JPH0548511A - Antenna hopping radio transmitter - Google Patents

Abstract

PURPOSE:To realize the improvement of the signal transmission quality due to the switching of an antenna relating to error correction coding in the radio transmitter used for transmitting a digital signal in a mobile communication. CONSTITUTION:An error caused by a propagation line is randomized by sending the information of optional single bit information of an input signal 1 of a transmitter from plural different antennas by the controlling an error correction coder 2 and an antenna switching device 4 to improve the capability of error correction decoding implemented by a signal receiver, thereby realizing the reduction in the error rate of a transmission signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for transmitting digital signals in mobile communication, for example,
The present invention relates to error correction coding and a technique for improving signal transmission quality by switching antennas.

[0002]

2. Description of the Related Art Recently, in the field of land mobile communication,
Research and development of digital communication systems are in progress. By the way, in such a digital communication system, a code error occurs due to fading peculiar to land mobile communication, and it is difficult to obtain sufficient transmission signal quality. Also, in general,
In mobile communication, when the speed of the mobile station is slow, the temporal correlation of fading between the transmitting and receiving antennas becomes high, so that code errors occur in bursts. An error correction code may be applied to reduce errors. However, although the error correction code has a high error correction capability when the errors occur randomly, the error correction capability is often not sufficient for the errors that occur in a remarkable burst in land mobile communication.

Therefore, a symbol interleave for converting a burst error into a random error, an error correction code suitable for a burst, and the like have been devised and used, but the error correction capability decreases as the vehicle speed of the mobile station decreases. was there. This drawback can be alleviated to some extent by increasing the interleave size and the code length of the error correction code, but there is a drawback that the signal processing delay increases with this increase. For this reason,
For example, when audio is digitized and transmitted, the processing delay cannot be increased, and there is a limit in improving the error correction capability by increasing the interleave size and the like.

[0004]

As described above, in the field of land mobile communication, it is required to develop a technique for randomizing burst errors without increasing processing delay.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an apparatus which can easily reduce the code error rate in land mobile communication.

[0006]

In order to randomize burst errors, a signal whose redundancy is increased by error correction coding is transmitted from a plurality of transmission antennas by transmitting antenna input signal information by switching antennas. .. At this time, information of arbitrary bits of the transmitter input signal is not transmitted from only a specific antenna. The purpose of randomizing burst errors was realized by switching antennas.

[0007]

According to the above configuration, the information of each bit of the signal to be transmitted is error-correction coded and then transmitted from the plurality of transmitting antennas. Since the transmitting station switches the transmitting antenna from time to time, the radio wave propagation path between the transmitting and receiving stations changes according to the switching period of the transmitting antenna. Therefore, the error occurring in the received signal before error correction decoding is randomized at the switching cycle of the transmitting antenna.

The error is reduced by performing error correction decoding on the randomized received signal in which the error has occurred.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a configuration of a transmission system of a radio communication apparatus according to an embodiment of the present invention. A transmitter input signal 1 is error correction coded by an error correction encoder 2 to become a transmission signal 3. Then, the antenna switching unit 4 transmits from one of a plurality of transmitting antennas.

Since the transmission signal 3 has a bit rate or symbol rate higher than that of the transmitter input signal 1 due to the action of the error correction encoder 2, any single bit information of the transmitter input signal 1 is transmitted signal. It is possible to transmit on a plurality of 3 bits or symbols. Therefore, the plurality of bits or symbols are divided into one bit or symbol by the control of the antenna switching unit 4, and are transmitted from mutually different transmitting antennas. Generally, when a mobile station has a slow moving speed and fading has high temporal correlation, code errors occur in bursts. According to the present invention, the transmission antennas are switched and transmitted one after another, so that even if the vehicle speed of the mobile station is slow, the varying speed of fading of the received signal does not fall below the antenna switching cycle.
Therefore, the code error occurring in the propagation path is randomized at the switching cycle of the transmitting antenna.

FIG. 2 shows the configuration of a receiving system of a radio communication apparatus according to an embodiment of the present invention. The receiver input signal 5 is a signal obtained by adding deterioration of a transmission signal 3 due to a propagation path. .. Since the code error generated in the propagation path due to the antenna switching is randomized at the switching cycle of the transmitting antenna, the receiver output 7 with an improved error rate is input by inputting the received signal 5 to the error correction decoder 6. Is obtained. Hereinafter, the error reduction method using the combination of antenna switching and error correction according to the present invention will be referred to as an antenna hopping method, and the transceiver manufactured based on this principle will be referred to as an antenna hopping wireless transmission device. In this embodiment, the transmission antenna switching period is twice or more the data rate before error correction coding, but the transmission antenna switching speed can be reduced by interleaving the signal after error correction coding. Is possible.

