JP2001127695A - Mobile wireless communication unit and mobile wireless communication system using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of a conventional mobile wireless communication unit such that the unit cannot estimate a radio propagation environment with high accuracy. SOLUTION: The mobile wireless communication unit and the mobile wireless communication system that can accurately estimate a radio wave propagation environment of a communication channel are disclosed. The Doppler frequency of a carrier if calculated on the basis of a mobile speed of the digital mobile wireless communication unit and a reception electric field strength is calculated from the received radio wave, the mobile wireless communication unit has a function of estimating and acquiring the radio wave propagation environment of the communication channel on the basis of two sets of the information above and a bit error rate versus reception electric field strength model using a shift from the carrier frequency (Doppler frequency) for parameters.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a digital mobile radio communication device and a digital mobile radio communication system using the same.

[0002]

2. Description of the Related Art Conventionally, in a digital portable radio telephone system having a zone configuration, a radio wave propagation environment changes from time to time due to fading caused by multipath. Maintain line quality.

In this case, since the change in the radio wave propagation environment between the communication paths greatly depends on the moving speed of the portable telephone, the moving speed is calculated first, and the switching is performed based on the speed.

For example, in Japanese Patent Application Laid-Open No. 9-98465, a plurality of Global Positioning Satellites (GPS)
The transmission signal from the satellite is the G signal of the mobile phone 900 shown in FIG.
High-frequency receiving circuit 9 received by PS receiving antenna 901
The signal is guided to 02, demodulated, and input to the GPS signal processing circuit 903. The signal processing circuit 903 decodes information such as satellite orbital position information and time information from the demodulated signal and sends it to the data processing circuit 904.

A data processing circuit 904 accurately calculates the current position of the portable telephone 900 and uses the information as a moving speed detection circuit 90.
Enter 5 Further, the speed detecting circuit 905 calculates the moving speed of the mobile phone 900 from the current position information obtained at regular time intervals and outputs the calculated moving speed to the control circuit 909. Control circuit 9
In step 09, a control signal corresponding to the magnitude of the moving speed is transmitted to the transmission / reception circuit 907, and a time interval (hereinafter, referred to as a monitoring cycle) for monitoring an adjacent communication channel of the currently used channel is switched.

As described above, if a channel having a better radio wave propagation environment than the currently used channel is found, the control circuit 909 switches the communication channel to that channel.

However, in such a conventional method, even if the moving speed of the portable telephone can be accurately detected, it is only reflected in the change of the monitoring cycle of the adjacent channel. It was not directly related to the physical quantity representing the radio wave propagation environment of the communication path.

[0008]

Accordingly, there has been a problem that it is not possible to obtain accurate information for determining the radio wave propagation environment. For example, it has not been associated with the degradation of the bit error rate caused by the Doppler shift (Doppler frequency) of the carrier frequency in a mobile phone moving at high speed.

Although this method is effective for finding a communication channel having a favorable radio wave propagation environment, it is not associated with the reception electric field strength of the portable telephone.
Therefore, for example, even when the mobile terminal is moving at a high speed in a situation where the received electric field strength is sufficiently large, that is, in a situation where the radio wave propagation environment is good, unnecessary switching of the monitoring period is performed in the same manner as in a situation where the received electric field strength is not good. As a result, there is a problem that instantaneous interruptions occur frequently.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problem, and it is possible to obtain a more accurate information by using both the moving speed information of a mobile radio communication device and the received electric field strength information. It is an object of the present invention to provide a mobile radio device that obtains good channel quality by estimating a radio wave propagation environment. The mobile radio of the present invention operates in the receiving section as follows.

[0011] 1) The moving speed signal generation unit receives moving speed information of the mobile radio, and converts the moving speed into an electric signal (hereinafter referred to as a moving speed signal).

2) The Doppler frequency calculation unit uses the moving speed signal as an input signal, calculates a Doppler frequency of a radio wave corresponding to the moving speed, and converts the Doppler frequency into an electric signal (hereinafter referred to as a Doppler frequency signal).

[0013] 3) The reception field strength signal generation section outputs the reception field strength at the input section of the mobile radio as an electric signal (hereinafter referred to as reception field strength signal).

