CN116056181A - Relay node selection method based on D2D communication - Google Patents

Relay node selection method based on D2D communication Download PDF

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CN116056181A
CN116056181A CN202310024193.3A CN202310024193A CN116056181A CN 116056181 A CN116056181 A CN 116056181A CN 202310024193 A CN202310024193 A CN 202310024193A CN 116056181 A CN116056181 A CN 116056181A
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relay node
communication
node
relay
signal
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CN116056181B (en
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何小利
曾震
尹晓冬
李宏伟
易海岷
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Sichuan University of Science and Engineering
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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W40/00Communication routing or communication path finding
    • H04W40/02Communication route or path selection, e.g. power-based or shortest path routing
    • H04W40/22Communication route or path selection, e.g. power-based or shortest path routing using selective relaying for reaching a BTS [Base Transceiver Station] or an access point
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W40/00Communication routing or communication path finding
    • H04W40/02Communication route or path selection, e.g. power-based or shortest path routing
    • H04W40/04Communication route or path selection, e.g. power-based or shortest path routing based on wireless node resources
    • H04W40/08Communication route or path selection, e.g. power-based or shortest path routing based on wireless node resources based on transmission power
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W40/00Communication routing or communication path finding
    • H04W40/02Communication route or path selection, e.g. power-based or shortest path routing
    • H04W40/12Communication route or path selection, e.g. power-based or shortest path routing based on transmission quality or channel quality
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W40/00Communication routing or communication path finding
    • H04W40/24Connectivity information management, e.g. connectivity discovery or connectivity update
    • H04W40/246Connectivity information discovery
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02DCLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00Reducing energy consumption in communication networks
    • Y02D30/70Reducing energy consumption in communication networks in wireless communication networks

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Abstract

The invention discloses a relay node selection method based on D2D communication, which comprises the following steps: before formal communication, a base station firstly transmits a broadcast signal, a circular range with a cluster range being a center of a circle and a midpoint of two ends of a target node being a radius is determined based on constraint of a distance and a social relationship, after receiving broadcast test information of the base station, a relay node in the cluster range returns corresponding signal-to-noise ratio information, meanwhile, the relay node transmits the test signal to the target node, the target node returns corresponding signal-to-noise ratio information to the base station, and a relay node with the minimum signal-to-noise ratio is continuously removed according to a threshold value of the distance and the social relationship, and a plurality of better relay nodes are selected. The invention adopts the relay node selection method based on D2D communication, and combines MRC by using the maximum ratio between the link between the relay node and the destination node, thereby converting the problem into selecting the optimal signal-to-noise ratio between the source node and the relay node.

Description

Relay node selection method based on D2D communication
Technical Field
The invention relates to the technical field of wireless communication, in particular to a relay node selection method based on D2D communication.
Background
D2D (device-to-device) communication is a popular technology in the current environment that does not require signaling through a base station while having lower energy consumption than conventional cellular networks. However, how to select an appropriate relay to assist the D2D device in communication is an urgent problem to be solved. Qian Hongzhi introduces a social threshold, and based on a Q learning algorithm, proposes an optimal relay selection algorithm for maximizing the total rate of the D2D link, so as to improve the system rate. Pan Xin and the like propose a mixed scheme based on distance and social relations, so that the communication rate of equipment is successfully improved. Ushik Shrestha Khwakhali et al propose a social relationship based relay selection scheme to improve the average throughput of the network by selecting a relay that is socially connected to the source and located near the midpoint of the source and destination. Zhang Mengyuan and the like propose an optimal social perception relay selection strategy based on an optimal stopping theory, so that the throughput of the system is improved. Zhang Zufang et al propose a self-adaptive relay selection method using a social network, and build a model based on a physical domain and a social domain, so as to improve the probability of successful relay selection, reduce the burden of a cellular network, and improve the system performance.
In the design of the prior relay node selection algorithm, the problems are mainly solved by methods such as a game algorithm, a traditional algorithm and the like, but the methods are poor in universality and inconsistent in performance under different scenes.
