CN109068337A - For moving the Energy-aware time of opportunistic network up to drawing method - Google Patents
For moving the Energy-aware time of opportunistic network up to drawing method Download PDFInfo
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- H—ELECTRICITY
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Abstract
The Energy-aware time that the invention discloses a kind of for moving opportunistic network, up to drawing method, the parameter of Energy-aware time reachability graph was constructed including obtaining；To calculating initialization of variable；Energy-aware time reachability graph is carried out in the case where that can not carry out data transmission corresponding direct communication energy diagram and occasional transmission time diagram is calculated；Energy-aware time reachability graph is carried out in the case where that can only carry out data and directly transmit corresponding DIRECT ENERGY figure is calculated；Data are directly transmitted and indirect communication in the case where carries out Energy-aware time reachability graph corresponding DIRECT ENERGY figure is calculated can carry out；Indirect energy figure is carried out to all vertex and possible path, indirect energy figure is calculated；The size for comparing data in DIRECT ENERGY figure and indirect energy figure obtains least energy figure；Judge the accessibility of data transmission and obtains the data of Energy-aware time reachability graph.Objective science of the present invention plays a significant role the performance for improving mobile opportunistic network.
Description
Technical field
The Energy-aware time that present invention relates particularly to a kind of for moving opportunistic network is up to drawing method.
Background technique
With the development of economic technology, movement opportunistic network (Mobile Opportunistic Networks, MONs) is
Through gradually popularizing in people's production and life, certain convenience is brought to people's production and life.
Time-varying figure is one of the important models of mobile opportunistic network.In mobile opportunistic network, between every a pair of node
Link is dynamically, to lead to have different topological structures in different moments network.The opportunistic and system of dynamic link variation
The finiteness of energy, result in mobile opportunistic network has many unknown characteristics on network connectivty and accessibility.
Energy-aware time reachability graph (Energy-aware Temporal Reachability Graph, ETRG) is one
Kind has the important models of wide application prospect and closing to reality situation.But at present for Energy-aware time reachability graph's
Research is few, and not comprehensive enough applied to the performance evaluation of mobile opportunistic network for Energy-aware time reachability graph, is difficult
Connectivity and accessibility to dynamic mobile opportunistic network are checked immediately.
Summary of the invention
It is an object of the invention to propose a kind of Energy-aware time for moving opportunistic network up to drawing method, the party
Method can effectively improve the performance of mobile opportunistic network, and can demonstrate the effective of this method under network environment in true moving machine
Property.
This Energy-aware time for moving opportunistic network proposed by the present invention walks up to drawing method, including as follows
It is rapid:
S1. the parameter of building Energy-aware time reachability graph is obtained；
S2. the calculating variable used is needed to initialize building Energy-aware time reachability graph；
S3. Energy-aware time reachability graph is calculated in the case where that can not carry out data transmission, obtains this kind of feelings
Direct communication energy diagram and occasional transmission time diagram under condition；
S4. Energy-aware time reachability graph is calculated in the case where that can only carry out data and directly transmit, is somebody's turn to do
DIRECT ENERGY figure in the case of kind；
S5. Energy-aware time reachability graph is counted in the case where that can carry out data and directly transmit with indirect communication
It calculates, obtains the DIRECT ENERGY figure in the case of this kind；
S6. the calculating that indirect energy figure is carried out to all vertex and possible path, to obtain indirect energy figure；
S7. according to time and delay allowance, the DIRECT ENERGY figure that is respectively compared in indirect energy figure data it is big
It is small, and select wherein lesser data composition least energy figure；
S8. the size relation between the data and energy budget value in least energy figure obtained according to step S7, judgement
The accessibility of data transmission, and obtain the data of Energy-aware time reachability graph.
The calculating variable used is needed to initialize building Energy-aware time reachability graph described in step S2, specifically
It is 0 to enable all χ (e) and φ (e), wherein χ (e) is accumulation transmission time, and φ (e) is direct communication energy.
Energy-aware time reachability graph is calculated in the case where that can not carry out data transmission described in step S3, is had
Body is to be calculated using following rule:
Design conditions: δ < τ；
Calculating process: carrying out accumulation calculating to each delay allowance, obtains the transmission time all in δ < τ and directly
Energy, thus direct communication energy diagram and occasional transmission time diagram in the case of obtaining this kind.
Energy-aware time reachability graph is counted in the case where that can only carry out data and directly transmit described in step S4
It calculates, is specially calculated using following rule:
Design conditions: 2 τ of τ≤δ <
Calculating process: accumulation calculating is carried out to each delay allowance；Meanwhile for directly transmitting, using following formula
Calculate average energy:
κm(e)=φ (e)/χ (e)+Inf (χ (e) < τ)
κ in formulamIt (e) is average energy, φ (e) is direct communication energy, and χ (e) is accumulation transmission time, and Inf's () takes
Value rule are as follows: if χ (e2) < τ, then Inf (χ (e2) < T)=∞, otherwise Inf (χ (e2) < τ)=0；Exist simultaneouslyWithIt according to corresponding time point and time interval in figure, and finds corresponding data and is calculated, to obtain this kind of situation
Under DIRECT ENERGY figure.
It can to the Energy-aware time in the case where that can carry out data and directly transmit with indirect communication described in step S5
It is calculated up to figure, is specially calculated using following rule:
Design conditions: 2 τ≤δ < n η
Calculating process: the calculating for directly transmitting energy is carried out first, then passes through all roads between two vertex of traversal
Diameter, the smallest path of energy needed for selecting, carries out the calculating of indirect energy transmission.
It is specially the size of data compared in DIRECT ENERGY figure and indirect energy figure described in step S7, selects wherein smaller
Data form least energy figure.
Sentenced described in step S8 according to the size relation between the data and energy budget value in obtained least energy figure
The accessibility of disconnected data transmission and the data for obtaining Energy-aware time reachability graph, if the data specially in least energy figure are big
In energy budget value, illustrate that data transmission is unreachable, otherwise reachable, the final data for obtaining Energy-aware time reachability graph.
It is proposed by the present invention this for moving Energy-aware time of opportunistic network up to drawing method, disclose energy by
The reachable characteristic of the mobile opportunistic network of limit, and in system performance and energy, postpone, the power between three parameters of size of data
Weighing apparatus relationship.Result of study is extended to its corresponding energy, delay and these three dimensions of size of data, Neng Gouke by the present invention
Sight, the connectivity and size of data that mobile opportunistic network is scientifically disclosed under real network environment, transmission delay and energy disappear
Relationship between consumption plays a significant role the performance for improving mobile opportunistic network.The method of the present invention is simple, and efficiency is higher.
