A hierarchical quadrature amplitude modulation multiple access method without serial interference cancellation

Abstract

The application discloses a layered quadrature amplitude modulation multiple access method without serial interference cancellation. User bits are mapped to constellation points of different levels, and the Euclidean distance between constellation points in each level is set according to the channel gain of the user, that is, the power of each user is adjusted. Finally, after superposition of multi-level constellation points, hierarchical constellation points are formed to carry the bits of multiple users. On this basis, multiple working configuration points are set, and one or more working configuration points are selected to complete the transmission task according to the number of users in the current transmission and the rate requirement of the user. The transmitter sends the corresponding position of each user in the bit string mapped by the constellation point, the Euclidean distance between the constellation points in each level and the corresponding origin in the complete constellation diagram to the receiver, and if multiple working configuration points are selected, the working configuration point matching information can enable the user to achieve the maximum capacity limit of the downlink multi-user transmission service without serial interference cancellation.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology, and in particular to a hierarchical quadrature amplitude modulation multiple access method that does not require serial interference cancellation. Background Technology

[0002] When a base station provides downlink transmission services to multiple users, it typically divides the radio spectrum into time-frequency resource blocks and allocates them to multiple users. This type of technology is collectively known as downlink multiple access (MOA) technology. Existing MOA technologies are divided into two categories: orthogonal multiple access (OMA) and non-orthogonal multiple access (NOA). OMA refers to allocating different resource units (time-frequency resource blocks) to different users; NOA allocates the same resource unit to multiple users for simultaneous use.

[0003] The implementation of non-orthogonal multiple access (NOA) technology mainly unfolds from two aspects: the power domain and the code domain. In the 3GPP TR 36.859 protocol (3GPP TR 36.859 V13.0.0 (2015-12), "Technical Specification Group Radio Access Network; Study on Downlink Multiuser Superposition Transmission (MUST) for LTE (Release 13)," Dec. 2015), several key implementation methods for downlink multiuser superposition transmission (hereinafter referred to as MUST technology) have been specified. MUST technology specifies the constellation mapping method used when transmitting multi-user signals. In these methods, several users with different channel gains form a transmission group. Within the group, users use their own constellation mapping and are configured with different powers before being superimposed; or bit mapping is performed on a unified constellation diagram. In these methods, each user is simultaneously modulated on both the I and Q branches, and the same power scaling factor is applied to both the I and Q branches. Meanwhile, on the receiving side, serial interference cancellation is an essential receiving technique. This means that users with better channel conditions within a group need to first decode and reconstruct the signals of users with poorer channel conditions, then cancel them out in the received signal, thus enabling the reception of their own signal. However, this method increases the reception complexity under non-orthogonal receiving conditions.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a hierarchical orthogonal amplitude modulation multiple access method that does not require serial interference cancellation. This method belongs to the category of non-orthogonal multiple access and allows receiving users to avoid serial interference cancellation, thereby reducing the receiving complexity under non-orthogonal receiving conditions. It also achieves the same capacity limit as when MUST uses serial interference cancellation and can easily realize non-orthogonal access for two or more users.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A hierarchical quadrature amplitude modulation multiple access method without serial interference cancellation includes:

[0008] The maximum number of constellation points that can be carried is decoupled into two parts, and each part is mapped onto the I-path and the Q-path respectively;

[0009] Bit mapping is performed on the I and Q paths respectively. In each path, the bits it carries are allocated to users, and the allocated bits to users are mapped to constellation points at different levels. The Euclidean distance between the constellation point and the corresponding origin in each level is set according to the user's channel gain, which is the power of each user. Finally, the constellation points of multiple levels are superimposed to form a hierarchical constellation point to carry the bits of multiple users. The hierarchical constellation points of the I and Q paths are combined into a complete constellation diagram.

[0010] Based on the Euclidean distance between constellation points and their corresponding origins in each level of the complete constellation diagram, multiple working configuration points are set. Each working configuration point corresponds to different user channel gains and received signal-to-noise ratios, and can meet the rate requirements of different users. According to the number of users and the rate required by the users, the corresponding working configuration point is selected for information transmission. The transmitter sends the bit position of each user in the constellation point mapping bit string, the Euclidean distance between constellation points and their corresponding origins in each level of the complete constellation diagram, and the working configuration point allocation information if multiple working configuration points are selected to the receiving side.

[0011] The receiving user obtains constellation points based on the amplitude and phase of the channel, maps the constellation points to the I-axis and Q-axis respectively, obtains the corresponding I-channel and Q-channel signals, and performs decoding operations by combining the Euclidean distance information between the constellation points and the corresponding origin in each level of the complete constellation diagram, the bit position of the user in the bit string, and the working configuration point ratio information.