They often have the following problems:
1. failing to accommodate as many relay nodes as possible;
2. the link with the minimum signal-to-noise ratio is generally selected from the source node to the relay node and from the relay node to the destination node, so that resource waste is caused;
3. the algorithm time complexity is high.
Based on the above analysis, existing studies mostly solve the resource allocation and energy efficiency problems from the physical layer or the social layer. The invention provides a relay selection scheme combining a social layer and a physical layer, so that the energy efficiency and throughput of a remote D2D user are improved.
Disclosure of Invention
The invention aims to provide a relay node selection method based on D2D communication, which solves the problems in the background technology.
In order to achieve the above object, the present invention provides a relay node selection method based on D2D communication, the method comprising: before formal communication, a base station firstly transmits a broadcast signal, a circular range with a cluster range being a center of a circle and a midpoint of two ends of a target node being a radius is determined based on constraint of a distance and a social relationship, after receiving broadcast test information of the base station, a relay node in the cluster range returns corresponding signal-to-noise ratio information, meanwhile, the relay node transmits the test signal to the target node, the target node returns corresponding signal-to-noise ratio information to the base station, and a relay node with the minimum signal-to-noise ratio is continuously removed according to a threshold value of the distance and the social relationship, and a plurality of better relay nodes are selected.
Preferably, assuming that there is no interference between nodes and between a node and D2D users within the cluster, only signal interference from the base station is received, and a set of channel resources can only be multiplexed by a pair of D2D users;
a set of D2D pairs, d= { D, is denoted by D 1 ,D 2 ,D 3 ,...,D n Di represents the ith D2D pair, P s Representing the maximum transmit power of a D2D user, P r Representing the maximum transmit power of the relay node, N 0 Representing additive white gaussian noise, eta i,j Representing trust value between two devices g i,j Representing channel gains between the devices i and j, wherein gi and ri represent channel gains between the device i and an ri-th relay node in the cluster range, and signal to noise ratios from a source node to the relay node and from the relay node to a destination node are respectively represented as
Figure BDA0004043873290000021
Order the
Figure BDA0004043873290000031
If the number of relay nodes in the cluster is not less than 2, the signal to noise ratios from the source node to the cluster and from the cluster to the destination node are respectively expressed as
γ s,r =min(γ s,ri ),γ r,d =min(γ ri,d )
Preferably, the whole communication process is divided into two phases, the first phase is from a source node to a relay node in the cluster, the second phase is from the relay node to a destination node, the spectrum resource is divided into two equal parts, one phase uses one part, and the total signal to noise ratio in the cluster is according to the principle of decoding and forwarding
γ s,r,d =min{γ s,rr,d }
The instantaneous data rate of the D2D link is expressed as
Figure BDA0004043873290000032
W represents the spectrum bandwidth used by the D2D link, while 1/2 represents half of the spectrum resources used by the communication link;
EE is defined as the ratio of data rate to power, P is used t Representing the total power in the entire link, the following equation is derived
Figure BDA0004043873290000033
Assuming that the circuit power of different users is the same and expressed, the total power of the D2D link may be expressed as
Figure BDA0004043873290000034
P cir Representing circuit power, 1/2 represents that the power consumption of two phases in the D2D link communication process are independent and do not occur simultaneously, and n represents the number of relay nodes in the cluster.
