Wireless Communication Device and Communication Terminal

1. A wireless communication device that establishes a digital link on a wireless channel and that performs a communication by a sound packet including a sound signal, which is encoded by means of adaptive differential pulse code modulation (ADPCM), and an error detection code, the wireless communication device comprising: an ADPCM encoding unit that divides a sampled sound signal into a high frequency signal and a low frequency signal and individually encodes the high frequency signal and the low frequency signal by means of adaptive differential pulse code modulation to thereby convert the high frequency signal into high frequency ADPCM data having a first number of bits, and convert the low frequency signal into low frequency ADPCM data having a second number of bits; an error detection code generation unit that generates an error detection code that is pertinent to the high frequency ADPCM data and the low frequency ADPCM data; a transmission data conversion unit that places the error detection code that is pertinent to the high frequency ADPCM data and the low frequency ADPCM data in only data pertinent to the low frequency ADPCM data; and a received data processing unit that receives the high frequency ADPCM data and the low frequency ADPCM data including the error detection code that is pertinent to the high frequency ADPCM data and the low frequency ADPCM data, and that individually processes the high frequency ADPCM data and the low frequency ADPCM data in accordance with a value of the error detection code that is pertinent to the high frequency ADPCM data and the low frequency ADPCM data.

2. The wireless communication device according to claim 1 , wherein a first number of bits of the high frequency ADPCM data and a second number of bits of the low frequency ADPCM data are fixed, and the transmission data conversion unit replaces bits with the error detection code generated by the error detection code generating unit, wherein the replaced bits are selected, except a plurality of bits to be input to an adaptive dequantizer of the ADPCM encoding unit, in data pertinent to the second number of bits which configure the low frequency ADPCM data.

3. The wireless communication device according to claim 1 , wherein the error detection code generation unit generates a first error detection code pertaining to the high frequent ADPCM data and a second error detection code pertaining to the low frequency ADPCM data, and the transmission data conversion unit replaces at least two bits of data among the plurality of bits that configure the low frequency ADPCM data with at least two bits of an error detection code including the first error detection code and the second error detection code.

4. The wireless communication device according to claim 3 , wherein the transmission data conversion unit replaces data pertinent to two lower order bits of the low frequency ADPCM with at least two bits of an error detection code including the first error detection code and the second error detection code.

5. The wireless communication device according to claim 1 , wherein the error detection code generation unit generates a first error detection code that acts as a parity signal for reversing bits in accordance with the number of “1s” in the high frequency ADPCM data and a second error detection code that acts as a parity signal for reversing bits in accordance with the number of “1s” in the low frequency ADPCM data.

6. The wireless communication device according to claim 1 , wherein the error detection code generation unit generates a third error detection code that acts as a parity signal for reversing bits in accordance with the number of “1s” in a series of data that include the high frequency ADPCM data and the low frequency ADPCM data.

7. The wireless communication device according to claim 1 , further comprising an ADPCM encoding unit that converts the received high frequency ADPCM data into high frequency digital sound data and the received low frequency ADPCM data into low frequency digital sound data.

8. The wireless communication device according to claim 1 , wherein when an error is detected by means of the received error detection code, the received data processing unit performs first signal processing on the high frequency ADPCM data that are received along with the error detection code and performs second signal processing on the low frequency ADPCM data that are received along with the error detection code.

9. The wireless communication device according to claim 3 , wherein the received data processing unit extracts the high frequency ADPCM data and a first error detection code from a received signal, and extracts the low frequency ADPCM data and a second error detection code from the received signal, and the received data processing unit detects an error occurred in the high frequency ADPCM data based on the first error detection code, and detects an error occurred in the low frequency ADPCM data based on the second error detection code.

10. The wireless communication device according to claim 3 , wherein the received data processing unit performs third signal processing on the high frequency ADPCM data received along with the error detection code and fourth signal processing on the low frequency ADPCM data received along with the error detection code when an error in a high frequency signal is detected by means of the received first error detection code, and the received data processing unit performs fifth signal processing on the high frequency ADPCM data received along with the error detection code and sixth signal processing on the low frequency ADPCM data received along with the error detection code when an error in a low frequency signal is detected by means of the received second error detection code.

11. The wireless communication device according to claim 10 , wherein the received data processing unit converts the high frequency ADPCM data into mute data when an error in the high frequency ADPCM data is detected based on a value of the first error detection code.

12. The wireless communication device according to claim 10 , wherein the received data processing unit converts both the high frequency ADPCM data and the low frequency ADPCM data sent along with the high frequency ADPCM data into mute data when an error in the high frequency ADPCM data is detected based on a value of the first error detection code.

