CN113794668A

CN113794668A - WiFi-ZigBee reliable data transmission method based on symbol-level chip combination mode

Info

Publication number: CN113794668A
Application number: CN202111082793.2A
Authority: CN
Inventors: 李士宁; 刘畅; 程涛; 李炳琪; 王长浩; 焦锋; 张南; 董博洋
Original assignee: Northwestern Polytechnical University
Current assignee: Northwestern Polytechnical University
Priority date: 2021-09-15
Filing date: 2021-09-15
Publication date: 2021-12-14
Anticipated expiration: 2041-09-15
Also published as: CN113794668B

Abstract

The invention relates to the technical field of digital information transmission, and discloses a WiFi-ZigBee reliable data transmission method based on a symbol-level chip combination mode, which comprises the following steps: the method comprises the following steps: determining a twin symbol corresponding to a ZigBee symbol; step two: combining the corresponding symbol and its twin symbol into a byte according to the content to be transmitted, to obtain a combined signal; step three: simulating a legal ZigBee frame by using the effective load of the WiFi frame; step four: carrying out chip combination on the simulated symbol frame at the WiFi end; step five: and sending out the symbol signal obtained by the symbol-level chip combination through a transmitter, and successfully identifying the signal sent by the WiFi simulation by the ZigBee receiver and demodulating the identified signal. The invention improves the receiving rate of the WiFi-ZigBee data packet, solves the problem of low CTC efficiency from the WiFi to the ZigBee physical layer at present, eliminates errors of ZigBee symbol segment simulation caused by a WiFi CP mechanism, and realizes the high-efficiency physical layer cross-technology communication of the WiFi-ZigBee.

Description

WiFi-ZigBee reliable data transmission method based on symbol-level chip combination mode

Technical Field

The invention relates to the technical field of digital information transmission, in particular to a WiFi-ZigBee reliable data transmission method based on a symbol-level chip combination mode.

Background

With the progress of the internet of things technology and the continuous expansion of the application field, typical applications represented by smart homes, smart transportation, health medical care, electronic commerce, logistics and the like appear, the application of the internet of things technology brings a new development opportunity for the industries, meanwhile, the continuous improvement of the industry demand quality also promotes the development of the internet of things core technology, namely the wireless network technology, and various wireless technologies represented by WiFi, ZigBee, Bluetooth, LoRa and the like and suitable for different scenes are generated. The continuous popularization of various applications of the internet of things promotes the explosive growth of different types of wireless intelligent equipment, and intelligent equipment of various wireless network technologies is widely used in daily life (families, offices, markets and the like) and specific scenes (hospitals, factories and the like), and plays an important role in the application scene. Meanwhile, various wireless technologies continuously expand their own living spaces in the field, and the situation that heterogeneous wireless network technologies coexist in the same physical space gradually appears. If the devices working in the same frequency band and conforming to different wireless standards are deployed in the same physical space, a heterogeneous wireless network coexistence environment is formed.

The current ways to implement heterogeneous network communication mainly include gateway-based indirect communication and cross-technology communication (CTC), wherein the cross-technology communication is specifically divided into two schemes, namely packet-based cross-technology communication and physical layer simulation-based cross-technology communication.

The heterogeneous network communication scheme based on the gateway mainly adopts a mode of receiving and forwarding different network signals by multiple antennas to coordinate communication activities among heterogeneous networks. The introduction of the gateway enables messages between different networks to be reliably converged and forwarded, but additional hardware cost is caused by the requirement on multiple radio frequency circuits and processors; in addition, the deployment of the gateway also depends on a specific wireless environment, and a proper position needs to be selected by synthesizing the signal strengths of various heterogeneous networks, which also brings larger deployment and maintenance costs; most importantly, network traffic is doubled due to the unique "receive-forward" mechanism of the gateway, which presents new challenges to the otherwise congested channel and also exacerbates cross-technology interference to some extent.

In order to avoid the above disadvantages, CTC has been proposed and extensively studied to lay the foundation for direct communication between heterogeneous wireless network devices. The earliest CTC mainly transfers information based on statistical characteristics of data packets, and considering that a receiving end cannot directly receive and analyze data packets sent by heterogeneous network devices, but can acquire energy information of carriers through energy detection, RSS sampling and other modes, a sending end can adjust the length, sending time characteristics and the like of the data packets or construct a proper sequence mode by using the data packets to transfer information, and a single data packet can represent information of a plurality of bits at most through reasonable design. Esense is the earliest work to study cross-technology communication, and Esense encodes information by the duration of signal energy. The GapSense adds a preamble containing a plurality of energy pulses to each standard data packet, and uses the time gap between the pulses for transmitting coordination information to realize cross-technology communication. The ToneSense completes information coding by controlling the wireless communication power of the transmitting end, and then completes data coding and cross-technology information transmission. In Wizig, the direct cross-technology communication of WiFi and ZigBee at a higher speed is realized by combining the transmission time and the transmission power of a disturbance data packet.