Preferably, when the relay nodes in the cluster range do not meet the requirements, a direct communication technology is adopted to perform data transmission, and the signal-to-noise ratio, the instantaneous data rate and the power loss from the destination node to the source node are respectively
Figure BDA0004043873290000041
R s,d =Wlog 2 (1+γ s,d )
P t1 =P s +P cir
Deriving EE for direct communication from instantaneous data rate and power loss
Figure BDA0004043873290000042
Preferably, the EE-based optimal power optimization model is denoted by P1:
P1:
Figure BDA0004043873290000049
Figure BDA0004043873290000043
Figure BDA0004043873290000044
η i,j ∈{0,1},i∈D,j∈n
γ s,r,d ≥γ d ,
α∈{0,1}
Figure BDA0004043873290000045
and->
Figure BDA0004043873290000046
Respectively representing the maximum transmitting power of the source node and the maximum transmitting power of the relay node, gamma d Representing the minimum signal-to-noise ratio requirement of the link for communication, wherein alpha represents the working coefficient of the system, and the direct communication and the relay communication are independent and do not simultaneously;
for the P1 problem, two cases are classified, and when α=1, only relay communication is performed to obtain the optimal power
Figure BDA0004043873290000047
And
Figure BDA0004043873290000048
two assumptions are made, assuming the following:
suppose 1: when gamma is s,r,d =min{γ s,rr,d }=γ s,r I.e. phi s,r ≤Φ r,d Then the objective function in P1 is rewritten as
Figure BDA0004043873290000051
As can be seen from the current assumption, when P s Φ s,r ≤P r Φ r,d ,P r Maximum value of (2)
Figure BDA0004043873290000052
Suppose 2: when gamma is s,r,d =min{γ s,rr,d }=γ r,d I.e. phi r,d ≤Φ s,r Then the objective function in P1 is rewritten as
Figure BDA0004043873290000053
/>
From the currentIt is assumed that when P r Φ r,d ≤P s Φ s,r ,P r Maximum value of (2)
Figure BDA0004043873290000054
From the above two assumptions, it can be seen if and only if gamma s,r =γ r,d At this time, EE takes its maximum value.
Preferably, use is made of
Figure BDA0004043873290000055
Replacing the objective function in the P1 problem to obtain the optimal power +.>
Figure BDA0004043873290000056
And->
Figure BDA0004043873290000057
Problem P1 is equivalently rewritten as problem P2:
Figure BDA0004043873290000058
Figure BDA0004043873290000059
Figure BDA00040438732900000510
η i,j ∈{0,1},i∈D,j∈n
γ s,r,d ≥γ d ,
P s Φ s,r ≤P r Φ r,d
preferably, problem P2 is converted to problem P3 according to a theoretical method,
where u=wleg 2 (1+P s Φ s,r )-q(P s +nP r +2(n+1)P cir )
Figure BDA0004043873290000061
Figure BDA0004043873290000062
γ s,r,d ≥γ d ,
EE takes the maximum value if and only if u=0, where q is a temporary optimal solution of EE maximum;
preferably, U is proved to be a concave function, and P is calculated for the function U respectively s And P r The first partial derivative of (2) gives the following formula
Figure BDA0004043873290000063
The first partial derivative is again derived to obtain the U's Heisen matrix as follows
Figure BDA0004043873290000064
The first-order cis-form main component of the Heisen matrix is complex, the second-order cis-form main component is zero, the Heisen matrix is a negative semi-definite matrix, and the function U is a concave function, so that the maximum value can be obtained;
after proving, use
Figure BDA0004043873290000065
P in substitution problem P3 r Then find the relation P for the function U s Is derived from the partial derivative of (2) to obtain the following formula
Figure BDA0004043873290000066
Wherein [ x ]] + Represents max {0, x }, in combination with constraint
Figure BDA0004043873290000071
Will be
Figure BDA0004043873290000072
Bringing in to an optimal transmit power of
Figure BDA0004043873290000073
Preferably, P s Iteration is continued until u=0, and P is solved according to the above derivation r Is the optimal solution of (a); when alpha=0, only direct communication is performed to make
Figure BDA0004043873290000074
Will phi s,d Substituted into
Figure BDA0004043873290000075
Is obtained by
Figure BDA0004043873290000076
Problem P1 is converted into problem P4 according to the theoretical method:
Figure BDA0004043873290000077
wherein z=wleg 2 (1+P s Φ s,d )-q(P s +P cir )
Figure BDA0004043873290000078
Figure BDA0004043873290000079
γ s,r,d ≥γ d ,
Regarding Z, regarding P s First and second partial derivatives of (2) to obtain
Figure BDA00040438732900000710
/>
Since the second derivative of Z is less than zero, Z is proved to be a concave function when
Figure BDA00040438732900000711
When Z is at a maximum value,
Figure BDA0004043873290000081
combining constraints
Figure BDA0004043873290000082
Obtaining the product
Figure BDA0004043873290000083
And finally obtaining the optimal transmitting power required by the source node in the direct communication scene.
