CN106793151A - Distributed random handshake method and its system in a kind of wireless built network - Google Patents
Distributed random handshake method and its system in a kind of wireless built network Download PDFInfo
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Abstract
The invention discloses distributed random handshake method and its system in a kind of wireless built network, methods described includes：Step 1, in t-th time slot, detection all accessible channels of terminal device formed the terminal device can access channel set；Step 2, according to the terminal device can access channel set in each channel history availability, sequentially arrange each channel formed terminal device can access channel order arrangement set；Step 3, each channel distribution that be can access for the terminal device in channel order arrangement set access select probability；Step 4, attempt shaking hands according to accessing select probability and select the terminal device to can access each channel in channel order arrangement set, until shaking hands successfully, otherwise return to step 1 and make t=t+1.The technical scheme that the present invention is provided, can effectively make communication terminal when wireless channel dynamic change environment causes can access passage dynamic change, realize that equipment room is shaken hands and then realizes smooth efficient communication.
Description
Technical Field
The invention relates to the technical field of wireless embedded network communication, in particular to a distributed random handshake method and a distributed random handshake system in a wireless embedded network.
Background
An Embedded System (Embedded System) is a computer System with a micro control unit as a core and specific functions. With the popularization and development of the internet of things, Embedded systems are widely applied to the fields of industrial control, electronic commerce, information and household appliances and the like, and the requirement for Wireless communication between Embedded terminal devices is higher and higher, so the research on the communication technology of Wireless Embedded Networks (WENs) is one of the important subjects of the research in the field.
The wireless Embedded network is composed of Embedded Terminal Devices (ETD), and the Terminal devices realize communication by accessing a wireless channel decomposed by available frequency spectrum through a wireless communication technology, and the wireless communication plays a key role in the normal operation of the wireless Embedded network. In the communication process, the embedded terminal device senses the available state of a frequency spectrum, accesses a certain accessible wireless Channel through a frequency Hopping (CH) technology, and then communicates with other embedded terminal devices accessing the same Channel, and the embedded terminal device accesses the same Channel through the frequency Hopping technology is called handshaking. Only through handshaking, the embedded terminal equipment can establish a corresponding communication link, and further communication is realized. Therefore, the handshaking method is more important, and the research on the handshaking problem in the wireless embedded network has important practical significance for improving the efficiency of the wireless embedded network.
The handshaking method in the wireless embedded network can be classified into a centralized type and a distributed type according to different network structures. Most of the centralized handshaking methods need to implement handshaking between wireless communication devices through a central controller configured in advance and a control channel, but the dynamic change characteristics of the wireless embedded network make the centralized handshaking methods difficult to implement.
Unlike the centralized handshake approach, the distributed handshake approach does not employ any central controller-assisted handshake, thereby avoiding single-point failures and congestion on the control channel. However, most of the current researches on wireless embedded network handshake problems only consider the case that the accessible channel is in a stable state, and the actual situation is that the accessible channel of the ETD changes along with the change of time and place, and the wireless channel environment has a dynamically changing characteristic, for example, some originally accessible channels become unusable due to interference caused by the occupation of the channel by nearby devices, thereby affecting the inter-device communication.
Accordingly, the prior art is yet to be improved and developed.
Disclosure of Invention
In view of the foregoing disadvantages of the prior art, an object of the present invention is to provide a distributed random handshake method in a wireless embedded network and a system thereof, which aim to solve the problem that communication between devices is affected by dynamic changes of a distributed accessible channel in the wireless embedded network.
The technical scheme adopted by the invention is as follows:
a distributed random handshake method in a wireless embedded network comprises the following steps:
step 1, detecting all accessible channels of a terminal device to form an accessible channel set of the terminal device in a tth time slot;
step 2, sequentially arranging each channel according to the historical availability ratio of each channel in the accessible channel set of the terminal equipment to form an accessible channel sequential arrangement set of the terminal equipment;
step 3, distributing access selection probability for each channel in the sequence arrangement set of the accessible channels of the terminal equipment;
and 4, selecting each channel in the sequence arrangement set of the accessible channels of the terminal equipment according to the access selection probability, and trying to handshake until the handshake is successful, otherwise, returning to the step 1, and enabling t to be t + 1.
The distributed random handshake method in the wireless embedded network, wherein the step 1 includes:
step 11, counting the total number of accessible channels in the wireless embedded network;
step 12, in the t-th time slot, detecting all accessible channels of the terminal equipment in the wireless embedded network to form an accessible channel set of the terminal equipment, and expressing by the following formula:
equation (1) is a boolean vector representing the accessible channel condition of terminal a in the tth time slot, where n represents the total number of accessible channels in the wireless embedded network, t represents the tth time slot, and t is 1,2iWhich represents the (i) th channel of the channel,indicating that terminal a can access channel c in the t-th time sloti，Indicating that terminal a cannot access channel c in the t-th sloti；
In the formula (2)Denotes the set of accessible channels, c, of terminal device A in the t-th time slotiWhich represents the (i) th channel of the channel,indicating that terminal a can access channel c in the t-th time sloti。
The distributed random handshake method in the wireless embedded network, wherein the step 2 specifically includes:
step 21, calculating the ith channel c in the t time slotiHistory availability for terminal device AThe calculation formula is as follows:
in formula (3), t 'is an integer of (1, t), i.e. the t' th time slot is represented.
