CN114142929B - Visible light communication system and method based on GMD-BD precoding - Google Patents

Visible light communication system and method based on GMD-BD precoding Download PDF

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CN114142929B
CN114142929B CN202111340920.4A CN202111340920A CN114142929B CN 114142929 B CN114142929 B CN 114142929B CN 202111340920 A CN202111340920 A CN 202111340920A CN 114142929 B CN114142929 B CN 114142929B
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user terminal
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signal
visible light
gmd
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CN114142929A (en
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李正权
关少义
洪焕东
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Jiangnan University
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/11—Arrangements specific to free-space transmission, i.e. transmission through air or vacuum
    • H04B10/114—Indoor or close-range type systems
    • H04B10/116—Visible light communication
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/516—Details of coding or modulation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/60—Receivers
    • H04B10/66—Non-coherent receivers, e.g. using direct detection
    • H04B10/69—Electrical arrangements in the receiver
    • H04B10/697—Arrangements for reducing noise and distortion
    • H04B10/6971—Arrangements for reducing noise and distortion using equalisation
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
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    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

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Abstract

The invention discloses a visible light communication system and method based on GMD-BD precoding, and belongs to the field of wireless optical communication. The transmitting end of the system performs GMD-BD precoding processing on the transmission information to be modulated; the receiving end adopts a GMD-BD decoding matrix and a decision feedback equalization DFE nonlinear receiver to jointly decode, and is used for eliminating intersymbol interference. The invention enables different receivers of the same user terminal to obtain similar error rate performance through GMD-BD precoding and DFE nonlinear receivers, improves the performance of the worst receiver and reduces the error rate of the user terminal. Compared with the existing visible light communication system, the system is more suitable for the situation that the same user terminal is provided with a plurality of optical receivers.

Description

Visible light communication system and method based on GMD-BD precoding
Technical Field
The invention relates to a visible light communication system and method based on GMD-BD precoding, belonging to the field of wireless optical communication.
Background
The visible light communication system (Visible Light Communication, VLC) generally includes three parts, a visible light transmitting end, a visible light channel, and a visible light receiving end. The visible light emitting end mainly carries out signal modulation and pre-coding treatment, and the electric signal subjected to the pre-coding treatment is added into the direct current signal for coupling, so that the LED is driven to emit visible light signals. The visible light signal reaches the visible light receiving end after being transmitted by the channel. At the receiving end, the optical receiver converts the optical signal into an electrical signal, decodes and demodulates the electrical signal to recover the information required by the user. Visible light communication systems are widely used in electromagnetic sensitive environments such as medical science, aviation, and the like.
LEDs have advantages of long life span, low power consumption, high photoelectric conversion efficiency, etc., and are expected to replace conventional light sources as main illumination devices, and are widely regarded as next-generation green illumination products. VLC utilizes white light LEDs as a light source, has been standardized by the IEEE 802.15.7 protocol as LEDs evolve rapidly, and is considered a powerful complement to indoor traditional radio frequency communications. The VLC transmits data by modulating the light intensity of the LED at high frequency on the premise of not affecting the lighting function of the LED, combines lighting with an information transmission technology, and has the advantages of low cost, good confidentiality, no need of spectrum permission, no electromagnetic interference and the like. However, the limited bandwidth of LEDs limits the high speed transmission of VLC, but for typical indoor environments, multiple LEDs are often installed to ensure adequate illumination, so MIMO technology naturally becomes an effective solution to increase data transmission rates.
In fact, VLC systems can support multiple users simultaneously due to the broadcasting characteristics of the optical signals, but multiple users can cause interference among the users, thereby reducing the user error rate performance. Therefore, the precoding algorithm is needed to eliminate the interference among multiple users, and the method can effectively reduce the complexity of the user terminal. In VLC systems, the precoding algorithms commonly used for multi-user MISO systems include ZF precoding, ZF-DPC precoding, SVD precoding, GMD precoding, and the like, the precoding algorithms commonly used for multi-user MIMO systems include SVD-BD precoding, and at the receiving end, the receiving ends of the above-mentioned precoding VLC systems all employ linear receivers, which cannot effectively eliminate signal interference generated between different LED optical transmitters.
In the multi-user VLC system based on SVD-BD precoding, due to miniaturization of the user terminals, the optical receivers of the same user terminal are closely spaced, and the received visible light signals are almost identical, resulting in high correlation of the user channel matrix. When the correlation of the channel matrix is larger, the singular value difference is larger after the SVD-BD precoding algorithm is processed, namely the equivalent sub-stream channel gain difference is larger, so that the error rate performance of different receivers is larger, and the error rate performance of the user terminal is limited by the receiver with the worst performance, so that the error rate performance of the user terminal is poorer.
Disclosure of Invention
In order to solve the problem of poor error rate performance of a user terminal in the current visible light communication system, the invention provides a multi-user MIMO indoor visible light communication system and a method.
The first object of the present invention is to provide a multi-user MIMO indoor visible light communication system, comprising a transmitting end, a channel and a receiving end, wherein a signal sent by the transmitting end is transmitted through the channel and received by the receiving end, and the first object of the present invention is characterized in that the transmitting end of the visible light communication system performs GMD-BD pre-coding processing on information to be transmitted;
the receiving end adopts a GMD-BD decoding matrix and a decision feedback equalization DFE nonlinear receiver to jointly decode, and is used for eliminating intersymbol interference.
