Clock-synchronization-free TDMA (Time Division Multiple Access) protocol of underwater acoustic communication network based on triangular inequality

Abstract

The invention discloses a clock-synchronization-free TDMA (Time Division Multiple Access) protocol of an underwater acoustic communication network based on a triangular inequality, relates to the technical field of underwater communication, and aims to solve the problem that the TDMA protocol is difficult to apply due to inconvenience in clock synchronization of the underwater acoustic communication network. According to the TDMA protocol provided by the invention, clock synchronization is not needed, a triangular inequality principle is utilized, and each node is stipulated to send a data packet immediately after receiving a data packet of a previous node according to a sequence, so that collision of each data packet in time can be avoided. In order to prevent the influence of the unstable underwater acoustic communication on the protocol, the invention also provides a timeout waiting mechanism. According to the invention, the TDMA protocol can be realized without depending on clock synchronization, the overhigh node cost caused by the installation of a high-precision clock module is reduced, the network overhead caused by clock synchronization messages is also reduced, and the application of the TDMA protocol is simpler, more convenient and quicker.

Description

Technical Field

[0001] The invention belongs to the technical field of underwater communication, and in particular relates to a clock-free synchronization TDMA protocol for underwater acoustic communication networks based on triangle inequalities. Background Art

[0002] The underwater acoustic communication network that uses the Time Division Multiple Access (TDMA) protocol can avoid collisions of various data packets in time, which greatly improves the success rate of sending underwater acoustic data packets. However, since the underwater acoustic communication nodes are deployed underwater, they cannot receive satellite timing signals via radio, and the underwater acoustic propagation delay is long. Clock synchronization through underwater acoustic communication will increase network overhead, so clock synchronization between nodes in the underwater acoustic communication network is relatively difficult. Summary of the invention

[0003] In view of the above technical deficiencies, the present invention does not require a TDMA protocol for clock synchronization to solve the problem that the underwater acoustic communication network is not convenient for clock synchronization, which makes the TDMA protocol difficult to apply. This method reduces the high cost caused by the high-precision clock module and reduces the network overhead caused by the clock synchronization message.

[0004] In order to solve the above technical problems, the present invention provides the following technical solutions: a clock-free synchronization TDMA protocol for underwater acoustic communication network based on triangular inequality, comprising:

[0005] In the underwater acoustic communication network, channels are allocated to nodes through the clock-free TDMA protocol. Before launching into the water, the node numbers are first sorted. After launching into the water, each node sends a data packet immediately after receiving the data packet from the previous node according to the sorting to avoid time collision of the data packets. In order to avoid the data packet of the current node being blocked due to the failure to receive the data packet from the previous node, a timeout waiting mechanism is specified. When a node receives a data packet sent by the n nodes before it (n>1), the timer is started to wait for the time (n×maximum propagation delay+(n-1)×maximum data packet length). If the data packet sent by the previous node is not received, the data packet is sent immediately after the waiting time.

[0006] Preferably, select any three nodes 1, 2, and 3 in the network, and set the data packet sent by node 1 as data 1 , the time it takes for its tail to travel from node 1 to node 3 is set to τ 13 , the time from node 1 to node 2 is set to τ 12 , node 2 demodulates data 1 The processing delay is set to τ dem , node 2 receives data 1 After that, the data packet of node 2 is immediately sent and set to data 2, data 2 The time it takes for the head to travel from node 2 to node 3 is τ 23 ;

[0007] From data 1 The end of the signal starts timing, and the data 2 The head reaches node 3, and the length of this period is τ 12 +τ dem +τ 23 ; According to the triangle inequality, if the sum of any two sides of a triangle is greater than the third side, then there must be l 12 +l 23 >l 13 , both sides of the inequality are divided by the signal propagation speed, that is, τ 12 +τ 23 >τ 13 ;

[0008] There must be τ 12 +τ dem +τ 23 >τ 12 +τ 23 >τ 13 ; that is, data 2 The head must be in the data 1 After the tail reaches node 3, data 2 With data 1 There will be no collision at node 3. Replace node 3 with any other node. Similarly, we can further conclude that data 2 With data 1 No collision will occur at any other nodes.

