CN104579467A - Frame positioning method for free space optical communication - Google Patents
Frame positioning method for free space optical communication Download PDFInfo
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- CN104579467A CN104579467A CN201410725719.1A CN201410725719A CN104579467A CN 104579467 A CN104579467 A CN 104579467A CN 201410725719 A CN201410725719 A CN 201410725719A CN 104579467 A CN104579467 A CN 104579467A
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Abstract
The invention discloses a frame positioning method for free space optical communication. The method comprises the following steps: differentiating information about 0 and 1 by utilizing brightness and darkness luminance by means of light intensity modulation after signal sources are subjected to serial coding and emitting by array light sources; receiving the array light sources by virtue of a two-dimensional dot-matrix photoelectric detector through diffuse reflection of free space and acquiring two-dimensional light information data through an embedded processor in accordance with Nyquist velocity, namely two folds of emission array velocity; scanning the two-dimensional light information data by virtue of the embedded processor in a transverse direction and a longitudinal direction, recording luminance numeric values of all points, and detecting whether the input data includes the data identical to a preset positioning frame rule namely positioning frame byte length and byte bit information; searching the identical data and using the data as data frame heads if the input data includes the data identical to a preset positioning frame rule namely positioning frame byte length and byte bit information; abandoning the input data if the input data does not include the identical data. According to the frame positioning method, positioning frames can be quickly scanned under a condition that a receiving end moves, and the information under the positioning frames is acquired, so that the synchronization of the data of all points in one frame can be guaranteed, and the frame synchronization function of the receiving end and a sending end is realized.
Description
Technical field
The present invention relates to a kind of method of the frame alignment for free space optical communication, for receiving terminal in the case of movement, still can fast searching to the method for information source, locator data frame head, improve traffic rate and the reliability of communication system greatly.
Background technology
Free space optical communication FSO (Free Space Optics), also known as light wireless communication.FSO utilizes the light beam of high concentration to pass through the transport vehicle of airspace as information.In free space, the spectrum of transmission light can be divided into infrared spectrum (100um ~ 700nm), visible spectrum (700nm ~ 400nm) and ultraviolet spectra (400nm ~ 1nm).A radio optical communication system comprises three essential parts: optical transmitter, optical receiver, optical antenna and light path system.When point-to-point transmission, every one end is all provided with optical sender and optical receiver, can realize full-duplex communication.The light source of optical sender is subject to the modulation of the signal of telecommunication, by the optical transmitting system as antenna, light signal is sent to receiver telescope by atmospheric channel; Receiver telescope is collected and is received light signal and focus in photoelectric detector by it, and photoelectric detector converts light signal to the signal of telecommunication.Because the transmitance of airspace to Different lightwave long letter number has larger difference, radio optical communication system generally selects the good wave band window of transmitance, and the most frequently used optical wavelength is the 850nm near infrared spectrum; Also have some radio optical communication systems to use 1500nm wavelength band, larger system power can be supported.
FSO technology has the following advantages compared with other access technologies: (1) frequency spectrum resource enriches, without the need to the demand frequency right to use; (2) bandwidth, speed is high; (3) protocol transparent; (4) rapid link is disposed; (5) level security is strong; (6) transfer of data not easily blocks; (7) can reuse.Therefore, it can play a significant role in fields such as mobile radio communication, enterprise network, metropolitan area networks; The optical fiber communication can interrupted as prevention service and the backup of microwave communication; Construction and " last one kilometer " access of interconnection, the closely High Speed Network of asking mobile communication base station can be applied to; Or build in should not connect up, difficulty of construction is large, across places such as river cross a river mines; The occasion holded in close confidence is needed for military installations or other key departments; And intranet interconnects and transfer of data.
FSO is with its capacity, environmental protection, the advantage such as flexible, and receive the concern of lot of domestic and foreign researcher, range of application constantly expands.This commercial type systematic, capacity is from 100Mbps ~ 110Gbps.Also some tests are had to adopt wavelength division multiplexing to reach the speed of 160Gbps.Although be subject to the restriction of meteorological condition, can only use in shorter distance, be generally limited to below 4km.But under many occasions, as a kind of mode of uniqueness, FSO becomes the current existing good means of supplementing out economy of several broadband access method.
Summary of the invention
Technical problem: the technical problem to be solved in the present invention is for receiving terminal provides a kind of frame alignment method for free space optical communication based on light carrier (infrared light, visible ray, ultraviolet light) radio communication when free space moves, can rapidly locating frame head, improve communication reliability.
