An inter-array coupling channel estimation method based on OFDM waveform

Abstract

The application discloses an array inter-coupling channel estimation method based on an OFDM waveform, and comprises the following steps: S1, a signal transmission model based on an OFDM waveform is given; S2, assuming that a self-interference channel is static, multiple times of changing a transmitting and receiving beamforming vector are given, and multiple groups of r(f k ) are obtained, so that a calculation formula of an H(f k ) estimation value is obtained; S3, zero space decomposition is carried out on a transmitting beam pointing direction vector q t and a receiving beam pointing direction vector q r , and a W and V selection strategy is given; S4, the transmitting beamforming vector is sequentially configured as a column vector in W, and the receiving beamforming vector is sequentially configured as a column vector in V, so that multiple groups of r(f k ) are obtained; S5, the step S4 is performed K*J times, so that an R(f k ) matrix is obtained, and an estimation value of H(f k ) is obtained, that is, a self-interference channel matrix on each subcarrier is obtained. The application can be performed when a transmitting and receiving array surface normally works, transmission efficiency of array service is improved, and changes of a channel state can be timely responded.

Description

Technical Field

[0001] This invention relates to the field of wireless communication, and in particular to an inter-array coupling channel estimation method based on OFDM waveforms. Background Technology

[0002] With the rapid development of wireless communication, limited spectrum resources are gradually being depleted. Traditional half-duplex wireless communication can no longer meet the demands for spectrum utilization and service diversity. Full-duplex communication can transmit and receive signals on the same time and frequency resources, greatly improving spectrum resource utilization and becoming one of the key technologies for next-generation wireless communication. The key issue of full-duplex technology lies in self-interference suppression. For single-antenna simultaneous transmission and reception at the same frequency, the academic community has conducted relatively thorough research. However, for multi-antenna arrays simultaneously transmitting and receiving at the same frequency in full-duplex mode, self-interference components originate from all transmitting elements, superimposing on the receiving array to form high-power self-interference, causing saturation of the receiver's RF front-end low-noise amplifier, severely affecting the normal operation of the receiver. A three-level self-interference suppression architecture has now been established, encompassing the spatial domain, RF domain, and digital domain. Among these, the active and passive isolation methods in the spatial domain can effectively reduce the coupling self-interference power of the receiver's RF front-end. Adaptive beamforming, as one of the active isolation methods, can adjust the phase and amplitude of the transmitting and receiving array signals using adjustable phase shifters and adjustable attenuators, forming a far-field beam in the desired transmission and reception direction, while simultaneously forming near-field nulls through signal superposition, improving the isolation between the transmitting and receiving arrays. Solving for adaptive beamforming vectors requires knowledge of self-interference channel information. How to obtain this self-interference channel information has become a key issue in spatial domain self-interference suppression. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide an inter-array coupling channel estimation method based on OFDM waveforms, which can be performed when the transceiver array is working normally, improves the transmission efficiency of array services, and can respond to changes in channel state in a timely manner.

[0004] The objective of this invention is achieved through the following technical solution: an inter-array coupling channel estimation method based on OFDM waveforms, comprising the following steps:

[0005] S1. Given a signal transmission model based on OFDM waveforms;

[0006] At the transmitting end, after inserting pilot signals into each sub-band of the desired signal, an IFFT transformation is performed. After passing through a DAC and a mixer, the signal is split into J paths by a power divider, and after beamforming, it is transmitted through a transmitting antenna array.

[0007] The transmitted signal is coupled to a nearby receiving antenna array through a near-field self-interference channel. The receiving array contains K receiving antennas. The signals received by the K receiving antennas are beamformed and then combined. The combined signal is then passed through a mixer and an ADC, followed by an FFT transformation. Dividing by the pilot symbol yields the desired received signal. The sub-frequency band f... k The received signal is denoted as r(f) k );

[0008] S2. Assuming the self-interference channel is static, multiple changes to the transmit and receive beamforming vectors are given, resulting in multiple sets of r(f) k Thus, we can obtain H(f) k The formula for the estimated value of ).