[0009] Preferably, if the latter node in the network sends a data packet immediately after receiving the data packet sent by the previous node, there will definitely be no collision with the data packet sent by the previous node; using this principle, the sending order of each node in the network is arranged, so that each node sends a data packet immediately after receiving the data packet sent by the previous node in order, thereby avoiding collision; however, it must be considered that since communication is not always reliable, the latter node may not receive the data packet sent by the immediately preceding node. Therefore, a timeout mechanism must be specified. When a node receives a data packet sent by the n nodes before it (n>1), a timer is started to wait for a time (n×maximum propagation delay+(n-1)×maximum data packet duration). If the data packet sent by the previous node has not been received, the data packet is sent immediately after the waiting time.

[0010] Preferably, a clock-free synchronization TDMA protocol for underwater acoustic communication network based on triangle inequality comprises the following specific steps:

[0011] (1) Before launching the underwater acoustic communication nodes, number each node and arrange all the node numbers in order;

[0012] (2) After each node is launched, the node starts the internal timer and waits for T w time, go to step (3);

[0013] (3) If the timing time is up, go to step (5); if the node receives a data packet sent by other nodes during the timing process, go to step (4);

[0014] (4) Read the sending node of the data packet, and calculate the sending node number before the current node according to the number sorting before launching. If n = 1, go to step (5); if n > 1, update the timing waiting time T of the current node. w , go to step (3);

[0015] (5) Send the data packet of this node. After the sending is completed, go to step (6);

[0016] (6) Start the timer T w , go to step (3).

[0017] Preferably, in step (2), the node numbered i further counts the waiting time T w The calculation method is:

[0018] T w =(N+i-1)·(τ delay-max +T data-max ) ①

[0019] Where N is the maximum number of nodes in the network;

[0020] i is the node number;

[0021] τ delay-max is the maximum propagation delay between nodes in the network;

[0022] T data-max The maximum length of a data packet.

[0023] Preferably, in step (4), the timing waiting time T is further updated. w The calculation method is:

[0024] T w =nτ delay-max +(n-1)T data-max ②

[0025] Where n is the number of bits of the sending node that receives the data packet before this node;

[0026] τdelay-max is the maximum propagation delay between nodes in the network;

[0027] T data-max The maximum length of a data packet.

[0028] Preferably, in step (6), the waiting time T is further measured. w The calculation method is:

[0029] Nτ delay-max +(N-1)T data-max ③

[0030] In the formula, N is the number of nodes in the whole network;

[0031] τ delay-max is the maximum propagation delay between nodes in the network;

[0032] T data-max The maximum length of a data packet.

[0033] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0034] 1. The TDMA protocol proposed in the present invention does not require the use of a high-precision clock module, which can reduce node production costs and operating power consumption, and can also avoid the impact of long-term clock offsets and extend network deployment time.

[0035] 2. The TDMA protocol proposed in the present invention does not require clock synchronization messages, which can reduce network overhead and node operation power consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the principle of the triangle inequality in the present invention;

[0037] Figure 2 Schematic diagram of the location of each node in the network of the present invention. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] Example 1

[0040] A method based on the triangle inequality (such as Figure 1 The underwater acoustic communication network does not require clock synchronization TDMA protocol.

[0041] In the network, select any three nodes 1, 2, and 3, and set the data packet sent by node 1 as data 1 , the time it takes for its tail to travel from node 1 to node 3 is set to τ 13 , the time from node 1 to node 2 is set to τ 12 , node 2 demodulates data 1 The processing delay is set to τ dem , node 2 receives data 1 After that, the data packet of node 2 is immediately sent and set to data 2 , data 2 The time it takes for the head to travel from node 2 to node 3 is τ 23 ;

[0042] From data 1 The end of the signal starts timing, and the data 2 The head reaches node 3, and the length of this period is τ 12 +τ dem +τ 23 ; According to the triangle inequality, if the sum of any two sides of a triangle is greater than the third side, then there must be l 12 +l 23 >l 13 , both sides of the inequality are divided by the signal propagation speed, that is, τ 12 +τ 23 >τ 13 ;

[0043] There must be τ 12 +τ dem +τ 23 >τ 12 +τ 23 >τ 13 ; that is, data 2 The head must be in the data 1 After the tail reaches node 3, data 2 With data 1 There will be no collision at node 3. Replace node 3 with any other node. Similarly, we can further conclude that data 2 With data 1 No collision will occur at any other nodes.

