JP2009153061A - Transmission device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve reliability and durability of a radio communication system inexpensively. <P>SOLUTION: In a transmission device which uses antennas 61, 62 to perform transmission diversity, a first switch SW1 is provided on a prestage of signal processing sections 21, 22 and a second switch SW2 is provided on a poststage of power amplifiers (PAs) 41, 42. A control section 10 includes: a first mode for leading out a main side signal to the signal processing section 21, leading out a transmission signal output from the PA 41 to the antenna 61, leading out a diversity side signal to the signal processing section 22 and leading out a transmission signal output from the PA 42 to the antenna 62; and a second mode for leading out the main side signal to the signal processing section 22, leading out the transmission signal output from the PA 41 to the antenna 61, leading out the diversity side signal to the signal processing section 21, and leading out the transmission signal output from the PA 42 to the antenna 62, and controls the first switch SW1 and the second switch SW2 so as to alternately switch the first and second modes. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a transmission apparatus that wirelessly transmits data using a plurality of antennas.

  Multi-antenna signal transmission method (MIMO: Multiple-Input Multiple-Output) is a method of spatially multiplexing by transmitting different data from each antenna to radio waves in the same frequency band using a plurality of transmission / reception antennas and radio equipment. It is effective in improving frequency utilization efficiency.

  In a transmission apparatus or a radio base station that transmits an OFDMA (Orthogonal Frequency Division Multiplexing Access) signal defined by IEEE 802.16E, two signals of main and diversity are transmitted in order to configure MIMO. In the OFDMA transmission frame, a downlink subframe from the base station to the terminal and an uplink subframe from the terminal to the base station are transmitted by time division multiplexing (TDD), and thereby, between the base station and the terminal. Communication with is established.

  On the main side, management information such as a preamble (Preamble), MAP information (Mapping message), and FCH (Frame Control Header) is output, so that the RF average power increases and transmission on the main side The temperature of the part tends to rise. On the other hand, since only the signal related to MIMO is transmitted on the diversity side, the RF average power on the diversity side is low, and the temperature of the transmitter on the diversity side remains relatively lower than that on the main side. When such a state continues, there is a problem that only the main-side transmission unit is deteriorated due to a temperature rise.

In addition, as a well-known document relevant to this application, there exist the following, for example (refer patent document 1 or 2).
Japanese Patent Laid-Open No. 10-336084 Japanese Patent No. 2871094

  As described above, since the management information is transmitted together with the transmission data on the main side, there is a problem that the temperature of the transmission unit is likely to rise, and that the deterioration is easier than the diversity side.

  The present invention has been made paying attention to the above circumstances, and an object of the present invention is to provide a transmitter capable of improving the reliability and durability of a wireless communication system at low cost.

  In order to achieve the above object, a transmission apparatus according to the present invention is a transmission apparatus used in a radio communication system that performs transmission diversity using first and second antennas, and transmits a first transmission signal and a second transmission signal respectively. First, first switch means that is selectively derived from the second output terminal, and first and second conversion means that convert transmission signals derived from the first and second output terminals into radio frequency transmission signals, respectively. Second switch means for selectively deriving the transmission signal converted by the first and second conversion means to either the first or second antenna, respectively, and the first transmission signal for the first conversion means. The transmission signal derived from the first conversion means and derived from the first conversion means is derived to the first antenna, and the second transmission signal is derived to the second conversion means and the transmission signal converted by the second conversion means. Said A first mode derived to an antenna, a first transmission signal derived to the second conversion means, a transmission signal converted by the second conversion means derived to the first antenna, and the second transmission signal A second mode for deriving the transmission signal derived to the first conversion means and converted by the first conversion means to the second antenna, and switching the first and second modes alternately. And control means for controlling the first and second switch means.

  By continuing the switching process in this way, the load applied to the first and second conversion means can be made almost equal, so that the situation where the reliability of only the transmission system on one side is degraded can be avoided. . Also, since the transmission signals output from each antenna are always the same system, the receiving side can use the existing system as it is.

  Therefore, according to the present invention, it is possible to provide a transmission apparatus that can improve the reliability and durability of a wireless communication system at low cost.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a configuration diagram showing an embodiment of a radio base station including a transmission apparatus according to the present invention. This radio base station transmits, for example, an OFDMA (Orthogonal Frequency Division Multiplexing Access) signal defined by IEEE 802.16E, and configures MIMO (Multiple-Input Multiple-Output). That is, two different signals of main and diversity are transmitted to radio waves having the same frequency. In the OFDMA transmission frame, a downlink subframe from the base station to the terminal and an uplink subframe from the terminal to the base station are transmitted by time division multiplexing (TDD), and thereby, between the base station and the terminal. Communication with is established.

