KR20090096068A - Cognitive UWB System Using Code Sequence and Time Sequence in Cognitive UWB - Google Patents

Abstract

A code sequence for reducing complexity by reducing the number of detectors and a UWB system using the time sequence are provided to improve the efficiency of frequency by transmitting data in a channel which is not used in UWB(Ultra Wideband) system. Error rate of each sub-band is obtained through a detector(72). The error rate of the fixed threshold value according to each SNR(Signal to Noise Ratio) and each subband are compared with a detector(73). In case of the error rate which the detector is greater than the threshold value, the influenced sub-band is determined. The threshold value is defined about the respective other SNR in advance. The complexity is decreased due to 1/n instead of the detector of n only one detector.

Description

Cognitive UWB System Using Code Sequence and Time Sequence in Cognitive UWB}

The present invention relates to a cognitive UWB system, and more particularly, to a cognitive UWB system using a code sequence and a time sequence that reduce complexity and improve frequency efficiency by reducing the number of detectors.

Ultra Wide Band (UWB) is a communication technology that transmits data using an ultra wide frequency band. The basic principle is to receive and process what is sent by generating a short pulse, such as an impulse. Short pulses in time have spectral characteristics that spread widely in the frequency band. Generally speaking, a system whose bandwidth is over 20% of the center frequency. Unlike the conventional RF communication technology that carries information on a narrowband carrier, the ultra-wideband method uses a technology in which a series of pulse energy is transmitted in time and energy is distributed over a very wide band when viewed on a reception frequency band. It means.

This UWB system is relatively low in spectral power density over a much wider frequency band than a conventional narrowband system or a wideband CDMA system, resulting in a noise level, so that it can coexist with existing RF communications.

UWB uses the pulse signal directly without any modulation process, so the transceiver is simple, has low power consumption, and has strong characteristics in external environment such as multipath delay of the pulse signal, and also uses short pulses of ns (nano second). It is easy for location recognition and strong against noise. Therefore, it is attracting much attention as a core technology in a wireless personal area network (WPAN) such as a digital home network in the future.

Recently, the Federal Communications Commission (FCC) announced the UWB radio emission mask. It transmits with low power of noise level because wide band is used. However, the impulse signal not only affects other wireless systems, but also the UWB signal. In addition, different UWB Masks are used in different countries, so the system is also different. In order to reduce mutual interference and not be affected by national policies, adaptive frequency distribution is required for the channel environment.

For such frequency distribution, detection of narrowband interference must first be made. For interference detection, there is a conventional method that uses a detector for each sub-frequency so that the sub-frequency band is not used when interference exceeds a certain standard. However, this conventional method uses a detector for each sub-frequency band, which increases the complexity and degrades the performance of the entire system, requiring a more efficient detection method.

The present invention has been made to solve the above-described problems of the prior art, by using a detector for each sub-frequency, which is a problem of the prior art, by reducing the use of the detector to solve the problem of increasing complexity, The purpose of the present invention is to provide a cognitive UWB system using a simple code sequence and a time sequence by checking a group of three or three.

A cognitive UWB system using a code sequence and a time sequence according to the present invention for solving the above problems includes a channel encoder for error correction of data, a preamble inserter for inserting a preamble for time synchronization into the data, and Mask information inserter for flexible adaptation to different frequency emission regulations, a first cognitive UWB pulse generator for generating pulses from the mask information and channel environment information, and a pulse position modulator for modulating the pulses with temporal position changes. And an cognitive UWB transmitter comprising an RF transmitter for wirelessly transmitting data output to the pulse position modulator. And an RF receiver for wirelessly receiving data transmitted from the RF transmitter, a synchronization unit for time synchronization with the preamble to the data, and a code for each of a plurality of sub-frequency bands to check an error for checking channel interference. Or grouping a plurality of sub-frequency bands and sequentially checking for channel interference, detecting a channel environment, a mask information extracting unit extracting mask information received from the cognitive UWB transmitter, and the mask information. And a second cognitive UWB pulse generator for generating a pulse using a frequency band satisfying the frequency emission specification with channel environment information, a pulse position demodulator for demodulating the pulse, and for error correction of the demodulated data. A cognitive UWB receiver consisting of a channel decoder.

In addition, the spectrum detector detects an empty channel without narrowband interference.

The spectrum detector may include: a detector configured to sequentially check the sub-frequency band to detect an error rate; And a serial detector for comparing the error rate with a predetermined threshold to determine whether narrowband interference occurs.

The detector detects an error rate by grouping two or more adjacent sub-frequency bands and sequentially checking the groups.

The spectral detector may include: a detector for assigning different codes to each sub-frequency band and detecting an error rate of the code for each sub-frequency band; And a serial detector for comparing the error rate with a predetermined threshold to determine whether narrowband interference occurs.

