CN115361725A

CN115361725A - Relay selection method in multi-hop D2D communication introducing social domain information

Info

Publication number: CN115361725A
Application number: CN202210794656.XA
Authority: CN
Inventors: 李良; 杨新杰; 褚翼飞
Original assignee: Ningbo University
Current assignee: Ningbo University
Priority date: 2022-07-07
Filing date: 2022-07-07
Publication date: 2022-11-18

Abstract

The invention discloses a relay selection method in multi-hop D2D communication introducing social domain information, which determines all candidate relays by a relay cluster-based method; determining the cellular equipment corresponding to each hop of the multiplexed frequency spectrum by using a method based on a protection area; determining the transmitting power of all candidate relays by using social relations and interference limitation, and further calculating the receiving signal power of receiving equipment when each candidate relay in each relay cluster sends signals to the receiving equipment corresponding to the candidate relay; selecting the best relay at each hop using a timer whose expiration time is inversely proportional to the received signal power of each candidate relay to its corresponding receiving device; the relay selection process runs reversely from the last hop until the optimal relay of the 2 nd hop is determined, and finally the source device starts to perform D2D communication; the method has the advantages that the load of the base station is effectively reduced, the throughput performance can be ensured, and the energy efficiency can be effectively improved.

Description

Relay selection method in multi-hop D2D communication introducing social domain information

Technical Field

The present invention relates to a Device-to-Device (D2D) communication technology, and more particularly, to a relay selection method in multi-hop D2D communication introducing social domain information.

Background

In recent years, with the rapid development of mobile communication technology and internet industry, intelligent wireless terminals have been rapidly developed and popularized, and the number of cellular network users has been explosively increased. According to Cisco annual Internet reports (2018-2023), by 2023, global cell phone users will increase to 57 billion people (71% of the total population) and global mobile devices will grow to 131 billions. The huge number of mobile phone users and mobile devices brings huge load to the base station of the cellular network, and meanwhile, the problems of radio spectrum resource shortage, low spectrum utilization rate, insufficient network capacity and the like are increasingly highlighted. Researchers have therefore proposed D2D (Device-to-Device) communication techniques to address the above-mentioned problems. Unlike conventional mobile communication technologies that only allow communication between mobile devices and base stations via uplink/downlink, D2D communication technology allows neighboring mobile devices to communicate directly, and this close-range communication method saves the amount of power consumed by mobile device communication and also reduces base station load and transmission delay. On the other hand, the D2D device can realize communication by using an unlicensed spectrum or a dedicated cellular spectrum, and also can realize communication by multiplexing a spectrum used by the cellular device, and this multiplexing mode can greatly improve the spectrum utilization rate, which is helpful for solving the problem of radio spectrum resource shortage. D2D communication technology is identified by the standardization organization 3GPP as one of 5G key technologies due to its many advantages, and is receiving increasing attention from researchers.

The traditional direct connection D2D communication has the problems of short communication distance, large electric quantity of consumed equipment, large interference on a cellular network and the like. Some researchers to solve these problems introduce relay technology into D2D communication, which further improves the performance of D2D communication, and relay selection is therefore an important research direction in D2D communication.

In order to reduce the burden on the base station caused by the execution of the algorithm, researchers have proposed some relay selection algorithms that do not require the participation of the base station. There is a document (MA X R, YIN R, YU G D, et al.a distributed relay selection method for relay assisted device-to-device communication system [ C ]//2012IEEE 23rd International Symposium on personal, inoore and Mobile Radio Communications (PIMRC), separation 9-12,2012, sydney, architecture, piscataway, IEEE press,2012, 1020-1024. (a distributed relay selection method for relay assist device-to-device communication system [ C ]//2012 twenty third IEEE personal, indoor and Mobile Radio communication International seminar (mrpic))) that proposes a timer-based relay selection method that can determine and select the best relay in a distributed manner. There is also a document (MISHRA P K, PANDEY S, bisswitch S K.A Device-central schedule for Relay Selection in a Dynamic Network hierarchy for 5G communication, IEEE Access,2016, 4. (a Relay Selection Scheme [ J ] centered around devices in a 5G communication Dynamic Network Scenario)) that proposes a Device-centered Relay Selection Scheme, which obtains common neighboring devices of D2D communication devices through a switching Device table, and then selects an optimal Device from the common neighboring devices as a Relay based on various parameters such as signal-to-interference-noise ratio and remaining power. These methods reduce base station load and network overhead compared to conventional network/base station centric schemes.

In addition, in order to further expand the D2D communication range and improve the communication performance, researchers will research the extension of single-hop to multi-hop D2D communication. There are documents (BHARDWAJ V, muthy C r. On optimal routing and power allocation for D2D communications [ C ]//2015IEEE International Conference on acoustics, speed and Signal Processing (ICASSP). April 19-24,2015, brisbane, australia. Piscataway, 2015 3063-3067. (optimal routing and power allocation [ C ]//2015 years IEEE International acoustic, voice and Signal Processing Conference (ICASSP)). There is also literature (YUAN H, GUO W S, jinn Y L, et al. Interference-aware multi-hop path selection for device-to-device communication in a cellular interference environment [ J ]. Iet Communications,2017,11 (11): 1741-1750. (interference-aware multi-hop path selection for device-to-device communication in a cellular interference environment [ J ]. British engineering technical institute Communications ]) that proposes an adaptive interference-aware multi-hop path selection algorithm for D2D communication that enables a multi-hop path from a D2D transmitting end to first reach a cell edge, then move along the cell edge, and finally return to the inside of a cell by knowing the user position, which significantly increases the overall network capacity at the expense of small-amplitude conventional cellular capacity.

Considering that in an actual system, a device has a self-willingness problem when acting as a relay, researchers consider a more realistic scenario and introduce social domain information of a terminal into D2D research. There is a document (ZHANG Z F, ZHANG P R, LIU D, et al.srsm-based Adaptive Relay Selection for D2D Communications [ J ]. IEEE Internet of Things Journal,2017, 2323-2332. (SRSM-based D2D communication Adaptive Relay Selection [ J ]. IEEE Internet of Things Journal)), which proposes a Relay Selection method using a social network, which comprehensively considers factors of a physical domain and a social domain of a Relay, selects a Relay using link transmission stability calculated according to a history encountered by a user and cooperation intention calculated according to user affinity as criteria, and can improve probability of success of Relay Selection and reduce burden of a cellular network compared with a conventional method. An innovative socially aware Energy-efficient Relay Selection mechanism is also proposed in the literature (LI Y, ZHANG Z F, WANG H G, et al SERS: social-aware Energy-efficient Relay Selection in D2D Communications [ J ]. IEEE Transactions on Vehicular Technology,2018, 5331-5345. (SERS: socially aware Energy-efficient Relay Selection in D2D communication [ J ]. IEEE vehicle technical book ]), which takes into account the hidden Social relationship between mobile users and can ensure that more users are willing to participate in cooperative communication.

The relay selection algorithm is applied to a cellular network scene, and a multi-hop D2D communication optimal routing algorithm applied to the scene of the Internet of Things is provided in documents (CHEN G J, TANG J C, COON J P. Optimal routing for multi-hop social-based D2D communications in the Internet of Things [ J ]. IEEE Internet of Things Journal,2018,5 (3): 1880-1889. (optimal routing [ J ]. IEEE Journal of the Internet of Things ] based on social multi-hop D2D communication in the Internet of Things), the algorithm integrates social domain information, the trust probability of D2D connection is deduced by using a ranking-based trust model, the trusted connection probability among nodes is obtained by the trust probability, the influence of the exhaustive connection probability is considered, and finally the proposed routing algorithm can enable any pair of D2D devices to achieve the highest trusted connection probability in a manner, and almost achieve distributed searching performance.

