Full-duplex underwater acoustic voice communication two-way prediction TDMA (Time Division Multiple Access) method

Abstract

The invention discloses a full-duplex underwater acoustic voice communication two-way prediction TDMA method, and relates to the field of underwater acoustic voice communication. The invention aims to solve the problems that in an underwater environment, propagation delay exists among devices in the TDMA technology, and communication burden is increased when a master device frequently inquires a slave device. According to the full-duplex underwater acoustic voice communication two-way prediction TDMA method, whether the actual moment when the current response signal sent by the slave device arrives at the master device is located in a safety interval or not is judged, if yes, the slave device keeps the reply time delay unchanged, otherwise, the reply time delay adjustment value of the slave device is calculated, and if the reply time delay adjustment value of the slave device is larger than 0, the slave device stops replying. If the adjustment value of the response time delay of the slave device is less than 0, the response time delay of the next frame of response signal of the slave device is advanced, and if the adjustment value of the response time delay of the slave device is less than 0, the response time delay of the next frame of response signal is delayed.

Description

Technical Field

[0001] The present invention belongs to the field of underwater acoustic voice communication. Background Art

[0002] In the field of underwater acoustic communication, Time Division Multiple Access (TDMA) technology is crucial for achieving efficient multi-user communication. With the increasing development of marine resources and underwater exploration activities, the importance of TDMA technology has become increasingly prominent. The existing technology has made significant progress in TDMA protocol optimization and signal processing, improving the reliability and efficiency of underwater communication. It has also actively promoted the research of TDMA technology in deep-sea exploration and marine resource development to solve problems such as signal attenuation and improve system performance.

[0003] However, traditional TDMA technology requires precise time synchronization between devices to ensure the accuracy and efficiency of data transmission. But in the underwater environment, due to propagation delay and the imprecision of device clocks, achieving strict time synchronization is both difficult and costly. In addition, the master device needs to frequently query the status of slave devices to adjust communication time slots, which not only increases the communication burden but also may lead to waste of time slot resources. Summary of the Invention

[0004] The present invention aims to solve the problem that there is propagation delay between devices in TDMA technology and the frequent querying of slave devices by the master device in the underwater environment also increases the communication burden, and provides a full-duplex underwater acoustic voice communication two-way prediction TDMA method.

[0005] A full-duplex underwater acoustic voice communication two-way prediction TDMA method includes:

[0006] Judging whether the actual arrival time t′ of the i-th frame response signal sent by the slave device at the master device Ari is within the safe interval. If so, the slave device keeps the reply delay unchanged; otherwise, calculates the adjustment value Δt′ of the slave device's reply delay i . If the adjustment value Δt′ of the slave device's reply delay i >0, the reply delay of the (i + 1)-th frame response signal of the slave device is advanced by Δt′ i . If the adjustment value Δt′ of the slave device's reply delay i <0, the reply delay of the (i + 1)-th frame response signal of the slave device is postponed by Δt′ i ;

[0007] The adjustment value Δt′ of the slave device's reply delay i is expressed as:

[0008] Δt′ i = t Bri -(t Bsi+1 + 2t s ),

[0009] where t Bri is the arrival time of the i-th frame request signal at the slave device, and t Bsi+1 is the transmission time of the (i + 1)-th frame response signal. T s = 4t s , and T s is the working cycle of the master device.

[0010] Furthermore, the above safety interval is:

[0011] The master device sets a safety interval t Ari for receiving the response signal centered around the predicted arrival time t safe of the response signal sent by the slave device to the master device, and it satisfies:

[0012] -t safe ≤ 2(t Ari - t′ Ari ) ≤ t safe ,

[0013] where t′ Ari is the actual arrival time of the response signal sent by the slave device to the master device.

[0014] Furthermore, when Δt′ i > 0, the reply delay ΔT i+1 of the (i + 1)-th frame response signal of the slave device is ΔT i - Δt′ i ;

[0015] When Δt′ i < 0, the reply delay ΔT i+1 of the (i + 1)-th frame response signal of the slave device is ΔT i + Δt′ i ,

[0016] where ΔT i is the reply delay of the i-th frame response signal.

