JPH11186941A - Spread spectrum radio communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the fluctuations in a reception level due to frequency selective fading in the case of conducting transmission and reception with a spread spectrum signal adopting the frequency hopping system. SOLUTION: This system is provided with a reception level detection means that detects respectively a reception level for each frequency hopping at a receiver side of a transmission signal from a communication opposite station, which has undergone the spread spectrum modulation of the frequency hopping system with prescribed test data, The system is also provided with a first memory section 24 that stores reception levels of detected respective hopping frequencies, a second memory section 25 that stores gain control data of an amplifier 15a in cross reference with the reception level, and a control section 27 that controls a gain of the amplifier 15a, so that the reception levels of the opposite station are nearly the same for each hopping frequency based on the first memory section 24 and the second memory section 25 or the like. Thus, when communications is made with the spread spectrum signal of the frequency hopping system, the system can cope with an adverse transmission environment, such as frequency selective fading.

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 communication apparatus, and more particularly, to transmission and reception using a spread spectrum signal of a frequency hopping method, which is mainly used to reduce a reception level fluctuation due to frequency selective fading. About prevention.

[0002]

2. Description of the Related Art In spread spectrum communication using the frequency hopping method, a frequency spectrum is spread by hopping the frequency of a carrier wave according to a predetermined hopping pattern. Therefore, for example, when the transmission path is affected by frequency selective fading,
Only certain carrier frequencies may be affected, causing code errors in the received data. For example, as shown in FIG. 2A, when the hopping frequency is f1 to fn, the reception level (spread demodulation output) of f1 to fn on the receiving side becomes uniform under normal transmission, Under the influence of the frequency selective fading, the level of some carriers (f3, fm in the figure) may be lower than that of other carriers. This lowering of the level may cause an error in the received data. Conventionally, the non-uniformity of the reception level has been corrected by an AGC (automatic gain control) function of an intermediate frequency circuit or the like.

[0003]

SUMMARY OF THE INVENTION However, AGC
There is a limit to the function, the effect of fading is large,
When the nonuniformity of the reception level is large, there is a case where the correction cannot be sufficiently performed only by the AGC. Therefore, it is necessary to minimize the non-uniformity of the reception level in the reception stage.
The present invention has been made in view of such a viewpoint,
It is an object of the present invention to provide a spread spectrum wireless communication device in which the reception levels of hopping carrier frequencies are made uniform.

[0004]

SUMMARY OF THE INVENTION The present invention is directed to a spread spectrum wireless communication apparatus for transmitting and receiving a frequency hopping spread spectrum signal from a communication partner station which has been subjected to frequency hopping spread spectrum modulation with predetermined test data. Receiving level detecting means for detecting the receiving level of the transmission signal at the receiving side for each hopping frequency, receiving level storing means for storing the detected receiving level of each of the hopping frequencies, Control means for controlling the transmission output level of each hopping frequency based on the data stored in the reception level storage means so that the reception level at the communication partner station becomes substantially the same at each hopping frequency. Spread spectrum radio communication There is provided an apparatus.

A switching circuit for switching between input information data and test data is provided under the control of the control means, so that a signal of spread spectrum modulation based on the test data can be transmitted to the communication partner station. ing.

[0006] The reception level detection means comprises a detection section for detecting the envelope of the spread spectrum demodulated signal, and a level detection section for detecting the level of the detection signal from the detection section.

Further, the control of the transmission output level by the control means is performed based on the gain control data of the memory section storing gain control data for the reception level provided in the control means. Is controlled by variably controlling the gain of the amplifier that amplifies the signal.

[0008] The test data is either digital "1" or "0".

The reception level storage means stores the reception levels of a plurality of communication partner stations.

Further, a timer unit is provided under the control of the control means, and the spread spectrum communication is performed by the test data at predetermined time intervals to update data stored in the reception level storage means. .

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment will be described with reference to the drawings. FIG. 1 is a main block diagram showing an embodiment of a spread spectrum wireless communication apparatus according to the present invention, wherein 1 is a communication apparatus A and 2 is a communication apparatus B. Since the communication device B has the same configuration as the communication device A, an internal block diagram is omitted. FIG. 2 is an explanatory diagram related to FIG. Hereinafter, the operation of the present invention will be described. The communication apparatus A1 and the communication apparatus B2 alternately perform test transmission and reception before performing the original data communication. First, the communication device A of FIG.
1 will be described. SW1 is a first switching circuit in which information data Di to be originally transmitted is transmitted.
And the test data Dt to be used when transmitting the test,
Switching is performed by the control unit 27. SW1 is set to a during test transmission.
Set to the side. As a result, the test data Dt is input to the information modulation unit 11. The test data Dt is either digital "1" or "0".

