WO2008000187A1

WO2008000187A1 - Method, device and system for detectinig interference in ofdm system

Info

Publication number: WO2008000187A1
Application number: PCT/CN2007/070156
Authority: WO
Inventors: Linjun Lv; Jun Rong
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2006-06-22
Filing date: 2007-06-21
Publication date: 2008-01-03
Also published as: CN101060511A; CN101060511B

Abstract

A method for detecting interference in OFDM system is provided. The method includes: Receiving OFDM signal and its orthogonal signal transmitted by the transmitter and interference signal transmitted by other system; Acquiring remainder signal through correlating the OFDM signal and its orthogonal signal; Detecting the power of the remainder signal and attaining the interference signal from other system. Moreover, a device and system that correspond to the above method is provided. The method has following merits: First, because the method does not need channel estimation, the error of the channel estimation has no impact on the effect of the detection. Second, the interference detecting of different distributed sampling points in time-domain or frequency-domain can adapt to different demands of accuracy. Third, the accuracy of the detection can be improved by multi-group data. Fourth, data communication and interference detection can be carried out simultaneous and the communication does not need to be interrupted; Last, the practicability can be improved by combining the other signal process module.

Description

Interference detection method, device and system for orthogonal frequency division multiplexing system The present application claims to be submitted to the Chinese Patent Office on June 22, 2006, the application number is 200610061272.8, and the invention name is "orthogonal frequency division multiplexing system interference detection method" The priority of the Chinese Patent Application, the entire disclosure of which is incorporated herein by reference. The present invention relates to the field of communications, and in particular, to an interference detection method, apparatus, and system for an orthogonal frequency division multiplexing system.

Background of the Invention Some license-exempt systems, such as WRA (Wireless Regional Area Network), WLAN (Wireless Local Area Network), and the like, are currently available. These systems are characterized by the fact that their operating frequency bands do not require authorization. In the operating band, these license-exempt systems need to coexist with the authorization system. For example, the WRAN system needs to coexist with the authorization system DTV (Digital Television). The license-exempt system cannot interfere with the licensed system. When a licensed or authorized system is used to use a certain frequency band, the license-exempt system must exit the frequency band without conditions and jump to other frequency bands to continue working. This mode of operation, also known as the SP (Pradition Pooling) system, LU (License User) has the priority to use the spectrum, RU (Rent User, license-free user or leased user) is not These bands can be used on the premise of affecting the LU. In addition, when implementing the above functions, the LU user does not have the obligation to detect the RU user signal, that is, when the RU user does not exist. RU users assume all obligations not to interfere with LU users.

The WRAN network is an emerging network technology that provides high-bandwidth and large-scale coverage for remote areas and low-density population areas. WRAN system is a license-free operation (license-exempt In the system of operation, the WRAN network uses cognitive radio technology to find the free frequency band of the LU for communication. For example, in a licensed band such as VHF/UHF of DTV, a frequency band that is not occupied is searched for as a bearer band of the WRAN network.

The physical technology of the current WRAN system uses OFDMA (Orthogonal Frequency Division Multiplexing Access) technology based on TDD (Time Division Duplex) for communication. Each frame structure is divided into two sub-frames, one downlink sub-frame, after a guard time (can be inserted into TRG or SSS sliding self-coexisting time slot) followed by an uplink sub-frame. The downlink subframe includes a Preamble, and the CPE (Customer Premises Equipment) can be used for synchronization and signal estimation. Then, the FCH (Frame Control Head) is used to carry information of the current frame, for example, in the current frame. Whether to include US-MAP messages, DS-MAP messages, UCD messages, DCD messages; wherein US-MAP and DS-MAP are used to allocate downlink and uplink channel assignments for each CPE, respectively.

In each frame, a TTG guard slot is inserted between the downlink subframe and the uplink subframe. The main function of the guard slot is that the RF (Radio Frequency) of the BS (Base Station) can be sufficient. The time is changed from sending to receiving. Similarly, there is also an RTG protection slot between the uplink subframe of the current frame and the downlink subframe of the next frame, and the protection slot is mainly for ensuring that the BS can receive signals of all CPEs.

In order to detect the LU user's signal, WRAN uses QP (Quiet Time) to specifically detect it. For example, energy detection performs fast detection, so the scheduling time is very short. After quickly detecting that there is interference in a certain sub-band, a longer QP is scheduled in a subsequent frame to further detect the characteristics of the LU user signal, thereby facilitating determination of the type of the LU user. The insertion of QP requires the entire system to remain silent during QP, thus having the following disadvantages:

1) put forward higher requirements for system scheduling;

2) The QP time is very short. Although the QP remains silent, if there is multipath, the QP cannot be too short. For example, some QPs are scheduled from tens of microseconds to hundreds of microseconds. For large coverage WRAN, the multipath delay may reach this time, or the QP time may be swallowed, resulting in inaccurate interference detection results.

