CN110350985B - Underwater sound parallel transmission method based on active time reversal - Google Patents

Underwater sound parallel transmission method based on active time reversal Download PDF

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CN110350985B
CN110350985B CN201910638157.XA CN201910638157A CN110350985B CN 110350985 B CN110350985 B CN 110350985B CN 201910638157 A CN201910638157 A CN 201910638157A CN 110350985 B CN110350985 B CN 110350985B
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CN110350985A (en
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赵瑞琴
刘智豪
龙浩
梅毫迪
刘媛
赵月瑶
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Northwestern Polytechnical University
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
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    • H04B13/02—Transmission systems in which the medium consists of the earth or a large mass of water thereon, e.g. earth telegraphy
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
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Abstract

The invention provides an underwater sound parallel transmission method based on active time reversal, which utilizes the weak spatial correlation of channel response among different links caused by complex underwater sound multipath propagation to obtain the space-time focusing of signals at a receiving position, combines with up/down sampling to effectively inhibit the influence of interference among the links under a parallel transmission scene, improves the spatial multiplexing degree, and combines with a power control method to minimize the transmitting power of a transmitting node on the premise of meeting the specific service quality of a receiving node. The invention weakens the broadcasting characteristic of the underwater acoustic channel and plays a key role in effectively isolating the signal interference between adjacent links in the distributed multi-hop environment; the up/down sampling method further restrains the interference between links and the interference between symbols, so that the space multiplexing degree is further improved; the power control method saves the transmitting power on the premise of effectively inhibiting the interference between the links, and the characteristics endow the invention with effectiveness in the underwater sound parallel transmission scene.

Description

Underwater sound parallel transmission method based on active time reversal
Technical Field
The invention relates to the field of underwater communication, in particular to a time reversal theory, an up-down sampling method, a power control method and the like.
Background
Ocean resources are abundant, and with continuous exploitation and exhaustion of onshore resources, the marching of the human army to the ocean is accelerated. Due to the fact that underwater communication is not available in ocean development and ocean military, people have greater and greater requirements for underwater communication, and compared with radio waves, sound waves are transmitted and attenuated underwater and are the best energy form of underwater communication, and therefore underwater acoustic communication is the content of important research in various countries.
Different from wireless channels, the underwater acoustic channel not only has large propagation delay and low information rate, but also is influenced by ocean severe multipath propagation, the channel impulse response seriously depends on the space position of a transmitting and receiving node, namely the underwater acoustic channel is space-variant, and the severe ocean environment causes the complex space-variant characteristic of the underwater acoustic channel, so that the ocean underwater acoustic channel becomes one of the worst wireless channels.
The underwater environment is complicated and has serious multipath effect, Inter-symbol Interference (ISI) occurs when an acoustic signal is received, and Inter-link Interference (ILI) occurs in the case of underwater parallel transmission. Aiming at the problem of serious interference in underwater sound parallel transmission channel multiplexing, a plurality of technologies such as a TDMA multiple access technology, a CDMA multiple access technology, an active time reversal technology and the like are proposed. The TDMA multiple access divides time into time slots, all nodes occupy channels according to the time slots, certain energy consumption can be saved while collision is avoided, however, the sound wave propagation speed is low and the influence of marine environment is large, so that the accurate time synchronization required by the TDMA multiple access is difficult to realize, the channel utilization rate is low, and the time delay is large. CDMA multiple access allows multiple users to transmit data simultaneously, nodes may utilize the entire bandwidth of a link, and a receiver distinguishes different users by using a pseudorandom sequence, however, the implementation of the receiver in an underwater acoustic network is complicated due to the high hardware requirement of the receiver by using CDMA. The active time reversal technology does not need prior knowledge of a channel, can adaptively match the channel, and utilizes the weak spatial correlation of channel response among different links caused by complex underwater acoustic multipath propagation to obtain the space-time focusing of a signal at a receiving position, thereby playing the key role of effectively