CN105611598B - Multi-hop cognitive radio network oriented reliable data transmission method - Google Patents

Abstract

The invention discloses a multi-hop cognitive radio network oriented reliable data transmission method. The method divides end-to-end transmission delay and data packet delivery rate into single-hop transmission delay and data packet delivery rate constraint in a multi-hop cognitive radio network, proposes a data packet single-hop effective advance rate and node reliability concept, and is used for calculating an optimal candidate forwarding node set for ensuring single-hop data packet delivery rate and single-hop transmission delay constraint. In the method, the data packet single-hop effective advance rate and the node reliability are used as comprehensive evaluation indexes for routing in order to meet the end-to-end transmission delay and data packet delivery rate constraint. The data packet transmission delay is reduced by selecting a route with high data packet single-hop effective advance rate; the channel switching frequency and the packet loss rate are effectively reduced by selecting a node which is influenced little by the activity of a master user and has low available channel utilization rate as a forwarding node.

Description

A kind of reliable data transmission method towards multi-hop cognition radio net

Technical field

The present invention relates to wireless communication field, particularly to a kind of reliable number towards multi-hop cognition radio net According to transmission method.

Background technology

With the appearance of radio communication new business and new product, wireless communications market is continuous to the demand of radio spectrum resources Increase, under static spectral allocation strategy, some unauthorized frequency range dimension users competition uses are very crowded, and many authorizes The frequency spectrum service efficiency of frequency range is low, there is substantial amounts of frequency spectrum cavity-pocket.Cognitive radio is effective as solve the above problems One of approach, is a kind of intelligent wireless communication system, it has the learning ability based on artificial intelligence technology, can be cognitive outer The change of portion's environment, and change some running parameters of its own, such as operating frequency, modulation technique, transmit power by real-time Deng so as to internal state can adapt to the statistical change of wireless propagation environment, so as to carrying out the purpose of reliable communication.

In the wireless sensor network being distributed using static spectral, due to sharing with increasing Wireless Telecom Equipment Unauthorized frequency range causes channel congestion, leads to bursts dropping ratio to increase, propagation delay time cannot be guaranteed end to end, therefore will Cognitive radio technology is applied to wireless sensor network, forms a kind of multi-hop cognition radio net.Multi-hop cognition radio Network is a kind of dynamic spectrum access realizing source node multi-hop wireless communication between destination node based on cognitive radio Network.In described network, primary user refers to obtain the user of frequency range mandate, and secondary user refers to not obtain the use of frequency range mandate Family.Primary user has preferential right to frequency spectrum, can be at any time using frequency spectrum.Secondary user must use authorization channel in primary user When, it is switched to another idle channel to avoid the interference of primary user's communication.Therefore, only consider the Routing Protocol of fixed frequency spectrum distribution No longer applicable, need to propose a kind of new Routing Protocol towards multi-hop cognition radio net.

Content of the invention

For above-mentioned subproblem, the invention provides a kind of reliable data transmission towards multi-hop cognition radio net Method；

The method comprising the steps of：

S100, the next-hop candidate forward node set F of calculating current data packet sending node i_i, and determine set F_iIn The preferential forwarding order of node；

S200, it is based on step S100, described node i is to described set F_iIn each node broadcasts packet；

S300, the described packet of transmission, and judge whether described packet sends successfully.

Brief description

Fig. 1 is the use example in one embodiment of the invention based on ON/OFF model PU channel；

Fig. 2 is the positive examples of ranges figure of one embodiment of the invention interior joint i；

Fig. 3 is the routing algorithm flow chart towards multi-hop cognition radio net proposing in one embodiment of the invention；

In the case of Fig. 4 is for having three both candidate nodes in one embodiment of the invention, each both candidate nodes single-hop delay Computational methods exemplary plot；

Fig. 5 is to calculate positive set C in one embodiment of the invention_iThe flow chart of interior joint weight；

Fig. 6 is to calculate orderly candidate forward node F in one embodiment of the invention_iFlow chart.

Specific embodiment

With specific embodiment, the present invention is further detailed below in conjunction with the accompanying drawings：

In one embodiment, the invention discloses a kind of authentic data method towards multi-hop cognition radio net,

The method comprising the steps of：

S100, the next-hop candidate forward node set F of calculating current data packet sending node i_i, and determine set F_iIn The preferential forwarding order of node；

S200, it is based on step S100, described node i is to described set F_iIn each node broadcasts packet；

S300, the described packet of transmission, and judge whether described packet sends successfully.

Method described in the present embodiment, in multi-hop cognition radio net, will be passed propagation delay time data bag end to end Friendship rate (i.e. QoS constraint end to end) is divided into the constraint of single-hop transmission time delay data Packet delivery ratio, and proposing packet single-hop has Effect advanced speed and node reliability concept, for ensureing the transmitting of data.Methods described combines consideration packet list Jump effective advanced speed and node reliability is routed.

In multi-hop cognition radio net, for ensureing the transmitting of data, Routing Protocol should ensure that packet at end Transmission between end has certain service quality (Quality of Service, QoS).QoS constraint end to end refers mainly to Constraint to end-to-end propagation delay time data Packet delivery ratio.Arrive due to there is not fixing end between source node and destination node End link, network topology has the shadow being vulnerable to primary user's activity and position in unstability, and node communication routine Ring, inter-node communication channel conditions are unstable, lead to be difficult to ensure packet propagation delay time and submit rate one end to end simultaneously Surely meet QoS constraint.Therefore, replace QoS with " soft QoS ".Soft QoS refers to meet QoS constraint with certain Probability p, that is, with one Fixed Probability p meets propagation delay time data Packet delivery ratio constraint end to end simultaneously.