The CTC based on the data packet provides a new method for heterogeneous network direct communication, but the method is difficult to realize wide application in practical scenes due to the defects that additional modulation and demodulation modules are required to be added at a sending end and a receiving end respectively, the throughput is low, the connection is difficult to establish and the like.

In order to solve the above problems, a CTC technique based on physical layer simulation is proposed, which is a method for implementing direct communication between heterogeneous network devices by simulating a time-domain waveform of a low-speed radio frame using a high-speed radio. Taking WiFi to ZigBee as an example, by carefully selecting the payload of the WiFi data packet, the finally transmitted WiFi waveform can be made to be similar to the ZigBee signal in the time domain, thereby implementing WiFi to ZigBee direct communication. The representative work of the mode is WEBee, on the premise of not changing WiFi equipment and firmware, the WEBee realizes direct high-speed communication from WiFi to ZigBee equipment on commercial equipment only by reasonably adjusting payload of a WiFi data packet, realizes direct communication of a heterogeneous network in the true sense, and can reach the upper limit of the communication rate of low-speed network equipment in theory. The development process of CTC from research to application is greatly promoted based on the proposal of the physical layer simulation technology, and actually, in the signal simulation process, due to the limitation of PHY standards (such as IEEE 802.11g and IEEE 802.15.4), such as the use of a WiFi CP mechanism, the WiFi technology cannot perfectly simulate a waveform conforming to IEEE802.15.4, which directly results in the low reliability of the current WiFi to ZigBee CTC.

The simulation error of WiFi mainly comes from two aspects, on one hand, the accuracy of simulation is limited because the current widely deployed WiFi devices generally adopt the 64QAM modulation technology, which causes partial deviation, and on the other hand, the CP mechanism forcibly used by WiFi. The WiFi technology adopts a CP mechanism to eliminate inter-symbol interference, as shown in fig. 1, each subcarrier signal of WiFi completes the conversion from a frequency domain signal to a time domain signal after undergoing inverse fourier transform, and in order to alleviate inter-symbol interference caused by doppler effect and other reasons in the time domain, the WiFi technology completes the recovery of inter-symbol overlapping error information by copying the last quarter segment of a single symbol and copying the same to the symbol as a guard interval. As shown in fig. 2, specifically, the duration of a single symbol without a guard interval in WiFi technology is 3.2us, and the quarter (0.8us) of the data after symbol is copied to symbol before it is used as a guard interval, so that a complete symbol duration is 4 us. It should be noted that the ZigBee technology based on IEEE802.15.4 is not compatible with the CP mechanism supported by the WiFi technology, so the ZigBee receiving end cannot effectively process the WiFi signal with CP, which results in that the WiFi to ZigBee cross-technology communication technology based on physical layer signal simulation naturally has a certain error rate, i.e. the ZigBee signal simulated by the WiFi end is an "imperfect" signal, although the ZigBee DSSS mechanism has a certain fault-tolerant mechanism, the generation of additional errors still causes the packet receiving rate of the ZigBee receiving end to be reduced, so the WiFi transmitting end must repeatedly transmit the original data many times, thereby improving the reliability of the transmitted data, but further causing the problem of performance reduction such as transmission efficiency and data throughput.

In addition to improving the reliability of data transmission by sending data packets multiple times, TwinBee proposes the idea of chip combination. TwinBee finds that most chip errors are positioned in the middle and at the two ends of a chip sequence when physical layer WiFi-ZigBee communication is carried out on the basis of WEBee. Namely, from 13 th to 20 th bit chips, the error of about 47 percent of the whole chip is formed; from the 1 st to 4 th bit chips and the 29 th to 32 th bit chips, an error of about 43% of the entire chip is formed, respectively. These chip errors are mainly due to CP and boundary effects. According to the above findings and the characteristic that 32-bit sequences mapped by ZigBee symbols in ieee802.15.4 cyclically move with each other, the ZigBee Symbol and the "Twin-Symbol" corresponding to the ZigBee Symbol are transmitted at the WiFi end, which is proposed by the TwinBee, and the two symbols are combined at the receiving end of the ZigBee. However, due to the hardware limitation, there is no information about chips in the ZigBee receiving end, so the received symbols can only be obtained from the radio. Without knowledge of the actual transmitted chips, the received symbols are mapped back into their respective PN chip sequences and then a combined coding of the "error-prone" position chips is performed. When the design is actually applied, as the number of ZigBee node devices is larger than that of WiFi devices and hardware limitation needs to upgrade the firmware of ZigBee, compared with other existing works, huge workload can be generated.

