CN109756283B - Spectrum sensing method, device and medium for downlink of GEO satellite communication system - Google Patents
Spectrum sensing method, device and medium for downlink of GEO satellite communication system Download PDFInfo
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Abstract
The invention provides a method and a device for sensing a frequency spectrum of a GEO satellite communication system downlink, which relate to the technical field of satellite communication and comprise the following steps: receiving an object to be detected; judging whether the satellite position angle of the object to be detected is in a peak area or a non-peak area; under the condition that the satellite position angle is in a non-peak area, judging whether a GEO signal exists in the object to be detected, if so, determining that the object to be detected is the GEO signal, and if not, determining that the object to be detected is noise; under the condition that the satellite position angle is in the peak value area, judging whether a GEO signal exists in the object to be detected, if the GEO signal exists, determining that the frequency band of the object to be detected is not accessed, and if the GEO signal does not exist, determining that the object to be detected is noise; the GEO signal is a signal transmitted by a GEO satellite, and the technical problem that the frequency spectrum utilization rate of a satellite communication system is low is solved.
Description
Technical Field
The invention relates to the technical field of satellite communication, in particular to a frequency spectrum sensing method and device for a downlink of a GEO satellite communication system.
Background
The satellite communication system is widely applied to military, public safety and commercial fields by virtue of the advantages of wide coverage range, large communication capacity, flexible networking, high reliability, no geographical environment and distance constraint and the like. Particularly, in recent years, with the rapid increase of the demand for broadband multimedia services, the invaluability of satellite orbital frequency resources and the urgency of preempting first opportunity are recognized everywhere, and the development of satellite communication networks is accelerated in many times.
However, with the rapid development of the ten years, the GEO satellite orbit resource tends to be saturated, and the common rail condition of multiple satellites is common. To meet the increasing global satellite broadband access demand, large-capacity and broadband NGEO (Non-geostationary orbit) satellite constellations are being vigorously developed in various places. The network data number of the NGEO satellite constellation of different frequency bands reported by ITU in recent seven years is counted, and it can be estimated that the number of the NGEO satellite constellations in orbit can reach more than 20, the number of the NGEO satellites in orbit can reach tens of thousands, and the non-stationary orbit satellite and the stationary orbit satellite present the coexistence and sharing trend by 2030.
Therefore, for the prior art, the spectrum resource of the satellite orbit is very scarce, and the spectrum utilization rate of the current satellite communication system is low.
Disclosure of Invention
In view of the above, an object of the present invention is to provide a method and an apparatus for sensing a spectrum of a downlink of a GEO satellite communication system, so as to solve the technical problem of low spectrum utilization rate of the satellite communication system in the prior art.
In a first aspect, an embodiment of the present invention provides a spectrum sensing method for a downlink of a GEO satellite communication system, which is applied to an earth station terminal device for sensing an NGEO system, and includes:
receiving an object to be detected;
judging whether the satellite position angle of the object to be detected is in a peak area or a non-peak area, wherein the satellite position angle represents the position of an interference NGEO satellite relative to a GEO satellite;
under the condition that the satellite position angle is in the non-peak area, judging whether a GEO signal exists in the object to be detected, if so, determining that the object to be detected is the GEO signal, and if not, determining that the object to be detected is noise;
under the condition that the satellite position angle is in the peak value area, judging whether the GEO signal exists in the object to be detected, if so, determining that the frequency band of the object to be detected is not accessed, and if not, determining that the object to be detected is noise;
wherein the GEO signal is a signal transmitted by the GEO satellite.
With reference to the first aspect, an embodiment of the present invention provides a first possible implementation manner of the first aspect, where the method further includes:
and dividing the satellite position angle into a peak area and a non-peak area according to the mobile position of the interference NGEO satellite.
With reference to the first aspect, an embodiment of the present invention provides a second possible implementation manner of the first aspect, where determining whether a GEO signal exists in the object to be detected includes:
and judging whether the GEO signal exists in the object to be detected or not by constructing a Gaussian Mixture Model (GMM) based on the frequency spectrum occupation state of the GEO system.
With reference to the first aspect, an embodiment of the present invention provides a third possible implementation manner of the first aspect, where after determining that the object to be detected is a GEO signal, the method further includes:
identifying a transmit power of the GEO signal;
and adjusting the signal transmission power of the perception NGEO system according to the transmission power.
With reference to the first aspect, an embodiment of the present invention provides a fourth possible implementation manner of the first aspect, where after determining that the object to be detected is noise, the method further includes:
and judging whether to access the frequency range of the object to be detected according to the power value of the noise and the interruption probability of the perception NGEO system.
In a second aspect, an embodiment of the present invention further provides a spectrum sensing apparatus for a downlink of a GEO satellite communication system, which is applied to an earth station terminal device for sensing an NGEO system, and includes:
the receiving module is used for receiving the object to be detected;
the judging module is used for judging that the satellite position angle of the object to be detected is in a peak area or a non-peak area, wherein the satellite position angle represents the position of an interference NGEO satellite relative to a GEO satellite;
the first determining module is used for judging whether a GEO signal exists in the object to be detected under the condition that the satellite position angle is in the non-peak area, if so, determining that the object to be detected is the GEO signal, and if not, determining that the object to be detected is noise;
the second determining module is configured to determine whether the GEO signal exists in the object to be detected under the condition that the satellite position angle is in the peak region, determine, if the GEO signal exists, that the frequency band of the object to be detected is not accessed, and determine, if the GEO signal does not exist, that the object to be detected is noise;
wherein the GEO signal is a signal transmitted by the GEO satellite.
