JP2003298670A - Transmitter and adaptive modulation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmitter capable of performing adaptive modulation by using small hardware scale. <P>SOLUTION: A modulation system deciding part 101 decides a modulation system suitable for modulating transmission data on the basis of receiving condition, and outputs command data for commanding the modulation system to an IQ data retrieving part 102. The IQ data retrieving part 102 is provided with an address generating part 103 and a storage device 104. The address generating part 103 generates an address from the command data and the transmission data, and outputs the address to the storage device 104. In accordance with the address, the storage device 104 outputs IQ data to a common modulation part 105 which are made to correspond to the address and stored. The common modulation part 105 generates a modulation wave having a prescribed amplitude and phase on the basis of the IQ data, and outputs the generated modulation wave to an amplitude adjustment circuit 106. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmitter and an adaptive modulation method for performing adaptive modulation, and is applicable to, for example, a mobile communication system.

[0002]

2. Description of the Related Art Heretofore, as a transmission apparatus using an adaptive modulation method, Japanese Patent Application Laid-Open No. 10-56420 and Japanese Patent Application Laid-Open No. 11-56420 have been known.
The one described in Japanese Patent No. 355373 is known.
FIG. 9 is a block diagram showing a part of a transmission device using a conventional adaptive modulation method. In FIG. 9, the adaptive modulator / encoder 11 includes a QPSK modulation circuit 12, an 8PSK modulation circuit 13, a 16QAM modulation circuit 14, and a 64QAM modulation circuit 15. The transmission data input to the adaptive modulator / encoder 11 is modulated for each modulation method and output to the data selector 17. The QPSK modulation circuit 12
A modulated wave is generated with 2 bits of transmission data as one symbol. The 8PSK modulation circuit 13 has 3 bits of transmission data, and the 16QAM modulation circuit 14 has 4 bits of transmission data.
The 64QAM modulation circuit 15 generates one modulated wave with 6 bits of transmission data. Each modulation circuit outputs the generated modulated wave to the data selector 17. In the case of QPSK, a specific example will be described. When the input transmission data is “10”, the first bit “1” corresponds to the I component (in-phase component) and the second bit “0”. Corresponds to the Q component (orthogonal component). The QPSK modulation circuit 12 combines the modulated waves of the respective components to generate a modulated wave of transmission data.

The modulation method determination unit 16 determines a modulation method suitable for the reception situation and outputs instruction data indicating the determined modulation method to the data selector 17. Data selector 17
Selects the modulated wave output from the adaptive modulator / encoder 11 according to the instruction data output from the modulation method determination unit 16 and outputs it as modulated data.

[0004]

However, in the conventional adaptive modulation method, it is necessary to provide a modulation circuit for each modulation method as described above, and there is a problem that the hardware scale becomes large. Further, as the modulation multi-level number increases, it is necessary to increase the bit accuracy of the data after modulation. Therefore, the hardware scale that actually configures the transmission device increases as the modulation multi-level number increases. There is a problem that it ends up.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a transmission apparatus and an adaptive modulation method capable of performing adaptive modulation with a small hardware scale.

[0006]

In order to solve such a problem, the transmitting apparatus of the present invention is determined as a modulation method determining means for determining one modulation method from a plurality of modulation methods based on the reception status. I indicating the in-phase component and the quadrature component of the modulated signal based on the information indicating the modulation method and the transmission data.
It is configured to include IQ data searching means for searching Q data, modulating means for modulating based on the searched IQ data, and transmitting means for transmitting a modulated signal.

According to this configuration, the in-phase component and the quadrature component of the modulation signal can be represented by IQ data, and the modulation wave corresponding to the IQ data can be generated by one modulation means. The scale can be reduced.

In the transmitting apparatus of the present invention, the IQ data search means searches the table in which the IQ data of all possible modulation schemes, the information indicating the modulation schemes, and the combination of transmission data are associated with each other. Adopt a configuration that does.

With this configuration, all possible in-phase components and quadrature components of the modulated signal can be represented by IQ data, and one modulating means can generate modulated waves corresponding to all signal points. Therefore, the hardware scale can be reduced.

The transmitting apparatus of the present invention comprises a correcting means for correcting the modulated signal by using a correction value according to each modulation method, and the IQ data searching means has a maximum modulation multilevel number. IQ of all modulation signals that can be adopted in the system
A configuration in which data is made to correspond to a modulation signal of another modulation scheme under a predetermined condition, and the IQ data is retrieved from a table in which a combination of the IQ data, information indicating the modulation scheme, and transmission data is associated take.

According to this configuration, the signal point of the modulation method having the maximum modulation multi-level number is arranged so as to approximate the signal point of the other modulation method, so that the IQ data can be represented by a small number of bits. It is possible to further reduce the hardware scale.

The adaptive modulation method of the present invention is based on a modulation method determining step of determining one modulation method from a plurality of modulation methods based on a reception situation, and information and transmission data indicating the determined modulation method. Thus, an IQ data search step of searching for IQ data indicating the in-phase component and the quadrature component of the modulated signal and a modulation step of performing modulation based on the searched IQ data are provided.

According to this method, the signal points whose arrangement positions are different for each modulation method can be represented by IQ data,
Since all the modulated waves of each component corresponding to the IQ data can be generated in one modulation process, the hardware scale can be reduced.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The essence of the present invention is that the I component and the Q component of all modulated waves indicated by each modulation method used for adaptive modulation are made to correspond to predetermined data in advance, and based on the data. It is to modulate with one modulation circuit. This makes it possible to reduce the hardware scale of the transmitting device that performs adaptive modulation.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the embodiment of the present invention, the modulation method used for the adaptive modulation method is QPSK, 8P.
It will be described as four types of SK, 16QAM, and 64QAM.

(Embodiment 1) In the present embodiment, IQ data indicating I component and Q component of a modulated wave corresponding to a combination of instruction data indicating a modulation method and transmission data is set in advance, and the IQ data is set. A case where modulation is performed by one modulation circuit will be described based on the above.

FIG. 1 is a block diagram showing the configuration of a transmitting apparatus according to Embodiment 1 of the present invention. In FIG. 1, a modulation scheme determination unit 101 determines a modulation scheme suitable for modulating transmission data based on an input reception status, and indicates data indicating the determined modulation scheme (hereinafter, simply “instruction data”). Is output to the address generation unit 103 of the IQ data search unit 102.

The IQ data search unit 102 includes an address generation unit 103 and a memory 104, and the I component of the modulated wave associated with the instruction data and the transmission data output from the modulation method determination unit 101 and IQ showing the Q component
The data is output to the common modulator 105.

The address generation unit 103 generates an address from the input transmission data and the instruction data output from the modulation method determination unit 101, and outputs the generated address to the memory 104.

The memory 104 outputs the IQ data stored in association with the address in the memory 104 to the common modulator 105 according to the address generated by the address generator 103. IQ data is expressed by 4 bits of I component (in-phase component) and 4 bits of Q component (quadrature component), and transmits an instruction for generating a predetermined modulated wave to the common modulation unit 105 by each bit data. You can

The common modulator 105 generates a modulated wave having a predetermined amplitude and phase based on the IQ data output from the memory 104, and the generated modulated wave is the amplitude adjusting circuit 1
It outputs to 06. Details of the IQ data search unit 102 and the common modulation unit 105 will be described later.

The amplitude adjusting circuit 106 includes a common modulator 105.
The modulated signal output from is adjusted to have a predetermined amplitude, and the amplitude-adjusted modulated signal is output to the wireless transmission unit 107. The wireless transmission unit 107 performs predetermined wireless transmission processing (D / A conversion, up conversion, etc.) on the amplitude-adjusted modulated signal.
Then, the signal is transmitted via the antenna 108.

Next, the modulation method determination unit 101 and the IQ data search unit 102 will be described in detail. The instruction data output from the modulation method determination unit 101 indicates the modulation method. For example, the instruction data “00” indicates QPSK, and the instruction data “01” indicates 8PSK. Similarly, the instruction data “10” is 16QAM, and the instruction data “11”.
Indicates 64 QAM, and instruction data indicating the modulation method is set in the modulation method determination unit 101 in advance.
The address generation unit 103 generates an address from the instruction data output from the modulation method determination unit 101 and the input transmission data. The transmission data is 2 bits for QPSK, 3 bits for 8PSK, 4 bits for 16QAM, and 6 bits for 64QAM, that is, the number of bits that can be represented by one signal point (1 symbol) in each modulation system is the unit of address generation. Become. The generated address is output to the memory 104.

The memory 104 stores I and Q components of IQ data which are associated with addresses in advance. Reference is now made to FIG. Figure 2 shows the address and IQ
It is a part of the data correspondence table. For example, when the address is generated from the instruction data “00” indicating the QPSK and the transmission data “01”, this address is the I of the IQ data.
It corresponds to the component “0101” and the Q component “1101”. In this way, a combination of the instruction data indicating each modulation method and all the transmission data for one symbol of each modulation method is defined as an address, and the I component and the Q of the corresponding IQ data are assigned to all the addresses. Each component is defined by 4 bits. In the memory 104, the IQ corresponding to the address output from the address generation unit 103
The data is searched and the corresponding data is searched for in the common modulation unit 105.
Is output to. The I component and the Q component of the IQ data correspond to the addresses, but are preset so as to cause the common modulation unit 105 to generate the modulated waves of the respective components.