Here, the serial detector weights each error code in each sub-frequency band, and if the weight is higher than a predetermined reference value, the serial detector determines that narrowband interference exists in the corresponding sub-frequency band.

A cognitive UWB system using a code sequence and a time sequence according to the present invention configured as described above may satisfy a mask regulation, which is a frequency emission regulation among divided frequencies, and may be used in combination with other frequencies without interference from other systems. Not only is it easy to avoid interference, but the wider frequency band can be used depending on the situation, which improves the performance of the system, and transmits data at a higher power than the UWB frequency emission regulation on unused channels. The effect can be increased.

In addition, by using a single detector by applying a time and code sequence to a detection method for determining whether an interference effect of another system is applied to each sub-frequency band, increasing complexity can be reduced to 1 / n.

Hereinafter, with reference to the accompanying drawings will be described specific details and embodiments of the present invention.

1 is a block diagram schematically illustrating a cognitive UWB system according to the present invention. As shown in the figure, the cognitive UWB system according to the present invention comprises a cognitive UWB transmitter 10 and a cognitive UWB receiver 30.

In addition, the cognitive UWB transmitter 10 includes a channel encoder 11, a preamble insert 12, a pulse position modulator 13 and a radio frequency transmitter. And 14), a mask information inserter 15 and a first cognitive UWB pulse generator 16.

Here, the channel encoder 11 is provided for error detection and correction when transmitting data input to the cognitive UWB transmitter 10, and the data passed through the channel encoder 11 is timed to the data. The preamble inserter 12 inserts a preamble for synchronization.

In addition, the mask information insertion unit 15 has a frequency defined so as not to interfere with an existing user such as PCS, WLAN, WiBro, S-DMB, etc. defined in different frequency bands according to each country in each country. Insert the mask information, which is the emission regulation.

The first cognitive UWB pulse generator 16 generates a UWB pulse using the mask information and the channel environment.

In addition, the pulse position modulator 13 selects the pulse generated by the cognitive UWB pulse generator 16 at a multiple of the maximum frequency included in the information content to transmit the repetition frequency of the constant amplitude pulse, and inputs the input signal. The data is modulated by a temporal position change that modulates by converting the generation position of the pulse.

And an RF transmitter 14 for wirelessly transmitting the data output from the pulse position modulator 13.

Meanwhile, the cognitive UWB receiver 30 includes a channel decoder 31, a synchronizer 32, a pulse position demodulator 33 (PPM), and an RF receiver 34. The mask information extractor 35 includes a mask information extrator 35, a cognitive UWB pulse generator 36, and a spectrum detector 37.

In addition, the RF receiver 34 is provided to receive data transmitted from the RF transmitter 14 and to use it as an input of the cognitive UWB receiver 30.

In addition, the synchronizer 32 is provided for synchronization for wireless communication with the cognitive UWB transmitter 10 with respect to the input data input to the RF receiver 34, and before modulating the data. Synchronize with the preamble.

In addition, the spectrum detector 37 detects the preamble signal input from the cognitive UWB transmitter 10 to find an empty channel that is not occupied, and acquires spectrum information. The mask information extractor 35 acquires the spectrum information. Mask information sent from the UWB transmitter 10 is obtained and extracted.

In addition, the cognitive UWB pulse generator 36 of the cognitive UWB receiver 30 uses the channel environment information of the spectrum detector 37 and the mask information of the mask information extractor 35 in the non-occupied frequency band. In order to flexibly change and efficiently operate, a pulse corresponding to the frequency is generated.

In addition, the pulse position demodulator 33 detects the position of the pulse by using the pulse generated from the cognitive UWB pulse generator 36, and demodulates the data by the temporal position change of the signal.

Finally, the modulated data is output by detecting and correcting errors in the channel decoder 31.

2 (a) is a diagram showing a band plan of a frequency band used in a cognitive UWB system according to the present invention. By dividing the band's frequency into dozens of sub-bands, frequency bands affected by interference from other systems can be avoided. Figure 2 (b) shows that interference occurs in the frequency band divided according to the band plan (band plan) of Figure 2 (a). Since the second, fourth, fifth, and seventh sub-frequency bands are affected by interference, except the four bands, the remaining frequency bands are used for communication.

Figure 3 (a) shows the UWB pulse generated by the cognitive UWB pulse generator excluding the sub-frequency band affected by the interference of other systems. The pulse obtained as described above also has the characteristics of the UWB pulse, and the PSD (Power Spectral Density) of the pulse in consideration of the mask information and the channel condition is generated as shown in FIG.