  The frame multiplexing / demultiplexing modulation / demodulation unit 1 generates two OFDMA transmission frame signals for main and diversity based on transmission data. The generated transmission frame signal is subjected to processing such as waveform shaping and D / A conversion in the signal processing units 21 and 22, and then converted into a radio frequency (RF) transmission signal in the modulation units 31 and 32. Converted. The RF transmission signals output from the modulation units 31 and 32 are up-converted by power amplifiers (PA) 41 and 42 and then transmitted from the antennas 61 and 62 at a transmission interval determined by the TDD units 51 and 52.

  On the other hand, RF signals arriving at the antennas 61 and 62 are captured at reception intervals determined by the TDD units 51 and 52, down-converted via low noise amplifiers (LNA) 71 and 72, and demodulated units 81 and 82 as bases. It is converted into a band signal. The baseband signal is subjected to A / D conversion in the signal processing units 21 and 22, and then separated into subframes in the frame multiplexing / separation modulation / demodulation unit 1 to obtain received data.

  Further, this radio base station includes a first switch SW1 and a second switch SW2. FIG. 2 shows a state where the first switch SW1 and the second switch SW2 are switched. The first switch SW1 is provided between the frame multiplexing / demultiplexing modulation unit 1 and the signal processing units 21 and 22, and outputs the main signal and the diversity signal to either the signal processing unit 21 or the signal processing unit 22, respectively. Switch to In addition, you may comprise so that the switch which functions similarly to 1st switch SW1 may be provided in the inside of the signal processing parts 21 and 22, respectively.

  The second switch SW2 is provided between the PAs 41 and 42 and the TDD units 51 and 52, and transmits the RF signal output from each of the modulation units 31 and 32 from either of the antennas 61 and 62. , 52 is switched. The control unit 10 supplies a timing signal that instructs the first switch SW1 and the second switch SW2 to switch.

  Here, FIG. 3 shows an example of the structure of an OFDMA transmission / reception frame. FIG. 4A is a diagram illustrating a signal state of a subframe in the downlink on the main side, and FIG. 4B is a diagram illustrating a signal state of a subframe in the downlink on the diversity side. The main-side subframe includes management information such as preamble (Preamble), MAP information (Mapping message), and FCH (Frame Control Header) together with transmission data. On the diversity side, these pieces of management information are not included, and are composed only of transmission data.

  Next, the transmission operation of the radio base station configured as described above will be described. FIG. 5 is a timing chart showing the switching timing of the first switch SW1 and the second switch SW2. As shown in FIG. 5, for example, in TDD communication, transmission and reception are switched at the same frequency in a determined cycle (TDDTIMG, TxEN in FIG. 5). In the present embodiment, the control unit 10 controls the first switch SW1 and the second switch SW2 in accordance with this transmission cycle, and switches the path through which the main-side signal and the diversity-side signal pass through the PAs 41 and 42.

  The control unit 10 manages transmission timing information (a signal α in FIG. 5) between the control unit 10 and the modulation units 31 and 32. A switching timing is generated in the managed timing information source. The first switch SW1 and the second switch SW2 are respectively controlled at the generated switching timing (SW1 switching TIMG, SW2 switching TIMG in FIG. 5). Each time the first switch SW1 and the second switch SW2 are switched, the paths of the main-side signal and the diversity-side signal are changed, and the signals passing through the PAs 41 and 42 are switched (SW1 switching signal and SW2 switching signal in FIG. 5). .

  FIG. 6 (a) is a diagram showing signal states of downlink subframes in a conventional main side and diversity side PA, and FIG. 6 (b) is a diagram of main side and diversity side in the radio base station of the above embodiment. It is a figure which shows the signal state of the downlink sub-frame in PA. As shown in FIG. 6A, if the path of the main-side signal and the diversity-side signal is not switched, a difference occurs in the time of the transmission state between PA1 and PA2, resulting in a difference in average power consumption. Was born. For this reason, there was a problem that only PA1 was easily deteriorated and durability was poor.

  On the other hand, in the present embodiment, as shown in FIG. 6B, the signal applied to PA1 and PA2 can be made uniform by switching the signals passing through PA1 and PA2 for each transmission cycle. Further, since the RF signals output from the antennas 61 and 62 are always the same system (main if main, diversity if diversity), it can be used without changing the existing system (receiving side).