isolating signal interference among adjacent links, obviously improving the space-time multiplexing degree of an underwater acoustic link, and having simple algorithm and easy realization, so the time reversal technology becomes a hotspot of underwater acoustic communication research in recent years. It is noted that the time reversal technique does not completely eliminate the presence of ISI and ILI, which makes the communication performance not good in the case of underwater acoustic parallel transmission. The power control method can enable the receiving node to reach a certain SINR by adjusting the transmitting power, and the purpose of effectively inhibiting the ILI is achieved, but the performance of the power control is limited by the channel correlation, namely the inhibiting capability to the ILI is limited when the channel correlation is strong, and the method of up/down sampling can reduce the influence of other paths except the maximum path in the time reversal composite channel, thereby further effectively inhibiting the ISI and the ILI.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides an underwater sound parallel transmission method based on active time reversal. In order to overcome the serious underwater complex multipath effect, when in parallel transmission, the intersymbol interference and the serious intersymbol interference appear when receiving signals, the active time reversal technology can be used for adaptively matching channels, and the space-time focusing of the signals at the receiving position is obtained by utilizing the space weak correlation of the channel response between different links caused by the complex underwater acoustic multipath propagation, thereby playing the key role of effectively isolating the signal interference between adjacent links, but the time reversal technology can not completely eliminate the ISI and the ILI, and the intersymbol interference IUI are further effectively inhibited, the performance of the whole communication system is improved, and the transmitting power of the transmitting node is minimum on the premise of meeting the specific quality of service (quality of service) of the receiving node, the invention changes the multipath effect existing in the underwater acoustic environment into the superiority by using the time reversal technology, and combines the up/down sampling, the influence of inter-link interference under a parallel transmission scene is effectively inhibited, the space multiplexing degree is improved, the transmitting power of a transmitting node is minimized on the premise of meeting the specific service quality of a receiving node by combining a power control method, and the underwater sound parallel transmission method based on active time reversal is provided.
The technical scheme adopted by the invention for solving the technical problem comprises the following detailed steps:
step 1: acquiring channel information: the transmitting node receives a probe signal sent by the receiving node through handshaking with the receiving node, and acquires channel information between the transmitting node and the receiving node by using the probe signal;
step 2: signal up-sampling: introducing upsampling at a transmitting node, wherein the sequence after the upsampling is as follows:
Figure GDA0003067062440000021
wherein, x [ k ]]Is a binary data character sequence, k represents the kth bit of the sequence, D is an up/down sampling factor, the value is any positive integer more than or equal to 1, and the pair { x [ k ]]Carry out upsampling operation, then xD[k]For the data sequence after up-sampling, the remainder obtained by dividing the serial number k of the data sequence by D is judgedIf the remainder is 0, the up-sampled data series xD[k]The kth data is equal to [ k/D ] th data of the data sequence before upsampling]Bit data, otherwise up-sampled data series xD[k]The kth bit data is 0;
and step 3: signal transmission power setting:
1) if the transmitting node 1 and the transmitting node 2 occupy the channel to send information at the same time, the receiving node 1 and the receiving node 2 at the receiving end respectively reach the corresponding signal-to-interference ratio threshold r according to the objective function and the constraint condition of the formula (2)1，r2On the premise that the sum of the transmitting power of the transmitting node 1 and the transmitting node 2 is minimum, and the signal transmitting power p of the transmitting node 1 is obtained1And signal transmission power p of transmitting node 22：
Figure GDA0003067062440000031
The SINR is the received signal-to-interference ratio (dB) of the receiving node, and the calculation formula is:
Figure GDA0003067062440000032
wherein, PSigFor node A signal transmission power, intersymbol interference PISIComprises the following steps:
Figure GDA0003067062440000033
inter-link interference PILIIs composed of
Figure GDA0003067062440000034
P is the power of the signal sequence at the transmitting end, l is the sequence number of the discrete impulse response sequence, σ2Is noise, hijIs the channel impulse response between node i and node j; gijTo make the channel between node i and node j have impulse response hij[k]The resulting channel impulse response is processed back-to-back in time,
Figure GDA0003067062440000035
l, L is the length of a binary data character sequence of a transmission signal;
