A relay selection method in multi-hop D2D communication with social domain information

Abstract

The present invention discloses a relay selection method in multi-hop D2D communication that introduces social domain information, which uses a relay cluster-based method to determine all candidate relays; uses a protection area-based method to determine the cellular device corresponding to the spectrum reused in each hop; uses social relationships and interference restrictions to determine the transmission power of all candidate relays, and then calculates the received signal power of the receiving device when each candidate relay in each relay cluster sends a signal to the receiving device corresponding to it; uses a timer whose termination time is inversely proportional to the received signal power of each candidate relay to the receiving device corresponding to it to select the best relay at each hop; the relay selection process runs in reverse from the last hop until the best relay for the second hop is determined, and finally the source device starts D2D communication; the advantage is that the base station load is effectively reduced, and it can ensure throughput performance and effectively improve energy efficiency.

Description

Technical Field

[0001] The present invention relates to a D2D (Device-to-Device) communication technology, and in particular to a relay selection method in multi-hop D2D communication that introduces social domain information. Background Art

[0002] In recent years, with the rapid development of mobile communication technology and the Internet industry, smart wireless terminals have been rapidly developed and popularized, and the number of cellular network users has exploded. According to Cisco's annual Internet report (2018-2023), by 2023, the number of mobile phone users worldwide will increase to 5.7 billion (accounting for 71% of the total population), and the number of mobile devices worldwide will grow to 13.1 billion. Such a large number of mobile phone users and mobile devices has brought huge loads to the base stations of cellular networks, and has also led to increasingly prominent problems such as shortage of wireless spectrum resources, low spectrum utilization, and insufficient network capacity. Researchers have therefore proposed D2D (Device-to-Device) communication technology to address the above problems. Unlike traditional mobile communication technologies that only allow mobile devices and base stations to communicate through uplink / downlink, D2D communication technology allows neighboring mobile devices to communicate directly. This close-range communication method saves the power consumed by mobile device communications and reduces base station load and transmission delay. On the other hand, D2D devices can communicate by using unlicensed spectrum or dedicated cellular spectrum, or by reusing the spectrum used by cellular devices. This reuse mode can greatly improve spectrum utilization and help solve the problem of wireless spectrum resource shortage. D2D communication technology has been identified as one of the key technologies of 5G by the standardization organization 3GPP due to its many advantages, and has attracted the attention of more and more researchers.

[0003] Traditional direct D2D communication has problems such as short communication distance, high power consumption of devices, and large interference to cellular networks. To solve these problems, some researchers introduced relay technology into D2D communication, which further improved the performance of D2D communication. Relay selection has thus become an important research direction in D2D communication.

[0004] In order to reduce the burden of algorithm execution on the base station, researchers have proposed some relay selection algorithms that do not require the participation of the base station. A literature (MA XR, YIN R, YU GD, et al. A distributed relay selection method for relay assisted device-to-device communication system [C] / / 2012 IEEE 23rd International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), September 9-12, 2012, Sydney, Australia. Piscataway: IEEE Press, 2012: 1020-1024. (A distributed relay selection method for relay assisted device-to-device communication system [C] / / 2012 23rd IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC))) proposed a timer-based relay selection method that can determine and select the best relay in a distributed manner. There is also a document (MISHRA PK, PANDEY S, BISWASH S KA Device-Centric Scheme for Relay Selection in a Dynamic Network Scenario for 5G Communication [J]. IEEE Access, 2016, 4: 3757-3768. (A device-centric relay selection scheme in a 5G communication dynamic network scenario [J])) that proposes a device-centric relay selection scheme, which obtains the common neighboring devices of D2D communication devices by exchanging device neighbor tables, and then selects the best device from the common neighboring devices as a relay based on multiple parameters such as signal-to-interference-noise ratio and remaining power. Compared with traditional network / base station-centric solutions, these methods reduce base station load and network overhead.

[0005] In order to further expand the range of D2D communication and improve communication performance, researchers have extended their research from single-hop to multi-hop D2D communication. A literature (BHARDWAJ V, MURTHY C R. On optimal routing and power allocation for D2D communications [C] / / 2015 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP). April 19-24, 2015, Brisbane, Australia. Piscataway: IEEE Press, 2015: 3063-3067. (Optimal routing and power allocation for device-to-device communication [C] / / 2015 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP))) proposed a D2D multi-hop routing algorithm based on the Dijkstra algorithm. The simulation results of the algorithm show that compared with single-hop direct D2D communication, multi-hop paths can achieve higher throughput. There is also a document (YUAN H, GUO WS, JIN YL, et al. Interference-aware multi-hop path selection for device-to-device communications in a cellular interference environment [J]. Iet Communications, 2017, 11 (11): 1741-1750. (Interference-aware multi-hop path selection for device-to-device communications in a cellular interference environment [J]. Communications of the Institution of Engineering and Technology)) that proposes an adaptive interference-aware multi-hop path selection algorithm for D2D communication. By understanding the user's location, the algorithm enables the multi-hop path to first reach the cell edge from the D2D transmitter, then move along the cell edge, and finally return to the cell when it reaches the vicinity of the receiver. This algorithm significantly improves the overall network capacity with a small sacrifice of traditional cellular capacity.

[0006] Considering that in actual systems, devices have their own willingness when acting as relays, researchers consider more realistic scenarios and introduce the social domain information of terminals into D2D research. A paper (ZHANG ZF, ZHANG PR, LIUD, et al. SRSM-based Adaptive Relay Selection for D2D Communications [J]. IEEE Internet of Things Journal, 2017: 2323-2332. (SRSM-based Adaptive Relay Selection for D2D Communications [J]. IEEE Internet of Things Journal)) proposed a relay selection method using social networks. This method comprehensively considers the physical domain and social domain factors of the relay, and selects the relay based on the link transmission stability calculated according to the user encounter history and the cooperation willingness calculated according to the user intimacy. Compared with traditional methods, this method can improve the probability of successful relay selection and reduce the burden on the cellular network. There is also a literature (LI Y, ZHANG ZF, WANG HG, et al. SERS: Social-aware Energy-efficient Relay Selection in D2D Communications [J]. IEEE Transactions on Vehicular Technology, 2018: 5331-5345. (SERS: Social-aware Energy-efficient Relay Selection in D2D Communications [J]. IEEE Transactions on Vehicular Technology, 2018: 5331-5345.)) proposed an innovative social-aware energy-efficient relay selection mechanism, which takes into account the hidden social relationships between mobile users and can ensure that more users are willing to participate in cooperative communication.

[0007] The above relay selection algorithms are all applied to cellular network scenarios. A literature (CHEN GJ, TANG JC, COONJ P. Optimal routing for multihop social-based D2D communications in the Internet of Things [J]. IEEE Internet of Things Journal, 2018, 5(3): 1880-1889.) proposed an optimal routing algorithm for multihop D2D communications applied to the Internet of Things scenario. The algorithm integrates social domain information and derives the trust probability of D2D connection by using a ranking-based trust model. The trusted connection probability between nodes is obtained from the trust probability, and the influence of the trusted connection probability is taken into account. Finally, the proposed routing algorithm can enable any pair of D2D devices to achieve the highest trusted connection probability in a distributed manner, almost reaching the performance achieved by exhaustive search.

[0008] In summary, there are some studies on distributed or device-centric relay selection algorithms in two-hop D2D communication, but the research on relay selection for multi-hop D2D communication basically does not consider the algorithm execution mode and complexity. On the other hand, the existing research on relay selection for multi-hop D2D communication is based on half-duplex relay, and the throughput performance of the algorithm is limited. At the same time, the research on the impact of social domain information on algorithm performance in actual systems is still insufficient. Therefore, it is very necessary to study a relay selection method for multi-hop D2D communication that introduces social domain information in cellular network scenarios, which can be executed in a semi-distributed manner in engineering implementation, effectively reduce the base station load, ensure throughput performance, and improve energy efficiency. Summary of the invention

[0009] The technical problem to be solved by the present invention is to provide a relay selection method in multi-hop D2D communication that introduces social domain information. It is applied to cellular network scenarios and can be executed in a semi-distributed manner in engineering implementation, effectively reducing the base station load, and it can ensure throughput performance and effectively improve energy efficiency.

