CN103840886A - Precoding method based on multiple light sources in visible light communication - Google Patents
Precoding method based on multiple light sources in visible light communication Download PDFInfo
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- CN103840886A CN103840886A CN201410035504.7A CN201410035504A CN103840886A CN 103840886 A CN103840886 A CN 103840886A CN 201410035504 A CN201410035504 A CN 201410035504A CN 103840886 A CN103840886 A CN 103840886A
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Abstract
The invention relates to a precoding method based on multiple light sources in visible light communication. After serial data bit streams receive planisphere mapping, the serial data bit streams receive series and parallel conversion to be N paths of parallel data, N orthogonal sub-carrier waves are used for modulating the N paths of parallel data respectively and according to the channel fading feature which is measured in advance, the flat fading gain sigma i of all the sub-channels is obtained, wherein i equals to 0, 1,..., N-1. If the expected received power of the sub-channel i is Pi, the channel flat fading gain is the sigma i and when the precoding is carried out, the transmitted power of the sub-channel i is Pi' which equals to the Pi or the sigma I. Afterwards, grouping is carried out according to the transmitted power of all the sub-channels, each group of signals are stacked up and loaded to different LED light sources. According to the precoding method based on multiple light sources in visible light communication, affection on a visible light transmission system by the high PAPR of an OFDM symbol is relieved, the power utilizing rate is improved and the SNR of a receiving end can be improved through channel fading reversing of a transmitting end.
Description
Technical field
The invention belongs to visible light communication technical field, particularly the method for precoding based on multiple light courcess in a kind of visible light communication.
Background technology
The later stage nineties 20th century, the semi-conductor LED illuminating technical development that is described as green illumination is swift and violent, the low-carbon (LC) that possesses due to white light LEDs, green and the feature such as efficient, government also releases policy and its development is encouraged in measure, in recent years, along with the maturation of LED technology and the reduction of cost, its application is sprawled and is come rapidly.The Novel Communication technology that visible light communication grows up just nearly ten years under this background, utilize the high speed electro-optical response characteristic of white light LEDs, information exchange is crossed its utilizing emitted light power of Current Control that injects LED, use photodetector to complete the conversion of photosignal at receiving terminal, further complete the demodulation of information.
The single-carrier modulated such as OOK, PPM mode is in high rate data transmission situation, and intersymbol interference will cause system performance degradation, becomes and affects the principal element that speed promotes.Therefore in visible ray high-speed communication system, OFDM (OFDM) technology becomes the focus of current research.Principle Shi Jiang mono-tunnel of OFDM technology serial data stream at a high speed converts the parallel low speed data in N road to, removes respectively afterwards to modulate the orthogonal subcarrier in N road, and N way carrier wave is launched with the form of base band or radio frequency after stack.In the time that number of sub carrier wave N is enough large, can effectively reduce the intersymbol interference that the temporal dispersion of channel brings, the use of orthogonal sub-carriers simultaneously also makes its availability of frequency spectrum have the lifting of nearly a times compared with single carrier transmission.In addition the modulation /demodulation of quadrature modulation can the very ripe IFFT/FFT of operation technique, and this has greatly simplified system and has realized difficulty.
The typical structure that tradition OFDM is applied to visible light communication system as shown in Figure 1, because OFDM symbol is that multiple sub-carrier signal stacks generate, in the time that multiple sub-carrier signal phase places are consistent, the instantaneous power of signal is by the average power much larger than signal, so OFDM symbol exists the higher problem of papr (PAPR).Consider non-linear (the non-linear and cut-off characteristics of transmission characteristic) of LED light source, current visible ray ofdm system need to use power attenuation to avoid signal generation slicing conventionally, this can cause the reduction of power efficiency, and therefore the transmission rate of system and coverage also can be affected.And the implementation complexity of additive method such as restricted coding, selectivity mapping meeting increase system.