Technical scheme: for solving the problems of the technologies described above, the present invention is achieved by the following technical solutions:
The free-space optical communication system that this frame alignment method adopts comprises transmitting terminal and receiving terminal, and described transmitting terminal comprises information source, deserializer, light source driving circuit, two-dimensional points configuration light source successively; Described receiving terminal comprises two-dimensional points configuration photoelectric detector, Embedded Processor, parallel-serial conversion, the stay of two nights successively;
When information source is after sequence encodes, adopt light intensity modulation mode, distinguish 0,1 information with brightness " bright ", " secretly ", launched by array light source;
Array light source by being received by two-dimensional points configuration photoelectric detector after the diffuse reflection of free space, and gathers two-dimentional optical information data by Embedded Processor according to the Nyquist rate i.e. emission array speed of 2 times;
Embedded Processor scans two-dimentional optical information data from transverse direction, longitudinal direction respectively, and record the brightness numerical value of each point, detect in input data and whether comprise and preset locating frame rule and locating frame byte length, data that byte bit information is identical, if so, these identical data are found out and as data frame head; If not, then these input data are abandoned.
Described frame alignment process is as follows:
When transmitting terminal is launched after a frame contains the array information of locating frame, arrive receiving terminal through free space, complete opto-electronic conversion by array-based photodetector and recover the signal of telecommunication, then by Embedded Processor scanning array each point magnitude of voltage V
i, and with the decay be pre-stored in processor after voltage range V
min, V
maxmake comparisons, remove the interference of redundancy light; Get minimum and maximum magnitude of voltage V
max, V
minaverage V
averageas threshold value, note is greater than V
averagefor bit symbol " 0 ", be less than V
averagefor bit symbol " 1 "; Successively, pair array each point V
iadjudicate, obtain inputting data;
Whether Embedded Processor, to input data rapid scanning, detects in input data and comprises and preset locating frame byte length, data that byte bit information is identical, if so, finds out these identical data and as data frame head; If not, then these input data are abandoned;
Receiving terminal continuous sweep input data, until locating frame detected, identify the beginning of frame, even if when receiving terminal moves, also can rapid scanning to locating frame, ensure that data in a frame can errorless being resumed and detecting simultaneously, thus achieve the object of sending and receiving end frame synchronization; In addition, while guarantee frame synchronization, also inhibits the impact that in frame data, intersymbol is harassed.
Described frame synchronization proposes a kind of locating frame on the basis of Array transfer, and when receiving terminal scans locating frame, namely defining this frame is data frame head, and recovers the array information under this data frame head, achieves the frame synchronization of transmitting terminal and receiving terminal.
Described locating frame is a string particular bit or special graph structure, and random length frame, frame length is determined by emission array size.
Described locating frame be positioned at emission array first trip or four edges long, or be arranged in emission array with special graph structure.
Beneficial effect: the present invention adopts array emitter, array received structure, improves system communication capacity greatly.
The present invention can when receiving terminal moves, and rapid scanning, to locating frame, obtains the information under this locating frame, ensures the synchronous of each point data in a frame, realizes the function of sending and receiving end frame synchronization.
The present invention ensures that intraframe data synchronously receives, and inhibits the intersymbol interference in frame data, improves communication reliability.
The present invention, without complex mechanical equipment, effectively utilizes existing intelligent software, and combination algorithm module expansion existing capability, reduces expending of hardware resource.
Accompanying drawing explanation
Fig. 1 is array emitter of the present invention, array received architecture system block diagram.
Fig. 2 is transmitter one frame of data information schematic diagram of the present invention.
Fig. 3 is locating frame schematic diagram of the present invention.
Fig. 4 is free-space optical communication system flow chart of the present invention.
Embodiment
A kind of free-space optical communication system proposed in the present invention comprises transmitting terminal and receiving terminal, and described transmitting terminal comprises information source, deserializer, light source driving circuit, two-dimensional points configuration light source successively; Described receiving terminal comprises two-dimensional points configuration photoelectric detector, Embedded Processor, parallel-serial conversion, the stay of two nights successively.
As can be seen from the free-space optical communication system that the present invention proposes, when information source is after sequence encodes, adopt light intensity modulation mode, 0,1 information is distinguished with brightness " bright ", " secretly ", launched by array light source, again through array detection, the parallel communications of transmission array pair array can be formed, realize the function of space division multiplexing.In addition, this array structure can merge the ACT of multiple maturation in one, as the reliability and the confidentiality that adopt pattern-coding communication then can improve communication.
The present invention proposes a kind of locating frame on the basis of above-mentioned Array transfer, and when receiving terminal scans locating frame, namely defining this frame is data frame head, and recovers the array information under this data frame head, achieves the frame synchronization of transmitting terminal and receiving terminal.
Locating frame in the present invention is a string particular bit or special graph structure, and random length frame, frame length is determined by emission array size.
Locating frame in the present invention be positioned at emission array first trip or four edges long, or be arranged in emission array with special graph structure.
