A multi-access method for underwater mobile gateways using multi-domain joint processing

Abstract

The present invention discloses a multi-access method for underwater mobile gateways with multi-domain joint processing, comprising a remote guidance phase, a short-range channel sensing phase, and a short-range data transmission phase. During the remote guidance phase, a user node that needs to transmit data first sends an RTS signal to a gateway node. Upon receiving the signal, if the gateway node is idle, it replies with a CTS signal to the user node. Simultaneously, the gateway node can preliminarily determine the user node's location based on the received RTS signal energy and the direction of arrival, and then move toward the user node based on this location. The present invention optimizes the multi-access protocol from the perspective of multi-domain joint processing, combining time and space dimensional information. This allows nodes closest to the gateway node but with a slightly later access time to transmit data first, without excessively delaying the data transmission needs of other users. This reduces the total distance the gateway node needs to travel during data recovery, thereby improving multi-user transmission efficiency.

Description

Technical field:

[0001] The present invention belongs to the technical field of underwater communications, and in particular relates to a multi-domain joint processing underwater mobile gateway multiple access method. Background technology:

[0002] Monitoring ocean hydrological data (including temperature and salinity) is essential for developing marine resources and protecting maritime security. Traditional monitoring methods involve placing sensors in the seawater to collect data, then periodically recovering the sensors to read and process the recorded data. This approach has numerous drawbacks: first, it lacks real-time data monitoring; second, when sensor equipment issues arise, they are not quickly detected and repaired.

[0003] A more efficient solution for collecting underwater sensor data is to form an underwater communication network, in which sensor nodes send the collected data to shore through the network. However, underwater sensor networks that use underwater acoustic communication as the main communication method have problems such as low underwater acoustic communication rate and large propagation delay, resulting in low communication efficiency. Summary of the invention:

[0004] The technical problem to be solved by the present invention is to provide a multi-domain joint processing underwater mobile gateway multi-access method to solve the problem of low underwater acoustic communication rate and large propagation delay in underwater sensor networks, resulting in low communication efficiency. This method fully improves the network throughput and shortens the end-to-end delay.

[0005] The technical solution of the present invention is to provide a multi-domain joint processing underwater mobile gateway multi-access method, which divides the overall multi-access process into three stages: long-range guidance stage, short-range channel perception stage and short-range data transmission stage, wherein:

[0006] During the remote bootstrapping phase, the user node that needs to transmit data first sends an RTS signal to the gateway node. After receiving the signal, if the gateway node is idle, it replies with a CTS signal to the user node. At the same time, the gateway node can preliminarily determine the location of the user node based on the received RTS signal energy and the direction of arrival of the signal, and move towards the user node based on this location. During the movement, the gateway node periodically shakes hands with the user node and continuously updates the user node's location information.

[0007] When the gateway node moves to within the underwater acoustic communication range of the user node, it enters the short-range channel perception phase. The gateway node first perceives the channel quality through the RTS signal and makes a comprehensive decision on which communication medium to use based on the channel quality and the data transmission volume information obtained during the remote guidance phase.

[0008] After channel sensing is completed, the short-range data transmission phase begins. The gateway node informs the user node through CTS that it can start transmitting data and the selected communication medium and parameters. Other unrelated user nodes remain silent after receiving this CTS to prevent interference with data transmission. After data transmission is completed, the gateway node replies ACK to the user node through low-frequency underwater acoustic communication to confirm that the data was received successfully, and at the same time informs other users that they can start new communication.

[0009] As a preference, a time-space hybrid competitive access mechanism is also introduced in the remote guidance stage. The user node that shakes hands with the gateway node first in time is given priority to send data. However, if the user node that accesses later in time is significantly closer to the gateway node in space, the right to send signals first is allocated to it, thereby reducing the movement distance of the gateway node in the process of recovering data and improving transmission efficiency.

[0010] Preferably, the SDMA-CDMA multi-signal parallel processing method is applied to the handshake process between users and gateways in the remote boot phase, and a channel is allocated to each node in the code domain and the spatial domain to avoid mutual interference caused by multiple nodes sending signals simultaneously in multi-user network communications. More importantly, the near-far effect characteristics of CDMA signals are utilized to perceive the near-far relationship between multiple user senders, and this near-far relationship information is applied to the time-space hybrid competitive access mechanism.

[0011] Preferably, the SDMA technology is also used to obtain the location information of each user, and the gateway node locates the user according to the location information.

[0012] Preferably, a multi-physical field adaptive communication mechanism is adopted in the short-range data transmission stage.

