Power Internet of Things Device Access Method and Communication System Based on Semi-Authorized Transmission

Abstract

The present invention provides a method for accessing power Internet of Things devices based on semi-grant transmission and a communication system. The method includes: a device based on grant transmission obtains communication authorization from a data center, and after successful authorization, sends a signal to a base station; the data center estimates a suitable number L of unauthorized device accesses according to the status information of the authorized devices; the L unauthorized devices with the optimal channel state obtain the right to transmit, and simultaneously send signals to the data center using uplink non-orthogonal multiple access technology together with the grant-based users; the data center receives the signals sent by the authorized devices and the L unauthorized devices with the optimal channel coefficients, and demodulates each signal through serial interference cancellation technology; the communication system includes a data center, authorized devices, and unauthorized devices. It takes into account the service requirements of different devices, avoids transmission collisions on the uplink channel, and at the same time greatly reduces the number of communication authorizations, thereby reducing the huge energy consumption caused by excessive signaling in the power Internet of Things.

Description

Technical Field

[0001] The present invention relates to the field of communication technologies, and in particular, to a method for accessing power Internet of Things devices based on semi-grant transmission and a communication system. Background Art

[0002] With the continuous intelligence of mobile communication devices, the power Internet of Things integrates more and more intelligent sensing devices. These intelligent devices constantly sense the status of various links such as power generation, power transmission, power transformation, and power distribution in the power grid, and send the collected information to the data center for processing, which makes the operation of the power grid more efficient and intelligent, but also brings huge challenges to communication. On the one hand, the number of terminal devices in the power Internet of Things is huge and distributed dispersedly. The simultaneous upload of massive data will bring huge bandwidth pressure and increase the control difficulty of the uplink, and it is very easy to have problems such as congestion and excessive control signaling. On the other hand, the data content of various devices in the power Internet of Things varies greatly, and it is difficult for traditional uplinks to provide corresponding communication services for each device. For example, the data generated by devices such as smart meters and temperature transmitters has the characteristics of short data, many times, and low latency sensitivity. The data generated by protection devices such as anomaly detectors has the characteristics of short data, few times, and high latency sensitivity. The data generated by control devices such as remote control robots has the characteristics of long data, many times, and high latency sensitivity.

[0003] The power Internet of Things is a complex large-scale machine communication scenario, and the amount of data collected is huge and may be highly heterogeneous. In order to ensure the reliable communication of devices with different communication requirements, existing power Internet of Things communication systems often solve the problem by increasing control signaling and the computing amount of the data center, which is a huge test for the computing power and energy consumption of the data center. Therefore, the power Internet of Things urgently needs a new uplink communication access strategy to reduce control signaling while ensuring communication reliability.

[0004] In the prior art, non-orthogonal multiple access (NOMA) is an access technology that allows multiple users to share the same frequency resource simultaneously, which can greatly improve the frequency band utilization rate and is regarded as an important technology to solve the massive access problem in the power Internet of Things. However, there are still many problems in the current application of this technology. For example, it cannot handle device communication scenarios with large differences, and each device needs to apply to the center for authorization to access. Facing the power Internet of Things with a huge number of devices, a large amount of control signaling will be generated, and there is too much interference between users, which is prone to interruption. On the one hand, although NOMA can enable multiple devices to share the same frequency band resource simultaneously, if the number of devices sharing the same resource block is not restricted, it will increase the decoding complexity at the receiving end, resulting in poor communication quality and a high probability of interruption. Therefore, the data center needs to continuously "communicate" with each device to reduce signal conflicts. This is feasible in scenarios with fewer devices, but in large-scale machine communication scenarios such as the power Internet of Things, this method will bring too much control signaling, which not only increases the computing difficulty of the data center but also generates huge energy consumption. On the other hand, to reduce the number of control signaling in the power Internet of Things, it is necessary to reduce the participation of the data center. How to control the number of users in each resource block has become a difficult problem, and how to balance the different communication requirements between devices in this case is also a challenge. Summary of the Invention

[0005] The present invention aims to at least solve one of the technical problems existing in the prior art, such as excessive control signaling in the power Internet of Things, large differences in communication requirements between devices, too much interference between users, and easy occurrence of interruption.

[0006] To this end, the first aspect of the present invention provides a method for accessing power Internet of Things devices based on semi-grant transmission.