Frame alignment process in the present invention is as follows:
When transmitting terminal is launched after a frame contains the array information of locating frame, arrive receiving terminal through free space, complete opto-electronic conversion by array-based photodetector and recover the signal of telecommunication, then by Embedded Processor scanning array each point magnitude of voltage V
i, and with the decay be pre-stored in processor after voltage range (V
min, V
max) make comparisons, remove the interference of redundancy light.Get minimum and maximum magnitude of voltage V
max, V
minaverage V
averageas threshold value, note is greater than V
averagefor bit symbol " 0 ", be less than V
averagefor bit symbol " 1 ".Successively, pair array each point V
iadjudicate, obtain inputting data.
Embedded Processor, to input data rapid scanning, detects in input data whether comprise the data identical with preset locating frame rule (locating frame byte length, byte bit information), if so, finds out these identical data and as data frame head; If not, then these input data are abandoned.
In the present invention, receiving terminal continuous sweep input data, until locating frame detected, identify the beginning of frame.Even if when receiving terminal moves, also can rapid scanning to locating frame, ensure that data in a frame can errorless being resumed and detecting simultaneously, thus achieve the object of sending and receiving end frame synchronization.In addition, while guarantee frame synchronization, also inhibits the impact that in frame data, intersymbol is harassed.
By the method for frame alignment provided by the invention, the repeat decoding computing existed in prior art can be reduced.This is because the receiving terminal in the present invention is only after scanning locating frame, just can orients data frame head, then start computing of decoding, if do not scan locating frame, can not decode, continue scanning, spent hardware resource can be reduced like this.
The following drawings illustrate embodiment of the present invention.
Namely array emitter, the array received architecture system block diagram of Fig. 1 illustrate N in free space
t* N
tthe process of road parallel light signal array transmission.Transmitter adopts two-dimensional points configuration light source (light source kind will not limit), light intensity modulation.Receiver adopts two-dimensional points configuration N
r* N
rindividual photodetector array, direct-detection mode, corresponding with transmitter, each road signal of transmitter can be detected in order to ensure receiver, must N be ensured
r>N
t.
Fig. 2 is transmitter one frame N
t* N
tcircuit-switched data information schematic diagram, distinguish Binary Zero, 1 information with brightness " bright ", " secretly ", in figure, white round dot represents light-source brightness " bright " i.e. bit " 0 ", and black round dot represents light-source brightness " secretly " i.e. bit " 1 ".Be modulated on each point-source of light by computer control by information source, each point-source of light carries different information, transmitted in parallel data, then a frame transmission array carries (N
t* N
t) bits data.
At this (N
t* N
t) in bits information, contain the location overhead section of (1*n) bits, i.e. locating frame, be arranged in Fig. 2 first trip (byte length of locating frame, position are not limited to the first trip of the present embodiment).Locating frame is made up of particular bit, does not carry any valid data information, is considered as locating expense, the position of flag data frame head.
Fig. 3 is the schematic diagram of locating frame of the present invention, frame length 2 byte, byte content " 1010101010101010 " bit.It is exactly light and dark structure that locating frame is shown by light source on the transmitter, and this structure is easy to detect at receiving terminal, and in valid data byte, there will not be this kind of combination, therefore locating frame can not collide with data message.Locating frame of the present invention is not limited to Fig. 3 structure, and meet mutually not overlapping with data byte bit requirement, can be compound mode or the special graph structure of other particular bit, frame length limit.
The free-space optical communication system flow chart of Fig. 4 describes information source (binary bit stream) and (supposes that transmitter point-source of light number is N according to the size of transmitter under the control of the computer
t* N
t), serial data stream is divided into N
t* N
tchannel parallel data, by light source driving circuit, launches N in light intensity modulation mode simultaneously
t* N
tindividual parallel light signal.
Transmitter send parallel data after free space transmission, arrive receiver, receiver in direct-detection mode to N
t* N
tindividual parallel light signal carries out opto-electronic conversion and obtains the signal of telecommunication.Each road signal V is scanned by Embedded Processor
i, and with the decay be pre-stored in processor after voltage range (V
min, V
max) make comparisons, remove the interference of redundancy light.Get minimum and maximum magnitude of voltage V
max, V
minaverage V
averageas threshold value, note is greater than V
averagefor bit symbol " 0 ", be less than V
averagefor bit symbol " 1 ".Successively, pair array each point V
iadjudicate, obtain N
r* N
rindividual parallel input data.
Embedded Processor is to N
r* N
rindividual parallel input data carries out horizontal, longitudinal scanning fast, detect in input data and whether comprise the bit identical with preset locating frame rule (locating frame byte length, byte bit information), if not, then abandon this frame input data, continue scanning next frame input data, until search out " 1010101010101010 " locating frame as Fig. 3 shows, namely navigate to data frame head.
