CN107302417B - Switching method for point-to-point link data transmission mechanism of passive sensing network - Google Patents

Switching method for point-to-point link data transmission mechanism of passive sensing network Download PDF

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CN107302417B
CN107302417B CN201710361737.XA CN201710361737A CN107302417B CN 107302417 B CN107302417 B CN 107302417B CN 201710361737 A CN201710361737 A CN 201710361737A CN 107302417 B CN107302417 B CN 107302417B
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data
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header
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CN107302417A (en
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邱树伟
李燕君
曹蓉
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SHANTOU POLYTECHNICAL
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
    • H04L1/0006—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission format
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
    • H04L1/1806—Go-back-N protocols
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
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    • H04W84/18—Self-organising networks, e.g. ad-hoc networks or sensor networks

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Abstract

A switching method of a point-to-point link data transmission mechanism of a passive sensing network comprises the following steps: the operation flow of the sender S is as follows: step 11, capturing energy from the RF signal with duration Th(ii) a Step 12, solving an optimization problem OP _ n to obtain the optimal block number n of the effective load in the data packet; step 13, judging whether n is equal to 1, if n is equal to 1, setting a TM field in the header of the data packet as 0, generating the data packet and transmitting data by adopting an ARQM; otherwise, setting the TM field to be 1, generating a data packet and transmitting data by adopting BRM; step 14, ending; the operation flow of the receiver R is as follows: step 21, capturing energy from the RF signal for a duration Th(ii) a Step 22, receiving the data packet from the S, checking the value of the TM field in the header of the data packet, and if the TM is 0, receiving and processing the data packet by using the ARQM; if TM is equal to 1, receiving and processing the data packet according to BRM; and step 23, ending. The invention has higher link throughput.

Description

Switching method for point-to-point link data transmission mechanism of passive sensing network
Technical Field
The invention belongs to the field of passive sensing networks, and particularly relates to a switching method of a point-to-point link data transmission mechanism of a radio frequency energy supply wireless sensor network, which can be used for capturing radio frequency energy to carry out communication on the wireless sensor network.
Background
A node of a passive Free Wireless Sensor Network (BF-WSN) captures energy through ubiquitous Radio Frequency (RF) signals in the environment, and a new way is provided for solving the problem of energy supply of the node of the traditional Wireless Sensor Network (WSN). The energy required for the operation of the BF-WSN node is from an RF signal transmitted by an RF energy supply point (such as a television tower, a cellular base station or Wi-Fi communication facilities), and the energy capture power is extremely low and is only mW or even muW level generally. With such poles for energy capture power, the power used by the node for data transmission is also reduced, which results in an increased error rate of the communication link. Moreover, since the communication link is often interfered by surrounding electromagnetic signals, the quality of the wireless link is good, bad and unstable.
In a Wireless Local Area Network (WLAN) based on IEEE 802.11 standard and a Wireless Personal Area Network (WPAN) based on IEEE 802.15.4 standard, an Automatic Repeat reQuest (ARQ) mechanism is widely used, and ARQ is mainly characterized in that a sender needs to retransmit a whole data packet after a retransmission timer expires until a receiver correctly receives the data packet or the number of retransmissions reaches an upper limit, as long as a bit error occurs in the data packet received by the receiver. Indeed, ARQ works well when the link quality is good (i.e., packet transmission success rate is high and retransmission times are few). However, when the link quality is poor, frequent bit errors trigger frequent data packet retransmission, which not only wastes bandwidth, but also increases transmission energy consumption and transmission delay of both the transmitter and the receiver, and reduces the network throughput. In order to overcome the disadvantages of ARQ, the patent document with publication number CN 102340391 provides a segmented ARQ automatic retransmission method, which divides the transmission path from the source node to the destination node into a plurality of ARQ segments, the end node of each ARQ segment is an ARQ node, the nodes except the ARQ node in the transmission path are common nodes, when transmitting data, the common nodes only forward data packets, and the ARQ node is responsible for sending confirmation and retransmitting data packets besides forwarding data packets; patent document CN 102684854 discloses an adaptive adjustment method for ARQ parameters in mac (medium Access control) layer, which divides the network condition into good, medium and bad according to the ratio of NACK (negative Acknowledgement) and ACK (Acknowledgement) received by the sender, and adjusts ARQ parameters (ARQ block size, timeout retransmission time, sliding window size, etc.) according to different conditions of the network.