2) if it is unknown whether the two transmitting nodes simultaneously transmit information, assuming that the transmitting node 1 preferentially accesses the channel and the channel information between the transmitting node 1 and the receiving node 1 is known, preferentially determining the signal transmitting power of the transmitting node 1 by adopting a distributed power control method, and calculating the signal transmitting power of the transmitting node 1 by using an equation (3):
Figure GDA0003067062440000036
wherein p is1For transmitting node 1 signal transmission power (dBm), r1Receiving signal-to-interference ratio threshold (dB), SINR for the receiving node 11Receive signal-to-interference ratio (dB) for node 1
Figure GDA0003067062440000037
PSig1In order for the receiving node 1 to receive the signal power,
Figure GDA0003067062440000038
P1for transmitting signal transmission power of node 1, h11For the channel impulse response between the transmitting node 1 and the receiving node 1, g11Receiving the channel impulse response after the response processing when the channel impulse response between the nodes 1 is received by the transmitting node 1; intersymbol interference
Figure GDA0003067062440000039
PILI1Setting a regular fixed 4-node topological model for the maximum inter-link interference value which can be tolerated by a receiving node 1, fixing the relative positions of a transmitting node and the receiving node, if the transmitting power of the transmitting node 1 and the transmitting node 2 is assumed to be equal and unknown, calculating the minimum transmitting power sum of the transmitting node 1 and the transmitting node 2 when the two transmitting nodes simultaneously transmit information by using a formula (3), and calculating inter-link interference by using an inter-link interference calculation formula
Figure GDA0003067062440000041
Let Ptot＝PILI 2，P2For signalling of transmitting node 2Radio power, h21For the channel impulse response between the transmitting node 2 and the receiving node 1, g22Receiving the channel impulse response after the response processing when the channel impulse response between the nodes 2 is received by the transmitting node 2;
then, the signal transmission power of the transmitting node 2 is calculated by equation (4):
Figure GDA0003067062440000042
wherein p is2Signal launch power (dBm) for the transmitting node 2; r is2Receiving a signal-to-interference ratio threshold (dB) for the receiving node 2; SINR2For the receiving node 2 signal-to-interference ratio threshold (dB),
Figure GDA0003067062440000043
PSig2in order for the receiving node 2 to receive the signal power,
Figure GDA0003067062440000044
P2for transmitting signal transmission power of node 2, h22For channel impulse response between transmitting node 2 and receiving node 2, g22Receiving the channel impulse response after the response processing when the channel impulse response between the nodes 2 is received by the transmitting node 2; intersymbol interference
Figure GDA0003067062440000045
Inter-link interference:
Figure GDA0003067062440000046
h21for the channel impulse response between the transmitting node 2 and the receiving node 1, g22Receiving the channel impulse response after the response processing when the channel impulse response between the nodes 2 is received by the transmitting node 2; pILI1: the receiving node 1 can tolerate the interference value between the maximum links;
and 4, step 4: signal emission:
1) if the transmitting node 1 and the transmitting node 2 occupy the channel to send information at the same time, the signal transmitting power of the transmitting node 1 and the transmitting node 2 is respectively set to be 3The transmission power p obtained in the formula (2)1，p2And transmitting the signal;
2) if the information sent by the two transmitting nodes is unknown at the same time, the transmitting node 1 is supposed to be preferentially accessed to the channel, and the transmitting power of the transmitting node 1 is set to be the transmitting power p obtained by the formula (3) in the step 31And transmitting a signal, and setting the transmission power of the transmitting node 2 as the transmission power p obtained by the formula (4) in the step 32And transmitting the signal;
and 5: the receiving node performs down-sampling to complete the whole communication process:
the signals transmitted in step 4 reach the receiving end through the underwater acoustic channel, and the signals received by the receiving node are as shown in formula (5):
Figure GDA0003067062440000051
wherein, yD[k]For the receiving node to receive the signal, hij[k]Is the channel impulse response between node i and node j; gij[k]To make the channel between node i and node j have impulse response hij[k]The resulting channel impulse response is processed back-to-back in time,
Figure GDA0003067062440000052
n[k]is noise; the receiver end carries out down sampling on the arriving receiving signal by using the same up/down sampling factor D, and restores to obtain an initial transmitting signal, wherein the down sampled signal is different from the signal obtained by the formula (6):
Figure GDA0003067062440000053
wherein, y [ k ]]For the receiving node to receive the signal, hijIs the channel impulse response between node i and node j; gijTo make the channel between node i and node j have impulse response hijPerforming time reversal processing on the obtained channel impact response; wherein:
Figure GDA0003067062440000054
is hij[k]And gij[k]A convoluted composite channel expression.
