JP2000349653A - Transmitter-receiver of base band signal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the control time and to reduce the cost of a transmitter- receiver to secure a stable error correction effect by optimizing automatically a frequency interleave cycle and also calculating and selecting an optimum interleave cycle despite the change of receiving level of a transmission line. SOLUTION: The frequency interleave cycle is automatically optimized and also an optimum frequency interleave cycle is calculated and selected despite the change of receiving level of a transmission line. A transmission line estimating means 14 of a frequency interleave cycle adapting means of this transmitter- receiver estimates the state of the transmission line from the information on every carrier given from a demodulation means and outputs this estimation value to an optimum frequency interleave cycle calculation means 15. The means 15 calculates an optimum frequency interleave cycle from the received estimation value. Then a frequency interleave cycle decision means 16 decides the frequency interleave cycle of a received modulated wave.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to baseband signal processing of a digital radio transmission apparatus, and has as its object to maintain and improve the accuracy of an error correction code technique used as a measure against transmission errors in transmission data.

[Prior art]

[0002] Multipath fading due to delayed waves is one of the factors that cause data transmission errors in wireless communication using a multicarrier transmission system. As a measure for reducing / preventing such transmission errors, an error correction coding technique is used in a multicarrier transmission apparatus. In particular, when data to be transmitted is image data or the like, its introduction is indispensable. Among them, concatenated coding using a plurality of error correction codes is actually used as a high-precision code. FIGS. 4A and 4B show configuration examples of a transmitter and a receiver when concatenated coding is used.

In the transmitter shown in FIG. 1A, information data input as transmission data is encoded as an outer code by an RS encoder 1 and the RS encoded information data is encoded by a convolutional encoder 2. Then, the convolutionally encoded information data is interleaved bit by bit by the bit interleaver 3, and the carrier frequency of the information data interleaved bit by bit is performed by the frequency interleaver 44. . The transmission radio section 45 performs the configuration and modulation of the frame of the encoded information data, generates a multicarrier modulated wave, and transmits the multicarrier modulated wave from the transmission antenna 6. FIG.
In the receiver (b), the modulated wave received by the receiving antenna 7 is demodulated by the receiving radio section 48 and output. Next, the carrier frequency of the output data is frequency-deinterleaved by a frequency deinterleaver 49, and the output data is deinterleaved for each bit by a bit deinterleaver 10, whereby the order of the output data is transmitted to the communication partner. Sort (return) to the order before bit interleaving on the machine. The rearranged data is decoded by a Viterbi decoder 11 which is a decoder for a convolutional code. Finally, the rearranged data is decoded by the RS decoder 12 and output to the next-stage circuit as received data. Note that frequency interleaving refers to dispersing data encoded by an outer code into a predetermined number of FDMA channels, and frequency deinterleaving refers to dispersing the number of distributed FDMA channels into an original data frame. It is to integrate.

[0004]

When performing frequency interleaving, it is necessary to optimize the frequency interleaving cycle in accordance with the state of the transmission line (such as the received electric field strength). However, in the conventional configuration, when the transceiver is installed in a specific place, it is necessary to perform an artificial optimization adjustment after the installation, which requires considerable time and cost. Further, since the state of the reception level in the transmission path fluctuates with time, the set frequency interleave cycle is not always optimal, and the frequency of transmission errors increases, leading to deterioration of characteristics. There was a problem that would be.

[0005] An object of the present invention is to solve the above problems by automatically optimizing the frequency interleave cycle and changing the reception level in the transmission path with time. In addition, by always calculating and selecting the optimal frequency interleave cycle, the time and cost required for adjustment can be reduced, and a stable error correction effect can be obtained.

[0006]

According to a first aspect of the present invention, there is provided an error correction coding means for adding an error correction code to information data to be transmitted, and a frequency interleave cycle. Frequency interleave cycle adaptation means for determining the frequency interleave cycle, frequency interleave means for performing frequency interleave at the optimum frequency interleave cycle calculated by the frequency interleave cycle adaptation means, and information data frequency-interleaved by the frequency interleave means are modulated and transmitted. Modulating means, receiving the modulated wave, demodulating means for demodulating, means for judging the frequency interleave cycle of the received modulated wave and, based on the judgment result, means for frequency deinterleaving the demodulated data and from the frequency deinterleaving means Decode the error correction code to the output data of Means for estimating the state of the transmission path from the received signal, means for calculating the optimal frequency interleaving cycle, and frequency interleaving means for performing frequency interleaving at the optimal frequency interleaving cycle. A transmission / reception means including means for determining a frequency interleaving cycle from a modulated wave and frequency interleaving adaptation means including frequency deinterleaving means for performing frequency deinterleaving based on the determination value is provided.

[0007]

FIG. 1 shows an embodiment of the present invention. In the transmitter, the transmission data is RS-encoded by the RS encoder 1 as an outer code, and is then encoded by the convolutional encoder 2 as an inner code.
, And the bit code of the transmission data is rearranged by the bit interleaver 3 and transmitted to the frequency interleaver 4. The frequency interleaving section 4 performs frequency interleaving on the bit-interleaved transmission data at the transmission frequency interleaving cycle output from the frequency interleaving cycle adapting section 13 and transmits the transmission data obtained thereby to the transmission radio section 5. The transmission data is modulated by the transmission radio means 5 and transmitted by the transmission antenna 6. In the receiver, the modulated wave received by the receiving antenna 7 is demodulated by the receiving radio means 8 and output to the frequency deinterleaving means 9 and the frequency interleaving cycle adapting means 13. The frequency deinterleaving means 9 performs frequency deinterleaving on the data inputted from the receiving radio means 8 at a designated cycle by the frequency interleaving cycle adapting means 13, and sends the data to the bit deinterleaver 10. The bit deinterleaver 10 deinterleaves the output data for each bit and sends the output data to the Viterbi decoder 11. A Viterbi decoder 11 decodes the output data, and outputs the RS decoder 1
Send to 2. The RS decoder 12 decodes the RS code,
The received data is output to the next circuit.

