CN111405593B - Bit error rate suppression and performance improvement method of non-orthogonal access technology under Nakagami-m channel - Google Patents

Abstract

A method for suppressing the error rate and improving the performance of a non-orthogonal access technology under a Nakagami-m channel relates to the technical field of information and communication, aims to realize the optimal network of multi-user error rate performance and improve the performance of the integral error rate of the network while ensuring the performance of a single user, and is summarized as follows: step one, setting a bit error rate tolerance; step two, setting a network error rate tolerance optimization range; determining the initial power distribution condition, and calculating a first derivative result according to a dichotomy until the first derivative result meets the tolerance optimization range; step four, verifying the power distribution result to determine whether the error rate tolerance of a single user given in the step one is met; step five, if not, enlarging the tolerance optimization range or reducing the error rate tolerance required by a single user according to the stepping; therefore, the power distribution result is obtained, and the method has the advantages of wide application scenes, simple calculation and great development potential.

Description

Bit error rate suppression and performance improvement of non-orthogonal access technology in Nakagami-m channel method

technical field

The invention relates to the field of information and communication technologies, in particular to a bit error rate optimization technology based on a nakagami-m channel model in a communication network.

Background technique

In view of the large number of users in the current network, the characteristics of dense distribution and the shortage of spectrum resources, it is urgent to provide a spectrum saving solution that can support a large number of user access, obtain higher spectrum utilization efficiency, and meet the increasing user access needs . In response to the above problems, non-orthogonal multiple access (NOMA) technology, as a relatively mature technology in recent years, can achieve higher frequency spectrum through superimposed transmission of multi-user information and demodulation one by one. Utilization efficiency. At the same time, NOMA technology has no carrier and bandwidth restrictions, and can be used in conjunction with multiple transmission systems to increase network load. At the same time, NOMA’s unique multi-user superimposed transmission characteristics can greatly reduce complex interference in spectrum sharing scenarios. At the same time, the NOMA technology is simple to implement, low in complexity, does not require large-scale improvements to existing systems, requires low channel feedback, and enhances access flexibility. It can be applied in three typical 5G application scenarios (eMBB, URLLC, mMTC). In the case of random access channel connection, scheduling requests can be saved, so as to save energy consumption and scheduling requests, and reduce response time. At the same time, NOMA technology has a wide application space in the future 6G and satellite-terrestrial hybrid networks.

As a spectrum non-orthogonal access technology, NOMA technology superimposes and transmits the information of multiple users at the transmitting end, allocates power factors according to the channel state, and demodulates information sequentially at the receiving end according to the power of the received signal. Therefore, NOMA technology is a technology that actively introduces interference to achieve greater user capacity. The receiving end mainly faces two problems. One is the interference cancellation technology based on the serial interference cancellation (SIC) technology, and its performance is affected by High-power users have a greater impact, and their error transmission is serious. Information errors in priority demodulation will have a great impact on subsequent information. Second, the requirements for power allocation factors are strict, and the performance of different power allocation factors varies greatly. Aiming at the above two problems, a new type of demodulation technology is needed, which can suppress the error transmission problem in the demodulation process, and optimize the power allocation factor at the same time to obtain the best bit error rate performance. At the same time, only focusing on the optimal bit error rate performance of a single user will lead to the deterioration of other users and lead to the deterioration of the overall reliability of the network. Therefore, it is necessary to pay attention to both the bit error rate performance of a single user and the bit error rate performance of the network to meet user needs in future communication scenarios.

As a typical communication attenuation channel model, the Nakagami-m channel is used in communication scenarios such as drones, base stations, and satellites. At the same time, the nakagami-m channel can degenerate into a traditional rayleigh channel model when m=1 , so it has a wide range of application scenarios. However, in the analysis process, the theoretical analysis of the Nakagami-m channel is more difficult, therefore, the theoretical analysis and proposal of the Nakagami-m channel is of considerable significance.

Contents of the invention

The present invention aims to realize network optimization of multi-user bit error rate performance, and improve performance of the overall network bit error rate while ensuring single-user performance, thereby providing a non-orthogonal access technology under Nakagami-m channel Bit error rate suppression and performance improvement methods.

