阅读说明：本技术 一种层映射光空间分集联合调制激光通信编解码方法 (Layer mapping optical space diversity combined modulation laser communication coding and decoding method ) 是由 何宁 邓乐坤 蒋红艳 廖欣 于 2021-08-04 设计创作，主要内容包括：本发明涉及一种层映射光空间分集联合调制激光通信编解码方法,解决的是频谱效率以及传输速率低的技术问题,通过采用激光通信技术构建空间多发多收传输机制,在空域上,通过光空间映射提高空间复用增益,在时域上,通过结合PAM的高频谱效率与PPM的高能量利用率,实现PPAM来共同传递信息的技术方案,较好的解决了该问题；在无线传输方式上以激光器索引号来完成,采用不同组合的激光器实现并行数据发送,克服了调制阶数升高对硬件设备的分辨率要求高的问题。同时利用多种调制技术组合复用有利于信息的安全传输,降低通信第三方对信息截获破译概率,采用字节组帧可缩短同步时间,进一步提高了信息传输可靠性和有效性。(The invention relates to a layer mapping optical space diversity combined modulation laser communication coding and decoding method, which solves the technical problems of low frequency spectrum efficiency and low transmission rate, constructs a space multi-transmitting and multi-receiving transmission mechanism by adopting a laser communication technology, improves the space multiplexing gain by optical space mapping in a space domain, and realizes the technical scheme that PPAM jointly transmits information by combining the high frequency spectrum efficiency of PAM and the high energy utilization rate of PPM in a time domain, thereby better solving the problems; the method is completed by laser index numbers in a wireless transmission mode, and adopts lasers with different combinations to realize parallel data transmission, so that the problem that the requirement on the resolution of hardware equipment is high due to the increase of modulation orders is solved. Meanwhile, the information is safely transmitted by utilizing the combination multiplexing of various modulation technologies, the information interception and decoding probability of a communication third party is reduced, the synchronization time can be shortened by adopting the byte framing, and the reliability and the effectiveness of information transmission are further improved.)

1. A layer mapping optical space diversity combined modulation laser communication coding and decoding method is characterized in that: the layer mapping optical space diversity combined modulation laser communication coding and decoding method comprises a coding method and a decoding method, wherein the coding method corresponds to the decoding method, and the coding method comprises the following steps:

step 1, establishing a layer mapping protocol, performing layer mapping on n-bit binary data to be transmitted according to the layer mapping protocol, wherein the layer mapping comprises PPM mapping and PAM mapping, and performing M-PPM modulation after the PPM mapping to obtain PPM pulses, wherein M is a PPM modulation order; performing PAM mapping and then performing L-PAM modulation to obtain PAM pulse, wherein L is a PAM modulation order;

step 2, fusing a PPM pulse and a PAM pulse by adopting a pulse amplitude position judgment method to obtain a PPAM pulse, wherein the PPAM pulse comprises amplitude information and position information;

and 3, mapping the PPAM pulse to a corresponding index laser by using OSM mapping, and transmitting information with position and amplitude by using the laser activated by the PPAM pulse, wherein the key technology is that the activated laser is used for sending an optical pulse corresponding to the mapping code to represent the amplitude information and the position information.

2. The layer-mapped optical space diversity combined modulation laser communication coding and decoding method according to claim 1, characterized in that: the layer mapping comprises allocating binary data with predefined number of bits of 2 into a group of data; numbering grouped data groups, carrying out PPM mapping on data with odd serial numbers, and adopting PAM mapping on data with even serial numbers; or PPM mapping is carried out on the data with even serial numbers, and PAM mapping is adopted on the data with odd serial numbers.

3. The layer-mapped optical space diversity combined modulation laser communication coding and decoding method according to claim 2, characterized in that: and step 2, also comprising byte framing, wherein the byte framing distributes bytes according to a preset framing protocol to obtain a plurality of groups of frame signals containing frame heads and data.

4. The layer-mapped optical space diversity combined modulation laser communication coding and decoding method according to claim 3, wherein: an empty time slot in which no pulse is transmitted by default is inserted between each group of frame signals as a guard segment.

