Abstract:
A CDMA mobile telephone allowing the drive mode to be automatically set and canceled without increasing the amount of hardware is disclosed. A frequency offset for each of N fingers is detected from despread data which are obtained by despreading received spectrum-spread data of M branches. Based on the detected N frequency offsets, it is determined whether the mobile telephone is moving at speeds higher than a predetermined speed. An operation mode of the mobile telephone switches between a drive mode and a normal mode depending on whether the mobile telephone is moving at speeds higher than the predetermined speed.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a CDMA (Code Division Multiple Access) mobile communications system, and in particular to a CDMA mobile telephone having a function of determining whether the CDMA mobile telephone is moving. 
   2. Description of the Related Art 
   There is a growing awareness of dangers that a driver takes a mobile telephone while driving a car or is surprised with a sudden beep. To avoid such a dangerous situation, there have been proposed several mobile telephones having an automatic drive-mode setting function. 
   In Japanese Patent Application Unexamined Publication No. 11-234756, for example, a mobile telephone Is provided with a received signal level detector and a fading decision section, which are used to detect a period of fading occurrence. When the detected fading period is smaller than a predetermined time period, a controller determines that the mobile telephone is on the move and sets the mobile telephone to an automatic answering mode in which, when an incoming call occurs, a response message is automatically sent to the caller without starting a ringer. 
   In the field of CDMA mobile communications, there has been disclosed a velocity detecting method using a Doppler frequency calculated based on variations in received signal level or widened frequency band due to fading (see Japanese Patent Application Unexamined Publication No. 11-98071). To calculate the Doppler frequency, a CDMA mobile terminal is provided with a circuit for counting the number of times a received signal level has changed across an average level or a circuit for measuring the amount of widened frequency band. 
   However, a conventional mobile station needs an extra circuit for detecting fading occurrence, variations in received signal level, or the amount of widened frequency band, resulting in increased amount of hardware. 
   SUMMARY OF THE INVENTION 
   An object of the present Invention is to provide a CDMA mobile telephone allowing the drive mode to be automatically set and canceled without Increasing the amount of hardware. 
   According to the present invention, a mobile telephone apparatus operable in a CDMA communications system includes: a despreading circuit for despreading received spectrum-spread data of a plurality of branches to produce despread data each corresponding a plurality of fingers; a frequency offset detector for detecting a frequency off set for each of the fingers from the despread data; a movement determiner for determining whether the mobile telephone is moving at speeds higher than a predetermined speed, based on frequency offsets received from the frequency offset detector: and a mode controller for switching an operation mode between a drive mode and a normal mode depending on whether the mobile telephone apparatus is moving at speeds higher than the predetermined speed. 
   The movement determiner may include a Doppler frequency calculator for calculating Doppler frequencies for respective ones of the branches by combining the frequency offsets for respective ones of the fingers; a first determiner for determining whether there is a pair of Doppler frequencies satisfying a first condition such that the Doppler frequencies are of opposite sign; a second determiner for determining whether the Doppler frequencies satisfy a second condition such that an absolute value of each of the Doppler frequencies is not smaller than a first reference value; and a determination controller for determining that the mobile telephone apparatus is moving at speeds higher than the predetermined speed when a pair of Doppler frequencies satisfying the first and second conditions exists. 
   The determination controller may output a first interrupt signal to the mode controller when the pair of Doppler frequencies satisfying the first and second conditions exist and outputs a second interrupt signal to the mode controller when a pair of Doppler frequencies satisfying the first and second conditions does not exist, wherein the mode controller sets the mobile telephone apparatus to the drive mode when receiving the first interrupt signal and sets the mobile telephone apparatus to the normal mode when receiving the second interrupt signal. 
