A method for selecting the best relay node in dense full-duplex relay networks

Abstract

The present invention discloses a method for selecting the best relay node of a dense full-duplex relay network, comprising: a source node sends a signal to K relay nodes in t time slots; the relay node decodes the received signal according to the estimated received signal-to-noise ratio; the relay node performs a cyclic redundancy check on the decoded signal; the relay node sends a pilot signal, and the destination node replies with a response signal after receiving the pilot signal sent by the relay node; the received signal-to-noise ratio of each relay node at the destination node is calculated; the best relay node is determined according to the received signal-to-noise ratio, and the re-encoded signal is forwarded to the destination node by the relay node; the destination node decodes the signal sent by the best relay node; each relay node performs interference elimination on the next time slot signal forwarded by the best relay node, and decodes the received next time slot signal according to the estimated signal-to-noise ratio. The present invention can reduce the interruption probability, solve the problem of inaccurate theoretical analysis in this scenario, and enhance the transmission stability at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless communication and signal processing, and in particular to a cooperative relay technology taking self-interference and mutual interference into consideration. Background Art

[0002] The rapid development of wireless communications and the emergence of a large number of emerging wireless applications have provided people with increasingly rich and convenient services in their work and life. However, with the rapid growth of mobile communication systems and wireless devices, the available spectrum has become increasingly tight and can no longer meet people's increasingly complex wireless application needs. Full-duplex technology can achieve simultaneous transmission and reception on the same frequency, providing effective support for spectrum reuse.

[0003] At the same time, compared with the direct transmission system, the system in which the relay node assists the source node in transmission can obtain capacity gain. The most typical cooperative relay transmission is a three-node single-relay two-hop cooperative relay transmission including the source node, the relay node and the destination node. In relay cooperative transmission, different transmission nodes share each other's antennas to form a virtual multi-input multi-output MIMO antenna array, so that single-antenna nodes can also obtain spatial diversity gain to achieve the effect of resisting the fading of wireless communication channels. Compared with MIMO technology, cooperative relay transmission technology does not require multiple antennas to be equipped on wireless terminals, providing a feasible way to increase channel capacity for handheld terminals, sensor nodes, etc. that are not suitable for installing multiple antennas.

[0004] Therefore, studying the transmission theory based on the idea of ​​cooperative relay has important research significance and value to ensure high-reliability transmission of wireless communication systems.

[0005] In a traditional two-hop relay cooperative network, the first time slot is used for the source to send a signal to the relay, and in the second time slot, the relay forwards the information to the destination node. It takes two time slots for the source information to be transmitted to the destination node, and the time utilization rate is low. If the delay is to be reduced, the frequency division multiplexing method is adopted, which will increase the demand for spectrum. Therefore, it is of great significance to study full-duplex relay forwarding technology. Gilan et al. studied a system consisting of a transmitter, a receiver and K FD decode and forward (DF) relays under Nakagami-m fading. Each repeater adaptively selects its transmit and receive antennas according to the instantaneous channel state, and selects a repeater to maximize the signal-to-interference-to-noise ratio (SINR) of the system. Yang et al. proposed a joint relay and transmit / receive (Tx / Rx) antenna mode selection scheme (RAMS) in a universal full-duplex (FD) relay network. Each repeater adaptively selects its transmit and receive antennas according to the instantaneous channel conditions, and selects the best single repeater with the best transmit / receive antenna configuration to maximize the end-to-end signal-to-interference-to-noise ratio (SINR) of the FD relay system.

[0006] However, full-duplex technology also faces some problems, the first of which is residual self-interference. Due to simultaneous and co-frequency transmission, a single-point transmission signal will cause serious interference to the received signal. Self-interference cancellation technology can eliminate this interference to the maximum extent, but there will still be a certain amount of self-interference signals that are not completely offset, especially during continuous transmission. Nomikos et al. modeled the evolution of the relay buffer as a Markov chain and analyzed the new relay selection strategy from the perspective of interruption probability and diversity to minimize the total energy consumption of each time slot.

[0007] However, in dense scenarios, there is both inter-relay interference and residual self-interference, and there is an error between the channel state information and the actual transmission channel due to delays and other reasons, which will affect the relay selection and thus affect the system performance. The existing technology does not comprehensively consider the above factors and lacks a research framework for continuous transmission scenarios. Summary of the invention

[0008] In order to solve the above problems, the present invention proposes a method for selecting the best relay node in a dense full-duplex relay network, studies the transmission performance of the full-duplex relay system under Rayleigh fading, proposes a relay selection scheme considering inter-relay interference and residual self-interference, and adopts a Markov model to simulate the state change of the number of selectable relays during continuous transmission. This scheme reduces the interruption probability of the system, solves the problem of inaccurate theoretical analysis in this scenario, and enhances the transmission stability of the system.