[0017] Furthermore, the constraint conditions include:

[0018] On the time axis of the master device, the response signal received by the master device and the request signal sent do not overlap in time;

[0019] On the time axis of the slave device, the request signal received by the slave device and the response signal sent do not overlap in time;

[0020] The relative speed v AB of the master and slave devices satisfies:

[0021]

[0022] Among them, C is the sound speed in water, and Δt BAi is the propagation delay of the i-th frame reply signal.

[0023] Furthermore, on the time axis of the master device, the reply signal received by the master device does not overlap with the sent request signal in time, and the expression is:

[0024] t Bri +ΔT i +Δt BAi =t Asi+1 +2t s ,

[0025] where t Asi+1 is the sending moment of the (i + 1)-th frame request signal.

[0026] Furthermore, on the time axis of the slave device, the request signal received by the slave device does not overlap with the sent reply signal in time, and the expression is:

[0027] ΔT i +T d ≤T s +Δt i+1 -Δt i ,

[0028] where T d is the length of the reply signal, and Δt i+1 and Δt i are the propagation delays of the (i + 1)-th and i-th frame request signals respectively.

[0029] For the two-way prediction TDMA method for full-duplex underwater acoustic voice communication described in the present invention, the beneficial effects are as follows:

[0030] (1) The present invention does not require strict time synchronization, and the master and slave devices work with the local clock as a reference.

[0031] (2) The present invention does not require the master device to repeatedly query the status of the slave device, but adjusts the time slot during the data transmission process.

[0032] (3) The data transmission times of the master and slave devices of the present invention are alternately allocated, and the time slot utilization rate is high.

[0033] In summary, for the two-way prediction TDMA method for full-duplex underwater acoustic voice communication described in the present invention, it does not require strict synchronization of clocks between devices, nor does it require the master device to repeatedly query the status of the slave device. It is a time division multiplexing (TDMA) method that uses two-way prediction of the master and slave devices. Description of the Drawings

[0034] Figure 1 It is a schematic diagram of the connection establishment process between the master and slave devices;

[0035] Figure 2 It is a schematic diagram of the bidirectional prediction TDMA technology;

[0036] Figure 3 It is a schematic diagram of the slave device predicting the master device time axis mapping;

[0037] Figure 4 It is a schematic diagram of the master device local time axis mapping. Specific implementation manner

[0038] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0039] In order to solve the problems existing in the prior art, this embodiment proposes a new TDMA protocol, which does not rely on strict time synchronization between devices, but dynamically adjusts the time delay through bidirectional prediction between the master and slave devices to optimize the data transmission process. This method reduces the need for precise synchronization, simplifies the communication process, and improves the time slot utilization rate. It is an important progress for the underwater acoustic voice communication system and helps to promote the development of underwater acoustic communication technology. A full-duplex underwater acoustic voice communication bidirectional prediction TDMA method described in this embodiment includes:

[0040] In the initialization stage, the master device obtains the propagation delay Δt with the slave device by means of response.

[0041] In the working stage, the master device sends a data frame with the propagation delay of the previous frame signal in a preset time slot to the slave device. The slave device predicts the sending time of the next two frames of signals of the master device based on the time when the data frame is received on the local time axis and the propagation delay obtained by the master device when the previous frame signal propagates, and determines the time to send a request signal according to the predicted time to adjust the reply delay and avoid preemption conflicts of channel resources.

[0042] The master device sets a safety interval between receiving time slots to prevent the data arrival time from drifting too much at the corresponding moment. At the same time, the master device tracks the data arriving at the master device. When the arrival time exceeds the preset drift range, the master device will return a notification signal to the slave device to inform the slave device that the next data sending time needs to be adjusted. If the arrival time does not exceed the preset drift range, no signal will be sent.

[0043] The following will describe this embodiment in more detail in conjunction with Figures 1 to 4 :

[0044] For underwater voice communication, the entire workflow includes three stages: master-slave device connection establishment, data transmission, and connection maintenance, that is, slave device delay prediction adjustment and master device delay tracking. In the master-slave device connection establishment stage, the determination of the propagation delay is mainly completed. After the connection is established, the master-slave devices enter the working state. After the master device sends data, the slave device predicts the reply delay of the master device's local clock adjustment, and the master device tracks the propagation delay to maintain the connection between the master-slave devices.

