JP2003289292A - Viterbi decoding method, short-range radio communication apparatus using the same and radio communication method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce circuit scale and power consumption, in executing Viterbi decoding and retain communication quality in executing short-range radio communication. <P>SOLUTION: A slave radio communication device conducts coding of humming codes, such as codes (7, 4) to form transmission data, and transmits the data to a master radio communication device, which detects the communication state, a hard decision decoding section 51A executes hard decision decoding when the communication state is excellent, and a soft decision decoding section 51B executes soft decision decoding such as Viterbi decoding, when the communication state is not proper. In executing soft decision decoding, on the basis of a trellis diagram, representing a 2<SP>m</SP>state of m bits in a lower order of redundancy bits, arithmetic operation of branch metric or path metric is performed for each of 2<SP>n</SP>states of upper n bits, thereby simplifying the calculation. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a short-distance wireless communication device for performing short-distance wireless communication between a master wireless communication device and a slave wireless communication device in an office, a home, a vehicle or the like.

[0002]

2. Description of the Related Art As a short-range wireless communication device of this type,
For example, the one described in 2001-128246 is known. In this conventional example, when performing short-range wireless communication using the 2.4 GHz ISM band, the wireless communication performance according to the mode instructed by the mode selection switch in the wireless communication device control unit of the wireless communication device, That is, in order to switch between the wireless transmission capability and the wireless reception capability, the gains of the transmission amplifier and the reception amplifier are set stepwise,
There is described a communication system in which the wireless communication capability is changed while ensuring a certain communication quality, so that the wireless reception capability is lowered so that transmission data from a device that does not need connection is received.

[0003]

However, in the above-mentioned conventional example, it is necessary to specify a personal computer as a master wireless communication device and a slave wireless communication device such as a mouse, a keyboard or a mobile phone wirelessly connected thereto. It is possible to prevent unnecessary power consumption and processing load while maintaining wireless communication quality.However, when the slave wireless communication device is far from the master wireless communication device, When the wireless communication state of the wireless communication device and the slave wireless communication device is poor, it is necessary to increase the gains of the transmission amplifier and the reception amplifier respectively to improve the communication capability. In this case, it is not possible to reduce the power consumption. There is a problem to be solved.

Therefore, the present invention has been made by paying attention to the unsolved problem of the above-mentioned conventional example, and by improving the receiving sensitivity in the master wireless communication device, the wireless communication capability in the slave wireless communication device is achieved. It is an object of the present invention to provide a short-range wireless communication device capable of reducing power consumption by reducing the power consumption. Another object of the present invention is to provide a Viterbi decoding method that can reduce the circuit scale and power consumption when performing soft-decision decoding for improving reception sensitivity.

[0005]

In order to achieve the above object, a Viterbi decoding method according to a first aspect of the present invention is a Viterbi decoding method for performing maximum likelihood decoding of encoded communication information using a decoding algorithm. , Pay attention to the lower m bits in the redundant bit state of the trellis diagram with the vertical axis representing the redundant bit status in the generator determinant and the horizontal axis representing time,
The redundancy is provided by using an addition unit that adds a branch metric and a path metric according to the number of states 2 ^m of the lower m bits so as to form a trellis diagram represented by the state of the lower m bits. It is characterized in that an individual operation corresponding to the number of states 2 ⁿ of the remaining upper n bits in the bit is performed, and all the operation results are summed to perform the decoding operation.

A Viterbi decoding method according to claim 2 is
In the invention according to claim 1, the encoded communication information is a (7,4) Hamming code, and lower two bits “0” of three redundant bits representing a trellis diagram.
An adding means for adding the branch metric and the path metric corresponding to the four states of "0", "11", "10" and "01" is provided, and the adding means adds the remaining 1 of the redundant bits.
It is characterized in that the two states of the bit are individually operated and the results of both operations are summed to perform the decoding operation.

Further, the short-range wireless communication device according to claim 3 is provided.
Is a mass communication device that performs short-distance wireless communication by encoding communication information.
Wireless communication devices and slave wireless communication devices.
In a short-range wireless communication device that also has,
The line communication device receives the data received from the slave wireless communication device.
Hard-decision decoding means for performing hard-decision decoding of communication information;
Soft decision decoding means for soft decision decoding communication information;
Communication status detection to detect communication status with wireless communication device
Means and a slave wireless communication device by the communication state detection means
Of the hard decision decoding means when the communication state of the
The soft-decision decoding means when the communication state is poor.
And a decoding selection means for selecting
Is the state of redundant bits in the generator determinant on the vertical axis and
In the state of the redundant bit of the trellis diagram with the time on the axis
Focusing on the lower m bits of the
To form the trellis diagram represented by
Number of states of multiple bits 2^mDepending on the branch metric
Using the adding means for adding the path metric and
Number of remaining high-order n bits in redundant bit 2 ⁿTo
Perform the corresponding individual calculation and add all the calculation results
Characterized by being configured to perform a decoding operation
There is.