With reference to the second aspect, an embodiment of the present invention provides a first possible implementation manner of the second aspect, where the method further includes:
and the adjusting module is used for identifying the transmitting power of the GEO signal and adjusting the signal transmitting power of the perception NGEO system according to the transmitting power.
With reference to the second aspect, an embodiment of the present invention provides a second possible implementation manner of the second aspect, where the method further includes:
and the judging module is used for judging whether to access the frequency band of the object to be detected according to the power value of the noise and the interruption probability of the perception NGEO system.
In a third aspect, an embodiment of the present invention further provides an electronic device, including a memory and a processor, where the memory stores a computer program operable on the processor, and the processor implements the steps of the method according to the first aspect when executing the computer program.
In a fourth aspect, the present invention also provides a computer-readable medium having non-volatile program code executable by a processor, where the program code causes the processor to execute the method according to the first aspect.
The technical scheme provided by the embodiment of the invention has the following beneficial effects: the embodiment of the invention provides a method and a device for sensing a frequency spectrum of a downlink of a GEO satellite communication system and electronic equipment. Firstly, receiving an object to be detected, then, judging that the satellite position angle of the object to be detected is in a peak area or a non-peak area, wherein the satellite position angle represents the position of an interference NGEO satellite relative to a GEO satellite, the GEO signal is a signal transmitted by the GEO satellite, under the condition that the satellite position angle is in the non-peak area, judging whether the GEO signal exists in the object to be detected, if the GEO signal exists, determining that the object to be detected is the GEO signal, and if the GEO signal does not exist, determining that the object to be detected is noise; under the condition that the satellite position angle is in the peak value area, judging whether the GEO signal exists in the object to be detected, if the GEO signal exists, determining the frequency band which is not accessed to the object to be detected, if the GEO signal does not exist, determining the object to be detected as noise, therefore, under the scene that the NGEO satellite communication system with multiple transmitting powers and the GEO satellite communication system share the frequency spectrum, the method for sensing the downlink frequency spectrum of the GEO satellite communication system based on the multiple transmitting powers is provided for the NGEO satellite communication system, by analyzing the received power characteristics of the object to be detected, combining the spatial position change relation of the interference NGEO satellite and adopting the spectrum sensing strategy aiming at different areas, so as to realize spectrum sharing under the condition of ensuring the normal work of the GEO satellite communication system, improve the utilization rate of the spectrum, therefore, the technical problem that the frequency spectrum utilization rate of a satellite communication system is low in the prior art is solved.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and drawings.
In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 is a flowchart illustrating a spectrum sensing method for a downlink of a GEO satellite communication system according to an embodiment of the present invention;
fig. 2 illustrates a downlink spectrum sensing scenario provided by an embodiment of the present invention;
FIG. 3 shows a graph of received signal power for a downlink-aware NGEO Earth station as a function of satellite position angle β as provided by an embodiment of the present invention;
fig. 4 is a flowchart illustrating a spectrum sensing method for a downlink of a GEO satellite communication system according to a second embodiment of the present invention;
FIG. 5 is a graph showing the detection probability as a function of SNR for different signal lengths in the off-peak region provided by an embodiment of the present invention;
FIG. 6 is a graph showing the probability of false alarm versus SNR for different signal lengths in the off-peak region provided by an embodiment of the present invention;
FIG. 7 shows a graph of probability of identification versus SNR for different signal lengths in the off-peak region provided by an embodiment of the present invention;
FIG. 8 is a graph showing the error probability with SNR for different signal lengths in the off-peak region provided by an embodiment of the present invention;
FIG. 9 is a graph showing the detection probability versus SNR for different signal lengths in the peak region provided by an embodiment of the present invention;
FIG. 10 is a graph showing the variation of false alarm probability with SNR for different signal lengths in the peak region provided by an embodiment of the present invention;
FIG. 11 is a graph showing the comparison of the performance of the algorithm of the present embodiment with that of the conventional algorithm when the downlink signal length provided by the embodiment of the present invention is 9000;
fig. 12 is a schematic structural diagram illustrating a spectrum sensing apparatus for a downlink of a GEO satellite communication system according to a third embodiment of the present invention;
fig. 13 is a schematic structural diagram of an electronic device according to a fourth embodiment of the present invention.
Detailed Description
To make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is apparent that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
At present, in order to solve the problem of scarce satellite orbital spectrum resources, a spectrum sensing technology based on cognitive radio is developed. The technology can be applied to a GEO and NGEO satellite communication system, and the NGEO satellite communication system (secondary user) can share the frequency spectrum under the condition of ensuring the normal work of the GEO satellite communication system (primary user), so that the frequency spectrum utilization rate is improved. But the key to completing spectrum sharing is to ensure that the NGEO system can sense whether the GEO system exists in the shared frequency band. For downlink, the research of the existing literature mainly focuses on interference analysis, spectrum sharing method based on angle isolation and power adaptive technology, and there is little research on spectrum sensing algorithm. Furthermore, with the increasing constellation of NGEO satellites in space, when a certain NGEO system senses GEO signals, it may be interfered by other NGEO systems. Therefore, the perceptual user (NGEO system) is to not only identify the GEO signal from the noise, but also to effectively distinguish the other NGEO signals from the GEO signal. At present, most spectrum sensing algorithms are based on the fact that the transmitting power of a master user is constant, and only whether the master user is in an idle state or a working state is judged, which is a binary hypothesis testing problem. Therefore, for the prior art, the spectrum resource of the satellite orbit is very scarce, and the spectrum utilization rate of the current satellite communication system is low.
Based on this, the spectrum sensing method and the spectrum sensing device for the downlink of the GEO satellite communication system provided by the embodiment of the invention can solve the technical problem that the spectrum utilization rate of the satellite communication system is low in the prior art.
