A fluidic antenna-assisted downlink direct transmission and cooperative power domain NOMA dual-mode hierarchical communication method

Abstract

This invention discloses a fluid antenna-assisted downlink direct transmission and cooperative power domain NOMA dual-mode hierarchical communication method, constructing a system. The system performs dual-mode transmission within one transmission cycle: In the first time period, the source end transmits a first signal to the near end through a first antenna, and simultaneously broadcasts a NOMA superimposed signal through a second antenna; each receiver utilizes the interference compression function of the fluid antenna to achieve hierarchical signal reception; In the second time period, the cooperating end forwards the far-end signal, and the source end transmits a second signal to the near end through the first antenna. The near end and far end decode based on the maximum signal-to-interference-plus-noise ratio (SINR) criterion, respectively. This invention, through the fusion design of fluid antenna interference suppression and port selection strategies, achieves zero SIC reception for both near-end and far-end devices and single SIC reception for cooperating devices, significantly reducing residual interference from imperfect SIC and effectively improving the system's sum rate and reliability.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology, specifically to a fluid antenna-assisted downlink direct transmission and cooperative power domain NOMA dual-mode hierarchical communication method. Background Technology

[0002] Current downlink NOMA-based CDRT (NOMA-CDRT) methods generally employ a single-antenna source-end transmit architecture, requiring the receiver to rely on serial interference cancellation (SIC) techniques to separate multi-user signals superimposed in the power domain. In real-world electromagnetic environments, due to channel state information acquisition errors and hardware non-ideals, the receiver typically faces imperfect SiC (Sequential Interference Cancellation). This is particularly true for near-end communication devices, which often need to demodulate and cancel signals from other communication devices to extract their desired signals. This multi-stage SiC not only increases the terminal's computational load and processing latency but also easily leads to the accumulation of residual interference across stages and error propagation. As transmit power increases, the performance limitations caused by such residual interference become increasingly significant, restricting the system's achievable throughput and transmission reliability under limited resources.

[0003] On the other hand, two-dimensional planar fluidic antennas (FAS), by arranging multiple switchable preset ports within a limited physical space, enable devices to select the port with the best channel conditions for transmission and reception, thus obtaining additional spatial diversity gain and providing a technical approach to alleviate channel fading and improve reception reliability. However, if fluidic antennas are only used as conventional receiving components in traditional NOMA-CDRT networks, their gain is mainly limited to improving local channel fading at the receiver. Since the source transmitter still uses a single-antenna power domain superposition transmission mechanism, fluidic antennas cannot effectively isolate and layer direct transmission links and cooperative links from a physical structure perspective. Therefore, they cannot avoid the multi-level SiC calculation load and the resulting residual interference accumulation problem faced by near-end communication equipment. Existing technical architectures cannot simultaneously meet the requirements of high spectral efficiency, wide-area coverage, and suppression of residual SiC interference. Summary of the Invention

[0004] Purpose of the Invention: The purpose of this invention is to provide a downlink direct transmission and cooperative power domain NOMA dual-mode hierarchical communication method assisted by a fluid antenna. This method addresses the problems inherent in existing downlink NOMA-CDRT methods, which commonly employ a single-antenna source-end communication device architecture and rely on multi-stage serial interference cancellation at the receiver. Specifically, under imperfect SiC conditions, residual interference easily accumulates and causes error propagation, making the decoding performance of near-end communication devices highly sensitive to SiC errors, thus limiting system reliability and achievable throughput. Simultaneously, this invention solves the problem that existing improvement methods that rely solely on receiver diversity gain are insufficient to effectively isolate power domain superimposed interference at the system architecture level.

[0005] Technical solution: The present invention provides a method for downlink direct transmission and cooperative power domain NOMA dual-mode hierarchical communication assisted by a fluidic antenna, comprising the following steps:

[0006] (1) Construct a downlink communication system including source communication equipment, near-end communication equipment, cooperative communication equipment and far-end communication equipment; wherein the source communication equipment is equipped with a first conventional fixed transmitting antenna and a second conventional fixed transmitting antenna; the near-end communication equipment, cooperative communication equipment and far-end communication equipment are all equipped with a single two-dimensional planar fluid antenna, the fluid antenna contains multiple preset receiving ports, and only one preset receiving port is activated at any time to receive signals;

[0007] (2) The information transmission cycle is divided into a first time period and a second time period. In the first time period, the source communication device transmits a first signal carrying the information required by the near-end communication device through a first conventional fixed transmitting antenna, and at the same time transmits a power domain non-orthogonal multiple access superimposed coded signal carrying the information required by the cooperative communication device and the remote communication device through a second conventional fixed transmitting antenna. The near-end communication device regards the superimposed coded signal of the second conventional fixed transmitting antenna as interference, selects a receiving port from multiple preset receiving ports based on the maximum signal-to-interference-plus-noise ratio criterion, and directly decodes the first signal without performing serial interference cancellation. The cooperative communication device regards the first signal of the first conventional fixed transmitting antenna as interference, selects a receiving port from multiple preset receiving ports based on the joint feasibility criterion, performs serial interference cancellation on the superimposed coded signal, and decodes the signal required by the remote communication device and the signal required by the cooperative communication device in sequence.

[0008] (3) During the second time period, the cooperative communication device forwards the signal required by the remote communication device to the remote communication device after decoding. At the same time, the source communication device transmits the second signal carrying the information required by the near-end communication device through the first conventional fixed transmitting antenna. The second conventional fixed transmitting antenna remains silent. The remote communication device selects a receiving port from multiple preset receiving ports based on the maximum signal-to-interference-plus-noise ratio criterion, receives and decodes the forwarded signal. The near-end communication device regards the forwarded signal as interference, selects a receiving port from multiple preset receiving ports based on the maximum signal-to-interference-plus-noise ratio criterion, receives and decodes the second signal.

[0009] Furthermore, in step (2), the first time period and the second time period are consecutive in time and have the same duration.

[0010] Furthermore, during the first time period, the source communication equipment uses an antenna-level power allocation method to distribute the total transmission power to the first conventional fixed transmitting antenna and the second conventional fixed transmitting antenna.