<Spectrum Detector>

4 is a block diagram illustrating a basic detection technique in a conventional cognitive UWB system.

Referring to FIG. 4, a detector 51 is required for each sub-frequency band in order to determine whether or not interference from another system is received when receiving data from a transmitter. The data passing through the detector 51 can use only the sub-frequency band without the influence of interference by the parallel detector 52.

FIG. 5 is a block diagram illustrating a detector part applying a time sequence method to a basic detection method in cognitive UWB.

After the detector 72 obtains the error rate of each subband, the detector 73 compares with a constant threshold according to each SNR, and if the error rate is larger than the threshold, the subband is determined to be affected by narrowband interference. Do not use.

However, it is assumed that the thresholds at this time are predefined for different SNRs. Using the statistical mathematical theory, the threshold of each SNR is preset in consideration of the BER (Beat Error Rate) when there is no interference proposed in the standard.

Each sub-frequency band 71 can be detected by the serial detector 73 by the serial detector 73 using only one detector 72 in time order. Using only one detector reduces the complexity to 1 / n by using a detector for each subfrequency in a basic detection technique.

FIG. 6 shows detection of each sub-frequency sequentially using a time sequence technique in cognitive UWB.

FIG. 7 is a diagram illustrating a method of grouping and detecting two subfrequencys when using a time sequence technique in cognitive UWB. In order to improve the complexity by checking the existing sub frequencies one by one, the time complexity can be reduced because the two sub frequencies are bundled and checked.

FIG. 8 is a block diagram illustrating a detection portion in which a code sequence method is applied to a basic detection technique in cognitive UWB. By applying different codes 91 to each sub-frequency band, only one detector 92 can be used to determine whether the interference of another system is affected by the serial detector 93. By using only one detector, the basic detection technique reduces the complexity to 1 / n by using a detector for each subfrequency.

9 is a diagram illustrating a state affected by interference of another system when a code is applied to each sub-frequency when using a code sequence technique in cognitive UWB. It can be seen that the second, fourth, fifth and seventh sub-frequency bands are affected by the interference.

FIG. 10 shows a metric of each sub-frequency affected by interference in FIG. 9. As a result of notching the largest negative frequency band of the accumulated weight value, it can be confirmed that the same value corresponds to the negative frequency band affected by the interference in FIG. 9.

The simulation environment uses an impulse system of the IEEE 802.15.4a Task group as shown in Table 1 below, and a modulation scheme uses a 2 PPM scheme, which transmits one bit of data at a pulse position.

The demodulation method uses the energy detection method, the channel coding uses the 1/2 convolution code, and the characteristics of the channel are shown in Table 2.

Under the above assumptions, FIG. 11 compares the cognitive UWB system when the time system according to the present invention is applied to the existing system. You can see that the check time is reduced by grouping m by detection.

12 is a comparison of the cognitive UWB system when the existing system and the time sequence method according to the present invention are applied in the indoor environment CM1, 2 and the industrial environment CM8. In a conventional system, CM1 with a direct pass has 2dB better functionality than CM2, but in this case it is subject to external interference, while in a cognitive UWB system that selectively uses only good channels, 4dB on the same channel. By removing the interference, only good channels are used, and the CM1 and 2 both show a 4dB performance improvement.

FIG. 13 is a comparison between a conventional system and a cognitive UWB system according to the present invention in an indoor environment (CM1, 2), where CM1 is an LOS situation and a direct path exists, and CM2 is not an NLOS situation. to be. Compared with the conventional system, the cognitive UWB system removes 3dB of interference on the same channel to use only good channels, and the CM1 and 2 show a 3dB performance improvement.

14 is a comparison of the conventional system and the cognitive UWB system in the external environment (CM7,8), CM7 is the LOS situation, CM8 is the NLOS situation, LOS situation CM7 has a 3dB better performance.

In addition, the external environment performs worse than the indoor environment, because a system that communicates with low power is weakened by an external strong frequency environment, but also shows a performance improvement of about 2 dB even in this situation.

In this way, when the time sequence method and the code sequence method are applied to the cognitive UWB system, the BER performance is equal to about 2dB by using a good channel for wireless communication by avoiding interference from other systems even in the same environment as in the previous case. The performance is shown and the complexity is reduced to 1 / n by using one detector.

As described above, a cognitive UWB system using a code sequence and a time sequence according to the present invention has been described with reference to the illustrated drawings. However, the present invention is not limited by the embodiments and drawings disclosed herein, and the technical concept is protected. It can be applied within the range.

1 is a block diagram schematically illustrating a cognitive UWB system in accordance with the present invention.

2 is a diagram illustrating a bandplan of a cognitive UWB system according to the present invention and a plurality of sub-frequencyes affected by interference of another system.