The invention has the beneficial effects that the parallel transmission method based on active time reversal is provided, the space-variant characteristic of the underwater acoustic channel is utilized, the disadvantages are converted into advantages, the broadcasting characteristic of the underwater acoustic channel is weakened, and the key effect of effectively isolating the signal interference between adjacent links in the distributed multi-hop environment is achieved; the up/down sampling method further restrains the interference between links and the interference between symbols, so that the space multiplexing degree is further improved; the power control method saves the transmitting power on the premise of effectively inhibiting the interference between the links, and the characteristics endow the method with effectiveness in the underwater sound parallel transmission scene.
Drawings
FIG. 1 is a diagram of a four-node underwater acoustic communication system model of the present invention;
FIG. 2 is a scheme diagram of an underwater acoustic parallel transmission system based on active time reversal;
FIG. 3 is the transmission signal after up-sampling according to the present invention;
FIG. 4 is a diagram of a communication system performance analysis of the present invention;
fig. 5 is a graph of performance analysis based on the power control method of the present invention.
Detailed Description
The invention is further illustrated with reference to the following figures and examples.
In the underwater acoustic communication system shown in fig. 1, the present invention proposes a scheme diagram of an underwater acoustic parallel transmission system based on active time reversal as shown in fig. 2, and the present invention is further explained with reference to the drawings and the embodiments.
As shown in fig. 1, the communication distance of the four nodes is 1km, the interference distance is 1.414km, and BPSK modulation is adopted.
Step 1: acquiring channel information: the transmitting nodes 1 and 2 receive the probe signals p (t) sent by the receiving nodes through two handshakes with the receiving nodes 1 and 2 respectively, channel information between the transmitting nodes and the receiving nodes is obtained by utilizing the probe signals, and channel impulse response information between the transmitting nodes and the receiving nodes is obtained by the transmitting nodes based on probe signal estimation after the transmitting nodes receive the probe signals.
Step 2: signal up-sampling: introducing upsampling at a transmitting node, wherein the sequence after the upsampling is as follows:
Figure GDA0003067062440000061
wherein, x [ k ]]Is a binary data character sequence, k represents the kth bit of the sequence, D is an up/down sampling factor, the value is any positive integer more than or equal to 1, and the pair { x [ k ]]Carry out upsampling operation, then xD[k]For the data sequence after the up-sampling, the remainder obtained by dividing the serial number k of the data series by D is judged, if the remainder is 0, the data series x after the up-samplingD[k]The kth data is equal to [ k/D ] th data of the data sequence before upsampling]Bit data, otherwise up-sampled data series xD[k]The kth bit data is 0; fig. 3 is the transmission signal after up-sampling according to the present invention.
And step 3: signal transmission power setting:
1) if the transmitting node 1 and the transmitting node 2 occupy the channel to send information at the same time, the receiving node 1 and the receiving node 2 at the receiving end respectively reach the corresponding signal-to-interference ratio threshold r according to the objective function and the constraint condition of the formula (2)1，r2On the premise that the sum of the transmitting power of the transmitting node 1 and the transmitting node 2 is minimum, and the signal transmitting power p of the transmitting node 1 is obtained1And signal transmission power p of transmitting node 22：
Figure GDA0003067062440000062
The SINR is the received signal-to-interference ratio (dB) of the receiving node, and the calculation formula is:
Figure GDA0003067062440000063
wherein, PSigFor node A signal transmission power, intersymbol interference PISIComprises the following steps:
Figure GDA0003067062440000071
inter-link interference PILIIs composed of
Figure GDA0003067062440000072
P is the power of the signal sequence at the transmitting end, l is the sequence number of the discrete impulse response sequence, σ2Is noise, hijIs the channel impulse response between node i and node j; gijTo make the channel between node i and node j have impulse response hij[k]The resulting channel impulse response is processed back-to-back in time,
Figure GDA0003067062440000073
l is the length of the binary data character sequence of the sending signal;
2) if it is unknown whether the two transmitting nodes simultaneously transmit information, assuming that the transmitting node 1 preferentially accesses the channel and the channel information between the transmitting node 1 and the receiving node 1 is known, preferentially determining the signal transmitting power of the transmitting node 1 by adopting a distributed power control method, and calculating the signal transmitting power of the transmitting node 1 by using an equation (3):
Figure GDA0003067062440000074
wherein p is1For transmitting node 1 signal transmission power (dBm), r1Receiving signal-to-interference ratio threshold (dB), SINR for the receiving node 11Receive signal-to-interference ratio (dB) for node 1