4) The radio wave propagation environment estimating section receives the above two signals, the Doppler frequency signal and the received electric field strength signal, as input signals, estimates the radio wave propagation environment of the mobile radio from these signals, and obtains an electric signal (hereinafter referred to as a radio wave signal). (Referred to as a propagation environment estimation signal).

In general, a mobile radio used in a digital communication system has a higher Doppler shift in its carrier frequency as its moving speed becomes higher, thereby deteriorating the bit error rate, and thus deteriorating the line quality. It is known to cause.

The relationship between the carrier frequency shift and its effect on the bit error rate depends on the digital modulation scheme, and these have been experimentally or theoretically clarified under a model radio wave propagation environment. Often.
Therefore, in an actual radio wave propagation environment, if a Doppler frequency can be calculated under a certain modulation scheme by applying data in a radio wave propagation environment model similar to that, a bit error rate corresponding to the Doppler frequency can be estimated.

Similarly, the relationship between the received electric field strength and the bit error rate also differs depending on the digital modulation method, and is often clarified experimentally or theoretically under a model radio wave propagation environment.

Therefore, in an actual radio wave propagation environment, if a received electric field strength can be calculated under a certain modulation scheme by applying data in a radio wave propagation environment model similar to that, a bit error rate corresponding to the received electric field strength is estimated. You can do it. The reason why the estimation is described here is that the radio wave propagation environment model from which the reference data is obtained may not be the same as the actual radio wave propagation environment for both the Doppler frequency and the received electric field strength.

As described above, the mobile radio of the present invention can calculate the two physical quantities of the Doppler frequency and the received electric field strength and can more accurately estimate the radio wave propagation environment of the communication path than before.

The moving speed information input to the moving speed signal generation unit includes the moving speed of a vehicle or an aircraft, the GPS
It may be satellite position or time information transmitted from the satellite.

The received signal strength signal generating section is provided with a Received Signal Strength Indicator (RSSI) provided to obtain a DC voltage proportional to the received field strength of the received radio wave.
It is also possible to generate a reception field strength signal from the output signal of the detection unit.

Furthermore, under a certain digital modulation, a radio wave propagation environment estimation signal based on data of a bit error rate versus a received electric field strength characteristic using a Doppler frequency as a parameter obtained from a radio wave propagation environment model similar to an actual radio wave propagation environment. May be provided.

Further, in communication between a mobile radio device and a plurality of base stations in mobile communication having a zone configuration, a radio wave propagation environment is estimated based on a signal from a communication partner in order to maintain better line quality. The base station can be changed.

Further, by providing the radio wave propagation environment estimation signal to the communication partner, the communication partner can take measures to improve the line quality.
For example, there is a method of changing a modulation method based on a radio wave propagation environment estimation signal acquired by a communication partner. Further, in the case of the spread spectrum communication system, the number of spread codes to be allocated can be appropriately changed in order to improve the line quality and the transmission speed.

Also, the transmission power of the mobile radio can be changed based on the radio wave propagation environment estimation signal obtained from the communication partner in order to improve the line quality.

In the present invention, two physical quantities, the Doppler frequency of the carrier frequency used in the mobile radio and the received electric field strength, are calculated inside the radio as described above. Next, the radio wave propagation environment of the communication path is estimated and output from the relationship between these two pieces of information and the bit error rate obtained separately in a radio wave propagation environment model similar to the actual radio wave propagation environment. Further change the base station of the communication partner by this output signal, or increase the transmission power or change the modulation method by notifying the communication partner of the output signal,
The number of spreading codes assigned to one user is changed using the spread spectrum method. As described above, the present invention can provide a mobile wireless device that obtains good channel quality.

[0027]

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

(Embodiment 1) FIGS. 1 to 3 show block diagrams of an embodiment of a mobile radio according to the present invention.
FIG. 1 is an overall configuration diagram, in which a moving speed 101 and a received signal 106 are input to a mobile wireless device. 2 and 3
1 is a partial configuration diagram of a mobile radio, and shows a moving speed signal generator 102 and a received electric field strength signal generator 107 shown in FIG.
Details of each example are shown.