5. The layer-mapped optical space diversity combined modulation laser communication coding and decoding method according to claim 4, wherein: the OSM mapping is sent by adopting a plurality of lasers, and the OSM demapping in the corresponding decoding is correspondingly collected by adopting the same plurality of laser receivers; and the OSM mapping carries out index numbering on the lasers, predefines an OSM mapping relation, maps the PPAM pulse to the lasers at corresponding positions to complete the activation of the lasers with corresponding amplitudes and send the lasers.

6. The layer-mapped optical space diversity combined modulation laser communication coding and decoding method according to any one of claims 1-5, characterized in that: the decoding method comprises the following steps:

step 4, demapping through OSM;

step 5, performing demapping on the PPAM pulse to obtain a PPM pulse and a PAM pulse;

and 6, combining the PPM pulse and the PAM pulse into a binary bit stream according to a layer mapping protocol, and finishing decoding.

7. The layer-mapped optical space diversity combined modulation laser communication coding and decoding method according to claim 6, wherein: and 5, adopting a joint decoding method, wherein the joint decoding method is used for restoring the corresponding PAM bit sequence according to the index number information of the laser to finish PAM identification, and restoring the corresponding PPM bit sequence by adopting the time slot position of the identification pulse in a frame signal to finish PPM identification.

8. The layer-mapped optical space diversity combined modulation laser communication coding and decoding method according to claim 7, wherein: the joint decoding method also comprises the steps of adopting a double-edge detection method to identify the index number of the laser and the time slot position where the corresponding light pulse is located;

the double-edge detection method simultaneously detects the number of the rising edges and the falling edges of the pulses, and judges the effectiveness of the frame header pulses of the PAM and the PPM according to the edge counting result;

the double-edge detection method also counts the pulse duration between each rising edge and each falling edge, filters out pulses whose duration does not meet a predefined time threshold, and only performs PPM identification and PAM identification on the filtered pulses.

9. The layer-mapped optical space diversity combined modulation laser communication coding and decoding method according to claim 6, wherein: the joint decoding method further includes: and a feedback protocol is established between the PPM identification and the PAM identification, namely, the result of the PAM frame header identification is sent to a pulse position judgment module, and meanwhile, the result of the PPM frame header identification is sent to a laser serial number identification module, and information recovery is carried out only when two frame header signals are correctly identified.

Technical Field

The invention relates to the field of laser communication, in particular to a layer mapping optical space diversity combined modulation laser communication coding and decoding method.

Background

The laser communication has the advantages of both microwave communication and optical fiber communication, and has the advantages of concentrated energy, long propagation distance, no need of laying large amount of optical fibers and capacity of ensuring high capacity information transmission. With the rapid development of high performance of user terminals in the communication field, high speed and high spectrum efficiency are always the targets pursued in the Wireless Optical Communication (WOC) field, and when the requirement of efficient transmission is met, the reliability is reduced, which includes direct influence on the error code performance caused by atmospheric turbulence and bad weather.

In the conventional single modulation technology, Pulse Position Modulation (PPM) utilizes pulse positions to transmit information, and although the transmission rate is low, the energy utilization rate is greatly improved along with the increase of modulation orders, so that the average transmission power of equipment is reduced. Pulse Amplitude Modulation (PAM) is a modulation technique with high spectral efficiency, but is limited by the resolution requirement of hardware devices due to the increase of the order, and can generate higher peak-to-average power, which causes the transmitter to work in a nonlinear field, resulting in the reduction of error code performance. In order to make reasonable use of the spatial bandwidth resources, the Optical Spatial Modulation (OSM) concept has been proposed, i.e. each link transmits information independently in the spatial domain, and the link itself carries the information. The modulation technology with outstanding advantages is subjected to fusion coding, the effect of spatial multiple transmission and multiple reception is fully exerted, and the effectiveness of communication is improved in a multiplexing mode.

The invention provides a layer mapping light space diversity combined modulation laser communication coding and decoding method, which adopts a diversity system structure by a space mapping and multiplexing technology and combines the high-frequency spectrum characteristic of PAM and the high-energy utilization characteristic of PPM, thereby not only reducing the average emission power of optical equipment in the aspect of power consumption, but also effectively utilizing spectrum resources to improve the spectrum efficiency and transmission rate on the basis of improving the error code performance. A secure and secret communication mechanism between the partner and the layer mapping protocol is constructed, so that the risk that information is decoded by an enemy can be reduced.