[0011] Furthermore, in the first time period, in the power domain non-orthogonal multiple access superimposed coded signal transmitted by the second conventional fixed transmitting antenna, the power of the signal allocated to the remote communication device is greater than the power of the signal allocated to the cooperative communication device.

[0012] Furthermore, in step (2), the near-end communication device selects the port using the maximum signal-to-interference-plus-noise ratio criterion in the first time period. The specific process is as follows: the superimposed coded signal of the second conventional fixed transmitting antenna is regarded as interference, the received signal-to-interference-plus-noise ratio of the first signal corresponding to each preset receiving port is calculated, and the preset receiving port with the largest signal-to-interference-plus-noise ratio is selected as the working port to directly decode the first signal.

[0013] Furthermore, in step (2), the specific process of port selection based on joint feasibility criteria for the cooperative communication device in the first time period is as follows: the first signal of the first conventional fixed transmitting antenna is regarded as interference, and the decoding signal-to-interference-plus-noise ratio of the remote communication device signal and the cooperative communication device signal corresponding to each preset receiving port is calculated respectively; according to the preset decoding threshold condition, the effective port set that can simultaneously satisfy the successful decoding of the remote communication device signal and the cooperative communication device signal is selected; if the effective port set is not empty, the preset receiving port that maximizes the decoding signal-to-interference-plus-noise ratio of the cooperative communication device signal is selected as the working port; if the effective port set is empty, the preset receiving port that maximizes the decoding signal-to-interference-plus-noise ratio of the remote communication device signal is selected as the working port from all preset receiving ports.

[0014] Furthermore, in step (2), when the cooperative communication device performs serial interference cancellation in the first time period, it first decodes the signal required by the remote communication device, and then decodes the signal required by the cooperative communication device.

[0015] Furthermore, in step (3), the remote communication device selects the port using the maximum signal-to-interference-plus-noise ratio criterion in the second time period. The specific process is as follows: calculate the decoding signal-to-interference-plus-noise ratio of the forwarded signal corresponding to each preset receiving port, and select the preset receiving port with the largest signal-to-interference-plus-noise ratio as the working port to receive and decode the forwarded signal.

[0016] Furthermore, in step (3), the near-end communication device selects the port using the maximum signal-to-interference-plus-noise ratio criterion in the second time period. The specific process is as follows: the forwarded signal is regarded as interference, the decoding signal-to-interference-plus-noise ratio of the second signal corresponding to each preset receiving port is calculated, and the preset receiving port with the largest signal-to-interference-plus-noise ratio is selected as the working port to receive and decode the second signal.

[0017] The present invention discloses a fluid antenna-assisted downlink direct transmission and cooperative NOMA dual-mode hierarchical communication system, comprising: a source-end communication device equipped with a first conventional fixed transmitting antenna and a second conventional fixed transmitting antenna; a near-end communication device, a cooperative communication device, and a far-end communication device, each equipped with a single two-dimensional planar fluid antenna, wherein the fluid antenna includes multiple preset receiving ports, and only one port is activated at any given time; the system is configured to perform any of the methods described herein.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0019] First, the fluid antenna-assisted downlink direct transmission and cooperative NOMA dual-mode hierarchical communication method and system of the present invention retains the advantage of traditional NOMA-CDRT in expanding coverage, while also improving system reliability. Compared with the problem that the near-end communication device usually needs to perform multi-stage serial interference cancellation in the traditional single-antenna method, which easily leads to residual interference accumulation and error propagation under imperfect SiC conditions, the present invention, through the dual-antenna separate transmission structure of the source-end communication device, enables the near-end communication device to treat the superimposed signal as interference and complete the required signal decoding. This effectively avoids the near-end communication device's dependence on SiC and effectively reduces the adverse effects of residual interference on system interruption performance.

[0020] Secondly, the fluidic antenna-assisted downlink direct transmission and cooperative NOMA dual-mode hierarchical communication method and system of the present invention incorporates a port selection strategy based on joint feasibility at the cooperative communication device end. Compared to traditional methods that optimize or randomly select receiving ports based on a single metric, the present invention utilizes the spatial degrees of freedom of a two-dimensional planar fluidic antenna to screen for an effective set of ports that simultaneously meet the two-level decoding threshold conditions of the remote communication device signal and the cooperative communication device signal. This strategy significantly improves the success rate of the cooperative communication device in decoding superimposed signals, ensuring the connectivity of the cooperative NOMA link in deep fading environments.

[0021] Third, the fluid antenna-assisted downlink direct transmission and cooperative NOMA dual-mode layered communication method and system of the present invention designs a dual-time-period parallel transmission protocol. Compared with the problem of insufficient utilization of time-frequency resources caused by the source communication device being silent during the cooperative period in the traditional half-duplex cooperative method, the present invention, while the cooperative communication device forwards the information of the remote communication device in the second time period, simultaneously transmits the second signal of the near-end communication device through the first conventional fixed transmitting antenna of the source communication device, and the second conventional fixed transmitting antenna remains silent to avoid introducing additional superimposed interference, thereby improving the data carrying efficiency within the limited time-frequency resources, which is beneficial to improving the system traversal rate and effective throughput.

[0022] Fourth, the fluidic antenna-assisted downlink direct transmission and cooperative NOMA dual-mode hierarchical communication method and system of the present invention introduces a two-dimensional planar fluidic antenna into the NOMA-CDRT receiver and adopts a port selection mechanism. Compared with the problem of traditional fixed single-antenna reception being easily limited by deep fading, the present invention obtains spatial diversity gain by switching preset ports in a small space; combined with the maximum signal-to-interference-plus-noise ratio criterion for port selection, it is beneficial to improve reception quality and suppress performance degradation in interference-constrained scenarios.

