CN107046655B - Mobile crowd sensing method and system - Google Patents
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Abstract
The application discloses a mobile crowd sensing method and a system, wherein the method comprises the following steps: screening all grid units which are uniformly and vertically in sufficient sensing coverage within a preset time span from the target sensing area to obtain a corresponding target grid unit set; screening out a mobile node subset which can meet the sensing coverage requirements of all grid cells in a target grid cell set in each coverage period from the mobile node set; merging all mobile node subsets corresponding to all coverage periods to obtain a target mobile node set; and carrying out crowd sensing by utilizing the target mobile node set. According to the method and the device, under the condition that sufficient coverage of the grid units is ensured, the number of the mobile nodes for sensing data sampling in each coverage period is reduced, and therefore sampling redundancy and energy loss in the crowd sensing process are effectively reduced.
Description
Technical Field
The invention relates to the technical field of crowd sensing, in particular to a mobile crowd sensing method and system.
Background
The mobile crowd sensing is a novel sensing mode, sensing devices such as a GPS (global positioning system), a microphone and a camera which are embedded in intelligent mobile equipment are utilized to efficiently collect sensing data, then the sensing data are sent to a remote sensing platform through a cellular mobile network (3G/4G) or WiFi, the sensing platform can carry out data cleaning on collected sensing data, and the data are stored in a database and analyzed and mined, so that good decision support is provided for service application of an upper layer, and further universal service is provided for users. The participation of mobile users is one of the most important characteristics of mobile crowd sensing, and the mobile characteristics of mobile users also provide unprecedented opportunities for sensing coverage and data transmission.
Coverage is typically used to represent the perceived quality of mobile crowd-sourcing perception, where coverage is of some unique nature, and above all, it is spatio-temporally related, e.g., the air quality somewhere in a monitored area at a time can represent the air quality of its neighborhood over a certain time frame, and thus mobile crowd-sourcing perception typically only requires that a sub-area be periodically covered, rather than every point in the sub-area being covered at all times. Second, as people often move around in the vicinity of some hot areas, it may result in better coverage in the hot areas than in other areas. Moreover, different nodes may contribute differently to coverage due to their respective diverse mobility areas. Finally, if and only if a mobile node samples a sub-area, the sub-area is considered to be covered really, and therefore the coverage is associated with the sampling frequency of the mobile node, and frequent sampling will make the area covered with a greater probability, but will also cause excessive energy consumption, thereby reducing the enthusiasm of the mobile user in participating in the information provision and further affecting the application quality of the mobile crowd sensing.
Currently, mobile crowd sensing applications generally utilize a certain incentive mechanism to attract mobile users to participate in a task of mobile crowd sensing, and in the process, a part of mobile users with less contribution to sensing coverage also participate in the sensing task, so that sampling redundancy and unnecessary energy consumption are caused.
In summary, it can be seen that how to reduce the sampling redundancy and the energy consumption in the crowd sensing process is still a problem to be solved.
Disclosure of Invention
In view of the above, the present invention provides a mobile crowd sensing method and system, which can effectively reduce sampling redundancy and energy consumption in the crowd sensing process. The specific scheme is as follows:
a mobile crowd-sourcing awareness method, comprising:
screening all grid units which are uniformly and vertically in sufficient sensing coverage within a preset time span from the target sensing area to obtain a corresponding target grid unit set;
screening out a mobile node subset which can meet the perception coverage requirements of all grid units in the target grid unit set in each coverage period from a mobile node set;
merging all mobile node subsets corresponding to all coverage periods to obtain a target mobile node set;
and carrying out crowd sensing by utilizing the target mobile node set.
Optionally, the process of screening all grid units that are uniformly and constantly in sufficient sensing coverage within a preset time span from the target sensing area includes:
calculating the coverage sufficiency of each grid unit of the target sensing area in each coverage period of the preset time span;
and screening all grid units with the coverage fullness greater than a preset fullness threshold in all coverage periods of the preset time span from the target sensing area to obtain the target grid unit set.
Optionally, the process of screening out, from the mobile node set, a subset of mobile nodes that can meet the perceived coverage requirement of all the grid cells in the target grid cell set in each coverage period includes:
step A1: screening out a mobile node subset which can meet the sensing coverage requirements of all grid units in the target grid unit set in the ith coverage period from the current mobile node set, wherein i is a positive integer;
step A2: deleting the mobile node subset corresponding to the ith coverage period from the current mobile node set to obtain a new mobile node set;
step A3: and adding 1 to the value i to update the value i, judging whether the current value i is greater than the preset total number of coverage cycles, if so, ending, and if not, re-entering the step A1.
Optionally, step a1 specifically includes:
and screening out a mobile node subset which can meet the sensing coverage requirements of all grid units in the target grid unit set in the ith coverage period from the current mobile node set based on a greedy strategy.
Optionally, the process of performing crowd sensing by using the target mobile node set specifically includes:
step B1: in the jth coverage period, carrying out crowd sensing by using a mobile node subset corresponding to the jth coverage period, and reducing the sampling times of the mobile nodes in the coverage period based on a cooperative sensing mechanism among different mobile nodes, wherein j is a positive integer;
step B2: and adding 1 to the j value to update the j value, judging whether the current j value is larger than the preset total number of the coverage cycles, if so, ending, and if not, re-entering the step B1.
The invention also correspondingly discloses a mobile crowd sensing system, which comprises:
the grid unit screening module is used for screening all grid units which are uniformly and directly in sufficient sensing coverage within a preset time span from the target sensing area to obtain a corresponding target grid unit set;
a mobile node screening module, configured to screen out, from a mobile node set, a mobile node subset that can meet the perceived coverage requirements of all grid cells in the target grid cell set in each coverage period;
a mobile node merging module, configured to merge all mobile node subsets corresponding to all coverage periods to obtain a target mobile node set;
and the crowd sensing module is used for carrying out crowd sensing by utilizing the target mobile node set.
Optionally, the grid unit screening module includes:
the sufficiency degree operator module is used for calculating the coverage sufficiency of each grid unit of the target sensing area in each coverage period of the preset time span;
and the grid unit screening submodule is used for screening all grid units with the coverage sufficiency greater than a preset sufficiency threshold value in all coverage cycles of the preset time span from the target sensing area to obtain the target grid unit set.
Optionally, the grid unit screening submodule includes a single-period node screening unit, a node deleting unit, and a first cycle control unit; wherein the content of the first and second substances,
the single-period node screening unit is configured to screen a mobile node subset capable of meeting the perceptual coverage requirements of all grid units in the target grid unit set in an ith coverage period from the current mobile node set, where i is a positive integer;
the node deleting unit is configured to delete the mobile node subset corresponding to the ith coverage period from the current mobile node set to obtain a new mobile node set, and then notify the first cyclic control unit to start working;
and the first cycle control unit is used for adding 1 to the value i to update the value i, judging whether the current value i is greater than the total number of the preset coverage periods, if so, ending, and if not, informing the single-period node screening unit to restart the work.
Optionally, the single-cycle node screening unit is specifically configured to screen, based on a greedy policy, a mobile node subset that can meet the coverage sensing requirements of all grid units in the target grid unit set in the ith coverage cycle from the current mobile node set.
Optionally, the crowd sensing module includes a crowd sensing unit and a second loop control unit; wherein the content of the first and second substances,
the crowd sensing unit is used for carrying out crowd sensing by utilizing the mobile node subset corresponding to the jth coverage period in the jth coverage period and reducing the sampling times of the mobile nodes based on a cooperative sensing mechanism among different mobile nodes in the coverage period, wherein j is a positive integer;
and the second cycle control unit is used for adding 1 to the j value to update the j value, judging whether the current j value is larger than the total number of the preset coverage period, if so, finishing, and if not, informing the crowd sensing unit to restart the work.
In the invention, the mobile crowd sensing method comprises the following steps: screening all grid units which are uniformly and vertically in sufficient sensing coverage within a preset time span from the target sensing area to obtain a corresponding target grid unit set; screening out a mobile node subset which can meet the sensing coverage requirements of all grid cells in a target grid cell set in each coverage period from the mobile node set; merging all mobile node subsets corresponding to all coverage periods to obtain a target mobile node set; and carrying out crowd sensing by utilizing the target mobile node set.