In FIG. 2, a signal transmitted from a GPS satellite is received by a GPS receiving antenna 201,
And demodulated, the demodulated signal 204 is input to a signal processing circuit 205. In circuit 205, three or more GPS
The current position of the mobile radio is calculated from the orbital position information and time information from the satellite, and is input to the moving speed calculation unit 207.
The calculation unit 207 acquires the current position information at regular time intervals, calculates the moving speed of the mobile radio, and outputs the moving speed signal 103
Is generated and output.

This is the moving speed signal 103 in FIG. 1 and is input to the Doppler frequency calculator 104. The Doppler frequency calculation unit 104 calculates the Doppler frequency (fd) of the mobile radio device based on the input moving speed signal 103 based on the following equation, outputs the Doppler frequency signal 105 as a Doppler frequency signal 105, and outputs a radio wave propagation environment estimation unit 109 To enter. fd = f · v / V where:
f, v, and V are a carrier frequency, a moving speed of the mobile radio, and a radio wave propagation speed used by the mobile radio, respectively.

On the other hand, the received electric field strength signal generating section 107 in FIG.
It comprises an SSI detection section 305 and a reception field strength calculation section 307. In FIG. 3, when the mobile wireless device is communicating with a communication partner, the received radio wave is received by the antenna unit 301 and guided to the high frequency unit 303, where it is amplified and frequency converted to generate the intermediate frequency signal 304. .

The RSSI detector 305 detects this signal and outputs a DC voltage 306. Receiving field strength calculation section 307 generates and outputs reception field strength signal 108 using the DC voltage as an input signal. Then, this is input to the radio wave propagation environment estimation unit 109 in FIG. However, the high frequency section 303 and RSS
Since the I detection unit 305 is set to operate in the linear region, the DC voltage 306 is proportional to the received electric field strength.

As described above, the two signals of FIG. 1, that is, the Doppler frequency signal 105 and the received field strength signal 108 are input to the radio wave propagation environment estimating unit 109 and processed. If the radio wave being communicated is subjected to a digital modulation of a certain method, the bit error rate (BER) vs. received electric field strength characteristic using the carrier frequency shift as a parameter is similar to the actual radio wave propagation environment. The characteristics as shown in FIG. 4 are obtained experimentally or theoretically in the propagation environment model.

In FIG. 4, curve 401 shows a case where the carrier frequency shift is large, and the Doppler frequency at this time is fa, and curve 402 shows a case where the shift is small, and the Doppler frequency at this time is fb.

From this figure, it can be seen that the bit error rate is larger when the frequency shift is larger, and the difference becomes more pronounced as the received electric field intensity is smaller. The radio wave propagation environment estimating unit 109 in FIG. 1 determines i) from the input Doppler frequency signal 105, whether the Doppler frequency fd is closer to the parameter fa or fb in FIG. i
i) Calculate the value Eb / No on the horizontal axis of FIG. 4 from the received electric field strength signal 108. iii) The bit error rate is calculated from a point on the curve corresponding to the parameter and the value (fd and Eb / No), and the numerical value is output as the radio wave propagation environment estimation signal 110.

Here, Eb is the signal energy per bit, and No is the noise power density. As described above, the radio wave propagation environment is quantitatively output, and the radio wave propagation environment can be estimated with accuracy that has not been achieved in the past. The bit error rate has two values L1 and L2 (L1> L2).
If the above calculated value is larger than L1, the radio wave propagation environment outputs a bad or bad judgment signal by a non-numeric value such as `` bad '', if it is between L1 and L2 it is `` normal '', and if it is smaller than L2 it is `` good '' You can also.

(Embodiment 2) FIG. 5A is a diagram showing an embodiment of a mobile radio communication system using a mobile radio according to the present invention. The mobile wireless device 501 is the mobile wireless device according to the first embodiment. If the mobile radio device 501 is currently communicating with the base station 502 and the radio wave propagation environment of the communication path is determined to be “good” by the radio wave propagation environment estimation signal, Communication with the station 502 is continued, and when it is determined to be “bad”, switching from the base station 502 to communication with the base station 503 is performed.

