JPH0690197A - Radio communication equipment - Google Patents

Abstract

PURPOSE:To improve line quality by channel switching at high speed under fading environment by providing a line quality deterioration detection circuit and a control part by whose instruction the channel switching is performed. CONSTITUTION:The control part 12 retrieves a null slot on another frequency to satisfy prescribed line quality when a frequency switching signal is inputted from the line quality deterioration detection circuit 11, and decides a channel switching destination slot. Thence, a transmission burst can be comprised by generating control data to designate the channel switching destination slot and multiplexing it on a transmission signal by a modulator 58, then, it is transmitted to a mobile station. The control part 12 switches the frequencies of local oscillation signals generated by frequency synthesizers 62, 63, and those signals are transmitted to receivers 53, 54 and a transmitter 59, and switching to a designated channel can be performed. The mobile station receiving a transmittion burst from a base station reads the slot of a channel switching destination from the control data, and switches the frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless communication device using the TDMA-TDD system. In particular, the present invention relates to a wireless communication device that enables high-quality communication in a fading environment in which line quality deterioration occurs due to fading and / or interference.

[0002]

2. Description of the Related Art In a radio communication apparatus using the TDMA-TDD system, a diversity technique is known as a method for improving the deterioration of channel quality due to fading. Diversity is a technique for suppressing fading distortion by reducing the probability that the reception level will decrease by selecting or combining those having a high reception level from a plurality of propagation paths.
However, when a general space diversity technique is applied, at least two antennas and two receivers are required, so that the scale of the wireless communication device becomes large.
Therefore, in a mobile communication system, it is difficult to perform diversity in a mobile station that requires downsizing and low power consumption. Therefore, a transmission diversity technique is used that brings about a diversity effect in a mobile station by switching the transmission antenna on the base station side by utilizing the characteristic that the uplink and downlink propagation paths have reversibility and time correlation.

FIG. 3 is a diagram for explaining the principle of transmission diversity. In the figure, the base station 30 is equipped with two antennas 31 and 32, and the mobile station 40 is equipped with one antenna 41. The base station 30 includes antennas 31,
At 32, the up signals a and b from the mobile station 40 are received, and first, reception diversity is performed to select an antenna having a higher reception level. Next, the downlink signal c is transmitted to the mobile station 40 using the antenna selected by the reception diversity. Due to such transmission diversity of the base station 30, the mobile station 40 can maintain a predetermined line quality with a small circuit scale.

However, when the reception level of the uplink signals a and b received by the base station 30 is significantly deteriorated due to the influence of fading and the required channel quality cannot be satisfied, the downlink signal transmitted to the mobile station 40. The transmission diversity effect on the signal c is reduced, and the mobile station 40 cannot secure the required channel quality. In other words, the effect of improving the line quality by transmit diversity is limited only when the receive diversity at the base station is functioning effectively, and when the receive level is significantly degraded due to the effect of fading, sufficient line quality improvement The effect could not be expected.

On the other hand, the base station and the mobile station are provided with an interference level detecting function for detecting deterioration of channel quality due to co-channel interference. This interference level detection function switches the channel between the base station and the mobile station when the interference level exceeds a predetermined value.

FIG. 4 is a block diagram showing the configuration of a conventional base station having the functions of diversity and channel switching. In the figure, received signals received by the two antennas 31 and 32 are hybrid circuits 51 and 52, respectively.
Via the receivers 53 and 54 and the reception level comparison unit 55
Entered in. Each of the receivers 53 and 54 converts the received signal from the radio frequency band to the intermediate frequency band, one of the intermediate frequency signals is selected by the switch circuit 56, is input to the demodulator 57, and is subjected to baseband detection. The reception level comparison unit 55 detects and compares the levels of the respective reception signals, and controls the switch circuit 56 so as to select the receiver output with the higher reception level to perform reception diversity.

On the other hand, the modulator 58 modulates the transmission signal and sends it to the transmitter 59. The transmitter 59 converts the modulated signal into a radio frequency band and transmits it from the corresponding antenna via the switch circuit 60 selected similarly to the switch circuit 56, and performs transmission diversity.

The frequencies used for transmission and reception are set to the same frequency by using the frequency synthesizers 62 and 63 according to an instruction from the control unit 61. further,
The control unit 61 controls the receiver 5 selected by the switch circuit 56.
One of the output signals of 3 and 54 is monitored to detect the interference level due to co-channel interference. Here, when the interference level exceeds a predetermined value, first, an empty slot on the same frequency that satisfies the required channel quality is searched, and if not, an empty slot on another frequency is searched and the channel switching destination slot is set. decide. Next, the control data including the information designating the channel switching destination slot is created, and the modulator 58
At, the signal is multiplexed into a transmission signal to form a transmission burst and transmitted to the mobile station. On the other hand, the mobile station receiving the transmission burst from the base station reads the channel switching destination slot from the control data and switches the channel.

With the above configuration, it is possible to improve channel quality deterioration by switching channels between the base station and the mobile station. Since channel switching functions independently of diversity, a wireless communication device with one transmission and one transmission system can be similarly configured.

[0010]

By the way, in the case of detecting the deterioration of the line quality by using the conventional interference level detecting function, a considerable detection time is required to obtain the required accuracy. Therefore, in a fading environment in which the state of the line quality changes from moment to moment, the conventional interference level detection function cannot detect the deterioration of the line quality with sufficient accuracy and at high speed.