Figure GDA0003067062440000075
PSig1In order for the receiving node 1 to receive the signal power,
Figure GDA0003067062440000076
P1for transmitting signal transmission power of node 1, h11For the channel impulse response between the transmitting node 1 and the receiving node 1, g11Receiving the channel impulse response after the response processing when the channel impulse response between the nodes 1 is received by the transmitting node 1; intersymbol interference
Figure GDA0003067062440000077
PILI1Setting a regular fixed 4-node topological model as shown in figure 1 for the maximum tolerable inter-link interference value of a receiving node 1, fixing the relative positions of a transmitting node and the receiving node, if the transmitting power of the transmitting node 1 and the transmitting node 2 is assumed to be equal and the transmitting power is unknown, calculating the minimum transmitting power sum of the transmitting node 1 and the transmitting node 2 when the two transmitting nodes simultaneously transmit information by using a formula (3), and calculating the inter-link interference by using an inter-link interference calculation formula
Figure GDA0003067062440000078
Let Ptot＝pILI1，P2For transmitting signal transmission power of node 2, h21For the channel impulse response between the transmitting node 2 and the receiving node 1, g22Receiving the channel impulse response after the response processing when the channel impulse response between the nodes 2 is received by the transmitting node 2;
then, the signal transmission power of the transmitting node 2 is calculated by equation (4):
Figure GDA0003067062440000081
wherein p is2Signal launch power (dBm) for the transmitting node 2; r is2Receiving a signal-to-interference ratio threshold (dB) for the receiving node 2; SINR2For the receiving node 2 Signal-to-interference ratio threshold (dB)
Figure GDA0003067062440000082
PSig2In order for the receiving node 2 to receive the signal power,
Figure GDA0003067062440000083
P2for transmitting signal transmission power of node 2, h22For channel impulse response between transmitting node 2 and receiving node 2, g22Receiving the channel impulse response after the response processing when the channel impulse response between the nodes 2 is received by the transmitting node 2; intersymbol interference
Figure GDA0003067062440000084
Inter-link interference:
Figure GDA0003067062440000085
h21for the channel impulse response between the transmitting node 2 and the receiving node 1, g22Receiving the channel impulse response after the response processing when the channel impulse response between the nodes 2 is received by the transmitting node 2; pILI1: the receiving node 1 can tolerate the interference value between the maximum links;
in fig. 5, compared with the centralized power control method, the transmission power required by the distributed power control method to achieve the same received SINR is larger, which indicates that the distributed power control method replaces the requirement of the transmission node for all channel state information at the expense of a certain power consumption. Therefore, in practical situations, the transmitting node selects to adopt a centralized or distributed power control method according to the knowledge degree of the transmitting node on the channel state information.
And 4, step 4: signal emission:
1) if the transmitting node 1 and the transmitting node 2 occupy the channel to send information at the same time, the signal transmitting power of the transmitting node 1 and the transmitting node 2 is respectively set as the transmitting power p obtained in the formula (2) in the step 31，p2And transmitting the signal;
2) if the information sent by the two transmitting nodes is unknown at the same time, the transmitting node 1 is supposed to be preferentially accessed to the channel, and the transmitting power of the transmitting node 1 is set to be the transmitting power p obtained by the formula (3) in the step 31And transmitting a signal, and setting the transmission power of the transmitting node 2 as the transmission power p obtained by the formula (4) in the step 32And transmitting the signal;
and 5: the receiving node performs down-sampling to complete the whole communication process:
the signals transmitted in step 4 reach the receiving end through the underwater acoustic channel, and the signals received by the receiving node are as shown in formula (5):
Figure GDA0003067062440000091
wherein, yD[k]For the receiving node to receive the signal, hij[k]Is the channel impulse response between node i and node j; gij[k]To make the channel between node i and node j have impulse response hij[k]The resulting channel impulse response is processed back-to-back in time,
Figure GDA0003067062440000092
n[k]is noise; the receiver end carries out down sampling on the arriving receiving signal by using the same up/down sampling factor D, and restores to obtain an initial transmitting signal, wherein the down sampled signal is different from the signal obtained by the formula (6):
Figure GDA0003067062440000093
wherein, y [ k ]]For the receiving node to receive the signal, hijIs the channel impulse response between node i and node j; gijTo make the channel between node i and node j have impulse response hijPerforming time reversal processing on the obtained channel impact response; wherein:
Figure GDA0003067062440000094
is hij[k]And gij[k]A convoluted composite channel expression.