[0023] Fifth, the fluid antenna-assisted downlink direct transmission and cooperative NOMA dual-mode hierarchical communication method and system of the present invention helps to reduce the implementation complexity of the receiver in the near-end communication equipment. Compared with the traditional NOMA-CDRT method, where the near-end communication equipment, as a communication device with strong channel gain, usually needs to be configured with a SIC receiver and perform multi-stage interference cancellation, the present invention enables the near-end communication equipment to directly decode the required signal without the interference cancellation step, thereby reducing the SIC-related signal processing flow, which helps to reduce processing latency and terminal power consumption, and improves the feasibility of practical deployment. Attached Figure Description

[0024] Figure 1 This is an overall flowchart of the present invention;

[0025] Figure 2 This is a schematic diagram of the signal transmission model of the direct transmission and relay coordinated transmission system of the present invention in the first and second time periods;

[0026] Figure 3 This is a comparison curve of the system interrupt throughput as a function of the transmit signal-to-noise ratio for different transmission methods of the present invention (conventional NOMA-CDRT, FAS-NOMA-CDRT and the method of the present invention);

[0027] Figure 4 This invention relates to a near-end communication device ( A comparison curve of the interruption probability as a function of the transmit signal-to-noise ratio in the first time period;

[0028] Figure 5 This invention relates to a near-end communication device ( A comparison curve showing the change in the interruption probability as a function of the transmit signal-to-noise ratio during the second time period;

[0029] Figure 6 The collaborative communication device of the present invention ( A comparison curve of the interruption probability as a function of the transmit signal-to-noise ratio;

[0030] Figure 7 The remote communication device of the present invention ( A comparison curve showing the change in the interruption probability of a transmitter with the transmit signal-to-noise ratio.

[0031] Figure 8 This is a comparison graph showing the system ergodicity and rate of different transmission methods of the present invention as a function of the transmit signal-to-noise ratio. Detailed Implementation

[0032] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0033] like Figure 1 As shown, this embodiment of the invention provides a method for downlink direct transmission and cooperative power domain NOMA dual-mode hierarchical communication assisted by a fluidic antenna, comprising: constructing a downlink direct transmission and cooperative NOMA dual-mode hierarchical communication system, which includes a source-end communication device, a near-end communication device, a cooperative communication device, and a far-end communication device; wherein, the source-end communication device is configured with a first conventional fixed transmitting antenna and a second conventional fixed transmitting antenna, and each receiving communication device is equipped with a single two-dimensional planar fluidic antenna; and dividing the information transmission period into a first time period and a second time period;

[0034] In the first time period, the source communication device transmits a first signal carrying information required by the near-end communication device through a first conventional fixed transmitting antenna, and transmits a power domain NOMA superimposed coded signal carrying information required by both the cooperative communication device and the remote communication device through a second conventional fixed transmitting antenna; the near-end communication device selects a preset receiving port based on the maximum signal-to-interference-plus-noise ratio criterion and directly decodes the first signal; the cooperative communication device selects a preset receiving port based on the joint feasibility criterion and performs serial interference cancellation;

[0035] During the second time period, the cooperative communication device forwards information from the remote communication device, while the source communication device sends a second signal to the near-end communication device through the first conventional fixed transmitting antenna, and the second conventional fixed transmitting antenna remains silent and does not transmit any signal; the remote communication device and the near-end communication device respectively use a two-dimensional planar fluidic antenna to perform port selection to optimize reception performance.

[0036] Example 1

[0037] Figure 1 This is a flowchart illustrating a method and system for downlink direct transmission and cooperative power domain NOMA dual-mode hierarchical communication assisted by a fluidic antenna, as described in this embodiment of the invention. This flowchart merely shows the logical sequence of the methods described in this embodiment; however, in other possible embodiments of the invention, different sequences may be used, provided they do not conflict. Figure 1 Complete the steps shown or described in the order indicated.

[0038] See Figure 1 The method implemented in this way specifically includes the following steps:

[0039] A downlink direct transmission and cooperative NOMA dual-mode hierarchical communication system is constructed, comprising a source-end communication device, a near-end communication device, a cooperative communication device, and a far-end communication device. The source-end communication device is equipped with a first conventional fixed transmitting antenna and a second conventional fixed transmitting antenna. Each of the near-end, cooperative, and far-end communication devices is equipped with a single two-dimensional planar fluidic antenna, each containing [a specific element / structure]. Two-dimensional grid arrangement One preset receiving port (of which ,and , All values ​​are positive integers, and only one of the preset receiving ports is activated at any given time.

[0040] The system's transmission modes include a direct transmission mode from the source communication device to the near-end communication device, and a cooperative NOMA transmission mode in which the source communication device communicates with the far-end communication device via a cooperative communication device.

[0041] The information transmission cycle is divided into a first time period and a second time period;

[0042] In the first time period, the source-end communication device transmits a first signal carrying information required by the near-end communication device through a first conventional fixed transmitting antenna, and transmits a power-domain NOMA superimposed coded signal carrying information required by both the cooperative communication device and the remote communication device through a second conventional fixed transmitting antenna; the near-end communication device treats the power-domain NOMA superimposed signal from the second conventional fixed transmitting antenna as interference. The signal receiving port is selected from the preset receiving ports based on the maximum signal-to-interference-plus-noise ratio criterion, and then the first signal required by the near-end communication device is directly decoded without performing serial interference cancellation; the cooperative communication device regards the first signal required by the near-end communication device from the first conventional fixed transmitting antenna as interference, in the A signal receiving port is selected from a set of preset receiving ports based on a joint feasibility criterion, and serial interference cancellation is performed on the power domain NOMA superimposed coded signal to sequentially decode the signals required by the remote communication device and the signals required by the cooperative communication device.

[0043] In the second time period, the cooperative communication device forwards the signal required by the remote communication device decoded in the first time period to the remote communication device. Simultaneously, the source communication device transmits a second signal carrying information required by the near-end communication device through the first conventional fixed transmitting antenna, while the second conventional fixed transmitting antenna remains silent. The remote communication device... Among the preset receiving ports, a receiving port is selected based on the maximum signal-to-interference-plus-noise ratio criterion to receive and decode the forwarded signal; the near-end communication device treats the forwarded signal as interference, and in the... A receiving port is selected from a set of preset receiving ports based on the maximum signal-to-interference-plus-noise ratio criterion to receive and decode the second signal.