Disclosure of Invention

The technical problem to be solved by the invention is the technical problem of low spectrum efficiency and transmission rate in the prior art. The layer mapping optical space diversity combined modulation laser communication coding and decoding method has the characteristics of high average emission power of optical equipment, and high spectrum efficiency, transmission rate and confidentiality by effectively utilizing spectrum resources.

In order to solve the technical problems, the technical scheme is as follows:

a layer mapping optical space diversity combined modulation laser communication coding and decoding method comprises a coding method and a decoding method, wherein the coding method corresponds to the decoding method, and the coding method comprises the following steps:

step 1, establishing a layer mapping protocol, performing layer mapping on n-bit binary data to be transmitted according to the layer mapping protocol, wherein the layer mapping comprises PPM mapping and PAM mapping, and performing M-PPM modulation after the PPM mapping to obtain PPM pulses, wherein M is a PPM modulation order; performing PAM mapping and then performing L-PAM modulation to obtain PAM pulse, wherein L is a PAM modulation order;

step 2, fusing a PPM pulse and a PAM pulse by adopting a pulse amplitude position judgment method to obtain a PPAM pulse, wherein the PPAM pulse comprises amplitude information and position information;

and 3, mapping the PPAM pulse to a corresponding index laser by using OSM mapping, and transmitting information with position and amplitude by using the laser activated by the PPAM pulse, wherein the key technology is that the activated laser is used for sending an optical pulse corresponding to the mapping code to represent the amplitude information and the position information.

The working principle of the invention is as follows: the invention adopts a diversity system structure, combines the high-frequency spectrum characteristic of PAM and the high-energy utilization characteristic of PPM and adopts a PAM and PPM combined modulation method through a space mapping and multiplexing technology, thereby not only reducing the average emission power of optical equipment in the aspect of power consumption, but also effectively utilizing frequency spectrum resources to improve the frequency spectrum efficiency and transmission rate on the basis of improving the error code performance. A secure and secret communication mechanism between the partner and the layer mapping protocol is constructed, so that the risk that information is decoded by an enemy can be reduced.

In the above scheme, for optimization, further, the layer map includes allocating binary data with predefined number of bits of 2 as a group of data; numbering grouped data groups, carrying out PPM mapping on data with odd serial numbers, and adopting PAM mapping on data with even serial numbers; or PPM mapping is carried out on the data with even serial numbers, and PAM mapping is adopted on the data with odd serial numbers.

Further, step 2 further includes byte framing, where the byte framing allocates bytes according to a preset framing protocol to obtain multiple groups of frame signals including the frame header and the data.

Further, an empty time slot in which no pulse is transmitted by default is inserted between each group of frame signals as a guard segment.

Further, the OSM mapping is sent by adopting multiple lasers, and the OSM demapping in the corresponding decoding is correspondingly collected by adopting the same multiple laser receivers; and the OSM mapping carries out index numbering on the lasers, predefines an OSM mapping relation, maps the PPAM pulse to the lasers at corresponding positions to complete the activation of the lasers with corresponding amplitudes and send the lasers.

Further, the decoding method comprises:

step 4, demapping through OSM;

step 5, performing demapping on the PPAM pulse to obtain a PPM pulse and a PAM pulse;

and 6, combining the PPM pulse and the PAM pulse into a binary bit stream according to a layer mapping protocol, and finishing decoding.

Further, a joint decoding method is adopted in the step 5, the PAM recognition is completed by restoring the corresponding PAM bit sequence according to the index number information of the laser, and the PPM recognition is completed by restoring the corresponding PPM bit sequence by adopting the time slot position in the frame signal where the recognition pulse is located.

Furthermore, the joint decoding method also comprises the steps of adopting a double-edge detection method to identify the index number of the laser and the time slot position where the corresponding light pulse is located; the double-edge detection method simultaneously detects the number of the rising edges and the falling edges of the pulses, and judges the effectiveness of the frame header pulses of the PAM and the PPM according to the edge counting result; the double-edge detection method also counts the pulse duration between each rising edge and each falling edge, filters out pulses whose duration does not meet a predefined time threshold, and only performs PPM identification and PAM identification on the filtered pulses. Not only judges whether the PAM signal is interfered or lost, but also judges whether the time slot position of the PPM signal is staggered.

Further, the joint decoding method further includes: and a feedback protocol is established between the PPM identification and the PAM identification, namely, the result of the PAM frame header identification is sent to a pulse position judgment module, and meanwhile, the result of the PPM frame header identification is sent to a laser serial number identification module, and information recovery is carried out only when two frame header signals are correctly identified. This is to improve the accuracy of information identification.

