CN101232452B - Broadcast channel data transmission method for industrial wireless sensor network - Google Patents

Abstract

The invention relates to a broadcast channel data transmission method of an industrial wireless sensor network. The utility model comprises the following steps that a deny message including data grouping is sent to a receiving end after the receiving end determines that the data grouping in the data grouping group is not received successfully; after the deny message is determined to be received by the receiving end, whether the passed time is more than a presetting time interval after the data grouping is sent is judged; the data grouping is resent to the receiving end.

Description

Broadcast channel data transmission method for industrial wireless sensor network

technical field

The invention relates to the field of industrial wireless communication, in particular to a broadcast channel data transmission method of an industrial wireless sensor network. the

Background technique

Industrial wireless technology is a hot technology in the field of industrial control after fieldbus. It is a revolutionary technology that reduces the cost of industrial measurement and control systems and improves the application range of industrial measurement and control systems. It will be a new growth point for industrial automation products in the next few years. the

Industrial wireless technology is a kind of wireless communication technology emerging at the beginning of this century, which is oriented to short-range and low-rate information interaction between devices. It is suitable for use in harsh industrial field environments, and has strong anti-interference ability, ultra-low energy consumption, real-time communication, etc. The technical feature is the functional expansion and technological innovation of the existing wireless technology in the direction of industrial application, and will eventually be transformed into a new wireless technology standard. It is developed from the emerging wireless sensor network technology. Industrial wireless technology is a type of wireless sensor network technology that meets the special needs of industrial applications such as high reliability, low power consumption, and hard real-time. Its development prospects are very promising. According to a recent wireless sensor market survey conducted by On World Company of the United States, 79% of the surveyed users are considering using wireless devices to complete remote monitoring, especially in the pipeline operation industry and water source monitoring. Almost all large oil and gas Companies are seeking solutions for networked real-time monitoring platforms. In the industrial automation market, end users and system integrators are showing strong interest in wireless networking technology, according to a survey reported by the American Journal of Control Engineering. 45% of respondents plan to trial wireless network technology in 2005. And nearly 70% of the respondents are concerned about the progress of wireless technology in industrial measurement and control applications. On the question of how much the wireless network can save, 58% of respondents believe that for each wireless sensor adopted, this technology saves more than $100 in wiring and labor costs; 33% of the respondents believe that Save over $250 per sensor. Venture Development Corporation pointed out in its "Market Research Report on RF/Microwave Wireless Monitoring and Control Products of Discrete and Process Manufacturing in North America" that the production volume of related wireless products in the field of industrial automation was 6.1 million US dollars in 2004, and it is expected to grow by 60.2% in the future annual growth rate is growing rapidly. the

Most industrial control applications require a reliable data transmission rate of more than 95%, which requires high reliability in channel data transmission. This patent is based on this and proposes a channel retransmission method that can improve reliability. the

In addition to the congestion problem in the wired channel, the performance of the mobile communication system is also mainly restricted by the time-varying channel. Various noises, interference, fading, etc. greatly reduce the quality of the wireless link. The propagation path between the transmitter and the receiver is very complex, ranging from simple line-of-sight propagation to encountering various complex ground objects, such as buildings, mountains and leaves; In a group or in an area with complex terrain, its antenna will receive signals from multiple paths, coupled with the movement of the mobile station itself, making the wireless channel between the mobile station and the base station variable and difficult to control, resulting in wireless channel Sudden reductions in signal strength, so-called fading, are common occurrences. the

The Wireless Application Protocol (WAP) has been developed to address the needs of mobile stations, since these devices have severe physical, storage and processing constraints. WAP can be applied to many different systems, including GSM-900, GAM-1800, GSM-1900, CDMA IS-95, TDMA IS-136, Broadband IS-95, and third-party systems such as IMT-2000, UMTS, and W-CDMA. Three generations of systems. the

According to WAP, there are three classes of transactions: class 0 for unreliable one-way requests, class 1 for reliable one-way requests, and class 2 for reliable two-way request-response transactions. A transaction is defined as a unit of interaction between an "initiator" (eg, sender or receiver) and a "responder" (eg, sender or receiver). A transaction begins with a request message generated by the sender. In a Category 2 transaction, the recipient replies with a result message that implicitly acknowledges the request message. If the receiver takes more than a specified time interval to process the request message, the receiver can reply with a "no hang up" acknowledgment message before sending the result message to avoid retransmitting the request message. The transaction ends when the sender receives the acknowledgment. the