   The movement determiner may include: a branch frequency offset calculator for calculating branch frequency offsets for respective ones of the branches by combining the frequency offsets for respective ones of the fingers: a first determiner for determining whether there is a branch frequency offset satisfying a first condition such that an absolute value of the branch frequency offset is greater than a second reference value; a second determiner for determining whether there is at least one branch frequency offset satisfying a second condition such that an absolute value of the branch frequency offset is not greater than a maximum correction threshold of AFC (automatic frequency control) operation performed in the mobile telephone apparatus; and a determination controller for determining that the mobile telephone apparatus is moving at speeds higher than the predetermined speed when there are both the branch frequency offset satisfying the first condition and the at least one branch frequency offset satisfying the second condition. 
   The determination controller may output a first interrupt signal to the mode controller when there are both the branch frequency offset satisfying the first condition and the at least one branch frequency offset satisfying the second condition, and outputs a second interrupt signal to the mode controller when there is neither the branch frequency offset satisfying the first condition nor the at least one branch frequency offset satisfying the second condition, wherein the mode controller sets the mobile telephone apparatus to the drive mode when receiving the first interrupt signal and sets the mobile telephone apparatus to the normal mode when receiving the second interrupt signal. 
   The mobile telephone apparatus may further include a display controller for controlling a display device when the mobile telephone apparatus is moving at speeds higher than the predetermined speed such that a message Indicating that the mobile telephone apparatus is moving at speeds higher than the predetermined speed is displayed on the display device. 
   The mobile telephone apparatus may further include: a voice message generator for generating a predetermined voice message when an incoming call occurs during the drive mode; and a communication controller for transmitting the predetermined voice message to a caller. 
   The mobile telephone apparatus may further include: a communication controller for transmitting a network system a drive-mode message indicating that the mobile telephone apparatus is moving at speeds higher than the predetermined speed, when the operation mode has been changed to the drive mode, wherein the network system has a voice message system in which, when an incoming call occurs after having received the drive-mode message from the mobile telephone apparatus, the voice message system transmits a predetermined voice message to a caller. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram showing a CDMA mobile telephone according to a first embodiment of the present invention; 
       FIG. 2  is a flow chart showing a movement decision method according to the first embodiment of the present invention; 
       FIG. 3  is a flow chart showing a drive-mode switch operation in the first embodiment; 
       FIG. 4  is a schematic diagram showing an example of a CDMA cellular system for explanation of a fundamental operation of the present invention; 
       FIG. 5  is a block diagram showing a CDMA mobile telephone according to a second embodiment of the present invention; 
       FIG. 6  is a flow chart showing a movement decision method according to the second embodiment of the present invention; and 
       FIG. 7  is a flow chart showing a drive-mode switch operation in the second embodiment. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIG. 1 , a CDMA mobile telephone includes a heterodyne radio transceiver. A radio-frequency (RF) signal received at an antenna  1  is amplified by a low-noise amplifier  2  and then is down-converted from RF to intermediate frequency (IF) by a down converter  3  using a first local signal LO 1 . The IF received signal is amplified by a variable-gain amplifier  4  depending on an automatic gain control signal so that the input level at an analog-to-digital converter  6  is kept constant. The IF received signal is output to a quadrature demodulator (DEM)  5 , which uses a second local signal LO 2  to demodulate the IF received signal to produce an analog baseband signal. The analog baseband signal is converted by the analog-to-digital converter  6  Into a digital baseband signal. 
   The first and second local signals LO 1  and LO 2  are generated by a phase-locked loop circuit  7  receiving a reference oscillation signal from a reference oscillator (here, TCXO)  8 . The reference oscillator  8  is a voltage-controlled oscillator having a control terminal connected to the output of an accumulator  9  (which will be described later). 
   The digital baseband signal is output from the analog-to-digital converter  6  to both a finger circuit  10  and a delay-profile searcher  12 . The finger circuit  10  is a RAKE-finger circuit composed of a predetermined number of fingers each including correlators. Each of the fingers in the finger circuit  10  produces despread data from the digital baseband signal based on a frame timing signal received from a timing generator  14 . The respective despread data of the finger are output to a frequency offset estimator  11  and a RAKE circuit  15 . 