[0012] As can be seen from the technical solution provided by the present invention, user bits are mapped to constellation points at different levels, and the Euclidean distance between constellation points within each level is set according to the user's channel gain, i.e., the power of each user is adjusted. Finally, after the multi-level constellation points are superimposed, a hierarchical constellation point is formed to carry the bits of multiple users. On this basis, multiple working configuration points are set, and one or more working configuration points are selected to complete the transmission task according to the number of users in the current transmission and the rate requirements of the users. This method allows users to reach the maximum capacity limit of downlink multi-user transmission service without serial interference cancellation. The following text... Figure 2 Related examples and explanations are provided. Attached Figure Description

[0013] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 A flowchart of a hierarchical quadrature amplitude modulation multiple access method without serial interference cancellation provided by an embodiment of the present invention;

[0015] Figure 2 This is a schematic diagram illustrating the capacity limit achieved by the QAMA scheme with a total of 64 constellation points provided in an embodiment of the present invention.

[0016] Figure 3 A schematic diagram of the rate space and corresponding working configuration points when the number of users is 3, as provided in an embodiment of the present invention;

[0017] Figure 4 A schematic diagram of bit mapping and Euclidean distance setting for a QAMA containing 64 constellation points provided in an embodiment of the present invention;

[0018] Figure 5 This is a schematic diagram of the constellation mapping process of 8-HPAM provided in an embodiment of the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0020] First, the following explanations are provided for the terms that may be used in this article:

[0021] The term "and / or" means that either or both can be achieved simultaneously. For example, X and / or Y means that it includes both "X" or "Y" as well as the three cases of "X and Y".

[0022] The terms “including,” “comprising,” “containing,” “having,” or other similar semantic descriptions should be interpreted as non-exclusive inclusion. For example, “including a technical feature element (such as raw material, component, ingredient, carrier, dosage form, material, size, part, component, mechanism, device, step, process, method, reaction conditions, processing conditions, parameter, algorithm, signal, data, product or article of manufacture, etc.)” should be interpreted as including not only the expressly listed technical feature element, but also other technical feature elements that are not expressly listed and are well-known in the art.

[0023] The term "composed of" excludes any technical features not expressly listed. When used in a claim, it closes the claim to exclude all technical features other than those expressly listed, except for associated conventional impurities. If the term appears only in a clause of a claim, it limits the claim to the elements expressly listed in that clause; elements recited in other clauses are not excluded from the overall claim.

[0024] This invention relates to HQAM technology (K. Ramchandran, A. Ortega, KMUz and M. Vetterli, "Multiresolution broadcast for digital HDTV using joint source / channel coding", IEEE J. Select. Areas Commun., vol. 11, pp. 6-23, Jan. 1993.). However, this technology is mainly used in the broadcast field rather than the multi-user access field, and it relies on the application of serial interference cancellation methods on the receiving side, resulting in high reception complexity. To solve these problems, this invention provides a hierarchical orthogonal amplitude modulation multiple access method that does not require serial interference cancellation.

[0025] The following is a detailed description of a hierarchical orthogonal amplitude modulation multiple access method without serial interference cancellation provided by the present invention. Contents not described in detail in the embodiments of the present invention are prior art known to those skilled in the art. Where specific conditions are not specified in the embodiments of the present invention, they should be performed according to conventional conditions in the art or conditions recommended by the manufacturer.

[0026] like Figure 1The diagram shows a flowchart of a hierarchical orthogonal amplitude modulation multiple access method without serial interference cancellation provided by an embodiment of the present invention, which mainly includes the following steps:

[0027] Step 1: Decouple the maximum number of constellation points that can be carried into two parts and map them onto the I-path and Q-path respectively.

[0028] In this embodiment of the invention, the maximum number of constellation points that can be supported is denoted as M, and it is decoupled into two parts, represented as: M = 2 m ·2 n ; among them, 2 m The constellation points are mapped onto road I, 2. n Each constellation point is mapped to the Q path, meaning the I path carries m bits and can be allocated to at most m users; the Q path carries n bits and can be allocated to at most n users. M, m, and n are all positive integers, and their specific values ​​can be determined based on the actual situation.

[0029] Step 2: Perform bit mapping on the I and Q paths respectively. In each path, allocate the bits it carries to users and map the allocated bits to constellation points at different levels. Set the Euclidean distance between the constellation point and the corresponding origin in each level according to the user's channel gain, which is the power of each level of user. Finally, after the constellation points of multiple levels are superimposed, a hierarchical constellation point is formed to carry the bits of multiple users. Combine the hierarchical constellation points of the I and Q paths into a complete constellation diagram.

[0030] In this embodiment of the invention, the description of mapping the bits allocated to the user to constellation points at different levels and setting the specific values ​​of the Euclidean distance between the constellation points and the corresponding origin in each level according to the user's channel gain includes: (1) Constellation point layering method: The number of levels is determined according to the decoupled information, that is, the number of levels is determined according to the value of m or n. The lower the level (the smaller the level number), the larger the Euclidean distance between the constellation points and the corresponding origin in the level. For example, the minimum Euclidean distance between the constellation points in the first level is the largest. The minimum Euclidean distance between the constellation points in the second level is the second largest, and so on for the third level and above; (2) The method of bit mapping for the user is: The mapping level is determined according to the user's channel gain. The lower the user's channel gain, the lower the mapping level. For example, the user with the lowest channel gain will be mapped to the first level; (3) Adjusting the Euclidean distance between the constellation points and the corresponding origin in each level according to the user's channel gain.