To facilitate understanding of the embodiment, first, a spectrum sensing method and a spectrum sensing device for a downlink of a GEO satellite communication system disclosed in the embodiment of the present invention are described in detail.
The first embodiment is as follows:
the spectrum sensing method for the downlink of the GEO satellite communication system provided by the embodiment of the invention is applied to sensing earth station terminal equipment of an NGEO system, and comprises the following steps as shown in figure 1:
s11: and receiving the object to be detected.
In this embodiment, the object to be detected is a signal to be detected. In the downlink scenario, the station terminals of the perceptual NGEO system (i.e. the perceptual NGEO station) receive the signal to be detected.
As shown in fig. 2, in a downlink spectrum sensing scenario, a GEO satellite sends a signal to a GEO earth station, and an earth station terminal device of the sensing NGEO system detects the GEO signal while the sensing NGEO earth station is likely to receive a signal from an interfering NGEO satellite. During the detection process, the antenna of the NGEO earth station is sensed to be directed to the GEO satellite, so that the GEO system signal can be detected more accurately.
In this embodiment, a spectrum sensing algorithm when a satellite system has multiple transmitting powers is considered, at this time, both the NGEO system and the GEO system have multiple transmitting power levels, and in addition to the presence of the master user GEO system and the sensing NGEO system, an interfering NGEO system also exists in the scene. In this embodiment, a spectrum sensing technology is adopted in an area where the GEO system is interfered by the NGEO system, and in order to protect the GEO system to the maximum extent, the NGEO system is sensed not to transmit a signal in sensing time.
S12: and judging that the satellite position angle of the signal to be detected is in a peak area or a non-peak area, wherein the satellite position angle represents the position of the interference NGEO satellite relative to the GEO satellite.
As shown in fig. 2, θ1Is the off-axis angle, θ, of the GEO satellite in the direction of the sensing NGEO Earth station2Is to sense the off-axis angle, theta, of the NGEO earth station in the direction of the interfering NGEO satellite3Is the off-axis angle of the interfering NGEO satellite in the direction of the perceived NGEO earth station, and satellite position angle β is the geocentric angle between the GEO satellite and the interfering NGEO satellite.
In the downlink, sensing the earth station of the NGEO system as the detection end, there are four possibilities for the received signal: GEO signals, interfering NGEO signals, GEO and interfering NGEO signals are present simultaneously and noise only.
As shown in fig. 3, in a curve of the power of a signal to be detected received by the sensing NGEO earth station changing with β, the power of a GEO signal received by the sensing NGEO system is constant, and the power of a received interfering NGEO signal changes with the satellite position angle β.
As shown in fig. 3, the sum of the simultaneously received GEO and interfering NGEO signal power is constant in some areas, except for the convex shape in some areas. In this step, the range of the satellite position angle is divided according to the convex shape presented by the power change curve to obtain a peak area and a non-peak area.
S13: and under the condition that the satellite position angle is in a non-peak area, judging whether the GEO signal exists in the signal to be detected. If yes, go to step S15; if not, the process proceeds to step S17.
Wherein, the GEO signal is a signal transmitted by a GEO satellite.
S14: and under the condition that the satellite position angle is in the peak value area, judging whether the GEO signal exists in the signal to be detected. If yes, go to step S16; if not, the process proceeds to step S17.
S15: and determining the signal to be detected as a GEO signal.
S16: and determining the frequency band which does not access the signal to be detected.
S17: and determining the signal to be detected as noise.
The spectrum sensing method for the downlink of the GEO satellite communication system provided by the embodiment can be used as a spectrum sensing method for the downlink of the GEO satellite communication system based on multiple transmitting powers, and is used in a scenario of multiple transmitting powers of the satellite communication system.
Therefore, under the scene that the NGEO satellite communication system with multiple transmitting powers and the GEO satellite communication system share the frequency spectrum, the GEO satellite communication system downlink frequency spectrum sensing method based on the multiple transmitting powers is provided for the NGEO satellite communication system.
Example two:
the spectrum sensing method for the downlink of the GEO satellite communication system provided by the embodiment of the invention is applied to sensing earth station terminal equipment of an NGEO system, and comprises the following steps as shown in fig. 4:
s21: and receiving the object to be detected.
In this embodiment, the object to be detected is a signal to be detected. As shown in fig. 2, in the downlink scenario, the earth station terminal equipment of the perceptual NGEO system (i.e., the perceptual NGEO earth station) receives the signal to be detected.
S22: the satellite position angle is divided into peak and off-peak areas based on the mobile position of the interfering NGEO satellite.
First, location information of interfering NGEO satellites is acquired. Location information for NGEO satellites can be obtained through a fence system. And then, calculating a geocentric angle between the interference NGEO satellite and the GEO satellite according to the position information to obtain a satellite position angle. The antenna types of GEO and NGEO system earth stations and satellites comply with ITU-R recommendations, and therefore, calculations can be performed based on the obtained location information of the NGEO satellite to obtain a real-time value of the satellite location angle β, which is the geocentric angle between the interfering NGEO satellite and the GEO satellite.
And then, analyzing the signal to obtain a power change curve, wherein the power change curve is a change curve of the power value of the signal along with different satellite position angles, and the satellite position angles represent the positions of the interference NGEO satellite relative to the GEO satellite.
Specifically, the process of analyzing the signal can be divided into two parts, namely GEO signal analysis and interference signal analysis.
