JP6549495B2 - Transmission apparatus and transmission method - Google Patents

Description

  The present invention relates to a transmission apparatus and transmission method.

  In radio transmission, fading occurs in which the reception level fluctuates due to multiple wave propagation, and the transmission quality may be greatly degraded due to the drop in the reception level. As a technique for reducing deterioration of transmission quality due to a drop in reception level, a diversity technique using reception signals received in each of two or more paths with low correlation of reception level variation is known.

  Among the diversity techniques, there is a frequency offset transmission diversity method as one of methods for performing space diversity without requiring channel information on the transmission side (Non-Patent Document 1). In the frequency offset transmission diversity system, a plurality of signals obtained by giving different frequency offsets to center frequencies of signals to be transmitted are respectively transmitted using a plurality of antennas. By transmitting a plurality of signals to which different frequency offsets are given, the reception level fluctuates on the reception side due to the frequency difference between each other, and it is possible to reduce the drop of the steady reception level.

  FIG. 2 is a diagram showing a configuration example of a wireless communication system to which the frequency offset transmission diversity scheme is applied. The wireless communication system includes a transmitting device 80 and a receiving device 90.

  The transmitter 80 includes an encoder 11, an interleaver 12, a symbol generator 13, M frequency offset adders 14 (14-1 to 14-M), and M radio units 16 (16 to 16 1 to 16 -M) and M transmitting antennas 17 (17-1 to 17 -M). The encoding unit 11 performs error correction coding on the input signal sequence to be transmitted. The interleaver 12 interleaves the signal sequence obtained by the coding by the coding unit 11. The symbol generation unit 13 generates a symbol sequence from the signal sequence obtained by interleaving by the interleaver 12.

  The frequency offset assignment unit 14 and the radio unit 16 are provided for each of the transmission antennas 17. That is, the number of frequency offset assignment units 14 and the number of radio units 16 are determined by the number of transmission antennas. The frequency offset assigning units 14-1 to 14 -M respectively assign different frequency offsets to the symbol strings generated by the symbol generator 13. Each of the radio units 16-1 to 16-M performs digital-analog conversion and frequency conversion on the symbol sequence to which the frequency offset is added by the corresponding frequency offset application unit 14. Each of the radio units 16-1 to 16-M transmits the transmission signal obtained by the conversion through the corresponding transmission antenna 17.

  The receiving apparatus 90 includes a receiving antenna 21, a wireless unit 22, a detecting unit 23, a symbol identifying unit 24, a deinterleaver 25, and a decoding unit 26. The receiving antenna 21 receives a signal transmitted from the transmitting device 80. The wireless unit 22 performs frequency conversion and analog-digital conversion on the signal received by the receiving antenna 21. The wireless unit 22 outputs the digital reception signal obtained by the conversion to the detection unit 23. The detection unit 23 performs detection on the received signal output from the wireless unit 22 and extracts a symbol sequence. The symbol identification unit 24 converts the symbol sequence obtained by the detection unit 23 into a signal sequence. The deinterleaver 25 deinterleaves the signal sequence obtained by the symbol identification unit 24. The decoding unit 26 corrects an error included in the signal sequence obtained by the deinterleaver 25 by the deinterleaver 25 and outputs the obtained signal sequence.

  In the transmitting device 80, different frequency offsets are assigned to the transmission signals transmitted from the transmission antennas 17-1 to 17-M. As a result, the steady drop of the reception level of the signal received by the receiving device 90 is reduced, and the transmission quality is improved.

Hiroki Fujino, 3 others, "BS-1-19 Wideband Ubiquitous Network Diversity Technology (2)-Frequency Offset Transmit Diversity", Proceedings of the IEICE General Conference 2008-Communications (1), 2008 3 May 5

  In the frequency offset transmission diversity system, a plurality of signals having different frequency offsets are simultaneously transmitted from different transmission antennas, and a beat is forcibly generated in a receiving apparatus which is a signal receiving point. That is, since there is a difference (frequency difference) in the center frequencies of the signals transmitted from the respective transmission antennas, the strength of the received signal is repeated in a cycle corresponding to the frequency difference.

  In out-of-sight wireless communication in a cellular environment or the like, radio waves transmitted from a transmitting antenna of a base station are reflected by radio scatterers such as buildings existing in the vicinity of the terminal and in the propagation path to the terminal to reach the terminal. The reflected waves that reach the terminal through different propagation paths are represented as vectors that are approximately equal in magnitude and different in phase. Since the phase rotation speed of the vector of the reflected wave is different for each transmitting antenna due to the different frequency offset given to the signal for each transmitting antenna of the base station, frequency beating occurs when the vector of the reflected wave is combined at reception in the terminal.

  At this time, the magnitude of the vector of the reflected wave is equal for every transmitting antenna, so that there is a problem that the reception level of the received signal drops significantly in the frequency beat cycle and a bit error occurs in the signal. The In addition, since the frequency beat period becomes short as the number of transmitting antennas increases, the number of times the reception level drops in one packet (frame) increases, and the error correction by error correction coding is not correctly performed and sufficient diversity. There is a problem that gain can not be obtained.

  In view of the foregoing, it is an object of the present invention to provide a transmission apparatus and transmission method capable of improving diversity gain in wireless communication to which a frequency offset transmission diversity scheme is applied.

  One aspect of the present invention includes a plurality of antennas, a frequency offset assigning unit that is provided for each of the antennas and assigns different frequency offsets to the symbol sequences to be transmitted, and is provided for each of the antennas. Transmitting apparatus comprising: an amplitude offset applying unit for applying different amplitude offsets to symbol sequences; and a radio unit for transmitting, from different antennas, a plurality of symbol sequences to which different frequency offsets and different amplitude offsets are applied. It is.

  Further, according to one aspect of the present invention, in the above transmission apparatus, the amplitude offset adding unit adds a total power of transmission power when a symbol sequence before giving an amplitude offset is transmitted and an amplitude offset. An amplitude offset that gives the same total power as that of the transmission power when the symbol sequence is transmitted is assigned to each symbol sequence to which a frequency offset is assigned by the plurality of frequency offset assigning units.

  Further, according to one aspect of the present invention, in the above transmission apparatus, where the number of antennas is M, the amplitude offset giving unit transmits from the Nth antennas (N = 1, 2,..., M) An amplitude offset is assigned to the symbol sequence to be transmitted such that the transmission power of the symbol sequence is allocated at a ratio of (2N-1) / (2M).

  Further, according to one aspect of the present invention, in the transmission apparatus described above, the amplitude offset giving unit gives the frequency offset given by the plurality of frequency offset giving units as the amplitude offset determined based on the number of the antennas. Assigned to each symbol series.

  Further, according to one aspect of the present invention, in the transmission apparatus described above, the amplitude offset giving unit is configured to provide a plurality of frequency offset giving units with amplitude offsets of which absolute values are set larger as the number of antennas increases. It gives to each symbol sequence to which the frequency offset was given by.

  Further, an aspect of the present invention is a transmission method performed by a transmission apparatus including a plurality of antennas, wherein a frequency offset giving step of giving a different frequency offset for each of the antennas to a symbol sequence to be transmitted; The antenna in which different amplitude offsets are applied to each of the symbol sequences to which different frequency offsets are applied in the application step, and a plurality of symbol sequences to which different frequency offsets and different amplitude offsets are applied And a transmitting step of transmitting from.

  According to the present invention, it is possible to improve the diversity gain in wireless communication to which the frequency offset transmission diversity scheme is applied.

FIG. 1 is a block diagram showing a configuration example of a wireless communication system in the present embodiment. The figure which shows the structural example of the radio | wireless communications system to which the frequency offset transmission diversity system was applied.

  Hereinafter, with reference to the drawings, a transmission apparatus and a transmission method in an embodiment of the present invention will be described. FIG. 1 is a block diagram showing a configuration example of a wireless communication system in the present embodiment. The wireless communication system of the present embodiment includes a transmitting device 1 and a receiving device 2. In addition, the same code | symbol is attached | subjected to the component which performs the operation | movement similar to the component in the radio | wireless communications system shown in FIG. 2, and the overlapping description is abbreviate | omitted.

