JPH0537490A - Spread spectrum radio communication system - Google Patents

Abstract

PURPOSE:To prevent communication from being interrupted by degrading a signal power/interrupting wave power ratio (SIR) by calculating interrupting wave power by subtracting signal power from total receiving power, calculating the SIR and raising an alarm when the SIR is made lower than a reference value. CONSTITUTION:The total receiving power at a receiver 1 is detected by a total receiving power detector 4 and inputted to an SIR detector 6. Next, the correlation detected result of a correlation detector 2 is inputted to a signal power detector 5, and the signal power is detected and inputted to the SIR detecting circuit 6. At the SIR circuit 6, the SIR is calculated from a ratio between the signal power and the total receiving power and when the SIR is made lower than the reference value, a communication defect signal is outputted. When the communication defect signal is detected, a communication defect alarming device 7 raises the communication defect alarm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread spectrum radio in which a transmitting side spreads an information signal by a spread signal and transmits the information signal, and a receiving side despreads the received signal using the spread signal to demodulate the information signal. The present invention relates to a communication system, and more particularly to detection of a signal power to interference wave power ratio (SIR) in a mobile station of a mobile communication system using the spread spectrum wireless communication system and a countermeasure when the SIR deteriorates.

[0002]

2. Description of the Related Art FIGS. 3 and 4 are diagrams for explaining a spread spectrum wireless communication system. FIG. 3 shows a spread spectrum modulator on the transmitting side, and FIG. 4 shows a demodulator on the receiving side. .. First, the operation of the spread spectrum modulator will be described with reference to FIG. In the figure, 11 is a carrier wave oscillator, 12 and 13 are multipliers, and 14 is an information signal (d
(T)) and 15 represent spread codes (p (t)).

The carrier wave input from the oscillator 11 is multiplied by the information signal (d (t)) 14 in the multiplier 12. The numeral 16 indicates the spectrum of the signal wave at point A at this time. This signal is further multiplied by the spread code (p
(T)) 15 is multiplied. As a result, the spectrum of the signal at point B becomes as shown by numeral mark 17. Then, this spread signal is transmitted.

Next, the operation of the receiving side demodulation section will be described with reference to FIG. A signal that has been spread and has a spectrum as shown in 17 of FIG. 3 described above is selected from the received waves by the bandpass filter 18, but the spectrum of the interference wave mixed in the transmission path exists. , The spectrum of the signal at the point C is a combination of the desired wave 25 and the interference wave 24 as shown in the figure.

Then, this signal and the spread code (p (t))
Are multiplied by the multiplier 20 and the signal spectrum at the point D obtained through the band pass filter 19 is shown as a desired wave 26 and an interference wave 27. Then, this signal and the output of the local oscillator 22 are multiplied by the multiplier 21 and then passed through the low-pass filter 23 to obtain the original information signal d.
(T) can be obtained.

As described above, in the spread spectrum wireless communication system, the information signal d (t) is transmitted to the spread signal p on the transmitting side.
(T) spreads and transmits, and the receiving side performs despreading with p (t) to demodulate d (t). At this time, even if the interference wave I (t) is mixed, by performing the despreading, the interference wave is spread over a wide band, so that the desired wave can be extracted.

[0007]

As described above, spread spectrum communication is a system that allows interference waves. For example, in the method (CDMA) in which the same frequency is shared by a number of stations and the stations are distinguished by the difference in spreading code, communication is performed in the presence of a large number of interference waves. Conventional F
In the DMA and TDMA communication systems, the SN ratio (signal power to noise power ratio) has been used as a parameter for defining the communication quality, but in the spread spectrum communication system, since interference waves exist, the communication quality is signal power to interfering wave power. Ratio (SI
R).

Conventionally, as a method for ensuring communication quality in a spread spectrum communication system, when the reception level from another base station becomes higher than the reception level of the base station in communication, zone switching is performed, There has been a method of avoiding deterioration of SIR by communicating with a base station having a high reception level.

However, in such a conventional system, when the zone structure becomes complicated and the interference waves from a plurality of base stations increase, the SIR deterioration due to the zone switching cannot be avoided and the line is disconnected. There was a problem of becoming. An object of the present invention is to provide means capable of coping with such conventional problems.

