CN110381473A - Network code assists D2D to communicate more relay selection methods - Google Patents
Network code assists D2D to communicate more relay selection methods Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
- H04W4/70—Services for machine-to-machine communication [M2M] or machine type communication [MTC]
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- H—ELECTRICITY
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- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W40/00—Communication routing or communication path finding
- H04W40/02—Communication route or path selection, e.g. power-based or shortest path routing
- H04W40/04—Communication route or path selection, e.g. power-based or shortest path routing based on wireless node resources
- H04W40/10—Communication route or path selection, e.g. power-based or shortest path routing based on wireless node resources based on available power or energy
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- H—ELECTRICITY
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- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W40/00—Communication routing or communication path finding
- H04W40/02—Communication route or path selection, e.g. power-based or shortest path routing
- H04W40/12—Communication route or path selection, e.g. power-based or shortest path routing based on transmission quality or channel quality
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- H—ELECTRICITY
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- H—ELECTRICITY
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- H04W—WIRELESS COMMUNICATION NETWORKS
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- H04W40/02—Communication route or path selection, e.g. power-based or shortest path routing
- H04W40/22—Communication 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
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Abstract
The present invention relates to fields of communication technology, specifically a kind of q&r that can guarantee communication, the network code auxiliary D2D for reducing the time slot of occupancy simultaneously communicates more relay selection methods, the present invention is compared with the existing technology, while guarantee system can continue reliable communication, reduce the number of transmission, improve efficiency, occupancy unnecessary to user is avoided to result in waste of resources, furthermore the complexity of this method is very low, it is easily achieved, reduces time delay, can solve the problem of hot spot region needs the communication scenes of high reliability.
Description
Technical field:
The present invention relates to field of communication technology, specifically a kind of q&r that can guarantee communication, simultaneously
The network code auxiliary D2D for reducing the time slot occupied communicates more relay selection methods.
Background technique:
In 5G, D2D communication proposition solve the problems, such as at a slow speed, short distance direct communication, effectively raise frequency spectrum money
The utilization rate in source reduces the load of base station, reduces the energy consumption etc. of user.But in continuous development, not only to meet
High capacity communication must also may be implemented continuously not interrupting the communication highly reliable with low time delay, so directly D2D communication and single-hop
There are limitations for D2D communication.Such as a hot spot region, when user communication distance farther out or user is located at cell side
Situations such as edge, all can not achieve reliable data using direct D2D or single-hop D2D communication and transmit.Therefore it is needed multiple altogether
The user for enjoying information, which is linked into constitute in communication, carries out multi-hop D2D communication by relaying group.It is by serial in many researchs
Relaying group is communicated, and this mode can expand communication range, but reliability is not improved, as long as because having
It is one of to interrupt, it will lead to entire communication failure.Because introducing multiple relayings, if in the communications
More time slot can be occupied using traditional store and forward message mode, result in waste of resources and increase delay.
Summary of the invention:
The present invention is directed to shortcoming and defect existing in the prior art, proposes a kind of D2D for network code auxiliary
The relaying group selection method of more relay communications systems considers channel conditions, communication distance, the number of transmissions and relaying by joint
Time-to-live several relaying groups for meeting communicating requirement because usually determining, improve compared with existing relay selection method and build
The probability of vertical link and the reliability of communication, and there is very low complexity, it is underway selected while selection it is optimal
Multiplexing phone user's resource, carry out the interference generated in inhibition system, guarantee the normal communication of other users in honeycomb.