However, in this case, as described in the first embodiment, a desired bit error rate is determined in advance as a threshold, and if the radio wave propagation environment estimation signal of the mobile radio is equal to or less than this threshold, If the radio wave propagation environment is “good” and the radio wave propagation environment estimation signal of the mobile radio is equal to or greater than this threshold, the radio wave propagation environment is determined to be “bad”.

By flexibly changing the base station in this manner, it is possible to construct a mobile radio communication system capable of securing a line quality that always exceeds a certain bit error rate.
In this case, the base station 502 and the base station 502 may belong to different service areas or may belong to the same service area.

FIG. 5B shows an example of a temporal change in the received electric field strength of a signal received by a moving terminal. This phenomenon is generally well known. If the moving speed is high, the time in which the radio wave propagation environment is poor is shortened, so the drop time of the received electric field strength is short, but if the moving speed is low, the time in which the radio wave propagation environment is bad. Becomes longer, the drop time of the received electric field strength becomes longer.

Instead of the radio wave propagation environment estimation signal based on the bit error rate shown in FIG. 4, the fall time of the received electric field strength can be calculated and the radio wave propagation environment estimation signal can be generated according to the calculated time. A time equal to or less than a predetermined reception electric field strength is calculated, and if the time is equal to or longer than the predetermined time, the radio wave propagation environment is determined to be “bad”, and if the time is equal to or shorter than the predetermined time, the radio wave propagation environment is determined to be “good”.

(Embodiment 3) FIG. 6 is a diagram showing another embodiment of a mobile radio communication system using a mobile radio according to the present invention. The mobile wireless device 601 is the mobile wireless device according to the first embodiment, and a case in which communication is currently being performed with the base station 602 using a certain digital modulation method will be described.

The mobile radio 601 outputs a bit error rate as a radio wave propagation environment estimation signal of a communication channel and transmits the bit error rate to the base station 602 by radio waves. The base station 602 receives this signal satisfactorily. Assume that the judgment has been made correctly. Further, the mobile communication system according to the present embodiment uses a quadrature phase shift keying (QPSK) as a digital modulation method.
And 16 Quadrature Amplitude Modulation (QAM).

In general, it is known that QPSK is stronger in error resilience and 16QAM is faster in transmission speed in these two modulation systems. This can be seen from FIG.
QPSK has a lower SNR (signal-to-noise) because SK only needs to identify four points that differ only in phase, while 16QAM has to identify 16 points that differ in both phase and amplitude. Ratio), that is, communication with high error resilience is possible.

On the other hand, since the information amount of each system is represented by the number of individual points, 16QAM can transmit a larger amount of information, that is, the transmission speed can be increased.

Now, when the base station 602 determines the radio wave propagation environment estimation signal transmitted from the mobile radio 601 and determines that the radio wave propagation environment is “good”, the bit error rate has a margin, so The modulation scheme is switched to 16QAM, which has a higher transmission rate, at the expense of some. On the other hand, if the radio wave propagation environment is “bad”, the bit error rate needs to be improved, so that the transmission rate is switched to QPSK at a slight cost.

As described above, it is possible to construct a mobile radio communication system that optimizes information quality and transmission speed by appropriately switching the modulation scheme of the base station using the radio wave propagation environment estimation signal from the mobile radio. it can. Although the above description is for the case of two modulation schemes, the present invention can be applied to the case of two or more modulation schemes.

Similarly, the base station and mobile station shown in FIG. 8 show how the information quality and transmission rate can be optimized when the mobile radio communication system of this embodiment uses a spread spectrum system. This will be described with reference to a block diagram of a wireless device.

Now, when the base station 602 determines the radio wave propagation environment estimation signal transmitted from the mobile radio 601 and determines that the radio wave propagation environment is “good”, there is a margin in the received electric field strength, so that the amount of information to be transmitted is large. Can be increased to increase the transmission speed.

