Band-limited mcap visible light communication system sub-band number modulation method

Abstract

The application relates to a band-limited mCAP visible light communication system sub-band number modulation method, which comprises the following steps: dividing an input bit sequence; determining the number of activated sub-bands of m time slots, and generating a sub-band activation mode vector of each time slot according to the low-pass frequency response characteristics of the system; generating constellation symbols; performing m time slot joint sub-band number modulation according to the sub-band activation mode vector of each time slot and the constellation symbols, and obtaining a transmission vector of each time slot; and obtaining an output signal according to m transmission data. The application has the beneficial effects that the error propagation problem caused by sub-band number decision error can be effectively solved through m time slot joint sub-band number modulation, so that an LLR detector can be used for signal detection, the detection complexity of the system is reduced, and the sub-bands to be activated can be adaptively selected according to the low-pass frequency response characteristics, so that the maximum channel gain is obtained, and the system error code performance is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of communication, more particularly, to a subband number modulation method for band-limited mCAP visible light communication system. BACKGROUND

[0002] Visible light communication is widely regarded as one of the key enabling technologies for realizing 6G communication and Internet of Things communication due to its inherent advantages such as rich and unrestricted spectrum resources, no electromagnetic radiation and anti-electromagnetic interference, and natural physical layer security. However, the visible light communication system based on commercial white light LED is a typical band-limited communication system, and its frequency response usually presents low-pass characteristics. In addition, the actual visible light communication system is also affected by the nonlinear effect of LED.

[0003] In order to improve the transmission performance of the band-limited visible light communication system, the multi-band carrier-less amplitude phase (mCAP) modulation technology is widely used in the band-limited visible light communication system. The mCAP modulation can achieve high spectral efficiency, and has a lower peak-to-average power ratio than the traditional orthogonal frequency division multiplexing (OFDM) modulation, so it is more suitable for band-limited visible light communication systems with severe nonlinearities. At the same time, in order to improve the error performance of the mCAP visible light communication system, researchers further proposed a subband index modulation mCAP technology. Although the subband index modulation mCAP can achieve better error performance than the traditional mCAP, it does not fully consider the influence of the low-pass frequency response of the band-limited visible light communication system on the error performance. When the high-frequency attenuation of the band-limited visible light communication system is large, the error performance of the subband index modulation mCAP is poor. SUMMARY

[0004] The purpose of the present application is to overcome the deficiencies in the prior art, and to provide a subband number modulation method for band-limited mCAP visible light communication system.

[0005] In a first aspect, a subband number modulation method for band-limited mCAP visible light communication system is provided, which is executed by a transmitting end and includes:

[0006] S1, obtaining an input bit sequence, and dividing the input bit sequence into a first input bit subsequence for m-slot joint subband number mapping and a second input bit subsequence for m-slot joint constellation mapping;

[0007] S2, determining the active subband number of m slots according to the first input bit subsequence and the m-slot joint subband number mapping relationship, and generating a subband activation mode vector for each slot according to the low-pass frequency response characteristics of the system;

[0008] S3, generating corresponding constellation symbols according to the second input bit subsequence and the m-slot joint subband number information;

[0009] S4. Based on the sub-band activation mode vector of each time slot and the constellation symbol, perform m-time slot joint sub-band number modulation to obtain the transmit vector of each time slot;

[0010] S5. Upsample each of the m transmitted data streams, then pass each transmitted data stream through a co-directional filter and a quadrature filter, and then combine them to obtain the output signal; combine the m output signals into one signal, then perform digital-to-analog conversion, add DC, and drive an LED or LD light source to emit light to generate an output light signal.

[0011] Preferably, in S2, given a given number of active sub-bands, a given number of low-frequency sub-bands are adaptively selected as active sub-bands to transmit constellation symbols.

[0012] Secondly, another subband number modulation method for band-limited mCAP visible light communication systems is provided, executed by the receiver, including:

[0013] S1. The output optical signal generated by the transmitter is converted into an electrical signal by PD detection; then the received signal is obtained by analog-to-digital conversion.

[0014] S2. The received signal is divided into m paths, and each path is passed through matched filter 1 and matched filter 2 that are matched with the transmitter, thereby recovering the m parallel signals.