In summary, the current research on the unidirectional communication of the WiFi and the ZigBee networks can ensure that the highest communication rate supported by the ZigBee technology is achieved; the reliability needs to improve the accuracy of data transmission, and currently, due to the limitation of physical layers among different technologies, the data packet receiving rate is low when WiFi communicates to ZigBee, and multiple transmissions are usually needed to realize effective transmission of a single data packet, which greatly reduces the availability of heterogeneous network communication technologies. At present, reliability becomes a main factor for restricting the communication quality of a heterogeneous network, and is also a key problem to be solved for realizing the cooperation of the heterogeneous network. On the premise of not using other devices, realizing high-speed and reliable communication from WiFi to ZigBee networks with lower complexity still is a problem worthy of research.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a WiFi-ZigBee reliable data transmission method based on a symbol-level chip combination mode.

In order to achieve the purpose, the invention adopts the following technical scheme:

a WiFi-ZigBee reliable data transmission method based on a symbol-level chip combination mode comprises the following steps:

the method comprises the following steps: determining a twin symbol corresponding to a ZigBee symbol

Determining a twin symbol corresponding to a ZigBee symbol according to the cyclic shift characteristics of the chip sequence of the ZigBee symbol;

step two: combining the corresponding symbol and its twin symbol into a byte according to the content to be transmitted, to obtain a combined signal;

step three: simulating a legal ZigBee frame by using the effective load of the WiFi frame;

step four: performing chip combination on the simulated symbol frame at the WiFi end

Extracting two continuous symbols at the WiFi end respectively, wherein one symbol is an analog original symbol, and a twin symbol of the original symbol is followed;

step five: and sending out the symbol signal obtained by the symbol-level chip combination through a transmitter, and successfully identifying the signal sent by the WiFi simulation by the ZigBee receiver and demodulating the identified signal.

Further, in the fourth step, the normal chip part of the twin symbol of the symbol is used to replace the error-prone chip of the symbol caused by the WiFi hardware device at the WiFi transmitting end.

Further, one symbol position is "0-3", "12-19" and "28-31", the symbol position is replaced by the symbol position of "8-11", "20-27" and "4-7" of the twin symbol, and the symbol position of the symbol position after the combination of the symbols is finally obtained is corrected to be "normal".

Further, the twin symbol refers to a new symbol obtained by circularly shifting any symbol to the right by 8 bits in the ZigBee physical layer symbol DSSS sequence, and the new symbol must be located in the sequence set.

Compared with the prior art, the invention has the following beneficial effects:

the invention realizes reliable data transmission from WiFi to ZigBee by symbol-level chip combination at WiFi terminal, defines 'twin symbol' for ZigBee physical layer by combining the cyclic shift characteristic of ZigBee physical layer DSSS sequence, by performing signal simulation on the target ZigBee symbol and the twin symbol thereof at the WiFi end, and the code chip combination of the symbol level is carried out after the CP is added, the normal positions of the two code chip sequences are combined to obtain a signal similar to the original ZigBee symbol, the signal distortion caused by the CP is reduced, the cross-technology communication of the WiFi-ZigBee of the physical layer level is realized, the receiving rate of a WiFi-ZigBee data packet is improved, the problem that the CTC efficiency from the current WiFi to the ZigBee physical layer is too low is solved, the simulation error of the ZigBee symbol segment caused by the WiFi CP mechanism is eliminated, and the high-efficiency physical layer cross-technology communication of the WiFi-ZigBee is realized.