Next, the common modulator 105 will be described in detail. The common modulation unit 105 includes an IQ data search unit 102.
Based on the I component and the Q component output from, the modulated wave of the I component and the modulated wave of the Q component are generated, and these are combined to generate the modulated wave of the transmission data.

This will be described in more detail with reference to FIG. Figure 3
[Fig. 4] is a correspondence diagram of IQ data in each modulation scheme and signal points representing each modulated wave. For example, focusing on QPSK, (I, Q) = (0101,0101) corresponds to the signal point 301 in the first quadrant as shown in FIG.
(I, Q) = (1101,0101) corresponds to the signal point 302 in the second quadrant, and (I, Q) = (1101,
1101) corresponds to the signal point 303 in the third quadrant, and (I, Q) = (0101, 1101) corresponds to the signal point 304 in the fourth quadrant. Similarly, in other modulation schemes, IQ data corresponds to each signal point, and I
The signal point can be determined by the Q data.

As shown in FIG. 3, each signal point corresponds to the transmission data in advance as in the conventional case. In QPSK, one signal point can represent 2-bit transmission data, and all possible values of the 2-bit data correspond to each signal point. Signal point 301 corresponds to transmission data “00” and signal point 3
02 is transmission data “10”, signal point 303 is transmission data “11”, signal point 304 is transmission data “01”,
Each corresponds. In other modulation schemes as well, the transmission data and the signal points correspond to each other as before. Therefore, the receiving side device can obtain the transmission data by demodulating the modulated wave generated by the IQ data in the same manner as the conventional method.

As described above, the IQ data corresponding to the combination of the instruction data indicating the modulation method and the transmission data can represent all the modulated waves in which the signal point arrangement positions are different for each modulation method. Since one common modulation circuit can generate modulated waves corresponding to all signal points, the hardware scale can be reduced.

(Embodiment 2) In the present embodiment, of the modulation methods used for adaptive modulation, the signal point of the modulation method having the maximum modulation multi-level number is approximated to the signal point of the other modulation method. A case will be described in which the error is caused by the approximation and the error is corrected.

FIG. 4 is a block diagram showing the configuration of the transmitting apparatus according to Embodiment 2 of the present invention. 4, the same parts as those in FIG. 1 are designated by the same reference numerals and detailed description thereof will be omitted.

The approximate IQ data search unit 401 generates an address based on the input transmission data and the instruction data output from the modulation method determination unit 101, and searches for IQ data corresponding to the generated address. The retrieved data are the I component and the Q component of the IQ data representing the approximate signal point. Here, the approximate signal point is a signal point arranged such that the coordinates of the 64QAM signal point are integer values. This is shown in FIG. FIG. 5 is a diagram in which signal points of each modulation method are arranged at approximate signal points. As shown in this figure, the signal points of modulation schemes other than 64QAM are also arranged at the approximate signal points, and the signal points of QPSK, 8PSK, and 16QAM are shown by thick circles. This placement method has certain conditions, "the approximate signal point having the closest phase distance from the signal point placed before the approximation""the approximate signal point having the closest amplitude ratio to the signal point placed before the approximation"" The signal point of each modulation method is arranged at an approximate signal point satisfying all the conditions of "an approximate signal point whose amplitude is closest to the signal point arranged before approximation".
As described above, by using the approximate signal points, the number of bits required to represent the signal point of the modulation method having the largest modulation multi-value number among the adaptive modulation methods (for example, I component and Q component are each 3 bits). Can represent all signal points of other modulation schemes. As a result, the approximate IQ data search unit 401
It is possible to reduce the hardware scale of the latter stage. The I and Q components representing the approximate signal points searched by the approximate IQ data search unit 401 are output to the common modulation unit 105.

The correction circuit 402 includes a memory 403 and a multiplier 404. The memory 403 stores a table in which the instruction data and the correction values shown in FIG. 6 are associated with each other. A correction value (cos (π / 4)) / 5 is given to the instruction data “00” indicating QPSK, and a correction value (cos (π /
8)) / 7 are associated with each other and stored in the memory 403. Similarly, the correction value 1 / √10 is associated with the instruction data “10” indicating 16QAM and the correction value 1 / √42 is associated with the instruction data “11” indicating 64QAM and stored in the memory 403. There is. Memory 403
Outputs a correction value corresponding to the instruction data output from the modulation method determination unit 101 to the multiplier 404. Multiplier 40
Reference numeral 4 multiplies the correction value output from the memory 403 by the modulation data output from the amplitude adjusting circuit 106. Since the approximate signal point is not an ideal signal point that can be demodulated on the receiving side, it is necessary to correct the error caused by the approximation.