[0044] Optionally, in one specific embodiment, the following specific steps are included:

[0045] Step 1: Construct a downlink direct transmission and cooperative NOMA dual-mode hierarchical communication system, which includes source-end communication equipment and near-end communication equipment. Collaborative communication equipment and remote communication equipment Collaborative communication devices Operating in half-duplex mode, it is used to communicate with remote devices in two time periods. The information is forwarded as an auxiliary message.

[0046] The source-end communication equipment is equipped with a first conventional fixed transmitting antenna and a second conventional fixed transmitting antenna. The two transmitting antennas are configured with sufficient spacing so that the channels to the same receiving communication equipment can be approximated as statistically independent. Near-end communication equipment... Collaborative communication equipment With remote communication equipment Each is equipped with a single two-dimensional planar fluidic antenna, and each fluidic antenna contains a... Two-dimensional grid arrangement One preset receiving port (of which ,and , (All are positive integers), the two-dimensional grid is distributed over a normalized size of Within a two-dimensional planar area, only one of the preset receiving ports is activated at any given time.

[0047] The information transmission cycle is divided into two equal-length time periods, namely the first time period and the second time period, such as... Figure 2 As shown.

[0048] Define the source communication device as a first conventional fixed transmitting antenna transmitting a near-end communication device. The first signal of information is The second conventional fixed transmitting antenna transmits data to remote communication equipment. and collaborative communication devices The information signals are respectively and Assume the total transmit power of the source communication equipment is... The transmission powers of the first conventional fixed transmitting antenna and the second conventional fixed transmitting antenna are respectively and And satisfy Define the remote communication equipment in the second conventional fixed transmitting antenna superimposed signal. and collaborative communication devices The power allocation coefficients are respectively and ,satisfy .

[0049] Step 2: In this embodiment, the wireless channel can be modeled as a quasi-static flat Rayleigh fading channel. Definition For source communication equipment Root transmitting antenna to receiving communication equipment Two-dimensional planar fluidic antenna The channel fading coefficient between several preset receiving ports. Where: These correspond to the first conventional fixed transmitting antenna and the second conventional fixed transmitting antenna of the source communication equipment, respectively. These correspond to near-end communication devices ( ), collaborative communication equipment ( ) and remote communication equipment ( ); , representing the port index of the fluid antenna. Also, define... For collaborative communication devices to receiving communication equipment The first fluid antenna The channel fading coefficient between several preset receiving ports. Where: These correspond to near-end communication devices ( ) and remote communication equipment ( ); , representing the port index of the flowing antenna. All the channel fading coefficients mentioned above... All follow an independent and identically distributed complex Gaussian distribution. .

[0050] Considering that the preset receiving ports of the fluid antenna are closely arranged in a limited space (typically with a spacing smaller than the carrier wavelength), the channel coefficients between different ports lose statistical independence and instead exhibit significant spatial cross-correlation characteristics. This embodiment uses the Jakes model to characterize this port correlation. Specifically, any two preset receiving ports in the fluid antenna... and Spatial correlation coefficient between Determined by the zeroth-order Bessel function of the first kind, its mathematical expression is:

[0051] (1)

[0052] in, Denotes the zeroth-order Bessel function of the first kind. Indicates the first The first preset receiving port and the first The physical spacing between the preset receiving ports This represents the signal carrier wavelength. Using this model, channel vectors with specific spatial cross-correlation characteristics can be generated, which can then be used to evaluate the system's diversity gain performance during port switching.

[0053] Furthermore, it is assumed that the receiver thermal noise of each receiving communication device in the system is modeled as having a mean of zero and a variance of . Additive complex white Gaussian noise (AWGN).

[0054] Step 3: In the first time period, the source communication device simultaneously activates the first conventional fixed transmitting antenna and the second conventional fixed transmitting antenna to perform signal transmission tasks; specifically, the source communication device transmits signals carrying the near-end communication device through the first conventional fixed transmitting antenna. The first signal of the required information Its transmission power is Simultaneously, the source communication equipment transmits data via a second conventional fixed transmitting antenna according to the downlink NOMA criterion, simultaneously carrying cooperative communication equipment. and remote communication equipment The power domain NOMA superimposed coded signal of the information, the superimposed coded signal It can be represented as:

[0055] (2)

[0056] in, This refers to the transmission power of the second conventional fixed transmitting antenna; and This refers to the power allocation coefficient defined in step one. Here, the principle of prioritizing communication devices with weaker NOMA channel gain is followed (i.e.,...). This is to ensure that the signal of the remote communication device with weak channel gain is allocated to a larger transmission power, thereby facilitating decoding at the receiving end.

[0057] Step 4: In the first time period, each receiving communication device activates the first of its flowing antennas. Each preset receiving port is used to receive signals; at this time, the near-end communication device and collaborative communication devices The received signal is specifically represented as follows:

[0058] For near-end communication equipment , its first Signal received by each port The signal, including the first signal from the first conventional fixed transmitting antenna, the interference signal from the second conventional fixed transmitting antenna, and noise, is represented as follows:

[0059] (3)

[0060] For collaborative communication devices , its first Signal received by each port The signal, comprising the power domain NOMA superposition coded signal (desired signal) from the second conventional fixed transmitting antenna, the interference signal from the first conventional fixed transmitting antenna, and noise, can be expressed as:

[0061] (4)

[0062] in, Indicates the source communication device number Root transmitting antenna ( ) to receiving communication equipment ( ) No. Channel fading coefficients for each preset receiving port; and They represent near-end communication devices. and collaborative communication devices The values ​​at each point have a mean of zero and a variance of . Complex Gaussian additive white noise.