Step 22, forming a channel c in the t time slotiHistorical availability set for terminal device A
Step 23, subjecting the mixture toAccording to each channel ciHistory availability ofDescending or ascending to obtain the sequence arrangement set of the accessible channels of the terminal equipment ANamely, it isAmong them, the channel …, ci,cj,ck…, corresponding to a channel history availability relationship ofOr
The distributed random handshake method in the wireless embedded network, wherein the step 11 specifically includes:
if it isThen
If it isThen
Wherein,indicating that terminal a can access channel c in the t-th time sloti，Indicating that terminal a cannot access channel c in the t-th sloti。
The distributed random handshake method in the wireless embedded network, wherein the step 3 specifically comprises:
each channel in the ordered set of accessible channels for the terminal deviceThe method for calculating the distribution access selection probability comprises the following steps: let terminal equipment A access channel sequence arrangement setAccording toHistorical availability corresponding to medium accessible channelAnd as weight distribution probability, calculating to obtain a channeli,cjAnd ck.., respectively, are selected as Andand is
The distributed random handshake method in the wireless embedded network, wherein the step 3 specifically comprises:
the method for calculating the access selection probability of each channel in the accessible channel sequence arrangement set of the terminal equipment A based on the class index distribution comprises the following steps: let terminal equipment A access channel sequence arrangement set
ej-1(6)；
Formula (6) representsThe jth channel element in (a) is assigned a weight,
formula (7) showsThe probability that the jth channel element in (j) is selected,
wherein e is the Euler number.
The distributed random handshake method in the wireless embedded network, wherein the step 3 specifically comprises:
the method for calculating the access selection probability of each channel in the accessible channel sequence arrangement set of the terminal equipment A based on the class geometric distribution comprises the following steps: let terminal equipment A access channel sequence arrangement set
λ(1-λ)j-1(8)；
Equation (8) representsThe j-th channel element, wherein,λ ∈ (0,1) is a constant parameter of the standard geometric distribution;
formula (9) representsThe corresponding selected probability of the jth channel element,
a distributed random handshake system in a wireless embedded network, comprising:
a detection module, configured to detect, in a tth timeslot, all accessible channels of a terminal device to form an accessible channel set of the terminal device;
the sequencing module is used for sequentially sequencing each channel according to the historical availability of each channel in the terminal equipment accessible channel set to form a terminal equipment accessible channel sequential arrangement set;
a selection probability distribution module, configured to distribute an access selection probability for each channel in the sequence arrangement set of accessible channels of the terminal device;
and the handshake module is used for selecting each channel in the sequence arrangement set of the accessible channels of the terminal equipment according to the access selection probability and trying to handshake until the handshake is successful, and otherwise, returning to the detection module and enabling t to be t + 1.
The distributed random handshake system in the wireless embedded network, wherein, the detection module includes:
the statistical unit is used for counting the total number of the accessible channels in the wireless embedded network;
a detecting unit, configured to detect all accessible channels of a terminal device in a wireless embedded network in a tth time slot to form an accessible channel set of the terminal device, where the accessible channel set is expressed by the following formula:
equation (1) is a boolean vector representing the accessible channel condition of terminal a in the tth time slot, where n represents the total number of accessible channels in the wireless embedded network, t represents the tth time slot, and t is 1,2iWhich represents the (i) th channel of the channel,indicating that terminal a can access channel c in the t-th time sloti，Indicating that terminal a cannot access channel c in the t-th sloti；
In the formula (2)Denotes the set of accessible channels, c, of terminal device A in the t-th time slotiWhich represents the (i) th channel of the channel,indicating that terminal a can access channel c in the t-th time sloti。
The distributed random handshake system in the wireless embedded network, wherein the sequencing module comprises:
a calculation unit for calculating the ith channel c in the tth time slotiHistory availability for terminal device AThe calculation formula is as follows:
in formula (3), t 'is an integer of (1, t), i.e. the t' th time slot is represented.
