JP4351672B2 - Transmitting apparatus and transmitting method - Google Patents

Description

  The present invention relates to a transmission apparatus and a transmission method that transmit signals from a plurality of transmission antennas, such as MIMO (Multi-Input / Multi-Output) communication, and that employ a Code Division Multiple Access (CDMA) system.

  In recent years, MIMO (Multi-Input / Multi-Output) communication has attracted attention as a technology that enables large-capacity data communication such as images. In MIMO communication, transmission data (substreams) different from each other are transmitted from a plurality of antennas on the transmission side, and a plurality of transmission data mixed on the propagation path are separated into original transmission data using a propagation path estimation value on the reception side. (For example, refer to Patent Document 1).

  In practice, in MIMO communication, a signal transmitted from a transmission apparatus is received by the number of antennas equal to or greater than the number of transmission apparatuses, and the pilot signals respectively inserted in the signals received by the antennas. Based on this, the channel characteristics between the antennas are estimated. The estimated propagation path characteristic H is represented by a matrix of 2 rows × 2 columns, for example, when there are two transmitting antennas and two receiving antennas. In MIMO communication, a transmission signal transmitted from each transmission antenna is obtained based on the inverse matrix of this propagation path characteristic H and the reception signal obtained by each reception antenna.

In this way, in MIMO communication, signals transmitted from a plurality of transmitting antennas at the same timing and the same frequency can be separated for each substream on the receiving side, so the amount of data proportional to the number of transmitting antennas can be reduced. It can be transmitted and high-speed and large-capacity communication becomes possible.
Japanese Patent Laid-Open No. 2002-44051 (FIG. 4)

  However, in a conventional receiving apparatus that performs MIMO communication, when an interference compensation error occurs due to noise or the like in the process of separating (interference compensation) a plurality of transmission data, there is a problem that the error rate characteristic of the received data deteriorates. is there. In particular, if the error rate characteristics of data for which better line quality is desired than other data, such as data addressed to users with poor line quality, communication system control information, or retransmission information, will be affected by the communication system, large.

  In order to prevent deterioration of error rate characteristics of received data due to interference compensation errors, there are a method in which specific data is allocated to only one antenna and transmitted, and a method in which the same data is allocated to a plurality of antennas and transmitted. . However, in such a case, the transmission rate of the communication system is decreased, which causes a problem that the data transmission efficiency deteriorates.

The present invention has been made in view of the above points, and provides a transmission device and a transmission method capable of improving reception performance on the reception side for specific data while maintaining the transmission efficiency of the communication system. The purpose is to do.

The transmission device of the present invention is a MIMO transmission device that transmits a plurality of different data addressed to the same transmission partner in parallel via a plurality of transmission antennas, and the plurality of data is transmitted to the plurality of transmission antennas. a signal arrangement means for arranging each of said arranged to each transmit antenna data, and a transmitting means for transmitting using a transmit antenna corresponding respectively, it said signal arranging means are replicated for systematic bits generates the respectively arranged their systematic bits to the plurality of transmitting antennas such that the systematic bits duplicating the systematic bits are transmitted redundantly from different antennas at the same time, the transmission unit, wherein Systematic bits and the replicated systematic bits In each transmit antenna for transmitting duplicate, a configuration of transmitting the same time a different data other than the systematic bits by code division multiplexing in the systematic bits.

  According to the present invention, it is possible to improve the reception performance on the reception side for specific data while maintaining the transmission efficiency of the communication system.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing the main configuration of a CDMA transmission apparatus according to Embodiment 1 of the present invention. Here, the case where the CDMA transmitter has two antennas will be described as an example. However, the number of antennas is not limited to this and may be three or more.

  This CDMA transmitter includes an S / P converter 101, spreaders 102 (102-1 to 102-N), 103 (103-1 to 103-N), adders 104-1 and 104-2, and a transmitter 105. -1, 105-2, antennas 106-1, 106-2, a diffusion control unit 107, and a control unit 110. Among these, the part from the spreading | diffusion part 102 to the antenna 106-1 will be called a 1st transmission system, and the part from the spreading | diffusion part 103 to the antenna 106-2 will be called a 2nd transmission system.