Fig. 4 shows the error rates of the underwater acoustic communication system under different D after applying the up/down sampling, and it can be seen that the performance of the communication system is greatly improved after applying the up/down sampling, and the larger the up/down sampling factor D is, the lower the error rate of the time reversal underwater acoustic communication system is, especially when D is 8, the error rate of the system is very low, and the performance is very good.
From the above conclusion, the active time reversal underwater acoustic parallel transmission method provided by the invention combines the up/down sampling and the power control method, not only saves energy consumption, but also inhibits inter-link interference and inter-symbol interference, greatly improves the utilization rate of a channel, and improves the underwater acoustic communication performance.

Claims (1)

1. An underwater sound parallel transmission method based on active time reversal is characterized by comprising the following steps:
step 1: acquiring channel information: the transmitting node receives a probe signal sent by the receiving node through handshaking with the receiving node, and acquires channel information between the transmitting node and the receiving node by using the probe signal;
step 2: signal up-sampling: introducing upsampling at a transmitting node, wherein the sequence after the upsampling is as follows:
Figure FDA0003067062430000011
wherein, x [ k ]]Is a binary data character sequence, k represents the kth bit of the sequence, D is an up/down sampling factor, the value is any positive integer more than or equal to 1, and the pair { x [ k ]]Carry out upsampling operation, then xD[k]For the data sequence after the up-sampling, the remainder obtained by dividing the serial number k of the data series by D is judged, if the remainder is 0, the data series x after the up-samplingD[k]The kth data is equal to [ k/D ] th data of the data sequence before upsampling]Bit data, otherwise up-sampled data series xD[k]The kth bit data is 0;
and step 3: signal transmission power setting:
1) if the transmitting node 1 and the transmitting node 2 occupy the channel to send information at the same time, the receiving node 1 and the receiving node 2 at the receiving end respectively reach the corresponding signal-to-interference ratio threshold r according to the objective function and the constraint condition of the formula (2)1，r2On the premise that the sum of the transmitting power of the transmitting node 1 and the transmitting node 2 is minimum, and the signal transmitting power p of the transmitting node 1 is obtained1And signal transmission power p of transmitting node 22：
Figure FDA0003067062430000012
The SINR is the received signal-to-interference ratio (dB) of the receiving node, and the calculation formula is:
Figure FDA0003067062430000013
wherein, PSigFor node A signal transmission power, intersymbol interference PISIComprises the following steps:
Figure FDA0003067062430000014
inter-link interference PILIIs composed of
Figure FDA0003067062430000015
P is the power of the signal sequence at the transmitting end, l is the sequence number of the discrete impulse response sequence, σ2Is noise, hijIs the channel impulse response between node i and node j; gijTo make the channel between node i and node j have impulse response hij[k]The resulting channel impulse response is processed back-to-back in time,
Figure FDA0003067062430000021
l, L is the length of a binary data character sequence of a transmission signal;
2) if it is unknown whether the two transmitting nodes simultaneously transmit information, assuming that the transmitting node 1 preferentially accesses the channel and the channel information between the transmitting node 1 and the receiving node 1 is known, preferentially determining the signal transmitting power of the transmitting node 1 by adopting a distributed power control method, and calculating the signal transmitting power of the transmitting node 1 by using an equation (3):
Figure FDA0003067062430000022
wherein p is1For transmitting node 1 signal transmission power (dBm), r1Receiving signal-to-interference ratio threshold (dB), SINR for the receiving node 11Receive signal-to-interference ratio (dB) for node 1
Figure FDA0003067062430000023
PSig1In order for the receiving node 1 to receive the signal power,
Figure FDA0003067062430000024
