JP4367380B2 - Microwave radio communication system - Google Patents

Description

  The present invention relates to a microwave radio communication system, and more particularly, to a microwave radio communication system having an error correction circuit that performs encoding and decoding for error correction on transmission data for the purpose of improving the quality of a radio channel.

  In order to improve the transmission reliability in microwave radio communication, error correction techniques for correcting transmission data errors that occur in a radio transmission path and error detection techniques for checking the presence or absence of errors in transmission data are used. FIG. 7 is a diagram showing the configuration of such a conventional microwave radio communication system.

  This microwave radio communication system includes a baseband interface circuit 21, an error correction circuit 22 that performs encoding / decoding for error correction on transmission data mainly for the purpose of improving the quality of a radio channel, and signal processing for error correction. The modulated digital signal is modulated into an intermediate frequency band by a method such as quadrature amplitude modulation (QAM), and the demodulator 23 demodulates the received intermediate frequency signal into a digital signal, and the modulated signal is converted into a radio frequency and output. And a transmitter / receiver 24 that converts a signal received by the antenna into a signal in an intermediate frequency band.

  FIG. 8 is a diagram showing the configuration of the error correction circuit 22 shown in FIG. The error correction circuit 22 includes an encoder 30 that adds an error correction code such as a Reed-Solomon code to the input digital signal, and an interleave circuit 31 that rearranges the data string in units of bits or bytes in order to improve the correction capability for burst errors. And a de-interleave circuit 32 that receives the demodulated digital signal as input and rearranges it into the original data string, and a decoder 33 that performs error correction from the decoding calculation result.

  In the above conventional microwave radio communication system, signal processing such as error correction and bit interleaving is constantly performed regardless of the state of the radio transmission path in order to increase the system gain and maintain the line quality. Therefore, there has been a problem in that the propagation delay time associated with signal processing such as error correction and bit interleaving becomes extremely large.

  In consideration of such a problem, for example, in Patent Document 1, audio and / or image data is made into one block for every predetermined number, and error correction coding is performed on an arbitrary number of data in one block. By providing a plurality of error correction coding schemes and performing communication by selecting one of the plurality of error correction coding schemes according to the error state of the communication channel or the received electric field strength, the information transmission efficiency is improved. There has been proposed a technique that enables communication with little quality deterioration even when the communication path is in a bad state while being kept constant.

  Further, in Patent Document 2, when the quality of the communication line between the receiver and the data transmission partner apparatus is good, the first communication is performed using only the information bits to which no redundant bit is added. If there is no response from the partner device for normal reception, the second communication is performed with an error correction code with redundant bits added, and no reply is received from the partner device even if the second communication means is used. In some cases, third communication is performed in which transmission is performed by performing interleave processing with N (N ≧ 2) error correction codes as a unit, and thereafter, N is changed according to information from the partner device. By performing the third communication without changing the number of redundant bits to be added, even if the line quality deteriorates, accurate data transmission can be performed without increasing the number of redundant bits added to information bits. Increase transmission efficiency Surgery has been proposed.

  In Patent Document 3, specific bit string information is transmitted for several frames when the transmitting side is silent by the voice detection function, and the receiving side measures the error rate on the transmission path from the received bit string, and the error rate is used to determine the transmission path. Select the optimal encoding / decoding method according to the state, map the information of the selected encoding method to the low-speed associated channel and transmit it to the transmission side, the transmission side changes the encoding method according to the information, The coding method change information is mapped to the low-speed associated channel and transmitted to the receiving side, and the receiving side changes the receiving side coding method according to the information, and the optimum error control method according to the state of the transmission path There has been proposed a wireless transmission system that performs efficient and optimum error control processing by selection.

Japanese Patent Laid-Open No. 08-088618 Japanese Patent Laid-Open No. 08-223624 JP 09-023212 A

  In general, a communication device having a smaller propagation delay time is required in broadband network transmission or the like. However, as described above, the signal processing such as error correction and bit interleaving is constantly performed as shown in FIGS. In the conventional microwave radio communication system as shown in FIG. 8, even when the radio transmission path is in good condition and the error rate is small, it is operated with a very large propagation delay time. When the signal is good, the transmission efficiency deteriorates.

