LoRa network-based non-persistent carrier sense multiple access system and method

Abstract

This solution relates to a LoRa network-based non-persistent carrier sense multiple access system and method in the field of low-power communications. It includes a network infrastructure that adopts the LoRa network architecture and replaces the ALOHA transmission scheduling mode of the LoRa network infrastructure with the NP-CSMA access mode. This solves the channel conflict problem in the current LoRa network and is applied to LoRa local area network signal transmission to improve the scalability and signal stability of the LoRa network.

Description

Technical Field

[0001] The present invention relates to the field of low-power communication technology, and in particular to a LoRa network-based non-persistent carrier sense multiple access system and method. Background Art

[0002] The LoRa network is an open-source standard proposed by the LoRa Alliance. Semtech has designed a proprietary physical layer modulation scheme, LoRa, that trades data rate for communication coverage. Essentially, LoRa is a linear chirp modulation (CSS)-based modulation technique that modulates the baseband signal based on the carrier frequency (CF), spreading factor (SF), bandwidth (BW), and code rate (CR).

[0003] The code rate (CR) is used in forward error correction technology, where a portion of the data in the LoRa data frame is used for error correction. The smaller the code rate (CR) (CR = 4 / (4+n)n∈{1,2,3,4}), the lower the bit error rate caused by short pulse interference, and the higher the transmission robustness, that is, the stronger the anti-interference ability. To improve the stability of data transmission, the Adaptive Data Rate (ADR) mechanism is designed into the LoRaWAN standard. It determines the optimal transmission rate for the end node based on the link budget and gateway sensitivity, and uses a higher spreading factor (SFs) to improve link robustness at the expense of a lower data rate. The Adaptive Data Rate (ADR) mechanism can increase LoRa network capacity, reduce transmitter power consumption, and extend communication range. Therefore, LoRaWAN has the characteristics of long distance, narrowband, low power consumption, multi-node, and low cost.

[0004] While LoRaWAN boasts a degree of scalability thanks to its LoRa modulation technology and Adaptive Rate Control (ADR) mechanism, long-term observations of actual signal transmission have shown that because LoRa network devices can transmit signals at any time, when multiple devices transmit using the same channel, signals collide and overlap. LoRa receivers demodulate signals using matched filtering. While a single LoRa receiver channel can simultaneously monitor six signals with different spreading factors (SFs), it can only process one signal at a time. When multiple LoRa signals modulated with the same spreading factor (SF) overlap, the demodulation process may produce multiple peaks, making it difficult for the receiver to correctly identify them. This situation can lead to severe channel contention when signals are transmitted on the same channel in a LoRaWAN network, significantly reducing link stability and service quality, and significantly reducing network scalability.

[0005] Another issue is the transmission of signals modulated with different spreading factors (SFs). It has long been believed that signals modulated with different spreading factors (SFs) are orthogonal. By leveraging the orthogonality of SFs, a protocol for SF allocation has been created. This protocol moves the RX2 window of Class A and Class B terminal devices before the data transmission window. Terminal nodes receive configuration frames sent by the gateway through the RX2 window. The configuration frames contain the SF parameters required for the node's current transmission, improving the stability of the transmission link, thereby reducing packet loss and improving network service quality.

[0006] However, when the amount of data is large, the new distribution mechanism still causes packet loss and signal interference. After long-term research, it was found that different spreading factors (SF) are not completely orthogonal, that is, signals between different spreading factors (SF) will also cause interference. Therefore, how to reduce or avoid interference with the same spreading factor (SF) and interference between different spreading factors (SF) in the LoRa network is a key issue in improving the scalability of the LoRa network. Summary of the Invention

[0007] The purpose of this application is to provide a non-persistent carrier sense multiple access system and method based on the LoRa network to solve the problem of insufficient scalability of the current LoRa network.

