A wireless optical communication method, system and device based on physical layer network coding

Abstract

This invention discloses a wireless optical communication method, system, and apparatus based on physical layer network coding. The method includes: acquiring channel characteristics from two user nodes A and B to a relay node R; acquiring a Gaussian prime number q; and generating complex signals s in user nodes A and B respectively based on the channel characteristics and the Gaussian prime number q. A and s B User nodes A and B, based on the generated complex signal s A and s B Obtain the real signal x respectively A and x B Then each transmits x through modulated wireless light. A and x B Transmitted to relay node R; relay node R simultaneously receives signals from users A and B, and determines the transmission method based on the received signal x. e Obtain complex signal s e Based on the Gaussian prime number q and the complex signal s e Obtain the encoded complex signal s coded According to the encoded complex signal s coded Obtain the real signal x coded Then, by modulating wireless light, x coded The data is sent back to user nodes A and B. This invention improves spectral efficiency and performance and can be widely applied in the field of communication technology.

Description

Technical Field

[0001] This invention relates to the field of communication technology, and in particular to a wireless optical communication method, system, and apparatus based on physical layer network coding. Background Technology

[0002] Wireless optical communication (WOC) is an effective supplement to wireless microwave communication technology, which is facing increasingly scarce spectrum resources. It boasts numerous advantages, including no electromagnetic interference, environmental friendliness, and high security, and is considered one of the key technologies for future 6G. WOC relies on line-of-sight links for transmission, and physical obstructions can lead to a decline in communication quality or even complete interruption. Relay networks expand the coverage of communication systems, enabling different nodes that were previously unable to communicate directly to exchange information via relays. Physical layer network coding (PLC) technology can reduce the time slots required for users to exchange information in relay-based WOC systems, thereby improving system throughput and reducing latency. The first existing paper introduces PLC in full-duplex optical relay systems based on amplification-forwarding mode, exploring encoding and decoding methods and bit error rate performance for modulation formats such as OOK, BPSK, and OFDM. The second existing paper introduces the adaptive bit loading method of OFDM into visible light communication systems based on PLC, solving not only the inherent frequency-selective fading problem in visible light systems but also reducing signal synchronization requirements at relay nodes. The third existing paper further extends the research on PLC to visible light communication systems under asymmetric channels. However, all of the above studies are based on amplification-forwarding mode. Decoding and forwarding systems offer superior performance by recoding signals at relay nodes to reduce the number of constellation points for signals superimposed from multiple users. However, current research on physical layer network coding for decoding and forwarding wireless optical communication systems is limited. The fourth existing paper proposes using XOR operations at relay nodes to recode signals from different users; however, this method is only applicable to low-order phase modulations such as BPSK and QPSK and cannot be ported to higher-order QAM signals. Furthermore, in decoding and forwarding systems, the phase and amplitude of signals transmitted by user nodes affect the constellation diagram of signals superimposed at relay nodes, thus influencing the coding method and performance. Therefore, design and optimization based on channel characteristics are necessary. Summary of the Invention

[0003] In order to at least partially solve one of the technical problems existing in the prior art, the purpose of this invention is to propose a wireless optical communication method, system and device based on physical layer network coding.

[0004] The technical solution adopted in this invention is: A wireless optical communication method based on physical layer network coding includes the following steps: It includes at least two user nodes A and B, and a relay node R, each of which includes at least one transmitter and one receiver; Obtain the channel characteristics from two user nodes A and B to relay node R, and obtain at least one Gaussian prime number. q Based on the channel characteristics and the Gaussian prime number q At least one complex signal is generated in user nodes A and B respectively. s A and s B The complex signal s A and s B The number of constellation points is not greater than a Gaussian prime number. q The square of the modulus; User nodes A and B, based on the at least one complex signal generated... s A and s B Obtain real signals respectively x A and x B Then, each transmits the real signal via modulated wireless light. x A and x B Transmit to relay node R; Relay node R simultaneously receives signals from user node B, and then... x e Obtain at least one complex signal s e According to the Gaussian prime number q With the at least one complex signal s e Obtain at least one encoded complex signal s coded According to the encoded complex signal s coded Obtain real signal x coded Then, the real signal is modulated by wireless light. x coded Send back to user nodes A and B; User nodes A and B respectively receive signals transmitted by relay node R. User node A then determines the signal based on the received signal and Gaussian prime numbers. q The complex signal s A Obtain complex signals s BThe information, user node B, is based on the received signal and Gaussian prime numbers. q The complex signal s B Obtain complex signals s A Information.