Furthermore, in the short-range wireless communication device according to claim 4, in the invention according to claim 3, the communication state detecting means is configured to measure the received signal strength of the received communication information. Is characterized by. Still further, in the short-range wireless communication device according to claim 5, in the invention according to claim 3, the communication state detecting means decodes one of the hard-decision decoding means and the soft-decision decoding means, which is decoded while being selected. It is characterized in that it is configured to measure the bit error rate of communication information.

Further, in the short-range wireless communication device according to claim 6, in the invention according to claim 3 or 5, the soft decision decoding means receives from the slave wireless communication device (15,
10) It is characterized in that the Hamming code is configured to be Viterbi-decoded. Further, the short-range wireless communication method according to claim 7 is a short-range wireless communication method for encoding and transmitting communication information between a master wireless communication device and a slave wireless communication device, wherein the master wireless communication device is a slave wireless communication device. It is characterized in that the received communication information received from the device is subjected to hard-decision decoding when the communication state is good, and soft-decision decoding according to claim 1 or 2 when the communication state is bad.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a first embodiment of the present invention, in which 1 is a printer as a master wireless communication device and 2 is a portable type driven by an internal power source as a slave wireless communication device. The information terminal 3 is a notebook personal computer driven by an internal power source as a slave wireless communication device, and print data of the portable information terminal 2 and the notebook personal computer 3 can be transmitted by short-distance wireless transmission to the printer 1 for printing. Is configured.

As shown in FIG. 2, the printer 1 comprises a short-range wireless communication device 10 and a baseband signal processing device 50 for processing transmitted / received data. In the short-range wireless communication device 10, a transmission / reception antenna 21 is connected to a transmission / reception switching circuit 23 via a bandpass antenna filter 22,
The receiving side output terminal of the transmission / reception switching circuit 23 is the receiving circuit 24.
, And the input terminal on the transmission side is connected to the transmission circuit 25.

The reception circuit 24 is a low noise amplifier (LN) to which the reception signal output from the transmission / reception switching circuit 23 is input.
A) 26 and a mixer 28 that mixes an output signal of the low noise amplifier 26 with a local oscillation signal input from a frequency synthesizer 15 for frequency hopping, which will be described later, via a buffer amplifier 27 to convert it into an intermediate frequency signal.
A band pass filter 29 for removing an image signal generated when the intermediate frequency signal output from the mixer 28 is input and mixed, and an intermediate frequency (IF) amplifier for amplifying a filter output of the band pass filter 29. 30, a limiter amplifier 32 connected to the intermediate frequency amplifier 30 via a bandpass filter 31 to make the output have a constant amplitude, and a detection circuit 33 to which the amplified output of the limiter amplifier 32 is input. The received data output from the detection circuit 33 is input to the baseband processing unit 50, and the received signal level output from the intermediate frequency amplifier 30 and the limiter amplifier 32 is expressed by RSSI (R
The receiver signal strength indicator) signal is also input to the baseband signal processing device 50.

On the other hand, the transmission circuit 25 has a power amplifier 35 to which the transmission signal output from the frequency synthesizer 15 is input, and the transmission signal output from this power amplifier 35 is input to the transmission side of the transmission / reception switching circuit 23. Is supplied to. Further, the frequency synthesizer 15 receives a phase-locked loop (PLL) circuit 41 to which a setting signal for setting frequency hopping output from the baseband signal processing device 50 is input, and an output signal of the phase-locked loop circuit 41. Low pass filter 42
And the filter output of the low-pass filter 42 and the transmission data from the baseband signal processing device 11
And a voltage controlled oscillator (V that forms a transmission signal that is input through the low pass filter 44 and is frequency hopped).
CO) 45 and a doubling circuit 46 for doubling the transmission signal output from the voltage controlled oscillator 45.
The transmission signal output from the voltage controlled oscillator 45 is fed back to the phase-locked loop circuit 41, the doubled signal output from the doubler circuit 46 is supplied to the power amplifier 35 of the transmitter circuit 25, and the buffer amplifier 27 is supplied. The signal is supplied as a local oscillation signal to the mixer 28 of the receiving circuit 24 via.