[0045] As Figure 1 shown, during the process of establishing a connection between the master and slave devices, the master device sends a request signal to the slave device and records the sending time t As of the master device. The slave device receives the request signal at time t Br , and after a given known time t m of processing, immediately replies with an acknowledgment signal at time t Bs . The master device receives the acknowledgment signal and records the time t Ar when it receives the acknowledgment signal, and then calculates the propagation delay Δt between the master device and the slave device:

[0046]

[0047] After the master-slave devices establish a connection, they enter the working mode. The master device performs timed transmissions to the slave device, and the slave device performs acknowledgment transmissions to the master device. At the same time, the information sent from the master device to the slave device includes the propagation delay of the previous frame signal.

[0048] Figure 2 is a schematic diagram of the master-slave device implementing the bidirectional prediction TDMA technology. Due to the limitations of the voice communication rate and the relative distance between the master and slave devices, one working cycle T s of the master device is divided into 4 time slots, and the length of each time slot is t s . It is assumed that data is transmitted in the first time slot, and the remaining time slots are used for receiving data.

[0049] The slave device determines the reply delay by predicting the master device's local time axis, ensuring that there is no time overlap between the acknowledgment signal of the slave device received by the master device and the request signal timed by the master device, that is, ensuring that the acknowledgment signal of the slave device received by the master device falls in the position of the third time slot. In conjunction with Figure 3 specifically described, Figure 3 is a schematic diagram of the slave device further adjusting the reply delay according to the known information by predicting the host time axis during the process of the master device transmitting data to the slave device after the master-slave devices establish a connection. The slave device determines the time t Bri when the i-th frame request signal timed by the master device arrives at the slave device according to the known information., the propagation delay Δt of the i-th frame request signal i and the main device working cycle T s Predict the main device time axis to obtain the transmission times t Asi+1 , t Asi+2 of the two frame request signals after the i-th frame request signal of the main device, and the mappings t′ Asi+1 , t′ Asi+2 :

[0050] t′ Asi+1 = t Asi+1 = t Bri -Δt i +T s (2),

[0051] t′ Asi+2 = t Asi+2 = t Bri -Δt i +2T s (3).

[0052] To ensure that the response signal received by the main device does not overlap in time with the request signal of the main device on the time axis of the main device, the slave device needs to adjust its response delay ΔT i , so that the response signal received by the main device falls at the start time of the third time slot in the main device working cycle, that is, t Ari = t Asi+1 +2t s .

[0053] The slave device sends a response signal at t Bsi = t Bri +ΔT i The i-th frame response signal reaches the main device after a propagation delay of Δt BAi Therefore, the time t Ari when the main device receives the i-th frame response signal is:

[0054] t Ari = t Bsi +Δt BAi = t Bri +ΔT i +Δt BAi (4),

[0055] where Δt BAi is the propagation delay of the i-th frame response signal.

[0056] It is required that the time when the main device receives the response signal is equal to the start time of its third time slot, so there is a constraint condition:

[0057] t Bri +ΔTi +Δt BAi =t Asi+1 +2t s (5).

[0058] Substitute Equation (2) into the above constraint Equation (5), then we have: t Bri +ΔT i +Δt BAi =t Bri -Δt i +T s +2t s (6),

[0059] After rearrangement, we get:

[0060] Meanwhile, the reply delay ΔT of the i-th frame reply signal i should also ensure that the reception of the (i + 1)-th frame request signal sent by the master device and the reply signal sent by the slave device do not overlap in time on the slave device's time axis. A constraint condition is required,

[0061] The derivation process of this condition is as follows:

[0062] The transmission time t of the (i + 1)-th frame request signal of the master device Asi+1 is:

[0063] t Asi+1 =t Asi +T s (8).

[0064] On the slave device's time axis, the arrival time t of the (i + 1)-th frame request signal Bri+1 needs to consider the propagation delay Δt i+1 :

[0065] t Bri+1 =t Asi+1 +Δt i+1 =(t Bri -Δt i +T s )+Δt i+1 (9).