[0005] This invention addresses the following scenario: Two user nodes, A and B, need to exchange information. However, since wireless optical communication relies on line-of-sight links, obstacles or the limited field of view of the transceiver prevent direct communication between nodes A and B. In such cases, a relay node R is needed to assist user nodes A and B in exchanging information. Physical layer network coding (PLC) technology can be used to improve throughput or reduce latency during this process. This invention targets a PLC-based wireless optical communication relay system based on decoding and forwarding, which mainly consists of the following steps: First, user nodes A and B send the information they need to exchange to relay node R. This information is simultaneously received by relay node R, resulting in the constellation diagrams of the two signals overlapping, leading to a large number of constellation points. The relay node re-encodes the overlapping signals to reduce the number of constellation points and improve the signal-to-noise ratio. Then, the re-encoded signal is simultaneously sent back to user nodes A and B. User node A (or B) uses the received re-encoded information and its own information to extract information from node B (or A).

[0006] In wireless optical communication, the signal modulated onto the optical path must be a real number. However, in this invention, the signals processed by user nodes A and B, as well as relay node R, for encoding and decoding are different. s A , s B , s e , s coded Both are represented using complex numbers; therefore, the complex signals used for encoding and decoding differ from the real signals used for transmitting or receiving. x A , x B , x e , x coded There is a certain conversion relationship between them, which can be achieved by using multi-carrier modulation or CAP modulation with conjugate symmetry of the spectrum. However, this invention does not limit the specific conversion method. In multi-carrier modulation, this invention only requires that at least one subcarrier uses the method of this invention. When different carriers use this method, the modulation format (or the number of constellation points) on different carriers and the Gaussian prime number are... q The numbers can differ; for example, an adaptive loading algorithm can be used to determine the number of constellation points carried by different carriers, and based on this, the Gaussian prime number used for each subcarrier can be determined.q Then each subcarrier according to its own q Each generates its own complex signal.

[0007] The complex signals processed by user nodes A and B and relay node R, including encoding and decoding, are based on Gaussian primes. q The principle of finite fields is applied. During encoding and decoding, the channel characteristics affecting the signals superimposed at relay node R are considered. s e The influence of constellation points, and adjust the complex signals generated at user nodes A and B accordingly. s A , s B The amplitude and / or phase enhancement performance.

[0008] Furthermore, at least one complex signal is generated in user nodes A and B respectively. s A and s B The steps include: According to the Gaussian prime number q Obtain its Gaussian integer finite field, and obtain the complex signal based on the Gaussian integer finite field. s A and s B .

[0009] User nodes A and B generate complex signals. s A and s B The steps include first determining s A and s B The number of constellation points used, such as 16QAM, 32QAM, or 64QAM, determines the Gaussian primes based on the number of constellation points. q Among them, Gaussian primes q The square of the modulus is not less than the number of constellation points in the proposed modulation scheme. Based on Gaussian primes... q Obtain the corresponding Gaussian integer finite field, where the number of elements in the Gaussian finite field is . q The square of the modulus, represented by different elements selected in the finite field of Gaussian integers. s A and s B Different constellation points.

[0010] Furthermore, at least one complex signal is generated in user nodes A and B respectively. s A ands B The steps include: Adjust the complex signal according to the channel characteristics from the two user nodes A and B to the relay node R. s A Complex signals s B Or at least one of the phase and amplitude of both.

[0011] Signals generated by user nodes A and B s A , s B Alternatively, at least one of the phase and amplitude of the two signals may be adjusted according to the channel characteristics from user nodes A and B to relay node R. The purpose is to make the signals superimposed at the relay node more favorable for physical layer network coding to improve performance. The channel characteristics here can be obtained by measuring training data and may include the response at different frequency points in the frequency domain. The specific implementation method and representation form of obtaining the channel characteristics are not limited in this invention.

[0012] Furthermore, the Gaussian prime number q The value is determined based on the channel characteristics.

[0013] Channel characteristics affect the number of complex signals that can be carried. s A and s B The number of constellation points. When the channel is poor, low-order modulation formats such as QPSK and 8QAM are suitable; when the channel is good, high-order modulation formats such as 16QAM and 32QAM are suitable. Correspondingly, complex signals... s A and s B The number of constellation points should not exceed the number of Gaussian primes. q The square of the modulus, therefore the value of the Gaussian prime should be selected based on the number of constellation points to be used. It should be noted that the generated complex number... s A and s B The constellation shape of QAM does not necessarily need to be maintained; it can be scaled in amplitude or rotated in phase according to the channel characteristics, as explained above.

