1. A terminal device in a transmission system where, to cause multiple users who use terminal devices to perform a communication, multiple sets of data are encoded, transmitted, and received via a network between the terminal devices, the terminal device comprising:
a data receiving unit that receives document data from an external device;
a network-information acquiring unit that acquires a network bandwidth that is available to transmit data;
an assigning unit that assigns a transmission rate to each set of data that is to be transmitted to a different terminal device in accordance with the network bandwidth that is available to transmit data;
a quality determining unit that determines a quality of the document data that is transmitted from the terminal device to a different terminal device in accordance with a transmission rate that is assigned to the document data;
a quality converting unit that converts a quality of the document data that is input from the external device such that equal to or less than the determined quality is obtained;
an encoding unit that encodes multiple sets of data that include the converted document data by using transmission rates that are assigned to the sets of data; and
a transmitting unit that transmits multiple sets of encoded data to a different terminal device.
2. The terminal device according to claim 1, wherein
the encoding unit further includes
a video input unit that generates video data by capturing an object; and
a sound input unit that generates audio data by collecting a sound, and
the encoding unit encodes each of the video data, the audio data, and the document data by using a transmission rate that is assigned to each set of data.
3. The terminal device according to claim 1, wherein
the document data is image data that is displayed on a screen by a computer as a result of a program execution,
the quality determining unit determines at least one of a resolution, a frame rate, and a color depth that are parameters that indicate qualities of the document data in accordance with a transmission rate that is assigned to the document data, and
the quality converting unit converts a quality of the document data that is input from the external device such that a resolution, a frame rate, or a color depth becomes equal to or less than a determined value.
4. The terminal device according to claim 3, further comprising a table storage unit that stores a table that stores set values of a resolution, a frame rate, and a color depth with regard to each transmission rate range, wherein
the quality determining unit
extracts, from the table storage unit, set values of a resolution, a frame rate, and a color depth that are stored and related to a transmission rate that is assigned to the document data, and
determines, as a parameter whose quality needs to be converted, a parameter that has a higher quality than the document data that is input from the external device, among the resolution, the frame rate, and the color depth that are extracted,
and
the quality converting unit converts the quality to the extracted set value with regard to a parameter whose quality is determined to be converted by the quality determining unit among the resolution, the frame rate, and the color depth.
5. The terminal device according to claim 4, wherein
a set value of each parameter that is stored in the table is a value where, when the document data is encoded by using a corresponding transmission rate and is then decoded, a degradation of an image falls within an acceptable range.
6. The terminal device according to claim 1, wherein
the quality determining unit further determines a quality of the document data in accordance with a characteristic of the document data and a transmission rate that is assigned to the document data.
7. The terminal device according to claim 6, wherein
the quality determining unit determines a quality of the document data based on whether the document data is a moving image or a still image.
8. The terminal device according to claim 6, wherein
the quality determining unit determines a quality of the document data based on whether the document data includes a character or not.
9. A data transmission method that is implemented by a terminal device in a transmission system where, to cause multiple users who use terminal devices to perform a communication, multiple sets of data are encoded, transmitted, and received via a network between the terminal devices, the data transmission method comprising:
receiving document data from an external device;
acquiring a network bandwidth that is available to transmit data;
assigning a transmission rate to each set of data that is to be transmitted to a different terminal device in accordance with the network bandwidth that is available to transmit data;
determining a quality of the document data that is transmitted from the terminal device to a different terminal device in accordance with a transmission rate that is assigned to the document data;
converting a quality of the document data that is input from the external device such that equal to or less than the determined quality is obtained;
encoding multiple sets of data that include the converted document data by using transmission rates that are assigned to the sets of data; and
transmitting multiple sets of encoded data to a different terminal device.
10. The data transmission method according to claim 9, wherein
in the encoding, video data is generated by capturing an object and audio data is generated by collecting a sound, and each of the video data, the audio data, and the document data are encoded by using a transmission rate that is assigned to each set of data.
