CN103248443A - Method for sensing OFDM spectrum under conditions of time asynchronization and known cyclic prefix length - Google Patents
Method for sensing OFDM spectrum under conditions of time asynchronization and known cyclic prefix length Download PDFInfo
- Publication number
- CN103248443A CN103248443A CN2013101682408A CN201310168240A CN103248443A CN 103248443 A CN103248443 A CN 103248443A CN 2013101682408 A CN2013101682408 A CN 2013101682408A CN 201310168240 A CN201310168240 A CN 201310168240A CN 103248443 A CN103248443 A CN 103248443A
- Authority
- CN
- China
- Prior art keywords
- signal
- sampled
- auto
- sampled signal
- ofdm
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Images
Landscapes
- Monitoring And Testing Of Transmission In General (AREA)
- Mobile Radio Communication Systems (AREA)
Abstract
The invention discloses a method for sensing an OFDM (Orthogonal Frequency Division Multiplexing) spectrum under conditions of time asynchronization and known cyclic prefix length. The processing procedure of the method comprises the following steps: at first, sampling a receipt signal from a monitoring channel to obtain a sampled signal; then, computing an autocorrelation function of the sampled signal according to the sampled value in the sampled signal; next, computing test statistic according to an autocorrelation coefficient in the autocorrelation function of the sampled signal under the condition of time asynchronization; and at last, judging whether the monitoring channel is in the idle state or not according to the test statistic and the judgment threshold. The method has the advantages that the spectrum sensing can be carried out by directly using the sampled signal, without the need of time synchronization, so that the computation complexity is reduced effectively. During the process of computing the test statistic, due to the use of the nonnegative characteristic of the autocorrelation coefficient corresponding to the cyclic premix part of the OFDM signal in the autocorrelation function of the sampled signal, the spectrum sensing performance of the OFDM signal is improved effectively.
Description
Technical field
The present invention relates to the frequency spectrum perception technology in a kind of cognitive radio system, especially relate to the OFDM frequency spectrum sensing method under the asynchronous and circulating prefix-length known case of a kind of time.
Background technology
Along with the fast development of various radio communication services, importance and the scarcity of frequency spectrum resource highlight day by day.A large amount of studies show that, current frequency spectrum shortage present situation is not owing to frequency resource deficiency physically, and mainly the availability of frequency spectrum is low to be caused because fixed frequency spectrum allocation manager mechanism causes.Cognitive radio is attempted to propose from the resource problem more and more in short supply that solves radio communication in essence by improving the availability of frequency spectrum just.Its communication environment around can real-time perception, identify available idle channel, adjust the system parameters of cognition wireless network then according to the frequency spectrum perception result adaptively, make cognitive radio system have intelligent identification and the ability that changes frequency spectrum use chance.In order to prevent that existing communication system is produced interference, cognitive radio system must identify idle channel effectively reliably, so frequency spectrum perception is one of key technology in the cognitive radio.
OFDM (Orthogonal frequency division multiplexing, OFDM) technology has characteristics such as availability of frequency spectrum height, and this technology is technology current and that future, wireless communication standard was widely adopted.Therefore the frequency spectrum perception (namely judge and whether have ofdm signal in the channel) to ofdm signal has very important significance.Existing frequency spectrum sensing method at ofdm signal mainly can be divided into frequency domain detection method and time domain detection method two classes.Wherein, the frequency domain detection method need be calculated the frequency spectrum of gathering signal, therefore has bigger amount of calculation; The time domain detection method mainly utilizes the autocorrelation performance of Cyclic Prefix in the ofdm signal to realize frequency spectrum perception.People such as Chaudhari have proposed to utilize the autocorrelation performance of Cyclic Prefix in " in the Autocorrelation-Based Decentralized Sequential Detection of OFDM Signals in Cognitive Radios(cognitive radio based on autocorrelative ofdm signal distributed sequential detection method) " in 2009, realize frequency spectrum perception by calculating the auto-correlation function that receives signal, but this method is not considered the non-stationary property of auto-correlation function.At this problem, people such as Axell have proposed a kind of frequency spectrum sensing method of new auto-correlation function based on the reception signal in " the optimum and suboptimum frequency spectrum sensing method of the OFDM during the known and unknown noise variance of Optimal and Sub-Optimal Spectrum Sensing of OFDM Signals in Known and Unknown Noise Variance() " in 2011, the method that people such as this method and Chaudhari propose is compared, this method has more excellent detection performance, but this method requires time synchronized.