To reduce congestion and the above problems in propagation, before a data message is sent, it is segmented into an ordered sequence of data packets. Each data packet has a Packet Sequence Number (PSN) assigned to it. Thus, for example, the first data packet of a split is assigned packet number 0, the second data packet is assigned packet number 1, the third data packet is assigned packet number 2, and so on. These data packets are transmitted independently or in combination, and are reassembled by the receiver upon receipt. The maximum number of packets that a message can be divided into is about 256 packets, and the maximum size of each packet is 1-2k bytes. Therefore, the maximum size of a message is typically less than 0.5 Mbytes. the

If the data packet is split into small groups, the sender does not send a new packet belonging to the same transaction until receipt of the previous packet group has been confirmed. Typically, the sender determines the number of packets in each group of packets and sends the packets of the group of packets in the same batch. The last data packet of each packet group has a group tail (GTR) flag set (flag set), which is called a GTR packet. The last data packet of the last group of packets of the entire message has a Transport Trailer (TTR) flag set, which is also referred to as a TTR packet. The receiver stores all received packets, and upon receiving a GTR packet, the receiver checks whether it has received all packets belonging to that particular group of packets. If it is detected that all the packets in the group have been received, the receiver returns an acknowledgment message containing the sequence number of the GTR packet. However, if a GTR or TTR packet is received, but one or more packets of that packet group are lost, the receiver waits for a period of time before sending a Negative (NACK) message containing the packet sequence numbers of the missing packets of that particular packet group , such as 1/2 the median round trip time (RTT). If the sender does not receive an acknowledgment within a specified time interval after sending a group of packets, then it only retransmits the GTR or TTR packets for that group of packets to the receiver. the

However, this can be problematic if during transmission one or more acknowledgment or acknowledgment or acknowledgment messages are lost due to, for example, handover errors or congestion of the wireless communication network, resulting in retransmission of data packets already received by the recipient. the

Contents of the invention

In order to solve the problems existing in the prior art, the present invention provides a broadcast channel data transmission method of an industrial wireless sensor network, thereby realizing the reliable transmission of information in the wireless channel. the

The wireless channel data transmission method provided by the present invention includes:

Step 1, the sender sends data packets to the receiver in the order of packet sequence numbers, and data packets with lower packet sequence numbers should arrive at the receiver before data packets with higher packet sequence numbers;

Step 2, if the receiver receives a data packet with a higher packet sequence number but does not receive a data packet with a lower packet sequence number, it is judged that the data packet with a lower packet sequence number is lost;

Step 3, the receiver will send a denial message to the sender, and the denial message lists the sequence of lost packet data;

Step 4, after receiving the acknowledgment message from the receiver, the sender detects whether the time elapsed since sending each lost data packet listed in the acknowledgment message is less than a predetermined time interval;

Step 5, if the elapsed time for the lost data packet is less than the predetermined time interval, the sender does not retransmit the requested lost data packet in the denied message; otherwise,

Step 6, if the elapsed time of the lost data packet is greater than the predetermined time interval, the sender retransmits the requested lost data packet in the deny message;

Step 7: After sending a deny message to the sender, the receiver waits for the sender to resend the lost data packet, but if the waiting time exceeds the preset threshold value, the receiver sends a deny message to the sender again;

Step 8, once all the data packets are received, the receiver sends an acknowledgment message to the sender to confirm receipt of all the data packets. the

Further, the deny message in step 3 not only lists the lost packet sequence numbers in the latest data packet group, but also lists all the lost packet sequence numbers before that. the

Further, the acknowledgment message not only lists the sequence number of the lost data packet, but also lists the highest packet sequence number among the data packets received by the receiver. the

Therefore, the present invention enables reliable transmission of information on wireless channels. the

Description of drawings

Fig. 1 is the structural representation of the data transmission system based on the broadcast channel data transmission method of the industrial wireless sensor network of the present invention;

Fig. 2 is a schematic diagram of the format of the segmented data message transmitted in the broadcast channel data transmission method of the industrial wireless sensor network of the present invention;

Fig. 3 is a flow chart of the broadcast channel data transmission method of the industrial wireless sensor network of the present invention. the

Detailed ways

The technical solutions of the embodiments of the present invention will be described in further detail below with reference to the drawings and embodiments. the

FIG. 1 is a schematic structural diagram of a data transmission system based on a broadcast channel data transmission method of an industrial wireless sensor network according to the present invention. The data transmission system 10 includes a mobile station 11 (such as a mobile phone) that communicates wirelessly with a gateway 13 through an air link 15 (including, for example, a base station and a switching control point), and the gateway 13 communicates with a server 17 through a wide area network such as the Internet or an intranet. connected. Data is transmitted to and from the mobile station 11 according to the data transmission method of the present invention. the