Therefore, the grid units which are always in sufficient sensing coverage are screened out from the target sensing area, then the mobile node subsets which can meet the sensing coverage requirements of all grid units in the target grid unit set are screened out from the mobile node set in each coverage period, namely, the mobile nodes which cannot meet the sensing coverage requirements of all grid units in the target grid unit set in each coverage period cannot be screened out from the mobile node subsets, so that the number of the mobile nodes which perform sensing data sampling in each coverage period is reduced under the condition that the grid units are ensured to be sufficiently covered, and the sampling redundancy and the energy loss in the crowd sensing process are effectively reduced.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
FIG. 1 is a flowchart of a mobile crowd sensing method according to an embodiment of the present invention;
FIG. 2 is a flowchart of a specific mobile crowd sensing method according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of spatial domain partitioning according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of time domain partitioning according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of a mobile crowd sensing system according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The embodiment of the invention discloses a mobile crowd sensing method, which is shown in figure 1 and comprises the following steps:
step S11: and screening all grid units which are uniformly and vertically in sufficient sensing coverage within a preset time span from the target sensing area to obtain a corresponding target grid unit set.
It is understood that, in the present embodiment, the target sensing region is already divided into a plurality of sub-regions in advance, and each sub-region is referred to as a grid unit in the present embodiment.
Step S12: and screening out a mobile node subset which can meet the perception coverage requirements of all the grid cells in the target grid cell set in each coverage period from the mobile node set.
Step S13: and merging all the mobile node subsets corresponding to all the coverage periods to obtain a target mobile node set.
Step S14: and carrying out crowd sensing by utilizing the target mobile node set.
Therefore, in the embodiment of the invention, grid units always in sufficient sensing coverage are screened out from the target sensing area, and then the mobile node subsets capable of meeting the sensing coverage requirements of all grid units in the target grid unit set are screened out from the mobile node set in each coverage period, that is, the mobile nodes which cannot meet the sensing coverage requirements of all grid units in the target grid unit set in each coverage period cannot be screened out from the mobile node subsets, so that the number of the mobile nodes for sensing data sampling in each coverage period is reduced under the condition of ensuring that the grid units are sufficiently covered, and the sampling redundancy and the energy loss in the crowd sensing process are effectively reduced.
Referring to fig. 2, an embodiment of the present invention discloses a specific mobile crowd sensing method, including the following steps:
step S21: and calculating the coverage sufficiency of each grid unit of the target perception area in each coverage period of a preset time span.
To better measure perceptual quality, the time-space domain of perceptual coverage needs to be discretized. We consider a crowd-sourcing aware network consisting of m mobile nodes, the set of nodes U ═ U1,u2,...,um}. Each mobile node is provided with a corresponding sensor and moves in a sensing area with a certain movement track, and a node u is arranged at the moment tiPosition of (D) is denoted as Loci(t) of (d). The mobile node samples the surrounding environment at a certain frequency, immediately sends sensing data to a remote server through WiFi if a WiFi hotspot is detected, temporarily stores the sensing data in a local cache of the mobile node if the WiFi hotspot is not detected temporarily, then sends the sensing data to the remote server through WiFi if the WiFi hotspot is detected within a certain time threshold, and otherwise directly sends the sensing data to the remote server through a cellular mobile network (3G/4G).
In the spatial domain, the present embodiment divides the whole target sensing region into a series of grid units in advance, i.e., C ═ C1,c2,...,cnThe size of the grid cell represents the granularity of spatial perception. The division into spatial domains is illustrated with reference to fig. 3.
In the time domain, the embodiment first defines a Sensing period (Sensing period), i.e. TspWhen each sensing period begins, the mobile node performs sampling operation, after sampling is completed, if a WiFi hotspot is detected, sensing data are immediately sent to a remote server through WiFi, and if the WiFi hotspot is not detected temporarily, the sensing data are sent to the remote server through WiFiThe sensing data is temporarily stored in a local cache of the mobile node, and then if a WiFi hotspot is detected within a certain time threshold, the sensing data is sent to a remote server through WiFi, otherwise, the sensing data is directly sent to the remote server through a cellular mobile network (3G/4G). Next, this embodiment defines a Coverage period (Coverage period), TcpEach covering period is composed of r sensing periods, i.e. Tcp＝rTsp. In addition, the present embodiment further defines a Time span (T), which represents the total sensing duration and is composed of r 'coverage periods, i.e., T ═ r' Tcp. The division of the time domain is illustrated with reference to fig. 4.
To effectively measure perceptual quality, we propose the concept of "overlay". A trellis cell is considered covered by a mobile node if and only if a new sensing period comes and the mobile node's location is within the area of the trellis cell. Order toj(Loci(t)) represents time u at tiWhether a node covers a trellis cell cj，j(Loci(t)) is specifically represented as follows:
from the above expression, if and only if the current time is the beginning of the sensing period and node uiAt a position of cjWhen the area of the lattice cell is within the range, c is consideredjLattice unit quilt uiNode is covered, i.e.j(Loci(t)) -1, otherwise, c is considered to bejLattice unit is not uiNode coverage, i.e.j(Loci(t))＝0。
In order to measure the Coverage quality, the present embodiment proposes the concept of Coverage Sufficiency Degree (Coverage Sufficiency Degree), and then defines the Sufficient Sensing Coverage (Coverage Sensing Coverage). Coverage sufficiency CSDj(x) Represents the grid cell c in the x-th coverage period (x ═ 1, 2.., r'),jall mobile nodes in the USum of times of covering, CSDj(x) Is specifically represented as follows:
step S22: and screening all grid units with the coverage fullness greater than a preset fullness threshold in all coverage periods of a preset time span from the target sensing area to obtain a target grid unit set.
Based on the coverage sufficiency, the present embodiment defines the sufficient perceptual coverage, which is defined as follows: a grid cell cjE C is considered to be sufficiently covered in the xth coverage period (x ═ 1, 2.. times, r'), if and only if the sum of the times it is covered by all mobile nodes in U in the coverage period is not less than η, where η is greater than or equal to 1, which is specifically expressed as follows:
CSDj(x)≥η,x＝1,2,...,r'
this embodiment also refers to the above coverage constraint η as a preset sufficiency threshold, and if the coverage sufficiency of a certain cell in all coverage periods of a preset time span is greater than the preset sufficiency threshold, the cell will be identified as a cell that is always in sufficient perceived coverage.
The η perceptual data of the same trellis unit may be fused in a manner to obtain more accurate measurements. In the current model, a larger η provides better perceptual quality for the trellis cells in the perceptual region at the cost of perceiving more redundant data and consuming more battery power.
Based on the various definitions described above and step S22 described above, the present embodiment can obtain the set C' ═ C of lattice cells that is always in sufficient coveragei1,ci2,...,cirWhich is a subset of C'.
Step S23: and screening out a mobile node subset which can meet the perception coverage requirements of all the grid cells in the target grid cell set in each coverage period from the mobile node set.
In this embodiment, the process of screening out the mobile node subset capable of meeting the perceived coverage requirement of all the grid cells in the target grid cell set in each coverage period from the mobile node set specifically includes the following steps a1 to A3:
step A1: and screening out a mobile node subset which can meet the sensing coverage requirements of all grid cells in the target grid cell set in the ith coverage period from the current mobile node set, wherein i is a positive integer.
Step A2: and deleting the mobile node subset corresponding to the ith coverage period from the current mobile node set to obtain a new mobile node set.
Step A3: and adding 1 to the value i to update the value i, judging whether the current value i is greater than the preset total number of coverage cycles, if so, ending, and if not, re-entering the step A1.
Wherein, the step a1 specifically includes: and screening out a mobile node subset which can meet the sensing coverage requirements of all grid units in the target grid unit set in the ith coverage period from the current mobile node set based on a greedy strategy.
Step S24: and merging all the mobile node subsets corresponding to all the coverage periods to obtain a target mobile node set.
As can be seen from the above, the embodiment of the present invention may specifically perform a single-cycle node selection process based on a greedy policy, and then combine all mobile node subsets corresponding to all coverage cycles, thereby obtaining a selected node set UxI.e. to obtain the set of target mobile nodes. Regarding the greedy policy, the present embodiment is for each node ukFirst, two evaluation functions are defined: f. of1(uk) And f2(uk). Wherein f is1(uk) Is represented in UxIn-increase node ukThe number of lattice cells which can be covered sufficiently later, f2(uk) Is represented in UxIn-increase node ukIncreased total number of coverage of later grid cells. In the greedy strategy of the present embodiment, f1(uk) The evaluation function is superior to f2(uk) Evaluating the function, i.e. if adding any node in any iteration fails to produce a new trellis cell that achieves sufficient coverage, the embodiment will use a second evaluation function f2(uk) To make the selection of the node, i.e. to select the node that maximizes f2(uk) The node of (2).