[0013] Furthermore, data transmission between the gateway node and the user node can be performed using either underwater acoustic communication or optical communication as needed. The choice of communication medium is determined by both the data transmission requirements at the top layer and the channel quality at the bottom layer. Optical communication offers higher transmission rates but shorter transmission distances, while underwater acoustic communication offers longer transmission distances but lower transmission rates. This invention combines the advantages and disadvantages of both communication media to determine the appropriate communication medium based on both data transmission requirements and channel quality.

[0014] Compared with the prior art, the present invention has the following advantages after adopting the above scheme:

[0015] Aiming at the problem of low communication efficiency in underwater communication networks, the present invention optimizes the multiple access protocol from the perspective of multi-domain joint processing, and proposes three improvement measures: a time-space hybrid contention access mechanism, an SDMA-CDMA multi-signal parallel processing method, and a multi-physical field adaptive communication mechanism.

[0016] The beneficial effect of the time-space hybrid competitive access mechanism is that it combines time and space dimension information, allowing the node closest to the gateway node but with a slightly later access time to transmit data first without delaying the data transmission needs of other users too much, reducing the total distance that the gateway node needs to move in the process of retrieving data, and improving the multi-user transmission efficiency.

[0017] The SDMA-CDMA multi-signal parallel processing method has the following benefits: it separates the transmitted signals of different user nodes in the code domain and spatial domain, reduces the probability of signal interference, and thus reduces the number of retransmissions required by the transmitter, thus improving communication efficiency. It can also use the near-far effect of CDMA signals to obtain the distance information of multiple user senders, providing support for time-space hybrid contention access. It also uses SDMA technology to obtain the direction information of user nodes so that gateway nodes can locate user nodes.

[0018] The beneficial effect of the multi-physics field adaptive communication mechanism is that it combines underwater acoustic communication with higher-speed optical communication, adaptively selects the optimal communication medium based on the amount of data and channel quality, and maximizes the communication rate while the channel quality allows. Description of the drawings:

[0019] Figure 1 This is a schematic diagram of the overall process of multiple access of underwater mobile gateways.

[0020] Figure 2 This is a schematic diagram of the time-space hybrid contention access process.

[0021] Figure 3 is the vector hydrophone directivity diagram.

[0022] Figure 4 Flowchart of multi-physics adaptive communication. Specific implementation method:

[0023] The present invention will be further described below with reference to the accompanying drawings:

[0024] The present invention discloses a multi-access method for underwater mobile gateways with multi-domain joint processing to solve the problem of low communication efficiency caused by low underwater acoustic communication rate and large propagation delay in underwater sensor networks. The method optimizes the multi-access protocol from the perspective of multi-domain joint processing, combines time and space dimension information, allows nodes closest to the gateway node but with slightly later access time to transmit data first, without excessively delaying the transmission data needs of other users, reduces the total distance that the gateway node needs to move in the process of recovering data, and improves the transmission efficiency of multiple users.

[0025] Figure 1This figure shows the overall process flow for multiple access using a mobile underwater gateway. It consists of three phases: long-range guidance, short-range channel sensing, and short-range data transmission. During the long-range guidance phase, the gateway node and user node establish a connection through an RTS-CTS handshake. A user node that wishes to transmit data first sends an RTS signal to the gateway node. Upon receiving the signal, if the gateway node is idle, it responds with a CTS signal to the user node. Simultaneously, the gateway node can roughly determine the user node's location based on the received RTS signal energy and direction of arrival, and then move toward the user node based on this location. During its movement, the gateway node periodically handshakes with the user node, continuously updating the user node's location information. Furthermore, the RTS signal also contains information such as the data transmission volume and data type. This RTS-CTS signal allows other nodes to detect that the gateway node is occupied. When the gateway node moves within the underwater acoustic communication range of the user node, it enters the short-range channel sensing phase. The gateway node first senses the underwater acoustic communication channel quality using the RTS signal sent by the user node. Based on the channel quality and the data transmission volume information contained in the RTS signal, it makes a comprehensive decision on the communication medium (underwater acoustic communication / optical communication) and communication parameters (communication standard, communication rate, etc.), and transmits this decision to the user node via the CTS signal. After channel sensing is complete, the short-range data transmission phase begins. The user node transmits data according to the communication medium and communication parameters contained in the CTS signal sent back by the gateway node. If the gateway node successfully receives the data, it responds with an ACK to the user node, indicating that the data transmission was successful. The ACK also indicates that the communication has ended. At this point, a round of data transmission is complete, and the gateway node returns to an idle state, allowing other nodes to schedule data transmissions.