In one embodiment, described step S100 specifically includes following steps,

S101：Judge destination node D whether within the communication range of current data packet sending node i, if so, then node I directly delivers a packet to destination node D；Otherwise, execution step S102；

S102：Described node i passes through CCCH to positive node set C_iIn node send routing request packet；

S103：Described set C_iIn node after receiving routing request packet, each to node i send route response bag；

S104：Node i calculates next-hop candidate's forward node according to the nodal information obtaining in the route response bag receiving Set F_i, and determine set F_iThe preferential forwarding order of interior joint.

In the present embodiment, described routing request packet includes sending node ID and destination node ID, for example currently transmitted section Point ID is 5, and destination node ID is 16, then routing request packet is (5,16).The content of described route response bag includes sending node ID, destination node ID, node ID, if idle, idle channel list.Described nodal information is the node letter in route response bag Breath, the main reliability including node and the effective advanced speed of single-hop.

Communication range described in the present embodiment applies to the concept of short-range wireless communications interfaces；For example, bluetooth and Wifi has certain communication range, 10 meters or 100 meters.Therefore the communication range in the present embodiment refers to present node I is the border circular areas with constant R as radius for the center of circle；As shown in Figure 2.

In one embodiment, described step S200 is specially：According to described route response bag, calculate node i and collection Close F_iIn each node j set of available channels CH (i, j), then node i pass through set of available channels CH (i, j) in reliability Highest channel is to F_iIn each node broadcasts packet.

In the present embodiment, because primary user position is different in described network, each node acceptor's User Activity Impact is different, and the reliability of each node available channel has notable difference.The impact of channel acceptor's User Activity is less, channel Utilization rate lower, the reliability of described channel is higher.The reliability of described node refers to that all available channels of this node can Mean value by property.Analyzed by above, methods described selects the higher node of reliability as forward node, Neng Gouyou Effect reduces channel switching times and packet loss, thus ensureing that packet submits rate.

In one embodiment, described S300 specifically includes following steps,

S301：Data in described packet, in transmission, if PU activity is detected, communication channel is switched to In CH (i, j), the channel of reliability suboptimum is transmitted；

S302：If node i receives the ACK that certain next-hop candidate's forward node feedback is successfully received data, count Send successfully according to bag；Otherwise, node i retransmits packet.

In the present embodiment, for each candidate's forward node, if being properly received packet, preferential according to itself Power sets a timer.The priority of node is higher, and timing length is shorter.If before timing terminates, having correctly received data Bag, then at the end of timing, this both candidate nodes passes through CCCH to node i and other both candidate nodes transmission ACK, statement This both candidate nodes has been successfully received packet, then this both candidate nodes becomes the actual forward node of this jump.Other both candidate nodes are received To after ACK, timing will be cancelled, no longer this packet be forwarded simultaneously.If at the end of timing, still confiscate packet, then Think that this both candidate nodes does not receive packet, can not carry out data forwarding.If all both candidate nodes all do not receive packet, Then node i retransmits to this packet.

In one embodiment, positive node set C described in step S102_iCalculating comprise the following steps,

S1021：Take out the neighbor node set N of current data packet sending node i_iOne of node, according to node Geographical location information, calculates the deflection θ of this node；

S1022：Judge whether described deflection θ belongs to (0, pi/2), if it is, turning to then S10221；Otherwise, turn to S10222；

S10221, this node is added to positive node set C_iIn；

S10222, steering next node, and execution step S1021 again.

In the present embodiment, described routing algorithm is in forwarder selection, node only to positioned at this node to purpose section Neighbor node set C in the range of point positive direction_iBroadcast route request is grouped, and by the packet of the route replies of node calculate from Present node is to set C_iIn each node effective advanced speed.

In one embodiment, the computing formula of the deflection of described neighbor node is：

$\mathrm{\θ}=arccos\frac{{\stackrel{\→}{a}}_{iD}\·{\stackrel{\→}{a}}_{ij}}{\left|{\stackrel{\→}{a}}_{iD}\right|*\left|{\stackrel{\→}{a}}_{ij}\right|},$

In above formula,Represent from node i to the direction of advance vector of destination node D；

Represent from node i to the direction of advance vector of destination node j.

In one embodiment, calculate next-hop candidate forward node set F in described step S104_iWalk including following Suddenly：

S1041：Initialization candidate's forward node set

S1042：Judge positive node set C_iWhether it is empty；If it is empty, then execution step S1045；

Otherwise, execution step S1043.

S1043：From positive node set C_iOne node of middle taking-up, this node is inserted into candidate forward node set F_i In can make candidate forward node set F_iNode weights are expected, at the maximum position of E (ω), to obtain current forward node sequence π_j (F_i)；

S1044：Judge in current forward node sequence π_j(F_i) under expectation E (t) of single-hop transmission time delay whether be less than or equal to Single-hop transmission delay constraint d_i, and single-hop packet submits expectation E (p) of rate and whether submits rate more than or equal to single-hop packet p_i；If so, then execution step S1045；Otherwise, repeated execution of steps S1042；

S1045：Return current forward node sequence π_j(F_i), then current forward node sequence is next-hop candidate and forwards Node set F_i.