3) Using QP, wasted system communication time and reduced system efficiency.

4) The timeliness of detection is related to the scheduling period of QP. QP scheduling is frequent, so as to ensure the timeliness of LU signal detection; however, QP scheduling is frequent, which causes waste of resources of the system, thereby reducing system usage efficiency.

In many technologies, such as CDMA (Code Division Multiple Access) systems, OFDM (Orthogonal Frequency Division Multiplexing) systems, interference detection techniques use squared coordinate errors on constellation maps. The expected value calculates the power of the interference and noise:

a ² =E[(Y _kl -X _kl ) ² ]

Here, it is the received data, the received signal that has been equalized; and X is the known transmitted signal.

For the OFDM system, it is assumed that the signal transmitted by the transmitter at subcarrier k at time i is Xk, Ηι^ is the channel at subcarrier k at time i; is that the receiver of the system receives the signal at subcarrier k at time i, I _t is the interference signal of other system transmitters on subcarrier k at time i. The relationship is as follows:

7, ^Χ^.χΗ^.+Ι^.+η^.

If the above technique is used, for the known data signal Χ, the power of the interference signal and the noise signal should be correctly calculated. The actual formula used is: σ ² = £[( -Χ^χΗ ) ² ].

Therefore, in the process of implementing the present invention, the inventors have found through research that: interference and noise power The calculation formula needs to obtain the channel H correctly, but if there is interference, the OFDM system will have a large deviation when performing channel estimation, so it directly affects the power calculation of the interference signal. Summary of the invention

Embodiments of the present invention provide an interference detection method, apparatus, and system for an orthogonal frequency division multiplexing system, which can achieve high accuracy detection without performing channel estimation. In an embodiment of the present invention, an interference detection method for an orthogonal frequency division multiplexing system may be provided, including: receiving an OFDM signal sent by a transmitter of the system, an orthogonal signal thereof, and an interference signal sent by another system transmitter; Performing an inner product on the OFDM signal and its orthogonal signal to obtain a residual signal; performing energy detection on the residual signal to obtain a metric of other system interference signals. In another embodiment of the present invention, an interference detection system for an Orthogonal Frequency Division Multiplexing system may be provided, including: a transmitter of the system, configured to transmit an OFDM signal and an orthogonal signal thereof; a system transmitter, configured to send an interference signal; a receiver of the system, configured to receive an OFDM signal sent by the transmitter of the system, an orthogonal signal, and an interference signal sent by another system transmitter; and the received OFDM signal The quadrature signal is subjected to an inner product operation to obtain a residual signal, and the remaining signal is subjected to energy detection to obtain a measure of interference signals of other systems. In another embodiment of the present invention, an interference detecting apparatus for an orthogonal frequency division multiplexing system may be provided, including: An OFDM demodulation module, configured to perform FFT transform and OFDM demodulation on the received OFDM signal sent by the transmitter of the system and the orthogonal signal thereof, and the interference signal sent by another system transmitter;

The interference detection module is configured to perform an inner product operation on the signal provided by the OFDM demodulation module to obtain a residual signal, perform energy detection on the remaining signal, and obtain a metric of other system interference signals.

In the embodiment of the present invention, by using the uncorrelation of the signals transmitted by the system and other systems, the detection of interference signals of other systems can be realized without interrupting the communication of the system. Since the channel estimation is not required in the process of implementing interference detection in the embodiment of the present invention, the error of the channel estimation does not affect the detection effect.

DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the prior art, the drawings used in the embodiments or the description of the prior art will be briefly described below. Obviously, the drawings in the following description For some embodiments of the present invention, other drawings may be obtained from those skilled in the art without departing from the drawings.

1 is a schematic diagram of an interference detection system of an OFDM system according to an embodiment of the present invention;

2a-c are schematic diagrams showing simulations of transmitting two pilot signals on one subcarrier according to an embodiment of the present invention; and FIGS. 3a-c are schematic diagrams showing simulations of transmitting five pilot signals on one subcarrier according to an embodiment of the present invention; Is a schematic diagram of an interference detecting apparatus jointly decoded by the embodiment of the present invention;

5 is a graph showing the probability of detection on an OFDM simulation platform at a drying ratio of 30 dB according to an embodiment of the present invention;

6 is a graph showing the probability of detection on an OFDM simulation platform at a drying ratio of 25 dB according to an embodiment of the present invention;

7-12 are respectively measured on an OFDM simulation platform at different drying ratios according to an embodiment of the present invention. Detect probability maps.

detailed description

BRIEF DESCRIPTION OF THE DRAWINGS The technical solutions in the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without creative work are within the scope of the present invention.