[0008] In order to solve the above problems, the present application first provides a non-persistent carrier sense multiple access system based on the LoRa network, including a network infrastructure adopting the LoRa network architecture, and the signal transmission scheduling module of the network infrastructure is an NP-CSMA access module.

[0009] By utilizing the NP-CSMA protocol function of the NP-CSMA access module, a listen-before-send mechanism is adopted for the signal to reduce the probability of signal collision, thereby reducing the occurrence of common channel suppression in the LoRa network. For the specific implementation process, see the following embodiments and advantages.

[0010] Furthermore, the network infrastructure also includes a channel activity detection unit (CAD), which acquires the preamble symbols of the LoRa signal to sense the channel status. After sensing the signal status, the CAD unit regulates any conflicting signals, preventing collisions during signal transmission and improving signal anti-interference capabilities.

[0011] Furthermore, the duration T of the channel activity detection unit is CAD At 1.75Ts SF＝7 and 2.25Ts SF＝12 It is used to avoid interference between different spreading factors SF in a wider area.

[0012] Furthermore, the NP-CSMA access module includes a distributed coordination function (DCF) unit, and a signal priority classification function is set in the distributed coordination function (DCF) unit, and the priority classification function is performed within the duration of the channel activity detection unit.

[0013] Furthermore, the duration of the avoidance space executed by the channel activity detection unit satisfies the following formula: T Random =rand(0,2 2n+2 -1)*(T data +T CAD )n∈{1,2,3,4}; where T Random Indicates: the length of the retreat space; T data is the data packet transmission time, also known as the air transmission time; rand is a random function determined according to actual use; T CAD is the CAD mode duration.

[0014] The setting of the cycle time increases the space of the backoff time, thereby further reducing the probability of signal conflict.

[0015] Furthermore, the existing Request to Send and Clear to Send (RTS / CTS) mechanism in the DCF can cause serious number restriction conflicts. The DCF unit only enables the basic distributed coordination function and disables the RTS / CTS mechanism in the distributed coordination function module.

[0016] Furthermore, the LoRa network's optimal frequency band is 470 MHz, and LoRa signal transmission provides eight aligned channels. This frequency band is well-established for base station deployment in China, maximizing signal strength. The LoRa network's gateway is equipped with an SX1301 module for monitoring the eight uplink channels, enhancing the solution's versatility.

[0017] In order to better solve the problem of channel conflict in LoRa network, the present application also provides a non-persistent carrier sense multiple access method based on LoRa network, including the following steps:

[0018] Step 1: Use the network infrastructure of the LoRa network architecture, its signal transmission scheduling module is the NP-CSMA access module, the signal adopts the NP-CSMA protocol transmission access, and complete the debugging;

[0019] Step 2: Use the NP-CSMA access module to pre-allocate the time for each node in the LoRa network to access the channel;

[0020] Step 3: The signal source is modulated by the LoRa modulation module to form a LoRa frequency signal;

[0021] Step 4: The LoRa frequency signal enters the channel and is first spread spectrum processed to form a spreading factor (SF);

[0022] Step 5: The NP-CSMA access module regulates the time and channel of the spreading factor entering the channel;

[0023] Step 6: Extend the frequency of the LoRa signal to the entire bandwidth; first obtain the preamble symbol of the LoRa signal through the channel activity detection unit in the LoRa modulation module, and then use the channel activity detection unit to adjust the conflict between the spreading factors, assign priorities to the conflicting spreading factors, actively avoid the spreading factors with smaller priorities, and then select idle time for retransmission; the duration of each adjustment by the channel activity detection unit is 1.75Ts SF＝7 and 2.25Ts SF＝12 between;

[0024] Step 7: The modulated signal is transmitted through a wireless transmitting base station;

[0025] Step 8: The LoRa receiver samples the LoRa signal within the effective signal receiving range to form a digital LoRa signal;

[0026] Step nine, multiplying the digital LoRa signal with the locally matched down-chirp signal to achieve de-chirp;

[0027] Step 10: demodulate all spreading factors (SF) and restore the signal source to display through the output device.