[0010] The technical solution adopted by the present invention to solve the above technical problems is: a relay selection method in multi-hop D2D communication introducing social domain information, characterized in that the method is applied to a cellular network scenario, all channels are set to be Rayleigh fading channels, and free space propagation path loss is considered at the same time, it is set that there is a source device and a destination device and the positions of the two are fixed, the base station and the source device are set to know the position of the destination device, the number of hops for multi-hop D2D communication between the source device and the destination device is set to M hops, M ≥ 3, and the relay between the source device and the destination device is set to work in frequency division duplex mode; the method comprises the following steps:

[0011] Step 1: The source device sends a D2D multi-hop communication request to the base station; then the base station determines the location of the source device and the location of the destination device;

[0012] Step 2: The base station uses a candidate relay determination method based on relay clusters to determine M-1 relay cluster circular areas between the source device and the destination device according to the location of the source device and the location of the destination device, and then determines all candidate relays between the source device and the destination device according to the M-1 relay cluster circular areas, determines the location of each candidate relay, and then notifies each candidate relay that it has been selected as a candidate relay; wherein there are more than two candidate relays in each relay cluster circular area;

[0013] Step 3: Calculate the transmission power of each candidate relay in the circular area of ​​each relay cluster under the condition of considering social relations; then form a set of the transmission powers of all candidate relays in the circular area of ​​each relay cluster under the condition of considering social relations in the order of the candidate relay numbers, and record the set of the transmission powers of all candidate relays in the circular area of ​​the m'th relay cluster under the condition of considering social relations in the order of the candidate relay numbers as P m' ; Then, the transmission power set consisting of the transmission powers of all candidate relays between the source device and the destination device in consideration of social relationships is recorded as P, P = P1∪P2∪…∪P m' ∪…∪P M-1 ; Where 1≤m'≤M-1, P1 represents the set of transmission powers of all candidate relays in the circular area of ​​the first relay cluster under the condition of considering social relations, P2 represents the set of transmission powers of all candidate relays in the circular area of ​​the second relay cluster under the condition of considering social relations, P M-1 represents the set of transmission powers of all candidate relays in the circular area of ​​the M-1th relay cluster under the condition of considering social relations, and the symbol “∪” is the symbol of the set union operation;

[0014] Step 4: The base station determines the cellular device corresponding to the spectrum reused in each hop of the multi-hop D2D communication between the source device and the destination device, determines a total of M cellular devices and reuses the uplink spectrum of the cellular devices; then the set of the spectrum of the determined M cellular devices in the order of each hop is recorded as F;

[0015] Step 5: The base station sends the channel gain between the source device and the base station, the channel gain between each candidate relay in each relay cluster circular area and the base station, together with the location of the source device, the location of the destination device, the location of each candidate relay in each relay cluster circular area, and P and F to the destination device;

[0016] Step 6: The destination device sends all data received from the base station to each candidate relay in the circular area of ​​the M-1th relay cluster, and sets its own signal receiving frequency to f M , f M The value of is equal to the channel frequency of the cellular device corresponding to the spectrum multiplexed for the Mth hop of multi-hop D2D communication between the source device and the destination device;

[0017] Step 7: Calculate the maximum transmit power of each candidate relay in the circular area of ​​the M-1th relay cluster under the condition of considering interference; then form a set of the maximum transmit powers of all candidate relays in the circular area of ​​the M-1th relay cluster under the condition of considering interference in the order of the candidate relay numbers, and record it as P' M-1 ; Compare P M-1 With P' M-1 The transmission power of the same candidate relay in the case of considering social relations and the maximum transmission power in the case of considering interference are compared, and the minimum value obtained by comparison is used as the transmission power of the corresponding candidate relay; then the transmission powers of all candidate relays in the circular area of ​​the M-1th relay cluster are formed into a set according to the sequence of the candidate relays, which is recorded as P * M-1 ; Among them, P M-1 represents the set of transmission powers of all candidate relays in the circular area of ​​the M-1th relay cluster in the order of the candidate relay numbers when considering social relationships;

[0018] Step 8: Assume that each candidate relay in the circular area of ​​the M-1th relay cluster can obtain the channel gain between itself and the destination device while receiving all data from the destination device; then according to P * M-1 and the channel gain between each candidate relay in the circular area of ​​the M-1th relay cluster and the destination device, and calculating the received signal power of the destination device when each candidate relay in the circular area of ​​the M-1th relay cluster sends a signal to the destination device;

[0019] Step 9: Each candidate relay in the circular area of ​​the M-1th relay cluster starts a timer whose expiration time is inversely proportional to the received signal power to the destination device; then the candidate relay corresponding to the timer that ends first is determined as the best relay in the circular area of ​​the M-1th relay cluster, that is, the best relay of the Mth hop, and is recorded as R M-1 , R M-1 Broadcast a message that it has been selected as the best relay to the other candidate relays in the circular area of ​​the M-1th relay cluster. After receiving the broadcast message, the other candidate relays in the circular area of ​​the M-1th relay cluster turn off the timer;

[0020] Step 10: R M-1 Send all data received from the destination device to each candidate relay in the circular area of ​​the M-2th relay cluster, and set its own signal transmission frequency to f M , set its own signal receiving frequency to f M-1 , f M-1 The value is equal to the channel frequency of the cellular device corresponding to the spectrum multiplexed for the M-1th hop of multi-hop D2D communication between the source device and the destination device;

[0021] Step 11: Follow the process from step 7 to step 10 to determine the best relay at the M-1th hop in the same way and record it as R M-2 , R M-2 From R M-1 All data received at the M-3rd relay cluster are sent to each candidate relay in the circular area, and R M-2 The signal transmission frequency is f M-1 , R M-2 The signal receiving frequency is f M-2 , f M-2 The value is equal to the channel frequency of the cellular device corresponding to the spectrum multiplexed for the M-2 hop in the multi-hop D2D communication between the source device and the destination device;

[0022] Step 12: Follow the process of step 11, and so on, until the best relay for the second hop is determined and recorded as R1. R1 sends all data received from R2 to the source device, and determines that the signal transmission frequency of R1 is f2, and the signal reception frequency of R1 is f1. The value of f1 is equal to the channel frequency of the cellular device corresponding to the spectrum multiplexed in the first hop of multi-hop D2D communication between the source device and the destination device;

[0023] Step 13: Calculate the maximum transmission power of the source device taking interference into account, and set the signal transmission frequency of the source device to f1; then the source device starts multi-hop D2D communication with the destination device.

[0024] In step 2, the specific process of the candidate relay determination method based on the relay cluster is as follows:

[0025] Step 2_1: Find M-1 relay cluster circular areas with a radius of r, with the center on the straight line connecting the source device and the destination device between the source device and the destination device. The distance between the center of the first relay cluster circular area and the source device is r, and the distance between the centers of two adjacent relay cluster circular areas is L. adj The distance between the center of the last circular area of ​​the M-1 relay cluster and the location of the destination device is L fin ; where r∈[10m,30m], L adj ∈(2r,100m],L fin ∈(0,L adj ];

[0026] Step 2_2: All idle devices within the circular area of ​​all relay clusters and on the border of the circular area of ​​the relay cluster are regarded as candidate relays between the source device and the destination device.

