CN103401622B - Joint spectrum sensing method for sensing primary user signal in the presence of cognitive user signal - Google Patents

Abstract

The invention relates to a joint spectrum sensing method for sensing a primary user signal in the presence of a cognitive user signal, and relates to a spectrum sensing method in the technical field of cognitive radio. The method solves the problem of the existing spectrum sensing method that whether the primary user signal exists cannot be effectively detected when the cognitive user signal exists in the sensing frequency band. The method comprises the following steps: 1, detecting the cognitive user signal by a cognitive user signal sensing module SSSB, and outputting channel gain; 2, reproducing the cognitive user signal in the received signal by a cognitive user signal reproducing module SSR; 3, subtracting output result of the cognitive user signal reproducing module SSR from an input signal to obtain an input signal of a primary user signal sensing module PSSB; and 4, performing frequency spectrum sensing by the primary user signal sensing module PSSB to judge whether the primary user signal exists. The method is suitable for sensing joint spectrum sensing of the primary user signal in the presence of the cognitive user signal.

Description

A kind of joint spectrum cognitive method of the perception primary user signal when there is cognitive user signal

Technical field

The present invention relates to the frequency spectrum sensing method in a kind of cognitive radio technology field.

Background technology

Along with the requirement that the multimedia services such as voice, data, image, video are more and more higher to transmission rate, wireless clustered system broadband is the inexorable trend of generation digital group system.In order to effectively improve the availability of frequency spectrum of wireless clustered system, wireless clustered system adopts cognitive radio technology to be the inexorable trend that it develops.

In cognitive radio technology field, frequency spectrum perception technology is an important component part of cognitive radio, and its effect finds the service condition of frequency spectrum also detects whether there is primary user's signal in current region.Frequency spectrum sensing method main at present has the detection of energy measuring, matched filter, cycle specificity detection and covariance detection etc.These frequency spectrum sensing methods have different choices at detecting period, complexity and detection perform.But above-mentioned frequency spectrum sensing method can only be operated in does not have the situation of cognitive user signal to remove perception primary user signal.When having there is cognitive user signal in the frequency range until perception, whether above-mentioned frequency spectrum sensing method will be difficult to the effective existence detecting primary user's signal.

Summary of the invention

The present invention is to solve the problem that effectively cannot to detect primary user's signal when existing frequency spectrum sensing method exists cognitive user signal in perception frequency range and whether exist, thus provides a kind of joint spectrum cognitive method of the perception primary user signal when there is cognitive user signal.

A joint spectrum cognitive method for perception primary user signal when there is cognitive user signal, it is realized by following steps:

Step one, in cognitive radio system, cognitive user signal sensing module SSSB is adopted to carry out cognitive user input to input signal, obtain and whether there is the judged result of cognitive user signal and the channel gain of cognitive user signal, and export cognitive user signal recurrent modules SSR to;

Step 2, employing cognitive user signal recurrent modules SSR are according to the judged result of cognitive user signal obtained and the channel gain of cognitive user signal, and local cognitive user signal, reappear, obtain reproduction signal to the cognitive user signal of reality;

Step 3, the reproduction signal that the input signal in step one and step 2 obtain to be subtracted each other, and input to primary user's signal sensing module PSSB;

Step 4, primary user signal sensing module PSSB is adopted to carry out primary user's frequency spectrum perception to the signal after subtracting each other in step 3, obtaining the judged result that whether there is primary user's signal, completing the joint spectrum perception of the perception primary user signal when there is cognitive user signal.

Adopting cognitive user signal sensing module SSSB to carry out cognitive user input to input signal in step one is adopt matched filter detection algorithm to realize.

Primary user's signal sensing module PSSB is adopted to carry out primary user's frequency spectrum perception by energy detection algorithm or other frequency spectrum perception algorithm realization existing to the signal after subtracting each other in step 3 in step 4.