In summary, some studies on distributed or device-centric relay selection algorithms have been made in two-hop D2D communication, but the studies on relay selection in multi-hop D2D communication basically do not consider the problem of execution mode and complexity of the algorithms. On the other hand, existing research on relay selection of multi-hop D2D communication is based on half-duplex relay, and the throughput performance of the algorithm is limited. Meanwhile, the research on the influence of social domain information on algorithm performance in an actual system is not sufficient. Therefore, it is very necessary to research a relay selection method applied to multi-hop D2D communication introducing social domain information in a cellular network scenario, which can be performed in a semi-distributed manner in terms of engineering implementation, effectively reduce base station load, ensure throughput performance, and improve energy efficiency.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a relay selection method in multi-hop D2D communication introducing social domain information, which is applied to a cellular network scene, can be executed in a semi-distributed manner in engineering implementation, effectively reduces the load of a base station, can ensure the throughput performance, and can effectively improve the energy efficiency.

The technical scheme adopted by the invention for solving the technical problems is as follows: a relay selection method in multi-hop D2D communication introducing social domain information is characterized in that the method is applied to a cellular network scene, all channels are set to be Rayleigh fading channels, free space propagation path loss is considered at the same time, a source device and a target device are set to exist, the positions of the source device and the target device are fixed, the positions of the base station and the known target device of the source device are set, the hop count of the multi-hop D2D communication between the source device and the target device is set to be M hops, M is more than or equal to 3, and the relay between the source device and the target device is set to work in a frequency division duplex mode; the method comprises the following steps:

step 1: the source equipment sends a D2D multi-hop communication request to the base station; then the base station determines the position of the source equipment and the position of the destination equipment;

step 2: the base station determines M-1 relay cluster circular areas between the source equipment and the destination equipment according to the position of the source equipment and the position of the destination equipment by using a relay cluster-based candidate relay determination method, then determines all candidate relays between the source equipment and the destination equipment according to the M-1 relay cluster circular areas, determines the positions of the candidate relays, and informs the candidate relays to inform that the candidate relays are selected as the candidate relays; wherein, each relay cluster circular area has more than 2 candidate relays;

and step 3: calculating the transmitting power of each candidate relay in each relay cluster circular area under the condition of considering the social relation; then, the transmitting power of all candidate relays in each relay cluster circular area under the condition of considering the social relationship forms a set according to the sequence number sequence of the candidate relays, and the set formed by the transmitting power of all candidate relays in the mth relay cluster circular area under the condition of considering the social relationship according to the sequence number sequence of the candidate relays is marked as P _m' (ii) a Then, the transmit power set formed by the transmit powers of all the candidate relays between the source device and the destination device under the condition of considering the social relationship is recorded as P, and P = P ₁ ∪P ₂ ∪…∪P _m' ∪…∪P _M-1 (ii) a Wherein M' is not less than 1 and not more than M-1,P ₁ Set of transmit powers, P, representing all candidate relays within the 1 st relay cluster circle area, considering social relationships ₂ Set of transmit powers, P, representing all candidate relays within the 2 nd relay cluster circle area, considering social relationships _M-1 Representing a set formed by the emission power of all candidate relays in the circular area of the M-1 th relay cluster under the condition of considering the social relationship, wherein the symbol 'U' is a combined operation symbol of the set;

and 4, step 4: the method comprises the steps that a base station determines cellular equipment corresponding to each hop of multiplexed frequency spectrum for multi-hop D2D communication between source equipment and target equipment, determines M cellular equipment in total and multiplexes uplink frequency spectrum of the cellular equipment; then, a set formed by the frequency spectrums of the M determined cellular devices according to the sequence of each hop is recorded as F;

and 5: the base station sends the channel gain between the source equipment and the base station, the channel gain between each candidate relay in each relay cluster circular area and the base station, the position of the source equipment, the position of the destination equipment, the position of each candidate relay in each relay cluster circular area and P, F to the destination equipment;

step 6: the destination device sends all the data received from the base station to each candidate relay in the circular area of the (M-1) th relay cluster, and sets the signal receiving frequency of the destination device to be f _M ，f _M The value of (a) is equal to the channel frequency of the cellular device corresponding to the frequency spectrum of the mth hop multiplexing for the multi-hop D2D communication between the source device and the destination device;

and 7: calculating the maximum transmission power of each candidate relay in the circular area of the M-1 relay cluster under the condition of considering interference; then, the maximum transmitting power of all candidate relays in the circular area of the M-1 relay cluster under the condition of considering interference is formed into a set according to the sequence number of the candidate relays and is marked as P' _M-1 (ii) a Re-comparison of P _M-1 And P' _M-1 The transmitting power of the same candidate relay under the condition of considering the social relation and the maximum transmitting power under the condition of considering the interference are compared to obtain the minimum value which is used as the transmitting power of the corresponding candidate relay; then, the transmitting powers of all the candidate relays in the circular area of the M-1 th relay cluster form a set according to the sequence of the candidate relays, and the set is marked as P ^* _M-1 (ii) a Wherein, P _M-1 Representing a set formed by the transmitting power of all candidate relays in the M-1 th relay cluster circular area according to the sequence of the sequence numbers of the candidate relays under the condition of considering the social relationship;

and 8: setting each candidate relay in the circular area of the (M-1) th relay cluster to obtain the channel gain between the candidate relay and the destination equipment while receiving all data from the destination equipment; then according to P ^* _M-1 And the M-1 relay cluster circleCalculating the channel gain between each candidate relay in the circular area of the (M-1) th relay cluster and the target equipment, and calculating the received signal power of the target equipment when each candidate relay in the circular area of the (M-1) th relay cluster sends a signal to the target equipment;

and step 9: starting a timer with the termination time inversely proportional to the received signal power from the candidate relay in the circular area of the M-1 th relay cluster; then, the candidate relay corresponding to the timer which is ended firstly is determined as the best relay in the circular area of the M-1 relay cluster, namely the best relay of the M hop and is marked as R _M-1 ，R _M-1 Broadcasting a message which is selected as the best relay to other candidate relays in the M-1 relay cluster circular area, and closing a timer after the other candidate relays in the M-1 relay cluster circular area receive the broadcast message;

step 10: r _M-1 All data received from the destination equipment is sent to each candidate relay in the circular area of the M-2 relay cluster, and the signal sending frequency of the relay cluster is set to be f _M Setting the signal receiving frequency of itself as f _M-1 ，f _M-1 The value of (1) is equal to the channel frequency of the cellular device corresponding to the frequency spectrum of the M-1 hop multiplexing for the multi-hop D2D communication between the source device and the destination device;

step 11: the optimal relay of the M-1 hop is determined in the same way according to the process from step 7 to step 10 and is marked as R _M-2 ，R _M-2 Will be selected from R _M-1 All the received data are sent to each candidate relay in the circular area of the M-3 relay cluster, and R is determined _M-2 Has a signal transmission frequency of f _M-1 ，R _M-2 Has a signal receiving frequency of f _M-2 ，f _M-2 The value of (2) is equal to the channel frequency of the cellular device corresponding to the frequency spectrum of the M-2 hop multiplexing for the multi-hop D2D communication between the source device and the destination device;

step 12: and (4) according to the process of the step 11, and the like until the optimal relay of the 2 nd hop is determined and is marked as R ₁ ，R ₁ Will be selected from R ₂ Where all received data is sent to the source device and R is determined ₁ Has a signal transmission frequency of f ₂ ，R ₁ Has a signal receiving frequency of f ₁ ，f ₁ The value of (1) is equal to the channel frequency of the cellular device corresponding to the frequency spectrum of the 1 st hop multiplexing for the multi-hop D2D communication between the source device and the destination device;

step 13: calculating the maximum transmitting power of the source device under the condition of considering interference, and setting the signal transmission frequency of the source device to be f ₁ (ii) a The source device then starts multi-hop D2D communication with the destination device.