In the present embodiment, ordered candidate as shown in Figure 6 forwards set F_iCalculation flow chart.Known current single-hop Delay constraint d_iSubmit rate p with single-hop packet_iWith positive node set C_i, calculate candidate using heuristic feasible operator and forward Node set F_i, and determine priority order π of candidate's forward node_j(F_i).

In one embodiment, in described step S1044, single-hop packet submits rate predicted value p_ijComputing formula be：

$p_{ij}=1-{\Π}_{k\∈CH(i,j)}^{CH(i,j)}{\stackrel{\‾}{\mathrm{\ξ}}}_{ik}{\stackrel{\‾}{\mathrm{\ξ}}}_{jk};$

Wherein

CH (i, j)=CH (i) ∩ CH (j), wherein CH (i) and CH (j) represent the idle channel of node i and node j respectively Set；I, j represent node i and node j；K represents the idle channel k that node i and node j can use, wherein k ∈ CH (i, j)；ξ_ikRepresent the idle probability of channel k in node i, the probability that is, node i is communicated using channel k and do not affected by PU activity； ξ_jkRepresent the idle probability of channel k in node j, the probability that is, node j is communicated using channel k and do not affected by PU activity；

The desired computing formula that described single-hop packet submits rate is：

$E\left(p\right)=1-{\Π}_{m=1}^n{\stackrel{\‾}{p}}_{{\mathrm{ij}}_m},E\left(p\right)\≥p_i$

WhereinM represents node j in candidate's forward node sequence π_j(F_i) in priority order, its Middle priority relationship is：j₁>j₂>...>j_n；

Single-hop packet for from node i to node jm submits the predicted value of rate.

In the present embodiment, rate predicted value p is submitted according to single-hop packet_ijThe single-hop packet calculating submits rate expectation E (p) must is fulfilled for single-hop packet and submits rate p_iConstraint, i.e. E (p) >=p_i.In the present embodiment, p_ijWithIt is identical concept Different expression symbols,In why many individual m illustrate that priority in forwarding candidate collection for the neighbor node j Sequentially, andTherefore single-hop packet submits rate expectation E (p) is that to submit rate according to single-hop packet pre- Measured value p_ijCalculate.

In one embodiment, the computing formula of expectation E (t) of single-hop transmission time delay described in described step S1044 For：E(t)≤d_i；

Wherein：K, m, n each mean node j in candidate's forward node sequence π_j(F_i) in priority order；I refers to current number According to bag sending node, j_k, j_m, j_nIt is the candidate neighbor nodes of node i；Represent that from node i transmits packets to node j_kSound The bright prediction time delay receiving used by packet；Represent that from node i transmits packets to node j_nStatement receives used by packet Prediction time delay.

In the present embodiment, single-hop transmission time delay d_iComputing formula be：

Wherein, T represents propagation delay time end to end, e_iRepresent the time used up from source node to node i, rh_iRepresent Node i estimates jumping figure to destination node D.

In the present embodiment, as the above analysis, the constraint d of single-hop QoS_iIt is as actually cumulative time delay and previously Link condition changing.Therefore, it is understood that increase with node weights, the i.e. effective advanced speed of node single-hop Increase and node reliability increase, can reduce thereafter single-hop QoS constraint, extend to packet data delivery when so end to end Friendship rate is easier to be protected.

In one embodiment, described step S1043 node weights computing formula is

Wherein, α is factor of influence, α ∈ [0,1]；ψ(v_ij) andRepresent that the single-hop of packet is effectively advanced speed respectively Rate v_ijReliability r with node j_jValue after standardization, 0≤ψ (v_ij)≤1,0≤φ(r_i)≤1.

In the present embodiment, factor of influence α is bigger, the priority of node affected by the effective advanced speed of single-hop bigger, Conversely, the reliability of node affects bigger, α ∈ [0,1] to the priority of node.

In one embodiment, the effective advanced speed computing formula of described packet single-hop is

Wherein,

θ is vectorWith vectorAngle；

${\stackrel{\→}{a}}_{ij}=(x_j,y_j)-(x_i,y_i),{\stackrel{\→}{a}}_{iD}=(x_D,y_D)-(x_i,y_i),$

Wherein：Represent from node i to the direction of advance vector of destination node D；

Represent from node i to the direction of advance vector of destination node j；

I represents currently transmitted node, and j is the neighbor node of node i, and D represents destination node；(x_i,y_i) represent node i Geographical coordinate；(x_j,y_j) represent node j geographical coordinate；(x_D,y_D) represent destination node D geographical coordinate；

t_ijRepresent that from node i transmits packets to the estimated time that node j statement receives this packet.

In the present embodiment, the effective advanced speed of the single-hop of described packet refers to that in the unit interval, packet is in positive direction The coverage of a upper jump of advancing.When being as actually cumulative due to the propagation delay time data Packet delivery ratio constraint of single-hop QoS Prolong and previous link condition is changing, the effective advanced speed of single-hop of therefore packet is bigger, more can effectively drop The low data packet transmission delay constraint often jumped thereafter, so propagation delay time constraint end to end is easier to be protected.