1, data D ₁ , D ₂ ,..., D _N , D _{N + 1} transmitted to users 1, 2,..., N, N + 1,. ,..., A transmission signal including D _2N is input to the control unit 110.

  Control unit 110 recognizes the type of data included in the input transmission signal, and then outputs the transmission signal to S / P conversion unit 101. Further, the control unit 110 outputs a control signal C1 to the S / P conversion unit 101 and the diffusion control unit 107 according to the recognized data type. Further, control unit 110 outputs control signal C2 to S / P conversion unit 101 and spreading control unit 107 in accordance with a retransmission flag notified from a reception unit (not shown) that has received a retransmission request from the reception side. . Detailed operation of the control unit 110 will be described later.

  The S / P conversion unit 101 converts the transmission signal output from the control unit 110 into parallel data separated for each transmission system, and the corresponding spreading units 102-1 to 102-N and spreading unit 103- respectively. 1 to 103-N.

  Spreading section 102 spreads each data under the control of spreading control section 107 in spreading sections 102-1 to 102-N corresponding to the respective parallel data output from S / P conversion section 101. Processing is performed and output to the adder 104-1. Similarly, the spreading unit 103 performs the respective data under the control of the spreading control unit 107 in the spreading units 103-1 to 103-N corresponding to the respective parallel data output from the S / P conversion unit 101. Is subjected to diffusion processing and output to the adder 104-2.

  Adders 104-1 and 104-2 add (multiplex) the parallel data output from spreading sections 102 and 103, respectively, and output the result to transmitters 105-1 and 105-2.

  Transmitting sections 105-1 and 105-2 perform predetermined radio transmission processing such as up-conversion on the multiplexed signals output from addition sections 104-1 and 104-2, and antennas 106-1 and 106-2 are connected. This data is transmitted wirelessly.

  FIG. 2 is a block diagram illustrating a main configuration inside the control unit 110. The control unit 110 includes a data recognition unit 111, a buffer 112, and a retransmission control unit 113.

  The data recognition unit 111 recognizes the type of data included in the transmission signal based on the line quality and moving speed on the receiving side output from the line quality measuring unit and the moving speed measuring unit (both not shown), Write the transmission signal to the buffer 112. Further, the data recognition unit 111 outputs a control signal C1 to the S / P conversion unit 101 and the diffusion control unit 107 according to the recognized data type. The retransmission control unit 113 outputs a control signal C2 to the S / P conversion unit 101 and the buffer 112 according to a retransmission flag notified from a reception unit (not shown) that has received a retransmission request from the reception side. The buffer 112 outputs the buffered data to the S / P conversion unit 101 based on the control signal C2 output from the retransmission control unit 113.

  Next, the operation of the CDMA transmission apparatus having the above configuration will be described.

  The above-described data type recognition process performed by the data recognition unit 111 is a process in which the CDMA transmission apparatus according to the present embodiment recognizes data (hereinafter referred to as specific data) to be prioritized at the time of transmission in distinction from other data. That is. Here, the specific data specifically refers to a control signal for controlling communication with the receiving side, or the receiving side with poor channel quality (the channel quality is below a predetermined level) or the moving speed is fast (moving This is the data that is about to be transmitted to the receiving side. The data recognition unit 111 notifies specific data information indicating which data is specific data to the S / P conversion unit 101 and the diffusion control unit 107 using the control signal C1.

  The specific data also includes data that is requested to be retransmitted by the receiving side (retransmission data) or data that has a large number of retransmissions (the number of retransmissions is a predetermined number or more). The retransmission control unit 113 notifies the specific data to the S / P conversion unit 101 and the spreading control unit 107 using the control signal C2.

  The S / P conversion unit 101 transmits the transmission data output from the control unit 110 based on the specific data information notified by the control signals C1 and C2 to the spreading units 102-1 to 102-N and 103-1 to 103-. Sort to N. When the transmission data is not specific data but data indicating only information, each transmission data is distributed almost evenly to each spreading unit in order to increase transmission efficiency. On the other hand, when the transmission data is specific data, this data is read from the buffer 112 at least twice, and when this data has both the first transmission system and the second transmission system (when there are three or more transmission systems). And at least two transmission systems).