[0028] In step 2, the NP-CSMA access module uses only the basic distributed coordination function (DCF) in the distributed coordination function, and the terminal node must continuously detect that the channel is idle for a period of time before sending data.

[0029] Furthermore, the processing steps of the channel activity detection unit (CAD) in step 6 include:

[0030] Step 1: Turn off the wireless receiver and phase-locked loop;

[0031] The second step is that the wireless receiver obtains the LoRa preamble symbol of the data from the channel;

[0032] In the third step, the modem searches for a correlation between the samples acquired by the chip and the ideal preamble waveform; establishing this correlation takes only slightly less than one symbol period.

[0033] Step 5. After step 4 is completed, the chip returns to standby mode and receives signal interrupts;

[0034] Step 6. If the preamble is found, clear the interrupt and start receiving data;

[0035] Step 7: When the distributed coordination function module detects that the channel is busy, the terminal node enters a sleep state to save energy, and waits for a random period of time before re-enabling the channel activity detection unit to listen for whether there is a transmission signal in the current channel.

[0036] Before step 3, the channel coded signal is amplified by a signal gain circuit to obtain coding gain, which can improve the system's anti-interference ability.

[0037] The working principle and advantages of this application scheme:

[0038] First, it aims to coordinate signals between different spreading factors (SFs). Because different spreading factors (SFs) exhibit an incomplete orthogonality, this solution allocates a unique channel to each spreading factor (SF), allowing the transmission of multiple signals with different spreading factors (SFs) to be accommodated in separate channels and transmitted in parallel, thereby effectively avoiding the signal suppression caused by the incomplete orthogonality of the spreading factors (SFs).

[0039] The coordination method for signals with the same spreading factor (SF) is relatively complex and is mainly implemented by using the distributed coordination function (DCF) mechanism within the NP-CSMA access module.

[0040] The NP-CSMA access module is used to replace the original ALOHA module in LoRaWAN; the problem of signal collision and signal overlap caused by the ALOHA module is eliminated. The NP-CSMA access module is added to the LoRa network architecture, and the NP-CSMA protocol function of the NP-CSMA access module is used to adopt a listen-before-send mechanism for the signal to reduce the probability of signal collision, thereby reducing the occurrence of common channel suppression in the LoRa network.

[0041] In the 802.11 standard, all CSMA protocols, including NP-CSMA, use the distributed coordination function (DCF) mechanism to allow end nodes to obtain channel usage rights through contention. However, the 802.11 standard includes a request-to-send (RTS / CTS) mechanism for the DCF. This mechanism includes the network allocation vector (NAV) in the RTS / CTS frame and reserves the channel through the RTS-CTS handshake, implementing a virtual carrier sensing mechanism to further reduce signal collisions.

[0042] However, in the frequency band used by LoRa, the transmission of terminal nodes is usually limited by the radio duty cycle, and the RTS / CTS mechanism will cause the network to have a large delay; therefore, the current distributed coordination function (DCF) is not suitable for use in LoRa networks; therefore, this application only adopts the basic distributed coordination function DCF processing mechanism. In a CSMA network, its terminal nodes must continuously detect that the channel is idle for a period of time (this period is called the interframe interval IFS) before they can send data. The 802.11 standard protocol defines multiple priorities for data frames based on their length. Using priority definitions and sorting the transmission of multiple signals can avoid signal conflicts. And the higher the priority, the smaller the interframe interval IFS.

[0043] The LoRa chip provides a channel activity detection mode, referred to as CAD mode. The terminal node can switch to CAD mode by request, and then obtain the leading code symbol of the LoRa signal from the channel to realize the perception of the channel status. The LoRa terminal can use the CAD mode to more accurately determine whether there is a transmission signal in the channel. This process requires the LoRa terminal to maintain the CAD mode for several LoRa symbol times. Depending on the SF, the duration of the CAD mode is T CAD At 1.75Ts SF＝7 and 2.25Ts SF＝12 between.