The present invention proposes a kind of novel joint spectrum cognitive method, when there is cognitive user signal in perception frequency range, whether can detect the existence of primary user's signal accurately and effectively.

Accompanying drawing explanation

Fig. 1 is the signal flow schematic diagram of frequency spectrum sensing method of the present invention.

Embodiment

Embodiment one, composition graphs 1 illustrate this embodiment, and a kind of joint spectrum cognitive method of the perception primary user signal when there is cognitive user signal, is characterized in that: it is realized by following steps:

Step one, in cognitive radio system, cognitive user signal sensing module SSSB is adopted to carry out cognitive user input to input signal, obtain and whether there is the judged result of cognitive user signal and the channel gain of cognitive user signal, and export cognitive user signal recurrent modules SSR to;

Step 2, employing cognitive user signal recurrent modules SSR are according to the judged result of cognitive user signal obtained and the channel gain of cognitive user signal, and local cognitive user signal, reappear, obtain reproduction signal to the cognitive user signal of reality;

Step 3, the reproduction signal that the input signal in step one and step 2 obtain to be subtracted each other, and input to primary user's signal sensing module PSSB;

Step 4, primary user signal sensing module PSSB is adopted to carry out primary user's frequency spectrum perception to the signal after subtracting each other in step 3, obtaining the judged result that whether there is primary user's signal, completing the joint spectrum perception of the perception primary user signal when there is cognitive user signal.

The difference of the joint spectrum cognitive method of a kind of perception primary user signal when there is cognitive user signal described in embodiment two, this embodiment and embodiment one is, adopting cognitive user signal sensing module SSSB to carry out cognitive user input to input signal in step one is adopt matched filter detection algorithm to realize.

The difference of the joint spectrum cognitive method of a kind of perception primary user signal when there is cognitive user signal described in embodiment three, this embodiment and embodiment one is, adopts primary user's signal sensing module PSSB to carry out primary user's frequency spectrum perception to the signal after subtracting each other in step 3 and realized by energy detection algorithm in step 4.

The difference of the joint spectrum cognitive method of a kind of perception primary user signal when there is cognitive user signal described in embodiment four, this embodiment and embodiment one is, adopts primary user's signal sensing module PSSB to carry out primary user's frequency spectrum perception by other frequency spectrum perception algorithm realization existing to the signal after subtracting each other in step 3 in step 4.

Principle: the signal flow of frequency spectrum sensing method of the present invention as shown in Figure 1: in Fig. 1, y [n] is through the sampled signal of the Received signal strength of A/D, s _su[n] is local known cognitive user signal, the channel gain of cognitive user signal, y _sSR[n] is the actual cognitive user signal of local reproduction, H _x1/ H _x0represent in the presence/absence of cognitive user signal, H _1x/ H _0xrepresent in the presence/absence of primary user's signal.

Cognitive user signal sensing module (SSSB) is used for perception and whether there is cognitive user signal, and exports the channel gain of actual cognitive user signal .Cognitive user signal recurrent modules (SSR) is according to the cognitive user signal y of the output of SSSB in this locality reproduction reality _sSR[n] also subtracts each other the input as primary user's signal sensing module (PSSB) with input signal, and PSSB adopts corresponding frequency spectrum sensing method to carry out perception whether to there is primary user's signal.

The present invention adopts quaternary hypothesized model:

$y\left[n\right]=\left\{\begin{array}{cc}w\left[n\right],& H_{00}\\ s_{\mathrm{su}}\left[n\right]+w\left[n\right],& H_{01}\\ s_{\mathrm{pu}}\left[n\right]+w\left[n\right],& H_{10}\\ s_{\mathrm{pu}}\left[n\right]+s_{\mathrm{su}}\left[n\right]+w\left[n\right],& H_{11}\end{array}\right.---\left(1\right)$

H ₀₀represent there is not cognitive user signal or primary user's signal, H ₀₁represent to there is cognitive user signal, H ₁₀represent to there is primary user's signal, H ₁₁represent to there is cognitive user signal and primary user's signal simultaneously.The Output rusults of joint spectrum perception algorithm and the corresponding relation of quaternary hypothesized model are in table 1.