The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

In the embodiment of the present invention, it is assumed that the RU system is a system using OFDM technology, and is called this system. The LU system is called another system. As long as the uncorrelation of the signals of the LU system and the RU system is satisfied, the technology used by the LU system is not limited. For example, the LU system may be a single carrier or a multi-carrier, and may be a digital signal or an analog signal. As shown in FIG. 1, it is a schematic diagram of an interference detection system of an OFDM system according to an embodiment of the present invention. These include: the system transmitter 101, other system transmitters 102, and the system receiver 103. Since OFDM is currently a popular technology, implementation and principles can be found in many monographs (for example, "Principles and Applications of OFDM Mobile Communication Technology", Yan Xueyu, Luo Tao, People's Posts and Telecommunications Press). Therefore, the OFDM technique will not be described in detail herein.

It is assumed that the signal transmitted by the transmitter 101 of the system at subcarrier k at time i is X _k ; : 3⁄4, _{1 is} the channel of subcarrier k at time 1; the receiver 103 of the present system receives the signal at subcarrier k at time i, I is the interference signal of the other system transmitter 102 on subcarrier k at time i.

When there is an interference signal I _t , the relationship between these signals is as follows:

7, ^Χ^. χΗ^.+Ι^.+η^. ( 1 )

When there is no interference signal I _t , the relationship between these signals is as follows:

Y _k =X _kj xH _k +n _k ( 2 ) In the embodiment of the present invention, it is assumed that the channel is static or quasi-static. That is to say, for a period of time, Hk is constant. In addition, it is also assumed that the channel is not frequency selective or that the coherence bandwidth of the channel is large, that is, Hk is constant within the coherent bandwidth for a period of time.

The signal selected by the detection algorithm is a signal for orthogonal operation in the coherent time and the coherent bandwidth. So the channel here can be simplified as H.

According to the above description, the interference signal detecting method of the embodiment of the present invention is given below. The method includes the following steps:

A. The transmitter sends the OFDM signal to the receiver;

Here the transmitter passes the data through binary phase shift keying, rotary binary phase shift keying, repeated binary phase shift keying, quadrature phase shift keying, rotary quadrature phase shift keying and/or repeated quadrature phase shift keying. The modulation obtains the modulation symbol Xk on the subcarrier k at the time i, passes the IFFT (Inverse Fast Fourier Transform) and adds the CP to obtain the transmitted OFDM signal.

B. The receiver receives the signal, performs OFDM demodulation on the received signal, and performs FFT (fast Fourier transform);

If the receiver wants to obtain the data transmitted by the transmitter, it needs to perform channel estimation as in the existing OFDM receiver, and further demodulate the data transmitted by the transmitter.

If the receiver uses the received signal for interference detection, then only FFT conversion is required to obtain Y _kJ without channel estimation and signal equalization.

C. It is assumed that the receiver knows or partially knows the OFDM modulation symbols transmitted by the transmitter.

According to the above assumption, when there is interference, the signal demodulated in step B is expressed as follows:

7, ^Χ^. χΗ+Ι^+η^. ( 3 )

When there is no interference, the signal demodulated in step 表示 is expressed as follows: 7, ^X^xH+n^ (4)

In order to perform interference detection, two received signals will be used for detection. For example, you can select two consecutive time signals on the same subcarrier: and ₊₁ ; you can also select the signals of two adjacent subcarriers at the same time: and 1 ₊₁ ; you can also select two different times and different children. Signal on the carrier: H _+u+1 . As long as the selected signal is within the coherence time and the coherence bandwidth. Without loss of generality, hereinafter, signals at different times on the same subcarrier will be used to illustrate the algorithm of an embodiment of the present invention.

Assume that the signal ( Q _t ,, Q,, ₊₁ ) is a signal orthogonal to the signal ( X _t ,, X _t , ₊₁ ), that is, satisfy: for any ( X,, , X _l+l ) signal vector , there is always its orthogonal signal ( Q _kl , Q,, ₊₁ ), for example, take

When there is interference and noise, the received signal is orthogonally calculated:

When there is no interference, only the noise, the orthogonal operation of the received signal: Comparing the formulas (5) and (6), it can be seen that after the orthogonal operation, (5) there are interference and bottom noise related items, (6) There is only a bottom noise related item. Through the non-correlated hypothesis of signal X, interference and noise, (5) and (6) can be distinguished by energy detection, and the correct probability is detected and the energy ratio of the interference signal ^ and the noise signal n is correlated, that is, and INR (interference) The ratio of noise to noise, ie dry noise ratio) is related.

When the INR is large, the energy of (5) will be significantly greater than (6). Based on this assumption, it can pass The energy of Y _kJ xQ,, +Y,, ₊₁ Q,, ₊₁ is detected to determine whether interference occurs.