A channel history availability set unit for forming a channel c in the t-th time slotiHistorical availability set for terminal device A
A sorting unit for sorting theAccording to each channel ciHistory availability ofDescending or ascending to obtain the sequence arrangement set of the accessible channels of the terminal equipment ANamely, it isAmong them, the channel …, ci,cj,ck…, corresponding to a channel history availability relationship ofOr
The selection probability distribution module comprises:
a first calculation unit of selection probability, which is used for calculating the access selection probability of each channel allocation in the sequence arrangement set of the accessible channels of the terminal equipment, and comprises the following steps: let terminal equipment A access channel sequence arrangement setAccording toHistorical availability corresponding to medium accessible channelAnd as weight distribution probability, calculating to obtain a channeli,cjAnd ck.., respectively, are selected asAndand is
A second calculation unit of selection probability, which is used for allocating access selection probability to each channel in the sequence arrangement set of the accessible channels of the terminal device a based on the class index distribution calculation method and comprises the following steps: let terminal equipment A access channel sequence arrangement set
ej-1(6)；
Formula (6) representsThe jth channel element in (a) is assigned a weight,
formula (7) showsThe probability that the jth channel element in (j) is selected,
wherein e is the Euler number;
a third calculation unit of selection probability, which is used for allocating access selection probability to each channel in the sequence arrangement set of the accessible channels of the terminal device a based on the class geometric distribution calculation method and comprises the following steps: let terminal equipment A access channel sequence arrangement set
λ(1-λ)j-1(8)；
Equation (8) representsThe j-th channel element, wherein,λ ∈ (0,1) is a constant parameter of the standard geometric distribution;
formula (9) representsThe corresponding selected probability of the jth channel element,
has the advantages that: compared with the prior art, the distributed random handshake method and the distributed random handshake system in the wireless embedded network provided by the invention have the advantages that the distributed handshake method based on the heuristic embedded terminal equipment is provided aiming at the characteristic of the dynamic change of the wireless channel environment in the wireless embedded network and the distributed characteristic of the network, the historical availability of the wireless channel is utilized, the random selection probability is reasonably distributed to the currently available channel, the wireless embedded terminal equipment randomly selects and accesses a certain channel in each time slice, the handshake is tried on the channel, and the handshake between the equipment of the communication terminal equipment can be effectively realized under the condition of the dynamic change of the accessible channel, so that the smooth and effective communication is realized.
Drawings
FIG. 1 is a flow chart of a distributed random handshake method in a wireless embedded network according to a preferred embodiment of the present invention
Fig. 2 is a functional block diagram of a distributed random handshake system in a wireless embedded network according to a preferred embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer and clearer, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The invention provides a distributed handshake method based on heuristic algorithm by counting channel state, aiming at embedded terminal equipment in distributed channel dynamic environment in wireless embedded network, and analyzes the method efficiency by simulation experiment, which is explained in detail below.
Referring to fig. 1, fig. 1 is a flowchart of a preferred embodiment of a distributed random handshake method in a wireless embedded network according to the present invention, including the steps of:
s100, detecting all accessible channels of the terminal equipment to form an accessible channel set of the terminal equipment in the t time slot;
described by a mathematical problem, for example, in a wireless embedded network, if there are two embedded terminal devices a and B, which are to establish a communication link by accessing a same wireless channel, the set of accessible wireless channels C ═ C is set1,c2,...,cnIn (b) }, wherein,indicating the ith channel. Without loss of generality, let us assume that wireless channels are Orthogonal pairwise (Orthogonal Frequency Division Multiplexing, OFDM, in which a channel is divided into a plurality of Orthogonal sub-channels, a high-speed data signal is converted into parallel low-speed sub-data streams, and the parallel low-speed sub-data streams are modulated to be transmitted on each sub-channel), we call time discretization into time slices with equal length, t represents the tth time slice, Δ t represents the length of each time slice, Δ t can be predetermined according to needs, and then the tth time slice is the tth time slot. It should be noted that the time slice, that is, the length of the time slot, may be specifically set according to different actual environment requirements, and is not limited herein.
Meanwhile, considering the dynamic characteristics of the channel, let the Boolean variableAndrespectively as follows: in the t-th time slice, channel ciThe accessible situation to terminal devices a and B, for example,indicating the channel c in the t-th slotiCan be accessed by terminal device a. For any one time slice t, terminal device a (or B) selects the current one of the accessible channels (i.e., frequency hopping operation) and attempts a handshake. We taste with representation of arbitrary user pairsThe minimum time required from the trial handshake to the successful handshake is Δ t ≧ t. As can be seen from the distributed nature of the wireless embedded network, the terminal devices a and B respectively only know the respective accessible channel conditions. We refer to successful handshake if and only if terminal devices a and B select the same channel, e.g. channel c at the same timeiThen terminal devices a and B can successfully handshake to achieve communication. We assume that at any time there is at least one identical accessible channel for terminal devices a and B.
In practice, step S100 specifically includes:
s110, counting the total number of accessible channels in the wireless embedded network;
s120, in the t-th time slot, detecting all accessible channels of the terminal equipment in the wireless embedded network to form an accessible channel set of the terminal equipment, and expressing by using the following formula:
equation (1) is a boolean vector representing the accessible channel condition of terminal a in the tth time slot, where n represents the total number of accessible channels in the wireless embedded network, t represents the tth time slot, and t is 1,2iWhich represents the (i) th channel of the channel,indicating that terminal a can access channel c in the t-th time sloti，Indicating that terminal a cannot access channel c in the t-th sloti；
In the formula (2)Denotes the set of accessible channels, c, of terminal device A in the t-th time slotiWhich represents the (i) th channel of the channel,indicating that terminal a can access channel c in the t-th time sloti。
In practical application, the total number n of accessible channels in the wireless embedded network depends on the specific application system environment, and the number n of channels depends on the factors: 1) the available frequency band range; 2) and the frequency band bandwidth allocated to each channel. For example, in a WiFi scenario, the frequency band of the 802.11b/g/n protocol is 2.412 Ghz-2.472 Ghz, and a total of 60Mhz, the frequency band of the 802.11a/n protocol available in china is 5.745 Ghz-5.825 Ghz, and is also 60 Mhz. Here if one channel is 20MHz, there are only about 3 channels; if 10MHz is allocated to one channel, there are about 6 channels, so that the channel is fixed in each system, and only detection statistics need to be performed in a specific system environment, which is not described herein again.