Therefore, the relay node selection method based on the D2D communication has the following beneficial effects:
1. the method provided by the invention is different from the traditional relay scheme, and a circular cluster area is constructed between the midpoints of the transmitting end and the receiving end, which is called a social-aware cellular cluster-assisted D2D communication network model, so that the problem of insufficient coverage of relay nodes in the traditional scheme is solved.
2. The method provided by the invention adopts a downlink to carry out D2D communication, a base station sends a broadcast signal, the signal-to-noise ratio information of relay nodes in a cluster is collected, and a plurality of better nodes far away from the base station are selected according to the threshold value of the distance and the social relationship; the MRC (maximum ratio combining) is used for the link between the relay node and the destination node, thereby converting the problem into selecting an optimal SNR (signal-to-noise ratio) between the source node and the relay node, and converting the conventional problem of selecting an optimal SNR between the source node and the relay node and between the relay node and the destination node into the problem of selecting an optimal SNR between the source node and the relay node.
3. An optimal power iterative algorithm based on social relation obtains optimal transmitting power through lower time complexity, and therefore optimal energy efficiency is calculated.
The technical scheme of the invention is further described in detail through the drawings and the embodiments.
Drawings
Fig. 1 is a schematic diagram of a relay node selection method based on D2D communication according to the present invention;
FIG. 2 is a schematic diagram of an optimal power iterative algorithm of the present invention;
fig. 3 is a schematic diagram of a trunking relay selection algorithm according to the present invention.
Detailed Description
The technical scheme of the invention is further described below through the attached drawings and the embodiments.
Unless defined otherwise, technical or scientific terms used herein should be given the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. The terms "first," "second," and the like, as used herein, do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The word "comprising" or "comprises", and the like, means that elements or items preceding the word are included in the element or item listed after the word and equivalents thereof, but does not exclude other elements or items. The terms "disposed," "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. "upper", "lower", "left", "right", etc. are used merely to indicate relative positional relationships, which may also be changed when the absolute position of the object to be described is changed.
Examples
Fig. 1 is a schematic diagram of a relay node selection method based on D2D communication according to the present invention; FIG. 2 is a schematic diagram of an optimal power iterative algorithm of the present invention; fig. 3 is a schematic diagram of a trunking relay selection algorithm according to the present invention.
As shown in the figure, the method for selecting a relay node based on D2D communication according to the present invention includes: before formal communication, the base station firstly transmits a broadcast signal, and determines a cluster range as a circular range with a center point of two ends of a source node and a destination node and a half of a distance as a radius based on constraint of the distance and a social relationship. After receiving the broadcast test information of the base station, the relay nodes in the cluster range return corresponding signal-to-noise ratio (SNR) information, meanwhile, the relay nodes send test signals to the target nodes, the target nodes return the corresponding signal-to-noise ratio (SNR) information to the base station, the relay nodes with the minimum signal-to-noise ratio are continuously removed according to the threshold value of the distance and the social relationship, and a plurality of better relay nodes are selected.
For ease of analysis, it is assumed that within the cluster of source and destination nodes, there is no interference between the nodes and D2D users, only signal interference from the base station. One set of channel resources can only be multiplexed by a pair of D2D users, so in this case, there is no interference between different D2D groups, and interference exists only within each D2D group user.
