阅读说明：本技术 一种认知无线电网络的功率控制方法及装置 (Power control method and device of cognitive radio network ) 是由 陈玲玲 高兴泉 姜德龙 艾学忠 孟亚男 林琳 郭帅飞 于 2021-07-15 设计创作，主要内容包括：本发明公开一种认知无线电网络的功率控制方法及装置,方法包括：构建状态空间模型,通过LMI方法对状态空间模型计算状态反馈增益；通过更新时隙k时次用户i发射功率、时隙k时次用户i的实际测量信噪比、时隙k时次用户i对主用户l产生的干扰,结合误差动态方程计算时隙k时的次用户信噪比跟踪误差和时隙k时干扰温度跟踪误差,并根据其正负来选择控制器,通过控制器使次用户的发射功率降低,根据状态反馈增益与时隙k的输入向量乘积等于次用户i的更新功率功率控制更新指令,再返回重新更新,直至次用户发射信号不占据频谱。本发明考虑远近效应、快速信道衰落、测量误差、多址干扰和链路时延等因素的影响,通过对次用户功率控制,呈现良好鲁棒跟踪性能。(The invention discloses a power control method and a device of a cognitive radio network, wherein the method comprises the following steps: constructing a state space model, and calculating a state feedback gain on the state space model by an LMI method; the transmitting power of the secondary user is reduced through the controller, the updating instruction is controlled according to the condition that the product of the state feedback gain and the input vector of the time slot k is equal to the updating power of the secondary user, and the updating is returned again until the transmitting signal of the secondary user does not occupy the frequency spectrum. The invention considers the influence of factors such as near-far effect, fast channel fading, measurement error, multi-access interference, link time delay and the like, and presents good robust tracking performance by controlling the power of the secondary user.)

1. A power control method of a cognitive radio network, comprising:

step 1, according to mixing H₂/H_∞Control theory construction of feedback controller with sub-user signal-to-noise ratioFeedback controller for interference of secondary user to primary userThe state space model of error tracking, the state space model comprising an input vector and an output vector,

wherein, the input vector of k +1 time slot is formed by the sum of the product of the constant coefficient matrix and the input vector of k time slot after adding the state feedback gain, the product of the constant coefficient matrix and the related influence coefficient of the secondary user interference to the primary user, and the product of the constant coefficient matrix and the related influence coefficient of the signal-to-noise ratio of the tested secondary user,

H₂the output vector corresponding to the norm is formed by the sum of products of the constant coefficient matrix and the input vector of the k time slot after adding the state feedback gain,

H_∞the output vector corresponding to the norm is formed by the product of a constant coefficient matrix and an input vector of a k time slot after adding a state feedback gain, and the sum of products of the constant coefficient matrix and a correlation influence coefficient of secondary user interference on a primary user;

step 2, calculating state feedback gain for the state space model by an LMI method;

step 3, step 31, updating the transmitting power of the secondary user i at the time slot k through the transmitting power of the secondary user i at the time slot k-1 and the transmitting power control updating instruction of the secondary user i at the time slot k;

step 32, passing the transmitting power of the sub-user i at the time slot k and the channel interference gain g from the transmitter of the sub-user j to the receiver of the sub-user i at the time slot k_ji(k) And a first multiple interference I experienced by a secondary user I during a time slot k_i(k) Calculating the actual measurement signal-to-noise ratio of a secondary user i at a time slot k, wherein the first multiple interference comprises multiple access interference, noise and fading;

step 33, calculating the interference temperature of the secondary user i in the time slot k to the primary user l through the transmitting power of the secondary user i in the time slot k and the channel interference gain between the transmitter of the secondary user i and the receiver of the primary user l in the time slot k;

and 4, calculating the signal-to-noise ratio tracking error of the secondary user i in the time slot k and the interference temperature tracking error of the secondary user i to the primary user in the time slot k through an error dynamic equation, selecting a controller according to the positive and negative of the tracking error, further reducing the transmitting power of the secondary user through the selected controller, updating the self-adaptive step length, calculating the power and updating the power control updating instruction according to the condition that the product of the state feedback gain and the input vector of the time slot k is equal to the power control updating instruction of the secondary user i, and then returning to the step 3 until the transmitting signal of the secondary user does not occupy the frequency spectrum.

2. The method for power control of a cognitive radio network as claimed in claim 1,

the state space model is as follows:

wherein k represents a time slot;

k represents a state feedback gain;

A，B，B₁，B₂，C₀，C₁，D₀₁，D₁₁，D₁₂is a constant coefficient matrix;

is the input state vector of the secondary user i at time slot k;

z₂(k)＝[e_i ^γ(k) u_i(k)]^Tis the output vector of the secondary user i at time slot k;

is the output vector of the secondary user i at time slot k;

e_i ^γ(k) the signal-to-noise ratio tracking error of the secondary user i at the time slot k;

the interference temperature tracking error of the secondary user i to the primary user l at the time slot k;

u_i(k) the power control updating instruction of the secondary user i when the time slot is k;

whereinRepresents the SNR related influence coefficient of the tested secondary user in time slot k,represents the difference between the sub-user i in time slots k + l and k given the desired signal-to-noise ratio threshold, [ g ]_ii(k+1)-g_ii(k)]Representing the difference of the channel interference gains of the secondary user i at time slots k +1 and k;

[I_i(k+1)-I_i(k)]representing the difference between a first multiple interference of a secondary user i at a time slot k +1 and a time slot k, wherein the first multiple interference comprises multiple access interference, noise and fading;

represents the interference correlation influence coefficient of the secondary user i measured in the time slot k to the primary user l,is the expected interference temperature threshold given by secondary user i to primary user i at time slot k, where M denotes M secondary users,the maximum interference power threshold value of all active secondary users which can be borne by the primary user l; h is_il(k) Is the channel interference gain between the secondary user i transmitter and the primary user i receiver at time slot k.

3. The method of cognitive radio network power control according to claim 2,

in step 31, the transmitting power p of the secondary user i at the time slot k is updated by the transmitting power of the secondary user i at the time slot k-1 and the power control updating instruction of the secondary user i at the time slot k_i(k) Its corresponding equation 6 is as follows:

p_i(k)＝p_i(k-1)+u_i(k) (6)

in step 32, the transmitting power p of the secondary user i when passing through the time slot k_i(k) Direct channel interference gain g from sub-user i transmitter to sub-user i receiver at time slot k_ii(k) And the first multiple interference I last experienced by user I in time slot k_i(k) Actual measured signal-to-noise ratio gamma of secondary user i when calculating time slot k_i(k) Its corresponding equation 2 is as follows:

γ_i(k)＝p_i(k)+g_ji(k)-I_i(k) (2)

the first multiple interference I last experienced by user I in time slot k_i(k) Is defined as follows

I_i(k)＝10 log₁₀[n_i(k)+∑_j≠ig_ji(k)p_j(k)+∑_lg_li(k)p_l(k)] (3)

j∈{1，2，…，M}，l∈{1，2，…，N}

Wherein M represents M secondary users, and N represents N primary users;

parameter n_i(k) Is the normalized background noise received by the secondary user i at time slot k;

w_i(k)＝∑_j≠ig_ji(k)p_j(k) represents the total interference power of all other secondary user transmitters to secondary user i at time slot k;

p_j(k) representing the transmitting power of the secondary user j at the time slot k;

non-negative parameter g_ji(k) Represents the channel interference gain from the secondary user j transmitter to the secondary user i receiver over time slot k;

IN_i(k)＝∑_lg_li(k)p_l(k) representing the total interference power of all primary user transmitters to a secondary user i in a time slot k;

p_l(k) representing the transmitting power of a main user l when a time slot k is formed;

non-negative parameter g_li(k) Represents the channel interference gain from the primary user i transmitter to the secondary user i receiver over time slot k;

in step 33, the transmitting power of the secondary user i when passing through the time slot k, and the channel interference gain h between the transmitter of the secondary user i and the receiver of the primary user l when passing through the time slot k_il(k) To calculate the interference temperature gamma generated by the secondary user i to the primary user l in the time slot k_il(k) Its corresponding equation 9 is as follows:

Γ_il(k)＝p_i(k)+h_il(k) (9)

wherein gamma is_il(k) Is the interference temperature generated by the secondary user i to the primary user l.