Whether a channel in the wireless embedded network can be accessed in the tth time slot is detected, and the judgment can be carried out by adopting the prior art, which is not described herein again.
S200, sequentially arranging each channel according to the historical availability ratio of each channel in the accessible channel set of the terminal equipment to form an accessible channel sequential arrangement set of the terminal equipment;
based on the characteristics of a wireless embedded network, the application provides a distributed self-adaptive random handshake method under a wireless channel dynamic change environment, under the handshake method, at the beginning of each time slice, namely the beginning of each time slot, each embedded terminal device firstly counts the historical access times of n channels, allocates randomly selected probability to the currently accessible channel based on the historical access frequency of each channel, namely the historical open rate of the channel, and finally randomly selects one channel based on the randomly selected probability distribution to perform handshake attempt. Specifically, the step S200 includes:
s210, calculating the ith channel c in the tth time slotiHistory availability for terminal device AThe calculation formula is as follows:
in formula (3), t 'is an integer of (1, t), i.e. the t' th time slot is represented.
S220, forming a channel c in the t time slotiHistorical availability set for terminal device A
S230, mixing the aboveAccording to each channel ciHistory availability ofDescending or ascending to obtain the sequence arrangement set of the accessible channels of the terminal equipment ANamely, it isAmong them, the channel …, ci,cj,ck…, corresponding to a channel history availability relationship ofOr
Further, step S210 specifically includes:
if it isThen
If it isThen
Wherein,indicating that terminal a can access channel c in the t-th time sloti，Indicating that terminal a cannot access channel c in the t-th sloti。
In practice, preferably according to each channel ciHistory availability ofArranging in descending order to obtain the ordered arrangement set of the channels accessible to the terminal equipment ATherefore, the method is beneficial to preferentially selecting the channel with high handshake success probability for trying in the subsequent steps, thereby shortening the time from the handshake trying to the successful handshake of any user as much as possible,the efficiency of communication between the terminal devices is improved more favorably.
S300, distributing access selection probability for each channel in the sequence arrangement set of the accessible channels of the terminal equipment;
for example, the terminal device a may access the channel sequence arrangement setThe access selection probability is distributed to each channel, which is the core step of the technical scheme, and based on the access selection probability, the probability that the handshake between the terminal devices is successful is determined by analyzing which channel is large, so that the channel is selected to try to handshake, and the probability of successful channel selection between the terminal devices is improved.
Specifically, there are three specific schemes for allocating the access selection probability to each channel in the step S300, and in specific implementation, one of the schemes may be arbitrarily selected according to actual needs, which are respectively discussed in detail below:
in the scheme ①, the method for calculating the access selection probability of each channel allocation in the access channel sequence arrangement set of the terminal equipment comprises the following steps that the access channel sequence arrangement set of the terminal equipment A is setAccording toHistorical availability corresponding to medium accessible channelCalculating to obtain the weight distribution probabilityi,cjAnd ck.., respectively, have probabilities of Andand is
The access selection probability distribution method is based onHistorical availability corresponding to channel elements in a wireless communication systemAs the weight assignment probability, the following is exemplified, provided thatComprising 3 channels ci,cj,ckThe ranking may be calculated according to their respective channel history availabilityArranged in descending order, i.e. by way of exampleWe will want toAs the weight, linear normalization processing is carried out, and c is obtained by calculationi,cjAnd ckRespectively has a probability of Andthis is in fact a normalization process, so that such an allocation guaranteesThe sum of the probabilities of the elements in (1), in the above example, it is obvious that we knowIn subsequent simulation experiments, the validity of the channel allocation access selection probability is verified by arranging the channel allocation access selection probability as an example in a descending order.
In the scheme ②, the method for calculating the access selection probability of each channel allocation in the access channel sequence arrangement set of the terminal equipment A based on the class index distribution comprises the following steps of setting the access channel sequence arrangement set of the terminal equipment A
ej-1(6)；
Formula (6) representsThe jth channel element in (a) is assigned a weight,
formula (7) showsThe probability that the jth channel element in (j) is selected,
wherein e is the Euler number.
The reason why the distribution is called "quasi-exponential distribution" is becauseThe number of elements in (a) is finite and the exponential distribution in the general sense takes into account an infinite range of values for the random variable.
In particular, the probability of randomly selecting access is assigned based on the accessible channel with class index distribution A, firstThe j-th element (channel) in (f) is assigned a weight ej-1,Wherein e is the Euler number; after the weight is distributed, the random selection probability of each channel is calculated through normalization processing, and then the selection probability corresponding to the jth element isIn this way, it can ensureThe sum of the probabilities of the medium elements is equal to 1, thereby ensuring that the selected channel belongs toThe validity of the channel allocation access selection probability is verified in subsequent simulation experiments.