In one embodiment, the neighbor node j Calculation of Reliability formula of described node i is Standardizing formula is

Wherein, Nc represents all available channel number of node j,ξ_jkRepresent channel in node j The idle probability of k,u_jThe utilization rate of k channel k that j-th node monitors of () expression arrive, T is that time window is big Little, in time window, the channel k occupied time is t_busy；

r_jRepresent the reliability of node j, r_jK () represents the reliability of k-th channel of node j；C_iJust represent node i To neighbor node set, | C_i| represent the positive neighbor node number of node i, r_kRepresent k-th neighbour in positive neighbor node set Occupy the reliability of node.

In this embodiment it is stipulated that end to end QoS be constrained to propagation delay time T data Packet delivery ratio P end to end.By In the unstability of communication link, the disposable time complexity obtaining all link informations end to end consumes greatly and extremely very much Node resource, and the link information of each jump can be obtained with relatively low cost.Therefore, we will qos requirement draw end to end The QoS being divided into every jump constrains.Use d_iAnd p_iRepresent the propagation delay time data Packet delivery ratio constraint of the next-hop of node i respectively, then It is constrained in single-hop QoS of node i：

$d_i=\frac{T-e_i}{{\mathrm{rh}}_i}$

$p_i=\sqrt[{\mathrm{rh}}_i]{P}$

In above formula, e_iRepresent time of having used up from source node to node i, node i estimates jump to destination node D Number scale is rh_i.

In one embodiment, towards multi-hop cognition radio net, a kind of reliable data transmission method is proposed, described Cognitive radio technology is applied in wireless sensor network method, sets up a multi-hop cognition radio net model.? Node in described network model is divided into two classes：Primary user (Primary User, PU) node and time user (Secondary User, SU) node.Using ON/OFF model, each authorization channel is modeled in shown network, as shown in Figure 1 based on The use exemplary plot of ON/OFF model PU channel.When PU uses channel transmission data, channel is in ON state；When PU does not use During this channel, channel is in OFF state.SU node can be used in the channel transmission data of OFF state.In described model, Assume that the state between PU channel is separate.

In described ON/OFF model, arrange the status switch { S representing channel k using random binary number_n, n >=1 }, its In " 1 " represent channel and be in ON state, " 0 " represents channel and is in OFF state.Use N respectively_tAnd F_tRepresent ON state lasting when Between and OFF state duration, N_tObedience parameter is λ_kExponential distribution, F_tObedience parameter is μ_kExponential distribution, then kth The probability that individual channel is in OFF state is：

${\mathrm{\ξ}}_k=\frac{{\mathrm{\μ}}_k}{{\mathrm{\λ}}_k+{\mathrm{\μ}}_k}---\left(1\right)$

All the sensors node is all SU node, heretofore described source node, destination node, head-end site, Neighbor node, forward node are all referring to sensor node.Each sensor is equipped with a cognitive radio receiver.Cognitive nothing Line electricity receiver has frequency spectrum perception function so that the idle frequency spectrum that SU node can periodically search in surrounding environment is believed Breath.On this basis, each SU node all each safeguards an available authorization channel status list and an idle channel list. Available authorization channel status list includes ID, current busy-idle condition, idle probability and utilization rate four part of each channel.Described The current busy-idle condition of channel represents that channel is currently idle (OFF) or busy (ON), and 1 represents busy, and 0 represents idle.Institute The idle probability stating channel k in node i refers to the probability that channel k is not affected by PU activity, and computing formula is：

${\mathrm{\ξ}}_{ik}=\left\{\begin{array}{cc}{\mathrm{\ξ}}_k,& x_i=1;\\ 1,& x_i=0;\end{array}\right.---\left(2\right)$

Wherein, x_i=1 represents that node i is located in the mandate PU node communication range of channel k, is affected by PU activity, x_i=0 Then represent that node i is not affected by this PU activity.

Communication range described herein applies to the concept of short-range wireless communications interfaces.

For example, bluetooth and wifi have certain communication range, 10 meters or 100 meters.Therefore communication range is typically Refer to present node i the border circular areas for the center of circle with constant R as radius.Can refer to Fig. 2 to be understood.

Described channel utilization represents the busy extent of channel, and the time of occupied equal to channel (being in busy condition) is with always The percentage of time.Setting time window size is T, and in time window, the channel k occupied time is t_busy, then i-th Shown in the utilization rate computational methods such as formula (3) of the channel k that node monitors arrive.Channel reliability refer to the idle probability of channel with The ratio of utilization rate.The idle probability of channel is bigger, utilization rate is lower, and the reliability of channel is higher, and computing formula is (4).

$u_i\left(k\right)=\frac{t_{busy}}{T}---\left(3\right)$

$r_i\left(k\right)=\frac{{\mathrm{\ξ}}_{ik}}{u_i\left(k\right)}---\left(4\right)$

The reliability of described node refers to the mean value of this node all available channels reliability, and the reliability of node is got over Height, is subject to the possibility of PU moving obstacle less, and available free channel time is longer, is more conducive to subtracting in node communication routine Channel switching times with reducing bursts dropping ratio, the therefore Calculation of Reliability formula for the neighbor node j of node i are less (5), wherein N_cRepresent all available channel number of node j.