Further, the baseband signal processing device 50 is
A reception data processing unit 51 that processes the reception data input from the reception circuit 24, and an ISM (Industrial Scientif) with a frequency of 2.4 GHz for the frequency synthesizer 40.
ic Medical) Frequency hopping control section 52 for controlling frequency hopping of the band in a predetermined pattern set in advance.
An RSSI signal input by adding the RSSI signal representing the received signal level output from the intermediate frequency amplifier 30 and the limiter amplifier 32 of the receiving circuit 24 And a communication control unit 55 for establishing a short-distance wireless communication network with another device, which detects a communication state based on the above and outputs the detection result to the reception data processing unit 51. There is.

Here, the transmission data processing unit 53 determines (7,
4) FEC (Forward error cor
rection) coder composed of an error correction coding circuit 53a
Have. This error correction coding circuit 53a, as shown in FIG. 3, has three stages of shift registers SR0 to SR2, an adder AD1 for adding transmission data to the final stage shift register SR2, and an output of this adder AD1. A switch SW1 for selecting any one of the transmission data, a switch SW2 for synchronizing with the switch SW1 for selecting any one of the output of the adder AD1 and the ground potential, that is, "0" and inputting it to the shift register SR0, and this switch SW2. And an adder AD2 for adding the selected output of the above to the output of the shift register SR0, and has the configuration of an FEC coder with a coding rate of 4/7.

Then, the transmission data is divided into 4 bits, and the divided 4 bits of data are sequentially input to the adder AD1 with the switches SW1 and SW2 switched to the normally closed terminal NC side. The 4-bit data is output as it is as transmission data, and the data added to the output of the shift register SR2 by the adder AD1 is input to the shift register SR0 and is added to the output of the shift register SR0 by the adder AD2. It

After that, the switches SW1 and SW2 are both switched to the normally open contact NO side, and then each shift register SR0.
To output 3-bit data stored in SR2 to form a total of 7-bit transmission data.
Also, the data is supplied to the frequency synthesizer 40 via the low-pass filter 44, and is repeatedly transmitted from the antenna 21 through the transmission circuit 25 and the transmission / reception switching circuit 23 to transmit the transmission data by 4 bits.

On the other hand, the received data processing unit 51 includes a hard decision decoding circuit 51A for performing hard decision decoding of the received data, a soft decision decoding circuit 51B including a Viterbi decoder for performing soft decision decoding of the received data, and these. A selection circuit 51C for selecting the hard decision decoding circuit 51A and the soft decision circuit 51B, and a selection control circuit 51D for controlling the selection circuit 51C are provided.

Here, as shown in FIG. 4, the hard-decision decoding circuit 51A includes six stages of buffer registers BR0 to BR6 to which received data is input, and a gate circuit to which received data forming a divider is input. G, 3-stage shift register SR
B0 to SRB2, adders AD1 to AD3, NOT circuit N
It has a division circuit DV including T1 and NT2 and an AND circuit AN.

In the hard-decision decoding circuit 51A, when the 7-bit reception sequence is sequentially input to the buffer registers BR0 to BR6 and the divider DV while the gate circuit G is open, the 7-bit reception sequence is obtained. The syndrome is obtained in the divider DV at the end of the input. At this time, the input gate circuit G of the divider DV is turned off, the data is read from the buffer registers BR0 to BR6, and at the same time, the contents of the divider DV are shifted to the right to make the NOT circuit N
When "001" is detected by T1, NT2 and the AND circuit AN, "1" is supplied to the adder AD3 so that the adder AD3 performs the operation of mod2 to correct the error bit. The received data corrected is output to the print data processing device 61.

Further, as shown in FIG. 5, the soft decision decoding circuit 51B calculates the code distance (branch metric) between the A / D converted input sequence R _T and the code sequence predicted in each branch. 2 ^m states “00”, “11”, “01” and “1” represented by lower m (m = 2) bits in the three redundant bits of the (7,4) Hamming code.
The branch metric calculator 55 that individually calculates the 2 ⁿ states “0” and “1” of the upper n (n = 1) bits for “0” and the states “00”, “11”, and “0”.
AC for calculating the cumulative value (path metric) of the branch metric to "1" and "10" and selecting the surviving path
An S (add-compare select) operation unit 56, a path metric rearrangement unit 57 that temporarily delays the path metric sequentially calculated by the ACS operation unit, and rearranges the path metric in a time series different from the time of calculation. A path metric storage unit 58 that stores a path metric in each state; a path selection signal storage unit 59 that stores information about the selected path;
It is composed of a traceback calculation unit 60 that searches for a maximum likelihood survival path based on the contents of the path selection signal storage unit 59, and outputs the received data decoded by the traceback calculation unit 60 to the print data processing unit 61. . Here, the branch metric calculation unit 55 and the ACS calculation unit 56 constitute an addition means.