[0014] Furthermore, the real-number signals obtained by user nodes A and B respectively x A and x B It can be a CAP signal or a multi-carrier signal; When it is a multi-carrier signal, the at least one complex signal sA Real number signal x A The signal on one or more subcarriers, the at least one complex signal s B Real number signal x B The signal on one or more subcarriers.

[0015] This invention provides a method for generating and encoding... s A and s B To convert to a method suitable for wireless optical modulation. s A and s B While the signal is complex, the transmission signal for wireless optical signals needs to be a non-negative real number. Therefore, this invention employs a spectrally conjugate symmetrical CAP or multi-carrier signal to ensure the real-valued characteristics of the transmitted signal. This invention does not limit the non-negative characteristic because, in practice, a DC bias can be added to the real-valued CAP or multi-carrier signal to obtain a non-negative signal. Alternatively, the real-valued signal can be directly modulated into an LED or LD, and a suitable signal for modulation can be obtained by controlling the bias voltage of the LED or LD. The complex signal... s A and s B Place x A and x B On a positive frequency subcarrier. It should be noted that this invention can generate multiple complex signals. s A and s B Placed on different subcarriers in a multicarrier signal, different subcarriers can have different modulation formats and their corresponding Gaussian primes. q The modulation format on different subcarriers can be determined based on the channel characteristics.

[0016] Furthermore, the statement based on the Gaussian prime number... q With the at least one complex signal s e Obtain at least one encoded complex signal s coded The steps include: complex signals s e Group the constellation points in the data and map the constellation points in the same group to... s coded The same constellation point in the map maps different groups of constellation points to... scoded The different constellation points in the array, where the number of groups is no greater than the number of Gaussian primes. q The square of the modulus.

[0017] The relay node will superimpose signals from multiple constellation points. s e Re-encoding is performed to reduce the number of constellation points, thereby improving the signal-to-noise ratio. The method to reduce the number of constellation points is to... s e Group the constellation points in the data, and map the constellation points in the same group to... s coded The same constellation point in the same constellation, different groups of constellation points are mapped to s coded Different constellation points in the constellation. s coded The constellation points in the diagram also use Gaussian primes. q The elements are represented in a finite field, so the number of groups must not exceed the Gaussian prime number. q The square of the modulus.

[0018] Furthermore, the statement based on the Gaussian prime number... q With the at least one complex signal s e Obtain at least one encoded complex signal s coded The steps include: According to the Gaussian prime number q Obtain its Gaussian integer finite field, and obtain at least two Gaussian integers in the Gaussian integer finite field. Then, based on the two Gaussian integers... s e Group the constellation points in the data and map the constellation points in the same group to... s coded The same constellation point in the map maps different groups of constellation points to... s coded Different constellation points in the constellation, wherein the two Gaussian integers make the s e Maximize the minimum distance between constellation points in different groups.

[0019] This invention provides a method for... s e The specific method for grouping constellation points in Gaussian primates involves finding two elements within a finite field of Gaussian primes. α and β Encoded signal s coded Characterized as s A and s B The linear superposition of, wheres A and s B The coefficients are respectively α and β Based on the properties of Gaussian integer finite fields, we can... s coded as well as s A and s B One of them obtains the value of the other, so when user nodes A and B receive and extract... s coded Afterwards, you can base your decisions on your own information and... s coded To obtain the information sent by the other party. Furthermore, α and β The choice should make the choice in the context of s e Maximize the minimum Euclidean distance between different groups when grouping constellation points.

[0020] Furthermore, the wireless light includes one or a combination of visible light, infrared light, and ultraviolet light.

[0021] This invention can be used in visible light communication systems, infrared or ultraviolet light communication systems.

[0022] Another technical solution adopted in this invention is: A wireless optical communication system based on physical layer network coding methods includes: At least two user nodes A and B, and one relay node R, each node including at least one transmitter and one receiver; User nodes A and B each generate at least one complex signal according to the method described above. s A and s B According to the at least one complex signal s A and s B Obtain real signals respectively x A and x B Then each transmits the wireless light through modulation. x A and x B Transmit to relay node R; Relay node R simultaneously receives signals from user node B and obtains the real number signal using the method described above. x codedThen, by modulating wireless light, x coded Send back to user nodes A and B; User nodes A and B respectively receive signals transmitted by relay node R and acquire complex signals according to the method described above. s B and s A Information.

