CN111245737A

CN111245737A - Method for selecting size of transmission data block in Internet of things system

Info

Publication number: CN111245737A
Application number: CN202010022683.6A
Authority: CN
Inventors: 段红光; 王月; 郑建宏; 罗一静
Original assignee: Chongqing University of Post and Telecommunications
Current assignee: Chongqing University of Post and Telecommunications
Priority date: 2020-01-09
Filing date: 2020-01-09
Publication date: 2020-06-05
Anticipated expiration: 2040-01-09
Also published as: CN111245737B

Abstract

The invention relates to a method for selecting the size of a transmission data block in an Internet of things system, and belongs to the field of Internet of things communication systems. The method comprises the following steps: s1: acquiring initial SNR of startup and the size of a transmission block, and generating an SNR-TbSize corresponding table; s2: extracting SNR value fed back from a sending end and whether a receiving end receives an indication correctly; s3: according to the SNR value fed back by the sending end and whether the indication is received correctly, the success rate of the receiving end for transmitting the corresponding transmission block size under the SNR value, the actual SNR, the transmission block and the success rate are counted, and an SNR-TbSize-PSR corresponding table is dynamically generated; s4: and selecting the transmission block with the maximum success rate for transmission according to the generated SNR-TbSize-PSR corresponding table and the SNR fed back by the receiving end. The invention can improve the success rate of data transmission in the Internet of things system.

Description

Method for selecting size of transmission data block in Internet of things system

Technical Field

The invention belongs to the field of communication systems of the Internet of things, relates to how to select the size of a transmission block in the Internet of things, and particularly relates to a transmission block size selection method capable of improving transmission performance.

Background

According to the data transmission requirement of the internet of things system and the adoption of the burst data transmission characteristic, the internet of things system only supports the transmission of several data blocks with fixed sizes, which are generally called transmission blocks. Larger transport blocks are used to transport large amounts of higher layer data and smaller transport blocks are used to transport small amounts of higher layer data.

In public network systems, such as 3G/4G and current 5G networks, since a complex common channel is defined and strict synchronization between a terminal and a network is required, a random access process is first required when the terminal performs a service in the public network system. In the process, the terminal mainly completes uplink synchronization and performs small data block transmission, a perfect Automatic Modulation Coding (AMC) mechanism exists in the public network data transmission process, and the terminal feeds back a modulation method and a transmission block size that can be supported by a network according to the received downlink service data and the received signal quality, as shown in fig. 1, a general solution for automatic modulation coding is provided. However, the scheme is not suitable for an internet of things system, many internet of things wireless communication have no special frequency bands, and can only adopt public frequency bands basically, and the frequency bands are shared by the internet of things with multiple purposes, so that one internet of things cannot independently occupy frequency spectrum resources for a long time. Secondly, the internet of things can only adopt a carrier sense multiple access technology (CSMA) to compete for using wireless resources, a complete wireless resource allocation signaling system is not available, and the wireless resources used by the internet of things equipment each time cannot be accurately defined, so that several common formats can be defined according to transmission requirements. Finally, in the internet of things system, because the CSMA mode is adopted for transmission, the interval between two data packets is uncertain, usually, there is no necessary relation between two bursts to be transmitted, there is no necessary relation between the end of one burst and the other outstanding transmission, and the transmission of one burst is a complete communication process. As shown in fig. 2, it is seen from fig. 2 that the size of a burst sent by a node device in an internet of things system is mainly determined according to the amount of traffic data, and it is assumed that the predefined transport block size in the internet of things system is 16 bytes, 72 bytes, 136 bytes, 264 bytes, etc. If the terminal transmits 70 bytes, the transmission size is selected to be 72 bytes for transmission, and if the terminal transmits 75 bytes, a transmission block with the length of 136 bytes is selected for transmission. The problem of selecting the size of the transmission block is that the channel quality of the transmission environment and the interference condition are not considered when the transmission block is selected, so that the transmission block is increased in an environment with poor wireless quality, the transmission time is increased, the probability of the burst interference is increased, and the burst transmission success rate is very low.