The present invention can be achieved by the following measures:
A kind of more relay selection methods of network code auxiliary D2D communication, it is characterised in that the following steps are included:
Step 1: first having to meet logical by the direct D2D that link between each user may be implemented after relaying subsidiary communications
Letter, therefore base station can be according to the positional relationship of two D2D users and the maximum communication distance that can be realized in available free
It is screened after user, the user that initial option goes out to meet on communication distance condition constitutes set, is sentenced by following formula
It is disconnected:
Wherein LmaxIt is the maximum distance that D2D user can communicate, lD1,D2,lD1,R,lD2,RIt is respectively to D2D to D1 to D2
Distance, D1 to relaying R distance and D2 to relaying R distance, if collect be combined into sky if be converted to honeycomb mode；Step 2:
According to channel conditions, the Signal to Interference plus Noise Ratio that each user in the set that step 1 determines constitutes link is calculated, selects that be greater than can be with
Realize the minimum threshold of success communication:
Wherein γ is the dry ratio of letter of communication link receiving end, PdIt is the transmission power of transmitting terminal, GdIt is channel gain,
PcGcIt is the interference that the phone user of multiplexing generates, I0It is the interference of neighboring community, N is white Gaussian noise, according to above formula to step
Relay collection in rapid 1 is further screened, and is converted to honeycomb mode if collection is combined into sky, is stopped if only one user
Only relay selection carries out single relayed communications, otherwise enters step 3；
Step 3: the expection the number of transmissions (ENT) of each of the links is calculated according to the packet loss of link:
Out-trunk R is calculated according to above formulajThe number of transmissions that must be expected in primary communication is
ENTj=entj,1+entj,2+entj,3+entj,4
Then it successively calculates needed for completing communication by each of set determining in step 2 trunk subscriber
ENT, the minimum ENT for finally enabling system allow are τ, then update set and retain the user for meeting following formula:
ENTj≤τ
It is same to be converted to honey mode if collection is combined into sky, terminate relay selection process if only one user,
It is communicated by single relaying；
Step 4: the time-to-live of relaying identified in step 3 being judged, this depends on the dump energy of user；
Assuming that the dump energy of each trunk subscriber is E1,E2,…Ej,…,EJ, relay RjTransimission power beWhen transmission
Energy consumption coefficient is η, then calculating power loss isIf the discharge voltage of each user is V,
Instant discharge current when calculating communication is
It is according to the time-to-live that Peukert rule calculates each relaying
Finally the minimum time that the time-to-live of each relaying is required with communication is completed, which is compared, selects satisfaction
The user of following formula is retained in set:
tj≥Mj/rj
Wherein MjIt is relaying RjThe total data volume for needing to transmit, rjIt is transmission rate；
Step 5: being converted to honeycomb mode if final collection is combined into sky after above step and communicated, if only
One user then carries out single relayed communications, is otherwise communicated by mostly relaying.
System model of the present invention is single cell, contains a base station in the cell and is responsible for resource pipe
Reason, a pair of of D2D user, the multiple phone users of random distribution and idle candidate relay user, when D2D user is due to distance and ground
When the factors such as reason environment not can be carried out direct communication, transmitted by qualified more relayings, other phone users use
The uplink resource being multiplexed in offer communication；The system model of network code subsidiary communications is divided into two parts, wherein one
Being divided to is two D2D users to relaying group transmission data progress multiple access access procedure, in first time slot and second time slot relaying
Group receives the data broadcasted from two users of D2D respectively；Another part is that relaying group carries out stochastic linear to the data received
Network code, then to the process of data packet after two D2D user's broadcast codes；The present invention is completed using three time slots
Communication, because, without the concern for stationary problem, more meeting actual signal intelligence compared to two slotted communications.
The present invention used rician fading channel of the present invention in D1 and D2 communication process, therefore D2 receives signal transient
The probability density function of power are as follows:
Wherein, prIt is the wink that D1 transmits a signal to D2
When receive power,It is the local mean value for the multi-path component that D2 is received, K is the Rice factor for showing channel quality, is
Constant, I0It is first-order bessel function.
