CN105071879B - The detection method of cognitive user region is judged in cross-channel gain estimation - Google Patents
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Abstract
The invention belongs to the cognitive radio full duplex relaying field in moving communicating field, more particularly to mobile communication.In present invention downlink transmission first, in downlink transmission, PT sends data using adaptive modulation system to PR, holding signal to noise ratio is constant in sending data procedures, monitor the SNR from PT ends transmission signal in CT ends, contrast the target SNR of PR, exclude noisy region i.e. Preliminary detection cognitive user region, CT is used as full duplex relaying, signal of the forwarding from PT ends is to PR, PR provides new SNR according to the both links signal for receiving, the CLPC systems of triggering PT PR, the transmission power of PT can make corresponding adjustment, CT obtains new SNR according to the new PT signals for receiving, CT is according to the SNR size variations detection cognitive user region before and after its unlatching.Using the method for the present invention, on the premise of probability of interference is 5%, as PT PR are apart from the change of r, probability is successfully selected more than 90%.
Description
Technical Field
The invention belongs to the field of mobile communication, and particularly relates to the field of cognitive radio full-duplex relay in mobile communication.
Background
In the last decade, cognitive radio technology has been extensively studied, and spectrum sharing technology becomes the hottest of future cognitive radio systems. In spectrum sharing, cross-channel gain estimation from the CT end to the PR end is an important factor affecting cognitive ability. However, cross-channel gain estimation for CT-PR remains a very challenging task. Because in a Frequency Division Duplex (FDD) system, the CT-PR cross-channel gain can only be estimated by the existing PR, and then the estimated result is transmitted to the CT through the backhaul link between the two systems, but in a cognitive radio system, such backhaul link is usually ineffective; to solve this problem, a method called active estimation has been proposed, which does not require a backhaul link and does not use PR for transmitting reverse power in the cross channel gain estimation process. The principle is as follows: the CT first transmits an interference signal through the cross-channel, causing the signal received by the PR to change. Because the PT-PR system has Closed Loop Power Control (CLPC), the PT can automatically adjust the transmitting power according to the difference of the received signal-to-noise ratio at the PR end, and the power change is accompanied with the information of CT-PR cross-channel gain. By the active estimation mode, the CT can estimate the cross channel gain value according to the detected PT transmitting power change carrying the cross channel gain information. However, such approaches are difficult to implement in practical systems because they require CT to transmit interference information, thereby inevitably causing interference with PR.
Recently, researchers have introduced full-duplex relay technology in the active estimation method. Since CT plays the role of a full-duplex relay, it forwards amplifies the transmitted signal from PT and then sends it to PR, so that it does not interfere with PR. This approach ingeniously lets the CT trigger the CLPC of the CT-PR system. However, in this method, PR treats the two signals of the direct and relay links as ideal signals, which requires that the time difference of arrival (TDOA) of the two paths is less than the maximum allowable delay of PR, which becomes a small delay (STD). However, if the TDOA of the two paths is greater than or equal to the maximum allowable delay, PR will consider the signal of one of the links (direct or relay link) as the ideal signal and the other as interference, which becomes large delay (LTD). In practical situations, we cannot guarantee the delay of the PR received signal within the control range at all, so this problem also becomes the bottleneck of cross-channel gain estimation.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a detection method for judging the area where the cognitive user is located in cross channel gain estimation. In the invention, the CT can accurately distinguish the time delay of the size on the premise of not causing interference to the PR section, namely, the area of the CT is judged.
For convenience in describing the contents of the present invention, terms and models used in the present invention will be described first:
definition 1 main base station (PT, Primary Transmitter): and a signal transmitting terminal in the main system.
Definition 2 Primary User (PR, Primary User): and a signal receiving end in the main system.
Definition 3 Cognitive Transmitter (CT, Cognitive Transmitter): and the secondary system is provided with a signal transmitting end with cognitive function.
Define 4 Signal-to-Noise Ratio (SNR, Signal Noise Ratio): the ratio of signal power to noise power.
Define 5 Closed Loop Power Control (CLPC): the transmitting end adjusts the transmitting power of the transmitting end according to the change of the signal-to-noise ratio of the receiving end, thereby ensuring the receiving quality of the receiving end.
Define 6 Frequency Division Duplex (FDD): the uplink communication and the downlink communication respectively adopt different frequency channels of the same time slot to work.
Definition 7 Full Duplex (FD, Full-Duplex): the uplink communication and the downlink communication respectively adopt the same time slot of the same frequency channel to work.
Define 8 Cross-Channel gains (CCG): channel gain between S-BS and M-UE.
Define 9 the Time Difference of Arrival (TDOA, Time Difference of Arrival): the time difference of the direct link signal and the relay signal reaching the PR terminal.
Define 10 Small Time Delays (STD): and if the time delay of the two paths of signals received by the PR is very small, the two paths of signals are combined and regarded as one path of signal.
Define 11 Large Time Delays (LTD): when the time delay of two paths of signals received by the PR is larger, one path of signal with stronger strength is selected as an ideal signal, and the other path of signal is selected as an interference signal.
The system used by the invention is as follows:
as shown in figure 1 of the drawings, in which,
the system has CLPC, PT and PR communicate in a certain frequency band, the position of PT is fixed, its coverage range R is defined as circle center PT and circle with radius R is circle A. The linear distance between PR and PT is L, and PR is positioned in the circular range taking PT as the center of circle and R as the radius, and then the center of circle is PT, and the circle with the radius of L is a circle B. The linear distance between the full-duplex CT and the PT is R, and the CT is positioned in a circular range taking the PT as the center of a circle and R as the radius. Wherein the linear distance between PR and CT is L, L is more than 0.035km and less than R, R is more than 0.035km and less than R, L is more than 0.035 km. Channel coefficients between PT, PR and CT ofWherein the channel coefficient of the PT-PR link isThe channel coefficient of the PT-CT link isThe channel coefficient of the CT-PR link ishkSubject to Rayleigh fading, g, for small-scale fading coefficientskLarge scale fading coefficients, which obey the following distribution: pL(dB)＝128.1+37.6log10(d) And for d is more than or equal to 0.035km, wherein d is the distance between two points.
Suppose the tolerant time delay of the received signal of the PR end is TmThen, the STD area of the PT and PR points forms an ellipse with PT and PR as the focus, and the distance between the end point of the ellipse and the nearest focus is knownWherein c is the transmission speed of electromagnetic wave, the outer part of the ellipse is the LTD region, the focus is PT, PR, the distance between the end point of the ellipse and the nearest focus isThe ellipse of (a) is ellipse C.
The ellipse C part of the circle B ∩ is region I, the ellipse B- (circle B ∩ C) part is region III, the ellipse C part of the circle A-circle B) ∩ is region II, the ellipse A- (region I + region II + region III) part is region IV, the ellipse C boundary represents the maximum allowable time delay TmThe boundary of (2).
The technical scheme of the invention is as follows:
in the invention, in downlink transmission, PT sends data to PR in a self-adaptive modulation mode, the signal-to-noise ratio is kept constant in the data sending process, a CT end monitors the SNR of a signal transmitted from the PT end, the target SNR of the PR is compared, the interference-free area is the primary detection cognitive user area, CT is used as a full-duplex relay to forward the signal from the PT end to the PR, the PR gives out a new SNR according to two received link signals and triggers a CLPC system of the PT-PR, the transmitting power of the PT can be correspondingly adjusted, the CT obtains the new SNR according to the received new PT signal, and the CT detects the cognitive user area according to the change of the SNR before and after the PT is started.
The principle of the invention is as follows:
the area of the cognitive user is estimated under the condition of not interfering PR, and if the CT relays and forwards the received main signals from the PT instead of directly interfering the PR, the interference on the PR can be avoided. The CT plays a role of full duplex relay in the communication process of PT and PR: receive, amplify, and forward the primary signal from the PT. Therefore, the PR side can receive signals from two links: a direct transmission link at the PT end and a relay link at the CT end. If CT is designed reasonably, this method may improve the SNR of PR end and reduce the PT emission power. The CT can detect the CT area of the cognitive user by using CLPC (closed loop power control) technique between PT and PR.
The detection method for judging the area where the cognitive user is located in the cross channel gain estimation comprises the following steps:
s1, in downlink transmission, PT sends data to PR in a self-adaptive modulation mode, the signal-to-noise ratio is kept constant in the data sending process, a CT end monitors the SNR of a transmission signal from the PT end, the target SNR of the PR is compared, and the interference area is eliminated, namely the area of a primary detection cognitive user, and the method specifically comprises the following steps:
s11, PT adopts adaptive modulation mode to transmit power p initially0Sending a signal x (i, j) to the PR, maintaining the signal-to-noise ratio during transmissionConstant, PR terminal receives a signal denoted asWherein,for the desired operation, i, j are the number of samples and the number of blocks, np(i, j) is desirably 0, and the variance is σ2Of complex white gaussian noise, PRg0Is the channel gain between PT and PR;
s12, CT receives PT signalThe average signal-to-noise ratio received by the CT isWherein,g1is the channel gain between CT and PT, nc(i, j) is desirably 0, and the variance is σ2Complex white gaussian noise;
s13, g by comparing S110And g at S121Can be derived fromAndthe magnitude relationship of (1), i.e.