Detailed description of the invention
Fig. 1 is the method flow schematic diagram of the method for the present invention.
Fig. 2 is that the averaging network of 4 cities real vehicles track of the embodiment of the method for the present invention in a short time is reachable
Property characteristic schematic diagram.
Fig. 3 is average net of Beijing vehicle motion track of the embodiment of the method for the present invention within one day and one week time
Network accessibility feature schematic diagram.
The Shanghai vehicle motion track and SLAW mobility model that Fig. 4 is the embodiment of the method for the present invention are in different-energy budget
The relation schematic diagram of average asymmetrical characteristic and maximum traffic delay in the case of value.
The SLAW mobility model and Shanghai vehicle motion track that Fig. 5 is the embodiment of the method for the present invention are in different transmission delays
In the case of connective stability and energy budget value relation schematic diagram.
Fig. 6 is Beijing vehicle motion track of the embodiment of the method for the present invention in different energy budget values and size of data
In the case of network connectivty schematic diagram.
Fig. 7 is Beijing vehicle motion track of the embodiment of the method for the present invention in fixed energies estimated value and different delays feelings
Average connectivity under condition and the relation schematic diagram between size of data.
Fig. 8 is the Shanghai vehicle motion track of the embodiment of the method for the present invention in fixed delay and different-energy budget situation
Under average connectivity and size of data between relation schematic diagram.
Fig. 9 is the Shanghai vehicle motion track of the embodiment of the method for the present invention when keeping 60% bonding ratio, minimum
Relation schematic diagram between energy consumption and delay and size of data.
Specific embodiment
Figure is a kind of means for describing static network characteristic, and time-varying figure is that one kind is very suitable to describe mobile opportunistic network
The model of dynamic characteristic, therefore, time-varying figure can effectively study the connectivity and accessibility of mobile opportunistic network.Start to be situated between as follows
Basic symbol and meaning in the time-varying that continues graph model.
Define 1 (time-varying figure): V is a vertex set (set of nodes), | V |=N indicates that node number is N,Indicate the set on the side between V interior joint.Without loss of generality, node serial number is set as from 1 to N.Assuming that dynamic thing
Part occur time span beReferred to as Network morals, whereinIt is time domain, i.e., in discrete time network
'sOr in Continuous NetworkUsually with 5 tuplesTo indicate time-varying figure, in which:
Referred to as existence function (presence function) indicates a line in the time givenInside it whether there is.
Referred to as delay function (latency function) indicates to transmit one after given time starts
The time that passed through side needs is traversed when data unit.(delay of a line can change over time).
The technical solution of the application is directed to discrete time time-varying figure, i.e.,Furthermore about existence and potential
Property, it is extended by the way that two functions are added.It is extended to number of a line within given time respectively by the two functions
According to communication energy and transmitting continuous time.Given a line e=(u, v), definition arrive (e)=v from (e)=u.It then will be different
Side on time point combines, so that it may obtain the path between node.The definition in path is given below.
Define 2 (paths): the path in figure G refers to by volume of data to the sequence formed
Wherein { e1, e2..., ekIt is Yi Tiaolu in G.In addition
WithRespectively indicate pathAt the beginning of t1With end time tk+ζ(ek, tk), whereinPath
It is that over time, a series of accesses from source node to destination node are formed.ByThe topology jump of expression refers toQuantity；ByThe time span of expression refers to end-to-end delay, and expression formula is
Transmission timeIt is by least side in path come the time used when transmitting data.(It is to indicate from source node to end
The transmission delay of point, such as, often there are many different accesses from source node to terminal, that is, have different paths,Indicate the time that the least path transmitting data in side in these paths Jing Guo transfer needs)
In mobile opportunistic network, one multi-hop sequence of path representation, the data of time-varying figure are to reach purpose by source
End, therefore time-varying figure can be used to describe the accessibility of dynamic network.For the description that standardizes, useIt indicates in time-varying figure G
All possible set of paths,It indicates since node u, the path terminated to node v.If there is from node
U is to the path of node v, i.e.,So just say that node u can reach node v.It is obvious that path is not symmetrically to exist
, that is to say, that node u can reach node v and be not meant to that node v can reach node u.
Next, combined data communication energy and transmission time define Energy-aware time reachability graph (ETRG).Fixed
Justice is joined with before calculating ETRG, needing to introduce the communication energy needed in mutual data transmission between two nodes in time-varying figure
Number, this depends on communication distance and transmission time.Therefore, on the basis of defining 1, Energy-aware time variation diagram is provided first
(Energy-aware Time Varying Graphs, ETVG).
Define 3 (Energy-aware time variation diagrams): V indicates vertex set,Indicate the set on side between vertex,
Time span{ t is divided by identical time slot η1, t2... ti... }.Energy-aware time-varying figure is defined
For 5 tuplesWhereinIt is energy function, indicates in the timeIt is interior, benefit
With to energy required for deckle e ∈ E transmission data, that is to say, thatRefer in time tiIt is interior, side e
It is not present, and if κ (e, ti) < ∞ explanation in time tiInterior, side e exists, and needs to consume κ (e, ti) energy completes data
Transmission.Indicate time slot tiInterior, transmission time used in the part data transmitted by side e indicates
For θ (e, ti)=η or 0.Duration θ (e, ti)=η is indicated in time slot tiMiddle side e exists, so in transmitting continuous time η
That is time tiTo time tiCarried out data transmission in+η by side e.If θ (e, ti)=0 item indicates to be not available for data transmission.
Transmitting continuous time of communication energy and side in above-mentioned Introduction To The Definition time-varying graph model, Energy-aware is obtained
Time-varying figure ETVG, it is evident thatIf κ (e, ti)=∞, then θ (e, ti)=0.In fact, with regard to communication energy and
Speech, obtainable information is usually the position of node in a network, because transmission range and transmitting continuous time will affect communication
Energy, so setting model makes in time slot tiThe proportional relationship of transmission range between interior communication energy and two node u, v, i.e.,WhereinIt indicates in time slot tiInterior, node u, the distance between v, η are transmission times, and α is one
Constant.In fact, one in this communication functions for being only possible to, because based on different network and different it is assumed that will
There is different communication energy functions.Further, it usesIndicate byThe matrix of composition.In order to closer to now
It is real, it is assumed that transmission range has a limits value d0, in this case, when the distance on side | e | it is greater than d0When, definition transmission Infinite Energy
Greatly, transmission time is equal to 0, i.e.,So κ (e, ti)=∞ and θ (e, ti)=0.
It is not defined distance function herein, because the data set used is different, the calculating adjusted the distance can be also different.
Meanwhile because that adjusts the distance calculates fairly simple and has fixed method, it is possible to omit.However, the definition adjusted the distance
But it is necessary, because transmission range is limited in the mobile opportunistic network of reality.For each side at each moment,
Need to calculate the distance between every two o'clock.If distance is greater than transmission range, data cannot be transmitted therebetween.Only work as distance
When less than transmission range, transmission energy can be just calculated.
1 conventional sign list of table
Based on Energy-aware time-varying figure, the connection that can analyze the mobile opportunistic network for taking into account communication energy is special
Property.Besides the energy, key factor in need of consideration when size of data and delay allowance are also analysis connectivity.In time ti
And the transmission that delay allowance time is δ refers to that the transmission time started is ti, the end time is ti+δ.It is δ in delay allowance, and false
If transmission speed is fixed, size of data is indicated by data transmission period.When transmission speed is constant, the data of transmission are big
Small and transmission time is directly proportional.To put it more simply, with the time come replacement data size in calculating.And in order to allow model energy
Applied to different size of data, the average communication energy of each cell data in end to end communication is considered, it is by total energy
It is calculated divided by size of data.In the following, providing the definition of Energy-aware time reachability graph.
Define 4 (Energy-aware time reachability graphs): for δ ∈ n η, τ ∈ m ηIt enablesIt is an Energy-aware reachability graph, it is from Energy-aware time-varying figureIt is derived come out, ε is energy
Estimated value, δ are the maximum delays of data transmission, and τ is size of data.Formally,Use γ
(e)=1 it indicates, and if only if there are one from node u to the path of node vAnd it needs to meet
Herein, we make energy estimated value have versatility to figure, and this can't lose too many generality.Cause
For in fact, network node is usually identical type, for example is all automobile when considering the accessibility of time-varying network.In this way
One, node device and energy are substantially similar, and therefore, the energy budget value of different nodes will not be differed too
Greatly.
In order to transmit data from node u to node v, the transmitting continuous time of two nodes and energy budget value require full
The certain condition of foot.It is obvious that if δ < τ, Rε, δ, τIt is empty graph, because before maximum delay allowance time, Lian Dan
Path is jumped all to complete to transmit without enough time.Consider usual situation, when constructing Energy-aware time-varying figure, from a node to
Often there are two types of data transmission methods for another node.One is directly transmitting, node u is connected with node v, can directly transmit
Data.In this case, the topological hop count of data transfer path meetsAnother kind is indirect communication, i.e. node u
By one or more intermediate node, carried out data transmission using multihop path and node v.In this case, path is opened up
Flutter hop count satisfactionEnergy-aware time reachability graph in order to obtain requires all possible every a pair of of node
Directly or indirectly find the path constituted by least transmitting energy value in transmission path, and the path can meet simultaneously and allow to prolong
Slow requirement.If required minimum energy value is less than energy budget value ε, node u and node v are exactly reachable.Below
It will discuss respectively to direct transmission and indirect communication.
1) directly transmit situation: for directly transmitting, can obtained in the Energy-aware time-varying figure two it is most important
Parameter is transmission time and communication energy.It whether there is between any two node in fact, the two parameters directly determine
Path.Below by from the formal definition of transmission time and communication energy and stringent derivation, direct transmission situation is divided
Analysis.
Define 5 (occasional transmission time diagrams): forIt enablesIt indicates from energy sense
Know time-varying figureIn it is derived in time tiOccasional transmission time diagram, wherein V indicateIn node collection, side e=(u, v) ∈ E
Value with χ (e) indicate, refer to from time point tiTo tiThe total transmission time of+δ, node u to node v.
For occasional transmission time diagramχ (e) can be calculated by following formula:
Wherein I [] is indicator function, if κ (e, ti) < ∞, then I [κ (e, ti) < ∞]=η, otherwise I [κ (e,
ti) < ∞]=0.κ (e, ti) under expression formulaIt is the explanation of opposite side e, indicates κ (e, ti) in e be to belong to
,WithSimilarly.
As δ=η, data transfer delay is only a time slot, therefore when accumulative transmission time is the transmission in single-hop path
Between.So as transmission energy κ (e, the t of needsi) it is limited when, the accumulation transmission time on side is χ (e)=η, as κ (e, ti) it is nothing
In limited time, χ (e)=0.It, can be by by time slot t as δ ∈ n ηiTo time slot tiThe transmission time of+n η is added to obtain accumulation biography
The defeated time.It therefore can be by the way that transmission time addition be obtained result repeatedly.
Define 6 (direct communication energy diagrams): forWithTo indicate in time slot ti
Under by Energy-aware time-varying figureDerived direct communication energy diagram, wherein V isIn node collection, side e=(u, v) ∈ E's
Value indicates that it refers to through single-hop path by φ (e)In time slot tiTo tiIn+δ, passed between node u, v
Energy required for transmission of data.For direct communication energy diagramφ (e) can be by
Following formula calculates:
Similar with the calculating of occasional transmission time diagram, as δ=η, communication energy is just the communication energy of a time slot,
Therefore it only needs to provide the communication energy of current time slots, i.e. κ (e, ti).It, can be by by time t and for δ=n ηiTo ti+nη
Interior communication energy phase Calais obtains φ (e), therefore, can obtain this letter by being repeatedly added transmission energy
Number.Further, since κ (e, ti)=∞, if side e is in time tiIt is not present, in order to avoid φ (e)=∞, be multiplied by (κ (e,
ti) < ∞), then as κ (e, tiWhen)=∞, φ will add 0.
For any time slot ti, can derive direct transmission time figureWith direct communication energy diagramIts
Required transmission time and communication energy when respectively indicating two nodes by single-hop path transmission data.Then, for each
Average energy needed for single-hop path transmission in time slot can be calculated with communication energy divided by accumulation transmission time, will
It is defined as DIRECT ENERGY figure.
Define 7 (DIRECT ENERGY figures): forWithIt enables
It indicates in time ti, when delay allowance is δ, by Energy-aware time-varying figureDerived DIRECT ENERGY figure, wherein V isIn section
Point set, the value of side e=(u, v) ∈ E is by κd(e) it indicates, indicates in each time slot, node u and node v pass through single-hop pathDirectly transmit required average energy when data.
Formalization is expressed as
Wherein
Herein, Inf () is a function, as χ (e2) < τ when, Inf (χ (e2) < τ)=∞, otherwise Inf (χ (e2)
< τ)=0.
2) the case where for indirect communication, data biography indirect communication situation: will be able to satisfy between all possible two o'clock
The least path of average energy consumption is found out in the indirect path of defeated latency requirement, then exports indirect communication figure.
Define 8 (indirect energy figures): forIt enablesIt indicates in time ti, allow
When delay is δ, by Energy-aware time-varying figureDerived indirect energy figure, wherein V beIn node collection, side e=(u, v) ∈ E
Value by κi(e) it indicates, refers to passing through multihop path in each time slotWhat is needed when transmitting data is flat
Equal energy.
Define 9 (least energy figures): forEnable εδ(ti)=(V, E) it indicates in time ti, allow to prolong
When being late δ, by Energy-aware time-varying figureDerived least energy figure, wherein V beIn node collection, side e=(u, v) ∈ E's
Value is by κm(e) it indicates, refers to passing through all possible directly or indirectly path in each time slotWhen carrying out data transmission
Required least energy.
Lemma 1: forWithIndirect energy figure κi(e) it can be calculated by following formula:
As δ 2 τ of <, indirect communication, therefore κ is not presenti(e)=∞.As δ >=2 τ, there can be a variety of possible roads
Diameter, it is therefore desirable to consider all possible intermediate node and time-divided method.Due to that can have any number of intermediate nodes,
The different situations using some intermediate node must be taken into consideration.When in | V |=N has N-2 possible intermediate nodes (excluding u, v).
For the intermediate node w that each may be used, the first step of transmission, can be in time t from node u to node wiTo tiIn+l η
Occur, because of τ ∈ m η, m≤l≤d-m,.In contrast, the second step of transmission, from node w to node v, meeting is in the time
ti+ l η to tiOccur in+δ, l is same as above.Therefore, it is necessary to consider different l (m to d-m) and different w (1 arrives N, does not include u, v)
Under all situations result in above-mentioned formula to obtain needing the smallest path of average energy consumption.
ForWithLeast energy figure εδ(ti)=(V, E),κm
(e) it can be calculated by following formula:
As δ < τ, transmission, therefore κ is not presentm(e)=∞.As τ≤δ 2 τ of <, direct transmission, therefore κ are only existedm
(e)=κd(e), as δ >=2 τ, for every a pair of of node, the minimum value of average energy consumption is average energy when directly transmitting
Consumption and that lesser value in average energy consumption when indirect communication.
It now begins to calculate Energy-aware time reachability graph.Obviously, as δ < τ, transmission can not occur, because
ThisIt as τ≤δ 2 τ of <, only can occur directly to transmit, therefore be put down required for only needing to consider directly to transmit
Equal energy.If required DIRECT ENERGY is less than energy budget value, this can be carried out connecting to communicate to node.Work as δ
It when >=2 τ, directly transmits situation and indirect communication situation requires to consider, therefore use εδ(ti) replaceIn conjunction with upper
Analysis is stated, obtains following theorem 1.
Theorem 1: forTime energy reachability graphγ (e) can be calculated by following formula:
Based on definition before, currently proposed algorithm 1 obtains ETRG, parameter therein
Energy budget value is ε, and number of nodes is N.
Flow chart as shown in Figure 1: proposed by the present invention this Energy-aware of the Energy-aware time up to drawing method
The construction method of time reachability graph, includes the following steps:
S1. the parameter of building Energy-aware time reachability graph is obtained；
S2. the calculating variable used is needed to initialize building Energy-aware time reachability graph；It specially enables all
χ (e) and φ (e) be 0, wherein χ (e) be accumulation transmission time, φ (e) be direct communication energy；
S3. Energy-aware time reachability graph is calculated in the case where that can not carry out data transmission, obtains this kind of feelings
Direct communication energy diagram and occasional transmission time diagram under condition；Specially calculated using following rule:
Design conditions: δ < τ；
Calculating process: carrying out accumulation calculating to each delay allowance, obtains the transmission time all in δ < τ and directly
Energy, thus direct communication energy diagram and occasional transmission time diagram in the case of obtaining this kind；
S4. Energy-aware time reachability graph is calculated in the case where that can only carry out data and directly transmit, is somebody's turn to do
DIRECT ENERGY figure in the case of kind；Specially calculated using following rule:
Design conditions: the τ of τ≤δ < 2；
Calculating process: accumulation calculating is carried out to each delay allowance；Meanwhile for directly transmitting, using following formula
Calculate average energy:
κm(e)=φ (e)/χ (e)+Inf (χ (e) < τ)
κ in formulamIt (e) is average energy, φ (e) is direct communication energy, and χ (e) is accumulation transmission time, and Inf's () takes
Value rule are as follows: if χ (e2) < T, then Inf (χ (e2) < τ)=∞, otherwise Inf (χ (e2) < τ)=0；Exist simultaneouslyWithIt according to corresponding time point and time interval in figure, and finds corresponding data and is calculated, to obtain this kind of situation
Under DIRECT ENERGY figure；
S5. Energy-aware time reachability graph is counted in the case where that can carry out data and directly transmit with indirect communication
It calculates, obtains the DIRECT ENERGY figure in the case of this kind；Specially calculated using following rule:
Design conditions: 2 τ≤δ < n η
Calculating process: the calculating for directly transmitting energy is carried out first, then passes through all roads between two vertex of traversal
Diameter, the smallest path of energy needed for selecting, carries out the calculating of indirect energy transmission；
S6. the calculating that indirect energy figure is carried out to all vertex and possible path, to obtain indirect energy figure；
S7. according to time and delay allowance, the DIRECT ENERGY figure that is respectively compared in indirect energy figure data it is big
It is small, and select wherein lesser data composition least energy figure；Specially compare the number in DIRECT ENERGY figure and indirect energy figure
According to size, wherein lesser data form least energy figure for selection；
S8. the size relation between the data and energy budget value in least energy figure obtained according to step S7, judgement
The accessibility of data transmission, and obtain the data of Energy-aware time reachability graph；If the data specially in least energy figure are big
In energy budget value, illustrate that data transmission is unreachable, otherwise reachable, the final data for obtaining Energy-aware time reachability graph.
Performance verification is carried out to the method for the present invention below in conjunction with specific embodiment:
The formal definitions of Energy-aware time reachability graph are completed in front, and propose the algorithm effectively calculated, existing
By the way that energy budget value, delay allowance, size of data etc. carries out different settings to study Energy-aware time reachability graph
The performance of mobile opportunistic network is influenced, correlative study includes: Energy-aware time reachability graph ETRG proposed by the invention is
How the connectivity of time-varying mobile opportunistic network is characterized according to time phenomenon, stability and asymmetry, and how in net
Weighed between the network metric values such as network connectivity, energy budget value, tolerable delay and size of data.
A. data set and matrix
There are many reachable graphs on mobile network's public data collection at present, however, the present embodiment will be based on four cities
City's real vehicles motion track and a mankind mobility model SLAW (Self-similar artificially synthesized being widely recognized as
Least Action Walk) verify performance.
Vehicle motion track: it is well known that vehicle network is the mobile opportunistic network of typical case formed by mobile vehicle.Cause
This present invention will apply proposed Energy-aware time reachability graph in move vehicle.Research is mainly for Shanghai and Beijing two
The real vehicles motion track in a city, record are loaded with the location information of GPS device vehicle.Specifically, the vehicle in Shanghai
Motion track is the running track of about 2100 operation taxis of Shanghai City 2 months in 2007, is moved collecting Pekinese's vehicle
When dynamic rail mark, the motion track day of whole month in May, 2,010 27,000 Beijing Taxi Industry for carrying GPS receiver has been used
Will.Place and the timestamp of taxi are namely collected using GPS device, and per minute using GPRS model come to
The record of mobile vehicle is reported.Pekinese's vehicle motion track is available maximum track of vehicle data set.
Mankind's motion track: two human motion tracks have been used, KAIST motion track and Orlando moving rail are passed through
Mark shares the mobile community network formed to capture the chance vision by the short-range communication interface of mobile device.KAIST be
It is collected in the campus of the Institute Of Science And Technologies such as South Korea's height of Taejon city, Korea, by using Garmin GPS 60CSx
Handheld device records GPS track, and this GPS device position precision within 95% time is less than 3m.More specifically,
The every 10s of GPS device reads its current location, and positional value is recorded in daily trace logs.The GPS track of Orlando is
It is obtained on Orlando Disney World website, mainly between Thanksgiving Day or Christmastime, volunteer is in Disney World
The movement track of generation, for these participants mainly in park walking, occasional takes electric car.
SLAW mobility model: typical set value is used to mobility model SLAW, i.e. movable length and time out is distributed
Levy index is set as 1, and minimum time out is set as 30s, and longest time out is set as 3,600s, and boundary condition is set as
It surround, analog network region is 5000 × 5000m2。
2 data set situation of table
Table 2 summarizes the five kinds of motion tracks and relevant parameter situation that experiment is used, it can be seen that the data of selection cover
Range is wide, and data source is from the intensive place of number (SLAW) to the relatively sparse campus of number (KAIST), and there are also parts
City (Orlando, Shanghai and Beijing).The size and delay allowance of data are set in emulation experiment, in large-scale data
It has chosen representative and studies to solving practical problems significant data.
It is recorded based on these by GPS device or the individual sports of model generation is formed by motion track, to every group of number
According to being sampled with a fixed frequency η=10s to mobile data collection.In each sampling time slot n η, to all sections
The network that point is formed is modeled, and G (n η)=(V (n η), E (n η)), wherein V (n η) is the node collection in data set, and E (n η) is
The existing side in sample time n η.It is obvious that E (n η) depends on the RF signal propagation model used, assume it is to use herein
Simple unit circle model.In fact, the complexity of data analysis can be greatly reduced in unit circle model, can also obtain
Take the average behavior of network.In data set processing, 50m is set by the mobile unit circle communication range of the mankind, vehicle moves
Dynamic communication range is set as 250m, and then the energy of setting transmission consumption and transmission range are proportional.That is if
Data are transferred to node B, transmission range dm, transmission time ts from node A, then the energy consumed is then dt.It is calculating
After the energy of complete all sample graph G (n η), just integrate them to obtain Energy-aware time reachability graph.Then this is utilized
The method of invention calculates Energy-aware time reachability graph.
Followed by one reachability graph's matrix of research, related definition and calculation method are as follows:
Network reachability: network reachability is all possibility between the quantity and network node on side in reachability graph in time t
Side quantity average ratio.Accessibility has measured the connectivity of nodes in a period of time, therefore the company of can also be used
The ratio connect pair indicates the measurement of average accessibility, and accessibility, which is recognized as, refers to connectivity.
Accessible stationary points: accessible stationary points refer to the mean change of network reachability, by the number for calculating the side being connected
The variation ratio of amount and obtain.
Average asymmetry: when asymmetry is time t, asymmetric node pair and at least section of a line in reachability graph
Ratio of the point between.Asymmetry can be carried out by time value average to obtain average asymmetry.For real network
For, transmission is unidirectional or two-way extremely important.For transmitted in both directions, it is only necessary to support transmission two paths, without
Whether path itself is symmetrical.In order to characterize the accessibility feature of network, asymmetry preferably is obtained from the angle in path, because
When only to there is path, transmission just can be carried out.
B. the connection attribute of mobile opportunistic network is disclosed
The dynamic change of reachability graph is it is emphasised that move the time response of opportunistic network, and moving opportunistic network is by moving
Trajectory extraction go out original time-varying figure at.The present invention utilizes proposed Energy-aware reachability graph, respectively averagely reachable
Property, stability and asymmetry etc. disclose the connection characteristic of mobile opportunistic network.
1) time connectivity: time connectivity (accessibility) shows the ability of mobile network, that is, is giving fixed number
According to size, in the case where maximum allowable delay and energy budget value, whether a node can complete the number to another node
According to transmission, the communication boundary of this and network is relevant.This be also mobile opportunistic network it is most important be also most basic attribute it
One.On the other hand, the attribute easily can be obtained by the Energy-aware time reachability graph proposed and it is carried out
Research.Dynamic connection characteristic can be observed in a shorter period first, then shows it one day and one week respectively
Time in connectivity situation of change.