The following describes the node selection process in a single cycle in detail:
first, the present embodiment initializes a set C of sufficient-coverage lattice cellseSet of mobile nodes U', selected set of nodes UxAnd a lattice cell c in the x-th overlay periodiQuilt UxNumber of node coverages CSDi(x) In that respect Then, in each iteration, a best candidate node u is selectedbWhen all the grid cells are from CeWhen the node is removed, the single-cycle node selection process is terminated. In each iteration, the embodiment first uses the two evaluation functions f1(uk) And f2(uk) For each node ukCalculating two evaluation function values related to the evaluation function values, and then selecting an optimal candidate node u according to a rule determined by a previous greedy strategyb. At ubAfter being selected, updating CSDi(x) If CSDi(x) If is greater than or equal to eta, c isiFrom CeWhile removing u, at the same timebRemoving U from U' and removing UbIs added to UxIn (1). When the node selection process of the single cycle is terminated, UxC can be satisfied in the current coverage periodeThe perceived coverage requirement of all the trellis cells in the trellis.
Step S25: and carrying out crowd sensing by utilizing the target mobile node set.
The above process of performing crowd sensing by using the target mobile node set specifically includes the following steps B1 and B2:
step B1: in the jth coverage period, carrying out crowd sensing by using a mobile node subset corresponding to the jth coverage period, and reducing the sampling times of the mobile nodes in the coverage period based on a cooperative sensing mechanism among different mobile nodes, wherein j is a positive integer;
step B2: and adding 1 to the j value to update the j value, judging whether the current j value is larger than the preset total number of the coverage cycles, if so, ending, and if not, re-entering the step B1.
As can be seen from the above, in each coverage period, the present embodiment may specifically determine, based on a cooperative sensing mechanism among different mobile nodes, which mobile nodes are specifically utilized to perform a sensing task in the current coverage period from the target mobile node set.
In order to indicate whether a certain mobile node in the target mobile node set should participate in the sensing task of the current coverage period, the embodiment proposes a concept of a Participation Control Table (Participation Control Table). Each mobile node locally stores a participation control table, the length of which is fixed to the total number of coverage periods i'. Each element in the participation control table is a binary digit, the value of which is determined by the screening result of the mobile node in each coverage period, and represents which coverage period sensing tasks the current node needs to participate in, if the current node needs to participate in the xth coverage period sensing task, the value of the xth element in the participation control table of the current node is set to 1, otherwise, the value is set to 0. An example of the participation control table can be seen in table one, in which 8 elements are stored, representing that the current node should participate in the sensing tasks of the first, third and seventh coverage periods, and keep the sleep state in the other five coverage periods.
Watch 1
| 1 | 0 | 1 | 0 | 0 | 0 | 1 | 0 |
In order to better represent the Coverage contribution of the mobile node to the grid cell, the embodiment also proposes a concept of a Sensing Coverage Table (Sensing Coverage Table). Each mobile node stores a sensing coverage table locally, and elements in the sensing coverage table are composed of a triple<ci，ni，fi>The structure of the sensing coverage table can be seen in table two. Wherein, ciNumber representing lattice cell, niRepresenting the number of samples present in the grid cell of the number, fiRepresents ciExisting number of samples n iniWhether all are adopted by the node, wherein fiWhere 1 represents all taken by this node, fi0 represents niAlready containing samples of other nodes.