Further, the selection control circuit 51D determines whether or not the reception strength RSSI is equal to or more than a preset reception strength threshold TH based on the reception strength signal detected by the communication state detecting section 54, and if RSSI ≧ TH. In some cases, it is determined that the reception intensity is sufficient, and the hard decision decoding circuit 51A is selected with respect to the selection circuit 51C. For example, the logical value "0".
Selection signal SL is output, and when RSSI <TH, it is determined that the reception strength is insufficient, and the selection circuit 5
For example, a selection signal SL having a logical value "1" for selecting the soft decision decoding circuit 51B for 1C is output.

Further, the portable information terminal 2 and the notebook personal computer 3 which are slave wireless communication devices,
A wireless communication device 10 and a baseband signal similar to those of the printer 1 except that the soft decision decoding circuit 51B, the selection circuit 51C, and the selection control circuit 51D are omitted in the reception data processing unit 51 of the baseband signal processing device 50. The processor 50 is provided.

Next, the operation of the first embodiment will be described. Now, when there is no portable information terminal 2 or notebook personal computer 3 which is a slave wireless communication device around the printer 1 which is a master wireless communication device, communication control in the baseband signal processing device 50 of the printer 1 is performed. In the unit 55, the peripheral wireless communication devices are periodically authenticated, and if the slave wireless communication devices do not exist, the short-range wireless communication network is not built, but as shown in FIG. When the portable information terminal 2 and the notebook personal computer 3 exist within the communication range of 1, the portable information terminal 2 and the notebook personal computer 3 that have recognized their existence when the authentication work is started An address of a predetermined bit is assigned to the printer 1 of the slave wireless communication devices to which this address is assigned. Assigning an address range wireless communication network of a predetermined bit to the slave wireless communication device that performs signal.

After that, the slave wireless communication device participates in the short-distance wireless network after performing the authentication with the encryption key, and becomes ready to transmit / receive data to / from the master wireless communication device. In this state, for example, when print data to be printed by the printer 1 on the portable information terminal 2 is generated,
Print data is transmitted from the portable information terminal 2 to the printer 1. At this time, the error correction coding circuit 53a of the transmission data processing unit 53 in the baseband signal processing device 50.
Then, the transmission data is divided into 4 bits each, which is used as an information bit, and 3 bits of redundant bits are added to this to perform (7, 4) encoding processing to create transmission data of 7 bits in total. Is transmitted to the voltage control starter 45 of the frequency synthesizer 40, the transmission data is transmitted from the antenna 21 via the transmission circuit 25 and the switching circuit 23 in the frequency hopping pattern.

In the printer 1, which is the master wireless communication device, the transmission data from the portable information terminal 2 is sent to the antenna 21.
This received data is received by the antenna filter 22.
Is supplied to the receiving circuit 24 to extract only the necessary band, and the extracted received data is supplied to the receiving circuit 24 via the switching circuit 23. In the receiving circuit 24, the received data is amplified by the low noise amplifier 26, and then the voltage controlled oscillator 4 by the mixer 28.
The oscillating output of 5 is mixed with a high-frequency signal that has been doubled to be converted into an intermediate-frequency signal, and this is converted into an intermediate-frequency amplifier 3 of two stages.
It is amplified by 0, 32, but in the meantime, the low-pass filter 31
The image signal generated at the time of mixing is removed and then supplied to the detection circuit 33, and the detected reception signal is input to the baseband signal processing device 50. On the other hand, R representing the reception intensity output from the two-stage intermediate frequency amplifiers 30 and 32
The SSI signals are added together and supplied to the communication state detection unit 54 of the baseband signal processing device 50.

At the start of reception by the printer 1, the reception intensity RSSI of the reception data detected by the communication state detecting section 54.
Is equal to or higher than the preset reception strength threshold TH, and when the communication is in a good state, the selection control circuit 51D supplies the selection signal of the logical value "0" to the selection circuit 51C. The decision decoding circuit 51A is selected.