13. The wireless communication device according to claim 10 , wherein the received data processing unit converts the low frequency ADPCM data into mute data when an error in the low frequency ADPCM data is detected based on a value of the second error detection code.

14. The wireless communication device according to claim 10 , wherein the received data processing unit converts both the low frequency ADPCM data and the high frequency ADPCM data sent along with the low frequency ADPCM data into mute data when an error in the low frequency ADPCM data is detected based on a value of the second error detection code.

15. The wireless communication device according to claim 1 , further comprising an error determination unit that determines a change in error rate of the digital link, wherein the transmission conversion unit selects, based on a determination result of the error determination unit, whether to transmit the low frequency ADPCM data to a communication opponent after replacing some of the low frequency ADPCM data with an error detection code or to transmit the low frequency ADPCM data without replacing the some of the low frequency ADPCM data with the error detection code.

16. The wireless communication device according to claim 15 , wherein the error determination unit increases or decreases the error rate according to a sync data error or an error detected by an error detection bit appended to control signal data or an entirety of a sound packet.

17. The wireless communication device according to claim 16 , wherein the error determination unit performs count-up of an error counter when occurrence of an error is determined from a value of the error detection bit and count-down of the error counter when an error does not occur, and increases or decreases the error rate by reference to the error counter.

18. The wireless communication device according to claim 15 , wherein the received data processing unit has a plurality of data conversion tables, and the received data processing unit selects one data conversion table from among the plurality of data conversion tables in accordance with a determination result of the error determination unit, and converts the high frequency ADPCM data and the low frequency ADPCM data received by means of the thus-selected data conversion table.

19. The wireless communication device according to claim 18 , wherein the received data processing unit sets an error rate range corresponding to the plurality of data conversion tables and selects a data conversion table conforming to an error rate counted by the error determination unit.

20. The wireless communication device according to claim 19 , wherein the received data processing unit converts the low frequency ADPCM data into amplitude attenuation data when the error rate falls within a range between a first threshold value and a second threshold value.

21. The wireless communication device according to claim 19 , wherein, when the error rate falls within a range which is in excess of a second threshold value, the received data processing unit converts the high frequency data into mute data, and converts the low frequency ADPCM data into mute data.

22. The wireless communication device according to claim 17 , further comprising a received signal strength indicator level determination section that determines a change in received signal strength indicator by monitoring the digital link, wherein the transmission data conversion unit determines, from a determination result of the received signal strength indicator level determination section, whether or not to convert some of the digital sound data into an error detection bit.

23. A communication terminal configuring a wireless communication device that establishes a digital link on a wireless channel and that performs communication by a sound packet which includes a sound signal encoded by adaptive differential pulse code modulation (ADPCM) and an error detection code, the communication terminal comprising: an ADPCM encoding unit that divides a sampled sound signal into a high frequency signal and a low frequency signal and individually encodes the high frequency signal and the low frequency signal by means of adaptive differential pulse code modulation to thereby convert the high frequency signal into high frequency ADPCM data having a first number of bits, and convert the low frequency signal into low frequency ADPCM data having a second number of bits; an error detection code generation unit that generates an error detection code pertinent to the high frequency ADPCM data having the first number of bits and the low frequency ADPCM data having the second number of bits; a transmission data conversion unit that replaces data pertinent to some of a plurality of bits which configure the low frequency ADPCM data with the error detection code generated by the error detection code generation unit; and a data transmission unit that is configured to transmit the high frequency ADPCM data and the low frequency ADPCM data which is partially replaced by the data conversion unit to a communication opponent.

24. The communication terminal according to claim 23 , further comprising an error determination unit that determines a change in error rate of the digital link, wherein the transmission conversion unit selects, based on a determination result of the error determination unit, whether to transmit the low frequency ADPCM data to a communication opponent after replacing some of the low frequency ADPCM data with an error detection code or to transmit the low frequency ADPCM data without replacing the some of the low frequency ADPCM data with the error detection code.

25. A communication terminal configuring a wireless communication device that establishes a digital link on a wireless channel and that performs a communication by a sound packet which includes a sound signal encoded by adaptive differential pulse code modulation (ADPCM) and an error detection code, the communication terminal comprising: a received data processing unit that extracts, from a received signal, high frequency ADPCM data, low frequency ADPCM data, and an error detection code, wherein, when an error is detected by means of the error detection code, the received data processing unit performs first signal processing on the high frequency ADPCM data received along with the error detection code, and second signal processing on the low frequency ADPCM data received along with the error detection code.