  On the other hand, in the transmission system described in Patent Document 1, communication is performed by selecting one of a plurality of error correction coding schemes having different numbers of target data in accordance with the error state of the communication path or the received electric field strength. Thus, even if the communication channel state is poor while keeping the information transmission efficiency constant, it is possible to perform communication with less quality degradation. However, in the case of the invention described in Patent Document 1, the error state of the communication channel or the received electric field strength is When there are fluctuations before and after the threshold for switching between multiple error correction coding systems, switching of the correction coding system frequently occurs, so communication for performing switching notification between transmission and reception increases, and transmission efficiency deteriorates. There is a fear.

  In the case of the invention described in Patent Document 1, as the error state or reception state becomes worse, selection control is performed so that the upper bit having more important information is subjected to aperture error correction coding, and an error is detected in the lower bit. However, there is also a problem that it is not suitable for a wireless transmission system in which the weights between bits are equal, since the data transmission system such as an image or sound is less affected.

  The wireless data transmission method described in Patent Document 2 enables accurate data transmission without increasing the number of redundant bits added to information bits even if the line quality deteriorates during data transmission from reception to the other device. However, in the case of the invention described in Patent Document 2, the data transmission method is switched when no response is received from the counterpart device, and the data transmission method can be switched only after non-delivery occurs. There is a problem that can not be done.

  In the digital mobile radio data transmission system described in Patent Document 3, it is possible to improve transmission efficiency by selecting an optimum error control method according to the state of the transmission path, but the invention described in Patent Document 3 In this case, it is necessary to provide a means for transmitting a specific bit string for monitoring the state of the wireless transmission path when there is no sound and a means for monitoring the state of the wireless transmission path by this bit string. There is a problem in that extra data transmission must be performed for path switching.

  An object of the present invention is to provide a microwave radio communication system and a radio apparatus that realize stable data transmission with a minimum propagation delay according to channel quality with a relatively simple configuration in view of the above-described problems of the prior art. There is.

  Another object of the present invention is to minimize the delay time in the equipment when the line quality is steady and stable, and to stably and quickly realize switching of data transmission giving priority to the line quality when the line quality deteriorates. To provide a microwave radio communication system and a radio.

  Another object of the present invention is to make it possible to variably control the delay time of the error correction circuit in a stable state according to the line quality information such as the received electric field and bit error, and to achieve a minimum propagation delay time according to the line quality. A wireless communication system and a wireless device are provided.

  The present invention relates to a reception electric field in a microwave radio communication system configured to be able to switch between a path through an error correction circuit for encoding / decoding for data error correction and a path not through the error correction circuit. Means for measuring the strength, and when the measured received electric field strength is equal to or lower than a first preset value during data transmission via the route not via the error correction circuit, according to the route via the error correction circuit Switch to data transmission, and when the measured received electric field strength is equal to or greater than a second value that is a predetermined level greater than the first value during data transmission via the path through the error correction circuit, the error correction circuit is Route selection means having a function of switching to data transmission not through is provided.

  The error correction circuit includes a path through a data string rearrangement circuit that interleaves encoded data and de-interleaves data before decoding, and a path that does not pass through the data string rearrangement circuit. The path selection means is configured to switch the data string rearrangement circuit when the measured received electric field strength is equal to or lower than a preset third value during data transmission through a route not via the data string rearrangement circuit. Switching to data transmission via the path, and during the data transmission via the data string rearrangement circuit, the measured received electric field strength is equal to or greater than a fourth value that is a predetermined level greater than the third value. Sometimes, it is possible to adopt a configuration having a function of switching to data transmission not via the data string rearrangement circuit.

  Alternatively, the error correction circuit has a path via a data string rearrangement circuit that interleaves the encoded data and deinterleaves the data before decoding, and a path not via the data string rearrangement circuit. And an error monitoring unit that measures an error rate by counting error pulses at the time of error correction, and the path selection unit is configured to measure the data during data transmission through a path not via the data string rearrangement circuit. When the error rate becomes equal to or higher than a preset first value, the data rate is switched to data transmission via the data string rearrangement circuit, and the measurement is performed during data transmission via the data string rearrangement circuit. When the error rate falls below a second value that is a predetermined level lower than the first value, the data string is rearranged. It can be configured to have a function of switching the data transmission not through the road.

  The present invention also relates to a microwave radio communication system configured to be able to switch between a path through an error correction circuit that performs encoding / decoding for data error correction and a path that does not pass through the error correction circuit. Means for measuring an error rate from the demodulated data, and when the measured error rate becomes equal to or higher than a first preset value during data transmission through a path not via the error correction circuit, The error correction is performed when the measured error rate becomes equal to or lower than a second value smaller than the first value by a predetermined level during data transmission via the error correction circuit. It is characterized by comprising route selection means having a function of switching to data transmission not via a circuit.