FIG. 3 shows an example thereof. In FIG. 3, the data rate is doubled by the error correction coding. The bit rate of the transmitter input signal 10 is doubled by the error correction encoder 11 and is passed through the switch A 12 to the FIFO A 13
And is temporarily recorded in FIFOB14. In addition, FIF
The minimum required memory length of O is (switching speed of switch A12) / (switching speed of switch B15).
The switching speed of the switch A12 is the same as the speed of the error correction coded data input to the switch A12. On the other hand, the switching of the switching device B15 can be performed at an arbitrary speed as long as the timing is synchronized with the switching device 12 and the speed is a fraction of the speed of the data input to the switching device A12. However, when the switching speed is lower than the maximum Doppler frequency of the facing, the error randomizing effect due to the antenna hopping is eliminated. The signal from the switch B15 is modulated by the modulator 16,
After performing frequency conversion and power increase as necessary, the transmission antenna switching unit 17 periodically switches the transmission antenna. The switching of the transmission antenna switching unit 17 needs to be synchronized with the switching of the switching unit B15. The arbitrary 1-bit information of the transmitter input signal 10 is temporarily stored in the FIFOA 13 and the FIFOB 14, and then transmitted from the transmitting antenna A18 and the transmitting antenna B19. Therefore, the transmitting antenna A18 and the transmitting antenna B1 are transmitted.
No error occurs in data transmission unless the signals from 9 are interrupted at the same time.

Generally, a mobile radio base station is provided with a plurality of transmitters. Therefore, in the transmitter installed in the base station,
By switching the transmission antennas according to the method described in "Claim 2", antenna hopping can be performed without adding the number of transmission antennas. An example thereof is shown in FIG. The transmitter input A20 and the transmitter input B22 are error correction coded by an error correction encoder A21 and an error correction encoder B23, respectively, and become a transmission signal A24 and a transmission signal B25, respectively. The antenna switching device 26 switches the antenna for transmitting the transmission signal A24 and the transmission signal B25 from the transmission antenna A27 and the transmission antenna B28.
Here, for example, when the transmission signal A24 is transmitted from the transmission antenna A27, the transmission signal B25 is
28, and the transmission signal A24 is transmitted from the transmission antenna B2.
8 is transmitted, the transmission signal B25 is transmitted from the transmission antenna A27. In this way, the transmitting antenna 2
7 and the transmitting antenna 28 do not have a time period in which no transmission is performed, and antenna hopping is realized by mutually utilizing transmitting antennas between transmitters. Figure 4
Shows an example in which antenna hopping is performed by using two transmitters and an antenna, but the antenna hopping described in "Claim 2" is realized not only by two transmitters but by using arbitrary plural transmitters. It is possible to Generally, as the number of transmitting antennas installed in the wireless tower increases, the number of power supply lines increases, and the weight burden of the wireless tower increases, so that the base station installation cost increases. Therefore, the merit of realizing the base station antenna hopping by the method described in "Claim 2" is very large.