A set of D2D pairs, d= { D, is denoted by D 1 ,D 2 ,D 3 ,...,D n Di represents the ith D2D pair, P s Representing the maximum transmit power of a D2D user, P r Representing the maximum transmit power of the relay node, N 0 Representing additive white gaussian noise, eta i,j Representing trust value between two devices g i,j Representing channel gains between the devices i and j, wherein gi and ri represent channel gains between the device i and an ri-th relay node in the cluster range, and signal to noise ratios from a source node to the relay node and from the relay node to a destination node are respectively represented as
Figure BDA0004043873290000101
For convenience of description, let
Figure BDA0004043873290000102
If the number of relay nodes in the cluster is not less than 2, the signal to noise ratios from the source node to the cluster and from the cluster to the destination node are respectively expressed as
γ s,r =min(γ s,ri ),γ r,d =min(γ ri,d )
The relay protocol can be roughly classified into Amplification Forwarding (AF) and Decoding Forwarding (DF) according to a signal processing procedure at the relay node. The whole communication process is divided into two phases, the first phase is from the source node to the relay node in the cluster, and the second phase is from the relay node to the destination node. At the same time, the spectrum resource is divided into two equal parts, and one part is used at one stage, so that the mutual interference in the cluster is eliminated. According to the principle of decoding and forwarding, the total signal to noise ratio in the cluster is
γ s,r,d =min{γ s,rr,d }
The instantaneous data rate of the D2D link is expressed as
Figure BDA0004043873290000103
W represents the spectrum bandwidth used by the D2D link, while 1/2 represents half of the spectrum resources used by the communication link;
EE is defined as the ratio of data rate to power, P is used t Representing the total power in the entire link, the following equation is derived
Figure BDA0004043873290000111
The total power is mainly composed of two parts, namely, the transmitting power and the circuit power. The transmit power is used to transmit data and the circuit power is used to process data, including mixing, analog-to-digital (a/D) conversion, and digital-to-analog (D/a) conversion. Assuming that the circuit power of different users is the same and expressed, the total power of the D2D link may be expressed as
Figure BDA0004043873290000112
P cir Representing circuit power, 1/2 represents that the power consumption of two phases in the D2D link communication process are independent and do not occur simultaneously, and n represents the number of relay nodes in the cluster.
Because of the selfish property of the relay nodes and the screening mechanism of the trust parameters, when the relay nodes in the cluster range do not meet the requirements, the direct communication technology is adopted for data transmission. The signal-to-noise ratio, the instantaneous data rate and the power loss from the destination node to the source node are respectively
Figure BDA0004043873290000113
R s,d =Wlog 2 (1+γ s,d )
P t1 =P s +P cir
Deriving EE for direct communication from instantaneous data rate and power loss
Figure BDA0004043873290000121
In the model, an optimal solution for energy efficiency needs to be obtained by obtaining an optimal transmit power and an optimal relay power in the link. The EE-based optimal power optimization model is denoted by P1:
Figure BDA0004043873290000122
Figure BDA0004043873290000123
Figure BDA0004043873290000124
η i,j ∈{0,1},i∈D,j∈n
γ s,r,d ≥γ d ,
α∈{0,1}
Figure BDA0004043873290000125
and->
Figure BDA0004043873290000126
Respectively representing the maximum transmitting power of the source node and the maximum transmitting power of the relay node, gamma d Representing the minimum signal-to-noise ratio requirement of the link for communication, alpha represents the working coefficient of the system, and the direct communication and the relay communication are independent and do not simultaneously. />
For the P1 problem, two cases are classified, when α=1, only relay communication is performed to solve the optimum power in the scenario
Figure BDA0004043873290000127
And->
Figure BDA0004043873290000128
Two assumptions are made, assuming the following:
suppose 1: when gamma is s,r,d =min{γ s,rr,d }=γ s,r I.e. phi s,r ≤Φ r,d Then the objective function in P1 is rewritten as
Figure BDA0004043873290000129
At R s,d =Wlog 2 (1+γ s,d ) EE is related to P r Monotonically decreasing function if one is to obtainMaximum of EE, then P r Is the minimum value. As can be seen from the current assumption, when P s Φ s,r ≤P r Φ r,d ,P r Maximum value of (2)
Figure BDA0004043873290000131
Suppose 2: when gamma is s,r,d =min{γ s,rr,d }=γ r,d I.e. phi r,d ≤Φ s,r Then the objective function in P1 is rewritten as
Figure BDA0004043873290000132
Obviously, in
Figure BDA0004043873290000133
Wherein EE is related to P s Monotonically decreasing function, if EE maximum is to be obtained, P is required r Is the minimum value. As can be seen from the current assumption, when P r Φ r,d ≤P s Φ s,r ,P r Maximum value of (2)
Figure BDA0004043873290000134
From the above two assumptions, it can be seen if and only if gamma s,r =γ r,d At this time, EE takes its maximum value.