The above scheme does not fully consider the characteristic that the quality of the wireless link is dynamically changed, and the data transmission mechanism adopted by the node is fixed and unchanged, so that the method is not well applicable to BF-WSN.
Disclosure of Invention
In order to overcome the defect that the throughput rate of a communication link is low due to the fact that a fixed data transmission mechanism is adopted by nodes in a passive sensing network, the invention provides a switching method of a point-to-point link data transmission mechanism of the passive sensing network, which is high in link throughput, wherein the method can automatically switch the data transmission mechanism according to the current link quality: when the link quality is good, the node adopts ARQM (Automatic Repeat reQuest Mechanism); when the link quality is poor, the node is automatically switched to BRM (Blocking Retransmission Mechanism), so that the throughput rate of the link is improved.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a switching method of a point-to-point link data transmission mechanism of a passive sensing network comprises the following steps:
the operation flow of the sender S is as follows:
step 11, capturing energy from the RF signal with duration Th；
Step 12, solving an optimization problem OP _ n to obtain the optimal block number n of the effective load in the data packet;
step 13, judging whether n is equal to 1, if n is equal to 1, setting a TM field in the header of the data packet as 0, generating the data packet and transmitting data by adopting an ARQM; if n is not equal to 1, setting the TM field to be 1, generating a data packet and transmitting data by adopting BRM;
step 14, ending;
the operation flow of the receiver R is as follows:
step 21, capturing energy from the RF signal for a duration Th；
Step 22, receiving the data packet from the S, checking the value of the TM field in the header of the data packet, and if the TM is 0, receiving and processing the data packet by using the ARQM; if TM is equal to 1, receiving and processing the data packet according to BRM;
and step 23, ending.
Further, the process of the ARQM is as follows: a sender S sends a data packet to a receiver R, and starts a retransmission timer after the sending is finished; if R receives the data packet correctly, it immediately replies an ACK to S to confirm the data packet reception. If the data packet has bit errors, R does nothing; then, S retransmits the data packet immediately after the retransmission timer expires, and stops transmitting the current data packet if the retransmission number reaches the preset maximum retransmission number.
The process of the BRM is as follows: the sender S first divides the payload of a data packet into n data blocks, each of whichThe data Block comprises two parts of effective data and a Block Check Sequence (BCS), wherein the Block Check Sequence is used for checking whether the data Block has errors, and the payload further comprises a Header Check Sequence (HCS) used for checking whether the Header of the data Block has errors; after the data packet is divided into n blocks, the payload of the data packet contains HCS, and n effective data D1,D2,…,DnAnd n block check sequences C1,C2,…,Cn(ii) a Then, the sender S sends the data packet to the receiver R, after the R receives the data packet, the R adopts the FCS in the tail part to check the data packet, and if the data packet is correct, an ACK is replied to the S; if the bit error exists, checking the header by adopting the HCS, if the header has the error, doing nothing, and waiting for the S to retransmit the original data packet; if the header is correct, then adopt C in turn1,C2,…,CnChecking the data block 1, the data block 2, the data block n, storing the correct data block into a corresponding storage area in a buffer area, discarding the data block with the error, and replying a Negative Acknowledgement (NACK) to the S to inform the S of which data blocks have errors; subsequently, S retransmits a data packet containing only erroneous data blocks in its payload to R, and so on until R successfully receives n data blocks or the number of retransmissions reaches an upper limit.