[0009] The technical solution adopted by the present invention is as follows:

[0010] A method for selecting an optimal relay node in a dense full-duplex relay network comprises the following steps:

[0011] S1. The source node s sends a signal x to K relay nodes in time slot t. s (t);

[0012] S2. The relay node decodes the received signal x according to the estimated received signal-to-noise ratio s (t);

[0013] S3. The relay node decodes the signal x s (t) performing a cyclic redundancy check. If all cyclic redundancy checks fail, the transmission is deemed to have failed. If any cyclic redundancy check succeeds, relay selection is performed and step S4 is executed;

[0014] S4. The relay node sends a pilot signal, and the destination node replies with a response signal after receiving the pilot signal sent by the relay node;

[0015] S5. Calculate the received signal-to-noise ratio γ of each relay node at the destination node rkd ;

[0016] S6. According to the received signal-to-noise ratio γ rkd Determine the best relay node r b , and forwards the re-encoded signal x s (t) to the destination node;

[0017] S7. Destination node to the best relay node r b The signal x is sent s (t) Decode and complete the signal x s (t) transmission;

[0018] S8. Each relay node is the best relay node r b The next time slot signal x is forwarded s (t+1) performs interference elimination and decodes the received next time slot signal x according to the estimated signal-to-interference-noise ratio s (t+1).

[0019] Furthermore, the relay node is a full-duplex relay node in decoding and forwarding mode.

[0020] Further, in step S2, the relay node estimates its received signal-to-noise ratio according to the received signal quality, and decodes the received signal x according to the estimated received signal-to-noise ratio. s (t).

[0021] Further, in step S3, the relay node decodes the signal x s (t) Perform cyclic redundancy check. If all cyclic redundancy checks fail, the transmission is considered a failure and the relay node no longer forwards the signal x from the source node s. s (t) to the destination node, the source node s sends the signal x in the next time slot, i.e., time slot t+1. s (t+1), execute step S2; if the cyclic redundancy check succeeds, perform relay selection and execute step S4.

[0022] Further, in step S4, the relay node sends a pilot signal, and the destination node replies with a response signal after receiving the pilot signal sent by the relay node; after receiving the pilot signal, the source node s waits for the relay selection to be completed and prepares to send the next time slot signal x s (t+1).

[0023] Further, in step S5, each relay node estimates the channel state information between itself and the destination node according to the received response signal of the destination node, and obtains the received signal-to-noise ratio γ of each relay node at the destination node. rkd .

[0024] Further, in step S6, the distributed timer is used to store 1γ in the distributed timer. rkdThe relay node that first decreases to 0 is selected as the best relay node r b , and forwards the re-encoded signal x s (t) to the destination node.

[0025] Further, in step S6, the best relay node r b Forward the re-encoded signal x s (t) to the destination node, the source node s sends the next time slot signal x s (t+1), each relay node executes step S8.

[0026] Further, in step S8, each relay node uses the signal x obtained by decoding the previous time slot s (t) For the best relay node r b The next time slot signal x is forwarded s (t+1) performs interference elimination.

[0027] Further, in step S8, the next time slot signal x s The signal quality of (t+1) estimates its received signal-to-interference-noise ratio, and decodes the received next time slot signal x according to the estimated signal-to-interference-noise ratio s (t+1), then execute step S3.

[0028] The beneficial effects of the present invention are:

[0029] 1. The present invention is implemented by a source node, multiple full-duplex decoding and forwarding relay nodes and a destination node, and each node cooperates with each other to jointly complete the collaborative transmission. The relay selection method can fully utilize system resources and effectively save energy. Therefore, the present invention reduces the probability of system interruption and improves transmission reliability through the relay selection scheme.

[0030] 2. Since full-duplex relays transmit at the same time and frequency, there is interference between relays and residual self-interference. Therefore, unlike the traditional probability-based method, the entire transmission process is considered, and the information of the previous time slot is taken into account for relay selection. Different interferences are distinguished by whether the previous time slot decoding is successful or not and whether it is selected as a forwarding relay, and the best relay is selected based on the signal-to-interference-to-noise ratio.

