CN102420791B - Bit zone difference pulse position modulation method and device - Google Patents
Bit zone difference pulse position modulation method and device Download PDFInfo
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Abstract
The invention discloses a bit zone difference pulse position modulation method which comprises the following steps of: a, receiving data in a coder circuit, subdividing the data into ordered sequences of groups of M bit binary data; b, modulating each group of M bit binary data into three parts of signals, wherein the signals sequentially comprise 1, a start bit '1' time slot represented by one light pulse, 2, bit zone time slot, and 3, continuous '0' time slot; and c, sending the data according to the demodulated signal sequences. The invention also discloses a bit zone difference pulse position modulation device. According to the invention, bandwidth utilization rate of a light communication system can be effectively increased, and packet error rate is reduced.
Description
Technical field
The present invention relates to the wireless light communication field, particularly a kind of flag bit differential pulse position modulation method and modulating device.
Background technology
In recent years, along with deepening continuously and the fast development of wireless communication technology of marine field research work, the underwater wireless optical communication technique need not physical connection, supports that reasons such as mobile flexibility, fail safe height are paid attention to deeply that because of it its using value is also embodied in all many-sides of marine field.Yet the communication performance of underwater wireless optical communication still has the space of significantly improving, and is mainly reflected in aspects such as communication distance, bandwidth availability ratio, capacity usage ratio, system complexity.
Under water in the wireless light communication, the optical characteristics of water body is unfavorable for the propagation of light beam, all can cause light beam decay [1] in communication process to the absorption of light beam and water body and suspended particles to the repeatedly scattering of light beam as water body, simultaneously, also have the quite big background light radiation of excursion in the seawater.In order to make light signal be fit to transmission under water, modulation technique just more highlights its importance, and the choosing influence to a great extent or determine communication performances such as communication distance, bandwidth availability ratio, capacity usage ratio of modulation technique.
In the communication theory, bandwidth availability ratio is following data transfer rate that can send of unit bandwidth condition, is often used as the performance index of communication system.Generally bandwidth resources are rare and expensive, and it is useful using less bandwidth under the situation that transmits certain data volume.For undersea optical communications system, the bandwidth demand that transmits data is more big, and is also more high to the performance requirement of laser and optical signal receiver, can cause increasing of system complexity and cost.
The modulation system that is applied at present in the undersea optical communications system mainly contains on-off keying (On-Off Keying, OOK) [2-6], pulse-position modulation (Pulse Position Modulation, PPM) [7-9] and difference pulse-position modulation (Differential Pulse Position Modulation, DPPM) [10,11] etc.OOK be utilize pulse have or not represent Binary Zero, 1 information, this modulation system is the simplest, but capacity usage ratio is low.PPM utilizes the position of pulse to come representative information, and OOK has improved capacity usage ratio but sacrificed bandwidth availability ratio to a great extent relatively.DPPM is the improvement to PPM, " 0 " time slot of PPM pulse slot back is removed, the PPM bandwidth efficiency is higher relatively, simultaneously do not need sign synchronization at receiving terminal, reduce system complexity largely, therefore cause people's more concern in recent years, but this modulation system of DPPM still can produce too much redundancy " 0 " time slot in cataloged procedure, make and utilize the communication system bandwidth availability ratio of this modulation system still not high enough, be not suitable for the transfer of data under water of big data quantity.
