JP2000134150A - Transmission power control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve communication quality by conducting transmission power control in response to reception power from a desired station, without being affected by the side of the reception power from an undesired station in the transmission power control in digital radio communication. SOLUTION: A transmission section 2 of a transmitter/receiver 1 applies error correction coding to a digital signal, interleaves a plurality of between plural transmission slots, modulates and amplifies the signal and transmits the resulting signal, a reception section 5 demodulates and de-interleaves the received signal, applies error correction decoding to a demodulation signal series, decides a most probable object signal series, and a CIR detection circuit 6 receiving the demodulation signal series and the object signal series from the reception section 5 obtains a desired wave power versus interference wave power ratio (C/I) by dividing a desired power (c) obtained by squaring the object signal series by an interrupt wave power (I) obtained by averaging the square of the difference between the object signal series and the demodulation signal series, and a power setting circuit 7 decides the transmission power, based on the desired wave power versus interference wave power ratio to control transmission power of the transmission section 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio communication environment in which an interference wave from another radio station exists, for example, a cellular system (a mobile radio communication system in which frequencies are repeatedly used in a location for effective use of frequencies). In this environment, a digital communication system, for example, a digital car phone, a digital mobile phone, a wireless LAN, etc., is a system for wirelessly transmitting a signal obtained by converting a digital signal or an analog signal to a digital signal, and is suitable for the communication environment. The present invention relates to a technique for controlling transmission power so that wireless communication can be performed with power.

[0002]

2. Description of the Related Art Transmission power control technology is used in various digital communication systems provided by communication companies around the world, including a digital car telephone system in Japan (standard: RCR STD-27). That is, if the transmission power is controlled according to the propagation environment of the radio wave, there are the following advantages.

(1) Since there is an effect of reducing the interference wave power between the wireless stations, the communication quality can be improved. (2) Since there is an effect of reducing the interference wave power between the wireless stations, in the cellular system, the frequency repetition use interval can be reduced, and the efficiency of frequency location utilization can be improved.
(3) Since transmission is not performed with more power than necessary, the power consumption is particularly small in the portable device, and the use time of the battery is prolonged.

[0004] However, the transmission power control method is arbitrarily determined by the communication company that provides the communication, but a method of determining the transmission power control amount based on the information on the reception power amount of the receiver is widely adopted. The basic principle is that, when the received power from the desired station is small, it is determined that the desired communication quality is not satisfied, and the transmission power is increased. Conversely, when the received power from the desired station is large, The transmission power is reduced by judging that the communication quality more than desired is obtained, and by lowering the communication quality from the excess communication quality to the desired communication quality, the power consumption is prevented from being consumed more than necessary. It suppresses.

[0005]

However, in the conventional transmission power control method as described above, the "reception power amount for an undesired wave (interference wave)" is added to the "reception power amount for a desired wave". Since the value is the amount of received power, it becomes impossible to distinguish the received power between the desired wave and the undesired wave.

When it is impossible to distinguish a desired wave from an undesired wave, for example, even if the received power from the desired station is small, if the received power from the undesired station is large, the received power as a whole increases. However, the receiving side may erroneously recognize that the desired communication quality is obtained, and in some cases, the transmission power should be increased, whereas the transmission power should be decreased, and the communication quality may be further deteriorated.

Accordingly, the present invention provides communication by performing power control to increase transmission power in response to reception power from a desired station being small even if reception power from a non-desired station is large. It is an object of the present invention to provide a transmission power control method capable of satisfactorily improving quality.

[0008]

According to a first aspect of the present invention, there is provided a transmission power control method comprising the steps of: transmitting a digital signal to a transmission station performing digital radio communication by error correction coding; Interleave with
A receiving station that performs modulation, high-frequency amplification, and transmission and performs digital wireless communication demodulates the received signal, deinterleaves the demodulated signal that spans multiple slots, and error-corrects and decodes the demodulated signal sequence to be the most probable candidate. A signal sequence is determined, its square value is determined as desired signal power, the square value of the difference between the candidate signal sequence and the demodulated signal sequence is averaged to determine interference signal power, and the desired signal power is divided by the interference signal power. The transmission power value is determined based on the desired wave power to interference wave power ratio obtained as described above, and the transmission power is controlled so as to transmit at the determined transmission power.

[0009]

Next, an embodiment of a transmission power control method according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic functional block diagram of a transceiver 1 having both a transmission function and a reception function for performing digital wireless communication to which the transmission power control method according to the present invention is applied. Note that the transceiver 1 functions as a transmitting station and a receiving station for implementing the transmission power control method according to the present invention. For example, in a cellular system, both the base station and the mobile radio station are used. It is necessary to have essential functions of the transceiver 1.

The transmitting section 2 of the transceiver 1 includes an encoding circuit 2a for performing error correction encoding by adding redundant bits to transmission data, and a plurality of slots for enhancing the effect of error correction on the encoded data sequence. Interleave circuit 2b for interleaving between signals, and modulation circuit 2c for modulating a signal
And an amplifier 2d for further amplifying the high frequency, and the transmission signal subjected to the high frequency amplification is supplied to the antenna 4 through the duplexer 3 for transmission and reception.

