A point-to-multipoint scatter communication system based on variable length time slots

Abstract

The application discloses a point-to-multipoint scattering communication system based on variable length time slot. The system comprises a master station and multiple slave stations. In a data transmission stage, the master station occupies a dominant position of data transmission, that is, the master station decides to communicate with a specific slave station in a time period, and the slave stations are passive and communicate with the master station. The slave stations cannot communicate with each other. Due to the characteristics of the scattering channel, the master station can only communicate with one slave station at the same time. The master station accesses multiple slave stations in a time division multiplexing mode, adjusts the time slot length of data transmission access according to the current data transmission requirement of the slave station, adopts different transmission modes, and turns to the next slave station after completing communication with the current slave station. According to the application, the time slot length is adjusted according to the data transmission requirement of the slave station, and compared with an equal length time slot allocation mechanism, the resource utilization rate can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the field of tropospheric point-to-multipoint scattering communication, and in particular to a point-to-multipoint scattering communication system based on variable-length time slots. Background Art

[0002] Tropospheric scatter communication utilizes the scattering of radio waves by the inhomogeneity of propagation media in the atmosphere to achieve beyond-line-of-sight (BLOS) long-distance communication. It features long single-hop distances, a wide available wireless frequency band, high communication capacity, and free access. Point-to-multipoint scatter communication systems typically consist of a master station and multiple slave stations. In point-to-multipoint communication, the master station must be capable of communicating with multiple slave stations. For example, the Chinese patent "A Point-to-Multipoint Scattering Communication System (Application No. 201020121765.8)" discloses a point-to-multipoint communication system suitable for tropospheric scatter communication. However, the multiple peripheral stations are connected to the base station (master station) in parallel, making multiple access between the multiple slave stations impossible.

[0003] In order to reduce the interference of concurrent transmissions from multiple slave stations, the access order of the slave stations must be controlled and multiple access must be provided. The Chinese invention patent "Adaptive wireless communication point-to-multipoint access method for communication mechanism between ships and shore stations (application number 201710598547.X)" discloses a form of multiple access between a shore-based base station and multiple ships. Its network structure is similar to point-to-multipoint scattering communication, and the access method adopts frequency division multiple access. In tropospheric scattering communication, multiple slave stations are generally located in relatively dispersed locations. In order to reduce power consumption and improve concealment, it is difficult for the master station to achieve one beam covering all slave stations. Therefore, the form of frequency division multiple access is not suitable for point-to-multipoint scattering communication.

[0004] In order to further improve the performance of point-to-multipoint scattering communication, it is necessary to explore the application of time division multiplexing technology in the point-to-multipoint scattering communication system, so that the master station communicates with multiple slave stations in the form of polling, each slave station occupies a time slot separately, and the different data transmission requirements of the slave stations need to be further considered. Summary of the Invention

[0005] The present invention provides a point-to-multipoint scattering communication system based on variable-length time slots, which consists of a master station and several slave stations. The master station accesses multiple slave stations in the form of time division multiplexing, and the time slots occupied by each slave station are of different lengths.

[0006] The purpose of the present invention is achieved by at least one of the following technical solutions.

[0007] A point-to-multipoint scattering communication system based on variable-length time slots includes a master station and multiple slave stations. During the data transmission phase, the master station occupies a dominant position in data transmission; that is, the master station decides to communicate with a specific slave station at a certain time period, while the slave stations communicate with the master station passively and cannot communicate with each other. Due to the characteristics of the scattering channel, the master station can only communicate with one slave station at a time. The master station accesses multiple slave stations through time division multiplexing, adjusts the time slot length of data transmission access according to the data transmission requirements of the current slave station, adopts different transmission modes, and switches to the next slave station after completing communication with the current slave station.

[0008] Furthermore, the time slot for data transmission access includes a frame header segment, a detection segment, a signaling segment, and a data segment in sequence according to the transmission time;

[0009] The data flow from the master station to each slave station is transmitted in bursts. Therefore, a frame header is required each time information transmission is started. This is used for frame arrival detection and symbol synchronization at the receiving end. In the frame header segment, the transmitter sends a frame header sequence to the receiver.

[0010] There may be a certain time interval between two communications between the master station and a slave station, during which the channel status between them may change. The role of the detection segment is to detect the channel between the master station and the slave station before each transmission of business information, providing a basis for selecting a better modulation mode and time slot allocation algorithm in subsequent data transmission;

[0011] The signaling segment is used by the slave station to report the channel detection results to the master station, and is also used for the master station and the slave station to exchange data segment information;

[0012] The function of the data segment is to construct the service information to be sent into a transmission signal based on the optimal mode information obtained in the detection segment and adopt the corresponding transmission mode before sending it.