  The error correction circuit includes a path through a data string rearrangement circuit that interleaves encoded data and de-interleaves data before decoding, and a path that does not pass through the data string rearrangement circuit. The path selection means passes the data string rearrangement circuit when the measured error rate becomes equal to or higher than a preset third value during data transmission via the path not via the data string rearrangement circuit. When the measured error rate becomes equal to or lower than a fourth value smaller than the third value by a predetermined level during the data transmission by the route via the data string rearrangement circuit It can be configured to have a function of switching to data transmission not via the data string rearrangement circuit.

Effect description

  According to the present invention, when the line quality is good and steady, the delay time in the device is minimized, and when the line quality is deteriorated, priority is given to the line quality by error correction or the like, so that the transmission efficiency in the radio transmission system can be improved. it can.

  In addition, the path switching control of the error correction circuit has a hysteresis characteristic, and even if the received electric field level used for the path switching control or the error rate of the received demodulated data fluctuates in the vicinity of the switching specified value, the path The switching efficiency of the wireless transmission system that further minimizes the delay time in the equipment when the line quality is steady and stable and gives priority to the line quality when the line quality deteriorates is further improved. be able to.

  The microwave radio communication system of the present invention is mainly used in point-to-point communication, and the error correction circuit, which is the main part of the present invention, has a minimum propagation delay time according to the line quality (received electric field level, etc.). And a switching control means to be described later.

  FIG. 1 is a diagram showing a configuration of a microwave radio communication system as an embodiment of the present invention.

  The microwave radio communication system according to the present embodiment uses a baseband signal (for example, 10 / 100BASE-T or a bipolar signal) used mainly in a broadband network as an input / output signal and an NRZ signal handled by a radio. A baseband interface circuit 1 for converting data, an error correction circuit 2 for encoding / decoding error correction for transmission data, mainly for the purpose of improving radio channel quality, and a digital signal subjected to signal processing by error correction. For example, a modulator / demodulator 3 that modulates to an intermediate frequency band using a technique such as quadrature amplitude modulation (QAM) and demodulates the received intermediate frequency signal into a digital signal, converts the modulated signal to a radio frequency, and outputs it to an antenna. A transmitter / receiver 4 for converting the received signal into a demodulation signal in the intermediate frequency band, and a received electric field level of the received radio signal. Nita was composed of more received field monitoring circuit 5 if you lower than compared to the preset specified value for outputting ALM (alarm) information as received field information.

  FIG. 2 is a diagram showing a first embodiment of an error correction circuit which is a main part of the microwave radio communication system of the present invention. This error correction circuit 2 uses a block error correction method such as a Reed-Solomon code, for example, and has a configuration that can sufficiently correct a burst error or the like when used in combination with a bit / byte interleave method.

  The error correction circuit 2 of the present embodiment selects an encoder 10 that adds an error correction code such as a Reed-Solomon code to an input digital signal, and a selection circuit 11 that selects and outputs either a signal that has passed or bypassed the encoder 10. In order to improve the correction capability for burst errors, an interleave circuit 12 that rearranges data strings in units of bits or bytes, a selection circuit 13 that selects and outputs a signal that has passed or bypassed the interleave circuit 12, and a demodulation From the de-interleave circuit 14 that receives the digital signal that has been input and rearranges it into the original data string, the selection circuit 15 that selects and outputs either the signal that has passed or bypassed the de-interleave circuit 14, and the decoding operation result Decoder 16 that performs error correction, and passes or bypasses decoder 16 A selection circuit 17 that selects and outputs one of the received signals, an error monitoring circuit 18 that counts error pulses during error correction and outputs error information, and received electric field information and error information output from the received electric field monitoring circuit 5 And a CONT circuit 19 that determines the logic of the selection circuits 11, 13, 15, and 17 from the above state.

  In the CONT circuit 19, based on the received electric field information output from the received electric field monitoring circuit 5, the error information output from the error monitoring circuit 18, or a combination of the received electric field information and error information, the encoder 10, the interleave circuit 12, The logic of the selection circuits 11, 13, 15, and 17 for bypassing the deinterleave circuit 14 and the decoder 16 is determined.