[0063] Step 5: In the first time period, near-end communication equipment Port selection is based on the Maximum Signal-to-Interference-Noise Ratio (Max-SINR) criterion, and the power-domain NOMA superimposed coded signal from the second conventional fixed transmit antenna is treated as interference, eliminating the need for serial interference cancellation (i.e., Zero-SIC). In this case, the near-end communication equipment... In its first The first signal is directly decoded on each preset receiving port. Signal-to-interference-to-noise ratio It can be represented as:

[0064] (5)

[0065] in, The first signal power comes from the first conventional fixed transmitting antenna; The total interference power from the second conventional fixed transmitting antenna (using [the relevant data]). The normalization characteristics treat the power-domain NOMA superimposed coded signal as interference. This represents noise power.

[0066] Subsequently, near-end communication equipment Select the port that maximizes the signal-to-interference-plus-noise ratio. As the activation port:

[0067] (6)

[0068] Finally, near-end communication equipment Activation port Directly decode the first signal .

[0069] Step 6: In the first time period, collaborative communication equipment The first signal required by the near-end communication equipment from the first conventional fixed transmitting antenna is considered as interference. Among a set of preset receiving ports, a signal receiving port is selected based on joint feasibility, and serial interference cancellation is performed on the power domain NOMA superimposed coded signal to sequentially decode the signals required by the remote communication device and the signals required by the cooperative communication device. Specifically, the cooperative communication device... Traversal Each preset receiving port is used to calculate and decode the remote communication device. Signal (Will (considered as interference) and decoding its own signal (Assuming) The signal-to-interference-plus-noise ratio (SINR) after elimination is expressed as follows:

[0070] (7)

[0071] (8)

[0072] in, The received power domain NOMA superimposed coded signal power from the second conventional fixed transmitting antenna of the source communication equipment; and The power allocation coefficient defined in step one; The interference power originating from the first conventional fixed transmitting antenna; The residual interference coefficient for imperfect SiC; This represents noise power.

[0073] Collaborative communication devices According to the preset decoding threshold (let the decoding threshold be set), The threshold is ,decoding The threshold is ), construct a valid port set And based on this, determine the optimal receiving port. :

[0074] (9)

[0075] (10)

[0076] Finally, collaborative communication devices At the port Execute SIC first, then decode... It then buffers the signal for subsequent forwarding and decodes the signal it needs. .

[0077] Step 7, in the second time period, collaborative communication equipment The remote communication device obtained from the first time segment Required signal Forwarded to remote communication equipment The transmit power is set to (In this embodiment, it is set) Simultaneously, the source communication device transmits at full power via a first conventional fixed transmitting antenna. Sending a message to a near-end communication device The second signal of the required information The second conventional fixed transmitting antenna remains silent and does not transmit signals to avoid introducing additional interference.

[0078] At this time, the source communication equipment and the cooperative communication equipment The transmitted signals in the second time period can be represented as follows:

[0079] (11)

[0080] (12)

[0081] in, The total transmit power of the source communication equipment (i.e., the transmit power of the first conventional fixed transmitting antenna at this time) ); This indicates that the second time period is when the source communication device sends a message to the near-end communication device. The second signal; For collaborative communication devices The forwarding power.

[0082] Step 8: In the second time period, each receiving communication device continues to receive signals through the two-dimensional planar fluid antenna.

[0083] For remote communication equipment Because the distance to the source communication device is relatively far, the weak signal leakage from the source communication device is ignored. Signal received by a preset receiving port Includes only from collaborative communication devices The forwarded signal and noise can be represented as:

[0084] (13)

[0085] in, For collaborative communication devices To remote communication equipment No. Channel coefficients for each port; It is additive white Gaussian noise.

[0086] For near-end communication equipment , its first Each preset receiving port simultaneously receives a second signal from the first conventional fixed transmitting antenna of the source communication device. and from collaborative communication devices Interference signals from cooperative signals. Received signal. It can be represented as:

[0087] (14)

[0088] in, For collaborative communication devices To near-end communication equipment No. Interference channel coefficients for each port. Due to cooperative communication equipment. Near-end communication equipment Given its proximity and significant transmission power, this interference cannot be ignored.

[0089] Step 9: Each receiving communication device selects its port and performs final decoding based on the maximum signal-to-interference-plus-noise ratio criterion according to the quality of the received signal.

[0090] For remote communication equipment The maximum signal-to-interference-plus-noise ratio criterion is adopted. Its first... Received signal-to-interference-plus-noise ratio of each port Represented as:

[0091] (15)

[0092] in, For from collaborative communication devices The power of the forwarding signal; This represents noise power.

[0093] Subsequently, remote communication equipment Select the port with the highest signal-to-interference-plus-noise ratio. Receive and directly decode the forwarded signal :

[0094] (16)

[0095] For near-end communication equipment The maximum signal-to-interference-plus-noise ratio criterion is adopted, and cooperative communication equipment is used. Forwarding signal Considered interference. Its first... Received signal-to-interference-plus-noise ratio of each port Represented as:

[0096] (17)

[0097] in, The second signal power comes from the first conventional fixed transmitting antenna of the source communication equipment; For from collaborative communication devices The interference power of the relayed signal; This represents noise power.

[0098] Subsequently, near-end communication equipment Select the port with the highest signal-to-interference-plus-noise ratio. Receive and decode the second signal :

[0099] (18)

[0100] To verify the beneficial effects of the present invention, the following steps will be implemented: First, in Example 1, the performance of a real communication scenario considering a fixed target rate and decoding threshold will be characterized. Under this general scenario, the theoretical calculation of the interruption probability of each communication device is as follows: Near-end communication device The interruption probabilities in the first and second time periods satisfy the following conditions:

[0101] (19)

[0102] (20)

[0103] in, and They represent near-end communication devices. The actual received signal-to-interference-plus-noise ratio obtained after activating the optimal preset receiving port in the first and second time periods; and They represent near-end communication devices. The target decoding signal-to-interference-plus-noise ratio threshold in the first and second time periods.

[0104] Collaborative communication devices The interruption probability is defined as the probability that it cannot find a valid port that simultaneously satisfies both levels of decoding thresholds, that is:

[0105] (twenty one)

[0106] in, This refers to the set of valid ports that meet the joint feasibility criterion constructed in step six above.

