CN103888458A - Point-to-point wireless transmission optimization method based on USRP N200 - Google Patents
Point-to-point wireless transmission optimization method based on USRP N200 Download PDFInfo
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- CN103888458A CN103888458A CN201410104725.5A CN201410104725A CN103888458A CN 103888458 A CN103888458 A CN 103888458A CN 201410104725 A CN201410104725 A CN 201410104725A CN 103888458 A CN103888458 A CN 103888458A
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Abstract
The invention discloses a point-to-point wireless transmission optimization method based on the USRP N200. By optimizing the data frame structure, the accuracy of software radio point-to-point communication is increased. By regulating an information source and data frames, while the maximum processing rate of the USRP N200 is achieved through transmission, multiple formats of files with unlimited sizes can be transmitted. The practicality of the transmission needs to be guaranteed through stable reliability. Considering that the stability of a channel in the early stage of establishment cannot be guaranteed, the transmission process is modified in order to improve the reliability of the transmission. Random bit stream and lead codes are added when receiving starts and ends, many times of verification is performed, and thus the reliability is remarkably improved.
Description
Technical field
The present invention relates to a kind of transmission of the point-to-point wireless based on USRP N200 and realize prioritization scheme, belong to software radio information transmission technology field.
Background technology
When the fast development of wireless communication technology brings convenience to people life, due to multiple communication system and deposit, communication standard emerges in an endless stream the compatibility and the succession that realize different communication systems caused to difficulty.Distinct communication standards has limited intercommunication and the compatibility of various hardware devices because radio frequency carrier frequency is different with modulation system, caused unnecessary overlapping investment and the wasting of resources.And software and radio technique (SDR) can fundamentally address these problems.Its basic thought is taking general a, standard, modular hardware platform as support, realize range radio communication function (as working frequency range, modulation /demodulation type, data format, encryption mode and communication protocol etc.) by Bootload, its core is: concentrate and use wideband A/D, D/A converter and be positioned as close to antenna; Radio function is realized by software as much as possible, is new change the again that hardware transforms to software.All radio station are all based on same general hardware platform, by different software modules is installed, utilize software upgrading or version to alternate to realize the compatibility between update and the old and new radio station of communication equipment, to reach intercommunication.
The existing source code benchmark of GNURadio3.5.0 platform has realized the basic communication of two USRP terminals, can transmit some simple characters, and receiving terminal can detect and can demonstrate to transmitted signal the accepting state of packet in transmitting procedure, ' ok=True ' or ' ok=False ', corresponding being respectively receives correct and reception mistake, can add up accordingly the packet loss that obtains final transmission, with auxiliary judgement reception contrast properties.But existing source code cannot transmit the file not of uniform size such as text, picture, and cannot be applicable to larger file transfer.In addition, show through many experiments, its transmission stability cannot ensure, bad when laser propagation effect fashion, when serious, a series of packet loss phenomenon can occur, and is unfavorable for actual transmissions application.
Summary of the invention
Technical problem to be solved by this invention is: for the defect of prior art, provide a kind of transmission of the point-to-point wireless based on USRP N200 to realize optimization method, under software radio thought, traditional communication is realized by software programming on general hardware platform USRP N200, can select different codings or modulation system according to different communication environments, any frequency within the scope of the support of selection equipment carries out the communication between user as required, solved between each version of existing communication system can not be compatible problem, by optimization data frame structure, adjust sending mode, can reach the object that improves software radio point-to-point communication accuracy.
The present invention is for solving the problems of the technologies described above by the following technical solutions:
Point-to-point wireless transmission based on USRP N200 realizes an optimization method, and detailed process is as follows:
Step 1, the multimedia file data that needs are transmitted are converted into bit stream, and are further packaged into Frame, deliver to radio-frequency front-end and send after modulation; First radio-frequency front-end sends one group of irrelevant bit or VB vacancy bit, then sends leading code, after leading code is sent, starts to transmit the multi-medium data of required transmission;
Step 2, receiving terminal start when transfer of data detected to receive, but will not preserve for one group before leading code irrelevant bit or VB vacancy bit, and the multi-medium data sending after leading code is preserved;
Step 3, radio-frequency front-end are sent follow-up supervention in efficient multimedia data and send second group of irrelevant bit or VB vacancy bit, and receiving terminal also receives as usual simultaneously, but refuses writing in files, until receive.
As present invention further optimization scheme, the concrete grammar that in described step 1, the multimedia file data of needs transmission is converted into bit stream is as follows:
The open () instrument that use python provides is by file bit fluidisation, the size of the multimedia file data of transmitting as required at radio-frequency front-end is adjusted read () function parameter, add corresponding write () module at receiving terminal, call read () function and read in the multimedia file data that need to transmit and process.
