Same-frequency interference suppression method and system during networking of multiple transformer areas and storage medium

Co-frequency interference suppression method, system and storage medium technology field when multiple stations are networked

[0001] The present invention relates to the field of communication technology, and in particular to a co-channel interference suppression method when multiple stations are networked, a co-channel interference suppression system when multiple stations are networked, and a computer-readable storage medium.

Background technique

[0002] At present, in the electricity consumption information collection system, adjacent station areas are divided according to the network topology of the power line, and the station areas cannot be distinguished strictly according to physical distance. Therefore, it will be interfered by signals from neighboring stations during wireless communication.

[0003] This interference may be very close to the receiver. If FSK technology is used, it can only be solved by collision retransmission. If LORA technology is used, Chirp modulation with different slopes can be used to solve it, but this limits the data rate. The choice of bandwidth and bandwidth leads to complex networking algorithms in practical applications and inflexible selection of wireless transmission parameters. If time division or frequency division is used to avoid interference from adjacent stations, strict synchronization and frequency scheduling between adjacent stations must be required, neighbouring stations need to communicate with each other, which increases the complexity of the system. If multiple clusters are designed in an ad hoc network, and network management and authentication are realized through the selection of cluster heads, complex protocol support is required, the update time is long, and the system overhead is high.

Summary of the invention

[0004] The present invention aims to solve one of the technical problems in the related art at least to a certain extent. For this reason, the first purpose of the present invention is to propose a co-channel interference suppression method when multiple stations are networked, which can reduce the frequency repetition probability of each station area, avoid co-channel interference between stations, and The networking protocol is simple, which is conducive to the realization of the network control and management of each station area.

[0005] The second object of the present invention is to provide a computer-readable storage medium.

[0006] The third object of the present invention is to propose a co-channel interference suppression system when multiple stations are networked.

[0007] In order to achieve the above objective, the co-channel interference suppression method when multiple stations are networked in the first embodiment of the present invention includes the following steps: obtaining identification information of each station; generating frequency hopping instructions, and The identification information of each station area and the frequency hopping instruction generate a frequency hopping control word, and the frequency hopping frequency point synthesizer is controlled according to the frequency hopping control word to synthesize the frequency points corresponding to each station area; according to the corresponding frequency points of each station area Generate the frequency hopping pattern of each station area so that each station area conducts network communication according to the corresponding frequency hopping pattern.

[0008] According to the method for co-channel interference suppression when multiple stations are networked according to the embodiment of the present invention, firstly, the identification information of each station is acquired, and then a frequency hopping instruction is generated, and according to the identification information of each station and The frequency hopping command generates the frequency hopping control word, and according to the frequency hopping control word, the frequency hopping frequency synthesizer synthesizes the frequency points corresponding to each station area. Finally, the frequency hopping of each station area is generated according to the frequency points corresponding to each station area. Pattern, so that each station area conducts network communication according to the corresponding frequency hopping pattern. Therefore, through the frequency hopping pattern generated by the corresponding frequency point of each station area, each station area is distinguished and frequency hopping networked, thereby reducing the frequency point repetition probability of each station area and avoiding inter-station area. Co-frequency interference and simple networking protocol are conducive to the realization of network control and management for each station area.

[0009] In addition, the co-channel interference suppression method when multiple stations are networked in the foregoing embodiment of the present invention may also have the following additional technical features:

[0010] According to an embodiment of the present invention, a frequency hopping instruction is generated by a PN code generator, wherein the PN code generator

The pseudo-random sequence used is an n-level m sequence.

[0011] According to an embodiment of the present invention, the n-level m sequence is associated with the number M of frequency points, the length L of the frequency hopping pattern, and the number K of stations.

[0012] According to an embodiment of the present invention, the frequency hopping period is T=L*K, the number of stages n of the m sequence is not less than log2(T), and satisfies 2n>M, the number of taps r of the n-stage m sequence Corresponding to the number of frequency points M, satisfies r = log2 (M).

