CN103825682A - Efficient and rapid method for transmitting WTB multicast message data - Google Patents

Abstract

The invention discloses an efficient and rapid method for transmitting WTB multicast message data. The method comprises the steps that (1) the WTB multicast message data start to be sent; (2) whether the message data is completely sent or not is judged, and if yes, sending is completed; if not, the part to be sent of the message data is filled into a data field of a BC packet, the maximum filling quantity is 119 Bytes, SEND_TMO is reset, and the BC packet is sent; (3) whether a retransmission request packet, namely a BR packet, is received or not is detected in the SEND_TMO waiting overtime period, if the BR packet is not received in the SEND_TMO period, the SEND_TMO is not completed, and a new round of BC packet sending is started; if the SEND_TMO is completed, the step (2) is executed again; if the BR packet is received in the SEND_TMO waiting overtime period, transmission pause is inserted, a message data transmission pointer is arranged according to data offset in the BR packet, and a new round of BC packet sending is started. The efficient and rapid method for transmitting the WTB multicast message data has the advantages of being smaller in transmission cost, higher in speed, capable of enabling an embedded environment to be implemented more conveniently and the like.

Description

Efficiently WTB multicast message data transmission method fast of one

Technical field

The present invention is mainly concerned with vehicle control network technical field, refers in particular to a kind of efficiently WTB multicast message data transmission method fast that is applicable to vehicle control network.

Background technology

The corresponding GB of international standard IEC61375(is GB/T28029.1) stipulate that the process data of WTB bus communicates by letter with message data.But in actual use, due to the restriction of bandwidth, WTB cannot transmit application required abundant train fault and state information in periodic process data send, this just need to adopt message data to make up.But the WTB multicast message data transmission mechanism speed of standard regulation is slower, and the byte limited (18 byte) of each transmission, cannot meet the needs of practical application.

At present, the each company of all field of track traffic all adopts standard prescribed manner to realize multicast message data communication, i.e. multicast transmission is divided into three phases: connect, transmit confirmed data and conciliate even, as shown in Figure 1.Wherein, BC(Brodcast Connect, broadcast connects) wrap to be used for setting up and broadcast connection, and always repeat to send three times.In BC bag, carry message length field and first data segment.If message-length is greater than BC bag data-field length, following adopted BD(Broadcast_Data, broadcast data) bag transmission.The packet format of BC bag and BD bag is shown in Figure 2.

The shortcoming of above-mentioned prior art is mainly manifested in:

(1) data field 144bit, control field (containing header) 72bit, expense accounting is not less than 33.3%, and efficiency of transmission is low.

(2) data field only 144bit(be 18byte), need to be divided into more parcel processing for the application (as diagnostic data transmission) that needs large message transfer of data, resource overhead is large and affect transmission rate.

(3) when BC bag connects, need repeat to send three times, this is complicated system, on the other hand shortage necessity for close network system with follow-up BD bag retransmission mechanism disunity on the one hand.

Summary of the invention

The technical problem to be solved in the present invention is just: the technical problem existing for prior art, the invention provides the WTB multicast message data transmission method that a kind of transport overhead is less, speed is convenient to embedded environment realization faster, more.

For solving the problems of the technologies described above, the present invention by the following technical solutions:

Efficiently WTB multicast message data transmission method fast of one, the steps include:

(1), start to send WTB multicast message data;

(2), judge whether message data is sent completely, as completed, send finish; Otherwise, part to be sent message data is inserted to the data field that BC wraps, insert at most 119Byte, and the SEND_TMO that resets, send BC bag;

(3), during waiting for SEND_TMO overtime arrival, monitor always and whether receive repeat requests (BR) bag.If do not receive BR bag during the overtime arrival of SEND_TMO, be judged as and send successfully, return to step 2; If receive BR bag during waiting for the overtime arrival of SEND_TMO, be judged as and need data retransmission, inserting after transmission time-out, according to data offset in BR bag, message data send finger is set, return to step 2.

As a further improvement on the present invention: the message length of BC bag is set as to 128byte, and corresponding data field expands to 119byte, i.e. 952bit.

Compared with prior art, the invention has the advantages that:

1, the present invention has reached the effect of less communication overhead, faster transmission rate by expansion BC bag data-field length, unified BC and BD packet format, simplification Retransmission control mechanism.

2, the present invention, after concrete application, expands data field to 952bit(119byte), making expense accounting minimum is only 7.0%, efficiency of transmission significantly improves; Data field has expanded 6.6 times, has reduced the large message transfer of data time-division and has unwrapped pin, has improved transmission rate.Because message packet total length is 128byte, be more convenient to embedded environment and realize.

Accompanying drawing explanation

Fig. 1 is IEC61375(GB/T28029.1) middle WTB multicast message data transmission method schematic diagram.

Fig. 2 is IEC61375(GB/T28029.1) in the schematic diagram of BC, BD packet format.

Fig. 3 is the schematic diagram of BC packet format in the present invention.

Fig. 4 is the schematic diagram of WTB multicast message data transmission method in the present invention (without BD bag).

Fig. 5 is the schematic flow sheet that multi-case data of the present invention sends.

Embodiment

Below with reference to Figure of description and specific embodiment, the present invention is described in further details.

As shown in Figure 5, efficiently WTB multicast message data transmission method fast of the present invention, the steps include:

1, start to send WTB multicast message data;

2, judge whether message data is sent completely, as completed, send and finish; Otherwise, part to be sent message data is inserted to the data field that BC wraps, insert at most 119Byte, and the SEND_TMO that resets, send BC bag;

3,, during waiting for the overtime arrival of SEND_TMO, monitor always and whether receive repeat requests (BR) bag.If do not receive BR bag during the overtime arrival of SEND_TMO, be judged as and send successfully, return to step 2; If receive BR bag during waiting for the overtime arrival of SEND_TMO, be judged as and need data retransmission, inserting after transmission time-out, according to data offset in BR bag, message data send finger is set, return to step 2.

For ease of realizing, real time communication message length (in byte) under embedded environment adopts 2 n power form conventionally, especially the Large Volume Data such as failure diagnosis transmission application is required to consider railway mainstream applications, message length is set as 128byte by the present invention, corresponding data field expands to 119byte(952bit), as Fig. 3.

By WTB multicast message data efficiency is derived and can be known the advantage of growth data field.Suppose that all WTB multicast message messages are isometric, the throughput of WTB multicast message is defined as follows:

$E\left[\mathrm{throughput}\right]={\lim }_{t\→\∞}\frac{N\left(t\right)\×\mathrm{packet}\_\mathrm{length}}{t}---\left(1\right)$

In formula: N (t) is the message number transmitting in system, and packet_length is message length.

Message service time is expected in definition

(1) formula can be expressed as:

$E\left[\mathrm{throughput}\right]=\frac{\mathrm{pachet}\_\mathrm{length}}{\stackrel{\‾}{T}}---\left(2\right)$

Again:

$\stackrel{\‾}{T}=T_{\mathrm{assig}}+T_{\mathrm{tx}}+T_{\mathrm{error}\_\mathrm{correction}}+T_{\mathrm{final}\_\mathrm{acks}}---\left(3\right)$

In formula:

T _assigto transmit and the processing time in channel allocation process;

T _txit is the data block delivery time first based on message length and encoding mechanism;

T _{error_correction}it is the backward error control processing time that comprises re-transmission;

T _{final_acks}it is final ACK message and control ACK Message Processing and delivery time.

From (2) formula, increase packet_length and reduce

it is the approach that improves throughput.In WTB multi-case data communication scenes, standard regulation packet_length loads small data quantity transmit mechanism in 216bit, BC three-way handshake mechanism and BC/BD bag.Consider multi-case data cycle of WTB bus communication accidental mutually in transmission, and WTB bus communication packet loss is minimum, therefore under the prerequisite of ignoring bus communication packet loss impact, can adopt and increase BC/BD bag data-field length and remove that BC wraps extra wrong controlling mechanism and affirmation mechanism (reduces T _{error_correction}and T _{final_acks}time) mode improve throughput.

Again, WTB multicast message data payload accounting is defined as the ratio of data-field length and message length (packet_length), therefore reach on the one hand by expansion BC, BD bag data field the object that increases packet_length raising throughput, also improved on the other hand payload accounting.

Therefore, the present invention expands to data field in BC bag after 119byte, and most application all can complete transfer of data (as Fig. 4) in BC bag, and minority application still needs follow-up BC bag transmission remaining data, but subpackage number greatly reduces.Consider the vehicle-carrying communication network application scene as close network environment, it is because disturbing the packet loss causing to be protected and to be weakened the effect by increase, therefore in the time that BC bag connects without 3 retransmission mechanism, tackle other reason and cause the retransmission mechanism of packet loss can be identical with the BD bag retransmission mechanism stipulating in standard, thereby simplify controlling mechanism.Due to after unified retransmission mechanism, the overtime SEND_TMO of the BD bag Retransmission control of employing is less than the overtime CONN_TMO of BC Retransmission control again, and the method also can improve efficiency of transmission.

Below be only the preferred embodiment of the present invention, protection scope of the present invention is also not only confined to above-described embodiment, and all technical schemes belonging under thinking of the present invention all belong to protection scope of the present invention.It should be pointed out that for those skilled in the art, some improvements and modifications without departing from the principles of the present invention, should be considered as protection scope of the present invention.

Claims (2)

1. an efficient WTB multicast message data transmission method fast, is characterized in that, step is:

(1), start to send WTB multicast message data;

(2), judge whether message data is sent completely, as completed, send finish; Otherwise, part to be sent message data is inserted to the data field that BC wraps, insert at most 119Byte, and the SEND_TMO that resets, send BC bag;

(3), during waiting for SEND_TMO overtime arrival, monitor always and whether receive repeat requests (BR) bag.If do not receive BR bag during the overtime arrival of SEND_TMO, be judged as and send successfully, return to step 2; If receive BR bag during waiting for the overtime arrival of SEND_TMO, be judged as and need data retransmission, inserting after transmission time-out, according to data offset in BR bag, message data send finger is set, return to step 2.

2. efficiently WTB multicast message data transmission method fast according to claim 1, is characterized in that, the message length of BC bag is set as to 128byte, and corresponding data field expands to 119byte, i.e. 952bit.

Images