In subsequent analysis, use is made of
Figure BDA0004043873290000135
Replacing the objective function in the P1 problem to obtain the optimal power +.>
Figure BDA0004043873290000136
And->
Figure BDA0004043873290000137
Problem P1Is equivalently rewritten as problem P2:
Figure BDA0004043873290000138
Figure BDA0004043873290000139
Figure BDA00040438732900001310
η i,j ∈{0,1},i∈D,j∈n
γ s,r,d ≥γ d ,
P s Φ s,r ≤P r Φ r,d
obviously, the objective function is a nonlinear partial programming problem that is difficult to solve for the problem P2, but can be transformed into a nonlinear parameter programming by using the transformation method in the existing document On nonlinear fractional programming. Therefore, problem P2 is converted to problem P3 according to the theoretical method,
where u=wleg 2 (1+P s Φ s,r )-q(P s +nP r +2(n+1)P cir )
Figure BDA0004043873290000141
Figure BDA0004043873290000142
γ s,r,d ≥γ d ,
It is known from document On nonlinear fractional programming that EE takes a maximum value if and only if u=0. Wherein q is a temporary optimal solution of EE maximum;
proving U as a concave function, firstly, respectively solving P for the function U s And P r The first partial derivative of (2) gives the following formula
Figure BDA0004043873290000143
The first partial derivative is again derived to obtain the U's Heisen matrix as follows
Figure BDA0004043873290000144
The first order cis-form of the jersey matrix is complex, the second order cis-form is zero, and the jessey matrix is a negative semi-definite matrix. Whereby the function U is a concave function, capable of taking a maximum value;
after proving, use
Figure BDA0004043873290000145
P in substitution problem P3 r Then find the relation P for the function U s Is derived from the partial derivative of (2) to obtain the following formula
Figure BDA0004043873290000146
Wherein [ x ]] + Represents max {0, x }, in combination with constraint
Figure BDA0004043873290000151
Will be
Figure BDA0004043873290000152
Bringing in to an optimal transmit power of
Figure BDA0004043873290000158
/>
So far, only the first calculated optimal transmit power is found, while the last power optimal solution is related to the iteration factor. Thus, P s The iteration needs to be continued until u=0. In a similar manner, according to the above-mentioned derivation,solving for P r Is a solution to the optimization of (3).
When alpha=0, only direct communication is performed, and for simplifying the description, the method comprises
Figure BDA0004043873290000153
From the following components
Figure BDA0004043873290000154
EE is known s,d Concerning P r Is a monotonically decreasing function of P r EE when the minimum value is obtained s,d The maximum value is taken. Will phi s,d Substituted into->
Figure BDA0004043873290000155
Is obtained by
Figure BDA0004043873290000156
Using the method in document On nonlinear fractional programming, problem P1 can be converted into problem P4:
Figure BDA0004043873290000157
wherein z=wleg 2 (1+P s Φ s,d )-q(P s +P cir )
Figure BDA0004043873290000161
Figure BDA0004043873290000162
γ s,r,d ≥γ d ,
Regarding Z, regarding P s First and second partial derivatives of (2) to obtain
Figure BDA0004043873290000163
Since the second derivative of Z is less than zero, Z is proved to be a concave function when
Figure BDA0004043873290000164
At this time, Z takes the maximum value.
Figure BDA0004043873290000165
Combining constraints
Figure BDA0004043873290000166
Obtaining the product
Figure BDA0004043873290000167
In summary, the optimal transmit power required by the source node in the direct communication scenario is obtained.
The calculated optimal power is only a solution of the P3 problem and is not a solution of the P2 problem, and the solution of the P2 problem is related to the iteration factor and can be obtained through iteration of an optimal power iteration algorithm and a cluster relay selection algorithm. The optimal power iterative algorithm is shown in fig. 2, and the cluster relay selection algorithm is shown in fig. 3. In fig. 3, the total number of idle nodes is represented by F, the relay radius r of D2D is half of that of the source node to the destination node, meanwhile, the distance between the idle nodes and the source node is represented by D, and the trust threshold is η.