[0031] 3. The proposed method is validated by comparison. Compared with the scheme without relay selection, the interruption probability of the present invention is still better than that of the scheme without selection even when there is an error between the rd link channel state information and the actual channel; compared with the scheme without using the decoding information of the previous time slot, the interruption probability of the present invention is significantly reduced, and the system reliability is higher.

[0032] In summary, the present invention studies the transmission performance of a full-duplex relay system under Rayleigh fading, proposes a relay selection scheme considering inter-relay interference and residual self-interference, and adopts a Markov model to simulate the state change of the number of selectable relays during continuous transmission. This scheme reduces the interruption probability of the system, solves the problem of inaccurate theoretical analysis in this scenario, and enhances the transmission stability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of a two-hop relay cooperative network scenario.

[0034] Figure 2 The present invention is a flow chart of a method for selecting an optimal relay node in a dense full-duplex relay network.

[0035] Figure 3 It is a curve graph showing the variation of the outage probability with the second-hop channel quality.

[0036] Figure 4 It is a curve graph showing the variation of the outage probability with the first-hop channel quality. DETAILED DESCRIPTION

[0037] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation methods of the present invention are now described. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0038] Example

[0039] This embodiment uses Figure 1 The two-hop relay cooperative network scenario shown in FIG. 1 is used as an example to illustrate the system, which includes a source node s, K decoding and forwarding full-duplex relay nodes {r1, r2…r K}, a destination node d. Assume that the destination node d is far away from the source node s, so the destination node d can only receive the signal forwarded by the relay node, that is, the sd channel can be ignored.

[0040] use and Represents s→r k and r k →d. All channels are Rayleigh fading. The transmission power of the source node s and the transmission power of the relay node P are both 1. Assume that the noise at node a is denoted by N a , a∈{r k ,d}, is a Gaussian random variable with zero mean and variance N0=1. Then, the corresponding signal-to-noise ratios are and All follow exponential distribution and

[0041] In the full-duplex scheme, the source node s sends a signal x in the (t+1) time slot. s (t+1), K relay nodes try to decode. At the same time, the relay node may also receive a signal x forwarded by a relay node. s (t). Considering the interference between relay nodes and residual self-interference, the set of decoding relay nodes D in the (t+1) time slot is defined as in, R0 is the transmission rate; Represents relay node r b to r k The signal-to-noise ratio of θ is used to describe whether the received signal is interfered by other relay nodes. If the decoding success set of the previous time slot Then θ = 0; otherwise, θ = 1. Select the relay node r with the maximum signal-to-noise ratio of the second hop from the set D(t) b To forward signal x s (t).

[0042] when When the relay node r b There is interference between relays when the source node s transmits simultaneously. i and j represent the relay numbers in set D and not in set D respectively, i∈{k|r k ∈D(t),k≠b}, Relay Node r i , r j and r b The received signal-to-noise ratios are:

[0043]

[0044] and r i The interference elimination efficiency is better than r j , that is, η1<η2. The signal-to-noise ratios of the relay channels are and The parameters are respectively and The exponential distribution of .

[0045] Assuming there is a delay between the relay node and the destination node d, the delayed channel state information of the kth relay node is where ρ k , 0≤ρ k ≤1, indicating the correlation between the real channel state information and the delayed channel state information of the rd link. kis an independent and identically distributed (iid) zero-mean complex Gaussian random variable with variance At the same time, assume that all relay nodes have k are equal. Delayed The expression is The received signal of destination node d is

[0046] if No relay node forwards signal x s (t), and this situation is regarded as a signal interruption in time slot t. In the next time slot (t+1), the source node s sends a signal x to the relay node. s (t+1), the corresponding relay node receives the signal:

[0047] Based on this, this embodiment provides a method for selecting the best relay node in a dense full-duplex relay network. Figure 2 As shown, the following steps are included:

[0048] S1. The source node s sends a signal x to K relay nodes in time slot t. s (t);

[0049] S2. The relay node decodes the received signal x according to the estimated received signal-to-noise ratio s (t);

[0050] S3. The relay node decodes the signal x s (t) performing a cyclic redundancy check. If all cyclic redundancy checks fail, the transmission is deemed to have failed. If any cyclic redundancy check succeeds, relay selection is performed and step S4 is executed;

[0051] S4. The relay node sends a pilot signal, and the destination node replies with a response signal after receiving the pilot signal sent by the relay node;

[0052] S5. Calculate the received signal-to-noise ratio γ of each relay node at the destination node rkd ;

[0053] S6. According to the received signal-to-noise ratio γ rkd Determine the best relay node r b , and forwards the re-encoded signal x s (t) to the destination node;

[0054] S7. Destination node to the best relay node r b The signal x is sent s (t) Decode and complete the signal x s (t) transmission;

[0055] S8. Each relay node is the best relay node r b The next time slot signal x is forwarded s (t+1) performs interference elimination and decodes the received next time slot signal x according to the estimated signal-to-interference-noise ratio s (t+1).