Table 1

If h _pufor the channel gain of primary user's signal, h _sufor the channel gain of cognitive user signal.

Definition y [n] is:

y[n]=h _pus _pu[n]+h _sus _su[n]+w[n]（2）

In formula, w [n] is additive white Gaussian noise, it be contemplated to be 0, variance is σ _n ², s _pu[n] and s _su[n] is primary user's signal and cognitive user signal respectively, and their expectation is 0, and variance is respectively with .

Then can obtain drawing a conclusion for SSSB module:

$y\left[n\right]=\left\{\begin{array}{cc}w\left[n\right],& H_{x0}\\ h_{\mathrm{su}}{s}_{\mathrm{su}}\left[n\right]+w\left[n\right],& H_{x1}\end{array}\right.---\left(3\right)$

${\hat{h}}_{\mathrm{su}}\≈h_{\mathrm{su}}---\left(4\right)$

According to the result of SSSB, the output of SSR is:

$y_{\mathrm{SSR}}\left[n\right]=\left\{\begin{array}{cc}0,& H_{x0}\\ {\hat{h}}_{\mathrm{su}}{s}_{\mathrm{su}}\left[n\right],& H_{x1}\end{array}\right.---\left(5\right)$

The input of PSSB can be obtained:

y[n]-y _SSR[n]≈h _pus _pu[n]+w[n]（6）

So can obtain:

$y\left[n\right]=\left\{\begin{array}{cc}w\left[n\right],& H_{0x}\\ h_{\mathrm{pu}}{s}_{\mathrm{pu}}\left[n\right]+w\left[n\right],& H_{1x}\end{array}\right.---\left(7\right)$

If PSSB adopts energy detection algorithm, SSSB adopts matched filter detection algorithm, analyzes, if Y with this _su, Y _pu, λ _su, λ _pube respectively the detection statistic of SSSB module, detection statistic, the detection threshold of SSSB module, the detection threshold of PSSB module of PSSB module with N and detect length, we can obtain drawing a conclusion:

Y _suobey following normal distribution:

In formula,

${\hat{h}}_{\mathrm{su}}=\frac{Y_{\mathrm{su}}}{\underset{N}{\mathrm{\Σ}}{s}_{\mathrm{su}}\left[n\right]s_{\mathrm{su}}^{*}\left[n\right]}=h_{\mathrm{su}}+\frac{\underset{N}{\mathrm{\Σ}}\left(h_{\mathrm{pu}}{s}_{\mathrm{pu}}\right[n]+w[n\left]\right)s_{\mathrm{su}}^{*}\left[n\right]}{\underset{N}{\mathrm{\Σ}}{s}_{\mathrm{su}}\left[n\right]s_{\mathrm{su}}^{*}\left[n\right]}---\left(10\right)$

${\hat{h}}_{\mathrm{su}}=h_{\mathrm{su}}+o\left(s_{\mathrm{su}}^2\right[n\left]\right)---\left(11\right)$

So the output of SSR module can be obtained:

$y_{\mathrm{SSR}}\left[n\right]=\left\{\begin{array}{cc}0,& H_{x0}\\ h_{\mathrm{su}}{s}_{\mathrm{su}}\left[n\right]+o\left(s_{\mathrm{su}}^2\right[n\left]\right),& H_{x1}\end{array}\right.---\left(12\right)$

Being input as of PSSB module:

$y\left[n\right]-y_{\mathrm{SSR}}\left[n\right]=\left\{\begin{array}{cc}{h}_{\mathrm{pu}}{s}_{\mathrm{pu}}\left[n\right]+w\left[n\right],& H_{x0}\\ h_{\mathrm{pu}}{s}_{\mathrm{pu}}\left[n\right]+w\left[n\right]-o\left(s_{\mathrm{su}}^2\right[n\left]\right),& H_{x1}\end{array}\right.---\left(13\right)$