S14, the method according to S13Andthe magnitude relationship of (A) excludes the region with interference, i.e. ExclusionI.e. region II, IV;
s2, CT forwards the signal from PT end to PR, PR gives out new SNR according to the received relay link signal, triggers CLPC system of PT-PR, PT transmitting power can make corresponding adjustment, CT obtains new SNR according to the received new PT signal, concretely, the following:
s21, CT transmits x (i, j) to PT by transmitting signal x (i, j) to PTct(i,j)＝Gxcr(i, j), at this time, the PT receives a signal of
g2For the channel gain from CT to PR, G is the amplification of the signal x (i, j) sent by CT to PT, and α is the number of sample and block cycles respectively;
s22, if y is S21pIn (i, j)Andtime delay between < TmIf two signals are merged and regarded as one signal, the two signals comprise a PT transmitted signal and a CT forwarding amplified signal received by PR, and then the signals are processed according to a formulaDetermining equivalent channel gain for PRTo maintain a constant target signal-to-noise ratioThen CLPC will be based on the formulaAutomatically adjusting the transmission power of PT, i.e. from p0Is changed into p1' the received SNR of the CT is updated toProceeding to S3;
s23, if y is S21pIn (i, j)Andtime delay is more than or equal to TmSelecting one path with stronger signal as ideal signal and the other path as interference signal from PT transmitted signal and CT transmitted and amplified signal received by PR, and calculating equivalent channel gain of PRTo maintain a constant target signal-to-noise ratioThen CLPC will be based on the formulaAutomatically adjusting the transmission power of PT, i.e. from p0Is changed into p1And then the received signal-to-noise ratio of CT is updated toProceeding to S3;
s3, detecting the cognitive user area to obtain that the area I is an interference-free area, namely,
according to a preset threshold valueComparison S22 ofAnd the size of the sum, ifThen the region III is excluded from the list,
according to a preset threshold valueComparison S23And the size of the sum, ifThen region III is excluded where K is an empirical value.
Further, the equivalent channel gain of PR is obtained in S23The specific method comprises the following steps:
step 1, if the signal sent by the PT received by the PR is taken as an ideal signal, the PR receives the ideal signal
The signal-to-noise ratio can be obtained
Due to the fact thatThen the situation is not considered;
step 2, if the CT received by the PR forwards the amplified signal as an ideal signal, the PR receives the signalThe signal-to-noise ratio can be obtained
Then the equivalent channel gain is
Further, S24 indicates K ∈ (0, 1).
The invention has the beneficial effects that:
the invention does not need the close cooperation of the return links of the CT and the PT ends, and does not cause interference to the PR, thereby greatly simplifying the complexity of the system and simultaneously not working in a limited small-delay scene. Namely, the CT can accurately distinguish the time delay of the size on the premise of not causing interference to the PR section and judge the area where the CT is positioned. By using the method of the invention, the successful selection probability is more than 90% along with the change of the PT-PR distance r on the premise that the interference probability is 5%.
Drawings
FIG. 1 is a system model diagram of the present invention.
Fig. 2 is a diagram of a cognitive user region model.
FIG. 3 is g0And geSchematic diagram of the relationship of (1).
Fig. 4 is a schematic diagram of the detection process.
Fig. 5 is a graph of probability density for STD and LTD at r-0.2 km.
Fig. 6 is a correlation coefficient of interference probability.
Fig. 7 shows the probability of successful selection of region I.
Detailed Description
The technical solution of the present invention will be described in detail below with reference to the embodiments and the accompanying drawings.
As shown in figure 1 of the drawings, in which,
PT is in the center of a circle with the radius R being 0.5km, CT and PR are randomly distributed in the circle, the distance PT is R km, and the distances of three points are all larger than 0.035km to avoid the near field effect. In the simulation process, the signal-to-noise ratio of the target is madeThe noise power is-114 dBm, the block number B is 200, the sample number in each block is 100, the Monte Carlo times M is 1000, and the maximum tolerant time delay is Tm1 μ s. Three points of wireless channel large-scale fading and small-scale fading, wherein the small scale obeys Rayleigh distribution, and lambdak1, (k 0,1,2) and a path loss PL(dB)＝128.1+37.6log10(d) And for d is more than or equal to 0.035km, shadow fading follows log-normal distribution, and the variance is 4.