[0031] After implementing the multi-level mapping method described in this invention, both the I-path and Q-path can independently form hierarchical constellation points to carry the bits of multiple users.

[0032] In this embodiment of the invention, 2 m and 2 nEach point is mapped onto the I-path and the Q-path, thus becoming a 2 on the I-path. m -PAM (Pulse Amplitude Modulation) mapping, and 2 on the Q-path n -PAM mapping. 2 on the I / Q path. m -PAM or 2 n -PAM can be viewed as a hierarchical PAM (HPAM) formed by superimposing m / n layers of constellation point mappings.

[0033] In this embodiment of the invention, the Euclidean distance between constellation points and the corresponding origin in each level of path I is expressed as: Where, d i This is a set of Euclidean distances between constellation points and their corresponding origins within all levels of the I-path. Each item represents the Euclidean distance between a constellation point and its corresponding origin within a level. The superscript i represents the I-path, the subscript value is the level number, and m is the number of bits that the I-path can carry, corresponding to the highest level. The Euclidean distances between constellation points and their corresponding origins within each level of the Q-path are expressed as follows: Where, d q It is a set of Euclidean distances between constellation points and their corresponding origins within all levels of the Q-path. Each item is the Euclidean distance between a constellation point and its corresponding origin within a level. The superscript q represents the Q-path, the subscript value is the level number, and n is the number of bits that the Q-path can carry, which also corresponds to the highest level.

[0034] All Euclidean distances between paths I and Q satisfy constant power, expressed as:

[0035] E s =||d i || 2 +||d q || 2

[0036] Among them, E s This represents the total power.

[0037] In this embodiment of the invention, bits on the I and Q paths are allocated to at most m users and n users respectively, including the case where a user occupies 2 or more bits. There are three key points to the bit mapping:

[0038] 1) I-path and Q-path can be bit-mapped separately.

[0039] 2) Gray mapping is used on every branch.

[0040] 3) Euclidean distance d between constellation points at each level on the I / Q branch i and d qOptimization is needed. The basic principle is that the lower the channel gain of a user, the larger the Euclidean distance (i.e., spacing) between the mapped constellation point and the corresponding origin. The specific value can be adjusted according to the user's channel gain. As an example, an exhaustive search method can be used to optimize the Euclidean distance d between constellation points at each level. i and d q .

[0041] In this embodiment of the invention, after mapping the I-path and Q-path respectively, the two paths are combined into a complete constellation diagram for subsequent work. Since each constellation point has I coordinates and Q coordinates, and the I-map and Q-map have been determined in the previous step, each I coordinate and each Q coordinate will be labeled with a constellation point.

[0042] Step 3: Based on the Euclidean distance between constellation points and their corresponding origins in each level of the complete constellation diagram, set multiple working configuration points. Each working configuration point corresponds to different user channel gains and received signal-to-noise ratios. Select the appropriate working configuration point for information transmission according to the number of users and the rate required by the users. Send the bit position of each user's corresponding constellation point, the Euclidean distance between constellation points and their corresponding origins in each level of the complete constellation diagram, and the working configuration point allocation information if multiple working configuration points are selected to the receiving side through the transmitter.

[0043] In this embodiment of the invention, multiple working configuration points can be set by continuously optimizing the Euclidean distance between constellation points and corresponding origins in each level, as well as the user's channel gain and signal-to-noise ratio. The specifics will be introduced later.

[0044] In this embodiment of the invention, the information sent by the transmitter specifically includes: 1) information on the working configuration points (one or more) used in a single transmission is sent to the receiving side. The information on the working configuration points is the Euclidean distance between the constellation points at each level in the complete constellation diagram and the corresponding origin, i.e., d as described above. i and d q Depending on the actual situation, this can be multiple Euclidean distances between constellation points and their corresponding origins at each level, i.e., multiple d... i and d q Each working configuration point corresponds to one d i and d q The working configuration points are affected by channel changes. If the channel is static or slowly changing, the corresponding d values ​​for all configuration points can be pre-allocated. i and d q Send the working configuration point sequence number (maximum two) to the receiving side each time data is transmitted; however, if the channel is rapidly changing, the working configuration point needs to be generated in real time, and the d of up to two of the configuration points should be sent. i and d q1) Send two copies of the information; 2) If multiple (e.g., two) working configuration points are selected, the working configuration point allocation information, i.e., the resource proportion of each working configuration point, also needs to be sent, and the receiver should be informed of the location of these resources in the form of preset rules; 3) The bit position occupied by each user in the bit string corresponding to the constellation point.

[0045] Figure 2 This example demonstrates multiple working configuration points, where p0 to p4 each correspond to one working configuration point. (Regarding...) Figure 2 A detailed explanation follows; this section primarily introduces the principle of selecting the required working configuration point during transmission. If the number of users in the current transmission is 2, the rate pair (R1, R2) for the two users can be determined, and then compared... Figure 2 In this regard, this rate has a specific location; similarly, each set working configuration point can meet the rate requirements of different users. Therefore, in Figure 2 The corresponding position is also provided. Based on the rate pair (R1,R2), one or more working configuration points closest to it are selected to complete the corresponding transmission work. This allows the user rate to be obtained at the receiving end with only low-complexity reception without serial interference cancellation, which is almost the same as that of MUST technology under serial interference cancellation conditions.