  FIG. 3 shows an example of the reception electric field level versus the bit error rate for each path selected by the selection circuits 11, 13, 15, and 17 in the error correction circuit 2 of the present embodiment. The graph (1) shows an error. In the case of correction OFF and interleave OFF, the graph (2) shows each graph in the case of error correction ON and interleave OFF, and the graph (3) shows the graph in the case of error correction ON and interleave ON.

The graph shown in FIG. 3 shows an example in which the signal being transmitted is STM-1 defined by ITU-T, and “error rate = 10 ⁻⁹ ” is 1 error / 1 min. “Error rate = 10 ⁻¹² ” corresponds to 1 error / 1000 min (over 16 hours). In this case, the characteristics of the graph (1) are determined by the modulation method and the characteristics of the device, the characteristics of the graph (2) are determined by the error correction method, and the characteristics of the graph (3) are determined by the error correction method and the interleaving method. . These values can be obtained in advance by measurement.

  FIG. 4 shows that, in the present embodiment, the selection circuits 11, 13, 15, and 17 perform error correction OFF, interleave OFF state (1), error correction ON, interleave OFF state (2), error correction ON, It is a figure for demonstrating the outline in the case of performing switching operation | movement between the states (3) of an interleave ON. Hereinafter, a device delay time control method, which is a feature of the present embodiment, will be described with reference to FIGS.

  In the microwave radio communication system according to the present embodiment, the reception electric field monitoring circuit 5 shown in FIG. 1 monitors the line quality of the radio propagation path, and the error monitoring circuit 18 related to the error correction circuit 2 shown in FIG. Each information is input to the CONT circuit 19 of the correction circuit 2. The CONT circuit 19 controls the delay time in the error correction circuit 2 in the following manner based on the information.

  First, regarding the reception state of the microwave radio communication system, on the assumption that the reception electric field is higher than a specified value, the reception electric field is reduced by fading or the like from the state set to minimize the delay time of the radio device. The operation when going will be described.

  In this operating state, if the reception electric field level when receiving the radio signal transmitted from the opposite station is higher than the specified value (V1) and the line quality is good, the CONT circuit 19 minimizes the delay time of the radio apparatus. Thus, the state of controlling the selection circuits 11, 13, 15, and 17 is maintained. Therefore, the selection circuits 11, 13, 15, and 17 bypass the encoder 10, the interleave circuit 12, the de-interleave circuit 14, and the decoder 16, and the path with the shortest delay time is selected. When the CONT circuit 19 determines to change the selection state of the selection circuits 11, 13, 15, and 17, a control signal indicating the change contents is sent to the opposite radio, and the answer is returned from the corresponding radio. Thereafter, control is performed so as to change the states of the selection circuits 11, 13, 15, and 17 simultaneously with the opposing radio device.

  When the received electric field drops below the specified value (V1) due to fading or the like from the above-mentioned line quality state, the CONT circuit 19 performs error correction instead of increasing the delay time of the system and performs bit error. The selection circuits 11, 13, 15, and 17 are controlled so that the rate can be improved. Accordingly, the selection circuits 11, 13, 15, and 17 select a path that passes through the encoder 10 / decoder 16 by bypassing the interleave circuit 12 / de-interleave circuit 14. Opposing radio devices are also controlled to be in the same state.

  Further, when the received electric field decreases and falls below the specified value (V3) due to an increase in fading or the like, the CONT circuit 19 operates the interleave function to select a route that makes the best use of the error correction capability. , 13, 15, and 17 are controlled. Therefore, the selection circuits 11, 13, 15, and 17 select paths that pass through all the circuits of the encoder 10 / interleave circuit 12 / de-interleave circuit 14 / decoder 16. Opposing radio devices are also controlled to be in the same state.

  Next, the selection circuits 11, 13, 15, and 17 select a path that passes through all the circuits of the encoder 10 / interleave circuit 12 / de-interleave circuit 14 / decoder 16 and perform microwave radio communication. , The reception state of the microwave radio communication system is gradually increased from a state where the reception electric field is equal to or less than the specified value (V3) due to fading or the like, and is shifted to a state of good radio channel quality in which the channel is not deteriorated. The operation when going will be described.