[0015] S3. After downsampling and frequency domain equalization of the m parallel signals, perform m-slot joint LLR detection on the obtained signals to estimate the corresponding transmit vector and constellation symbol;

[0016] S4. The transmitted constellation bit sequence and number modulation bit sequence are recovered by m-slot joint sub-band number demapping and m-slot joint constellation demapping, and finally merged to obtain the output bit sequence.

[0017] Thirdly, a sub-band number modulation device for a band-limited mCAP visible light communication system is provided. This device serves as a transmitter, used to execute any of the sub-band number modulation methods described in the first aspect. The sub-band number modulation device comprises:

[0018] The acquisition module is used to acquire the input bit sequence and divide the input bit sequence into a first input bit subsequence for mapping the number of m-slot joint sub-bands and a second input bit sequence for mapping the number of m-slot joint constellations;

[0019] The determination module is used to determine the number of active sub-bands in the m-slot based on the mapping relationship between the first input bit sub-sequence and the number of joint sub-bands in the m-slot, and to generate a sub-band activation mode vector for each slot based on the low-pass frequency response characteristics of the system.

[0020] The generation module is used to generate the corresponding constellation symbol based on the second input bit subsequence and the number of m-slot joint subbands;

[0021] The modulation module is used to perform m-slot joint sub-slot number modulation based on the sub-slot activation mode vector of each time slot and the constellation symbol, and obtain the transmit vector of each time slot;

[0022] The driver module is used to upsample m transmitted data separately, and then each transmitted data is passed through a co-directional filter and a quadrature filter, and then combined together to obtain the output signal; the m output signals are combined into one signal, and after digital-to-analog conversion and DC addition, the signal drives an LED or LD light source to emit light and generate an output light signal.

[0023] Fourthly, another sub-band number modulation device for a band-limited mCAP visible light communication system is provided. This band-limited mCAP visible light communication system sub-band number modulation device is a receiver used to execute the band-limited mCAP visible light communication system sub-band number modulation method described in the second aspect. The band-limited mCAP visible light communication system sub-band number modulation device includes:

[0024] The conversion module is used to convert the output optical signal generated by the transmitter into an electrical signal via PD detection; then, it undergoes analog-to-digital conversion to obtain the received signal.

[0025] The first recovery module is used to divide the received signal into m paths, each path passing through matched filters 1 and 2 that are matched with the transmitter, thereby recovering the m parallel signals.

[0026] The detection module is used to perform m-slot joint LLR detection on the m parallel signals after downsampling and frequency domain equalization, and estimate the corresponding transmit vector and constellation symbol.

[0027] The second recovery module is used to recover the transmitted constellation bit sequence and number modulation bit sequence from the m-slot joint sub-band number demapping and the m-slot joint constellation demapping, and finally merge them to obtain the output bit sequence.

[0028] Fifthly, a communication system is provided, the communication system comprising: a first node and a second node; the first node is the transmitting end described in the third aspect, and the second node is the receiving end described in the fourth aspect.

[0029] In a sixth aspect, a computer storage medium is provided, wherein a computer program is stored therein; when the computer program is run on a computer, the computer causes the computer to execute the subband number modulation method for the band-limited mCAP visible light communication system described in either the first or second aspect.

[0030] In a seventh aspect, a computer program product is provided, which, when run on a computer, causes the computer to execute the band-limited mCAP visible light communication system subband number modulation method described in either the first or second aspect.

[0031] The beneficial effects of this invention are:

[0032] (1) The present invention can effectively solve the error propagation problem caused by the incorrect sub-band number decision by using m-slot joint sub-band number modulation, so that LLR detector can be used for signal detection, reducing the detection complexity of the system.

[0033] (2) The present invention can adaptively select one or more sub-bands to be activated based on the low-pass frequency response characteristics of the band-limited visible light communication system, thereby obtaining the maximum channel gain and improving the system bit error rate performance. Attached Figure Description

[0034] Figure 1 Schematic diagram of a visible light communication system with mCAP subband number modulation;

[0035] Figure 2 A schematic diagram of adaptive subband selection based on system frequency response;

[0036] Figure 3 This is a schematic diagram of the transmitter's structure;

[0037] Figure 4 This is a schematic diagram of the receiver. Detailed Implementation

[0038] The present invention will be further described below with reference to embodiments. The description of the embodiments below is only for the purpose of helping to understand the present invention. It should be noted that those skilled in the art can make several modifications to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0039] like Figure 1 As shown, the communication system provided in this application includes a transmitter and a receiver. The transmitter can generate an output optical signal based on an input bit sequence, and the receiver receives the output optical signal generated by the transmitter and obtains an output bit sequence based on the output optical signal.