[0046] More specifically: the working configuration point selected each time depends entirely on the rate required by the user in the current transmission. For example, (R1,R2) = (1.175,4.0), placing this position at... Figure 2 After marking it, the two closest operating points are p1 and p2, which are represented by rate pairs (R1,R2) = (0.75, 4.5) and (R1,R2) = (1.6, 3.5). Therefore, one or both of these operating points can be selected. Taking these two operating configuration points as an example, let them each work on half of the time-frequency resources (i.e., the resource ratio of each operating configuration point is 0.5), and their combined rate is exactly (1.175, 4.0).

[0047] Step 4: The user obtains constellation points based on the amplitude and phase of the channel, maps the constellation points to the I-axis and Q-axis respectively, obtains the corresponding I-path and Q-path signals, and performs decoding operations by combining the Euclidean distance information between the constellation points and the corresponding origin in each level of the complete constellation diagram, the bit position of the user in the bit string, and the working configuration point ratio information.

[0048] In this step, after the receiving user performs frequency offset calibration, constellation points are obtained based on the channel amplitude and phase, and these constellation points are mapped to the I-axis and Q-axis respectively to obtain the corresponding I-channel and Q-channel signals (2). m -HPAM or 2 n -HPAM signal).

[0049] The solution provided in this embodiment of the invention is for multi-user reception. Since the signal processing for the I-channel and Q-channel is the same, the following processing will use the I-channel as an example. For the current receiving user, the obtained I-channel signal y is represented as:

[0050]

[0051] Where s is the normalized effective signal, η is the noise, and G is the channel power gain of the current receiving user.

[0052] Each receiving user performs decoding operations on the obtained I-channel and Q-channel signals based on the bit position information in the bit string, the Euclidean distance information between constellation points and corresponding origins in each level of the complete constellation diagram, and the working configuration point ratio information (i.e., α described later), to obtain the bit likelihood value, and then performs back-end decoding decision.

[0053] Specifically: The receiver determines the working configuration point of each resource unit in the current transmitted signal based on the working configuration point ratio information and preset rules, and then uses the corresponding d for each working configuration point. i and d q The value is then combined with the I-channel and Q-channel signals obtained from the corresponding resource units, and the z-value is calculated using formulas (1)-(6). κ The values ​​are calculated to obtain the likelihood values ​​of the bits corresponding to each bit position. Taking OFDM signals as an example, if the current signal transmits a resource block (RB) containing 84 REs (resource units), and the selected working configuration points are p1 and p2, with a configuration ratio α = 0.5, we can set the preset rule as follows: for the first α part, i.e., the first half, 42 REs operate at p1, and for the second half, the REs operate at p2. For I-path, each RE has an observed signal y and a d corresponding to the working configuration point. i and d q The value can be obtained using formulas (1)-(6) introduced later. κ Calculation of values.

[0054] Among them, bit b κ The likelihood value Λ(b) κ ):

[0055]

[0056] Where the subscript κ represents bit position information, b κ It is the bit at the κ position.

[0057] The simplified expression can be represented as:

[0058]

[0059] Where ∝ means "proportional to", σ 2 =N0 / 2 is the variance of the noise component, and S is the set of s signals that satisfy a given condition, for example, s∈S(b κ =0) means b κ The signal s is equal to 0, and N0 is the noise power spectral density.

[0060] z κ It is bit b κ The likelihood value of , which does not consider channel gain and noise power, can be calculated with low complexity using the following methods, with relevant examples provided below.

[0061] 1, 2-PAM: Only one layer of user bits.

[0062] z1=d1y (1)

[0063] 2. 4-HPAM (2 levels):

[0064]

[0065]

[0066] 3. 8-HPAM (3 levels):

[0067]

[0068]

[0069]

[0070] As mentioned before, the processing of I-path and Q-path is the same. The subscript symbols in d1, d2, and d3 above are omitted. They represent the Euclidean distances between the constellation points and the corresponding origin in the first, second, and third levels of a path (I-path or Q-path), respectively.

[0071] Based on the above simplified expression and z κ The calculation method can calculate the bit likelihood value, which is used for backend decoding decisions. Considering that this part can be implemented by conventional techniques, it will not be elaborated on.

[0072] In the scheme described above, once the dimension of the constellation diagram (i.e., the maximum number of constellation points) M and the downlink rate required by each user are specified, several suitable working configuration points are selected and denoted as: {p0, p1, ..., p L}, where each item is a working configuration point, and L is the maximum number of working configuration points. In the case of two users, p0 and p LThis indicates the case where only one user has exclusive access to all bits, which can be naturally determined based on the channel gain and signal-to-noise ratio. For example, in the case of three users, there are three operating points, each representing the case where only one user has exclusive access to all bits. Other user cases follow the same logic and will not be elaborated upon here.

