CN108206798B - Communication method for inhibiting interference of adjacent transmitters - Google Patents
Communication method for inhibiting interference of adjacent transmitters Download PDFInfo
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- CN108206798B CN108206798B CN201611184277.XA CN201611184277A CN108206798B CN 108206798 B CN108206798 B CN 108206798B CN 201611184277 A CN201611184277 A CN 201611184277A CN 108206798 B CN108206798 B CN 108206798B
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- 238000004891 communication Methods 0.000 title claims abstract description 31
- 238000000034 method Methods 0.000 title claims abstract description 27
- 230000002401 inhibitory effect Effects 0.000 title abstract description 5
- 230000002452 interceptive effect Effects 0.000 claims description 6
- 238000006243 chemical reaction Methods 0.000 claims description 4
- 238000007476 Maximum Likelihood Methods 0.000 claims description 3
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- 238000005516 engineering process Methods 0.000 description 4
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/02—Amplitude-modulated carrier systems, e.g. using on-off keying; Single sideband or vestigial sideband modulation
- H04L27/04—Modulator circuits; Transmitter circuits
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/18—Phase-modulated carrier systems, i.e. using phase-shift keying
- H04L27/20—Modulator circuits; Transmitter circuits
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2689—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation
- H04L27/2691—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation involving interference determination or cancellation
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Abstract
The invention discloses a communication method for inhibiting interference of adjacent transmitters, which is applied to a wireless communication system comprising three communication nodes N1, N2 and N3, wherein N1 transmits a target signal to N2, and a signal transmitted by N3 causes interference on a receiver of N2. By designing the signal formats of a specific N1 target signal transmitter and an N3 interference signal transmitter and adopting a nonlinear interference elimination method at an N2 receiver, the receiver effectively suppresses interference and improves the signal demodulation quality.
Description
Technical Field
The invention relates to a modulation and demodulation method and an interference elimination method of a communication system, in particular to a technology for inhibiting interference of adjacent transmitters, belonging to the field of wireless communication.
Background
In recent years, spectrum resources in wireless communication have become more scarce, and how to effectively reduce interference in a system and accurately transmit data at high speed, thereby improving spectrum efficiency and system capacity of the system, has become an important target of wireless communication research. In the presence of interference on a communication link, the communication quality and spectral efficiency of the system can be significantly improved if the interference can be effectively suppressed or eliminated. The existing interference cancellation technology mostly adopts a linear processing mode. For example: utilizing a beam forming technology to form a zero gain point on a receiver equipped with multiple antennas in the interference direction; or a serial interference elimination method is adopted, namely, the interference signal is demodulated firstly, then the interference signal is reconstructed and subtracted from the received signal. Linear interference cancellation usually comes at the cost of spectral or spatial resources.
Disclosure of Invention
The invention aims to provide a technology and a system for suppressing adjacent transmitter interference. By designing the signal formats of the specific target signal transmitter and the specific interference signal transmitter and adopting a nonlinear interference elimination method at the receiver, the receiver can effectively inhibit interference and improve the signal demodulation quality.
The technical scheme provided by the invention is as follows:
a communication method for suppressing adjacent transmitter interference is applied to a wireless communication system comprising three communication nodes N1, N2 and N3, wherein N1 transmits a target signal to N2, and a signal transmitted by N3 causes interference to a receiver of N2, and the interference is suppressed by the following methods: n1 transmits a digitally modulated signal; n3 first performs MPSK (multiple phase shift keying) modulation on the signal, and then transmits the phase value of MPSK only in the imaginary part, i.e., transmits the phase value on the Q path of baseband modulation, and transmits zero on the I path; the signal received by the N2 is processed by the following steps:
1) carrying out down-conversion on the received signals to obtain I, Q paths of baseband signals;
2) inputting I, Q baseband signals into an equalizer to equalize interference signal components;
3) multiplying the signal obtained in the step 2) by the MPSK signal modulation order M transmitted by N3, and then performing exponential operation with e as the base;
4) solving the natural logarithm and the phase of the absolute value of the signal obtained in the step 3), and respectively using the natural logarithm and the phase as a real part and an imaginary part to form a complex signal;
5) and (4) equalizing the complex signal obtained in the step (4), and then demodulating the signal to obtain information bits.
In the above method, the information bits transmitted by the communication node N1 are digitally modulated, for example, by QAM (quadrature amplitude modulation), and the modulated baseband signal is modulated with a complex number xiWhere i represents the number of symbols.
The signal transmitted by the communication node N3 adopts an MPSK (multiple phase Shift keying) modulation mode, and the phase after the ith symbol modulation is set as thetaiThen, the baseband transmission signal is an imaginary number, and the imaginary part is the phase of MPSK modulation, which is expressed as:
Ii＝jθi，
wherein
M is the modulation order, k is 0,1, …, M-1.
The signal received by the communication node N2 is firstly subjected to down-conversion in the step 1) to obtain a baseband signal yiIt can be expressed as:
yi＝hxxi+hIjθi+ni
wherein h isxParameter, h, representing the channel experienced by the target signalIParameter, n, representing the channel experienced by the interfering signaliRepresenting noise.
Assuming that the receiver of N2 knows the channel parameters of the target signal and the interfering signal, in step 2) the baseband signal y is filterediThe equalization may be performed by using an existing method, such as a zero-forcing equalization method, in which the received signal is divided by the channel parameters of the interference channel, and the obtained signal is expressed as:
step 3) multiplying the MPSK signal modulation order M transmitted by N3 by the signal obtained in step 2), wherein the obtained signal is represented as:
for the signal ri,2Taking an exponential function with e as a base, the resulting signal is expressed as:
due to M thetai2k pi (k is 0,1,2 …, M-1), so there are
Namely, the method comprises the following steps:
step 4) to the complex signal r obtained in step 3)i,3The absolute value of (a) is taken from the natural logarithm, and there are:
a＝ln|ri,3|
and to evaluate the complex signal ri,3The method may divide the real part of the complex signal by the imaginary part and take the inverse tangent function to obtain:
the results are used as a real part and an imaginary part respectively to form a complex signal:
wherein m is any integer.
Step 5) to the complex signal r obtained in step 4)i,4Equalization is performed and the resulting signal is represented as:
for the signal ri,5And performing signal demodulation to obtain information bits. E.g. using maximum likelihood demodulation, i.e. finding suitable transmitted symbols xiAnd the integer m, such that xiAnd ri,5The euclidean distance of (c) is minimum.
The invention has the beneficial effects that: the invention provides a method for inhibiting interference of adjacent transmitters, which can effectively inhibit interference of a receiver and improve signal demodulation quality by designing signal formats of a specific target signal transmitter and an interference signal transmitter and adopting a nonlinear interference elimination method at the receiver.
Drawings
Fig. 1 is a technical diagram of a wireless communication system suppressing adjacent transmitter interference according to the present invention.
Fig. 2 is a schematic diagram of a communication node N2 in the wireless communication system shown in fig. 1
Detailed Description
The invention is described in further detail below with reference to the drawings, without in any way limiting the scope of the invention.
As shown in fig. 1, a wireless communication system includes 3 communication nodes: n1, N2 and N3. N1 sends information to N2, N3 being adjacent transmitters that transmit signals that interfere with the N3 receiver. The receiver N2 receives the target signal transmitted by N1 and is also interfered by the transmitted signal of N3.
The information bits transmitted by the communication node N1 are digitally modulated, for example by QAM (quadrature amplitude modulation), the modulated baseband signal being modulated with a complex number xiWhere i represents the number of symbols.
The signal transmitted by the communication node N3 adopts MPSK (multiple phase shift keying) modulation mode, and transmits the phase value of MPSK only in the imaginary part, for example, the phase value is transmitted in the Q path of baseband modulation, and the zero is transmitted in the I path. Let the phase after the ith symbol modulation be thetaiThen, the baseband transmission signal is an imaginary number, and the imaginary part is the phase of MPSK modulation, which is expressed as:
Ii＝jθi，
wherein
M is the modulation order, k is 0,1, …, M-1.