In order to implement the above energy detection algorithm, an embodiment of the present invention provides a method of determining a threshold. First, for a given signal ( Χ^·, Χ„. ₊₁ ), that is, (Q _k Q,, ₊₁ ) given the assumption that the interference signal and the noise signal are complex Gaussian signals, then the complex The linear combination of Gaussian signals is a complex Gaussian signal whose modulus square satisfies the distribution and has a degree of freedom of 2. Therefore, for (Q _t ,, Q _t , ₊₁ ) given cases, that is, ( X , X _t , _{+ 1} ) Given a situation, a threshold T (X,,, x,, ₊₁ ) can be given to detect interference. Therefore, for fixed (Q _t , Q, ₊₁ ), The formula detects whether interference exists: When | xQw+ ₊₁ xQ ₊₁ | ² 〉T (X,,, X,, ₊₁ ) (7 ) is established, it can be determined that there is interference, otherwise there is no interference.

In order to increase the accuracy of the detection, the detection algorithm of the embodiment of the present invention may use multiple sets of data. Because the different sets of signals (Q _kJ , Q _{k +l} ) may be different.

If you use different sets of signals at different times, use the following formula to determine if there is interference: 〉1 (8.a) When it is established, it can be judged that there is interference.

N _\

Otherwise there is no interference.

When different sets of signals at different times are used, these different time signals are not necessarily within the coherence time. But as long as the two signals of the same group are within the coherence time. All signals need to be within the time and timeliness of the detection signal.

If different sets of signals of different subcarriers can be used, the detection algorithm is as follows: When 〉1 ( 8.b ) is established, it can be judged that there is interference, NO N _ \

There is no interference.

When different sets of signals of different subcarriers are used, these signals are not necessarily satisfied within the coherent bandwidth, as long as the two signals of the same group are within the coherent bandwidth.

The number of interference detection signal groups used can be as long as the interference detection sensitivity is satisfied. For example, five sets of signals can be used to detect.

Based on the above description, the embodiments of the present invention have the following beneficial effects:

1. Embodiments of the present invention do not require channel estimation.

2. Embodiments of the present invention can adapt to different precisions by performing interference detection in different distributions in the time domain and the frequency domain. For example, only one signal in the subcarrier wave is taken, so that the interference signal can be detected by using the subcarrier as the granularity; the signal in the same time can also be taken, so that the instantaneous interference generated in one OFDM symbol can be detected.

3. The embodiment of the present invention takes multiple sets of signals, which can increase the correctness of the detection. This can be clearly seen from the simulations that follow.

4. The embodiment of the present invention does not need to interrupt the current communication. Data communication and interference detection can be performed simultaneously.

In an OFDM system, the transmitted signals are roughly classified into two types: one is a data signal, and the other is a pilot signal.

The purpose of the pilot signal is for channel estimation and is located at a previously known location (time, subcarrier). Therefore, the pilot can be used for interference detection, as follows:

In general, pilots are symbols that use BPSK fixed modulation 1. However, it may also be for other The purpose is to design the pilot to a 1,7-phase BPSK modulation symbol.

For the symbol of BPSK fixed modulation 1, that is, Χι^ at the pilot position is 1, that is, the transmitted symbol can be regarded as (11), and the orthogonal signal vector is (1 -1). The orthogonal operation of the received signal Y _kt on two adjacent pilots is Y _kt -Y _l+l .

For the BPSK modulation symbols between 1, 1 and 1, that is, between 1 and -1 between X _k and S at the pilot position. At this time, the transmitted signal can be regarded as (1 - 1), and its orthogonal signal vector is (11), and the orthogonal operation of the received signals on two adjacent pilots is ^ + . ₊₁ . The detecting step of the embodiment of the present invention includes:

A. The transmitter constructs a pilot signal;

B. The transmitter sends the constructed pilot signal to the receiver;

C. The receiver performs interference detection by using the received pilot signal.

Since the transmitted signal vector is fixed (1 -1), that is, a symmetrical signal. Therefore, for all the different groups of | + ₊₁ | ² , the same distribution is satisfied, and the detection thresholds are also the same. Assuming the threshold is threshokL, the decision threshold can be determined by the following formula: > threshold I HO) = Palarm

Among them, Palarm is the false alarm probability, HO is the condition without interference, and Threshold is the judgment threshold to be sought.

The H0 indicates that: the power of the pilot signal and the power is only the noise component, and there is no interference component. The formula is expressed as follows:

HO: |Y _kjl + Y _kjl+ i| ² = |P _kjl *H _k + n _kjl + P _k , ₁₊₁ * H _k + _3⁄4 ₁₊₁ | ² = | _3⁄41 - _3⁄41+1 | ² The decision threshold can also be determined by:

P(^i > threshold I HI) = Pdetection where Pdetection is the detection probability, HI is the condition with interference, and Threshold is the threshold to be sought.

The HI indicates that: the pilot signal and the power have both a noise component and an interference component, and the formula is expressed as follows:

_{_{HI: | Y kjl + Y kjl}} + i | 2 = | P kjl * H k + I kjl + ¾1 + P kjl +1 * H k + I k, 1 + 1 + ¾1 + 1 | 2

If there are N>2 pilot signals on one subcarrier of a frame, the threshold is not changed but interference detection is used instead of |++ ₁ . The test formula is as follows:

N.

> threshold

Then there is interference on subcarrier k; otherwise there is no interference on subcarrier k.

Similarly, for the pilot to use BPSK fixed modulation 1 symbol, the following formula is used to determine whether there is interference: > threshold , where threshold is the threshold,

N - l When the above formula is established, there is interference on the subcarrier k; otherwise, there is no interference on the subcarrier k. According to the embodiment of the present invention, the channel sum is not required to be estimated when calculating the signal sum. By constructing a symmetric pilot signal on the same subcarrier, the symmetric pilot signal is then transmitted on the pilot subcarriers. In the transmission process, if there is interference, it is assumed that the interference is not a symmetric signal at the pilot position, and the power of the received pilot signal sum increases. Embodiments of the present invention determine whether interference exists based on the magnitude of power received by the signal. In order to verify the result of the embodiment of the present invention, the interference detection method of the embodiment of the present invention is simulated. It can be seen from the simulation result that the embodiment of the present invention can effectively perform interference detection, and the detection success rate is high.

According to the embodiment of the present invention, the interference detection algorithm of the embodiment of the present invention is simulated by using different INRs. FIG. 2 shows a simulation diagram of transmitting two pilot signals on one subcarrier, as shown in FIG. The axis represents the subcarrier subscript and the ordinate axis represents the detection probability. When INR=0db, the probability of detection is about 0.08; when INR=10db, the probability of detection is about 0.68; when INR=20db, the probability of detection is about 0.95. Figure 3 shows a simulation of the transmission of five pilot signals on one subcarrier, as shown in Figure 3, where the abscissa axis represents the subcarrier subscript and the ordinate axis represents the detection probability. When INR=0db, the probability of detection is about 0.04; when INR=10db, the probability of detection is about 0.88; when INR=20db, the probability of detection is about 1. From the simulation results, it can be found that as long as the dry-to-noise ratio is high, in addition, according to the method of the embodiment of the present invention, decoding and interference detection can also be combined. As shown in FIG. 4, it is a schematic diagram of an interference detecting apparatus jointly decoded by an embodiment of the present invention. For the sake of convenience, only the relevant module for receiver interference detection is shown here. For other descriptions, reference may be made to the aforementioned portion for detecting interference using pilots. The specific implementation is as follows:

In one aspect, the receiver receives the signal for FFT conversion and performs the OFDM demodulation module 411.

OFDM demodulation (that is, correcting the demodulated data using the value after channel estimation), note that the channel estimation is not performed here, and the signal of the corresponding position (time, subcarrier) is buffered according to the detection requirement. Then, the interference detection module 412 is provided to perform interference detection.

On the other hand, the receiver performs FFT conversion on the received signal and performs OFDM demodulation through the OFDM demodulation module 411. The subsequent decoding module 421 is then decoded (including deinterleaving, descrambling, etc.). If the decoding is correct, the decoded data is encoded into the subsequent encoding module 422 (including interleaving, scrambling, etc.), and then modulated by the modulation module 423 to obtain the modulated signal X _t transmitted by the transmitter. Then, in combination with the aforementioned interference detection algorithm, the interference signal can be detected. If the decoding is not correct, then the FER (Frame Error Rate) is calculated. If the FER exceeds a certain threshold, the current FER is reported. The system calculates that the FER exceeds a certain threshold and considers that there may be interference currently. At this time, the QP is scheduled to perform interference detection for the CPE.

After the above combination, on the one hand, the frequency of interference detection is reduced, the resources of the system are saved, and the working efficiency of the system is improved; on the other hand, the requirement of detection probability can be met. Therefore, the detection algorithm has strong practicability, and the subsequent simulation tests have also confirmed and supported this.

Of course, the decoding may also be omitted. The receiver 103 of the present system as shown in FIG. 1 includes:

The OFDM demodulation module 1031 performs FFT conversion and OFDM demodulation on the received OFDM signal sent by the transmitter of the system and its orthogonal signal, and the interference signal sent by other system transmitters;

The interference detecting module 1032 performs interference detection on the signal provided by the OFDM demodulation module 1031.