FIG. 7 is a diagram showing ideal signal points in each modulation method. The ideal signal point 701 of QPSK is
(I, Q) = (cos (π / 4), cos (π / 4))
And at the approximate signal point, it corresponds to (I, Q) = (5,5). Therefore, the correction value (co
It is possible to return to the ideal signal point by multiplying by s (π / 4)) / 5. Similarly, the signal points in the other quadrants can be returned to the ideal signal points by multiplying them by the correction value (cos (π / 4)) / 5.

The ideal signal point 702 of 8PSK is (I,
Q) = (cos (π / 8), sin (π / 8)), which corresponds to (I, Q) = (7,3) at the approximate signal point. Therefore, a correction value (cos
By multiplying by (π / 8)) / 7, it is possible to approach the ideal signal point. Similarly, correction values (c
By multiplying by os (π / 8)) / 7, it is possible to approach the ideal signal point. Note that in the case of 8PSK, it is not possible to completely return to the ideal signal point, but there is accuracy that can be demodulated on the receiving side.

The 16QAM approximated modulated signal has a correction value of 1 / √10, and the 64QAM approximated modulated signal is
By multiplying by the correction value 1 / √42, each can be returned to the ideal signal point. FIG. 8 is a conceptual diagram showing how the 16QAM approximate signal points are corrected to ideal signal points. In the case of 16QAM, the correction value 1 / √10 is applied to the approximate signal point.
By multiplying by, the amplitudes of all modulated waves can be reduced.

As described above, according to the present embodiment, of the modulation methods used for adaptive modulation, the signal point of the modulation method having the maximum modulation multi-level number is approximated to the signal point of the other modulation method. By arranging them, IQ data can be represented by a small number of bits, and the hardware scale can be further reduced as compared with the first embodiment. Further, by correcting the error caused by the approximation, it is possible to avoid the deterioration of the demodulation accuracy.

In each of the above-described embodiments, the modulation method used for the adaptive modulation method is QPSK, 8PSK, 16Q.
Although AM and 64QAM have been described, the present invention is not limited to this, and modulation methods may be arbitrarily combined.

[0038]

As described above, according to the present invention,
Adaptive modulation is performed by preliminarily correlating the I component and Q component of all the modulation signals indicated by each modulation method used for adaptive modulation with predetermined data, and performing modulation by one modulation circuit based on the data. It is possible to reduce the hardware scale of the transmitting device that performs the.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a transmission apparatus according to Embodiment 1 of the present invention.

[Figure 2] Part of the correspondence table of addresses and IQ data

FIG. 3 is a correspondence diagram of IQ data in each modulation method and signal points representing each modulated wave.

FIG. 4 is a block diagram showing a configuration of a transmission apparatus according to Embodiment 2 of the present invention.

FIG. 5 is a diagram in which signal points of each modulation method are arranged at approximate signal points.

FIG. 6 is a correspondence table between instruction data and correction values.

FIG. 7 is a diagram showing ideal signal points in each modulation method.

FIG. 8 is a conceptual diagram showing how to approximate 16QAM approximate signal points to ideal signal points.

FIG. 9 is a block diagram showing a part of a transmission device to which a conventional adaptive modulation method is applied.

[Explanation of symbols]

101 Modulation method determination unit 102 IQ data search section 103 address generator 104,403 memory 105 common modulator 106 Amplitude adjustment circuit 401 Approximate IQ data search unit 402 correction circuit 404 multiplier

Claims (4)

[Claims] 1. A modulation method determining means for determining one modulation method from a plurality of modulation methods based on a reception situation, and an in-phase component of a modulation signal based on information indicating the determined modulation method and transmission data. And IQ data search means for searching IQ data indicating orthogonal components, modulation means for performing modulation based on the searched IQ data, and transmission means for transmitting a modulated signal. Transmitting device. 2. The IQ data searching means searches the IQ data from a table in which combinations of IQ data of all possible modulation schemes, information indicating the modulation schemes, and transmission data are associated with each other. The transmitter according to claim 1. 3. A correction means for correcting the modulated signal using a correction value according to each modulation method, wherein the IQ data search means has all possible values in the modulation method having the maximum modulation multi-value number. The IQ data of the modulation signal of No. 1 is made to correspond to the modulation signal of another modulation system under a predetermined condition, and the I
The transmission device according to claim 1, wherein Q data is searched. 4. A modulation method determining step of determining one modulation method from a plurality of modulation methods based on a reception situation, and an in-phase component of a modulation signal based on information indicating the determined modulation method and transmission data. And an IQ data search step of searching for IQ data indicating a quadrature component, and a modulation step of performing modulation based on the searched IQ data.