In step 2, the method for determining candidate relays based on the relay cluster includes the following specific processes:

step 2_1: finding out M-1 circular areas of relay clusters with the radius of r, the circle centers of which are positioned on a straight line connecting the position of the source equipment and the position of the destination equipment, between the source equipment and the destination equipment, wherein the distance between the circle center of the 1 st circular area of relay clusters and the position of the source equipment is r, and the distance between the circle centers of two adjacent circular areas of relay clusters is L _adj The distance between the center of the circle of the last (M-1) th relay cluster circular area and the position of the destination device is L _fin (ii) a Wherein r ∈ [10m,30m]，L _adj ∈(2r,100m]，L _fin ∈(0,L _adj ]；

Step 2_2: and taking idle devices in all the relay cluster circular areas and on the boundary of the relay cluster circular area as candidate relays between the source device and the destination device.

In the step 3, the nth relay cluster in the circular area of the mth' relay cluster is divided into _m' The transmission power of the candidate relay under the condition of considering the social relation is recorded as

Indicates the number of candidate relays within the m' th relay cluster circular area, N _m' Max () denotes a maximum function, P _max Indicating the maximum transmit power for which the idle device is rated,

indicating that the user holding the source device and the n-th relay cluster in the circular area holding the m' th relay cluster _m' In a candidateThe strength of the social relationship between the users of the relay,

indicating that the user holding the source device and the n-th relay cluster in the circular area holding the m' -th relay cluster _m' The total number of calls between users of the candidate relay,

indicating that the user holding the source device and the n-th relay cluster in the circular area holding the m' th relay cluster _m' Total duration of call, fre, between users of candidate relays _S Representing the total number of calls, dur, made by a user having an active device _S Representing the total duration of all calls made by the user holding the source device,

indicating the user holding the target device and the n-th relay cluster in the circular area holding the m' th relay cluster _m' The strength of the social relationship between users of the candidate relays,

indicating the user holding the target device and the n-th relay cluster in the circular area holding the m' th relay cluster _m' The total number of calls between users of the candidate relay,

indicating the user holding the target device and the n-th relay cluster in the circular area holding the m' th relay cluster _m' Total duration of call, fre, between users of candidate relays _D Indicating the total number of calls, dur, made by the user holding the destination device _D Indicating the total duration of all calls made by the user holding the destination device.

The specific process of the step 4 comprises the following steps:

step 4_1: for the mth hop for 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 marked as TX _m And RX _m (ii) a It is composed ofM is more than or equal to 1 and less than or equal to M, when M =1, the transmitting device and the receiving device of the 1 st hop correspond to the optimal relay determined in the circular area of the source device and the 1 st relay cluster, and when M = M, the transmitting device and the receiving device of the M-th hop correspond to the optimal relay and the destination device determined in the circular area of the M-1 st relay cluster;

step 4_2: in RX when M ≠ M _m Making a straight line segment between the center of the circular area of the relay cluster and the position of the base station, extending the straight line segment to the base station side, and when M = M, at RX _m Namely, a straight line segment is made between the position of the target equipment and the position of the base station and is extended to the base station side; then, a point on the extension line is taken as the center of a circle and the radius is taken as the radius

Making a circular area internally tangent to the boundary of the protection area as a cellular equipment selection area, wherein at least one cellular equipment is arranged in the cellular equipment selection area; wherein r represents the radius of the circular area of the relay cluster, the boundary of the protection area takes the position of the base station as the center of a circle and the radius is r _b A circular area of (a), within the boundary of the protection area, no D2D communication is allowed, r _b ∈[50m,150m]；

Step 4_3: and finding out the cellular equipment with the maximum received signal power of the base station from all the cellular equipment in the cellular equipment selection area, and taking the cellular equipment as the cellular equipment corresponding to the m-th hop multiplexing frequency spectrum for carrying out multi-hop D2D communication between the source equipment and the target equipment.

In the step 7, the nth relay cluster in the circular area of the M-1 th relay cluster is divided into _M-1 Maximum transmit power of a candidate relay under interference consideration is recorded as

Wherein n is more than or equal to 1 _M-1 ≤N _M-1 ，N _M-1 Indicates the number of candidate relays in the circular area of the M-1 th relay cluster, N _M-1 ≥2，

Representing multi-hop D2D communication between a source device and a destination deviceCellular device C corresponding to frequency spectrum multiplexed by Mth hop _M The transmission power of the antenna is set to be,

is represented by C _M The distance to the base station(s) from the base station(s),

is represented by C _M The channel gain with the base station is,

represents the n-th relay cluster within the circular area of the M-1 th relay cluster _M-1 The distance between the candidate relay and the base station,

represents the n-th relay cluster within the circular area of the M-1 th relay cluster _M-1 Channel gain, N, between candidate relays and base station ₀ Representing the power of background white Gaussian noise, alpha representing the path loss exponent, th _M Indicating that the base station can correctly decode C _M The minimum signal to interference plus noise ratio required for the transmitted signal.

In the step 8, the nth relay cluster in the circular area of the M-1 th relay cluster is divided into _M-1 The received signal power of the destination device when the candidate relay sends a signal to the destination device is recorded as

Represents the n-th relay cluster within the circular area of the M-1 th relay cluster _M-1 The transmit power of the one candidate relay is,

represents the n-th relay cluster within the circular area of the M-1 th relay cluster _M-1 The channel gain between the candidate relay and the destination device,

represents the n-th relay cluster within the circular area of the M-1 th relay cluster _M-1 The distance between the candidate relay and the destination device, α, represents the path loss exponent.

In step 13, the maximum transmission power of the source device under the condition of considering the interference is recorded as P' _S ，

Wherein the content of the first and second substances,

cellular device C corresponding to frequency spectrum of 1 st hop multiplexing representing multi-hop D2D communication between source device and destination device ₁ The transmission power of the antenna is set to be,

is represented by C ₁ The distance to the base station(s),

is represented by C ₁ The channel gain with the base station is,

indicating the distance between the source device and the base station,

denotes the channel gain, th, between the source device and the base station ₁ Indicating that the base station can correctly decode C ₁ The minimum signal to interference plus noise ratio required for the transmitted signal.

Compared with the prior art, the invention has the advantages that:

1) In order to improve the throughput of the multi-hop D2D link, the method is different from the previous research on the assumption that the relay is half-duplex equipment, is based on full-duplex relay, and then enables the relay to work in a frequency division duplex mode in order to avoid serious self-interference caused by the full-duplex.

2) The method of the invention considers the willingness problem of idle equipment serving as a relay, introduces the social relationship among users holding the idle equipment in the relay selection process, namely introduces the social domain information, so that the method of the invention has more practical significance, and the results obtained through a large number of Monte Carlo simulations show that when the social domain information is considered, the throughput performance of multi-hop D2D communication is ensured by using full-duplex relay, and although the throughput is naturally reduced, the energy efficiency is greatly improved, so that the method of the invention has certain practical application value at present without breakthrough progress in battery technology and advocating energy conservation and emission reduction.