List of references:
[1] B. Cochenour, L. Mullen, and A. Laux, “Spatial and temporal dispersion in high bandwidth underwater laser communication links,” in Proc. of MILCOM '08, San Diego, CA, USA, Nov. 16-19, 2008, pp.1-7；
[2] J. B. Snow et al., “Underwater propagation of high-data-rate laser communications pulses,” in Proc. of SPIE 1750, doi:10.1117/12.140670；
[3] M. Wang, and W. Liu, “Study on optical characteristics of seawater in blue-green laser uplink propagation model,” Journal of East China Shipbuilding Institute (Natural Science Edition), vol. 19, no. 1, Feb. 2005, pp.21-27；
[4] Y. Zhou, Y. Liu, and Y. Zhao, “The current situation and development trend of visible-light wireless communication by LED,” Journal of Huaiyin Institute of Technology, vol. 13, no. 3, Jun. 2006. pp. 142-147；
[5] J. Kahn, “Modulation and detection techniques for optical communication system,” in Optical Amplifiers and Their Applications and Coherent Optical Technologies and Applications, Technical Digest (CD) (Optical Society of America, Washington, DC, 2006), paper CThC1；
[6] W.C. Cox, et al. “An underwater optical communication system implementing reed-solomon channel coding,” in Proc. of OCEANS '08, Quebec City, QC, Canada, Sep. 15-18, 2008, pp. 1-10；
[7] M. Chen, S. Zhou, and T. Li, “The implementation of PPM in underwater laser communications system,” in Proc. of ICCCAS '09, vol.3, pp.1901-1903, Guilin, China, Jun. 25-28, 2006；
[8] M. Sui, X. Yu, and Z. Zhou, “The modified PPM modulation for underwater wireless optical communication,” in Proc. of ICCSN '09, Macau, Feb. 27-28, 2009, pp. 173-177；
[9] T. Zhou, and N. He, “The realization of PPM digital receiver with DSP in underwater optical communication,” Optical Technique, vol. 32, Aug. 2006. pp.147-152.；
[10] M. Doniec, I. Vasilescu, M. Chitre, and C. Detweiler, “AquaOptical: a lightweight device for high-rate long-range underwater point-to-point communication,” in Proc. of OCEANS '09, pp. 1-6, Oct. 26-29, 2009；
[11] M. Doniec, C. Detweiler, I. Vasilescu, “Using Optical communication for remote underwater robot operation,” in Proc. of IEEE/RSJ IROS '10, pp. 4017-4022, 2010。
Summary of the invention
Main purpose of the present invention is exactly at the deficiencies in the prior art, and a kind of flag bit differential pulse position modulation method is provided, and improves bandwidth availability ratio, reduces Packet Error Ratio.
Another object of the present invention provides a kind of corresponding flag bit differential pulse position modulation device.
For achieving the above object, the present invention is by the following technical solutions:
A kind of flag bit differential pulse position modulation method may further comprise the steps:
A. data are received in the encoder circuit, and described data subdividing is become
MThe ordered sequence of the group of bit binary data;
B. with each group
MBit binary data is modulated into the signal with three parts, and described signal comprises successively: 1) start bit " 1 " time slot, represent with a light pulse; 2) flag bit time slot; 3) continuous " 0 " time slot;
When
The time,
MThe flag bit of bit binary data correspondence is " 0 ", and the number of " 0 " time slot of flag bit back is
Individual;
When
The time,
MThe flag bit of bit binary data correspondence is " 1 ", represents with a light pulse, and the number of " 0 " time slot of flag bit back is
Individual;
Wherein
MBit binary data is
,
C. send data according to the burst that modulates.
A kind of flag bit differential pulse position modulation device comprises:
Be used for receiving the input unit of data;
Be used for described data subdividing is become
MThe device of the ordered sequence of the group of bit binary data;
Signal generating apparatus is for each group
MBit binary data produces the signal with three parts, and described signal comprises successively: 1) start bit " 1 " time slot, represent with a light pulse; 2) flag bit time slot; 3) continuous " 0 " time slot;
When
The time,
MThe flag bit of bit binary data correspondence is " 0 ", and the number of " 0 " time slot of flag bit back is
Individual;
When
The time,
MThe flag bit of bit binary data correspondence is " 1 ", represents with a light pulse, and the number of " 0 " time slot of flag bit back is
Individual;
Wherein
MBit binary data is
,
And
Send the dispensing device of data according to the burst that modulates.