[0013] According to an embodiment of the present invention, generating a frequency hopping control word according to the identification information of each station area and the frequency hopping instruction includes: generating an m sequence through a PN code generator under clock control, and from The r taps are extracted among the n-level registers of the m sequence, and when the status in the r registers changes cyclically, they are added to the identification information of each station area to obtain the frequency hopping control word.

[0014] In order to achieve the above objective, the computer-readable storage medium provided by the embodiment of the second aspect of the present invention stores a co-channel interference suppression program when multiple stations are networked, and the co-channel interference suppression program is executed by a processor. When realizing the same frequency interference suppression method when multiple stations are networked as described above.

[0015] According to the computer-readable storage medium of the embodiment of the present invention, the same frequency interference suppression program is executed by the processor when multiple stations are networked, which can reduce the frequency point repetition probability of each station area, and avoid the interference between stations. Co-frequency interference and simple networking protocol are conducive to the realization of network control and management for each station area.

[0016] In order to achieve the above-mentioned objective, the co-channel interference suppression system for multi-zone networking proposed by the embodiment of the third aspect of the present invention includes: an acquisition module for acquiring identification information of each zone; a generation module for To generate a frequency hopping instruction, generate a frequency hopping control word according to the identification information of each station area and the frequency hopping instruction, and control the frequency hopping frequency synthesizer to synthesize the corresponding information of each station area according to the frequency hopping control word Frequency point, and generate the frequency hopping pattern of each station area according to the corresponding frequency point of each station area, so that each station area conducts network communication according to the corresponding frequency hopping pattern.

[0017] According to the co-frequency interference suppression system when multiple stations are networked in the embodiment of the present invention, the identification information of each station is obtained through the acquisition module, and the frequency hopping instruction is generated through the generation module, and the frequency hopping instruction is generated according to the The identification information and frequency hopping instructions generate frequency hopping control words, and control the frequency hopping frequency synthesizer according to the frequency hopping control words to synthesize the frequency points corresponding to each station area, and generate the frequency points corresponding to each station area according to the frequency points corresponding to each station area. Frequency hopping pattern, so that each station area conducts network communication according to the corresponding frequency hopping pattern. Therefore, through the frequency hopping pattern generated by the frequency point corresponding to each station area, each station area is distinguished and the frequency hopping network is formed, thereby reducing the frequency repetition probability of each station area and avoiding the interference between the station areas. Co-channel interference and simple networking protocol are conducive to the realization of network control and management for each station area.

[0018] In addition, the co-channel interference suppression system when multiple stations are networked in the foregoing embodiment of the present invention may also have the following additional technical features:

[0019] According to an embodiment of the present invention, the generating module generates a frequency hopping instruction through a PN code generator, wherein the pseudo-random sequence adopted by the PN code generator is an n-level m sequence.

[0020] According to an embodiment of the present invention, the n-level m sequence is associated with the number of frequency points M, the length of the frequency hopping pattern L, and the number of stations K, where the frequency hopping period is T=L*K, m sequence The number of series n is not less than log2 and satisfies 2n>M. The number of taps r of the n-level m sequence corresponds to the number of frequency points M, and satisfies r = log2 (M).

[0021] According to an embodiment of the present invention, the generating module is also used to generate m sequence through a PN code generator under clock control, and extract r taps from n-level registers of the m sequence, and When the status in the register changes cyclically, it is added to the identification information of each station area to obtain the frequency hopping control word.

[0022] Additional aspects and advantages of the present invention will be partly given in the following description, and part of it will become obvious from the following description, or be understood through the practice of the present invention.

Description of the drawings

[0023] FIG. 1 is a schematic flowchart of a method for co-channel interference suppression when multiple stations are networked according to an embodiment of the present invention;

[0024] FIG. 2 is a schematic flowchart of a method for co-channel interference suppression when multiple stations are networked according to an embodiment of the present invention;

[0025] FIG. 3 is a schematic flowchart of a method for co-channel interference suppression when multiple stations are networked according to a specific embodiment of the present invention;

[0026] FIG. 4 is a schematic diagram of a frequency hopping pattern generation structure according to an embodiment of the present invention;

[0027] FIG. 5 is a schematic structural diagram of a PN code generator according to an embodiment of the present invention;

[0028] FIG. 6 is a block diagram of a co-channel interference suppression system when multiple stations are networked according to an embodiment of the present invention.