Therefore, the received data is the hard decision decoding circuit 5
It is supplied to 1A, the syndrome of the (7,4) Hamming code is calculated by the division circuit DV, and 1 of this division circuit DV is calculated.
When the term corresponding to x, x ² becomes 0, 0, 1 by supplying “1” to the adder AD3, the shift output of the corresponding buffer register BR0 to BR5 and the calculation of mod2 are performed. , The error code can be corrected, and the error-corrected received data is supplied to the print data processing device 61 to be printed.

However, the receiving circuit 2 at the start of reception
RSS output from the intermediate frequency amplifiers 30 and 32 of No. 4
When I is smaller than the preset reception strength threshold TH, the selection control unit 51D of the reception data processing unit 51 determines that the communication state is poor, and the selection signal S of the logical value "1" is selected.
By supplying L to the selection circuit 51C, the selection circuit 51C selects the soft-decision decoding circuit 51B, and the received data is supplied to the soft-decision decoding circuit 51B and Viterbi-decoded.

Here, the parity code string check sequence H of the (7,4) Hamming code transmitted from the portable information terminal 2 serving as the slave radio communication device can be expressed by the following equation (1), and the generator matrix G Can be expressed by the following equation (2).

[0031]

[Equation 1] In these equations (1) and (2), the left 4 bits are information bits and the right 3 bits are redundant bits. Then, the lower m of the redundant bits in the generator determinant G
2 ^m states of (m = 2) bits, that is, the encoding circuit 53a
Of each state of the shift registers SR0 and SR1 in
Paying attention to "0", "11", "01", and "10", these are plotted on the vertical axis, the time k is plotted on the horizontal axis, and each column bit of the information bits in the parity check matrix H is plotted on the lower stage, with redundant bits 2 ⁿ of the remaining upper n (n = 1) bits in
The trellis diagram for the state “0” of the states is calculated by collectively performing the three steps from the first time k = 1 to K = 3 as shown by the broken line in FIG. 6, and then the time k = 4 and It can be created by collectively calculating 2 steps of k = 5 and finally by calculating 2 steps of times k6 and k = 7. Similarly, a trellis diagram for the state “1” of the upper 1 bit is also obtained. It can be created by a similar method as shown by the solid line in FIG. 6, and both converge at time k = 7.

The transmission data is "0000000".
When a code error occurs in the second of the transmission data and "0100000" is received as the reception data, the reception sequence Y ^T is multiplied by the parity check matrix H in the hard decision decoding described above. When the syndrome series S ^T is calculated, this becomes “011”, which corresponds to the second column of the parity check bit, and therefore the mod2 operation of the second code of the reception series Y ^T and “1” is performed. Due to
Code errors can be corrected.

On the other hand, the received data is soft-decision decoding circuit 51B.
In the case of Viterbi decoding, the branch metric calculation unit 55 individually obtains the metric (branch metric) of the reception code pattern of each reception code in the reception sequence for each of the high-order bits “0” and “1”. The computing unit 56 calculates the likelihood of the path by combining with the metric (path metric) of the previous time, selects the surviving path, and stores and holds the path metric for the next time in the path metric storage unit 59. To do. Then, the traceback calculation unit 60 reads out the path selection signal data from the path selection signal storage unit 59, and performs the traceback process of updating the shift register in the next cycle by the path selection signal extracted from the path selection signal to perform the Viterbi decoding. And then
The decrypted received data is supplied to the print data processing device 61 to perform print processing.

In this way, when the reception strength RSSI is smaller than the reception strength threshold TH in the communication state detecting section 54, the soft decision decoding circuit 51B performs soft decision decoding on the received data of the (7,4) Hamming code received. Therefore, the relationship between the received power-to-noise power density ratio (E _b / N ₀ ) and the bit error rate (BER) per information bit is as shown in FIG.
The bit error rate is 10 ^{−5 in the} case of performing the soft-decision decoding shown in the solid line as compared with the case of performing the hard-decision decoding shown in the broken line.
In this case, the coding gain can be improved by about 1.5 dB, and accurate data transmission can be ensured even when the reception strength is low.

Moreover, as shown in FIG. 6, the trellis diagram is 2 in comparison with the usual 8 states of 3 bits of redundant bits.
It can be created in four states of bits, the circuit scale of the branch metric calculation unit 55 and the ACS calculation unit 56 can be reduced by half, and the storage capacity of the path metric storage unit 59 can also be reduced by half. Circuit 51B
The overall circuit scale and power consumption can be greatly reduced.