Y _puobey the distribution of following evolution:

$\frac{Y_{\mathrm{pu}}}{{\mathrm{\σ}}_{\mathrm{signal}}^2}=\left\{\begin{array}{cc}\frac{Y_{\mathrm{pu}}}{{\mathrm{\σ}}_n^2}~{\mathrm{\χ}}_N^2,& H_{0x}\\ \frac{Y_{\mathrm{pu}}}{h_{\mathrm{pu}}^2{\mathrm{\σ}}_{\mathrm{pu}}^2+{\mathrm{\σ}}_n^2}~{\mathrm{\χ}}_N^2,& H_{1x}\end{array}\right.---\left(14\right)$

If Pf ^sfor the false alarm probability of SSSB, Pd ^sfor the detection probability of SSSB, Pf ^pfor the false alarm probability of PSSB, Pd ^pfor the detection probability of PSSB.We can obtain the detection perform of joint spectrum perception algorithm.

$\left\{\begin{array}{c}{\mathrm{Pf}}^P=\mathrm{\Γ}(\frac{N}{2},\frac{{\mathrm{\λ}}_{\mathrm{pu}}}{{2\mathrm{\σ}}_n^2})/\mathrm{\Γ}\left(\frac{N}{2}\right)\\ {\mathrm{Pd}}^P=\mathrm{\Γ}(\frac{N}{2},\frac{{\mathrm{\λ}}_{\mathrm{pu}}}{2(h_{\mathrm{pu}}^2{\mathrm{\σ}}_{\mathrm{pu}}^2+{\mathrm{\σ}}_n^2)})/\mathrm{\Γ}\left(\frac{N}{2}\right)\end{array}\right.---\left(16\right)$

From upper analysis, it doesn't matter for the detection perform of primary user's signal sensing module of joint spectrum perception algorithm and cognitive user signal, only relevant with the intensity of noise and primary user's signal, so when there is cognitive user signal in this algorithm, primary user's signal can be detected effectively and accurately, and the interference of cognitive user signal need not be considered.

Claims (3)

1. the joint spectrum cognitive method of perception primary user signal when there is cognitive user signal, is characterized in that: it is realized by following steps:

Step one, in cognitive radio system, cognitive user signal sensing module SSSB is adopted to carry out cognitive user input to input signal, obtain and whether there is the judged result of cognitive user signal and the channel gain of cognitive user signal, and export cognitive user signal recurrent modules SSR to;

Step 2, employing cognitive user signal recurrent modules SSR are according to the judged result of cognitive user signal obtained and the channel gain of cognitive user signal, and local cognitive user signal, reappear, obtain reproduction signal to the cognitive user signal of reality;

Step 3, subtracted each other by the reproduction signal that the input signal in step one and step 2 obtain, the signal after subtracting each other inputs to primary user's signal sensing module PSSB;

Step 4, primary user signal sensing module PSSB is adopted to carry out primary user's frequency spectrum perception to the signal after subtracting each other in step 3, obtaining the judged result that whether there is primary user's signal, completing the joint spectrum perception of the perception primary user signal when there is cognitive user signal.

2. the joint spectrum cognitive method of a kind of perception primary user signal when there is cognitive user signal according to claim 1, is characterized in that adopting cognitive user signal sensing module SSSB to carry out cognitive user input to input signal in step one is adopt matched filter detection algorithm to realize.

3. the joint spectrum cognitive method of a kind of perception primary user signal when there is cognitive user signal according to claim 1, be is characterized in that adopting in step 4 primary user's signal sensing module PSSB to carry out primary user's frequency spectrum perception to the signal after subtracting each other in step 3 and is realized by energy detection algorithm.