  As described above, in the above-described embodiment, in the transmission apparatus that performs transmission diversity using the antennas 61 and 62, the first switch SW1 is provided before the signal processing units 21 and 22, and the second switch is provided after the power amplifiers 41 and 42. A switch SW2 is provided. The control unit 10 derives the main-side signal to the signal processing unit 21 and derives the transmission signal output from the PA 41 to the antenna 61, and derives the diversity-side signal to the signal processing unit 22 and outputs the signal from the PA 42. A first mode for deriving a signal to the antenna 62, a main-side signal to the signal processing unit 22, a transmission signal output from the PA 42 to the antenna 61, and a diversity-side signal to the signal processing unit 21 And a second mode for deriving the transmission signal output from the PA 41 to the antenna 62, and the first switch SW1 and the second switch SW2 are controlled so that the first and second modes are alternately switched in the transmission frame period. To do.

  By continuing the switching process in this way, the RF average power output from the main-side and diversity-side PAs can be made almost equal, and therefore the reliability of only the main-side transmitting unit deteriorates. It can be avoided. Further, since the RF signals output from the antennas on the main side and diversity side are always the same system, the receiving system can use the existing system as it is.

  Therefore, according to the embodiment, it is possible to realize a transmission apparatus that can improve the reliability and durability of the wireless communication system at low cost.

  In addition, this invention is not limited to the said embodiment as it is. The transmission apparatus according to the present invention can be applied not only to a MIMO diversity wireless communication system but also to a single input multiple output (SIMO) system and a transmission diversity system that transmits the same signal on the main side and the diversity side.

  In the above embodiment, the path through which the main-side signal and the diversity-side signal pass is alternately switched in the transmission frame period. However, the following configuration can be adopted. For example, the first switch SW1 and the second switch SW2 can be switched every several frames by providing the control unit 10 with a counter for counting transmission frames.

  In addition, for example, a measuring instrument that measures the temperatures of PA1 and PA2 is provided, and the control unit 10 switches the first switch SW1 and the second switch SW2 when any of the measured temperatures exceeds a threshold value. To. Even if comprised in this way, the state where the reliability of only the transmission part of one side deteriorates can be avoided. In addition, the number of times the first switch SW1 and the second switch SW2 are switched can be reduced, and durability can be improved.

  In short, the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

The block diagram which shows one Embodiment of a wireless base station provided with the transmitter which concerns on this invention. The figure which shows the state which switched the 1st switch and the 2nd switch. The figure which shows an example of a structure of the transmission / reception frame of OFDMA. The figure which shows the signal state of the sub-frame transmitted by the main side and a diversity side. The timing chart which shows the switching timing of a 1st switch and a 2nd switch. The figure which shows the signal state of the sub-frame transmitted in the in-side and diversity side in the radio base station of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Frame multiplexing / separation modulation / demodulation part, 21, 22 ... Signal processing part, 31, 32 ... Modulation part, 41, 42 ... Power amplifier (PA), 51, 52 ... TDD part, 61, 62 ... Antenna, 71, 72 ... Low noise amplifiers 81, 82 ... Demodulator, 10 ... Controller, SW1 ... First switch, SW2 ... Second switch.

Claims (5)

A transmission device used in a wireless communication system that performs transmission diversity using first and second antennas,
First switch means for selectively deriving the first and second transmission signals from the first and second output terminals, respectively;
First and second conversion means for converting transmission signals derived from the first and second output terminals into radio frequency transmission signals, respectively;
Second switch means for selectively deriving the transmission signal converted by the first and second conversion means to either the first or second antenna, respectively;
Deriving the first transmission signal to the first conversion means, deriving the transmission signal converted by the first conversion means to the first antenna, and deriving the second transmission signal to the second conversion means, A first mode for deriving the transmission signal converted by the second conversion means to the second antenna; and a transmission signal derived by the second conversion means for deriving the first transmission signal to the second conversion means. A second mode for deriving to the first antenna and deriving the second transmission signal to the first conversion means and deriving the transmission signal converted by the first conversion means to the second antenna; And a control means for controlling the first and second switch means so as to alternately switch between the first and second modes.     The transmission apparatus according to claim 1, wherein an information amount of the second transmission signal is smaller than an information amount of the first transmission signal.   2. The transmission apparatus according to claim 1, wherein the control means switches between the first and second modes at a transmission frame period of the transmission signal.   2. The transmission apparatus according to claim 1, wherein the control unit switches the first and second modes for each predetermined number of transmission frames of the transmission signal. A measuring means for measuring the temperature of the first and second converting means;
2. The transmission device according to claim 1, wherein the control unit switches between the first mode and the second mode when one of the measured temperatures exceeds a threshold value. 3.

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