3) The method can be executed in a semi-distributed mode in engineering realization, namely, the method can operate under the condition of less dependence on the base station, and the load of the base station is effectively reduced.

Drawings

Fig. 1 is a schematic diagram of a physical model of multi-hop D2D communication in a single cell cellular network;

fig. 2 is a schematic diagram of a relay Cluster (Cluster) based candidate relay determination method in the method of the present invention;

fig. 3 is an interference diagram of an m-th hop of multi-hop D2D communication;

fig. 4 is a schematic diagram of a cellular device corresponding to a frequency spectrum for determining an m-th hop multiplexing for multi-hop D2D communication between a source device and a destination device in the method of the present invention;

fig. 5 is a schematic diagram showing comparison of throughput performance of the SA method, SUA method, MLS method, HTPRS method according to the variation of the distance between the source device (S) and the destination device (D);

FIG. 6 is a schematic diagram of a comparison of throughput performance of the SA method, SUA method, MLS method, and HTPRS method with a variation in the number of candidate relays within a circular area of each relay cluster;

fig. 7 is a graph showing comparison of energy efficiency performance of the SA method, SUA method, MLS method, HTPRS method in case of varying distance between the source device (S) and the destination device (D);

FIG. 8 is a schematic diagram illustrating energy efficiency performance comparison of SA, SUA, MLS, and HTPRS methods with varying number of candidate relays within a circular area of each relay cluster;

fig. 9 is a block diagram of the overall implementation of the method of the present invention.

Detailed Description

The invention is described in further detail below with reference to the following examples of the drawings.

At some point the source device wants to communicate D2D with the destination device, and due to the too great distance between them, the 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 data between the source device and the destination device. However, the number of idle devices between the source device and the destination device is large, and the performance of the D2D communication link is different when different idle devices are used as relays, so how to select a relay becomes an important problem. Meanwhile, when relay selection is performed in actual D2D communication, a user holding a relay may be unwilling to act as a relay of another person or unwilling to contribute too much power to forward data of another person due to communication demand of the user or limited battery power. However, if the user holding the relay and the user conducting the D2D communication have a close social relationship, then the user is likely to be willing to act as a relay or contribute more power to forward the data of the D2D communication. Therefore, in practical systems, it is necessary to introduce social domain information into the relay selection algorithm of multi-hop D2D communication. The method is applied to a Cellular network scenario, and fig. 1 shows a physical model of multi-hop D2D communication in a single-cell Cellular network, and as shown in fig. 1, the method includes a Base Station (Base Station, denoted by BS) located at a cell center, a plurality of Cellular (terminal) devices (Cellular devices, denoted by CE) communicating with the Base Station through an uplink orthogonal channel, a plurality of Idle devices (Idle devices, denoted by IE) not currently having a communication demand, a Source device (Source, denoted by S) of the multi-hop D2D communication, a Destination device (Destination, denoted by D) of the multi-hop D2D communication, and a plurality of relays (Relay, denoted by R, selected from the Idle devices) forwarding data for communication between the Source device and the Destination device. The base station is equipped with an omni-directional antenna and all devices are equipped with two antennas and operate in full duplex mode.

The invention provides a relay selection method in multi-hop D2D communication introducing social domain information, which is applied to a cellular network scene, sets all channels to be Rayleigh fading channels, simultaneously considers free space propagation path loss, sets that a source device and a target device exist and the positions of the source device and the target device are fixed, sets the positions of the known target devices of a base station and the source device, sets the hop count of the multi-hop D2D communication between the source device and the target device to be M hops, wherein M is more than or equal to 3, and sets the relay between the source device and the target device to work in a frequency division duplex mode; the general implementation block diagram is shown in fig. 9, and includes the following steps:

step 1: the source equipment sends a D2D multi-hop communication request to the base station; then the base station determines the position of the source device and the position of the destination device, the base station can determine the position of the source device after receiving the D2D multi-hop communication request sent by the source device, and the position of the destination device is determined in the previous communication between the base station and the destination device, that is, the base station is set to know the position of the destination device.

And 2, step: the base station determines M-1 relay Cluster circular areas between the source equipment and the destination equipment according to the position of the source equipment and the position of the destination equipment by using a relay Cluster (Cluster) -based candidate relay determination method, then determines all candidate relays between the source equipment and the destination equipment according to the M-1 relay Cluster circular areas, determines the positions of the candidate relays, and informs the candidate relays to inform that the candidate relays are selected as the candidate relays; wherein, each relay cluster circular area has more than 2 candidate relays.

If all idle devices between the source device and the destination device are regarded as candidate relays, then selecting the best relay from the candidate relays can obtain more accurate results, but doing so can cause the complexity of the algorithm to be too high, which is not beneficial to practical application. The invention is inspired by research related to relay selection and routing strategy directions in a multi-hop cognitive wireless network and a cognitive relay network, and simultaneously provides a relay Cluster (Cluster) -based candidate relay determination method for reducing algorithm complexity. In this embodiment, in step 2, the specific process of the relay Cluster (Cluster) -based candidate relay determination method is as follows:

step 2_1: as shown in fig. 2, M-1 circular relay cluster regions with a radius of r and with a circle center on a straight line connecting the position of the source device and the position of the destination device are found between the source device and the destination device, the distance between the circle center of the 1 st circular relay cluster region and the position of the source device is r, and the distance between the circle centers of two adjacent circular relay cluster regions is L _adj The distance between the center of the circle of the last (M-1) th relay cluster circular area and the position of the destination device is L _fin (ii) a Wherein r ∈ [10m,30m]In this example, r is 20m, L _adj ∈(2r,100m]，L _fin ∈(0,L _adj ]。

In FIG. 2, S denotes a source device, D denotes a destination device, cluster 1 denotes a 1 st relay Cluster circular area, cluster 2 denotes a 2 nd relay Cluster circular area, cluster M-2 denotes an M-2 nd relay Cluster circular area, and Cluster M-1 denotes an M-1 th relay Cluster circular area.

And step 3: calculating the transmitting power of each candidate relay in each relay cluster circular area under the condition of considering the social relation; then, the transmitting power of all candidate relays in each relay cluster circular area under the condition of considering the social relationship forms a set according to the sequence of the sequence numbers of the candidate relays, and a set formed by the transmitting power of all candidate relays in the mth relay cluster circular area under the condition of considering the social relationship according to the sequence of the sequence numbers of the candidate relays is marked as P _m' (ii) a Then connecting the source equipment and the destination equipmentThe transmission power set formed by the transmission power of all the candidate relays in the social relation is taken as P, and P = P ₁ ∪P ₂ ∪…∪P _m' ∪…∪P _M-1 (ii) a Wherein M' is not less than 1 and not more than M-1,P ₁ Set of transmit powers, P, representing all candidate relays within the 1 st relay cluster circle area, considering social relationships ₂ Set of transmit powers, P, representing all candidate relays within the 2 nd relay cluster circle area, considering social relationships _M-1 And the symbol is a union operation symbol of the set, and represents a set formed by the emission powers of all the candidate relays in the circular area of the (M-1) th relay cluster under the condition of considering the social relationship.