[0023] Another technical solution adopted in this invention is: A wireless optical communication device based on a physical layer network coding method includes: At least one processor; At least one memory for storing at least one program; When the at least one program is executed by the at least one processor, the at least one processor performs the above method.

[0024] The beneficial effects of this invention are: This invention solves the problem that current wireless optical communication systems based on physical layer network coding are mainly oriented towards amplification and forwarding and are not applicable to high-performance decoding and forwarding modes, or are only applicable to low-order phase modulation. At the same time, it considers the impact of user-end signal design on coding, and adjusts the phase and / or amplitude of the transmitted signal of the user node according to the characteristics of the link channel, thereby improving spectral efficiency and performance. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following description is provided with accompanying drawings of the relevant technical solutions in the embodiments of the present invention or the prior art. It should be understood that the accompanying drawings described below are only for the purpose of clearly illustrating some embodiments of the technical solutions of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of a wireless optical communication system based on physical layer network coding in an embodiment of the present invention; Figure 2 To select Gaussian primes q =2+i constellation diagram; where the corresponding finite field z[i] / (2+i) has two sets (star and dots) representing elements, and the 4 dots in the rectangle in the diagram constitute the 4QAM constellation points; Figure 3 According to s A (or s B Get x A (or xB ) and according to x e Get s e Flowchart; Figure 4 For when the channel h A =0.9, h B =1, using ( α , β When )=(1, 2i) s e The diagram shows the grouping results of the constellation points and the minimum Euclidean distance between different groups; five symbols represent five groups. Figure 5 For when the channel h A =0.9, h B =1, using ( α , β When )=(1, 2) s e The diagram shows the grouping results of the constellation points and the minimum Euclidean distance between different groups; five symbols represent five groups. Figure 6 for d min,opt along with ( h A / h B A graph showing the changes; Figure 7 For when the channel h A =0.9e jπ / 3 , h B =1, using optimized ( α , β When )=(1, i) s e Grouping results of constellation points and d min,opt A schematic diagram; Figure 8 To be based on the actual channel h A / h B A flowchart for adjusting the amplitude and / or phase of signals in user nodes; Figure 9 This is a hardware schematic diagram of a wireless optical communication system based on physical layer network coding in an embodiment of the present invention; Figure 10 This is a flowchart of a wireless optical communication method based on physical layer network coding in an embodiment of the present invention. Detailed Implementation

[0027] The embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. The step numbers in the following embodiments are set only for ease of explanation, and there is no limitation on the order between the steps. The execution order of each step in the embodiments can be adaptively adjusted according to the understanding of those skilled in the art.

[0028] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0029] In the description of this invention, "several" means one or more, "more than" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0030] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0031] like Figure 10 As shown, this embodiment provides a wireless optical communication method based on physical layer network coding, suitable for high-performance decoding and forwarding as well as high-order QAM modulation. It also considers the impact of channel characteristics on the modulation, phase, and amplitude design at the user end, thereby improving spectral efficiency and performance. The method specifically includes the following steps: Step 1: Obtain the channel characteristics from two user nodes A and B to relay node R, and obtain at least one Gaussian prime number. q Based on the channel characteristics and the Gaussian prime number q At least one complex signal is generated in user nodes A and B respectively. s A ands B The complex signal s A and s B The number of constellation points is not greater than a Gaussian prime number. q The square of the modulus; Step 2: User nodes A and B, based on the at least one complex signal generated... s A and s B Obtain real signals respectively x A and x B Then, each transmits the real signal via modulated wireless light. x A and x B Transmit to relay node R; Step 3: Relay node R simultaneously receives signals from user node B, and then... x e Obtain at least one complex signal s e According to the Gaussian prime number q With the at least one complex signal s e Obtain at least one encoded complex signal s coded According to the encoded complex signal s coded Obtain real signal x coded Then, the real signal is modulated by wireless light. x coded Send back to user nodes A and B; Step 4: User nodes A and B respectively receive the signals transmitted by relay node R. User node A then determines the signal based on the received signal and the Gaussian prime number. q The complex signal s A Obtain complex signals s B The information, user node B, is based on the received signal and Gaussian prime numbers. q The complex signal s B Obtain complex signals s A Information.