[0026] On this basis, in the remote guidance phase, the user node adopts a time-space hybrid competitive access mechanism for the connection to the gateway node. The user node that successfully shakes hands with the gateway node first in time gives priority to sending data, but if the user node that accesses later in time is obviously closer to the gateway node in space, the right to send signals first will be allocated to it.

[0027] The specific process is as follows Figure 2As shown in the figure, user node 1 first establishes a connection with the gateway node through the RTS-CTS handshake signal. When the gateway node moves toward the user node, user node 2 has data to send to the gateway node and also sends RTS to the gateway node. Based on the received signal energy, the gateway node knows that user node 2 is obviously closer to the gateway node than user node 1. Therefore, the gateway node replies CTS to user node 2 and gives the right to send signals first to user node 2. Then, when the gateway node moves within the communication distance of user node 2, user node 2 transmits data to the gateway node. After the transmission is completed, the gateway node re-establishes a connection with user node 1.

[0028] The time-space hybrid competitive access mechanism combines time and space dimension information, appropriately receives the data transmitted by the nearest user 2 according to the principle of proximity, without excessively delaying the data transmission needs of user 1, reducing the total distance that the gateway node needs to move to receive data from users 1 and 2, and improving transmission efficiency.

[0029] At the same time, as an improvement, during the remote boot phase, multiple user nodes may have data to send to the gateway node at the same time. These user nodes all send RTS signals. In this way, the gateway node may receive RTSs sent by multiple user nodes at the same time. In this case, in order to avoid mutual interference between multiple signals, the present invention adopts the SDMA-CDMA multi-signal parallel processing method to allocate a channel to each user node in the code domain and the spatial domain to avoid mutual interference caused by multiple nodes sending signals at the same time.

[0030] CDMA assigns mutually orthogonal spreading codes to each node, mapping them to an orthogonal or quasi-orthogonal set of code sequences. This orthogonality of the code sequences prevents conflicts caused by multiple nodes simultaneously occupying the channel. Even if signals from different nodes overlap in the time or frequency domain, the orthogonality of the code sequences can be used to separate the signals of multiple users, enabling multiple access. A characteristic of CDMA signals is the near-far effect. When a node simultaneously receives two signals with significantly different energy, the stronger signal closer to the receiving node interferes with the weaker signal farther away. The present invention exploits this phenomenon. When a gateway node simultaneously receives two user signals and experiences the near-far effect, it indicates that one user is significantly closer than the other. Using the time-space hybrid contention access mechanism described above, the gateway node can first establish a connection with the closer user and transmit data. After the transmission is complete, it can then establish a connection with the more distant node. This reduces the total distance the gateway node must travel while minimizing the data transmission needs of the more distant user, thereby improving transmission efficiency.

[0031] The specific implementation of SDMA technology uses a vector hydrophone, which can output the sound pressure p and the particle vibration velocity v in three mutually perpendicular directions.x ,v y ,v z , the sound pressure and particle velocity are combined through some operation to form spatial directivity. For example, the combination With Figure 3 Directivity shown:

[0032] The direction of directivity will change with the combined expression Therefore, the directivity of the vector hydrophone can be artificially controlled by signal processing operations. Using this principle, first, the incident direction of the signal can be measured to know the orientation of the node; secondly, since the orientation of each node is different, in the process of use, by controlling By pointing the directivity axis toward the signal direction of different user nodes, the interference of other node signals can be weakened. By taking different values, it is possible to receive signals from all directions, realize multiple access, and avoid mutual interference caused by multiple nodes sending signals at the same time.

[0033] Furthermore, during the data transmission phase, the present invention utilizes a multi-physics field adaptive communication mechanism. Gateway nodes and user nodes can choose between two communication media: underwater acoustic communication and optical communication. The present invention determines the communication medium based on both the top-level data transmission requirements and the underlying channel quality. Optical communication offers a higher transmission rate but a shorter transmission distance, while underwater acoustic communication offers a longer transmission distance but a lower transmission rate. The present invention combines the advantages and disadvantages of both communication media, determining the appropriate medium based on both data transmission requirements and channel quality.