[0044] Since the LoRa terminal often needs to maintain the CAD mode for a period of time during the channel listening process, this application uses the CAD mode duration to design the channel usage priority in the LoRa network, and introduces signals into different priority channels according to the strength of the signal or the importance of the mark.

[0045] When the terminal node detects that the channel is busy, it enters the sleep state to save energy, and waits for a random period of time before switching back to the CAD mode to listen for whether there is a transmission signal in the current channel, thereby avoiding the problem of superposition distortion or loss of signals with the same spreading factor (SF).

[0046] In addition, the NP-CSMA access module can maintain relatively low power consumption operating conditions for the LoRa terminal node, which can not only provide a better data packet delivery rate and channel utilization for the LoRa network, but also increase the number of nodes accommodated by the network, fully demonstrating that the application of the NP-CSMA access mode in the LoRa network can effectively improve the scalability of the LoRa network. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 The LoRa network topology diagram for the non-persistent carrier sense multiple access system;

[0048] Figure 2 This is a diagram showing the distribution of terminal nodes in the circular area where signals are received;

[0049] Figure 3 A graph comparing the application modes of unconfirmed LoRaWAN and confirmed LoRaWAN;

[0050] Figure 4 Flowchart of channel activity detection processing steps;

[0051] Figure 5 Schematic diagram of the backoff mechanism for the NP-CSMA access mode. DETAILED DESCRIPTION

[0052] The following is a further detailed description through specific implementation methods:

[0053] Here is a comparison of the English abbreviations and Chinese names that appear in the text, or the Chinese explanations of the English abbreviations are as follows:

[0054] LoRa network or LoRaWAN: An open-source standard for network signal transmission proposed by the LoRa Alliance;

[0055] CSS: linear chirp;

[0056] CF: carrier frequency;

[0057] SF: spreading factor;

[0058] SFs: multiple spreading factors;

[0059] BW: bandwidth;

[0060] CR: coding rate;

[0061] ADR: Adaptive Rate Mechanism;

[0062] Class A, Class B: terminal equipment;

[0063] RX2: terminal device window;

[0064] CSMA: Carrier Sense Multiple Access;

[0065] NP-CSMA: Non-persistent carrier sense multiple access;

[0066] ALOHA: Random Contact Channel Access Control Protocol;

[0067] CAD: Channel Activity Detection Mode;

[0068] DCF: distributed coordination function;

[0069] SX1301: LoRa modulation baseband chip;

[0070] SX1276: LoRa wireless RF transceiver;

[0071] RTS: request to send frame;

[0072] CTS: Clear to send frame;

[0073] NAV: Network Allocation Vector;

[0074] PDR: packet delivery rate;

[0075] LBT: Listen before talk mechanism;

[0076] IFS: Interframe interval;

[0077] RSSI value: the received signal strength indicator value of the wireless network;

[0078] ISM: Open to industrial, scientific and medical institutions to use network frequency bands.

[0079] Example 1:

[0080] Provided is a LoRa network-based non-persistent carrier sense multiple access system, comprising a network infrastructure adopting the LoRa network architecture, wherein a signal transmission scheduling module of the network infrastructure is an NP-CSMA access module.

[0081] like Figure 1 Figure 2 shows the LoRa network topology for a non-persistent carrier sense multiple access (CSMA) system. LoRa network terminal devices establish wireless connections with the gateway via a single hop in a designated ISM band. The LoRa network utilizes the ISM band, where transmission channels operating in different frequency bands do not interfere with each other. By allocating a unique channel for each spreading factor (SF), multiple signals with different SFs can be transmitted in separate channels in parallel, effectively avoiding signal suppression caused by incomplete orthogonality of the SFs.

[0082] Figure 1 The functions and bit widths of all physical quantities are as follows:

[0083]

[0084] In the process of applying the NP-CSMA access mode to the LoRa network, the main focus is on scheduling transmissions between terminal nodes with the same spreading factor SF to reduce the probability of signal collisions.

[0085] In this example, we demonstrate the NP-CSMA scheduling mechanism in a LoRa network for a single gateway and a single spreading factor (SF). The gateway in this example is equipped with the SX1301 chip, the baseband chip used by LoRa gateways. In the LoRa network architecture, the LoRa chip provides a channel activity detection mode, or CAD mode for short. End nodes can request to switch to CAD mode and then obtain the preamble symbols of the LoRa signal from the channel, thereby realizing channel status awareness.

[0086] like Figure 4 As shown: the processing steps of the channel activity detection unit: step 1, turn off the wireless receiver and phase-locked loop; step 2, the wireless receiver obtains the LoRa preamble code symbol of the data from the channel; step 3, the modem searches for the correlation between the sample obtained by the chip and the ideal preamble code waveform; the time required to establish such a correlation is only slightly less than one symbol period; step 5. After the fourth step is completed, the chip returns to standby mode and receives signal interrupts; step 6, if the preamble code is found, clear the interrupt and then start receiving data; step 7, when the distributed coordination function module detects that the channel is busy, the terminal node enters a sleep state to save energy, and after a random wait period of time, the channel activity detection unit is restarted to listen for whether there is a transmission signal in the current channel.

[0087] Compared with the method of directly determining the channel status through the received signal strength indicator RSSI of the wireless network, the LoRa terminal can more accurately determine whether there is a transmission signal in the channel by using the CAD mode. This process requires the LoRa terminal to maintain the CAD mode for multiple LoRa symbol times. Depending on the spreading factor SF, the duration of the CAD mode T CAD At 1.75Ts SF＝7 and 2.25Ts SF＝12 This time period is the time between SF 7 and SF 12.

[0088] As for the specific practice of LoRa modulation, LoRa modulation uses a chirp signal and performs linear frequency modulation on the basic chirp signal by cyclic shift to obtain a modulated signal; the LoRa symbol time is also called the sweep period, which is represented by Ts. The duration of a symbol Ts can be regarded as 2 SF The length is T chip The time slice is composed of time slices, and the time length of each chip is T chip =0.78us. By cyclic shifting integer multiples of T chip Time shows 2 SF kind of information.

[0089] The key to applying the NP-CSMA mode to the LoRa network is how to coordinate the time for each node in the LoRa network to access the channel to avoid conflicts as much as possible.

[0090] In the 802.11 standard, all CSMA protocols utilize a distributed coordination function (DCF) to allow end nodes to compete for channel usage rights, thereby coordinating node sharing of the channel. This mechanism is typically applicable to single-hop distributed networks, similar to the single-hop star network structure of LoRa. Therefore, it is feasible to apply NP-CSMA to LoRa networks.

[0091] In this embodiment, all nodes in the LoRa network send data with the same priority, and the data is sent to the node with the same priority. CAD In this case, if the channel is idle, the terminal node can send data.

[0092] like Figure 5 As shown in the figure, the backoff mechanism of the NP-CSMA access mode: when a terminal node detects that the channel is busy, it enters a sleep state to save energy. After a random wait period, it switches back to CAD mode to listen for transmission signals on the current channel. The maximum number of reswitching times is set to four in this embodiment. If the number of reswitching times exceeds four, the transmission is considered a failure.

[0093] By increasing the backoff time space, we can reduce the number of terminal nodes selecting the same backoff time, thereby further reducing the probability of signal conflict. The backoff space satisfies:

[0094] T Random =rand(0,2 2n+2 -1)*(T data +T CAD )n∈{1,2,3,4}, where T data is the data packet transmission time, also known as the air transmission time, rand is a random function, determined according to actual use; T CAD is the CAD mode duration.