[0073] In this embodiment of the invention, when performing bit mapping according to the aforementioned mapping criteria, it is also necessary to adjust the Euclidean distance between adjacent constellation points within the corresponding level according to the channel gain of each user, that is, to adjust the power of each user and select a suitable operating configuration point. After the transmitter informs the receiver of the necessary information mentioned in step 3 above, the receiver can receive the data using the aforementioned formulas (1)-(6). The obtained bit likelihood value will be directly output to the back-end error correction code decoder for decoding to obtain the source information bits, without the need for re-encoding, re-modulation, and interference cancellation. In other words, it is possible to obtain almost the same user rate as the MUST technology under serial interference cancellation conditions by performing low-complexity reception at the receiving end without serial interference cancellation.

[0074] Figure 2 Five (L=5) working placement points are provided as examples. The selection criteria for these working placement points are: based on the Euclidean distance between constellation points and the corresponding origin within each level of the complete constellation map, the first working placement point p0 and the last working placement point p... L Since the channel gain and signal-to-noise ratio are already uniquely determined, all other operating configuration points need to be as far away from p0 and p1 as possible. L The lines connecting all the working points form a sufficiently convex envelope, maximizing the area enclosed by the horizontal and vertical axes. This indicates that they cover a maximum possible capacity region. Each of these working points corresponds to a pair of d... i and d q (The Euclidean distance between constellation points and their corresponding origins within each level of the complete constellation diagram), during transmission, the d corresponding to the selected working configuration point. i and d q All of these need to be sent to the receiving side. It should be noted that when the number of users is 3, there are 3 single-user exclusive operating configuration points that are naturally determined based on channel gain and signal-to-noise ratio. These 3 operating configuration points form a plane in three-dimensional space. Connecting these planes with the remaining operating configuration points selected through subsequent optimization will form a most convex approximate curved surface. See [link to relevant documentation]. Figure 3 If it supports more than 3 users, the same logic can be applied to higher-dimensional spaces. Since this cannot be visually represented in a chart, it will not be elaborated upon here.

[0075] also, Figure 2In the diagram: R1 is the rate of user 1, and R2 is the rate of user 2. The meanings of each curve are as follows: (1) NOMA, Gaussian: The theoretical capacity limit curve of NOMA technology with Gaussian input signal; (2) OMA, 64QAM: The capacity limit of orthogonal multiple access technology using 64QAM modulation; (3) OMA+MUST, M=64: The capacity limit obtained by switching between MUST and OMA technologies; (4) QAMA, M=64: The capacity limit obtained by using the technology of this invention; (5) A1: Under MUST technology, the user rates that two users can achieve by using BPSK+32QAM respectively; (6) A2: Under MUST technology, the user rates that two users can achieve by using QPSK+16QAM respectively. The user rate that M can achieve; (7) Under A3:MUST technology, the user rate that two users can achieve using 8QAM+8QAM respectively; (8) The curve marked with a QAMA equilateral triangle is the rate that two users can achieve when they take the configuration of (i1,{q1,i2,q2,i3,q3} respectively; (9) The curve marked with a QAMA diamond is the rate that two users can achieve when they take the configuration of ({i1,q1},{i2,q2,i3,q3} respectively; (10) The curve marked with a QAMA inverted triangle is the rate that two users can achieve when they take the configuration of ({i1,q1,i2},{q2,i3,q3} respectively). Among them, QAMA is Quadrature Amplitude Modulation Multiple Access, which is the English abbreviation of the technology of this invention.

[0076] Note: QAMA technology uses the receiving methods of formulas (1)-(6). The backend can be connected to a conventional error correction code decoder to directly output the bits required by the user, without the need for serial interference cancellation. From Figure 2 It can be seen that it is inferior to the MUST technique, which uses serial interference cancellation, in many cases. However, it is tangent to or close to the MUST technique only at certain locations, and these tangent or close locations are the working configuration points selected by this invention. As a result, the rate range enclosed by the lines connecting these working configuration points and the horizontal and vertical axes is almost identical to the rate range of MUST, which is also the key to this invention.

[0077] In this embodiment of the invention, the selection of working configuration points is not arbitrary and can satisfy the above conditions. Such working configuration points are also affected by factors such as dimension M, channel gain of each user, and signal-to-noise ratio. After selecting working configuration points, one or more working configuration points are selected based on the number of accessing users and the corresponding rate requirements. The time-frequency resource ratio of the working configuration points (i.e., the working configuration point allocation information mentioned above) is set in conjunction with the users' rate requirements. At the transmitting end, the transmitter informs the receiver via signaling of the distance between the constellation points in each level corresponding to the I and Q paths and their corresponding origins, as well as the time-frequency resource ratio of each working point. For example, the transmitter selects two working points with rates p...l =(R1,R2),p l+1 = (R′1, R′2), where R1 and R2 are the working placement points p. l The rates allocated to user 1 and user 2, R′1 and R′2 are the working configuration points p, respectively. l+1 The rates allocated to User 1 and User 2; during a single transmission, the transmitter will use a segment of time-frequency resources (such as resource elements RE in OFDM), if the transmitter allocates α (α < 1) of the total number of these resource elements to the working configuration point p. l The 1-α portion is allocated to the working configuration point p. l+1 Then the receiver can receive at these two working configuration points using a simple method that does not require serial interference cancellation, and the achieved rate is (αR1+(1-α)R′1,αR2+(1-α)R′2). By setting α, any rate pairing within the achievable capacity range can be achieved.