The detection method for judging the area where the cognitive user is located in the cross channel gain estimation comprises the following steps:
s1, in downlink transmission, PT sends data to PR in a self-adaptive modulation mode, the signal-to-noise ratio is kept constant in the data sending process, a CT end monitors the SNR of a transmission signal from the PT end, the target SNR of the PR is compared, and the interference area is eliminated, namely the area of a primary detection cognitive user, and the method specifically comprises the following steps:
s11, PT adopts adaptive modulation mode to transmit power p initially0Sending a signal x (i, j) to the PR, maintaining the signal-to-noise ratio during transmissionConstant, PR terminal receives a signal denoted asWherein,for the desired operation, i, j are the number of samples and the number of blocks, np(iJ) is desirably 0 and the variance is σ2Of complex white gaussian noise, PRg0Is the channel gain between PT and PR;
s12, CT receives PT signalThe average signal-to-noise ratio received by the CT isWherein,g1is the channel gain between CT and PT, nc(i, j) is desirably 0, and the variance is σ2Complex white gaussian noise;
s13, g by comparing S110And g at S121Can be derived fromAndthe magnitude relationship of (1), i.e.
S14, the method according to S13Andthe magnitude relationship of (A) excludes the region with interference, i.e.ExclusionI.e. region II, IV;
s2, CT forwards the signal from PT end to PR, PR gives out new SNR according to the received relay link signal, triggers CLPC system of PT-PR, PT transmitting power can make corresponding adjustment, CT obtains new SNR according to the received new PT signal, concretely, the following:
s21, CT transmits x (i, j) to PT by transmitting signal x (i, j) to PTct(i,j)＝Gxcr(i, j), at this time, the PT receives a signal of
g2For the channel gain from CT to PR, G is the amplification of the signal x (i, j) sent by CT to PT, and α is the number of sample and block cycles respectively;
s22, if y is S21pIn (i, j)Andtime delay between < TmIf two signals are merged and regarded as one signal, the two signals comprise a PT transmitted signal and a CT forwarding amplified signal received by PR, and then the signals are processed according to a formulaDetermining equivalent channel gain for PRTo maintain a constant target signal-to-noise ratioThen CLPC will be based on the formulaAutomatically adjusting the transmission power of PT, i.e. from p0Is changed into p1' the received SNR of the CT is updated toProceeding to S3;
s23, if y is S21pIn (i, j)And
time delay is more than or equal to TmSelecting one path with stronger signal as ideal signal and the other path as interference signal from PT transmitted signal and CT transmitted and amplified signal received by PR, and calculating equivalent channel gain of PRTo maintain a constant target signal-to-noise ratioThen CLPC will be based on the formulaAutomatically adjusting the transmission power of PT, i.e. from p0Is changed into p1And then the received signal-to-noise ratio of CT is updated toGo to S3, where the equivalent channel gain of PR is found in S23The specific method comprises the following steps:
step 1, if the signal sent by the PT received by the PR is taken as an ideal signal, the PR receives the ideal signal
The signal-to-noise ratio can be obtained
Due to the fact thatThen the situation is not considered;
step 2, if the CT received by the PR forwards the amplified signal as an ideal signal, the PR receives the signalThe signal-to-noise ratio can be obtained
Then the equivalent channel gain is
As shown in figure 3 of the drawings,
in fig. 3(a), regions I and III make the relay link channel stronger than the direct link channel in case of the first hop, i.e. g1＞g0In region I, g of its EEECG according to theorem 1eIs constantly greater than g0In region III, the rootAccording to theory 2, when(or) With EEECG less than (or greater than) the main link channel gain g0. In region I, STD, PR sees the two signals as ideal, and in region III, whenIn time, similar to the traditional method, the PR direct view link signal is an ideal signal, and the relay link signal is interference; when in useIn time, the PR looks at the relay link signal as an ideal signal and the direct link signal as interference.
If in fig. 3(b), i.e. the II, IV area, the main link signals are all stronger than the trunk link signals. As can be seen, the EEECG is constantly less than the main link channel gain, g, for either STD or LTD0＜ge。
By combining the analysis, when the CT is in the I area, the non-interference detection can be ensured; when CT is in the III region, it is necessary to ensureInterference with the PR can be avoided.