Further, in said steps 1.1 and 2.1, the node energy capture time ThDetermination of (1): with PhEnergy capture power of the node is represented, and is known from Friss transmission equation:
wherein G issAnd GrRespectively representing the antenna gain at the energy supply point and at the node, λ being the wavelength of the electromagnetic wave, PlostIs the path power loss, d is the distance between the node and the energy supply point, PsIs the transmission power of the energy supply point, mu is the efficiency coefficient of converting the RF signal into electric energy;
with e0Representing the initial energy of the node, in ethEnergy threshold representing node operationI.e. only if the residual energy of both nodes S and R is greater than or equal to ethThen S starts to transmit data; let τ denote the node's initial energy e0Begin capturing energy until its remaining energy reaches ethThe duration of time, using equation (1), can be:
τ＝(eth-e0)/Ph (2)
at τSAnd τRRepresenting the energy capture times of S and R, respectively, then the remaining energy from the moment when S and R begin capturing energy until they are both greater than or equal to ethThe duration of time is:
Th＝max{τS,τR} (3)。
still further, the determination of the data block length in the data packet: the length of each data block is denoted by l:
Figure BDA0001300558430000032
wherein L isPacketIndicates the total length of the data packet, LHeadIndicates the length of the header, LHCSIndicates the length, L, of the header check sequence HCSFCSIndicates the length of the tail;
probability of successful header and data block transmission: the communication link between S and R is represented by < S, R > and the error rate of the link < S, R > is represented by b, so that when S transmits a packet to R, the probability q of successful transmission of the header and the probability p of successful transmission of each data block are respectively:
Figure BDA0001300558430000033
p＝(1-b)l (6)
probability of successful kth transmission of data packet: with Pk(x) Indicates the probability of success of the kth transmission of a data packet containing x data blocks, where x is 1, 2. K is 1, 2.. K, where K represents the maximum number of transmissions of the same packet, and the solution P can be obtained by combining equations (5) and (6)k(x) Has the formula asThe following:
Figure BDA0001300558430000041
the probability of a node transmitting a data packet successfully is:
Figure BDA0001300558430000042
with LkThe bit number which represents the average transmission of the kth transmission of the node comprises the following bits:
Figure BDA0001300558430000043
wherein the content of the first and second substances,
Figure BDA0001300558430000044
representing the probability of the first k-1 transmission failures; ek(x) Represents the accumulation of the product of the data packet containing 1 data block, 2 data blocks, x data blocks and the corresponding probability sent by the node at the kth transmission, and the expression is as follows:
Figure BDA0001300558430000045
average delay of a node transmitting a data packet: the rate of data transmission of the node is represented by r and LAAnd LNIndicates the length of ACK and NACK, respectively, in TrRepresents a retransmission timer, and represents an average delay of a node transmitting a data packet by t, and comprises:
and M represents the total number of data packets transmitted from S to R, the throughput rate in the link (S, R) is as follows:
Figure BDA0001300558430000051
wherein L isBCSRepresents the length of the BCS;
the optimization problem OP _ n that maximizes the throughput in the link < S, R > is as follows:
in the above formula, nminAnd nmaxA lower bound and an upper bound respectively representing the number of data packet blocks;
the optimal value n of the number of data packet blocks can be obtained by solving equation (13)*When n is*When the value is 1, it indicates that the throughput rate of the payload of the packet is the maximum for 1 block under the current link environment, and therefore, the TM field in the packet header may be set to 0, and the ARQM may be used for transmission; when n is*>1, it means that in the current link environment, the throughput rate can be maximized by dividing the payload of the data packet into 2 blocks or more, and then, the TM field may be set to 1, and BRM is used for transmission.
Preferably, n isminAnd nmaxDetermination of (1): in formula (13), n is takenmin1, the number of the blocks of the data packet is at least 1; meanwhile, in order to ensure the transmission efficiency of the data packet, the length of each data block is not less than the header L of the data packetHeadPlus a header check sequence LHCSObtaining nmaxThe calculation formula of (a) is as follows:
Figure BDA0001300558430000053
the invention has the following beneficial effects: the method can automatically switch between two data transmission mechanisms of automatic request retransmission and block retransmission according to the current link quality, adapts to the characteristic of dynamic change of the communication link quality, and improves the throughput rate of the communication link.
Drawings
Fig. 1 is a packet format of the ARQM.
Fig. 2 is a packet format of the BRM.