For the process of GEO signal analysis, in order to obtain a GEO signal model, it is assumed in this embodiment that the GEO satellite either does not transmit signals or is from a preset transmit power set { P }gs1,Pgs2,...,PgsNSelecting the transmitting power as PgsiWherein i ═ {1, 2.., N }. Without loss of generality, assume 0 < Pgsi＜Pgs(i+1). In satellite communication systems, it is reasonable to assume that the transmit power of the satellite remains constant for the sensing time and for the subsequent transmission period. Thus, the downlink, perceived GEO satellite signals received by an NGEO earth station are expressed as:
in addition, G isner,maxIs sensing the maximum gain, G, of the receiving antenna of the NGEO earth stationgst(θ1) Is GEO satellite transmitting antenna at theta1Gain in direction, c is the speed of light, f denotes the center frequency, dgs→neRepresenting the range of GEO satellites and the sensing NGEO earth station. In addition to this, the present invention is,
represents the assumption that the GEO system is not present;
representing the presence of a GEO system and having a transmission power PgsiAn assumption of (2); sgskRepresenting the kth symbol transmitted by the GEO satellite, subject to a circularly symmetric complex gaussian distribution (CSCG) with a mean value of 0 and a variance of 1; phi is the channel phase; n iskIs a mean of 0 and a variance of
Additive White Gaussian Noise (AWGN). Thus, xgskAlso subject to the CSCG distribution, can be expressed as:
as can be seen from the above formula, xgskThe variance of (c) is the GEO satellite power received by the sensing system. Since the positions of GEO satellites and NGEO Earth stations are fixed, θ1And dgs→neAre all constants. Thus, the GEO signal power received by the NGEO earth station is perceived to be constant when the GEO satellite transmit power is constant.
For the process of interference signal analysis, as shown in fig. 2, when the interfering NGEO satellite moves into a certain area, the interfering signal may be received by the sensing NGEO earth station. Similarly, the method and apparatus assumes that the interfering NGEO satellite is either not transmitting signals or is transmitting from a predetermined set of transmit powers { P }ns1,Pns2,...,PnsMSelecting the transmitting power as PnsjWhere j is {1, 2.., M }, again, it is assumed that 0 < P ≦ Pnsj＜Pns(j+1). Thus, the perceived interfering NGEO satellite signals received by an NGEO earth station may be expressed as:
in addition, G isnst(θ3) Is interference with NGEO satellite transmitting antenna at theta3Gain in direction, Gner(θ2) Is to sense the receiving antenna of NGEO earth station at theta2Gain in direction, dns→neRepresenting the distance between interfering NGEO satellites and sensing NGEO earth stations. From the above equation, θ can be easily derived2、θ3And dns→neWith β, hngeoAnd dgnA form of expression wherein hngeoIndicating the altitude of interfering NGEO satellites, dgnRepresenting the distance between the GEO satellite and the interfering NGEO earth station. h isngeoAnd dgnCan be known in advance, therefore, hnsWhich can be expressed as a function of β:
in addition to this, the present invention is,
the hypothesis that interference with the NGEO system is not present;
indicating the presence of an interfering NGEO system and a transmit power level of PnsjAn assumption of (2); snskIt is the interfering satellite that transmits the kth symbol, subject to a CSCG distribution with a mean of 0 and a variance of 1. Thus, xnskSubject to CSCG distribution, it can be expressed as:
from the above formula, xnskI.e., the perceived interfering NGEO satellite signal power received by the NGEO system, the received interfering NGEO satellite signal power is a function of β, i.e., varies as the interfering NGEO satellite moves.
In this embodiment, the following assumptions are given at the same time so as to make a perception policy later:
i. since the transmit power set is pre-established and can be obtained from the ITU database or historical information, it can be assumed that the sensing NGEO system knows the GEO system in advance and the transmit power set of the interfering NGEO system.
ii.
Indicating the spectral state of the GEO system as
Wherein i is 0,1,2, a.
Indicating an interfering NGEO system spectral state of
Where j is 0,1, 2. Given that this a priori information is known to the sensing NGEO system, it can be estimated from statistical variations in historical transmissions of GEO systems and interfering NGEO systems.
In the downlink, sensing the earth station of the NGEO system as the detection end, there are four possibilities for the received signal: GEO signals, interfering NGEO signals, GEO and interfering NGEO signals are present simultaneously and noise only.
As shown in fig. 3, in the curve of the power of the signal received by the sensing NGEO earth station as a function of β, the power of the GEO signal received by the sensing NGEO system is constant, and the power of the received interfering NGEO signal as a function of the satellite position angle β, which is consistent with the descriptions of equations (3) and (7).
And then, dividing the range of the satellite position angle according to the power change curve to obtain a peak area and a non-peak area.
Specifically, as shown in fig. 3, the sum of the simultaneously received GEO and interfering NGEO signal power is constant in some areas, except for the convex shape in some areas. This is because, in other areas, the received interfering NGEO signal power is very little compared to the received GEO signal power, and is thus buried in the GEO signal power. Here, the range of the satellite position angle β angle corresponding to the convex portion is referred to as a peak region, and only when the interfering NGEO satellite moves into the peak region, the sum of the received GEO and NGEO signal powers is significantly changed compared with the GEO signal power; when the interfering NGEO satellite is outside the peak region, the sum of the power of the two signals is equal to the GEO signal power. Therefore, in the downlink, based on the mobile position of the interfering NGEO satellite, i.e. the value of the satellite position angle β, there are two cases to analyze: the satellite position angle β is not in the peak region (i.e., non-peak region); the satellite position angle β is in the peak region (i.e., peak region).
S23: and judging that the satellite position angle of the signal to be detected is in a peak area or a non-peak area, wherein the satellite position angle represents the position of the interference NGEO satellite relative to the GEO satellite.