[0107] Remote communication equipment The end-to-end interruption probability depends on the cooperative communication device. The probability expression for either failure to decode the remote communication device's signal in the first time period, or failure of the remote communication device itself to receive the signal in the second time period, is as follows:

[0108] (twenty two)

[0109] in, Indicates collaborative communication devices After activating the optimal port, decode the actual received signal-to-interference-plus-noise ratio of the remote communication device signal. Indicates remote communication equipment The actual received signal-to-interference-plus-noise ratio (SINR) of the forwarded signal after activating the optimal port; For remote communication equipment The target decoding signal-to-interference-plus-noise ratio (SIN / NNR) threshold for the desired signal.

[0110] Furthermore, based on the outage probability of each of the aforementioned communication devices, the total outage throughput of the system is... This can be expressed as the sum of the expected target transmission rates of each device when successful decoding (i.e., no interruption occurs), and its theoretical expression is:

[0111] (twenty three)

[0112] in, and They represent near-end communication devices. First phase, second phase, and cooperative communication equipment Remote communication equipment The target transmission rate. It should be noted that the target transmission rate... Compared with the aforementioned decoding signal-to-interference-plus-noise ratio threshold Satisfying a rigorous mathematical mapping relationship (i.e.) ).

[0113] Assume the path loss exponent is 3 in the path loss model and the reference distance is 20m. The communication equipment topology is set as follows: from the source communication device to the near-end communication device. Collaborative communication equipment The distance between them is 75m, and the collaborative communication equipment To near-end communication equipment Remote communication equipment The distance between them is 100m. The total number of ports of the two-dimensional planar fluidic antenna is set to... ,use The two-dimensional grid arrangement, with the normalized region size set to In this embodiment, all small-scale channel fading coefficients are modeled as independent and identically distributed complex Gaussian random variables (i.e., The key system parameters are set as follows: The source-end communication equipment adopts antenna-level power allocation, and the power allocation of the first conventional fixed transmitting antenna and the second conventional fixed transmitting antenna are respectively... and ( (Total transmit power); the NOMA power allocation factor inside the second conventional fixed transmit antenna is set to... and The residual interference coefficient of imperfect SIC is uniformly set to... .

[0114] To demonstrate the performance advantages of the method proposed in this invention, this embodiment introduces two comparative methods for simulation comparison: Traditional NOMA-CDRT refers to the traditional fixed-antenna NOMA transmission method. In this method, each receiving communication device is equipped with only a traditional fixed-position single antenna (i.e., equivalent to...). Spatial diversity gain cannot be obtained, and near-end communication equipment SIC must be performed to decode its own signal. FAS-NOMA-CDRT refers to the traditional single-antenna NOMA transmission method based on a two-dimensional planar fluidic antenna. In this method, although each receiving communication device is equipped with a two-dimensional planar fluidic antenna ( However, the source-end communication equipment uses a conventional single antenna to transmit power domain NOMA superimposed signals. Therefore, the near-end communication equipment... Unable to take advantage of the physical isolation of dual antennas, a complex SIC process is still required to eliminate interference.

[0115] Figure 3 The graph shows the system interruption throughput of different transmission methods described in this embodiment as a function of the transmit signal-to-noise ratio (SNR). The green dotted triangle in the graph represents the simulated system interruption throughput of the transmission method described in this embodiment, while the blue solid square and orange dashed diamond represent the system interruption throughput of traditional NOMA-CDRT and FAS-NOMA-CDRT, respectively. As shown in the graph, the method of this invention improves transmission rate while maintaining reliability. With increasing SNR, the interruption throughput of all three methods increases to varying degrees, but the interruption throughput of the method of this invention reaches saturation first, indicating that it can meet the system's target rate requirements with lower transmit power. This is because although FAS-NOMA-CDRT also introduces a two-dimensional planar fluidic antenna, due to the lack of a dual-antenna cooperative design at the source end, its near-end communication equipment... The current method is still limited by residual SIC interference, resulting in limited effective throughput. However, the method of this invention completely solves the throughput bottleneck problem in high-interference environments through the joint design of dual-antenna physical isolation and two-dimensional planar fluidic antenna diversity, and can meet the system's target rate requirements with lower transmit power. For example, at a signal-to-noise ratio of 30 dB, the throughput of the method of this invention is stable at around 2.10 bps / Hz, close to the theoretical upper limit of the system design; while at this time, the throughput of FAS-NOMA-CDRT is only 1.20 bps / Hz, and that of traditional NOMA-CDRT is only 0.95 bps / Hz.

[0116] Figure 4 and Figure 5 This embodiment demonstrates near-end communication devices in different transmission methods. The graph shows the intermittent probability as a function of the transmission signal-to-noise ratio (SNR) in the first and second time periods. The green dotted triangle represents the simulated intermittent probability of the transmission method described in this embodiment, while the blue solid square and orange dashed diamond represent the intermittent probabilities of traditional NOMA-CDRT and FAS-NOMA-CDRT, respectively. As shown in the graph, the method proposed in this invention achieves a lower intermittent probability than traditional NOMA-CDRT in different time periods. Furthermore, as the SNR increases, the intermittent probabilities of all three methods show varying degrees of decrease (or tend to stabilize), with the method of this invention showing the most significant performance improvement. This is because in the first time period, this invention utilizes a dual-antenna physical isolation strategy of the source-end communication device to achieve "zero-SIC" reception, eliminating interference from imperfect SIC. In the second time period, it further resists fading by utilizing the diversity gain of a two-dimensional planar fluidic antenna. For example, when the SNR is 30 dB in the first time period, the near-end communication device of this invention... The probability of interruption decreased to Meanwhile, the interruption probability of traditional NOMA-CDRT and FAS-NOMA-CDRT is still approximately 1; when the signal-to-noise ratio is 25 dB in the second time period, the interruption probability of the method proposed in this invention has been reduced to While traditional NOMA-CDRT is still approximately .