Summary of the invention
Technical problem to be solved by this invention provides the OFDM frequency spectrum sensing method under the asynchronous and circulating prefix-length known case of a kind of time, and it can improve the frequency spectrum perception performance of ofdm signal effectively, and computation complexity is low.
The present invention solves the problems of the technologies described above the technical scheme that adopts: the OFDM frequency spectrum sensing method under the asynchronous and circulating prefix-length known case of a kind of time, the processing procedure that it is characterized in that it is: at first, reception signal from supervisory channel is sampled, obtain sampled signal; Then, according to the sampled value in the sampled signal, the auto-correlation function of calculating sampling signal; Then, under the time asynchronous condition, according to the auto-correlation coefficient in the auto-correlation function of sampled signal, calculate test statistics; At last, according to the size of test statistics and decision threshold, judge whether supervisory channel is in idle condition.
It specifically may further comprise the steps:
1. utilize the sampling module in the cognitive radio system that the reception signal from supervisory channel is carried out M sampling, obtain the sampled signal that the sampled value by M sampled point constitutes, wherein, M=K * (N
c+ N
d)+N
d, K represents any positive integer, N
cThe length of the Cyclic Prefix of expression ofdm signal, N
dThe number of the subcarrier of expression ofdm signal;
2. according to the sampled value in the sampled signal, the auto-correlation function of calculating sampling signal is designated as ρ (t) with t auto-correlation coefficient in the auto-correlation function of sampled signal,
Wherein, the number of the auto-correlation coefficient in the auto-correlation function of sampled signal is N
c+ N
d, t is positive integer, and 1≤t≤N
c+ N
d, k is positive integer, and 1≤k≤K, x ((k-1) * (N
c+ N
d((k-1) * (N in the expression of the)+t) sampled signal
c+ N
dThe individual sampled value of)+t), x ((k-1) * (N
c+ N
d)+N
d+ t) ((k-1) * (N of expression in the sampled signal
c+ N
d)+N
d+ t) individual sampled value, m is positive integer, and 1≤m≤M, m sampled value in x (m) the expression sampled signal;
3. under the time asynchronous condition, according to the auto-correlation coefficient in the auto-correlation function of sampled signal, calculate test statistics, be designated as T,
Wherein, symbol " || " is the symbol that takes absolute value;
4. test statistics T and decision threshold λ are compared, if T, judges then that supervisory channel is in busy condition greater than λ, if T is less than or equal to λ, judge that then supervisory channel is in idle condition, wherein, λ=[F
-1(P
f)]
2, P
fThe expression false alarm probability, span is 0<P
f<0.5, F
-1() is the inverse function of F (),
Compared with prior art, the invention has the advantages that:
1) the inventive method since when not required synchronously, directly utilize sampled signal to carry out frequency spectrum perception, therefore reduced computation complexity effectively.
2) the inventive method is in the process of calculating test statistics, owing to the non-negative characteristic that auto-correlation coefficient corresponding with the Cyclic Prefix part of ofdm signal in the auto-correlation function that has utilized sampled signal has, therefore improved the frequency spectrum perception performance of ofdm signal effectively.
Description of drawings
Fig. 1 is the FB(flow block) of frequency spectrum sensing method of the present invention;
Fig. 2 is under different state of signal-to-noise, and the frequency spectrum sensing method that people such as Axell propose and the detection probability of the inventive method be schematic diagram relatively.
Embodiment
Describe in further detail below in conjunction with the present invention of accompanying drawing embodiment.
OFDM frequency spectrum sensing method under the asynchronous and circulating prefix-length known case of a kind of time that the present invention proposes, its FB(flow block) as shown in Figure 1, its main processing procedure is: at first, the reception signal from supervisory channel is sampled, obtain sampled signal; Then, according to the sampled value in the sampled signal, the auto-correlation function of calculating sampling signal; Then, under the time asynchronous condition, according to the auto-correlation coefficient in the auto-correlation function of sampled signal, calculate test statistics; At last, according to the size of test statistics and decision threshold, judge whether supervisory channel is in idle condition.