   The delay-profile searcher  12  produces delay-profile data and an amount of frame-timing correction from the digital baseband signal based on a frame timing signal received from the timing generator  14 . The frame-timing correction amount is output to the timing generator  14 . The timing generator  14  generates an ideal frame timing signal based on the reference oscillation signal received from the reference oscillator  8  and then produces the frame timing signal by adding the frame-timing correction amount received from the delay-profile searcher  12  to the ideal frame timing signal. The frame timing signal is supplied to the finger circuit  10  and the delay-profile searcher  12 . Then, the-profile searcher  12  produces an updated amount of frame-timing correction based on the frame timing signal received from the timing generator  14  and outputs the updated frame-timing correction amount to the timing generator  14 . In this manner, the timing generator  14  can supply a precise frame timing signal to the finger circuit  10  and the delay-profile searcher  12  at all times. 
   The frequency offset estimator  11  calculates a frequency offset for each finger by using known data such as pilot data included in the despread data received from the finger circuit  10 . The calculated frequency offset for each finger is output to the RAKE circuit  15  and a high-speed-movement decision section  16 . Further, the frequency offset estimator  11  combines the frequency offsets that are weighted taking into account an electric field level and signal-to-noise ratio of a received signal to produce a combined frequency offset, which is output to the accumulator  9 . The accumulator  9  adds the combined frequency offset to a current frequency offset to output a frequency control voltage to the reference oscillator  8 . In this way, the AFC (Automatic Frequency Control) operation is performed. 
   The high-speed-movement decision section  16  uses the calculated frequency offset for each finger to determine whether the mobile telephone is moving at high speeds. The high-speed-movement decision section  16  generates an interrupt signal to a micro processor (CPU)  13  so as to notify it whether the mobile telephone is moving at high speeds The details will be described later by referring to  FIG. 2 . 
   The RAKE circuit  15  weights the despread data received from the finger circuit  10  taking into account an electric field level and signal-to-noise ratio of a received signal and combines the weighted despread data to produce demodulated data. The demodulated data is output to a speech DSP (digital signal processor)  17 , which performs coding/decoding according to a predetermined codec algorithm such as G 729 . The decoded data is output to a codec  18 , which produces an analog voice signal from the decoded data to drive a speaker  19 . 
   On the other hand, an analog voice signal inputted by a microphone  20  is converted to a digital voice signal by the codec  18  and then the digital voice signal is encoded by the speech codec  17 . The encoded data is output to a channel codec  23 , which performs error-correcting coding and channel control of the encoded data to produce transmission data. The transmission data is converted by a digital-to-analog converter  24  to an analog transmission baseband signal. A modulator  25  modulates the second local oscillation signal LO 2  according to the analog transmission baseband signal to produce an IF-band transmission signal. After the IF-band transmission signal is amplified by a variable-gain amplifier  26 , it is up-converted by an up converter  27  using the first local oscillation signal LO 1  into transmission radio frequency. The transmission RF signal is amplified by a power amplifier  28  before transmitted through the antenna  1 . 
   The mobile telephone is further provided with a liquid crystal display (LCD) device  22 , which is driven by a LCD driver  21  under control of the CPU  13 . 
   Referring to  FIG. 2 , the high-speed-movement decision section  16  inputs N frequency offsets Δf 1 –Δf N  each corresponding to N fingers from the frequency offset estimator  11  (step S 101 ). Thereafter, the high-speed-movement decision section  16  calculates Doppler frequencies Df 1 –Df M  for respective ones of the receiving branches by combining the frequency offsets Δf 1 –Δf N  which are weighted for respective ones of receiving branches taking into account an electric field level, a signal-to-noise ratio and the like of a received signal (step S 102 ). 