As present invention further optimization scheme, the Frame that in described step 1, the packing of multimedia file data forms, its concrete structure comprises: preamble, access code, header, albefaction device, valid data, cyclic redundancy check (CRC) code and stop bits, wherein, described valid data comprise the package number information of multimedia file data message and the 2bytes of required transmission.
As present invention further optimization scheme, call read () function read in need transmission multimedia file data time, first described multimedia file is carried out to segmentation.
The present invention adopts above technical scheme compared with prior art, has following technique effect: in this programme, optimized data frame structure, improved data-transmission mode, effectively improved the reliability of system, can realize preferably the effectively correct transmission of data.
Brief description of the drawings
Fig. 1 is USRP terminal transmitting terminal multi-medium data transmission flow figure.
Fig. 2 is that USRP terminal receiving terminal multi-medium data receives flow chart.
Fig. 3 is data frame format schematic diagram in the present invention.
Fig. 4 is system block diagram of the present invention.
Embodiment
The present invention relates to software radio, using under the prerequisite of software radio, by optimization data frame structure, improve the accuracy of software radio point-to-point communication.To the adjustment of information source and Frame, make transmission in meeting the maximum processing speed of USRP N200, realize the transmission of the big or small multiple format file not limiting.The practicality of transmission needs stable reliability as guarantee.Considering that channel sets up primary stability and cannot ensure, is to improve transmission reliability, and the present invention revises transmitting procedure.In the time receiving beginning and finish, added random bit stream and lead code, through multiple authentication, reliability is significantly improved.
Below in conjunction with accompanying drawing, technical scheme of the present invention is described in further detail:
Communicating pair identical frequency with under code check, can carry out transfer of data and communicate by letter.USRP terminal transmitting terminal multi-medium data transmission flow figure as shown in Figure 1, at transmitting terminal, thereby obtains bit stream by program to reading of multimedia file, and the data that read is packaged into Frame by data frame format requirement, delivers to radio-frequency front-end and send after modulation.Consider the maximum data length (in [0,4096] bits) that needs the file of transmission to support much larger than equipment, therefore, in the time file being read to processing, need to select rational length to carry out segmentation to file and read.Due to the unsteadiness of channel, inevitable time delay in transfer of data, may strengthen the packet loss in transmission in addition, and the correct effectively transmission to data and the recovery of file cause and have a strong impact on, and when serious, may cannot effectively accept file data completely.Find through practice, channel is least stable in the time that transmission starts and finish, and it is comparatively fierce to change, and packet loss when packet loss now can be much higher than stable transfer, therefore, has adopted certain processing means to effectively reduce this impact in invention.Before transmission valid data, the irrelevant bit of some or VB vacancy bit are delivered to radio-frequency front-end to be sent, this change is for the ingenious of short duration amphibolic stage of channel of avoiding, therefore do not need channel estimating, leading code plays synchronous effect here, informs that receiving terminal starts the multi-medium data for required transmission from leading code.To be sent when complete, channel is basicly stable, can start to transmit the multi-medium data of required transmission, and receiving terminal also can start to receive in the time detecting that this frequency has transfer of data, but irrelevant bit or VB vacancy bit for previous some will not be preserved (writing), but the valid data that after this send are preserved.The benefit of doing is like this sending after the hash of this some, and channel is relatively stable, and now the packet loss of system is relatively low, is conducive to effective transmission of data.
USRP terminal receiving terminal multi-medium data receives flow chart as shown in Figure 2, at receiving terminal, has same problem, while receiving, the characteristic of channel is unstable, and docking is knocked off and impacted, therefore, similarly also need to do relevant treatment, to improve transmission accuracy.In the time that valid data receive, be not termination system at once, but allow transmitting terminal continue to send irrelevant bit stream, receiving terminal also receives as usual simultaneously, but refuses writing in files, in the time receiving, ordinary circumstance can effectively receive recovery original, receives accuracy and relatively increases.
In the present invention, as shown in Figure 3, functions is specific as follows for data frame format schematic diagram:
1. preamble (Preamble): length is 2bytes, realizes receiving-transmitting sides synchronous.
2. access code (Access Code): access code carries out related calculation for receiver, and length is 8bytes.Access code has been realized correlation capturing, when there is correlation peak, looks this packet for effectively wrapping, and ensuing bit stream is done to subsequent treatment.
3. header (Header): the length information that header comprises valid data (Payload) and cyclic check information, length is 4bytes.
4. albefaction device (Whitener Offset): albefaction device is the linear feedback shift register of 15, is used for albefaction Payload with prevention phase error.
5. valid data (Payload): the package number information that valid data comprise required transmitting data information and 2bytes.
6. cyclic redundancy check (CRC) code (CRC-32): the means of error detection, in data storage and data communication field, in order to ensure the correct of data, are just had to adopt in CRC check utility program storehouse.In many error detection means, CRC is foremost one.The full name of CRC is cyclic redundancy check (CRC), is characterized in: error detecing capability is extremely strong, and expense is little, is easy to realize with encoder and testing circuit.From its error detecing capability, it not the probability of detectable mistake be only below 0.0047%.Performance, consider with expense, be all far superior to the mode such as parity check and arithmetic sum verification.Thereby in data storage and data communication field, CRC is ubiquitous.