Incidentally, each state "000" to "1" in the three redundant bits in the (7,4) Hamming code.
When a trellis diagram is created for the eight states of “11”, as shown in FIG.
The circuit scale of the CS calculation unit 56 is required to be double that of this embodiment,
The power consumption is doubled accordingly. In the above embodiment, the case where data is transmitted and received with the (7,4) Hamming code has been described, but the present invention is not limited to this, and is used in a normal short-range wireless communication network (15,10). ) Also for the shortened Hamming code, the transmission data processing unit 53 in the baseband signal processing device 50.
As shown in FIG. 9, the encoding circuit 53a in FIG. 9 includes an adder AD for the five-stage shift registers SR0 to SR4 and the transmission data provided on the output side of the final-stage shift register SR4.
1, a switch SW1 for selecting the transmission data and the addition output of the adder AD1, a switch SW1 for selecting the addition output of the adder AD1 and the ground potential, that is, "0", and inputting the selection output to the shift register SR0. The switch SW2 interlocking with the switch SW2 and adders AD2 and AD3 for adding the selected output of the switch SW2 to the outputs of the shift registers SR1 and SR3.

In this case, the transmission data is divided into 10-bit units, and the switches SW1 and SW2 are normally closed terminals NC.
1 is input by sequentially inputting the separated 10-bit data to the adder AD1 in the state of being switched to the side.
The 0-bit data is output as it is as transmission data, the data added to the output of the shift register SR4 by the adder AD1 is input to the shift register SR0, and the adders AD2 and AD3 add the shift register SR.
1 and the output of SR3.

After that, both the switches SW1 and SW2 are switched to the normally open contact NO side, and then each shift register SR0.
5 bits of data stored in SR4 are output to form a total of 15 bits of transmission data.
3 and the low-pass filter 44 to the frequency synthesizer 40, and the transmission from the antenna 21 through the transmission circuit 25 and the transmission / reception switching circuit 23 is repeated to transmit the transmission data 10 bits at a time.

Similarly, the hard decision decoding circuit 51A and the soft decision decoding circuit 51B of the data receiving circuit 51 are also (15, 10).
The configuration is such that the shortened Hamming code can be decoded. This (1
5, 10) Even when the shortened Hamming code is used, the parity check matrix H can be expressed by the following expression (3) and the generator matrix G can be expressed by the following expression (4).

[0040]

[Equation 2] Here, generator polynomial G (x) becomes G (x) = (1 + x) (1 + x + x 4) = 1 + x 2 + x 4 + x 5.

For this (15,10) shortened Hamming code, each state of the 5-bit redundant bit is plotted on the vertical axis.
As shown in FIG. 10, a trellis diagram in which time is plotted above the horizontal axis and each bit string in the information bits of the parity check matrix H is plotted below the horizontal axis is shown in FIG. By collectively expressing the above 5 steps, the calculation for this can be simplified. By the way, when a trellis diagram for each time from x = 1 to x = 5 is created, it becomes as shown in FIG. 11, and many calculations are required by time x = 5, and at time x = 5 Each state 0 (0000
The path reaches all states of 0) to 31 (11111).

Therefore, for the (15,10) Hamming code, soft decision decoding can be easily performed as well as hard decision decoding. Also in this case, the relationship between the received power-to-noise power density ratio E _b / E ₀ and the bit error rate BER is shown in FIG.
As shown in FIG. 2, it has been proved that the coding gain at the bit error rate of 10 ⁻⁵ is improved by about 2 dB in the soft decision decoding shown by the solid line as compared with the hard decision decoding shown by the broken line.

In the above embodiment, the case where the communication state is judged by the magnitude of the reception intensity signal RSSI output from the intermediate frequency amplifiers 30 and 32 has been described, but the present invention is not limited to this, and an error may occur. The bit error rate BER before correction is detected, and when the bit error rate is less than or equal to a predetermined value, it is determined that the communication state is good,
The communication may be determined to be defective when the value exceeds the predetermined value. Furthermore, in the case of Viterbi decoding, the level of soft decision is proportional to the level of the received signal, and since it is a block code, every path is received at the trailing edge of each received data frame. Since it converges to a specific state, a reception signal level calculation map showing the relationship between the path metric value and the reception signal level set in advance based on the path metric value output from the ACS calculator 56 at this time is displayed. The received signal level may be calculated with reference.