11. The data transmission method according to claim 9, wherein
the document data is image data that is displayed on a screen by a computer as a result of a program execution,
in the quality determining, at least one of a resolution, a frame rate, and a color depth that are parameters that indicate qualities of the document data are determined in accordance with a transmission rate that is assigned to the document data, and
in the quality converting, a quality of the document data that is input from the external device is converted such that a resolution, a frame rate, or a color depth becomes equal to or less than a determined value.
12. The data transmission method according to claim 11, further comprising storing a table that stores set values of a resolution, a frame rate, and a color depth with regard to each transmission rate range, wherein
in the quality determining,
set values of a resolution, a frame rate, and a color depth that are stored and related to a transmission rate that is assigned to the document data are extracted from the table, and
a parameter that has a higher quality than the document data that is input from the external device is determined, as a parameter whose quality needs to be converted, among the resolution, the frame rate, and the color depth that are extracted,
and
in the quality converting, with regard to a parameter whose quality is determined to be converted by the quality determining unit among the resolution, the frame rate, and the color depth, the quality is converted to the extracted set value.
13. The data transmission method according to claim 12, wherein
a set value of each parameter that is stored in the table is a value where, when the document data is encoded by using a corresponding transmission rate and is then decoded, a degradation of an image falls within an acceptable range.
14. The data transmission method according to claim 9,
wherein
in the quality determining, further determining a quality of the document data in accordance with a characteristic of the document data and a transmission rate that is assigned to the document data.
15. The data transmission method according to claim 14, wherein
in the quality determining, a quality of the document data is determined based on whether the document data is a moving image or a still image.
16. The data transmission method according to claim 14, wherein
in the quality determining, a quality of the document data is determined based on whether the document data includes a character or not.
17. A non-transitory computer-readable recording medium having computer readable program codes, performed by a computer as a terminal device in a transmission system where, to cause multiple users who use terminal devices to perform a communication, multiple sets of data are encoded, transmitted, and received via a network between the terminal devices, the program codes when executed causing the computer to function as:
a data receiving unit that receives document data from an external device;
a network-information acquiring unit that acquires a network bandwidth that is available to transmit data;
an assigning unit that assigns a transmission rate to each set of data that is to be transmitted to a different terminal device in accordance with the network bandwidth that is available to transmit data;
a quality determining unit that determines a quality of the document data that is transmitted from the terminal device to a different terminal device in accordance with a transmission rate that is assigned to the document data;
a quality converting unit that converts a quality of the document data that is input from the external device such that equal to or less than the determined quality is obtained;
an encoding unit that encodes multiple sets of data that include the converted document data by using transmission rates that are assigned to the sets of data; and
a transmitting unit that transmits multiple sets of encoded data to a different terminal device.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A multi-antenna reception apparatus that receives by a plurality of antennas a plurality of modulated signals transmitted simultaneously from a plurality of antennas and reconstructs data sequences corresponding respectively to said plurality of modulated signals from the received signals, the multi-antenna reception apparatus comprising:
a provisional decision section that provisionally decides all or at least one of the modulated signals from the received signals;
a signal point reduction section that reduces candidate signal points for a subject modulated signal using provisional decision results with respect to the modulated signals other than the subject modulated signal; and
a main decision section that obtains digital data with respect to the subject modulated signal based on a signal point distance between reduced candidate signal points and reception points of the received signals.
2. The multi-antenna reception apparatus according to claim 1, further comprising a channel fluctuation estimation section that estimates a channel fluctuation value between each transmit antenna and receive antenna based on a known signal inserted in each modulated signal, wherein:
said provisional decision section comprises:
a separation section that associates the modulated signal transmitted from each transmit antenna with the received signal received at each receive antenna using a channel fluctuation matrix comprising said channel fluctuation values as elements and carries out an inverse matrix calculation of said channel fluctuation matrix and thereby separates the received signal into the modulated signals transmitted from the respective transmit antennas; and
a decision section that obtains a digital signal by making a soft decision or a hard decision on each separated modulated signal and uses said digital signal as a provisional decision value; and
said signal point reduction section obtains all candidate signal points for said plurality of modulated signals multiplexed based on said channel fluctuation values, narrows down the candidate signal points for the subject modulated signal using said provisional decision value from all the candidate signal points and thereby reduces the candidate signal points for the subject modulated signal.