[0040] The subband number modulation method for band-limited mCAP visible light communication systems executed by the transmitter includes:

[0041] S1. Obtain the input bit sequence and divide the input bit sequence into a first input bit subsequence for mapping the number of m-slot joint subbands and a second input bit subsequence for mapping the number of m-slot joint constellations.

[0042] It should be noted that the size of m determines the length of the first input bit subsequence, which can also be called the number-mapped bit sequence. For example, when m is 4, the length of the number-mapped bit sequence is also 4.

[0043] S2. Based on the mapping relationship between the first input bit subsequence and the number of joint sub-bands in the m-slot, determine the number of active sub-bands in the m-slot, and generate the sub-band activation mode vector for each slot based on the low-pass frequency response characteristics of the system.

[0044] For example, the m-slot joint sub-band number mapping is performed according to the m-slot joint sub-band number mapping table shown in Table 1, and the sub-band activation mode vector c for each slot is generated according to the low-pass frequency response characteristics of the system.

[0045] Table 1. Mapping table of the number of joint sub-bands in time slot m (taking m=4 as an example)

[0046]

[0047]

[0048] Table 1 shows the joint subband number mapping table for m-slots using 4CAP (m=4) as an example. For 4CAP modulation, the four time slots need to be treated as a whole for joint subband number modulation. Therefore, the length of the number mapping bit sequence that can be transmitted in each time slot is floor(log2(4!)) = 4. Simultaneously, the number of subbands activated in each time slot can only be selected from the four numbers 1, 2, 3, and 4, and the number of activated subbands selected by the four time slots is different for each other. Therefore, for any number mapping bit sequence, the total number of activated subbands selected by the four time slots is a constant, i.e., 1+2+3+4 = 10. Because the total number of activated subbands selected by the four time slots is fixed, the number of constellation symbols transmitted is also fixed, thus effectively avoiding the error propagation problem caused by incorrect subband number decision, thereby allowing the use of a low-complexity LLR detector for signal detection. It should be noted that this application does not limit the specific mapping relationship between the number-mapped bit sequence and the number of m-slot joint sub-bands. This application uses Table 1 as an example for illustration. Of course, mapping relationships other than those in Table 1 can also be used to determine the number of m-slot joint sub-bands corresponding to the number-mapped bit sequence.

[0049] S3. Generate the corresponding constellation symbol based on the second input bit subsequence and the number of joint subbands in the m-slot.

[0050] S4. Based on the sub-band activation mode vector of each time slot and the constellation symbol, perform m-time slot joint sub-band number modulation to obtain the transmit vector of each time slot.

[0051] S5. Upsample each of the m transmitted data streams, then pass each transmitted data stream through a co-directional filter and a quadrature filter, and then combine them to obtain the output signal; combine the m output signals into one signal, then perform digital-to-analog conversion, add DC, and drive an LED or LD light source to emit light to generate an output light signal.

[0052] Based on S1-S5 above, assuming the number mapping bit is 0011, according to Table 1, the number of active subbands in the four time slots of the 4CAP visible light communication system are 1, 3, 2, and 4, respectively. Taking the second time slot as an example, the corresponding number of active subbands is 3. After adaptive subband selection under the low-pass frequency response characteristics, c = [1,1,1,0]. Simultaneously, in the second time slot, the m-time slot joint constellation mapping will generate three different constellation symbols s1, s2, and s3. Therefore, after m-time slot joint subband number modulation, the transmission vector of the second time slot is s = [s1,s2,s3,0]. Similarly, after adaptive subband selection under the low-pass frequency response characteristics, the subband activation mode vectors corresponding to the four time slots are [1,0,0,0], [1,1,1,0], [1,1,0,0], and [1,1,1,1]. Assume that the 10 different constellation symbols to be transmitted in the 4 time slots are s1 to s2. 10 The emission vectors corresponding to the four time slots are [s1,0,0,0], [s2,s3,s4,0], [s5,s6,0,0] and [s7,s8,s9,s4,0], respectively. 10 After completing the m-slot joint sub-band modulation, the m transmitted data are upsampled separately, and then each data path is passed through in-phase and quadrature filters before being combined to obtain the output signal x. i (i = 1, 2, ..., m). Finally, the m output signals are combined into one signal x, which, after digital-to-analog conversion and the addition of DC, can be used to drive LEDs or LD light sources to emit light and generate output light signals.