Detailed ways

[0029] The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings, in which the same or similar reference numerals indicate the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the drawings are exemplary, and are intended to explain the present invention, but should not be construed as limiting the present invention.

[0030] The following describes the co-channel interference suppression method in the multi-zone networking, the co-channel interference suppression system and the computer-readable storage medium in the multi-zone networking of the embodiments of the present invention with reference to the accompanying drawings.

[0031] FIG. 1 is a schematic flowchart of a method for co-channel interference suppression when multiple stations are networked according to an embodiment of the present invention. As shown in Figure 1, the co-channel interference suppression method when multiple stations are networked includes the following steps:

[0032] S101. Obtain identification information of each station area.

[0033] Optionally, the identification information of each station area may include the ID of each station area or a preset initial value of the specific phase of the station area.

[0034] S102. Generate frequency hopping instructions, and generate frequency hopping control words according to the identification information and frequency hopping instructions of each station area, and control the frequency hopping frequency synthesizer to synthesize the frequency points corresponding to each station area according to the frequency hopping control words .

[0035] It can be understood that after synthesizing the frequency points corresponding to each station area, an available frequency point set can also be formed according to the frequency points corresponding to each station area, so that each station area can share the available frequency point set The internal frequency point resources, so that the frequency point distribution between multiple stations can have randomness and uniformity.

[0036] S103: Generate a frequency hopping pattern for each station area according to the frequency points corresponding to each station area, so that each station area performs networking communication according to the corresponding frequency hopping pattern.

[0037] It should be understood that since the frequency point corresponding to each station area is synthesized by the frequency hopping frequency point synthesizer according to the frequency hopping control word, and the frequency hopping pattern of each station area is generated according to the frequency point corresponding to each station area, Therefore, the correlation of the frequency hopping pattern between each station area can be reduced, thereby reducing the probability of collision of frequency points in adjacent areas.

[0038] Therefore, the frequency hopping pattern of each station area is generated according to the corresponding frequency point of each station area, so that each station area performs network communication according to the corresponding frequency hopping pattern, which can reduce the frequency point of each station area. The repetition probability avoids co-frequency interference between stations, and the networking protocol is simple, which is conducive to the realization of network control and management for each station area.

[0039] Further, the frequency hopping instruction is generated by the PN code generator, wherein the pseudo-random sequence adopted by the PN code generator is an n-level m sequence.

[0040] That is to say, the PN code generator generates frequency hopping instructions based on n-level m sequences to generate frequency hopping control words according to the identification information and frequency hopping instructions of each station area, thereby controlling the frequency hopping according to the frequency hopping control words The point synthesizer synthesizes the frequency points corresponding to each zone.

[0041] Further, the n-level m sequence is associated with the number M of frequency points, the length L of the frequency hopping pattern, and the number K of stations.

[0042] The number of frequency points M, the length L of the frequency hopping pattern, and the number of stations K are respectively described below: 1) The number of frequency points M: can be selected at equal intervals in the 470MHz~510MHz frequency band, for example, can be adjusted according to the working bandwidth The number of frequency points M is set accordingly, and the value is 8, 16, 32, or 64; 2) The length of the frequency hopping pattern L: related to the symbol duration, for example, a short symbol uses one frequency point for each symbol, and L symbols are aggregated into One group, using a frequency hopping pattern of length L, and each long symbol can be divided into L segments, or multiple (less than L) long symbols can be aggregated into a group, using a frequency hopping pattern of length L, in order to Make full use of frequency point resources, the value can be L=M, in addition, support L<M at the same time; 3) Number of stations K: It can support multiple values, for example, the value K=16.