  The transmitter 1 includes an encoder 11, an interleaver 12, a symbol generator 13, M frequency offset adders 14 (14-1 to 14-M), and M amplitude offset adders 15 15-1 to 15-M), M radio units 16 (16-1 to 16-M), and M transmission antennas 17 (17-1 to 17-M). The transmission device 1 includes, in FIG. 2, the point that the amplitude offset applying units 15-1 to 15 -M are provided between the frequency offset applying units 14-1 to 14 -M and the radio units 16-1 to 16 -M. It differs from the transmitter 80 shown. The receiving device 2 includes a receiving antenna 21, a wireless unit 22, a detecting unit 23, a symbol identifying unit 24, a deinterleaver 25, and a decoding unit 26. The receiver 2 has the same configuration as the receiver 90 shown in FIG.

  The amplitude offset giving unit 15 is provided for each of the transmission antennas 17 in the same manner as the frequency offset giving unit 14 and the radio unit 16. The amplitude offset applying units 15-1 to 15-M apply amplitude offsets to the respective symbol sequences to which the frequency offset is applied by the corresponding frequency offset applying unit 14. The frequency offsets provided by the amplitude offset applying units 15-1 to 15-M are different from each other. The amplitude offset assigning units 15-1 to 15-M output the symbol sequences obtained by assigning the amplitude offsets to the radio units 16-1 to 16-M. The radio units 16-1 to 16-M are for the symbol sequence to which the frequency offset and the amplitude offset are given by the frequency offset giving units 14-1 to 14-M and the amplitude offset giving units 15-1 to 15-M, respectively. Perform digital-to-analog conversion and frequency conversion. The transmission device 1 transmits the transmission signal to which a different amplitude offset is added for each of the transmission antennas 17-1 to 17-M by including the amplitude offset addition units 15-1 to 15-M. The amplitude offsets given by the amplitude offset giving units 15-1 to 15-M are determined, for example, as follows.

  The total power of the transmission power when the symbol sequence before giving the amplitude offset is transmitted from each of the transmission antennas 17-1 to 17-M and the symbol sequence after giving the amplitude offset are the transmission antennas 17-1 to 17 M Each amplitude offset is determined so that it is the same as the total power of transmission power when each signal is transmitted. Specifically, when the transmission device 1 includes M transmission antennas 17, the transmission power of the signal transmitted from the Nth transmission antenna 17-N (N = 1, 2,..., M) is (2N). The amplitude offset which the amplitude offset giving units 15-1 to 15-M give the symbol sequence is determined so as to be assigned at the ratio -1) / (2M).

  Further, the amplitude offsets given by the amplitude offset giving units 15-1 to 15-M may be determined based on the number of transmission antennas 17 provided in the transmission device 1. Specifically, as the number of transmission antennas 17 included in the transmission device 1 increases, the absolute value of the amplitude offset provided by the amplitude offset giving units 15-1 to 15-M is increased.

  According to the wireless communication system of the present embodiment, the transmitter 1 applies different amplitude offsets to the signals transmitted from the transmission antennas 17-1 to 17-M in addition to applying different frequency offsets. Thus, the magnitude of the reflected wave vector in the multiple wave propagation environment is different for each of the transmission antennas 17-1 to 17-M. This makes it possible to reduce the amplitude drop caused by the frequency beating caused by the different frequency offset for each of the transmitting antennas 17-1 to 17-M, and to improve the diversity gain in the receiving device 2. As a result, it is possible to improve the diversity gain in wireless communication to which the frequency offset transmission diversity scheme is applied.

  Also, in the wireless communication system of the present embodiment, when the amplitude offset is determined so that the total transmission power does not increase, the diversity gain can be improved without increasing the total transmission power in the transmission apparatus 1.

  Further, in the radio communication system of the present embodiment, since the transmission quality can be improved by the improvement of the diversity gain, the total transmission power required to obtain a predetermined transmission quality can be reduced.

  Further, in the wireless communication system according to the present embodiment, when the number of transmission antennas 17 included in the transmission apparatus 1 is large, even if the number of reception level drops in one packet increases, the reception level drop width can be reduced. Therefore, the effect of the error correction by the error correction code can be improved, and a good diversity gain can be obtained.

  Further, in the wireless communication system of the present embodiment, when the amplitude offset is determined according to the number of transmission antennas included in the transmission device 1, when the number of transmission antennas 17 is small, the frequency beats by reducing the absolute value of the amplitude offset. Can be prevented from decreasing the average reception power (average reception level) of the reception signal generated in Thereby, the diversity gain can be improved while maintaining the effect of the error correction by the error correction code.

  In the transmitting apparatus 1 of the present embodiment, after the frequency offset assigning units 14-1 to 14-M assign frequency offsets to the symbol sequence, the amplitude offset assigning units 15-1 to 15-M symbolize the amplitude offsets. An example of the configuration given to However, after the amplitude offset applying units 15-1 to 15-M apply amplitude offsets to the symbol sequences, the frequency offset applying units 14-1 to 14-M may apply frequency offsets to the symbol sequences.

  In addition, the amplitude offset that the amplitude offset adding units 15-1 to 15-M add to the symbol sequence may be defined as an increase / decrease amount to be added to the amplitude of the symbol sequence, or multiplied by the amplitude of the symbol sequence. It may be defined as a ratio.

  In addition, each amplitude offset that the amplitude offset assigning units 15-1 to 15-M assign to the symbol sequence may be a value that changes periodically or may be a fixed value. When the amplitude offset is periodically changed, it is preferable to change it at a cycle different from the cycle of the frequency beat.

  All or part of the transmission device 1 in the above-described embodiment may be realized by a computer. For example, a program for realizing each component of the transmission device 1 is recorded in a computer readable recording medium, and the computer system reads and executes the program recorded in the recording medium to realize it. It is also good. Here, the “computer system” includes an OS and hardware such as peripheral devices. The term "computer-readable recording medium" refers to a storage medium such as a flexible disk, a magneto-optical disk, a ROM, a portable medium such as a ROM or a CD-ROM, or a hard disk built in a computer system. Furthermore, the "computer-readable recording medium" dynamically holds a program for a short time, like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. It may also include one that holds a program for a certain period of time, such as volatile memory in a computer system that becomes a server or a client in that case. Further, this program may be for realizing a part of the above-mentioned components, and the above-mentioned components can be realized in combination with a program already recorded in a computer system. It may be realized using hardware such as PLD (Programmable Logic Device) or FPGA (Field Programmable Gate Array).

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design and the like within the scope of the present invention.

  The present invention can also be applied to applications where it is essential to improve the diversity gain in a wireless communication applying a frequency offset transmission diversity scheme.

  DESCRIPTION OF SYMBOLS 1 ... Transmission apparatus, 11 ... Encoding part, 12 ... Interleaver, 13 ... Symbol generation part, 14 ... Frequency offset provision part, 15 ... Amplitude offset provision part, 16 ... Radio | wireless part, 17 ... Transmission antenna, 2 ... Reception apparatus , 21: reception antenna, 22: radio unit, 23: detection unit, 24: symbol identification unit, 25: deinterleaver, 26: decoding unit, 80: transmission device, 90: reception device

Claims (9)

With multiple antennas,
A frequency offset assignment unit provided for each of the antennas and assigning different frequency offsets to the symbol sequences to be transmitted;
An amplitude offset application unit provided for each of the antennas and applying different fixed amplitude offsets to the symbol sequences to be transmitted;
A radio unit for transmitting, from different antennas, a plurality of symbol sequences to which different frequency offsets and different fixed amplitude offsets are given;
A transmitter comprising: The amplitude offset giving unit
Applying an amplitude offset determined based on the number of antennas to each symbol sequence;
The transmitter according to claim 1. With multiple antennas,
A frequency offset assignment unit provided for each of the antennas and assigning different frequency offsets to the symbol sequences to be transmitted;
An amplitude offset application unit provided for each of the antennas and applying different amplitude offsets to the symbol sequences to be transmitted;
A radio unit for transmitting, from different antennas, a plurality of symbol sequences to which different frequency offsets and different amplitude offsets are given;
Equipped with
The amplitude offset giving unit
The total power of the transmission power when the symbol sequence prior to the application of an amplitude offset is transmitted, the total power and amplitude offset is the same transmission power when the symbol sequence after applying an amplitude offset is transmitted Given to each symbol series,
Send apparatus. With multiple antennas,
A frequency offset assignment unit provided for each of the antennas and assigning different frequency offsets to the symbol sequences to be transmitted;
An amplitude offset application unit provided for each of the antennas and applying different amplitude offsets to the symbol sequences to be transmitted;
A radio unit for transmitting, from different antennas, a plurality of symbol sequences to which different frequency offsets and different amplitude offsets are given;
Equipped with
When the number of antennas is M,
The amplitude offset giving unit
For the symbol sequence transmitted from the Nth antenna (N = 1, 2,..., M), the transmission power of the symbol sequence is allocated such that the transmission power of the symbol sequence is (2N-1) / (2M) Give an offset,
Send apparatus. With multiple antennas,
A frequency offset assignment unit provided for each of the antennas and assigning different frequency offsets to the symbol sequences to be transmitted;
An amplitude offset application unit provided for each of the antennas and applying different amplitude offsets to the symbol sequences to be transmitted;
A radio unit for transmitting, from different antennas, a plurality of symbol sequences to which different frequency offsets and different amplitude offsets are given;
Equipped with
The amplitude offset giving unit
An amplitude offset having an absolute value of the amplitude offset set larger as the number of antennas increases is given to each symbol sequence.
Send apparatus. A transmission method performed by a transmission apparatus provided with a plurality of antennas, wherein
Applying a frequency offset different for each antenna to a symbol sequence to be transmitted;
An amplitude offset applying step of applying a fixed amplitude offset different for each antenna to a symbol sequence to be transmitted ;
Transmitting, from different antennas, a plurality of symbol sequences given different frequency offsets and different fixed amplitude offsets;
Transmission method. A transmission method performed by a transmission apparatus provided with a plurality of antennas, wherein
Applying a frequency offset different for each antenna to a symbol sequence to be transmitted;
An amplitude offset applying step of applying an amplitude offset different for each antenna to a symbol sequence to be transmitted;
Transmitting, from different antennas, a plurality of symbol sequences to which different frequency offsets and different amplitude offsets are given;
Have
In the amplitude offset applying step,
Amplitude offset at which the total power of transmission power when the symbol sequence before applying the amplitude offset is transmitted and the total power of transmission power when the symbol sequence after applying the amplitude offset is transmitted are the same Given to each symbol series,
How to send A transmission method performed by a transmission apparatus provided with a plurality of antennas, wherein
Applying a frequency offset different for each antenna to a symbol sequence to be transmitted;
An amplitude offset applying step of applying an amplitude offset different for each antenna to a symbol sequence to be transmitted;
Transmitting, from different antennas, a plurality of symbol sequences to which different frequency offsets and different amplitude offsets are given;
Have
When the number of antennas is M,
In the amplitude offset applying step,
For the symbol sequence transmitted from the Nth antenna (N = 1, 2,..., M), the transmission power of the symbol sequence is allocated such that the transmission power of the symbol sequence is (2N-1) / (2M) Give an offset,
How to send A transmission method performed by a transmission apparatus provided with a plurality of antennas, wherein
Applying a frequency offset different for each antenna to a symbol sequence to be transmitted;
An amplitude offset applying step of applying an amplitude offset different for each antenna to a symbol sequence to be transmitted;
Transmitting, from different antennas, a plurality of symbol sequences to which different frequency offsets and different amplitude offsets are given;
Have
In the amplitude offset applying step,
An amplitude offset having an absolute value of the amplitude offset set larger as the number of antennas increases is given to each symbol sequence.
How to send

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