Optionally, the transmitting end transmits information in a process that includes:
firstly, converting information from a serial signal to a parallel signal through serial-parallel conversion, then carrying out bipolar on-off keying OOK modulation on the parallel signal,
Figure BDA0003351952800000021
the signal after OOK modulation is the user information, K is the number of the user terminals at the receiving end; />
Figure BDA0003351952800000022
Modulated signal representing information of kth user terminal, the kth user terminal having N Rk K is more than or equal to 1 and less than or equal to K;
GMD-BD pre-coding processing is carried out on the modulated signals, wherein the GMD-BD pre-coding matrix is as follows:
Figure BDA0003351952800000023
wherein ,
Figure BDA0003351952800000024
a precoding matrix corresponding to the kth user terminal; />
Figure BDA0003351952800000025
The total number of the optical receivers at the receiving end; n (N) T N LEDs are arranged for each LED array of the emitting end;
the pre-coded signals are added with direct current bias to drive the Light Emitting Diode (LED) array to emit visible light signals, and finally the visible light signals x emitted by the LED array are as follows:
Figure BDA0003351952800000026
wherein ,PLED For the power of a single LED, m I In order to modulate the index of the light,
Figure BDA0003351952800000027
is N of all 1 T And (5) maintaining the column vector.
Optionally, the channel adopts a direct link model, and the channel matrix of the visible light communication system is:
Figure BDA0003351952800000028
wherein
Figure BDA0003351952800000029
Representing the channel matrix between the LED array and the kth user terminal.
Optionally, the receiving end converts the received visible light signal into an electrical signal, and after filtering the direct current component, the signal received by the kth user terminal is:
Figure BDA0003351952800000031
wherein, gamma is the photoelectric conversion factor of the receiver,
Figure BDA0003351952800000032
representing a precoding matrix corresponding to the jth user terminal, d j A signal representing the information of the jth user terminal after modulation, j is 1-K and/or K #>
Figure BDA0003351952800000033
N representing the noise contribution of the optical receiver received signal of the kth user terminal Rk And (5) a dimension vector.
Optionally, in the transmitting end, the step of solving the precoding matrix corresponding to the kth user terminal includes:
step one: in the visible light communication system, it is assumed that a precoding matrix corresponding to a kth user is composed of two parts
Figure BDA0003351952800000034
Marking the channel complement matrix of the kth user as
Figure BDA0003351952800000035
Its rank is->
Figure BDA0003351952800000036
For->
Figure BDA0003351952800000037
SVD decomposition is carried out to obtain: />
Figure BDA0003351952800000038
wherein ,
Figure BDA0003351952800000039
by->
Figure BDA00033519528000000310
Left singular vector component,/>
Figure BDA00033519528000000311
Is->
Figure BDA00033519528000000312
Diagonal matrix of singular values, +.>
Figure BDA00033519528000000313
To supplement matrix->
Figure BDA00033519528000000314
Before->
Figure BDA00033519528000000315
Right singular vectors, ">
Figure BDA00033519528000000316
For leaving->
Figure BDA00033519528000000317
Right singular vectors, constitute->
Figure BDA00033519528000000318
A set of orthonormal bases for the null space of ∈ ->
Figure BDA00033519528000000319
Step two: equivalent channel matrix for kth user terminal
Figure BDA00033519528000000320
GMD decomposition is carried out to obtain the following components:
Figure BDA00033519528000000321
wherein if it
Figure BDA00033519528000000322
Rank->
Figure BDA00033519528000000323
Then->
Figure BDA00033519528000000324
and />
Figure BDA00033519528000000325
Is a semi-orthogonal matrix, ">
Figure BDA00033519528000000326
Is an upper triangular matrix with equal diagonal elements, note +.>
Figure BDA00033519528000000327
Step three: the GMD-BD precoding matrix corresponding to the kth user terminal finally comprises the following steps:
Figure BDA00033519528000000328
the decoding matrix of the kth user terminal is:
W k ＝Q k 。
optionally, in the receiving end, the decoding step of the kth user terminal is as follows:
step one: f (F) k From H k The zero space vector of the complement matrix is composed, so the encoding matrix satisfies:
Figure BDA0003351952800000041
indicating interference terms in received signals
Figure BDA0003351952800000042
Can be cancelled, i.e. the multiuser interference can be completely cancelled, and thus the received signal y k The method comprises the following steps:
y k ＝γP LED m I H k F k d k +n k ；
step two: using DFE nonlinear receivers and decoding matrices
Figure BDA0003351952800000043
Joint slave y k To recover the data d required by the user k ；
First receive L of kth user k With one linear decoding vector for each data stream
Figure BDA0003351952800000044
Decoding the L k The data stream leading decoding decision recovers user information +.>
Figure BDA0003351952800000045
And then sequentially removing the recovered user information d from the decoded symbols k,v To reduce inter-code crosstalk, the recovered user information is：
Figure BDA0003351952800000046
in the formula ,bk(u,v) ＝γP LED m I R k(u,v), wherein Rk(u,v) R represents k (u, v) Q [ ] the]Representing the decisions of the signal.
A second object of the present invention is to provide a multi-user MIMO indoor visible light communication method, the method comprising:
the information sent by the transmitting end is modulated and then subjected to GMD-BD pre-coding treatment, and then a direct current bias is added to drive a Light Emitting Diode (LED) to transmit visible light signals;
the visible light signal is transmitted to a receiving end through a channel;
at the receiving end, the optical receiver converts the received visible light signal into an electric signal, then the electric signal is decoded by the GMD-BD decoding matrix and the decision feedback equalization DFE nonlinear receiver to eliminate ISI, and finally the information required by the user is recovered through decision.