7. stop bits: stop bits taking ' x55' as mark.
The present invention improves to realize on the basis of the existing source code benchmark of gnuradio3.5.0 platform.Corresponding system block diagram as shown in Figure 2, improves as follows:
The first, the present invention is intended to realize the formatted files such as wireless transmission text, picture, needs first to convert file to bit stream and transmits as information source.Here we use the open () instrument that python provides to realize file bit fluidisation, then process in being read into system calling read () function.Consider that the each maximum treatable bit number of USRP N200 is 4096bits, therefore in the time that being set, read () function parameter can make the appropriate adjustments according to file size, for compared with large file, read bit number at every turn and can extend very little the overall transfer time, relatively large parameter should be set to shorten the transmission time, also this parameter should not be arranged excessively for less file, produce else if packet loss and easily cause losing bulk information and can not correctly recover original.Only need to add corresponding write () module at receiving terminal equally.
The second, many experiments demonstration, USRP equipment channel stability in initial and a bit of time of end are communicated by letter in foundation is poor, and packet loss is relatively high, and packet loss is continuous often.For the file compared with little, the packet loss can bear is also lower than large file, otherwise it is very difficult to recover original.In order to address the above problem, in design, add the lead code of some, lead code is made up of random bit stream and synchronous code, the data of random bit stream do not belong to Transmit message originally, therefore receiving end does not write after detecting and receiving and receives in file, and random bit stream part is set to full 0 herein.Synchronous code, for telling that the data that next receiving terminal receives are data of original, should write and receive in document.The benefit of processing is like this, the random bit stream that sends some can ingeniously avoid needing the data that send to produce too much packet loss, that is to say, although set up traffic channel immediately when bit stream packet loss serious, do not affect the next transmission of file, on the contrary, in the time of the random bit stream end of transmission, channel is basicly stable, is conducive to the correct reception of data.Equally, in the time sending end, people, for having added some random bit streams, changes suddenly to weaken or to eliminate channel the continual data package dropout phenomenon causing.Final practice shows that this scheme can ensure transmission reliability preferably.
By reference to the accompanying drawings embodiments of the present invention are explained in detail above, but the present invention is not limited to above-mentioned execution mode, in the ken possessing those of ordinary skill in the art, can also under the prerequisite that does not depart from aim of the present invention, makes a variety of changes.
Claims (4)
1. the transmission of the point-to-point wireless based on USRP N200 realizes an optimization method, it is characterized in that, detailed process is as follows:
Step 1, the multimedia file data that needs are transmitted are converted into bit stream, and are further packaged into Frame, deliver to radio-frequency front-end and send after modulation; First radio-frequency front-end sends one group of irrelevant bit or VB vacancy bit, then sends leading code, after leading code is sent, starts to transmit the multi-medium data of required transmission;
Step 2, receiving terminal start when transfer of data detected to receive, but will not preserve for one group before leading code irrelevant bit or VB vacancy bit, and the multi-medium data sending after leading code is preserved;
Step 3, radio-frequency front-end are sent follow-up supervention in efficient multimedia data and send second group of irrelevant bit or VB vacancy bit, and receiving terminal also receives as usual simultaneously, but refuses writing in files, until receive.
2. a kind of transmission of the point-to-point wireless based on USRP N200 as claimed in claim 1 realizes optimization method, it is characterized in that, the concrete grammar that in described step 1, the multimedia file data of needs transmission is converted into bit stream is as follows:
The open () instrument that use python provides is by file bit fluidisation, the size of the multimedia file data of transmitting as required at radio-frequency front-end is adjusted read () function parameter, add corresponding write () module at receiving terminal, call read () function and read in the multimedia file data that need to transmit and process.
3. a kind of transmission of the point-to-point wireless based on USRP N200 as claimed in claim 1 realizes optimization method, it is characterized in that, the Frame that in described step 1, the packing of multimedia file data forms, its concrete structure comprises: preamble, access code, header, albefaction device, valid data, cyclic redundancy check (CRC) code and stop bits, wherein, described valid data comprise the package number information of multimedia file data message and the 2bytes of required transmission.
4. a kind of point-to-point wireless based on USRP N200 transmission as claimed in claim 2 realizes optimization method, it is characterized in that: when calling read () function and reading in the multimedia file data that needs transmit, first described multimedia file is carried out to segmentation.
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| CN108233993A (en) * | 2017-01-22 | 2018-06-29 | 南京邮电大学 | Optimization method is realized in a kind of wireless relay transmission based on USRPN200 |
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| US20100207739A1 (en) * | 2003-11-07 | 2010-08-19 | John Stephen Smith | Methods and apparatuses to identify devices |
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