CN117952133A - Efficient sensor information acquisition method under large-scale RFID system - Google Patents
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Abstract
The invention relates to the technical field of information acquisition, in particular to a high-efficiency sensor information acquisition method under a large-scale RFID system. The BPIC protocol excludes most of the non-local tags by bloom filters constructed from the local tag responses, then excludes part of the local non-target tags by indicating the vector and schedules the response time slots at the information gathering stage for the target tags. And then in the third stage and the fourth stage, all local non-target tags are forbidden through a minimum perfect hash filter and incremental polling, so that the target tags are not interfered by the non-target tags in the information collection stage, the information collection efficiency is greatly improved, and the problem of low channel utilization rate of the target tag information collection protocol in the existing multi-reader RFID system scene is solved.
Description
Technical Field
The invention relates to the technical field of RFID information acquisition, in particular to a high-efficiency sensor information acquisition method under a large-scale RFID system.
Background
The Radio Frequency Identification (RFID) tag of the sensor can not only provide the identity Identification (ID) of an object, but also provide real-time information of the state of the object or the surrounding environment, and is greatly beneficial to practical application such as warehouse management and inventory control. How to efficiently collect information within integrated microsensor tags (i.e., target tags) is critical to inventory management and in-warehouse environmental monitoring.
Most of the existing tag information collection protocols in the multi-reader scene are based on bloom filters and indication vectors. Although bloom filter-based tag information collection protocols can help readers to quickly find out tag sets in their query areas, the most basic indication vector method is still adopted in the way of collecting tag information, and there are many places that can be optimized.
Disclosure of Invention
The invention aims to provide a high-efficiency sensor information acquisition method under a large-scale RFID system, and aims to solve the problem of low utilization rate of a target tag information acquisition protocol channel under the existing multi-reader RFID system scene.
In order to achieve the above purpose, the invention provides a method for efficiently collecting sensor information under a large-scale RFID system, which comprises the following steps:
Identifying tags located within the reader query area using a bloom filter;
arranging a response sequence for the target tags in the query area by broadcasting multiple rounds of allocation vectors;
deactivating non-target tags in the query region using a minimum perfect hash filter and an incremental polling technique;
The target tag information is collected sequentially using a frame slot ALOHA protocol.
The labels in the query area are divided into target labels needing to collect information and non-target labels not needing to collect information.
Wherein the using a bloom filter to validate tags located within a reader query area comprises:
constructing a bloom filter by collecting responses of the tags;
the bloom filter is used to find a set of local tags.
Wherein the construction of the bloom filter by means of collecting the responses of the tags comprises:
the reader constructs bloom filter parameters by broadcasting;
Each tag issuing a response signal based on the bloom filter parameters;
The reader constructs a bloom filter based on the response signal.
The method comprises the steps of using a minimum perfect hash filter and an incremental polling technology to deactivate non-target tags in the query area, and comprises the following steps:
The reader constructs a perfect minimum hash filter according to the response sequence of the target tag and broadcasts the perfect minimum hash filter;
The label performs deactivation operation on the label when the result of the label after receiving the minimum perfect hash filter is not matched with the label;
And the reader uses an increment round sequence to deactivate non-target labels which do not deactivate in the query area.
The invention discloses a high-efficiency sensor information acquisition method under a large-scale RFID system, which comprises the following steps: identifying tags located within the reader query area using a bloom filter; arranging a response sequence for the target tags in the query area by broadcasting multiple rounds of allocation vectors; deactivating non-target tags in the query region using a minimum perfect hash filter and an incremental polling technique; the target tag information is collected sequentially using a frame slot ALOHA protocol. The method is a bloom-perfect hash target tag information collection (BPIC) protocol proposed based on a bloom filter and a minimum perfect hash filter. The BPIC protocol excludes most of the non-local tags by bloom filters constructed from the local tag responses, then excludes part of the local non-target tags by indicating the vector and schedules the response time slots at the information gathering stage for the target tags. And then, in the third stage and the fourth stage, all local non-target tags are forbidden through a minimum perfect hash filter and incremental polling, so that the information collection stage of the target tags in the fifth stage is interfered by the non-target tags, the information collection efficiency is greatly improved, and the problem of low utilization rate of the target tag information collection protocol channels in the existing multi-reader RFID system scene is solved.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a flowchart of a method for collecting information of a high-efficiency sensor in a large-scale RFID system.
Fig. 2 is a non-local tag validation phase execution.
Fig. 3 is an allocation phase flow.
Fig. 4 is an example of mapping between labels and slots in a non-target label filtering stage.
Fig. 5 is an incremental polling phase execution.