3. The multi-antenna reception apparatus according to claim 1, further comprising a signal point reduction section that reduces candidate signal points for the subject modulated signal using digital data other than the subject modulated signal out of the digital data obtained by said main decision section.
4. The multi-antenna reception apparatus according to claim 1, further comprising a signal point reduction section that reduces the candidate signal points for the subject modulated signal using the digital data other than the subject modulated signal out of the digital data obtained by said main decision section,
wherein the candidate signal points are reduced by recursively using the digital data obtained by said main decision section sequentially.
5. The multi-antenna reception apparatus according to claim 1, wherein said plurality of modulated signals comprise signals modulated in such a way that reception quality varies between said modulated signals.
6. The multi-antenna reception apparatus according to claim 1, wherein said main decision section makes a decision using reliability of a decision made by said provisional decision section.
7. The multi-antenna reception apparatus according to claim 6, wherein said main decision section uses a path metric of each symbol at said provisional decision section as said reliability and makes a decision with a branch metric weighted with said path metric.
8. The multi-antenna reception apparatus according to claim 1, wherein said provisional decision section classifies candidate signal points into a plurality of sets for each transmission bit and performs soft decision decoding using a minimum square Euclid distance between points of each set and the point of the received signal.
9. A multi-antenna reception method for reconstructing data sequences which correspond respectively to modulated signals from a received signal made up of a plurality of simultaneously transmitted modulated signals multiplexed on a propagation path, the multi-antenna reception method comprising:
a provisional decision step of provisionally deciding all or at least one of said modulated signals from said received signal;
a signal point reduction step of reducing candidate signal points for a subject modulated signal using provisional decision results with respect to the modulated signals other than the subject modulated signal; and
a main decision step of obtaining digital data with respect to the subject modulated signal based on the reduced candidate signal points and the reception point of said received signal.
10. The multi-antenna reception method according to claim 9, wherein a rough decision is made in said provisional decision step and a detailed decision is made in said main decision step.
11. The multi-antenna reception method according to claim 10, wherein in said decision step, each modulated signal is separated by an inverse matrix calculation of a channel fluctuation matrix and each modulated signal after the separation is decided for each modulated signal and in said main decision step, a calculation including a maximum likelihood detection is carried out.
12. The multi-antenna reception method according to claim 9, further comprising a signal point reduction step of reducing candidate signal points used in said main decision step through iteration processing recursively using the digital data obtained in said main decision step.
13. The multi-antenna reception method according to claim 9, wherein in said main decision step, a decision is made using reliability of a decision in said provisional decision step.
14. A multi-antenna transmission apparatus comprising:
a plurality of antennas; and
an interleaver that interleaves signals transmitted from said antennas in different interleaving patterns.
15. The multi-antenna transmission apparatus according to claim 14, wherein the interleaving patterns of said interleaver is selected so as to have no correlation between the antennas.
16. The multi-antenna transmission apparatus according to claim 14, further comprising an OFDM modulation section that OFDM-modulates each transmission signal after interleaving,
wherein said interleaver selects an interleaving pattern in which data is arranged from low frequency subcarriers to high frequency subcarriers as a first interleaving pattern and selects an interleaving pattern in which data is arranged from high frequency subcarriers to low frequency subcarriers as a second interleaving pattern.
17. The multi-antenna transmission apparatus according to claim 14, further comprising an OFDM modulation section that OFDM-modulates each transmission signal after interleaving,
wherein said interleaver selects an interleaving pattern in which data is arranged from earlier times to later times in the time direction of subcarriers as a first interleaving pattern and selects an interleaving pattern in which data is arranged from later times to earlier times in the time direction of subcarriers as a second interleaving pattern.
18. The multi-antenna transmission apparatus according to claim 14, further comprising a space-time code insertion section that inserts space-time codes between data symbols.
19. The multi-antenna transmission apparatus according to claim 14, further comprising a special symbol insertion section that inserts special symbols having smaller decision errors than data symbol between data symbols.
20. The multi-antenna transmission apparatus according to claim 14, further comprising an antenna switching section that necessarily switches between the antennas for transmission at least once within a coded block.