[0117] Figure 6 This embodiment demonstrates cooperative communication devices in different transmission methods. The graph shows the interruption probability as a function of the transmission signal-to-noise ratio. The green dotted triangle in the graph represents the simulated interruption probability of the transmission method described in this embodiment, while the blue solid square and orange dashed diamond represent the interruption probabilities of traditional NOMA-CDRT and FAS-NOMA-CDRT, respectively. As can be seen from the graph, the method of this invention is effective in cooperative communication devices. The decoding reliability of this method is significantly better than that of traditional NOMA-CDRT and FAS-NOMA-CDRT. Furthermore, the interruption probability of this method decreases rapidly with increasing signal-to-noise ratio (SNR), while the other two methods only show a decreasing trend at high SNR. This is because of the cooperative communication device... Simultaneous decoding of two signals is required. This invention utilizes a "port selection based on joint feasibility" strategy to fully leverage the spatial degrees of freedom of a two-dimensional planar fluidic antenna, thus satisfying the dual decoding requirement. In contrast, comparative methods struggle to meet this requirement under constrained conditions. For example, when the signal-to-noise ratio is 30 dB, the method proposed in this invention, in cooperation with communication devices… The probability of interruption has dropped significantly. Meanwhile, the interruption probability of traditional NOMA-CDRT and FAS-NOMA-CDRT remains around 1 at this signal-to-noise ratio, demonstrating the significant advantages of the method of this invention in complex relay scenarios.

[0118] Figure 7 This embodiment demonstrates remote communication devices using different transmission methods. The graph shows the interruption probability as a function of the transmission signal-to-noise ratio. The green dotted triangle in the graph represents the simulated interruption probability of the transmission method described in this embodiment, while the blue solid square and orange dashed diamond represent the interruption probabilities of traditional NOMA-CDRT and FAS-NOMA-CDRT, respectively. As can be seen from the graph, the method proposed in this invention and FAS-NOMA-CDRT are comparable in remote communication equipment. The performance of this method is superior to that of traditional NOMA-CDRT, and the outage probability of all three methods decreases with increasing signal-to-noise ratio, but the rate of decrease is faster for the method of this invention and FAS-NOMA-CDRT. This is because the remote communication device... By utilizing the diversity gain of a two-dimensional planar fluid antenna, the port with the optimal channel state can be searched in space for reception, thereby significantly improving the received signal-to-interference-plus-noise ratio (SNR). For example, when the SNR is 25 dB, the method proposed in this invention is compatible with remote communication equipment such as FAS-NOMA-CDRT. The probability of interruption has decreased to approximately This achieves highly reliable reception, while the interruption probability of traditional NOMA-CDRT is still as high as [missing information]. This proves that the method of the present invention effectively achieves a reliable extension of the coverage area.

[0119] Example 2

[0120] To further evaluate the performance boundaries of the technical method described in this invention under different transmission conditions, this embodiment explores an ideal adaptive transmission degradation scenario without considering the user quality of service (QoS) decoding threshold limitation, based on the system model of Embodiment 1.

[0121] In this degradation scenario, it is assumed that the decoding threshold of all communication devices is infinitely small (i.e. The effective port set of collaborative communication devices is always a non-empty set (i.e., The received signal-to-interference-plus-noise ratio (SNR) of each communication device can support uninterrupted decoding. At this point, the system primarily focuses on its ergodicity and rate performance, which can be theoretically expressed as the sum of the statistical expectations of the achievable rates of each communication device over two time periods:

[0122] (twenty four)

[0123] in, Indicates the expected statistical operation; and Near-end communication equipment The achievable rates in the first and second time periods, For collaborative communication devices The achievable rate for successfully decoding the signal it needs. For remote communication equipment The end-to-end achievable rate.

[0124] Since the entire communication cycle is divided into two equal-length time periods, a time factor needs to be introduced. , and Specifically, it is expressed as follows:

[0125] (25)

[0126] (26)

[0127] Similarly, collaborative communication devices achievable rate Specifically, it is expressed as follows:

[0128] (27)

[0129] For remote communication equipment Because the cooperative transmission link is limited by the "bottleneck effect" of cooperative decoding and its own reception, its achievable speed is limited. Determined by the poorer signal-to-interference-plus-noise ratio in the two-hop link, specifically expressed as:

[0130] (28)

[0131] To further verify the performance advantages of this embodiment in the ideal adaptive transmission degradation scenario, the same system parameter settings as in Embodiment 1 were used, and the two comparison methods mentioned above were introduced for simulation demonstration.

[0132] Figure 8The graphs show the system ergodic and rate variations of the different transmission methods described in this embodiment as a function of the transmit signal-to-noise ratio (SNR). The green dotted triangles represent the simulated values ​​of the ergodic and rate of the transmission method described in this embodiment, while the solid blue squares and dashed orange diamonds represent the ergodic and rate of traditional NOMA-CDRT and FAS-NOMA-CDRT, respectively. As can be seen from the graphs, the method proposed in this invention achieves better system ergodic and rate performance than traditional NOMA-CDRT and FAS-NOMA-CDRT across almost the entire SNR range, and the ergodic and rate of all three methods improve to varying degrees with increasing SNR. This is because this invention eliminates the need for near-end communication devices... The SIC decoding burden is reduced, and combined with the spatial diversity gain of the two-dimensional planar fluidic antenna, interference is effectively suppressed, thereby supporting higher spectral efficiency. For example, at a signal-to-noise ratio of 30 dB, the ergodic sum and rate of the fluidic antenna-assisted downlink direct transmission and cooperative NOMA dual-mode hierarchical communication method and system proposed in this invention is 5.86 bps / Hz, while the ergodic sum and rate of the traditional NOMA-CDRT is 2.71 bps / Hz, and the ergodic sum and rate of FAS-NOMA-CDRT is 4.61 bps / Hz.

[0133] The physical meanings of the parameters are shown in Tables 1 and 2.

[0134] Table 1 Physical meaning of parameters 1

[0135] ;

[0136] Table 2 Physical Meaning of Parameters

[0137] .