The averaging network reachability characteristic of 4 cities real vehicles track in a short time is illustrated on Fig. 2 (a)-(d).
For mankind's motion track, Fig. 2 (a) illustrates the average connection of the track KAIST according to the time, at different-energy budget ε
Property, due to the regular movement of the mankind, the ratio connected pair changes always quickly.The connection of Orlando shown in Fig. 2 (b)
Property it is almost unchanged after t > 70s, this is because t > 70s posterior nodal point movement tail off.Simultaneously as can be seen that when budget energy is reduced
When, average connectivity declines quickly, but variation tendency is but held essentially constant.For KAIST, when energy budget value is 20
When, the average proportions connected pair are only 25% or so.When energy budget value increases to 150, connection than rising to 90%, and
Maximum ratio nearly reaches 100%, that is to say, that all nodes are all connections.This two tracks, which are also shown, not to be considered to pass
The case where delivery of energy amount, that is, ε=∞.If the result of (a) can be seen that the energy value in KAIST budget and reach 150 according to fig. 2,
System has nearly reached the maximum boundary of performance.That is, remaining all possible enough using the energy value of this budget
Network connection.However for Orlando, just shown as shown in Fig. 2 (b), 150 energy value is not enough to reach this effect.At these
In the case of, since energy is not limited, data can be carried out in mobile opportunistic network by various paths that may be present
Transmission, it represents the boundary of the communication capacity of mobile opportunistic network.Energy-aware time reachability graph proposed by the present invention also can
The limitation for directly giving communication capacity, the average connectivity in a given time slot are exactly equal in optimal opportunistic routing protocol
Under maximum transfer rate, the delay allowance of opportunistic routing protocol at this time is δ, and data transmission period τ is equivalent to size of data.
In addition to the mobile mobile opportunistic network formed of the mankind, the present invention also studied Shanghai and Pekinese's vehicle opportunistic network
Dynamic characteristic.The result in Shanghai is shown in Fig. 2 (c).It can be seen from the chart for track of vehicle, influenced by energy budget value
It is more obvious.When energy budget value is 100, network can only maintain about 25% connection pair.However when energy budget value is super
When 300, network can maintain about 60% connection pair, this is few when being only infinitely great than optimal cases, that is, energy estimated value
15%.Simultaneously it is observed that when energy budget value is up to 500, performance bounds of the Dynamic link library characteristic very close to network.This
Illustrate in the transmission of most of data, consumed energy is less than 500.Fig. 2 (d) shows Pekinese's track of vehicle figure, it
With Dynamic link library characteristic similar with Shanghai, therefore also available identical conclusion.But Pekinese connects sex ratio ratio
Shanghai wants lower, this is because the vehicle moving range in Beijing selection is wider than Shanghai.
Result above not only can reveal that the Dynamic link library characteristic of different types of mobile opportunistic network, can also be by more
Systematic research shows the long-time evolution condition of network connectivty, in order to reach this purpose, has selected have maximum move
Beijing of dynamic rail mark is studied, and shows according to one day and one week time the ratio situation of connection pair respectively, such as
Fig. 3 (a) and (b) are shown.For one day connectivity, it can be seen that the connection ratio on daytime is higher than at night.Reason is very bright
Aobvious, vehicle is more frequent in movement on daytime.At night, from 9 points to 5 points of morning, because most of vehicles are all at a stop in city, institute
It can be reduced with connectivity.Since 5:00 AM, connectivity is just always maintained at growth, it can be seen that daytime there are two peak period, one
It is a be 7 points to 9 people of the morning on the way to work, the other is afternoon 5 points to 7 people come off duty road on, the two times
Section, traffic is most congestion, therefore is also most intensively that connectivity is strongest by the opportunistic network that vehicle is formed.And for one week
For, it can be found that similar situation occurs repeatedly daily, especially in energy larger (ε=200) or without energy limit
When (ε=∞).Specifically, it can be found that connectivity can be 0 to 40% under lesser energy budget value (ε=100)
Between rapidly alternately change.Because in this case, the performance of opportunistic network can due to lesser energy budget value and compared with
Short delay allowance and larger impact by connectivity.However if energy value is increased (ε=200), the company on daytime
The general character has just reached 40% to 60%, this means that the node of half can be connected with each other, with when communication boundary (ε=∞) only
Difference 20%.And at night, even if energy is infinitely great, connectivity also can be very poor.By the comparisons of these results it can be concluded that, it is right
In opportunistic communication system, mobile connectivity and the data transmission to network of daily vehicle is extremely important.The above performance point
Analysis discloses the daily routines of the mankind and vehicle are how to influence the connectivity of vehicle opportunistic network.
2) asymmetry: actual opportunistic communication system prefers symmetrically to connect, that is, node u and node v can be mutually
Transmit data.Existing many researchs symmetrical connection of concern mostly, and contact interval time and duration of contact are too paid close attention to,
And ignore asymmetry.In fact, asymmetry is an importance of opportunistic communication, is in mobile opportunistic network
It cannot ignore.Energy-aware time reachability graph proposed by the invention is capable of providing a kind of nature and quick method to study
And quantify the asymmetry of mobile opportunistic network.On the one hand asymmetrical characteristic is analyzed by the vehicle motion track in Shanghai.Separately
On the one hand, other than real-life motion track, performance verification also is carried out using SLAW mobility model.
It is that the vehicle motion track in Shanghai is average asymmetric special in different energy budget values shown in Fig. 4 (a)
The relationship of property and maximum traffic delay.As can be seen that when energy budget value increase when, the asymmetry of network have it is increased become
Gesture, because in biggish energy budget value, a possibility that long distance transmission, just be will increase.When energy budget value is from 300
When increasing to 500, asymmetry connection increases 50%.In addition, the asymmetry of network first increases when transmission delay δ increases
After reduce, and this phenomenon is not by the constraint of energy budget value.The potential cause of this phenomenon is the master in network when δ very little
If directly transmitting, asymmetry is very low at this time.In this case, increasing δ is mainly not have before will increase between node
Path, and these it is increased connection it is often indirect.Since δ is merely added a bit, so new indirect path is general
It is unidirectional, then asymmetric connection ratio just will increase.And when δ is sufficiently large, transmitted in both directions is easier to occur, increased δ
Mainly it will increase the path having existed between the node of connection, so many one-way transmissions can become transmitted in both directions, it is asymmetric
Property also just therefore reduce.
