JP2006203410A - Interference wave detecting circuit and transmitter/receiver having this interference wave detecting circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable detecting an interference wave with a simple circuit configuration in a transmitter/receiver of digital radio communication. <P>SOLUTION: This apparatus is provided with a frequency converting circuit 12 for performing frequency conversion for a reception signal to output a reception IF signal; a quadrature detection circuit 13 for performing quadrature detection processing for the reception IF signal to output a reception baseband signal; a power detection circuit 16 for detecting power of the reception IF signal to output RSSI; an equalization circuit 14 for correcting a transmission path distortion for the reception baseband signal by adaptive signal processing to output an equalized reception baseband signal to a decoding circuit 15, and outputting equalization error power conversion CNIR (carrier to noise and interference ratio) to be generated in a process of the adaptive signal processing; and an interference wave detecting means 17 for referring to the RSSI to be detected by the circuit 16 and the equalization error power conversion CNIR to be output by the circuit 14 and outputting interference wave information for controlling a used frequency band. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a transceiver for digital wireless communication, and more particularly to an interference wave detection circuit and a transceiver having the interference wave detection circuit.

  As a conventional interference wave detection method, a method of stopping transmission waves for the purpose of performing interference wave detection and determining the presence or absence of interference from the power received on the frequency used for communication is used. There is also a method in which a non-transmission symbol for interference wave detection is set in a radio frame, and the interference state is always observed. (See Patent Document 1)

As another interference wave detection device, an RF-AGC circuit that performs auto gain control on an RF signal and an IF-AGC circuit that performs auto gain control on an intermediate frequency signal are separately provided, and these AGC circuits are further provided. There are some which are provided with an interference wave detection circuit that receives the RF-RSSI signal and the IF-RSSI signal generated in step 1 and detects the presence and intensity of the interference wave and the desired wave independently. For example, by comparing these RSSI signals, this interference wave detection circuit identifies the state where only the interference wave exists, the state where both the interference wave and the desired signal exist, and the state where only the desired wave exists, and transmits the transmission power. Is to control. (See Patent Document 2)
Japanese Patent No. 2590441 JP 2004-180156 A

In order to perform accurate measurement using the conventional interference wave detection method, a section in which data transmission is not performed is necessary, and a reduction in frame efficiency is inevitable. Further, since a circuit for stopping the transmission signal is required, there is a problem such as an increase in circuit scale.
Further, the interference wave detection device has a problem that the detection accuracy of the interference wave is not sufficient.
The present invention has been made to remedy such drawbacks, and it is an object of the present invention to provide an optimum interference wave detection method for a radio communication system having an equalizer in a receiving circuit.

  In order to achieve the above object, an interference wave detection circuit according to the present invention includes a frequency conversion circuit that amplifies and frequency-converts a received signal and outputs a received IF signal, and performs orthogonal detection processing on the received IF signal. A quadrature detection circuit that outputs a reception baseband signal composed of two I-phase and Q-phase sequences, a power detection circuit that detects the power of the reception IF signal and outputs RSSI, and adapts the reception baseband signal The signal processing corrects the transmission path distortion and the waveform distortion generated in the transmitter / receiver to output the equalized reception baseband signal to the decoding circuit, and the equalization error power generated in the process of the adaptive signal processing as symbol power. An equalization circuit for outputting a normalized equalization error power conversion CNIR, an RSSI and a CNIR respectively corresponding to the input level of the receiver in a certain interference situation; The conversion data is stored in advance, the RSSI / CNIR conversion circuit that outputs the RSSI conversion CNIR from the RSSI detected by the power detection circuit with reference to the conversion data, and the RSSI conversion CNIR from the RSSI / CNIR conversion circuit and the And an interference wave detecting means comprising a comparison circuit for comparing the equalization error power conversion CNIR from the equalization circuit.

  The transceiver according to the present invention is a transceiver in a digital radio communication system, wherein the receiver amplifies and frequency-converts a received signal and outputs a received IF signal, and the received IF signal. A quadrature detection circuit that performs quadrature detection processing and outputs a received baseband signal consisting of two I-phase and Q-phase sequences, a power detection circuit that detects the power of the received IF signal and outputs RSSI; The received baseband signal is subjected to adaptive signal processing to correct transmission path distortion and waveform distortion generated in the transmitting / receiving device, and the equalized received baseband signal is output to the decoding circuit, and is generated in the adaptive signal processing process, etc. Equalization error power conversion CNIR output equalization circuit, RSSI detected by the power detection circuit, and equalization error power conversion output by the equalization circuit Interference wave detecting means for outputting interference information for controlling the frequency band used for communication with reference to NIR, and the transmitter switches the used frequency as needed based on the interference information A communication frequency control circuit is provided.