For the existing problems, the conventional wireless communication system of the internet of things is solved by adopting a mode as shown in fig. 3, and the implementation steps of the mode are as follows: 1) in system simulation, SNR and the size of a transmission block are simulated, an AWGN noise adding mode is adopted for a channel, a minimum SNR value required by each transmission size is simulated, and the block error rate of the transmission block is generally required to be lower than 10%. A correspondence table is derived for SNR and transport blocks. Then, some typical scenes are selected to adjust the SNR and transport block table to obtain a general SNR and transport block mapping table, as shown in step 1 in fig. 3. 2) When the sending end starts to send data, the SNR value of the signal received by the receiving end is not determined, so that a smaller data block is selected for transmission first, and the transmission success rate is improved. In some systems, an appropriate transmission size is also selected according to the traffic data volume, as shown in step 2 in fig. 3. 3) After the transmitting end transmits a block of data burst, an acknowledgment/non-acknowledgment packet is received from the receiving end, where the data includes the SNR value of the received data, as in step 3 in fig. 3. 4) The sending end selects to send the size of the next block of transmission block according to the SNR of the burst signal received by the receiving end, and the size of the transmission block is determined according to the SNR value and the transmission size correspondence table, as shown in steps 4 and 5 in fig. 3. 5) The sending end selects the size of the next transmission block in turn according to the SNR value fed back by the receiving end, and the SNR and transmission block size table is kept unchanged all the time in the process.

In light of the above, the present needs are substantially met, but the following deficiencies still exist, which will affect the transmission success rate. The problems that exist are specifically as follows:

firstly, the method comprises the following steps: the SNR and transmission block corresponding table is a fixed table, cannot be corrected according to each independent scene in use, and is a universal table, so that the table is not the optimal SNR and transmission block corresponding relation in some scenes, and particularly needs to be flexibly adjusted on site for complex application scenes of the Internet of things.

Secondly, the method comprises the following steps: the radio frequency of each terminal device in the internet of things is different, so the difference also exists in the received signal and SNR calculation, and the preset SNR and transmission block corresponding table is not the optimal corresponding relation for specific devices.

Disclosure of Invention

In view of this, an object of the present invention is to provide a method for selecting a size of a transmission data block in an internet of things system, which automatically adjusts an SNR and a transmission block mapping table according to an actual transmission condition, so as to improve a success rate of data transmission in the internet of things system.

In order to achieve the purpose, the invention provides the following technical scheme:

a method for selecting the size of a transmission data block in an Internet of things system is characterized in that a sending end collects feedback information from a receiving end, records and counts SNR and transmission block success rate of the receiving end, and corrects a SNR and transmission block success rate corresponding table in real time, wherein the table is used as a basis for selecting the size of the transmission block next time. In the wireless communication system of the internet of things, in order to facilitate wireless resource use and channel coding and decoding, each burst transmission data volume is divided into a plurality of grades, and the grades are recorded as TbSize _1, TbSize _ 2. Referring to fig. 4 and 5, the method specifically includes the steps of:

s1: acquiring initial starting SNR and transmission block size from system simulation and actual measurement data correction results, and generating an SNR-TbSize corresponding table;

s2: extracting feedback information from a sending end, wherein the feedback information comprises SNR values measured by a sending transmission block at a receiving end and an indication whether the receiving end receives the feedback information correctly;

s3: according to the SNR value fed back by the sending end and whether the indication is received correctly, the success rate of the receiving end for transmitting the corresponding transmission block size under the SNR value, the actual SNR, the transmission block and the success rate are counted, and an SNR-TbSize-PSR corresponding table is dynamically generated;

s4: selecting a transmission block size: selecting a transmission block with the largest success rate for transmission according to the generated SNR-TbSize-PSR corresponding table and the SNR fed back by the receiving end; at the first transmission moment, the sending end does not have an effective SNR value, and then the sending end selects a proper transmission block size according to the service data volume.