[0056] Preferably, the relay node is a full-duplex relay node in decode-and-forward mode.

[0057] Preferably, in step S2, the relay node estimates the received signal-to-noise ratio according to the received signal quality, and decodes the received signal x according to the estimated received signal-to-noise ratio. s (t).

[0058] Preferably, in step S3, the relay node decodes the signal x s (t) Perform cyclic redundancy check. If all cyclic redundancy checks fail, the transmission is considered a failure and the relay node no longer forwards the signal x from the source node s. s (t) to the destination node, the source node s sends the signal x in the next time slot, i.e., time slot t+1. s (t+1), execute step S2; if the cyclic redundancy check succeeds, perform relay selection and execute step S4.

[0059] Preferably, in step S4, the relay node sends a pilot signal, and the destination node replies with a response signal after receiving the pilot signal sent by the relay node; after receiving the pilot signal, the source node s waits for the relay selection to be completed and prepares to send the next time slot signal x s (t+1).

[0060] Preferably, in step S5, each relay node estimates the channel state information between itself and the destination node according to the received response signal of the destination node, and obtains the received signal-to-noise ratio γ of each relay node at the destination node. rkd .

[0061] Preferably, in step S6, the distributed timer is used to store 1γ in the distributed timer. rkd The relay node that first decreases to 0 is selected as the best relay node r b , and forwards the re-encoded signal x s (t) to the destination node.

[0062] Preferably, in step S6, the best relay node r b Forward the re-encoded signal x s (t) to the destination node, the source node s sends the next time slot signal x s (t+1), each relay node executes step S8.

[0063] Preferably, in step S8, each relay node uses the signal x obtained by decoding the previous time slot s (t) For the best relay node r b The next time slot signal x is forwarded s (t+1) performs interference elimination.

[0064] Preferably, in step S8, the next time slot signal x s The signal quality of (t+1) estimates its received signal-to-interference-noise ratio, and decodes the received next time slot signal x according to the estimated signal-to-interference-noise ratio s (t+1), then execute step S3.

[0065] Verification Example

[0066] The effect of the present invention can be further illustrated by simulation:

[0067] A. Simulation Conditions

[0068] represents the variance of the Rayleigh channel fading coefficient between the source node s and the relay node;

[0069] represents the variance of the Rayleigh channel fading coefficient between the selected relay and itself;

[0070] represents the variance of the Rayleigh channel fading coefficient between the selected relay and the relay that was successfully decoded in the previous time slot;

[0071] represents the variance of the Rayleigh channel fading coefficient between the selected relay and the relay that failed to decode in the previous time slot;

[0072] η1 and η2 represent the self-interference elimination factors;

[0073] represents the variance of the Rayleigh channel fading coefficient between the relay node and the destination node;

[0074] ρ k Represents the correlation between the real channel state information and the delayed channel state information of the rd link;

[0075] K represents the number of relays.

[0076] B. Simulation content and results

[0077] Simulation 1: In ρ k Under the changing conditions, take R0 = 1bit / s / Hz, K = 5, η1 = 0.1 and η2 = 0.2, the interruption probability of the present invention and the fixed relay transmission is simulated as the second hop channel quality changes. The results are as follows: Figure 3 As shown. Figure 3 It can be seen that the interruption probability increases with decreases with the increase of As increases, the interruption probability decreases gradually. When a certain k The larger the value, the smaller the outage probability and the better the system performance. In addition, even when ρ k = 0, the interruption probability will still increase with decreases with the increase of k = 0 when the relay selection method is not used. It can be seen that even in this case, the relay selection method proposed in the present invention is still better than the transmission scheme without relay selection, and can significantly improve the system performance.

[0078] Simulation 2: Take K = 10, ρ k =0.9, R0=1bit / s / Hz, η1=0.05 or 0.1, η2=0.1, The simulation results of the interruption probability of the present invention and the solution without using the previous time slot decoding information as the first hop channel quality changes are as follows: Figure 4 As shown. Figure 4 It can be seen that the interruption probability of the two curves increases with The interruption probability of the present invention is smaller than that of the transmission scheme that does not utilize the decoding information of the previous time slot, and the performance is better.