Optionally, the method includes:
when the transmitting end transmits user information, firstly, the information is converted from a series flow signal into a parallel flow signal through serial-parallel conversion, then bipolar on-off keying OOK modulation is carried out on the parallel flow signal,
Figure BDA0003351952800000047
the signal after OOK modulation is the user information, K is the number of the user terminals at the receiving end; />
Figure BDA0003351952800000051
Modulated signal representing information of kth user, kth user terminal having N Rk K is more than or equal to 1 and less than or equal to K;
GMD-BD pre-coding processing is carried out on the modulated signals, wherein the GMD-BD pre-coding matrix is as follows:
Figure BDA0003351952800000052
wherein ,
Figure BDA0003351952800000053
a precoding matrix corresponding to the kth user terminal; />
Figure BDA0003351952800000054
The total number of the optical receivers at the receiving end; n (N) T N LEDs are arranged for each LED array of the emitting end;
the pre-coded signals are added with direct current bias to drive the Light Emitting Diode (LED) array to emit visible light signals, and finally the visible light signals x emitted by the LED array are as follows:
Figure BDA0003351952800000055
wherein ,PLED For the power of a single LED, m I In order to modulate the index of the light,
Figure BDA0003351952800000056
is N of all 1 T A dimension column vector;
the transmission channel of the visible light communication method adopts a direct link model, and the channel matrix is as follows:
Figure BDA0003351952800000057
wherein ,
Figure BDA0003351952800000058
representing a channel matrix between the LED array and a kth user terminal;
the receiving end converts the received visible light signal into an electric signal, and after the direct current component is filtered, the signal received by the kth user terminal is:
Figure BDA0003351952800000059
wherein, gamma is the photoelectric conversion factor of the receiver,
Figure BDA00033519528000000510
representing a precoding matrix corresponding to the jth user terminal, d j A signal representing the information of the jth user terminal after modulation, j is 1-K and/or K #>
Figure BDA00033519528000000511
N representing the noise contribution of the optical receiver received signal of the kth user terminal Rk And (5) a dimension vector.
Optionally, in the transmitting end, the pre-coding matrix solving process corresponding to the kth user terminal includes:
step one: assume that the precoding matrix corresponding to the kth user is composed of two parts
Figure BDA00033519528000000512
Marking the channel complement matrix of the kth user as
Figure BDA00033519528000000513
Its rank is->
Figure BDA00033519528000000514
For->
Figure BDA00033519528000000515
SVD decomposition is carried out to obtain:
Figure BDA0003351952800000061
wherein ,
Figure BDA0003351952800000062
by->
Figure BDA0003351952800000063
Left singular vector component,/>
Figure BDA0003351952800000064
Is->
Figure BDA0003351952800000065
Diagonal matrix of singular values, +.>
Figure BDA0003351952800000066
To supplement matrix->
Figure BDA0003351952800000067
Before->
Figure BDA0003351952800000068
Right singular vectors, ">
Figure BDA0003351952800000069
For leaving->
Figure BDA00033519528000000610
Right singular vectors, constitute->
Figure BDA00033519528000000611
A set of orthonormal bases for the null space of ∈ ->
Figure BDA00033519528000000612
Step two: equivalent channel matrix for kth user terminal
Figure BDA00033519528000000613
GMD decomposition can be performed:
Figure BDA00033519528000000614
wherein if it
Figure BDA00033519528000000615
Rank->
Figure BDA00033519528000000616
Then->
Figure BDA00033519528000000617
and />
Figure BDA00033519528000000618
Is a semi-orthogonal matrix, ">
Figure BDA00033519528000000619
Is an upper triangular matrix with equal diagonal elements, note +.>
Figure BDA00033519528000000620
Step three: the GMD-BD precoding matrix corresponding to the kth user terminal finally comprises the following steps:
Figure BDA00033519528000000621
the decoding matrix of the kth user terminal is:
W k ＝Q k 。
optionally, when the receiving end of the method receives the signal, the decoding step of the kth user terminal includes:
step one: f (F) k From H k The zero space vector of the complement matrix is composed, so the encoding matrix satisfies:
Figure BDA00033519528000000622
indicating interference terms in received signals
Figure BDA00033519528000000623
Can be cancelled, i.e. the multiuser interference can be completely cancelled, and thus the received signal y k The method comprises the following steps:
y k ＝γP LED m I H k F k d k +n k ；
step two: using DFE nonlinear receivers and decoding matrices
Figure BDA00033519528000000624
Joint slave y k To recover the data d required by the user k ；
First receive L of kth user k With one linear decoding vector for each data stream
Figure BDA00033519528000000625
Decoding the L k The data stream leading decoding decision recovers user information +.>
Figure BDA00033519528000000626
And then sequentially removing the recovered user information d from the decoded symbols k,v To reduce inter-code crosstalk, the recovered user information is: />
Figure BDA0003351952800000071
wherein ,bk(u,v) ＝γP LED m I R k(u,v), wherein Rk(u,v) R represents k (u, v) Q [ ] the]Representing the decisions of the signal.