  As described above in detail, by implementing the present invention, there is an advantage that interference waves can be detected without adding a special circuit for detecting the interference waves.

  The present invention will be described in detail below. FIG. 1 is a block circuit diagram of a configuration example of a receiver according to the present invention, CNIR (Carrier to Noise and Interference Ratio) and RSSI (Received Signal Strength Indicator) with respect to the receiver input level. 2), FIG. 3 is a graph showing an example of the influence of an interference wave on CNIR, FIG. 4 is a block circuit diagram of a configuration example of an interference wave detection unit according to the present invention, and FIG. FIG. 5 is a graph showing an example of the / CNIR conversion table, and FIG. 6 is a graph showing an example of the calculation result by the expression (2) in the comparison circuit of the interference wave detection unit. The detection of the interference wave is performed by the receiver alone.

  In the receiver 10 shown in FIG. 1, a signal transmitted from a transmitter (not shown) is received by an antenna 11, and the received signal is amplified and frequency converted by a frequency conversion circuit 12 to obtain a received IF signal. Output. The quadrature detection circuit 13 performs quadrature detection processing on the received IF signal and outputs a received baseband signal composed of two I-phase and Q-phase sequences. Further, the power detection circuit 16 detects the power of the reception IF signal described above, and outputs RSSI to the interference wave detection unit 17. As a circuit element of the power detection circuit 16, a log amplifier or the like is generally used.

  The reception baseband signal output from the quadrature detection circuit 13 is subjected to adaptive signal processing in the equalization circuit 14 to correct transmission path distortion and waveform distortion generated in the transmission / reception apparatus, and the equalization reception baseband signal is decoded into a decoding circuit 15. And the equalization error power generated in the process of adaptive signal processing is output to the interference wave detector 17. Note that the equalization circuit 14 performs a training operation in a pilot section inserted in a radio frame, and performs a tracking operation in other sections. For example, it is an MMSE (Minimum Mean Square Error) type adaptive filter, and the equalization error power is preferably output after averaging a plurality of symbols (for example, 16 samples) or more so as to reduce the influence of noise. . The interference wave detection unit 17 detects the interference wave power in the frequency band used for communication by referring to the RSSI output from the power detection circuit 16 and the equalization error power output from the equalization circuit 14. Then, interference information for performing control such as continuation or change of the use frequency band is output.

Next, details of the operation in the interference wave detection unit 17 will be described. First, an equalization error power converted CNIR value is examined based on the equalization error power of the output of the equalization circuit 14 in a state where no interference wave exists. If the power of a reference sequence used for equalization processing (known pilot symbol data for training, the size is constant regardless of the receiver input level) is P _UW , and the equalization error power is P _ERR , the equalization error Electric power conversion CNIR (CNIR _EQL ) [dB] is calculated by the following equation.

CNIR _EQL = (P _ERR −P _UW ) × (−1) (1)
FIG. 2 shows measured values of equalization error power conversion CNIR and RSSI with respect to an input level of a certain receiver in a state where the interference wave does not exist. Such measurement can be performed by inputting the RF or IF electrical signal of the signal generator directly into the input terminal of the antenna 11 or the frequency conversion circuit 12 and operating the equalization circuit 14. If the RSSI is used within the range where the linearity of the power detection device is guaranteed, the relationship with the receiver input level becomes linear, but the CNIR limits the receiver CNR limit, quantization accuracy, signal processing dynamic range, etc. Saturation tends to occur due to these factors. In the example of FIG. 2, the linearity starts to break from about CNIR = 35 dB and is saturated at a maximum of 40 dB.

  The RSSI value in the presence of an interference wave increases according to the power of the interference wave, but in a situation where the desired wave can be demodulated (that is, when the desired wave is sufficiently larger than the interference wave), an increase in interference component can be ignored. . On the other hand, the CNIR value in the presence of an interference wave is observed as a phenomenon equivalent to giving a noise equivalent to the level of the interference wave power. For example, the CNIR value saturates at X dB in an environment where there is interference of X dB lower than the desired wave power.