That is, 1 in the spread spectrum system.
The number of spreading codes assigned to the user can be increased. As shown in the lower block diagram of FIG. 8, the transmitting section on the base station side transmits a plurality of modulated signals 819 and 826 (for convenience of explanation, the case of two modulated signals is shown in the figure) and spread sections 822 and 830. , And are spread separately using separate spreading codes 824 and 831 to generate spread signals 825 and 832.

Thereafter, these are combined by an adder to become a combined spread signal 833, which is frequency-converted by a high-frequency unit 834 and transmitted from an antenna 836.

On the other hand, on the mobile radio side, the signal 8 is received by the antenna 837 and frequency-converted by the high-frequency section 839.
40 is despread by despreading sections 841 and 845 to become despread signals 842 and 846, respectively, and then demodulated by two demodulating sections 843 and 847 to obtain desired demodulated signals 844 and 8
It will be 48. As described above, the transmission speed can be increased by increasing the number of spreading and despreading codes allocated on the transmitting side and the receiving side.

When the radio wave propagation environment is "bad", on the contrary, the number of allocated spreading codes is reduced to reduce the transmission speed and give priority to information quality. In this case, the number of 801 of the modulated signal on the base station side is reduced in the transmitting section on the base station side as in the upper block diagram shown in FIG. 8 (for convenience of explanation,
The figure shows a case where the modulation signal is reduced to one.)
After being modulated by the modulation unit 802, the spectrum is spread by the spreading unit 804 by one spreading code 806 to become a spread spectrum signal 807, which is frequency-converted by the high frequency unit 808 and transmitted from the antenna 810.

On the other hand, on the mobile radio side, the signal 814 received by the antenna 811 and frequency-converted by the high frequency unit 813 is:
One despreading section 815 performs a despreading process to form a despread signal 816, and then demodulates in a demodulation section 817 to obtain a desired demodulated signal
It becomes 818. As described above, when the radio wave propagation environment is poor, the number of signals is reduced on the transmission side and the reception side, so that the transmission speed cannot be increased, but the information quality can be improved.

When the mobile radio communication system of this embodiment is a mobile radio communication system in which the base station 602 can change the transmission power, the information quality is improved by controlling the transmission power as follows. be able to.

Now, when the base station 602 determines the radio wave propagation environment estimation signal transmitted from the mobile radio 601 and determines that the radio wave propagation environment is “good”, the base station maintains or reduces the transmission power of the base station, When the radio wave propagation environment is “bad”, the transmission power of the base station is increased to improve the reception electric field strength, so that a certain bit error rate can always be secured.

As described in the above three embodiments, the mobile radio device of the present invention calculates the Doppler frequency of a carrier from its moving speed, and also calculates the received electric field strength from its received radio wave. From the physical quantity and data obtained for a certain radio wave propagation environment model similar to the actual radio wave propagation environment, the quality of the radio wave propagation environment of the used communication path is quantitatively estimated.

Using the estimated value obtained in this way on the mobile radio device itself or on the base station side, it is possible to optimize the bit error rate and the transmission rate, thereby achieving good channel quality.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a mobile wireless device according to Embodiment 1 of the present invention.

FIG. 2 is a diagram illustrating a configuration of a moving speed signal generation unit according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a reception field strength signal generation unit according to Embodiment 1 of the present invention.

FIG. 4 is a diagram illustrating a bit error rate versus received electric field strength characteristic in a radio wave propagation environment model according to the first embodiment of the present invention.

FIG. 5 is a diagram showing an example of a wireless communication mode according to Embodiment 2 of the present invention.

FIG. 6 is a diagram showing an example of a wireless communication mode according to the second embodiment of the present invention.

FIG. 7 is a diagram illustrating an arrangement of signal points on an IQ (in-phase and quadrature) plane of QPSK modulation and 16QAM according to the third embodiment of the present invention.

FIG. 8 is a diagram showing an example of a wireless communication mode when changing the number of assigned spreading codes according to Embodiment 3 of the present invention.

FIG. 9 is a diagram showing a configuration of a conventional mobile radio device.