[0043] Specifically, the n-level m sequence is associated with the number of frequency points M, the length of the frequency hopping pattern L, and the number of stations K, which is specifically embodied as: The frequency hopping period is T=L*K, and the number of m sequences n is not Less than log2 (T), and satisfying 2n>M, the number of taps r of the n-level m sequence corresponds to the number of frequency points M, and satisfies r = log2 (M).

[0044] Taking the number of frequency points M as 64, the length L of the frequency hopping pattern as 64, and the number of stations as an example, it can be obtained by the above calculation formula that n=10 and r=6.

[0045] Further, as shown in FIG. 2, the frequency hopping control word is generated according to the identification information of each station area and the frequency hopping instruction, including:

[0046] S1021: Generate m sequence through PN code generator under clock control, and extract r taps from n-level registers of m sequence, as well as the identification of each zone when the state of r registers changes cyclically The information is added to obtain the frequency hopping control word.

[0047] Optionally, the specific manner of extracting r taps from among the n-level registers of the m sequence may include, but is not limited to, adjacent extraction and equal interval extraction.

[0048] Specifically, as shown in FIG. 3, the co-channel interference suppression method when multiple stations are networked in the embodiment of the present invention specifically includes the following steps:

[0049] S1, frequency synthesis.

[0050] Specifically, as shown in FIG. 4, the PN code generator is connected to the frequency hopping frequency point synthesizer, and the PN code generator can select m-sequence or other pseudo-random sequences. Among them, the m-sequence-based frequency hopping sequence is composed of linear The feedback shift register (LFSR) generates and takes the r bits of the m sequence state sequence to combine to form a new sequence as a frequency hopping sequence, which is used to control the frequency hopping frequency point synthesizer.

[0051] In other words, as shown in Figure 5, based on the n-level m sequence generator on the finite field GF2, the frequency synthesizer is weighted by r taps, where the PN code generator generates the m sequence under clock control, r When the status in each register changes cyclically, it is added to the identification information of each station area. Each time 1 bit is shifted out, a frequency hopping control word is obtained. Therefore, the frequency hopping frequency point synthesizer is controlled according to the frequency control word to synthesize each station area's corresponding Frequency point, where n-level m sequence is generated and processed, and each log2 (M) bit is combined into a byte, and the decimal value corresponding to the byte is the frequency point number.

[0052] S2. Obtain a frequency list of the current station.

[0053] It should be noted that if the maximum value of the station area ID is less than 2r, part of the bits in the identification information of each station area can be fixed to 0, and according to the parameters, each bit shifted by 1 will output the S of a transformation equation. The value is used as the frequency point sequence number of the current station area until L frequency point sequence numbers are obtained, and at the same time, the frequency point list of the current station area is saved.

[0054] S3, it is judged whether to traverse all the stations, if yes, then step S4 is executed; if not, then step S1 is executed.

[0055] That is to say, if all the stations are not traversed, steps S1 and S2 are repeatedly executed to ensure that the frequency point list of all stations is obtained.

[0056] S4, save a list of all station frequency points.

[0057] In the following, in conjunction with a specific embodiment of the present invention, the above-mentioned execution steps will be further described.

[0058] Taking the value of the frequency point M as 64, the m-sequence order n as 10, the number of stations K as 16, and the number of taps as an example, they are adjacent to each other in the 10-level register of the m-sequence Select 6 taps and control the output of the frequency synthesizer after transformation.

[0059] The m sequence generator has additional taps, and the transformation equation is expressed as: S = 32* (X3+U5) +16* (X4+U4) +8* (X5+U3) +4* (X6+U2) +2 * (X7+U1) + (X8+U0), the above-mentioned additions are all modulo-2 additions, among which, the value of U is 0 or 1, a total of 64 kinds, that is, up to 64 frequency hopping sequences can be generated.

[0060] It can be understood that since the number of stations K=16, only 16 sequences U are needed. At this time, U5=U4=0, so that the calculated S value corresponds to the M frequency point sequence numbers. Make full use of frequency resources.

[0061] In addition, the frequency synthesizer continues to output the S value corresponding to the current U value. For example, according to the aforementioned parameters and transformation equations, each bit is shifted and an S value is output as the frequency point number of the current station area until L is obtained. Frequency point serial number, at the same time, save the frequency point list of the current station area.