[0013] Furthermore, the frame header sequence is usually composed of a pseudo-random sequence with a sharp autocorrelation peak. The receiver performs a correlation operation on the received signal and the local frame header sequence. Based on the peak position of the correlation operation, it detects the arrival of the frame header and locates the starting point of the symbol in the subsequent detection segment.

[0014] The success or failure of a transmission is directly determined by the receiver's ability to capture the frame header. Therefore, the frame header sequence must be of a certain length to achieve sufficient signal-to-noise ratio gain during the correlation process, ensuring reliable detection even under low signal-to-noise ratios and deep channel fading. To ensure sufficient noise immunity for the frame header, the frame header sequence is modulated using the binary modulation method with the highest noise tolerance.

[0015] Furthermore, to prevent the multipath tailing of the frame header from interfering with the detection segment and affecting the channel detection results, a guard interval is added before the detection segment;

[0016] In terms of modulation method, the detection segment still uses BPSK with the largest noise tolerance.

[0017] Furthermore, the remaining data and the end of the frame need to be marked at the end of the data segment;

[0018] The reason for marking the remaining data is that the allocation of time slots is not necessarily accurate. It is possible that the allocated time slot is too small to transmit all the data to be sent. Therefore, when this happens, the sender needs to tell the receiver that there is remaining data to be sent, and remind the receiver to mark the received data so that the next data transmission can connect the bit data and obtain the correct information.

[0019] The purpose of marking the end of a frame is to inform the receiver that the data transmission has ended.

[0020] Furthermore, the following transmission modes are included:

[0021] Transmission mode 1: data is transmitted unidirectionally from the master station to the slave station;

[0022] Transmission mode 2: data is transmitted unidirectionally from the slave station to the master station;

[0023] Transmission mode 3: Data is transmitted bidirectionally between the master and slave stations.

[0024] Furthermore, when transmission mode 1 or transmission mode 3 is used for data transmission, data transmission includes downlink signaling transmission and uplink signaling transmission. Therefore, the time slot for data transmission access includes a downlink signaling segment and an uplink signaling segment. The downlink signaling segment is used to transmit downlink communication parameters, including downlink data transmission duration, coding rate, and modulation order. The uplink signaling segment is used to transmit uplink communication parameters, including uplink data transmission duration, coding rate, and modulation order.

[0025] When transmission mode 2 is used for data transmission, data transmission only includes uplink signaling transmission, so no downlink signaling segment is required in the time slot for data transmission access.

[0026] Furthermore, when transmission mode 1 or transmission mode 2 is used for data transmission, the duration of data transmission, i.e., the time slot for data transmission access, is determined by the following three parameters:

[0027] The amount of data that the sender needs to send, the transmission rate obtained according to the channel detection result and the priority level of the sender channel access; the data transmission time T between the master station and the slave station i i Determined by the following formula:

[0028]

[0029] Among them, D i Indicates the amount of data waiting to be sent or received from station i; R i It represents the transmission rate obtained based on the channel detection results and the modulation mode; T i_max Represents the maximum transmission time that slave station i can occupy.

[0030] Furthermore, when transmission mode 3 is used for data transmission, the duration of downlink data transmission is determined by the following three parameters:

[0031] The amount of data that the sender needs to send, the transmission rate obtained based on the channel detection results, and the priority level of the sender's channel access;

[0032] Downlink data transmission time T between the master station and slave station i i_down Determined by the following formula:

[0033]

[0034] Among them, D i_down R represents the amount of downlink data waiting to be received from station i; i_down It represents the downlink transmission rate obtained based on the channel detection result and the modulation mode; T i_max represents the maximum transmission time that can be occupied by slave station i; α represents the time ratio occupied by downlink transmission.

[0035] Furthermore, when using transmission mode 3 for data transmission, the duration of uplink data transmission is determined by the following three parameters: the amount of data that the transmitter needs to send, the transmission rate obtained based on the channel sounding results, and the priority level of the channel access of the transmitter;

[0036] Uplink data transmission duration T between the master station and slave station i i_up Determined by the following formula:

[0037]

[0038] Among them, D i_up Indicates the amount of uplink data waiting to be sent from station i, R i_up Indicates the uplink transmission rate after channel detection results and modulation mode determination.

[0039] Compared with the prior art, the present invention has the following advantages:

[0040] (1) The present invention adjusts the time slot length according to the data transmission requirements of the slave station, and can effectively improve resource utilization compared with the equal-length time slot allocation mechanism.

[0041] (2) The present invention can change the priority of a slave station by controlling its maximum transmission time. The greater the maximum transmission time, the longer the transmission time obtained when burst service information occurs, indicating a higher priority. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 2 is a schematic diagram of a pitch angle search of a slave station in an embodiment of the present invention.

[0043] Figure 2 This is a diagram of a frame structure for downlink unidirectional data transmission from a master station to a slave station in an embodiment of the present invention.

[0044] Figure 3 This is a diagram of a frame structure for uplink unidirectional transmission of data from a slave station to a master station in an embodiment of the present invention.

[0045] Figure 4 This is a diagram of a bidirectional transmission frame structure in which data is transmitted first downstream and then upstream between a master station and a slave station in an embodiment of the present invention. DETAILED DESCRIPTION

[0046] The present invention will be further described in detail below with reference to examples. This example illustrates one use of the present invention, but the embodiments of the present invention are not limited thereto.

[0047] Example:

[0048] A point-to-multipoint scattering communication system based on variable-length time slots includes a master station and multiple slave stations;

[0049] In one embodiment, Figure 1 As shown in the figure, after the master station is powered on, it enters the slave station search phase. Generally, it can be assumed that the slave station already knows the master station's location in advance and sets the antenna to face the master station based on its own location information and the master station's location information. The master station needs to adjust the antenna direction to determine the exact location of each slave station. This process is called the slave station search phase. The specific process is as follows:

[0050] 1. The master station scans horizontally at fixed angle intervals at a 0° pitch, transmitting a scan sequence at a fixed frequency for each scan angle. The fixed angle interval depends on the antenna's beamwidth, which in turn depends on the antenna aperture. A larger antenna aperture allows for more concentrated transmission energy and a narrower beamwidth.

[0051] 2. After receiving the scan sequence, the slave station sends a response sequence to the master station after a specific delay.

[0052] 3. After receiving the response signals from each slave station, the master station selects a slave station that is not connected to the network to send a response sequence.

[0053] After the master station determines the orientation on the horizontal plane, it needs to perform a secondary calibration on the new slave station in terms of pitch angle. In one embodiment, the specific process is as follows:

[0054] 1. The new slave station sends multiple segments of PN code to the master station continuously after receiving the PN code from the master station.

[0055] 2. The master station fixes the horizontal direction as the direction of the new slave station scanned in the discovery sub-phase, and then scans in the pitch angle, receives the PN code and correlates it with the local PN code.

[0056] 3. Compare the correlation values ​​of the received signals at each pitch angle to find the maximum value, and point the slave station at that pitch angle to complete the pitch angle alignment.

[0057] During the data transmission phase, the master station takes a dominant position in data transmission; that is, the master station decides to communicate with a specific slave station at a certain time period, while the slave stations communicate with the master station passively and cannot communicate with each other; due to the characteristics of the scattering channel, the master station can only communicate with one slave station at the same time. The master station accesses multiple slave stations through time division multiplexing, adjusts the time slot length of data transmission access according to the current slave station data transmission requirements, adopts different transmission modes, and moves on to the next slave station after completing the communication with the current slave station.

[0058] Furthermore, the time slot for data transmission access includes a frame header segment, a detection segment, a signaling segment, and a data segment in sequence according to the transmission time;

[0059] The data flow from the master station to each slave station is transmitted in bursts. Therefore, a frame header is required each time information transmission is started. This is used for frame arrival detection and symbol synchronization at the receiving end. In the frame header segment, the transmitter sends a frame header sequence to the receiver.

[0060] There may be a certain time interval between two communications between the master station and a slave station, during which the channel status between them may change. The role of the detection segment is to detect the channel between the master station and the slave station before each transmission of business information, providing a basis for selecting a better modulation mode and time slot allocation algorithm in subsequent data transmission;

[0061] The signaling segment is used by the slave station to report the channel detection results to the master station, and is also used for the master station and the slave station to exchange data segment information;

[0062] The function of the data segment is to construct the business information to be sent into a transmission signal based on the optimal mode information obtained from the detection segment and adopt the corresponding transmission mode, and then send it out. The business information must undergo communication signal processing such as encoding and modulation before becoming a transmission signal.

[0063] Furthermore, the frame header sequence is usually composed of a pseudo-random sequence with a sharp autocorrelation peak. The receiver performs a correlation operation on the received signal and the local frame header sequence. Based on the peak position of the correlation operation, it detects the arrival of the frame header and locates the starting point of the symbol in the subsequent detection segment.

[0064] In one embodiment, the success or failure of a transmission is directly determined by the success or failure of the frame header at the receiving end. Therefore, the frame header sequence needs to have a certain time length to obtain sufficient signal-to-noise ratio gain during the correlation process, ensuring that it can still be reliably detected under low signal-to-noise ratio and deep channel fading. At the same time, in order to make the frame header have sufficient noise resistance, the modulation method of the frame header sequence adopts the binary modulation method with the highest noise tolerance.

[0065] In one embodiment, in order to prevent the multipath tailing of the frame header from interfering with the detection segment and affecting the channel detection result, an additional line is added before the detection segment;

[0066] In terms of modulation method, the detection segment still uses BPSK with the largest noise tolerance.

[0067] Furthermore, the remaining data and the end of the frame need to be marked at the end of the data segment;

[0068] The reason for marking the remaining data is that the allocation of time slots is not necessarily accurate. It is possible that the allocated time slot is too small to transmit all the data to be sent. Therefore, when this happens, the sender needs to tell the receiver that there is remaining data to be sent, and remind the receiver to mark the received data so that the next data transmission can connect the bit data and obtain the correct information.

[0069] The purpose of marking the end of a frame is to inform the receiver that the data transmission has ended.

[0070] Furthermore, the following transmission modes are included:

[0071] Transmission mode 1: Data is transmitted from the master station to the slave station in one direction, such as Figure 2 As shown;

[0072] Transmission mode 2: Data is transmitted from the slave station to the master station in one direction, such as Figure 3 As shown;

[0073] Transmission mode 3: Data is transmitted bidirectionally between the master and slave stations, such as Figure 4 shown.

[0074] Furthermore, when transmission mode 1 or transmission mode 3 is used for data transmission, data transmission includes downlink signaling transmission and uplink signaling transmission. Therefore, the time slot for data transmission access includes a downlink signaling segment and an uplink signaling segment. The downlink signaling segment is used to transmit downlink communication parameters, including downlink data transmission duration, coding rate, and modulation order. The uplink signaling segment is used to transmit uplink communication parameters, including uplink data transmission duration, coding rate, and modulation order.

[0075] When transmission mode 2 is used for data transmission, data transmission only includes uplink signaling transmission, so no downlink signaling segment is required in the time slot for data transmission access.

[0076] Furthermore, when transmission mode 1 or transmission mode 2 is used for data transmission, the duration of data transmission, i.e., the time slot for data transmission access, is determined by the following three parameters:

[0077] The amount of data that the sender needs to send, the transmission rate obtained according to the channel detection result and the priority level of the sender channel access; the data transmission time T between the master station and the slave station i i Determined by the following formula:

[0078]

[0079] Among them, D i Indicates the amount of data waiting to be sent or received from station i; R i It represents the transmission rate obtained based on the channel detection results and the modulation mode; T i_max Represents the maximum transmission time that slave station i can occupy.

[0080] Furthermore, when transmission mode 3 is used for data transmission, the duration of downlink data transmission is determined by the following three parameters:

[0081] The amount of data that the sender needs to send, the transmission rate obtained based on the channel detection results, and the priority level of the sender's channel access;

[0082] Downlink data transmission time T between the master station and slave station i i_down Determined by the following formula:

[0083]

[0084] Among them, D i_down R represents the amount of downlink data waiting to be received from station i; i_down It represents the downlink transmission rate obtained based on the channel detection result and the modulation mode; T i_max represents the maximum transmission time that can be occupied by slave station i; α represents the time ratio occupied by downlink transmission.

[0085] Furthermore, when using transmission mode 3 for data transmission, the duration of uplink data transmission is determined by the following three parameters: the amount of data that the transmitter needs to send, the transmission rate obtained based on the channel sounding results, and the priority level of the channel access of the transmitter;

[0086] Uplink data transmission duration T between the master station and slave station i i_up Determined by the following formula:

[0087]

[0088] Among them, D i_up Indicates the amount of uplink data waiting to be sent from station i, R i_up Indicates the uplink transmission rate after channel detection results and modulation mode determination.

[0089] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A point-to-multipoint scattering communication system based on variable-length time slots, comprising a master station and multiple slave stations, characterized in that: In the data transmission phase, the master station occupies the dominant position in data transmission; that is, the master station decides to communicate with a specific slave station at a certain time period, and the slave stations communicate with the master station passively, and the slave stations cannot communicate with each other; Due to the characteristics of the scattering channel, the master station can only communicate with one slave station at a time. The master station accesses multiple slave stations through time division multiplexing, adjusts the data transmission access time slot length according to the current slave station's data transmission requirements, and adopts different transmission modes. After completing the communication with the current slave station, it switches to the next slave station. The time slot for data transmission access includes the frame header segment, detection segment, signaling segment and data segment in order of transmission time; The data flow from the master station to each slave station is transmitted in bursts. Therefore, a frame header is required each time information transmission is started. This is used for frame arrival detection and symbol synchronization at the receiving end. In the frame header segment, the transmitter sends a frame header sequence to the receiver. There may be a certain time interval between two communications between the master station and a slave station, during which the channel status between them may change. The role of the detection segment is to detect the channel between the master station and the slave station before each transmission of business information, providing a basis for selecting a better modulation mode and time slot allocation algorithm in subsequent data transmission; The signaling segment is used by the slave station to report the channel detection results to the master station, and is also used for the master station and the slave station to exchange data segment information; The function of the data segment is to construct the service information to be sent into a transmission signal based on the optimal mode information obtained in the detection segment and adopt the corresponding transmission mode before sending it.