  In this operating state, when the received electric field gradually increases and exceeds the specified value (V4) higher than the specified value (V3) by a predetermined level set in advance, the CONT circuit 19 reduces the delay time of the system. Instead of increasing, the selection circuits 11, 13, 15 and 17 are controlled so that error correction is performed and the bit error rate can be improved. Accordingly, the selection circuits 11, 13, 15, and 17 select a path that passes through the encoder 10 / decoder 16 by bypassing the interleave circuit 12 / de-interleave circuit 14. Opposing radio devices are also controlled to be in the same state.

  Further, when the received electric field becomes higher and exceeds the specified value (V2) higher than the specified value (V1) by a predetermined level set in advance, the CONT circuit 19 minimizes the delay time of the wireless device. The selection circuits 11, 13, 15, and 17 are controlled. Therefore, the selection circuits 11, 13, 15, and 17 select the path with the shortest delay time by bypassing the encoder 10 / interleave circuit 12 / de-interleave circuit 14 / decoder 16. Opposing radio devices are also controlled to be in the same state.

  In this way, in the present invention, since the delay time of the error correction circuit 2 can be varied and controlled by the line quality information such as the received electric field and bit error, it can be switched to the minimum propagation delay time according to the line quality. A wireless device can be provided. Note that the specified values (V1) and (V3) when switching to a direction in which the delay time of the wireless device is increased are such that the error rate of received data output to the baseband interface 1 is equal to or less than a predetermined value (E0). It can be set to an appropriate value, for example.

  Further, in this embodiment, the specified values (V2) and (V4) that cause switching when the reception electric field increases, and the specified values (V1) and (V3) that cause switching when the reception electric field decreases. Since the switching operation with hysteresis characteristics is performed by setting a higher value than this, the switching operation is prevented from being repeated frequently in situations where the received electric field fluctuates before and after each specified value. Therefore, transmission delay associated with the switching operation can be minimized.

  In the above embodiment, the CONT circuit 19 controls the path selection of the selection circuits 11, 13, 15, and 17 based on the received electric field level input from the received electric field monitoring circuit 5. Even if the path selection of the selection circuits 11, 13, 15, 17 is controlled based on the error information, or the path selection of the selection circuits 11, 13, 15, 17 is controlled based on the received electric field level and the error information. Good.

  For example, between the path having the shortest delay time by bypassing the encoder 10 / interleave circuit 12 / de-interleave circuit 14 / decoder 16, and between the path having the interleave circuit 12 / de-interleave circuit bypassed and passing through the encoder 10 / decoder 16 Switching is controlled based on the prescribed values (V1) and (V2) of the received electric field strength, the interleave circuit 12 / de-interleave circuit is bypassed, the path passing through the encoder 10 / decoder 16, and the encoder 10 / interleave Regarding switching between paths passing through all the circuits of the circuit 12 / de-interleave circuit 14 / decoder 16, an error rate measured from the error pulse count value at the time of error correction output from the error monitoring circuit 18 is used. To set two values Ri can be realized by a method for performing a switching control having a hysteresis characteristic.

  In the above embodiment, the configuration including the encoder 10 / interleave circuit 12 / de-interleave circuit 14 / decoder 16 has been described. For example, the interleave circuit 12 / de-interleave circuit 14 is omitted, and the encoder 10 / decoder 16 It is also possible to select a path and a path that bypasses the encoder 10 / decoder 16.

  FIG. 5 is a diagram showing a configuration as a second embodiment of the error correction circuit in the microwave radio communication system of the present invention.

  Similarly to the error correction circuit 2 shown in FIG. 2, this error correction circuit 2 ′ also uses a block error correction method such as a Reed-Solomon code, and sufficiently corrects burst errors and the like by using it together with the bit / byte interleave method. The block having the same number as the error correction circuit 2 shown in FIG. 2 has the same function.

  The error correction circuit 2 ′ of this embodiment includes an error detection circuit 20 that detects an error bit from received data and measures an error rate. The CONT circuit 19 adds error information output from the error detection circuit 20 to the error information. Based on this, the logic of the selection circuits 11, 13, 15, 17 for bypassing the encoder 10, the interleave circuit 12, the de-interleave circuit 14, and the decoder 16 is determined. Inspection data having a fixed number of bits is added to the transmission data, and the error detection circuit 20 detects the presence / absence of an error from the actual data and the inspection data sent to the data. Then, the error rate is measured and output to the CONT circuit 19 as error information.

  FIG. 6 shows that, in this embodiment, the selection circuits 11, 13, 15, and 17 have error correction OFF, interleave OFF state (1), error correction ON, interleave OFF state (2), error correction ON, It is a figure for demonstrating the outline in the case of performing switching operation | movement between the states (3) of an interleave ON. Hereinafter, a device delay time control method that is a feature of the present embodiment will be described with reference to FIGS.