The information modulator 11 performs a predetermined digital modulation process such as QPSK, and then the spread modulator 12 performs frequency hopping spread spectrum modulation. An oscillating signal from an oscillator 14 that oscillates according to a frequency hopping pattern from a hopping pattern generator 13 is input to the spread modulation unit 12. What is necessary is just to process the information modulation and the spread modulation in the same manner as in the prior art. The frequency hopping spread spectrum modulation signal from the spread modulation unit 12 is input to the transmission unit 15, where it is transmitted from the antenna 16 via the second switching circuit SW2 (a side) after power amplification and other predetermined processing. You. In this case, the amplifier 15 constituting the transmitting unit 15
The gain of a is fixed. The setting of SW2 is performed by the control unit 27.

Next, reception of a transmission signal related to the test transmission will be described with reference to the block diagram of the communication apparatus A1 in FIG. In the receiving state, SW2 is controlled by the control unit 27 on the receiving side (b).
Side). As a result, the signal received by the antenna 16 is input to the RF / IF unit 17 and after being subjected to predetermined processing such as high-frequency amplification, conversion to an intermediate frequency, and amplification thereof, is sent to the spread demodulation unit 18 and is subjected to frequency hopping Demodulate the spread spectrum modulated signal. In this case, the spread demodulation unit 18 includes an oscillator 20 that oscillates according to a frequency hopping pattern from a hopping pattern generator 19 having the same pattern as that on the transmission side.
Oscillating signal is input. The demodulated output of the spread demodulation unit 18 branches to an information demodulation unit 21 and a detection unit 22. The one information demodulation unit 21 performs demodulation processing for information modulation on the transmission side such as QPSK, for example. This allows data Do
Is demodulated. What is necessary is just to process the spread demodulation and the information modulation in the same manner as in the prior art.

On the other hand, the other detector 22 detects the envelope of the spread demodulation output. By this envelope detection, a detection signal having an envelope waveform indicating a substantially peak value of the signal obtained by frequency hopping is obtained. This envelope detection signal is subjected to level detection in the level detection unit 23. Since the detected level means a reception level, it is referred to as a reception level. If the reception level shows a constant value for each hopping frequency, it means that the reception level of each carrier frequency formed by hopping is uniform, and the transmission path has a good propagation situation without frequency selective fading and the like. I can say. On the other hand, when the reception level partially has a depression (recess), it means that the frequency of that portion is affected by the frequency selective fading. On the other hand, it can be specified from the hopping pattern data of the hopping pattern generator 19 which of the hopping carrier frequencies the spread demodulation output corresponds to. Therefore, the depression (recess) of the reception level
Can be specified.

The control section 27 stores the reception level detected by the level detection section 23 in the first memory section 24 in correspondence with the frequency. The test transmission and reception described above are performed between the communication devices, and the reception level data is stored in the first memory unit 24. When communication is performed with a plurality of communication devices having different transmission paths, the reception level data for each communication device is stored in the first memory unit 24. Further, it is preferable that the test transmission and reception between the communication devices are periodically performed. This is because the fading phenomenon varies. Therefore, a timer unit 26 is provided below the control unit 27, and test transmission and reception are performed between communication devices at predetermined time intervals, and the reception level data in the first memory unit 24 of each communication device is updated.

Next, the transmission control of the information data Di based on the data relating to the reception level stored in the first memory unit 24 will be described with reference to the block diagram of the communication device A1 in FIG. After the test transmission and reception have been completed, the information data Di, which is the original transmission target, is transmitted. In this case, SW1 is set to the b side by the control unit 27, the information data Di is input to the information modulation unit 11, and the information modulation is performed as described above.
Next, spread modulation is performed by the spread modulation unit 12, and the spread modulation signal is sent to the transmission unit 15. Here, a second memory unit 25 is provided below the control unit 27. In the second memory unit 25, gain control data for the amplifier 15a corresponding to the reception level stored in the first memory unit 24 is stored in advance. This gain control data is data for which the amplification degree is higher at frequencies where the reception level is lower than at other frequencies.

