WIRELESS COMMUNICATION METHOD, WIRELESS COMMUNICATION SYSTEM, AND WIRELESS TRANSMISSION DEVICE
The wireless transmission device includes a power amplifier that varies transmission power. An SNR degradation amount calculation unit calculates an SNR degradation amount {QAM} caused by QAM and an SNR degradation amount {APSK} caused by APSK on the basis of input/output characteristics of the power amplifier acquired from an input/output characteristic storage unit, a QAM modulated signal acquired from a QAM modulation unit, an APSK modulated signal acquired from an APSK modulation unit, and the transmission power of the power amplifier. A modulation scheme selection unit acquires a required SNR {QAM} of QAM and a required SNR {APSK} of APSK from a required SNR storage unit, compares “required SNR {QAM}+SNR degradation amount {QAM}” with “required SNR {APSK}+SNR degradation amount {APSK}”, and selects the modulation scheme with the smaller value.
1 . A wireless communication method using a wireless transmitter and a wireless receiver that support at least two multi-level modulation schemes,
the at least two multi-level modulation schemes including a first modulation scheme and a second modulation scheme, and
the wireless transmitter including a power amplifier that varies transmission power, the wireless communication method comprising:
acquiring, by the wireless transmitter, a first required signal-noise ratio (SNR) to be ensured when using the first modulation scheme and a second required SNR to be ensured when using the second modulation scheme;
modulating, by the wireless transmitter, a transmission signal using the first modulation scheme to generate a first modulated signal;
modulating, by the wireless transmitter, a transmission signal using the second modulation scheme to generate a second modulated signal;
calculating, by the wireless transmitter, a first SNR degradation amount predicted to occur when the first modulated signal is amplified by the power amplifier at desired transmission power, on the basis of input/output characteristics of the power amplifier;
calculating, by the wireless transmitter, a second SNR degradation amount predicted to occur when the second modulated signal is amplified by the power amplifier at the desired transmission power, on the basis of the input/output characteristics;
calculating, by the wireless transmitter, a first index representing appropriateness of using the first modulation scheme for communication on the basis of the first required SNR and the first SNR degradation amount;
calculating, by the wireless transmitter, a second index representing appropriateness of using the second modulation scheme for communication on the basis of the second required SNR and the second SNR degradation amount;
selecting, by the wireless transmitter, one of the first modulation scheme and the second modulation scheme as a scheme to be used for communication on the basis of a result of comparison between the first index and the second index;
commanding, by the wireless transmitter, the wireless receiver to perform communication using the selected modulation scheme; and
communicating, by the wireless receiver, with the wireless transmitter using the commanded modulation scheme.
2 . The wireless communication method according to claim 1 , wherein the first required SNR is a fixed value set for the first modulation scheme, and the second required SNR is a fixed value set for the second modulation scheme.
3 . The wireless communication method according to claim 1 , wherein each of the first required SNR and the second required SNR is a value set on the basis of quality of communication to be established.
4 . The wireless communication method according to claim 1 , wherein
calculating the first SNR degradation amount includes:
estimating a first error vector magnitude (EVM), which is an EVM for the first modulated signal included in the transmission signal of one frame; and
calculating the first SNR degradation amount on the basis of the first EVM, and
calculating the second SNR degradation amount includes:
estimating a second EVM, which is an EVM for the second modulated signal included in the transmission signal of one frame; and
calculating the second SNR degradation amount on the basis of the second EVM.
5 . The wireless communication method according to claim 1 , wherein
calculating the first SNR degradation amount includes:
estimating a first EVM, which is an EVM for the first modulated signal included in the transmission signal over a plurality of frames; and
calculating the first SNR degradation amount on the basis of the first EVM, and
calculating the second SNR degradation amount includes:
estimating a second EVM, which is an EVM for the second modulated signal included in the transmission signal over a plurality of frames; and
calculating the second SNR degradation amount on the basis of the second EVM.
6 . The wireless communication method according to claim 4 , wherein
calculating the first SNR degradation amount further includes:
calculating a first average SNR, which is an average SNR for the first modulation scheme;
calculating a first predicted SNR on the basis of the first EVM, the first predicted SNR being an SNR predicted to occur when the first modulated signal is transmitted; and
calculating a difference between the first average SNR and the first predicted SNR as the first SNR degradation amount, and
calculating the second SNR degradation amount further includes:
calculating a second average SNR, which is an average SNR for the second modulation scheme;
calculating a second predicted SNR on the basis of the second EVM, the second predicted SNR being an SNR predicted to occur when the second modulated signal is transmitted; and
calculating a difference between the second average SNR and the second predicted SNR as the second SNR degradation amount.
7 . A wireless communication system using a wireless transmitter and a wireless receiver that support at least two multi-level modulation schemes, wherein
the at least two multi-level modulation schemes include a first modulation scheme and a second modulation scheme,
the wireless transmitter
includes a power amplifier that varies transmission power, and
being configured to execute:
acquiring a first required SNR to be ensured when using the first modulation scheme and a second required SNR to be ensured when using the second modulation scheme;
modulating a transmission signal using the first modulation scheme to generate a first modulated signal;
modulating a transmission signal using the second modulation scheme to generate a second modulated signal;
calculating a first SNR degradation amount predicted to occur when the first modulated signal is amplified by the power amplifier at desired transmission power, on the basis of input/output characteristics of the power amplifier;
calculating a second SNR degradation amount predicted to occur when the second modulated signal is amplified by the power amplifier at the desired transmission power, on the basis of the input/output characteristics;
calculating a first index representing appropriateness of using the first modulation scheme for communication on the basis of the first required SNR and the first SNR degradation amount;
calculating a second index representing appropriateness of using the second modulation scheme for communication on the basis of the second required SNR and the second SNR degradation amount;
selecting one of the first modulation scheme and the second modulation scheme as a scheme to be used for communication on the basis of a result of comparison between the first index and the second index; and
commanding the wireless receiver to perform communication using the selected modulation scheme, and
the wireless receiver is configured to communicate with the wireless transmitter using the commanded modulation scheme.
8 . A wireless transmitter that supports at least two multi-level modulation schemes and has a function of communicating with a wireless receiver that supports the at least two multi-level modulation schemes, wherein
the at least two multi-level modulation schemes include a first modulation scheme and a second modulation scheme, and
the wireless transmitter
comprises a power amplifier that varies transmission power, and
being configured to execute:
acquiring a first required SNR to be ensured when using the first modulation scheme and a second required SNR to be ensured when using the second modulation scheme;
modulating a transmission signal using the first modulation scheme to generate a first modulated signal;
modulating a transmission signal using the second modulation scheme to generate a second modulated signal;
calculating a first SNR degradation amount predicted to occur when the first modulated signal is amplified by the power amplifier at desired transmission power, on the basis of input/output characteristics of the power amplifier;
calculating a second SNR degradation amount predicted to occur when the second modulated signal is amplified by the power amplifier at the desired transmission power, on the basis of the input/output characteristics;
calculating a first index representing appropriateness of using the first modulation scheme for communication on the basis of the first required SNR and the first SNR degradation amount;
calculating a second index representing appropriateness of using the second modulation scheme for communication on the basis of the second required SNR and the second SNR degradation amount;
selecting one of the first modulation scheme and the second modulation scheme as a scheme to be used for communication on the basis of a result of comparison between the first index and the second index; and
commanding the wireless reception device receiver to perform communication using the selected modulation scheme.
9 . The wireless communication method according to claim 2 , wherein
calculating the first SNR degradation amount includes:
estimating a first error vector magnitude (EVM), which is an EVM for the first modulated signal included in the transmission signal of one frame; and
calculating the first SNR degradation amount on the basis of the first EVM, and
calculating the second SNR degradation amount includes:
estimating a second EVM, which is an EVM for the second modulated signal included in the transmission signal of one frame; and
calculating the second SNR degradation amount on the basis of the second EVM.
10 . The wireless communication method according to claim 3 , wherein
calculating the first SNR degradation amount includes:
estimating a first error vector magnitude (EVM), which is an EVM for the first modulated signal included in the transmission signal of one frame; and
calculating the first SNR degradation amount on the basis of the first EVM, and
calculating the second SNR degradation amount includes:
estimating a second EVM, which is an EVM for the second modulated signal included in the transmission signal of one frame; and
calculating the second SNR degradation amount on the basis of the second EVM.
11 . The wireless communication method according to claim 2 , wherein
calculating the first SNR degradation amount includes:
estimating a first EVM, which is an EVM for the first modulated signal included in the transmission signal over a plurality of frames; and
calculating the first SNR degradation amount on the basis of the first EVM, and
calculating the second SNR degradation amount includes:
estimating a second EVM, which is an EVM for the second modulated signal included in the transmission signal over a plurality of frames; and
calculating the second SNR degradation amount on the basis of the second EVM.
12 . The wireless communication method according to claim 3 , wherein
calculating the first SNR degradation amount includes:
estimating a first EVM, which is an EVM for the first modulated signal included in the transmission signal over a plurality of frames; and
calculating the first SNR degradation amount on the basis of the first EVM, and
calculating the second SNR degradation amount includes:
estimating a second EVM, which is an EVM for the second modulated signal included in the transmission signal over a plurality of frames; and
calculating the second SNR degradation amount on the basis of the second EVM.
13 . The wireless communication method according to claim 5 , wherein
calculating the first SNR degradation amount further includes:
calculating a first average SNR, which is an average SNR for the first modulation scheme;
calculating a first predicted SNR on the basis of the first EVM, the first predicted SNR being an SNR predicted to occur when the first modulated signal is transmitted; and
calculating a difference between the first average SNR and the first predicted SNR as the first SNR degradation amount, and
calculating the second SNR degradation amount further includes:
calculating a second average SNR, which is an average SNR for the second modulation scheme;
calculating a second predicted SNR on the basis of the second EVM, the second predicted SNR being an SNR predicted to occur when the second modulated signal is transmitted; and
calculating a difference between the second average SNR and the second predicted SNR as the second SNR degradation amount.
14 . The wireless communication method according to claim 9 , wherein
calculating the first SNR degradation amount further includes:
calculating a first average SNR, which is an average SNR for the first modulation scheme;
calculating a first predicted SNR on the basis of the first EVM, the first predicted SNR being an SNR predicted to occur when the first modulated signal is transmitted; and
calculating a difference between the first average SNR and the first predicted SNR as the first SNR degradation amount, and
calculating the second SNR degradation amount further includes:
calculating a second average SNR, which is an average SNR for the second modulation scheme;
calculating a second predicted SNR on the basis of the second EVM, the second predicted SNR being an SNR predicted to occur when the second modulated signal is transmitted; and
calculating a difference between the second average SNR and the second predicted SNR as the second SNR degradation amount.
15 . The wireless communication method according to claim 10 , wherein
calculating the first SNR degradation amount further includes:
calculating a first average SNR, which is an average SNR for the first modulation scheme;
calculating a first predicted SNR on the basis of the first EVM, the first predicted SNR being an SNR predicted to occur when the first modulated signal is transmitted; and
calculating a difference between the first average SNR and the first predicted SNR as the first SNR degradation amount, and
calculating the second SNR degradation amount further includes:
calculating a second average SNR, which is an average SNR for the second modulation scheme;
calculating a second predicted SNR on the basis of the second EVM, the second predicted SNR being an SNR predicted to occur when the second modulated signal is transmitted; and
calculating a difference between the second average SNR and the second predicted SNR as the second SNR degradation amount.
16 . The wireless communication method according to claim 11 , wherein
calculating the first SNR degradation amount further includes:
calculating a first average SNR, which is an average SNR for the first modulation scheme;
calculating a first predicted SNR on the basis of the first EVM, the first predicted SNR being an SNR predicted to occur when the first modulated signal is transmitted; and
calculating a difference between the first average SNR and the first predicted SNR as the first SNR degradation amount, and
calculating the second SNR degradation amount further includes:
calculating a second average SNR, which is an average SNR for the second modulation scheme;
calculating a second predicted SNR on the basis of the second EVM, the second predicted SNR being an SNR predicted to occur when the second modulated signal is transmitted; and
calculating a difference between the second average SNR and the second predicted SNR as the second SNR degradation amount.
17 . The wireless communication method according to claim 12 , wherein
calculating the first SNR degradation amount further includes:
calculating a first average SNR, which is an average SNR for the first modulation scheme;
calculating a first predicted SNR on the basis of the first EVM, the first predicted SNR being an SNR predicted to occur when the first modulated signal is transmitted; and
calculating a difference between the first average SNR and the first predicted SNR as the first SNR degradation amount, and
calculating the second SNR degradation amount further includes:
calculating a second average SNR, which is an average SNR for the second modulation scheme;
calculating a second predicted SNR on the basis of the second EVM, the second predicted SNR being an SNR predicted to occur when the second modulated signal is transmitted; and
calculating a difference between the second average SNR and the second predicted SNR as the second SNR degradation amount.