In this embodiment, in step 3, the nth relay cluster in the circular area of the mth' relay cluster is divided into _m' The transmission power of the candidate relay under the condition of considering the social relation is recorded as

1≤n _m' ≤N _m' ，N _m' Indicates the number of candidate relays within the m' th relay cluster circular area, N _m' Max () denotes a maximum function, P _max Representing the maximum transmit power for which the idle device is rated,

indicating that the user holding the source device and the n-th relay cluster in the circular area holding the m' th relay cluster _m' The strength of social relationships between users of the candidate relays,

indicating that the user holding the source device and the n-th relay cluster in the circular area holding the m' th relay cluster _m' The total number of calls between users of the candidate relay,

indicating that the user holding the source device and the n-th relay cluster in the circular area holding the m' th relay cluster _m' Call aggregation between users of a candidate relayDuration, fre _S Representing the total number of calls, dur, made by a user having an active device _S Representing the total duration of all calls made by the user holding the source device,

indicating the user holding the target device and the n-th relay cluster in the circular area holding the m' th relay cluster _m' The strength of social relationships between users of the candidate relays,

indicating the user holding the target device and the n-th relay cluster in the circle area holding the m' th relay cluster _m' Total duration of call, fre, between users of candidate relays _D Indicating the total number of calls, dur, made by the user holding the destination device _D Indicating the total duration of all calls made by the user holding the destination device.

fre _D 、dur _D In practical applications, the data base stations may count data for a period of time, such as the last 30 days of calls.

In real life, two closely related people are frequently connected through a telephone or social software, and the duration of each connection is long; while two distantly related people are generally in less contact and the duration of contact is relatively short. On the other hand, the number and the duration of the contact between the users holding the device through the telephone or the social software are used for quantifying the strength of the social relationship between the users holding the device, considering that the base station can obtain call records of the users from the database and conveniently record the data such as the number, the duration and the like when the users are connected through the social software. According to the study in LI H X, WU C, LI Z P, et al, stochastic optimal multi-rate multicasts in social networks [ C ]// 2012Procedents IEEE INFOCOM. March 25-30,2012, orlando, FL, USA, IEEE Press,2012, 172-180. (stochastic optimal Multi-Rate multicast [ C ]//2012IEEE International computer conference report records in social selfish Wireless networks), the social relationship between the vast majority of users is weak, and only a few users have a strong social relationship with other users, similar to pareto distribution. The strength of the social relationship between users is modeled by a pareto distribution, and the transmission power of relays is specified to be related to the strength of the social relationship between the users and the source device and the destination device.

And 4, step 4: the method comprises the steps that a base station determines cellular equipment corresponding to each hop of multiplexed frequency spectrum for multi-hop D2D communication between source equipment and target equipment, determines M cellular equipment in total and multiplexes uplink frequency spectrum of the cellular equipment; and then, a set formed by the determined frequency spectrums of the M cellular devices according to the sequence of each hop is recorded as F.

In order to improve the spectrum utilization rate, the invention provides that the D2D equipment realizes communication by multiplexing the frequency spectrum of the cellular equipment. In order to avoid mutual interference between multi-hop links and self-interference caused by a full duplex mode, each hop of the multi-hop D2D communication multiplexes frequency spectrums of different cellular devices, i.e. the relay operates in a frequency division duplex mode. In addition, D2D communication multiplexes the uplink spectrum of cellular devices because: on one hand, when multiplexing the downlink frequency spectrum, the cellular device receives an interference signal, when multiplexing the uplink frequency spectrum, the base station receives the interference signal, and the interference processing capability of the base station is generally stronger than that of the cellular device; on the other hand, the uplink spectrum is typically underutilized compared to the downlink spectrum. In addition, since each hop of the multi-hop D2D communication multiplexes the frequency spectrum of different cellular devices, although all relays between the source device and the destination device operate in the frequency division duplex mode, the channel interference situation of each hop can be analyzed separately.

FIG. 3 is a multi-hop D2D channelInterference diagram of the mth hop of the signal, TX in FIG. 3 _m And RX _m Transmitting and receiving devices corresponding to the m-th hop of a multi-hop D2D communication, C _m The method comprises the steps that cellular equipment corresponding to a frequency spectrum multiplexed by the mth hop of multi-hop D2D communication is provided, BS is a base station, and M is larger than or equal to 1 and smaller than or equal to M.

To ensure proper communication of the cellular device, the base station slave C _m To the signal-to-interference-and-noise ratio of the received signal

Need to reach a certain threshold value th _m Namely:

wherein the content of the first and second substances,

is represented by C _m Sets the cellular device C corresponding to the frequency spectrum multiplexed by the 1 st hop of the multi-hop D2D communication ₁ Cellular device C corresponding to spectrum multiplexed to Mth hop of multi-hop D2D communication _M Are all the same in terms of the transmitted power,

express TX _m The transmission power of the antenna is set to be,

is represented by C _m The distance to the base station(s),

is represented by C _m The channel gain with the base station is,

express TX _m The distance to the base station(s),

express TX _m Channel gain with base station, N ₀ Representing the power of background white Gaussian noise, alpha representing the path loss exponent, th _m Indicating that the base station can correctly decode C _m The minimum signal to interference plus noise ratio required for the transmitted signal.

By

Can obtain

Then taking out

From

As can be seen in (a) to (b),

followed by

Is increased by the decrease in the number of the terminal,

ensure that

Is established, i.e. the base station is from C _m To the signal-to-interference-and-noise ratio of the received signal

Must reach a certain threshold value th _m 。

RX _m From TX _m To the signal-to-interference-and-noise ratio of the received signal

Is composed of

Wherein the content of the first and second substances,

to representTX _m And RX _m In between the distance between the first and second electrodes,

represents TX _m And RX _m The gain of the channel in between is increased,

is represented by C _m And RX _m The distance between the two or more of the two or more,

is represented by C _m And RX _m The channel gain between. From

As can be seen in (a) to (b),

followed by

And

is increased. Throughput and of mth hop of multi-hop D2D communication according to Shannon's formula

Direct correlation, to improve the throughput of the hop, can be increased

(i.e., decrease)

) Or increase in

To be implemented. In addition, consider TX _m Distance from base station

When the distance is too close, it will cause serious interference to base station, so that said invention sets a base station position as centre of circle and radius as r _b The circular area of (a) is defined as a guard area boundary, and D2D communication is not permitted within the guard area boundary.

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

step 4_1: for the mth hop for 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 marked as TX _m And RX _m (ii) a M is greater than or equal to 1 and less than or equal to M, when M =1, the transmitting device and the receiving device of the 1 st hop correspond to the optimal relay determined in the circular area of the source device and the 1 st relay cluster, and when M = M, the transmitting device and the receiving device of the M-th hop correspond to the optimal relay and the destination device determined in the circular area of the M-1 st relay cluster.

Step 4_2: as shown in fig. 4, in RX when M ≠ M _m Making a straight line segment between the center of the circular area of the relay cluster and the position of the base station, extending the straight line segment to the base station side, and when M = M, at RX _m Namely, a straight line segment is made between the position of the target equipment and the position of the base station and is extended to the base station side; then, a point on the extension line is taken as the center of a circle and the radius is taken as the radius

Making a circular area internally tangent to the boundary of the protection area as a cellular equipment selection area, wherein at least one cellular equipment is in the cellular equipment selection area; wherein r represents the radius of the circular area of the relay cluster, the boundary of the protection area takes the position of the base station as the center of a circle and the radius is r _b A circular area of (a), protection area boundaries within which no D2D communication is allowed, r is set reasonably _b The numerical value of (2D) can avoid serious interference of D2D equipment to the base station and reduce

Increase of

By

It can be known that

Will increase, i.e. the throughput of the m-th hop of the multi-hop D2D communication will increase, r _b Has a value range of r _b ∈[50m,150m]In this embodiment r _b The value is 100m.