Further, in channel switching due to co-channel interference, a search procedure from a vacant slot on the same frequency to a vacant slot on another frequency is performed. However, in a fading environment, channel quality is improved even if switching is performed on the same frequency. Couldn't hope. That is, time is wasted on useless processing procedures, which hinders high-speed switching.

It is an object of the present invention to provide a radio communication device capable of improving line quality by switching channels at high speed in a fading environment in which line quality is deteriorated by fading and / or interference.

[0013]

SUMMARY OF THE INVENTION The present invention is a TDMA-T.
In a wireless communication device provided in at least one of a base station and a mobile station that perform communication using the DD system, channel quality deterioration detecting means for detecting channel quality deterioration due to fading or interference, or both from the demodulator detection output. And channel switching means for controlling the frequency of the local oscillation signal used in the receiver and the transmitter to switch the channel when the channel quality detected by the channel quality deterioration detecting means falls below a predetermined value. Constitute.

[0014]

Since the line quality deterioration detecting means according to the present invention detects the line quality deterioration from the detection output of the demodulator, it is possible to detect the line quality deterioration due to fading or interference, or both at high speed and with high accuracy. . In addition, since the channel switching means switches the frequency used for transmission and reception according to the detection of deterioration of the line quality, it is possible to improve the line quality by switching the channel at high speed in a fading environment and realize high quality communication. Can be made.

[0015]

1 is a block diagram showing the configuration of an embodiment in which a radio communication apparatus of the present invention is applied to a base station.

In the figure, the antennas 31 and 32, the hybrid circuits 51 and 52, the receivers 53 and 54, the reception level comparison unit 55, the switch circuit 56 and the demodulator 57 constitute a reception diversity structure, and further a modulator 58 and a transmitter 59.
The transmission diversity configuration of the switch circuit 60 and the switch circuit 60 is the same as the conventional configuration shown in FIG.

The feature of the present invention lies in that in this embodiment, the detection output of the demodulator 57 causes fading or interference,
Alternatively, the line quality deterioration detection circuit 11 for detecting the line quality deterioration due to both of them is provided, and the control unit 12 switches the channel according to the frequency switching instruction.

That is, when the frequency switching instruction signal is input from the channel quality deterioration detection circuit 11, the control unit 12 searches for an empty slot on another frequency that satisfies the required channel quality from the beginning, and switches to the channel switching destination. Determine the slot. Next, control data including information designating the channel switching destination slot is created, multiplexed with the transmission signal by the modulator 58 to form a transmission burst, and transmitted to the mobile station. Further, the control unit 61 controls the frequency synthesizer 6
The frequency of the local oscillation signal generated at 2, 63 is switched. This local oscillation signal is used for frequency conversion processing of the receivers 53 and 54 and the transmitter 59, and switching to the designated channel is performed. On the other hand, the mobile station receiving the transmission burst from the base station reads the channel switching destination slot from the control data and switches the frequency.

With the above configuration, between the base station and the mobile station, a predetermined channel quality is ensured by the reception diversity and the transmission diversity, and the channel quality is deteriorated by switching the channel at high speed even when the diversity is difficult to improve. Can improve and keep communicating.

As described above, in the configuration of the present invention, it is possible to detect the line quality deterioration due to fading at high speed and switch the frequency without interruption. FIG. 2 shows an example of the line quality improvement effect associated with this frequency switching.

In the figure, the horizontal axis is Eb / No [dB] and the vertical axis is the bit error rate. When the fading frequency is changed to 1 [Hz], 5 [Hz], 10 [Hz]. Eb /
It is the result of measuring the bit error rate with respect to No. Note that, here, by using the CRC error detection method, it is determined that the line quality is below a predetermined value when two consecutive CRC errors are detected, and the line quality deterioration detection circuit 11 switches the frequency used for transmission and reception. The signal is output and the frequency is switched.

As shown in the figure, the bit error rate is significantly increased by detecting the line quality deterioration due to fading at high speed and switching the frequency without interruption, as compared with the conventional configuration in which the frequency is not switched for fading. You can see that it can be improved. In particular, the smaller the fading frequency, the greater the effect of improving the floor error.

[0023]

As described above, according to the present invention, it is possible to detect line quality deterioration due to fading or interference, or both at high speed and with high accuracy, and to perform frequency switching in accordance with line quality deterioration at high speed. High quality communication can be realized in a fading environment.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment when a wireless communication device of the present invention is applied to a base station.

FIG. 2 is a diagram showing an example of a channel quality improvement effect due to frequency switching according to the present invention.

FIG. 3 is a diagram illustrating the principle of transmission diversity.

FIG. 4 is a block diagram showing the configuration of a conventional base station having the functions of diversity and channel switching.

[Explanation of symbols]

 11 line quality deterioration detection circuit 12 control unit 31, 32 antenna 51, 52 hybrid circuit 53, 54 receiver 55 reception level comparison unit 56, 60 switch circuit 57 demodulator 58 modulator 59 transmitter 61 control unit 62, 63 frequency synthesizer

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Shuzo Kato 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (1)

[Claims] 1. In a wireless communication apparatus provided in at least one of a base station and a mobile station that perform communication using the TDMA-TDD system, fading or interference from the detection output of the demodulator, or line quality deterioration due to both of them. Channel quality deterioration detecting means for detecting, and when the line quality detected by the line quality deterioration detecting means falls below a predetermined value, the frequency of the local oscillation signal used in the receiver and the transmitter is controlled to switch the channel. A wireless communication device, comprising: a channel switching unit for performing.