[0007] The second aspect of the present invention provides a communication system.

[0008] The present invention provides a method for accessing power Internet of Things devices based on semi-grant transmission, including the following steps:

[0009] S1. The authorized device obtains authorization from the data center based on the authorized transmission mode. During the process of obtaining authorization, estimate the channel coefficient between itself and the data center, and transmit its own status information to the data center;

[0010] S2. The data center calculates the maximum interference that the authorized device can tolerate according to the status information of the authorized device, and estimates the number of unauthorized devices that can be allowed to access without affecting the normal communication of the authorized device according to this value;

[0011] S3. The data center broadcasts the number of unauthorized devices allowed to access and the pilot signal for channel estimation to all unauthorized devices. The unauthorized devices estimate the channel coefficient between them and the data center based on this broadcast signal.

[0012] S4. Compare the channel coefficients between several unauthorized devices and the data center. The L unauthorized devices with the optimal channel coefficients obtain the transmission right to send signals to the data center.

[0013] S5. The data center receives the signals sent by the authorized devices and the L unauthorized devices with the optimal channel coefficients, and demodulates each signal using the serial interference cancellation technology.

[0014] According to the above technical solution of the present invention, the access method of power Internet of Things devices based on semi - authorized transmission may further have the following additional technical features:

[0015] Further, step S1 includes the following steps:

[0016] S11. The data center broadcasts the available random access preamble sequences to the devices.

[0017] S12. The authorized device selects a preamble from the available random access preamble sequences and uploads it to the data center to identify the occupied channel.

[0018] S13. The data center sends a random access response, including the highest data rate, resource allocation, and synchronization message.

[0019] S14. The authorized device sends a radio resource control request to the data center, and the data center responds to this request to identify the temporary terminal identifier used.

[0020] S15. Arrange the authorized device into the target resource block and perform a scheduling request. If there is no conflict, the authorized device occupies the current channel and sends a connection request; otherwise, the authorized device will experience a contention access period to resolve the conflict.

[0021] S16. After obtaining the permission from the data center, start transmitting data.

[0022] Further, the status information of the authorized device includes the transmit power, channel coefficient, and target rate.

[0023] In S2, the data center calculates the maximum inter - device interference that the authorized device can tolerate based on the status information of the authorized device and the channel noise. The specific method is as follows:

[0024]

[0025] Wherein, The maximum interference between devices that an authorized device can tolerate; P 0 The transmission power of the authorized device; h 0 The channel coefficient; R 0 The target rate; M is the channel noise.

[0026] Furthermore, the data center estimates the number of unauthorized devices L that can access based on the maximum interference between devices that an authorized device can tolerate and the statistical characteristics of the received power of unauthorized devices at the base station. The specific method is as follows:

[0027]

[0028] Among them, μ W Is the mean value of the received power of unauthorized devices at the base station; σ W Is the variance of the received power of unauthorized devices at the base station; D is the protection difference, which is a monotonically increasing function of σ W Of.

[0029] Furthermore, step S4 includes the following steps:

[0030] S41. After all unauthorized devices receive the number L of unauthorized devices allowed to access broadcast by the data center, set a counter with a value of L locally;

[0031] S42. All unauthorized devices back off for a period of time according to their own channel coefficients. The back-off time is a strictly decreasing function of the channel gain;

[0032] S43. The unauthorized device with the optimal channel coefficient finishes the back-off time first and preferentially sends a signal to the data center;

[0033] S44. After the remaining unauthorized devices still in the back-off state hear this transmission, subtract 1 from the counter value to become L - 1;

[0034] S45. The remaining unauthorized devices finish the back-off time in descending order of channel coefficients and send signals to the data center. After the data center receives the signal of the Lth unauthorized device, the counters of the remaining unauthorized devices still in the back-off state are reduced to 0 and no longer send signals.

[0035] Furthermore, ignoring the back-off time of unauthorized devices, the unauthorized devices accessing the data center are regarded as establishing connections with the data center simultaneously.

