CN101026605A - Interference detecting method - Google Patents
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- CN101026605A CN101026605A CN 200610009192 CN200610009192A CN101026605A CN 101026605 A CN101026605 A CN 101026605A CN 200610009192 CN200610009192 CN 200610009192 CN 200610009192 A CN200610009192 A CN 200610009192A CN 101026605 A CN101026605 A CN 101026605A
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- interference
- pilot signal
- interference detection
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Abstract
The method includes steps: transmitter constructs symmetrical pilot signal; transmitter sends symmetrical pilot signal to receiver; through the received pilot signal, the receiver carries out interference detection. The idea uses pilot signal designed to estimate channel usually. Thus, additional overhead is not needed, and it is applicable no matter whether interference changes or not. Another feature is accuracy of interference detection. Detection is only dependent on ratio between interference and noise. When interference power is equal to signal power nearly, the invention possesses better performance. The invention also discloses a simple algorithm for implementing the idea of interference detection. Under condition of narrowband interference, the invention validates the algorithm, and simulation result shows that the algorithm possesses favorable performance.
Description
Technical field
The present invention relates to the interference detection technique in the wireless communication system.Especially interference detection method in the system that adopts the OFDM technology.
Background technology
Because OFDM (OFDM) technology can realize high-speed transfer under no communication environments, and the anti-multipath interference is strong, makes the OFDM technology have a wide range of applications in the various wireless communication system.As in WRAN (radio area network) system, just used the OFDM technology, the OFDM technology is when providing broadband access, and also frequency spectrum resource distributes for the WRAN system provides flexibly, becomes the best-of-breed technology that interference is avoided in the WRAN system.The WRAN system just must detect and comes from the interference that has service-user such as TV or wireless microphone for fear of existing service-user being produced service quality that harmful interference guarantees self system simultaneously.Therefore, detecting interference is the important component part that adopts in the WRAN system of OFDM technology.So solving the technology of disturbing in the system that adopts the OFDM technology becomes a hot technology.
In the prior art, multiple interference detection method is arranged.U.S. Patent number US5488632, exercise question are in the patent of " Transmission and reception in a hostile interference environment ", have proposed a kind of interference detection method based on the in advance known hypothesis of interference position.U.S. Patent number US6445693, exercise question is in the patent of " Method and apparatus for estimating power of fist adjacentanalog FM interference in an in-band on-channel (IBOC) communication system ", and the power that the utilization of DAB (digital audio broadcasting) system is measured on each subcarrier and the prior information of interference power slope are estimated the existence disturbed.U.S. Patent number US6603734, exercise question is in the patent of " Method for eliminating interference in an OFDM radio receiver ", and the amplitude that the amplitude of interference can be by calculating one group of selecteed signal obtained with respect to the departing from of average amplitude of this group signal.European patent number EP1349337, exercise question are in the patent of " Multicarrier reception withinterference detection ", and interference can be detected by utilize the demodulating data that obtains from equalizer.Japanese Patent No. JP2004072724, exercise question is in the patent of " METHOD ANDINSTRUMENT FOR MEASURING SINR FOR OFDM COMMUNICATIONSYSTEM ", and the SINR of the OFDM sub-channel signal that receives (system interference ratio) measured value can obtain by the Nonparametric signal processing method of using a kind of novelty at frequency domain.Patent No. WO2004104530, exercise question is in the patent of " INTERFERENCE AND NOISE ESTIMATION IN ANOFDM SYSTEM ", and the summation of the received power by measuring the subcarrier do not distribute to the Any user in the sub-district is determined noise and disturbed total value.
Yet, in above-mentioned prior art, all be to adopt shutdown to detect interference, will reduce the efficient of system like this.
Summary of the invention
The invention provides the method for Interference Detection in a kind of system of the OFDM of employing technology, can detect interference and whether exist.
The invention provides the method for Interference Detection in a kind of system that adopts orthogonal frequency division multiplexi, comprising:
A, transmitter structure symmetrical pilot signal;
B, transmitter are issued receiver with symmetrical pilot signal;
C, receiver carry out Interference Detection by the pilot signal that receives.
Described symmetrical pilot signal is binary phase shift keying, rotation binary phase shift keying, repeats binary phase shift keying, Quadrature Phase Shift Keying, rotating orthogonal phase shift keying and/or repeat the signal that Quadrature Phase Shift Keying is modulated.
Described step B specifically comprises: transmitter is issued receiver with symmetrical pilot signal by pilot sub-carrier.
Described step C specifically comprises: receiver can by the pilot signal that receives and power and decision threshold determine to disturb existence.