[0027] In step 3, the nth m' The transmission power of candidate relays considering social relationships is recorded as N represents the number of candidate relays in the circular area of ​​the m'th relay cluster. m' ≥2, max() means taking the maximum value function, P max Indicates the maximum transmit power rated for an idle device. Indicates that the user holding the source device and the user holding the nth relay cluster in the circular area of ​​the m'th relay cluster m' The social relationship strength between users of candidate relays, Indicates that the user holding the source device and the user holding the nth relay cluster in the circular area of ​​the m'th relay cluster m' The total number of calls between users of candidate relays, Indicates that the user holding the source device and the user holding the nth relay cluster in the circular area of ​​the m'th relay cluster m' The total call duration between users of candidate relays, fre S Indicates the total number of calls made by the user holding the source device, dur S Indicates the total duration of all calls made by the user holding the source device. Indicates that the user holding the destination device and the user holding the nth relay cluster in the circular area of ​​the m'th relay cluster m' The social relationship strength between users of candidate relays, Indicates that the user holding the destination device and the user holding the nth relay cluster in the circular area of ​​the m'th relay cluster m' The total number of calls between users of candidate relays, Indicates that the user holding the destination device and the user holding the nth relay cluster in the circular area of ​​the m'th relay cluster m' The total call duration between users of candidate relays, fre D Indicates the total number of calls made by the user holding the destination device, dur D Indicates the total duration of all calls made by the user holding the destination device.

[0028] The specific process of step 4 is as follows:

[0029] Step 4_1: For the mth hop of multi-hop D2D communication between the source device and the destination device, the transmitting device and the receiving device of the mth hop are correspondingly recorded as TX m and RX m ; Wherein, 1≤m≤M, when m=1, the transmitting device and receiving device of the first hop correspond to the source device and the best relay determined in the circular area of ​​the first relay cluster, and when m=M, the transmitting device and receiving device of the Mth hop correspond to the best relay and destination device determined in the circular area of ​​the M-1th relay cluster;

[0030] Step 4_2: When m≠M, in RX m Draw a straight line segment between the center of the circular area of ​​the relay cluster and the position of the base station and extend it to the base station side. When m = M, at RX m That is, draw a straight line between the location of the target device and the location of the base station and extend it to the base station side; then take a point on the extension line as the center of the circle and a radius of A circular area inscribed in the protection area boundary is made as the cellular device selection area, and there is at least one cellular device in the cellular device selection area; where r represents the radius of the relay cluster circular area, and the protection area boundary is a circle with the base station location as the center and a radius of r. b D2D communication is not allowed within the protection area boundary. b ∈[50m,150m];

[0031] Step 4_3: Find the cellular device with the largest received signal power to the base station from all cellular devices in the cellular device selection area, and use the cellular device as the cellular device corresponding to the mth hop multiplexed spectrum for multi-hop D2D communication between the source device and the destination device.

[0032] In step 7, the nth relay cluster in the circular area of ​​the M-1th relay cluster is M-1 The maximum transmission power of candidate relays considering interference is recorded as Where 1≤n M-1 ≤N M-1 , N M-1 N represents the number of candidate relays in the circular area of ​​the M-1th relay cluster.M-1 ≥2, Indicates the cellular device C corresponding to the spectrum reused by the Mth hop for multi-hop D2D communication between the source device and the destination device M The transmission power, Represents C M The distance from the base station, Represents C M The channel gain between the base station and the Indicates the nth relay cluster in the circular area of ​​the M-1th relay cluster. M-1 The distance between the candidate relays and the base station, Indicates the nth relay cluster in the circular area of ​​the M-1th relay cluster. M-1 The channel gain between the candidate relay and the base station, N0 represents the power of the background Gaussian white noise, α represents the path loss index, and th M Indicates that the base station can correctly decode C M The minimum signal-to-interference-noise ratio required for the transmitted signal.

[0033] In step 8, the nth M-1 When a candidate relay sends a signal to the destination device, the received signal power of the destination device is recorded as Where 1≤n M-1 ≤N M-1 , N M-1 N represents the number of candidate relays in the circular area of ​​the M-1th relay cluster. M-1 ≥2, Indicates the nth relay cluster in the circular area of ​​the M-1th relay cluster. M-1 The transmit power of candidate relays, Indicates the nth relay cluster in the circular area of ​​the M-1th relay cluster. M-1 The channel gain between the candidate relays and the destination device, Indicates the nth relay cluster in the circular area of ​​the M-1th relay cluster. M-1 The distance between a candidate relay and the destination device, α represents the path loss exponent.

[0034] In step 13, the maximum transmission power of the source device under the condition of considering interference is recorded as P' S , in, Indicates the transmission power of the cellular device C1 corresponding to the spectrum multiplexed in the first hop of multi-hop D2D communication between the source device and the destination device, represents the distance between C1 and the base station, represents the channel gain between C1 and the base station, Indicates the distance between the source device and the base station. represents the channel gain between the source device and the base station, and th1 represents the minimum signal to interference and noise ratio required for the base station to correctly decode the signal sent by C1.

[0035] Compared with the prior art, the advantages of the present invention are:

[0036] 1) In order to improve the throughput of multi-hop D2D links, the method of the present invention is different from previous studies that assume that the relay is a half-duplex device. The method of the present invention is based on a full-duplex relay. Then, in order to avoid the serious self-interference caused by full-duplex, the relay is made to work in frequency division duplex mode.

[0037] 2) The method of the present invention takes into account the willingness of idle devices to act as relays, and introduces the social relationship between users holding idle devices in the relay selection process, that is, introduces social domain information, making the method of the present invention more realistic. The results obtained through a large number of Monte Carlo simulations show that when considering social domain information, the throughput performance of multi-hop D2D communication is guaranteed by using full-duplex relays. Although its throughput will naturally decrease, its energy efficiency has been greatly improved, so that the method of the present invention has certain practical application value today when there is no breakthrough in battery technology and energy conservation and emission reduction are advocated. .

[0038] 3) The method of the present invention can be executed in a semi-distributed manner in engineering implementation, that is, it can be run with less reliance on base stations, effectively reducing the base station load. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a schematic diagram of a physical model of multi-hop D2D communication in a single-cell cellular network;

[0040] Figure 2 A schematic diagram of a candidate relay determination method based on a relay cluster (Cluster) in the method of the present invention;

[0041] Figure 3 Schematic diagram of interference in the mth hop of multi-hop D2D communication;

[0042] Figure 4 A schematic diagram of a cellular device corresponding to a spectrum multiplexed for the mth hop of multi-hop D2D communication between a source device and a destination device in the method of the present invention;

[0043] Figure 5 Schematic diagram of throughput performance comparison among the SA method, the SUA method, the MLS method, and the HTPRS method when the distance between the source device (S) and the destination device (D) changes;

[0044] Figure 6It is a schematic diagram of throughput performance comparison of the SA method, the SUA method, the MLS method, and the HTPRS method when the number of candidate relays in the circular area of ​​each relay cluster changes;

[0045] Figure 7 Schematic diagram of energy efficiency performance comparison among SA method, SUA method, MLS method and HTPRS method when the distance between source device (S) and destination device (D) changes;

[0046] Figure 8 It is a schematic diagram of energy efficiency performance comparison of the SA method, the SUA method, the MLS method, and the HTPRS method when the number of candidate relays in the circular area of ​​each relay cluster changes;

[0047] Fig. 9 The figure is a general implementation block diagram of the method of the present invention. DETAILED DESCRIPTION

[0048] The present invention is further described in detail below with reference to the accompanying drawings.

[0049] At a certain moment, the source device wants to conduct D2D communication with the destination device. Since the distance between them is too far, D2D communication can only be successfully established with the help of multiple relays. In this case, it is necessary to select a suitable idle device from the idle devices between the source device and the destination device as a relay to help forward the data between the source device and the destination device. However, there are a large number of idle devices between the source device and the destination device, and the performance of the D2D communication link is different when different idle devices are used as relays. Therefore, how to select a relay becomes an important issue. At the same time, when selecting relays in actual D2D communication, due to their own communication needs or limited battery power, the user holding the relay may be unwilling to act as a relay for others, or unwilling to contribute too much power to forwarding other people's data. However, if the user holding the relay has a close social relationship with the user conducting D2D communication, then the user is likely to be willing to act as a relay or contribute more power to forwarding the data of D2D communication. Therefore, in actual systems, it is necessary to introduce social domain information into the relay selection algorithm for multi-hop D2D communication. Therefore, the present invention proposes a relay selection method in multi-hop D2D communication that introduces social domain information. The method is applied to cellular network scenarios. Figure 1 A physical model of multi-hop D2D communication in a single-cell cellular network is given, such as Figure 1As shown, it includes a base station (Base Station, represented by BS) located at the center of the cell, multiple cellular (terminal) devices (Cellular Equipment, represented by CE) communicating with the base station through uplink orthogonal channels, multiple idle devices (Idle Equipment, represented by IE) that currently have no communication needs, a source device (Source, represented by S) of multi-hop D2D communication, a destination device (Destination, represented by D) of multi-hop D2D communication, and multiple relays (Relay, represented by R, selected from the idle devices) that forward data for communication between the source device and the destination device. The base station is equipped with an omnidirectional antenna, and all devices are equipped with two antennas and work in full-duplex mode.