4. The cognitive radio network power control method of claim 3,

in step 4, the calculating, by an error dynamic equation, a signal-to-noise ratio tracking error of the secondary user i at the time slot k and an interference temperature tracking error of the secondary user i to the primary user at the time slot k includes:

tracking error e according to signal-to-noise ratio of time slot k-1 secondary user i_i ^γ(k-1), power control update command u of secondary user i at time slot k-1_i(k-1) and the signal-to-noise ratio related influence coefficient f of the secondary user i at the time slot k-1_i(k-1) SNR tracking error e when calculating time slot k_i ^γ(k)；

Interference temperature tracking error of secondary user i according to time slot k-1Power control update command u for secondary user i at time slot k-1_i(k-1) and a correlation influence coefficient v of interference of a secondary user i measured in a time slot k-1 to a primary user l_il(k-1) calculating interference error of the sub-user i at the time of the time slot k

The error dynamic equation is as follows:

e_i ^γ(k)＝e_i ^γ(k-1)-u_i(k-1)+f_i(k-1) (10)

whereinRepresents the SNR related influence coefficient of the tested secondary user in time slot k-1,representing the difference between the desired signal-to-noise ratio thresholds given by secondary user i at time slots k and k-1, [ g ]_ii(k)-g_ii(k-1)]Representing the difference of the channel interference gains of the secondary user i in the time slots k and k-1; [ I ] of_i(k)-I_i(k-1)]Representing the difference between the first multiple interference of the secondary user i in time slot k and in time slot k-1, said first multipleInterference includes multiple access interference, noise and fading;

representing the interference related impact coefficient of the secondary user i on the primary user l measured at time slot k-1,the method is that a secondary user i gives an expected interference temperature threshold value h to a primary user l at a time slot k_il(k) Is the channel interference gain between the secondary user transmitter and the primary user receiver at slot k.

5. The method for controlling power of a cognitive radio network according to claim 1, wherein the formula for updating the adaptive step size is as follows:

wherein the controllerAnd a controllerAre respectively a_i(k) And a_il(k) And epsilon is a forgetting factor,is the sample standard deviation of the sub-user signal-to-noise ratio tracking error,is the sampling standard deviation of the tracking error of the main user interference temperature,

where G is the update window length.

6. The method of claim 1, wherein a second multiple interference factor is considered in the state space model, the second multiple interference includes near-far effect, link delay, noise and measurement error, and the corresponding error dynamic equation considering the second multiple interference is:

the signal-to-noise ratio tracking error of the secondary user i when considering the time slot k of the second multiple interference;

the interference temperature tracking error of the secondary user i to the primary user l is considered when the time slot k of the second multiple interference is considered;

a power control updating instruction which represents that the time delay of a secondary user i is d when a time slot k of second multiple interference is considered;

is the quantization error;

a power control update command of the secondary user i when considering the time slot k of the second multiple interference;

representing the SNR dependent impact coefficient of the measured sub-user i taking into account the time slot k-1 of the second multiple interference, whereinRepresents the SNR related influence coefficient of the tested secondary user in time slot k-1,represents the difference between the sub-user i in time slots k and k-1 given the desired signal-to-noise ratio threshold, [ g ]_ii(k)-g_ii(k-1)]Representing the channel interference gain of the secondary user i in time slots k and k-1A difference of (d); [ I ] of_i(k)-I_i(k-1)]Representing the difference between the first multiple interferences of the secondary user i at the time slot k and the time slot k-1, wherein the first multiple interferences comprise multiple access interferences, noises and fading;

indicating the relative influence coefficient of the interference of the secondary user i on the primary user l measured in time slot k taking into account the second multiple interference,is the time slot k, the secondary user i gives the primary user l an expected interference temperature threshold, where,is the maximum interference power threshold, λ, of all active secondary users that the primary user l can withstand_il(k) Is a weighting factor;considering the channel interference gain between the transmitter of the secondary user i and the receiver of the primary user l at the time slot k of the second multiple interference;

interference measurement errors to the primary user generated by the secondary user when considering the time slot k-1 of the second multiple interference;

to account for the SNR tracking error at time slot k-1 of the second multiple interference;

to account for the noise of the feedback channel to the secondary user i on slot k of the second multiple interference.

7. The power control method of cognitive radio network according to claim 6, wherein the state space model considering the second multiple interference corresponding to the error dynamic equation considering the second multiple interference is as follows:

wherein k represents a time slot;

K₂is the state feedback gain;

is a constant coefficient matrix;

is the input state vector of the secondary user i when considering the slot k of the second multiple interference;

is the output vector of the secondary user i when considering the slot k of the second multiple interference;

is the output vector of the secondary user i when considering the slot k of the second multiple interference;

the signal-to-noise ratio tracking error of the secondary user i when considering the time slot k of the second multiple interference;

the temperature tracking error of the interference of the secondary user i to the primary user l is considered when the time slot k of the second multiple interference is considered;

the power control update commands for the sub-user i in the time slots k-1 to k-d of the second multiple interference are considered.

8. The method for power control of a cognitive radio network as claimed in claim 7,

in step 31, updating the power control command of the secondary user i by considering the transmitting power of the secondary user i in the time slot k-1 of the second multiple interference and the power control command of the secondary user i in the time slot k-d of the second multiple interference, and considering the noise of the feedback channel to the secondary user i in the time slot k of the second multiple interferenceTo update the transmission power of the secondary user i in the time slot k considering the second multiple interferenceIts corresponding equation 15 is as follows:

in step 32, the transmission power p of the secondary user i passes through the time slot k_i(k) Direct channel interference gain g from sub-user j transmitter to sub-user i receiver at time slot k_ji(k) And the first multiple interference I last experienced by user I in time slot k_i(k) And interference measurement error to primary user generated by secondary user considering secondary multiple interferenceActual measured signal-to-noise ratio of secondary user i when calculating time slot kIts corresponding equation 17 is as follows:

I_i(k) the definition is as follows:

wherein M represents M secondary users, and N represents N primary users;

actual measured signal-to-noise ratio of the secondary user i when considering the time slot k of the second multiple interference;

parameter n_i(k) Is the normalized background noise received by the secondary user i at time slot k;

w_i(k)＝∑_j≠ig_ji(k)p_j(k) representing the total interference of other secondary users to the secondary user i in the time slot k;

p_j(k) representing the transmitting power of the transmitter of the secondary user j at the time slot k;

non-negative parameter g_ji(k) Represents the channel interference gain from the secondary user j transmitter to the secondary user i receiver over time slot k;

IN_i(k)＝∑_lg_li(k)p_l(k) the total interference power of all primary user transmitters to a secondary user i receiver in a time slot k;

p_l(k) representing the transmitting power of a primary user I transmitter at a time slot k;

non-negative parameter g_li(k) Represents the channel interference gain from the primary user i transmitter to the secondary user i receiver over time slot k;

for the transmission of the secondary user i in step 33 by taking into account the time slot k of the second multiple interferenceCalculating the interference of a secondary user i of a k-slot taking into account a second multiple interference on a primary user l taking into account the power, the channel interference gain between the secondary user transmitter and the primary user l receiver taking into account the k-slot of the second multiple interference and the interference measurement error to the primary user generated by the secondary user taking into account the second multiple interferenceIts corresponding equation 20 is as follows:

the interference temperature generated by the secondary user i of the second multiple interference to the primary user l is considered.

9. The method for power control of a cognitive radio network as claimed in claim 1,

the positive and negative selection controller for tracking error according to the signal-to-noise ratio of the secondary user and the interference temperature tracking error of the secondary user to the primary user comprises:

when the signal-to-noise ratio tracking error of the secondary user is more than 0 and the interference temperature tracking error of the secondary user to the primary user is less than 0, the controller is closedUsing only the controllerReducing the transmission power p of a secondary user i_i(k) Until the tracking error of the interference temperature is more than or equal to 0;

when the signal-to-noise ratio tracking error of the secondary user is less than 0 and the interference temperature tracking error of the secondary user to the primary user is more than 0, the controllerAndsimultaneously reducing the transmitting power of the secondary user i until the signal-to-noise ratio tracking error is equal to a near-zero threshold value;

when the signal-to-noise ratio tracking error of the secondary user and the interference temperature tracking error of the secondary user to the primary user are both larger than zero or smaller than zero, the controllerAndand simultaneously reducing the transmitting power of the secondary user i until the signal-to-noise ratio tracking error and the interference temperature tracking error are equal to a near-zero threshold value, wherein the near-zero threshold value is a preset threshold value close to zero.