In FIG. 4, TX _m And RX _m Transmitting and receiving devices corresponding to the m-th hop of a multi-hop D2D communication, C _m And the BS is a base station for the cellular equipment corresponding to the frequency spectrum multiplexed by the mth hop of the multi-hop D2D communication.

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

And 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, and the position of the source device, the position of the destination device, the position of each candidate relay in each relay cluster circular area, and P, F to the destination device.

Step 6: the destination device sends all the data received from the base station to each candidate relay in the circular area of the (M-1) th relay cluster, and sets the signal receiving frequency of the destination device to be f _M ，f _M Is equal to the channel frequency of the cellular device corresponding to the spectrum multiplexed by the mth hop for multi-hop D2D communication between the source device and the destination device.

And 7: calculating the maximum transmission power of each candidate relay in the circular area of the M-1 relay cluster under the condition of considering interference; then all the candidate relays in the circular area of the M-1 relay cluster are consideredThe maximum transmitting power under the interference condition forms a set according to the sequence number of the candidate relays and is marked as P' _M-1 (ii) a Re-comparison of P _M-1 And P' _M-1 The transmitting power of the same candidate relay under the condition of considering the social relation and the maximum transmitting power under the condition of considering the interference are compared to obtain the minimum value which is used as the transmitting power of the corresponding candidate relay; then, the transmitting powers of all the candidate relays in the circular area of the M-1 th relay cluster form a set according to the sequence of the candidate relays, and the set is marked as P ^* _M-1 (ii) a Wherein, P _M-1 And the set is formed by the transmission power of all candidate relays in the circular area of the M-1 th relay cluster according to the sequence of the sequence numbers of the candidate relays under the condition of considering the social relationship.

In this embodiment, in step 7, the nth relay cluster within the circular area of the M-1 st relay cluster is divided into _M-1 Maximum transmit power of a candidate relay under interference consideration is recorded as

Wherein n is more than or equal to 1 _M-1 ≤N _M-1 ，N _M-1 Indicates the number of candidate relays within the circular area of the (M-1) th relay cluster, N _M-1 ≥2，

Cellular device C corresponding to spectrum of Mth hop multiplexing representing multi-hop D2D communication between source device and destination device _M The transmission power of the antenna is set to be,

is represented by C _M The channel gain with the base station(s),

represents the n-th relay cluster within the circular area of the M-1 th relay cluster _M-1 A candidate relay andthe distance between the base stations is such that,

And 8: setting each candidate relay in the circular area of the M-1 relay cluster to obtain the channel gain between the candidate relay and the destination equipment while receiving all data from the destination equipment; then according to P ^* _M-1 And calculating the received signal power of the target equipment when each candidate relay in the M-1 relay cluster circular area sends a signal to the target equipment.

In the present embodiment, in step 8, the nth relay cluster within the circular area of the M-1 st relay cluster is divided into _M-1 The received signal power of the destination device when the candidate relay sends a signal to the destination device is recorded as

And step 9: starting a timer with the termination time inversely proportional to the received signal power from the candidate relay in the circular area of the M-1 th relay cluster; then, the candidate relay corresponding to the timer which ends first is determined as the best relay in the circular area of the (M-1) th relay cluster, namely the best relay of the M-th hop, and is marked as R _M-1 ，R _M-1 Broadcasting a message which is selected as the best relay to other candidate relays in the M-1 relay cluster circular area, and closing a timer after the other candidate relays in the M-1 relay cluster circular area receive the broadcast message; the greater the received signal power, the greater the throughput of the hop and the smaller the expiration time of the timer.

Step 10: r _M-1 All data received from the destination equipment is sent to each candidate relay in the circular area of the M-2 relay cluster, and the signal sending frequency of the relay cluster is set to be f _M Setting the signal receiving frequency of itself as f _M-1 ，f _M-1 Is equal to the channel frequency of the cellular device corresponding to the spectrum multiplexed by the M-1 hop of the multi-hop D2D communication between the source device and the destination device.

Step 11: the optimal relay of the M-1 hop is determined in the same way according to the process from step 7 to step 10 and is marked as R _M-2 ，R _M-2 Will be selected from R _M-1 All the received data are sent to each candidate relay in the circular area of the M-3 relay cluster, and R is determined _M-2 Has a signal transmission frequency of f _M-1 ，R _M-2 Has a signal receiving frequency of f _M-2 ，f _M-2 Is equal to the channel frequency of the cellular device corresponding to the spectrum of the M-2 hop multiplexing for the multi-hop D2D communication between the source device and the destination device.

Step 12: and (4) according to the process of the step 11, and the like until the optimal relay of the 2 nd hop is determined and is marked as R ₁ ，R ₁ Will be selected from R ₂ Sends all the received data to the source device, and determines R ₁ Has a signal transmission frequency of f ₂ ，R ₁ Has a signal receiving frequency of f ₁ ，f ₁ Is equal to the channel frequency of the cellular device corresponding to the spectrum of the 1 st hop reuse for the multi-hop D2D communication between the source device and the destination device.

Step 13: according to the process of calculating the maximum transmission power of each candidate relay in the circular area of the (M-1) th relay cluster under the condition of considering the interference in the step 7, the maximum transmission power of the source equipment under the condition of considering the interference is calculated in the same way, and the cellular equipment C corresponding to the frequency spectrum multiplexed by the 1 st hop of the multi-hop D2D communication is avoided ₁ Causes too much interference and sets the signal transmission frequency of the source device to f ₁ (ii) a The source device then begins multihop D2D communication with the destination device.

In this embodiment, in step 13, the maximum transmission power of the source device under the condition of considering the interference is recorded as P' _S ，

Wherein, P _C1 Cellular device C corresponding to frequency spectrum of 1 st hop multiplexing representing multi-hop D2D communication between source device and destination device ₁ The transmission power of (a) is set,

is represented by C ₁ The distance to the base station(s),

is represented by C ₁ The channel gain with the base station is,

indicating the distance between the source device and the base station,

indicating the channel gain, th, between the source device and the base station ₁ Indicating that the base station can correctly decode C ₁ The minimum signal to interference plus noise ratio required for the transmitted signal.

In the multi-hop D2D communication, in each hop, not only the cellular device of the multiplexed spectrum is selected from the multiple cellular devices, but also the best relay is selected from the multiple candidate relays in the circular area of each relay cluster, the number of the related devices is too large, and if the relay selection process is completely completed by the base station in a centralized manner, excessive load and a large amount of signaling overhead are inevitably brought to the base station. Therefore, the invention provides an optimal relay selection method which can be executed in a semi-centralized manner, a base station only needs to complete the collection of information such as channel parameters and node positions and the like at the beginning of multi-hop D2D communication and a small amount of data processing, and the optimal relay selection is automatically completed by equipment participating in the multi-hop D2D communication.