S24: and under the condition that the satellite position angle is in a non-peak area, judging whether the GEO signal exists in the signal to be detected or not by constructing a Gaussian Mixture Model (GMM) based on the spectrum occupation state of the GEO system. If yes, go to step S26; if not, the process proceeds to step S30.
Wherein, the GEO signal is a signal transmitted by a GEO satellite.
The GEO signal determination module may determine whether the GEO signal exists from the received signal, that is, determine whether the spectrum occupation state of the GEO signal exists or does not exist. Wherein, the detection probability P for sensing the existence of GEO signal statedAnd false alarm probability PfThe expression of (a) is:
if the satellite position angle β is not in the peak region (i.e., off-peak region), assuming the sensing NGEO system is in the detection time, L samples are received, x ═ x1,x2,...,xL]. Definition of
The assumption that the GEO signal is present is represented,
the assumption that the GEO signal is not present, i.e., that an interfering NGEO signal is present or that only noise is present, wherein,
indicating that only noise is present. This is a hypothesis testing problem, and two hypotheses are compared by using posterior probability and expanded by using a Bayesian formula, so that the following can be obtained:
the direct solution of the above equation is quite complex, and the numerator and denominator simultaneously construct a Gaussian Mixture Model (GMM). For convenient presentation, order
Thus, equation (8) can be converted into:
order to
It can be seen that f (x) and g (x) are both GMM. Thus, the mean E [ f (x) ] of f (x) can be derived]And variance D [ f (x)]The expression of (a) is as follows:
similarly, the mean E [ g (x) ] and variance D [ g (x) ] of g (x) are expressed as:
E[g(x)]＝0
then, the distribution of f (x) and g (x) can be expressed as:
substituting formula (12) and formula (13) into formula (9) can be simplified:
wherein,
as can be seen, A and B are the variances D [ f (x) of f (x) and g (x), respectively]And D [ g (x)]。
Order to
That is, the received signal energy, we replace v (x) with v (y), and we can obtain:
obviously, the decision criteria are related to the values A, B, T and Z, as will be discussed in more detail below.
When A is more than or equal to B: i. if ZBL≥TALSince y > 0, then there is always: nu (y) is more than or equal to 1. At this time, the GEO signal is present. ii if ZBL＜TALIn this chapter, Maximum A Posteriori (MAP) criterion is used to solve the detection threshold, that is, v (y) is 1. As can be seen from equation (15), when A.gtoreq.B, ν (y) is a strictly increasing function of y. Note that when ZB is usedL＜TALWhere ν (0) < 1, then there is and only one y (y > 0) that satisfies ν (y) ═ 1. By derivation, the threshold value En is detectedthCan be expressed as:
the decision criterion is:
when A < B: i. if ZBL＜TALIt is clear that v (y) < 1 regardless of the value of y (y > 0). At this time, the GEO signal is not present. ii if ZBL≥TALThe MAP criterion is also adopted to solve the detection threshold EnthThe expression is the same as formula (16). When A < B, v (y) is a decreasing function of y, and, when ZBL＞TALWhere ν (0) > 1, then, there is, and only one, y (y > 0) that satisfies ν (y) ═ 1.
The decision criterion is:
in summary, the decision criteria for determining whether a GEO signal is present in the downlink are summarized as follows:
as shown in fig. 3, when the satellite position angle β is not in the peak region (i.e., non-peak region), the received interfering NGEO signal power is negligible compared to the received GEO signal power. Then, from a power perspective, the GEO and NGEO signals received simultaneously may be considered to be only GEO signals present. Therefore, when β is not in the peak region, the types of signals that may be received are classified into three types: GEO signals, interfering NGEO signals, and noise only.
S25: and under the condition that the satellite position angle is in the peak value area, judging whether the signal to be detected has a GEO signal or not by constructing a Gaussian Mixture Model (GMM) based on the spectrum occupation state of the GEO system. If yes, go to step S29; if not, the process proceeds to step S30.
In this step, a specific method for determining whether there is a GEO signal in the signal to be detected by constructing a gaussian mixture model GMM based on the spectrum occupation state of the GEO system is similar to the process of the previous step S24.
Specifically, if the satellite position angle β is in the peak region (i.e., peak region):
definition of
Representing the state in which the GEO signal is present,
indicating a state in which the GEO signal is not present. x ═ x1,x2,...,xL]Indicating the signal received by the sensing NGEO system during the detection time. Two hypotheses are compared using a posterior probability:
the numerator denominator constructs a Gaussian Mixture Model (GMM) and then finds its distribution function. By derivation, equation (23) can be simplified to:
wherein,
finally, the decision criteria for determining the working state of the GEO system can be summarized as follows:
wherein,
when the satellite position angle β is in the peak region (i.e., the peak region), it can be known from the foregoing analysis that there are four possible received signals when the satellite position angle β is in the peak region: GEO signals, interfering NGEO signals, GEO and interfering NGEO signals are present simultaneously and noise only.
The above four possibilities are divided into two categories: the GEO signal is present, or the GEO signal is not present. There are two possibilities for the GEO signal to exist, only the GEO signal exists, or both the GEO signal and the interfering NGEO signal exist. Likewise, there are two possibilities for the absence of a GEO signal: interfering NGEO signals are present, or only noise is present. The following formula:
combining equations (3) and (7), the distribution of the presence of GEO signals can be collectively expressed as:
wherein, i is 1,2, N and j is 0, 1. When j is defined as 0, P ns00. Then, when j is 0,
equation (31) is equivalent to equation (3), and indicates that only the GEO signal is present.
Likewise, the distribution of the absence of the GEO signal can be expressed as:
definition of
The assumption that the GEO signal is present is represented,
representing the prior probability of the presence of a GEO signal. Then it is determined that,
wherein, i is 1,2, N, j is 0, 1. Due to the fact that
And
known in advance and can be calculated
S26: and determining the signal to be detected as a GEO signal.
If the GEO signal is present in the signal to be detected, it is determined that the signal to be detected is the GEO signal, and then proceeds to the next step S27.
S27: the transmit power of the GEO signal is identified.
The transmit power decision module further identifies the specific transmit power of the GEO signal, such that it is perceived that the NGEO system adjusts the transmission strategy accordingly based on the GEO signal power. Specifically, the perception NGEO system can select to transmit signals by adopting a certain power lower than the energy level of the GEO system, and higher system throughput is obtained as far as possible on the premise of ensuring that the GEO system is not interfered.
In the process of identifying the transmitting power of the GEO signal, multiple hypothesis detection problems (multiple hypotheses) are utilized, and each group of hypotheses is compared
Wherein,
indicating that the presence of a GEO signal has been detected. This formula can be shown to be equivalent to:
i.e. finding the largest
The corresponding p-values, namely:
the distribution of the GEO signal is shown in formula (3), and (x) is defined:
obviously, (x) is the energy of the received signal
And (6) determining. For convenience of description, (x) is replaced with (y). If P isgsp＞PgsqThen, (y) is an increasing function of y and vice versa. Let (y) be 1, obtain the detection threshold
It is noted that the premise for identifying a particular transmit power of a GEO signal is that the GEO signal is present. Then, the value of y must satisfy the formula (19), the combined formula (19) and the formula (24), which are obtained by derivation, assuming that
Established decision region
The specific analytical formula of (A) is: if A is greater than or equal to B,
if A < B,
introducing a recognition probability PrecAnd error probability PerrDescribing the performance of identifying the transmitting power of the GEO system by the algorithm, wherein the specific expressions are respectively as follows:
s28: the signal transmit power of the perceptual NGEO system is adjusted based on the transmit power.
The perceptual NGEO system may adjust the transmission strategy (i.e., signaling power) accordingly based on the GEO signal power. Specifically, the perception NGEO system can select to transmit signals by adopting a certain power lower than the energy level of the GEO system, and higher system throughput is obtained as far as possible on the premise of ensuring that the GEO system is not interfered.
S29: and determining the frequency band which does not access the signal to be detected.
Under the condition that the satellite position angle is in a peak value area, if a GEO signal exists, because an interference NGEO signal and the GEO signal both have a plurality of transmitting powers, the existence of the NGEO signal may cause inaccurate judgment on the power of the GEO signal, and the transmitting power of the GEO signal is not further identified for the maximum protection of a GEO system. As long as the GEO signal is present, the sensing NGEO system does not access this frequency band regardless of the transmit power level.
S30: and determining the signal to be detected as noise.
If the GEO signal does not exist in the signal to be detected, whether the interference NGEO signal exists or not does not need to be specifically identified at the moment, and the signal to be detected is uniformly regarded as noise, so that the signal to be detected is determined to be noise, wherein the noise comprises channel noise and an interference signal.
S31: and judging whether to access the frequency band of the signal to be detected according to the power value of the noise and the interruption probability of the perception NGEO system.
This frequency band may be used if the power of the noise does not affect the probability of interruption of the perceived NGEO system. Specifically, the interruption probability judgment module judges whether the noise power affects the interruption probability of the sensing NGEO system, so as to judge whether to access the frequency band of the signal to be detected, namely, whether to use the frequency band is judged according to the power of the noise and interference NGEO signal, namely, the following formula is satisfied: pr [ T ]0≤C0]η (41) or less, wherein T is0Is the transmission rate of the NGEO system, η (0 & lt, η & lt, 1) is the interruption probability, C0This constraint ensures that the minimum transmission rate of the NGEO system is at least C outside of η0. According to shannon's theorem, the transmission rate of the NGEO system can be expressed as:
where I is the noise power, PgrThe received power of the NGEO system is shown, N indicates that the NGEO system noise value is N ═ KTW, K is boltzmann constant, T is the noise temperature of the NGEO system, and W is the bandwidth. By substituting equation (28) for equation (27), the equation that the noise power needs to satisfy can be obtained:
the present embodiment is described with reference to O3b and One Web satellite system as simulation examples for sensing NGEO satellite and interference NGEO satellite systems, respectively. Assume that a GEO satellite has three non-zero powers available: pgs1＝6dBW、Pgs212dBW and Pgs3The corresponding prior probabilities are respectively 20 dBW:
and
wherein
Representing the probability of the GEO satellite not operating. On the other hand, suppose that there are four available powers for interfering with the NGEO satellite: pns1＝5dBW、Pns2＝8dBW、Pns312dBW and Pns415dBW, the prior probabilities are:
and
wherein,
representing the probability of the NGEO system not working. According to GEO and interference NGEO system parameters, calculating peak value area as [ -0.5 DEG, 0.5 DEG]. Wherein the non-peak region is
It can be seen from the figure that the longer the signal length, the better the detection performance of the algorithm, and the lower the required SNR, which is because the larger the amount of the acquired detection signal information, the higher the SNR is-10 dB, and the signal length reaches 9000, the higher the detection probability is than 90%, and the lower the false alarm probability is than 0.5%.
The peak region, i.e., β ∈ [ -0.5 °,0.5 ° ], β is 0 °. As shown in fig. 9 and 10, the detection probability and the false alarm probability are plotted against the signal-to-noise ratio when determining whether a GEO signal is present or not at different signal lengths. Obviously, the longer the signal length, the better the performance of the algorithm, and as the SNR increases, the performance difference of the algorithm decreases gradually for different signal lengths. That is, when the channel condition is good, the signal can be recognized in a short time; when the signal-to-noise ratio is low, a higher detection performance needs to be obtained at the cost of an increased observation time.
As can be seen from the example simulation, for a downlink scenario, the spectrum sensing algorithm provided by the method and the device can effectively detect the GEO signal spectrum occupation condition, and can further identify the specific GEO transmitting power.
It should be noted that, compared with the performance of the conventional sensing algorithm, when the GEO system uses multiple transmission powers, the algorithm in this embodiment is compared with the conventional spectrum sensing algorithm, and a downlink scenario is selected. The conventional algorithm is based on a common hypothesis testing model, i.e. it is assumed that the transmission power of the primary user is constant, and therefore, the average transmission power of the GEO system is taken as the constant power in the example simulation. As shown in FIG. 11, P of the two algorithms is comparedf+PmPerformance, select Signal Length 9000, where PmIndicating probability of false alarm (P)m＝1-Pd). When the SNR is less than or equal to 15dB, the traditional binary algorithm basically fails, and the sum of the false alarm probability and the false alarm probability is less than 10 percent when the SNR is more than or equal to-8 dB.
In this embodiment, under a scenario where the GEO system and the NGEO system have multiple transmit powers, a signal and interference modeling analysis in a downlink scenario of the GEO and NGEO satellite communication systems can design spectrum sensing strategies for different areas on the premise of protecting the communication quality of the GEO system, thereby improving the spectrum utilization rate. And moreover, the solving process is simplified by constructing a Gaussian mixture model, the hypothesis testing problem is converted into energy detection by adopting a maximum posterior criterion, and all analytical expressions of the detection threshold and the judgment area are deduced.
In the spectrum sensing method for the downlink of the GEO satellite communication system provided by the embodiment, sensing of the spectrum of the downlink of the GEO satellite communication system is considered under the scene that the satellite system has multiple transmitting powers, and starting from analysis of GEO signals and interference signals under the downlink scene, the existence of the GEO signals is judged by adopting a hypothesis test problem and decision work of executing the multiple transmitting powers is executed, so that a relatively complete spectrum sensing strategy is provided for spectrum sharing of the NGEO and the GEO satellite communication system on the downlink, and therefore, the spectrum utilization rate is improved.
Thus, with power control techniques, the transmit power is adjusted based on different channel conditions, adjacent satellite angular separation, earth station distribution, user quality of service requirements, and so on. When the satellite system uses a plurality of transmitting power levels, if the NGEO system can recognize the used transmitting power while sensing the occupied state of the GEO system spectrum, the NGEO system can adjust the transmitting power according to the power of the GEO system, and when the GEO system exists, an underlay spectrum access mode is adopted, so that higher system throughput can be obtained.
Example three:
the spectrum sensing device for the downlink of the GEO satellite communication system provided by the embodiment of the invention is applied to sensing earth station terminal equipment of an NGEO system, and as shown in fig. 12, the spectrum sensing device 3 for the downlink of the GEO satellite communication system comprises: a receiving module 31, a judging module 32, a first determining module 33 and a second determining module 34.
The receiving module is used for receiving the signal to be detected. The judging module is used for judging whether the satellite position angle of the signal to be detected is in a peak area or a non-peak area, wherein the satellite position angle represents the position of the interference NGEO satellite relative to the GEO satellite.
The first determining module is used for judging whether a GEO signal exists in the signal to be detected under the condition that the satellite position angle is in a non-peak area, if the GEO signal exists, the signal to be detected is determined to be the GEO signal, and if the GEO signal does not exist, the signal to be detected is determined to be noise.
The second determining module is used for judging whether the GEO signal exists in the signal to be detected under the condition that the satellite position angle is in the peak value area, if the GEO signal exists, determining that the frequency band of the signal to be detected is not accessed, and if the GEO signal does not exist, determining that the signal to be detected is noise. Wherein, the GEO signal is a signal transmitted by a GEO satellite.
The spectrum sensing device for the downlink of the GEO satellite communication system further comprises: an adjusting module 35 and a decision module 36. The adjusting module is used for identifying the transmitting power of the GEO signal and adjusting the signal transmitting power of the perception NGEO system according to the transmitting power. The judgment module is used for judging whether to access the frequency band of the signal to be detected according to the power value of the noise and the interruption probability of the perception NGEO system.
Example four:
as shown in fig. 13, the electronic device 4 includes a memory 41 and a processor 42, where the memory stores a computer program that can run on the processor, and the processor executes the computer program to implement the steps of the method provided in the first embodiment or the second embodiment.
Referring to fig. 13, the electronic device further includes: a bus 43 and a communication interface 44, the processor 42, the communication interface 44 and the memory 41 being connected by the bus 43; the processor 42 is for executing executable modules, such as computer programs, stored in the memory 41.
The Memory 41 may include a high-speed Random Access Memory (RAM) and may also include a non-volatile Memory (non-volatile Memory), such as at least one disk Memory. The communication connection between the network element of the system and at least one other network element is realized through at least one communication interface 44 (which may be wired or wireless), and the internet, a wide area network, a local network, a metropolitan area network, and the like can be used.
The memory 41 is used for storing a program, and the processor 42 executes the program after receiving an execution instruction, and the method executed by the apparatus defined by the flow process disclosed in any of the foregoing embodiments of the present invention may be applied to the processor 42, or implemented by the processor 42.