[0050] The present invention proposes a relay selection method in multi-hop D2D communication that introduces social domain information, which is applied to cellular network scenarios, sets all channels as Rayleigh fading channels, considers free space propagation path loss, sets the existence of a source device and a destination device and their positions are fixed, sets the base station and the source device to know the position of the destination device, sets the number of hops for multi-hop D2D communication between the source device and the destination device to M hops, M ≥ 3, and sets the relay between the source device and the destination device to work in frequency division duplex mode; its overall implementation block diagram is as follows Fig. 9 As shown, the following steps are included:

[0051] Step 1: The source device sends a D2D multi-hop communication request to the base station; then the base station determines the location of the source device and the location of the destination device. After receiving the D2D multi-hop communication request sent by the source device, the base station can determine the location of the source device, while the location of the destination device has been determined in the previous communication between the base station and the destination device, that is, it is set that the base station knows the location of the destination device.

[0052] Step 2: The base station uses a candidate relay determination method based on a relay cluster to determine M-1 relay cluster circular areas between the source device and the destination device according to the location of the source device and the location of the destination device, and then determines all candidate relays between the source device and the destination device based on the M-1 relay cluster circular areas, determines the location of each candidate relay, and then notifies each candidate relay that it has been selected as a candidate relay; wherein there are more than 2 candidate relays in each relay cluster circular area.

[0053] If all idle devices between the source device and the destination device are regarded as candidate relays, more accurate results can be obtained by selecting the best relay from them. However, this will lead to high algorithm complexity, which is not conducive to practical application. Inspired by the research on relay selection and routing strategy in multi-hop cognitive wireless networks and cognitive relay networks, and in order to reduce the complexity of the algorithm, the present invention proposes a candidate relay determination method based on relay clusters (Cluster), in which only idle devices in certain areas are regarded as candidate relays during relay selection. In this embodiment, in step 2, the specific process of the candidate relay determination method based on relay clusters (Cluster) is as follows:

[0054] Step 2_1: If Figure 2 As shown, between the source device and the destination device, find M-1 relay cluster circular areas with a radius of r, with the center on the straight line connecting the position of the source device and the position of the destination device. The distance between the center of the first relay cluster circular area and the position of the source device is r, and the distance between the centers of two adjacent relay cluster circular areas is L adj The distance between the center of the last circular area of ​​the M-1 relay cluster and the location of the destination device is L fin ; where r∈[10m,30m], in this embodiment, r is taken as 20m, L adj ∈(2r,100m],L fin ∈(0,L adj ].

[0055] exist Figure 2 In the figure, S represents the source device, D represents the destination device, Cluster 1 represents the circular area of ​​the first relay cluster, Cluster 2 represents the circular area of ​​the second relay cluster, Cluster M-2 represents the circular area of ​​the M-2 relay cluster, and Cluster M-1 represents the circular area of ​​the M-1 relay cluster.

[0056] Step 2_2: All idle devices within the circular area of ​​all relay clusters and on the border of the circular area of ​​the relay cluster are regarded as candidate relays between the source device and the destination device.

[0057] Step 3: Calculate the transmission power of each candidate relay in the circular area of ​​each relay cluster under the condition of considering social relations; then form a set of the transmission powers of all candidate relays in the circular area of ​​each relay cluster under the condition of considering social relations in the order of the candidate relay numbers, and record the set of the transmission powers of all candidate relays in the circular area of ​​the m'th relay cluster under the condition of considering social relations in the order of the candidate relay numbers as P m' ; Then, the transmission power set consisting of the transmission powers of all candidate relays between the source device and the destination device in consideration of social relationships is recorded as P, P = P1∪P2∪…∪Pm' ∪…∪P M-1 ; Where 1≤m'≤M-1, P1 represents the set of transmission powers of all candidate relays in the circular area of ​​the first relay cluster under the condition of considering social relations, P2 represents the set of transmission powers of all candidate relays in the circular area of ​​the second relay cluster under the condition of considering social relations, P M-1 represents the set consisting of the transmission powers of all candidate relays in the circular area of ​​the M-1th relay cluster taking into account the social relationship, and the symbol “∪” is the union symbol of the set.

[0058] In this embodiment, in step 3, the nth relay cluster in the circular area of ​​the m'th relay cluster is m' The transmission power of candidate relays considering social relationships is recorded as 1≤n m' ≤N m' , N m' N represents the number of candidate relays in the circular area of ​​the m'th relay cluster. m' ≥2, max() means taking the maximum value function, P max Indicates the maximum transmit power rated for an idle device. Indicates that the user holding the source device and the user holding the nth relay cluster in the circular area of ​​the m'th relay cluster m' The social relationship strength between users of candidate relays, Indicates that the user holding the source device and the user holding the nth relay cluster in the circular area of ​​the m'th relay cluster m' The total number of calls between users of candidate relays, Indicates that the user holding the source device and the user holding the nth relay cluster in the circular area of ​​the m'th relay cluster m' The total call duration between users of candidate relays, fre S Indicates the total number of calls made by the user holding the source device, dur S Indicates the total duration of all calls made by the user holding the source device. Indicates that the user holding the destination device and the user holding the nth relay cluster in the circular area of ​​the m'th relay cluster m' The social relationship strength between users of candidate relays, Indicates that the user holding the destination device and the user holding the nth relay cluster in the circular area of ​​the m'th relay cluster m' The total number of calls between users of candidate relays, Indicates that the user holding the destination device and the user holding the nth relay cluster in the circular area of ​​the m'th relay cluster m' The total call duration between users of candidate relays, fre D Indicates the total number of calls made by the user holding the destination device, dur DIndicates the total duration of all calls made by the user holding the destination device. fre D 、dur D These data are available in base stations, and in practical applications, statistics can often be collected over a period of time, such as the number of calls in the last 30 days.

[0059] In real life, two people who are closely related usually contact each other frequently through phone calls or social software, and each contact lasts for a long time; while two people who are distantly related usually contact each other seldom, and the contact lasts for a short time. On the other hand, considering that the base station can obtain the user's call records from the database, and it is very convenient to record the number of times and duration when users contact each other through social software, the number and duration of contact between device users through phone calls or social software are used to quantify the strength of their social relationship. According to the research in LI HX, WU C, LI ZP, et al. Stochastic optimal multirate multicast in socially selfish wireless networks [C] / / 2012 Proceedings IEEE INFOCOM. March 25-30, 2012, Orlando, FL, USA. Piscataway: IEEE Press, 2012: 172-180. (Stochastic optimal multirate multicast in socially selfish wireless networks [C] / / 2012 IEEE International Conference on Computer Communications Report Records), the social relationship strength between most users is relatively weak, and only a few users have strong social relationships with other users, similar to Pareto distribution. The strength of social relationships between users is modeled using Pareto distribution, and the transmission power of the relay is specified to be related to the strength of social relationships between them and the source device and the destination device.

[0060] Step 4: The base station determines the cellular device corresponding to the spectrum reused in each hop of multi-hop D2D communication between the source device and the destination device, determines a total of M cellular devices and reuses the uplink spectrum of the cellular devices; then the set of the spectrum of the determined M cellular devices in the order of each hop is recorded as F.