   Subsequently, it is determined whether there is a pair of Doppler frequencies (Df i , Df j ) satisfying Df i ×Df j &lt;0 (step S 103 ). In other words, the high-speed-movement decision section  16  searches the Doppler frequencies Df 1 –Df M  for a pair of Doppler frequencies (Df 1 , Df j ) satisfying that Df i  and Df j  are of opposite sign. 
   When such a pair of Doppler frequencies (Df i , Df j ) is found (YES at step S 103 ), it is further determined whether the absolute values |Df 1 | and |Df 1 | are equal to or greater than a predetermined reference set value f REF1  (step S 104 ). If the absolute values |Df 1 | and |Df j | are not smaller than the predetermined reference set value f REF1  (YES at step S 104 ), then the high-speed-movement decision section  16  generates an Interrupt signal IS H  to the CPU  13  to indicate that the mobile telephone is on the move (step S 105 ). 
   If there is no pair of Doppler frequencies (Df i , Df j ) satisfying Df 1 ×Df j &lt;0 (NO at step S 103 ) or if at least one of the absolute values |Df 1 | and |Df j | is smaller than the predetermined reference set value f REF1  (NO at step S 104 ), then the high-speed-movement decision section  16  generates an interrupt signal IS L  to the CPU  13  to Indicate that the mobile telephone stops or does not move at high speeds (step S 106 ). 
   Referring to  FIG. 3 , the CPU  13  in standby status determines whether an interrupt occurs (step S 201 ). When the interrupt signal IS H  is generated (YES at step S 201 ), the CPU  13  controls the LCD driver  21  so that a message “on high-speed move” is displayed on the LCD  22  (step S 202 ). Such a message makes the driver aware of setting the mobile telephone to the drive mode in which the ringer is not started but an automatic answering function when an incoming call occurs. 
   The CPU  13  determines whether an incoming call occurs on the move (step S 203 ). If an incoming call occurs on the move (YES at step S 203 ), the CPU  13  does not make a beep but reads preset voice guidance data from a memory (not shown) and instructs the speech DSP  17  to transmit it to the transmission system (step S 204 ). Accordingly, the preset voice guidance message, for example, “now driving a car”, is automatically transmitted to the caller. The CPU  13  sets the mobile telephone to a standby mode by repeatedly performing the steps S 203 –S 204  until the interrupt signal IS L  is generated (NO at step S 205 ). 
   When the Interrupt signal IS L  is generated (YES at step S 205 ), the CPU  13  stops displaying “On high speed move” on the LCD  22  and cancels the preset voice guidance transmission (step S 206 ). In other words, when the mobile telephone does not move at high speeds, the drive mode is automatically canceled. In this manner, the drive mode is automatically set and reset depending on the interrupt signal generated by the high-speed-movement decision section  16  without driver&#39;s attention to the mobile telephone. The high-speed-movement decision section  16  is allowed to be turn on and off depending on a user&#39;s instruction through a keypad (not shown). 
   Referring to  FIG. 4 , it is assumed for simplicity that three base transceiver stations  301 – 303  forms service areas SA 1 –SA 3  which are in part overlapped with each other and further that a mobile station MS is moving toward the base transceiver station  303  as indicated by an arrow at a constant velocity 100 Km/h while receiving three branches corresponding to the base transceiver stations  301 – 303 . 
   Assuming that the carrier frequency is 2 GHz, the Doppler frequency Df 1  for the base transceiver station  301  is about −185 Hz, Df 3  for the base transceiver station  303  Is about +185 Hz, and Df 2  for the base transceiver station  302  is almost 0 Hz. In this case, when the predetermined reference set value f REF1  is previously set to 100 Hz, the first condition (Df 1 ×Df 3 &lt;0) and the second condition (|Df 1 |=|Df 3 |=185 is greater than f REF1  =100) are both satisfied. Accordingly, the high-speed-movement decision section  16  generates the interrupt signal IS H  to the CPU  13  and thereby the message indicating that the mobile telephone is on the move is displayed on the LCD  22 . Such a message makes the driver aware of setting the mobile telephone to the drive mode. Therefore, when an incoming call occurs on driving, the automatic answering function is automatically set to send the preset voice guidance to the caller. 