Ofdm signal frequency spectrum sensing method of the present invention, it specifically may further comprise the steps:
1. utilize the sampling module in the cognitive radio system that the reception signal from supervisory channel is carried out M sampling, obtain the sampled signal that the sampled value by M sampled point constitutes, wherein, M=K * (N
c+ N
d)+N
d, K represents any positive integer, as gets K=10, N
cThe length of the Cyclic Prefix of expression ofdm signal, N
dThe number of the subcarrier of expression ofdm signal.
2. according to the sampled value in the sampled signal, the auto-correlation function of calculating sampling signal is designated as ρ (t) with t auto-correlation coefficient in the auto-correlation function of sampled signal,
Wherein, the number of the auto-correlation coefficient in the auto-correlation function of sampled signal is N
c+ N
d, t is positive integer, and 1≤t≤N
c+ N
d, k is positive integer, and 1≤k≤K, x ((k-1) * (N
c+ N
d((k-1) * (N in the expression of the)+t) sampled signal
c+ N
dThe individual sampled value of)+t), x ((k-1) * (N
c+ N
d)+N
d+ t) ((k-1) * (N of expression in the sampled signal
c+ N
d)+N
d+ t) individual sampled value, m is positive integer, and 1≤m≤M, m sampled value in x (m) the expression sampled signal.
3. under the time asynchronous condition, according to the auto-correlation coefficient in the auto-correlation function of sampled signal, calculate test statistics, be designated as T,
Wherein, symbol " || " is the symbol that takes absolute value.
4. test statistics T and decision threshold λ are compared, if T, judges then that supervisory channel is in busy condition greater than λ, if T is less than or equal to λ, judge that then supervisory channel is in idle condition, wherein, λ=[F
-1(P
f)]
2, P
fThe expression false alarm probability, span is 0<P
f<0.5, F
-1() is the inverse function of F (),
E is the nature radix, e=2.71828 ..., y is variable.
By feasibility and the validity of following emulation to further specify frequency spectrum sensing method of the present invention.
The number of supposing the subcarrier of ofdm signal is N
d=32, the length of the Cyclic Prefix of ofdm signal is N
c=8, get K=10, then total sampling number is M=432, and is P according to the value that false alarm probability is established in the requirement of IEEE802.22 standard
f=0.1.Fig. 2 provided signal to noise ratio from-when 20dB changes to 5dB, the frequency spectrum sensing method that people such as Axell propose and the comparison of the inventive method by the detection probability of 100000 Monte Carlo simulation acquisitions.As can be seen from Figure 2, the detection probability of the inventive method is far superior to the detection probability of the frequency spectrum sensing method that people such as Axell proposes.Analysis chart 2, when signal to noise ratio be-during 1dB, the detection probability of the inventive method is 0.94, reached detection probability in the IEEE802.22 standard more than or equal to 0.9 requirement, and this moment the frequency spectrum sensing method that people such as Axell proposes detection probability can only reach 0.8, this does not reach detection probability in the IEEE802.22 standard more than or equal to 0.9 requirement; When signal to noise ratio is 1dB, the detection probability 0.93 of the frequency spectrum sensing method that people such as Axell propose, and the detection probability of the inventive method is near 1 at this moment, this is enough to illustrate feasibility and the validity of the inventive method.
Claims (2)
1. the OFDM frequency spectrum sensing method under the asynchronous and circulating prefix-length known case of time is characterized in that its processing procedure is: at first, the reception signal from supervisory channel is sampled, obtain sampled signal; Then, according to the sampled value in the sampled signal, the auto-correlation function of calculating sampling signal; Then, under the time asynchronous condition, according to the auto-correlation coefficient in the auto-correlation function of sampled signal, calculate test statistics; At last, according to the size of test statistics and decision threshold, judge whether supervisory channel is in idle condition.