Summary of the invention
In order to overcome the shortcoming of above-mentioned prior art, the object of the present invention is to provide the method for precoding based on multiple light courcess in a kind of visible light communication, not only can reduce PAPR that OFDM symbol the is higher impact on transmission of visible light system, improve power utilization, and by the channel fading reversion of transmitting terminal, can improve the signal to noise ratio of receiving terminal.
To achieve these goals, the technical solution used in the present invention is:
Method for precoding based on multiple light courcess in a kind of visible light communication, the data bit flow of serial is after through planisphere mapping, through going here and there and being converted to N channel parallel data, use respectively N orthogonal sub-carriers to modulate N channel parallel data, according to the channel fading characteristic recording in advance, draw the flat decline gain σ of each subchannel
i, i=0,1 ..., N-1, if the received power that subchannel i expects is P
i, the flat decline gain of channel is σ
i, while adopting precoding, the transmitting power of subchannel i is P
i'=P
i/ σ
i, divide into groups according to the transmitting power of each subchannel afterwards, then, by every group of signal stack, be loaded on different LED light sources.
Consider more general situation, can, according to the relation between each sub-channel transmission power, choose suitable value P', carry out subchannel grouping.As in the situation that each sub-channel transmission power difference is less, as subchannel maximum transmission power and the ratio of minimum emissive power are less than or equal to k (the desirable scope of k is 9 to 16), the P' here can be the two or several sub-channel transmission power sums of transmitting power maximum, then start grouping from low sequence number subcarrier, grouping standard is that the transmitting power sum of every group of subcarrier comprising is about P'.As in the situation that each sub-channel transmission power difference is larger, as subchannel maximum transmission power and the ratio of minimum emissive power are more than or equal to k(k desirable approximately 16), now desirable P' is the sub-channel transmission power of transmitting power maximum, start grouping from low sequence number subcarrier, grouping standard is that every group of subcarrier transmitting power sum comprising is about P'.
Compared with prior art, because total transmitting power of every group of signal of the present invention is consistent, and every group of subchannel number limited (as can be artificially every group of subcarrier number be controlled in 4 by the selection of P'), is therefore strict controlled in its amplitude by control signal power the linear work region of LED light source.
Through flat decline σ
iafterwards, received power remains P
iσ
i/ σ
i=P
i.Channel is reversed in transmitting terminal and completes, and receiving terminal noise power is still N
0b
n, played the effect that improves receiving terminal signal to noise ratio.
Brief description of the drawings
Fig. 1 is visible ray ofdm communication system exemplary block diagram.
Fig. 2 is the pre-coding scheme system configuration schematic diagram that the present invention is based on multiple light courcess.
Fig. 3 is the channel frequency response curve that uses a normalized typical visible ray direct-view link of impulse response method test gained.
embodiment
Describe embodiments of the present invention in detail below in conjunction with drawings and Examples.
As shown in Figure 2, the present invention is the method for precoding based on multiple light courcess in a kind of visible light communication, and the data bit flow of serial is through after planisphere mapping, through going here and there and being converted to N channel parallel data, use respectively N orthogonal sub-carriers to modulate N channel parallel data, use cos2 π f
0t modulates first via data, uses cos2 π f
1t modulates the second circuit-switched data ..., use cos2 π f
n-1t modulates N circuit-switched data.
With respect to wireless radiofrequency channel, the decline of visible light communication channel is metastable, thus can carry out test evaluation to channel fading characteristic in advance, as used the frequency response of frequency sweep method or impulse response method test channel.Be illustrated in figure 3 the channel frequency response curve of a normalized typical visible ray direct-view link that uses impulse response method test gained.
According to the channel fading characteristic recording, can draw the flat decline gain σ of each subchannel
i, i=0,1 ..., N-1, if the received power that subchannel i expects is P
i, the flat decline gain of channel is σ
i, while adopting precoding, the transmitting power of subchannel i is P
i'=P
i/ σ
i.
Divide into groups according to the transmitting power of each subchannel afterwards, consider more general situation, can, according to the relation between each sub-channel transmission power, choose suitable value P', carry out subchannel grouping.In the situation that each sub-channel transmission power difference is less, as subchannel maximum transmission power and the ratio of minimum emissive power are less than or equal to k (the desirable scope of k is 9 to 16), desirable P' is the two or several sub-channel transmission power sums of transmitting power maximum, then start grouping from low sequence number subcarrier, grouping standard is that the transmitting power sum of every group of subcarrier comprising is about P'.In the situation that each sub-channel transmission power difference is larger, as subchannel maximum transmission power and the ratio of minimum emissive power are more than or equal to k(k desirable approximately 16), now desirable P' is the sub-channel transmission power of transmitting power maximum, start grouping from low sequence number subcarrier, grouping standard is that every group of subcarrier transmitting power sum comprising is about P'.
Afterwards by every group of signal stack, be loaded on different LED light sources, because total transmitting power of every group of signal is consistent, and every group of subchannel number is limited (as can be artificially every group of subcarrier number be controlled in 4 by the selection of P', prevent high-power peaks), therefore by control signal power, its amplitude is strict controlled in to the linear work region of LED light source.
Through flat decline σ
iafterwards, received power remains P
iσ
i/ σ
i=P
i.Channel is reversed in transmitting terminal and completes, and receiving terminal noise power is still N
0b
n, played the effect that improves receiving terminal signal to noise ratio.
Wherein digital-to-analogue conversion is to be completed by digital to analog converter (DAC), and direct current biasing can use bias-T device or complete through the analog circuit of design, and direct current biasing point needs meticulously to select to ensure that signal is operated in the range of linearity of LED lamp transmission curve.
At receiving terminal, by photoelectric detector, light signal is converted to the signal of telecommunication, by analog to digital converter, by analog electrical signal, it is converted to digital electric signal afterwards, in digital device (FPGA/DSP), settling signal is synchronous, remove Cyclic Prefix, FFT operation, planisphere inverse mapping and parallel-serial conversion, output decoding bit stream.
Claims (3)
1. the method for precoding based on multiple light courcess in a visible light communication, the data bit flow of serial is after through planisphere mapping, through going here and there and being converted to N channel parallel data, it is characterized in that, use respectively N orthogonal sub-carriers to modulate N channel parallel data, according to the channel fading characteristic recording in advance, draw the flat decline gain σ of each subchannel
i, i=0,1 ..., N-1, if the received power that subchannel i expects is P
i, the flat decline gain of channel is σ
i, while adopting precoding, the transmitting power of subchannel i is P
i'=P
i/ σ
i, divide into groups according to the transmitting power of each subchannel afterwards, then, by every group of signal stack, be loaded on different LED light sources.
2. the method for precoding based on multiple light courcess in a kind of visible light communication according to claim 1, it is characterized in that, as subchannel maximum transmission power and the ratio of minimum emissive power are less than or equal to k, the desirable scope of k is 9 to 16, getting P' is the two or several sub-channel transmission power sums of transmitting power maximum, then start grouping from low sequence number subcarrier, grouping standard is that the transmitting power sum of every group of subcarrier comprising is about P'.
3. the method for precoding based on multiple light courcess in a kind of visible light communication according to claim 1, it is characterized in that, as subchannel maximum transmission power and the ratio of minimum emissive power are more than or equal to k, the desirable of k is 16, getting P' is the sub-channel transmission power of transmitting power maximum, start grouping from low sequence number subcarrier, grouping standard is that every group of subcarrier transmitting power sum comprising is about P'.