S3, detecting the cognitive user area to obtain that the area I is an interference-free area, namely,
according to a preset threshold valueComparison S22 ofAnd the size of the sum, ifThen the region III is excluded from the list,
according to a preset threshold valueComparison S23And the size of the sum, ifThen region III is excluded, where K ∈ (0, 1).
As shown in figure 4 of the drawings,
FIGS. 4 (a) and (b) provide STD and LTD, respectivelyProcess with change of forwarding gain G value. By comparisonAndis determined without interference, i.e. whenCT does not interfere with PR, otherwise, there is interference. The specific detection process is G from GmaxBy DeltaGGradually adjust the step size of (1) and detect that it is in region I or III at that timeValue up toBut in region I, G is 35dB, while in region III,and isIt is possible to rely on this property, namelyTo distinguish the region I or III from the threshold, G is the numerical statistic, defined as Ω.
Theoretically, the forwarding gain G value is gradually reduced, the minimum decision threshold omega can be obtained without interference, and the minimum decision threshold omega is keptBut in practice the forward gain is in steps deltaGAdjusted so that CT gradual decision occursWhich can cause interference with the PR. To limit this interference situation, the threshold is stoppedIs adjusted toAs shown in fig. 4. By selecting proper K value, CT can effectively control the interference probability
FIG. 5 provides a PDF curve of the statistical test quantity Ω, where PR is randomly distributed over the coverage area of PT, the distance of PT-PR is 0.2km, and the test step Δ of the G valueGAt 0.5dB, the parameter K has a value of 0.9, and as can be seen from fig. 4, CT distinguishes the regions I and III by:
to maximize the decision probability, threshold GtCan be obtained by the following formula: pr { omega < GtI III } < 5% (i.e., the probability that CT, when in region III, is erroneously determined to be in region I), and the probability of successful selection of STD is: J-Pr { omega < Gt|I}。
In the inequality, Pr { I } and Pr { III } represent the probabilities of CT in the I region and III region, respectively.
Fig. 6 provides an interference probability curve when the CT performs relay-assisted detection at different PT-CT distances, and it can be seen that the interference probability is continuously increased from 0.7 to 1 for the K value, and is also continuously increased as the r distance is decreased. This is because the slope of the SNR curve at the CT end is at the point when the CT is closer to the PTThe larger the dot, as in FIG. 4- (b). The SNR reduction is larger when the step ag of the forwarding gain is a given value. At this time, the test statistic Ω obtained by CT is such thatIs more probable and thus the probability of interference is greater. In the rest of the simulations, we chose K0.9 such that the interference probability P isI＜5％。
As can be seen from fig. 7, on the premise that the interference probability is 5%, the successful selection probability is greater than 90% with the change of the PT-PR distance r.
Claims (3)
1. The detection method for judging the area where the cognitive user is located in the cross channel gain estimation is characterized by comprising the following steps of:
s1, setting B ∩ ellipse C part as region I, B- (circle B ∩ ellipse C) part as region III, B- (circle A-circle B) ∩ ellipse C part as region II, A- (region I + region II + region III) part as region IV, and C boundary of ellipse representing maximum allowable time delay TmIn downlink transmission, PT sends data to PR in adaptive modulation mode, and the signal-to-noise ratio is kept constant in the process of sending data, and CT end monitors the data from PT endSNR of transmission signal is compared with target SNR of PR, the interference-eliminated region is the primary detection cognitive user region, wherein the left focus of an ellipse C is PT, the right focus is PR, a circle B takes PT as the center of a circle, the distance from PT to PR is the radius, a circle A takes PT as the center of a circle, and T is the distance between PT and PRmaxIs a radius, said TmaxThe method comprises the following steps of (1) a major axis of an ellipse C, PT (potential transformer) as a main base station, PR (primary user), CT (cognitive transmitter), SNR (signal-to-noise ratio), and the following steps:
s11, PT adopts adaptive modulation mode to transmit power p initially0Sending a signal x (i, j) to the PR, maintaining the signal-to-noise ratio during transmissionConstant, PR terminal receives a signal denoted asWherein, for the desired operation, i, j are the number of samples and the number of blocks, np(i, j) is desirably 0, and the variance is σ2Of complex white gaussian noise, PR Is the channel coefficient of the PT-PR link, g0Is the channel gain between PT and PR;
s12, CT receives PT signalThe average signal-to-noise ratio received by the CT isWherein, is the channel coefficient of the PT-CT link, g1Is the channel gain between CT and PT, nc(i, j) is desirably 0, and the variance is σ2Complex white gaussian noise;
s13, g by comparing S110And g at S121Can be derived fromAndthe magnitude relationship of (1), i.e.