[0034] The gateway node selects the communication medium based on two criteria: the bottom channel quality and the top data transmission volume. The decision process for the communication medium is as follows: Figure 4 As shown, it is done in two steps:

[0035] The first step is that in the remote guidance phase, after the gateway node receives the RTS, it reads the transmission data volume information contained in the RTS frame and makes a preliminary decision on the communication medium. Since the communication rate of optical communication is much higher than that of underwater acoustic communication, the decision criterion for the communication medium at this stage is the transmission data volume. A data volume threshold is set. If the data volume is higher than this threshold, optical communication is selected, and if it is lower than this threshold, underwater acoustic communication is selected. Calculation of the data volume threshold: When the data volume is too large and the underwater acoustic signal is too long, due to the time-varying nature of the underwater acoustic channel, the channel parameters passed by the second half of a signal are different from those passed by the first half, which leads to signal demodulation failure. Therefore, the underwater acoustic signal should not be too long. In this invention, 10s is used as the limit. If the length of the data packet sent is less than the communication rate (bit / s) × 10s, underwater acoustic communication is used, and underwater acoustic communication transmission can be started at a longer distance. Otherwise, optical communication is used, and the gateway node needs to move to the optical communication distance of the user node before optical communication data transmission can be started.

[0036] In the second step, during the short-range data transmission phase, the communication medium is further determined by the channel quality. The communication medium selected in the first step is used to transmit data. If the receiving end verifies correctly (indicating that the channel quality of the communication medium is good), the communication ends. Otherwise, it means that the channel quality of the selected communication medium is poor, and another communication medium is switched. It should be noted that if switching from underwater acoustic communication to optical communication, the gateway node needs to continue moving toward the user node until it moves within the optical communication range of the user node.

[0037] The above description is only for the preferred embodiment of the present invention, which should not be understood as limiting the claims. Any equivalent structure or equivalent process transformation made by using the description of the present invention is included in the patent protection scope of the present invention.

Claims

1. A multi-domain joint processing underwater mobile gateway multiple access method, characterized by: This method divides multiple access into three stages: long-range guidance stage, short-range channel sensing stage and short-range data transmission stage, among which, During the remote bootstrapping phase, the user node first sends an RTS signal to the gateway node. After receiving the signal, if the gateway node is idle, it replies with a CTS signal to the user node. At the same time, the gateway node can preliminarily determine the location of the user node based on the received RTS signal energy and the direction of arrival of the signal, and move towards the user node based on this location. During the movement, the gateway node periodically shakes hands with the user node and continuously updates the user node's location information. When the gateway node moves within the underwater acoustic communication range of the user node, it enters the short-range channel perception phase. The gateway node first perceives the channel quality through the RTS signal and determines the communication medium based on the channel quality and the data transmission volume information obtained in the remote guidance phase. After channel sensing is completed, the short-range data transmission phase begins. The gateway node informs the user node through CTS to start transmitting data and the selected communication medium and parameters. Other unrelated user nodes remain silent after receiving this CTS to prevent interference with data transmission. After data transmission is completed, the gateway node replies ACK to the user node through low-frequency underwater acoustic communication to confirm that the data was received successfully, and at the same time informs other users to start new communication.

2. The underwater mobile gateway multiple access method for multi-domain joint processing according to claim 1 is characterized in that: The remote guidance phase also introduces a time-space hybrid competitive access mechanism. The user node that shakes hands with the gateway node first in time is given priority to send data. However, if the user node that accesses later in time is significantly closer to the gateway node in space, the right to send signals first is allocated to it, thereby reducing the distance the gateway node moves during the data recovery process.

3. The underwater mobile gateway multiple access method for multi-domain joint processing according to claim 2 is characterized in that: The SDMA-CDMA multi-signal parallel processing method is applied to the handshake process between users and gateways in the remote boot phase. A channel is allocated to each node in the code domain and the spatial domain to avoid mutual interference caused by multiple nodes sending signals simultaneously in multi-user network communications. At the same time, the near-far effect characteristics of CDMA signals are utilized to perceive the near-far relationship between multiple user senders, and this near-far relationship information is applied to the time-space hybrid contention access mechanism.

4. The underwater mobile gateway multiple access method for multi-domain joint processing according to claim 3 is characterized by: SDMA technology is also used to obtain the location information of each user, and the gateway node locates the user based on the location information.

5. The underwater mobile gateway multiple access method for multi-domain joint processing according to claim 1 is characterized in that: A multi-physics field adaptive communication mechanism is adopted in the short-range data transmission stage.

6. The underwater mobile gateway multiple access method for multi-domain joint processing according to claim 5, characterized in that: The data transmission between the gateway node and the user node can select either of the two communication media, underwater acoustic communication and optical communication, as needed.

Images