[0036] Furthermore, step S5 includes the following steps:

[0037] S51. The data center receives the signals sent by the authorized device and the L unauthorized devices with the optimal channel coefficients. The signal is expressed as:

[0038]

[0039] Among them, P N-L+1 , …, P N respectively represent the signal transmission powers of the unauthorized devices U N-L+1 , …, U N , and h N-L+1 , …, h N respectively represent the channel coefficients between the unauthorized devices U N-L+1 , …, U N and the data center. x 0 (t), x N-L+1 (t), …, x N (t) respectively represent the signals sent by the authorized user U 0 and the unauthorized devices U N-L+1 , …, U N to the data center.

[0040] S52. The data center demodulates the signals of each device through serial interference cancellation technology. Among them, the signal x 0 (t) of the authorized device is demodulated first, and the corresponding decoded signal-to-interference-plus-noise ratio γ 0 can be expressed as:

[0041]

[0042] S53. The data center demodulates in the order of x N (t) → x N-L+1 (t). The signals x N (t), …, x N-L+2 (t) being demodulated in the middle are interfered by noise and the remaining signals during demodulation, and their decoded signal-to-interference-plus-noise ratios can be expressed as:

[0043]

[0044] S54. The signal x N-L+1 (t) demodulated last is only interfered by noise, and its decoded signal-to-noise ratio γ N-L+1 can be expressed as:

[0045]

[0046] The present invention provides a communication system, including a data center, an authorized device, and unauthorized devices. The authorized device obtains authorization from the data center based on an authorized transmission method; the unauthorized devices obtain authorization from the data center through a power Internet of Things device access method based on semi-authorized transmission.

[0047] According to the communication system of the above technical solution of the present invention, it may also have the following additional technical features:

[0048] Furthermore, the authorized device and / or unauthorized device are disposed at the user station of the power system, and the data center is disposed at the base station of the power system.

[0049] Furthermore, the unauthorized device and / or authorized device are disposed in the intelligent meter copying system to enable the intelligent meter to send meter information to the data center.

[0050] In summary, due to the adoption of the above technical features, the beneficial effects of the present invention are as follows:

[0051] 1. The present invention realizes the transmission of multiple devices sharing the same resource block through non-orthogonal multiple access technology, effectively improving the spectrum efficiency and alleviating the bandwidth pressure of the power Internet of Things.

[0052] 2. By introducing a semi-authorized transmission strategy into the uplink communication system of the power Internet of Things, the present invention authorizes communication for delay-sensitive devices, allocates dedicated resource blocks to ensure high-quality communication that meets their requirements, and does not authorize communication for non-delay-sensitive devices, allowing them to share resource blocks with authorized devices in an opportunistic manner. This not only takes into account the different communication requirements of different devices but also reduces the control signaling in the system.

[0053] 3. By introducing a distributed control method into the semi-authorized transmission strategy, the present invention successfully avoids conflicts in device transmissions in the absence of base station authorization and strictly controls the number of unauthorized devices sharing resource blocks to ensure that the communication of unauthorized devices does not affect the normal communication of authorized devices.

[0054] The additional aspects and advantages of the present invention will become apparent in the following description section or be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the description of the embodiments in conjunction with the following drawings, wherein:

[0056] Figure 1 is a flowchart of a method for accessing power Internet of Things devices based on semi-authorized transmission according to an embodiment of the present invention;

[0057] Figure 2 is a model diagram of a communication system according to an embodiment of the present invention;

[0058] Figure 3 is a curve graph showing the relationship between the interruption probability of an authorized device and the number of unauthorized devices competing for the same resource block under different strategies in a method for accessing power Internet of Things devices based on semi-authorized transmission according to an embodiment of the present invention;

[0059] Figure 4It is a curve graph showing the relationship between the outage probability of unlicensed devices and the number of unlicensed devices competing for the same resource block under different strategies in the power IoT device access method based on semi - licensed transmission according to an embodiment of the present invention;

[0060] Figure 5 It is a curve graph showing the relationship between the outage probability of licensed devices and the number of unlicensed devices competing for the same resource block under different numbers of allowed - access unlicensed devices in the power IoT device access method based on semi - licensed transmission according to an embodiment of the present invention. Detailed implementation manners

[0061] In order to more clearly understand the above - mentioned objects, features and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific implementation manners. It should be noted that, without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other.

[0062] Many specific details are set forth in the following description in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0063] Next, refer to Figures 1 to 5 to describe the power IoT device access method and communication system based on semi - licensed transmission according to some embodiments of the present invention.