[0078] To facilitate understanding, the constellation mapping and Euclidean distance setting scheme will be introduced below using M=64 as an example.

[0079] like Figure 4 The diagram shows the bit mapping and Euclidean distance settings for a QAMA constellation containing 64 constellation points. The constellation points are mapped separately for the I-path and Q-path, with m=3 and n=3, meaning both the I-path and Q-path undergo three layers of mapping. The constellation diagram mapping process is explained below using the I-path as an example.

[0080] like Figure 5 As shown, it is 8-HPAM(2 3 The constellation mapping process is illustrated using HPAM as an example. Figure 5 In part (a), the x-coordinate of the black constellation point is determined by the first-level user, and the Euclidean distance between the constellation points in the I-axis direction is 2d1. Since this specifically refers to the mapping process of the I-path, the subscript symbol i representing the I-path is omitted, and the power of the black constellation point is (d1). 2 The black constellation points correspond to the users with the worst channel gain, and the two black constellation points correspond to bits 0 and 1 respectively; Figure 5 In part (b), the I-axis coordinate of the gray constellation point is determined by the Euclidean distance obtained after superimposing the second layer of users. The distance between its I-axis direction and the black constellation point is d2. Therefore, the power of the second layer of users is (d2). 2 The sum of the power of the first-layer and second-layer users is (d1). 2 +(d2) 2The second layer is determined by bit 2, and the mapping method is Gray mapping. The four gray constellation points correspond to 00, 01, 11, and 10 of bits 1 and 2, respectively. That is to say, the first bit of these four numbers is determined by the corresponding bit of the first layer (i.e., determined by 0 and 1 of bit 1). For example, the first bit of 00 and 01 is 0, which corresponds to bit 0 of the first layer. The first bit of 11 and 10 is 1, which corresponds to bit 1 of the first layer. Figure 5 In part (c), the I-axis coordinates between the white constellation points are determined by the power after the third layer of users is superimposed. The distance between the white and gray constellation points in the I-axis direction is d3. The third layer is determined by bit 3. The eight white constellation points correspond to bits 1, 2, and 3: 000, 001, 011, 010, 110, 111, 101, and 100, respectively. Similarly, the first bit of these eight numbers is determined by the corresponding bit of the first layer, and the second bit is determined by the corresponding bit of the second layer. The numbers corresponding to each constellation point mentioned here are the bit strings carried by the constellation points. Figure 5 Taking the rightmost white constellation point in part (c) as an example, it carries a bit string of 100. Then, the bit b at the position κ=0... κ It is bit b at position 1, κ = 1, 2. κ If all are 0, the bit position information is actually determined by the constellation point level assigned to the user. The above describes the mapping process of three levels of constellation points. Each level actually has only two constellation points, and the final three levels combined result in a total of eight constellation points. In other words, the final constellation map is actually eight white constellation points in the third level. Specifically: the first level has two constellation points, and the second level also has two constellation points. However, after the first and second levels are combined, the second level has 2 × 2 = 4 constellation points (i.e., gray constellation points). The third level also has two constellation points, but after being combined with the previous two levels, the three levels combined result in 2 × 4 = 8 constellation points (i.e., white constellation points). On each of the left and right sides of the second level, there are two gray points. Here, the left and right sides refer to the two sides formed by folding the constellation diagram along the Q axis. Taking either side as an example, the black constellation point between the two gray constellation points is the origin. The Euclidean distance between them and the corresponding origin is d2. Therefore, the Euclidean distance between the two gray constellation points is 2d2. Similarly, on either side of the third level, the gray constellation points (i.e., the constellation points of the second level) are taken as the origin, and the distance between the white constellation point and the corresponding origin is d3.

[0081] To illustrate this more clearly, specific numerical values ​​will be used as examples below:

[0082] If the constellation point of the first layer user is (-1, +1), then d1 = 1, and the distance between the two constellation points is 2d1 = 2. The constellation point of the second layer is (-0.5, 0.5), which is also two points centered at the origin. Here, d2 = 0.5, which means 2d2 = 1. When the second layer is superimposed on the first layer, there will be four possible results: (-1-0.5, -1+0.5, 1-0.5, 1+0.5), or (-1.5, -0.5, 0.5, 1.5). As mentioned before, the second layer actually only has 2 constellation points, but after superimposing with the first layer, it forms 2 × 2 = 4 constellation points. Similarly, when the third layer appears, the third layer also actually has 2 points, but when superimposed on the constellation points of the first two layers, it forms 8 constellation points.

[0083] Similar to the I-axis direction, the coordinates of the layered constellation points in the Q-axis direction can also be determined in the same way. As can be seen above, this 64-point constellation diagram is constructed by superimposing three layers of sub-constellation points on each of the I and Q axes, resulting in a final composite constellation diagram with non-uniform Euclidean distance. Each layer of constellation points is determined by a single bit from a user; different bits from the same user can be used to determine multiple layers of the constellation diagram. The final composite constellation diagram uses Gray mapping for bit mapping on both the I and Q axes.