2. the OFDM frequency spectrum sensing method under the asynchronous and circulating prefix-length known case of time according to claim 1 is characterized in that it specifically may further comprise the steps:
1. utilize the sampling module in the cognitive radio system that the reception signal from supervisory channel is carried out M sampling, obtain the sampled signal that the sampled value by M sampled point constitutes, wherein, M=K * (N
c+ N
d)+N
d, K represents any positive integer, N
cThe length of the Cyclic Prefix of expression ofdm signal, N
dThe number of the subcarrier of expression ofdm signal;
2. according to the sampled value in the sampled signal, the auto-correlation function of calculating sampling signal is designated as ρ (t) with t auto-correlation coefficient in the auto-correlation function of sampled signal,
Wherein, the number of the auto-correlation coefficient in the auto-correlation function of sampled signal is N
c+ N
d, t is positive integer, and 1≤t≤N
c+ N
d, k is positive integer, and 1≤k≤K, x ((k-1) * (N
c+ N
d((k-1) * (N in the expression of the)+t) sampled signal
c+ N
dThe individual sampled value of)+t), x ((k-1) * (N
c+ N
d)+N
d+ t) ((k-1) * (N of expression in the sampled signal
c+ N
d)+N
d+ t) individual sampled value, m is positive integer, and 1≤m≤M, m sampled value in x (m) the expression sampled signal;
3. under the time asynchronous condition, according to the auto-correlation coefficient in the auto-correlation function of sampled signal, calculate test statistics, be designated as T,
Wherein, symbol " || " is the symbol that takes absolute value;
4. test statistics T and decision threshold λ are compared, if T, judges then that supervisory channel is in busy condition greater than λ, if T is less than or equal to λ, judge that then supervisory channel is in idle condition, wherein, λ=[F
-1(P
f)]
2, P
fThe expression false alarm probability, span is 0<P
f<0.5, F
-1() is the inverse function of F (),
E is the nature radix, e=2.71828 ..., y is variable.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CN201310168240.8A CN103248443B (en) | 2013-05-06 | 2013-05-06 | Method for sensing OFDM spectrum under conditions of time asynchronization and known cyclic prefix length |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CN201310168240.8A CN103248443B (en) | 2013-05-06 | 2013-05-06 | Method for sensing OFDM spectrum under conditions of time asynchronization and known cyclic prefix length |
Publications (2)
Publication Number | Publication Date |
---|---|
CN103248443A true CN103248443A (en) | 2013-08-14 |
CN103248443B CN103248443B (en) | 2015-04-29 |
Family
ID=48927684
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CN201310168240.8A Expired - Fee Related CN103248443B (en) | 2013-05-06 | 2013-05-06 | Method for sensing OFDM spectrum under conditions of time asynchronization and known cyclic prefix length |
Country Status (1)
Country | Link |
---|---|
CN (1) | CN103248443B (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN107196721A (en) * | 2017-06-21 | 2017-09-22 | 宁波大学 | It is asynchronous and there is the ofdm signal frequency spectrum sensing method under offset frequency situation for the time |
CN107222870A (en) * | 2017-06-21 | 2017-09-29 | 宁波大学 | For the ofdm signal frequency spectrum sensing method that the time is asynchronous and is not present under offset frequency situation |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2001047204A1 (en) * | 1999-12-22 | 2001-06-28 | Thomson Licensing S.A. | Correction of a sampling frequency offset in an orthogonal frequency division multiplexing system by sidelobe analysis of pilot subcarriers |
CN101630983A (en) * | 2009-07-30 | 2010-01-20 | 哈尔滨工业大学 | Idle frequency spectrum detecting method by using cyclic spectrum statistic value in cognitive radio |
CN101848046A (en) * | 2010-06-22 | 2010-09-29 | 上海交通大学 | Method for increasing detection probability of frequency spectrum perception |
CN102404063A (en) * | 2011-12-26 | 2012-04-04 | 电子科技大学 | GLRT (General Likelihood Ratio Test) detection method based on oversampling |
CN102710345A (en) * | 2012-04-27 | 2012-10-03 | 宁波大学 | Cognition radio frequency spectrum sensing method based on multi-antenna Friedman inspection |
-
2013
- 2013-05-06 CN CN201310168240.8A patent/CN103248443B/en not_active Expired - Fee Related
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2001047204A1 (en) * | 1999-12-22 | 2001-06-28 | Thomson Licensing S.A. | Correction of a sampling frequency offset in an orthogonal frequency division multiplexing system by sidelobe analysis of pilot subcarriers |