[0062] Then, take U=U+1, and repeat the aforementioned frequency point generation step, traverse all the station areas to obtain the frequency point sequence numbers of all the station areas, until the frequency point sequence number list of all K station areas is completed.

[0063] It should be noted that the co-channel interference suppression method when multiple stations are networked in the embodiment of the present invention can output corresponding frequency points according to the input station area number, and the frequency point repetition probability is low, so as to avoid the same frequency between stations. At the same time, the networking protocol is simple, which is easy for network control and management.

[0064] In summary, according to the method for co-channel interference suppression when multiple stations are networked according to the embodiment of the present invention, firstly, the identification information of each station is obtained, and then the frequency hopping instruction is generated, and the frequency hopping command is generated according to the Identification information and frequency hopping instructions generate frequency hopping control words, and control the frequency hopping frequency synthesizer according to the frequency hopping control words to synthesize the frequency points corresponding to each station area, and finally, generate each station area according to the frequency points corresponding to each station area Frequency hopping pattern, so that each station area carries out networking communication according to the corresponding frequency hopping pattern. Therefore, through the frequency hopping pattern generated by the corresponding frequency point of each station area, each station area is distinguished and frequency hopping networked, thereby reducing the frequency point repetition probability of each station area and avoiding inter-station area. Co-frequency interference and simple networking protocol are conducive to the realization of network control and management for each station area.

[0065] Further, the embodiment of the present invention also provides a computer-readable storage medium, on which is stored a co-channel interference suppression program when multiple stations are networked, and the co-channel interference suppression program is implemented when executed by a processor. The same frequency interference suppression method when multiple stations are networked in the above embodiment of the present invention.

[0066] In summary, according to the computer-readable storage medium of the embodiment of the present invention, the same-frequency interference suppression program when multiple stations are networked is executed by the processor, which can reduce the probability of repetition of frequency points in each station area and avoid the station area. The same frequency interference between the two and the simple networking protocol is conducive to the realization of the network control and management of each station area.

[0067] FIG. 6 is a block diagram of a co-channel interference suppression system when multiple stations are networked according to an embodiment of the present invention. As shown in FIG. 6, the co-channel interference suppression system 100 when multiple stations are networked includes: an acquisition module 1 and a generation module 2.

[0068] Specifically, the acquisition module 1 is used to acquire the identification information of each station area; the generation module 2 is used to generate frequency hopping instructions, and generate frequency hopping control words according to the identification information and frequency hopping instructions of each station area, and According to the frequency hopping control word, the frequency hopping frequency point synthesizer is controlled to synthesize the corresponding frequency points of each station area, and the frequency hopping pattern of each station area is generated according to the corresponding frequency point of each station area, so that each station area is based on the corresponding hop Frequency pattern for networking communication.

[0069] Therefore, the generating module generates the frequency hopping pattern of each station area according to the corresponding frequency point of each station area, so that each station area performs network communication according to the corresponding frequency hopping pattern, which can reduce the frequency of each station area. The probability of repetition of frequency points avoids co-frequency interference between stations, and the networking protocol is simple, which is conducive to the realization of network control and management for each station area.

[0070] Further, the generating module 2 generates a frequency hopping instruction through a PN code generator, where the pseudo

The random sequence is an n-level m sequence.

[0071] Further, the n-level m sequence is associated with the number of frequency points M, the length of the frequency hopping pattern L, and the number of stations K, where the frequency hopping period is T=L*K, and the number of m sequences n is not less than 10g2 (T), and satisfies 2n>M, the number of taps r of the n-level m sequence corresponds to the number of frequency points M, and satisfies r = 1og2(M).

[0072] Further, the generating module 2 is also used to generate m sequence through a PN code generator under clock control, and extract r taps from n-level registers of the m sequence, and the state cyclic change in the r registers Time is added to the identification information of each station area to obtain the frequency hopping control word.