The present invention is based on above-mentioned model of communication system, communication process is as follows:
Step 1: two users communicated send to base station and request, and base station judges whether two users meet
The condition established the link distributes resource to two users if meeting and directly carries out D2D communication, otherwise carries out step 2；
Step 2: base station is requested to idle user's broadcast relay, is selected in the candidate relay collection that can be communicated
The trunk subscriber for meeting condition constitutes relaying group, if occurring relay collection in the selection process is empty situation, is converted to
Traditional cellular communication；
Step 3: base station the user into D2D user and relaying group distribute resource, establishes the link completion communication, is passing through
Relaying group carry out data transmission in present invention employs random linear network encoding (RLNC) subsidiary communications, because of the reality of RLNC
Matter is the related operation that matrix is carried out to received information, so not needing the topological structure for being concerned about locating network, it is only necessary to root
Received number is subjected to linear combination according to code coefficient, coding packet and coefficient matrix are then transmitted to receiving end together, even if
Transmitting terminal can also recover required signal departing from network, receiving end, according to this characteristic thus RLNC be well suited for it is more
The D2D of relaying is communicated；Specific communication process is divided into two processes: in multiple access access procedure, each of relaying group is used
First, family time slot receives the data packet of D1 transmissionSecond time slot receives the data packet of D2 transmissionThe reception condition of data can be recorded by cache list for each trunk subscriber, if be properly received
Some data packet sent from two D2D users then indicates the corresponding state of the data packet with 1, is otherwise 0, in this way
It is encoded according to the data that RLNC principle can be 1 to numerical value in state table；Assuming that being received in the first two time slot relaying group
To data packet beOne shared m+n data packet, therefore from GF (2m) generate in finite field
Random coefficient matrix M is
Data packet Y after relaying group is encoded is
Relaying group enters broadcasting process after completing coding, the data packet after third time slot sends coding to D1 and D2 with
Code coefficient matrix, latter two right D2D user are decoded according to the data received, and essence is exactly the mistake of matrix inversion
Journey,
Xde=M-1Y
Two users can recover required data, complete the transmitting of information.
The present invention compared with the existing technology, while guarantee system can continue reliable communication, reduces time of transmission
Number, improves efficiency, avoids occupancy unnecessary to user and results in waste of resources, furthermore the complexity of this method is very low, easily
In realization, time delay is reduced, can solve the problem of hot spot region needs the communication scenes of high reliability.
Detailed description of the invention:
Attached drawing 1 is that network code assists the more relay communications system schematic diagrames of D2D in the present invention, and wherein Fig. 1 (a) is multiple access
Access procedure schematic diagram, Fig. 1 (b) are broadcast transmission process schematics.
Attached drawing 2 is that RLNC assists the more relayed communications process schematics of D2D in the present invention.
Attached drawing 3 is more relay selection process block diagrams in the present invention.
Attached drawing 4 is cell all types of user distribution map in relay selection process in the present invention.
Attached drawing 5 is the interruption performance for singly relaying and relaying more auxiliary D2D communication in the present invention.
Attached drawing 6 is the comparison of coding forwarding and store-and-forward system capacity in the present invention.
Attached drawing 7 is that network code assists packet drop during the more relayed communicationss of D2D in the present invention
Attached drawing 8 is relay selection scheme interruption performance analogous diagram in the present invention.
Specific embodiment:
The present invention constructs model of communication system, and the model of communication system is that single cell is as shown in Figure 1.At this
A base station is contained in cell is responsible for resource management, a pair of of D2D user, the multiple phone users of random distribution and free time candidate
Trunk subscriber.When D2D user not can be carried out direct communication due to factors such as distances and geographical environment, by qualified
More relayings are transmitted.Other phone users are used to provide the uplink resource being multiplexed in communication.Network code auxiliary is logical
The system model of letter is divided into two parts, and that wherein a of Fig. 1 is indicated, which is two D2D users, sends data to relaying group and carry out multiple access
Access procedure receives the data broadcasted from two users of D2D in first time slot and second time slot relaying group respectively.Fig. 1's
What b was indicated is that relaying group carries out random linear network encoding to the data received, then to two D2D user's broadcast codes
The process of data packet afterwards.
The present invention completes communication using three time slots, because asking compared to two slotted communications without the concern for synchronizing
Topic, more meets actual signal intelligence.It can be found that corresponding interference can be generated during each of communication, such as
Phone user can generate interference to D2D user and relaying, so just needing suitable multiple by selecting from multiple phone users
With object, the interference generated is made to reach minimum.D2D user also can generate interference to base station simultaneously, it is therefore desirable to which base station is to D2D
The transmission power of user is controlled to inhibit to interfere, to guarantee that the interference of each link all can guarantee communication
Receive in range, not will cause communication failure.The used rician fading channel of the present invention in D1 and D2 communication process, therefore
The probability density function of D2 reception signal transient power are as follows:
Wherein, prIt is the instantaneous received power that D1 transmits a signal to D2,It is the part for the multi-path component that D2 is received
Mean value, K are the Rice factors for showing channel quality, are constant, I0It is first-order bessel function.