The control unit 27 receives hopping pattern data from the transmission hopping pattern generator 13. Therefore, the frequency of the signal input to the amplifier 15a can be determined from the hopping pattern data. Therefore, the control unit 27 sets the hopping pattern data
Based on the data of the reception level stored in the memory unit 24 and the gain control data of the second memory unit 25, the amplification degree is adjusted so as to compensate for the decrease in the frequency where the reception level is reduced. Increase the required ratio. The reception level on the receiving side is made uniform by increasing the level reduction and transmitting the signal. For example, as shown in FIG. 2A, if the hopping frequencies are f1 to fn and the reception levels of the frequencies f3 and fm among them are lower than the others, the control unit 27
For f3 and fm, the degree of amplification is made higher by a required ratio than other frequency components. As a result, the reception level on the receiving side is reduced as shown in FIG.
As shown in (B), the uniformity is achieved, and the effect of frequency selective fading can be dealt with.

[0018]

As described above, according to the present invention, it is possible to cope with a transmission path environment such as frequency selective fading when performing communication using a frequency hopping spread spectrum signal. That is, before transmitting the original information data, a trial transmission / reception is performed between the communication devices, the reception level is stored for each hopping frequency, and the transmission output level is varied according to the strength of the reception level during transmission. Therefore, even under a transmission path environment such as frequency selective fading, the reception level on the receiving side can be made uniform. Conventionally, fluctuations in the reception level due to the effects of the above fading or the like are caused by the
The C (automatic gain control) function was able to repair to some extent, but there was a limit to this repair when the effects of fading and the like were large. On the other hand, according to the present invention, since the reception level is made uniform, the above-mentioned AGC also functions satisfactorily, and it is possible to prevent occurrence of errors in demodulated data due to fluctuations in the reception level. Thus, it can be said that the present invention can contribute to the improvement of the performance of the frequency hopping spread spectrum wireless communication apparatus.

[Brief description of the drawings]

FIG. 1 is a main block diagram showing an embodiment of a spread spectrum wireless communication apparatus according to the present invention.

FIG. 2 is an explanatory diagram related to FIG. 1;

[Explanation of symbols]

 1 Communication device A 11 Information modulator 12 Spread modulator 13, 19 Hopping pattern generator 14, 20 Oscillator 15 Transmitter 15a Amplifier 16 Antenna 17 RF / IF unit 18 Spread demodulator 21 Information demodulator 22 Detector 23 Level detector 24 First memory unit 25 Second memory unit 26 Timer unit 27 Control unit SW1 First switching circuit SW2 Second switching circuit 2 Communication device B

Claims (7)

[Claims] In a spread spectrum wireless communication apparatus for transmitting and receiving a frequency hopping spread spectrum signal, a reception side of a transmission signal from a communication partner station which has been subjected to frequency hopping spread spectrum modulation with predetermined test data is received. Reception level detection means for detecting a level for each hopping frequency, reception level storage means for storing the reception level of each detected hopping frequency, and the reception level storage means when the reception side transmits to the communication partner station. Control means for controlling the transmission output level of each hopping frequency such that the reception level at the communication partner station becomes substantially the same at each hopping frequency based on the stored data of Wireless communication device. 2. A switching circuit for switching between input information data and test data is provided under the control of the control means so that a signal of spread spectrum modulation based on the test data can be transmitted to the communication partner station. 2. The spread spectrum wireless communication apparatus according to claim 1, wherein: 3. The reception level detection means comprises: a detection section for detecting an envelope of a spread spectrum demodulated signal; and a level detection section for detecting a level of a detection signal from the detection section. The spread spectrum wireless communication device according to claim 1. 4. The control of the transmission output level by the control means, based on the gain control data in a memory unit provided in the control means and storing gain control data for the reception level. 2. The spread spectrum wireless communication apparatus according to claim 1, wherein the gain is variably controlled by an amplifier that amplifies the signal. 5. The spread-spectrum wireless communication apparatus according to claim 1, wherein the test data is one of digital “1” and “0”. 6. The spread spectrum wireless communication apparatus according to claim 1, wherein said reception level storage means stores reception levels of a plurality of communication partner stations. 7. A timer section is provided under the control of said control means, performs said spread spectrum communication by said test data at predetermined time intervals, and updates data stored in said reception level storage means. The spread spectrum wireless communication apparatus according to claim 1 or 6, wherein: