KR101068974B1 - Spectrum sensing apparatus for cognitive system - Google Patents

Abstract

The present invention relates to a technique for determining whether a licensed user occupies the spectrum by a delay diversity scheme or a technique of performing a local decision by combining two antenna signals in a wireless recognition system. The present invention comprises: a plurality of local determination units including an adder for adding a high frequency signal directly transmitted through an antenna after being transmitted from a licensed user station and a high frequency signal delayed by a predetermined time through a delay unit; And a global determination unit that makes an overall determination as to whether or not the licensed user uses the spectrum based on local determination by the plurality of local determination units. Accordingly, the spectrum detection performance of the wireless cognitive device is improved and the complexity is reduced.

Wireless Cognitive System, Licensed User, Unlicensed User, Spectrum Sensing, Delay Diversity

Description

SPECTRUM SENSING APPARATUS FOR COGNITIVE SYSTEM}

The present invention relates to a spectrum sensing technique for detecting a licensed user in a wireless recognition system. In particular, the present invention relates to a delay diversity scheme or a combination of two antenna signals to perform local decision. A spectral sensing device having high performance and low complexity in a wireless cognitive system that is suitable.

Spectrum sensing technology in a wireless cognitive system is a technology that examines the spectrum of a frequency band to see if a licensed user has appeared on that frequency channel while the wireless cognitive device is using the licensed user's frequency channel.

However, since the wireless recognition system should guarantee the vested interest in the use of the frequency channel of the licensee as much as possible, there is a need for a spectrum sensing technology that can more accurately detect whether the radio recognition device has appeared in the corresponding frequency channel of the licensee. .

In order to improve the performance of spectrum sensing, cooperative spectrum sensing is used to determine the use of spectrum by licensed users after sensing the spectrum by using a plurality of wireless cognitive devices.

FIG. 1 shows a conventional wireless cognitive system to which cooperative spectrum sensing technology is applied, and is composed of a licensed user station 11, a plurality of wireless cognitive devices 12A-12N, and a convergence center 13.

A plurality of wireless cognitive devices 12A-12N use an energy detection or cyclo-stationary detection method for signals in each frequency band to determine whether a licensed user uses a wireless channel. Use

Then, the wireless recognition device 12A-12N determines whether the licensed user uses the wireless channel as described above, and transmits the result of the determination to the convergence center 13. The wireless recognition device 12A-12N and the fusion center 13 may be connected by wire or wirelessly. Generally, each wireless recognition device 12A-12N should be separated by a distance or more to ensure independence of each channel. It is possible to ensure the reliability of their sensing results. Therefore, the determination result of the radio recognition device 12A-12N is an example of being transmitted to the convergence center 13 as a radio signal RF.

However, in the case of transmitting the determination result of the radio recognition device 12A-12N to the fusion center 13 as a radio signal RF, the noise and the interference signal are affected during the transmission process. Therefore, the signal received by the fusion center 13 from the radio recognition device 12A-12N becomes a signal different from the original signal, so that an error in determination may occur.

In another conventional technique for preventing such an error and improving spectrum sensing performance, a diversity technique using multiple antennas ANT_1 to ANT_N in one wireless recognition device 22 is used as shown in FIG. 2.

FIG. 3 is a detailed block diagram of a wireless recognition device as shown in FIG. 2, as shown in FIG. 2, which includes an antenna ANT_1, a high frequency and intermediate frequency signal processor 31A, an A / D converter 32A, and power / characteristics. N local determination units 30A to 30N including the measuring unit 33A and the local determination unit 34A are provided, and the global determination unit 35 connected to the output terminals of the N local determination units 30A to 30N is provided. It is provided.

After transmitting from the licensed user station, the high frequency signal received through the antenna ANT_1 is converted into a baseband signal by the high frequency and intermediate frequency signal processor 31A, and then converted into a digital signal through the A / D converter 32A. do.

The power / characteristic measuring unit 33A detects power or characteristics (eg, periodicity) of the digital signal output from the A / D converter 32A.

The local determiner 34A makes a local decision on whether to use the spectrum of the licensed user based on the power or characteristic detected by the power / feature measurer 33A.

The above description shows that the local determination unit 30A locally determines the signal received through one antenna ANT_1, and the remaining local determination units 30B to 30N also determine the corresponding antennas ANT_2 to ANT_N. Local judgment is made with the same process for the received signal.

Then, the global judging unit 35 determines whether or not the licensed user uses the spectrum based on the local decision made by the local judging units 30A to 30N in order to make a reliable and efficient decision on whether or not the licensed user uses the spectrum. A global decision is made.

However, in the case of a wireless recognition system employing a diversity scheme in which a plurality of antennas are applied to one wireless recognition device, additional hardware and space are required as the number of additional antennas, which increases the complexity of the wireless recognition device. There was this.

Accordingly, an object of the present invention is to determine whether a licensed user occupies the spectrum by applying a delay diversity scheme in a wireless recognition system.

Another object of the present invention is to determine whether a licensed user occupies the spectrum by applying a technique of performing a local decision by combining two antenna signals in a wireless recognition system.

The objects of the present invention are not limited to the above-mentioned objects. Other objects and advantages of the invention will be more clearly understood by the following description.

delete

delete

delete

delete

delete

delete

delete

In order to achieve the above object, the present invention provides an antenna for receiving a high frequency signal transmitted from a licensed user station, a delay unit for delaying the high frequency signal received through the antenna by a predetermined time, and received through the antenna. An adder for adding the high frequency signal and the delayed signal by the delayer, a high frequency and intermediate frequency signal processor for converting a high frequency signal output from the adder into a baseband signal, and a high frequency and intermediate frequency signal processor An A / D converter for converting the baseband signal into a digital signal, a power / characteristic measuring unit for detecting power or characteristics of the digital signal output from the A / D converter, and the power / characteristic measuring unit Local judgment of the licensee's use of the spectrum based on power or characteristics ( a plurality of local decision units each including a local decision unit for making local decisions; And a global decision unit that globally determines whether or not the licensed user uses spectrum based on local decisions of the plurality of local decision units.
In addition, in order to achieve the above object, the present invention is to combine the first and second antennas and the high-frequency signals received through the first and second antennas, respectively, for receiving high-frequency signals transmitted from a licensed user station. A combiner, a high frequency and intermediate frequency signal processor for converting a high frequency signal output from the combiner into a baseband signal, and an A / D for converting the baseband signal converted by the high frequency and intermediate frequency signal processor into a digital signal A converter, a power / characteristic measuring unit for detecting power or characteristics of the digital signal output from the A / D converter, and whether or not the licensee uses spectrum based on the power or characteristics detected by the power / characteristic measuring unit A plurality of local determination units each comprising: a local determination unit making local decisions about the local decision unit; And a global decision unit that globally determines whether the licensed user uses the spectrum based on local decisions of the plurality of local decision units.

delete

delete

delete

delete

delete

delete

The present invention is to determine whether the licensed user occupies the spectrum by a delay diversity scheme or a combination of two antenna signals in a wireless recognition system to perform local decision, thereby improving the spectrum detection performance of the wireless recognition device. The effect is to reduce the degree.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

4 is a block diagram of a spectral sensing device having high performance and low complexity in a wireless recognition system according to the present invention. As shown therein, an antenna ANT_1, a delay 41A, an adder 42A, The high frequency and intermediate frequency signal processor 43A, the A / D converter 44A, the power / characteristics measurer 45A and the local determiner 46A constitute one local determiner 40A, The apparatus further includes a plurality of local determination units 40B to 40M configured as described above, and a global determination unit 47 connected to output terminals of the plurality of local determination units 40A to 40M.

The high frequency signal received through the antenna ANT_1 after being transmitted from the licensed user station is directly input to one input terminal of the adder 42A, and on the other hand, is delayed by a predetermined time through the delay unit 41A and then added to the adder ( 42A) is input to the other input terminal and added to the signal input to the one input terminal.

However, in order to prevent the two signals input to one side and the other input terminal of the adder 42A from overlapping and to ensure independence, a time delayed through the delay unit 41A after being received through the antenna ANT_1. Must be set longer than the maximum delay path delay for the entire path (multi-path). Here, the entire path means all paths between the transmitter and the receiver, and the maximum delay time of the entire path means the maximum delay time that can occur in all paths between the transmitter and the receiver.