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Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105553554A (en) * | 2016-01-25 | 2016-05-04 | 中国人民解放军信息工程大学 | Visible light communication signal constellation design method, device and system |
| CN107181531A (en) * | 2017-05-22 | 2017-09-19 | 南京邮电大学 | Bit mapping method when LED numbers are any in light spatial modulation communication system |
| CN104253647B (en) * | 2014-09-25 | 2017-11-03 | 佛山职业技术学院 | Outdoor visible light communication system based on MIMO technology and OFDM technology |
| WO2018094650A1 (en) * | 2016-11-24 | 2018-05-31 | 华为技术有限公司 | Modulation method and apparatus |
| CN108809885A (en) * | 2018-04-27 | 2018-11-13 | 中国矿业大学 | A kind of novel orthogonal space modulator approach based on indoor visible light communication |
| CN110324266A (en) * | 2019-05-16 | 2019-10-11 | 华南师范大学 | A kind of visible optical transceiving method of OFDM of Adaptive Transmission amplitude digit compression |
| CN111934769A (en) * | 2020-08-14 | 2020-11-13 | 东南大学 | Multi-input multi-output visible light and coding method |
| CN112367123A (en) * | 2020-11-10 | 2021-02-12 | 兰州理工大学 | Light space-time keying modulation method suitable for turbulent flow channel |
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| US20100218066A1 (en) * | 2007-07-30 | 2010-08-26 | Panasonic Corporation | Encoding device and decoding device |
| CN103299558A (en) * | 2011-01-07 | 2013-09-11 | 交互数字专利控股公司 | Communicating channel state information (CSI) of multiple transmission points |
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Patent Citations (2)
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| US20100218066A1 (en) * | 2007-07-30 | 2010-08-26 | Panasonic Corporation | Encoding device and decoding device |
| CN103299558A (en) * | 2011-01-07 | 2013-09-11 | 交互数字专利控股公司 | Communicating channel state information (CSI) of multiple transmission points |
Cited By (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104253647B (en) * | 2014-09-25 | 2017-11-03 | 佛山职业技术学院 | Outdoor visible light communication system based on MIMO technology and OFDM technology |
| CN105553554A (en) * | 2016-01-25 | 2016-05-04 | 中国人民解放军信息工程大学 | Visible light communication signal constellation design method, device and system |
| CN105553554B (en) * | 2016-01-25 | 2017-12-12 | 中国人民解放军信息工程大学 | Visible light communication signal constellation (in digital modulation) design method, apparatus and system |
| WO2018094650A1 (en) * | 2016-11-24 | 2018-05-31 | 华为技术有限公司 | Modulation method and apparatus |
| CN107181531B (en) * | 2017-05-22 | 2019-05-07 | 南京邮电大学 | Bit mapping method when LED number is any in light spatial modulation communication system |
| CN107181531A (en) * | 2017-05-22 | 2017-09-19 | 南京邮电大学 | Bit mapping method when LED numbers are any in light spatial modulation communication system |
| CN108809885A (en) * | 2018-04-27 | 2018-11-13 | 中国矿业大学 | A kind of novel orthogonal space modulator approach based on indoor visible light communication |
| CN108809885B (en) * | 2018-04-27 | 2021-07-23 | 中国矿业大学 | Novel space orthogonal modulation method based on indoor visible light communication |
| CN110324266A (en) * | 2019-05-16 | 2019-10-11 | 华南师范大学 | A kind of visible optical transceiving method of OFDM of Adaptive Transmission amplitude digit compression |
| CN110324266B (en) * | 2019-05-16 | 2022-03-11 | 华南师范大学 | OFDM visible light receiving and transmitting method and system for self-adaptive transmission amplitude and digit compression |
| CN111934769A (en) * | 2020-08-14 | 2020-11-13 | 东南大学 | Multi-input multi-output visible light and coding method |
| CN111934769B (en) * | 2020-08-14 | 2023-02-14 | 东南大学 | Multi-input multi-output visible light communication precoding method |
| CN112367123A (en) * | 2020-11-10 | 2021-02-12 | 兰州理工大学 | Light space-time keying modulation method suitable for turbulent flow channel |
| CN112367123B (en) * | 2020-11-10 | 2022-08-12 | 兰州理工大学 | Light space-time keying modulation method suitable for turbulent flow channel |
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