10. A power control apparatus of a cognitive radio network, comprising:

a model construction module for constructing a model from the mixture H₂/H_∞Control theory construction of feedback controller with sub-user signal-to-noise ratioFeedback controller for interference of secondary user to primary userThe state space model of error tracking, the state space model comprising an input vector and an output vector,

wherein, the input vector of k +1 time slot is formed by the sum of the product of the constant coefficient matrix and the input vector of k time slot after adding the state feedback gain, the product of the constant coefficient matrix and the related influence coefficient of the secondary user interference to the primary user, and the product of the constant coefficient matrix and the related influence coefficient of the signal-to-noise ratio of the tested secondary user,

H₂norm pairThe corresponding output vector is formed by the sum of the constant coefficient matrix plus the state feedback gain multiplied by the input vector for k time slots,

H_∞the output vector corresponding to the norm is formed by the product of a constant coefficient matrix and an input vector of a k time slot after adding a state feedback gain, and the sum of products of the constant coefficient matrix and a correlation influence coefficient of secondary user interference on a primary user;

the state feedback gain acquisition module is used for calculating the state feedback gain of the state space model by an LMI method;

the signal-to-noise ratio and interference temperature acquisition module is used for updating the transmitting power of the secondary user i at the time slot k through the transmitting power of the secondary user i at the time slot k-1 and a transmitting power control updating instruction of the secondary user i at the time slot k;

transmitting power of sub-user i in time slot k, and channel interference gain g from transmitter of sub-user j to receiver of sub-user i in time slot k_ji(k) And a first multiple interference I experienced by a secondary user I during a time slot k_i(k) Calculating the actual measurement signal-to-noise ratio of a secondary user i at a time slot k, wherein the first multiple interference comprises multiple access interference, noise and fading;

calculating the interference temperature of the secondary user i to the primary user l at the time slot k through the transmitting power of the secondary user i at the time slot k and the channel interference gain between a transmitter of the secondary user i and a receiver of the primary user l at the time slot k;

and the power updating module is used for calculating the signal-to-noise ratio tracking error of the secondary user i in the time slot k and the interference temperature tracking error of the secondary user i to the primary user in the time slot k through an error dynamic equation, selecting the controller according to the positive and negative values of the tracking error, further reducing the transmitting power of the secondary user through the selected controller, updating the self-adaptive step length, calculating the power and updating the power control updating instruction according to the condition that the product of the state feedback gain and the input vector of the time slot k is equal to the power control updating instruction of the secondary user i, and then returning to the step 3 until the transmitting signal of the secondary user does not occupy the frequency spectrum.

Technical Field

The invention relates to the technical field of radio networks, in particular to a power control method and device of a cognitive radio network.

Background

In recent years, with the rapid development of modern wireless communication technology services, limited spectrum resources have been unable to meet the increasing demands of people. The effective improvement of spectrum utilization is an important issue in the field of communications. The cognitive radio can independently search for the idle frequency spectrum, and the utilization efficiency of the frequency spectrum can be improved to a certain extent. Compared with the existing communication systems (4G, 4.5G), the Secondary Users (SU) and the Primary Users (PU) share the authorized frequency band in the underlay-type Cognitive Radio Networks (CRNs) so as to improve the frequency spectrum utilization rate. Meanwhile, the mode can be directly constructed on a mobile wireless network, so that the construction cost is saved, and the network investment is reduced. Therefore, in the existing network, the underlay-type cognitive radio network has become an increasingly important issue for improving the spectrum efficiency.

In the underlay-type cognitive radio network, power control is one of the key technologies for realizing spectrum resource sharing. On the premise of not influencing the QoS (quality of service) of a primary user in the underlay type cognitive network, the transmitting power is controlled by adaptively adjusting the parameters of a secondary user, so that the QoS of the secondary user is ensured. At present, the majority of researchers have achieved good results in solving the power control problem in the underlying cognitive radio network by combining methods such as game theory, group intelligent optimization, robust optimization, random optimization and the like. However, in the underlay-type cognitive network, the power control based on the above method cannot be accurately described in real time when the system state of the user in the next time slot is updated in the last time slot.

In addition, the limitation of the interference temperature is a key constraint condition for realizing power control in the underlay type cognitive radio network, and is also an important factor for limiting dynamic multiplexing and improving spectrum efficiency. However, in the above algorithm, a fixed interference temperature threshold is clearly inappropriate to describe the effect of the secondary user on the primary user. Meanwhile, the actual channel state information is inevitably affected by quantization errors, measurement errors and uncertain interferences, thereby causing degradation of system performance.

Until now, power control methods have not incorporated the effects of interference temperature, quantization error, measurement error, uncertain interference, etc. into power control, and there has been no better solution to solve the above problems.

Disclosure of Invention

From the viewpoint of dynamic process control in the underlay-type cognitive radio network, there are few algorithms applied to power control. In CDMA cellular communication system, a robust power control method H is provided_∞In the worst case, the expected signal-to-noise ratio (SINR) is tracked to be minimized, thereby achieving better communication quality and higher system capacity. For QoS of users, hybrid H is proposed₂/H_∞Distributed Power Control algorithm (Chaves F D S, Abbas-Turki M, Abou-Kandil H, et al. Transmission Power Control for Opportunistic QoS Provisions in Wireless Networks [ J]IEEE Transactions on Control Systems Technology,2013,21(2): 315-.

Based on the above consideration, the application provides a robust hybrid H with adaptive step length₂/H_∞The power control problem of the secondary user in the underlying cognitive radio network is solved by the algorithm. In order to track the expected SINR (signal to noise ratio) of the secondary user and the expected interference to the primary user in case of channel fading and noise uncertainty, a state space model with two state feedback controllers is established, which takes into account the constraints of the average interference temperature value. In addition, under the condition that other conditions are unchanged, the state space model is reconstructed by considering the link delay, the measurement error and the weighted interference temperature constraint. Further, by expandingExtended Linear Matrix Inequality (LMI) (M.C. De Oliveira, J.C. Geromel, J.Bernoussou. extended H2 and H norm characters and controller parameters for discrete-time systems [ J.]International Journal of Control,2002,75(9):666-₂And H_∞By introducing additional variables to reduce conservatism and increase freedom. The power tracking control problem is then solved by means of an LMI algorithm. Simulation results show that compared with power control algorithms of a traditional fixed step CPCA algorithm and a self-adaptive step CPCA algorithm, the method and the device can well adapt to the actual dynamic communication environment, and improve the QoS of secondary users along with the change of the number of the primary users. The technical scheme adopted by the invention is as follows:

a power control method of a cognitive radio network comprises the following steps:

step 1, according to mixing H₂/H_∞Control theory construction of feedback controller with sub-user signal-to-noise ratioFeedback controller for interference of secondary user to primary userThe state space model of error tracking, the state space model comprising an input vector and an output vector,

wherein, the input vector of k +1 time slot is formed by the sum of the product of the constant coefficient matrix and the input vector of k time slot after adding the state feedback gain, the product of the constant coefficient matrix and the related influence coefficient of the secondary user interference to the primary user, and the product of the constant coefficient matrix and the related influence coefficient of the signal-to-noise ratio of the tested secondary user,

H₂the output vector corresponding to the norm is formed by the sum of products of the constant coefficient matrix and the input vector of the k time slot after adding the state feedback gain,

H_∞the output vector corresponding to the norm is formed by the product of a constant coefficient matrix and an input vector of a k time slot after state feedback gain is added, and the correlation influence of the constant coefficient matrix and secondary user interference on a primary userSum of products of coefficients;

step 2, calculating state feedback gain for the state space model by an LMI method;

step 3, step 31, updating the transmitting power of the secondary user i at the time slot k through the transmitting power of the secondary user i at the time slot k-1 and the transmitting power control updating instruction of the secondary user i at the time slot k;

step 32, passing the transmitting power of the sub-user i at the time slot k and the channel interference gain g from the transmitter of the sub-user j to the receiver of the sub-user i at the time slot k_ji(k) And a first multiple interference I experienced by a secondary user I during a time slot k_i(k) Calculating the actual measurement signal-to-noise ratio of a secondary user i at a time slot k, wherein the first multiple interference comprises multiple access interference, noise and fading;

step 33, calculating the interference temperature of the secondary user i in the time slot k to the primary user l through the transmitting power of the secondary user i in the time slot k and the channel interference gain between the transmitter of the secondary user i and the receiver of the primary user l in the time slot k;

and 4, calculating the signal-to-noise ratio tracking error of the secondary user i in the time slot k and the interference temperature tracking error of the secondary user i to the primary user in the time slot k through an error dynamic equation, selecting a controller according to the positive and negative of the tracking error, further reducing the transmitting power of the secondary user through the selected controller, updating the self-adaptive step length, calculating the power and updating the power control updating instruction according to the condition that the product of the state feedback gain and the input vector of the time slot k is equal to the power control updating instruction of the secondary user i, and then returning to the step 3 until the transmitting signal of the secondary user does not occupy the frequency spectrum.

Optionally, the state space model is as follows:

wherein k represents a time slot;

k represents a state feedback gain;

A,B,B₁,B₂,C₀,C₁,D₀₁,D₁₁,D₁₂is constant coefficient momentArraying;

is the input state vector of the secondary user i at time slot k;

z₂(k)＝[e_i ^γ(k) u_i(k)]^Tis the output vector of the secondary user i at time slot k;

is the output vector of the secondary user i at time slot k;

e_i ^γ(k) the signal-to-noise ratio tracking error of the secondary user i at the time slot k;

the interference temperature tracking error of the secondary user i to the primary user l at the time slot k;

u_i(k) the power control updating instruction of the secondary user i when the time slot is k;

whereinRepresents the SNR related influence coefficient of the tested secondary user in time slot k,represents the difference between the sub-user i at time slots k +1 and k given the desired signal-to-noise ratio threshold, [ g ]_ii(k+1)-g_ii(k)]Representing the difference of the channel interference gains of the secondary user i at time slots k +1 and k;

[I_i(k+1)-I_i(k)]representing the difference between a first multiple interference of a secondary user i at a time slot k +1 and a time slot k, wherein the first multiple interference comprises multiple access interference, noise and fading;

pair of secondary users i measured in time slot kThe primary user l interferes with the relevant influence coefficient,is the expected interference temperature threshold given by secondary user i to primary user i at time slot k, where M denotes M secondary users,the maximum interference power threshold value of all active secondary users which can be borne by the primary user l; h is_il(k) Is the channel interference gain between the secondary user i transmitter and the primary user i receiver at time slot k.