  First, regarding the reception state of the microwave radio communication system, fading or the like from the state set to minimize the delay time of the radio device on the assumption that the measurement error rate by the error detection circuit 20 is smaller than a specified value. The operation when the error rate increases will be described.

  In this operating state, if the error rate when receiving the radio signal transmitted from the opposite station is smaller than the specified value (E1) and the line quality is good, the CONT circuit 19 minimizes the delay time of the radio device. In addition, the state in which the selection circuits 11, 13, 15, and 17 are controlled is maintained. Therefore, the selection circuits 11, 13, 15, and 17 bypass the encoder 10, the interleave circuit 12, the de-interleave circuit 14, and the decoder 16, and the path with the shortest delay time is selected.

  When the received electric field drops due to fading or the like and the error rate exceeds the specified value (E1) from the state where the line quality is good as described above, the CONT circuit 19 performs error correction instead of increasing the delay time of the system. The selection circuits 11, 13, 15, and 17 are controlled so that the bit error rate can be improved. Accordingly, the selection circuits 11, 13, 15, and 17 select a path that passes through the encoder 10 / decoder 16 by bypassing the interleave circuit 12 / de-interleave circuit 14. At that time, the facing wireless devices are also controlled to be in the same state.

  Further, when the received electric field decreases due to an increase in fading or the like and the error rate becomes equal to or greater than the specified value (E3), the CONT circuit 19 operates the interleave function so as to select a route that makes maximum use of the error correction capability. The selection circuits 11, 13, 15, and 17 are controlled. Therefore, the selection circuits 11, 13, 15, and 17 select paths that pass through all the circuits of the encoder 10 / interleave circuit 12 / de-interleave circuit 14 / decoder 16. Opposing radio devices are also controlled to be in the same state.

  Next, the selection circuits 11, 13, 15, and 17 select a path that passes through all the circuits of the encoder 10 / interleave circuit 12 / de-interleave circuit 14 / decoder 16 and perform microwave radio communication. , The reception state of the microwave radio communication system gradually decreases from a state where the error rate is equal to or higher than the specified value (E3) due to fading or the like, and shifts to a state of good radio channel quality in which the channel is not deteriorated. Will be described.

  In this operating state, when the received electric field gradually increases and the error rate becomes equal to or lower than the specified value (E4) smaller than the specified value (E3) by a predetermined level, the CONT circuit 19 Instead of increasing the delay time, the selection circuits 11, 13, 15, and 17 are controlled so that error correction is performed and the bit error rate can be improved. Accordingly, the selection circuits 11, 13, 15, and 17 select a path that passes through the encoder 10 / decoder 16 by bypassing the interleave circuit 12 / de-interleave circuit 14. Opposing radio devices are also controlled to be in the same state.

  When the received electric field further increases and the error rate becomes equal to or less than the specified value (E2) smaller than the specified value (E1) by a predetermined level, the CONT circuit 19 minimizes the delay time of the wireless device. Thus, the selection circuits 11, 13, 15, and 17 are controlled. Therefore, the selection circuits 11, 13, 15, and 17 select the path with the shortest delay time by bypassing the encoder 10 / interleave circuit 12 / de-interleave circuit 14 / decoder 16. Opposing radio devices are also controlled to be in the same state.

  As described above, in this embodiment, the specified values (E2) and (E4) of the error rate that cause the switching when the error rate is lowered are the specified values (E1) that cause the switching when the error rate is increased. ) And (E3) are set to a value smaller than (E3) to provide hysteresis characteristics, so that switching operations are frequently performed in situations where the received electric field fluctuates before and after each specified value. Transmission delay associated with the switching operation can be minimized.

It is a figure which shows the structure of the microwave radio | wireless communications system as one Embodiment of this invention. It is a figure which shows the structure of the error correction circuit 2 which is the principal part of this invention. It is a graph which shows the example of the received electric field level versus bit error rate for every path | route in the error correction circuit of this embodiment. It is a figure for demonstrating the switching operation | movement between the paths in the error correction circuit of this embodiment. It is a figure which shows the structure as other embodiment of the error correction circuit in the microwave radio | wireless communications system of this invention. It is a figure for demonstrating the switching operation | movement between the paths in the error correction circuit of other embodiment. It is a figure which shows the structure of the conventional microwave radio | wireless communications system. It is a figure which shows the structure of the error correction circuit 22 in FIG.