The bit error rate suppression and performance improvement method of non-orthogonal access technology under Nakagami-m channel, it comprises the following steps:

Step 1, grouping users, determining far and near users, determining the data modulation order, and giving an initial power allocation factor;

Step 2, determining the multi-user superposition information according to the modulation order and the user distance;

Step 3. Optimizing the multi-user power allocation factor according to the user and network bit error rate tolerance, and according to the theoretical derivation results;

First, considering the downlink NOMA communication technology, the received signal of downlink user k is expressed as:

y _k ＝h _k s+n _k ,(1)

Among them, h _k represents the channel state information of the ^kth user, which is dimensionless, and _nk represents the additive white Guassian noise (AWGN) of the channel, with a mean value of 0 and a variance of N ₀ /2. According to the proposed The encoding and superposition method, the signal s in the above formula (1) can be further expressed as:

其中：2Q_ir表示相邻调制点的距离，接收端最终的解调信号表示为

表示经过串行干扰消除的信号，

表示最终的恢复信号，考虑两用户情况，其中，功率较高的用户信息直接解调，功率较低的用户信息经由串行干扰消除后得到，基于公式(1)，公式(2)中表示的接收信号及发送信号形式，经过串行干扰消除后的剩余信号表示为：Among them: α ₁ and α ₂ represent the power allocation factors allocated to far users and near users, which are dimensionless and need to meet the restriction conditions α ₁ + α ₂ = 1 and α ₁ > α ₂ , in order to ensure user fairness, the distance is relatively long The power obtained by user allocation is relatively large; in formula (2), ε is expressed as

Among them: 2Q _ir represents the distance between adjacent modulation points, and the final demodulated signal at the receiving end is expressed as

Indicates the serial interference-canceled signal,

Indicates the final recovery signal, considering the case of two users, in which the user information with higher power is directly demodulated, and the user information with lower power is obtained after serial interference cancellation, based on formula (1), expressed in formula (2) The form of received signal and transmitted signal, the remaining signal after serial interference elimination is expressed as:

Among them, the formula (a) indicates that the demodulation of the high-power user is successful, and the formula (b) indicates that after the serial interference cancellation technology, the demodulation error of the user with _high power is wrong. Considering low-power users, that is, post-demodulation users, the theoretical expression of the bit error rate is expressed as the sum of two parts. One is the residual information interference of other users caused by unsuccessful SIC, and the other is is the demodulation error caused by its own demodulation error, and the above two parts are expressed as:

For the secondary demodulation user, the total bit error rate is expressed as the sum of the above equations (4) and (5), while for the first demodulation user, the bit error rate is directly expressed as the demodulation under the interference of the secondary demodulation user probability of success,

Under the Nakagami-m channel, combined with the channel fading characteristics, the bit error rate is expressed as:

The probability density function of the Nakagami-m channel:

According to the moment generator function, the final bit error rate result is obtained. When the nakagami-m fading m is an integer,

And when m is a non-integer, get:

The variables in the above formula (8), (9) are expressed as:

表示当信道h₂服从Nakagami-m分布时的分布参数，该参数为Nakagami-m分布固有参数，所述信道h₂为发送端到用户2之间的衰落信道；above formula

Represent the distribution parameter when the channel h ₂ obeys the Nakagami-m distribution, this parameter is the inherent parameter of the Nakagami-m distribution, and the channel h ₂ is a fading channel between the sending end and the user 2;

In step 1, the users are grouped according to the channel state, and the far and near users are determined, which is determined according to the user channel state;

When m is an integer, the first derivative of the bit error rate to the power allocation factor _α2 is expressed as:

When m is a non-integer, the first derivative of the bit error rate to the power allocation factor _α2 is expressed as:

The present invention is different from the traditional non-orthogonal multiple access technology, and can realize the improvement of the bit error rate performance of the network, and effectively reduce the error transmission phenomenon caused by the early demodulation error.

The bit error rate optimization scheme proposed by the present invention can greatly reduce the amount of calculation in the optimization process. The present invention is applicable to a wide range of scenarios, simple to calculate, and has great development potential.

Description of drawings

Fig. 1 is the single-user bit error rate performance simulation schematic diagram of the variation of power allocation factor of the method proposed by the present invention; Among the figures: the abscissa is the power allocation factor variation value, and the ordinate is the user bit error rate performance.