Further, before dynamically establishing an SNR-TbSize-PSR corresponding table, a sending end and a receiving end are powered on, the SNR-TbSize table is imported into the SNR-TbSize-PSR table, PSR in the SNR-TbSize-PSR corresponding to the SNR-TbSize-PSR is set to be 100%, and PSR of other transmission blocks is set to be 0%; and the sending end starts a Tidle timer every time the sending end receives the feedback information from the receiving end.

Further, the step S1 specifically includes: in the time interval of the Tidle, no data burst is sent between the sending end and the receiving end, and the effective SNR between the sending end and the receiving end is unknown by the default sending end at the moment; if the sending end needs to send the data block, the sending end selects the size suitable for the transmission block to transmit according to the service data volume; if the transmission data volume is TbSize _ data and the TbSize _ m is not less than the TbSize _ data and not more than the TbSize _ m +1, selecting the size of a transmission block as TbSize _ m +1, and if the transmission data block is less than the minimum transmission block, selecting the minimum transmission block; and if the sending data block is larger than the maximum transmission block, selecting the maximum transmission block.

Further, the step S2 specifically includes: the receiving end detects that the sending end sends a data packet (packet), and the data packet also becomes a burst on a wireless air interface; the receiving end measures the signal-to-noise ratio (SNR) of the burst, analyzes the burst to obtain a data block, and judges whether the data block is received correctly; and then, the SNR and the indication whether the data block is correctly received are replied to the transmitting end through an acknowledgement packet/non-acknowledgement packet.

Further, the step S3 specifically includes: the sending end receives the confirmation packet/non-confirmation packet to analyze SNR and whether to correctly receive the indication, then selects the size of the TbSize _ m +1 transmission block when combining the sending end to send, counts the success rate of sending the TbSize _ m +1 by the sending end in the SNR range, and modifies the SNR-TbSize-PSR table.

Further, the step S4 specifically includes: if the sending end receives the non-confirmation indication (the receiving end indicates that the receiving is incorrect), retransmitting the data block, and if the sending end receives the confirmation indication (the receiving end indicates that the receiving is correct), newly transmitting the data; whether the data is newly transmitted or retransmitted, the transmitting end selects the transmission block with the largest success rate for transmission according to the SNR value.

The invention has the beneficial effects that:

1) in the wireless transmission system of the internet of things, in order to provide wireless resource utilization and transmission success rate, the size of a data block (transport block size) that can be transmitted is classified into several levels. In the past, the internet of things system basically selects the size of a corresponding transmission block according to the service data volume for transmission. The method can basically meet the requirements, but in some internet of things systems, application scenes are complex, interference is serious, and spectrum resources are not shared independently, so that the transmission success rate is low. The invention provides that the transmission block with the highest transmission success rate is selected for transmission each time by referring to the SNR value on the communication line and the success rate of the size of each transmission block.

2) The method needs to establish an SNR-TbSize table before using the Automatic Modulation Coding (AMC) technology used by the public network system, and a sending end can select the transmission size and the modulation mode according to the SNR value. The method is widely applied to 3G/4G and 5G systems, but the SNR-TbSize corresponding table used by the method is fixed and cannot be automatically adjusted according to actual scenes, and the SNR-TbSize value cannot be corrected according to the environment because the terminal moves, but in some scenes of the Internet of things system, the position of a communication terminal is relatively fixed, and the terminal can automatically adjust the SNR-TbSize relation table only meeting the current scene according to the application environment.

3) The invention provides a scheme for recording SNR (signal to noise ratio) values of past transmission and transmission result states, generating an SNR-TbSize-PSR (Power ratio transmission ratio-maximum transmission ratio-minimum transmission ratio) table, and then selecting the transmission size with the highest success rate for transmission according to the effective SNR value, thereby improving the transmission success rate.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the means of the instrumentalities and combinations particularly pointed out hereinafter.