The invention has the beneficial effects that:
the visible light communication system of the invention carries out GMD-BD pre-coding processing on the modulated signal at the transmitting end, and utilizes a GMD-BD decoding matrix and a Decision Feedback Equalization (DFE) nonlinear receiver to jointly decode and eliminate intersymbol interference (ISI) at the receiving end. At the receiving end, the signal recovered by the common linear receiver has ISI, and the invention can eliminate the interference of the recovered signal when the residual signal is recovered by adopting the DFE nonlinear receiver, so that the recovery of the signal is more reliable; after GMD decomposition, the equivalent sub-channels of a single user have the same singular value, namely the equivalent sub-stream channels have the same gain, so that different receivers of the same user terminal obtain similar bit error rate performance, the performance of the worst receiver is improved, and the bit error rate of the user terminal is reduced.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a basic schematic diagram of a GMD-BD precoded multi-user MIMO indoor VLC system.
Fig. 2 is a graph of the error rate of a single optical receiver compared to other systems for a system of the present invention when both optical receivers of the same user terminal employ the same field of view (FOV) of 70 °.
Fig. 3 is a graph of error rate of a user terminal compared to other systems for a system of the present invention, where both optical receivers of the same user terminal employ the same FOV at 70 °.
Fig. 4 is a graph showing the error rate of a single optical receiver compared to other systems when two optical receivers of the same user terminal respectively use different FOVs, respectively 70 ° and 50 °.
Fig. 5 is a graph of error rate of a user terminal compared to other systems for the system of the present invention, where two optical receivers of the same user terminal respectively employ different FOVs, respectively 70 ° and 50 °.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the embodiments of the present invention will be described in further detail with reference to the accompanying drawings.
Embodiment one:
the embodiment provides a multi-user MIMO indoor visible light communication system, which comprises a transmitting end, a channel and a receiving end, wherein a signal sent by the transmitting end is transmitted through the channel and received by the receiving end;
the receiving end adopts a GMD-BD decoding matrix and a decision feedback equalization DFE nonlinear receiver to jointly decode, and is used for eliminating intersymbol interference.
Example two
The embodiment provides a multi-user MIMO indoor visible light communication system, which comprises a transmitting end, a channel and a receiving end, wherein a signal sent by the transmitting end is transmitted through the channel and received by the receiving end;
the receiving end adopts a GMD-BD decoding matrix and a decision feedback equalization DFE nonlinear receiver to jointly decode, and is used for eliminating intersymbol interference.
The process of transmitting information by the transmitting end comprises the following steps:
firstly, converting information from a serial signal to a parallel signal through serial-parallel conversion, then carrying out bipolar on-off keying OOK modulation on the parallel signal,
Figure BDA0003351952800000081
the signal after OOK modulation is the user information, K is the number of the user terminals at the receiving end; />
Figure BDA0003351952800000082
Modulated signal representing information of kth user, kth user terminal having N Rk K is more than or equal to 1 and less than or equal to K;
GMD-BD pre-coding processing is carried out on the modulated signals, wherein the GMD-BD pre-coding matrix is as follows:
Figure BDA0003351952800000083
wherein ,
Figure BDA0003351952800000084
a precoding matrix corresponding to the kth user terminal; />
Figure BDA0003351952800000085
The total number of the optical receivers at the receiving end; n (N) T N LEDs are arranged for each LED array of the emitting end;
the pre-coded signals are added with direct current bias to drive the Light Emitting Diode (LED) array to emit visible light signals, and finally the visible light signals x emitted by the LED array are as follows:
Figure BDA0003351952800000091
wherein ,PLED For the power of a single LED, m I In order to modulate the index of the light,
Figure BDA0003351952800000092
is N of all 1 T And (5) maintaining the column vector.
The pre-coding matrix solving step corresponding to the kth user terminal comprises the following steps:
step one: in the visible light communication system, it is assumed that a precoding matrix corresponding to a kth user terminal is composed of two parts
Figure BDA0003351952800000093
Marking the channel complement matrix of the kth user terminal as
Figure BDA0003351952800000094
Its rank is->
Figure BDA0003351952800000095
For->
Figure BDA0003351952800000096
SVD decomposition is carried out to obtain:
Figure BDA0003351952800000097
wherein ,
Figure BDA0003351952800000098
by->
Figure BDA0003351952800000099
Left singular vector component,/>
Figure BDA00033519528000000910
Is->
Figure BDA00033519528000000911
Diagonal matrix of singular values, +.>
Figure BDA00033519528000000912
To supplement matrix->
Figure BDA00033519528000000913
Before->
Figure BDA00033519528000000914
Right singular vectors, ">
Figure BDA00033519528000000915
For leaving->
Figure BDA00033519528000000916
Right singular vectors, constitute->
Figure BDA00033519528000000917
A set of orthonormal bases for the null space of ∈ ->
Figure BDA00033519528000000918
Step two: equivalent channel matrix for kth user terminal
Figure BDA00033519528000000919
GMD decomposition is carried out to obtain the following components:
Figure BDA00033519528000000920
/>
wherein if it
Figure BDA00033519528000000921
Rank->
Figure BDA00033519528000000922
Then->
Figure BDA00033519528000000923
and />
Figure BDA00033519528000000924
Is a semi-orthogonal matrix, ">
Figure BDA00033519528000000929
Is an upper triangular matrix with equal diagonal elements, note +.>
Figure BDA00033519528000000925
Step three: the GMD-BD precoding matrix corresponding to the kth user terminal finally comprises the following steps:
Figure BDA00033519528000000926
the decoding matrix of the kth user terminal is:
W k ＝Q k 。
the channel of this embodiment adopts a direct link model, and the channel matrix is:
Figure BDA00033519528000000927
wherein
Figure BDA00033519528000000928
Representing the channel matrix between the LED array and the kth user terminal.