Detailed Description
Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative and intended to explain the present invention and should not be construed as limiting the invention.
Referring to fig. 1 to 5, the present invention provides a method for collecting information of a high-efficiency sensor in a large-scale RFID system, comprising the following steps:
s1, confirming labels located in a query area of a reader by using a bloom filter;
The tags in the query area are divided into target tags requiring information collection and non-target tags not requiring information collection.
S11, constructing a bloom filter by means of collecting responses of the tags;
S111, the reader constructs bloom filter parameters through broadcasting;
specifically, the reader r first broadcasts a query command containing two parameters, m r and k r, where m r is the length of the bloom filter and k r is the number of independent hash functions used to construct the bloom filter.
S112, each tag sends out a response signal based on the bloom filter parameters;
Specifically, each tag receiving a request generates a vector of length m r bits and initializes all bits to 0. Then, the tags perform hash operation with their own ID using k r hash functions defined by the reader, and the calculation result of each hash function is mapped to a corresponding position in the vector, and is set to 1.
The reader builds a bloom filter based on the response signal S113.
Specifically, as shown in fig. 2 (b), at the physical layer, a binary "0" corresponds to an idle carrier, i.e., no transmission signal is detected in the channel; a binary "1" corresponds to a busy carrier, i.e. a transmission signal is detected in the channel. When receiving the response of the tag, the reader sets the value of a certain bit to 0 if it does not receive any transmission signal in the channel. If any tag has transmitted a signal in this bit, the value of this bit is set to 1. After the transmission of the bloom filter bitmap generated by the tag in the query area is completed, the reader can obtain a new bloom filter B r with a length of m r.
S12 finds a set of local tags using the bloom filter.
Specifically, as shown in fig. 2 (c), for each ID of the tag in the set U of all the tags in the system, the same k r hash functions as received by the tag are used to test, if the calculation result of one hash function is mapped to a value of 0 at the corresponding position in B r, the corresponding tag is definitely not in the set L r of the tag compositions in the query area, otherwise, the tag is considered to be included in L r. The reader extracts a new set L' r from U according to B r, which contains all tags located in the query area of the reader. However, since bloom filters may produce false positive results, L' r may contain non-local tags that are not partially within the query region of the reader, denoted asFinally, the reader then finds out all target tag sets W 'r from the set L' r, which may be located in the query region, as such/>
To determine the parameters of the bloom filter, τ bit is first defined as the length of time required for the reader to transmit 1 bit; defining τ inf as the length of time it takes for a tag to show its presence in one slot and transmit all necessary data, i.e., the length of time a tag takes part in a reply; defining t id as the time required by the reader to transmit the 96-bit ID of the tag, t bit as the time required by the reader to transmit 1-bit data, and t e as the interval between two transmissions of the reader; p is defined as the probability of false positives in the bloom filter.
In addition, the approximate number of tags within the query range of the reader (i.e., local tags) must be estimated by other means at a very low time costAnd according to/>Finding the proportion/>, of the local tags in all tags in the system
Wherein the best false positive probability of the readerThe calculation formula of (2) is as follows:
At the same time, when Time/>
Based on false positive probability of bloom filterThe sizes of m r and k r can be determined.
S2, arranging response sequences for target tags in the query area by broadcasting multiple rounds of allocation vectors.
S21, constructing an allocation vector.
Specifically, each tag in the set W 'r needs to be assigned one to the consecutive time slots from 0 to W' r -1, with one and only one tag in each time slot. The dispensing phase consists of a plurality of rounds. Before each round starts, the reader predicts the time slot selected by the tag to which the time slot has not been allocated using a hash function, and then creates an indication vector based on the result. Assuming that the set of unassigned target tags is N i at the beginning of the ith round, the reader calculates the length V i of the indication vector V i from the number of tags in set N i. How the v i size is determined will be explained later. The reader then generates two random number seeds r 1 and r 2 and, based on the target tag ID that has not yet been assigned, brings the hash function H (ID, r 1)modvi calculates the position of the tag map in the indicator vector V i:
(1) If the element of the target tag map location is '00', it is set to '01'.
(2) If the element of the target label mapping location is '01', it indicates that there is already one label allocated to this location, let the two labels allocated there coordinate with the hash function H (ID, r 2) mod2 using the random number seed r 2, if the two labels calculate the result to be unequal, coordinate successfully, set the element of this location to '10', if the two labels coordinate using r 2 to be equal, set this location to '11', representing that the labels mapped to this location do not need to do any operation, and wait for the allocation of the next round.
(3) If the element of the target tag map location is '10', it means that there are already two tags assigned to the location, and the third tag can no longer be reconciled, thus setting the element of the location to '11'.