According to the scheme ③, the method for calculating the access selection probability of each channel in the access channel sequential arrangement set of the terminal equipment A based on the class geometric distribution comprises the steps of setting the access channel sequential arrangement set of the terminal equipment A
λ(1-λ)j-1(8)；
Equation (8) representsThe j-th channel element, wherein,λ ∈ (0,1) is a constant parameter of the standard geometric distribution;
formula (9) representsThe corresponding selected probability of the jth channel element,
also, the reason for this is called "geometric-like distribution" becauseThe number of elements in (a) is finite, while the geometric distribution in the general sense takes into account an infinite range of values for the random variable.
The access selection probability distribution method is based on the probability of random selection access of the accessible channel with the class geometric distribution of A, specifically, the probability of random selection access is firstly distributedThe assigned weight of the jth element (channel) in (1-lambda)j-1,Wherein, λ ∈ (0,1) is constant parameter of standard geometric distribution, after weight distribution, random selection probability of each channel is calculated by normalization processing to ensureThe sum of the probabilities of the elements in (1) and the probability corresponding to the jth element isIn this way, it can ensureThe probability sum of the middle elements is equal to 1, and therefore the effectiveness of the scheme is guaranteed. The validity of the channel allocation access selection probability is verified in subsequent simulation experiments.
S400, selecting each channel in the access channel sequence arrangement set of the terminal equipment according to the access selection probability, and trying to handshake until the handshake is successful, otherwise, returning to the step S100, and making t equal to t + 1.
In this embodiment, for example, the sets are arranged according to the sequence of the channels accessible by the terminal device aThe access selection probability distribution of each channel allocation in the network is selected one by one in orderThe channels in (1) are typically tried according to the access selection probability from large to small, and a handshake is attempted on the selected channel. If the terminal device a and the terminal device B can access the same channel at the same time to establish the communication connection, the terminal device a and the terminal device B handshake successfully, otherwise, if each channel in the accessible channel sequence arrangement set of the terminal device a and the terminal device B cannot enable the terminal device a and the terminal device B to access the same channel at the same time, the handshake does not succeed, which indicates that the terminal device a and the terminal device B do not have the same accessible channel in the same tth time slot, the step S100 is returned, and t +1 is made to enter the next cycle to continue to try until the terminal device a and the terminal device B try to handshake successfully establish the communication connection.
In order to more clearly understand the technical scheme and verify the feasibility and the effectiveness of the wireless embedded network handshake method, a MATLAB programming language is used for simulating a handshake situation in a real wireless embedded network, a simulation experiment is performed on the technical scheme, and the advantages and the disadvantages of three methods of allocating access selection probability to each channel can be compared, and the specific process is as follows:
(1) mathematical description of the problem: the description of the mathematical problem is as described above and will not be repeated herein. It should be noted that, in the simulation experiment, the handshake time T is selected as an evaluation parameter of a handshake method. Here, T is defined as the number of time slices required from the first simultaneous handshake attempt by the terminal devices a and B to the final handshake. Specifically, the expected value e (t) and the maximum value m (t) of the handshake time are considered as evaluation indexes of one handshake method.
(2) The technical solution of the present invention is described basically: taking the embedded terminal device a as an example, a specific algorithm description is given below:
symbol description:
n: total number of accessible channels in the wireless embedded network;
c: accessible radio channel set C ═ C1,c2,...,cnIn (b) }, wherein,represents the ith channel;
ci: the ith channel (here we have assigned corresponding reference numerals to the channels);
t: the t-th time slice, t ═ 1,2,. infinity;
a boolean vector representing the case of an accessible channel of a at the t-th time slice; for example,indicating that terminal device A may be in the t-th time sliceAccess channel c1，It means that terminal a cannot access channel c in the t-th time slice1。
In the t-th time slice, the accessible channel set of a,
indicating the number of accessible channels of terminal A in the t time slice, i.e.
In the t-th time slice, the channel availability of terminal device a,
in the t-th time slice, channel ciHistorical availability for terminal equipment A, i.e.
A set of historical utilizable rates for a channel,
the algorithm process is as follows:
step 1: inputting n and C, initializing t to 0,
step 2: the number of update time slices t is t +1,
and 3, step 3: sensing the accessible condition of the channel, and calculating to obtain At；
And 4, step 4: computingHere, one memory variable is used for storage so as to reduce space complexity;
ifThen
IfThen
And 5, step 5: according to AtIs calculated to obtain
And 6, step 6: will be provided withOf the channel elements, based on respective channel history availabilityArranging in descending order to obtain an arrangement(here, the number of the first and second electrodes,)；
and 7, step 7: is composed ofThe element in (1) allocates the probability of random selection access, and three methods of allocating the access selection probability for each channel in the step (S300) are adopted as three probability allocation schemes;
and 8, step 8: selecting one by one according to the probability distribution in the step 7 in sequenceIn the simulation experiment, the probability is increased to be smaller, and handshake is tried on the selected channel;
step 9: if no handshake is implemented, step 2 is executed; otherwise, the algorithm is ended.