On the other hand, a receiving section 5 to which a high frequency signal received from the antenna 4 is supplied through the duplexer 3 is provided with a demodulation circuit 5a for demodulating the received signal and a deinterleave (interleave) for a demodulated signal spanning a plurality of slots. And reverse operation)
A deinterleaving circuit 5b, and a composite circuit 5c for error correcting and decoding the deinterleaved demodulated signal sequence to determine the most probable candidate signal sequence.

Thus, the demodulated signal sequence deinterleaved by the deinterleave circuit 5b is, for example, shown in FIG.
In the case where the signal sequence is obtained as a demodulated signal sequence as shown in (1), the decoding circuit 5c selects the most probable candidate signal sequence n from the candidate signal sequence group from the candidate signal sequence 1 to the candidate signal sequence N.

The demodulated signal sequence deinterleaved by the deinterleaving circuit 5b and the candidate signal sequence n selected by the decoding circuit 5c are combined with a desired-to-interference-wave power ratio (Carrier-to-Interference).
(Ratio: CIR) detection circuit 6
In the R detection circuit 6, a desired signal power (Carrier power: C), which is a square value of the demodulated signal sequence, and a square value of a difference between the candidate signal sequence and the demodulated signal sequence (FIG. 2C)
(See Interferenc)
e power: I), and the desired signal power (C) is divided by the interference signal power (I) to obtain a desired signal power to interference signal power ratio (CIR).

The CIR determined by the CIR detection circuit 6 as described above is supplied to a power setting circuit 7,
By determining the transmission power value based on the IR and controlling the amplifier 2d of the transmission unit 2 based on the determined power value, it is possible to transmit at an appropriate transmission power according to the communication environment.

That is, in the transceiver 1 according to the present embodiment, an accurate CIR is obtained by using the process of error correction coding and decoding used for high quality transmission of digital data, Based on the high CIR, the quality of the communication environment with the desired station to be communicated with is determined, and the transmission power is controlled and transmitted according to the determination. Therefore, the reception power from the non-desired station is large. Also, if the received power from the desired station is small, it is possible to perform power control to increase the transmission power accordingly,
Communication quality can be improved satisfactorily. Of course, by the transmission power control, reduce the interference wave power between wireless stations, reduce the frequency repeated use interval in the cellular system, the effect of improving the efficiency of the frequency location,
By not transmitting with more power than necessary, there is also an effect that power consumption can be suppressed, and in particular, the battery usage time in the portable device can be extended.

The method for determining the transmission power value from the CIR by the power setting circuit 7 is not particularly limited. For example, a data table in which the relationship between the CIR and the transmission power control amount is determined in advance is prepared. Alternatively, the corresponding transmission power control amount may be specified from the obtained CIR and used for power control, or if the obtained CIR is 1/10, this is set to “1”. Transmit power 10
Simple control such as doubling may be used. That is, as a method of determining the transmission power value from the CIR, an appropriate determination method may be selected according to the communication environment, communication characteristics, and the like, and any technique may be employed within the range of any design item.

[0018]

As described above, according to the transmission power control method according to the first aspect, an accurate error correction encoding and decoding process used for high quality transmission of digital data is utilized. CIR is calculated and this highly reliable C
Based on the IR, the quality of the communication environment with the desired station to be communicated is determined, and the transmission power is controlled according to the determined transmission power. Therefore, even if the reception power from the non-desired station is large, If the received power from the desired station is small, it is possible to perform power control such that the transmission power is increased accordingly, and the communication quality can be improved satisfactorily.

Further, since transmission is not performed with an excessively high power, it is possible to reduce the interference wave power between the radio stations, and to reduce the frequency use interval of the frequency in the cellular system, thereby improving the efficiency of use of the frequency. Can be improved. Further, by not transmitting with excessive power, the power consumption on the transmitting station side can be suppressed, and in particular, there is an effect that the use time of the battery in the portable device can be prolonged.

[Brief description of the drawings]

FIG. 1 is a schematic functional block diagram of a transceiver capable of performing digital wireless transmission to which a power control method is applied in transmission according to the present invention.

FIG. 2 is a waveform chart showing a process of CIR detection.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transceiver 2 Transmission part 2a Encoding circuit 2b Interleave circuit 2c Modulation circuit 2d Amplifier 3 Duplexer 4 Antenna 5 Receiver 5a Demodulation circuit 5b Deinterleave 5c Decoding circuit 6 CIR detection circuit 7 Power setting circuit

Claims (1)

[Claims] In a transmitting station performing digital radio communication, a digital signal is subjected to error correction coding, interleaving is performed among a plurality of transmission slots, modulated, high-frequency amplified and transmitted, and a receiving station performing digital radio communication is provided. Demodulate the received signal, deinterleave the demodulated signal spanning a plurality of slots, determine the most probable candidate signal sequence by error correction decoding of the demodulated signal sequence, find the square of the candidate signal power as the desired wave power, The interference power is calculated by averaging the square value of the difference between the sequence and the demodulated signal sequence, and the transmission power value is calculated based on a desired power to interference power ratio obtained by dividing the desired power by the interference power. A transmission power control method comprising: determining a transmission power so as to transmit at the determined transmission power.