Watch two
| <c1：n1：f1> | <c2：n2：f2> | ...... | ...... | <ck：nk：fk> |
The size of the sensing coverage table is dynamically changed, at the starting time of each coverage period, the mobile node will clear the local sensing coverage table, when two mobile nodes enter into the communication range of each other, the two mobile nodes will exchange the sensing coverage table with each other and perform fusion processing on the sensing coverage table, and the fusion rule of the sensing coverage table (hereinafter abbreviated as SCT) is as follows:
when two mobile nodes ui，ujWhen entering into the communication range of each other, the two mobile nodes exchange their respective sensing coverage tables SCTi，SCTjAnd performing fusion processing on the perception coverage table. Here with ujNode SCT (stream control Transmission) its perception coverage tablejIs transmitted to uiThe fusion process after the nodes is described as an example, and the rest can be analogized. For SCTjEach tuple in<cj，nj，fj>Setting the count value to 0, representing temporary considering SCTiIs not associated with cjCell related overlay information. Then sequentially traverse the SCTiEach tuple in<ci，ni，fi>When c isiIs equal to cjWhen the SCT is started, the count value is set to 1, which represents that the SCT is already existediTherein is found outjCell related overlay information. When c is going toiIs equal to cjWhen, if fi，fjIf both are 1, it indicates node uiAnd node ujTotal number of samples n for current trellis uniti，njAll are collected by the local node, and the SCT is updated at the momentiIn niHas a value of ni，njSum if ni，njIf the sum is greater than eta, the value is updated to eta, and then f is addediThe value of (d) is set to 0. If fi，fjNot all are 1 and niLess than njThen n will beiIs updated to njAnd will fiIs set to 0. SCT is waited to be traversediAfter all tuples in the SCT are processed, the value of the count at the moment is judged, and if the value is still 0, the SCT is indicatediIs not associated with cjThe covering information related to the grid cell will be<cj,nj,0>Adding to SCTiIn (1).
Based on the foregoing sensing coverage table fusion rule, this embodiment further provides a mobile node cooperative sensing mechanism based on a fusion SCT, and an operation flow of the mechanism is as follows:
at the beginning of each coverage cycle, the mobile node will clear the local perceived coverage table. And then judging whether to participate in the sensing task of the current coverage period according to the participation control table of the user. If participation is needed, when the sensing period comes, once the node uiPrepared in lattice cell cjThe sampling process is carried out, and whether the grid unit c exists in the sensing coverage table of the self-sensing coverage table or not is judged firstlyjAnd if the corresponding tuple exists and the sampling times in the tuple are equal to eta, the node does not sample at this time, otherwise, the node samples and updates the sample to the perception coverage table, and the updating process is as follows: if the sensing coverage table has the grid cell cjCorresponding tuple, then njIs updated to nj+1 if no trellis cell c is present in the perceptual coverage tablejCorresponding tuple, then the tuple is<cj,nj,fj>Adding to node uiAnd updating n in the perceptual coverage tablej＝1，fj＝1。
Correspondingly, the embodiment of the present invention further discloses a mobile crowd sensing system, as shown in fig. 5, the system includes:
the grid unit screening module 11 is configured to screen all grid units that are uniformly and directly in sufficient sensing coverage within a preset time span from the target sensing area to obtain a corresponding target grid unit set;
a mobile node screening module 12, configured to screen out, from the mobile node set, a mobile node subset that can meet the perceptual coverage requirements of all grid cells in the target grid cell set in each coverage period;
a mobile node merging module 13, configured to merge all mobile node subsets corresponding to all coverage periods to obtain a target mobile node set;
and the crowd sensing module 14 is used for carrying out crowd sensing by utilizing the target mobile node set.
The grid unit screening module in this embodiment may include an sufficiency meter operator module and a grid unit screening submodule; wherein the content of the first and second substances,
the sufficiency degree calculating operator module is used for calculating the coverage sufficiency of each grid unit of the target sensing area in each coverage period of a preset time span;
and the grid unit screening submodule is used for screening all grid units with the coverage sufficiency greater than a preset sufficiency threshold value in all coverage cycles of a preset time span from the target sensing area to obtain a target grid unit set.
Specifically, the grid unit screening submodule may include a single-period node screening unit, a node deleting unit, and a first cycle control unit; wherein the content of the first and second substances,
the single-period node screening unit is used for screening a mobile node subset which can meet the sensing coverage requirements of all grid units in a target grid unit set in the ith coverage period from the current mobile node set, wherein i is a positive integer;
a node deleting unit, configured to delete the mobile node subset corresponding to the ith coverage period from the current mobile node set, obtain a new mobile node set, and then notify the first cyclic control unit to start working;
and the first cycle control unit is used for adding 1 to the value i to update the value i, judging whether the current value i is greater than the total number of the preset coverage periods, if so, ending, and if not, informing the single-period node screening unit to restart the work.