The communication node N2 firstly carries out down-conversion on the received signal to obtain a baseband I, Q path signal; inputting I, Q baseband signal into equalizer to equalize its interference signal component; multiplying the obtained signal by the MPSK signal modulation order M transmitted by N3, and then taking an exponential operation with e as a base; then, solving the natural logarithm and the phase of the absolute value of the signal, and forming a complex signal by respectively serving as a real part and an imaginary part; and finally, carrying out symbol demodulation on the output signal to obtain information bits. As shown in fig. 2, the method specifically includes:
the signal received by the communication node N2 is down-converted to obtain a baseband signal yiIt can be expressed as:
yi＝hxxi+hIjθi+ni
wherein h isxParameter, h, representing the channel experienced by the target signalIParameter, n, representing the channel experienced by the interfering signaliRepresenting noise.
Assuming that the N2 receiver knows the channel parameters of the target signal and the interfering signal, the receiver processes the received signal by the following steps:
(1) equalizing the received baseband signal, and expressing the obtained signal as:
(2) multiplying the MPSK signal modulation order M transmitted by N3 by the signal obtained in the previous step, and expressing the obtained signal as:
(3) taking an exponential function with e as a base number for the signal obtained in the last step, and expressing the obtained signal as:
due to M thetai＝2kπ(k＝0,1,2… …), therefore there are
Namely, the method comprises the following steps:
(4) taking the natural logarithm of the absolute value of the complex signal obtained in the previous step, the following are:
a＝ln|ri,3|
and the phase of the complex signal obtained in the previous step is determined by dividing the real part by the imaginary part of the complex signal and inverting
Tangent function, we get:
the results are used as a real part and an imaginary part respectively to form a complex signal:
wherein m is any integer.
(5) And (3) equalizing the signal obtained in the last step, and expressing the obtained signal as:
and performing signal demodulation on the signal obtained in the last step to obtain information bits. E.g. using maximum likelihood demodulation, i.e. finding suitable transmitted symbols xiAnd the integer m, such that xiAnd ri,5The euclidean distance of (c) is minimum.
Claims (3)
1. A communication method for suppressing adjacent transmitter interference is applied to a wireless communication system comprising three communication nodes N1, N2 and N3, wherein N1 transmits a target signal to N2, a signal transmitted by N3 causes interference to a receiver of N2, and the target signal is transmitted by the N1The method suppresses the interference: n1 transmitting the digital modulated signal, the ith baseband signal transmitted by N1 is used as complex number xiRepresents; n3 first MPSK modulates the transmitted signal, then transmits the phase value of MPSK only in imaginary part, and uses theta to modulate the phase of the ith symbol transmitted by N3iThen, the baseband transmission signal is represented as: i isi＝jθi，
Wherein
M is the modulation order, k is 0,1, …, M-1; the signal received by the N2 is processed by the following steps:
1) carrying out down-conversion on the received signal to obtain a baseband signal: y isi＝hxxi+hIjθi+niWherein h isxParameter, h, representing the channel experienced by the target signalIParameter, n, representing the channel experienced by the interfering signaliRepresenting noise, i represents the number of symbols;
2) inputting the baseband signal into an equalizer to equalize the interference signal component: let the channel parameter h of the target signal and the interfering signal known to the receiver of N2xAnd hIFor the baseband signal yiAnd (3) equalizing by adopting a zero-forcing equalization method, and obtaining a signal represented as:
3) multiplying the signal obtained in step 2) by the modulation order M of the MPSK signal transmitted by N3, and expressing the obtained signal as:
for the signal ri，2Taking an exponential operation with e as the base, the resulting signal is represented as:
due to M thetai2k pi, where k is 0,1, …, M-1, so there are
Namely, the method comprises the following steps:
4) solving the signal r obtained in the step 3)i，3The natural logarithm of the absolute value of, and the phase of, wherein, for a complex signal ri，3The absolute value of (a) is taken from the natural logarithm, and there are: a ═ ln | ri，3Using complex signals ri，3The real part of the phase is divided by the imaginary part, and then the inverse tangent function is taken to obtain the phase as:
and a and b are respectively used as a real part and an imaginary part to form a complex signal:
wherein m is any integer;
5) for the complex signal r obtained in the step 4)i，4Equalization is performed and the resulting signal is represented as:
then to the signal ri，5And carrying out signal demodulation to obtain information bits.
2. The communication method of claim 1, wherein N1 transmits QAM modulated signals.
3. The communication method of claim 1, wherein step 5) employs a maximum likelihood demodulation method pairSignal ri，5Signal demodulation is performed.
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