[0064] Some embodiments of the present application provide a power IoT device access method based on semi - licensed transmission.

[0065] As Figures 1 to 5 shown, the first embodiment of the present invention proposes a power IoT device access method based on semi - licensed transmission. In the power IoT, it includes a data center, a licensed device U 0 based on licensed transmission, such as a latency - sensitive device like a remote control device; N unlicensed devices U n based on unlicensed transmission, such as a non - latency - sensitive device like a smart meter, (n ∈ {1, …, N}); among them, the N unlicensed devices opportunistically share the same frequency - band resource with the licensed device to send data to the data center;

[0066] The method specifically includes the following steps:

[0067] S1. The licensed device U 0 obtains authorization from the data center based on the traditional licensed transmission method (such as NOMA). During the process of obtaining authorization, it estimates the channel coefficient between itself and the data center and transmits its own status information to the data center;

[0068] S11. The data center broadcasts the available random access preamble sequences to all devices;

[0069] S12. The authorized device U 0 selects a preamble from the available random access preamble sequences and uploads the preamble to the data center to identify the occupied channel;

[0070] S13. The data center sends a random access response, including the highest data rate, resource allocation, and synchronization messages, such as the primary synchronization signal and the secondary synchronization signal;

[0071] S14. The authorized device U 0 sends a radio resource control request to the data center, and the data center responds to the request to identify the used temporary terminal identifier;

[0072] S15. Arrange the authorized device U 0 into the target resource block and make a scheduling request. If there is no conflict, the authorized device occupies the current channel and sends a connection request; otherwise, the authorized device U 0 will experience a contention access period to resolve the conflict, such as waiting randomly for a period of time and retrying the channel;

[0073] S16. After obtaining the permission from the data center, start transmitting data.

[0074] The status information of the authorized device includes the transmit power, channel coefficient, and target rate;

[0075] S2. The data center calculates the maximum interference that the authorized device can tolerate according to the status information of the authorized device U 0 and estimates the number L of unauthorized devices that can be allowed to access without affecting the normal communication of the authorized device U 0 , where L ≤ N;

[0076] In S2, the data center calculates the maximum inter-device interference that the authorized device can tolerate according to the status information of the authorized device and the channel noise. The specific method is as follows:

[0077]

[0078] where is the maximum inter-device interference that the authorized device can tolerate; P 0 is the transmit power of the authorized device; h 0 is the channel coefficient; R 0 is the target rate; M is the channel noise.

[0079] In S2, the data center estimates the number L of unauthorized devices accessing according to the maximum inter-device interference that the authorized device can tolerate and the statistical characteristics of the received power of the unauthorized devices at the base station. The specific method is as follows:

[0080]

[0081] Among them, μ W is the mean value of the received power of the unauthorized device at the base station; σ W is the variance of the received power of the unauthorized device at the base station; D is the protection difference, which is a monotonically increasing function of σ W .

[0082] S3. The data center broadcasts the number L of allowed unauthorized devices to be accessed and the pilot signal for channel estimation to all unauthorized devices. The unauthorized devices estimate the channel coefficient between them and the data center according to the broadcast signal;

[0083] S4. Based on a distributed control method, compare the channel coefficients between several unauthorized devices and the data center. The L unauthorized devices with the optimal channel coefficients obtain the transmission right to send signals to the data center;

[0084] The data center estimates the number L of unauthorized devices to be accessed according to the maximum inter-device interference that the authorized device can tolerate. The unauthorized devices do not need to perform the "handshake behavior" of traditional authorized transmission with the data center. The number of unauthorized devices accessing is strictly controlled not to exceed L through a distributed control method; among them, the unauthorized device with the optimal channel coefficient accesses the data center first; it can be understood that the N unauthorized devices are sorted in ascending order of channel coefficient as {U 1 , …, U N}, and the L unauthorized devices with the optimal channel coefficients {U N-L+1 , …, U N} obtain the access right.