After the multi-hop D2D communication link is determined according to the method, the signal-to-interference-and-noise ratio of each hop is also determined, so that the throughput of each hop can be calculated by using a Shannon formula. Assuming that the spectral bandwidth of the cellular device is denoted by B, the throughput of the 1 st hop is Ω ₁ ，

Throughput of the middle mth hop is Ω _m ，

Here M =2,3, …, M-1; throughput of last hop is Ω _M ，

Wherein, P _S Which is indicative of the transmit power of the source device,

indicating the best relay R for the source device to hop 2 ₁ The distance between the two or more of the two or more,

indicating the best relay R for the source device to hop 2 ₁ The gain of the channel in between (a) and (b),

cellular device C corresponding to spectrum representing 1 st hop reuse ₁ The transmission power of the antenna is set to be,

is represented by C ₁ And R ₁ The distance between the two or more of the two or more,

is represented by C ₁ And R ₁ The gain of the channel in between is increased,

best relay R representing mth hop _m-1 The transmission power of the antenna is set to be,

represents R _m-1 Optimal relay R with m +1 hop _m The distance between the two or more of the two or more,

represents R _m-1 And R _m The gain of the channel in between is increased,

cellular device C corresponding to spectrum representing m-th hop reuse _m The transmission power of the antenna is set to be,

is represented by C _m And R _m In between the distance between the first and second electrodes,

is represented by C _m And R _m The gain of the channel in between is increased,

best relay R representing Mth hop _M-1 The transmission power of (a) is set,

represents R _M-1 With destination equipmentThe distance between the first and second electrodes,

represents R _M-1 The channel gain with the destination device is,

is represented by C _M The distance from the destination device to the destination device,

is represented by C _M Channel gain with the destination device.

Since all relays work in a full-duplex mode, the throughput of the whole multi-hop D2D communication link is determined by the throughput of the hop with the minimum throughput, that is, the throughput of the multi-hop D2D communication is Ω, Ω = min (Ω = min) ₁ ,…,Ω _m ,…,Ω _M ) (ii) a Wherein min () is a minimum function.

To further illustrate the feasibility and effectiveness of the method of the present invention, simulation experiments were performed on the method of the present invention.

A circular single-cell cellular scene with the radius of 500 meters and the base station equipped with an omnidirectional antenna as the center is simulated, and cellular equipment and idle equipment are randomly and uniformly distributed in a cell. The detailed simulation parameters are shown in table 1.

TABLE 1 simulation parameters and values thereof

The SA (Social Aware) algorithm in the simulation is a modification algorithm of the method of the present invention (the transmission power of idle devices considers both interference to cellular devices and Social relations), the SUA (Social Un-Aware) algorithm is a modification algorithm of the method of the present invention under the condition that only interference to cellular devices is considered and no Social relations are considered, and the comparison methods are MLS method (noddopatiti H K, BHATNAGAR M R, PRAKRIYA s.performance Analysis of client-Based Multi-Hop outstanding crusing Max-Link-Selection Protocol [ J ] IEEE Transactions on Cognitive Communications and networks, 2017,4 (1): 15-29) (the ad hoc network system model Using the maximum Link Selection Protocol [ J ]/IEEE standards for Cognitive Communications and networks ], and the methods of ad-hoc networks (ad 2016, 2016) for wireless network Selection systems, peer-Link Selection systems, ad-coherent ad 2016, ad-coherent ad-Link Selection methods, ad-coherent systems, ad-Link Selection methods [ J ] and network (IEEE for Cognitive networks).

Fig. 5 shows a comparison of throughput performance of the SA method, SUA method, MLS method, HTPRS method in case of a distance change between the source device (S) and the destination device (D). As can be seen from fig. 5, the throughput of all methods decreases with increasing distance, because with increasing distance, the increased hops only result in the minimum value of the throughput of each hop being unchanged or decreased, and therefore the throughput of the whole link decreases accordingly. The SUA method has higher throughput than the MLS method and the HTPRS method when the distances are equal, because the SUA method selects the relay, and the relay with better performance can be selected because the index of the relay selected by the SUA method is directly related to the signal to interference plus noise ratio of each hop. The SA method is inferior to the SUA method in throughput when the distances are equal, because the SA method imposes an additional social relationship constraint on the transmission power of all idle devices, so the transmission power of the relay selected by the SA method is necessarily smaller than that of the relay selected by the SUA method.

Fig. 6 shows a comparison of throughput performance of the SA method, SUA method, MLS method, HTPRS method in the case where the number of candidate relays within the circular area of each relay cluster varies. As can be seen from fig. 6, the throughput of the three methods, i.e., SUA, SA and MLS, increases with the number of candidate relays, because the three methods have a higher probability of selecting a candidate relay with better performance as the best relay, and the HTPRS method has the advantage of being more random when selecting a relay and cannot utilize more idle devices. The throughput of the SUA method is greater than that of the MLS method and the HTPRS method in the case where the number of candidate relays is the same, whereas the throughput of the SA method is inferior to that of the SUA method.

Fig. 7 shows a comparison of energy efficiency performance of SA method, SUA method, MLS method, HTPRS method with varying distance between source device (S) and destination device (D), energy efficiency being defined as the ratio of link throughput to the sum of the actual transmit power of all devices participating in a multi-hop D2D communication. As can be seen from fig. 7, the energy efficiency of all methods decreases with increasing distance, because the number of relays participating in D2D communication increases with increasing distance, which results in an increase in the sum of the transmit powers, while the throughput of all methods decreases with increasing distance, and thus the energy efficiency decreases. The energy efficiency of the SUA method is superior to the MLS method and the HTPRS method in the case of equal distances, while the energy efficiency of the SA method is far superior to the other three methods. This is because the SA method reduces the transmit power of the relay selected per hop by imposing additional social relationship constraints on all candidate relays, and thus the sum of the transmit powers is greatly reduced, although the SA method has a lower throughput than the SUA method, and its energy efficiency far exceeds the other three methods.

Fig. 8 shows energy efficiency performance comparison of the SA method, SUA method, MLS method, and HTPRS method in the case where the number of candidate relays in each relay cluster circular area varies. As can be seen from fig. 8, the energy efficiencies of the three methods, SUA, SA and MLS, all increase with the number of candidate relays, and the energy efficiencies of the HTPRS methods all remain substantially unchanged with the number of candidate relays. The SUA method is superior in energy efficiency to the MLS method and the HTPRS method in the case where the number of candidate relays is the same, while the SA method is far superior in energy efficiency to the other three methods.

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).

TABLE 2 comparison of SA and SUA Process Performance

As can be seen from table 2, the performance of the SA and SUA methods greatly differs in terms of throughput and energy efficiency, and the SA method has a great advantage over the SUA method in terms of energy efficiency, so the role of social domain information cannot be ignored in the research of the D2D relay selection algorithm.

Claims

1. A relay selection method in multi-hop D2D communication introducing social domain information is characterized in that the method is applied to a cellular network scene, all channels are set to be Rayleigh fading channels, free space propagation path loss is considered at the same time, a source device and a target device are set to exist, the positions of the source device and the target device are fixed, the positions of the base station and the known target device of the source device are set, the hop count of the multi-hop D2D communication between the source device and the target device is set to be M hops, M is more than or equal to 3, and the relay between the source device and the target device is set to work in a frequency division duplex mode; the method comprises the following steps:

step 1: the method comprises the steps that source equipment sends a D2D multi-hop communication request to a base station; then the base station determines the position of the source equipment and the position of the destination equipment;