(3) Simulation experiment and result analysis: assuming the total number of channels is n, without loss of generality, assuming that for any t,that is, the number of accessible channels of a and B is the same and constant (but the set of accessible channels is not necessarily the same) in any time slice, i.e. the channel availabilityIn order to simulate the characteristic of dynamic change of an accessible channel set of different handshake scenarios in a wireless embedded network in a real environment, an experiment parameter of a channel dynamic change rate η is introduced, so that the characteristic of no access channel set dynamic change can be simulated in a large number of experimentsThe effectiveness of the technical scheme of the invention under different channel sets is respectively verified under the same experimental environment and different channel sets, thereby verifying the effectiveness of the technical scheme of the invention under different handshake situations caused by the dynamic change of the channel environment in actual communication.
We define the ratio of the changed accessible channel (compared with the previous time slice) to the total number of accessible channels per time slice as the dynamic change rate η of the channel, and we assume η to be constant without loss of generalityIn selectionA channel, which is made available at the t +1 time slice; from the set with equal probability at the same timeIn selectionOne channel, available in the t-1 time slice. These selected channels will all appearIn (1). At the beginning of each time slice (taking the tth time slice as an example), we compareAndif it is notTo ensure that A and B have the opportunity to handshake successfully in this slice, we replaceOrIs such that a certain element (channel) inWherein, it should be noted that,the cases of (2) rarely occur in reality; furthermore, ifThe algorithm of the present invention will lose the basic feasibility premise and will not consider this scenario.
According to the channel availability, the embedded terminal equipment can be divided into a symmetric case and an asymmetric case. For symmetrical embedded terminal devices, their channel availability per time slice is the same, i.e.For asymmetric embedded terminal devices, in the same time slice,andmay be different. Because both symmetric and asymmetric situations are likely to occur in real scenes, it is necessary to experiment and analyze their situations in simulation experiments.
As mentioned above, the evaluation indicators of algorithmic performance are the expected value E (T) and the maximum value M (T) of the handshake time. Because of the randomness of experimental settings and algorithms, in order to obtain more objective results, the invention calculates E (T) and M (T) through a large number of experiments, namely, each experiment is repeated for 500 times, and verifies the effectiveness of the three probability distribution schemes proposed in the invention.
Under the conditions of symmetrical and asymmetrical terminal equipment, three probability distribution schemes provided by the invention are tested, and the obtained experimental results are shown in the following tables 1-6:
table 1 simulation experiment result of wireless embedded symmetrical terminal equipment implementation scheme (I)
Table 2 simulation experiment result of wireless embedded asymmetric terminal device execution scheme (i)
TABLE 3 simulation experiment results of wireless embedded symmetrical terminal device execution scheme-
TABLE 4 simulation experiment results of wireless embedded asymmetric terminal device execution scheme 2
TABLE 5 simulation experiment results of the execution scheme of the wireless embedded symmetric terminal device
Table 6. simulation experiment result of wireless embedded asymmetric terminal device execution scheme c
The experimental results can observe that all experiments finally successfully realize handshaking, which shows that the three probability distribution schemes of the wireless embedded network provided by the invention are effective methods under the situation of dynamic change of channel environment.
Referring to fig. 2, fig. 2 is a functional block diagram of a preferred embodiment of a distributed random handshake system in a wireless embedded network according to the present invention, including:
a detecting module 10, configured to detect, in a tth timeslot, all accessible channels of a terminal device to form an accessible channel set of the terminal device, specifically according to the method described above;
a sorting module 20, configured to sequentially sort each channel according to a historical availability of each channel in the terminal device accessible channel set to form a terminal device accessible channel sequential arrangement set, specifically according to the method described above;
a selection probability distribution module 30, configured to distribute an access selection probability for each channel in the sequence arrangement set of accessible channels of the terminal device, specifically as described in the foregoing method;
and a handshake module 40, configured to select each channel in the channel sequence permutation set accessible to the terminal device according to the access selection probability, and attempt handshake until handshake succeeds, otherwise, return to the detection module, and make t equal to t +1, specifically as described in the foregoing method.
The distributed random handshake system in the wireless embedded network, wherein the detection module 10 includes:
a counting unit, configured to count a total number of accessible channels in the wireless embedded network, specifically according to the method described above;
a detecting unit, configured to detect all accessible channels of a terminal device in a wireless embedded network in a tth time slot to form an accessible channel set of the terminal device, where the accessible channel set is expressed by the following formula:
equation (1) is a boolean vector representing the accessible channel condition of terminal a in the tth time slot, where n represents the total number of accessible channels in the wireless embedded network, t represents the tth time slot, and t is 1,2iWhich represents the (i) th channel of the channel,indicating that terminal a can access channel c in the t-th time sloti，Indicating that terminal a cannot access channel c in the t-th sloti；
In the formula (2)Denotes the set of accessible channels, c, of terminal device A in the t-th time slotiWhich represents the (i) th channel of the channel,indicating that terminal a can access channel c in the t-th time slotiAs described in the above method.