Optionally, in step 31, the transmission power p of the secondary user i at time slot k is updated by the transmission power of the secondary user i at time slot k-1 and the power control update instruction of the secondary user i at time slot k_i(k) Its corresponding equation 6 is as follows:

p_i(k)＝p_i(k-1)+u_i(k) (6)

in step 32, the transmitting power p of the secondary user i when passing through the time slot k_i(k) Direct channel interference gain g from sub-user i transmitter to sub-user i receiver at time slot k_ii(k) And the first multiple interference I last experienced by user I in time slot k_i(k) Actual measured signal-to-noise ratio gamma of secondary user i when calculating time slot k_i(k) Its corresponding equation 2 is as follows:

γ_i(k)＝p_i(k)+g_ji(k)-I_i(k) (2)

the first multiple interference I last experienced by user I in time slot k_i(k) Is defined as follows

I_i(k)＝10log₁₀[n_i(k)+∑_j≠ig_ji(k)p_j(k)+∑_lg_li(k)p_l(k)] (3)

j∈{1,2,…,M},l∈{1,2,…,N}

Wherein M represents M secondary users, and N represents N primary users;

parameter n_i(k) Is the normalized background noise received by the secondary user i at time slot k;

w_i(k)＝∑_j≠ig_ji(k)p_j(k) represents the total interference power of all other secondary user transmitters to secondary user i at time slot k;

p_j(k) representing the transmitting power of the secondary user j at the time slot k;

non-negative parameter g_ji(k) Represents the channel interference gain from the secondary user j transmitter to the secondary user i receiver over time slot k;

IN_i(k)＝∑_lg_li(k)p_l(k) representing the total interference power of all primary user transmitters to a secondary user i in a time slot k;

p_l(k) representing the transmitting power of a main user l when a time slot k is formed;

non-negative parameter g_li(k) Represents the channel interference gain from the primary user i transmitter to the secondary user i receiver over time slot k;

in step 33, the transmitting power of the secondary user i when passing through the time slot k, and the channel interference gain h between the transmitter of the secondary user i and the receiver of the primary user l when passing through the time slot k_il(k) To calculate the interference temperature Γ i generated by the secondary user i to the primary user l in the time slot k_il(k) Its corresponding equation 9 is as follows:

Γ_il(k)＝p_i(k)+h_il(k) (9)

wherein gamma is_il(k) Is the interference temperature generated by the secondary user i to the primary user l.

Optionally, in step 4, the calculating, by using an error dynamic equation, a signal-to-noise ratio tracking error of the secondary user i at the time slot k and an interference temperature tracking error of the secondary user i to the primary user at the time slot k includes:

tracking error e according to signal-to-noise ratio of time slot k-1 secondary user i_i ^γ(k-1), power control update command u of secondary user i at time slot k-1_i(k-1) and the signal-to-noise ratio related influence coefficient f of the secondary user i at the time slot k-1_i(k-1) SNR tracking error e when calculating time slot k_i ^γ(k)；

Interference temperature tracking error of secondary user i according to time slot k-1Power control update command u for secondary user i at time slot k-1_i(k-1) and a correlation influence coefficient v of interference of a secondary user i measured in a time slot k-1 to a primary user l_il(k-1) calculating interference error of the sub-user i at the time of the time slot k

The error dynamic equation is as follows:

e_i ^γ(k)＝e_i ^γ(k-1)-u_i(k-1)+f_i(k-1) (10)

whereinRepresents the SNR related influence coefficient of the tested secondary user in time slot k-1,representing the difference between the desired signal-to-noise ratio thresholds given by secondary user i at time slots k and k-1, [ g ]_ii(k)-g_ii(k-1)]Representing the difference of the channel interference gains of the secondary user i in the time slots k and k-1; [ I ] of_i(k0-I_i(k-1)]Representing the difference of a first multiple interference of a secondary user i at a time slot k and a time slot k-1, wherein the first multiple interference comprises multiple access interference, noise and fading;

representing the interference related impact coefficient of the secondary user i on the primary user l measured at time slot k-1,the method is that a secondary user i gives an expected interference temperature threshold value h to a primary user l at a time slot k_il(k) Is time slot k time secondary user transmissionChannel interference gain between the transmitter and the primary user/receiver.

Optionally, a second multiple interference factor is considered in the state space model, where the second multiple interference includes near-far effect, link delay, noise, and measurement error, and a corresponding error dynamic equation considering the second multiple interference is:

the signal-to-noise ratio tracking error of the secondary user i when considering the time slot k of the second multiple interference;

the interference temperature tracking error of the secondary user i to the primary user l is considered when the time slot k of the second multiple interference is considered;

a power control updating instruction which represents that the time delay of a secondary user i is d when a time slot k of second multiple interference is considered;

is the quantization error;

is an examinationConsidering the power control updating instruction of the secondary user i when the time slot k of the second multiple interference is considered;

representing the SNR dependent impact coefficient of the measured sub-user i taking into account the time slot k-1 of the second multiple interference, whereinRepresents the SNR related influence coefficient of the tested secondary user in time slot k-1,represents the difference between the sub-user i in time slots k and k-1 given the desired signal-to-noise ratio threshold, [ g ]_ii(k)-g_ii(k-1)]Representing the difference of the channel interference gains of the secondary user i in the time slots k and k-1; [ I ] of_i(k)-I_i(k-1)]Representing the difference between the first multiple interferences of the secondary user i at the time slot k and the time slot k-1, wherein the first multiple interferences comprise multiple access interferences, noises and fading;

indicating the relative influence coefficient of the interference of the secondary user i on the primary user l measured in time slot k taking into account the second multiple interference,is the time slot k, the secondary user i gives the primary user l an expected interference temperature threshold, where,is the maximum interference power threshold, λ, of all active secondary users that the primary user l can withstand_il(k) Is a weighting factor;considering the channel interference gain between the transmitter of the secondary user i and the receiver of the primary user l at the time slot k of the second multiple interference;

interference measurement errors to the primary user generated by the secondary user when considering the time slot k-1 of the second multiple interference;

to account for the SNR tracking error at time slot k-1 of the second multiple interference;

to account for the noise of the feedback channel to the secondary user i on slot k of the second multiple interference.

Optionally, the state space model considering the second multiple interference corresponding to the error dynamic equation considering the second multiple interference is as follows:

wherein k represents a time slot;

K₂is the state feedback gain;

is a constant coefficient matrix;

is time slot k time slot of second multiple interferenceAn input state vector of user i;

is the output vector of the secondary user i when considering the slot k of the second multiple interference;

is the output vector of the secondary user i when considering the slot k of the second multiple interference;

the signal-to-noise ratio tracking error of the secondary user i when considering the time slot k of the second multiple interference;

the temperature tracking error of the interference of the secondary user i to the primary user l is considered when the time slot k of the second multiple interference is considered;

the power control update commands for the sub-user i in the time slots k-1 to k-d of the second multiple interference are considered.

Optionally, in step 31, the transmission power of the secondary user i in the time slot k-1 considering the second multiple interference and the power control update command of the secondary user i in the time slot k-d considering the second multiple interference are used, and the noise of the feedback channel to the secondary user i in the time slot k considering the second multiple interferenceTo update the transmission power of the secondary user i in the time slot k considering the second multiple interferenceIts corresponding equation 15 is as follows:

in step 32, the transmission power p of the secondary user i passes through the time slot k_i(k) Direct channel interference gain g from sub-user j transmitter to sub-user i receiver at time slot k_ji(k) And the first multiple interference I last experienced by user I in time slot k_i(k) And interference measurement error to primary user generated by secondary user considering secondary multiple interferenceActual measured signal-to-noise ratio of secondary user i when calculating time slot kIts corresponding equation 17 is as follows:

I_i(k) the definition is as follows:

wherein M represents M secondary users, and N represents N primary users;

actual measured signal-to-noise ratio of the secondary user i when considering the time slot k of the second multiple interference;

parameter n_i(k) Is the normalized background noise received by the secondary user i at time slot k;

w_i(k)＝∑_j≠ig_ji(k)p_j(k) representing the total interference of other secondary users to the secondary user i in the time slot k;

p_j(k) representing the transmitting power of the transmitter of the secondary user j at the time slot k;

non-negative parameter g_ji(k) Represents the channel interference gain from the secondary user j transmitter to the secondary user i receiver over time slot k;

IN_i(k)＝∑_lg_li(k)p_l(k) the total interference power of all primary user transmitters to a secondary user i receiver in a time slot k;

p_l(k) representing the transmitting power of a primary user I transmitter at a time slot k;

non-negative parameter g_li(k) Represents the channel interference gain from the primary user i transmitter to the secondary user i receiver over time slot k;

in step 33, the interference caused by the secondary user i considering the k time slot of the secondary multiple interference to the primary user l is calculated by considering the transmission power of the secondary user i considering the k time slot of the secondary multiple interference, the channel interference gain between the secondary user transmitter and the primary user l receiver considering the k time slot of the secondary multiple interference, and the interference measurement error caused by the secondary user considering the secondary multiple interference to the primary userIts corresponding equation 20 is as follows:

the interference temperature generated by the secondary user i of the second multiple interference to the primary user l is considered.