Drawings

For the purposes of promoting a better understanding of the objects, aspects and advantages of the invention, reference will now be made to the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a flow chart of automatic modulation and coding in a public network system;

FIG. 2 is a flow chart of a CSMA transmission mode in an Internet of things system;

FIG. 3 is a flow chart of a general transport block size selection method;

FIG. 4 is a block diagram illustrating the generation and use of a dynamic SNR and transport block size table in accordance with the present invention;

FIG. 5 is a flow chart of the present invention for dynamically establishing SNR and transport block size correspondence;

fig. 6 is a flow of dynamically establishing a SNR and transport block size correspondence table in an exemplary embodiment.

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention in a schematic way, and the features in the following embodiments and examples may be combined with each other without conflict.

The broadband wireless micropower power meter reading system is a typical Internet of things application system, uses a public frequency band of 470MHz to 510MHz, belongs to ISM frequency bands, namely Industrial (Industrial), Scientific (Scientific) and Medical (Medical), and is applied to the frequency bands without license or cost according to the requirements of the national wireless committee, only certain transmitting power (generally lower than 1W) needs to be observed, and interference to other frequency bands is avoided, and the frequency band is mainly used for frequency modulation, broadband wireless micropower power meter reading, LoRa system and the like in China.

In addition, in the application of electric power meter reading, the electric meter is usually placed in a hidden place, mainly in a corridor, a basement and the like, and the use scene is complicated. In general, the signal quality of the scenes is poor, multipath and diffraction are serious, and the scenes are often subjected to power line radiation and the like, so that the power meter reading has high requirements on communication in the application of the internet of things, and a universal channel model is difficult to find.

In order to adapt to complex environment and meet the requirement of electric power meter reading data transmission, the system adopts a Chirp modulation mode, the working frequency range is 470MHz to 510MHz, and the modulation bandwidth is supported to be 3.6MHz and various modulation rates. In the Chirp modulation system, the modulation performance is usually expressed by using a time bandwidth product (TxB, product of Chirp symbol time and Chirp modulation bandwidth). In this embodiment, it is assumed that the supported modulation bandwidth is 4MHz (where 400KHz is the bandwidth guard interval, and the actual modulation bandwidth is 3.6MHz), and the supported SNR and modulation rate table corresponds to a table (SNR-chirp table), which is obtained by using system simulation in the system development stage, as shown in table 1.

Table 1: chirp modulation rate table (SNR-ChirpRate table)

In this embodiment, the supported transport block size is divided into a plurality of levels as defined in table 2.

Table 2: transport block size table

According to the requirements of the invention, in the standard preparation and development stage, firstly on a system simulation platform, in an AWGN environment, the signal is subjected to noise addition, continuous SNR simulation is performed on different TbSize, a turning point with 10% of block error rate is obtained, and the SNR value of the point is recorded. On the basis of simulation, a common actual scene is selected for testing, theoretical simulation results are corrected, and an SNR and TbSize correspondence table which basically meets the actual scene is obtained, and is shown in a table 3.

TABLE 3 initial SNR-TbSize correspondence table in electric power meter reading

Transport block size number (TbSize _ no)	Transmission block size (TbSize)	SNR value
			0	16	PSR16
1	72	PSR72
			2	136	PSR136
3	264	PSR264
			4	520	PSR520

Then, according to a simulation and actual measurement table, the SNR is divided into a plurality of grades to be processed, and the SNR is smaller than the SNR16, and corresponds to a transmission block with 16 bytes of TbSize; the signal-to-noise ratio corresponds to a transport block with TbSize of 72 bytes between SNR72_ down and SNR72_ up; the signal-to-noise ratio corresponds to a transport block with TbSize of 136 bytes between SNR136_ down and SNR136_ up; the signal-to-noise ratio corresponds to a transport block with TbSize of 264 bytes between SNR264_ down and SNR264_ up; signal to noise ratio greater than SNR520 corresponds to a transport block with TbSize of 520 bytes as shown in table 4.