The distributed random handshake system in the wireless embedded network, wherein the sorting module 20 includes:
a calculation unit for calculating the ith channel c in the tth time slotiHistory availability for terminal device AThe calculation formula is as follows:
in formula (3), t 'is an integer of (1, t), i.e. represents the t' th timeslot, specifically as described in the above method;
channel history may be profitableA rate aggregation unit for forming a channel c in the t-th slotiHistorical availability set for terminal device AAs described in the above method;
a sorting unit for sorting theAccording to each channel ciHistory availability ofDescending or ascending to obtain the sequence arrangement set of the accessible channels of the terminal equipment ANamely, it isAmong them, the channel …, ci,cj,ck…, corresponding to a channel history availability relationship ofOrAs described in the above-mentioned method.
The selection probability distribution module 30 includes:
a first calculation unit of selection probability, which is used for calculating the access selection probability of each channel allocation in the sequence arrangement set of the accessible channels of the terminal equipment, and comprises the following steps: let terminal equipment A access channel sequence arrangement setAccording toHistorical availability corresponding to medium accessible channelCalculating to obtain the weight distribution probabilityi,cjAnd ck.., respectively, have probabilities ofAndand is
As described in the above method;
a second calculation unit of selection probability, which is used for allocating access selection probability to each channel in the sequence arrangement set of the accessible channels of the terminal device a based on the class index distribution calculation method and comprises the following steps: let terminal equipment A access channel sequence arrangement set
ej-1(6)；
Formula (6) representsThe jth channel element in (a) is assigned a weight,
formula (7) showsTo middleThe probability that j channel elements are selected,wherein e is the Euler number, as specified above;
a third calculation unit of selection probability, which is used for allocating access selection probability to each channel in the sequence arrangement set of the accessible channels of the terminal device a based on the class geometric distribution calculation method and comprises the following steps: let terminal equipment A access channel sequence arrangement set
λ(1-λ)j-1(8)；
Equation (8) representsThe j-th channel element, wherein,λ ∈ (0,1) is a constant parameter of the standard geometric distribution;
formula (9) representsThe corresponding selected probability of the jth channel element,
in summary, the distributed random handshake method and the system thereof in the wireless embedded network provided by the present invention, aiming at the distributed handshake adaptive random handshake method of the embedded terminal device in the distributed wireless accessible channel dynamic environment in the wireless embedded network, provide the distributed handshake method based on the heuristic embedded terminal device by counting the channel state, can effectively enable the communication terminal device to realize the handshake between devices under the condition of dynamic change of the accessible channel, thereby realizing smooth and effective communication.
It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by a computer program that can be stored in a computer-readable storage medium and that can include the processes of the embodiments of the methods described above. The storage medium may be a memory, a magnetic disk, an optical disk, etc.
It is to be understood that the invention is not limited to the examples described above, but that modifications and variations may be effected thereto by those of ordinary skill in the art in light of the foregoing description, and that all such modifications and variations are intended to be within the scope of the invention as defined by the appended claims.
Claims (10)
1. A distributed random handshake method in a wireless embedded network is characterized by comprising the following steps:
step 1, detecting all accessible channels of a terminal device to form an accessible channel set of the terminal device in a tth time slot;
step 2, sequentially arranging each channel according to the historical availability ratio of each channel in the accessible channel set of the terminal equipment to form an accessible channel sequential arrangement set of the terminal equipment;
step 3, distributing access selection probability for each channel in the sequence arrangement set of the accessible channels of the terminal equipment;
and 4, selecting each channel in the sequence arrangement set of the accessible channels of the terminal equipment according to the access selection probability, and trying to handshake until the handshake is successful, otherwise, returning to the step 1, and enabling t to be t + 1.
2. The distributed random handshake method in wireless embedded network according to claim 1, wherein the step 1 includes:
step 11, counting the total number of accessible channels in the wireless embedded network;
step 12, in the t-th time slot, detecting all accessible channels of the terminal equipment in the wireless embedded network to form an accessible channel set of the terminal equipment, and expressing by the following formula:
equation (1) is a boolean vector representing the accessible channel condition of terminal a in the tth time slot, where n represents the total number of accessible channels in the wireless embedded network, t represents the tth time slot, and t is 1,2iWhich represents the (i) th channel of the channel,indicating that terminal a can access channel c in the t-th time sloti，Indicating that terminal a cannot access channel c in the t-th sloti；
In the formula (2)Denotes the set of accessible channels, c, of terminal device A in the t-th time slotiWhich represents the (i) th channel of the channel,indicating that terminal a can access channel c in the t-th time sloti。
3. The distributed random handshake method in the wireless embedded network according to claim 2, wherein the step 2 specifically includes:
step 21, calculating the ith channel c in the t time slotiHistory availability for terminal device AThe calculation formula is as follows:
in formula (3), t 'is an integer of (1, t), i.e. the t' th time slot is represented.