[0032] The above method will be explained in detail below with reference to the accompanying drawings and specific embodiments.

[0033] like Figure 1 As shown, two user nodes A and B, obstructed by an obstacle, can exchange information with each other in two time slots via a relay node R. The first time slot is called the multiple access phase. Nodes A and B send signals, which are superimposed at relay R to form a superimposed signal with a higher-order format or more constellation points. The second time slot is called the broadcast phase. In the conventional amplify-forward mode physical layer network coding scheme, the detected superimposed signal is amplified and sent back to nodes A and B during the broadcast phase. Then, node A (or B) obtains the information sent by node B (or A) by using the superimposed signal and its own information. In contrast, in the decode-forward mode, the relay node re-encodes the superimposed signal before broadcasting it back to both nodes to reduce the number of constellation points and improve the signal-to-noise ratio. For formats such as BPSK and QPSK, re-encoding can be achieved using XOR operations. However, this method cannot be applied to higher-order QAM.

[0034] To address the aforementioned problems, this invention proposes a decoding and forwarding physical layer network coding method based on Gaussian integer finite field, and simultaneously designs the amplitude and / or phase of the transmitter signal according to channel characteristics to improve the signal-to-noise ratio. The specific implementation will be described below using an OFDM visible light communication system as an example. First, the channels from user node A and user node B to relay node R are estimated, and their frequency response is assumed to be... h A ( ω )and h B ( ω Channel estimation can be obtained by transmitting training sequences. The modulation order of each subcarrier is set according to the estimated channel, such as QPSK, 8QAM, 16QAM, etc. In practice, an adaptive bit loading algorithm can be used to assign a suitable modulation order to each subcarrier. It should be noted that in OFDM, as long as only one subcarrier uses the method of this invention, it is within the scope of protection of this invention. For simplicity, we will only introduce the signal design and encoding / decoding principles for one subcarrier below. Assuming the modulation signal of this subcarrier is QPSK, we obtain the Gaussian prime number. q ,in q The square of the modulus must be greater than the number of constellation points. M That is, greater than 4. In this example, we choose Gaussian primes. q =2+i. All Gaussian integers in the complex plane are divided by Gaussian primes. q The remainder obtained after division can be divided into several categories, defined as z[i] / q ,form q A finite field of Gaussian integers. When q When z[i] = 2 + i, it can be divided into 5 categories. It should be noted that z[i] / q The representative element can be chosen in different ways, such as Figure 2 As shown. Figure 2 The 5 stars in the image form z[i] / q The set, denoted as set 1. In addition, z[i] / q You can also use a set of black dots set 2 indicates, set 2. Using elements b k +λq Replaced set 1. Elements in a set b k ,in λ It is a Gaussian integer. In this example, we use... set 2. Perform 4QAM modulation, such as Figure 2 As shown in the rectangle in the image, named set QAM Similarly, 8QAM and 16QAM can be adopted respectively. q =3 and q =4+i is obtained.

[0035] Perform similar operations on different subcarriers, that is, for the first... j OFDM subcarriers, nodes A and B from set set j,QAM Select symbol s j,QAM,A and s j,QAM,B When adaptive bit loading is used, different subcarriers can use different... q This is used to generate QAM signals of different orders. For simplicity, we will omit the index in the following discussion. j Soon s j,QAM,A and s j,QAM,B Simplified to s QAM,A and s QAM,B First of all, s QAM,A and s QAM,B Normalization yields:

[0036] in s CENTER It is the average value of the QAM signal. p A and p B They are ( s QAM ,A - s CENTER )and( s QAM , B - s CENTER The average power of ). Then, in formula (1) s A and s B The signal is loaded into the OFDM's first... j Each subcarrier is processed similarly. Then, the OFDM signal is Hermitian conjugate symmetric spread to generate a real-time signal. A cyclic prefix (CP) is added to resist inter-symbol interference in the channel, and an offset is added to obtain a non-negative real-number signal. x A and x B Then, the LED or LD is modulated and transmitted to the relay node R. This step is as follows: Figure 3 As shown. It should be noted that this invention is not limited. x A and x B Since it is a non-negative signal, in practice, it is not necessary to add a DC bias; the real signal can be directly applied. x A and x B The signal is applied to an LED or LD, and a signal suitable for modulation is obtained through the bias voltage of the LED or LD.