[0044] If the latter node in the network sends a data packet immediately after receiving the data packet sent by the previous node, there will definitely be no collision with the data packet sent by the previous node. Using this principle, the sending order of each node in the network can be arranged so that each node can send a data packet immediately after receiving the data packet sent by the previous node in order to avoid collision. However, it should also be considered that since communication is not always reliable, the latter node may not receive the data packet sent by the previous node immediately before it. Therefore, a timeout mechanism should be specified. When a node receives a data packet sent by the n nodes before it (n>1), it starts a timer waiting time (n×maximum propagation delay + (n-1)×maximum data packet length). If it has not received the data packet sent by the previous node, it will send the data packet immediately after the waiting time.

[0045] A clock-free TDMA protocol for underwater acoustic communication network based on triangular inequality, the specific steps are as follows:

[0046] (1) Before launching the underwater acoustic communication nodes, number each node and arrange all the node numbers in order;

[0047] (2) After each node is launched, the node starts the internal timer and waits for T w time, go to step (3);

[0048] (3) If the timing time is up, go to step (5); if the node receives a data packet sent by other nodes during the timing process, go to step (4);

[0049] (4) Read the sending node of the data packet, and calculate the sending node number before the current node according to the number sorting before launching. If n = 1, go to step (5); if n > 1, update the timing waiting time T of the current node. w , go to step (3);

[0050] (5) Send the data packet of this node. After the sending is completed, go to step (6);

[0051] (6) Start the timer T w , go to step (3).

[0052] In step (2), the node numbered i further counts the waiting time T w The calculation method is:

[0053] T w =(N+i-1)·(τ delay-max +T data-max ) ①

[0054] Where N is the maximum number of nodes in the network;

[0055] i is the node number;

[0056] τ delay-max is the maximum propagation delay between nodes in the network;

[0057] T data-max The maximum length of a data packet.

[0058] In step (4), the waiting time T is updated. w The calculation method is:

[0059] T w =nτ delay-max +(n-1)T data-max ②

[0060] Where n is the number of bits of the sending node that receives the data packet before this node;

[0061] τ delay-max is the maximum propagation delay between nodes in the network;

[0062] T data-max The maximum length of a data packet.

[0063] In step (6), the waiting time T is further calculated. w The calculation method is:

[0064] Nτ delay-max +(N-1)T data-max ③

[0065] In the formula, N is the number of nodes in the whole network;

[0066] τ delay-max is the maximum propagation delay between nodes in the network;

[0067] T data-max The maximum length of a data packet.

[0068] Example 2

[0069] A clock-free TDMA protocol for underwater acoustic communication network based on triangular inequality, the specific steps are as follows:

[0070] (1) Assume that the locations of the nodes in the underwater acoustic communication network are as follows: Figure 2 As shown, there are 7 nodes in total. Before launching, each node is numbered 1-7 and arranged in order 1-7;

[0071] (2) After each node is launched, the node starts the internal timer and waits for T w time, assuming that the maximum propagation delay between nodes in this network is τ delay-max , assuming that the maximum time to send a data packet is T data-max, according to the above formula ①, the timing waiting time T of each node is calculated w As shown in the following table:

[0072]

[0073] After the timing starts, go to step (3);

[0074] (3)7(τ delay-max +T data-max ) time, the timing time of node 1 arrives, and the data packet is sent. After sending, it waits for 7τ according to formula ③ delay-max +6T data-max ;

[0075] (4) When node 2 receives the data packet sent by node 1, it immediately sends the data packet and waits for 7τ according to formula ③. delay-max +6T data-max ;

[0076] After nodes 6 and 7 receive the data packet sent by node 1, they update the timing waiting time according to formula ② as shown in the following table:

[0077] Node Number The value of n in formula ② <![CDATA[Waiting time T w / s]]> 6 5 <![CDATA[5τ delay-max +4T data-max ]]> 7 6 <![CDATA[6τ delay-max +5T data-max ]]>

[0078] Nodes 3, 4, and 5 are far away from node 1 and cannot receive the data packet sent by node 1, so the waiting time is not updated;

[0079] (5) When node 3 receives the data packet sent by node 2, it immediately sends the data packet and waits for 7τ according to formula ③. delay-max +6T data-max ;

[0080] After nodes 1 and 7 receive the data packet sent by node 2, they update the timing waiting time according to formula ② as shown in the following table:

[0081] Node Number The value of n in formula ② <![CDATA[Waiting time T w / s]]> 1 6 <![CDATA[6τ delay-max +5T data-max ]]> 7 5 <![CDATA[5τ delay-max +4T data-max ]]>

[0082] Nodes 4, 5, and 6 are far away from node 2 and cannot receive the data packet sent by node 2, so the waiting time is not updated;

[0083] (6) When node 4 receives the data packet sent by node 3, it immediately sends the data packet and waits for 7τ according to formula ③. delay-max +6T data-max ;

[0084] After nodes 2 and 7 receive the data packet sent by node 3, they update the timing waiting time according to formula ② as shown in the following table:

[0085] Node Number The value of n in formula ② <![CDATA[Waiting time T w / s]]> 2 6 <![CDATA[6τ delay-max +5T data-max ]]> 7 4 <![CDATA[4τ delay-max +3T data-max ]]>

[0086] Nodes 1, 5, and 6 are far away from node 3 and cannot receive the data packet sent by node 3, so the waiting time is not updated;

[0087] (7) When node 5 receives the data packet sent by node 4, it immediately sends the data packet and waits for 7τ according to formula ③. delay-max +6T data-max ;

[0088] After nodes 3 and 7 receive the data packet sent by node 4, they update the timing waiting time according to formula ② as shown in the following table:

[0089] Node Number The value of n in formula ② <![CDATA[Waiting time T w / s]]> 3 6 <![CDATA[6τ delay-max +5T data-max ]]> 7 3 <h2 style=";text-align:left;direction:ltr"><![CDATA[3τ <h2 style=";text-align:left;direction:ltr"> delay-max <h2 style=";text-align:left;direction:ltr"> +2T<h2 style=";text-align:left;direction:ltr"> data-max <h2 style=";text-align:left;direction:ltr"> ]]><h2 style=";text-align:left;direction:ltr">

[0090] Nodes 1, 2, and 6 are far away from node 4 and cannot receive the data packet sent by node 4, so the waiting time is not updated;

[0091] (8) When node 6 receives the data packet sent by node 5, it immediately sends the data packet and waits for 7τ according to formula ③. delay-max +6T data-max ;

[0092] After nodes 4 and 7 receive the data packet sent by node 5, they update the timing waiting time according to formula ② as shown in the following table:

[0093] Node Number The value of n in formula ② <![CDATA[Waiting time T w / s]]> 4 6 <![CDATA[6τ delay-max +5T data-max ]]> 7 2 <![CDATA[2τ delay-max +T data-max ]]>

[0094] Nodes 1, 2, and 3 are far away from node 5 and cannot receive the data packet sent by node 5, so the waiting time is not updated;

[0095] (9) When node 7 receives the data packet sent by node 6, it immediately sends the data packet and waits for 7τ according to formula ③. delay-max +6T data-max ;

[0096] After nodes 1 and 5 receive the data packet sent by node 6, they update the timing waiting time according to formula ② as shown in the following table:

[0097] Node Number The value of n in formula ② <![CDATA[Waiting time T w / s <!-- 5 -->]]> 1 2 <![CDATA[2τ delay-max +T data-max ]]> 5 6 <![CDATA[6τ delay-max +5T data-max ]]>