Drawings

Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:

FIG. 1 is a physical layer cross-technology communication workflow;

FIG. 2 is an OFDM symbol with a guard interval added;

FIG. 3 is a symbol level chip combined WiFi-ZigBee CTC implementation diagram;

FIG. 4 is a diagram of an error prone chip distribution;

FIG. 5 is a schematic diagram of signal simulation of symbols "0000" and "0010";

FIG. 6 is a simulated symbol "0000" and "0010" for WiFi;

FIG. 7 is the simulated symbols "0000" and "0010" for the extracted WiFi;

FIG. 8 is a diagram of a chip replacement process;

FIG. 9 is a time domain waveform diagram of a symbol "0000" and an original ZigBee symbol "0000" after chip combination;

FIG. 10 is a flow chart of a ZigBee receiving terminal;

FIG. 11 is a statistical chart of the chip reception rate at the receiving end;

fig. 12 is a statistical chart of symbol reception rate at the receiving end.

Detailed Description

The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.

In the existing WiFi-ZigBee cross-technology communication at the physical layer level, the finally transmitted WiFi waveform can be similar to a ZigBee signal in the time domain by carefully selecting the effective load of a WiFi data packet, so that the finally transmitted WiFi waveform can generate an approximate ZigBee time domain waveform after being modulated by QAM and subjected to OFDM, and further the WiFi-ZigBee communication is completed. The invention provides a symbol-level chip combination mode to realize reliable transmission of WiFi-ZigBee communication on the basis of the existing WiFi-ZigBee cross-technology communication at a physical layer level, as shown in figure 3.

The symbol-level chip combination of the invention utilizes the cyclic shift characteristic of a 32-bit PN sequence (namely a chip sequence) corresponding to a ZigBee symbol to 'move' the chip which is easy to make errors to other positions so as to correct the errors caused by the WiFi CP and the discontinuous boundary as much as possible. Since the error-prone chips occur at the "0-3", "12-19" and "28-31" th bits, the blank portion is "normal" chips as shown by the shaded portion in fig. 4. From the perspective of cyclic shift, consecutive chips of one ZigBee symbol that are prone to errors can be considered as two segments of 8 chips in length.

According to the table 1, the 32-bit chip sequences corresponding to the ZigBee symbols have cyclic shift characteristics, the present invention defines the concept of "twin symbol" for each ZigBee symbol, where the "twin symbol" refers to a new symbol obtained by cyclically shifting any symbol to the right by 8 bits in the ZigBee physical layer symbol DSSS sequence, and the new symbol must also be located in the sequence set. Continuous ZigBee symbols and twin symbols thereof are simulated at a WiFi sending end, and the two symbols are combined into normal chips after CP is added, so that the formed original symbols with all the normal chips can be accurately demodulated at a receiving end, and the data packet receiving rate of the receiving end is improved.

TABLE 1 data symbol-chip sequence mapping

Specifically, the invention realizes the reliable data transmission method of WiFi-ZigBee by using a combination mode based on symbol-level chips at a WiFi terminal, which comprises the following steps:

And determining a twin symbol corresponding to the ZigBee symbol according to the cyclic shift characteristics of the chip sequence of the ZigBee symbol. For example, the PN sequence of symbol "0010" is obtained by cyclically shifting the PN sequence of symbol "0000" by 8 bits to the right, so "0010" is used as its twin symbol. Similarly, a twin symbol corresponding to each ZigBee symbol may be determined. Specifically, as shown in table 2.

TABLE 2 data symbol-twin symbol correspondence table

Step two: the corresponding symbol is combined with its twin symbol into one byte (since one symbol is four bits) depending on what is to be transmitted, resulting in a combined signal. Fig. 5 is a schematic diagram of simulation of signals with symbols "0000" and "0010".

Step three: according to the existing concept of physical layer WiFi-ZigBee communication, a valid ZigBee frame is simulated with the payload of a WiFi frame according to the flow shown in fig. 1. In order to simulate an ideal ZigBee signal, the steps shown in fig. 1 are performed in the reverse direction, the CP of the original ZigBee signal is removed, the frequency domain signal obtained through FFT is QAM quantized to select an input WiFi data bit, and the obtained WiFi data bit is performed in the forward direction as the payload of the WiFi frame according to the steps shown in fig. 1. For example, the symbols "0000" and "0010" are simulated from the final WiFi frame as shown in fig. 6.