[0073] It should be noted that the co-channel interference suppression system in the multi-zone networking of the embodiment of the present invention is the same as the above-mentioned co-channel interference suppression method in the multi-zone networking of the embodiment of the present invention. Correspondence, I won't repeat it here.

[0074] In summary, according to the same-frequency interference suppression system when multiple stations are networked in the embodiment of the present invention, the identification information of each station is obtained through the acquisition module, and the frequency hopping instruction is generated through the generation module, and the frequency hopping instruction is generated according to each The identification information of the station area and the frequency hopping command generate frequency hopping control words, and the frequency hopping frequency point synthesizer controls the frequency hopping frequency point synthesizer to synthesize the frequency points corresponding to each station area according to the frequency hopping control word, and generates each frequency point according to the frequency points corresponding to each station area. The frequency hopping pattern of the station area, so that each station area conducts network communication according to the corresponding frequency hopping pattern. Therefore, through the frequency hopping pattern generated by the corresponding frequency point of each station area, each station area is distinguished and frequency hopping networked, thereby reducing the frequency point repetition probability of each station area and avoiding inter-station area. Co-frequency interference and simple networking protocol are conducive to the realization of network control and management for each station area.

[0075] It should be noted that the logic and/or steps shown in the flowchart or described herein in other ways, for example, can be considered as a sequence table of executable instructions for implementing logic functions, and can be specifically implemented In any computer-readable medium, for use by an instruction execution system, device, or device (such as a computer-based system, a system including a processor, or other systems that can fetch instructions from an instruction execution system, device, or device and execute the instructions), Or it can be used in combination with these instruction execution systems, devices or equipment. For this purpose, a "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device, or device or in combination with these instruction execution systems, devices, or devices. More specific examples (non-exhaustive list) of computer readable media include the following: electrical connections (electronic devices) with one or more wiring, portable computer disk cases (magnetic devices), random access memory (RAM), Read only memory (ROM), erasable and editable read only memory (EPROM or flash memory), fiber optic devices, and portable compact disk read only memory (CDROM). In addition, the computer-readable medium can even be paper or other suitable media on which the program can be printed, because it can be done, for example, by optically scanning the paper or other media, and then editing, interpreting, or necessarily When necessary, the program is processed in other suitable ways to obtain the program electronically, and then it is stored in the computer memory.

[0076] It should be understood that each part of the present invention can be implemented by hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if it is implemented by hardware, as in another embodiment, it can be implemented by any one or a combination of the following technologies known in the art: Discrete logic circuits, application specific integrated circuits with suitable combinational logic gates, programmable gate array (PGA), field programmable gate array (FPGA), etc.

[0077] In the present description, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. means to describe in conjunction with this embodiment or example Specific features, structures, materials or characteristics are included in at least one embodiment or example of the present invention. In this context, the schematic representations of the above-mentioned terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be in any

One or more of the embodiments or examples of are combined in a suitable manner.

[0078] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front" ", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axis The orientation or positional relationship indicated by "direction", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying. The device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention.

[0079] In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined with "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0080] In the present invention, unless otherwise clearly defined and limited, the terms "installation", "connected", "connected", "fixed" and other terms should be understood in a broad sense, for example, it may be a fixed connection or It can be detachably connected or integrated; it can be mechanically or electrically connected; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two components or the interaction relationship between two components, unless There are other clear restrictions. For those of ordinary skill in the art, the specific meanings of the above-mentioned terms in the present invention can be understood according to specific situations.

[0081] In the present invention, unless expressly stipulated and defined otherwise, the first feature "on" or "under" the second feature may be in direct contact with the first and second features, or the first and second features may pass through Indirect contact with intermediaries. Moreover, the "above", "above" and "above" of the first feature on the second feature may mean that the first feature is directly above or obliquely above the second feature, or it simply means that the level of the first feature is higher than the second feature. The first feature "below", "below" and "below" the second feature can mean that the first feature is directly below or obliquely below the second feature, or it simply means that the level of the first feature is smaller than the second feature.

[0082] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art are within the scope of the present invention. Variations, modifications, substitutions, and modifications can be made to the above-mentioned embodiments.