  The spreading control unit 107 performs spreading modulation on the specific data distributed to the first transmission system and the second transmission system using different spreading codes (different between the first transmission system and the second transmission system). The diffusion units 102 and 103 are controlled using the control signal C3.

  The specific data spread and modulated by each spreading section and the other data are multiplexed for each transmission system by the adding sections 104-1 and 104-2, respectively, and the transmitting sections 105-1 and 105-2 and the antenna 106-1, It is wirelessly transmitted via 106-2.

  FIG. 3 is a diagram illustrating an example of a configuration of a transmission signal of the CDMA transmission apparatus according to the present embodiment. Here, a case where the specific data is retransmission data is taken as an example.

  As shown in this figure, data 1 transmitted at the first transmission timing is data transmitted to the users from user 1 to user 2N. From the first transmission system (antenna 1), user 1 to user 1 Data 1 addressed up to N is transmitted, and data 1 addressed from user (N + 1) to user 2N is transmitted from the second transmission system (antenna 2). Note that these data are not specific data. On the other hand, retransmission data is also transmitted with data 1. This retransmission data is specific data, and is distributed to both the first transmission system and the second transmission system by the configuration of the CDMA transmission apparatus according to the present embodiment, and is spread-modulated by different spreading codes. The data 2 transmitted at the next transmission timing also has the same configuration as the data 1 as shown in the figure.

  FIG. 4 is a diagram showing another example of the configuration of the transmission signal of the CDMA transmission apparatus according to the present embodiment. Here, at the first transmission timing, the data 1 addressed from the user 1 to the user N and the data 2 similarly addressed from the user 1 to the user N are converted into the first transmission system (antenna 1) and the second transmission system ( The case of transmitting simultaneously using antenna 2) is shown as an example. As before, these data are not specific data. On the other hand, retransmission data is also transmitted along with data 1 and data 2. This retransmission data is specific data, and is distributed to both the first transmission system and the second transmission system by the configuration of the CDMA transmission apparatus according to the present embodiment, and is spread-modulated by different spreading codes. The data transmitted at the next transmission timing is data addressed from the user (N + 1) to the user 2N as shown in the figure.

  FIG. 5 is a diagram illustrating an example of a configuration of a signal transmitted by a conventional CDMA transmission apparatus under the same condition setting as described above. For example, when an interference compensation error occurs in a signal transmitted from the antenna 1, since retransmission data becomes a reception error, the transmission side further repeats retransmission, and the transmission efficiency of the communication system deteriorates.

  As described above, since the CDMA transmission apparatus according to the present embodiment transmits different data using two transmission systems, the high transmission efficiency that is the original characteristic of MIMO communication is maintained. On the other hand, for data to be transmitted with priority, two transmission systems (or at least two transmission systems when there are three or more transmission systems) are used, and spread modulation is performed using different spreading codes. Even if the interference compensation error becomes large due to noise mixing on the receiving side, that is, even when the separation performance by the MIMO technology cannot be obtained sufficiently, the signal is separated by the despreading process. be able to.

  Thus, according to the present embodiment, it is possible to improve the reception performance on the reception side for specific data while maintaining the transmission efficiency of the communication system.

  In the CDMA transmitter according to the present embodiment, when a turbo code is used as an error correction code, systematic bits may be used as specific data. Systematic bits have a great influence on the error rate characteristics of data after turbo decoding when turbo decoding is performed using systematic bits and parity bits. Therefore, by using the systematic bit as the specific data, the reception quality of the systematic bit can be improved, and the error rate characteristic of the data after turbo decoding can be improved.

  When transmission power control is performed, transmission power may be used instead of line quality. This is because when the transmission power control is performed, if the line quality is poor, the transmission power should increase according to the line quality.

  Further, the number of data retransmissions may be used instead of the line quality. This is because when the line quality is poor, the number of data retransmissions should increase.