Therefore, the invention adopts the relay node selection method based on D2D communication, D2D communication is carried out through a downlink, the base station sends a broadcast signal, the signal-to-noise ratio information of the relay nodes in the cluster is collected, and a plurality of better nodes far away from the base station are selected according to the threshold value of the distance and the social relationship. The link between the relay node and the destination node uses a maximum ratio combining MRC to translate the problem into selecting an optimal signal-to-noise ratio SNR between the source node and the relay node.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention and not for limiting it, and although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that: the technical scheme of the invention can be modified or replaced by the same, and the modified technical scheme cannot deviate from the spirit and scope of the technical scheme of the invention.

Claims (9)

1. A relay node selection method based on D2D communication is characterized in that: the method comprises the following steps: before formal communication, a base station firstly transmits a broadcast signal, a circular range with a cluster range being a center of a circle and a midpoint of two ends of a target node being a radius is determined based on constraint of a distance and a social relationship, after receiving broadcast test information of the base station, a relay node in the cluster range returns corresponding signal-to-noise ratio information, meanwhile, the relay node transmits the test signal to the target node, the target node returns corresponding signal-to-noise ratio information to the base station, and a relay node with the minimum signal-to-noise ratio is continuously removed according to a threshold value of the distance and the social relationship, and a plurality of better relay nodes are selected.
2. The relay node selection method based on D2D communication according to claim 1, wherein: assuming that there is no interference between nodes and between a node and D2D users within the cluster, only signal interference from the base station is received, and a set of channel resources can only be multiplexed by a pair of D2D users;
a set of D2D pairs, d= { D, is denoted by D 1 ,D 2 ,D 3 ,...,D n Di represents the ith D2D pair, P s Representing the maximum transmit power of a D2D user, P r Representing the maximum transmit power of the relay node, N 0 Representing additive white gaussian noise, eta i,j Representing trust value between two devices g i,j Representing channel gains between devices i to j, where gi, ri represent channel gains between device i and the ri-th relay node in the cluster range, source node to relay node, relay node to destinationThe signal to noise ratio of the nodes of (a) are respectively expressed as
Figure QLYQS_1
Order the
Figure QLYQS_2
If the number of relay nodes in the cluster is not less than 2, the signal to noise ratios from the source node to the cluster and from the cluster to the destination node are respectively expressed as
γ s,r =min(γ s,ri ),γ r,d =min(γ ri,d )
3. The relay node selection method based on D2D communication according to claim 2, wherein: dividing the whole communication process into two phases, wherein the first phase is from a source node to a relay node in a cluster, the second phase is from the relay node to a destination node, spectrum resources are divided into two equal parts, one phase uses one part, and the total signal to noise ratio in the cluster is according to the principle of decoding and forwarding
γ s,r,d =min{γ s,rr,d }
The instantaneous data rate of the D2D link is expressed as
Figure QLYQS_3
W represents the spectrum bandwidth used by the D2D link, while 1/2 represents half of the spectrum resources used by the communication link;
EE is defined as the ratio of data rate to power, P is used t Representing the total power in the entire link, the following equation is derived
Figure QLYQS_4
Assuming that the circuit power of different users is the same and expressed, the total power of the D2D link may be expressed as
Figure QLYQS_5
P cir Representing circuit power, 1/2 represents that the power consumption of two phases in the D2D link communication process are independent and do not occur simultaneously, and n represents the number of relay nodes in the cluster.