[0009] S3. By directing the transmitted beam to the guiding vector q t and the receiving beam pointing guide vector q r Perform null space decomposition and propose strategies for selecting W and V;

[0010] S4. Sequentially configure the transmit beamforming vector as a column vector in W; sequentially configure the receive beamforming vector as a column vector in V, obtaining multiple sets of r(f) k )

[0011] S5. Perform step S4 K·J times to obtain R(f) k ) matrix, thus obtaining H(f k The estimated value of ) is obtained, that is, the self-interference channel matrix on each subcarrier is obtained.

[0012] The beneficial effects of this invention are: unlike the traditional method of sequentially measuring the channel between each pair of transceiver array elements, the proposed channel estimation can be performed when the transceiver array is working normally, which improves the efficiency of array service transmission and can respond to changes in channel state in a timely manner. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of a full-duplex analog array simultaneous transmission and reception system. Detailed Implementation

[0014] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the following description.

[0015] like Figure 1 As shown, Figure 1As shown, in the full-duplex analog array system, the analog transmit array and analog receive array are equipped with J antennas and K antennas, respectively. The baseband transmit signal passes through a DAC and mixer, is split into K paths by a power divider, and is then weighted by different adjustable phase shifters and adjustable attenuators before being transmitted. The signal causes strong self-interference to the adjacent receive array through a near-field coupling channel. The received signal is then weighted by different adjustable phase shifters and adjustable attenuators before being combined. The combined signal passes through a mixer and ADC before undergoing signal processing in the baseband.

[0016] For full-duplex analog arrays, this patent proposes a self-interference channel estimation method based on OFDM waveforms. Since all transmit and receive channels in the analog array share a single DAC and ADC, the transmitted and received signal data are consistent across all channels. Therefore, traditional algorithms that use different pilots for channel estimation in different channels are not suitable for analog full-duplex arrays.

[0017] This patent proposes a novel method for estimating the self-interference channel of a simulated array using pilot signals. This method requires no additional analog components; it relies solely on the hardware of the original array's simultaneous transmit / receive system to perform channel estimation at the baseband level. The channel estimated in this patent includes the physical space propagation channel between each pair of transmit / receive array elements, rather than an equivalent or statistically significant channel.

[0018] Specifically, an inter-array coupling channel estimation method based on OFDM waveforms includes the following steps:

[0019] S1. Given a signal transmission model based on OFDM waveforms;

[0020] At the transmitting end, the transmitted signal undergoes serial-to-parallel conversion followed by IFFT transformation, then passes through a DAC and mixer, and is split into J paths by a power divider. These paths are then weighted by different adjustable phase shifters and adjustable attenuators before being transmitted. Pilot signals are inserted into each sub-band of the OFDM signal. For ease of derivation of the following formulas, it is assumed that the inserted pilot symbol is 1.

[0021] The transmitted signal is coupled to a nearby receiving array through a near-field self-interference channel. The received signal is weighted by different adjustable phase shifters and adjustable attenuators before being combined. The combined signal is then processed in the baseband after passing through a mixer and an ADC. An FFT is performed on the received signal, and it is divided by the pilot symbol.

[0022] In each sub-band, we have:

[0023] r(f k ) = v H {H(f k )[wx(f k )+z t [+z r +s(f k )} (1)

[0024] Where r(f) k ) represents each sub-band. k The received signal on the device, (·) H Denotes the conjugate transpose of a matrix, x(f k ) represents the sub-band f k The transmitted signal on This represents the transmit beamforming vector, which is changed by adjusting the adjustable phase shifter and adjustable attenuator at the transmitter. t The transmitter's Gaussian white noise, z r This represents the receiver's white Gaussian noise. This represents the received beamforming vector, which can be changed by adjusting the adjustable phase shifter and adjustable attenuator at the receiver. Indicates sub-band f k Self-interference coupling channel on, s(f k ) represents the desired received signal in the far field.

[0025] S2. Assuming the self-interference channel is static, multiple changes to the transmit and receive beamforming vectors are given, resulting in multiple sets of r(f) k ), thereby obtaining H(f) k The formula for the estimated value of ).