$r_j=\frac{{\Σ}_{k=1}^{N_c}{r}_j\left(k\right)}{N_c}---\left(5\right)$

Idle channel list refers to that in available authorization channel status list, the current busy-idle condition of channel is idle channel List, including channel id, the idle probability of channel and utilization rate.Represent the sky of node i and node j with CH (i) and CH (j) respectively Idle channel set, then node i and node j can only be communicated by the channel in CH (i, j)=CH (i) ∩ CH (j), channel k Reliability definition for communicating between node i and node j is：

$r_{ij}\left(k\right)=\underset{k\∈CH(i,j)}{min}\{r_i\left(k\right),r_j\left(k\right)\}---\left(6\right)$

In two node communication, described Channel assignment principle is：Prioritizing selection has the r of maximum_ijK the channel of () is as number According to bag transmission channel, if PU activity being detected by frequency spectrum perception in transmitting procedure interior joint, being switched to and there is less r_ij(k) Idle channel be transmitted.

Can node i be successfully transmitted packet to node j, has substantial connection, therefore from node i with the idle probability of channel Submit predicted value p of rate to node j_ijComputing formula is (7), wherein ${\stackrel{\‾}{\mathrm{\ξ}}}_{ik}=1-{\mathrm{\ξ}}_{ik},{\stackrel{\‾}{\mathrm{\ξ}}}_{jk}=1-{\mathrm{\ξ}}_{jk}.$

$p_{ij}=1-{\Π}_{k\∈CH(i,j)}^{CH(i,j)}{\stackrel{\‾}{\mathrm{\ξ}}}_{ik}{\stackrel{\‾}{\mathrm{\ξ}}}_{jk}---\left(7\right)$

In this embodiment, each SU node stores all immediate neighbor nodes (only including SU node) and destination node The geographical location information of (sink node).As shown in Figure 2 it is assumed that node i will send packet to destination node D in example, j is One neighbor node of i, the wherein geographical coordinate of node i are (x_i,y_i), the geographical coordinate of node j is (x_j,y_j), destination node The geographical coordinate of D is (x_D,y_D), the direction of advance from i to D is defined as vectorDirection.Fixed The deflection θ of adopted node is vectorWith vectorAngle, computational methods are as shown in formula (8).If θ ∈ (0, π 2), then node j is called the positive node to destination node D direction for the node i.Packet from node i to node j effectively advance away from Exist from for geographic distance between i and jProjection on direction, computing formula is (9).

$\mathrm{\θ}=arccos\frac{{\stackrel{\→}{a}}_{iD}\·{\stackrel{\→}{a}}_{ij}}{\left|{\stackrel{\→}{a}}_{iD}\right|*\left|{\stackrel{\→}{a}}_{ij}\right|}---\left(8\right)$

${\mathrm{\Δa}}_{ij}={\stackrel{\→}{a}}_{ij}*cos\mathrm{\θ}---\left(9\right)$

Use N_iRepresent all immediate neighbor node set of node i, C_iRepresent the set of all forward direction nodes of node i, F_i Represent candidate's forward node set of next-hop, then have

Positive node set C_iCalculation procedure as follows：

S11：Take out set N_iOne of node, according to the geographical location information of node, calculate the deflection of this node θ.

S12：Judge whether θ belongs to (0, pi/2), if so, then this node is added to positive node set C_iIn.Otherwise, Execution step S101.

Give towards multi-hop cognition radio net method flow diagram in the present invention in Fig. 3, step is：

S21：Judge destination node D whether within the communication range of present node i, if so, then node i directly by data Bag is sent to destination node D；Otherwise, execution step S22.

S22：Node i passes through CCCH to positive node set C_iIn node send routing request packet (<Send Node ID, destination node ID>).

S23：C_iIn node after receiving routing request packet each to node i send route response bag (<Sending node ID, destination node ID, node ID, if idle, idle channel list>).

S24：Node i calculates next-hop candidate's forward node collection according to the nodal information obtaining in the route response bag receiving Close F_i, and determine F_iThe preferential forwarding order of interior joint.

S25：Route response bag, calculate node i and F according to node_iIn each node j set of available channels CH (i, J), then node i passes through in each CH (i, j) reliability highest channel to F_iIn each node broadcasts packet.

S26：Data is in transmission, if by frequency spectrum perception Function detection to PU activity, communication channel is switched To CH (i, j), the channel of reliability suboptimum is transmitted.

S27：If node i receives the ACK that certain both candidate nodes feedback is successfully received data, packet sends into Work(；Otherwise, node i retransmits packet.

For each candidate's forward node, if being properly received packet, according to itself one meter of priority settings When device.The priority of node is higher, and timing length is shorter.If before timing terminates, have correctly received packet, then tie in timing During bundle, this both candidate nodes passes through CCCH to node i and other both candidate nodes transmission ACK, states that this both candidate nodes becomes Work(receives packet, then this both candidate nodes becomes the actual forward node of this jump.After other both candidate nodes receive ACK, will cancel Timing, no longer forwards to this packet simultaneously.If at the end of timing, still confiscate packet then it is assumed that this both candidate nodes Do not receive packet, can not carry out data forwarding.If all both candidate nodes all do not receive packet, node i is to this number Retransmitted according to bag.

