Transmitting apparatus, receiving apparatus, communication system, transmission method, reception method, and communication method
View Patent ↗A transmitting apparatus, receiving apparatus, communication system, and a signal processing method for each apply a suitable modulation method and transmission path estimation method in accordance with the characteristics of the transmission information and capable of improving the transmission efficiency. At the transmission side, the method of estimation of the transmission path and the modulation method are selected in accordance with an attribute of the data to be transmitted, for example, the size of a packet to be transmitted, the transmission data is mapped by the selected modulation method, the signal is processed in accordance with the transmission path estimation method, and a transmission signal is created by increase fast Fourier transform processing and transmitted. At the reception side, the received signal is fast Fourier transformed, the transmission path is estimated by the transmission path estimation method selected at the transmission side, the received signal is corrected in accordance with the result, and the received data is reproduced in accordance with the modulation method. Therefore, it is possible to always adopt the optimum transmission method in accordance with the attribute of the transmission data etc. and possible to realize an improvement of a transmission efficiency and an enhancement of the quality of communication.
1. A communication system for transmitting and receiving a plurality of channels of multi-carrier modulated signals each created in accordance with transmission data, comprising:
a transmission path estimation method selection circuit for each channel for selecting a transmission path estimation method in accordance with an attribute of said transmission data,
a mapping circuit for each channel for arranging signal points based on said transmission data by modulation methods set with respect to a plurality of sub-carriers,
a transmission path estimation processing circuit for each channel for signal processing for estimating the transmission path in accordance with said selected transmission path estimation method for an output signal of said mapping circuit,
a multiplex circuit for multiplexing output signals for each channel from each transmission path estimation processing circuit and outputting a multiplexed signal a reception circuit for receiving a transmission signal from said transmission path,
a first orthogonal transform circuit for orthogonally transforming the multiplexed signal from said multiplex circuit, a transmission circuit for transmitting an output signal of said first orthogonal transform circuit to the transmission path,
a second orthogonal transform circuit for orthogonally transforming an output signal of said reception circuit,
a transmission path estimation circuit for estimating a characteristic of the transmission path based on processing of an estimation of the transmission path carried out by said transmission path estimation processing circuit based on the output signal of said second orthogonal transform circuit, and
a data output circuit for correcting said signal received by said reception circuit in accordance with the result of the estimation of said transmission path estimation circuit and outputting the predetermined received data, and
a deinterleave circuit for rearranging the data in an output signal from data output circuit to restore the data to an original order.
2. The communication system as set forth in claim 1 , wherein said transmission path estimation method selection circuit selects said transmission path estimation method in accordance with a size of said transmission data.
3. The communication system as set forth in claim 1 , wherein said transmission path estimation method selection circuit selects said transmission path estimation method in accordance with a perceived importance of said transmission data.
4. The communication system as set forth in claim 1 , wherein said transmission. path estimation method selection circuit selects said transmission path estimation method in accordance with a state of a transmission channel.
5. The communication system as set forth in claim 1 , wherein said transmission path estimation method selection circuit selects said transmission path estimation method in accordance with a possibility of retransmission of said transmission data when said transmission fails.
6. The communication system as set forth in claim 1 , wherein said transmission path estimation method selection circuit has a differential modulation circuit for differentially modulating an output signal of said mapping circuit.
7. The communication system as set forth in claim 6 , wherein said differential modulation circuit outputs a modulated signal in accordance with a phase difference between a transmission signal and a reference with an adjoining transmission signal on a time axis as a reference.
8. The communication system as set forth in claim 6 , wherein said differential modulation circuit outputs a modulated signal in accordance with a phase difference between a transmission signal and a reference with an adjoining transmission signal on a frequency axis as a reference.
9. The communication system as set forth in claim 6 , wherein said differential modulation circuit outputs a modulated signal in accordance with a phase difference between a transmission signal and a reference with an adjoining transmission signal on a time axis and frequency axis as a reference.
10. The communication system as set forth in claim 1 , wherein said transmission path estimation processing circuit has a pilot addition circuit adding a transmission path estimation pilot signal to a transmission signal output by said mapping circuit.
11. The communication system as set forth in claim 10 , wherein said pilot addition circuit adds said pilot signal to said transmission signal at a constant rate from a time of starting transmission.
12. The communication system as set forth in claim 10 , wherein said pilot addition circuit reduces the number of pilot signals to be added each modulation time after a start of transmission.
13. The communication system as set forth in claim 10 , wherein said pilot addition circuit holds a ratio of said pilot signals added to said transmission signal at a constant when a predetermined time elapses after a start of transmission.
14. The communication system as set forth in claim 10 , wherein said pilot addition circuit stops the adding of said pilot signal when a predetermined time elapses after a start of transmission.
15. The communication system as set forth in claim 1 , wherein said orthogonal transform circuit performs an inverse fast Fourier transform on an output signal of said transmission path estimation processing circuit.
16. The communication system as set forth in claim 1 , wherein said second orthogonal transform circuit performs a fast Fourier transform on said received signal.
17. The communication system as set forth in claim 1 , wherein said transmission path estimation circuit includes:
a differential demodulation circuit for differentially demodulating the output signal of said second orthogonal transform circuit with the output signal of said orthogonal transform circuit at a predetermined time as a reference signal when said transmitting apparatus is engaged in differential modulation, and
a transmission path equalization circuit for extracting a pilot signal from the output signal of said second orthogonal transform circuit when adding the pilot signal to the transmission data by said transmitting apparatus and estimating characteristics of the transmission path in accordance with the extracted pilot signal.
18. The communication system as set forth in claim 17 , wherein said differential demodulation circuit includes:
a storage circuit for storing the output signal of said orthogonal transform circuit, and a phase correction circuit for correcting a phase of the output signal of said second orthogonal transform circuit with a predetermined storage signal in said stored signal as the reference in accordance with a modulation method of differential modulation in the transmitting apparatus.
19. The communication system as set forth in claim 17 , wherein said transmission path equalization circuit includes:
a pilot extraction circuit for extracting said pilot signal from the output signal of said second orthogonal transform circuit,
a first addition circuit, in a case where said extracted pilot signal is divided into groups established in accordance with frequency bands, for adding pilot signals of each group with at least one pilot signal from an adjoining group,
a multiplication circuit for multiplying a result of addition of pilot signals at an adjoining previous modulation time on the time axis by a predetermined coefficient, and
a second addition circuit for adding a result of addition of the addition circuit at a present point of time and an output signal of said multiplication circuit.
20. The communication system as set forth in claim 1 , wherein said data output circuit outputs the received data of a predetermined number of bits based on said received signal in accordance with a modulation method of the received signal.