[0010]

Means for Solving the Problems The present invention provides a mobile station of a spread spectrum wireless communication system for performing two-way communication, a means for detecting signal power from a correlation detection result, and a total receiver input level at a receiver input. A means for detecting the received power, a means for obtaining the interference wave power by subtracting the signal power from the total received power, a means for obtaining the ratio (SIR) of the signal power and the interference wave power, and the signal power to interference This is a spread spectrum wireless communication system provided with means for issuing an alarm when the wave power ratio (SIR) falls below a reference value.

[0011]

In the mobile station of the present invention, the signal power is detected from the correlation detector of the receiving system, and the total received power of the receiver is also detected.
R). When the SIR value falls below a predetermined value (reference value), an alarm is issued to inform the mobile station user (carryer) that the SIR has deteriorated.

In the conventional FDMA and TDMA communications, the SN ratio is used as a parameter for defining the communication quality, and since the noise power does not fluctuate so much, the SN ratio is measured by measuring the total received input power with a power meter or the like. The required communication quality was specified. However, since the spread spectrum communication allows interference waves, it is not possible to measure the signal power only from the total received input power. Therefore, the present invention adopts the method of obtaining the signal power from the correlation detection result as described above. Hereinafter, the operation and the like of the present invention will be described in more detail based on examples.

[0013]

1 is a block diagram showing the configuration of an embodiment of the present invention, showing a receiving system of a mobile station. In the figure, the signal received by the receiver 1 is detected by the correlation detector 2 and then demodulated by the demodulator 3. At this time, the total received power in the receiver 1 is detected by the total received power detector 4. Then, the SIR detector 6
The total received power is input to. On the other hand, the correlation detection result by the correlation detector 2 is input to the signal power detector 5, the signal power is detected by the signal power detector 5, and the signal power is input to the SIR detection circuit 6.

The SIR detection circuit 6 obtains the SIR from the ratio of the input signal power and the total received power, and outputs the communication failure signal when the SIR is below the reference value. The communication failure alarm device 7 issues a communication failure alarm when the communication failure signal is detected. As the communication failure alarm, there are a method using a warning light and a method using a buzzer.

FIG. 2 is a diagram showing an example of changes in SIR for explaining the operation of the SIR detection circuit. In the figure, the vertical axis represents the SIR at the mobile station,
The horizontal axis indicates time. L0 is the reference SIR,
L1 indicates SIR in which the communication circuit is disconnected.

When the SIR gradually deteriorates and reaches the reference SIR at time t0, if the mobile station continues to move as it is, the line is disconnected at time t1. Therefore, in the present invention, the signal power is detected from the correlation detection result,
The total received power is detected from the total receiver input level at the receiver input, the interfering wave power is obtained by subtracting the signal power from the total received power, and the signal power to interfering wave power ratio (SIR) is obtained from them. When the SIR falls below the reference value, a communication failure alarm is issued at time t0 to notify the user.

By notifying the deterioration of the SIR in this way, the user can know that the communication condition has deteriorated, and therefore the user who does not want the deterioration of the communication condition moves the receiving antenna of the mobile station. It is possible to prevent the communication from being interrupted due to things.

[0018]

As described above, according to the present invention,
When the user of a mobile station (for example, a mobile phone) moves during a call and the SIR deteriorates, it is possible to know that the communication condition has deteriorated. Therefore, the user may move the receiving antenna of the mobile station. There is an advantage that the disconnection of communication can be avoided.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an exemplary embodiment of the present invention.

FIG. 2 is a diagram showing an example of changes in SIR.

FIG. 3 is a diagram showing a modulator of a spread spectrum communication system.

FIG. 4 is a diagram showing a demodulation unit of a spread spectrum communication system.

[Explanation of symbols]

 1 receiver 2 correlation detector 3 demodulator 4 total received power detector 5 signal power detector 6 SIR detector 7 communication failure alarm device

Claims (1)

Claim: What is claimed is: 1. A mobile station of a spread spectrum wireless communication system for performing bidirectional communication, means for detecting signal power from a correlation detection result, and total reception from all receiver input levels at receiver input. Means for detecting electric power, means for obtaining the interference wave power by subtracting the signal power from the total received power, means for obtaining the ratio (SIR) between the signal power and the interference wave power, and the signal power to the interference wave A spread spectrum wireless communication system, comprising means for issuing an alarm when the power ratio (SIR) falls below a reference value.