The processor 42 may be an integrated circuit chip having signal processing capabilities. In implementation, the steps of the above method may be performed by instructions in the form of hardware, integrated logic circuits, or software in the processor 42. The Processor 42 may be a general-purpose Processor, and includes a Central Processing Unit (CPU), a Network Processor (NP), and the like; the device can also be a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field-Programmable Gate Array (FPGA) or other Programmable logic device, a discrete Gate or transistor logic device, or a discrete hardware component. The various methods, steps and logic blocks disclosed in the embodiments of the present invention may be implemented or performed. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like. The steps of the method disclosed in connection with the embodiments of the present invention may be directly implemented by a hardware decoding processor, or implemented by a combination of hardware and software modules in the decoding processor. The software module may be located in ram, flash memory, rom, prom, or eprom, registers, etc. storage media as is well known in the art. The storage medium is located in a memory 41, and a processor 42 reads information in the memory 41 and performs the steps of the method in combination with hardware thereof.
The electronic device provided by the embodiment of the invention has the same technical characteristics as the method and the device for sensing the frequency spectrum of the downlink of the GEO satellite communication system provided by the embodiment, so that the same technical problems can be solved, and the same technical effects can be achieved.
Unless specifically stated otherwise, the relative steps, numerical expressions, and values of the components and steps set forth in these embodiments do not limit the scope of the present invention.
It is clear to those skilled in the art that, for convenience and brevity of description, the specific working processes of the system and the apparatus described above may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures.
The functions, if implemented in the form of software functional units and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention may be embodied in the form of a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: various media capable of storing program codes, such as a usb disk, a removable hard disk, a Read-Only Memory (ROM), a magnetic disk, or an optical disk.
Finally, it should be noted that: the above-mentioned embodiments are only specific embodiments of the present invention, which are used for illustrating the technical solutions of the present invention and not for limiting the same, and the protection scope of the present invention is not limited thereto, although the present invention is described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: any person skilled in the art can modify or easily conceive the technical solutions described in the foregoing embodiments or equivalent substitutes for some technical features within the technical scope of the present disclosure; such modifications, changes or substitutions do not depart from the spirit and scope of the embodiments of the present invention, and they should be construed as being included therein. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (8)
1. A frequency spectrum sensing method of a GEO satellite communication system downlink is applied to sensing earth station terminal equipment of an NGEO system, and is characterized by comprising the following steps:
receiving an object to be detected;
judging whether the satellite position angle of the object to be detected is in a peak area or a non-peak area, wherein the satellite position angle represents the position of an interference NGEO satellite relative to a GEO satellite;
under the condition that the satellite position angle is in the non-peak area, judging whether a GEO signal exists in the object to be detected or not by constructing a Gaussian Mixture Model (GMM) based on the spectrum occupation state of a GEO system, if the GEO signal exists, determining that the object to be detected is the GEO signal, and if the GEO signal does not exist, determining that the object to be detected is noise;
under the condition that the satellite position angle is in the peak value area, judging whether a GEO signal exists in the object to be detected or not by constructing a Gaussian Mixture Model (GMM) based on the spectrum occupation state of a GEO system, if so, determining that the frequency band of the object to be detected is not accessed, and if not, determining that the object to be detected is noise;
wherein the GEO signal is a signal transmitted by the GEO satellite;
further comprising:
and dividing the satellite position angle into a peak area and a non-peak area according to the mobile position of the interference NGEO satellite, the power of the GEO signal and the signal power of the interference NGEO satellite.
2. The method of claim 1, wherein after determining that the object to be detected is a GEO signal, further comprising:
identifying a transmit power of the GEO signal;
and adjusting the signal transmission power of the perception NGEO system according to the transmission power.
3. The method of claim 1, wherein after determining that the object to be detected is noise, further comprising:
and judging whether to access the frequency range of the object to be detected according to the power value of the noise and the interruption probability of the perception NGEO system.
4. A spectrum sensing device of a GEO satellite communication system downlink is applied to sensing earth station terminal equipment of an NGEO system, and is characterized by comprising:
the receiving module is used for receiving the object to be detected;
the judging module is used for judging that the satellite position angle of the object to be detected is in a peak area or a non-peak area, wherein the satellite position angle represents the position of an interference NGEO satellite relative to a GEO satellite;
the first determining module is used for judging whether a GEO signal exists in the object to be detected or not by constructing a Gaussian Mixture Model (GMM) based on the spectrum occupation state of a GEO system under the condition that the satellite position angle is in the non-peak area, if the GEO signal exists, determining that the object to be detected is the GEO signal, and if the GEO signal does not exist, determining that the object to be detected is noise;
a second determining module, configured to determine whether a GEO signal exists in the object to be detected by constructing a gaussian mixture model GMM based on a spectrum occupation state of a GEO system when the satellite position angle is in the peak region, determine that a frequency band of the object to be detected is not accessed if the GEO signal exists, and determine that the object to be detected is noise if the GEO signal does not exist;
wherein the GEO signal is a signal transmitted by the GEO satellite;
the judging module is also used for:
and dividing the satellite position angle into a peak area and a non-peak area according to the mobile position of the interference NGEO satellite, the power of the GEO signal and the signal power of the interference NGEO satellite.
5. The apparatus of claim 4, further comprising:
and the adjusting module is used for identifying the transmitting power of the GEO signal and adjusting the signal transmitting power of the perception NGEO system according to the transmitting power.
6. The apparatus of claim 4, further comprising:
and the judging module is used for judging whether to access the frequency band of the object to be detected according to the power value of the noise and the interruption probability of the perception NGEO system.
7. An electronic device comprising a memory and a processor, wherein the memory stores a computer program operable on the processor, and wherein the processor implements the steps of the method of any of claims 1 to 3 when executing the computer program.
8. A computer-readable medium having non-volatile program code executable by a processor, wherein the program code causes the processor to perform the method of any of claims 1 to 3.
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