[0061] In order to improve the spectrum utilization rate, the present invention proposes that D2D devices realize communication by reusing the spectrum of cellular devices. In order to avoid mutual interference between multi-hop links and self-interference caused by full-duplex mode, each hop of multi-hop D2D communication reuses the spectrum of different cellular devices, that is, the relay works in frequency division duplex mode. In addition, D2D communication reuses the uplink spectrum of cellular devices. This is because: on the one hand, when the downlink spectrum is reused, the cellular device receives the interference signal, and when the uplink spectrum is reused, the base station receives the interference signal, and the base station's ability to handle interference is generally stronger than that of the cellular device; on the other hand, compared with the downlink spectrum, the uplink spectrum is usually not fully utilized. In addition, since each hop of multi-hop D2D communication reuses the spectrum of different cellular devices, although all relays between the source device and the destination device work in frequency division duplex mode, the channel interference of each hop can be analyzed separately.

[0062] Figure 3 Schematic diagram of interference in the mth hop of multi-hop D2D communication. Figure 3 TX m and RX m Corresponding to the transmitting device and receiving device of the mth hop of multi-hop D2D communication, C m is the cellular device corresponding to the spectrum multiplexed by the mth hop of multi-hop D2D communication, BS is the base station, 1≤m≤M.

[0063] In order to ensure the normal communication of cellular devices, the base station m The signal-to-interference-noise ratio of the signal received at Need to reach a certain threshold value th m ,Right now: in, Represents C m The transmission power is set to the cellular device C1 corresponding to the spectrum reused in the first hop of the multi-hop D2D communication to the cellular device C corresponding to the spectrum reused in the Mth hop of the multi-hop D2D communication. M The transmission power is the same. Indicates TX m The transmission power, Represents C m The distance from the base station, Represents C m The channel gain between the base station and the Indicates TX m The distance from the base station, Indicates TX m The channel gain between the base station and the receiver, N0 represents the power of the background Gaussian white noise, α represents the path loss index, and th m Indicates that the base station can correctly decode C m The minimum signal-to-interference-noise ratio required for the transmitted signal.

[0064] Depend on Can get Then take from It can be seen that Follow decreases and increases, Guaranteed The establishment of the base station from C m The signal-to-interference-noise ratio of the signal received at It must reach a certain threshold value th m .

[0065] RX m From TX m The signal-to-interference-noise ratio of the signal received at for in, Indicates TX m With RX m The distance between Indicates TX m With RX m The channel gain between Represents C m With RX m The distance between Represents C m With RX m The channel gain between It can be seen that Follow and According to Shannon’s formula, the throughput of the mth hop of multi-hop D2D communication is Directly related, in order to improve the throughput of this hop, you can increase (i.e. reduce ) or increase In addition, considering TX m Distance from the base station If the distance is too close, it will cause serious interference to the base station. Therefore, the present invention sets a circle with the base station as the center and a radius of r. b The circular area is used as the protection area boundary, and it is stipulated that D2D communication is not allowed within the protection area boundary.

[0066] In this embodiment, the specific process of step 4 is:

[0067] Step 4_1: For the mth hop of multi-hop D2D communication between the source device and the destination device, the transmitting device and the receiving device of the mth hop are correspondingly recorded as TX m and RX m; Wherein, 1≤m≤M, when m=1, the transmitting device and receiving device of the first hop correspond to the source device and the best relay determined within the circular area of ​​the first relay cluster, and when m=M, the transmitting device and receiving device of the Mth hop correspond to the best relay and destination device determined within the circular area of ​​the M-1th relay cluster.

[0068] Step 4_2: If Figure 4 As shown, when m≠M, in RX m Draw a straight line segment between the center of the circular area of ​​the relay cluster and the position of the base station and extend it to the base station side. When m = M, at RX m That is, draw a straight line between the location of the target device and the location of the base station and extend it to the base station side; then take a point on the extension line as the center of the circle and a radius of A circular area inscribed in the protection area boundary is made as the cellular device selection area, and there is at least one cellular device in the cellular device selection area; where r represents the radius of the relay cluster circular area, and the protection area boundary is a circle with the base station location as the center and a radius of r. b D2D communication is not allowed within the protection area boundary. b The value of can not only avoid the D2D device from causing serious interference to the base station, but also reduce Increase Depend on Knowable will increase, that is, the throughput of the mth hop of multi-hop D2D communication will increase, r b The value range is r b ∈[50m,150m], in this embodiment r b The value is 100m.

[0069] exist Figure 4 China, TX m and RX m Corresponding to the transmitting device and receiving device of the mth hop of multi-hop D2D communication, C m is the cellular device corresponding to the spectrum multiplexed by the mth hop of multi-hop D2D communication, and BS is the base station.

[0070] Step 4_3: Find the cellular device with the largest received signal power to the base station from all cellular devices in the cellular device selection area, and use the cellular device as the cellular device corresponding to the mth hop multiplexed spectrum for multi-hop D2D communication between the source device and the destination device.

[0071] The cellular device selected according to the above process can improve the throughput performance of the D2D link while ensuring the quality of service (QoS) of the cellular device.

[0072] Step 5: The base station sends the channel gain between the source device and the base station, the channel gain between each candidate relay in each relay cluster circular area and the base station, together with the location of the source device, the location of the destination device, the location of each candidate relay in each relay cluster circular area, and P and F to the destination device.

[0073] Step 6: The destination device sends all data received from the base station to each candidate relay in the circular area of ​​the M-1th relay cluster, and sets its own signal receiving frequency to f M , f M The value of is equal to the channel frequency of the cellular device corresponding to the spectrum multiplexed in the Mth hop for multi-hop D2D communication between the source device and the destination device.

[0074] Step 7: Calculate the maximum transmit power of each candidate relay in the circular area of ​​the M-1th relay cluster under the condition of considering interference; then form a set of the maximum transmit powers of all candidate relays in the circular area of ​​the M-1th relay cluster under the condition of considering interference in the order of the candidate relay numbers, and record it as P' M-1 ; Compare P M-1 With P' M-1 The transmission power of the same candidate relay in the case of considering social relations and the maximum transmission power in the case of considering interference are compared, and the minimum value obtained by comparison is used as the transmission power of the corresponding candidate relay; then the transmission powers of all candidate relays in the circular area of ​​the M-1th relay cluster are formed into a set according to the sequence of the candidate relays, which is recorded as P * M-1 ; Among them, P M-1 It represents a set of transmission powers of all candidate relays in the circular area of ​​the M-1th relay cluster in the order of the candidate relay numbers when the social relationship is taken into consideration.

[0075] In this embodiment, in step 7, the nth relay in the circular area of ​​the M-1th relay cluster is M-1 The maximum transmission power of candidate relays considering interference is recorded as Where 1≤n M-1 ≤N M-1 , N M-1 N represents the number of candidate relays in the circular area of ​​the M-1th relay cluster. M-1 ≥2, Indicates the cellular device C corresponding to the spectrum reused by the Mth hop for multi-hop D2D communication between the source device and the destination device M The transmission power, Represents C M The distance from the base station, Represents C MThe channel gain between the base station and the Indicates the nth relay cluster in the circular area of ​​the M-1th relay cluster. M-1 The distance between the candidate relays and the base station, Indicates the nth relay cluster in the circular area of ​​the M-1th relay cluster. M-1 The channel gain between the candidate relay and the base station, N0 represents the power of the background Gaussian white noise, α represents the path loss index, and th M Indicates that the base station can correctly decode C M The minimum signal-to-interference-noise ratio required for the transmitted signal.

[0076] Step 8: Assume that each candidate relay in the circular area of ​​the M-1th relay cluster can obtain the channel gain between itself and the destination device while receiving all data from the destination device; then according to P * M-1 and the channel gain between each candidate relay in the circular area of ​​the M-1th relay cluster and the destination device, and calculating the received signal power of the destination device when each candidate relay in the circular area of ​​the M-1th relay cluster sends a signal to the destination device.