The present invention also provides a power control apparatus of a cognitive radio network, including:

a model construction module for constructing a model from the mixture H₂/H_∞Control theory construction of feedback controller with sub-user signal-to-noise ratioFeedback controller for interference of secondary user to primary userThe state space model of error tracking, the state space model comprising an input vector and an output vector,

wherein, the input vector of k +1 time slot is formed by the sum of the product of the constant coefficient matrix and the input vector of k time slot after adding the state feedback gain, the product of the constant coefficient matrix and the related influence coefficient of the secondary user interference to the primary user, and the product of the constant coefficient matrix and the related influence coefficient of the signal-to-noise ratio of the tested secondary user,

H₂the output vector corresponding to the norm is formed by the sum of products of the constant coefficient matrix and the input vector of the k time slot after adding the state feedback gain,

H_∞the output vector corresponding to the norm is formed by the product of a constant coefficient matrix and an input vector of a k time slot after adding a state feedback gain, and the sum of products of the constant coefficient matrix and a correlation influence coefficient of secondary user interference on a primary user;

the state feedback gain acquisition module is used for calculating the state feedback gain of the state space model by an LMI method;

the signal-to-noise ratio and interference temperature acquisition module is used for updating the transmitting power of the secondary user i at the time slot k through the transmitting power of the secondary user i at the time slot k-1 and a transmitting power control updating instruction of the secondary user i at the time slot k;

transmitting power of sub-user i in time slot k, and channel interference gain g from transmitter of sub-user j to receiver of sub-user i in time slot k_ji(k) And a first multiple interference I experienced by a secondary user I during a time slot k_i(k) Calculating the actual measurement signal-to-noise ratio of a secondary user i at a time slot k, wherein the first multiple interference comprises multiple access interference, noise and fading;

calculating the interference temperature of the secondary user i to the primary user l at the time slot k through the transmitting power of the secondary user i at the time slot k and the channel interference gain between a transmitter of the secondary user i and a receiver of the primary user l at the time slot k;

and the power updating module is used for calculating the signal-to-noise ratio tracking error of the secondary user i in the time slot k and the interference temperature tracking error of the secondary user i to the primary user in the time slot k through an error dynamic equation, selecting the controller according to the positive and negative values of the tracking error, further reducing the transmitting power of the secondary user through the selected controller, updating the self-adaptive step length, calculating the power and updating the power control updating instruction according to the condition that the product of the state feedback gain and the input vector of the time slot k is equal to the power control updating instruction of the secondary user i, and then returning to the step 3 until the transmitting signal of the secondary user does not occupy the frequency spectrum.

From the perspective of automatic control, the method provides a state space dynamic model for tracking the signal-to-noise ratio expected by a secondary user and tracking the interference expected by a primary user. The model considers the constraint condition of average interference temperature, and can ensure the service quality of a primary user and a secondary user in the underlay type cognitive radio communication network. In addition, in order to compensate the influence of interference, noise, channel fading and link delay on the cognitive radio communication environment, a time delay state space model and a two-state feedback controller under the constraint of weighted interference temperature are provided. Finally, a hybrid H with adaptive step size is used₂/H_∞The power control tracking algorithm solves the model. In the cognitive radio communication environment, the robust tracking performance is presented well under the influence of factors such as near-far effect, fast channel fading, measurement error, multiple access interference, link delay and the like through controlling the power of a secondary user. Compared with the traditional power control method, the hybrid H proposed in the text is under the basic model₂/H_∞And the power control algorithm can obviously improve the tracking control performance under the constraint of the average interference temperature, and reduce the interference of a secondary user to a primary user during high-speed movement. Especially, the method still has good tracking performance on the service quality of the secondary user and has obvious constraint on the interference of the secondary user to the primary user by considering factors such as the distance between the secondary user and the primary user, system measurement errors, quantization errors, link delay and the like.

Drawings

The above features and technical advantages of the present invention will become more apparent and readily appreciated from the following description of the embodiments thereof taken in conjunction with the accompanying drawings.

FIG. 1 is a schematic diagram showing the relationship between primary users and secondary users of a cognitive radio network;

FIG. 2 is a block diagram of a closed-loop control of a state space model that represents an embodiment of the present invention;

FIG. 3 is a block diagram of a closed loop control of a state space model that accounts for interference temperature constraints, link delays, and measurement errors that represents an embodiment of the present invention;

fig. 4 is a graph showing the relationship between SINR standard deviation and the moving speed (10-100) of the corresponding SU according to the embodiment of the present invention;

FIG. 5 is a diagram showing the relationship between the SINR standard deviation and the moving speed (100-300) of the corresponding SU according to the embodiment of the present invention;

FIG. 6 is a graph showing the IT standard deviation of an SU to a PU and the moving speed (10-100) of the corresponding SU according to an embodiment of the present invention;

FIG. 7 is a graph showing the IT standard deviation of an SU to a PU and the moving speed (100-300) of the corresponding SU according to the embodiment of the present invention;

FIG. 8 is a graph showing the relationship between the SINR standard deviation of the secondary user and the measurement error when the moving speed of the corresponding secondary user is 10-100 according to the embodiment of the present invention;

FIG. 9 is a diagram showing the relationship between the SINR standard deviation of the secondary user and the measurement error when the moving speed of the corresponding secondary user is 100-300 according to the embodiment of the present invention;

fig. 10 is a diagram showing the relationship between the effect of round trip delay on the SINR standard deviation of the secondary user according to the embodiment of the present invention;

FIG. 11 is a graph showing the effect of round trip delay on primary user IT standard deviation in accordance with an embodiment of the present invention;

FIG. 12 is a graph showing the relationship between the number of secondary users and the corresponding standard deviation of the secondary users in accordance with an embodiment of the present invention;

FIG. 13 is a graph of outage probability versus corresponding secondary user target signal-to-noise ratio;

fig. 14 is a diagram showing the SINR standard deviation of the secondary user and the distance relationship between the corresponding primary user and the secondary user in the embodiment of the present invention;

fig. 15 is a diagram showing interference temperature standard deviation of secondary users and distance relationship between corresponding primary users and secondary users according to an embodiment of the present invention.

Detailed Description

The embodiments of the present invention will be described below with reference to the accompanying drawings. Those of ordinary skill in the art will recognize that the described embodiments can be modified in various different ways, or combinations thereof, without departing from the spirit and scope of the present invention. Accordingly, the drawings and description are illustrative in nature and not intended to limit the scope of the claims. Furthermore, in the present description, the drawings are not to scale and like reference numerals refer to like parts.

The embodiment provides a power control method of a cognitive radio network, which comprises the following steps:

step 1, constructing a feedback controller with a sub-user signal-to-noise ratioFeedback controller for interference of secondary user to primary userThe error tracking state space model of (1).

The state space model is as follows:

wherein k represents a time slot;

k represents a state feedback gain;

A,B,B₁,B₂,C₀,C₁,D₀₁,D₁₁,D₁₂is a matrix of constant coefficients and is,

D₀₁＝[0 1]^TD₁₁＝[1 0]^TD₁₂＝[0 1]^T；

r represents a numerical space;

is the input state vector of the secondary user i at time slot k;

is the output vector of the secondary user i at time slot k;

is the output vector of the secondary user i at time slot k;

the signal-to-noise ratio tracking error of the secondary user i at the time slot k;

the interference temperature tracking error of the secondary user i to the primary user l at the time slot k;

whereinRepresents the SNR related influence coefficient of the tested secondary user in time slot k,represents the difference between the desired SNR threshold given by secondary user i at time slot k +1 and time slot k, [ g [_ii(k+1)-g_ii(k)]Representing the difference of the channel interference gain of the secondary user i at the time slot k +1 and the time slot k;

[I_i(k+1)-I_i(k)]representing the difference between the first multiple interference of the secondary user i at the time slot k +1 and the time slot k, wherein the first multiple interference comprises multiple access interference, noise and fading;

representing the relative influence coefficient of the interference of the secondary user i measured at the time slot k on the primary user l,it is time slot k that secondary user i gives the desired interference temperature threshold to the primary user of link l,^h _il(k) is the channel interference gain between the secondary user i transmitter and the primary user i receiver at k slots.