Can determine to disturb by following formula and exist:
If
Then exist and disturb, otherwise do not have interference;
Wherein,
The pilot signal that expression receives and power, threshold shows decision threshold.
Described decision threshold can determine by following formula,
Wherein, P
AlarmBe false alarm probability, the condition when H0 is noiseless, Threshold is a judgement thresholding to be asked.
Described H0 represents: pilot signal and power have only noise component, do not have interference components, formulae express is as follows:
H0：|Y
k，i+Y
k，i+1|
2＝|P
k，i*H
k+n
k，i+P
k，i+1*H
k+n
k，i+1|
2＝|n
k，i+n
k，i+1|
2。
Described decision threshold can also be determined by following formula:
Wherein, P
DetectionBe detection probability, H1 is the condition that has when disturbing, and Threshold is a thresholding to be asked.
Described H1 represents: pilot signal and power have noise component and interference components simultaneously, formulae express is as follows:
H1：|Y
k，i+Y
k，i+1|
2＝|P
k，i*H
k+I
k，i+n
k，i+P
k，i+1*H
k+I
k，i+1+n
k，i+1|
2＝|I
k，i+I
k，i+1+n
k，i+n
k，i+1|
2。
Signal calculated and the time do not need channel estimating.
According to the present invention,, symmetrical pilot signal is transmitted on pilot sub-carrier by on same subcarrier, constructing symmetrical pilot signal.In transmission course, disturb if exist, whether change no matter disturb, symmetrical structure is all with destroyed, and the power of the feasible pilot signal that receives increases.The present invention is based on received signal and the size of power judge whether interference exists.In order to verify result of the present invention, interference detection method of the present invention has been carried out emulation, from simulation result as can be seen, the present invention can carry out Interference Detection effectively, and is detected as the power height.
Description of drawings
Fig. 1 is the planisphere of the pilot signal of being constructed according to the present invention;
Figure 2 shows that the design drawing of subcarrier of the present invention;
When Fig. 3 fails two pilot signals for uploading at a subcarrier, the simulation result figure of Interference Detection probability;
When Fig. 4 fails five pilot signals for uploading at a subcarrier, the simulation result figure of Interference Detection probability.
Embodiment
Understand and realization the present invention the existing embodiment that describes Interference Detection of the present invention in conjunction with the accompanying drawings for the ease of persons skilled in the art.
Suppose that channel is constant in a frame period.Two are used the pilot signal of different BPSK (binary phase shift keying) constellation point to be transmitted in Fig. 1.If these two pilot signals are assigned on the different OFDM symbols of the same sub-carrier in the same number of frames, this just means that they have experienced identical channel fading, received signal corresponding to these two pilot signals will have a planisphere that is obtained by the original constellation rotation, so the symmetrical structure of planisphere will can not change.Yet if interference is arranged on subcarrier, the symmetrical structure of planisphere changes easily, and this is exactly the central idea of our interference detection method.
According to above-mentioned channel hypothesis, structure symmetrical pilot signal (as the pilot signal of BPSK modulation), the symmetrical pilot signal of transmission structure on same subcarrier.As shown in Figure 1, wherein " X " represents pilot signal, and described symmetrical pilot signal has symmetrical structure on planisphere.In the transmission course of pilot signal, as (a) among Fig. 1 (b) shown in, interference if there is no has only some end noises, very little to pilot signal symmetrical structure influence on planisphere so, the symmetrical pilot signal sum power that the result receives is less.In the transmission course of pilot signal, as (c) among Fig. 1 (d) shown in, if the symmetrical structure of the interference that exists shown in during greater than a certain value (as threshold values), not only can destroying on the planisphere can make that also to receive pilot signal sum power very big.Therefore, according to the present invention, can judge the existence of interference by the watt level of all received signal sums.
In fact this thought can also be applied in other any planispheres except BPSK, no matter also can use under whether another OFDM piece changes situation from an OFDM piece disturbing simultaneously.Do not change if disturb, the symmetrical structure of planisphere will be deterministic change so, and this is because will have a relative drift in the planisphere of received signal.Change if disturb, symmetrical structure also will change, and has only very little chance that the influence identical to planisphere with channel arranged because disturb.Above employed pilot signal only need be symmetrical, for example can adopt through as the pilot signal of modulated:
1) pilot signal of BPSK modulation: (1 ,+1);
2) pilot signal of rotation BPSK modulation: e
J θ* (1 ,+1), wherein θ ∈ [0,2 π);
3) repeat the pilot signal that BPSK modulates: (1 ,-1 ,+1 ,+1...);
4) pilot signal of QPSK (Quadrature Phase Shift Keying) modulation: (+1+j ,+1-j ,-1+j ,-1-j);
5) pilot signal of rotation QPSK modulation: e
J θ* (+1+j ,+1-j ,-1+j ,-1-j), wherein θ ∈ [0,2 π);
6) repeat the pilot signal that QPSK modulates: (+1+j ,+1+j ,-1-j ,-1-j...).