As shown in FIG. 5, it is the detection probability measured on the OFDM simulation platform when the INR is 30 dB. Among them, the above figure shows the effect of single point calculation using equation (7), and the figure below shows the effect detection diagram of 8 points average calculation using (8.a). The abscissa is the subcarrier number and the ordinate is the detection probability. The figure above shows the effect of a single point calculation using equation (7). The figure below shows the average of 8 points using (8.a). Calculated effect detection map. The abscissa is the subcarrier number and the ordinate is the detection probability.

They are respectively the detection probability maps measured on the OFDM simulation platform at different drying ratios according to the embodiment of the present invention. In the figures shown in Figure 7-12, except for the INR, other simulation conditions are the same as those described above, and are not described here.

In addition, it should be understood that those skilled in the art can understand that all or part of the steps of implementing the above embodiments may be completed by hardware related to program instructions, and the program may be stored in a computer readable storage medium. The storage medium is, for example, a ROM/RAM, a magnetic disk, an optical disk, or the like.

While the above description is only an embodiment, it is not intended that the scope of the invention be limited to the embodiments described. All other embodiments obtained by modifications, equivalents, and substitutions by those skilled in the art based on the embodiments of the present invention are within the scope of the present invention.

Claims

Rights request

1. An interference detection method for an orthogonal frequency division multiplexing system, comprising:

Receiving an OFDM signal sent by the transmitter of the system and its orthogonal signal, and an interference signal sent by another system transmitter;

Performing an inner product operation on the OFDM signal and its orthogonal signal to obtain a residual signal;

Energy detection is performed on the remaining signals to obtain metrics of other system interference signals.

2. The method according to claim 1, further comprising:

For the received OFDM signals (X _ti , X^. ₊₁ ) at different times i on the same subcarrier k and their orthogonal signals (Q, Q, ₊₁ ), an interference threshold T (X,, , Χ,, ₊₁ ), the T (X,,, U is a function, that is, the threshold of the orthogonal interference detection when the transmission signal is ( x _ti , x ₊₁ );

Check if interference exists according to the following formula:

^{> Ύ (x} w ^χ ₊ ι>' where ₊₁ respectively represent the received signals at different times i on the same subcarrier k,

When the above formula is established, there is interference, otherwise there is no interference.

3. The method according to claim 1, further comprising:

Setting an interference threshold T (X,,, Χ, ₊₁ for the OFDM signal (X _ti , X _k+ ) and its orthogonal signal ( Q , Q _k+ ) on the different subcarriers k of the received same time instant i ,), the T (X,,, X, ₊₁ ,) is a function, the threshold of the orthogonal interference detection when the transmitted signal is (X^., X _t+1 , ); and is determined according to the following formula Whether interference exists:

|χ(^+ ₊ χ(^ ₊ | ² 〉τ (X _t ,, X _t+1 ,), where ₊ respectively represent the received signals on different subcarriers k at the same time i,

4. Method according to claim 2 or 3, characterized in that the OFDM signal (X _ti . , X _k+ ) and its quadrature signals ( Q _t ,, Q, ₊₁ , ) are in coherence time and coherent Within the bandwidth.

5. The method according to claim 2, characterized in that: if different sets of signals at different times are used, the following formula is used to determine whether there is interference:

6. The method according to claim 5, wherein: the two signals of the same group are located within a time and time range of the detection signal, and all the signals satisfy the time and time range of the detection signal.

7. The method according to claim 3, characterized in that: if different signals of different subcarriers are used, the following formula is used to determine whether there is interference: k = i τ ( ^x t, !, U > ₁

N _ \

8. The method according to claim 7, wherein: the two signals of the same group are located within a coherent bandwidth, and the number of interference detection signal groups used satisfies the accuracy of the interference detection frequency band.

9. The method according to claim 1, wherein: the OFDM signal is a known pilot signal, and the pilot signal uses a fixed 1, 1 BPSK modulation symbol or a BPSK between 1 and -1 phases. Modulation symbol.

10. The method according to claim 9, further comprising:

If the pilot signal uses a fixed 1, 1 BPSK modulation symbol, set the corresponding interference threshold. Threshold; and determine if interference exists according to the following formula: > threshold,

N - l When the above formula holds, there is interference on subcarrier k; otherwise there is no interference on subcarrier k.

11. The method according to claim 9, further comprising: if the pilot signal uses a BPSK modulation symbol between 1 and _1, setting a corresponding interference threshold threshold; and determining whether interference exists according to the following formula :

> threshold,

When the above formula is established, there is interference on the subcarrier k; otherwise there is no interference on the subcarrier k.

12. The method according to claim 1, wherein: if the received OFDM signal is unknown, further comprising:

The received OFDM signal is subjected to orthogonal frequency division multiplexing demodulation.