Step 22, forming a channel c in the t time slotiHistorical availability set for terminal device A
Step 23, subjecting the mixture toAccording to each channel ciHistory availability ofDescending or ascending to obtain the sequence arrangement set of the accessible channels of the terminal equipment ANamely, it isAmong them, the channel …, ci,cj,ck…, corresponding to a channel history availability relationship ofOr
4. The distributed random handshake method in a wireless embedded network according to claim 3, wherein the step 11 specifically includes:
if it isThen
If it isThen
Wherein,indicating that terminal a can access channel c in the t-th time sloti，Indicating that terminal a cannot access channel c in the t-th sloti。
5. The distributed random handshake method in the wireless embedded network according to claim 3 or 4, wherein the step 3 specifically is:
the method for calculating the access selection probability of each channel allocation in the sequence arrangement set of the accessible channels of the terminal equipment comprises the following steps: let terminal equipment A access channel sequence arrangement setAccording toHistorical availability corresponding to medium accessible channelAs weight scoresMatching probability, calculating to obtain channeli,cjAnd ck.., the probability of being selected is, and.., and
6. the distributed random handshake method in the wireless embedded network according to claim 3 or 4, wherein the step 3 specifically is:
the method for calculating the access selection probability of each channel in the accessible channel sequence arrangement set of the terminal equipment A based on the class index distribution comprises the following steps: let terminal equipment A access channel sequence arrangement set
ej-1(6)；
Formula (6) representsThe jth channel element in (a) is assigned a weight,
formula (7) showsThe probability that the jth channel element in (j) is selected,
wherein e is the Euler number.
7. The distributed random handshake method in the wireless embedded network according to claim 3 or 4, wherein the step 3 specifically is:
the method for calculating the access selection probability of each channel in the accessible channel sequence arrangement set of the terminal equipment A based on the class geometric distribution comprises the following steps: let terminal equipment A access channel sequence arrangement set
λ(1-λ)j-1(8)；
Equation (8) representsThe j-th channel element, wherein,λ ∈ (0,1) is a constant parameter of the standard geometric distribution;
formula (9) representsThe corresponding selected probability of the jth channel element,
8. a distributed random handshake system in a wireless embedded network, comprising:
a detection module, configured to detect, in a tth timeslot, all accessible channels of a terminal device to form an accessible channel set of the terminal device;
the sequencing module is used for sequentially sequencing each channel according to the historical availability of each channel in the terminal equipment accessible channel set to form a terminal equipment accessible channel sequential arrangement set;
a selection probability distribution module, configured to distribute an access selection probability for each channel in the sequence arrangement set of accessible channels of the terminal device;
and the handshake module is used for selecting each channel in the sequence arrangement set of the accessible channels of the terminal equipment according to the access selection probability and trying to handshake until the handshake is successful, and otherwise, returning to the detection module and enabling t to be t + 1.
9. The distributed random handshake system in a wireless embedded network according to claim 8, wherein the detection module includes:
the statistical unit is used for counting the total number of the accessible channels in the wireless embedded network;
a detecting unit, configured to detect all accessible channels of a terminal device in a wireless embedded network in a tth time slot to form an accessible channel set of the terminal device, where the accessible channel set is expressed by the following formula:
equation (1) is a boolean vector representing the accessible channel condition of terminal a in the tth time slot, where n represents the total number of accessible channels in the wireless embedded network, t represents the tth time slot, and t is 1,2iWhich represents the (i) th channel of the channel,indicating that terminal a can access channel c in the t-th time sloti，Indicating that terminal a cannot access channel c in the t-th sloti；
In the formula (2)Denotes the set of accessible channels, c, of terminal device A in the t-th time slotiWhich represents the (i) th channel of the channel,indicating that terminal a can access channel c in the t-th time sloti。
10. The distributed random handshake system in a wireless embedded network according to claim 8, wherein the sorting module includes:
a calculation unit for calculating the ith channel c in the tth time slotiHistory availability for terminal device AThe calculation formula is as follows:
in formula (3), t 'is an integer of (1, t), i.e. the t' th time slot is represented.
A channel history availability set unit for forming a channel c in the t-th time slotiHistorical availability set for terminal device A
A sorting unit for sorting theAccording to each channel ciHistory availability ofDescending or ascending to obtain the sequence arrangement set of the accessible channels of the terminal equipment ANamely, it isAmong them, the channel …, ci,cj,ck…, corresponding to a channel history availability relationship ofOr
The selection probability distribution module comprises:
a first calculation unit of selection probability, which is used for calculating the access selection probability of each channel allocation in the sequence arrangement set of the accessible channels of the terminal equipment, and comprises the following steps: let terminal equipment A access channel sequence arrangement setAccording toHistorical availability corresponding to medium accessible channelAnd as weight distribution probability, calculating to obtain a channeli,cjAnd ck.., respectively, are selected asAndand is
A second calculation unit of selection probability, which is used for allocating access selection probability to each channel in the sequence arrangement set of the accessible channels of the terminal device a based on the class index distribution calculation method and comprises the following steps: let terminal equipment A access channel sequence arrangement set
ej-1(6)；
Formula (6) representsThe jth channel element in (a) is assigned a weight,
formula (7) showsThe probability that the jth channel element in (j) is selected,
wherein e is the Euler number;
a third calculation unit of selection probability, which is used for allocating access selection probability to each channel in the sequence arrangement set of the accessible channels of the terminal device a based on the class geometric distribution calculation method and comprises the following steps: let terminal equipment A access channel sequence arrangement set
λ(1-λ)j-1(8)；
Equation (8) representsThe j-th channel element, wherein,λ ∈ (0,1) is a constant parameter of the standard geometric distribution;
formula (9) representsThe corresponding selected probability of the jth channel element,
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