[0066] On the slave device's time axis, at t Bri +ΔT i the i-th frame reply signal starts to be sent, and the signal length of each frame reply signal is T d , and the end time t Bsend is:

[0067] t Bsend =t Bri +ΔTi +T d (10).

[0068] It is required that the end time \(t\) of the response signal transmission of the slave device Bsend is not later than the arrival time \(t\) of the request signal of the \(i + 1\)-th frame of the master device Bri+1 :

[0069] t Bsend ≤t Bri+1 (11).

[0070] It can be sorted out as follows:

[0071] ΔT i +T d ≤T s +Δt i+1 -Δt i (12).

[0072] The above formula restricts the response delay ΔT i and the length T of the response signal d of the slave device, ensuring that there is no time overlap between the request signal of the next frame of the master device and the response signal of the slave device.

[0073] Assume that the relative speed of the master and slave devices is \(v\) AB , the speed of sound in water is \(C\), and the change amount of the propagation delay between two adjacent times of the master device is:

[0074]

[0075] Substituting formula (7) into formula (12) gives:

[0076] 6t s +T d -Δt BAi ≤T s +Δt i+1 (14).

[0077] Substituting formula (13) into formula (14) gives:

[0078]

[0079] Since T d <<T s , ignoring T d , formula (15) gives:

[0080]

[0081] Dividing both sides of formula (16) by \(2t\) s , and sorting it out gives the speed constraint:

[0082]

[0083] Assume that the propagation delays of the master and slave devices are symmetric, i.e., Δt BAi ≈Δt i , then there is a final velocity constraint:

[0084]

[0085] Equation (18) indicates that the relative velocity of the master and slave devices needs to satisfy the above constraints; otherwise, the delay fluctuation will exceed the system tolerance range, resulting in communication failure.

[0086] The master device determines whether the next data transmission time of the slave device needs to be adjusted according to the arrival time of the slave device's response signal. If adjustment is required, the signal sent by the master device in the next frame contains the information to be adjusted; if no adjustment is required, no new information is added to the signal sent by the master device in the next frame. Specifically as follows:

[0087] As Figure 4 shown, after the master and slave devices establish a connection, the master device sets a safety interval t Ari for receiving the response signal centered around the predicted time t safe when the response signal sent by the slave device arrives at the master device:

[0088]

[0089] where t′ Ari is the actual time when the response signal sent by the slave device arrives at the master device. From Figure 2 it can be known that:

[0090] Δt BAi = t′ Ari - t Bri - ΔT i (20),

[0091] Substituting Equation (7) into Equation (20) gives:

[0092] t′ Ari = 6t s + t Bri - Δt i (21).

[0093] When the actual time t′ Ari when the response signal sent by the slave device arrives at the master device is within the safety interval, i.e., satisfies Equation (19), the master device does not need to inform the slave device of the prediction deviation. When the actual time t′ Ari when the response signal sent by the slave device arrives at the master device exceeds the safety interval, i.e., does not satisfy Equation (19), the signal of the (i + 1)-th frame sent by the master device contains the reply delay adjustment value Δt′ ito inform the slave device. The slave device adjusts the reply time delay ΔT i and then adjusts the next frame of data transmitted by the slave device so that the arrival time at the host falls within the safe interval.

[0094] The adjusted value of the slave device reply time delay Δt′ i :

[0095] Δt′ i = t Bri -(t Bsi+1 + 2t s )(22).

[0096] If Δt′ i > 0, the reception time is postponed, and the next frame reply time delay ΔT of the slave device i+1 needs to be advanced by Δt′ i , and the adjusted reply time delay ΔT′ i+1 = ΔT i+1 -Δt′ i ;

[0097] If Δt′ i < 0, the reception time is advanced, and the next frame reply time delay ΔT of the slave device i+1 needs to be postponed by Δt′ i , and the adjusted reply time delay ΔT′ i+1 = ΔT i+1 +Δt′ i ;

[0098] For the adjusted reply time delay ΔT′ i+1 , if the formula (12) is not satisfied, the slave device stops sending; at the same time, if the master device does not receive a signal during the reception time slot in a working cycle, the master device sends a request signal for the next frame and re - establishes a connection with the slave device.