Fig. 3 is a buffer partition number.
Fig. 4 is a format of NACK.
Fig. 5 is a TM field diagram.
Fig. 6 is a flow chart of sender operation.
Fig. 7 is a flow chart of the receiver operation.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
Referring to fig. 1 to 7, a method for switching a point-to-point link data transmission mechanism of a passive sensing network includes selecting two data transmission mechanisms, namely ARQM and BRM.
The process of ARQM is as follows: and S (representing a sending party) sends a data packet to R (representing a receiving party), and a retransmission timer is started after the sending is finished. If R receives the data packet correctly, it immediately replies an ACK to S to confirm the data packet reception. If the data packet has bit errors, R does nothing. Then, S retransmits the data packet immediately after the retransmission timer expires, and stops transmitting the current data packet if the retransmission number reaches the preset maximum retransmission number. The data packet format of the ARQM is shown in fig. 1.
The process of BRM is as follows: the method comprises the steps of dividing a payload of a data packet into n data blocks, wherein each data Block comprises two parts of effective data and a Block Check Sequence (BCS), the Block Check Sequence is used for checking whether the data Block has errors, and the payload further comprises a Header Check Sequence (HCS) used for checking whether the Header of the data packet has errors. After the data packet is divided into n blocks, the payload of the data packet contains HCS, and n effective data D1,D2,…,DnAnd n block check sequences C1,C2,…,Cn. Then, S sends the data packet to R, after R receives the data packet, it adopts FCS in the tail to check the data packet, if it is correct, it replies an ACK to S; if the bit error exists, checking the header by adopting the HCS, if the header has the error, doing nothing, and waiting for the S to retransmit the original data packet; if the header is correct, then adopt C in turn1,C2,…,Cn Check data block 1, data block 2,. and data block n, and then checkThe correct data block is stored in the corresponding memory area in the buffer (see fig. 3) and the data block with the error is discarded, and then a NACK (negative acknowledgement) is replied to S to inform S which data blocks are in error. Subsequently, S retransmits a packet whose payload contains only the erroneous data block to R. And repeating the steps until the R successfully receives the n data blocks or the retransmission times reach the upper limit. The data packet format of the BRM is shown in fig. 2.
As described above, in each transmission, R stores the correct data block in the corresponding storage area in the buffer and discards the data block in which the error occurred, and at the same time, must find the sequence number of the erroneous data block. To this end, the buffer used by the BRM is specially designed, and besides being used for temporarily storing the data packet (or data block), another function is to record the relative position of each data block in the data packet by block numbering the buffer, as shown in fig. 3. In fig. 3, buffer block No. 1 stores data block 1, buffer block No. 2 stores data block 2, and so on, and buffer block No. n stores data block n. In addition, buffer block No. 0 stores the header and the header check sequence, and buffer block No. n +1 stores the trailer. The receiving side can know which data blocks are wrong by checking the number of the storage area which is not stored with the correct data block in the buffer area, and then generates NACK and replies to the sending side. The format of NACK is shown in FIG. 4, where b1,b2,…,bnIs a string of binary numbers, when bxWhen 0, it indicates that the x-th block is correct; when b isxWhen the value is 1, x ∈ {1,2, …, n }, which indicates an xth block error. When the sender receives a NACK, check b1,b2,…,bnThe value of (c) can be known which data blocks are in error and need to be retransmitted.
A switching method of a point-to-point link data transmission mechanism of a passive sensing network comprises the following steps:
the operation flow of the sender S is as follows:
step 11, capturing energy from the RF signal with duration Th；
Step 12, solving an optimization problem OP _ n to obtain the optimal block number n of the effective load in the data packet;
step 13, judging whether n is equal to 1, if n is equal to 1, setting a TM field in the header of the data packet as 0, generating the data packet according to the format of the figure 1, and transmitting data by adopting ARQM; if n is not equal to 1, setting the TM field to be 1, generating a data packet according to the format of the figure 2, and transmitting data by adopting BRM;
and step 14, ending.