[0084] The following constellation diagram is still based on M=64 ( Figure 1 Taking this as an example, let's introduce how this 64-point hierarchical constellation diagram can be used for multi-user access:

[0085] Taking the 64-point constellation diagram as an example, which is decomposed into two 8-HPAMs in the I / Q direction, it can support a variety of user numbers. The following describes the implementation examples for 2 and 3 users.

[0086] The case of 1 or 2 users.

[0087] Assume that the channel gain of user 1 is lower than that of user 2, and their respective received signal-to-noise ratios are 0dB and 12dB.

[0088] The system can carry 3 bits along the I-axis, denoted as (i1, i2, i3); and 3 bits along the Q-axis, denoted as (q1, q2, q3). Therefore, the system can allocate these 6 bits to 2 users. Among the various possible combinations, the following set of operating points is selected as an example:

[0089] 1) User 1: No bits; User 2: 6 bits, denoted as d i =(0.617,0.309,0.154), d q = (0.617, 0.309, 0.154);

[0090] 2) User 1: 1 ratio; User 2: 5 bits (i1, {q1, i2, q2, i3, q3}), d i =(0.67,0.38,0.19), d q = (0.53, 0.26, 0.13);

[0091] 3) User 1: 2 bits; User 2: 4 bits ({i1,q1},{i2,q2,i3,q3}), d i =(0.62,0.31,0.15), d q = (0.62, 0.31, 0.15);

[0092] 4) User 1: 2 bits; User 2: 4 bits ({i1,q1},{i2,q2,i3,q3}), d i =(0.68,0.2,0), d q = (0.68, 0.2, 0);

[0093] 5) User 1: 6 bits; User 2: No bits, denoted as d i =(0.707,0,0), d q = (0.707, 0, 0).

[0094] 2. Supports 3 users.

[0095] The channel gain increases sequentially from user 1 to user 3. Only the bit allocation method is listed here:

[0096] 1) User 1: 1 bit; User 2: 1 bit; User 3: 4 bits; The above allocation method is abbreviated as 1-1-4: The allocation method is (i1,q1,{i2,q2,i3,q3}).

[0097] 2)1-2-3: (i1,{q1,i2}:{q2,i3,q3});

[0098] 3)2-2-2: ({i1,q1},{i2,q2},{i3,q3});

[0099] 4) 1-5-0:

[0100] 5) 2-4-0:

[0101] 6) 3-3-0:

[0102] 7) 1-0-5:

[0103] 8)2-0-4:

[0104] 9)3-0-3:

[0105] 10)0-1-5:

[0106] 11)0-2-4:

[0107] 12)0-3-3:

[0108] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A hierarchical quadrature amplitude modulation multiple access method without serial interference cancellation, characterized in that, include: The maximum number of constellation points that can be carried is decoupled into two parts, and each part is mapped onto the I-path and the Q-path respectively; Bit mapping is performed on the I and Q paths respectively. In each path, the bits it carries are allocated to users, and the allocated bits to users are mapped to constellation points at different levels. The Euclidean distance between the constellation point and the corresponding origin in each level is set according to the user's channel gain, which is the power of each user. Finally, the constellation points of multiple levels are superimposed to form a hierarchical constellation point to carry the bits of multiple users. The hierarchical constellation points of the I and Q paths are combined into a complete constellation diagram. Based on the Euclidean distance between constellation points and their corresponding origins in each level of the complete constellation diagram, multiple working configuration points are set. Each working configuration point corresponds to different user channel gains and received signal-to-noise ratios, and can meet the rate requirements of different users. According to the number of users and the rate required by the users, the corresponding working configuration point is selected for information transmission. The transmitter sends the bit position of each user in the constellation point mapping bit string, the Euclidean distance between constellation points and their corresponding origins in each level of the complete constellation diagram, and the working configuration point allocation information if multiple working configuration points are selected to the receiving side. The receiving user obtains constellation points based on the amplitude and phase of the channel, maps the constellation points to the I-axis and Q-axis respectively, obtains the corresponding I-channel and Q-channel signals, and performs decoding operations by combining the Euclidean distance information between the constellation points and the corresponding origin in each level of the complete constellation diagram, the bit position of the user in the bit string, and the working configuration point ratio information.

2. The hierarchical orthogonal amplitude modulation multiple access method without serial interference cancellation according to claim 1, characterized in that, The process of decoupling the maximum number of constellation points that can be carried into two parts, and mapping them respectively onto the I-path and Q-path, includes: Let M be the maximum number of constellation points that can be accommodated. Decouple it into two parts, represented as: M = 2 m ·2 n ; among them, 2 m The constellation points are mapped onto road I, 2. n Each constellation point is mapped to the Q path, meaning the I path carries m bits and can be allocated to at most m users; the Q path carries n bits and can be allocated to at most n users.