This will be described with reference to the example of the relationship graph of CNIR with respect to the receiver input level shown in FIG. 3. For example, when an interference wave having a power -30 dB lower than the desired signal power exists, the observed CNIR value is -X- When a CNR = 30 dB saturation is present as shown in the graph shown in FIG. 6 and an interference wave having a power -20 dB lower than the desired wave power exists, the observed CNIR value is CNR = A characteristic of saturation at 20 dB is shown.
As described above, since the influence of the interference wave is different between RSSI and CNIR, the interference state can be grasped by observing these two values.

Next, a configuration example of the interference wave detection unit 17 constituted by the RSSI / CNIR conversion circuit 41 and the comparison circuit 42 shown in FIG. Based on
First, the relationship between the RSSI and the receiver input level and the relationship between the CNIR and the receiver input level in the situation where there is no interference wave as shown in FIG. 2 is stored in the RSSI / CNIR conversion circuit 41. Based on this, the relation data between RSSI and CNIR shown in the graph of FIG. 5 is held in, for example, a nonvolatile memory of the RSSI / CNIR conversion circuit 41. Therefore, the corresponding CNIR value can be referred to using the RSSI value as an address input.

Next, in the comparison circuit 42, an equalization error power conversion CNIR estimated from the RSSI conversion CNIR (CNIR _RSSI ) output from the RSSI / CNIR conversion circuit 41 and the equalization error power output from the equalization circuit 14 described above. Compare the values (CNIR _EQL ). As a comparison method, processing by subtraction is simple as shown in the following equation.

Interference power [dB] = CNIR _RSSI −CNIR _EQL (2)
Since CNIR _EQL shows a small value when an interference wave exists, the interference power can be calculated by the above calculation. For example, when there is an interference wave equivalent to CNR = 30 dB, the calculation result of Expression (2) becomes a graph as shown by -O- in FIG. 6. Similarly, when there is an interference wave equivalent to CNR = 20 dB, the expression ( The calculation result of 2) becomes a graph as shown by-*-in FIG. 6, and it can be seen that the interference power corresponding to the interference situation is calculated. As a result, the interference power of equation (2) can be used as an amount indicating the degree of degradation of CNIR observed at the receiver, that is, how much the performance of the communication channel has deteriorated due to the influence of the interference wave. The calculation of CNIR _EQL is not limited to the pilot period, and the power of the data symbol determined instead of the known reference sequence power (P _UW ) may be used. Further, if multi-level modulation is not performed, P _UW may be given as an arbitrary fixed value.

Next, FIG. 7 shows a block circuit diagram of a configuration example of a transmitter / receiver using the interference wave detection circuit of the present invention, and FIG. 8 shows a schematic diagram of an example of a use frequency limiting method according to the present invention. . 7 that are the same as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.
The transmitter / receiver of FIG. 7 selects the frequency used for communication using the interference information detected by the interference wave detector 17 of FIG. That is, the receiver 71 inputs the interference information (interference power) detected by the interference wave detection unit 17 in the frequency band used for communication obtained by the reception process to the communication frequency control circuit 72.

In the communication frequency control circuit 72, when it is determined that the interference power detected by the interference wave detection unit 17 reaches a level (threshold value) that does not satisfy the required performance (CNIR), the communication frequency control circuit 72 uses a frequency other than that frequency at the next radio link establishment. The frequency is used, and interference information indicating that the frequency is not used during the wireless link establishment operation is notified to the frequency conversion circuit 12 of the transmitter 73 and the receiver 71 as usable frequency information to limit the communication frequency.
For example, as shown in the example shown in FIG. Assume a situation in which there are three F3s, and an interference source 84 that communicates at the frequency F1 between the radio station A81 and the radio station B82 and transmits an interference wave at the frequency F1 is present near the radio station B82. In this example, it is assumed that TDD (Time Division Duplex) using the same frequency for both the transmitter and the receiver is applied as a duplex method.

In this case, the observed interference power levels are different between the radio station A81 and the radio station B82, and the radio station B82 having a short distance receives more interference.
When the communication frequency control circuit 72 of the radio station B82 determines that the interference power observed at the radio station B82 has exceeded the threshold, the frequency F1 is excluded from the radio link candidates that the radio station 2 will start up next time. F2 and F3 are output as usable frequency information.
On the other hand, in the communication frequency control circuit 72 of the wireless station A81, when it is determined that the interference power observed at the wireless station A81 does not exceed the threshold, F1, F2, and F3 are output as usable frequency information.