[0077] In this embodiment, in step 8, the nth relay in the circular area of ​​the M-1th relay cluster is M-1 When a candidate relay sends a signal to the destination device, the received signal power of the destination device is recorded as Where 1≤n M-1 ≤N M-1 , N M-1 N represents the number of candidate relays in the circular area of ​​the M-1th relay cluster. M-1 ≥2, Indicates the nth relay cluster in the circular area of ​​the M-1th relay cluster. M-1 The transmit power of candidate relays, Indicates the nth relay cluster in the circular area of ​​the M-1th relay cluster. M-1 The channel gain between the candidate relays and the destination device, Indicates the nth relay cluster in the circular area of ​​the M-1th relay cluster. M-1 The distance between a candidate relay and the destination device, α represents the path loss exponent.

[0078] Step 9: Each candidate relay in the circular area of ​​the M-1th relay cluster starts a timer whose expiration time is inversely proportional to the received signal power to the destination device; then the candidate relay corresponding to the timer that ends first is determined as the best relay in the circular area of ​​the M-1th relay cluster, that is, the best relay of the Mth hop, and is recorded as R M-1 , R M-1A message is broadcasted to the other candidate relays in the circular area of ​​the M-1th relay cluster that they have been selected as the best relay. After receiving the broadcast message, the other candidate relays in the circular area of ​​the M-1th relay cluster turn off the timer. The greater the received signal power, the greater the throughput of the hop and the smaller the expiration time of the timer.

[0079] Step 10: R M-1 Send all data received from the destination device to each candidate relay in the circular area of ​​the M-2th relay cluster, and set its own signal transmission frequency to f M , set its own signal receiving frequency to f M-1 , f M-1 The value of is equal to the channel frequency of the cellular device corresponding to the spectrum multiplexed for the M-1th hop for multi-hop D2D communication between the source device and the destination device.

[0080] Step 11: Follow the process from step 7 to step 10 to determine the best relay at the M-1th hop in the same way and record it as R M-2 , R M-2 From R M-1 All data received at the M-3rd relay cluster are sent to each candidate relay in the circular area, and R M-2 The signal transmission frequency is f M-1 , R M-2 The signal receiving frequency is f M-2 , f M-2 The value is equal to the channel frequency of the cellular device corresponding to the spectrum multiplexed for the M-2 hop in the multi-hop D2D communication between the source device and the destination device.

[0081] Step 12: Follow the process of step 11, and so on, until the best relay for the second hop is determined and recorded as R1. R1 sends all data received from R2 to the source device, and determines that R1's signal transmission frequency is f2, and R1's signal reception frequency is f1. The value of f1 is equal to the channel frequency of the cellular device corresponding to the spectrum multiplexed in the first hop of multi-hop D2D communication between the source device and the destination device.

[0082] Step 13: According to the process of calculating the maximum transmission power of each candidate relay in the circular area of ​​the M-1th relay cluster taking interference into account in step 7, the maximum transmission power of the source device taking interference into account is calculated in the same way to avoid causing too much interference to the cellular device C1 corresponding to the spectrum reused by the first hop of the multi-hop D2D communication, and the signal transmission frequency of the source device is set to f1; then the source device starts multi-hop D2D communication with the destination device.

[0083] In this embodiment, in step 13, the maximum transmission power of the source device under the condition of considering interference is recorded as P'S , Among them, P C1 Indicates the transmission power of the cellular device C1 corresponding to the spectrum multiplexed in the first hop of multi-hop D2D communication between the source device and the destination device, represents the distance between C1 and the base station, represents the channel gain between C1 and the base station, Indicates the distance between the source device and the base station. represents the channel gain between the source device and the base station, and th1 represents the minimum signal to interference and noise ratio required for the base station to correctly decode the signal sent by C1.

[0084] In each hop of multi-hop D2D communication, it is necessary to select a cellular device with reused spectrum from multiple cellular devices, and select the best relay from multiple candidate relays in the circular area of ​​each relay cluster. There are too many devices involved. If the relay selection process is completed completely by the base station in a centralized manner, it will inevitably bring excessive load and a large amount of signaling overhead to the base station. Therefore, the present invention proposes an optimal relay selection method that can be executed in a semi-centralized manner. The base station only needs to complete the collection of information such as channel parameters and node locations at the beginning of multi-hop D2D communication and a small amount of data processing, and the best relay selection is completed by the devices participating in the multi-hop D2D communication.

[0085] After the multi-hop D2D communication link is determined according to the method of the present invention, the signal-to-interference-to-noise ratio of each hop is also determined, so the throughput of each hop can be calculated using the Shannon formula. Assuming that the spectrum bandwidth of the cellular device is represented by B, the throughput of the first hop is Ω1, The throughput of the middle m-th hop is Ω m , Here m = 2, 3, ..., M-1; the throughput of the last hop is Ω M , Among them, P S Indicates the transmit power of the source device. Indicates the distance between the source device and the second-hop best relay R1, represents the channel gain between the source device and the second-hop best relay R1, Indicates the transmit power of the cellular device C1 corresponding to the spectrum reused in the first hop, represents the distance between C1 and R1, represents the channel gain between C1 and R1, represents the best relay R at the mth hop m-1 The transmission power, Represents R m-1 The best relay R at the m+1th hop m The distance between Represents R m-1 With Rm The channel gain between Indicates the cellular device C corresponding to the spectrum reused by the mth hop m The transmission power, Represents C m With R m The distance between Represents C m With R m The channel gain between represents the best relay R at the Mth hop M-1 The transmission power, Represents R M-1 The distance to the destination device, Represents R M-1 The channel gain between the target device and the Indicates the cellular device C corresponding to the spectrum reused by the Mth hop M The transmission power, Represents C M The distance to the destination device, Represents C M Channel gain between the device and the destination device.

[0086] Since all relays work in full-duplex mode, the throughput of the entire multi-hop D2D communication link is determined by the throughput of the hop with the smallest throughput, that is, the throughput of multi-hop D2D communication is Ω, Ω = min(Ω1,…,Ω m ,…,Ω M ); where min() is the minimum value function.

[0087] In order to further illustrate the feasibility and effectiveness of the method of the present invention, a simulation experiment was carried out on the method of the present invention.

[0088] The simulation simulates a circular single-cell cellular scenario with a radius of 500 meters and centered on a base station equipped with an omnidirectional antenna. Cellular devices and idle devices are randomly and evenly distributed in the cell. The detailed simulation parameters are shown in Table 1.

[0089] Table 1 Simulation parameters and their values

[0090]

[0091]

[0092] The SA (Social Aware) algorithm in the simulation is the method of the present invention (the transmission power of the idle device takes into account both the interference to the cellular device and the social relationship), and the SUA (Social Un-Aware) algorithm is a modified algorithm of the method of the present invention that only considers the interference to the cellular device without considering the social relationship. The comparison methods include the MLS method (BODDAPATI HK, BHATNAGAR MR, PRAKRIYA S. Performance Analysis of Cluster-Based Multi-Hop Underlay CRNs Using Max-Link-Selection Protocol [J]. IEEE Transactions on Cognitive Communications and Networking, 2017, 4 (1): 15-29. (Performance Analysis of Cluster-Based Multi-Hop Underlay CRNs Using Max-Link-Selection Protocol [J]. IEEE Transactions on Cognitive Communications and Networking, 2017, 4 (1): 15-29.) and the HTPRS method (BODDAPATI HK, BHATNAGAR MR, PRAKRIYA S. Ad-hoc relay selection protocols for multi-hop underlay cognitive radio networks [C] / / 2016 IEEE Globecom Workshops (GC Wkshps). December 4-8, 2016, Washington, DC, USA. Piscataway: IEEE Press, 2016: 1-6. (Self-organizing relay selection protocol for multi-hop underlying cognitive wireless networks [C] / / 2016 IEEE Global Communications Symposium (GC Wkshps))), since the system models considered by some multi-hop relay selection algorithms in cognitive wireless networks are similar to the system model of the method of the present invention, the MLS method and the HTPRS method are both selected from relevant literature on cognitive wireless networks.