Fig. 2 is a schematic diagram of the format of the data message after the data flow is divided in the broadcast channel data transmission method of the industrial wireless sensor network according to the present invention. The data message includes a plurality of groups of data packets such as Group 1, Group 2... GroupM. Each group includes one or more data packets 30 without a flag set and data packets 32 with a GTR flag set. The set of GTR criteria indicates the last data packet of a group of data packets. The last packet 34 of the entire data message contains the TTR flag set. Each data packet 30 of a data message is associated with a unique identification number, such as a Packet Sequence Number (PSN), so that a recipient (eg, mobile station 11) can identify missing data packets in the data message based on the identification number. These data packets have consecutive numbers (for example: 0, 1, 2, 3, 4...). the

Fig. 3 is the flow chart of the broadcast channel data transmission method of industrial wireless sensor network of the present invention, step 1, sender (for example, gateway 13 or server 17) sends data grouping 30 to receiver according to PSN order, so that PSN is lower Data packets 30 are sent before data packets with higher PSNs (eg, data packets with PSN=3 are sent before data packets with PSN=4). Step 2, if the receiver determines that the data packet 30 is lost (for example, the receiver has received the data packet of PSN=3 but has not received the data packet of PSN=1), then in step 3, the receiver will send a denial (NACK) message to Sender, lists lost packets (eg, PSN=1). Wherein, the preferred NACK message not only lists the lost packets in the latest data packet group, but also lists all the lost packets before that. For example, if a data packet with PSN=3 is lost (not yet received) from packet group 1, and a data packet with PSN=18 is lost from packet group 4, then the NACK message will also list the lost data packets (PSN=3 and PSN=18). This is particularly convenient because even if a previous NACK message is lost, the sender can still be notified of the missing data packets in the previously sent group of packets. Consider that a NACK message can be sent before or after the GTR data packet of each data packet group is received by the receiver. the

Step 4, after receiving the NACK message from the receiver, the sender detects whether the time elapsed since sending each missing data packet listed in the NACK message is less than a predetermined time interval (e.g., about A round trip time (RTT) required for transmission between the receiver and the receiver), step 5 If the time elapsed for the lost data packet is less than the RTT, the sender does not retransmit the requested (lost) data packet . Otherwise, in step 6, if the elapsed time of the lost data packet is greater than the predetermined time interval, the sender retransmits the lost data packet. In this process, the receiver waits for the sender to return the lost data packet, but if the waiting time exceeds the preset threshold value, that is, a threshold value of the elapsed time from the receiver sending NACK to receiving the lost data packet T2, the receiver will resend the deny message;

Upon receipt of all data packets in the group, the receiver sends an acknowledgment (ACK) message to the sender, acknowledging receipt of all data packets in the group, and then begins assembling the received data packets to reconstruct the data message. Similar to the sending of a NACK message, the receiver can send an ACK message after receiving the group's GTR data packet. After receiving the TTR data packet, the receiver can also send an ACK message to confirm receipt of all data packets in the data message. Alternatively, the receiver may send a NACK message listing no lost data packets of a particular group, thereby implicitly acknowledging receipt of all data packets in that particular group. the

In a particularly preferred embodiment, the NACK message lists not only the missing data packets, but also the highest packet sequence number among the data packets received by the receiver. With such a NACK message, the recipient can thus implicitly acknowledge receipt of all data packets with a lower PSN (except for the listed missing packets). An example illustrating such a NACK message is as follows. The sender sends two sets of data packets: packets with PSN=N, N+1, N+2 (GTR); and packets with PSN=N+3, N+4, N+5 (GTR). The two data packets with PSN=N+2 and N+5 include the GTR flag set and are therefore the last data packets in their respective groups. Data packets with PSN=N and N+1 are lost during transmission. The receiver then sends a NACK message (NACK_1), listing data packets with PSN=N and N+1 as lost packets, and data packets with PSN=N+2 as the last data packet received by the receiver (i.e., the data packet with the highest PSN ). However, NACK_1 is also lost during transmission. Meanwhile, the receiver continues to receive data packets of the next packet group: data packets with PSN=N+3, N+4 and N+5. After determining that the data packets with PSN=N and N+1 are still lost, the receiver sends a second NACK message (NACK_2) listing the last data packet received (for example, the data packet with PSN=N+5) and the remaining Lost data packets (data packets with PSN=N and N+1). The receiver receives NACK_2 and realizes that the receiver has received all data packets in these two groups of data packets except those with PSN=N and N+1. The sender then resends the lost data packets (PSN=N and N+1). Consider that this NACK message can be combined with an acknowledgment message to further enhance the communication reliability between the sender and receiver. the