When the transmission power input to the transmission antenna is large, the power loss due to switching cannot be ignored. Also, the switching device must have high power resistance. In particular, in a base station, signals from a plurality of transmitters are shared by a junction box or the like and one transmission antenna is used to form one system, so that the input power of the transmission antenna is extremely large. Therefore, it is extremely difficult to switch a high-power signal with low loss while maintaining high isolation at each port of the switch. Therefore, instead of switching the transmission signal at the input stage of the transmission antenna, as described in "Claim 3", this problem can be solved by performing it at a stage other than the transmission antenna input stage. For example, a method of switching the transmission signal before the power amplification stage of each transmitter can be considered. A method of switching the transmission signal at the intermediate frequency stage or the baseband stage is also conceivable. With these methods, the level or frequency of the signal to be switched becomes low, so that the antenna hopping wireless transmission device can be easily configured. FIG. 5 shows “Claim 3”
2 is an embodiment of an antenna hopping wireless transmission device according to the present invention. The transmitter input signal A30 is error-correction coded by the error correction encoder A31 to become the transmission signal A, and then input to the modulator A34 or the modulator B44 by the baseband signal switch 33. In the example of FIG. 5, the signal is switched in the baseband, but the signal may be switched after the modulation. The modulated signal is frequency-converted by the mixer A35 or the mixer B45, and is transmitted from the power amplifier A38 or the power amplifier B48 from the transmission antenna A39 or the transmission antenna B49. Here, the transmission antenna and the power amplifier are directly connected, and even though there is no antenna switching device between them, the baseband signal switching device 33 and the local oscillator signal switching device 40 work similarly to the case where the antenna switching device is used. The effect can be obtained. Ie transmitter input A
30 is a transmission antenna A at the frequency from the local oscillator A36.
In the first cycle of transmission from 39, the transmission signal A32 is sent to the modulator A34 and the signal from the local oscillator A36 is sent to the mixer A34.
Baseband signal switcher 3 so that
3 and the local oscillator signal switch 40 are switched. next,
In the second cycle in which the transmitter input A30 is transmitted from the transmission antenna A49 at the frequency from the local oscillator A36, the transmission signal A32 is input to the modulator B44 and the signal from the local oscillator A36 is input to the mixer B45. Then, the baseband signal switch 33 and the local signal switch 40 are switched. In this way, although the modulator and power amplifier used differ depending on the period, antenna hopping can be realized without changing the frequency. In addition, transmitter input A
The signal from the transmitter input B41 is transmitted from the transmitter antenna B49 when the signal from the transmitter antenna A39 is transmitted from the transmitter antenna A39, and the transmitter input B41 is transmitted from the transmitter antenna A49 when the signal from the transmitter input A30 is transmitted. Is transmitted from the transmitting antenna A39. In addition, it is also possible to adopt a configuration in which the same effect is obtained by switching between the power amplifier A input signal 37 and the power amplifier B input signal 47 instead of switching between the local oscillation signals.
Since the frequencies of the local oscillator A36 and the local oscillator B46 are different, it is possible to cause frequency hopping and antenna hopping to occur in a superposed manner when the transmission signal is switched only at the baseband stage.

If the antenna switching is performed independently of the data transmission cycle, data error may occur at the moment of switching the antenna. In this case, if antenna switching is performed during a time period when no data is transmitted, it is possible to prevent data loss due to antenna switching. Therefore, as described in "Claim 5", the antenna switching is synchronized with the frame period or the time slot period of the TDMA, TDM or TDD system, and the switching period is an integral multiple of the frame length or the time slot length of the TDMA, TDM or TDD system. By doing so, data loss is prevented.

In a normal antenna, one antenna element is connected to one feeder line. However, depending on the antenna, a plurality of feeder lines may be connected to one antenna element. For example, in some patch antennas, there are two feeding points to the radiating element, corresponding to right-handed and left-handed polarization planes. Polarization diversity can be realized at the time of reception by using the plurality of feeding points. In this type of antenna, it is possible to realize antenna hopping by changing the feeding point by switching the feeding line. If there is a land mobile communication line that has already been error-correction coded,
There is an advantage that the configurations of FIG. 1 and FIG. 2 can be realized only by adding a transmitting antenna switching device to the existing transmitting device. Further, by combining claim 1 and claim 4, it is possible to improve the transmission signal quality by antenna hopping only for the base station. That is, in a mobile communication line that has already been served, without making any changes to the mobile station,
By adding the antenna hopping radio transmission device only to the base station, it is possible to improve the transmission signal quality of both lines from the base station to the mobile station and from the mobile station to the base station. Generally, in a mobile communication line, the number of mobile stations is much larger than the number of base stations communicating with the mobile station, so that most of the cost of the entire communication system is the cost of the mobile station device. Therefore, the advantage of introducing the antenna hopping method by changing only the base station equipment is extremely large. In this case, whether or not to hop the antenna depends on the control of the antenna switch of the base station. In the case where a plurality of users use one radio base station as a repeater such as a trunked system, it is possible to control whether or not to perform antenna hopping for each user by controlling the antenna switching device. The flexibility of this method is high in terms of operation of communication systems.

Further, the present apparatus is extremely easy to combine with a space diversity technique using a plurality of antennas. When antenna hopping is not performed, only one antenna among the plurality of antennas used for reception diversity is used for transmission. By using this antenna that is not used at the time of transmission, transmission antenna hopping can be realized without adding the number of antennas. Further, a configuration in which a large number of antennas are used and signals after antenna hopping are input to the diversity receiver can be considered.