For an n-bit binary data, the bit block b is obtained by hierarchical processing₁、b₂Wherein b is₁Corresponding to L-PAM, carries a number of bits ofL is a PAM modulation order; b₂Corresponding to M-PPM, carries a number of bits ofM is PPM modulation order, so that the data amount carried by each light emission isThe mapping relation of L-PAM can be represented by an M X1 dimensional vector XL, and X_L＝[0₁0₂···A_l···0_M]T; wherein A is_lRepresents the light intensity transmitted by the L-PAM modulation symbol, A_lΔ is a priority increment symbol, Δ is 2/(L + 1); l denotes the transmission of an L-PAM signal at the slot location, L ═ 1,2, … L, [ ·]^TRepresenting a transpose operation. The mapping relation of M-PPM can be realized by a vector X with the dimension of 1X M_MIs represented by X_M＝[0₁02···Sm···0_M](ii) a Wherein S_mThe average light intensity sent by the M-PPM modulation symbol is represented, and M represents that the M-PPM signal is sent at the time slot position.

The fused signal can be represented by matrix X:

wherein A is_lS represents the light intensity emitted by the final activated laser, and the row represents the specific laser sequence number mapped by the signal¹²···L]^TThe columns indicate the slot positions to which the signal pulses correspond.

The invention adopts a multi-transmitting multi-receiving mechanism, and can design different array diversity forms and working mechanisms according to actual requirements. The 4 × 4 array transceiving mode, i.e. both modulation orders are 4-order, is taken as an example for explanation. According to the 4-PAM coding rule, a mapping module is divided into 4 pulse signals with different amplitudes according to different code words of a bit stream, wherein four bit combinations (00,01,10 and 11) correspond to four amplitudes (V1, V2, V3 and V4), and each amplitude is mapped to a specific transmission link serial number (1,2,3 and 4). According to the 4-PPM coding rule, the mapping module divides the bit stream code word into 4 time slot positions according to the bit stream code word sequence, and maps the bit block into pulses corresponding to the information in the 4 time slots.

When information transmission starts, each frame adopts a frame header as the guidance of information, and only under the condition that the frame header detection is correct, the trailing information frame is identified. The simplest way to frame bytes is to match a header to a byte to form a frame signal.

In the layer demapping, bit sequence combination is carried out on the restored information according to a layer mapping protocol of a sending end, and finally demodulation and decoding of binary information are completed.

The invention has the beneficial effects that: the invention utilizes the laser communication technology to construct a space multi-transmitting and multi-receiving transmission mechanism, improves the space multiplexing gain through optical space mapping in a space domain, and realizes Pulse Position Amplitude Modulation (PPAM) to jointly transmit information through Time Division Multiplexing (TDM) technology combined with the high spectral efficiency of PAM and the high energy utilization rate of PPM in a time domain. This patent technique fuses multiple amplitude pulse on traditional PPM pulse basis, adopts the diversity system structure, improves the signalling rate simultaneously at the improvement frequency spectrum efficiency. The traditional PAM modulation symbol is replaced by the index number of the laser in a wireless transmission mode, and the problem that the resolution requirement of hardware equipment is high due to the fact that the modulation order is increased is solved. Meanwhile, the combination and multiplexing of multiple modulation technologies are utilized to facilitate the safe transmission of information, the probability of information interception and decryption by a communication third party is reduced, the synchronization time can be shortened by adopting byte framing, the reliability and effectiveness of information transmission are further improved, and important reference and application values are realized in multiple fields.

Drawings

The invention is further illustrated with reference to the following figures and examples.

Fig. 1 is a schematic diagram of a 4 × 4 optical spatial diversity joint modulation coding and decoding method in embodiment 1.

Fig. 2 is a schematic diagram of a joint modulation coded frame format according to embodiment 1.