[0079] In summary, the method of the present invention has better performance than the existing methods in the dense full-duplex decoding and forwarding relay transmission scenario.

[0080] It should be noted that, for the above method embodiments, for the sake of simplicity of description, they are expressed as a series of action combinations, but those skilled in the art should be aware that the present application is not limited by the order of the actions described, because according to the present application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily required by the present application.

Claims

1. A method for selecting the best relay node in a dense full-duplex relay network, characterized in that: The following steps are involved: S1. The source node s sends a signal x to K relay nodes in time slot t. s (t); S2. The relay node decodes the received signal x according to the estimated received signal-to-noise ratio s (t); S3. The relay node decodes the signal x s (t) Perform cyclic redundancy check. If all cyclic redundancy checks fail, the transmission is considered failed; If the cyclic redundancy check succeeds, relay selection is performed and step S4 is executed; S4. The relay node sends a pilot signal, and the destination node replies with a response signal after receiving the pilot signal sent by the relay node; S5. Calculate the received signal-to-noise ratio γ of each relay node at the destination node rkd ; S6. According to the received signal-to-noise ratio γ rkd Determine the best relay node r b , and forwards the re-encoded signal x s (t) to the destination node; S7. Destination node to the best relay node r b The signal sent is x s (t) Decode and complete the signal x s (t) transmission; S8. Each relay node is the best relay node r b The next time slot signal x is forwarded s (t+1) performs interference elimination and decodes the received next time slot signal x according to the estimated signal-to-interference-noise ratio s (t+1).

2. The method for selecting the best relay node in a dense full-duplex relay network according to claim 1, characterized in that: The relay node is a full-duplex relay node in a decoding and forwarding mode.

3. The method for selecting the best relay node in a dense full-duplex relay network according to claim 1, characterized in that: In step S2, the relay node estimates the received signal-to-noise ratio according to the received signal quality, and decodes the received signal x according to the estimated received signal-to-noise ratio. s (t).

4. The method for selecting the best relay node in a dense full-duplex relay network according to claim 1, characterized in that: In step S3, the relay node decodes the decoded signal x s (t) Perform cyclic redundancy check. If all cyclic redundancy checks fail, the transmission is considered a failure and the relay node no longer forwards the signal x from the source node s. s (t) to the destination node, the source node s sends the signal x in the next time slot, i.e., time slot t+1. s (t+1), execute step S2; if the cyclic redundancy check succeeds, perform relay selection and execute step S4.

5. The method for selecting the best relay node in a dense full-duplex relay network according to claim 1, characterized in that: In step S4, the relay node sends a pilot signal, and the destination node replies with a response signal after receiving the pilot signal sent by the relay node; after receiving the pilot signal, the source node s waits for the relay selection to complete and prepares to send the next time slot signal x s (t+1).

6. The method for selecting the best relay node in a dense full-duplex relay network according to claim 1, characterized in that: In step S5, each relay node estimates the channel state information between itself and the destination node based on the response signal received from the destination node, and obtains the received signal-to-noise ratio γ of each relay node at the destination node. rkd .

7. The method for selecting the best relay node in a dense full-duplex relay network according to claim 1, characterized in that: In step S6, the distributed timer is used to store 1γ in the distributed timer. rkd The relay node that first decreases to 0 is selected as the best relay node r b , and forwards the re-encoded signal x s (t) to the destination node.

8. The method for selecting the best relay node in a dense full-duplex relay network according to claim 1, characterized in that: In step S6, the best relay node r b Forward the re-encoded signal x s (t) to the destination node, the source node s sends the next time slot signal x s (t+1), each relay node executes step S8.

9. The method for selecting the best relay node in a dense full-duplex relay network according to claim 1, characterized in that: In step S8, each relay node uses the signal x obtained by decoding the previous time slot s (t) For the best relay node r b The next time slot signal x is forwarded s (t+1) performs interference elimination.

10. The method for selecting the best relay node in a dense full-duplex relay network according to claim 1, characterized in that: In step S8, the next time slot signal x s The signal quality of (t+1) estimates its received signal-to-interference-noise ratio, and decodes the received next time slot signal x according to the estimated signal-to-interference-noise ratio s (t+1), then execute step S3.

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