[0053] It should be noted that, given a given number of active sub-bands, this application adaptively selects a given number of low-frequency sub-bands as active sub-bands to transmit constellation symbols. For example... Figure 2As shown, when the system exhibits typical low-pass frequency response characteristics, the power attenuation of low-frequency subbands is relatively small, while the power attenuation of high-frequency subbands is relatively large. Therefore, given a certain number of active subbands, to maximize the channel gain of the active subbands, a given number of low-frequency subbands are adaptively selected as active subbands for transmitting constellation symbols. Assuming the given number of active subbands is 2, i.e., N=2, subbands 1 and 2, located in the low-frequency region, are preferentially selected as active subbands, while subbands 3 and 4, located in the high-frequency region, are not activated. Since the proposed system frequency response-aware adaptive subband selection scheme can maximize the channel gain of the active subbands, it can significantly improve the system's bit error rate performance.

[0054] Furthermore, the subband number modulation method for the band-limited mCAP visible light communication system executed at the receiver includes:

[0055] S1. After transmission through the channel, the output optical signal generated by the transmitter is converted into an electrical signal by PD detection; then, the received signal is obtained by analog-to-digital conversion.

[0056] S2. The received signal is divided into m paths, and each path is passed through matched filters 1 and 2 that are matched with the transmitter, thereby recovering the m parallel signals.

[0057] S3. After downsampling and frequency domain equalization of the m parallel signals, perform m-slot joint LLR detection on the obtained signals to estimate the corresponding transmit vector and constellation symbol.

[0058] S4. The transmitted constellation bit sequence and number modulation bit sequence are recovered by m-slot joint sub-band number demapping and m-slot joint constellation demapping, and finally merged to obtain the output bit sequence.

[0059] Assume the transmission vectors corresponding to the four time slots at the transmitter are [s1,0,0,0], [s2,s3,s4,0], [s5,s6,0,0] and [s7,s8,s9,s4,0], respectively. 10 At the receiving end, the positions of these 10 different constellation symbols in each transmit vector can be estimated by joint LLR detection in m time slots. Therefore, the corresponding subband active mode vector and constellation symbols can be recovered, thus completing the final demodulation and recovering the transmitted bit data.

[0060] The above example uses 4CAP. However, 4CAP modulation can be replaced with arbitrary subband number mCAP modulation. Multiple subbands can be grouped, and then subband number modulation can be performed within each group. Multi-slot joint subband number modulation and system frequency response-aware adaptive subband selection can be implemented within each group. Alternatively, mCAP modulation can be replaced with multi-carrier OFDM modulation. OFDM subcarriers can be grouped, and then subcarrier number modulation can be performed within each group. Multi-slot joint subcarrier number modulation and system frequency response-aware adaptive subcarrier selection can be implemented within each group.

[0061] In summary, this application can adaptively select one or more sub-bands to be activated based on the low-pass frequency response characteristics of the band-limited visible light communication system to obtain the maximum channel gain. Therefore, it can effectively overcome the impact of the low-pass frequency response of the band-limited visible light communication system on the system's bit error rate performance and achieve better bit error rate performance than the traditional sub-band index modulation method of the band-limited mCAP visible light communication system. Furthermore, by using m-slot joint sub-band number modulation, the error propagation problem caused by sub-band number decision errors can be effectively solved, thereby enabling the use of a low-complexity log-likelihood ratio (LLR) detector for signal detection.