The receiving end converts the received visible light signal into an electric signal, and after the direct current component is filtered, the signal received by the kth user terminal is:
Figure BDA0003351952800000101
wherein, gamma is the photoelectric conversion factor of the receiver,
Figure BDA0003351952800000102
representing a precoding matrix corresponding to the jth user terminal, d j A signal representing the information of the jth user terminal after modulation, j is 1-K and/or K #>
Figure BDA0003351952800000103
N representing the noise contribution of the optical receiver received signal of the kth user terminal Rk And (5) a dimension vector.
In the receiving end, the decoding steps of the kth user terminal are as follows:
step one: f (F) k From H k The zero space vector of the complement matrix is composed, so the encoding matrix satisfies:
Figure BDA0003351952800000104
indicating interference terms in received signals
Figure BDA0003351952800000105
Can be cancelled, i.e. the multiuser interference can be completely cancelled, and thus the received signal y k The method comprises the following steps:
y k ＝γP LED m I H k F k d k +n k ；
step two: using DFE nonlinear receivers and decoding matrices
Figure BDA0003351952800000106
Joint slave y k To recover the data d required by the user k ；
First receive L of kth user k With one linear decoding vector for each data stream
Figure BDA0003351952800000107
Decoding the L k The data stream leading decoding decision recovers user information +.>
Figure BDA0003351952800000108
And then sequentially removing the recovered user information d from the decoded symbols k,v To reduce inter-code crosstalk, the recovered user information is:
Figure BDA0003351952800000109
in the formula ,bk(u,v) ＝γP LED m I R k(u,v), wherein Rk(u,v) R represents k (u, v) Q [ ] the]Representing the decisions of the signal.
Example III
The embodiment provides a visible light communication method based on GMD-BD precoding, which comprises the following steps:
the information sent by the transmitting end is modulated and then subjected to GMD-BD pre-coding treatment, and then a direct current bias is added to drive a Light Emitting Diode (LED) to transmit visible light signals;
the visible light signal is transmitted to a receiving end through a channel;
at the receiving end, the optical receiver converts the received visible light signal into an electric signal, then the electric signal is decoded by the GMD-BD decoding matrix and the decision feedback equalization DFE nonlinear receiver in a combined way to eliminate intersymbol interference ISI, and finally the information needed by the user is recovered through decision.
Example IV
The embodiment provides a visible light communication method based on GMD-BD precoding, which comprises the following steps:
the information sent by the transmitting end is modulated and then subjected to GMD-BD pre-coding treatment, and then a direct current bias is added to drive a Light Emitting Diode (LED) to transmit visible light signals;
the visible light signal is transmitted to the receiving end through a channel;
at the receiving end, the optical receiver converts the received visible light signal into an electric signal, then the electric signal is decoded by the GMD-BD decoding matrix and the decision feedback equalization DFE nonlinear receiver in a combined way to eliminate intersymbol interference ISI, and finally the information needed by the user is recovered through decision.
When the transmitting end transmits user information, firstly, the information is converted from a series flow signal into a parallel flow signal through serial-parallel conversion, then bipolar on-off keying OOK modulation is carried out on the parallel flow signal,
Figure BDA0003351952800000111
the signal after OOK modulation is the user information, K is the number of the user terminals at the receiving end; />
Figure BDA0003351952800000112
Modulated signal representing information of kth user, kth user terminal having N Rk K is more than or equal to 1 and less than or equal to K;
GMD-BD pre-coding processing is carried out on the modulated signals, wherein the GMD-BD pre-coding matrix is as follows:
Figure BDA0003351952800000113
wherein ,
Figure BDA0003351952800000114
a precoding matrix corresponding to the kth user terminal; />
Figure BDA0003351952800000115
The total number of the optical receivers at the receiving end; n (N) T N LEDs are arranged for each LED array of the emitting end;
the pre-coded signals are added with direct current bias to drive the Light Emitting Diode (LED) array to emit visible light signals, and finally the visible light signals x emitted by the LED array are as follows:
Figure BDA0003351952800000116
wherein ,PLED For the power of a single LED, m I In order to modulate the index of the light,
Figure BDA0003351952800000117
is N of all 1 T A dimension column vector;
the transmission channel of the visible light communication method adopts a direct link model, and the channel matrix is as follows:
Figure BDA0003351952800000121
wherein ,
Figure BDA0003351952800000122
representing a channel matrix between the LED array and a kth user terminal;
the receiving end converts the received visible light signal into an electric signal, and after the direct current component is filtered, the signal received by the kth user is:
Figure BDA0003351952800000123
wherein, gamma is the photoelectric conversion factor of the receiver,
Figure BDA0003351952800000124
representing a precoding matrix corresponding to the jth user terminal, d j A signal representing the information of the jth user after modulation, j is greater than or equal to 1 and less than or equal to K,>
Figure BDA0003351952800000125
n representing the noise contribution of the optical receiver received signal of the kth user terminal Rk And (5) a dimension vector.
In the transmitting end, the pre-coding matrix solving process corresponding to the kth user terminal comprises the following steps:
step one: assume that the precoding matrix corresponding to the kth user terminal is formed by two parts
Figure BDA0003351952800000126
Marking the channel complement matrix of the kth user as
Figure BDA0003351952800000127
Its rank is->
Figure BDA0003351952800000128
For->
Figure BDA0003351952800000129
SVD decomposition is carried out to obtain:
Figure BDA00033519528000001210
wherein ,
Figure BDA00033519528000001211
by->
Figure BDA00033519528000001212
Left singular vector component,/>
Figure BDA00033519528000001213
Is->
Figure BDA00033519528000001214
Diagonal matrix of singular values, +.>
Figure BDA00033519528000001215
To supplement matrix->
Figure BDA00033519528000001216
Before->
Figure BDA00033519528000001217
Right singular vectors, ">
Figure BDA00033519528000001218
For leaving->
Figure BDA00033519528000001219
Right singular vectors, constitute->
Figure BDA00033519528000001220
A set of orthonormal bases for the null space of ∈ ->
Figure BDA00033519528000001221
Step two: equivalent channel matrix for kth user terminal
Figure BDA00033519528000001222
GMD decomposition can be performed:
Figure BDA00033519528000001223
wherein if it
Figure BDA00033519528000001224
Rank->
Figure BDA00033519528000001225
Then->
Figure BDA00033519528000001226
and />
Figure BDA00033519528000001227
Is a semi-orthogonal matrix, ">
Figure BDA00033519528000001228
Is an upper triangular matrix with equal diagonal elements, note +.>
Figure BDA00033519528000001229
Step three: the GMD-BD precoding matrix corresponding to the kth user terminal finally comprises the following steps:
Figure BDA00033519528000001230
the decoding matrix of the kth user terminal is:
W k ＝Q k 。
when the receiving end receives the signal, the decoding step of the kth user terminal comprises the following steps:
step one: f (F) k From H k The zero space vector of the complement matrix is composed, so the encoding matrix satisfies:
Figure BDA0003351952800000131
indicating interference terms in received signals
Figure BDA0003351952800000132
Can be cancelled, i.e. the multiuser interference can be completely cancelled, and thus the received signal y k The method comprises the following steps:
y k ＝γP LED m I H k F k d k +n k ；
step two: using DFE nonlinear receivers and decoding matrices
Figure BDA0003351952800000133
Joint slave y k To recover the data d required by the user k ；
First receive L of kth user k With one linear decoding vector for each data stream
Figure BDA0003351952800000134
Decoding the L k The user information d is recovered by the data stream leading decoding decision k,Lk Then sequentially removing recovered symbols from the decoded symbolsUser information d reproduced k,v To reduce inter-code crosstalk, the recovered user information is:
Figure BDA0003351952800000135
wherein ,bk(u,v) ＝γP LED m I R k(u,v), wherein Rk(u,v) R represents k (u, v) Q [ ] the]Representing the decisions of the signal.
In order to further verify that the invention can obtain better bit error rate performance, a series of simulation experiments are performed for the method of the fourth embodiment, and the experimental results are shown in fig. 2 to 5.
The simulation system selects a typical indoor room model, the room size is 5m and 3m, and N is symmetrically arranged on the ceiling T Each of the LED arrays has n=3600 LED lamps arranged in a 60×60 square matrix, and adjacent LED lamps are spaced apart by 0.01m. In this case, there are k=2 user terminals in the room, and the user terminals 1 and 2 are respectively provided with N R1＝2 and NR2 =2 optical receivers, which are 0.85m from the ground. In view of miniaturization of the user terminal, 2 optical receivers of the same user terminal are spaced apart by 0.1m, the user terminal 1 is located near the LED, and the user terminal 2 is located at an indoor edge position. In both cases, the bit error rate performance of the optical receiver and the user terminal of the GMD-BD system and the SVD-BD system of the present invention are compared by simulation analysis. Case 1: both optical receivers of the same user terminal employ the same fov=70°; case 2: two optical receivers of the same user terminal respectively adopt different FOVs, which are respectively 70 degrees and 50 degrees. Finally, under the condition of the situation 2, the influence of the position of the user terminal 2 of the system of the invention on the error rate performance of the user terminal is analyzed.
Fig. 2 and fig. 3 are respectively the relation between the emission power of a single LED and the error rate of a single optical receiver of a user terminal and the error rate of the user terminal under the condition that two optical receivers of the same user terminal both adopt the same FOV. Compared with the traditional SVD-BD system, the system of the invention enables the optical receivers 1 and 2 of the same user terminal to obtain similar error rates, improves the error rate performance of the worst receiver, and thus reduces the error rate of the user terminal.
Fig. 4 and fig. 5 are respectively the relations between the single LED emission power and the single optical receiver error rate of the user terminal and the error rate of the user terminal under the condition that two optical receivers of the same user terminal both adopt different FOVs. As can be seen from fig. 2 and 3, the error rate performance of the user terminal 1 is slightly improved, because the user terminal 1 is located near the LED array, and the optical receiver thereof uses different FOVs to have less influence on the optical signals received by the optical receiver. The error rate performance of the user terminal 2 is obviously improved, and the phenomenon is that the user terminal 2 is positioned at the indoor edge, when the optical receivers of the user terminal 2 respectively adopt different FOVs, the method ensures that the optical signals received by the optical receivers have larger difference, and the correlation between channels of the user terminal 2 can be effectively reduced, thereby improving the error rate performance of the optical receivers. Under this condition, as can be seen from fig. 4 and 5, the system of the present invention also enables the user terminal to obtain better bit error rate performance compared to the conventional SVD-BD system.
Some steps in the embodiments of the present invention may be implemented by using software, and the corresponding software program may be stored in a readable storage medium, such as an optical disc or a hard disk.
The foregoing description of the preferred embodiments of the invention is not intended to limit the invention to the precise form disclosed, and any such modifications, equivalents, and alternatives falling within the spirit and scope of the invention are intended to be included within the scope of the invention.

Claims (2)

1. The indoor visible light communication system of multi-user MIMO, including transmitting end, signal channel and receiving end, the signal that the transmitting end sends is transmitted through the signal channel, received by the receiving end, characterized by that, the transmitting end of the said visible light communication system carries on GMD-BD pre-coding treatment to the information to be sent;
the receiving end adopts a GMD-BD decoding matrix and a decision feedback equalization DFE nonlinear receiver to jointly decode;
the process of transmitting information by the transmitting end comprises the following steps:
firstly, converting information from a serial signal to a parallel signal through serial-parallel conversion, then carrying out bipolar on-off keying OOK modulation on the parallel signal,
Figure FDA0004069411940000011
the signal after OOK modulation is the user information, K is the number of the user terminals at the receiving end; />
Figure FDA0004069411940000012
Modulated signal representing information of kth user terminal, the kth user terminal having N Rk K is more than or equal to 1 and less than or equal to K;
GMD-BD pre-coding processing is carried out on the modulated signals, wherein the GMD-BD pre-coding matrix is as follows:
Figure FDA0004069411940000013
wherein ,
Figure FDA0004069411940000014
a precoding matrix corresponding to the kth user terminal; />
Figure FDA0004069411940000015
The total number of the optical receivers at the receiving end; n (N) T N LEDs are arranged for each LED array of the emitting end;
the pre-coded signals are added with direct current bias to drive the Light Emitting Diode (LED) array to emit visible light signals, and finally the visible light signals x emitted by the LED array are as follows:
Figure FDA0004069411940000016
wherein ,PLED For the power of a single LED, m I In order to modulate the index of the light,
Figure FDA0004069411940000017
is N of all 1 T A dimension column vector;
the channel adopts a direct link model, and the channel matrix of the visible light communication system is as follows:
Figure FDA0004069411940000018
wherein
Figure FDA0004069411940000019
Representing a channel matrix between the LED array and a kth user terminal;
the receiving end converts the received visible light signal into an electric signal, and after the direct current component is filtered, the signal received by the kth user terminal is:
Figure FDA00040694119400000110
wherein, gamma is the photoelectric conversion factor of the receiver,
Figure FDA00040694119400000111
representing a precoding matrix corresponding to the jth user terminal, d j A signal representing the information of the jth user terminal after modulation, j is 1-K and/or K #>
Figure FDA00040694119400000112
N representing the noise contribution of the optical receiver received signal of the kth user terminal Rk A dimension vector;
in the transmitting end, the pre-coding matrix solving step corresponding to the kth user terminal comprises the following steps:
step one: in the visible light communication system, it is assumed that a precoding matrix corresponding to a kth user terminal is composed of two parts
Figure FDA0004069411940000021
Marking the channel complement matrix of the kth user terminal as
Figure FDA0004069411940000022
Its rank is->
Figure FDA0004069411940000023
For->
Figure FDA0004069411940000024
SVD decomposition is carried out to obtain:
Figure FDA0004069411940000025
wherein ,
Figure FDA0004069411940000026
by->
Figure FDA0004069411940000027
Left singular vector component,/>
Figure FDA0004069411940000028
Is->
Figure FDA0004069411940000029
Diagonal matrix of singular values, +.>
Figure FDA00040694119400000210
To supplement matrix->
Figure FDA00040694119400000211
Before->
Figure FDA00040694119400000212
Right singular vectors, ">
Figure FDA00040694119400000213
For leaving->
Figure FDA00040694119400000214
Right singular vectors, constitute->
Figure FDA00040694119400000215
A set of orthonormal bases for the null space of ∈ ->
Figure FDA00040694119400000216
Step two: equivalent channel matrix for kth user terminal
Figure FDA00040694119400000217
GMD decomposition is carried out to obtain the following components:
Figure FDA00040694119400000218
wherein if it
Figure FDA00040694119400000219
Rank->
Figure FDA00040694119400000220
Then->
Figure FDA00040694119400000221
and />
Figure FDA00040694119400000222
Is a semi-orthogonal matrix of the type,
Figure FDA00040694119400000223
is an upper triangular matrix with equal diagonal elements, note +.>
Figure FDA00040694119400000224
Step three: the final GMD-BD precoding matrix of the kth user terminal is as follows:
Figure FDA00040694119400000225
the decoding matrix of the kth user terminal is:
W k ＝Q k
in the receiving end, the decoding steps of the kth user terminal are as follows:
step one: f (F) k From H k The zero space vector of the complement matrix is composed, so the encoding matrix satisfies:
Figure FDA00040694119400000226
indicating interference terms in received signals
Figure FDA00040694119400000227
Can be cancelled, i.e. the multiuser interference can be completely cancelled, and thus the received signal y k The method comprises the following steps:
y k ＝γP LED m I H k F k d k +n k ；
step two: using DFE nonlinear receivers and decoding matrices
Figure FDA0004069411940000031
Joint slave y k To recover the data d required by the user k ；
First receiving L of kth user terminal k With one linear decoding vector for each data stream
Figure FDA0004069411940000032
Decoding the L k The data stream leading decoding decision recovers user information +.>
Figure FDA0004069411940000033
And then sequentially removing the recovered user information d from the decoded symbols k,v To reduce inter-code crosstalk, the recovered user information is:
Figure FDA0004069411940000034
in the formula ,bk(u,v) ＝γP LED m I R k(u,v), wherein Rk(u,v) R represents k (u, v) Q [ ] the]Representing the decisions of the signal.
2. A visible light communication method based on GMD-BD precoding, the method comprising:
the information sent by the transmitting end is modulated and then subjected to GMD-BD pre-coding treatment, and then a direct current bias is added to drive a Light Emitting Diode (LED) to transmit visible light signals;
the visible light signal is transmitted to a receiving end through a channel;
at a receiving end, an optical receiver converts the received visible light signal into an electric signal, then the electric signal is decoded by a GMD-BD decoding matrix and a decision feedback equalization DFE nonlinear receiver in a combined way to eliminate ISI, and finally information required by a user is recovered through judgment;
when the transmitting end transmits user information, firstly, the information is converted from a series flow signal into a parallel flow signal through serial-parallel conversion, then bipolar on-off keying OOK modulation is carried out on the parallel flow signal,
Figure FDA0004069411940000035
the signal after OOK modulation is the user information, K is the number of the user terminals at the receiving end; />
Figure FDA0004069411940000036
Modulated signal representing information of kth user terminal, the kth user terminal having N Rk K is more than or equal to 1 and less than or equal to K;
GMD-BD pre-coding processing is carried out on the modulated signals, wherein the GMD-BD pre-coding matrix is as follows:
Figure FDA0004069411940000037
wherein ,
Figure FDA0004069411940000038
a precoding matrix corresponding to the kth user terminal; />
Figure FDA0004069411940000039
For the receiving end to sum up
The number of optical receivers; n (N) T N LEDs are arranged for each LED array of the emitting end;
the pre-coded signals are added with direct current bias to drive the Light Emitting Diode (LED) array to emit visible light signals, and finally the visible light signals x emitted by the LED array are as follows:
Figure FDA0004069411940000041
wherein ,PLED For the power of a single LED, m I In order to modulate the index of the light,
Figure FDA0004069411940000042
is N of all 1 T A dimension column vector;
the transmission channel of the visible light communication method adopts a direct link model, and the channel matrix is as follows:
Figure FDA0004069411940000043
wherein ,
Figure FDA0004069411940000044
Representing a channel matrix between the LED array and a kth user terminal;
the receiving end converts the received visible light signal into an electric signal, and after the direct current component is filtered, the signal received by the kth user terminal is:
Figure FDA0004069411940000045
wherein, gamma is the photoelectric conversion factor of the receiver,
Figure FDA0004069411940000046
representing a precoding matrix corresponding to the jth user terminal, d j A signal representing the information of the jth user terminal after modulation, j is 1-K and/or K #>
Figure FDA0004069411940000047
N representing the noise contribution of the optical receiver received signal of the kth user terminal Rk A dimension vector;
in the transmitting end, the pre-coding matrix solving process corresponding to the kth user terminal comprises the following steps:
step one: assume that the precoding matrix corresponding to the kth user terminal is formed by two parts
Figure FDA0004069411940000048
Marking the channel complement matrix of the kth user terminal as
Figure FDA0004069411940000049
Its rank is->
Figure FDA00040694119400000410
For->
Figure FDA00040694119400000411
SVD decomposition is carried out to obtain:
Figure FDA00040694119400000412
wherein ,
Figure FDA00040694119400000413
by->
Figure FDA00040694119400000414
Left singular vector component,/>
Figure FDA00040694119400000415
Is->
Figure FDA00040694119400000416
Diagonal matrix of singular values, +.>
Figure FDA00040694119400000417
To supplement matrix->
Figure FDA00040694119400000418
Before->
Figure FDA00040694119400000419
Right singular vectors, ">
Figure FDA00040694119400000420
For leaving->
Figure FDA00040694119400000421
Right singular vectors, constitute->
Figure FDA00040694119400000422
A set of orthonormal bases for the null space of ∈ ->
Figure FDA00040694119400000423
Step two: equivalent channel matrix for kth user terminal
Figure FDA00040694119400000424
GMD decomposition can be performed:
Figure FDA0004069411940000051
wherein if it
Figure FDA0004069411940000052
Rank->
Figure FDA0004069411940000053
Then->
Figure FDA0004069411940000054
and />
Figure FDA0004069411940000055
Is a semi-orthogonal matrix of the type,
Figure FDA0004069411940000056
is an upper triangular matrix with equal diagonal elements, note +.>
Figure FDA0004069411940000057
Step three: the GMD-BD precoding matrix corresponding to the kth user terminal finally comprises the following steps:
Figure FDA0004069411940000058
the decoding matrix of the kth user terminal is:
W k ＝Q k
when the receiving end of the method receives signals, the decoding step of the kth user terminal comprises the following steps:
step one: f (F) k From H k The zero space vector of the complement matrix is composed, so the encoding matrix satisfies:
Figure FDA0004069411940000059
indicating interference terms in received signals
Figure FDA00040694119400000510
Can be cancelled, i.e. the multiuser interference can be completely cancelled, and thus the received signal y k The method comprises the following steps:
y k ＝γP LED m I H k F k d k +n k ；
step two: using DFE nonlinear receivers and decoding matrices
Figure FDA00040694119400000511
Joint slave y k To recover the data d required by the user k ；
First receive L of kth user k With one linear decoding vector for each data stream
Figure FDA00040694119400000512
Decoding the L k The user information d is recovered by the data stream leading decoding decision k,Lk And then sequentially removing the restored user information d from the decoded symbol k,v To reduce inter-code crosstalk, the recovered user information is:
Figure FDA00040694119400000513
wherein ,bk(u,v) ＝γP LED m I R k(u,v), wherein Rk(u,v) R represents k (u, v) Q [ ] the]Representing the decisions of the signal.
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