The derivation of the state space model is described below:

consider a underlay-type cognitive network in which secondary users co-exist with primary users to utilize licensed spectrum and meet interference power constraints. Assuming that there are M secondary user transmitter-receivers and N primary user transmitter-receivers in the fading channel of the network, as shown in fig. 1, PU _ Rx denotes the primary user receiver, PU _ Tx denotes the primary user transmitter, SU _ Rx denotes the secondary user receiver, and PU _ Tx denotes the secondary user transmitter. ith represents a secondary user i, j th represents a secondary user j, l th represents a primary user l, and s th represents a primary user s. Sigma_iIs the background noise, σ, for the secondary user i_jIs the background noise, σ, for the secondary user j_lIs the background noise, σ, to the primary user l_sIs the background noise to the primary user s.

The signal-to-noise ratio at each active secondary user receiver cannot be less than the minimum signal-to-noise ratio threshold. For convenience, all parameters are described in the log domain in order to ensure reliable communication for the secondary user. Let gamma_i(k) Representing the actual measured signal-to-noise ratio of the secondary user i received in time slot k,is the minimum signal-to-noise ratio of the secondary user i.

Therefore, the method has the advantages that,

wherein, γ_i(k)＝p_i(k)+g_ii(k)-I_i(k) (2)

Wherein g is_ii(k) Is the direct channel interference gain of time slot k from secondary user i to secondary user i. The first multiple interference I last experienced by user I in time slot K_i(k) Is defined as follows

Wherein the parameter n_i(n_i> 0) is the normalized background noise received by secondary user i at time slot k. w is a_i(k)＝∑_{j≠ i}g_ji(k)p_j(k) Representing the total interference of other secondary users to the secondary user i in the time slot k;

p_j(k) representing the transmit power of the transmitter of secondary user j at time slot k. Non-negative parameter g_jiRepresenting the channel interference gain from the secondary user j transmitter to the secondary user i receiver over time slot k. IN_i(k)＝∑_lg_li(k)p_l(k) Is the total interference power of all primary user transmitters to secondary user i in slot k. p is a radical of_l(k) Representing the transmit power of the primary user transmitter on the slot k link l. Non-negative parameter g_li(k) Representing the channel interference gain from the primary user/transmitter to the secondary user i receiver over time slot k.

G above_ii(k),g_li(k) Is the time-varying power transmission gain in the wireless communication channel, collectively referred to as g (k).

The total interference generated by all SUs cannot exceed the maximum interference power threshold of all active secondary users borne by the primary user lFor convenience, the SU is evenly distributed around the PU. Thus, the interference constraint per secondary user SU can be written as

Wherein h is_il(k) Channel interference between a secondary user i transmitter and a primary user l receiver at time slot kAnd (4) interference gain.Representing the average interference temperature threshold for M secondary users.

Considering the limitation of battery capacity, the transmission power of each SU-Tx (secondary user's transmitter) should be lower than the battery power p_maxMaximum threshold of

p_min≤p_i(k)≤p_max (5)

Wherein p is_minIndicating the minimum power when the SINR of the SU is minimum. p is a radical of_maxIs the maximum power.

From the point of view of distributed transmission power control of secondary users, a closed-loop control system in the log domain is shown in fig. 2. As can be seen from fig. 2, each mobile terminal includes a quantization reconstructor, a power multiplier, a power limiter, an SINR measurement circuit, an SINR comparator, a controller, and a quantizer. When the mobile terminal acts as a transmitter, the quantization reconstructor, the power multiplier and the power limiter start to calculate the transmit power. When the mobile terminal acts as a receiver, the SINR measurement circuit, SINR comparator, controller, quantizer begin calculating and updating transmit power instructions.

To improve QoS for SU and PU, the state feedback controller comprises a sub-user SNR feedback controller, as shown in FIG. 2Feedback controller for interference of secondary user to primary userThe state feedback controller tracks in real time a given desired signal-to-noise ratio threshold for the SUAnd giving the PU a desired interference temperature thresholdAnd tracking error e according to SINR of SU_i ^γ(k) And interfering temperature tracking with PUError of the measurementAdjusting power control update commands u_i(k) To the secondary user transmitter. Transmission power p_i(k) SINR tracking error e of SU_i ^γ(k) And SU to PU interference temperature tracking error can be expressed as follows respectively

p_i(k)＝p_i(k-1)+u_i(k) (6)

Wherein, gamma is_il(k)＝p_i(k)+h_il(k) (9)

Γ_il(k) Is the interference of the secondary user i to the primary user l, u_i(k) Representing a power control update command generated by the power controller.

From (1), (6), (7) and (8), the SINR tracking error of the secondary user and the interference temperature tracking error to the primary user can be obtained by the following error dynamic equation

WhereinRepresenting the signal-to-noise ratio related influence coefficient of the tested secondary user,represents the difference between the desired SNR threshold given by secondary user i at time slot k and time slot k-1, [ g_ii(k)-g_ii(k-1)]Representing the difference value of the channel interference gain of the secondary user i in the time slot k and the time slot k-1; [ I ] of_i(k)-I_i(k-1)]Representing the difference between the secondary user i in time slot k-1 and the first multiple interference of time slot k-1, the first multiple interference comprising multiple access interference, noise and fading;

representing the relative impact coefficient of the measured interference on primary user i. Wherein the content of the first and second substances,representing the difference between the desired interference temperature threshold for time slot k and time slot k-1.

The error dynamic equations in the above equation (10) and equation (11) can be converted into a state space model, forming state feedback control. Defining an input state vector x (k) which is related to the SINR tracking error e of the secondary user i at the time slot k of SU_i ^γ(k) Interfering the temperature tracking error with PUAnd the previous power control update command, can be defined as the following equation

At the same time, according to the mixing H₂H_∞Control theory, defining system output vectors as z₂(k)＝(C₀+D₀₁K)x(k)、Then, based on equations (10), (11), the tracking error dynamic equation can be described by the following state space model

Wherein

D₀₁＝[0 1]^TD₁₁＝[1 0]^TD₁₂＝[0 1]^T。

In the state space model 13, a state feedback controller u is introduced in order to maintain the stability of the system under external disturbances_i(k)

u_i(k)＝Kx(k) (29)

Where K is the state feedback gain of the controller.

After substituting the state feedback controller 29 into equation 13, the state space model can be rewritten as

And 2, calculating a state feedback gain K for the state space model by an LMI method.

The following describes the calculation process of the state feedback gain K, and the problem of improving the SU communication quality under the interference constraint can be regarded as a hybrid H₂H_∞The state feedback control problem is to find the state feedback gain K of equation 30. Further, according to H₂H_∞Theoretical, signal-to-noise ratio-related influence coefficient f_i(k) For SINR tracking error e_i ^γ(k) Can be minimized by the state feedback gain K, while the SU interferes with the PU temperature tracking errorInfluence v_il(k) Less than a given upper bound. Therefore, the problem can be described as follows

Wherein:indicating input f from outside_i(k) To the output z₂(k) Closed loop transfer function H₂Norm of (d).Indicating input H from outside_∞To the output z_∞(k) Closed loop transfer function H_∞Norm of (d).

For this purpose, the symmetric matrix X is present if and only if₂，Z＝C₀X₂C₀And X_∞It converts equation (31) to the following inequality:

wherein ξ₁Is the threshold value of the maximum interference temperature which can be borne by the main user l, and the formula (32) is solved by adopting an LMI method. In the LMI method, the same matrix variables are used to represent the tracking error for the convenience and effectiveness of calculating the tracking error. However, this approach may make the closed loop control system of fig. 2 more conservative. To reduce this conservatism, the extended LMI method is implemented by introducing an additional auxiliary variable V₁＝V₂V, and an alignment matrix X_∞Symmetric positive definite matrix X₂The matrix H is transposed to process the above equation (32). Therefore, it can be converted into the following expression

By solving for the above inequalityFormula and feedback channel interference gain to obtain a set of optimal solutions V, H, X_∞，X₂. Feedback channel interference gain K-HV^-1Thus, the extended LMI-based approach solves hybrid H₂H_∞The problem of state feedback.

Further, in order to achieve optimal performance of the power control system, the controllerAnd a controllerAn adaptive adjustment scheme is introduced, and therefore, the formula for updating the adaptive step size is as follows:

wherein the controllerAnd a controllerAre respectively a_i(k) And a_il(k) And epsilon is a forgetting factor,is the sample standard deviation of the sub-user signal-to-noise ratio tracking error,is the sampling standard deviation of the tracking error of the main user interference temperature,

where G is the update window length.

In the step 3, the step of,

step 31, updating the transmitting power p of the secondary user i at the time slot k by the transmitting power of the secondary user i at the time slot k-1 and the power control updating instruction of the secondary user i at the time slot k_i(k) I.e., equation 6 above.

Step 32, passing the transmitting power of the secondary user I in time slot k, the channel interference gain from the transmitter of the secondary user j to the receiver of the secondary user I in time slot k, and the multiple interference I received by the primary user I in time slot k_i(k) Calculating the actual measured signal-to-noise ratio gamma of the sub-user i of the time slot k_i(k) I.e., equation 2 above.

Step 33, calculating the interference gamma generated by the secondary user i of the time slot k to the primary user l through the transmitting power of the secondary user i of the time slot k and the channel interference gain between the transmitter of the secondary user i and the receiver of the primary user l of the time slot k_il(k) Which corresponds to equation 9 above.

Step 4, calculating e of time slot k through error dynamic equations 10 and 11_i ^γ(k) Andaccording to the error e_i ^γ(k) Andfurther, the transmission power of the secondary user is reduced through the selected controller, the adaptive step length is updated, and the power control update instruction u is calculated according to the formula 29_i(k) And then returns to step 3 until the secondary user does not occupy the spectrum.

u_i(k)＝Kx(k) (29)。

Further, a second multiple interference is also considered in the state space model, the second multiple interference includes near-far effect, link delay and measurement error, and considering the influence of near-far effect on the performance of the PU, the most important constraint of the interference can be rewritten as

WhereinConsidering the channel interference gain of the secondary user i transmitter and the primary user l receiver of the second multiple interference in the time slot k;

D_il(k) the actual distance from the transmitter of the secondary user i to the receiver of the primary user l at the time slot k;

μ_ilis the path attenuation exponent;

λ_il(k) is a weighting factor.

The state space model is improved by increasing the near-far effect, the link delay and the measurement error, and it should be specifically explained that the parameter representation of the related formula with the parameter having the superscript is an improvement of the corresponding parameter without the superscript under the condition of considering the near-far effect, the link delay, the measurement error and other factors, and is called as a related parameter considering the second multiple interference.

If the path attenuation indexes are the same in the communication environment, the weighting factor can be simply designed to be lambda_il(k)＝10log₁₀D_il(k)-10log₁₀∑_jD_il(k) In that respect Otherwise, if the maximum transmitting power of the SU still cannot guarantee the basic SINR requirement of the SU itself under a severe channel, the transmitting power of the SU is set to zero, which can avoid unnecessary energy consumption and reduce interference to other users. Transmission power taking into account second multiple interferenceInfluenced by feedback channel noise and link delay d generated by the power controller, including the sum of the uplink delay and the downlink delayAnd (c). Due to SINR measurement errors, interference temperature measurement errors on the PU, quantization errors, multiple access interference, near-far effects, link delay and other factors can influence the performance of the cognitive radio network system. Therefore, as shown in fig. 3, the transmission power is rewritten by the quantization reconstructor and the power multiplier as follows

Wherein the content of the first and second substances,a power control update command representing a link delay d on a time slot k considering the second multiple interference;

the noise of the feedback channel to the secondary user i over time slot k of the second multiple interference is taken into account.

At the same time, the power control update command is also subject to quantization errorBecause a quantizer is used to convert the update command into digital bits. Therefore, the power control update instruction is rewritten as follows:

furthermore, the power control system may also take into account measurement errors, the accuracy of which depends on the estimation algorithm, the computational complexity, the measurement length and the fading rate. Therefore, the measurement error generated by the SINR measurement circuit of the SU receiver is considered in the power control systemThe SINR for each active SU-rx may be rewritten as follows

Measured to track the desired target SINR of the SU and the desired IT of the PU, taking into account the second multiple interferenceAnd IT to the primary user must actually interact with the targetAnd an objectA comparison was made in order to obtain the differences between them, as follows

Wherein

To account for interference measurement errors to the PU caused by SUs of the second multiple interference.

From equation 15 to equation 20, the error dynamics equation can be modified to:

a power control update command representing a link delay d on a time slot k considering the second multiple interference; time delay d ═ d₁+d₂，d₁、d₂Representing the time delays of the uplink and downlink, respectively.

Correspondingly, the factors of near-far effect, link delay and measurement error are also added in the state space model, and under the interference constraint of the SU to the PU in the underlay-type cognitive radio network and the influence of the measurement error and the delay, the actual SINR of the SU and the interference of all the SUs to the PU are expected to reach the target SINR and the ideal interference threshold. That is to say thatAndis near zero. To maintain communication system interference externallyAndstability of the lower, lead-in state feedback controller

Wherein K₂Is the state feedback gain, and the purpose of the secondary user power tracking is in interference and fadingControl under the influence of noise, MAI (multiple Access interference) and non-linearitiesTo facilitate inAndthe allocation is as small as possible.

The state space model considering the second multiple interference is as follows:

wherein the output variable is defined as

Input state vector taking into account second multiple interference

R is the numerical space and d is the time delay;

the snr tracking error of the secondary user i of the second multiple interference is considered,the temperature tracking error of the interference of the secondary user i with the secondary multiple interference to the primary user l is considered,Is to consider the power control update command in the time period from the time slot k to the time delay d of the second multiple interference.

The method for solving the state space model considering the second multiple interference is the same as the method for solving the state space model, and is not described in detail here.

Further, the selecting the controller according to the positive and negative of the error to reduce the transmission power of the secondary user includes:

when e is_i ^γ(k)>0 andthe actual interference gamma of SU to PU_il(k) Exceeds the target IT thresholdThe controller is closed when normal communication of the PU is influencedUsing only the controllerReducing the transmission power p of a secondary user_i(k) Up to

When e is_i ^γ(k)<0 andtime controllerAndat the same timeReducing the transmission power p of a secondary user_i(k) Up to e_i ^γ(k) Equal to a near zero threshold;

when e is_i ^γ(k) Andwhen the voltage is larger than zero or smaller than zero, the controllerAndwhile reducing the transmission power p of the secondary users_i(k) Until the error equals a near zero threshold, which is a pre-set threshold close to zero.

For the state space model considering the second multiple interference, the method of selecting the controller according to the positive and negative of the error is the same as above, but will adoptAndand (4) judging.

Further, after the step 4, the method further comprises the following steps:

and 5, outputting the signal-to-noise ratio standard deviation of all secondary users and the interference standard deviation to the primary user.

Following comparison of the blends H of the present application using computer simulation₂/H_∞The power control algorithm (RPCA) is different from the traditional fixed step size power control method (CPCA) and the adaptive step size CPCA method in ensuring the SU to have minimum interference to the PU and the SU service quality.

In the cognitive radio network, the sampling frequency is set to 900MHz, and the channel bandwidth is set to 1.23 MHz. The data rate was set to 9.6kbps, i.e., the signal processing gain was 21 dB. The channel fading is related to the user moving speed and the system sampling period, and the simulated sampling period is TS 1/9600 s. Thus, the low speed of the user is set to 0-100km @h, the high speed is set to be 100km/h-300 km/h. The standard deviation of the shaded logarithm is set to about 4.3 dB. To ensure the communication quality of the link, the minimum value of SINR is assumed to be-14 dB (gamma)_min-14 dB). In fact, since the communication environment of the system is time-varying, the actual SINR of the SU may be less than the SINR threshold γ_min. When the actual signal-to-noise ratio γ_i(k) Much less than the SINR threshold gamma_minIn time, the communication quality inevitably drops immediately, and communication interruption inevitably occurs. Thus, the outage probability η may represent the performance of the communication system. Can be expressed as

η＝prob{γ_i(k)＜γ_min} (43)

The power control update command performs interval update at a period TP of 1.25ms of 12TS for each power control. The SINR standard deviation and interference standard deviation results may evaluate the performance of the power control algorithm. The differences of the method from the conventional fixed step size power control method (CPCA) and the adaptive step size CPCA method in ensuring the interference of SU to PU is minimum and the quality of service of SU are compared in the following aspects of moving speed, measurement error, delay and number of secondary users.

(1) Influence of moving speed (channel fading and interference)

Fig. 4 is a graph of SINR standard deviation versus moving speed of corresponding SU (number of secondary users is 10, forgetting factor β is 0.97, interference expectation for primary userSignal to noise ratio expected valueThe delay d is 1TS, the period interval TP is 1.25ms, the shaded logarithmic standard deviation ω is 4.3dB, and the moving speed of the PU is 220km/h, where f and a represent step sizes, PCB represents a unit of step size, NS represents a state space model, and NFS, NFMS, and NFMDS all represent state space models that consider the second multiple interference).

Fig. 5 is a graph of SINR standard deviation versus moving speed of corresponding SU (number of secondary users is 10, forgetting factor β is 0.97, interference expectation for primary userSignal to noise ratio expected valued is 1TS, the period interval TP is 1.25ms, the shaded logarithmic standard deviation ω is 4.3dB, and the moving speed of PU is 220 km/h).