Fig. 2 is a schematic diagram of the simulation of the performance of the proposed method in the overall bit error rate with the change of the power allocation factor; in the figure: the abscissa is the change value of the power allocation factor, and the ordinate is the user's overall bit error rate performance.

Detailed ways

Embodiment 1. The bit error rate suppression and performance improvement method of non-orthogonal access technology under Nakagami-m channel, which includes the following steps:

Step 1, grouping users, determining far and near users, determining the data modulation order, and giving an initial power allocation factor;

Step 2, determining the multi-user superposition information according to the modulation order and the user distance;

Step 3. Optimizing the multi-user power allocation factor according to the user and network bit error rate tolerance, and according to the theoretical derivation results;

First, considering the downlink NOMA communication technology, the received signal of downlink user k is expressed as:

y _k ＝h _k s+n _k ,(1)

Among them, h _k represents the channel state information of the ^kth user, which is dimensionless, and _nk represents the additive white Guassian noise (AWGN) of the channel, with a mean value of 0 and a variance of N ₀ /2. According to the proposed The encoding and superposition method, the signal s in the above formula (1) can be further expressed as:

其中：2Q_ir表示相邻调制点的距离，接收端最终的解调信号表示为

表示经过串行干扰消除的信号，

表示最终的恢复信号，考虑两用户情况，其中，功率较高的用户信息直接解调，功率较低的用户信息经由串行干扰消除后得到，基于公式(1)，公式(2)中表示的接收信号及发送信号形式，经过串行干扰消除后的剩余信号表示为：Among them: α ₁ and α ₂ represent the power allocation factors allocated to far users and near users, which are dimensionless and need to meet the restriction conditions α ₁ + α ₂ = 1 and α ₁ > α ₂ , in order to ensure user fairness, the distance is relatively long The power obtained by user allocation is relatively large; in formula (2), ε is expressed as

Among them: 2Q _ir represents the distance between adjacent modulation points, and the final demodulated signal at the receiving end is expressed as

Indicates the serial interference-canceled signal,

Indicates the final recovery signal, considering the case of two users, in which the user information with higher power is directly demodulated, and the user information with lower power is obtained after serial interference cancellation, based on formula (1), expressed in formula (2) The form of received signal and transmitted signal, the remaining signal after serial interference elimination is expressed as:

Among them, the formula (a) indicates that the demodulation of the high-power user is successful, and the formula (b) indicates that after the serial interference cancellation technology, the demodulation error of the user with _high power is wrong. Considering low-power users, that is, post-demodulation users, the theoretical expression of the bit error rate is expressed as the sum of two parts. One is the residual information interference of other users caused by unsuccessful SIC, and the other is is the demodulation error caused by its own demodulation error, and the above two parts are expressed as:

For the secondary demodulation user, the total bit error rate is expressed as the sum of the above equations (4) and (5), while for the first demodulation user, the bit error rate is directly expressed as the demodulation under the interference of the secondary demodulation user probability of success,

Under the Nakagami-m channel, combined with the channel fading characteristics, the bit error rate is expressed as:

The probability density function of the Nakagami-m channel:

According to the moment generator function, the final bit error rate result is obtained. When the nakagami-m fading m is an integer,

And when m is a non-integer, get:

The variables in the above formula (8), (9) are expressed as:

表示当信道h₂服从Nakagami-m分布时的分布参数，该参数为Nakagami-m分布固有参数，所述信道h₂为发送端到用户2之间的衰落信道；above formula

Represent the distribution parameter when the channel h ₂ obeys the Nakagami-m distribution, this parameter is the inherent parameter of the Nakagami-m distribution, and the channel h ₂ is a fading channel between the sending end and the user 2;

In step 1, the users are grouped according to the channel state, and the far and near users are determined, which is determined according to the user channel state;

When m is an integer, the first derivative of the bit error rate to the power allocation factor _α2 is expressed as:

When m is a non-integer, the first derivative of the bit error rate to the power allocation factor _α2 is expressed as:

The present invention has the following outstanding substantive features and remarkable progress:

1. The present invention is different from the traditional non-orthogonal multiple access technology, which can improve the performance of the network bit error rate and effectively reduce the error transmission phenomenon caused by the early demodulation error.

2. The present invention proposes an easy-to-operate bit error rate optimization scheme. It only needs to calculate the first-order derivative value according to the given formula, that is, the optimal power allocation scheme can be obtained to meet the optimization requirements of the network bit error rate, and at the same time , aiming at the bit error rate requirement of a single user, the present invention introduces two concepts of network optimization tolerance and single user bit error rate tolerance, within the scope of satisfying the network bit error rate tolerance, the single user bit error rate It is worth noting that since the demodulation sequence is determined by the actual transmission power, the bit error rate tolerance of users with higher power is required to be smaller than that of users with lower power, so as to simplify the problem and find the power allocation factor pair that satisfies the conditions .

3. The bit error rate optimization scheme proposed by the present invention can greatly reduce the amount of calculation in the optimization process. At the same time, after several iterations, the power allocation factor pair that meets the conditions can be found. In different scenarios, different users' Reliability requirements and the reliability requirements of the system as a whole are quite different, and it is only necessary to adjust the corresponding tolerance according to the requirements without re-analyzing the problem. development potential.

Claims (1)

1. The bit error rate suppression and the method for performance improvement of the non-orthogonal access technology under the Nakagami-m channel are characterized in that: it comprises the following steps: Step 1, grouping users, determining far and near users, determining the data modulation order, and giving an initial power allocation factor; Step 2, determining the multi-user superposition information according to the modulation order and the user distance; Step 3. Optimizing the multi-user power allocation factor according to the user and network bit error rate tolerance, and according to the theoretical derivation results; First, considering the downlink NOMA communication technology, the received signal of downlink user k is expressed as: y _k ＝h _k s+n _k ,(1) Among them, h _k represents the channel state information of the ^kth user, which is dimensionless, and _nk represents the additive white Guassian noise (AWGN) of the channel, with a mean value of 0 and a variance of N ₀ /2. According to the proposed The encoding and superposition method, the signal s in the above formula (1) can be further expressed as:

Among them: α ₁ and α ₂ represent the power allocation factors allocated to far users and near users, which are dimensionless and need to meet the restriction conditions α ₁ + α ₂ = 1 and α ₁ > α ₂ , in order to ensure user fairness, the distance is relatively long The power obtained by user allocation is relatively large; in formula (2), ε is expressed as

Among them: 2Q _ir represents the distance between adjacent modulation points, and the final demodulated signal at the receiving end is expressed as

Indicates the serial interference-canceled signal,

represents the final recovery signal, Consider the case of two users, in which the information of the user with higher power is directly demodulated, and the information of the user with lower power is obtained after serial interference cancellation, based on formula (1), the received signal and the transmitted signal form expressed in formula (2) , the remaining signal after serial interference cancellation is expressed as:

Among them, the formula (a) indicates that the demodulation of the high-power user is successful, and the formula (b) indicates that after the serial interference cancellation technology, the demodulation error of the user with _high power is wrong. the tune interferes, Considering the low-power user, that is, the post-demodulation user, the theoretical expression of the bit error rate is expressed as the sum of two parts, one is the residual information interference of other users caused by the unsuccessful SIC, and the other is the self-demodulation error The resulting demodulation error, the above two parts are expressed as:

For the secondary demodulation user, the total bit error rate is expressed as the sum of the above equations (4) and (5), while for the first demodulation user, the bit error rate is directly expressed as the demodulation under the interference of the secondary demodulation user probability of success, Under the Nakagami-m channel, combined with the channel fading characteristics, the bit error rate is expressed as:

The probability density function of the Nakagami-m channel:

According to the moment generator function, the final bit error rate result is obtained. When the nakagami-m fading m is an integer,

And when m is a non-integer, get:

The variables in the above formula (8), (9) are expressed as:

above formula

Represent the distribution parameter when the channel h ₂ obeys the Nakagami-m distribution, this parameter is the inherent parameter of the Nakagami-m distribution, and the channel h ₂ is a fading channel between the sending end and the user 2; In step 1, the users are grouped according to the channel state, and the far and near users are determined, which is determined according to the user channel state; When m is an integer, the first derivative of the bit error rate to the power allocation factor _α2 is expressed as:

When m is a non-integer, the first derivative of the bit error rate to the power allocation factor _α2 is expressed as:

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