By such control, it is possible to avoid using the frequency F1 for communication between the radio station A81 and the radio station B82 shown in FIG. Even in this situation, communication at the frequency F1 is possible between the radio station A81 and the radio station C83. Regarding the reuse of frequencies once prohibited from being used, it is necessary to perform optimal control according to the characteristics of the wireless communication system. The interference wave detection circuit of the present invention can be used for adaptive modulation control as disclosed in JP-A-10-93650 in addition to the above-described channel selection. In addition to the interference power that is the output of the comparison circuit 42, CNIR _EQL and RSSI may be used in combination as the interference information. The output of comparator circuit 42 is not limited to digitized interference power, whether CNIR _RSSI substantially coincides with the CNIR _EQL (i.e., whether CNIR _EQL indicates the CNIR of the received signal) just for It may be a comparison result.

  The present invention can be applied to interference wave detection circuits of various transceivers and receivers in a digital wireless communication system.

It is a block circuit diagram which shows the example of 1 structure of the receiver based on this invention. It is a graph which shows an example of the relationship between CNIR and RSSI with respect to a receiver input level. It is a graph which shows an example of the influence which an interference wave has on CNIR. It is a block circuit diagram which shows one structural example of the interference wave detection part which comprises the principal part of the interference wave detection circuit of this invention. It is a graph which shows an example of an RSSI / CNIR conversion table. It is a graph which shows an example of the calculation result by Formula (2) in the comparison circuit of an interference wave detection part. It is a block circuit diagram which shows an example of the transmitter / receiver using the interference wave detection circuit of this invention. It is a schematic diagram which shows an example of the use frequency limiting method in the radio station using the interference wave detection circuit of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,71 Receiver 11,74 Antenna 12 Frequency conversion circuit 13 Orthogonal detection circuit 14 Equalization circuit 15 Decoding circuit 16 Power detection circuit 17 Interference wave detection part 41 RSSI / CNIR conversion circuit 42 Comparison circuit 72 Communication frequency control circuit 73 Transmitter 81, 82, 83 Radio station 84 Interference source

Claims (2)

A frequency conversion circuit for amplifying and frequency converting the received signal and outputting a received IF signal;
A quadrature detection circuit that performs quadrature detection processing on the received IF signal and outputs a received baseband signal composed of two I-phase and Q-phase sequences;
A power detection circuit for detecting the power of the received IF signal and outputting RSSI;
The received baseband signal is subjected to adaptive signal processing to correct transmission path distortion and waveform distortion generated in the transmitting / receiving device, and the equalized received baseband signal is output to the decoding circuit, and is generated in the adaptive signal processing process, etc. An equalization circuit that outputs equalization error power conversion CNIR obtained by normalizing equalization error power with symbol power;
Conversion data of RSSI and CNIR respectively corresponding to the input level of the receiver in a certain interference situation is held in advance, and RSSI conversion CNIR is output from RSSI detected by the power detection circuit with reference to the conversion data An interference wave detection means comprising: an RSSI / CNIR conversion circuit; and a comparison circuit that compares the RSSI conversion CNIR from the RSSI / CNIR conversion circuit with the equalization error power conversion CNIR from the equalization circuit;
Interference wave detection circuit equipped with. A transceiver in a digital wireless communication system, comprising:
The receiver performs amplification and frequency conversion on the received signal and outputs a received IF signal; and
A quadrature detection circuit that performs quadrature detection processing on the received IF signal and outputs a received baseband signal consisting of two I-phase and Q-phase sequences;
A power detection circuit for detecting the power of the received IF signal and outputting RSSI;
The received baseband signal is subjected to adaptive signal processing to correct transmission path distortion and waveform distortion generated in the transmission / reception device, and the equalized received baseband signal is output to the decoding circuit, and is generated in the process of the adaptive signal processing, etc. An equalization circuit that outputs an equalization error power conversion CNIR;
Referring to the RSSI detected by the power detection circuit and the equalization error power conversion CNIR output from the equalization circuit, interference wave detection for outputting interference information for controlling a frequency band used for communication Means and
The transmitter is a transceiver configured to include a communication frequency control circuit that switches a use frequency as needed based on the interference information.

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