[0037] The delays between nodes A and B and relay node R may differ, but this issue can be resolved using a cyclic prefix in OFDM. The received signal at relay node R is... x e After removing the CP and transforming back to the frequency domain, the first... j The signal of each subcarrier s e ,like Figure 3 As shown. This signal can be represented as s A and s B Signal superposition:

[0038] in h A and h B These are the links AR and BR in the first... j The channel response on the OFDM subcarrier is ignored here. jThe index of OFDM subcarriers j To simplify the expression. n r It's noise at the relay node. Clearly, s e have M 2 A constellation point. In this embodiment, s A and s B Each constellation point is used, so s e have M 2 =16 constellation points. Relay node R pairs s e ( s A , s B Re-encoding is needed to reduce the number of superimposed constellation points. Therefore, it is necessary to... s e Grouping constellation points in the data, mapping constellation points in the same group to... s coded ( s A , s B The same constellation point symbol in the () maps constellation points from different groups to s coded ( s A , s B Different constellation point symbols in ). Figure 4 and Figure 5 This represents two different grouping methods, with different groups represented by circles, triangles, squares, rhombuses, and stars, respectively. For convenience, we define... C e ( s A , s B )for s e ( s A , s B The set of constellation points in the group to which () belongs, that is, if ( s A1 , s B1 )and( s A1 , s B1 In the same Ce In the middle, then s coded ( s A1 , s B1 )= s coded ( s A2 , s B2 (mod) q ),otherwise, s coded ( s A1 , s B1 ) s coded ( s A2 , s B2 (mod) q The grouping of constellation points needs to meet two basic requirements: 1) To ensure that decoding can be achieved at nodes A and B, s A (or s B ) should be by s B (or s A )and s coded ( s A , s B 1) Uniquely identifiable; 2) Belongs to different C e In s e The minimum distance between them should be maximized.

[0039] To achieve the first requirement, we use formula (3) from the finite field set Choose from 1 s coded :

[0040] in α and β yes set The elements in 1\{0}. According to the properties of finite fields, for set Any element in 1\{0} α and β ,exist set 1\{0} contains α-1 and β -1 ,satisfy α α -1 =1(mod q )and β β -1 =1(mod q ).therefore, s B It can be done s A and s coded ( s A , s B Unique achievement:

[0041] Similarly, given s A and s coded ( s A , s B In the case of ), it can be uniquely obtained s B .

[0042] Equation (3) is not correct. α and β Adding constraints should be done with caution in practice. α and β To meet the second requirement. We still use s A and s B Using QPSK at four constellation points as examples, at the relay node... s e There are 16 overlapping constellation points, classified into 5 groups, defined as The five groups are represented by circles, triangles, squares, rhombuses, and stars, respectively. These five groups are mapped to five constellation points in z[i] / (2+i), representing... s coded The five constellation dots in the image. You can see that... Figure 4 The mapping method is superior to Figure 5 The minimum distance between constellation points belonging to different groups is:

[0043] Therefore, we need to find optimization.α and β satisfy:

[0044] relay node will s e Remapping to s coded A similar operation is performed on each subcarrier, then the OFDM signal is Hermitian conjugate symmetric spread to generate a real-time signal, CP is added to resist inter-symbol interference in the channel, and an offset is added to obtain a non-negative real signal. x coded Then, the LED or LD is modulated and sent back to nodes A and B. This step of converting a complex signal into a real signal is the same as the step in user nodes A and B.

[0045] Apart from( α , β ), It also depends on the channel. h A and h B .because s e = h B ( h A / h B s A + s B )+ n r ,so h A / h B It has an impact s A and s B The way constellation points are superimposed affects... s e Grouping method of constellation points. h A / h B This can be changed by adjusting the power and / or phase of the transmitted signals at user nodes A and B. Figure 6 When h A / h B =0.9, 1 and 1.1 dmin,opt Follow ( h A / h B The changes in ) d min,opt Is it to adopt the optimal ( α , β The minimum distance that is maximized when ) d min . Figure 7 Showing when h A =0.9e jπ / 3 , h B =1 s e Grouping results of constellation points and d min,opt ,in( α , β ) represents the optimized coding coefficient (1,i). Clearly, d min,opt This can be boosted by controlling the phase of the transmitted signals in nodes A and B. When h A / h B When the phase is between 0.9 and 1.1, the optimal phase is 0 or π / 2. Therefore, we use the following phase alignment method when transmitting signals at nodes A and B:

[0046] Furthermore, different h A / h B Each has its corresponding d min,opt In practice, it is possible to establish [something] in advance. h A,t / h B,t and d min,opt The relationships between them are stored in a lookup table, which we use here. h A,t and h B,t To distinguish it from the actual measured channel response. During operation, the actual channel response is first estimated. h A / h B If only user nodes A and B are required to adjust their phases, then according to h A,t / h B,t = h A / h B Find the maximum value by looking up the table. d min,opt of ( h A,t / h B,t ), defined as ( h A,t,opt / h B,t,opt Based on this, the phase of the signal of user node A is adjusted:

[0047] If user nodes A and B can simultaneously adjust both amplitude and phase, then the maximum value can be obtained by searching the lookup table. d min,opt of h A,t / h B,t Defined as h A,t,opt / h B,t,opt Adjust the amplitude and phase of the signal from user node A:

[0048] The above process can be summarized as follows: Figure 8 As shown.

[0049] As an alternative implementation, see Figure 9 , Figure 9 A specific hardware implementation scheme for a wireless optical communication system based on physical layer network coding is presented. The transmitter in node A or B includes a signal generation module, a digital-to-analog converter, an amplifier, a biaser, and a light-emitting diode connected in sequence. The receiver in node A or B includes a lens, a photodetector, an amplifier, an analog-to-digital converter, and a signal decoding module connected in sequence. The transceiver in relay node R includes a photodetector, an amplifier, an analog-to-digital converter, a signal decoding module, a re-coding module, a signal generation module, a digital-to-analog converter, an amplifier, a biaser, and a light-emitting diode connected in sequence.

[0050] This embodiment also provides a wireless optical communication device based on a physical layer network coding method, including: At least one processor; At least one memory for storing at least one program; When the at least one program is executed by the at least one processor, the at least one processor implements Figure 10 The method shown.

[0051] This embodiment of a wireless optical communication device based on a physical layer network coding method can execute a wireless optical communication method based on a physical layer network coding method provided in the method embodiment of the present invention. It can execute any combination of implementation steps of the method embodiment and has the corresponding functions and beneficial effects of the method.

[0052] In some alternative embodiments, the functions / operations mentioned in the block diagrams may not occur in the order shown in the operation diagrams. For example, depending on the functions / operations involved, two consecutively shown blocks may actually be executed substantially simultaneously, or the blocks may sometimes be executed in reverse order. Furthermore, the embodiments presented and described in the flowcharts of this invention are provided by way of example to provide a more comprehensive understanding of the technology. The disclosed methods are not limited to the operations and logic flows presented herein. Alternative embodiments are contemplated in which the order of various operations is altered and sub-operations described as part of a larger operation are executed independently.

[0053] Furthermore, although the invention has been described in the context of functional modules, it should be understood that, unless otherwise stated, one or more of the described functions and / or features may be integrated into a single physical device and / or software module, or one or more functions and / or features may be implemented in a separate physical device or software module. It is also understood that a detailed discussion of the actual implementation of each module is unnecessary for understanding the invention. Rather, given the properties, functions, and internal relationships of the various functional modules in the apparatus disclosed herein, the actual implementation of the module will be understood within the scope of conventional skill of an engineer. Therefore, those skilled in the art can implement the invention as set forth in the claims using ordinary techniques without excessive experimentation. It is also understood that the specific concepts disclosed are merely illustrative and not intended to limit the scope of the invention, which is determined by the full scope of the appended claims and their equivalents.

[0054] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, essentially, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0055] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-including system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device.

[0056] More specific examples of computer-readable media (a non-exhaustive list) include: electrical connections (electronic devices) having one or more wires, portable computer disk drives (magnetic devices), random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Furthermore, computer-readable media can even be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in computer memory.