Further, in the above embodiment, the case where the portable information terminal 2 or the notebook personal computer 3 is applied as the slave wireless communication device has been described, but the present invention is not limited to this, and it is driven by an internal power supply. Any device driven by an internal power source such as a mouse, a keyboard, and other computer peripheral devices driven by an internal power source and a remote control device driven by an internal power source can be applied.

Furthermore, in the above embodiment, the case where the printer 1 is applied as the master wireless communication device has been described, but the present invention is not limited to this, and a desktop personal computer, an image scanner, an overhead projector, a home electric appliance. A device that uses an external power source such as

[0046]

As described above, according to the Viterbi decoding method according to the first aspect, the redundant bit state of the trellis diagram in which the vertical axis represents the state of the redundant bits in the generator matrix and the horizontal axis represents the time. Focusing on the lower m bits in the state, add the branch metric and the path metric according to the number of states 2 ^m of the lower m bits so as to form the trellis diagram represented by the state of the lower m bits. Using the addition means for
Since the individual calculation corresponding to the number of bit states 2 ⁿ is performed and all the calculation results are summed to perform the decoding calculation, the circuit scale and power consumption of the entire Viterbi decoding circuit can be significantly reduced. available.

According to the Viterbi decoding method of the second aspect, when the (7,4) Hamming code is used, the branch metric and the path metric are calculated in the four states represented by the lower 2 bits of the redundant bit. The circuit scale of the entire Viterbi decoding circuit can be halved, and
The effect that the power consumption can be halved can be obtained.

Further, according to the short-range wireless communication device of the third or seventh aspect, the master wireless communication device has a hard-decision decoding means for performing hard-decision decoding of the received communication information received from the slave wireless communication device, and the reception. When soft-decision decoding means for soft-decision decoding communication information, communication state detecting means for detecting a communication state with the slave wireless communication device, and communication state detecting means for good communication with the slave wireless communication device To the soft-decision decoding means for selecting the hard-decision decoding means, and selecting the soft-decision decoding means when the communication state is poor. Focusing on the lower m bits in the state of redundant bits of the trellis diagram with the time on the horizontal axis, the trellis diagram represented by the state of the lower m bits is constructed. Sea urchin, low-order m bits state number 2
Using the adding means for adding the branch metric and the path metric according to ^m , an individual operation corresponding to the number of states 2 ⁿ of the remaining upper n bits in the redundant bit is performed, and all the operation results are added up. Since it is configured to perform the decoding operation by using the hard decision decoding when the communication state is good, the data receiving process can be simplified.
By performing soft-decision decoding when the communication state is poor, the bit error rate can be reduced and highly sensitive data reception processing can be performed, and the circuit scale and power consumption for soft-decision decoding can be greatly reduced. The effect that can be obtained is obtained.

Further, according to the short-range wireless communication device of the fourth aspect, since the communication state detecting means is configured to measure the received signal strength of the received communication information, the master wireless communication device receives the signal. The effect that the situation can be accurately detected is obtained. Further, according to the short-range wireless communication device of claim 5, the communication state detecting means measures the bit error rate of the received communication information decoded while being selected from the hard decision decoding means and the soft decision decoding means. Since it is configured so that the actual bit error rate at the time of decoding the received data is measured, the effect that the receiving state can be accurately detected is obtained.

Furthermore, according to the short-distance wireless communication device of the sixth aspect, the soft-decision decoding means is configured to Viterbi-decode the (15,10) Hamming code received from the slave wireless communication device. The effect that high-quality decoding can be performed is obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a block diagram showing a wireless communication device of a printer as a master wireless communication device.

FIG. 3 is a block diagram showing an encoding circuit for a (7,4) shortened Hamming code in a transmission data processing unit.

FIG. 4 is a block diagram showing a hard decision decoding circuit of a received data processing unit.

FIG. 5 is a block diagram showing a soft decision decoding circuit of a received data processing unit.

FIG. 6 is an explanatory diagram showing a trellis diagram in four states of a (7,4) Hamming code.

FIG. 7 is a characteristic diagram showing a relationship between a received power-to-noise power density ratio and a bit error rate when a (7,4) Hamming code is subjected to hard decision decoding and soft decision decoding.

FIG. 8 is an explanatory diagram showing a trellis diagram in eight states of a (7,4) Hamming code.

FIG. 9 is a block diagram showing an encoding circuit for a (15,10) shortened Hamming code in a transmission data processing unit.

FIG. 10 is an explanatory diagram showing a trellis diagram of a (15,10) Hamming code.

FIG. 11 is an explanatory diagram showing a conventional trellis diagram for a (15,10) Hamming code.