Beneficial technical effects of the present invention is:
The present invention has proposed a kind of new modulator approach and modulating device by improving DPPM, wherein adopt flag bit differential pulse position modulation (Flag Differential Pulse Position Modulation, F-DPPM).The same with DPPM, this modulation system does not equally need sign synchronization yet, and can obtain higher bandwidth availability ratio with respect to DPPM, Packet Error Ratio is lower under the situation of identical signal peak power (light pulse intensity unanimity), can improve optical communication distance under water effectively.
By improving bandwidth availability ratio and the communication distance of wireless light communication, the present invention promoted optical communication especially the underwater wireless optical communication communication performance and enlarged its application scenarios, have superiority with respect to prior art.
Description of drawings
Fig. 1 is
M=3 o'clock, the symbolic construction of OOK, PPM, DPPM, four kinds of modulation systems of F-DPPM;
Fig. 2 illustrates OK, PPM, the bandwidth demand of four kinds of modulation systems of DPPM, F-DPPM under the same data rate situation;
Fig. 3 illustrates the Packet Error Ratio that OK, DPPM, three kinds of modulation systems of F-DPPM change with communication distance;
Fig. 4 is the flow chart of a kind of embodiment of flag bit differential pulse position modulation method of the present invention.
Embodiment
By reference to the accompanying drawings the present invention is further described in detail by the following examples.
Referring to Fig. 4, in one embodiment, flag bit differential pulse position modulation method may further comprise the steps:
A. data are received in the encoder circuit, and described data subdividing is become
MThe ordered sequence of the group of bit binary data;
B. for each group
MBit binary data produces the signal with three parts, and described signal comprises successively: 1) start bit " 1 " time slot, represent with a light pulse; 2) flag bit time slot; 3) continuous " 0 " time slot;
When
The time,
MThe flag bit of bit binary data correspondence is " 0 ", and the number of " 0 " time slot of flag bit back is
Individual;
When
The time,
MThe flag bit of bit binary data correspondence is " 1 ", represents with a light pulse, and the number of " 0 " time slot of flag bit back is
Individual;
Wherein
MBit binary data is
,
C. send data according to the burst that modulates.
Preferably, before step c sends data, earlier with some groups
MBit binary data namely
MThe code signal of position information bit is formed packet, separates with the protection time slot between the packet.According to scheme in the past, the judgement of misunderstanding follow-up all symbols that misdeems of time slot exerts an influence, in the preferred embodiment of the invention, with some groups
MThe coded identification of position information bit is formed packet, separates with the protection time slot between the packet, and whether the correct judgment of previous packet can not influence next packet, improves the accuracy to test and the judgement of communication quality.Typically, can be with 10 groups
MThe position information bit is formed a bag.
Traditional DPPM at the PPM mode with pulse slot after " 0 " time slot omit, and when the coded identification figure place
MWhen increasing, the code word average length increases, also corresponding increase of the par of " 0 " time slot in the code word.For the bandwidth availability ratio of further raising system, need to reduce " 0 " number of timeslots, compressed character code average length.DPPM is introduced a bit flag position: before flag bit is 0 representative
Individual than the short code word; After flag bit is 1 representative
Individual than long code word, can be with preceding
Individual code word size correspondence is identical.Produce the F-DPPM modulation system among the present invention in this way.
According to embodiments of the invention, the F-DPPM coded identification comprises three parts: 1) start bit, represent with a pulse, i.e. " 1 " time slot; 2) flag bit; 3) continuous " 0 " time slot.
Can be optimized at the symbolic construction of DPPM modulation system, in symbol, increase by a bit flag position, remove some redundant digits.
Determine the number of flag bit and continuous " 0 " time slot in the following manner:
It is right to press F-DPPM
MBit binary data is encoded, and original binary data is write as
, definition
,
1) if
:
Start bit is 1, and flag bit is 0, and " 0 " number of time slots of flag bit back is
2) if
:
Start bit is 1, and flag bit is 1, and " 0 " number of time slots of flag bit back is:
Fig. 1 is
M=3 o'clock, the symbolic construction of OOK, PPM, DPPM, four kinds of modulation systems of F-DPPM, the corresponding codes symbol is as shown in table 1.
Table 1.
M=3 o'clock PPM, DPPM, F-DPPM coded identification
On the other hand, the present invention also provides a kind of flag bit differential pulse position modulation device.In one embodiment, flag bit differential pulse position modulation device comprises:
Be used for receiving the input unit of data;
Be used for described data subdividing is become
MThe device of the ordered sequence of the group of bit binary data;
Signal generating apparatus is for each group
MBit binary data produces the signal with three parts, and described signal comprises successively: 1) start bit " 1 " time slot, represent with a light pulse; 2) flag bit time slot; 3) continuous " 0 " time slot;
When
The time,
MThe flag bit of bit binary data correspondence is " 0 ", and the number of " 0 " time slot of flag bit back is
Individual;
When
The time,
MThe flag bit of bit binary data correspondence is " 1 ", represents with a light pulse, and the number of " 0 " time slot of flag bit back is
Individual;
Wherein
MBit binary data is
,
And
Send the dispensing device of data according to the burst that modulates.
Performance evaluation
1, bandwidth availability ratio
The timeslot number that average each symbol of DPPM comprises is, and the time slot numerical digit that average each symbol of F-DPPM comprises is.When
MWhen big, the average timeslot number of the symbol of F-DPPM only is about half of DPPM, and bandwidth availability ratio promotes very obvious.Under identical data transfer rate situation, Fig. 2 has shown the bandwidth demand curve of several modulation systems.By curve as can be seen, when coded identification figure place M was big, the bandwidth demand of F-DPPM had been saved nearly 1/2 than DPPM, and in other words, bandwidth availability ratio has improved nearly 100%.
2, Packet Error Ratio
For with a kind of environment of optical communication under water, under the situation of fixing transmission pulse height, the size of Packet Error Ratio depends on noise size and each number of time slots that comprises.When the more big noise that comprises of the identical Time Bandwidth of noise power spectral density also more big.Each number of time slots that comprises is then determined by the modulation system that adopts.Fig. 3 has provided the Packet Error Ratio of three kinds of modulation systems of optical communication in the pure seawater with the communication distance change curve.Emulation arranges the coded identification figure place
M=4, every bag bit number
N=40, bit rate
R b =105bps, figure cathetus are notional result, and symbol is the Monte-Carlo Simulation result.As can be seen, under a kind of modulation system, Monte-Carlo Simulation meets notional result.In addition, under identical communication distance, the Packet Error Ratio under the F-DPPM modulation system is less than DPPM.When communication distance was 60 meters, the F-DPPM Packet Error Ratio was than the little 8dB of DPPM.This is because F-DPPM has shortened symbol lengths, has reduced signal bandwidth, and less than DPPM, so signal quality is better through the noise power introduced behind the channel under water.In addition, under same communication quality situation, be 10 as Packet Error Ratio
-4, adopt the system communication of F-DPPM modulation system to improve 10m apart from Billy with DPPM, amplification is 20%, this is to improving optical communication under water apart from having produced positive meaning.
Above content be in conjunction with concrete preferred implementation to further describing that the present invention does, can not assert that concrete enforcement of the present invention is confined to these explanations.For the general technical staff of the technical field of the invention, without departing from the inventive concept of the premise, can also make some simple deduction or replace, all should be considered as belonging to protection scope of the present invention.
Claims (3)
1. a flag bit differential pulse position modulation method is characterized in that, may further comprise the steps:
A. data are received in the encoder circuit, and described data subdividing is become the ordered sequence of the group of M bit binary data;
B. each group M bit binary data is modulated into the signal with three parts, described signal comprises successively: 1) start bit " 1 " time slot that characterizes with binary data " 1 ", represent with a light pulse; 2) flag bit time slot; 3) continuous " 0 " time slot;
When L＜2
M-1The time, the flag bit of M bit binary data correspondence is " 0 ", the number of " 0 " time slot of flag bit back is L;
When L 〉=2
M-1The time, the flag bit of M bit binary data correspondence is " 1 ", represents with a light pulse, the number of " 0 " time slot of flag bit back is 2
M-1-L;
Wherein the M bit binary data is S=(s
1, s
2, s
M), L=s
M+ 2s
M-1+ ... + 2
M-1s
1
C. send data according to the burst that modulates.
2. flag bit differential pulse position modulation method according to claim 1 is characterized in that, and is further comprising the steps of: before step c, earlier the code signal of some groups of M bit binary data is formed packet, separate with the protection time slot between the packet.