(4) If the element of the target tag map location is '11', it remains unchanged.
After calculating the indication vector V i, the reader first broadcasts necessary parameters including the indication vector length V i, the random number seeds r 1 and r 2, the number of assigned target tags a, and the like, and then broadcasts the indication vector V i.
Assume that the number of '01' elements preceding the mapped position in the indication vector V i is x 1 and the number of '10' elements is x 2. As shown in fig. 3, after receiving the indication vector V i and other parameters, the tag calculates its position mapped in the allocation vector according to its ID:
(1) If the element of the location is '00', the tag is a non-target tag, which is deactivated and remains silent in a later stage.
(2) If the element of this position is '01', its slot sequence number x in the collection phase is calculated from x=a+x 1+2x2.
(3) If the element of this position is '10', its slot sequence number x in the collect phase is calculated according to the formula x=a+x 1+2x2+(H(ID,r2) mod 2).
(4) If the element corresponding to the tag is '11', no operation is performed.
S22, calculating relevant parameters.
In the ith round of the allocation phase, in order to determine the length of the indication vector v i, the number of target tags defining the remaining unallocated slot order in the ith round is w i
Therefore, the length v i of the indication vector in the ith round is calculated in the following manner:
In addition, in the ith round in the allocation phase, the number of non-target tags that are not deactivated is defined as m i, and after the allocation vector V i is broadcast by the reader, the number of deactivated tags e i is calculated in the following manner:
Wherein:
Assuming that the reader has broadcast k rounds of allocation vectors in total during the allocation phase, the number of non-target tags n eli that are deactivated during the entire allocation phase can be calculated according to equation 5 as:
s3, using a minimum perfect hash filter and an incremental polling technology to deactivate non-target tags in the query area.
S31, the reader constructs a perfect minimum hash filter according to the response sequence of the target labels and broadcasts the perfect minimum hash filter.
S311, constructing a minimum perfect hash filter;
In particular, the reader needs to construct a Minimum Perfect Hash Filter (MPHF) to filter out most non-target tags, preventing them from interfering with the information collection of target tags. MPHF is a filter made up of w' r elements, each element being a hashed fingerprint of the corresponding target tag, with a length of d bits. How the length of the hashed fingerprint d is determined will be explained later. The reader transmits the entire MPHF sequence according to the slot order assigned by the target tag in the assignment phase. If the tag that was scheduled to reply in the x-th time slot finds that the x-th fingerprint in MPHF does not match its own fingerprint, the tag will deactivate and remain silent in later stages. Most non-target tags can be filtered out through MPHF filtering, without interference when the reader collects target tag information, because each fingerprint is calculated based on the ID of the corresponding target tag. When the reader broadcasts MPHF sequences, tag 7 and tag 8, which are scheduled to respond at time slot 1, are brought into the hash function that computes MPHF fingerprints based on their IDs, the results of which are shown in table 1. The calculation result of the tag 7 is the same as the 1 st hash fingerprint in MPHF sequences broadcast by the reader, which means that the tag 7 is the target tag and does not do any action, while the calculation result of the tag 8 is different from the calculation result broadcast by the reader, which means that the tag 8 is a non-target tag, and the silence needs to be maintained in the subsequent stage.
Table 1 hash fingerprint of a tag
S312 related parameter calculation
The calculation formula of the length d of the hash fingerprint is as follows:
S32, if the result of the label after receiving the minimum perfect hash filter is not matched with the label, the label deactivates the label.
And S33, the reader uses an increment order to deactivate non-target tags which do not deactivate in the query area.
In particular, the purpose of incremental polling is to exclude false positive tags that occur during the non-target tag filtering stage. False positive tags such as tag 9 in fig. 4, if not excluded, may send data simultaneously with the target tag during the information collection phase, forming conflicting time slots, affecting the collection of target tag information by the reader. At the same time, the probability of false positives is low, so that the labels can be rapidly removed by adopting a polling mechanism.
Before the polling phase begins, the reader first generates an 8-bit random number seed r s, then finds the spacing s n between all adjacent non-target tags based on the positions that the non-target tags map in the collection phase slot, and finds the maximum value of the spacing s n, finding its length s max in binary representation. Then, the reader finds out the time slot with the largest number of tags in the time slots mapped with the non-target tags, and according to the number of tags mapped in the time slot, calculates the bit length y l of the acknowledgement value y,Where n represents the number of tags mapped to the slot, including the target tag. If the number of tags mapped to the slot does not exceed 4, then n=4 is taken. Meanwhile, let the time slot sequence of the tag in the collection stage be c slot, that is, the value in the slot counter of the tag be c slot, and the tag step counter be c step.