[0085] Step S4 includes the following steps:

[0086] S41. After all unauthorized devices receive the number L of allowed unauthorized devices to be accessed broadcast by the data center, set a counter with a value of L locally;

[0087] S42. All unauthorized devices back off for a period of time according to their own channel coefficients. The back-off time is a strictly decreasing function of the channel gain, and the back-off time is small enough;

[0088] S43. The unauthorized device U N with the optimal channel coefficient finishes the back-off time first and preferentially sends signals to the data center;

[0089] S44. The remaining unauthorized devices still in the back-off state subtract 1 from the counter value after hearing this transmission and change it to L - 1;

[0090] S45. The remaining unauthorized devices end their backoff times in descending order of channel coefficients and send signals to the data center. After the data center receives the signal from the L-th unauthorized device, the counters of the remaining unauthorized devices still in the backoff state are reset to 0 and they stop sending signals. It can be understood that the L - 1 unauthorized devices U N ,…,U N-L+1 end their backoff times in sequence and send signals to the data center. When the unauthorized device U N-L+1 sends a signal, the counters of the remaining unauthorized devices still in the backoff state are reset to 0 and they stop sending signals.

[0091] Although the backoff times of the devices are inconsistent and the signal transmissions have a sequence, the backoff times of the unauthorized devices are short enough to be ignored. The unauthorized devices accessing the data center can be approximately regarded as establishing connections with the data center simultaneously.

[0092] S5. The data center receives the signals sent by the authorized device and the L unauthorized devices with the best channel coefficients, and demodulates each signal using the serial interference cancellation technique.

[0093] Step S5 includes the following steps:

[0094] S51. The data center receives the signals sent by the authorized device and the L unauthorized devices with the best channel coefficients. The signal is expressed as:

[0095]

[0096] where P N-L+1 ,…,P N respectively represent the signal transmission powers of the unauthorized devices U N-L+1 ,…,U N , h N-L+1 ,…,h N respectively represent the channel coefficients between the unauthorized devices U N-L+1 ,…,U N and the data center, and x 0 (t), x N-L+1 (t),…, x N (t) respectively represent the signals sent by the authorized user U 0 and the unauthorized devices U N-L+1 ,…,U N to the data center.

[0097] S52. The data center demodulates the signals of each device using the serial interference cancellation technique. Among them, the signal x 0 (t) of the authorized device is demodulated first, and the corresponding decoded signal-to-interference-plus-noise ratio γ 0 can be expressed as:

[0098]

[0099] S53. The data center demodulates in the order of x N (t) → x N-L+1 (t). The signals x N (t), …, x N-L+2 (t) will be interfered by noise and other signals during demodulation. The signal-to-interference-plus-noise ratio of its decoding can be expressed as:

[0100]

[0101] S54. The last demodulated signal x N-L+1 (t) is only interfered by noise. The signal-to-noise ratio γ N-L+1 of its decoding can be expressed as:

[0102]

[0103] Figure 3 The figure shows the relationship curve between the outage probability of the authorized device and the number of unauthorized devices competing for the same resource block under different strategies, that is, the performance graph of the outage probability of the authorized device of the present invention changing with the number of unauthorized devices competing for the same resource block in comparison with other technologies. It can be seen from the figure that as the number of unauthorized devices competing for the same resource block increases, the outage probability of the authorized device gradually rises. Compared with the non-distributed control scheme, the outage probability of the authorized device of the present invention is generally lower, which can better ensure the communication reliability of the authorized device. And the slope of the performance curve of the present invention is lower than that of the non-distributed control scheme, indicating that the present invention can better handle the conflicts of multiple devices.

[0104] Figure 4 The figure shows the relationship curve between the outage probability of the unauthorized device and the number of unauthorized devices competing for the same resource block under different strategies, that is, the performance graph of the outage probability of the unauthorized device of the present invention changing with the number of unauthorized devices competing for the same resource block in comparison with other technologies. It can be seen from the figure that as the number of unauthorized devices competing for the same resource block increases, the outage probability of the unauthorized device first decreases rapidly and then increases slowly, indicating that the present invention can effectively handle the conflicts of multiple devices and also takes into account the reliability of the unauthorized device on the premise of ensuring the communication reliability of the authorized device. Compared with the non-distributed control scheme, the present invention significantly improves the reliability of the unauthorized device.