P1for transmitting signal transmission power of node 1, h11For the channel impulse response between the transmitting node 1 and the receiving node 1, g11Receiving the channel impulse response after the response processing when the channel impulse response between the nodes 1 is received by the transmitting node 1; intersymbol interference
Figure FDA0003067062430000025
PILI1Setting a regular fixed 4-node topological model for the maximum inter-link interference value which can be tolerated by a receiving node 1, fixing the relative positions of a transmitting node and the receiving node, if the transmitting power of the transmitting node 1 and the transmitting node 2 is assumed to be equal and unknown, calculating the minimum transmitting power sum of the transmitting node 1 and the transmitting node 2 when the two transmitting nodes simultaneously transmit information by using a formula (3), and calculating inter-link interference by using an inter-link interference calculation formula
Figure FDA0003067062430000026
Let Ptot＝PILI1，P2For transmitting signal transmission power of node 2, h21For the channel impulse response between the transmitting node 2 and the receiving node 1, g22Receiving the channel impulse response after the response processing when the channel impulse response between the nodes 2 is received by the transmitting node 2;
then, the signal transmission power of the transmitting node 2 is calculated by equation (4):
Figure FDA0003067062430000027
wherein p is2Signal launch power (dBm) for the transmitting node 2; r is2Receiving a signal-to-interference ratio threshold (dB) for the receiving node 2; SINR2For the receiving node 2 signal-to-interference ratio threshold (dB),
Figure FDA0003067062430000031
PSig2in order for the receiving node 2 to receive the signal power,
Figure FDA0003067062430000032
P2for transmitting signal transmission power of node 2, h22For channel impulse response between transmitting node 2 and receiving node 2, g22Receiving the channel impulse response after the response processing when the channel impulse response between the nodes 2 is received by the transmitting node 2; intersymbol interference
Figure FDA0003067062430000033
Inter-link interference:
Figure FDA0003067062430000034
h21for the channel impulse response between the transmitting node 2 and the receiving node 1, g22Receiving the channel impulse response after the response processing when the channel impulse response between the nodes 2 is received by the transmitting node 2; pILI1Receiving node 1 can tolerate the maximum inter-link interference value;
and 4, step 4: signal emission:
1) if the transmitting node 1 and the transmitting node 2 occupy the channel to send information at the same time, the signal transmitting power of the transmitting node 1 and the transmitting node 2 is respectively set as the transmitting power p obtained in the formula (2) in the step 31，p2And transmitting the signal;
2) if the information sent by the two transmitting nodes is unknown at the same time, the transmitting node 1 is supposed to be preferentially accessed to the channel, and the transmitting power of the transmitting node 1 is set to be the transmitting power p obtained by the formula (3) in the step 31And transmitting a signal, and setting the transmission power of the transmitting node 2 as the transmission power p obtained by the formula (4) in the step 32And transmitting the signal;
and 5: the receiving node performs down-sampling to complete the whole communication process:
the signals transmitted in step 4 reach the receiving end through the underwater acoustic channel, and the signals received by the receiving node are as shown in formula (5):
Figure FDA0003067062430000035
wherein, yD[k]For the receiving node to receive the signal, hij[k]Is the channel impulse response between node i and node j; gij[k]To make the channel between node i and node j have impulse response hij[k]The resulting channel impulse response is processed back-to-back in time,
Figure FDA0003067062430000036
n[k]is noise; the receiver end carries out down sampling on the arriving receiving signal by using the same up/down sampling factor D, and restores to obtain an initial transmitting signal, wherein the down sampled signal is as shown in the formula (6):
Figure FDA0003067062430000041
wherein, y [ k ]]For the receiving node to receive the signal, hijIs the channel impulse response between node i and node j; gijTo make the channel between node i and node j have impulse response hijPerforming time reversal processing on the obtained channel impact response; wherein:
Figure FDA0003067062430000042
is hij[k]And gij[k]A convoluted composite channel expression.
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