[0095] Example 2:

[0096] like Figure 1 and Figure 2 As shown in the figure, this embodiment proves that the NP-CAMA access mode has a positive impact on the scalability of the LoRa network. A simulation scenario is used for verification. The simulation scenario consists of a gateway equipped with an SX1301 chip and an antenna height of 15m and several terminal nodes equipped with SX1276 chips and an antenna height of 1m. The positions of the terminal nodes are randomly scattered in a circular area centered on the gateway.

[0097] To avoid large differences in experimental results due to the randomness of terminal node locations, this paper tests the packet delivery rate, channel utilization, latency, and energy consumption under a single spreading factor (SF) under ideal conditions. That is, for a single terminal node, in the absence of interference, any data packet sent by the node can be correctly received by the receiver.

[0098] exist Figure 2 The figure shows the distribution of 400 terminal nodes within the circular area. The coverage range of SF = 7 in the 470 MHz band is approximately 2640 meters. The radius of the circular area where the nodes are randomly scattered is 2 km, indicating that NP-CAMA has a positive impact on the scalability of the LoRa network.

[0099] Example 3:

[0100] This embodiment also focuses on the difference between the applications of unconfirmed LoRaWAN and confirmed LoRaWAN.

[0101] like Figure 3 As shown in Figure 1, the PDR curves of unacknowledged LoRaWAN and NP-CSMA at SF = 7 and SF = 10 are almost identical. Unacknowledged LoRaWAN also has almost the same PDR as theoretical ALOHA. As the number of terminal nodes increases, the PDR eventually remains almost zero.

[0102] Whether SF=7 or SF=10, when the network load is low, the PDR of confirmed LoRaWAN is about three to ten percentage points higher than that of unconfirmed LoRaWAN.

[0103] For unacknowledged LoRaWAN, the PDR at SF=10 is approximately three to six percentage points higher than that at SF=7 when the load is low. This is because a larger SF increases the air transmission time, the probability of retransmission collisions, and the average number of retransmissions. Furthermore, the number of packets sent at SF=7 is greater than that at SF=10. When the load is high, the PDR at SF=10 degrades rapidly to that of unacknowledged LoRaWAN compared to SF=7. Therefore, under high load, acknowledged LoRaWAN at SF=7 has a better PDR than SF=10.

[0104] As the number of nodes in the network increases, NP-CSMA can provide better PDR. Especially when the network accommodates 100 nodes, that is, when the network communication load rate G=1, the PDR performance of NP-CSMA is almost 58.09% higher than that of LoRaWAN.

[0105] from Figure 3We can see that compared with LoRaWAN, with the same number of nodes, NP-CSMA has significantly higher channel utilization at SF=7 and SF=10 than non-acknowledged LoRaWAN and acknowledged LoRaWAN. In particular, compared with LoRaWAN's 18.8% saturated channel utilization, NP-CSMA's saturated channel utilization is nearly 59.2%. Moreover, when the channel utilization is at the same saturated state, NP-CSMA can accommodate more terminal nodes than LoRaWAN.

[0106] In a LoRa network with a high node density, due to the influence of distance conditions and the collision of multiple signals, the incomplete orthogonality between SFs cannot suppress the signal interference between SFs.

[0107] In this scheme, the NP-CSMA protocol replaces the random scheduling protocol ALOHA in LoRaWAN and uses the listen-before-transmit (LBT) mechanism to minimize the probability of signal collisions between the same SF on the same channel. For transmission between different SFs, a unique channel is allocated to each SF, so that different signal transmissions of multiple SFs are accommodated in separate channels to avoid interference between SFs.

[0108] Experimental results show that under the same conditions, although LoRa nodes in NP-CSMA need to consume a certain amount of energy to maintain CAD mode for channel detection, compared with confirmed LoRaWAN, NP-CSMA can provide better PDR performance by sacrificing lower additional energy consumption, and its saturated channel utilization is also significantly higher than LoRaWAN.