The method according to claim 12, further comprising: performing FFT transform on the received OFDM signal and performing OFDM demodulation; and performing decoding, including deinterleaving and descrambling code processing.

14. The method according to claim 13, wherein: if the decoding is correct, the method further comprises: The decoded data is encoded, including interleaving, scrambling, and modulation, to obtain a modulated signal transmitted by the transmitter.

15. The method according to claim 13, wherein: if the decoding is incorrect, the method further comprises:

Calculate the frame error rate FER. If the FER exceeds a certain threshold, then the current FER is reported; and if the calculated FER exceeds a certain threshold, it is determined that there is interference currently, and the quiet time QP is scheduled to perform interference detection on the user equipment CPE.

16. The method according to claim 1, wherein: the OFDM signal is data through binary phase shift keying, rotational binary phase shift keying, repeated binary phase shift keying, quadrature phase shift keying, Rotate quadrature phase shift keying and/or repeat quadrature phase shift keying modulation, and then IFFT transform and add CP.

An interference detection system for an Orthogonal Frequency Division Multiplexing system, comprising: the transmitter of the system, configured to transmit an OFDM signal and an orthogonal signal thereof; and other system transmitters, Sending an interference signal;

The receiver of the system is configured to receive an OFDM signal sent by the transmitter of the system, an orthogonal signal thereof, and an interference signal sent by another system transmitter; and perform an inner product operation on the received OFDM signal and the orthogonal signal thereof The residual signal is subjected to energy detection of the remaining signals to obtain a measure of interference signals of other systems.

18. The system according to claim 17, wherein: the OFDM signal transmitted by the transmitter of the system and the interference signal transmitted by other systems are uncorrelated signals.

19. The system according to claim 17, wherein: the system is a renting user RU system, and the other system is a licensed user LU system.

20. The system according to claim 17, wherein: the system receiver performs OFDM signals (X _ti . , X^. ₊₁ ) at different times i on the same subcarrier k received and orthogonal _thereto . The signal (Q _kl , Q,, ₊₁ ) sets the interference threshold T (X _t , X^. ₊₁ ), and the T (X _l , Χ ₊₁ ) is a function, that is, when the signal is sent ( ^. , x _l+1 ), the threshold of the orthogonal interference detection, and determine whether the interference exists according to the formula |3⁄4xQw+ Q ₊₁ | ² 〉T (X,,, X _t , ₊₁ ), where ₊₁ represents The received signals at different times i on the same subcarrier k, when the above formula is established, there is interference, otherwise there is no interference.

21. System according to claim 17, characterized in that the system receiver is OFDM signal (X _ti , X _k+ ) and its quadrature signal on the different subcarriers k of the received same time instant i (Q) _k+ ) , setting an interference threshold τ (x _k , x _k+ ), the τ (x _k , x _t+1 is a function, that is, when the transmitted signal is ( x _k ,, , x _{k+ l} ), orthogonal Interval detection threshold, and determine whether interference exists according to the formula |3⁄4χ(^+ί^χ(^ ₊ | ² 〉τ (x _t ,, x _t+u ), where _+u respectively represent different subcarriers at the same time i The received signal on k, when the above formula is established, there is interference, otherwise there is no interference.

22. The system of claim 20 or 21, wherein: said OFDM signal

(X, X _k+ ) and its quadrature signals ( Q _t ,, Q, ₊₁ , ) are within the coherence time and coherence bandwidth.

23. The system according to claim 20, wherein: if different sets of signals at different times are used, the formula ≤ - ^ ^ ⁺¹ ^ > 1 is used to determine whether there is interference, when

N _\

The system according to claim 23, wherein: the two signals of the same group are located within a time and time range of the detection signal, and all the signals satisfy the time and time of the detection signal. Within the scope.

25. The system according to claim 21, wherein: if different signals of different subcarriers are used, the formula ^ - ^k '', ^{k +} ^ > 1 is used to determine whether there is interference,

N _ \

When the formula is established, there is interference, otherwise there is no interference.

26. The system according to claim 25, wherein: the two signals of the same group are located within a coherent bandwidth, and the number of interference detection signal groups used satisfies the accuracy of the interference detection frequency band.

27. The system according to claim 17, wherein: the OFDM signal transmitted by the transmitter of the system is a known pilot signal, and the pilot signal is fixed with a fixed 1, 1 BPSK modulation symbol or 1 , - 1 BPSK modulation symbol between phases.

28. The system according to claim 27, wherein: if the pilot signal uses a fixed 1, 1 BPSK modulation symbol, setting a corresponding interference threshold threshold, and according to the formula >The threshold determines whether the interference exists. When the above formula is established, it is in the sub-load.

There is interference on the N - 1 wave k; otherwise there is no interference on the subcarrier k.