[0026] It is expressed as follows:

[0027] R(f k )≈V H H(f k )Wx(f k (2)

[0028] Wherein, R(f) k )∈￡ K×J Represents multiple sets of r(f) k The matrix is ​​composed of ) . Assuming that the transmit noise, receive noise and far-field signal power are all sufficiently small, then equation (2) can be obtained. Where,

[0029] W = (w1, w2, K, w J (3)

[0030] V = (v1, v2, K, v K (4)

[0031] These represent matrices composed of the J-group transmit beamforming vectors and the K-group receive beamforming vectors, respectively.

[0032] w j (j = 1, 2, ..., J) represents the j-th transmit beamforming vector. Each transmit beamforming vector contains J sets of configuration parameters. Each set of configuration parameters is used to configure the adjustable phase shifter and adjustable attenuator through which one transmit signal passes.k (k = 1, 2, ..., K) represents the k-th receive beamforming vector. Each receive beamforming vector contains K sets of configuration parameters. Each set of configuration parameters is used to configure the adjustable phase shifter and adjustable attenuator through which one transmitted signal passes.

[0033] When W and V are invertible, H(f) k The estimated value of ) is expressed as:

[0034]

[0035] in,(·) -1 This represents finding the inverse of a matrix.

[0036] S3. By directing the transmitted beam to the guiding vector q t and the receiving beam pointing guide vector q r Perform null space decomposition and propose strategies for selecting W and V;

[0037] Assume the pointing guide vector of the transmitted beam is q t .right X is obtained by null space decomposition t X t The null space is represented by a set of orthonormal bases, denoted as X. t =span{x t1 ,x t2 ,...,x tJ-1}.make

[0038] W = (q t ,q t +x t1 ,q t +x t2 ,K,q t +x tJ-1 (6)

[0039] Clearly, W is reversible.

[0040] Assume the receiving beam pointing steering vector is q r .right X is obtained by null space decomposition r X r The null space is represented by a set of orthonormal bases, denoted as X. r =span{x r1 ,x r2 ,...,x rK-1}.make

[0041] V=(q r ,q r +x r1 ,q r +xr2 ,K,q r +x rK-1 (7)

[0042] S4. Sequentially configure the transmit beamforming vector as a column vector in W; sequentially configure the receive beamforming vector as a column vector in V, obtaining multiple sets of r(f) k ).

[0043] Because x tk Taken from the null space, therefore q t Add any x tk Or x ti and x tk All combinations can ensure that the transmitted beam pointing and gain remain unchanged. Similarly, q r Add any x rk Or x ri and x rk The proposed combination of methods ensures that the received beam pointing and gain remain unchanged. Therefore, the proposed channel estimation method can operate in parallel with transceiver array services.

[0044] S5. Perform step S4 K·J times to obtain R(f) k Substituting the matrix into formula (5), we can obtain H(f) k The estimated value of ) is obtained, that is, the self-interference channel matrix on each subcarrier is obtained.