2. A point-to-multipoint scattering communication system based on variable length time slots according to claim 1, characterized in that: The frame header sequence consists of a pseudo-random sequence with a sharp autocorrelation peak. The receiver performs a correlation operation on the received signal and the local frame header sequence. The peak position of the correlation operation is used to detect the arrival of the frame header and locate the starting point of the symbol in the subsequent detection segment. In order to make the frame header have sufficient anti-noise capability, the modulation mode of the frame header sequence adopts the binary modulation mode with the highest noise tolerance.

3. A point-to-multipoint scattering communication system based on variable length time slots according to claim 1, characterized in that: To prevent the multipath tailing of the frame header from interfering with the detection segment and affecting the channel detection results, a guard interval is added before the detection segment. In terms of modulation mode, the detection segment adopts BPSK with the largest noise tolerance.

4. A point-to-multipoint scattering communication system based on variable length time slots according to claim 1, characterized in that: The remaining data and the end of the frame must be marked at the end of the data segment.

5. The point-to-multipoint scattering communication system based on variable length time slots according to claim 1, characterized in that: The following transmission modes are included: Transmission mode 1: data is transmitted unidirectionally from the master station to the slave station; Transmission mode 2: data is transmitted unidirectionally from the slave station to the master station; Transmission mode 3: Data is transmitted bidirectionally between the master and slave stations.

6. A point-to-multipoint scattering communication system based on variable length time slots according to claim 5, characterized in that: When transmission mode 1 or transmission mode 3 is used for data transmission, data transmission includes downlink signaling transmission and uplink signaling transmission. Therefore, the time slot for data transmission access includes a downlink signaling segment and an uplink signaling segment. The downlink signaling segment is used to transmit downlink communication parameters, including downlink data transmission duration, coding rate, and modulation order. The uplink signaling segment is used to transmit uplink communication parameters, including uplink data transmission duration, coding rate, and modulation order. When transmission mode 2 is used for data transmission, data transmission only includes uplink signaling transmission, so no downlink signaling segment is required in the time slot for data transmission access.

7. A point-to-multipoint scattering communication system based on variable length time slots according to claim 6, characterized in that: When using transmission mode 1 or transmission mode 2 for data transmission, the duration of data transmission, that is, the time slot for data transmission access, is determined by the following three parameters: The amount of data that the sender needs to send, the transmission rate obtained according to the channel detection result and the priority level of the sender's channel access; the data transmission time T between the master station and the slave station i i Determined by the following formula: Among them, D i Indicates the amount of data waiting to be sent or received from station i; R i It represents the transmission rate obtained based on the channel detection results and the modulation mode; T i_max Represents the maximum transmission time that slave station i can occupy.

8. The point-to-multipoint scattering communication system based on variable length time slots according to claim 7, characterized in that: When using transmission mode 3 for data transmission, the duration of downlink data transmission is determined by the following three parameters: The amount of data that the sender needs to send, the transmission rate obtained based on the channel detection results, and the priority level of the sender's channel access; Downlink data transmission time T between the master station and slave station i i_down Determined by the following formula: Among them, D i_down R represents the amount of downlink data waiting to be received from station i; i_down It represents the downlink transmission rate obtained based on the channel detection result and the modulation mode; T i_max represents the maximum transmission time that can be occupied by slave station i; α represents the time ratio occupied by downlink transmission.

9. The point-to-multipoint scattering communication system based on variable length time slots according to claim 8, characterized in that: When using transmission mode 3 for data transmission, the duration of uplink data transmission is determined by the following three parameters: the amount of data that the sender needs to send, the transmission rate obtained based on the channel sounding results, and the priority of the sender's channel access; Uplink data transmission duration T between the master station and slave station i i_up Determined by the following formula: Among them, D i_up Indicates the amount of uplink data waiting to be sent from station i, R i_up Indicates the uplink transmission rate after channel detection results and modulation mode determination.

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