[0109] NP-CSMA reduces packet loss rate through the backoff mechanism, reducing the increase in delay caused by retransmission; under medium communication load conditions in the network, the average delay of NP-CSMA is better than that of confirmed LoRaWAN, which can provide better service quality for the LoRa network, which clearly shows that NP-CSMA can improve the scalability of the LoRa network.

[0110] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A LoRa network non-persistent carrier sense multiple access system, including a network infrastructure using a LoRa network architecture, characterized in that: The signal transmission scheduling module of the network infrastructure is an NP-CSMA access module; the network infrastructure also includes a channel activity detection unit (CAD), which obtains the preamble symbol of the LoRa signal for sensing the channel state; the duration of the execution of the channel activity detection unit is At 1.75 and 2.25 The NP-CSMA access module includes a distributed coordination function (DCF) unit, which sets a signal priority classification function in the distributed coordination function (DCF) unit and performs the priority classification function within the duration of the channel activity detection unit; the duration of the avoidance space executed by the channel activity detection unit satisfies the following formula: ;in Indicates: the duration of the retreat space; It is the data packet transmission time, also known as air transmission time; is a random function; is the duration of CAD mode; The distributed coordination function (DCF) unit only enables the basic distributed coordination function and turns off the request to send frame and clear to send frame (RTS / CTS) mechanism in the distributed coordination function module; the frequency band of the LoRa network is 470MHz.

2. A non-persistent carrier sense multiple access method based on a LoRa network includes the following steps: Step 1: Use the network infrastructure of the LoRa network architecture, its signal transmission scheduling module is the NP-CSMA access module, the signal adopts the NP-CSMA protocol transmission access, and complete the debugging; Step 2: Use the NP-CSMA access module to pre-allocate the time for each node in the LoRa network to access the channel; Step 3: The signal source is modulated by the LoRa modulation module to form a LoRa frequency signal; Step 4: The LoRa frequency signal enters the channel and is first spread spectrum processed to form a spreading factor (SF); Step 5: The NP-CSMA access module regulates the time and channel of the spreading factor entering the channel; Step 6: Expand the frequency of the LoRa signal to the entire bandwidth; The channel activity detection unit in the LoRa modulation module first obtains the preamble symbol of the LoRa signal, and then uses the channel activity detection unit to control the conflict between the spreading factors. The conflicting spreading factors are assigned priority, the spreading factors with lower priority are actively avoided, and then retransmission is performed in idle time. The duration of each adjustment of the channel activity detection unit is 1.75 and 2.25 between; Step 7: The modulated signal is transmitted through a wireless transmitting base station; Step 8: The LoRa receiver samples the LoRa signal within the effective signal receiving range to form a digital LoRa signal; Step nine, multiplying the digital LoRa signal with the locally matched down-chirp signal to achieve de-chirp; Step 10: demodulate all spreading factors (SF) and restore the signal source to display through the output device.

3. The LoRa network non-persistent carrier sense multiple access method according to claim 2, wherein: In step 2, the NP-CSMA access module uses only the basic distributed coordination function (DCF) in the distributed coordination function, and the terminal node must continuously detect that the channel is idle for a period of time before sending data.

4. The LoRa network non-persistent carrier sense multiple access method according to claim 3, characterized in that: The processing steps of the channel activity detection unit (CAD) in step 6 include: Step 1: Turn off the wireless receiver and phase-locked loop; The second step is that the wireless receiver obtains the LoRa preamble symbol of the data from the channel; In the third step, the modem searches for a correlation between the samples acquired by the chip and the ideal preamble waveform; establishing this correlation takes only slightly less than one symbol period. Step 5. After step 4 is completed, the chip returns to standby mode and receives signal interrupts; Step 6. If the preamble is found, clear the interrupt and start receiving data; Step 7: When the distributed coordination function module detects that the channel is busy, the terminal node enters a sleep state to save energy, and waits for a random period of time before re-enabling the channel activity detection unit to listen for whether there is a transmission signal in the current channel.

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