[0093] Figure 5 The figure shows the throughput performance comparison of the SA method, SUA method, MLS method, and HTPRS method as the distance between the source device (S) and the destination device (D) changes. Figure 5It can be seen that the throughput of all methods decreases with the increase of distance. This is because as the distance increases, the additional hops will only cause the minimum value of the throughput of each hop to remain unchanged or decrease, so the throughput of the entire link will decrease accordingly. When the distance is equal, the throughput of the SUA method is higher than that of the MLS method and the HTPRS method. This is because the indicator of the SUA method for selecting relays is directly related to the signal-to-interference-to-noise ratio of each hop, and it can select relays with better performance. When the distance is equal, the throughput of the SA method is not as good as that of the SUA method. This is because the SA method imposes additional social relationship constraints on the transmission power of all idle devices, so the transmission power of the relay selected by the SA method must be smaller than that of the relay selected by the SUA method.

[0094] Figure 6 The figure shows the throughput performance comparison of the SA method, SUA method, MLS method, and HTPRS method when the number of candidate relays in each relay cluster circular area changes. Figure 6 It can be seen that the throughput of the three methods SUA, SA and MLS increases with the increase in the number of candidate relays. This is because as the number of candidate relays increases, these three methods have a greater probability of selecting candidate relays with better performance as the best relay, while the HTPRS method is more random when selecting relays and cannot take advantage of more idle devices. When the number of candidate relays is the same, the throughput of the SUA method is greater than that of the MLS method and the HTPRS method, while the throughput of the SA method is not as good as that of the SUA method.

[0095] Figure 7 The figure shows the energy efficiency performance comparison of the SA method, SUA method, MLS method, and HTPRS method as the distance between the source device (S) and the destination device (D) changes. The energy efficiency is defined as the ratio of the link throughput to the sum of the actual transmission power of all devices participating in the multi-hop D2D communication. Figure 7 It can be seen that the energy efficiency of all methods decreases with the increase of distance. This is because the number of relays participating in D2D communication increases with the increase of distance, which leads to the increase of the sum of transmission power. The throughput of all methods decreases with the increase of distance, so the energy efficiency decreases. When the distance is equal, the energy efficiency of the SUA method is better than that of the MLS method and the HTPRS method, while the energy efficiency of the SA method far exceeds that of the other three methods. This is because the SA method reduces the transmission power of each selected relay by imposing additional social relationship constraints on all candidate relays, so the sum of transmission power is greatly reduced. Although the throughput of the SA method is lower than that of the SUA method, its energy efficiency far exceeds that of the other three methods.

[0096] Figure 8The figure shows the energy efficiency performance comparison of the SA method, SUA method, MLS method, and HTPRS method when the number of candidate relays in each relay cluster circular area changes. Figure 8 It can be seen that the energy efficiency of the three methods SUA, SA and MLS increases with the increase of the number of candidate relays, and the energy efficiency of the HTPRS method remains basically unchanged with the increase of the number of candidate relays. When the number of candidate relays is the same, the energy efficiency of the SUA method is better than that of the MLS method and the HTPRS method, while the energy efficiency of the SA method far exceeds that of the other three methods.

[0097] Table 2 summarizes the performance comparison of the SA and SUA methods at different distances between the source device (S) and the destination device (D).

[0098] Table 2 Performance comparison of SA and SUA methods

[0099]

[0100] As can be seen from Table 2, the performance of the SA and SUA methods in terms of throughput and energy efficiency is very different, and the SA method has a great advantage over the SUA method in terms of energy efficiency. Therefore, the role of social domain information cannot be ignored in the study of D2D relay selection algorithms.

Claims

1. A relay selection method in multi-hop D2D communication introducing social domain information, characterized in that The method is applied to a cellular network scenario, and all channels are set to be Rayleigh fading channels, and free space propagation path loss is considered. It is set that there is a source device and a destination device, and the positions of the two are fixed. It is set that the base station and the source device know the position of the destination device, and the number of hops for multi-hop D2D communication between the source device and the destination device is set to M hops, M ≥ 3, and the relay between the source device and the destination device is set to work in frequency division duplex mode. The method includes the following steps: Step 1: The source device sends a D2D multi-hop communication request to the base station; then the base station determines the location of the source device and the location of the destination device; Step 2: The base station uses a candidate relay determination method based on relay clusters to determine M-1 relay cluster circular areas between the source device and the destination device according to the location of the source device and the location of the destination device, and then determines all candidate relays between the source device and the destination device according to the M-1 relay cluster circular areas, determines the location of each candidate relay, and then notifies each candidate relay that it has been selected as a candidate relay; wherein there are more than two candidate relays in each relay cluster circular area; Step 3: Calculate the transmission power of each candidate relay in the circular area of ​​each relay cluster under the condition of considering social relations; then form a set of the transmission powers of all candidate relays in the circular area of ​​each relay cluster under the condition of considering social relations in the order of the candidate relay numbers, and record the set of the transmission powers of all candidate relays in the circular area of ​​the m'th relay cluster under the condition of considering social relations in the order of the candidate relay numbers as P m' ; Then, the transmission power set consisting of the transmission powers of all candidate relays between the source device and the destination device in consideration of social relationships is recorded as P, P = P1∪P2∪…∪P m' ∪…∪P M-1 ; Where 1≤m'≤M-1, P1 represents the set of transmission powers of all candidate relays in the circular area of ​​the first relay cluster in the order of the candidate relay numbers when considering social relationships, P2 represents the set of transmission powers of all candidate relays in the circular area of ​​the second relay cluster in the order of the candidate relay numbers when considering social relationships, P M-1 represents the set of transmission powers of all candidate relays in the circular area of ​​the M-1th relay cluster in the order of the candidate relay numbers when considering social relationships, and the symbol "∪" is the symbol for the union operation of the set; Step 4: The base station determines the cellular device corresponding to the spectrum reused in each hop of the multi-hop D2D communication between the source device and the destination device, determines a total of M cellular devices and reuses the uplink spectrum of the cellular devices; then the set of the spectrum of the determined M cellular devices in the order of each hop is recorded as F; Step 5: The base station sends the channel gain between the source device and the base station, the channel gain between each candidate relay in each relay cluster circular area and the base station, together with the location of the source device, the location of the destination device, the location of each candidate relay in each relay cluster circular area, and P and F to the destination device; Step 6: The destination device sends all data received from the base station to each candidate relay in the circular area of ​​the M-1th relay cluster, and sets its own signal receiving frequency to f M , f M The value of is equal to the channel frequency of the cellular device corresponding to the spectrum multiplexed for the Mth hop of multi-hop D2D communication between the source device and the destination device; Step 7: Calculate the maximum transmit power of each candidate relay in the circular area of ​​the M-1th relay cluster under the condition of considering interference; then form a set of the maximum transmit powers of all candidate relays in the circular area of ​​the M-1th relay cluster under the condition of considering interference in the order of the candidate relay numbers, and record it as P' M-1 ; then compare P M-1 With P' M-1 The transmission power of the same candidate relay in the case of considering social relations and the maximum transmission power in the case of considering interference are compared, and the minimum value obtained by comparison is used as the transmission power of the corresponding candidate relay; then the transmission powers of all candidate relays in the circular area of ​​the M-1th relay cluster are formed into a set according to the sequence of the candidate relays, which is recorded as P * M-1 ; Step 8: Assume that each candidate relay in the circular area of ​​the M-1th relay cluster can obtain the channel gain between itself and the destination device while receiving all data from the destination device; then according to P * M-1 and the channel gain between each candidate relay in the circular area of ​​the M-1th relay cluster and the destination device, and calculating the received signal power of the destination device when each candidate relay in the circular area of ​​the M-1th relay cluster sends a signal to the destination device; Step 9: Each candidate relay in the circular area of ​​the M-1th relay cluster starts a timer whose expiration time is inversely proportional to the received signal power to the destination device; then the candidate relay corresponding to the timer that ends first is determined as the best relay in the circular area of ​​the M-1th relay cluster, that is, the best relay of the Mth hop, and is recorded as R M-1 , R M-1 Broadcast a message that it has been selected as the best relay to the other candidate relays in the circular area of ​​the M-1th relay cluster. After receiving the broadcast message, the other candidate relays in the circular area of ​​the M-1th relay cluster turn off the timer; Step 10: R M-1 Send all data received from the destination device to each candidate relay in the circular area of ​​the M-2th relay cluster, and set its own signal transmission frequency to f M , set its own signal receiving frequency to f M-1 , f M-1 The value is equal to the channel frequency of the cellular device corresponding to the spectrum multiplexed for the M-1th hop of multi-hop D2D communication between the source device and the destination device; Step 11: Follow the process from step 7 to step 10 to determine the best relay at the M-1th hop in the same way and record it as R M-2 , R M-2 From R M-1 All data received at the M-3rd relay cluster are sent to each candidate relay in the circular area, and R M-2 The signal transmission frequency is f M-1 , R M-2 The signal receiving frequency is f M-2 , f M-2 The value is equal to the channel frequency of the cellular device corresponding to the spectrum multiplexed for the M-2 hop in the multi-hop D2D communication between the source device and the destination device; Step 12: Follow the process of step 11, and so on, until the best relay for the second hop is determined and recorded as R1. R1 sends all data received from R2 to the source device, and determines that the signal transmission frequency of R1 is f2, and the signal reception frequency of R1 is f1. The value of f1 is equal to the channel frequency of the cellular device corresponding to the spectrum multiplexed in the first hop of multi-hop D2D communication between the source device and the destination device; Step 13: Calculate the maximum transmission power of the source device taking interference into account, and set the signal transmission frequency of the source device to f1; then the source device starts multi-hop D2D communication with the destination device.