Fig. 3 is a waveform diagram of the (4,4) -PPAM actual transmission of the optical spatial joint modulation codec of embodiment 1.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example 1

The embodiment provides a layer mapping optical space diversity combined modulation laser communication coding and decoding method, which includes a coding method and a decoding method, where the coding method corresponds to the decoding method, and the coding method includes:

step 1, establishing a layer mapping protocol, performing layer mapping on n-bit binary data to be transmitted according to the layer mapping protocol, wherein the layer mapping comprises PPM mapping and PAM mapping, and performing M-PPM modulation after the PPM mapping to obtain PPM pulses, wherein M is a PPM modulation order; performing PAM mapping and then performing L-PAM modulation to obtain PAM pulse, wherein L is a PAM modulation order;

step 2, fusing a PPM pulse and a PAM pulse by adopting a pulse amplitude position judgment method to obtain a PPAM pulse, wherein the PPAM pulse comprises amplitude information and position information;

and 3, mapping the PPAM pulse to a corresponding index laser by using OSM mapping, and transmitting information with position and amplitude by using the laser activated by the PPAM pulse, wherein the key technology is that the activated laser is used for sending an optical pulse corresponding to the mapping code to represent the amplitude information and the position information.

As shown in fig. 1, each character is respectively subjected to joint coding modulation in each group of data, each character corresponds to 8-bit information, and the first character information can be represented as follows from high order to low order:

B₁＝[b₈,b₇,b₆,b₅,b₄,b₃,b₂,b₁]。

and performing layered processing on each byte respectively. Specifically, the layer map includes allocation of binary data of bits with a predefined number of bits of 2 as a set of data; numbering grouped data groups, carrying out PPM mapping on data with odd serial numbers, and adopting PAM mapping on data with even serial numbers; or PPM mapping is carried out on the data with even serial numbers, and PAM mapping is adopted on the data with odd serial numbers.

In the layer mapping, two binary bits are allocated as one group, and each group of data is numbered. Each group of bits is distributed to different layers in a layer mapping mode, wherein arrays with odd numbers are distributed to a PAM module, arrays with even numbers are distributed to a PPM module, and each module processes binary bit streams according to a specific modulation mode.

B₁In odd blocks [ b ]₈,b₇]And [ b)₄,b₃]Corresponding to the bit blocks (10,00) in fig. 1, respectively, in the process of performing 4-PAM modulation, the amplitudes (V3, V1) corresponding to the information are output according to the bit information content, respectively.

B₁In which is an even block [ b₆,b₅]And [ b)₂,b₁]Corresponding to the bit block (11,01) in fig. 1, respectively, during the 4-PPM modulation, the pulse generated by the fourth and the second time slot are mapped according to the bit information.

When the PAM module activates a transmission link once, the PPM module correspondingly generates a pulse of a specific time slot, so that each byte correspondingly transmits two PPAM pulses which carry position information and are correspondingly specific in transmission link serial number. And in the judgment of pulse amplitude and position, fusing the two modulated signals to obtain a pulse serial multiplexing signal which contains different amplitudes and carries position information.

Preferably, the step 2 further includes byte framing, where the byte framing allocates bytes according to a preset framing protocol to obtain multiple groups of frame signals including the frame header and the data. In order to improve the synchronization efficiency.

As shown in fig. 2, in each frame signal format, the waveform at the frontmost end is a frame header pulse, an information pulse is triggered following the frame header pulse, and when the first information is sent, a second frame header pulse and an information pulse are sent, so that the process is repeated.

Preferably, an empty time slot in which no burst is transmitted by default is inserted between each group of frame signals as a guard segment. The method aims to prevent intersymbol interference caused by pulse coincidence among pulses and facilitate edge detection of a demodulation end, and the duration is freely set according to the actual system performance so as to improve the reliability of the receiver for detecting pulse signals.

Specifically, each laser has a fixed index number, each index number corresponds to a specific modulation symbol, and the pulse multiplexed by the fusion coding is mapped to the specific laser to be transmitted according to the OSM mapping relationship. In OSM demapping, a receiver array is placed according to a corresponding relation matched with a transmitting end index number, optical signal collection is carried out in a one-to-one receiving mode, the index number of an activated laser is identified by a signal through an OSM demapping module, meanwhile, multiple paths of signals are fused into a single path of signal which carries laser index number information and changes the positions of pulses, the signal is sent to a corresponding PAM and PPM demodulation module to be demodulated at the same time, bit blocks corresponding to the PAM are restored according to the index number information, and bit blocks corresponding to the PPM are restored according to the time slot positions of the pulses.

Specifically, the decoding method includes:

step 4, demapping through OSM;

step 5, performing demapping on the PPAM pulse to obtain a PPM pulse and a PAM pulse;

and 6, combining the PPM pulse and the PAM pulse into a binary bit stream according to a layer mapping protocol, and finishing decoding.