Due to the impact of PU activity, channel may be needed in data transmission procedure to switch it is assumed that node j is candidate's forwarding Node set F_iIn sort from high to low according to priority after m-th both candidate nodes, last logical of from node i and node j In letter, channel switching times are κ, and one time handover delay is constant η, uses τ_mRepresent from node i to F_iAccording to priority from height to Low sequence after m-th both candidate nodes when transmission time on channel for the data, q_mWhen representing last communication, from node i is to the The queuing delay of m both candidate nodes, T_DATARepresent that node i transmits data to m-th both candidate nodes under dynamic frequency spectrum deployment Predicted time, computing formula is as follows：

T_DATA=q_m+τ_m+κ*η (10)

Use t_ijRepresent from node i to the single-hop delay of m-th both candidate nodes j, i.e. from node i broadcast data packet to m-th The statement of both candidate nodes j is successfully received the time of ACK, and computing formula is：

t_ij=T_DB+T_DATA+m*(T_AB+T_ACK) (11)

Wherein, T_DBRepresent packet send when keep out of the way time delay, T_ABRepresent send ACK when keep out of the way time delay, both at Constant.T_ACKRepresent that sending ACK from m-th both candidate nodes receives the time used by this ACK to node i and other both candidate nodes. Fig. 4 be there are three both candidate nodes in the case of, the computational methods exemplary plot of each both candidate nodes single-hop delay.

When selecting forward node, the not only propagation delay time of single-hop to be considered, it is also contemplated that before the single-hop of packet is effective Enter speed and therefore define single-hop effective advanced speed v_ijRepresent an effective forward travel distance of jump of packet in the unit interval, v_ijEnergy The speed that effecting reaction packet transmits in jumping one, computing formula is as follows：

$v_{ij}=\frac{{\mathrm{\&Delta;a}}_{ij}}{t_{ij}}---\left(12\right)$

According to above-mentioned analysis and calculating, when selecting forward node, answer prioritizing selection node reliability high and make packet list Jump the big node of effective advanced speed, therefore, the weight of calculation procedure calculate node as shown in Figure 5, formula is defined as：

ω_j=α * ψ (v_ij)+(1-α)*φ(r_j) (13)

In formula (13), factor of influence α is bigger, the priority of node affected by the effective advanced speed of single-hop bigger, Conversely, the reliability of node affects bigger, α ∈ [0,1] to the priority of node.ψ(v_ij) and φ (r_i) represent packet respectively Single-hop effective advanced speed v_ijReliability r with node j_jValue after standardization, i.e. 0≤ψ (v_ij)≤1,0≤φ(r_i)≤ 1, computing formula is as follows：

$\mathrm{\&psi;}\left(v_{ij}\right)=\frac{v_{ij}}{{\&Sigma;}_{k=1}^{\left|C_i\right|}{v}_{ik}}---\left(14\right)$

$\mathrm{\&phi;}\left(r_j\right)=\frac{r_j}{{\&Sigma;}_{k=1}^{\left|C_i\right|}{r}_k}---\left(15\right)$

In this embodiment it is stipulated that end to end QoS be constrained to propagation delay time T data Packet delivery ratio P end to end.By In the unstability of communication link, the disposable time complexity obtaining all link informations end to end consumes greatly and extremely very much Node resource, and the link information of each jump can be obtained with relatively low cost.Therefore, we will qos requirement draw end to end The QoS being divided into every jump constrains.Use d_iAnd p_iRepresent the propagation delay time data Packet delivery ratio constraint of the next-hop of node i respectively, then It is constrained in single-hop QoS of node i：

$d_i=\frac{T-e_i}{{\mathrm{rh}}_i}---\left(16\right)$

$p_i=\sqrt[{\mathrm{rh}}_i]{P}---\left(17\right)$

In formula (16) (17), e_iRepresent the time used up from source node to node i, node i is to destination node D Jumping figure of estimating be designated as rh_i, computing formula is (18).Wherein, Dist (i, D) represents node i to the Euclidean distance of node D,Represent h_iJump the mean value of effective forward travel distance, computing formula is (19).

$\stackrel{\&OverBar;}{a\left(h_i\right)}=\frac{(h_i-1)*\stackrel{\&OverBar;}{a(h_i-1)}+a\left(h_i\right)}{h_i}---\left(19\right)$

In formula (19), h_iRepresent the jumping figure being passed through from source node to node i, a (h_i) represent h_iJump actual advance Coverage,H before expression_iThe mean value of -1 effective forward travel distance of jump.

Use π_j(F_i)={ j₁,j₂,...,j_nRepresent F_iThe preferential sequence forwarding of interior joint, wherein priority relationship is：j₁> j₂>...>j_n.Calculate according to π_j(F_i) in order carry out forwarder selection, then single-hop packet submits the expectation of rate, single-hop The expectation of propagation delay time and π_j(F_i) the expectation computing formula of interior joint weight is：

$E\left(p\right)=1-{\&Pi;}_{m=1}^n{\stackrel{\&OverBar;}{p}}_{{\mathrm{ij}}_m}---\left(20\right)$

$E\left(t\right)={\&Sigma;}_{k=1}^n\left(t_{j_k}{p}_{{\mathrm{ij}}_k}{\&Sigma;}_{m=0}^{k-1}{\stackrel{\&OverBar;}{p}}_{{\mathrm{ij}}_m}\right)+t_{j_n}{\&Pi;}_{m=1}^n{\stackrel{\&OverBar;}{p}}_{{\mathrm{ij}}_m}---\left(21\right)$