Claims

1. A method for downlink direct transmission and cooperative power domain NOMA dual-mode hierarchical communication assisted by a fluidic antenna, characterized in that, Includes the following steps: (1) Construct a downlink communication system including source communication equipment, near-end communication equipment, cooperative communication equipment and far-end communication equipment; wherein the source communication equipment is equipped with a first conventional fixed transmitting antenna and a second conventional fixed transmitting antenna; the near-end communication equipment, cooperative communication equipment and far-end communication equipment are all equipped with a single two-dimensional planar fluid antenna, the fluid antenna contains multiple preset receiving ports, and only one preset receiving port is activated at any time to receive signals; (2) Divide the information transmission cycle into a first time period and a second time period; In the first time period, the source communication device transmits a first signal carrying information required by the near-end communication device through a first conventional fixed transmitting antenna, and simultaneously transmits a power domain non-orthogonal multiple access superimposed coded signal carrying information required by the cooperative communication device and the remote communication device through a second conventional fixed transmitting antenna. The near-end communication device regards the superimposed coded signal of the second conventional fixed transmitting antenna as interference, selects a receiving port from multiple preset receiving ports based on the maximum signal-to-interference-plus-noise ratio criterion, and directly decodes the first signal without performing serial interference cancellation. The collaborative communication device treats the first signal from the first conventional fixed transmitting antenna as interference. Based on the joint feasibility criterion, it selects a receiving port from multiple preset receiving ports and performs serial interference cancellation on the superimposed coded signal. It then decodes the signals required by the remote communication device and the collaborative communication device in sequence. The specific process of port selection based on the joint feasibility criterion in the first time period is as follows: the first signal from the first conventional fixed transmitting antenna is treated as interference. The decoding signal-to-interference-plus-noise ratio (SIR) of the remote communication device signal and the collaborative communication device signal corresponding to each preset receiving port is calculated. According to the preset decoding threshold condition, an effective set of ports that can simultaneously satisfy the successful decoding of the remote communication device signal and the collaborative communication device signal is selected. If the effective port set is not empty, the preset receiving port that maximizes the decoding SIR of the collaborative communication device signal is selected as the working port. If the set of valid ports is empty, then select the preset receiving port that maximizes the signal-to-interference-plus-noise ratio of the remote communication device signal decoding from all preset receiving ports as the working port; (3) During the second time period, the cooperative communication device forwards the decoded signal required by the remote communication device to the remote communication device. At the same time, the source communication device transmits a second signal carrying the information required by the near-end communication device through the first conventional fixed transmitting antenna. The second conventional fixed transmitting antenna remains silent. The remote communication device selects a receiving port from multiple preset receiving ports based on the maximum signal-to-interference-plus-noise ratio criterion, receives and decodes the forwarded signal. The near-end communication device treats the forwarded signal as interference, selects a receiving port from multiple preset receiving ports based on the maximum signal-to-interference-plus-noise ratio criterion, and receives and decodes the second signal.

2. The method for downlink direct transmission and cooperative power domain NOMA dual-mode hierarchical communication assisted by a fluidic antenna according to claim 1, characterized in that, In step (2), the first time period and the second time period are consecutive in time and have the same duration.

3. The method for downlink direct transmission and cooperative power domain NOMA dual-mode hierarchical communication assisted by a fluidic antenna according to claim 2, characterized in that, During the first time period, the source communication equipment uses an antenna-level power allocation method to distribute the total transmission power to the first conventional fixed transmitting antenna and the second conventional fixed transmitting antenna.

4. The method for downlink direct transmission and cooperative power domain NOMA dual-mode hierarchical communication assisted by a fluidic antenna according to claim 3, characterized in that, In the first time period, in the power domain non-orthogonal multiple access superimposed coded signal transmitted by the second conventional fixed transmitting antenna, the power of the signal allocated to the remote communication equipment is greater than the power of the signal allocated to the cooperative communication equipment.

5. The method for downlink direct transmission and cooperative power domain NOMA dual-mode hierarchical communication assisted by a fluidic antenna according to claim 1, characterized in that, In step (2), the near-end communication device selects the port using the maximum signal-to-interference-plus-noise ratio (SINR) criterion in the first time period. The specific process is as follows: the superimposed coded signal of the second conventional fixed transmitting antenna is regarded as interference. The received SINR of the first signal corresponding to each preset receiving port is calculated. The preset receiving port with the largest SINR is selected as the working port and the first signal is directly decoded.

6. The method for downlink direct transmission and cooperative power domain NOMA dual-mode hierarchical communication assisted by a fluidic antenna according to claim 1, characterized in that, In step (2), when the cooperative communication device performs serial interference cancellation in the first time period, it first decodes the signal required by the remote communication device, and then decodes the signal required by the cooperative communication device.

7. The method for downlink direct transmission and cooperative power domain NOMA dual-mode hierarchical communication assisted by a fluidic antenna according to claim 1, characterized in that, In step (3), the remote communication device selects the port using the maximum signal-to-interference-plus-noise ratio (SINR) criterion in the second time period. The specific process is as follows: calculate the decoding SINR of the forwarded signal corresponding to each preset receiving port, and select the preset receiving port with the largest SINR as the working port to receive and decode the forwarded signal.

8. The method for downlink direct transmission and cooperative power domain NOMA dual-mode hierarchical communication assisted by a fluidic antenna according to claim 1, characterized in that, In step (3), the near-end communication device selects the port using the maximum signal-to-interference-plus-noise ratio criterion in the second time period. The specific process is as follows: the forwarded signal is regarded as interference, the decoding signal-to-interference-plus-noise ratio of the second signal corresponding to each preset receiving port is calculated, and the preset receiving port with the largest signal-to-interference-plus-noise ratio is selected as the working port to receive and decode the second signal.

9. A fluid antenna-assisted downlink direct transmission and cooperative power domain NOMA dual-mode hierarchical communication system, characterized in that, include: The source-end communication device is equipped with a first conventional fixed transmitting antenna and a second conventional fixed transmitting antenna; the near-end communication device, the cooperative communication device, and the far-end communication device are all equipped with a single two-dimensional planar fluid antenna, wherein the fluid antenna includes multiple preset receiving ports, and only one port is activated at any given time; the system is configured to perform the method described in any one of claims 1-8.

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