[0105] Figure 5The figure shows a curve graph of the relationship between the interruption probability of authorized devices and the number of unauthorized devices competing for the same resource block under different numbers of allowed-access unauthorized devices, that is, in comparison with other technologies, for the present invention, under different conditions of the number of allowed-access unauthorized devices, the curve of the change in the interruption probability of authorized devices with the number of unauthorized devices competing for the same resource block. It can be seen from this figure that as the number of allowed-access unauthorized devices increases, the overall interruption probability of authorized devices will increase. Therefore, in actual transmission, the number of allowed-access unauthorized devices can be adjusted accordingly according to the change in the number of unauthorized devices competing for the same resource block, so that the system transmission meets the requirement indicators.

[0106] Some embodiments of the present application provide a communication system.

[0107] The second embodiment of the present invention proposes a communication system, and on the basis of the first embodiment, as Figures 1 to 5 shown, it includes a data center, authorized devices, and unauthorized devices. The authorized devices obtain authorization from the data center based on the authorized transmission method; the unauthorized devices obtain authorization from the data center through the access method of power Internet of Things devices based on semi-authorized transmission. Specifically, it is a wireless communication system that uses the access method of power Internet of Things devices based on semi-authorized transmission given in the first embodiment to implement the function of users sending information to the base station in this wireless communication system.

[0108] The third embodiment of the present invention proposes a communication system, and on the basis of any of the above embodiments, as Figures 1 to 5 shown, it includes a data center, authorized devices, and unauthorized devices. The authorized devices obtain authorization from the data center based on the authorized transmission method; the unauthorized devices obtain authorization from the data center through the access method of power Internet of Things devices based on semi-authorized transmission. Specifically, it is a power Internet of Things uplink communication system that uses the access method of power Internet of Things devices based on semi-authorized transmission given in the first embodiment to implement the function of power devices sending monitoring information to the data center in this power Internet of Things uplink communication system.

[0109] The fourth embodiment of the present invention proposes a communication system, and on the basis of any of the above embodiments, as Figures 1 to 5 shown, it includes a data center, authorized devices, and unauthorized devices. The authorized devices obtain authorization from the data center based on the authorized transmission method; the unauthorized devices obtain authorization from the data center through the access method of power Internet of Things devices based on semi-authorized transmission. Specifically, it is a massive machine communication system that uses the access method of power Internet of Things devices based on semi-authorized transmission given in the first embodiment to implement the function of machine devices sending information to the base station in this massive machine communication system.

[0110] The fifth embodiment of the present invention proposes a communication system, and on the basis of any of the above embodiments, as Figures 1 to 5 shown, it includes a data center, an authorized device, and an unauthorized device. The authorized device obtains authorization from the data center based on an authorized transmission method; the unauthorized device obtains authorization from the data center through a power Internet of Things device access method based on semi-authorized transmission. Specifically, it is an intelligent meter copying system, which uses the power Internet of Things device access method based on semi-authorized transmission given in the first embodiment to implement the function of the intelligent meter in the intelligent meter copying system to send meter information to the data center.

[0111] In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiments or examples. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0112] Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for accessing power Internet of Things devices based on semi - authorized transmission, characterized in that, it includes the following steps: S1. The authorized device obtains authorization from the data center based on the authorized transmission method. During the process of obtaining authorization, estimate the channel coefficient between itself and the data center, and transmit its own status information to the data center; S2. The data center calculates the maximum interference that the authorized device can tolerate according to the status information of the authorized device, and estimates the number of unauthorized devices that can be allowed to access without affecting the normal communication of the authorized device according to this value; S3. The data center broadcasts the number of unauthorized devices allowed to access and the pilot signal for channel estimation to all unauthorized devices, and the unauthorized devices estimate the channel coefficient between themselves and the data center according to this broadcast signal; S4. Compare the channel coefficients between several unauthorized devices and the data center. The L unauthorized devices with the optimal channel coefficients obtain the transmission right to send signals to the data center; S5. The data center receives the signals sent by the authorized device and the L unauthorized devices with the optimal channel coefficients, and demodulates each signal using the serial interference cancellation technology; The status information of the authorized device includes transmission power, channel coefficient and target rate; In S2, the data center calculates the maximum inter - device interference that the authorized device can tolerate according to the status information of the authorized device and the channel noise. The specific method is as follows: Among them, is the maximum interference between devices that the authorized device can tolerate; P 0 is the transmission power of the authorized device; h 0 is the channel coefficient; R 0 is the target rate; M is the channel noise; The data center estimates the number of unauthorized devices accessing L according to the maximum inter - device interference that the authorized device can tolerate and the statistical characteristics of the received power of unauthorized devices at the base station. The specific method is as follows: Among them, μ W is the mean of the received power of the unauthorized device at the base station; σ W is the variance of the received power of the unauthorized device at the base station; D is the protection difference, which is a monotonically increasing function of σ W .