S14, the method according to S13Andthe magnitude relationship of (A) excludes the region with interference, i.e.ExclusionI.e. region II, IV;
s2, CT forwards signals from PT end to PR, PR gives out new SNR according to received relay link signals, and triggers CLPC system of PT-PR, PT transmitting power can make corresponding adjustment, CT obtains new SNR according to received new PT signals, wherein CLPC is closed loop power control, and the details are as follows:
s21, CT transmits x (i, j) to PT by transmitting signal x (i, j) to PTct(i,j)＝Gxcr(i, j), at this time, the PT receives a signal of
g2For the channel gain from CT to PR, G is the amplification of the signal x (i, j) sent by CT to PT, and α is the number of sample and block cycles respectively;
s22, if y is S21pIn (i, j)Andtime delay between < TmIf two signals are merged and regarded as one signal, the two signals comprise a PT transmitted signal and a CT forwarding amplified signal received by PR, and then the signals are processed according to a formulaDetermining equivalent channel gain for PRTo maintain a constant target signal-to-noise ratioThen CLPC will be based on the formulaAutomatically adjusting the transmission power of PT, i.e. from p0Is changed into p1' the received SNR of the CT is updated toProceeding to S3;
s23, if y is S21pIn (i, j)Andtime delay is more than or equal to TmSelecting one path with stronger signal as ideal signal and the other path as interference signal from PT transmitted signal and CT transmitted and amplified signal received by PR, and calculating equivalent channel gain of PRTo maintain a constant target signal-to-noise ratioThen CLPC will be based on the formulaAutomatically adjusting the transmission power of PT, i.e. from p0Is changed into p1And then the received signal-to-noise ratio of CT is updated toThe process proceeds to S3 where,is the channel coefficient of the CT-PR link;
s3, detecting the cognitive user area to obtain that the area I is an interference-free area, namely,
according to a preset threshold valueComparison S22 ofAnd the size of the sum, ifThen the region III is excluded from the list,
according to a preset threshold valueComparison S23And the size of the sum, ifThen region III is excluded where K is an empirical value.
2. The detection method for determining the area where the cognitive user is located in the cross-channel gain estimation as claimed in claim 1, wherein: s23 obtaining equivalent channel gain of PRThe specific method comprises the following steps:
step 1, if the signal sent by the PT received by the PR is taken as an ideal signal, the PR receives the ideal signalThe signal-to-noise ratio can be obtained
Due to the fact thatThen the situation is not considered;
step 2, if the CT received by the PR forwards the amplified signal as an ideal signal, the PR receives the signalThe signal-to-noise ratio can be obtained
，
The equivalent channel gain is
3. The detection method for determining the area where the cognitive user is located in the cross-channel gain estimation as claimed in claim 1, wherein: s3 the K ∈ (0, 1).
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| CN101419276A (en) * | 2008-12-10 | 2009-04-29 | 清华大学 | Method for positioning main user in cognition radio network |
| CN102790995A (en) * | 2012-08-16 | 2012-11-21 | 电子科技大学 | Information channel gain estimation method based on cognitive radio |
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| NL1016609C2 (en) * | 2000-11-15 | 2002-05-16 | Innospecial Products B V | Method and device for packaging cocoa beans and similar natural products. |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101419276A (en) * | 2008-12-10 | 2009-04-29 | 清华大学 | Method for positioning main user in cognition radio network |
| CN102790995A (en) * | 2012-08-16 | 2012-11-21 | 电子科技大学 | Information channel gain estimation method based on cognitive radio |
Non-Patent Citations (3)
| Title |
|---|
| Cross-Channel Gain Estimation with Amplify-and-Forward Relaying in Cognitive Radio;Lin Zhang,Guodong Zhao等;《2013 IEEE Golbal Communication Conference (GLOBECOM)》;20131231;第1003页-第1008页 * |
| Interference-Free Proactive Channel Gain Estimation in Cognitive Radio;Mengsheng Rui,Lin Zhang,Guodong Zhao等;《2014 IEEE 25th Annual International Symposium on Personal, Indoor,and Mobile Radio Communication (PIMRC)》;20141231;第453页-第458页 * |
| Relay-Assisted Proactive Channel Gain Estimation in Cognitive Radio;Lin Zhang、Guodong Zhao等;《2013IEEE78th Vehicular Technology Conference(VCT Fall)》;20121231;第1页-第5页 * |
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