The operation flow of the receiver R is as follows:
step 21, capturing energy from the RF signal for a duration Th；
Step 22, receiving the data packet from the S, checking the value of the TM field in the header of the data packet, and if the TM is 0, receiving and processing the data packet by using the ARQM; if TM is 1, receiving and processing data packet according to BRM.
And step 23, ending.
In the Frame Control field in the header of the packet, 3 bits are reserved bits, and 1 bit of the 3 reserved bits may be defined as a Transmission Mechanism (TM) field, where the TM field is used to indicate what data Transmission Mechanism is used for the Transmission. As shown in fig. 5.
Node energy capture time ThDetermination of (1): with PhEnergy capture power of the node is represented, and is known from Friss transmission equation:
Figure BDA0001300558430000071
wherein G issAnd GrRespectively representing the antenna gain at the energy supply point and at the node, λ being the wavelength of the electromagnetic wave, PlostIs the path power loss, d is the distance between the node and the energy supply point (cellular base station, Wi-Fi access point or television tower, etc.), PsIs the transmit power of the energy supply point and μ is the efficiency factor of the conversion of the RF signal into electrical energy.
With e0Representing the initial energy of the node, in ethEnergy threshold representing node operation, i.e. only if the remaining energy of both nodes S and R is greater than or equal to ethThen S starts transmitting data. At τRepresenting the node from the initial energy e0Begin capturing energy until its remaining energy reaches ethThe duration of time, using equation (1), can be:
τ＝(eth-e0)/Ph (2)
at τSAnd τRRepresenting the energy capture times of S and R, respectively, then the remaining energy from the moment when S and R begin capturing energy until they are both greater than or equal to ethThe duration of time is:
Th＝max{τS,τR} (3)
determination of the length of the data block in the data packet: the length (unit) of each data block is expressed by l
Bits), as can be seen from fig. 2:
wherein L isPacketIndicates the total length of the data packet, LHeadIndicates the length of the header, LHCSIndicates the length, L, of the header check sequence HCSFCSIndicating the length of the tail.
Probability of successful header and data block transmission: the communication link between S and R is represented by < S, R > and the error rate of the link < S, R > is represented by b, so that when S transmits a packet to R, the probability q of successful transmission of the header and the probability p of successful transmission of each data block are respectively:
Figure BDA0001300558430000082
p＝(1-b)l (6)
probability of successful kth transmission of data packet: with Pk(x) Indicates the probability of success of the kth transmission of a data packet containing x data blocks, where x is 1, 2. K is 1, 2.. K, where K represents the maximum number of transmissions of the same packet, and the solution P can be obtained by combining equations (5) and (6)k(x) The recursion of (c) is as follows:
Figure BDA0001300558430000083
the probability of a node transmitting a data packet successfully is:
Figure BDA0001300558430000084
with LkThe bit number which represents the average transmission of the kth transmission of the node comprises the following bits:
Figure BDA0001300558430000085
wherein the content of the first and second substances,representing the probability of the first k-1 transmission failures; ek(x) Represents the accumulation of the product of the data packet containing 1 data block, 2 data blocks, x data blocks and the corresponding probability sent by the node at the kth transmission, and the expression is as follows:
Figure BDA0001300558430000091
average delay of a node transmitting a data packet: the rate of data transmission of the node is represented by r and LAAnd LNIndicates the length of ACK and NACK, respectively, in TrRepresents a retransmission timer, and represents an average delay of a node transmitting a data packet by t, and comprises:
Figure BDA0001300558430000092
and M represents the total number of data packets transmitted from S to R, the throughput rate in the link (S, R) is as follows:
Figure BDA0001300558430000093
wherein L isBCSIndicating the length of the BCS.
The optimization problem OP _ n that maximizes the throughput in the link < S, R > is as follows:
Figure BDA0001300558430000094
in the above formula, nminAnd nmaxRespectively representing the lower bound and the upper bound of the number of the data packet blocks.