Claims

1. A subband number modulation method for a band-limited mCAP visible light communication system, characterized in that, Executed by the transmitter, including: S1. Obtain the input bit sequence and divide the input bit sequence into parts for use with... m The first input bit subsequence for the time slot joint subband number mapping and the bit subsequence used for m The second input bit subsequence of the time-slot joint constellation mapping; S2, based on the first input bit subsequence and m The mapping relationship between the number of joint sub-bands in the time slot is used to determine the number of active sub-bands in the m time slot, and the sub-band activation mode vector of each time slot is generated according to the low-pass frequency response characteristics of the system. S3, based on the second input bit subsequence and m The number of time slot joint sub-bands generates the corresponding constellation symbol; S4. Based on the sub-band activation mode vector of each time slot and the constellation symbol, perform... m Time slot joint sub-band number modulation is used to obtain the transmit vector of each time slot; S5, to m Each transmitted data stream is upsampled, and then each transmitted data stream passes through a co-directional filter and a quadrature filter before being combined to obtain the output signal. m The output signals of the circuits are combined into one signal, which is then converted from digital to analog and DC is added to drive an LED or LD light source to emit light and generate an output light signal. Executed by the receiving end, including: a. The output optical signal generated by the transmitter is converted into an electrical signal by a PD detector; then, the received signal is obtained by analog-to-digital conversion. b. Divide the received signal into m Each path passes through matched filter 1 and matched filter 2, which are matched to the transmitter, to recover the signal. m Parallel signals; c. The above m After the parallel signals are downsampled and frequency domain equalized, the resulting signals are then... m Time-slot joint LLR detection is used to estimate the corresponding emission vector and constellation symbol; d. By m Demapping of the number of joint subbands in time slots and slot joint subbands m The time-slot joint constellation demapping recovers the transmitted constellation bit sequence and number modulation bit sequence, which are then combined to obtain the output bit sequence.

2. The subband number modulation method for a band-limited mCAP visible light communication system according to claim 1, characterized in that, In S2, given a certain number of active sub-bands, a given number of low-frequency sub-bands are adaptively selected as active sub-bands to transmit constellation symbols.

3. A subband number modulation device for a band-limited mCAP visible light communication system, characterized in that, The band-limited mCAP visible light communication system sub-band number modulation device is a transmitter used to execute the band-limited mCAP visible light communication system sub-band number modulation method according to claim 1 or 2. The band-limited mCAP visible light communication system sub-band number modulation device includes: The acquisition module is used to acquire the input bit sequence and divide the input bit sequence into segments for use with... m The first input bit subsequence for the time slot joint subband number mapping and the bit subsequence used for m The second input bit subsequence of the time-slot joint constellation mapping; The determining module is configured to determine the first input bit subsequence and m The mapping relationship between the number of joint sub-bands in the time slot is used to determine the number of active sub-bands in the m time slot, and the sub-band activation mode vector of each time slot is generated according to the low-pass frequency response characteristics of the system. The generation module is used to generate based on the second input bit subsequence and m The number of time slot joint sub-bands generates the corresponding constellation symbol; The modulation module is used to perform modulation based on the sub-band activation mode vector of each time slot and the constellation symbol. m Time slot joint sub-band number modulation is used to obtain the transmit vector of each time slot; Driver module, used for m Each transmitted data stream is upsampled, and then each transmitted data stream passes through a co-directional filter and a quadrature filter before being combined to obtain the output signal. m The output signals are combined into one signal, which is then converted from digital to analog and a DC signal is added to drive an LED or LD light source to emit light and generate an output light signal.

4. A subband number modulation device for a band-limited mCAP visible light communication system, characterized in that, The band-limited mCAP visible light communication system sub-band number modulation device is a receiver used to execute the band-limited mCAP visible light communication system sub-band number modulation method of claim 1. The band-limited mCAP visible light communication system sub-band number modulation device includes: The conversion module is used to convert the output optical signal generated by the transmitter into an electrical signal via PD detection; then, it undergoes analog-to-digital conversion to obtain the received signal. The first recovery module is used to divide the received signal into... m Each path passes through matched filters 1 and 2, which are matched to the transmitter, to recover the signal. m Parallel signals; The detection module is used to detect the m After the parallel signals are downsampled and frequency domain equalized, the resulting signals are then... m Time-slot joint LLR detection is used to estimate the corresponding emission vector and constellation symbol; The second recovery module is used by... m Demapping of the number of joint subbands in time slots and slot joint subbands m The time-slot joint constellation demapping recovers the transmitted constellation bit sequence and number modulation bit sequence, which are then combined to obtain the output bit sequence.

5. A communication system, characterized in that, The communication system includes: a first node and a second node; The first node is the transmitting end as described in claim 3, and the second node is the receiving end as described in claim 4.

6. A computer storage medium, characterized in that, The computer storage medium stores a computer program; when the computer program is run on the computer, it causes the computer to execute the subband number modulation method for the band-limited mCAP visible light communication system as described in any one of claims 1 to 2.

7. A computer program product, characterized in that, When the computer program product is run on a computer, it causes the computer to perform the subband number modulation method for a band-limited mCAP visible light communication system as described in any one of claims 1 to 2.

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