Specifically, a joint decoding method is adopted in the step 5, the PAM recognition is completed by restoring the corresponding PAM bit sequence according to the index number information of the laser, and the PPM recognition is completed by restoring the corresponding PPM bit sequence by adopting the time slot position in the frame signal where the recognition pulse is located.

Specifically, the joint decoding method further comprises identifying the index number of the laser and the time slot position where the corresponding light pulse is located by adopting a double-edge detection method; the double-edge detection method simultaneously detects the number of the rising edges and the falling edges of the pulses, and judges the effectiveness of the frame header pulses of the PAM and the PPM according to the edge counting result; the double-edge detection method also counts the pulse duration between each rising edge and each falling edge, filters out pulses whose duration does not meet a predefined time threshold, and only performs PPM identification and PAM identification on the filtered pulses.

Not only judges whether the PAM signal is interfered or lost, but also judges whether the time slot position of the PPM signal is staggered.

In the joint coding, the present embodiment maps each bit information to a specific time slot according to the processing mode of inter-module parallel and intra-module serial.

In order to ensure the reliability of actual transmission and frame signal synchronization, a barker code with good autocorrelation can be added as a frame header before reading the data stored in each address. Wherein, the frame header data can be selected from 0111_0010 to form two frame header pulses with different amplitudes and different time slot positions, so as to complete the guidance and data information framing.

In fig. 3, firstly, a coded signal waveform is transmitted in a joint modulation experiment in the embodiment, and a transmitting end transmits the coded signal waveform according to a sending mode of 2 characters in each group; wherein each short frame contains 4 pulses of varying amplitude and position. The PAM and PPM modulation orders are both 4 orders, and the default of each pulse width and the time slot duration is 1 ms.

The waveform of the signal restored by the receiving end is shown in fig. 3, the delay time of the actual wireless transmission signal is about 1us, and the waveform in the figure can know that each pulse retains the characteristics of amplitude and position change, namely, each data pulse simultaneously hides the amplitude and position information and carries out multiplexing transmission.

The data waveforms are respectively corresponding to four sending amplitude values of characters m and 8, 4-PAM, and are respectively corresponding to 1V, 2V, 3V, 5.5V, and the time slot position of each data pulse corresponds to 4-PPM information.

Each pulse in the waveform carries a 2-bit PAM signal and a 2-bit PPM signal respectively, wherein the two pulses at the forefront are frame header pulses and correspond to Barker code information 0111_0010, the information carried by the first pulse in the frame header is 0111 with high four bits, and the information carried by the second pulse is 0010 with low four bits, so that the frame header corresponds to two pulses with fixed amplitudes of 2V and 1V. The character of two pulse transmission of data is m (0110_1101), the amplitude is 2V and 5.5V respectively, and the position of the pulse is the 3 rd time slot and the 2 nd time slot in the PPM time slot respectively.

In each short frame, in order to achieve the purposes of reducing intersymbol interference and conveniently carrying out edge detection on the pulse, after 4 time slots containing the PPAM pulse are ended, the default time slots are sent again by 4, no signal is sent in the period, after the time of the 4 time slots is ended, the 4 time slots containing the PPAM pulse are continuously sent, and the steps are repeated in sequence. Therefore, the amplitude of two pulses of the frame header is fixed to be 2V and 1V, and the interval time of the two pulses is fixed to be 6 ms. And after the two data pulses are transmitted, continuously transmitting the frame header pulse to send the next round of information, and repeating the steps in sequence.

In order to improve the communication spectrum efficiency, the PAM modulation order may be increased appropriately, but more transmission links need to be equipped in the implementation manner, thereby increasing the hardware complexity.

On the premise of ensuring a certain error code, the duration of each time slot can be properly shortened, and the communication rate is improved.

In order to reduce power consumption, the PPM modulation order can be properly increased under the condition that the communication rate is not limited, and the power utilization rate of the equipment is improved.

Although the illustrative embodiments of the present invention have been described above to enable those skilled in the art to understand the present invention, the present invention is not limited to the scope of the embodiments, and it is apparent to those skilled in the art that all the inventive concepts using the present invention are protected as long as they can be changed within the spirit and scope of the present invention as defined and defined by the appended claims.