According to above-mentioned model of communication system, entire communication process is as follows:
Step 1: two users communicated send to base station and request, and base station judges whether two users meet
The condition established the link distributes resource to two users if meeting and directly carries out D2D communication, otherwise carries out step 2；
Step 2: base station is requested to idle user's broadcast relay, is selected in the candidate relay collection that can be communicated
The trunk subscriber for meeting condition constitutes relaying group, if occurring relay collection in the selection process is empty situation, is converted to
Traditional cellular communication；
Step 3: base station the user into D2D user and relaying group distribute resource, establishes the link completion communication；Passing through
Relaying group carry out data transmission in present invention employs random linear network encoding (RLNC) subsidiary communications, because of the reality of RLNC
Matter is the related operation that matrix is carried out to received information, so not needing the topological structure for being concerned about locating network, it is only necessary to root
Received number is subjected to linear combination according to code coefficient, coding packet and coefficient matrix are then transmitted to receiving end together, even if
Transmitting terminal can also recover required signal departing from network, receiving end, according to this characteristic thus RLNC be well suited for it is more
The D2D of relaying is communicated, and specific communication process is as shown in Fig. 2, be broadly divided into two processes；In multiple access access procedure, relaying
Each of group first time slot of user receives the data packet of D1 transmissionSecond time slot receives D2 hair
The data packet sentThe reception condition of data can be recorded by cache list for each trunk subscriber, such as
Fruit has been properly received some data packet sent from two D2D users and has then indicated the corresponding state of the data packet with 1, no
Then it is 0, is encoded in this way according to the data that RLNC principle can be 1 to numerical value in state table；
Assuming that being in the data packet that the first two time slot relaying group receivesOne shared m+n
A data packet.Therefore from GF (2m) generate random coefficient matrix M in finite field and be
Data packet Y after relaying group is encoded is
Relaying group enters broadcasting process after completing coding, the data packet after third time slot sends coding to D1 and D2 with
Code coefficient matrix, latter two right D2D user are decoded according to the data received, and essence is exactly the mistake of matrix inversion
Journey；Xde=M-1Two users of Y can recover required data, complete the transmitting of information.
Carry out performance evaluation to the present invention below: the packet loss of link is in the communication system constructed by the present invention
Disconnected probability is the key index for measuring system performance, and the relationship for defining the two is following formula
pl=f (pout)=pout
Wherein plFor packet loss, poutFor outage probability.It is in data transmission procedure because logical by multiple relayings auxiliary
Letter then just communicates successfully so completing data transmitting simply by the presence of a link for each stage, if all
Data are not received by, then communication failure interrupts.Therefore it from D1 and D2 to relaying group, is connect from relaying group to D1 with the success of D2
Receive data packet probability be
Because it is separate state that each user, which does not interfere with the reception of data packet mutually, D2 receives data from D1
The probability of packet is
If carried out data transmission using traditional store and forward message mode, D1 → R → D2 packet loss is
D2 → R → D1 packet loss is
To sum up, the end-to-end packet loss of communication system is
It needs to be divided into two processes when through network code subsidiary communications to be analyzed, in the access of relaying group multiple access,
Network code, institute can be just carried out after only successfully receiving data packet from D1 and D2 for each trunk subscriber
The probability of coding can be completed with relaying group are as follows:
In relaying group broadcast data, D2 received data packet probability and packet loss are as follows:
D1 received data packet probability and packet loss areBecause only being needed by network code complete by three time slots
At communication, so the end-to-end packet loss of system are as follows:
In the network code auxiliary more relay communications systems of D2D, if reliable and effective communication can be carried out, relaying group rises
Critical effect.Because for the system compared to single relayed communications, carrying out communication by relaying group can be occupied more
Resource and need more energy, if while excessive relaying can meet communication condition and will also result in information redundancy, such as
Fruit trunk subscriber loses interest in the information, will result in waste unnecessary.Therefore, it is necessary in idle trunk subscriber
Number few as far as possible is selected to realize optimal system performance.So invention proposes a kind of joint consideration communication distance, channel
Situation, the number of transmissions and the relay selection method for relaying time-to-live several factors, relay selection process is as shown in figure 3, specific
Steps are as follows:
Step 1: first having to meet logical by the direct D2D that link between each user may be implemented after relaying subsidiary communications
Letter, therefore base station can be according to the positional relationship of two D2D users and the maximum communication distance that can be realized in available free
It is screened after user, the user that initial option goes out to meet on communication distance condition constitutes set, is sentenced by following formula
It is disconnected:Wherein LmaxIt is the maximum distance that D2D user can communicate, lD1,D2,lD1,R,lD2,RIt is to D2D pairs respectively
The distance of D1 to D2, the distance of D1 to relaying R and the distance of D2 to relaying R, are converted to honeycomb mode if collection is combined into sky；
Step 2: according to channel conditions, calculating the Signal to Interference plus Noise Ratio that each user in the set that step 1 determines constitutes link, choosing
The minimum threshold for being greater than and success communication may be implemented is selected out,Wherein γ is that communication link connects
The dry ratio of the letter of receiving end, PdIt is the transmission power of transmitting terminal, GdIt is channel gain, PcGcIt is the dry of phone user's generation of multiplexing
It disturbs, I0It is the interference of neighboring community, N is white Gaussian noise, is further screened according to above formula to the relay collection in step 1, such as
Fruit collection is combined into sky and is then converted to honeycomb mode, stops relay selection if only one user and carries out single relayed communications, otherwise
Enter step 3；
Step 3: the expection the number of transmissions (ENT) of each of the links is calculated according to the packet loss of link:
Out-trunk R can be calculated according to above formulajThe number of transmissions must be expected in primary communication are as follows:
ENTj=entj,1+entj,2+entj,3+entj,4
Then complete communication needed for ENT is successively calculated each of the set determined by step 2 trunk subscriber；
The minimum ENT for finally enabling system allow is τ, then updates set and retain the user ENT for meeting following formulaj≤ τ, if same set
Honey mode is then converted to for sky, terminates relay selection process if only one user, is communicated by single relaying；
Step 4: in order to guarantee that relaying can communicate for a long time, while there is stronger wish to be established the link,
So next to judge the time-to-live of relaying identified in step 3, the residue of user is depended primarily on
Energy, it is assumed that the dump energy of each trunk subscriber is E1,E2,…Ej,…,EJ, relay RjTransimission power beTransmission
When energy consumption coefficient be η, then calculating power loss and beingIf the discharge voltage of each user is
V, then instant discharge current when can calculate communication is
The time-to-live of each relaying is calculated according to Peukert rule are as follows:Finally by each relaying
Time-to-live with complete communication needed for minimum time be compared and select the user for meeting following formula and be retained in set: tj
≥Mj/rj, wherein MjIt is relaying RjThe total data volume for needing to transmit, rjIt is transmission rate.
Step 5: being converted to honeycomb mode if final collection is combined into sky after above step and communicated, if only
One user then carries out single relayed communications, is otherwise communicated by mostly relaying.
Emulation point is carried out to the correlated performance of more relay selection methods of the network code auxiliary D2D communication mentioned below
Analysis, specific parameter setting are as shown in table 1.