Two consecutive symbols are extracted separately at the WiFi end, one of which is an analog original symbol followed by a twinned symbol of the original symbol. As shown in fig. 7, the simulated symbols "0000" and "0010" for the extracted WiFi;

for two successive symbols, since the latter symbol is the twin symbol of the former symbol, and the distribution of the "error-prone" chips of the twin symbol is also shown in fig. 4, the original signal of the error-prone chip portion of one symbol is the same as the signal of the "normal" chip portion of the twin symbol, so that the normal chip portion of the twin symbol of one symbol is used to replace the error-prone chip of one symbol due to the WiFi hardware at the WiFi transmitting end, and the specific replacement process is shown in fig. 8:

as can be seen from fig. 8, the positions of symbol-error-prone chips are "0-3", "12-19" and "28-31", these error-prone chips are replaced by the chips at the "8-11", "20-27" and "4-7" positions of the twin symbol, respectively, and the resulting chip-combined symbol-error-prone chip is corrected to "normal" chip.

Fig. 9 is a comparison graph of time domain waveforms of the symbol "0000" and the original ZigBee symbol "0000" after chip combination, and it can be seen from fig. 9 that the time domain waveform obtained by the WiFi terminal after chip processing the simulated symbol is very close to the time domain waveform of the original ZigBee symbol.

Step five: and sending out the symbol signal obtained by the symbol-level chip combination through a transmitter. The ZigBee receiver successfully identifies the signal transmitted by the WiFi simulation and demodulates the identified signal.

IEEE802.15.4 uses O-QPSK for demodulation, and since O-QPSK modulation with a half-sinusoidal pulse shape is equivalent to Minimum Shift Keying (MSK), signal demodulation can be accomplished using a quadrature demodulator. And demodulating the signal according to the angle between two adjacent complex signals acquired by the receiving end. The mathematical principle is to calculate the product of the input of the single sample delay and the conjugate non-delayed signal, and then calculate the argument of the obtained complex number:

let x be a complex sinusoidal signal with amplitude A > 0, frequency f ∈ R and initial phase of the signal φ₀∈[0；2π]. The sampling frequency of the signal being f_s> 0, the expression for x can be found as:

then, solving the above equation, we can obtain:

due to A²Is a number greater than 0, so the above formula is equivalent to:

the working flow of the ZigBee receiving end applying the above demodulation method is shown in fig. 10. Firstly, ZigBee captures signals on a 2.4GHz frequency band through an analog-to-digital converter (ADC) to obtain a sampling value of an I/Q signal. The I/Q signal sample values are commonly referred to as complex samples and can be formulated as: s (n) ═ i (n) + jq (n). The phase offset between successive sampled signal points is then calculated by the quadrature demodulation principle described above. The forward and reverse phase shifts in the phase offset sequence are then quantized to 1 and-1, respectively, corresponding to the chip values 1 and 0 of ZigBee. And finally, the ZigBee receiving end obtains different ZigBee data symbols by completing mapping on the chip values, and the analyzed data are delivered to an upper layer for processing.

Through the steps, reliable data transmission from the WiFi technology to the ZigBee technology physical layer cross-technology communication is completed.

And (4) carrying out simulation experiments on the key technologies. Simulation results for the combination of the WeBee and symbol-level chip patterns are shown in FIGS. 11 and 12. The experiment statistics shows that the chip receiving rate and the Symbol receiving rate of 16 ZigBee Symbol receiving ends are obtained after the ZigBee and Symbol-level chip combination mode. According to fig. 11 and fig. 12, it can be seen that the symbol-level chip combination mode significantly improves the receiving rate of the ZigBee receiving end for the chips and symbols, and the symbol chip receiving rate of the ZigBee receiving end reaches 98.5%, and the symbol receiving rate can reach 100%, thereby reducing retransmission of data packets and ensuring the reliability of data reception.

The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes and modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention.

Claims

1. A WiFi-ZigBee reliable data transmission method based on a symbol-level chip combination mode is characterized by comprising the following steps:

2. The method of claim 1, wherein in step four, a normal chip part of a twin symbol of symbol is used at the WiFi transmitting end to replace an error-prone chip of symbol due to WiFi hardware.

3. The WiFi-ZigBee reliable data transmission method based on symbol-level chip combination mode as claimed in claim 2, wherein a symbol-level chip-prone position is "0-3", "12-19" and "28-31", the symbol-level chip-prone position is replaced with the chip at "8-11", "20-27" and "4-7" position of the twin symbol, respectively, and the chip at the symbol-level chip-prone position after the chip combination is finally obtained is corrected to "normal" chip.

4. The WiFi-ZigBee reliable data transmission method based on the symbol-level chip combination mode as claimed in claim 1, wherein the twin symbol refers to a new symbol obtained by circularly shifting any one symbol to the right by 8 bits in a ZigBee physical layer symbol (DSSS) sequence, and the new symbol must be located in the sequence set.