4. The relay node selection method based on D2D communication according to claim 3, wherein: when the relay nodes in the cluster range do not meet the requirements, adopting a direct communication technology to perform data transmission, wherein the signal-to-noise ratio, the instantaneous data rate and the power loss from the destination node to the source node are respectively as follows
Figure QLYQS_6
R s,d =Wlog 2 (1+γ s,d )
P t1 =P s +P cir
Deriving EE for direct communication from instantaneous data rate and power loss
Figure QLYQS_7
5. The relay node selection method based on D2D communication according to claim 4, wherein: the EE-based optimal power optimization model is denoted by P1:
Figure QLYQS_8
s.t.0<P≤P max
s s
0<P≤P max
r r
η i,j ∈{0,1},i∈D,j∈n
γ s,r,d ≥γ d ,
α∈{0,1}
P s max and P r max Respectively representing the maximum transmitting power of the source node and the maximum transmitting power of the relay node, gamma d Representing the minimum signal-to-noise ratio requirement of the link for communication, wherein alpha represents the working coefficient of the system, and the direct communication and the relay communication are independent and do not simultaneously;
for the P1 problem, two cases are classified, and when α=1, only relay communication is performed to obtain the optimal power P s opt And P r opt Two assumptions are made, assuming the following:
suppose 1: when gamma is s,r,d =min{γ s,rr,d }=γ s,r I.e. phi s,r ≤Φ r,d Then the objective function in P1 is rewritten as
Figure QLYQS_9
/>
As can be seen from the current assumption, when P s Φ s,r ≤P r Φ r,d ,P r Maximum value of (2)
Figure QLYQS_10
Suppose 2: when gamma is s,r,d =min{γ s,rr,d }=γ r,d I.e. phi r,d ≤Φ s,r Then the objective function in P1 is rewritten as
Figure QLYQS_11
As can be seen from the current assumption, when P r Φ r,d ≤P s Φ s,r ,P r Maximum value of (2)
Figure QLYQS_12
From the above two assumptions, it can be seen if and only if gamma s,r =γ r,d At this time, EE takes its maximum value.
6. The relay node selection method based on D2D communication according to claim 5, wherein: using
Figure QLYQS_13
Replacing the objective function in the P1 problem to obtain the optimal power P s opt And P r opt Problem P1 is equivalently rewritten as problem P2:
Figure QLYQS_14
s.t.0<P≤P max
s s
0<P≤P max
r r
η i,j ∈{0,1},i∈D,j∈n
γ s,r,d ≥γ d ,
P s Φ s,r ≤P r Φ r,d
7. the relay node selection method based on D2D communication according to claim 6, wherein: problem P2 is converted to problem P3 according to a theoretical method,
where u=wleg 2 (1+P s Φ s,r )-q(P s +nP r +2(n+1)P cir )
Figure QLYQS_15
Figure QLYQS_16
γ s,r,d ≥γ d ,
EE takes the maximum value if and only if u=0, where q is a temporary optimal solution of EE maximum.
8. The relay node selection method based on D2D communication according to claim 7, wherein: proving U as a concave function, firstly, respectively solving P for the function U s And P r The first partial derivative of (2) gives the following formula
Figure QLYQS_17
The first partial derivative is again derived to obtain the U's Heisen matrix as follows
Figure QLYQS_18
The first-order cis-form main component of the Heisen matrix is complex, the second-order cis-form main component is zero, the Heisen matrix is a negative semi-definite matrix, and the function U is a concave function, so that the maximum value can be obtained;
after proving, use
Figure QLYQS_19
P in substitution problem P3 r Then find the relation P for the function U s Is derived from the partial derivative of (2) to obtain the following formula
Figure QLYQS_20
Wherein [ x ]] + Represents max {0, x }, in combination with constraint
Figure QLYQS_21
Will->
Figure QLYQS_22
Bringing in to an optimal transmit power of
Figure QLYQS_23
9. The D2D communication based relay node selection method according to claim 8, wherein: p (P) s Iteration is continued until u=0, and P is solved according to the above derivation r Is the optimal solution of (a); when alpha=0, only direct communication is performed to make
Figure QLYQS_24
Will phi s,d Substituted into
Figure QLYQS_25
Is obtained by
Figure QLYQS_26
Problem P1 is converted into problem P4 according to the theoretical method:
Figure QLYQS_27
wherein z=wleg 2 (1+P s Φ s,d )-q(P s +P cir )
s.t.0<P≤P max
s s
0<P≤P max
r r
γ s,r,d ≥γ d ,
Regarding Z, regarding P s First order partial derivative and second order partial derivative of (2)The order partial derivative is obtained
Figure QLYQS_28
Since the second derivative of Z is less than zero, Z is proved to be a concave function when
Figure QLYQS_29
When Z is at a maximum value,
Figure QLYQS_30
combining constraint condition 0 < P s ≤P s max Obtaining the product
P s =min{P s * ,P s max }
And finally obtaining the optimal transmitting power required by the source node in the direct communication scene.
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