The setting of the specific simulation parameter of table 1
| Parameter index | Value |
| Radius of society (R) | 500(m) |
| Channel width | 20(MHz) |
| Noise power | -174dBm/Hz |
| The transmission power of phone user | 24dBm |
| Signal to Interference plus Noise Ratio threshold value | 3~7dB |
| Rice factor K | 1 |
| Maximum transmission distance between D2D user | 200m |
| Energy consumption coefficient | 30% |
The distribution situation of user and relay selection process in cell are as shown in figure 4, Fig. 5 is ought to carry out relay selection at random
When, influences of the different relaying numbers to the end-to-end outage probability of communication system, show to compare by simulation result in relaying group
Outage probability can be effectively reduced in the D2D communication of the system singly relayed, more relaying auxiliary, because single relay system is logical
Transmission failure, which occurs, for any jump during letter can all cause system communication to be interrupted, and carries out communication by relaying more
This case is effectively reduced, so enhancing the reliability of system；Conventional store forwarding and network code are turned in Fig. 6
Difference of the both of which in D2D communication in power system capacity is sent out, is led to it can be found that network code can be obviously improved multi-hop D2D
The power system capacity of letter；In Fig. 7 to the packet drops of the network code auxiliary more relayed communicationss of D2D and direct more relay transmissions into
It has gone and has compared.The difference that simulation result both shows when the data packet number of transmission is less be not it is obvious that still with
The increase of data packet number can significantly reduce the number of packet loss by network code subsidiary communications, on the one hand reduce in this way
The possibility of communication disruption, on the other hand decreases re-transmission, has saved resource, reduce delay and energy consumption；In fig. 8 I
The relay selection scheme that is mentioned of the present invention and traditional relay selection scheme interrupt end to end to communication system
Impact probability is compared, by simulation result it can be found that carrying out communication distance, channel shape to the user in relaying group
After the joint screening of condition, the number of transmissions and relaying time-to-live, the outage probability of system can be significantly reduced, therefore
The reliability of communication is greatly strengthened, and as the difference that the increase of transmitting terminal signal-to-noise ratio generates is more obvious.
To sum up, the present invention constructs network code auxiliary D2D and relays more according to network code and D2D communication relevance energy
The system model of communication, is described in detail entire session establishment and communication process and network code subsidiary communications
In each time slot all analyzed.By emulation it can be found that network code and more relayed communicationss using raising system
Handling capacity reduces outage probability.The invention proposes a kind of joints to consider communication distance, channel conditions, expected the number of transmissions
With the relay selection method of relaying time-to-live, the specific steps of this method are described in detail.Finally by this method
With traditional relay selection method and whether carry out network code subsidiary communications to system performance application emulated, can
Knowing relay selection method of the invention clearly reduces the outage probability of communication, and by reducing after network code again
The data packet of loss, relay selection method proposed by the present invention reduce while guarantee system can continue reliable communication
The number of transmission, improves efficiency, avoids occupancy unnecessary to user and results in waste of resources, furthermore the complexity of this method
It spends very low, it is easy to accomplish, time delay is reduced, can solve the problem of hot spot region needs the communication scenes of high reliability.
Claims (4)
1. a kind of network code auxiliary D2D communicates more relay selection methods, it is characterised in that the following steps are included:
Step 1: it first has to meet the direct D2D communication by the way that link between each user may be implemented after relaying subsidiary communications,
Therefore base station can use available free relaying with the maximum communication distance that can be realized according to the positional relationship of two D2D users
Family is screened, and the user that initial option goes out to meet on communication distance condition constitutes set, is judged by following formula:
Wherein LmaxIt is the maximum distance that D2D user can communicate, lD1,D2,lD1,R,lD2,RBe respectively to D2D to D1 to D2 away from
From the distance of D1 to relaying R and the distance of D2 to relaying R are converted to honeycomb mode if collection is combined into sky；
Step 2: according to channel conditions, calculating the Signal to Interference plus Noise Ratio that each user in the set that step 1 determines constitutes link, select
Greater than the minimum threshold that success communication may be implemented:
Wherein γ is the dry ratio of letter of communication link receiving end, PdIt is the transmission power of transmitting terminal, GdIt is channel gain, PcGcIt is multiple
The interference that phone user generates, I0It is the interference of neighboring community, N is white Gaussian noise, according to above formula in step 1
After set further screening, honeycomb mode is converted to if collection is combined into sky, stops relay selection if only one user
Single relayed communications is carried out, otherwise enters step 3；
Step 3: the expection the number of transmissions (ENT) of each of the links is calculated according to the packet loss of link:
Out-trunk R is calculated according to above formulajThe number of transmissions that must be expected in primary communication is
ENTj=entj,1+entj,2+entj,3+entj,4
Then successively to the ENT calculated by each of set determining in step 2 trunk subscriber needed for completing to communicate, most
The minimum ENT for enabling system allow afterwards is τ, then updates set and retain the user for meeting following formula:
ENTj≤τ
It is same to be converted to honey mode if collection is combined into sky, terminate relay selection process if only one user, passes through
Single relaying is communicated；
Step 4: the time-to-live of relaying identified in step 3 being judged, this depends on the dump energy of user；Assuming that
The dump energy of each trunk subscriber is E1,E2,…Ej,…,EJ, relay RjTransimission power be PRj, energy when transmission disappears
Consumption coefficient is η, then calculating power loss isIf the discharge voltage of each user is V, calculate
Instant discharge current when communication is
It is according to the time-to-live that Peukert rule calculates each relaying
Finally the minimum time that the time-to-live of each relaying is required with communication is completed, which is compared to select, meets following formula
User be retained in set:
tj≥Mj/rj
Wherein MjIt is relaying RjThe total data volume for needing to transmit, rjIt is transmission rate；
Step 5: honeycomb mode, which is converted to, if final collection is combined into sky after above step is communicated, if only one
User then carries out single relayed communications, is otherwise communicated by mostly relaying.