[Explanation of symbols]

 Reference Signs List 101 moving speed 102 moving speed signal generation unit 103 moving speed signal 104 Doppler frequency calculation unit 105 Doppler frequency signal 106 reception signal 107 reception electric field intensity signal generation unit 108 reception electric field intensity signal 109 radio wave propagation environment estimation unit 201 GPS reception antenna 202 reception signal 203 High frequency section 204 Demodulated signal 205 Signal processing circuit 207 Calculation section

Continuation of front page (72) Inventor Masayuki Orihashi 3-10-1, Higashi-Mita, Tama-ku, Kawasaki-shi, Kanagawa Prefecture Inside Matsushita Giken Co., Ltd. (72) Inventor Akihiko Matsuoka 3-1-1, Higashi-Mita, Tama-ku, Kawasaki-shi, Kanagawa No. Matsushita Giken Co., Ltd. F-term (reference) 5K067 AA01 CC10 DD20 DD43 DD44 DD45 DD46 EE02 EE10 FF16 GG08 GG09 GG11 HH21 JJ52 JJ56

Claims (13)

[Claims] 1. A digital mobile radio communication device that moves at a certain moving speed, wherein a moving speed signal generation unit converts the information of the moving speed input into an electric signal to a receiving unit and outputs the electric signal as a moving speed signal. A Doppler frequency calculation unit that calculates a Doppler frequency from the input moving speed signal and a carrier frequency used by the mobile radio communication device, converts the Doppler frequency into an electric signal, and outputs the electric signal as a Doppler frequency signal; A reception field strength signal generation unit that calculates a reception field strength from the received reception signal, converts the received field strength into an electric signal, and outputs the signal as a reception field strength signal; and a radio wave from the input Doppler frequency signal and reception field strength signal. A mobile radio system including a radio wave propagation environment estimator that estimates and acquires propagation environment information, converts it to an electric signal, and outputs it as a radio wave propagation environment estimation signal Communication machine. 2. The mobile wireless communication device according to claim 1, wherein the moving speed is a moving speed of a vehicle. 3. The mobile radio communication device according to claim 1, wherein said moving speed is a moving speed of an aircraft. 4. The mobile radio communication device according to claim 1, wherein the mobile speed is calculated from position information of the mobile radio communication device obtained by receiving a GPS transmission signal. Machine. 5. The mobile radio communication device according to claim 1, wherein the level of the input reception signal is detected via a high-frequency unit of the mobile radio device.
A mobile radio communication device, wherein the received electric field strength signal is generated from an output signal of I (Received Signal Strength Indicator). 6. The mobile radio communication device according to claim 1, wherein a bit error rate and a received electric field strength are obtained by using a Doppler frequency as a parameter, obtained in a predetermined radio propagation environment model. A mobile radio communication device for outputting the radio wave propagation environment estimation signal based on characteristics. 7. The mobile radio communication device according to claim 1, wherein when the radio wave propagation environment is determined to be good based on the radio wave propagation environment estimation signal, the communication partner and the communication partner are set. A mobile wireless communication device that changes a communication partner or a communication method when the radio wave propagation environment is determined to be bad without changing the method. 8. The mobile radio communication device according to claim 7, wherein when the mobile radio communication device is in a service area of a zone configuration, the communication partner is in the same service area. Wireless communicator. 9. The mobile radio communication device according to claim 7, wherein when the mobile radio communication device is in a service area of a zone configuration, the communication partner is in a different service area. Wireless communicator. 10. The apparatus according to claim 1, further comprising a function of transmitting the information on the radio wave propagation environment to a communication partner.
A mobile radio communication system comprising the mobile radio communication device according to any one of the above. 11. The mobile radio communication system according to claim 10, further comprising a function of acquiring information on a radio wave propagation environment of a radio wave transmitted by the radio communication system from a communication partner, and changing a modulation method based on the information. A mobile radio communication system characterized by the above-mentioned. 12. The mobile radio communication system according to claim 10, wherein when the mobile radio communication device uses a spread spectrum communication system, the mobile radio communication device transmits information of a radio wave propagation environment of a radio wave transmitted by the mobile radio communication device. A mobile radio communication system which acquires from a partner and changes the number of spread codes assigned to the partner. 13. The mobile radio communication system according to claim 11, wherein a transmission power of a radio wave transmitted by the mobile radio communication system is changed.