Explanation of symbols

1, 21 Baseband interface circuit 2, 2 ', 22 Error correction circuit 3, 23 Modulation / demodulation circuit 4, 24 Transmission / reception circuit 5 Received electric field monitoring circuit 10, 30 Encoder 11, 13, 15, 17 Selection circuit 12, 31 Interleaving circuit 13 Selection circuit 14, 32 De-interleave circuit 16, 33 Decoder 18 Error monitoring circuit 20 Error detection circuit

Claims (2)

Switching between a path through an error correction circuit for encoding / decoding for data error correction and a path not through the error correction circuit , and interleaving the encoded data to de-decode the data before decoding In a microwave radio communication system configured to be able to switch between a path via a data string rearrangement circuit to be interleaved and a path not via the data string rearrangement circuit ,
Means for measuring received field strength;
Error monitoring means for measuring an error rate by counting error pulses at the time of error correction;
When the measured received electric field strength is less than or equal to a preset first value during data transmission through the path not passing through the error correction circuit, switching to data transmission through the path through the error correction circuit is performed. A function of switching to data transmission not via the error correction circuit when the measured received electric field strength becomes greater than or equal to a second value larger than the first value by a predetermined level during data transmission via a path via the correction circuit. First route selection means comprising:
When the measured error rate becomes equal to or higher than a preset first value during data transmission via a route not via the data string rearrangement circuit, switching to data transmission via the route via the data string rearrangement circuit is performed. When the measured error rate becomes equal to or lower than a second value smaller than the first value by a predetermined level during data transmission through a path via the data string rearrangement circuit, the data string rearrangement circuit passes through the data string rearrangement circuit. A second route selection means for switching to no data transmission;
A microwave radio communication system comprising: A baseband interface circuit that converts between a baseband signal and a signal that is handled by the radio, and a baseband interface circuit that is connected between the baseband interface circuit and the modem, and performs encoding / decoding for transmission data for error correction An error correction circuit; the modulator / demodulator that modulates the digital signal that has been signal-processed by error correction into an intermediate frequency band; and that demodulates the received intermediate frequency signal into a digital signal; In addition, in a microwave radio apparatus having a transceiver that converts a signal received by an antenna into a demodulation signal in an intermediate frequency band, and a reception electric field monitoring circuit that monitors a reception electric field level of the received radio signal,
The error correction circuit includes an encoder that performs error correction coding on data input from the baseband interface circuit, and data encoded by the encoder or the baseband interface circuit without error correction coding. A first selection circuit for selecting and outputting any of the directly input data; a decoder for decoding the received demodulation data that has been subjected to error correction coding; and data decoded by the decoder or error correction coding. A second selection circuit that selects and outputs any of the received demodulated data, an interleave circuit that rearranges the data string after the error correction encoding, and the interleaved error correction encoded data or the original that is not interleaved A third selection circuit that selects and outputs one of the error correction encoded data; A de-interleave circuit for rearranging the received received demodulated data to the original data string, and selecting either the de-interleaved error correction encoded data or the uninterleaved received demodulated data to the decoder A fourth selection circuit for outputting, an error monitoring circuit for measuring an error rate by counting error pulses at the time of error correction, a received electric field level measured by the received electric field monitoring circuit, and an error monitoring circuit When the received electric field level is equal to or lower than a preset first value in a state where the error rate is input and the first and second selection circuits select a path that is not subjected to the error correction coding. The first and second selection circuits are switched to paths that pass through the encoder and the decoder, and the first and second selection circuits are switched. When the circuit selects a path that passes through the encoder and the decoder, the first electric field level and the second electric field level when the received electric field level is equal to or higher than a second value that is a predetermined level greater than the first value. In a state where the selection circuit is switched to the path that does not perform the error correction coding and the third and fourth selection circuits select the path that is not interleaved, the error rate becomes equal to or higher than a preset first value. Then, the third and fourth selection circuits are switched to a path that passes through the interleave circuit and the de-interleave circuit, and the third and fourth selection circuits pass through the interleave circuit and the de-interleave circuit. Before the error rate falls below a second value that is a predetermined level lower than the first value in a state where a route is selected A microwave radio apparatus comprising: a control circuit that switches a path that does not interleave the third and fourth selection circuits .

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