  Note that the CDMA transmitter according to the present invention can also be used in a transmitter using a multicarrier scheme such as OFDM (Orthogonal Frequency Division Multiplex), and thus, a multicarrier transmitter having the same effects as described above. Can be provided. Since the transmission method using multicarrier is set to a low symbol rate (long symbol length), there is an effect of reducing intersymbol interference due to multipath in a multipath environment. In addition, intersymbol interference due to multipath can be removed by inserting a guard interval.

  Furthermore, although the case where each element constituting the present invention is provided in one CDMA transmission device has been described as an example here, the present invention is not limited to the spreading unit 102 to the antenna 106-1, and the spreading unit 103 to the antenna 106. -2, the spreading control unit 107 and the control unit 110 are installed in different devices, respectively, and can be applied to a case where one communication system is configured as a whole.

  Furthermore, although MIMO communication has been described as an example here, the present invention is not limited to MIMO communication, and can be applied to cases where different data is transmitted in parallel from a plurality of antennas (transmission systems).

  The CDMA transmission apparatus according to the present invention can be mounted on a communication terminal apparatus and a base station apparatus in a mobile communication system, thereby providing a communication terminal apparatus and a base station apparatus having the same operational effects as described above. be able to.

  Here, although the case where the present invention is configured by hardware has been described as an example, it can also be realized by software.

The transmission apparatus and the transmission method according to the present invention can be applied to uses such as a transmission apparatus and a transmission method that transmit signals from a plurality of transmission antennas as in MIMO communication and that employ a CDMA scheme.

FIG. 2 is a block diagram showing the main configuration of a CDMA transmission apparatus according to Embodiment 1 of the present invention. The block diagram which shows the main structures inside the control part which concerns on Embodiment 1 of this invention. The figure which shows an example of the structure of the transmission signal of the CDMA transmitter which concerns on Embodiment 1 of this invention. The figure which shows another example of the structure of the transmission signal of the CDMA transmitter which concerns on Embodiment 1 of this invention. The figure which shows an example of a structure of the signal which the conventional CDMA transmitter transmits.

Explanation of symbols

101 S / P conversion unit 102, 103 spreading unit 104 adding unit 105 transmitting unit 106 antenna 107 spreading control unit 110 control unit 111 data recognition unit 112 buffer 113 retransmission control unit C1-3 control signal

Claims (4)

A MIMO (Multi-Input / Multi-Output) scheme transmission device that transmits a plurality of different data addressed to the same transmission destination in parallel via a plurality of transmission antennas,
Signal placement means for placing the plurality of data on the plurality of transmission antennas, respectively;
Transmission means for transmitting data respectively arranged on each transmission antenna using a corresponding transmission antenna, and
The signal arrangement unit generates duplicated for systematic bits, transmit their systematic bits as a systematic bit replicated to the systematic bits are transmitted redundantly from different antennas at the same time of the plurality each on the antenna,
The transmission means code-division-multiplexes different data other than the systematic bits into the systematic bits and transmits them at the same time in each transmission antenna that transmits the systematic bits and the duplicated systematic bits in an overlapping manner.
Transmitter device. Communication terminal apparatus comprising the transmission apparatus according to claim 1 Symbol placement. The base station apparatus comprising a transmission apparatus according to claim 1 Symbol placement. A MIMO method of transmitting a plurality of different data addressed to the same transmission destination in parallel via a plurality of transmission antennas,
A signal placement step of placing the plurality of data on the plurality of transmission antennas, respectively;
Transmitting each of the data arranged in each of the transmission antennas using a corresponding transmission antenna,
The signal arranging step generates a replicated for systematic bits, transmit their systematic bits as a systematic bit replicated to the systematic bits are transmitted redundantly from different antennas at the same time of the plurality each on the antenna,
In the transmission step, in each transmission antenna that transmits the systematic bit and the duplicated systematic bit in an overlapping manner, different data other than the systematic bit is code-division multiplexed to the systematic bit and transmitted at the same time.
Transmission method.

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