2. a kind of network code auxiliary D2D according to claim 1 communicates more relay selection methods, it is characterised in that adopted
System model is single cell, contains a base station in the cell and is responsible for resource management, a pair of of D2D user, with
Machine is distributed multiple phone users and idle candidate relay user, as D2D user since the factors such as distance and geographical environment cannot be into
When row direct communication, transmitted by qualified more relayings, other phone users are used to provide communicate in be multiplexed
Uplink resource；The system model of network code subsidiary communications is divided into two parts, and a portion is two D2D users in
Multiple access access procedure is carried out after a group transmission data, is received respectively in first time slot and second time slot relaying group from D2D two
The data of user's broadcast；Another part is that relaying group carries out random linear network encoding to the data received, then to two
The process of data packet after D2D user's broadcast code；Communication is completed using three time slots.
3. a kind of network code auxiliary D2D according to claim 1 communicates more relay selection methods, it is characterised in that in D1
With the used rician fading channel of the present invention in D2 communication process, therefore the probability density function of D2 reception signal transient power
Are as follows:Wherein, prIt is that D1 transmits a signal to instantaneously connecing for D2
Power is received,It is the local mean value for the multi-path component that D2 is received, K is the Rice factor for showing channel quality, is constant, I0
It is first-order bessel function.
4. a kind of network code auxiliary D2D according to claim 2 communicates more relay selection methods, it is characterised in that be based on
Above-mentioned model of communication system, communication process are as follows:
Step 1: two users communicated send to base station and request, and base station judges whether two users meet foundation
The condition of link distributes resource to two users if meeting and directly carries out D2D communication, otherwise carries out step 2；
Step 2: base station is requested to idle user's broadcast relay, selects to meet in the candidate relay collection that can be communicated
The trunk subscriber of condition constitutes relaying group, if occurring relay collection in the selection process is empty situation, is converted to traditional
Cellular communication；
Step 3: base station the user into D2D user and relaying group distribute resource, establishes the link completion communication, is passing through relaying
Group carry out data transmission in present invention employs random linear network encoding (RLNC) subsidiary communications because the essence of RLNC is pair
Received information carries out the related operation of matrix, so not needing the topological structure for being concerned about locating network, it is only necessary to according to coding
Received number is carried out linear combination by coefficient, coding packet and coefficient matrix is then transmitted to receiving end together, even if transmitting terminal
Departing from network, receiving end can also recover required signal, according to this characteristic so what RLNC was well suited for relaying more
D2D communication；Specific communication process is divided into two processes: in multiple access access procedure, each of relaying group user first
A time slot receives the data packet of D1 transmissionSecond time slot receives the data packet of D2 transmission
The reception condition of data can be recorded by cache list for each trunk subscriber, if be properly received from two D2D
Some data packet that user sends then indicates the corresponding state of the data packet with 1, is otherwise 0, in this way according to RLNC principle
The data that can be 1 to numerical value in state table encode；Assuming that being in the data packet that the first two time slot relaying group receivesOne shared m+n data packet, therefore from GF (2m) random coefficient matrix M is generated in finite field
For
Data packet Y after relaying group is encoded is
Relaying group enters broadcasting process after completing coding, data packet from coding to D1 and D2 and coding after third time slot sends
Coefficient matrix, latter two right D2D user are decoded according to the data received, and essence is exactly the process of matrix inversion,
Xde=M-1Y
Two users can recover required data, complete the transmitting of information.
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