After navigating to data frame head, the valid data information that computer will receive under this data frame head, carries out parallel-serial conversion, recovers raw information (stay of two nights).
The present invention lays special stress on protecting in free-space optical communication system with the method for the frame alignment of array structure transmission information.This method ensure that the frame synchronization of sending and receiving end, suppresses the intersymbol interference in frame data, reduces repeat decoding operation times, reduces hardware resource loss.
The method for application that the present invention proposes is extensive, military affairs, medical treatment, mine, under water, space, indoor, intelligent transportation, each field such as " last one kilometer " wireless light communication technology can apply, algorithm is flexible, expense is few, greatly improves validity and the reliability of communication system.
Claims (5)
1. the frame alignment method for free space optical communication, it is characterized in that the free-space optical communication system that this frame alignment method adopts comprises transmitting terminal and receiving terminal, described transmitting terminal comprises information source, deserializer, light source driving circuit, two-dimensional points configuration light source successively; Described receiving terminal comprises two-dimensional points configuration photoelectric detector, Embedded Processor, parallel-serial conversion, the stay of two nights successively;
When information source is after sequence encodes, adopt light intensity modulation mode, distinguish 0,1 information with brightness " bright ", " secretly ", launched by array light source;
Array light source by being received by two-dimensional points configuration photoelectric detector after the diffuse reflection of free space, and gathers two-dimentional optical information data by Embedded Processor according to the Nyquist rate i.e. emission array speed of 2 times;
Embedded Processor scans two-dimentional optical information data from transverse direction, longitudinal direction respectively, and record the brightness numerical value of each point, detect in input data and whether comprise and preset locating frame rule and locating frame byte length, data that byte bit information is identical, if so, these identical data are found out and as data frame head; If not, then these input data are abandoned.
2. a kind of frame alignment method for free space optical communication according to claim 1, is characterized in that described frame alignment process is as follows:
When transmitting terminal is launched after a frame contains the array information of locating frame, arrive receiving terminal through free space, complete opto-electronic conversion by array-based photodetector and recover the signal of telecommunication, then by Embedded Processor scanning array each point magnitude of voltage V
i, and with the decay be pre-stored in processor after voltage range V
min, V
maxmake comparisons, remove the interference of redundancy light; Get minimum and maximum magnitude of voltage V
max, V
minaverage V
averageas threshold value, note is greater than V
averagefor bit symbol " 0 ", be less than V
averagefor bit symbol " 1 "; Successively, pair array each point V
iadjudicate, obtain inputting data;
Whether Embedded Processor, to input data rapid scanning, detects in input data and comprises and preset locating frame byte length, data that byte bit information is identical, if so, finds out these identical data and as data frame head; If not, then these input data are abandoned;
Receiving terminal continuous sweep input data, until locating frame detected, identify the beginning of frame, even if when receiving terminal moves, also can rapid scanning to locating frame, ensure that data in a frame can errorless being resumed and detecting simultaneously, thus achieve the object of sending and receiving end frame synchronization; In addition, while guarantee frame synchronization, also inhibits the impact that in frame data, intersymbol is harassed.
3. a kind of frame alignment method for free space optical communication according to claim 2, it is characterized in that described frame synchronization proposes a kind of locating frame on the basis of Array transfer, when receiving terminal scans locating frame, namely defining this frame is data frame head, and the array information recovered under this data frame head, achieve the frame synchronization of transmitting terminal and receiving terminal.
4. a kind of frame alignment method for free space optical communication according to claim 2, it is characterized in that described locating frame is a string particular bit or special graph structure, random length frame, frame length is determined by emission array size.
5. a kind of frame alignment method for free space optical communication according to claim 2, it is characterized in that described locating frame be positioned at emission array first trip or four edges long, or be arranged in emission array with special graph structure.
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| CN109474348A (en) * | 2018-11-29 | 2019-03-15 | 南京邮电大学 | The calculation method of optical antenna for wireless light communication parallel transmission system |
| CN113093105A (en) * | 2021-04-09 | 2021-07-09 | 中国人民解放军战略支援部队信息工程大学 | Visible light indoor positioning method, device and system and related products |
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| CN109474348A (en) * | 2018-11-29 | 2019-03-15 | 南京邮电大学 | The calculation method of optical antenna for wireless light communication parallel transmission system |
| CN113093105A (en) * | 2021-04-09 | 2021-07-09 | 中国人民解放军战略支援部队信息工程大学 | Visible light indoor positioning method, device and system and related products |
| CN113093105B (en) * | 2021-04-09 | 2023-09-12 | 中国人民解放军战略支援部队信息工程大学 | Visible light indoor positioning method, device and system and related products |
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| CN104579467B (en) | 2017-02-22 |
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