2. According to claim 1, a relay selection method in multi-hop D2D communication introducing social domain information is characterized in that In step 2, the specific process of the candidate relay determination method based on the relay cluster is as follows: Step 2_1: Find M-1 relay cluster circular areas with a radius of r, with the center on the straight line connecting the source device and the destination device between the source device and the destination device. The distance between the center of the first relay cluster circular area and the source device is r, and the distance between the centers of two adjacent relay cluster circular areas is L. adj The distance between the center of the last circular area of ​​the M-1 relay cluster and the location of the destination device is L fin ; where r∈[10m,30m], L adj ∈(2r,100m],L fin ∈(0,L adj ]; Step 2_2: All idle devices within the circular area of ​​all relay clusters and on the border of the circular area of ​​the relay cluster are regarded as candidate relays between the source device and the destination device.

3. A relay selection method in multi-hop D2D communication introducing social domain information according to claim 1 or 2, characterized in that In step 3, the nth m' The transmission power of candidate relays considering social relationships is recorded as 1≤n m' ≤N m' , N m' N represents the number of candidate relays in the circular area of ​​the m'th relay cluster. m' ≥2, max( ) represents the maximum value function, P max Indicates the maximum transmit power rated for an idle device. Indicates that the user holding the source device and the user holding the nth relay cluster in the circular area of ​​the m'th relay cluster m' The social relationship strength between users of candidate relays, Indicates that the user holding the source device and the user holding the nth relay cluster in the circular area of ​​the m'th relay cluster m' The total number of calls between users of candidate relays, Indicates that the user holding the source device and the user holding the nth relay cluster in the circular area of ​​the m'th relay cluster m' The total call duration between users of candidate relays, fre S Indicates the total number of calls made by the user holding the source device, dur S Indicates the total duration of all calls made by the user holding the source device. Indicates that the user holding the destination device and the user holding the nth relay cluster in the circular area of ​​the m'th relay cluster m' The social relationship strength between users of candidate relays, Indicates that the user holding the destination device and the user holding the nth relay cluster in the circular area of ​​the m'th relay cluster m' The total number of calls between users of candidate relays, Indicates that the user holding the destination device and the user holding the nth relay cluster in the circular area of ​​the m'th relay cluster m' The total call duration between users of candidate relays, fre D Indicates the total number of calls made by the user holding the destination device, dur D Indicates the total duration of all calls made by the user holding the destination device.

4. The relay selection method in multi-hop D2D communication introducing social domain information according to claim 3 is characterized in that The specific process of step 4 is as follows: Step 4_1: For the mth hop of multi-hop D2D communication between the source device and the destination device, the transmitting device and the receiving device of the mth hop are correspondingly recorded as TX m and RX m ; Wherein, 1≤m≤M, when m=1, the transmitting device and receiving device of the first hop correspond to the source device and the best relay determined in the circular area of ​​the first relay cluster, and when m=M, the transmitting device and receiving device of the Mth hop correspond to the best relay and destination device determined in the circular area of ​​the M-1th relay cluster; Step 4_2: When m≠M, in RX m Draw a straight line segment between the center of the circular area of ​​the relay cluster and the position of the base station and extend it to the base station side. When m = M, at RX m That is, draw a straight line between the location of the target device and the location of the base station and extend it to the base station side; then take a point on the extension line as the center of the circle and a radius of A circular area inscribed in the protection area boundary is made as the cellular device selection area, and there is at least one cellular device in the cellular device selection area; where r represents the radius of the relay cluster circular area, and the protection area boundary is a circle with the base station location as the center and a radius of r. b D2D communication is not allowed within the protection area boundary. b ∈[50m,150m]; Step 4_3: Find the cellular device with the largest received signal power to the base station from all cellular devices in the cellular device selection area, and use the cellular device as the cellular device corresponding to the mth hop multiplexed spectrum for multi-hop D2D communication between the source device and the destination device.

5. The relay selection method in multi-hop D2D communication introducing social domain information according to claim 4 is characterized in that In step 7, the nth relay cluster in the circular area of ​​the M-1th relay cluster is M-1 The maximum transmission power of candidate relays considering interference is recorded as Where 1≤n M-1 ≤N M-1 , N M-1 N represents the number of candidate relays in the circular area of ​​the M-1th relay cluster. M-1 ≥2, Indicates the cellular device C corresponding to the spectrum reused by the Mth hop for multi-hop D2D communication between the source device and the destination device M The transmission power, Represents C M The distance from the base station, Represents C M The channel gain between the base station and the Indicates the nth relay cluster in the circular area of ​​the M-1th relay cluster. M-1 The distance between the candidate relays and the base station, Indicates the nth relay cluster in the circular area of ​​the M-1th relay cluster. M-1 The channel gain between the candidate relay and the base station, N0 represents the power of the background Gaussian white noise, α represents the path loss index, and th M Indicates that the base station can correctly decode C M The minimum signal-to-interference-noise ratio required for the transmitted signal.

6. The relay selection method in multi-hop D2D communication introducing social domain information according to claim 5, characterized in that In step 8, the nth M-1 When a candidate relay sends a signal to the destination device, the received signal power of the destination device is recorded as Where 1≤n M-1 ≤N M-1 , N M-1 N represents the number of candidate relays in the circular area of ​​the M-1th relay cluster. M-1 ≥2, Indicates the nth relay cluster in the circular area of ​​the M-1th relay cluster. M-1 The transmit power of candidate relays, Indicates the nth relay cluster in the circular area of ​​the M-1th relay cluster. M-1 The channel gain between the candidate relays and the destination device, Indicates the nth relay cluster in the circular area of ​​the M-1th relay cluster. M-1 The distance between a candidate relay and the destination device, α represents the path loss exponent.

7. The relay selection method in multi-hop D2D communication introducing social domain information according to claim 5, characterized in that In step 13, the maximum transmission power of the source device under the condition of considering interference is recorded as P' S , in, Indicates the transmission power of the cellular device C1 corresponding to the spectrum multiplexed in the first hop of multi-hop D2D communication between the source device and the destination device, represents the distance between C1 and the base station, represents the channel gain between C1 and the base station, Indicates the distance between the source device and the base station. represents the channel gain between the source device and the base station, and th1 represents the minimum signal to interference and noise ratio required for the base station to correctly decode the signal sent by C1.

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