×K(including large scale decline and multipath fading).Owing to antenna number M tends to infinite Time, the impact of multipath fading can be averaged, so large scale fading coefficients can basisEstimate Meter obtains.
Described step 2) in channel condition information G=[g1,g2…gK]；Wherein Wherein k=1,2 ..., K；gkRepresent the user k channel vector to base station；hkRepresent little to base station of user k Yardstick fading coefficients；βkRepresent the user k large scale fading coefficients to base station,Wherein dkTable Showing the kth user distance to base station, γ is damped expoential, zkRepresent a lognormal stochastic variable.
Described hkObey average be 0 variance be the round symmetric complex random distribution of 1；Described βkBag Include geometry decline and shade falls；Described zkIt is lognormal stochastic variable, i.e. a 10log10(zk) obey Zero-mean, standard deviation are σshadowGauss distribution, under different scenes, standard deviation sigmashadowHave not Same span.
Described step 3) middle approximation Signal to Interference plus Noise RatioWherein puRepresent that user launches letter Number power, M represents the antenna amount that base station has, βkRepresent that user k declines to the large scale of base station Coefficient.
Owing to the instantaneous SINR of each user can be joined by multipath fading coefficient and large scale fading coefficients Group photo rings, so the SINR of user kkCan 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, captures the change of decline.So instantaneous SINR once changes, base station will be to user Feed back, adjust user and send the modulation system of signal.But in extensive mimo system, with The increase of antenna number M, (i.e. the impact of multipath fading can be by for multipath fading rapidly " hardening " Averagely).Therefore can obtain according to the law of large numbers:
So,Obtain
It can thus be seen that in extensive mimo system, when base station uses ZF detection, user Approximation Signal to Interference plus Noise RatioOnly relevant with the large scale fading coefficients of oneself, with multipath fading coefficient without Close.
Described step 3) in implement Adaptive Modulation and Coding refer 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 approximation Signal to Interference plus Noise Ratio of user kFall in regionIn, then user k UseCorresponding modulation system.
Described different modulating mode refers to: BPSK, QPSK, 8-PSK, 16-QAM, 32-QAM And 64QAM.
Described step 4) in the detection method of ZF receiver be: base station receives the transmitting of K user After signal, according to the channel condition information G estimated, calculate ZF linearity test matrix W=(GHG)-1GH, then process the transmitting signal received.
Compared with the existing technology, beneficial effects of the present invention is embodied in:
(1) feedback information is decreased: according to the approximation Signal to Interference plus Noise Ratio of each userCarry out Adaptive Modulation and Coding, the SINR of user is only relevant with large scale fading coefficients, and large scale fading coefficients Coherence time much larger than coherence time of multipath fading coefficient, decrease the base station feedback letter to user Breath.
(2) reducing computation complexity: in Adaptive Modulation and Coding based on instantaneous SINR, base station needs Calculate each user and comprise large scale fading coefficients and the SINR of multipath fading coefficient, including Matrix inversion operation；But at extensive mimo system, based on approximation Signal to Interference plus Noise Ratio Adaptive Modulation and Coding, base station has only to user feedback large scale fading coefficients, it is not necessary to meter Calculate matrix inversion.
Accompanying drawing explanation
Fig. 1 is application scenarios schematic diagram of the present invention；
Fig. 2 is the Adaptive Modulation of the present invention extensive mimo system of multi-user based on ZF receiver The flow chart of method；
Fig. 3 is that the self adaptation of the extensive mimo system of multi-user based on ZF receiver in the present invention is adjusted The average spectral efficiency (ase) of system (LAM) and tradition Adaptive Modulation based on instantaneous SINR (FAM) compares Analogous diagram.
Detailed description of the invention
Below in conjunction with embodiment and accompanying drawing, the present invention is further described.
As it is shown in figure 1, in the extensive mimo system of multi-user, base station has large-scale antenna array, Antenna number is M, has K user, each user to be equipped with single antenna in community.Anti-by base station Feedforward information, user is according to only relevant with large scale fading coefficients approximation Signal to Interference plus Noise RatioCarry out self adaptation Modulation.
As in figure 2 it is shown, the Adaptive Modulation of the extensive mimo system of multi-user based on ZF receiver Method, comprises the steps:
1) K user is respectively to Base Transmitter pilot frequency sequence；Described base station has M root antenna；
2) base station is according to pilot signal Y received, and estimates each user channel condition information G to base station, And large scale fading coefficients β is fed back to user；
The extensive mimo system of described multi-user is at the MODE of operation of TDD, and base station can be by upper Pilot signal Y of line link is estimated to obtain good channel condition information G.
Described step 2) in pilot signal Y=G φ, φ be to be made up of the pilot frequency sequence of K a length of τ Matrix.It is multiplied by pilot frequency sequence φK×τConjugate transpose, accurately estimate all users channel shape to base station State information G ∈ CM×K(including large scale decline and multipath fading).Owing to antenna number M tends to infinite Time, the impact of multipath fading can be averaged, so large scale fading coefficients can basisEstimate Meter obtains.
Described step 2) in channel condition information G=[g1,g2…gK]；Wherein Wherein k=1,2 ..., K；gkRepresent the user k channel vector to base station；hkRepresent little to base station of user k Yardstick fading coefficients, obey average be 0 variance be the round symmetric complex random distribution of 1；βkRepresent and use Family k, to the large scale fading coefficients of base station, falls including geometry decline and shade,Wherein dkTable Showing the kth user distance to base station, γ is damped expoential, zkRepresent a lognormal stochastic variable, I.e. 10log10(zk) to obey zero-mean, standard deviation be σshadowGauss distribution, under different scenes, mark Quasi-difference σshadowThere is different spans.