In the wireless recognition system as shown in FIG. 4, since the N / 2 normal antenna paths directly inputted from the antenna to the adder and the N / 2 delayed antenna paths inputted to the adder after being delayed through the delay from the antenna, the entire reception path N pieces.

The high frequency signal output from the adder 42A is converted into a baseband signal by the high frequency and intermediate frequency signal processor 43A, and then converted into a digital signal through the A / D converter 44A.

The power / characteristic measuring unit 45A detects power or characteristics (eg, periodicity) of the digital signal output from the A / D converter 44A.

The local determiner 46A makes a local decision on whether to use the spectrum of the licensed user based on the power or characteristic detected by the power / characteristic measurer 45A.

The above description shows that the local determination unit 40A locally determines a signal received through one antenna ANT_1, and the other local determination units 40B to 40M also have corresponding antennas ANT_2 to ANT_N / 2. Local determination is made in the same process for the signal received through.

In addition, the global judging unit 47 determines whether the licensed user uses the spectrum based on the local decision made by the local judging units 40A to 40M in order to make a reliable and efficient decision on whether or not to use the spectrum of the licensed user. Global Decisions will be made.

5 and 6 illustrate detection probabilities of wireless cognitive devices to which conventional diversity is applied and wireless cognitive devices to which delay diversity of the present invention is applied when AND and OR are determined.

In the case of the AND determination method, it is determined that the licensed user exists only when the results of the local decision, that is, the individual sensing results are all “1”, and when any one of the individual sensing results is “0”, the licensed user. Is determined to not exist in the spectrum. In contrast, the oar determination method determines that a licensed user exists if any one of the individual sensing results is "1".

In the case of applying the AND determination method in FIG. 5, it can be seen that the detection probability decreases as the number of antennas increases. Since the principle of the end determination method is determined by the global sensing only when the principle of the local sensing is detected by all local sensing antennas, the probability that all antennas will simultaneously detect the detection as the number of antennas increases. Decreases. Therefore, the detection probability of the global determination unit 47 is also reduced. In addition, it can be seen that the detection performance is improved in all cases including the case where the number of antennas is the same when the delay diversity is applied than when the antenna diversity is applied. In fact, 8, 4, and 2 antennas of antenna diversity are the same as those of 4, 2, and 1 antennas of delay diversity, based on the number of paths of a received signal. However, even when the paths are the same, it can be seen that the delay diversity is much better than the antenna diversity.

Fig. 6 shows the detection performance results in the case of applying the oar determination method. Here, when the number of antennas is the same, it can be seen that delay diversity exhibits better performance than antenna diversity. However, if you compare the same number of paths, you can see that the performance is almost the same.

The experimental results show that the same number of antennas significantly improves the spectrum detection performance by adding delay elements without many modifications of the receiver. In the case where the number of paths is the same, it can be seen that the case of applying delay diversity has a similar or superior performance and lower complexity than the case of applying antenna diversity.

7 is another exemplary block diagram of a spectrum sensing device using diversity of a radio recognition system according to the present invention. As shown therein, the antennas ANT_1 and ANT_2, the combiner 71A, high frequency and intermediate frequency, The local processor 70A is constituted by the signal processor 72A, the A / D converter 73A, the power / characteristics measurer 74A, and the local determiner 75A. The apparatus further includes determining units 70B to 70M, and includes a global determining unit 76 connected to output terminals of the plurality of local determining units 40A to 40M.

The radio frequency signals received from the licensed user station and received through the antennas ANT_1 and ANT_2, respectively, are input to both input terminals of the combiner 71A and are combined with each other.

The combiner 71A combines the received high frequency signals and calculates and outputs 1/2 to output their average values.

The process of the combined signal is the same as in FIG.

That is, the high frequency signal output from the combiner 71A is converted into a baseband signal by the high frequency and intermediate frequency signal processor 72A, and then converted into a digital signal through the A / D converter 73A.

The power / characteristic measuring unit 74A detects power or characteristics (eg, periodicity) of the digital signal output from the A / D converter 73A.

The local determiner 75A makes a local decision on whether to use the spectrum of the licensed user based on the power or characteristic detected by the power / characteristic measurer 74A.