21. The multi-antenna transmission apparatus according to claim 14, comprising an LDPC (Low Density Parity Check) coder instead of said interleaver,
wherein signals transmitted from said respective antennas are interleaved in different interleaving patterns by changing a generation matrix of said LDPC coder.
22. The multi-antenna transmission apparatus according to claim 14, further comprising:
an OFDM modulation section that OFDM-modulates each transmission signal after interleaving; and
a signal assignment section that assigns signals transmitted from the respective antennas to subcarriers in different patterns instead of said interleaver.
23. The multi-antenna transmission apparatus according to claim 14, wherein said interleaver applies interleaving processing for every xth symbol to transmission signals transmitted from a first antenna out of said plurality of antennas and applies interleaving processing for every yth (x\u2260y) symbol to transmission signals transmitted from a second antenna.
24. The multi-antenna transmission apparatus according to claim 23, wherein said interleaver applies interleaving processing in a block size equal to the least common multiple of said x and y.
25. The multi-antenna transmission apparatus according to claim 23, wherein said interleaver applies interleaving processing using a prime number for at least one of said x, y.
26. The multi-antenna transmission apparatus according to claim 23, wherein said interleaver further applies interleaving processing whereby an offset is provided in the frequency direction or in the time direction between block interleaving on the transmission signal transmitted from the first antenna and block interleaving on the transmission signal transmitted from the second antenna.
27. A multi-antenna communication system comprising a multi-antenna transmission apparatus provided with a plurality of antennas that transmits different modulated signals from the respective antennas simultaneously and a multi-antenna reception apparatus provided with a plurality of antennas that reconstructs a data sequence which corresponds to each modulated signal by demodulating a received signal received using said plurality of antennas, wherein:
said multi-antenna transmission apparatus comprises an interleaver that interleaves signals transmitted from said respective antennas in different interleaving patterns; and
said multi-antenna reception apparatus comprises:
a provisional decision section that provisionally decides all or at least one of said modulated signals from said received signal;
a signal point reduction section that reduces candidate signal points about the subject modulated signal using the provisional decision result about the modulated signals other than the subject modulated signal; and
a main decision section that obtains digital data about the subject modulated signal by calculating a signal point distance between the reduced candidate signal points and the reception point of said received signal.
28. The multi-antenna communication system according to claim 27, further comprising a space-time code insertion section that inserts space-time codes between data symbols.
29. The multi-antenna communication system according to claim 27, further comprising a special symbol insertion section that inserts special symbols having smaller decision errors than data symbol between data symbols.
30. The multi-antenna communication system according to claim 27, further comprising an antenna switching section that necessarily switches between antennas for transmission at least once within a coded block.
31. The multi-antenna communication system according to claim 27, comprising an LDPC (Low Density Parity Check) coder instead of said interleaver,
wherein signals transmitted from said respective antennas are interleaved in different interleaving patterns by changing a generation matrix of said LDPC coder.
32. The multi-antenna communication system according to claim 27, further comprising an OFDM modulation section that OFDM-modulates each transmission signal after interleaving,
wherein said interleaver assigns transmission symbols transmitted from the respective antennas to subcarriers in different patterns in the time direction or the frequency direction.
33. A multi-antenna communication system comprising a multi-antenna transmission apparatus provided with a plurality of antennas that transmits different modulated signals simultaneously from the respective antennas and a multi-antenna reception apparatus provided with a plurality of antennas that reconstructs a data sequence which corresponds to each modulated signal by demodulating a received signal received using said plurality of antennas, wherein:
said multi-antenna reception apparatus comprises:
a provisional decision section that provisionally decides all or at least one of said modulated signals from said received signal;
a signal point reduction section that reduces candidate signal points about the subject modulated signal using the provisional decision result about the modulated signals other than the subject modulated signal; and
a main decision section that obtains digital data about the subject modulated signal by calculating a signal point distance between the reduced candidate signal points and the reception point of said received signal; and
said multi-antenna transmission apparatus transmits a smaller number of modulated signals at the time of retransmission than modulated signals transmitted at any time other than retransmission.
34. The multi-antenna communication system according to claim 33, wherein said multi-antenna transmission apparatus forms said modulated signal using a space-time code or cycled delay diversity at the time of retransmission.