[0057] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0058] In the foregoing description of this specification, references to terms such as "one embodiment," "another embodiment," or "some embodiments" indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of the present invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0059] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

[0060] The above describes the preferred embodiments of the present invention in detail. However, the present invention is not limited to the above embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A wireless optical communication method based on physical layer network coding, characterized in that, Includes the following steps: Obtain the channel characteristics from two user nodes A and B to relay node R, and obtain at least one Gaussian prime number. q Based on the channel characteristics and the Gaussian prime number q At least one complex signal is generated in user nodes A and B respectively. s A and s B The complex signal s A and s B The number of constellation points is not greater than a Gaussian prime number. q The square of the modulus; The user nodes A and B, and the relay node R, each include at least one transmitter and one receiver; at least one complex signal is generated in user nodes A and B respectively. s A and s B The steps include: based on the Gaussian prime number q Obtain a Gaussian integer finite field, and obtain the complex signal based on the Gaussian integer finite field. s A and s B ; User nodes A and B, based on at least one complex signal generated s A and s B Obtain real signals respectively x A and x B Then, each transmits the real signal via modulated wireless light. x A and x B Transmit to relay node R; Relay node R simultaneously receives signals from user nodes A and B, and then... x e Obtain at least one complex signal s e According to the Gaussian prime number q With the at least one complex signal s e Obtain at least one encoded complex signal s coded According to the encoded complex signal s coded Obtain real signal x coded Then, the real signal is modulated by wireless light. x coded Send back to user nodes A and B; User nodes A and B respectively receive signals transmitted by relay node R. User node A then determines the signal based on the received signal and Gaussian prime numbers. q The complex signal s A Obtain complex signals s B The information, user node B, is based on the received signal and Gaussian prime numbers. q The complex signal s B Obtain complex signals s A Information; According to the Gaussian prime number q With the at least one complex signal s e Obtain at least one encoded complex signal s coded The steps include: complex signals s e Group the constellation points in the data and map the constellation points in the same group to... s coded The same constellation point in the map maps different groups of constellation points to... s coded The different constellation points in the array, where the number of groups is no greater than the number of Gaussian primes. q The square of the modulus, the grouping method of the constellation points satisfies: s A Depend on s B and s coded Uniquely certain, or s B Depend on s A and s coded The only certainty.

2. The wireless optical communication method based on physical layer network coding according to claim 1, characterized in that, At least one complex signal is generated in user nodes A and B respectively. s A and s B The steps include: Adjust at least one of the following based on the channel characteristics from the two user nodes A and B to the relay node R: the complex signal s A The phase of the complex signal s A The amplitude of the complex signal s B The phase or the complex signal s B The range.

3. The wireless optical communication method based on physical layer network coding according to claim 1, characterized in that, The Gaussian primes q The value is determined based on the channel characteristics.

4. The wireless optical communication method based on physical layer network coding according to claim 1, characterized in that, Real signals obtained by user nodes A and B respectively x A and x B It can be a CAP signal or a multi-carrier signal; When it is a multi-carrier signal, the at least one complex signal s A Real number signal x A The signal on one or more subcarriers, the at least one complex signal s B Real number signal x B The signal on one or more subcarriers.

5. A wireless optical communication method based on physical layer network coding according to claim 1, characterized in that, According to the Gaussian prime number q With the at least one complex signal s e Obtain at least one encoded complex signal s coded The steps include: According to the Gaussian prime number q Obtain its Gaussian integer finite field, and obtain at least two Gaussian integers in the Gaussian integer finite field. Then, based on the two Gaussian integers... s e Group the constellation points in the data and map the constellation points in the same group to... s coded The same constellation point in the map maps different groups of constellation points to... s coded Different constellation points in the constellation, wherein the two Gaussian integers make the s e Maximize the minimum distance between constellation points in different groups.

6. A wireless optical communication method based on physical layer network coding according to any one of claims 1-5, characterized in that, The wireless light includes one or a combination of visible light, infrared light, and ultraviolet light.

7. A wireless optical communication system based on physical layer network coding, characterized in that, include: At least two user nodes A and B, and one relay node R, wherein user nodes A and B and relay node R each include at least one transmitter and one receiver; User nodes A and B each generate at least one complex signal according to the method described in any one of claims 1-6. s A and s B According to the at least one complex signal s A and s B Obtain real signals respectively x A and x B Then each transmits the wireless light through modulation. x A and x B Transmit to relay node R; Relay node R simultaneously receives signals from user nodes A and B, and obtains a real number signal according to any one of claims 1-6. x coded Then, by modulating wireless light, x coded Send back to user nodes A and B; User nodes A and B respectively receive signals transmitted by relay node R, and respectively acquire complex signals according to the method described in any one of claims 1-6. s B and s A Information.

8. A wireless optical communication device based on physical layer network coding, characterized in that, include: At least one processor; At least one memory for storing at least one program; When the at least one program is executed by the at least one processor, the at least one processor performs the method according to any one of claims 1-6.

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