$E\left(\mathrm{\&omega;}\right)={\&Sigma;}_{k=1}^n({\mathrm{\&omega;}}_{j_k}-p_{{\mathrm{ij}}_k}{\&Pi;}_{m=0}^{k-1}{\stackrel{\&OverBar;}{p}}_{{\mathrm{ij}}_m})---\left(22\right)$

Wherein,

As the above analysis, the constraint d of single-hop QoS_iAnd r_iIt is as actually cumulative time delay and previous link condition Changing.Therefore, it is understood that increase with node weights, the i.e. increase of the effective advanced speed of node single-hop and section The increase of point reliability, can reduce single-hop QoS constraint thereafter, extend to packet data delivery friendship rate and just more hold when so end to end Easily it is protected.Therefore, towards multi-hop cognition wireless reliable data transmission problem model it is：

maxE(ω)

Solve during this problem it is necessary to meet：

$F_i\&SubsetEqual;C_i\&SubsetEqual;N_i$

min|F_i|

E(t)≤d_i

E(p)≥p_i

Provide ordered candidate in Fig. 6 and forward set F_iCalculation flow chart.Known current single-hop delay constraint d_iAnd single-hop Packet submits rate p_iWith positive node set C_i, being critical that of solving the above problems calculate candidate with heuristic feasible operator Forward node set F_i, and determine priority order π of candidate's forward node_j(F_i), calculation procedure：

S31：Initialization candidate's forward node set

S32：Judge positive node set C_iWhether it is empty.If so, then execution step S35.Otherwise, execution step S33.

S33：From C_iOne node of middle taking-up, this node is inserted into F_iIn can make set F_iNode weights expectation E (ω) are At big position, obtain current forward node sequence π_j(F_i).

S34：Judge in current forward node sequence π_j(F_i) under single-hop transmission time delay expectation E (t) whether less than or equal to single Jump propagation delay time d_i, and single-hop packet submits expectation E (p) of rate and whether submits rate p more than or equal to single-hop packet_iIf, It is, then execution step S35；Otherwise, repeated execution of steps S32.

S35：Return forward node sequence π_j(F_i).

Above example only not limits the technical scheme described by patent of the present invention in order to patent of the present invention to be described；Cause Although this this specification has been carried out to patent of the present invention describing in detail with reference to each above-mentioned embodiment, this area It will be appreciated by the skilled person that still patent of the present invention can be modified or equivalent；And all are special without departing from the present invention The technical scheme of spirit and scope of profit and its improvement, it all should be covered in the right of patent of the present invention.

Claims (7)

1. a kind of reliable data transmission method towards multi-hop cognition radio net it is characterised in that methods described include with Lower step：

S100：Calculate the next-hop candidate forward node set F of current data packet sending node i_i, and determine set F_iInterior joint Preferential forwarding order；

S200：Based on step S100, described node i is to described set F_iIn each node broadcasts packet；

S300：Transmit described packet, and judge whether described packet sends successfully；

Wherein, described step S100 specifically includes following steps：

S101：Judge destination node D whether within the communication range of current data packet sending node i, if so, then node i is straight Connect and deliver a packet to destination node D；Otherwise, execution step S102；

S102：Described node i passes through CCCH to positive node set C_iIn node send routing request packet；

S103：Described set C_iIn node after receiving routing request packet, each to node i send route response bag；

S104：Node i calculates next-hop candidate's forward node set according to the nodal information obtaining in the route response bag receiving F_i, and determine set F_iThe preferential forwarding order of interior joint；

Wherein, calculate next-hop candidate forward node set F in described step S104_iComprise the following steps：

S1041：Initialization candidate forward node set F_i=φ；

S1042：Judge positive node set C_iWhether it is empty；If it is empty, then execution step S1045；

Otherwise, execution step S1043；

S1043：From positive node set C_iOne node of middle taking-up, this node is inserted into candidate forward node set F_iMiddle energy Make candidate forward node set F_iNode weights are expected, at the maximum position of E (ω), to obtain current forward node sequence π_j(F_i)；

S1044：Judge in current forward node sequence π_j(F_i) under expectation E (t) of single-hop transmission time delay whether be less than or equal to single-hop Propagation delay time constrains d_i, and single-hop packet submits expectation E (p) of rate and whether submits rate p more than or equal to single-hop packet_i；If It is, then execution step S1045；Otherwise, repeated execution of steps S1042；

S1045：Return current forward node sequence π_j(F_i), then current forward node sequence is next-hop candidate's forward node Set F_i；

The desired computing formula that in described step S1044, single-hop packet submits rate is：

$E\left(p\right)=1-{\mathrm{\&Pi;}}_{m=1}^n{\stackrel{\&OverBar;}{p}}_{{\mathrm{ij}}_m},E\left(p\right)\&GreaterEqual;p_i$

Expectation E (ω) computing formula of described node weights is：

$E\left(\mathrm{\&omega;}\right)={\mathrm{\&Sigma;}}_{k=1}^n\left({\mathrm{\&omega;}}_{j_k}{p}_{{\mathrm{ij}}_k}{\mathrm{\&Pi;}}_{m=0}^{k-1}{\stackrel{\&OverBar;}{p}}_{{\mathrm{ij}}_m}\right);$