FIG. 2 shows a configuration example of the frequency interleave cycle adapting means 13. The transmission path estimating means 14 estimates the approximate state of the transmission path using information such as the reception level of each carrier from the demodulating means, and outputs the estimated value to the optimum frequency interleave cycle calculating means 15. The optimum frequency interleave cycle calculating means 15 calculates an optimum frequency interleave cycle from the estimated value, and outputs it to the frequency interleave means 4 and the transmission radio means 5.
Further, the frequency interleaving cycle determining means 16 determines the frequency interleaving cycle of the modulated wave received from the receiving radio means 8 and outputs the result to the frequency deinterleaving means 9. As such a determination method, a method of separating and using frequency interleaved cycle data multiplexed with demodulated data obtained by demodulating a received signal, and the like can be realized.

Next, a method of calculating an optimum frequency interleave and a method of determining the frequency interleave will be described in detail. Consider an example in which the present invention is applied to a 96-wave multi-carrier modulation / demodulation system. 16Q modulation method
AM, quasi-synchronous detection using a pilot symbol inserted at a cycle of 1.25 ms in a demodulation method, the bandwidth of a modulated wave per carrier is 8 kHz, and the carrier interval is 12.5 k.
Hz, the transmission / reception band is 90 MHz, and the maximum value of the delay time of the delay wave generated in the propagation path is about 5 μs. In this case, it is known that the frequency correlation of fading is sufficiently small in a band separated by about 100 kHz, and that it can be regarded as a different propagation state. I can do it. Therefore, in the case of this example, 100 kHz /
With 12.5 kHz = 8, it can be seen that frequency interleaving should be performed at least in a period of 8 carriers. The transmission path estimating means 14 reads the received power of each carrier in units of 10 ms, that is, every eight symbol intervals, and sends it to the optimum frequency interleave cycle calculating means 15. The frequency interleave cycle calculating means 15 stores each carrier and its received electric field strength in the memory table A in the optimum frequency interleave cycle calculated means 15 shown in FIG. A carrier that has dropped by 3 dB or more is obtained, and the difference between the drop carrier number and the next drop carrier number is stored in the memory table B. Then, an average value of the differences stored in the memory table B is calculated, and the calculated average value is temporally averaged (for example, every 100 ms), and is regarded as a drop period. For example, if the frequency interleaving cycle is 8, 12, 16,
In the case of 24 types, the frequency interleave is performed by selecting the cycle of the closest value that is equal to or longer than the drop cycle from among these. Then, the calculated interleaving cycle is output to the transmitting radio means and the frequency interleaving means 4.
After performing such calculations, transmission and reception as described in the preceding section are performed.

【The invention's effect】

According to the present invention, the adjustment required for optimizing the frequency interleave cycle, which is a problem of the prior art, is automated, and even if the state of the transmission path changes over time, By optimizing the frequency interleave cycle, the frequency of transmission errors was suppressed, and stable characteristics were obtained. In the past, after the installation of infrastructure equipment such as base stations, it was necessary to make manual judgments and adjustments at any time, resulting in an increase in time and cost. This eliminates the need for artificial judgment and adjustment after installation, so that time and cost can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 shows a frequency interleaving cycle adapting means 1 according to the present invention.
3 is a block diagram illustrating a specific configuration example of FIG.

FIG. 3 is a memory table for calculating and determining an optimum value of a frequency interleave cycle according to the present invention.

FIG. 4 is a block diagram illustrating a configuration example of a conventional transceiver.

[Description of Code] 1, 21 Encoding means 2, 22 Convolutional encoding means 3, 23 Bit interleaving means 4, 24 Frequency interleaving means 5, 25 Transmitting radio means 6, 26 Transmitting antenna 7, 27 Receiving antenna 8, 28 Receiving radio means 9, 29 frequency deinterleaving means 10, 30-bit deinterleaving means 11, 31 Viterbi decoding means 12, 32 RS decoding means 13 frequency interleaving cycle adaptation means 14 transmission path estimating means 15 optimal frequency interleaving cycle calculation means 16 Frequency interleave cycle determination means

Claims (1)

[Claims] 1. An error correction coding means for adding an error correction code to information data to be transmitted, a frequency interleave cycle adaptation means for obtaining a frequency interleave cycle, and the optimum frequency interleave cycle calculated by the frequency interleave cycle adaptation means. Frequency interleaving means for performing frequency interleaving at, modulating the information data frequency-interleaved by the frequency interleaving means,
A modulating means for transmitting; a demodulating means for receiving and demodulating the modulated wave; a means for determining a frequency interleave cycle of the received modulated wave; a means for frequency deinterleaving the demodulated data based on the result of the determination; Means for decoding the output data from the deinterleaving means, decoding the error correction code, and outputting the result; means for estimating the state of the transmission path from the received signal; and means for calculating the optimal frequency interleaving cycle. Frequency interleaving means for performing frequency interleaving with the optimal frequency interleaving cycle, means for determining a frequency interleaving cycle from a received modulated wave, and frequency deinterleaving means for performing frequency deinterleaving based on the determination value. A transmitting / receiving device including means.