[0045] The above description represents preferred embodiments of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in other combinations, modifications, and environments, and can be altered within the scope of the concept described herein through the above teachings or related technical or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A method of inter-array coupling channel estimation based on OFDM waveform, characterized by: The method comprises the following steps: S1. A given OFDM waveform-based signal transmission model; At the sending end, after inserting a pilot on each sub-band of the expected signal, performing IFFT transformation, passing through a DAC and a mixer, being divided into J paths by a power divider, performing transmit beamforming, and being transmitted through a transmit antenna array; The transmitting signal is coupled to the adjacent receiving antenna array through the near-field self-interference channel, the receiving array contains K receiving antennas, the signals received by the K receiving antennas are subjected to receiving beamforming, then the signals are combined, the combined signals are subjected to FFT transformation after passing through the mixer and the ADC, and are divided by the pilot symbol to obtain the required receiving signal; wherein, the sub-band f k The receiving signal is denoted as r(f k ). In the step S1, on each sub-band, there are: r(f k ) = v H {H(f k )[wx(f k )+z t ]+z r +s(f k )} (1) where r(f k ) represents the received signal in each sub-band sub-band f k , (·) H represents the matrix conjugate transpose, x(f k ) represents the transmitted signal in sub-band f k , represents the transmit beamforming vector, which is changed by adjusting the adjustable phase shifter and adjustable attenuator at the sending end, z t represents the transmitter Gaussian white noise, z r represents the receiver Gaussian white noise; represents the receive beamforming vector, which is changed by adjusting the adjustable phase shifter and adjustable attenuator at the receiving end; represents the self-interference coupling channel in sub-band f k , s(f k ) represents the desired received signal in the far field; S2. Assuming that the self-interference channel is static, give multiple changes to the transmit and receive beamforming vectors, get multiple sets of r(f k ), so as to get the formula for solving the estimated value of H(f k ). The step S2 comprises: Assuming that the self-interference channel is static, multiple sets of r(f k ) are obtained by changing the transmit and receive beamforming vectors multiple times Assuming that the transmit noise, the receive noise and the far-field signal power can be ignored, the channel is least square estimated through the pilot to obtain formula (2): R(f k )≈V H H(f k )W (2) wherein represents a matrix of groups r(f k ) groups; wherein, W=(w1,w2,...,w J ) (3) V=(v1,v2,...,v K ) (4) W and V respectively represent matrices composed of J groups of transmit beamforming vectors and K groups of receive beamforming vectors; w j (j = 1, 2,..., J) represents the jth transmit beamforming vector, each of which contains J sets of configuration parameters, each set of configuration parameters being used to configure a tunable phase shifter and a tunable attenuator through which a transmit signal passes, k (k = 1, 2,..., K) represents the kth receive beamforming vector, each of which contains K sets of configuration parameters, each set of configuration parameters being used to configure a tunable phase shifter and a tunable attenuator through which a receive signal passes; When W and V are invertible, H(f k ) is estimated as where (·) -1 denotes matrix inversion; S3. Perform null space decomposition on the transmit beam pointing steering vector q t and the receive beam pointing steering vector q r to give W and V selection strategies; The step S3 comprises: Assume the pointing guide vector of the transmitted beam is q t ,right X is obtained by null space decomposition t X t The null space is represented by a set of orthonormal bases, denoted as X. t =span{x t1 ,x t2 ,...,x tJ-1 },make W = (q t , q t + x t1 , q t + x t2 ,..., q t + x tJ-1 ) (6) Assume the receiving beam pointing steering vector is q r ,right X is obtained by null space decomposition r X r The null space is represented by a set of orthonormal bases, denoted as X. r =span{x r1 ,x r2 ,...,x rK-1 },make V = (q r , q r + x r1 , q r + x r2 ,..., q r + x rK-1 ) (7) Wherein, W and V are reversible; S4. Configure the transmit beamforming vectors as the column vectors in W in turn; configure the receive beamforming vectors as the column vectors in V in turn, obtaining multiple groups of r(f k ) S5. Step S4 is performed K*J times to obtain R(f k ) matrices, and thus an estimate of H(f k ) is obtained, i.e. the self-interference channel matrix at each subcarrier.

2. The method of claim 1, wherein: In the step S1, each path signal output by the power divider corresponds to a transmit antenna in the transmit antenna array, each path signal is weighted through different adjustable phase shifters and adjustable attenuators, and then is transmitted to the corresponding transmit antenna for signal transmission; the transmit beamforming is realized by connecting the adjustable attenuator and the adjustable phase shifter of each path signal; The signal received by each receive antenna is weighted through different adjustable phase shifters and adjustable attenuators to realize receive beamforming.

3. The method of claim 1, wherein: The step S5, R(f k ) matrix into formula (5), thus obtain the estimate value of H(f k ), that is, the self-interference channel matrix on each sub-carrier. Because x tk Taken from the null space, therefore q t Add any x tk Or x ti and x tk All combinations can ensure that the transmitted beam pointing and gain remain unchanged. Similarly, q r Add any x rk Or x ri and x rk All combinations can ensure that the receiving beam pointing and gain remain unchanged.

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