and step 3: calculating the transmitting power of each candidate relay in each relay cluster circular area under the condition of considering the social relation; then, the transmitting power of all candidate relays in each relay cluster circular area under the condition of considering the social relationship forms a set according to the sequence of the sequence numbers of the candidate relays, and a set formed by the transmitting power of all candidate relays in the mth relay cluster circular area under the condition of considering the social relationship according to the sequence of the sequence numbers of the candidate relays is marked as P _m' (ii) a Then, the transmit power set formed by the transmit powers of all the candidate relays between the source device and the destination device under the condition of considering the social relationship is recorded as P, and P = P ₁ ∪P ₂ ∪…∪P _m' ∪…∪P _M-1 (ii) a Wherein M' is not less than 1 and not more than M-1,P ₁ Set of transmit powers, P, representing all candidate relays within the 1 st relay cluster circle area, considering social relationships ₂ Set of transmit powers, P, representing all candidate relays within the 2 nd relay cluster circle area, considering social relationships _M-1 Representing a set formed by the emission power of all candidate relays in the circular area of the M-1 th relay cluster under the condition of considering the social relationship, wherein the symbol 'U' is a combined operation symbol of the set;

step 6: the destination device transmits all data received from the base station to the M-1 th base stationSetting the signal receiving frequency of each candidate relay in the circular area of the relay cluster as f _M ，f _M The value of (a) is equal to the channel frequency of the cellular device corresponding to the frequency spectrum of the mth hop multiplexing for the multi-hop D2D communication between the source device and the destination device;

and 7: calculating the maximum transmission power of each candidate relay in the circular area of the M-1 relay cluster under the condition of considering interference; then, the maximum transmitting power of all candidate relays in the circular area of the M-1 relay cluster under the condition of considering interference is formed into a set according to the sequence number of the candidate relays and is marked as P' _M-1 (ii) a Re-comparison of P _M-1 And P' _M-1 The transmitting power of the same candidate relay under the condition of considering the social relation and the maximum transmitting power under the condition of considering the interference are compared to obtain the minimum value, and the minimum value is used as the transmitting power of the corresponding candidate relay; then, the transmitting powers of all the candidate relays in the circular area of the M-1 th relay cluster form a set according to the sequence of the candidate relays, and the set is marked as P ^* _M-1 (ii) a Wherein, P _M-1 Representing a set formed by the transmitting power of all candidate relays in the M-1 th relay cluster circular area according to the sequence of the sequence numbers of the candidate relays under the condition of considering the social relationship;

and 8: setting each candidate relay in the circular area of the M-1 relay cluster to obtain the channel gain between the candidate relay and the destination equipment while receiving all data from the destination equipment; then according to P ^* _M-1 And the channel gain between each candidate relay in the M-1 relay cluster circular area and the target equipment, and calculating the received signal power of the target equipment when each candidate relay in the M-1 relay cluster circular area sends a signal to the target equipment;

step 10: r _M-1 All data received from the destination equipment is sent to each candidate relay in the circular area of the M-2 relay cluster, and the signal sending frequency of the relay cluster is set to be f _M Let the signal receiving frequency of the receiver be f _M-1 ，f _M-1 The value of (1) is equal to the channel frequency of the cellular device corresponding to the frequency spectrum of the M-1 hop multiplexing for the multi-hop D2D communication between the source device and the destination device;

step 11: the optimal relay of the M-1 hop is determined in the same way according to the process from the step 7 to the step 10 and is recorded as R _M-2 ，R _M-2 Will be selected from R _M-1 All the received data are sent to each candidate relay in the circular area of the M-3 relay cluster, and R is determined _M-2 Has a signal transmission frequency of f _M-1 ，R _M-2 Has a signal receiving frequency of f _M-2 ，f _M-2 The value of (2) is equal to the channel frequency of the cellular device corresponding to the frequency spectrum of the M-2 hop multiplexing for the multi-hop D2D communication between the source device and the destination device;

step 12: according to the process of step 11, repeating the steps until the optimal relay of the 2 nd hop is determined and marked as R ₁ ，R ₁ Will be selected from R ₂ Sends all the received data to the source device, and determines R ₁ Has a signal transmission frequency of f ₂ ，R ₁ Has a signal receiving frequency of f ₁ ，f ₁ The value of (1) is equal to the channel frequency of the cellular device corresponding to the frequency spectrum of the 1 st hop multiplexing for the multi-hop D2D communication between the source device and the destination device;

step 13: calculating the maximum transmitting power of the source device under the condition of considering the interference, and setting the signal transmitting frequency of the source device as f ₁ (ii) a The source device then begins multihop D2D communication with the destination device.

2. The method for selecting a relay in multi-hop D2D communication introducing social domain information as claimed in claim 1, wherein in step 2, the method for determining candidate relays based on relay clusters comprises:

3. The method for relay selection in multi-hop D2D communication introducing social domain information as claimed in claim 1 or 2, wherein in step 3, the nth relay cluster in the circular area of the mth relay cluster is selected _m' The transmission power of the candidate relay under the condition of considering the social relation is recorded as

1≤n _m' ≤N _m' ，N _m' Indicates the number of candidate relays within the m' th relay cluster circular area, N _m' Max () denotes a maximum function, P _max Indicating the maximum transmit power for which the idle device is rated,

indicating that the user holding the source device and the n-th relay cluster in the circular area holding the m' -th relay cluster _m' Use of a candidate relayThe strength of the social relationship between the users,

indicating the user holding the target device and the n-th relay cluster in the circular area holding the m' th relay cluster _m' Total duration of call, fre, between users of a candidate relay _D Indicating the total number of calls, dur, made by the user holding the destination device _D To representThe total duration of all calls made by the user holding the destination device.

4. The method according to claim 3, wherein the specific process of step 4 is as follows:

step 4_1: for the mth hop for 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 marked as TX _m And RX _m (ii) a M is greater than or equal to 1 and less than or equal to M, when M =1, the transmitting device and the receiving device of the 1 st hop correspond to the optimal relay determined in the circular area of the source device and the 1 st relay cluster, and when M = M, the transmitting device and the receiving device of the M-th hop correspond to the optimal relay and the destination device determined in the circular area of the M-1 st relay cluster;

Making a circular area internally tangent to the boundary of the protection area as a cellular equipment selection area, wherein at least one cellular equipment is in the cellular equipment selection area; wherein r represents the radius of the circular area of the relay cluster, the boundary of the protection area takes the position of the base station as the center of a circle and the radius is r _b A circular area of (a), within the boundary of the protection area, no D2D communication is allowed, r _b ∈[50m,150m]；

5. The method of claim 4, wherein the social interaction is introducedThe relay selection method in the multi-hop D2D communication of the domain information is characterized in that in the step 7, the nth relay cluster in the circular area of the M-1 st relay cluster is selected _M-1 The maximum transmission power of the candidate relay under the condition of considering the interference is recorded as

is represented by C _M The distance to the base station(s),

is represented by C _M The channel gain with the base station is,

represents the n-th relay cluster within the circular area of the M-1 th relay cluster _M-1 Channel gain, N, between candidate relays and base station ₀ Represents the power of the background Gaussian white noise, alpha represents the pathloss exponent, th _M Indicating that the base station can correctly decode C _M The minimum signal to interference plus noise ratio required for the transmitted signal.

6. The method as claimed in claim 5, wherein in step 8, the nth relay cluster in the circular area of the M-1 st relay cluster is selected _M-1 The received signal power of the destination device when the candidate relay sends a signal to the destination device is recorded as

7. The method of claim 5, wherein in step 13, the maximum transmission power of the source device under interference consideration is denoted as P' _S ，

Wherein the content of the first and second substances,

is represented by C ₁ The distance to the base station(s),

is represented by C ₁ The channel gain with the base station is,

indicating the distance between the source device and the base station,

indicating the channel gain, th, between the source device and the base station ₁ Indicating that the base station can correctly decode C ₁ The minimum signal to interference and noise ratio required for the transmitted signal.