To illustrate the wireless channel data transmission method of the present invention, the receiver sends a data request to the air link 15, and the link 15 sends the request to the sender in turn. The sender receives the data request and sends to the air link 15 data packets 30 with PSN=N, N+1 and N+2. However, the air link only sends the data packets with PSN=N+1 and N+2, and the data packets with PSN=N are missed. The receiver determines that the data packets with PSN=N are lost and sends to the airlink 15 a NACK message (NACK_1) listing the data packets with PSN=N. But the NACK message is also lost, and the air link 15 cannot forward the NACK message to the sender. the

Still in response to the original data request, the sender sends another packet group of data packets 30 with PSN=N+3 and N+4. Airlink 15 sends data packets to recipients PSN=N+3 and N+4. After the waiting time exceeds the set threshold value, the receiver confirms the loss of the data packet with PSN=N again, and sends another NACK message (NACK_2) listing the lost data packet to the air link 15, and the link 15 successfully Forward the NACK_2 message to the sender. The sender responds to NACK_2 by sending the missing data packet with PSN=N to the receiver over the air link 15 . the

In another example, the receiver sends a data request to the air link 15, which in turn sends the request to the sender. The sender then sends a data packet with PSN=N, N+1 to the air link 15 . The data packet with PSN=N is lost in the air link, and only the data packet with PSN=N+1 is sent to the receiver. The receiver sends an airlink 15 acknowledgment message (NACK_1) listing the data packets with PSN=N. The sender continues to send data packets with PSN=N+2 to the air link 15, which successfully sends the data packets to the receiver. The receiver determines (either before or after receiving the GTR packet) that the data packet with PSN=N is lost, and then sends another acknowledgment message (NACK_2). However, the airlink finally sends NACK_1 to the sender, which responds by sending a data packet with PSN=N to the airlink 15 . The air link 15 transmits data packets with PSN=N to the recipient. The sender pre-sets T1 to control the retransmission time of the lost data packet. During this time, no matter what is received, the sender will not resend the lost data packet. Only when the time is greater than T1, the NACK is received. Resend lost data packets. After the sender sends the data packet (PSN=N) within a time interval less than one T1 (ie, a predetermined time interval), the sender receives NACK_2 requesting the same data packet (ie, PSN=N). Since NACK_2 was received within less than one T1, the sender ignores NACK_2, refusing to send the requested data packet. the

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the embodiments of the present invention rather than limit them. Although the embodiments of the present invention have been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can Modifications or equivalent replacements are made to the technical solutions of the embodiments of the present invention without departing from the spirit and scope of the technical solutions of the embodiments of the present invention. the

Claims (3)

1. A broadcast channel data transmission method of an industrial wireless sensor network, characterized in that it comprises: Step 1, the sender sends data packets to the receiver in the order of packet sequence numbers, and data packets with lower packet sequence numbers should arrive at the receiver before data packets with higher packet sequence numbers; Step 2, if the receiver receives a data packet with a higher packet sequence number but does not receive a data packet with a lower packet sequence number, then judge that the data packet with a lower packet sequence number is lost; Step 3, the receiver will send a denial message to the sender, and the denial message lists the sequence of lost packet data; Step 4, after receiving the acknowledgment message from the receiver, the sender detects whether the time elapsed since sending each lost data packet listed in the acknowledgment message is less than a predetermined time interval; Step 5, if the elapsed time for the lost data packet is less than the predetermined time interval, the sender does not retransmit the requested lost data packet in the denied message; otherwise, Step 6, if the elapsed time of the lost data packet is greater than a predetermined time interval, the sender retransmits the requested lost data packet in the deny message; Step 7, after the receiver sends a deny message to the sender, it waits for the sender to resend the lost data packet, but if the waiting time exceeds a preset threshold value, the receiver sends a deny message to the sender again; Step 8, once all the data packets are received, the receiver sends an acknowledgment message to the sender to confirm receipt of all the data packets. 2. The method according to claim 1, characterized in that the deny message in said step 3 not only lists the packet sequence numbers lost in the latest data packet group, but also lists all the packet sequence numbers lost before this . 3. The method according to claim 1 or 2, characterized in that the acknowledgment message not only lists the missing data packet sequence numbers, but also lists the highest packet sequence number among the data packets already received by the receiver.

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