Figure 3 is a combination of the pulses of each sub-frequency by detecting the interference of other systems of the cognitive UWB system according to the present invention and a diagram showing the pulse in PSD.

4 is a diagram illustrating a basic detection method of a cognitive UWB system according to the present invention.

5 is a block diagram showing a detection part of applying the time sequence method to the detection method of the cognitive UWB system according to the present invention.

6 is a diagram schematically illustrating a sequential detection method applying a time sequence of a cognitive UWB system according to the present invention.

7 is a diagram schematically illustrating grouping detection of a time sequence detection method of a cognitive UWB system according to the present invention.

8 is a block diagram showing a detection part of applying the code sequence method to the detection method of the cognitive UWB system according to the present invention.

9 is a diagram showing whether or not interference of the sub-frequency applied to the code sequence scheme in the cognitive UWB system according to the present invention.

FIG. 10 is a diagram illustrating detection of interference of sub-frequency applying a code sequence scheme to a cognitive UWB system according to the present invention through weights of metrics.

11 is a graph comparing performance by applying m time sequence detection schemes to groupings in a cognitive UWB system according to the present invention.

12 is a graph comparing the performance of the conventional system with the application of the time sequence detection method to the cognitive UWB system according to the present invention.

Figure 13 is a graph comparing the application of the code sequence detection method to the cognitive UWB system according to the present invention and the existing system performance in the indoor environment (CM1,2).

14 is a graph comparing the application of the code sequence detection method to the cognitive UWB system according to the present invention in the industrial environment (CM7,8).

      <Brief description of reference numerals for the main parts of the drawings>

1: Cognitive UWB System 10: Cognitive UWB Transmitter

11: channel encoder 12: preamble insert

13: pulse position modulator 14: RF transmitter

15: Mask Information Insertion 16: Cognitive UWB Pulse Generator

16a: basic pulse generator 16a ': frequency generator

16a '': Sinc Windows 16b: PMC Generator

16c: Multiplier 16d: Adder

30: Cognitive UWB Receiver 31: Channel Decoder

32: synchronizer 33: pulse position demodulator

34: RF receiver 35: mask information extraction unit

36: Cognitive UWB Pulse Generator 37: Spectrum Detector

50: basic interference detection technique 51: detector

52: parallel detector 70: time sequence detector

71: negative frequency 72: detector

73: serial detector 90: code sequence detector

91: Code of each subfrequency 92: Detector

93: detector

Claims (6)

A channel encoder for error correction of data, a preamble inserter for inserting a preamble for time synchronization into the data, a mask information inserter for fluid adaptation to different frequency emission regulations, the mask information and channel environment information A cognitive UWB transmitter comprising a first cognitive UWB pulse generator for generating a low pulse, a pulse position modulator for modulating the pulse with a temporal position change, and an RF transmitter for wirelessly transmitting data output to the pulse position modulator. ; And RF receiver for wirelessly receiving data transmitted from the RF transmitter, a synchronization unit for time synchronization with the preamble to the data, and a code for a plurality of sub-frequency bands to check an error by checking an error by checking an error A spectral detector for detecting a channel environment by sequentially examining a plurality of sub-frequency bands for channel interference, a mask information extractor for extracting mask information received from the cognitive UWB transmitter, and the mask information and channel A second cognitive UWB pulse generator for generating a pulse using a frequency band satisfying the frequency emission specification with environmental information, a pulse position demodulator for demodulating the pulse, and a channel decoder for error correction of the demodulated data Cognitive UWB receiver consisting of; A cognitive UWB system using a code sequence and time sequence comprising a. The method according to claim 1, The spectral detector detects an empty channel free of narrowband interference. The method according to claim 1, The spectrum detector includes one detector for sequentially detecting the sub-frequency band to detect an error rate; And A cognitive UWB system using a code sequence and a time sequence comprising a serial detector for comparing the error rate with a predetermined threshold to determine whether or not narrowband interference. The method according to claim 3, The detector is a cognitive UWB system using a code sequence and a time sequence, characterized in that for detecting the error rate by grouping two or more adjacent sub-frequency bands, and sequentially checking for each group. The method according to claim 1, The spectrum detector may include: a detector for applying a different code to each sub-frequency band and detecting an error rate of a code for each sub-frequency band; And A cognitive UWB system using a code sequence and a time sequence comprising a serial detector for comparing the error rate with a predetermined threshold to determine whether or not narrowband interference. The method according to claim 5, The serial detector weights whenever an error occurs in the code for each sub-frequency band. If the weight is higher than a predetermined reference value, the serial detector uses a code sequence and a time sequence to determine that narrowband interference exists in the corresponding sub-frequency band. Ever UWB System.

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