In order to verify observed asymmetrical characteristic, under the mobility model of SLAW to a relatively large network into
Simulation is gone.It is the average asymmetry figure under SLAW mobility model shown in Fig. 4 (b).As can be seen from the figure similar existing
As that is, when energy budget value increases, the asymmetry of network also be will increase.When energy budget value increases to 40 from 30, no
Although symmetrical pair increased relatively small, 20% is also increased.In addition, asymmetry takes place mostly in δ in 10s to 30s
When variation.When δ is less than 10s, only directly transmission can occur, therefore there is no asymmetric transmission.When δ is greater than 30s
When, delay is sufficiently large, so that within delay time, when a node i finds the path of an arrival node j, section
Point j can also find the path of an arrival node i.
Above-mentioned analysis discloses in mobile opportunistic network, the variation of energy budget value and delay allowance to opportunistic communication not
The influence of symmetry characteristic.On the whole, sufficiently large energy budget value can be enhanced the asymmetry of communication, and delay allowance
Increase can then generate different influences to it.
3) stability: asymmetry describes the variation of connectivity between node pair, and stability can then measure connection
Property produces how many variation as time goes by, this also characterizes the communication capacity of mobile opportunistic network on the other hand.With not
Symmetrical analysis is similar, and the stability of connection is also studied with Shanghai vehicle motion track and SLAW model.Fig. 5 (a) is presented
Stability (average rate of change of connectivity) under the track SLAW.When energy budget value increases, mean change takes the lead in will increase,
When energy budget value is after increasing above some value, the average rate of change can be reduced.As delay δ=20s, energy budget value is from 10
When increasing to 80, mean change takes the lead in increasing general 200%, and then energy budget value continues to rise to 200, and the average rate of change is just
65% can be reduced.In fact, the variation of connectivity is caused caused by the unreliability in path as movement.When energy budget value very
Hour, transmitting data between nodes are mainly to pass through the less short path of hop count to carry out, and data transmission only can be by a small amount of several
Node.So a possibility that path disappears when node motion is smaller.When energy budget value increases, the machine of multihop path transmission
It can increase, will also connect more nodes, so path is also just more likely to the influence by node motion.When energy budget value
When increasing to sufficiently large, almost there is path between each pair of node, at this moment connectivity variation can be slack-off, because of road that can not be all
Diameter all disappears simultaneously.Further, it is also possible to observe that connectivity variation is slack-off when postponing to increase, this is because possible path increases
Add.When δ increases to 50 from 20, the average rate of change of connectivity reduces 30%.
Fig. 5 (b) is the connection implementations of Shanghai vehicle motion track.It can be seen from the figure that when energy budget value increases
When, the average rate of change increases quickly.As δ=140s, energy budget value from 200 increase to 600 when, the average rate of change increases greatly
About 300%.The variation of actually connectivity is mainly caused caused by the unreliability in path as node motion.Work as energy budget
When being worth smaller, mainly carried out data transmission by short distance path between node, contain only a few node, so when section
When point is mobile, a possibility that path disappears, is little.With the increase of energy budget value, multi-hop transmission becomes more, so in path just
More nodes can be connected, so path is influenced to become larger by node motion.
Network connectivty and energy budget value are directly observed and analyzed to the above research by Energy-aware time reachability graph,
Relationship between delay allowance discloses the dynamic connectivity and stability of two mobile opportunistic networks.Due to different types of
Moving machine meeting network has different performances under Move Mode, so its connectivity is affected by node motion.In difference
Move Mode under, although the movement of node will produce a very large impact the connectivity of network, can pass through increase energy
Estimated value or delay allowance are measured to weaken this influence.
C. the performance tradeoff of opportunistic network is moved
It is proved and demonstrates Energy-aware time reachability graph proposed by the present invention to can reveal that mobile opportunistic network above
Connectivity, stability and asymmetry.Importantly, it can disclose size of data, delay allowance, the reality such as communication energy
Restriction effect of the system parameter to communication capacity.When considering these limitations, a basic problem be these parameters with
How to be weighed between system performance.When the reality system demand for providing a mobile opportunistic network, i.e. size of data, transmission
When than, delay allowance, transmission energy, the Energy-aware time, reachability graph needed to consider following problems: this movement opportunistic network can
To support this service? need how to weigh between system requirements and could support this service? Energy-aware will be utilized below
Time reachability graph discloses how under the extensive situation of change of network to metric parameter energy budget value, delay allowance and data
Size is weighed connectivity and accessibility to guarantee system, superfluous to reduce using Shanghai and Pekinese's vehicle motion track
It is remaining.
Fig. 6 (a) and (b) are illustrated respectively under different delay allowance and data size cases, average connectivity and energy
Relationship between budget.It can be seen from the figure that system connectivity is kept substantially when energy value is in the range of 400-500
Constant, this energy budget value of explanation within this range has reached communication boundary.In fact, herein, averaging network connection
Property is equivalent to data transmission ratio example.It can be seen directly that, Beijing vehicle motion track is formed by mobile opportunistic network from figure
Whether can support some there is under energy budget value, delay allowance or size of data limited conditions the transmission ratio demand to be
System, can also be observed that the performance tradeoff between energy budget value and delay allowance or size of data.It can in Fig. 6 (a)
To see, if transmission ratio is required to be greater than 70%, the smallest delay allowance of data should be greater than 360s.But if only
It is intended to transmission ratio and reaches 50%, then ε=140, δ=360 or ε=350, δ=250 can meet.And in Fig. 6
(b) in, if size of data is greater than 160, transmission ratio can not be higher than 50%.From curve as can be seen that if passing through
The data of compression transmission reduce size of data, so that it may save energy consumption for system.From this figure it can be seen that passing through increasing
Big transmission delay reduces size of data how many gain can be obtained from energy budget value.In practical applications, Ke Yican
It examines these curves and comes design vehicle opportunistic network and application plan.
In order to observe the trade-off relationship between size of data and delay allowance, it is assumed that energy budget value ε=300, not
Under same delay allowance, the change curve between average connectivity and size of data is drawn, as shown in Figure 7.It can from Fig. 7
Out, (it is less than 120s) when delay allowance is relatively small, data transmission rate is below 20%.Influence of the size of data to performance has
Limit.When delay allowance increases to 360s, if the size for transmitting data can be compressed to 40s from 320s, that transmission rate is just
60% can be increased from 20%.It further demonstrates needs and makes tradeoff in network design.For example, only when transmission
When postponing sufficiently large, the compression of data is just obvious.In addition, that can also transmit bigger if can increase transmission delay
Data.In short, the rule that can be disclosed according to curve in figure, is weighed to reach desired system performance.