3. a flag bit differential pulse position modulation device is characterized in that, comprising:
Be used for receiving the input unit of data;
Be used for described data subdividing is become the device of ordered sequence of the group of M bit binary data;
Signal generating apparatus for each group M bit binary data, produces the signal with three parts, and described signal comprises successively: 1) start bit " 1 " time slot that characterizes with binary data " 1 ", represent with a light pulse; 2) flag bit time slot; 3) continuous " 0 " time slot;
When L＜2
M-1The time, the flag bit of M bit binary data correspondence is " 0 ", the number of " 0 " time slot of flag bit back is L;
When L 〉=2
M-1The time, the flag bit of M bit binary data correspondence is " 1 ", represents with a light pulse, the number of " 0 " time slot of flag bit back is 2
M-1-L;
Wherein the M bit binary data is S=(s
1, s
2, s
M), L=s
M+ 2s
M-1+ ... + 2
M-1s
1And
Send the dispensing device of data according to the burst that modulates.
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|---|---|---|---|
| CN2011103316873A CN102420791B (en) | 2011-10-27 | 2011-10-27 | Bit zone difference pulse position modulation method and device |
| HK12107113A HK1166565A1 (en) | 2011-10-27 | 2012-07-19 | Method of flag differential pulse position modulating and flag differential pulse position modulation device |
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| CN2011103316873A CN102420791B (en) | 2011-10-27 | 2011-10-27 | Bit zone difference pulse position modulation method and device |
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| TWI471723B (en) * | 2012-04-20 | 2015-02-01 | Nat Univ Tsing Hua | Debugging system using optical transmission |
| CN102694598B (en) * | 2012-04-28 | 2015-04-15 | 深圳光启创新技术有限公司 | Coding method and transmission method of visible light signals |
| CN102694597B (en) * | 2012-04-28 | 2015-05-27 | 深圳光启创新技术有限公司 | Decoding method and controlling method of visible light signal |
| CN104168066B (en) * | 2014-07-11 | 2016-08-24 | 天津理工大学 | A kind of method that pulse position modulation signal produces |
| CN106788889B (en) * | 2016-12-12 | 2019-09-17 | 天津大学 | A kind of iteration detection method of the Differential Pulse Position Modulation using convolutional code |
| CN107659360A (en) * | 2017-10-25 | 2018-02-02 | 长春理工大学 | A kind of difference multi-pulse position modulation device |
| CN112953646B (en) * | 2021-03-01 | 2022-04-19 | 长春理工大学 | Differential multi-pulse position modulation method and system |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101488804A (en) * | 2009-01-04 | 2009-07-22 | 程刚 | Double wide pulse position modulation method for wireless light communication |
| CN101494507A (en) * | 2009-02-19 | 2009-07-29 | 程刚 | Dipulse interval modulation method of wireless optical communication system |
| US7706460B2 (en) * | 2003-07-03 | 2010-04-27 | Samsung Electronics Co., Ltd. | QAM signal decoding |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7706460B2 (en) * | 2003-07-03 | 2010-04-27 | Samsung Electronics Co., Ltd. | QAM signal decoding |
| CN101488804A (en) * | 2009-01-04 | 2009-07-22 | 程刚 | Double wide pulse position modulation method for wireless light communication |
| CN101494507A (en) * | 2009-02-19 | 2009-07-29 | 程刚 | Dipulse interval modulation method of wireless optical communication system |
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