Since the fading gain of the entire channel depends on the moving speed, the fading gain of the channel is rapidly increased as the moving speed of the user increases. In the simulation experiment, it is assumed that the PU moves at a high speed at 220km/h, 10 SUs all move in the mobile communication system at a speed of 10km/h-100km/h, and TP is 1.25ms and ω is 4.3 dB. FIG. 4 shows the standard deviation σ of SINR tracking error for SUs at different speeds under different methods^γ. It can be observed from FIG. 5 that in the case of mixing H₂H_∞Standard deviation sigma in adaptive power control algorithm and adaptive step size CPCA algorithm^γAre all lower than the fixed step CPCA algorithm, especially in the environment of the mobile speed of 60km/h to 100 km/h. The method of the present application is superior to improving state space models.

FIG. 6 is the IT standard deviation σ of SU versus PU^ΓGraph of the moving speed of the corresponding SU (number of secondary users is 10, forgetting factor beta is 0.97, interference expectation value for primary userSignal to noise ratio expected valueThe delay d is 1TS, the period interval TP is 1.25ms, the logarithmic standard deviation ω is 4.3dB, and the moving speed of PU is 220 km/h).

FIG. 7 is the IT standard deviation σ of SU versus PU^ΓGraph of the moving speed of the corresponding SU (number of secondary users is 10, forgetting factor beta is 0.97, interference expectation value for primary userSignal to noise ratio expected valueThe delay d is 1TS, the period interval TP is 1.25ms, the logarithmic standard deviation ω is 4.3dB, and the moving speed of PU is 220 km/h).

In fig. 6 and 7, the IT standard deviation of the SU to the PU decreases sharply as the SU moving speed decreases. It is apparent that when the actual SINR is greater than the desired SINR (i.e., the desired SINR), as shown in equations (7) and (8)) If the actual IT value of SU to PU is lower than the target IT value in FIG. 6 (i.e., SU to PU is not updated to the target IT value)) In order to obtain the target SINR required by the SU, the power controller can reduce the transmission power of the SU without affecting the communication quality of the SU, and meanwhile, the PU communication quality is improved.

In addition, as shown in fig. 4 to 7, the present application can minimize the standard deviation of the SINR tracking error of the SU and the standard deviation of the IT tracking error of the SU to the PU in the speed interval of 100km/h to 300km/h in the closed-loop mobile communication system. Thus, the above-mentioned pictures show that the proposed robust mixture H in an improved state-space model₂/H_∞The power control algorithm can compensate for link delay and reduce the effects of channel fading, interference, noise, MAI, and measurement errors. It is noted, however, that the standard deviation of the conventional power control fixed step quantization scheme is lower than that of the adaptive step quantization scheme when the relative speed is higher than 160 km/h. These results demonstrate that conventional power control with an adaptive step-size quantization scheme solves the power control problem in open-loop communication systems. In summary, the method of the present application is superior to the other two algorithms in terms of robustness.

(2) Influence of measurement error

Figure 8 is a graph of SINR standard deviation for secondary users versus measurement error for the corresponding secondary users (number of secondary users 10, d＝1TS,TP＝1.25ms,ω＝4.3dB).

figure 9 is a graph of SINR standard deviation for secondary users versus measurement error for the corresponding secondary users (number of secondary users 10, d＝1TS,TP＝1.25ms,ω＝4.3dB).

taking into account measurement errors, quantization errors, channel noise and interference to primary users in practical communication systems, in particular the proposed robust hybrid H₂/H_∞Adaptive power control algorithms are easier to handle tracking control problems. In addition, assume that the measurement error range is [ -0.5dB, 0.5dB]. As shown in FIG. 8 and FIG. 9, the standard deviation of the signal-to-noise ratio tracking error of the secondary user is smaller than that of the conventional algorithm at higher speed, especially in the range of 100km/h-300km/h, by the hybrid power control algorithm adopting the adaptive model. However, the opposite is true at lower speeds. This is because in these algorithms the standard deviation of the signal-to-noise ratio tracking error of the secondary user is small, and the introduced error has a relatively large effect on it. Simulation results show that the method has robustness on the uncertainty aspect of errors.

(3) Effects of round-trip delay

Fig. 10 shows the effect of round trip delay on the SINR standard deviation of the secondary user (v 80km/h, TP 1.25ms, ω 4.3 dB);

fig. 11 shows the effect of round trip delay on the primary user IT standard deviation (v 80km/h, TP 1.25ms, ω 4.3 dB).

The effect of link delay on tracking performance is shown in fig. 10 and 11. Fig. 10 shows the standard deviation of the snr tracking error of a secondary user versus the link delay for a normalized time slot (Ts) and a user speed of 80 km/h. Meanwhile, under the same conditions, fig. 11 shows the standard deviation and chain of interference temperatures for primary usersThe relationship of the path delay. It can be seen from the figure that, as the time delay increases, the interference temperature of the primary user increases more slowly, and compared with other algorithms, the method has better performance. Since link delay is achieved through a state space model with time lags, it can be represented by H₂/H_∞The state feedback control is designed to compensate. Furthermore, system instability due to uncertainty factors can be overcome. However, conventional control algorithms do not account for or compensate for the effects of link delays in the system. Therefore, the tracking control algorithm proposed herein is superior to other algorithms in terms of robustness.

(4) Influence of the number of sub-users

FIG. 12 shows the relationship between the number of sub-users and the SINR standard deviation of the corresponding sub-users (γ)_min＝-14dB,TP＝1.25ms,ω＝4.3dB)。

In FIG. 12, the moving speeds of the secondary users are 50km/h and 200km/h, respectively. When the number of the secondary users is gradually increased, the interruption probability is hardly changed without considering the influence of the near-far effect, namely the signal-to-noise ratio of the secondary users is hardly influenced by the increase of the number of the secondary users in the traditional model. However, as the number of secondary users increases, the standard deviation of the snr tracking error gradually increases under the influence of the near-far effect, and the outage probability inevitably increases. Thus, H as referred to herein₂/H_∞The closed loop power control method is more adaptive to the actual communication environment.

(5) Influence of target signal-to-noise ratio on outage probability

FIG. 13 is a graph of outage probability versus corresponding secondary user target signal-to-noise ratio (γ)_min＝-14dB,TP 1.25ms, ω 4.3dB, and the secondary user speed 120 km/h).

The relationship between the target signal-to-noise ratio of the secondary user and the outage probability of the secondary user is shown in fig. 13. It is apparent that as the target signal-to-noise ratio of the secondary user increasesThe outage probability for the secondary user decreases. Furthermore, the results show that the proposed hybrid H is either high or low in the value of the secondary user signal-to-noise ratio₂/H_∞The average interruption probability of the algorithm to the secondary users is less than that of other methods. The communication of the secondary user may be interrupted because the actual signal-to-noise ratio is less than the minimum signal-to-noise ratio. Therefore, the outage probability of the secondary user depends not only on the minimum signal-to-noise ratio, but also on the target signal-to-noise ratio.

(6) Influence of near-far effect

SINR standard deviation σ of fig. 14 secondary user^γAnd the distance relationship between the corresponding primary user and secondary user (the primary user speed is 220km/h, and the secondary user speed is 200 km/h);

fig. 15 interference temperature standard deviation σ for sub-users^ΓAnd the distance relationship between the corresponding primary user and the secondary user (the speed of the primary user is 220km/h, and the speed of the secondary user is 200km/h).

In fig. 14-15, the effect of the distance between the primary and secondary users is plotted. As can be seen from FIGS. 14 and 15, in CPCA and hybrid H₂/H_∞Standard deviation sigma under constraint condition of weighted interference temperature in RPCA algorithm^ΓAnd σ^γThe range of variation is very small. But the standard deviation sigma of the above algorithm under the weighted disturbance temperature constraint^ΓAnd σ^γAre all higher than mixed H₂H_∞The RPCA algorithm. In FIG. 15, mixing H₂H_∞σ of RPCA Algorithm (NFS)^ΓIncreases with increasing distance and is smaller than other algorithms. This is because the interference target with the weighted interference temperature constraint model can be changed by the distance between the primary and secondary users. Thus, mixing H₂/H_∞The interference target of the RPCA algorithm (NFS) is dynamic. The larger the distance is, the smaller the channel interference gain between the primary user and the secondary user is, and the interference of the secondary user to the primary user is correspondingly reduced. Meanwhile, the model can reduce the interference target under the constraint of weighted interference temperature. The secondary user may then increase the transmission power and thus the quality of service, and the signal-to-noise ratio of the secondary user may also exceed the target signal-to-noise ratio, while also increasing the standard deviation σ^γ. Thus, the disclosure is directed to a composition havingWeighted disturbance temperature constrained mixing H₂/H_∞The RPCA algorithm (NFS) outperforms the other algorithms.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.