TABLE 4 SNR-TbSize correspondence table of electric power meter reading system

Introduction above, in the present embodiment, the method of generating the SNR-TbSize table further needs to be converted into the SNR-TbSize-PSR table at the time of starting power-up of the device according to the description of the present invention. When the SNR-TbSize table is imported into the SNR-TbSize-PSR table, the TbSize success rate corresponding to the SNR is set to be 100%, and the other is set to be 0. As shown in table 5.

TABLE 5 SNR-TbSize-PSR corresponding table in power meter reading system

The SNR-TbSize-PSR correspondence table plays a key role in selecting the transmission size by the transmitting end. How to modify and use the SNR-TbSize-PSR correspondence table is described in detail below, as shown in fig. 6.

Step 1: the power equipment node needs to send a meter reading data packet or a signaling data packet, and if the length of the meter reading data packet is 245 bytes, the equipment selects the size of a transmission block to be 264 bytes according to the requirements of the invention, and the serial number of the size of the transmission block TbSize _ no is 3. Then, the transmission block is processed according to the physical channel coding and decoding requirements in the broadband wireless micro-power system, synchronous preambles are added, and physical layer signaling forms a complete frame data packet. And finally, transmitting the transmission block in a burst data packet mode in the air by adopting a Chirp modulation mode.

Selecting a Chirp modulation rate, preferentially selecting the SNR with the highest transmission success rate corresponding to the size of the transmission block according to the selection result of the size of the transmission block, and then selecting a corresponding Chirp modulation rate parameter according to the SNR. Such as shown in table 7. Assuming that the size of the selected transport block is 264 bytes, a success rate record of searching all the transport blocks for the length of 264 bytes is sent, and an SNR value with the highest success rate is selected. And then according to the SNR value and the content in the lookup table 1, finding out a corresponding Chirp modulation rate, and determining that the rate is the Chirp modulation rate used by the first transmission block. As in step 1 of fig. 6.

Step 2: and the receiving end carries out burst detection at an air interface, receives the burst data if a valid burst is detected, analyzes the data of the transmission block in the burst by using the preamble and the physical layer signaling content, and measures the SNR value of the data. And carrying out physical layer channel analysis on the data of the transmission block, and checking whether the cyclic check is correct or not. If correct, it indicates confirmation, and if false, it indicates non-confirmation. As shown in steps 2, 3 and 4 in fig. 6.

And step 3: the receiving end feeds back to the transmitting end according to the result of receiving the burst, i.e. the measured SNR value and whether the indication is received correctly, as in step 5 in fig. 6.

And 4, step 4: and the sending end modifies the SNR-TbSize-PSR table according to the feedback information of the receiving end, assumes that the fed back signal-to-noise ratio is SNR _ packet and correctly receives the signal, increases 1 for the total number of TbSize successes and the number of successes in the SNR range corresponding to the SNR-TbSize-PSR table, and then calculates the value of the success ratio PSR. If the receiving end can not receive correctly, the total number of successful TbSize is increased by 1, and the number of successful times is decreased by 1 (if the number of successful times is 0, the number is kept to be 0).

Assuming that the SNR value fed back by the receiving end is SNR _ packet, which is between SNR72_ down and SNR72_ up, TbSize _ no selected at the time of the transmission sent by the sending end is 3 (transport block 264 byte size), and the reception is correct, the SNR-Tbize-PSR table is modified, as shown in table 6. The total number of TbSize transmission size 264 bytes corresponding to the original SNR range [ SNR72_ down, SNR72_ up ] is modified from 10 to 11, the number of successes 0 to 1, and then the PSR value is calculated. As shown in step 6 of fig. 6.

SNR-TbSize-PSR dynamic correspondence table in meter 6 electric meter reading

The sending end starts a T each time it receives the feedback information from the receiving end_idleA timer, which in this embodiment is set to 10 seconds. T is_idleDuring the timer starting period, the sending end can use the SNR value fed back by the receiving end to select the size of the transport block. If T_idleIf the timer is overtime, the sending end considers that the SNR fed back by the receiving end is invalid, the SNR value cannot be referred to when the transmission size is selected, and the transmission size can only be selected according to the method in the step 1.