29. The system according to claim 27, wherein: if the pilot signal uses a BPSK modulation symbol of 1 , -1 phase, the corresponding interference threshold is set, and according to the formula

>The threshold determines whether the interference exists. When the above formula is established, it is in the sub-load. There is interference on wave k; otherwise there is no interference on subcarrier k.

30. The system according to claim 17, wherein: if the signal transmitted by the transmitter of the system is unknown, the receiver of the system receives the signal and performs OFDM demodulation thereon.

31. The system according to claim 30, wherein: the receiver of the system performs FFT transformation on the received signal, performs OFDM demodulation, and decodes the subsequent decoding module, including deinterleaving, and decoding. Scrambling code processing.

32. The system of claim 31, wherein: if the decoding is correct, the decoded data is encoded, including interleaving, scrambling, and modulation, to obtain a modulated signal transmitted by the transmitter.

33. The system according to claim 31, wherein: if the decoding is incorrect, the frame error rate FER is calculated. If the FER exceeds a certain threshold, then the current FER is reported, and if the calculated FER exceeds a certain threshold, it is determined. Currently, there is interference, and the scheduling quiet time QP performs interference detection on the user equipment CPE.

34. The system according to claim 17, wherein: said OFDM signal is data subjected to binary phase shift keying, rotational binary phase shift keying, repeated binary phase shift keying, quadrature phase shift keying, Rotate quadrature phase shift keying and/or repeat quadrature phase shift keying modulation, and then IFFT transform and add CP.

35. An interference detecting apparatus for an orthogonal frequency division multiplexing system, comprising:

An OFDM demodulation module, configured to perform FFT transform and OFDM demodulation on the received OFDM signal sent by the transmitter of the system and its orthogonal signal, and the interference signal sent by another system transmitter;

The interference detection module is configured to perform inner product calculation on the signal provided by the OFDM demodulation module to obtain a residual signal, perform energy detection on the remaining signal, and obtain a metric of other system interference signals.

36. Apparatus according to claim 35 wherein: said OFDM signal and said interference signal are uncorrelated signals.

37. The apparatus according to claim 35, wherein: said interference detecting module is based on The OFDM signals (X _ti . , X^. ₊₁ ) and their orthogonal signals ( Q _kl , Q, ₊₁ ) at different times i on the same subcarrier k are described, and the interference threshold T (X _t , X is set) ^. ₊₁ ), the T (X _l , Χ ₊₁ ) is a function, that is, the threshold of the orthogonal interference detection when the transmitted signal is ( χ^. , x _l+1 ), and according to the formula |3⁄4xQw+ Q ₊₁ | ² 〉T (x _t ,, x _t , ₊₁ ) determines whether interference exists, where ₊₁ respectively represents the received signals at different times i on the same subcarrier k. When the above formula is established, there is interference. Otherwise there is no interference.

38. The apparatus according to claim 35, wherein: the interference detection module is configured to: according to the received OFDM signal (X _kJ , X _k+ ) and its orthogonal signal on different subcarriers k at the same time i ( Q , _k+ ) , setting the interference threshold τ (X,,, χ, ₊₁ ,), the τ (X,,, x _t+1 ,) is a function, that is, when the transmission signal is ( x^. x _{k+ l} ), the threshold of the orthogonal interference detection, and determine whether the interference exists according to the formula |3⁄4χ(^+ί^χ(^ ₊ | ² 〉τ (x _t ,, x _t+u ), where _+u respectively Representing the received signal on the different subcarriers k at the same time i, when the above formula is established, there is interference, otherwise there is no interference.

39. Apparatus according to claim 37 or claim 38 wherein: said OFDM signal ( _Xk , _Xk+ ) and its quadrature signals ( _Qkl , _Qk+ ) are within coherence time and coherence bandwidth.

40. The apparatus according to claim 35, wherein: said OFDM signal is a known pilot signal, said pilot signal being modulated by a fixed 1, 1 BPSK modulation symbol or a phase-to-phase BPSK modulation. symbol.

41. The apparatus according to claim 40, wherein: if the pilot signal uses a fixed 1, 1 BPSK modulation symbol, setting a corresponding interference threshold threshold, and according to the formula >The threshold determines whether the interference exists. When the above formula is established, it is in the sub-load.

N- \ There is interference on wave k; otherwise there is no interference on subcarrier k.

42. The apparatus according to claim 40, wherein: if the pilot signal uses a BPSK modulation symbol between 1 and -1, a corresponding interference threshold is set, and according to the formula

43. The device according to claim 35, further comprising:

a decoding module, configured to perform decoding processing on a signal provided by the OFDM demodulation module, and an encoding module, configured to perform coding processing on the decoded data when the decoding module is correctly decoded;

And a modulation module, configured to modulate data provided by the coding module, and provide the obtained modulation signal to the interference detection module.