Further, the single-cycle node screening unit may be specifically configured to screen, based on a greedy policy, a mobile node subset that can meet the perceptual coverage requirements of all grid units in the target grid unit set in the ith coverage cycle from the current mobile node set.
In addition, the crowd sensing module in this embodiment may specifically include a crowd sensing unit and a second loop control unit; wherein the content of the first and second substances,
the crowd sensing unit is used for carrying out crowd sensing by utilizing the mobile node subset corresponding to the jth coverage period in the jth coverage period and reducing the sampling times of the mobile nodes based on a cooperative sensing mechanism among different mobile nodes in the coverage period, wherein j is a positive integer;
and the second cycle control unit is used for adding 1 to the j value to update the j value, judging whether the current j value is larger than the total number of the preset coverage period, if so, finishing, and if not, informing the crowd sensing unit to restart the work.
For more detailed working processes of the above modules and units, reference may be made to corresponding contents disclosed in the foregoing embodiments, and details are not described herein again.
Therefore, in the embodiment of the invention, grid units always in sufficient sensing coverage are screened out from the target sensing area, and then the mobile node subsets capable of meeting the sensing coverage requirements of all grid units in the target grid unit set are screened out from the mobile node set in each coverage period, that is, the mobile nodes which cannot meet the sensing coverage requirements of all grid units in the target grid unit set in each coverage period cannot be screened out from the mobile node subsets, so that the number of the mobile nodes for sensing data sampling in each coverage period is reduced under the condition of ensuring that the grid units are sufficiently covered, and the sampling redundancy and the energy loss in the crowd sensing process are effectively reduced.
Finally, it should also be noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The mobile crowd sensing method and system provided by the invention are introduced in detail, and a specific example is applied in the text to explain the principle and the implementation of the invention, and the description of the above embodiment is only used for helping to understand the method and the core idea of the invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.
Claims (10)
1. A mobile crowd-sourcing awareness method, comprising:
screening all grid units which are uniformly and vertically in sufficient sensing coverage within a preset time span from the target sensing area to obtain a corresponding target grid unit set;
screening out a mobile node subset which can meet the perception coverage requirements of all grid units in the target grid unit set in each coverage period from a mobile node set;
merging all mobile node subsets corresponding to all coverage periods to obtain a target mobile node set;
carrying out crowd sensing by utilizing the target mobile node set;
wherein the sufficient perceptual coverage is defined as: if the sum of the times that any grid cell is covered by all the mobile nodes in the mobile node set in the xth coverage period is not less than eta, wherein eta is a preset sufficiency threshold value, and eta is greater than or equal to 1, the grid cell is represented to be adequately covered in the xth coverage period.
2. The mobile crowd sensing method of claim 1, wherein the step of screening all grid cells in the target sensing area that are uniformly and constantly in sufficient sensing coverage within a preset time span comprises:
calculating the coverage sufficiency of each grid unit of the target sensing area in each coverage period of the preset time span;
screening all grid units with coverage sufficiency greater than the preset sufficiency threshold in all coverage periods of the preset time span from the target sensing area to obtain a target grid unit set;
wherein, the grid unit cjThe corresponding expression of the coverage sufficiency is as follows:
in the formula, Loci(t) denotes the node u at time tiIn the position of (a) in the first,j(Loci(t)) represents time u at tiWhether a node covers a trellis cell cjJ 1,2, n, n represents the number of lattice cells, TcpRepresenting the coverage period, r' representing the number of coverage periods, and m representing the number of mobile nodes in the set of mobile nodes.
3. The method of claim 2, wherein the process of screening out from the set of mobile nodes a subset of mobile nodes that can satisfy the perceived coverage requirements of all the cells in the target set of cells in each coverage period comprises:
step A1: screening out a mobile node subset which can meet the sensing coverage requirements of all grid units in the target grid unit set in the ith coverage period from the current mobile node set, wherein i is a positive integer;
step A2: deleting the mobile node subset corresponding to the ith coverage period from the current mobile node set to obtain a new mobile node set;
step A3: and adding 1 to the value i to update the value i, judging whether the current value i is greater than the preset total number of coverage cycles, if so, ending, and if not, re-entering the step A1.
4. The mobile crowd sensing method according to claim 3, wherein the step A1 specifically includes:
and screening out a mobile node subset which can meet the sensing coverage requirements of all grid units in the target grid unit set in the ith coverage period from the current mobile node set based on a greedy strategy.
5. The method as claimed in any one of claims 1 to 4, wherein the process of performing crowd sensing with the set of target mobile nodes specifically comprises:
step B1: in the jth coverage period, carrying out crowd sensing by using a mobile node subset corresponding to the jth coverage period, and reducing the sampling times of the mobile nodes in the coverage period based on a cooperative sensing mechanism among different mobile nodes, wherein j is a positive integer;
step B2: and adding 1 to the j value to update the j value, judging whether the current j value is larger than the preset total number of the coverage cycles, if so, ending, and if not, re-entering the step B1.
6. A mobile crowd-sourcing awareness system, comprising:
the grid unit screening module is used for screening all grid units which are uniformly and directly in sufficient sensing coverage within a preset time span from the target sensing area to obtain a corresponding target grid unit set;
a mobile node screening module, configured to screen out, from a mobile node set, a mobile node subset that can meet the perceived coverage requirements of all grid cells in the target grid cell set in each coverage period;
a mobile node merging module, configured to merge all mobile node subsets corresponding to all coverage periods to obtain a target mobile node set;
the crowd sensing module is used for carrying out crowd sensing by utilizing the target mobile node set;
wherein the sufficient perceptual coverage is defined as: if the sum of the times that any grid cell is covered by all the mobile nodes in the mobile node set in the xth coverage period is not less than eta, wherein eta is a preset sufficiency threshold value, and eta is greater than or equal to 1, the grid cell is represented to be adequately covered in the xth coverage period.
7. The mobile crowd-sourcing perception system of claim 6, wherein the grid cell screening module comprises:
the sufficiency degree operator module is used for calculating the coverage sufficiency of each grid unit of the target sensing area in each coverage period of the preset time span;
a grid unit screening submodule, configured to screen all grid units, of which coverage sufficiency is greater than the preset sufficiency threshold, in all coverage periods of the preset time span from the target sensing area, so as to obtain the target grid unit set;
wherein, the grid unit cjThe corresponding expression of the coverage sufficiency is as follows:
in the formula, Loci(t) denotes the node u at time tiIn the position of (a) in the first,j(Loci(t)) represents time u at tiWhether a node covers a trellis cell cjJ 1,2, n, n represents the number of lattice cells, TcpRepresenting the coverage period, r' representing the number of coverage periods, and m representing the number of mobile nodes in the set of mobile nodes.
8. The mobile crowd-sourcing perception system of claim 7, wherein the trellis unit filter submodule includes a single-cycle node filter unit, a node delete unit, and a first loop control unit; wherein the content of the first and second substances,
the single-period node screening unit is configured to screen a mobile node subset capable of meeting the perceptual coverage requirements of all grid units in the target grid unit set in an ith coverage period from the current mobile node set, where i is a positive integer;
the node deleting unit is configured to delete the mobile node subset corresponding to the ith coverage period from the current mobile node set to obtain a new mobile node set, and then notify the first cyclic control unit to start working;
and the first cycle control unit is used for adding 1 to the value i to update the value i, judging whether the current value i is greater than the total number of the preset coverage periods, if so, ending, and if not, informing the single-period node screening unit to restart the work.
9. The mobile crowd sensing system of claim 8, wherein,
the single-period node screening unit is specifically configured to screen, based on a greedy policy, a mobile node subset that can meet the perceptual coverage requirements of all grid units in the target grid unit set in an ith coverage period from the current mobile node set.
10. The mobile crowd sensing system according to any one of claims 6 to 9, wherein the crowd sensing module comprises a crowd sensing unit and a second loop control unit; wherein the content of the first and second substances,
the crowd sensing unit is used for carrying out crowd sensing by utilizing the mobile node subset corresponding to the jth coverage period in the jth coverage period and reducing the sampling times of the mobile nodes in the coverage period based on a cooperative sensing mechanism among different mobile nodes, wherein j is a positive integer;
and the second cycle control unit is used for adding 1 to the j value to update the j value, judging whether the current j value is larger than the total number of the preset coverage period, if so, finishing, and if not, informing the crowd sensing unit to restart the work.
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