And 5: at T_idleAnd during the starting period of the timer, the sending end continuously sends the next data block, and then selects the transmission block with the maximum sending success rate and the Chirp modulation rate according to the SNR value in the received confirmation/non-confirmation packet. Suppose that after a certain period of time, [ SNR72_ down, SNR72_ up ] in the SNR-TbSize-PSR table]Modified to the contents of table 7.

TABLE 7SNR-TbSize-PSR results of SNR transmissions between SNR72_ down to SNR72_ up

If the SNR of the received signal fed back by the receiving end is between [ SNR72_ down, SNR72_ up ] in table 8, when the transmitting end selects the size of the transport block, the transmitting end preferentially selects the size of the transport block with the largest success rate for transmission, that is, selects TbSize _ no equal to 3, and the transmission size is 264 bytes long. If the SNR is greater than or equal to SNR-1200K in Table 1, then 1200Kbps modulation rate is selected. As shown in step 7 of fig. 6.

Finally, the above embodiments are only intended to illustrate the technical solutions of the present invention and not to limit the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions, and all of them should be covered by the claims of the present invention.

Claims

1. A method for selecting the size of a transmission data block in an Internet of things system is characterized by comprising the following steps:

2. The method according to claim 1, wherein before dynamically establishing the SNR-TbSize-PSR mapping table, the method first powers on a transmitting end and a receiving end, imports the SNR-TbSize table into the SNR-TbSize-PSR table, sets PSRs in the SNR-TbSize table corresponding to the SNR-TbSize-PSRs to 100%, and sets PSRs of other transmission blocks to 0%; the sending end starts a T each time it receives the feedback information from the receiving end_idleA timer.

3. The method as claimed in claim 2, wherein the step S1 is specifically executed in the method for selecting the size of the data block to be transmitted in the internet of things systemThe method comprises the following steps: at interval T_idleIn time, no data burst is sent between the sending end and the receiving end, and the effective SNR between the sending end and the receiving end is unknown by the default sending end at the moment; if the sending end needs to send the data block, the sending end selects the size suitable for the transmission block to transmit according to the service data volume; if the transmission data volume is TbSize _ data and the TbSize _ m is not less than the TbSize _ data and not more than the TbSize _ m +1, selecting the size of a transmission block as TbSize _ m +1, and if the transmission data block is less than the minimum transmission block, selecting the minimum transmission block; and if the sending data block is larger than the maximum transmission block, selecting the maximum transmission block.

4. The method for selecting the size of the data block to be transmitted in the internet of things system according to claim 3, wherein the step S2 specifically includes: the receiving end detects that the sending end sends a data packet and becomes a burst on a wireless air interface; the receiving end measures the signal-to-noise ratio of the burst, analyzes the burst to obtain a data block, and judges whether the data block is received correctly; and then, the SNR and the indication whether the data block is correctly received are replied to the transmitting end through an acknowledgement packet/non-acknowledgement packet.

5. The method for selecting the size of the data block to be transmitted in the internet of things system according to claim 4, wherein the step S3 specifically includes: the sending end receives the confirmation packet/non-confirmation packet to analyze SNR and whether to correctly receive the indication, then selects the size of the TbSize _ m +1 transmission block when combining the sending end to send, counts the success rate of sending the TbSize _ m +1 by the sending end in the SNR range, and modifies the SNR-TbSize-PSR table.

6. The method for selecting the size of the data block to be transmitted in the internet of things system according to claim 5, wherein the step S4 specifically includes: if the sending end receives the non-confirmation indication, the data block is retransmitted, and if the sending end receives the confirmation indication, the data is newly transmitted; whether the data is newly transmitted or retransmitted, the transmitting end selects the transmission block with the largest success rate for transmission according to the SNR value.