Below we will provide at disturbing on the subcarrier and change, and suppose that the intersymbol interference of different OFDM on the same subcarrier is algorithm and the decision threshold under the independent identically distributed Gaussian random variable.
Figure 2 shows that the design drawing of pilot sub-carrier of the present invention, it is the Comb Pilot structure.As shown in Figure 2, wherein, laterally represent the subcarrier sequence number of frequency domain, vertically expression is the time shaft of unit (block) with the OFDM symbol, " ● " expression pilot sub-carrier (pilot subcarrier), and described pilot sub-carrier is used to transmit pilot signal." o " represents data subcarrier (data subcarrier).As seen from Figure 2, between adjacent two pilot sub-carriers, be separated with the data subcarrier (three data subcarriers have been shown among Fig. 2) of similar number.The pilot signal of above-mentioned structure is transmitted on the pilot sub-carrier of design.
Make H
kRepresent k subcarrier channel estimation, suppose that channel is stable in entire frame.Make P
K, iRepresent i pilot signal of k subcarrier, Y
K, iRepresent i the pilot signal that receives on k the pilot sub-carrier, suppose that pilot signal is the signal of BPSK modulation, that is: P
K, i=-P
K, i+1By following hypothesis testing:
H0：|Y
k，i+Y
k，i+1|
2＝|P
k，i*H
k+n
k，i+P
k，i+1*H
k+n
k，i+1|
2＝|n
k，i+n
k，i+1|
2
H1：|Y
k，i+Y
k，i+1|
2＝|P
k，i*H
k+I
k，i+n
k，i+P
k，i+1*H
k+I
k，i+1+n
k，i+1|
2＝|I
k，i+I
k，i+1+n
k，i+n
k，i+1|
2
Can obtain signal and power probability distribution under the signal under the H0 condition and power probability distribution and H1 condition, there is the situation of disturbing in H1 representative here, and the H0 representative does not have the situation of interference.l
K, iRepresent the interference on i the pilot signal on the k subcarrier, n
K, lRepresent the noise on i the pilot signal on the k subcarrier.We further suppose l
i, l
I+1Be that variance is σ
i 2Independent identically distributed Gaussian random variable.| Y
K, i+ Y
K, i+1|
2Obey X
2Distribute.The existence of disturbing is by judging | Y
K, i+ Y
K, i+1|
2Whether surpassing a thresholding judges.
The false alarm probability of our configuration-system target is P
Alarm, thresholding can be obtained by following formula so.
P(|Y
k，i+Y
k，i+1|
2＞threshold|H0)＝P
alarm
In addition, we also the detection probability of configuration-system target be P
Detection, thresholding can be obtained by following formula so.
If on a subcarrier of a frame, N＞2 pilot signal is arranged, works as use
Replace
| Y
K, i+ Y
K, i+1|
2When doing the hypothesis check, can calculate thresholding equally, and not change thresholding.
Calculate to receive adjacent pilot symbols and performance number | Y
K, i+ Y
K, i+1|
2After, should value compare with thresholding, determine whether like this to exist and disturb.Detection algorithm is as follows:
If | Y
K, i+ Y
K, i+1|
2＞threshold
Then on subcarrier k, exist and disturb;
Otherwise
On subcarrier k, there is not interference.
If on a subcarrier of a frame N＞2 pilot signal is arranged, we do not change thresholding but are to use
Replace | Y
K, i+ Y
K, i+1|
2Do Interference Detection.Detection algorithm is as follows:
If
Then on subcarrier k, exist and disturb;
Otherwise
On subcarrier k, there is not interference.
According to the present invention, signal calculated and the time do not need channel estimating.
According to the present invention, adopt different dried making an uproar Interference Detection algorithm of the present invention to be carried out emulation than (INR), Fig. 3 is illustrated in the analogous diagram that a subcarrier is uploaded defeated two pilot signals, as shown in Figure 3, here axis of abscissas is represented the subcarrier subscript, axis of ordinates is represented detection probability, and 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.Fig. 4 shows the analogous diagram of uploading defeated five pilot signals at a subcarrier, and as shown in Figure 4, axis of abscissas is represented the subcarrier subscript here, and axis of ordinates is represented detection probability, and 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.We can find to need only dried making an uproar than very high from simulation result, and the success rate that interference detection method so of the present invention detects will be very high.
