CN114696848A - Method for suppressing self-interference of simultaneous same-frequency full-duplex relay amplification forwarding residue - Google Patents
Method for suppressing self-interference of simultaneous same-frequency full-duplex relay amplification forwarding residue Download PDFInfo
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- H—ELECTRICITY
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- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
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- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
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Abstract
The invention provides a method for inhibiting the self-interference of the amplified forwarding residue of a simultaneous co-frequency full duplex relay, which comprises the steps of carrying out channel estimation on each point-to-point link in the link by means of channel estimation methods such as pilot frequency and the like to obtain the channel coefficient of each link; solving an optimal relay amplification factor by using a gradient descent method by taking the signal-to-interference-and-noise ratio of the target node as a target function; the source node signal is subjected to OFDM modulation and added with a cyclic prefix and then transmitted, and the relay node performs full-duplex forwarding after performing zero setting coding and amplification processing on the received signal; the target node carries out cyclic prefix removal, equalization and OFDM demodulation on the received signal; the invention carries out diversity utilization and suppression on the residual self-interference signals subjected to self-interference suppression at the full-duplex relay node at the target node, eliminates the inter-symbol interference component of the residual self-interference signals, obtains the diversity gain of the intra-symbol interference component of part of cyclic orthogonality, and greatly improves the link capacity of the relay link.
Description
Technical Field
The invention belongs to the technical field of signal transmission, and particularly relates to a method for suppressing self-interference of simultaneous same-frequency full-duplex relay amplification forwarding residues.
Background
The relay technology utilizes the inherent diversity characteristic to resist fading channels, provides a low-cost solution for expanding the coverage area of wireless connection, mainly comprises two protocols of amplification forwarding and decoding forwarding, and the amplification forwarding protocol has outstanding advantages in the aspects of processing time delay and complexity.
Meanwhile, the same-frequency full duplex technology aims to transmit and receive information by using the same frequency and the same time slot, so that compared with the traditional frequency division duplex technology and time division duplex technology, the frequency spectrum efficiency is increased by one time or the point-to-point time delay is reduced by half theoretically.
The relay node receives and forwards the signals at the same frequency in the same time slot by using the simultaneous same-frequency full duplex technology, which greatly improves the link capacity of the relay link, but introduces self-interference signals into the relay node. The existing method is to equivalently use the residual self-interference signal as a multipath signal, adopt OFDM modulation, and utilize the characteristics of OFDM to perform diversity utilization on the residual self-interference signal at a target node, so as to achieve the purpose of suppressing the residual self-interference signal. The method improves the performance of the full-duplex relay link, but has more strict cyclic prefix length and still has larger improvement space for the performance and the efficiency.
Disclosure of Invention
The invention provides a method for inhibiting residual self-interference of simultaneous co-frequency full-duplex relay amplification forwarding, which inhibits inter-symbol interference components in the residual self-interference by adopting OFDM modulation and carrying out zero setting coding on relay forwarding signals at a relay node, improves the link capacity of a relay link and provides an optimal relay amplification factor calculation method.
The invention is realized by the following technical scheme:
a method for suppressing the self-interference of the amplified and forwarded residue of the simultaneous co-frequency full duplex relay comprises the following steps:
the method specifically comprises the following steps:
step one, channel estimation is carried out through pilot frequency to obtain channel coefficients among a source node S, a relay node R and a destination node D, and the length N of an OFDM cyclic prefix is determinedcpAnd the number of subcarriers Nsc;
Step two, taking the signal-to-interference-and-noise ratio of the destination node D as an objective function, and solving an optimal relay amplification factor by using a gradient descent method;
step three, the source node S according to the OFDM cyclic prefix length N of the step onecpAnd the number of subcarriers NscTransmitting a signal after OFDM modulation;
after the relay node R receives the signal and carries out self-interference elimination, carrying out zero setting coding and amplification processing according to the optimal relay amplification coefficient obtained in the step two, and carrying out full-duplex forwarding;
and step four, the destination node D receives the forwarding signal of the relay node R and the direct signal of the source node S, and cyclic prefix removal, equalization and OFDM demodulation are carried out.
Further, in the first step,
the coefficient of the channel between the source node S and the destination node D is hSDThe channel coefficient between the source node S and the relay node R is hSRThe channel coefficient between the relay node R and the destination node D is hRDThe equivalent self-interference suppression channel of the relay node R is hRR。
Further, in the second step,
the destination node receives a signal-to-interference-and-noise ratio of
Wherein μ is a normalized power amplification factor, and μ ═ α2=|βhRR|2The mu belongs to (0,1), and alpha is a normalized amplification coefficient of the relay node;
in terms of SINRZS,ofdmIs a target letterObtaining the optimal normalized power amplification coefficient mu of mu epsilon (0,1) by utilizing a gradient descent methodZS,ofdm_optFurther obtain the optimal relay amplification factor betaZS,ofdm_opt。
Further, in the third step,
the source node S determines the OFDM cyclic prefix length N according to the step onecpAnd the number of subcarriers NscTransmitting the signal after OFDM modulation, wherein the symbol length after modulation is N ═ Ncp+Nsc;
The relay node receives the signal, performs self-interference elimination and then performs zero setting coding and amplification processing, and the transmission signal t (i) processed by the relay node is:
where, r (i) is the relay node received signal, k is 0,1,2, … …, and N is the symbol length;
the relay node carries out zero setting in the sampling time slot of i-kN, and other time slots carry out amplification forwarding; beta is the relay amplification factor, and the value is the optimal relay amplification factor beta obtained in the step twoZS,ofdm_opt。
An electronic device comprising a memory storing a computer program and a processor implementing the steps of any of the above methods when the computer program is executed by the processor.
A computer readable storage medium storing computer instructions which, when executed by a processor, implement the steps of any of the above methods.
The invention has the beneficial effects that
The method is characterized in that the residual self-interference of the relay node is equivalent to the multipath signal at the destination node, OFDM modulation is carried out on the source node, and the zero setting coding is carried out on the relay forwarding signal when the relay node is amplified and forwarded; the zero setting code eliminates the inter-symbol interference part of the equivalent multipath signal caused by the residual self-interference, inhibits the inter-symbol interference component in the residual self-interference and improves the link capacity of the relay link; the introduction of OFDM and the cyclic prefix thereof carries out diversity utilization and suppression on the intra-symbol interference part of the equivalent multi-signal; meanwhile, the optimal relay amplification coefficient is solved by using a gradient descent method and is used as the amplification coefficient for the relay node to amplify and forward so as to obtain the optimal link capacity;
the invention carries out diversity utilization and suppression on residual self-interference signals subjected to self-interference suppression at a full-duplex relay node at a target node, eliminates inter-symbol interference components of the signals, obtains diversity gain of intra-symbol interference components of partial cyclic orthogonality, and greatly improves the link capacity of a relay link.
Drawings
FIG. 1 is a system model diagram of the present invention, wherein S is a source node, R is a relay node, and D is a destination node;
FIG. 2 is a flow chart of the present invention;
FIG. 3 is a block diagram of a source node transmitter;
fig. 4 is a block diagram of relay node signal processing;
FIG. 5 is a block diagram of a destination node receiver;
FIG. 6 shows performance gain of zeroed coded OFDM versus OFDM;
figure 7 is an optimal normalized amplification factor validation.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
With reference to figures 1 to 7.
A method for suppressing the self-interference of the amplified and forwarded residue of the simultaneous co-frequency full duplex relay comprises the following steps:
the method specifically comprises the following steps:
step one, channel estimation is carried out through methods such as pilot frequency, channel coefficients among a source node S, a relay node R and a destination node D are obtained, and the length N of an OFDM cyclic prefix is determinedcpAnd the number of subcarriers Nsc;
Step two, taking the signal to interference plus noise ratio of the destination node D as a target function, and solving an optimal relay amplification factor by using a gradient descent method;
step three, the source node S according to the OFDM cyclic prefix length N of the step onecpAnd the number of subcarriers NscTransmitting a signal after OFDM modulation;
after the relay node R receives the signal and carries out self-interference elimination, carrying out zero setting coding and amplification processing according to the optimal relay amplification coefficient obtained in the step two, and carrying out full-duplex forwarding;
and step four, the destination node D receives the forwarding signal of the relay node R and the direct signal of the source node S, and cyclic prefix removal, equalization and OFDM demodulation are carried out.
In the first step, the first step is carried out,
the channel between the nodes is a quasi-static flat fading channel, and the coefficient of the channel between the source node S and the destination node D is hSDThe channel coefficient between the source node S and the relay node R is hSRThe channel coefficient between the relay node R and the destination node D is hRDAnd obtaining an equivalent self-interference suppression channel h of the relay node R according to the self-interference suppression theoryRR。
3. The method of claim 2, further comprising: in the second step of the method, the first step of the method,
the destination node receives a signal-to-interference-and-noise ratio of
Wherein μ is a normalized power amplification factor, and μ ═ α2=|βhRR|2The mu belongs to (0,1), and alpha is a normalized amplification coefficient of the relay node;
in terms of SINRZS,ofdmObtaining the optimal normalization of the mu epsilon (0,1) for the objective function by using a gradient descent methodCoefficient of power amplification muZS,ofdm_optFurther obtain the optimal relay amplification factor betaZS,ofdm_opt。
In the third step, the first step is carried out,
the source node S determines the OFDM cyclic prefix length N according to the step onecpAnd the number of subcarriers NscTransmitting the signal after OFDM modulation, wherein the symbol length after modulation is N ═ Ncp+Nsc;
The relay node receives the signal, performs self-interference elimination and then performs zero setting coding and amplification processing, and the transmission signal t (i) processed by the relay node is:
where, r (i) is the relay node received signal, k is 0,1,2, … …, and N is the symbol length;
the relay node carries out zero setting in the sampling time slot of i-kN, and other time slots carry out amplification forwarding; beta is the relay amplification factor, and the value is the optimal relay amplification factor beta obtained in the step twoZS,ofdm_opt。
An electronic device comprising a memory storing a computer program and a processor implementing the steps of any of the above methods when the processor executes the computer program.
A computer readable storage medium storing computer instructions which, when executed by a processor, implement the steps of any of the above methods.
The working process of the method for inhibiting the self-interference of the simultaneous co-frequency full-duplex relay amplification forwarding residual based on the zero-set coded OFDM is assumed as follows:
the relay node works in a simultaneous same-frequency full duplex mode, self-interference suppression is incomplete, the self-interference suppression can be equivalent to a quasi-static flat fading channel, and the channel coefficient is hRR;
The channel between nodes is quasi-static flat fading channel, and the coefficient of the channel between the source node S and the destination node D is hSDSource nodeThe channel coefficient between S and the relay node R is hSRThe channel coefficient between the relay node R and the destination node D is hRD。
The source node S sends a signal to carry out OFDM modulation, and the symbol length is N-Ncp+Nsc,NcpIs a cyclic prefix length, NscIs the number of subcarriers.
The relay node receives the signal, performs self-interference elimination and then performs zero setting coding and amplification processing,
carrying out simulation according to the parameters shown in the table 1; the simulation result is shown in FIG. 3
TABLE 1 simulation parameters
When the length of the cyclic prefix, the number of the subcarriers and the normalized amplification factor are the same, the zero setting code is added into the relay node to obtain a certain performance gain.
Traversing the normalized amplification factor alpha in the range of alpha epsilon (0,1) by 0.05 step length, drawing a performance curve when the bit error rate is minimum, and simultaneously calculating the optimal relay amplification factor beta obtained in the step twoZS,ofdm_optThe optimal normalized relay amplification coefficient alpha is obtained after normalizationZS,ofdm_optPerformance simulation was performed to obtain a bit error rate curve, as shown in fig. 4.
The square frame and the diamond frame in fig. 7 are the theoretical optimal normalized relay amplification factor alphaZS,ofdm_optThe bit error rate performance is coincided with two performance curves obtained by traversing alpha when the bit error rate is minimum, and the optimal relay amplification factor beta obtained by theoretical solution in the step two is verifiedZS,ofdm_optThe amplification factor is the amplification factor when the bit error rate performance is optimal.
The method for suppressing the simultaneous same-frequency full-duplex relay amplification forwarding residual self-interference provided by the invention is described in detail, the principle and the implementation mode of the invention are explained, and the description of the embodiment is only used for helping to understand the method and the core idea of the invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.
Claims (6)
1. A method for suppressing the self-interference of the amplified and forwarded residue of the simultaneous co-frequency full duplex relay is characterized in that:
the method specifically comprises the following steps:
step one, channel estimation is carried out through pilot frequency to obtain channel coefficients among a source node S, a relay node R and a destination node D, and the length N of an OFDM cyclic prefix is determinedcpAnd the number of subcarriers Nsc;
Step two, taking the signal-to-interference-and-noise ratio of the destination node D as an objective function, and solving an optimal relay amplification factor by using a gradient descent method;
step three, the source node S according to the OFDM cyclic prefix length N of the step onecpAnd the number of subcarriers NscTransmitting a signal after OFDM modulation;
after the relay node R receives the signal and carries out self-interference elimination, carrying out zero setting coding and amplification processing according to the optimal relay amplification coefficient obtained in the step two, and carrying out full-duplex forwarding;
and step four, the destination node D receives the forwarding signal of the relay node R and the direct signal of the source node S, and cyclic prefix removal, equalization and OFDM demodulation are carried out.
2. The method of claim 1, further comprising: in the first step, the first step is carried out,
the coefficient of the channel between the source node S and the destination node D is hSDThe channel coefficient between the source node S and the relay node R is hSRThe channel coefficient between the relay node R and the destination node D is hRDThe equivalent self-interference suppression channel of the relay node R is hRR。
3. The method of claim 2, further comprising: in the second step, the first step is carried out,
the destination node receives a signal to interference plus noise ratio of
Wherein μ is a normalized power amplification factor, and μ ═ α2=|βhRR|2The mu belongs to (0,1), and alpha is a normalized amplification coefficient of the relay node;
in terms of SINRZS,ofdmObtaining the optimal normalized power amplification coefficient mu of mu epsilon (0,1) by using a gradient descent method as an objective functionZS,ofdm_optFurther obtain the optimal relay amplification factor betaZS,ofdm_opt。
4. The method of claim 3, further comprising: in the third step, the first step is carried out,
the source node S determines the OFDM cyclic prefix length N according to the step onecpAnd the number of subcarriers NscTransmitting the signal after OFDM modulation, wherein the symbol length after modulation is N ═ Ncp+Nsc;
The relay node receives the signal, performs self-interference elimination and then performs zero setting coding and amplification processing, and the transmission signal t (i) processed by the relay node is:
where, r (i) is the relay node received signal, k is 0,1,2, … …, and N is the symbol length;
the relay node carries out zero setting in the sampling time slot of i-kN, and other time slots carry out amplification forwarding; beta is the relay amplification factor, and the value is the optimal relay amplification factor beta obtained in the step twoZS,ofdm_opt。
5. An electronic device comprising a memory and a processor, the memory storing a computer program, wherein the processor implements the steps of the method of any one of claims 1 to 4 when executing the computer program.
6. A computer readable storage medium storing computer instructions, which when executed by a processor implement the steps of the method of any one of claims 1 to 4.
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