[0098] Nodes 2, 3, and 4 are far away from node 6 and cannot receive the data packet sent by node 6, so the waiting time is not updated;

[0099] (10) When node 1 receives the data packet sent by node 7, it immediately sends the data packet and waits for 7τ according to formula ③. delay-max +6T data-max ;

[0100] After nodes 2, 3, 4, 5, and 6 receive the data packet sent by node 7, they follow formula ②

[0101] The update timing wait time is shown in the following table:

[0102] Node Number The value of n in formula ② <![CDATA[Waiting time T w / s]]> 2 2 <![CDATA[2τ delay-max +T data-max ]]> 3 3 <h2 style=";text-align:left;direction:ltr"><![CDATA[3τ <h2 style=";text-align:left;direction:ltr"> delay-max <h2 style=";text-align:left;direction:ltr"> +2T<h2 style=";text-align:left;direction:ltr"> data-max <h2 style=";text-align:left;direction:ltr"> ]]><h2 style=";text-align:left;direction:ltr"> 4 4 <![CDATA[4τ delay-max +3T data-max ]]> 5 5 <![CDATA[5τ delay-max +4T data-max ]]> 6 6 <![CDATA[6τ delay-max +5T data-max ]]>

[0103] Go to step (4).

[0104] Although specific embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit thereof, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A clock-free TDMA protocol for underwater acoustic communication network based on triangular inequality, characterized in that: include: In the underwater acoustic communication network, channels are allocated to nodes through the clock-free TDMA protocol. Before launching, the node numbers are sorted first. After launching, each node sends a data packet immediately after receiving the data packet from the previous node according to the sorting to avoid time collisions of the data packets. In order to avoid the data packet of the node being blocked due to the failure to receive the data packet from the previous node, a timeout waiting mechanism is specified. When a node receives a data packet sent by the n nodes before it (n>1), it starts a timer waiting time (n×maximum propagation delay+(n-1)×maximum data packet length). If the data packet sent by the previous node has not been received, the data packet is sent immediately after the waiting time.

2. According to claim 1, a triangular inequality-based underwater acoustic communication network clock-free synchronization TDMA protocol is characterized in that: The specific steps are as follows: (1) Before launching the underwater acoustic communication nodes, number each node and arrange all the node numbers in order; (2) After each node is launched, the node starts the internal timer and waits for T w time, go to step (3); (3) If the timing time is up, go to step (5); if the node receives a data packet sent by other nodes during the timing process, go to step (4); (4) Read the sending node of the data packet, and calculate the sending node number before the current node according to the number sorting before launching. If n = 1, go to step (5); if n > 1, update the timing waiting time T of the current node. w , go to step (3); (5) Send the data packet of this node. After the sending is completed, go to step (6); (6) Start the timer T w , go to step (3).

3. The clock-free TDMA protocol for underwater acoustic communication network based on triangular inequality according to claim 2 is characterized in that: In step (2), the node numbered i is further counted to wait for a time T w The calculation method is: T w =(N+i-1)·(τ delay-max +T data-max ) ① Where N is the maximum number of nodes in the network; i is the node number; τ delay-max is the maximum propagation delay between nodes in the network; T data-max The maximum length of a data packet.

4. The clock-free TDMA protocol for underwater acoustic communication network based on triangular inequality according to claim 2, characterized in that: In step (4), the timing waiting time T is further updated. w The calculation method is: T w =nτ delay-max +(n-1)T data-max ② Where n is the number of bits of the sending node that receives the data packet before this node; τ delay-max is the maximum propagation delay between nodes in the network; T data-max The maximum length of a data packet.

5. The clock-free TDMA protocol for underwater acoustic communication network based on triangle inequality according to claim 2, characterized in that: In step (6), the waiting time T is further measured. w The calculation method is: Nτ delay-max +(N-1)T data-max ③ In the formula, N is the number of nodes in the whole network; τ delay-max is the maximum propagation delay between nodes in the network; T data-max The maximum length of a data packet.

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