The above description shows that the local determination unit 70A determines locally the signal received through the pair of antennas ANT_1 and ANT_2, and the remaining local determination units 70B to 70M also use the corresponding antenna. Local judgment is made on the received signal in the same process.

In addition, the global judging unit 76 may determine whether the licensed user uses the spectrum based on the local determination of the local judging units 70A to 70M in order to make a reliable and efficient determination of whether the licensed user uses the spectrum. A global decision is made.

Compared to the embodiment of FIG. 7 described above with the embodiment of FIG. 4 to which delay diversity is applied, the number of antennas is doubled, while no delay element is required.

FIG. 8 compares the performance of the system of FIG. 7 and the system of FIG. 4 to which delay diversity is applied.

As can be seen in FIG. 8, the detection probability performance has almost no difference in performance when the delay diversity is applied and when the combiner is applied to the antenna diversity. Therefore, it is advantageous to use the system of FIG. 7 when the precise delay element cannot be applied or when the cost of the antenna is lower than that of the delay element.

Although the preferred embodiment of the present invention has been described in detail above, the scope of the present invention is not limited thereto, and may be implemented in various embodiments based on the basic concept of the present invention defined in the following claims. Such embodiments are also within the scope of the present invention.

1 is a block diagram of a conventional wireless cognitive system to which cooperative spectrum sensing technology is applied.

2 is a block diagram of a conventional wireless cognitive system to which antenna diversity is applied.

3 is an internal block diagram of a conventional wireless cognitive device to which antenna diversity is applied.

4 is a block diagram of a spectrum sensing device having high performance and low complexity in a wireless cognitive system according to the present invention.

5 is a graph of an AND determination method comparing performance of antenna diversity and delay diversity.

6 is a graph of an ora determination method comparing performance of antenna diversity and delay diversity.

7 is a block diagram of another embodiment of a spectrum sensing device having high performance and low complexity in a wireless cognitive system in accordance with the present invention.

8 is a graph comparing performance when antenna diversity and combiner are applied and when delay diversity is applied;

*** Description of the symbols for the main parts of the drawings ***

40A-40M: Local Decision Unit 41A-41M: Delay

42A-42M: Adder 43A-43M: High Frequency and Intermediate Frequency Signal Processing Unit

44A-44M: A / D Converter 45A-45M: Power / Character Measuring Unit

46A-46M: Local Judgment 47: Global Judgment

Claims (4)

An antenna for receiving a high frequency signal transmitted from a licensed user station; A delay unit for delaying the high frequency signal received through the antenna by a predetermined time period; An adder for adding the high frequency signal received through the antenna and the signal delayed by the delay unit; A high frequency and intermediate frequency signal processor for converting a high frequency signal output from the adder into a baseband signal; An A / D converter for converting the baseband signal converted by the high frequency and intermediate frequency signal processing unit into a digital signal; A power / characteristic measuring unit which detects power or characteristics of the digital signal output from the A / D converter; A plurality of local determination units each comprising: a local determination unit locally determining whether the licensed user uses a spectrum based on power or characteristics detected by the power / characteristic measurement unit; And And a global decision unit that globally determines whether the licensed user uses the spectrum based on local decisions of the plurality of local decision units. The method of claim 1, wherein the preset time is a maximum delay time that can be generated when receiving the high frequency signal through a plurality of antennas in order to prevent the high frequency signal received through the antenna and the signal delayed by the delay unit from overlapping. Spectrum sensing device of a wireless cognitive system, characterized in that set longer. First and second antennas for receiving high frequency signals transmitted from a licensed user station, respectively; A combiner for coupling the high frequency signals received through the first and second antennas; A high frequency and intermediate frequency signal processor for converting a high frequency signal output from the combiner into a baseband signal; An A / D converter for converting the baseband signal converted by the high frequency and intermediate frequency signal processing unit into a digital signal; A power / characteristic measuring unit detecting power or characteristics of the digital signal output from the A / D converter; A plurality of local determination units each comprising: a local determination unit locally determining whether the licensed user uses a spectrum based on power or characteristics detected by the power / characteristic measurement unit; And And a global decision unit that globally determines whether the licensed user uses the spectrum based on local decisions of the plurality of local decision units. 4. The apparatus of claim 3, wherein the combiner is configured to output an average of the combined signal.

Images