FIG. 12 is a characteristic diagram showing the relationship between the received power-to-noise power density ratio and the bit error rate when a (15, 10) shortened Hamming code is hard-decided and soft-decided.

[Explanation of symbols]

1 Printer (Master Wireless Communication Device) 2 Portable Information Terminal (Slave Wireless Communication Device) 3 Notebook Personal Computer (Slave Wireless Communication Device) 10 Wireless Communication Device 21 Transmission / Reception Antenna 22 Transmission / Reception Switching Circuit 24 Reception Circuit 25 Transmission Circuit 26 Low Noise Amplifier 27 mixer 30, 32 intermediate frequency amplifier 33 detection circuit 40 frequency synthesizer 50 baseband signal processing device 51 received data processing unit 51A hard decision decoding unit 51B soft decision decoding unit 51C selection unit 51D selection control unit 51E bit error measurement unit 51F transmission power Control unit 52 Frequency hopping control unit 53 Transmission data processing unit 54 Communication state detection unit 55 Communication control unit

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04B 7/26 109M F term (reference) 5J065 AA01 AB05 AC02 AD05 AD10 AF03 AG05 AH02 AH04 AH06 AH21 AH23 5K014 AA01 BA10 EA01 5K067 AA33 AA43 BB21 DD45 DD46 DD51 EE02 EE10 FF02 FF20 HH22 HH26

Claims (7)

[Claims] 1. A Viterbi decoding method for performing maximum likelihood decoding of encoded communication information using a decoding algorithm, wherein a trellis in which a state of redundant bits in a generator matrix is plotted on the vertical axis and a time is plotted on the horizontal axis. Focusing on the lower m bits in the redundant bit state of the diagram, a branch metric corresponding to the number of ^m states of the lower m bits is configured so as to form a trellis diagram represented by the state of the lower m bits. The number of states of the remaining upper n bits in the redundant bit is 2 ⁿ
The Viterbi decoding method is characterized by performing an individual operation corresponding to, and adding up all operation results to perform a decoding operation. 2. The encoded communication information is (7,4).
It is a Hamming code, and the lower two bits “00”, “11”, among the three redundant bits representing the trellis diagram,
An adding unit is provided for adding the branch metric and the path metric corresponding to the four states of “10” and “01”,
2. The Viterbi decoding method according to claim 1, wherein the adding means individually performs an operation on two states of the remaining 1 bit of the redundant bits and adds the results of both operations to perform a decoding operation. 3. A short-distance wireless communication device having at least a master wireless communication device and a slave wireless communication device for encoding short-distance wireless communication by encoding communication information, wherein the master wireless communication device receives from the slave wireless communication device. Hard-decision decoding means for performing hard-decision decoding of the received communication information, soft-decision decoding means for performing soft-decision decoding of the received communication information, communication state detecting means for detecting a communication state with the slave wireless communication device, and the communication Decoding and selecting means for selecting the hard-decision decoding means when the communication state with the slave wireless communication device is good in the state detection means, and selecting the soft-decision decoding means when the communication state is poor, The soft-decision decoding means has a lower order in the state of redundant bits in a trellis diagram in which the vertical axis represents the state of redundant bits in the generator matrix and the horizontal axis represents time. Focusing on several m bits, the low-order m so as to constitute a trellis diagram which is represented by state bits adding means for adding the branch metric and the path metric corresponding to low-order m bits of the state number 2 ^m Is used to perform an individual operation corresponding to the number of states 2 ⁿ of the remaining upper n bits in the redundant bit, and add all operation results to perform a decoding operation. Short-range wireless communication device. 4. The short-range wireless communication apparatus according to claim 3, wherein the communication state detecting means is configured to measure a received signal strength of received communication information. 5. The communication state detecting means is configured to measure a bit error rate of received communication information decoded by the selected one of the hard decision decoding means and the soft decision decoding means. The short-range wireless communication device according to claim 3. 6. The near-field decoder according to claim 3, wherein the soft-decision decoding means is configured to Viterbi-decode the (15,10) Hamming code received from the slave wireless communication device. Range wireless communication device. 7. A short-range wireless communication method for encoding and transmitting communication information between a master wireless communication device and a slave wireless communication device, wherein the master wireless communication device receives received communication information from a slave wireless communication device, Hard-decision decoding is performed when the communication state is good, and when the communication state is poor.
Alternatively, the short-distance wireless communication method is characterized by performing soft-decision decoding according to item 2.