Though described the present invention by embodiment, those of ordinary skills know, without departing from the spirit and substance in the present invention, just can make the present invention that many distortion and variation are arranged, and scope of the present invention is limited to the appended claims.
Claims (10)
1, the method for Interference Detection in a kind of system that adopts orthogonal frequency division multiplexi is characterized in that, comprising:
A, transmitter structure symmetrical pilot signal;
B, transmitter are issued receiver with symmetrical pilot signal;
C, receiver carry out Interference Detection by the pilot signal that receives.
2, the method for Interference Detection according to claim 1, it is characterized in that described symmetrical pilot signal is binary phase shift keying, rotation binary phase shift keying, repeats binary phase shift keying, Quadrature Phase Shift Keying, rotating orthogonal phase shift keying and/or repeat the signal that Quadrature Phase Shift Keying is modulated.
3, the method for Interference Detection according to claim 1 is characterized in that, described step B specifically comprises: transmitter is issued receiver with symmetrical pilot signal by pilot sub-carrier.
4, the method for Interference Detection according to claim 1 is characterized in that, described step C specifically comprises: receiver can by the pilot signal that receives and power and decision threshold determine to disturb existence.
5, the method for Interference Detection according to claim 4 is characterized in that, can determine to disturb by following formula to exist:
If
Then exist and disturb, otherwise do not have interference;
Wherein,
The pilot signal that expression receives and power, threshold shows decision threshold.
6, the method for Interference Detection according to claim 5 is characterized in that, described decision threshold can determine by following formula,
Wherein, P
AlarmBe false alarm probability, the condition when H0 is noiseless, Threshold is a judgement thresholding to be asked.
7, the method for Interference Detection according to claim 6 is characterized in that, described H0 represents: pilot signal and power have only noise component, do not have interference components, formulae express is as follows:
H0：|Y
k，i+Y
k，i+1|
2＝|P
k，i*H
k+n
k，i+P
k，i+1*H
k+n
k，i+1|
2＝|n
k，i+n
k，i+1|
2。
8, the method for Interference Detection according to claim 7 is characterized in that, described decision threshold can be determined by following formula:
Wherein, P
DetectionBe detection probability, H1 is the condition that has when disturbing, and Threshold is a thresholding to be asked.
9, the method for Interference Detection according to claim 8 is characterized in that, described H1 represents: pilot signal and power have noise component and interference components simultaneously, formulae express is as follows:
H1：|Y
k，i+Y
k，i+1|
2＝|P
k，i*H
k+I
k，i+n
k，i+P
k，i+1*H
k+I
k，i+1+n
k，i+1|
2＝|I
k，i+I
k，i+1+n
k，i+n
k，i+1|
2。
10, according to the method for the described Interference Detection of above-mentioned arbitrary claim, it is characterized in that, signal calculated and the time do not need channel estimating.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101437244B (en) * | 2007-11-16 | 2010-04-14 | 大唐移动通信设备有限公司 | Method and apparatus for implementing link emulation and system emulation interface |
| CN101848480A (en) * | 2010-05-06 | 2010-09-29 | 上海大学 | Signal-to-interference ratio decision method in actual ICI (Inter-Carrier Interference) elimination of high-mobility OFDM (Orthogonal Frequency Division Multiplexing) cooperative system |
| CN105703856A (en) * | 2016-03-14 | 2016-06-22 | 电子科技大学 | Adaptive interference detection method |
-
2006
- 2006-02-20 CN CNB2006100091928A patent/CN100563230C/en active Active
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101437244B (en) * | 2007-11-16 | 2010-04-14 | 大唐移动通信设备有限公司 | Method and apparatus for implementing link emulation and system emulation interface |
| CN101848480A (en) * | 2010-05-06 | 2010-09-29 | 上海大学 | Signal-to-interference ratio decision method in actual ICI (Inter-Carrier Interference) elimination of high-mobility OFDM (Orthogonal Frequency Division Multiplexing) cooperative system |
| CN101848480B (en) * | 2010-05-06 | 2013-04-03 | 上海大学 | Signal-to-interference ratio decision method in actual ICI (Inter-Carrier Interference) elimination of high-mobility OFDM (Orthogonal Frequency Division Multiplexing) cooperative system |
| CN105703856A (en) * | 2016-03-14 | 2016-06-22 | 电子科技大学 | Adaptive interference detection method |
| CN105703856B (en) * | 2016-03-14 | 2018-08-24 | 电子科技大学 | A kind of adaptive disturbance detection method |
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|---|---|
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