As described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

[0020]

In general, in a mobile communication base station, signals from a plurality of transmitters are shared by a junction box,
Transmitting from one transmitting antenna. The system consisting of the antenna shared with this transmitter group is called a system here. The number of transmitters that can be shared by a junction box is technically limited. Therefore, in the mobile communication base station, the number of transmitters installed in the base station is large, and it is difficult to accommodate all the transmitters in one system. Therefore, in a general wireless base station, the transmitter is divided into a plurality of systems and installed in the base station. In this case, as many transmitting antennas as the system are installed in the base station tower. Therefore, reduction of error rate can be expected by antenna hopping between systems. As described above in detail, according to the present invention, it is possible to easily realize the reduction of the error rate of the land mobile digital communication.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a transmission system of an antenna hopping wireless transmission device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a receiving system of an antenna hopping wireless transmission device according to an embodiment of the present invention.

FIG. 3 is a diagram showing an example of a case where interleaving is used in combination with the present invention.

FIG. 4 is a diagram showing an example of a transmission system of an antenna hopping wireless transmission device according to an embodiment of claim 2;

FIG. 5 is a diagram showing an example of a transmission system of an antenna hopping wireless transmission device according to an embodiment of claim 3;

[Explanation of symbols]

1 ... Transmitter input signal, 2 ... Error correction encoder, 3 ... Transmission signal, 4 ... Antenna switcher, 5 ... Receiver input signal, 6
... error correction decoder, 7 ... receiver output, 10 ... transmitter input signal, 11 ... error correction encoder, 12 ... switch A, 1
3 ... FIFOA, 14 ... FIFOB, 15 ... Switcher B, 16 ... Modulator, 17 ... Transmission antenna switcher, 1
8 ... Transmission antenna A, 19 ... Transmission antenna B, 20 ... Transmitter input A, 21 ... Error correction encoder A, 22 ... Transmitter input B, 23 ... Error correction encoder B, 24 ... Transmission signal A, 2
5 ... Transmission signal B, 26 ... Antenna switcher, 27 ... Transmission antenna A, 28 ... Transmission antenna B, 30 ... Transmitter input A, 31 ... Error correction encoder A, 32 ... Transmission signal A, 3
3 ... Baseband signal switcher, 34 ... Modulator A, 3
5 ... Mixer A, 36 ... Local oscillator A, 37 ... Power amplifier A input signal, 38 ... Power amplifier A, 39 ... Transmission antenna A, 40 ... Local signal switcher, 41 ... Transmitter input B,
42 ... Error correction encoder B, 43 ... Transmission signal B, 44 ... Modulator B, 45 ... Mixer B, 46 ... Local oscillator B, 47 ...
Power amplifier B input signal, 48 ... Power amplifier B, 49 ... Transmission antenna B,

Claims (5)

[Claims] 1. A transmission antenna for transmitting an error correction coded signal from a plurality of transmission antennas or a transmission antenna having a plurality of inputs, an error correction coding device, and a plurality of transmission antennas or a transmission antenna having a plurality of inputs. In a wireless communication device including a wireless transmission device including an antenna or an antenna switching device that switches input and a receiving device having an error correction decoding function, a signal to be transmitted by control of the error correction coding device and the antenna switching device. Wireless transmission characterized by having a transmitter having means for transmitting information of each arbitrary bit of from a plurality of different transmitting antennas or transmitting antennas having a plurality of inputs, and a receiver having an error correction decoder apparatus. 2. A group of wireless communication devices comprising a plurality of wireless communication devices according to claim 1, wherein any wireless communication device A belonging to said group of wireless communication devices.
The antenna switch of B is an arbitrary antenna belonging to A
During a period in which the wireless communication device C is not switched to, the antenna switch of any wireless communication device C different from A in the group switches to the antenna B, and the wireless communication device C
A wireless communication device capable of transmitting a signal from the antenna B. 3. The wireless communication device according to claim 2, wherein the error correction coded signal transmitted from the transmitting antenna is switched at a stage other than the transmitting antenna input stage. 4. A receiving antenna having a plurality of receiving antennas or a plurality of outputs, an antenna switching device for switching one receiving antenna or an output from the plurality of receiving antennas or a receiving antenna having a plurality of outputs, and error correction decoding. A wireless communication device comprising a receiving device having a function and a transmitter having an error correction coding device, wherein the transmitter is controlled by the control of an antenna switcher for switching the receiving antenna or the output and the error correction encoder. Information of each bit of the signal before error correction coding input to is received by the plurality of receiving antennas or outputs. 5. Claim 1 or claim 2 or claim 3.
Alternatively, in the wireless communication device according to claim 4, antenna switching is performed by TDMA, TDM, or TDD.
4. The method according to claim 1, wherein the switching period is synchronized with the frame period or time slot period of the system, and the switching period is an integral multiple of the frame length or time slot length of the TDMA, TDM, or TDD system.
Alternatively, the wireless communication device according to claim 4.