2. The method for accessing power Internet of Things devices based on semi - authorized transmission according to claim 1, characterized in that, step S1 includes the following steps: S11. The data center broadcasts the available random access preamble sequence to the device; S12. The authorized device selects a preamble from the available random access preamble sequence and uploads the preamble to the data center to identify the occupied channel; S13. The data center sends a random access response, including the highest data rate, resource allocation and synchronization message; S14. The authorized device sends a radio resource control request to the data center, and the data center responds to this request to identify the temporary terminal identifier used; S15. Arrange the authorized device into the target resource block and make a scheduling request. If there is no conflict, the authorized device occupies the current channel and sends a connection request; otherwise, the authorized device will experience a contention access period to resolve the conflict; S16. After obtaining the permission of the data center, start transmitting data.

3. The method for accessing power Internet of Things devices based on semi - authorized transmission according to claim 1, characterized in that, step S4 includes the following steps: S41. After all unauthorized devices receive the number L of unauthorized devices allowed to access broadcast by the data center, set a counter with a value of L locally; S42. All unauthorized devices back off for a period of time according to their own channel coefficients. The back - off time is a strictly decreasing function of the channel gain; S43. The unauthorized device with the optimal channel coefficient finishes the back - off time first and preferentially sends a signal to the data center; S44. After the unauthorized devices that are still in the backoff state hear this transmission, they decrement the counter value by 1 to become L - 1; S45. The remaining unauthorized devices end their backoff times in descending order according to the channel coefficients and send signals to the data center. After the data center receives the signal from the Lth unauthorized device, the counters of the remaining unauthorized devices that are still in the backoff state are decremented to 0 and they no longer send signals.

4. The method for accessing power Internet of Things devices based on semi - authorized transmission according to claim 3, characterized in that, ignoring the backoff time of the unauthorized devices, the unauthorized devices accessing the data center are regarded as establishing connections with the data center simultaneously.

5. The method for accessing power Internet of Things devices based on semi - authorized transmission according to claim 1, characterized in that, step S5 includes the following steps: S51. The data center receives signals sent by the authorized device and the L unauthorized devices with the optimal channel coefficients, and the signal is expressed as: Among them, P N-L+1 , …, P N respectively represent the signal transmission powers of unauthorized devices U N-L+1 , …, U N , h N-L+1 , …, h N respectively represent the channel coefficients between unauthorized devices U N-L+1 , …, U N and the data center, and x 0 (t), x N-L+1 (t), …, x N (t) respectively represent the signals sent by authorized user U 0 and unauthorized devices U N-L+1 , …, U N to the data center; S52. The data center demodulates the signals of each device through the serial interference cancellation technology. Among them, the signal x 0 (t) of the authorized device is demodulated first, and the corresponding decoded signal-to-interference-plus-noise ratio γ 0 can be expressed as: S53. The data center demodulates in the order of x N (t) → x N-L+1 (t). The signals x N (t), …, x N-L+2 (t) will be interfered by noise and other signals during demodulation, and the signal-to-interference-plus-noise ratio of its decoding can be expressed as: S54, the finally demodulated signal x N-L+1 (t), will only be interfered by noise, and its decoded signal-to-noise ratio γ N-L+1 can be expressed as:

6. A communication system, characterized in that, it includes a data center, an authorized device, and an unauthorized device. The authorized device obtains authorization from the data center based on the authorized transmission method; the unauthorized device obtains authorization from the data center through the method for accessing power Internet of Things devices based on semi - authorized transmission according to any one of claims 1 to 5.

7. The communication system according to claim 6, characterized in that, the authorized device and / or the unauthorized device are arranged at the power system user station, and the data center is arranged at the power system base station.

8. The communication system according to claim 6, characterized in that, the unauthorized device and / or the authorized device are arranged in the intelligent meter copying system to enable the intelligent meter to send meter information to the data center.

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