The reader broadcasts the relevant parameters r, s max and y l to begin the polling phase. After the tag receives the polling parameter, it sets the step counter to 0. The incremental polling phase is performed by the reader sending s n = 2 and y = 1, starting to check the first time slot containing a non-target tag, where y is the result of the target tag calculation H mapped in this time slot (ID, r s)mod2yl. When the tag receives s n, the step counter is incremented by this value, i.e. c step＝cstep+sn. If c step＝cslot +1 is this time, its ID is brought into the hash function with the random number seed r s to calculate the validation value y, if y is the same as the value of y broadcast by the reader, this represents that the tag is the target tag, if not, this tag is a non-target tag, and the tag is deactivated to keep it silent in the subsequent collection phase.
If the same situation occurs for the acknowledgement value y for both the target and non-target tags, the reader sends a poll command with an increment step size of s n = 0, while the acknowledgement value y becomes the target tag calculation H (ID, the result after r s+1)mod2yl. When the tag receives the command with an increment step size of 0, the value of the random number seed r s for all tags in the slot becomes r s＝rs +1, the acknowledgement value y is recalculated and compared with the new acknowledgement value y broadcast by the reader.
S4, sequentially collecting target tag information by using a frame time slot ALOHA protocol.
Specifically, the reader issues a Query command to initiate a special frame slot ALOHA protocol having w' r slots to collect tag data. After receiving the Query instruction, if the slot counter c slot =0, the tag immediately sends the information recorded in the storage area to the reader. Since a separate response time slot has been scheduled for each target tag and all non-target tags are deactivated during the allocation phase, no tag response collision occurs during the collection phase and data for each tag can be successfully collected. At the end of each slot, the reader broadcasts a QueryRep instruction to start the next slot. After receiving the QueryRep command, the tag decrements its slot counter by 1, i.e., c slot＝cslot -1, and if the tag's slot counter is equal to zero at this time, then a reply is made in that slot.
The beneficial effects are that:
Bloom-perfect hash target tag information collection (BPIC) protocol based on bloom filter and minimum perfect hash filter. The BPIC protocol excludes most of the non-local tags by bloom filters constructed from the local tag responses, then excludes part of the local non-target tags by indicating the vector and schedules the response time slots at the information gathering stage for the target tags. And then, in the third stage and the fourth stage, all local non-target tags are forbidden through a minimum perfect hash filter and incremental polling, so that the target tags are not interfered by the non-target tags in the information collecting stage, and the information collecting efficiency is greatly improved.
The foregoing disclosure is only a preferred embodiment of a method for collecting information of a high-efficiency sensor in a large-scale RFID system, but it should be understood that the scope of the invention is not limited thereto, and those skilled in the art will understand that all or part of the procedures for implementing the above embodiments are equivalent and still fall within the scope of the invention.
Claims (5)
1. The efficient sensor information acquisition method under the large-scale RFID system is characterized by comprising the following steps of:
Identifying tags located within the reader query area using a bloom filter;
arranging a response sequence for the target tags in the query area by broadcasting multiple rounds of allocation vectors;
deactivating non-target tags in the query region using a minimum perfect hash filter and an incremental polling technique;
The target tag information is collected sequentially using a frame slot ALOHA protocol.
2. A method for efficient sensor information collection in a large-scale RFID system as recited in claim 1, wherein,
The tags in the query area are divided into target tags requiring information collection and non-target tags not requiring information collection.
3. A method for efficient sensor information collection in a large-scale RFID system as recited in claim 2, wherein,
The use of a bloom filter to validate tags located within a reader query area includes:
constructing a bloom filter by collecting responses of the tags;
the bloom filter is used to find a set of local tags.
4. A method for efficient sensor information collection in a large-scale RFID system as defined in claim 3,
The construction of the bloom filter by collecting the responses of the tags comprises the following steps:
the reader constructs bloom filter parameters by broadcasting;
Each tag issuing a response signal based on the bloom filter parameters;
The reader constructs a bloom filter based on the response signal.
5. A method for efficient sensor information collection in a large-scale RFID system as recited in claim 4, wherein,
The deactivating non-target tags within the query region using a minimum perfect hash filter and incremental polling technique includes:
The reader constructs a perfect minimum hash filter according to the response sequence of the target tag and broadcasts the perfect minimum hash filter;
The label performs deactivation operation on the label when the result of the label after receiving the minimum perfect hash filter is not matched with the label;
And the reader uses the increment round sequence to deactivate the non-target labels which do not deactivate in the query area.
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