[0099] To sum up, this embodiment proposes a time - division multiplexing (TDMA) protocol for full - duplex underwater acoustic voice communication, aiming to achieve underwater acoustic communication without strict time synchronization. This method optimizes the data transmission process by bidirectionally predicting the propagation delay between the master and slave devices. The advantages of this method are reducing the synchronization requirements between devices, simplifying the communication process, and improving the time - slot utilization rate, which is applicable to the field of underwater acoustic voice communication.

[0100] Although the present invention has been described herein with reference to particular embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should thus be understood that numerous modifications may be made to the exemplary embodiments, and that other arrangements may be devised, without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that different dependent claims and the features described herein may be combined in ways different from those described in the original claims. It should also be understood that features described in connection with separate embodiments may be used in other described embodiments.

Claims

1. A two-way prediction TDMA method for full-duplex underwater acoustic voice communication, characterized in that, including: Determine the actual arrival time t′ of the i-th frame response signal sent by the slave device at the master device Ari Whether it is within the safe interval. If so, the slave device keeps the reply delay unchanged; otherwise, calculate the adjustment value Δt of the slave device's reply delay i ′. If the adjustment value Δt of the slave device's reply delay i ′ > 0, then the reply delay of the (i + 1)-th frame response signal of the slave device is advanced by Δt i ′. If the adjustment value Δt of the slave device's reply delay i ′ < 0, then the reply delay of the (i + 1)-th frame response signal of the slave device is postponed by Δt i ′; The slave device reply delay adjustment value Δt i 's expression is: Δt i ′ = t Bri -(t Bsi+1 + 2t s ), where t Bri is the arrival time of the i-th frame request signal at the slave device, and t Bsi+1 is the transmission time of the (i + 1)-th frame response signal, and T s = 4t s , and T s is the working cycle of the master device.

2. The two-way prediction TDMA method for full-duplex underwater acoustic voice communication according to claim 1, wherein, The safety interval is: The master device sets a safety interval \(t\) for receiving the response signal centered around the predicted time \(t\) when the response signal sent by the slave device arrives at the master device Ari and satisfies: safe ​ -t safe ≤2(t Ari -t′ Ari )≤t safe , where t′ Ari is the actual time when the response signal sent from the slave device arrives at the master device.

3. A two-way prediction TDMA method for full-duplex underwater acoustic voice communication according to claim 1 or 2, characterized in that, When Δt i '> 0, the reply delay ΔT of the response signal of the (i + 1)-th frame of the device i+1 = ΔT i - Δt i '; When Δt i ′ < 0, the reply delay ΔT of the response signal of the (i + 1)-th frame of the slave device i+1 = ΔT i + Δt i ′ where ΔT i is the reply delay of the i-th frame reply signal.

4. A two-way prediction TDMA method for full-duplex underwater acoustic voice communication according to claim 3, characterized in that The constraint conditions include: On the time axis of the master device, the response signal received by the master device does not overlap in time with the request signal sent; On the time axis of the slave device, the request signal received by the slave device does not overlap in time with the response signal sent; The relative speed v of the master and slave devices AB Satisfies: where C is the speed of sound in water, and Δt BAi is the propagation delay of the i-th frame reply signal.

5. A two-way prediction TDMA method for full-duplex underwater acoustic voice communication according to claim 4, characterized in that On the time axis of the master device, the response signal received by the master device does not overlap in time with the request signal sent, and the expression is: t Bri +ΔT i +Δt BAi =t Asi+1 +2t s , where t Asi+1 is the transmission time of the (i + 1)-th frame request signal.

6. A two-way prediction TDMA method for full-duplex underwater acoustic voice communication according to claim 4, characterized in that On the time axis of the slave device, the request signal received by the slave device does not overlap in time with the response signal sent, and the expression is: ΔT i +T d ≤T s +Δt i+1 -Δt i , Among them, T d is the response signal length, and Δt i+1 and Δt i are the propagation delays of the (i + 1)-th and i-th frame request signals, respectively.

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