Fig. 8 be in the case where delay allowance δ=100s energy budget value is different, average connectivity and size of data it
Between relationship.It can be seen from the figure that average connectivity is reduced quickly, when size of data increases from 10s when size of data increases
When being added to 50s, average connectivity reduces about 30%.On the contrary, connection comparative example also will increase when energy budget value increases,
Energy budget value increases to 300 from 100, and the ratio connected pair increases about 100%.And can see, when energy is pre-
When calculation value reaches 500, system is already close to optimum performance.Usually, a higher connectivity is maintained if necessary to network,
Then size of data cannot be arranged too big, because connection logarithm drops quickly now when size of data increases.Similar,
In the case where keeping connectivity constant, increasing energy budget value also will increase maximum data size.
Fig. 9 illustrates in the performance metric index for reaching specific connectivity that (Shanghai vehicle motion track keeps 60%
Connection ratio), energy ε, the trade-off relationship between delay allowance δ and size of data τ.In the case of, for τ=30s, if
Delay is less than 90s, that is much regardless of energy has, and the ratio connected pair is impossible to reach 60%.Therefore only give δ > 90s's
Situation.When postponing δ increase, minimal consumption energy is reduced, especially when size of data τ is larger.For τ=30s, when δ=
When 90s, minimal consumption energy is about 550.When δ increases to 140s, consumption energy reduces 60%, becomes 220.It is similar
, if energy increases to 550 from 220, that minimum delay just needs to reduce 35%.It is big in different data for δ=100
In small situation, it can be seen that when size of data is reduced to 10s from 30s, the energy of consumption reduces 55%.Usually, most
Big delay allowance is a finite value δ.In order to obtain preferable connectivity, need for ability estimated value to be arranged enough to big.Together
Sample, if energy budget value is smaller, that just needs to tolerate that delay increases to meet preferable connectivity.
Different delay allowances, size of data and energy budget value pair are disclosed above by Energy-aware time reachability graph
The performance of mobile opportunistic network influences and trade-off relationship, to handle energy in actual mobile opportunistic network, size of data and
The trade-off problem of delay allowance provides useful information.
Claims (6)
1. a kind of Energy-aware time for moving opportunistic network up to drawing method, includes the following steps:
S1. the parameter of building Energy-aware time reachability graph is obtained；
S2. the calculating variable used is needed to initialize building Energy-aware time reachability graph；
S3. Energy-aware time reachability graph is calculated in the case where that can not carry out data transmission, in the case of obtaining this kind
Direct communication energy diagram and occasional transmission time diagram；
S4. Energy-aware time reachability graph is calculated in the case where that can only carry out data and directly transmit, obtains this kind of feelings
DIRECT ENERGY figure under condition；
S5. data are directly transmitted and indirect communication in the case where calculates Energy-aware time reachability graph can carry out,
Obtain the DIRECT ENERGY figure in the case of this kind；
S6. the calculating that indirect energy figure is carried out to all vertex and possible path, to obtain corresponding indirect energy figure；
S7. the size of data in the DIRECT ENERGY figure and indirect energy figure being respectively compared, and select wherein lesser data
Form least energy figure；
S8. the size relation between the data and energy budget value in least energy figure obtained according to step S7, judges data
The accessibility of transmission, and obtain the data of Energy-aware time reachability graph.
2. the Energy-aware time according to claim 1 for moving opportunistic network is up to drawing method, it is characterised in that
It needs the calculating variable used to initialize building Energy-aware time reachability graph described in step S2, specially enables all
χ (e) and φ (e) be 0, wherein χ (e) be accumulation transmission time, φ (e) be direct communication energy.
3. the Energy-aware time according to claim 2 for moving opportunistic network is up to drawing method, it is characterised in that
Energy-aware time reachability graph is calculated in the case where that can not carry out data transmission described in step S3, is specially used
Following rule is calculated:
Design conditions: δ < τ；
Calculating process: accumulation calculating is carried out to each delay allowance, obtains the transmission time all in δ < τ and direct energy
Amount, thus direct communication energy diagram and occasional transmission time diagram in the case of obtaining this kind.
4. the Energy-aware time according to claim 3 for moving opportunistic network is up to drawing method, it is characterised in that
Energy-aware time reachability graph is calculated in the case where that can only carry out data and directly transmit described in step S4, specially
It is calculated using following rule:
Design conditions: 2 τ of τ≤δ <；
Calculating process: accumulation calculating is carried out to each delay allowance；Meanwhile for directly transmitting, calculated using following formula
Average energy:
κm(e)=φ (e)/χ (e)+Inf (χ (e) < τ)
κ in formulamIt (e) is average energy, φ (e) is direct communication energy, and χ (e) is accumulation transmission time, the value rule of Inf ()
Then are as follows: if χ (e2) < τ, then Inf (χ (e2) < τ)=∞, otherwise Inf (χ (e2) < τ)=0；Exist simultaneouslyWithFigure
It is middle and to find corresponding data according to corresponding time point and time interval and calculated, thus straight in the case of obtaining this kind
Connect energy diagram.
5. the Energy-aware time according to claim 4 for moving opportunistic network is up to drawing method, it is characterised in that
Energy-aware time reachability graph is carried out in the case where that can carry out data and directly transmit with indirect communication described in step S5
It calculates, is specially calculated using following rule:
Design conditions: 2 τ≤δ < n η
Calculating process: the calculating for directly transmitting energy is carried out first, then passes through all paths between two vertex of traversal, choosing
The smallest path of required energy is selected, the calculating of indirect energy transmission is carried out.
6. the Energy-aware time according to claim 5 for moving opportunistic network is up to drawing method, it is characterised in that
Judge that data pass according to the size relation between the data and energy budget value in obtained least energy figure described in step S8
Defeated accessibility and the data for obtaining Energy-aware time reachability graph, if to be greater than energy pre- for the data specially in least energy figure
Calculation value illustrates that data transmission is unreachable, otherwise reachable, the final data for obtaining Energy-aware time reachability graph.
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