WhereinM represents node j in candidate's forward node sequence π_j(F_i) in priority order, wherein priority Relation is：j₁＞ j₂＞ ... ＞ j_n；

Single-hop packet for from node i to node jm submits the predicted value of rate；

ω_jFor node weights；

Single-hop packet submits rate predicted value p_ijComputing formula be：

$p_{ij}=1-{\mathrm{\&Pi;}}_{k\&Element;CH(i,j)}^{CH(i,j)}{\stackrel{\&OverBar;}{\mathrm{\&xi;}}}_{ik}{\stackrel{\&OverBar;}{\mathrm{\&xi;}}}_{jk};$

Wherein

CH (i, j)=CH (i) ∩ CH (j), wherein CH (i) and CH (j) represent node i and the idle channel set of node j respectively； I, j represent node i and node j；K represents the idle channel k that node i and node j can use, wherein k ∈ CH (i, j)；ξ_ik Represent the idle probability of channel k in node i；ξ_jkRepresent the idle probability of channel k in node j；

The computing formula of expectation E (t) of single-hop transmission time delay described in described step S1044 is：

$E\left(t\right)={\mathrm{\&Sigma;}}_{k=1}^n\left(t_{{\mathrm{ij}}_k}{p}_{{\mathrm{ij}}_k}{\mathrm{\&Pi;}}_{m=0}^{k-1}{\stackrel{\&OverBar;}{p}}_{{\mathrm{ij}}_m}\right)+t_{{\mathrm{ij}}_n}{\mathrm{\&Pi;}}_{m=1}^n{\stackrel{\&OverBar;}{p}}_{{\mathrm{ij}}_m},E\left(t\right)\&le;d_i;$

Wherein：K, m, n each mean node j in candidate's forward node sequence π_j(F_i) in priority order；I refers to current data packet Sending node, jk, jm, jn are the candidate neighbor nodes of node i；Represent that from node i transmits packets to node jk statement Receive the prediction time delay used by packet；Represent that from node i transmits packets to node jn statement and receives used by packet Prediction time delay；

Described step S1043 node weights computing formula is

Wherein, α is factor of influence, α ∈ [0,1]；ψ(v_ij) andRepresent single-hop effective advanced speed V of packet respectively_ijWith Reliability r of node j_jValue after standardization, 0≤ψ (v_ij)≤1,

2. according to claim 1 method it is characterised in that described step S200 specifically includes following steps：

S201：According to described route response bag, calculate node i and set F_iIn each node j set of available channels CH (i, j)；

S202：Node i passes through in set of available channels CH (i, j) reliability highest channel to F_iIn each node broadcasts data Bag.

3. according to claim 2 method it is characterised in that described S300 specifically includes following steps：

S301：Data in described packet, in transmission, if primary user PU activity is detected, communication channel is switched To CH (i, j), the channel of reliability suboptimum is transmitted；

S302：If node i receives the ACK that certain next-hop candidate's forward node feedback is successfully received data, packet Send successfully；Otherwise, node i retransmits packet.

4. according to claim 1 method it is characterised in that in step S102 described forward direction node set C_iBy with Lower step obtains：

S1021：Take out the neighbor node set N of current data packet sending node i_iOne of node, according to the geographical position of node Confidence ceases, and calculates the deflection θ of this node；

S1022：Judge whether described deflection θ belongs to (0, pi/2), if it is, execution step S10221；Otherwise, execute step Rapid S10222；

S10221, this node is added to positive node set C_iIn；

S10222, steering next node, and execution step S1021 again.

5. according to claim 4 method it is characterised in that：

The computing formula of the deflection of described neighbor node is

In above formula,Represent from node i to the direction of advance vector of destination node D；

Represent from node i to the direction of advance vector of destination node j.

6. according to claim 1 method it is characterised in that：

The effective advanced speed computing formula of described packet single-hop is

Wherein,

θ is vectorWith vectorAngle；

${\stackrel{\&RightArrow;}{a}}_{ij}=(x_j,y_j)-(x_i,y_i),$

${\stackrel{\&RightArrow;}{a}}_{iD}=(x_D,y_D)-(x_i,y_i),$

Wherein：

Represent from node i to the direction of advance vector of destination node D；

Represent from node i to the direction of advance vector of destination node j；

I represents currently transmitted node, and j is the neighbor node of node i, and D represents destination node；(x_i, y_i) represent node i geography Coordinate；(x_j, y_j) represent node j geographical coordinate；(x_D, y_D) represent destination node D geographical coordinate；

t_ijRepresent that from node i transmits packets to the estimated time that node j statement receives this packet.

7. according to claim 1 method it is characterised in that

The neighbor node j Calculation of Reliability formula of described node i isStandardizing formula is

Wherein, N_cRepresent all available channel number of node j,ξ_jkRepresent the free time of channel k in node j Probability,u_jThe utilization rate of k channel k that j-th node monitors of () expression arrive, T is time window size, in the time In window, the channel k occupied time is t_busy；

r_jRepresent the reliability of node j, r_jK () represents the reliability of k-th channel of node j；C_iRepresent the positive adjacent of node i Occupy node set, | C_i| represent the positive neighbor node number of node i, r_kRepresent k-th neighbours' section in positive neighbor node set The reliability of point.