The optimal value n of the number of data packet blocks can be obtained by solving equation (13)*When n is*When the value is 1, it indicates that the throughput rate of the payload of the packet is the maximum for 1 block under the current link environment, and therefore, the TM field in the packet header may be set to 0, and the ARQM may be used for transmission; when n is*>1, it means that in the current link environment, the throughput rate can be maximized by dividing the payload of the data packet into 2 blocks or more, and then, the TM field may be set to 1, and BRM is used for transmission.
nminAnd nmaxDetermination of (1): in formula (13), n ismin1, the number of the blocks of the data packet is at least 1; meanwhile, in order to ensure the transmission efficiency of the data packet, the length of each data block is not less than the header L of the data packetHeadPlus a header check sequence LHCSObtaining nmaxThe calculation formula of (a) is as follows:
Figure BDA0001300558430000095
in this example, the parameter settings are shown in table 1.
Figure BDA0001300558430000101
TABLE 1
From the parameter values in Table 1 and equation (14), n can be obtainedmax11. That is, in the optimization problem OP _ n, n ∈ [1,11 ]]The number n of the optimal blocks can be solved by an enumeration method.
In addition, links are separately provided<S,R>Bit error rate of (b) 1000-1,2000-1,3000-1,4000-1,5000-1. The distance between the energy supply points and the S and the distance between the energy supply points and the R are randomly selected from 5 meters to 15 meters, the number M of data packets transmitted from the S to the R is 5000, and the energy consumption of 1-bit data received or sent by the node is 10 nJ.

Claims (3)

1. A switching method of a point-to-point link data transmission mechanism of a passive sensing network is characterized in that: the method comprises the following steps:
the operation flow of the sender S is as follows:
step 11, capturing energy from the RF signal with duration Th；
Step 12, solving an optimization problem OP _ n to obtain the optimal block number n of the effective load in the data packet;
determination of the length of the data block in the data packet: the length of each data block is denoted by l:
Figure FDA0002238517040000011
wherein L isPacketIndicates the total length of the data packet, LHeadIndicates the length of the header, LHCSIndicates the length, L, of the header check sequence HCSFCSIndicates the length of the tail;
probability of successful header and data block transmission: the communication link between S and R is represented by < S, R > and the error rate of the link < S, R > is represented by b, so that when S transmits a packet to R, the probability q of successful transmission of the header and the probability p of successful transmission of each data block are respectively:
p＝(1-b)l (6)
probability of successful kth transmission of data packet: with Pk(x) Indicates the probability of success of the kth transmission of a data packet containing x data blocks, where x is 1, 2. K is 1,2, K, where K represents the maximum number of transmissions of the same packet, and equation (5) and equation (6) are combined to obtain a solutionPk(x) The recursion of (c) is as follows:
the probability of a node transmitting a data packet successfully is:
Figure FDA0002238517040000014
with LkThe bit number which represents the average transmission of the kth transmission of the node comprises the following bits:
Figure FDA0002238517040000015
wherein the content of the first and second substances,
Figure FDA0002238517040000016
representing the probability of the first k-1 transmission failures; ek(n) represents the accumulation of the product of the data packet containing 1 data block, 2 data blocks, n data blocks and the corresponding probability when the node transmits the kth time, and the expression is as follows:
Figure FDA0002238517040000021
average delay of a node transmitting a data packet: the rate of data transmission of the node is represented by r and LAAnd LNIndicates the length of ACK and NACK, respectively, in TrRepresents a retransmission timer, and represents an average delay of a node transmitting a data packet by t, and comprises:
Figure FDA0002238517040000022
and M represents the total number of data packets transmitted from S to R, the throughput rate in the link (S, R) is as follows:
Figure FDA0002238517040000023
wherein L isBCSRepresents the length of the BCS;
the optimization problem OP _ n that maximizes the throughput in the link < S, R > is as follows:
Figure FDA0002238517040000024
in the above formula, nminAnd nmaxA lower bound and an upper bound respectively representing the number of data packet blocks;