CN101630983A (en) * | 2009-07-30 | 2010-01-20 | 哈尔滨工业大学 | Idle frequency spectrum detecting method by using cyclic spectrum statistic value in cognitive radio |
CN101848046A (en) * | 2010-06-22 | 2010-09-29 | 上海交通大学 | Method for increasing detection probability of frequency spectrum perception |
CN102404063A (en) * | 2011-12-26 | 2012-04-04 | 电子科技大学 | GLRT (General Likelihood Ratio Test) detection method based on oversampling |
CN102710345A (en) * | 2012-04-27 | 2012-10-03 | 宁波大学 | Cognition radio frequency spectrum sensing method based on multi-antenna Friedman inspection |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN107196721A (en) * | 2017-06-21 | 2017-09-22 | 宁波大学 | It is asynchronous and there is the ofdm signal frequency spectrum sensing method under offset frequency situation for the time |
CN107222870A (en) * | 2017-06-21 | 2017-09-29 | 宁波大学 | For the ofdm signal frequency spectrum sensing method that the time is asynchronous and is not present under offset frequency situation |
CN107222870B (en) * | 2017-06-21 | 2019-09-03 | 宁波大学 | Ofdm signal frequency spectrum sensing method asynchronous for the time and being not present under offset frequency situation |
CN107196721B (en) * | 2017-06-21 | 2020-07-28 | 宁波大学 | OFDM signal spectrum sensing method under time asynchronization and frequency offset condition |
Also Published As
Publication number | Publication date |
---|---|
CN103248443B (en) | 2015-04-29 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
EP2439973B1 (en) | Detection method and apparatus based on random access process | |
US20140219268A1 (en) | Synchronization mechanism | |
US20120195214A1 (en) | Multitaper spectrum sensing systems and methods | |
CN108924943B (en) | Maximum correlation estimation detection method based on narrowband Internet of things random access channel | |
CN103248441B (en) | Method for sensing OFDM spectrum under conditions of time asynchronization and unknown cyclic prefix length | |
CN102546061B (en) | Self-adaptive time-frequency hole detection method based on wavelet transformation | |
CN103237311A (en) | Orthogonal frequency division multiplexing (OFDM) frequency domain interpolation pilot frequency-based cyclostationary feature spectrum sensing method | |
CN102271022B (en) | Spectrum sensing method based on maximum generalized characteristic value | |
Chen et al. | Sensing orthogonal frequency division multiplexing systems for cognitive radio with cyclic prefix and pilot tones | |
Gaddam et al. | Robust sensing of DVB-T signals | |
CN103108338A (en) | Detection method, device and base station for random access signal | |
CN103248442B (en) | Method for sensing OFDM signal frequency spectrum under condition of time synchronization | |
CN101635598A (en) | Method and device for estimating noise power | |
CN102137051B (en) | Interference detection method used in wireless sensor network and detection device thereof | |
CN103248443B (en) | Method for sensing OFDM spectrum under conditions of time asynchronization and known cyclic prefix length | |
CN104821856B (en) | Noise power estimation method for OFDM frequency spectrum sensing | |
CN102238123B (en) | Ranging code detecting method and device | |
CN101895370A (en) | Method for detecting interference of OFDM communication system | |
CN110149160B (en) | Method, system and storage medium for TD-LTE interference detection | |
CN101820407B (en) | Serial interference cancellation based frequency domain initial ranging method and system | |
CN102111228A (en) | Cognitive radio frequency spectrum sensing method based on circulation symmetry | |
CN102685058B (en) | Interference-to-noise ratio evaluation method of blind single of orthogonal frequency division multiplexing (OFDM) system under pulse interference environment | |
Blad et al. | Spectrum sensing of OFDM signals in the presence of CFO: New algorithms and empirical evaluation using USRP | |
CN114584232A (en) | Wireless communication sub-band signal-to-noise ratio measuring method based on channel detection reference signal | |
Zhao et al. | Cyclic spectrum based intelligent modulation recognition with machine learning |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
C06 | Publication | ||
PB01 | Publication | ||
C10 | Entry into substantive examination | ||
SE01 | Entry into force of request for substantive examination | ||
C14 | Grant of patent or utility model | ||
GR01 | Patent grant | ||
CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20150429 Termination date: 20180506 |
|
CF01 | Termination of patent right due to non-payment of annual fee |