3. A hierarchical orthogonal amplitude modulation multiple access method without serial interference cancellation as described in claim 1 or 2, characterized in that, The Euclidean distance between constellation points and the corresponding origin in each level of path I is expressed as: Where, d i It is a set of Euclidean distances between constellation points and corresponding origins in all levels of I-path. Each item is the Euclidean distance between constellation points and corresponding origins in a level. The superscript i represents I-path, the subscript value is the level number, and m is the number of bits that I-path can carry, which also corresponds to the highest level. The Euclidean distance between constellation points in each level of the Q-path and the corresponding origin is expressed as: Where, d q It is a set of Euclidean distances between constellation points and corresponding origins in all levels of Q-path. Each item is the Euclidean distance between constellation points and corresponding origins in a level. The superscript q represents Q-path, the subscript value is the level number, and n is the number of bits that Q-path can carry, which also corresponds to the highest level. All Euclidean distances between paths I and Q satisfy constant power, expressed as: E s =||d i || 2 +||d q || 2 Among them, E s This represents the total power.

4. The hierarchical quadrature amplitude modulation multiple access method without serial interference cancellation according to claim 1, characterized in that, The process of mapping the bits allocated to the user to constellation points at different levels, and setting the Euclidean distance between the constellation points at each level and the corresponding origin based on the user's channel gain, includes: The number of levels is determined based on the decoupled information. The lower the level, the greater the Euclidean distance between the constellation point and the corresponding origin within the level. The mapping level is determined based on the user channel gain. The lower the user's channel gain, the lower the mapping level. Then, the Euclidean distance between the constellation point and the corresponding origin within each level is adjusted based on the user channel gain.

5. The hierarchical quadrature amplitude modulation multiple access method without serial interference cancellation according to claim 1, characterized in that, Gray mapping is used when performing bit mapping on both the I-path and Q-path.

6. The hierarchical quadrature amplitude modulation multiple access method without serial interference cancellation according to claim 1, characterized in that, The multiple working configuration points are denoted as: {p0, p1, ..., p L Each item in the set is a working configuration point, and L is the maximum number of working configuration points. Each working configuration point has the Euclidean distance between the constellation point in each level of the complete constellation diagram and the corresponding origin. The appropriate working configuration point is selected according to the number of users and the rate required by the users. In combination with the rate requirements of the users, the time-frequency resource ratio of the working configuration point is set, that is, the working configuration point allocation information.

7. The hierarchical orthogonal amplitude modulation multiple access method without serial interference cancellation according to claim 6, characterized in that, The method for setting multiple working configuration points is as follows: Based on the Euclidean distances between constellation points and their corresponding origins at each level in the complete constellation diagram, when the number of users is 2, there will be two working configuration points p0 and p1. L The bit strings corresponding to the exclusive constellation points of each of the two users are naturally determined based on channel gain and signal-to-noise ratio. In the multi-user rate interval diagram, the remaining operating configuration points need to be far from p0 and p1. L The connections between them make the connections between all working configuration points form the most convex envelope, that is, the area enclosed by this envelope and the horizontal and vertical axes is the largest. When the number of users is 3, there will be 3 working configuration points where a single user occupies all bits. These are naturally determined based on the channel gain and signal-to-noise ratio. These 3 working configuration points form a plane in three-dimensional space. When connected with the remaining working configuration points selected by subsequent optimization, they will form the most convex approximate curved surface. When the number of users is more than 3, the same principle applies to higher-dimensional spaces.

8. The hierarchical orthogonal amplitude modulation multiple access method without serial interference cancellation according to claim 1, characterized in that, The decoding operation, which involves receiving information from the user about the Euclidean distance between constellation points and their corresponding origins at each level of the complete constellation diagram, the user's bit position in the bit string, and the working configuration point ratio, includes: The signal processing procedures for I-channel and Q-channel are the same. For the current receiving user, the obtained I-channel signal y is represented as: Where G is the channel power gain of the current receiving user, s is the normalized effective signal, and η is the noise; Each receiving user performs decoding operations on the obtained I-channel and Q-channel signals based on the mapping position information in the bit string, the Euclidean distance information between constellation points and corresponding origins in each level of the complete constellation diagram, and the working configuration point ratio information, to obtain the likelihood value of the bits, and then performs back-end error correction code decoding decision; wherein, based on the working configuration point ratio information, the working configuration point of each resource unit in the current transmission signal is determined, and then the Euclidean distance information between constellation points and corresponding origins in each level of the complete constellation diagram corresponding to the working configuration point is used, combined with the I-channel and Q-channel signals obtained by the corresponding resource unit, to calculate the likelihood value of the bit corresponding to each bit position.

9. A hierarchical orthogonal amplitude modulation multiple access method without serial interference cancellation as described in claim 8, characterized in that, bit b κ The likelihood value Λ(b) κ ) is represented as: Where the subscript κ represents bit position information, b κ It is the bit at the κ position, ∝ means proportional to, σ 2 =N0 / 2, where N0 is the noise power spectral density, and z κ Represents bit b κ The likelihood value without considering channel gain and noise power.

10. A hierarchical orthogonal amplitude modulation multiple access method without serial interference cancellation according to claim 9, characterized in that, z κ The calculation method is as follows: When there is only one layer of user bits: z1 = d1y; When the number of levels in the hierarchical constellation points is 2: When the number of levels in the hierarchical constellation points is 3: Where d1, d2, and d3 represent the Euclidean distances between constellation points and the corresponding origin in the first, second, and third levels of a path, respectively.

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