3) user k is according to large scale fading coefficients β obtainedkCalculate approximation Signal to Interference plus Noise RatioAnd based on Approximation Signal to Interference plus Noise RatioImplement Adaptive Modulation, adjust and launch the modulation system of signal or launch merit Rate, wherein k=1,2 ..., K；
Described step 3) middle approximation Signal to Interference plus Noise RatioWherein puRepresent that user launches letter Number power, M represents the antenna amount that base station has, βkRepresent that user k declines to the large scale of base station Coefficient.
Approximation Signal to Interference plus Noise RatioCan be obtained by below equation, due to the instantaneous SINR of each user Meeting is by multipath fading coefficient and the combined effect of large scale fading coefficients, so the SINR of user kkCan To 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, captures the change of decline.So instantaneous SINR once changes, base station will be to user Feed back, adjust user and send the modulation system of signal.But in extensive mimo system, with The increase of antenna number M, (i.e. the impact of multipath fading can be by for multipath fading rapidly " hardening " Averagely).Therefore can obtain according to the law of large numbers:
So,Obtain
It can thus be seen that in extensive mimo system, when base station uses ZF detection, user Approximation Signal to Interference plus Noise RatioOnly relevant with the large scale fading coefficients of oneself, with multipath fading coefficient without Close.
Described step 3) in implement Adaptive Modulation and Coding refer to: at the restriction bar of desired bit error rate Under part, obtain the threshold value of SINR under different modulating modeDescribed different modulating mode refers to: BPSK, QPSK, 8-PSK, 16-QAM, 32-QAM and 64QAM.When the approximation of user k is believed dry Make an uproar ratioFall in regionIn, then user k can useCorresponding modulation methods Formula.
4), after base station receives the transmitting signal of K user, the detection of ZF receiver is used.
In order to make the channel between user mutually orthogonal, eliminating the interference between user, base station uses ZF inspection Survey.Described step 4) in the detection method of ZF receiver be: base station receives the transmitting of K user After signal, according to the channel condition information G estimated, calculate ZF linearity test matrix W=(GHG)-1GH, then process the transmitting signal received.
Fig. 3 is the Adaptive Modulation (LAM) of the extensive mimo system of multi-user based on ZF receiver, Adaptive Modulation based on instantaneous SINR with tradition (FAM), in antenna for base station number M=32 and 128 In the case of average spectral efficiency (ase) compare, can obtain along with the increase of antenna for base station number, LAM Performance be closer to FAM.And, along with antenna for base station number increases further, LAM relative to FAM has the advantage reducing feedback information with reducing computation complexity.

Claims (7)

1. a self-adaptive modulation method for the extensive mimo system of multi-user based on ZF receiver, It is characterized in that, comprise the steps:
1) K user is respectively to Base Transmitter pilot frequency sequence；Described base station has M root antenna；
2) base station is according to pilot signal Y received, and estimates each user channel condition information G to base station, And large scale fading coefficients β is fed back to user；
3) user k is according to large scale fading coefficients β obtainedkCalculate approximation Signal to Interference plus Noise RatioAnd based on Approximation Signal to Interference plus Noise RatioImplement Adaptive Modulation, adjust and launch the modulation system of signal or launch merit Rate, wherein k=1,2 ..., K；
4), after base station receives the transmitting signal of K user, the detection of ZF receiver is used.
The extensive mimo system of multi-user based on ZF receiver the most according to claim 1 Self-adaptive modulation method, it is characterised in that described step 2) in pilot signal Y=G φ, φ be by K The matrix that the pilot frequency sequence of individual a length of τ is constituted.
The extensive mimo system of multi-user based on ZF receiver the most according to claim 2 Self-adaptive modulation method, it is characterised in that described step 2) in channel condition information G=[g1,g2…gK]；
WhereinWherein k=1,2 ..., K；gkRepresent user k to base station channel to Amount；hkRepresent the user k multipath fading coefficient to base station；βkRepresent that user k declines to the large scale of base station Fall coefficient,Wherein dkRepresenting the kth user distance to base station, γ is damped expoential, zkTable Show a lognormal stochastic variable.
The extensive mimo system of multi-user based on ZF receiver the most according to claim 1 Self-adaptive modulation method, it is characterised in that described step 3) middle approximation Signal to Interference plus Noise Ratio Wherein puRepresenting that user launches the power of signal, M represents the antenna amount that base station has, βkRepresent user K is to the large scale fading coefficients of base station.
The extensive mimo system of multi-user based on ZF receiver the most according to claim 4 Self-adaptive modulation method, it is characterised in that described step 3) in implement Adaptive Modulation and Coding refer 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 approximation Signal to Interference plus Noise Ratio of user kFall in regionIn, then user k UseCorresponding modulation system.
The extensive mimo system of multi-user based on ZF receiver the most according to claim 5 Self-adaptive modulation method, it is characterised in that described different modulating mode refers to: BPSK, QPSK, 8-PSK, 16-QAM, 32-QAM and 64QAM.
The extensive mimo system of multi-user based on ZF receiver the most according to claim 1 Self-adaptive modulation method, it is characterised in that described step 4) in the detection method of ZF receiver be: After base station receives the transmitting signal of K user, according to the channel condition information G estimated, calculate ZF Linearity test matrix W=(GHG)-1GH, then process the transmitting signal received.
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