the optimal value n of the number of data packet blocks can be obtained by solving equation (13)*When n is*When the value is 1, it indicates that the throughput rate of the payload of the packet is the maximum for 1 block under the current link environment, and therefore, the TM field in the packet header may be set to 0, and the ARQM may be used for transmission; when n is*>1, it means that under the current link environment, the throughput rate can be maximized by dividing the payload of the data packet into 2 blocks or more, and then, the TM field can be set to 1, and BRM is used for transmission;
step 13, judging whether n is equal to 1, if n is equal to 1, setting a TM field in the header of the data packet as 0, generating the data packet and transmitting data by adopting an ARQM; if n is not equal to 1, setting the TM field to be 1, generating a data packet and transmitting data by adopting BRM;
step 14, ending;
the operation flow of the receiver R is as follows:
step 21, capturing energy from the RF signal for a duration Th；
Step 22, receiving the data packet from the S, checking the value of the TM field in the header of the data packet, and if the TM is 0, receiving and processing the data packet by using the ARQM; if TM is equal to 1, receiving and processing the data packet according to BRM;
step 23, ending;
the process of the ARQM is as follows: a sender S sends a data packet to a receiver R, and starts a retransmission timer after the sending is finished; if the R correctly receives the data packet, an ACK is replied to the S immediately to confirm the receipt of the data packet; if the data packet has bit errors, R does nothing; then, S immediately retransmits the data packet after the retransmission timer is overtime, and if the retransmission times reaches the preset maximum retransmission times, S stops transmitting the current data packet;
the process of the BRM is as follows: a sender S divides a payload of a data packet into n data blocks, each data block comprises two parts of effective data and a block check sequence BCS, the block check sequence is used for checking whether the data block has errors, and in addition, the payload also comprises a head check sequence HCS which is used for checking whether the head of the data packet has errors; after the data packet is divided into n blocks, the payload of the data packet contains HCS, and n effective data D1,D2,…,DnAnd n block check sequences C1,C2,…,Cn(ii) a Then, the sender S sends the data packet to the receiver R, after the R receives the data packet, the R adopts the FCS in the tail part to check the data packet, and if the data packet is correct, an ACK is replied to the S; if the bit error exists, checking the header by adopting the HCS, if the header has the error, doing nothing, and waiting for the S to retransmit the original data packet; if the header is correct, then adopt C in turn1,C2,…,CnChecking the data block 1, the data block 2, the data block n, storing the correct data block into a corresponding storage area in a buffer area, discarding the data block with the error, and replying a Negative Acknowledgement (NACK) to the S to inform the S of which data blocks have errors; then S retransmits a data packet containing only error data block in the effective load to R; and repeating the steps until the R successfully receives the n data blocks or the retransmission times reach the upper limit.
2. The method of claim 1, wherein the method comprises: in the steps 11 and 21, the node energy capture time ThDetermination of (1): with PhEnergy capture power of the node is represented, and is known from Friss transmission equation:
Figure FDA0002238517040000031
wherein the content of the first and second substances,Gsand GrRespectively representing the antenna gain at the energy supply point and at the node, λ being the wavelength of the electromagnetic wave, PlostIs the path power loss, d is the distance between the node and the energy supply point, PsIs the transmission power of the energy supply point, mu is the efficiency coefficient of converting the RF signal into electric energy;
with e0Representing the initial energy of the node, in ethEnergy threshold representing node operation, i.e. only if the remaining energy of both nodes S and R is greater than or equal to ethThen S starts to transmit data; let τ denote the node's initial energy e0Begin capturing energy until its remaining energy reaches ethThe duration of time, using equation (1), can be:
τ＝(eth-e0)/Ph (2)
at τSAnd τRRepresenting the energy capture times of S and R, respectively, then the remaining energy from the moment when S and R begin capturing energy until they are both greater than or equal to ethThe duration of time is:
Th＝max{τS,τR} (3)。
3. the method of claim 2, wherein the method comprises: n isminAnd nmaxDetermination of (1): in formula (13), n is takenmin1, the number of the blocks of the data packet is at least 1; meanwhile, in order to ensure the transmission efficiency of the data packet, the length of each data block is not less than the header L of the data packetHeadPlus a header check sequence LHCSObtaining nmaxThe calculation formula of (a) is as follows:
Figure FDA0002238517040000041
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