   When the velocity of the mobile telephone is reduced to some extent without changing in direction, |Df 1 | and |Df 3 | become smaller than F REF1 =100 and therefore the interrupt signal IS L  is generated (YES at step S 205 ). At this time, the message indicating that the mobile telephone is on the move disappears on the LCD  22  and the automatic answering function becomes inactive. That is, the drive mode is automatically canceled. 
   The high-speed-movement decision section  16  may be Implemented with software. In other words, the above-described high-speed-movement decision can be realized by only adding a high-speed-movement decision program to the existing control program to run on the CPU  13 . Accordingly, the drive mode can be automatically switched on and off without increasing the amount of hardware. 
   Referring to  FIG. 5 , a second embodiment of the mobile telephone has a function of notifying the network that the mobile telephone is moving at high speeds. Such a notification is performed by the CPU  13  controlling a transmission system  30  including the channel codec  23 . When an incoming call occurs after receiving such a notification from the mobile telephone, the network does not call the mobile telephone but sends a preset voice message indicating that the destination terminal is moving at high speeds to the caller. In  FIG. 5 , circuit blocks similar to those previously described with reference to  FIG. 1  are denoted by the same reference numerals and the descriptions are omitted. Hereafter, the high-speed-movement decision method will be described in detail. 
   Referring to  FIG. 6 , the high-speed-movement decision section  16  inputs N frequency offsets Δf 1 –Δf N  each corresponding to N fingers from the frequency offset estimator  11  (step S 401 ). Thereafter, the high-speed-movement decision section  16  calculates branch frequency offsets ΔBf 1 –ΔBf M  for respective ones of the receiving branches by combining the frequency offsets Δf 1 –Δf N  which are weighted for respective ones of receiving branches taking into account an electric field level, a signal-to-noise ratio and the like of a received signal (step S 402 ). 
   Subsequently, it is determined whether there is a branch frequency offset Bf 1  satisfying that the absolute value of ΔBf i  is greater than a predetermined reference set value f REF2 , that is, |ΔBf i |&gt;f REF2  (step S 403 ). 
   When such a branch frequency offset ΔBf 1  is found (YES at step S 403 ). It is further determined whether there is at least one branch frequency offset ΔBf j  satisfying that the absolute value of ΔBf j  is equal to or smaller than the maximum AFC correction threshold L AFC , that is, |ΔBf 1 | L AFC  (step S 404 ). If at least one branch frequency offset ΔBf j  satisfying the condition is found (YES at step S 404 ), then the high-speed-movement decision section  16  generates an interrupt signal IS H  to the CPU  13  to indicate that the mobile telephone is on the move (step S 405 ). 
   If no branch frequency offset Bf i  satisfying |ΔBf i |&gt;f REF2  is found (NO at step S 403 ) or if no branch frequency offset ΔBf j  satisfying |ΔBf i | L AFC  found (NO at step S 404 ), then the high-speed-movement decision section  16  generates an interrupt signal IS L  to the CPU  13  to Indicate that the mobile telephone stops or-does not move at high speeds (step S 406 ). 
   Referring to  FIG. 7 , the CPU  13  in standby status determines whether an interrupt occurs (step S 501 ). When the high-speed-movement interrupt signal IS H  is generated (YES at step S 501 ), the CPU  13  controls the transmission system  30  such that a message indicating that the mobile telephone is moving at high speeds is transmitted to the network (step S 502 ). Such a message may be displayed on the LCD  22  to make the driver aware of setting the mobile telephone to the drive mode. Thereafter, the CPU  13  returns to the standby status (step S 503 ) and sets the mobile telephone to the standby mode until the not-movement interrupt signal IS L  Is generated (NO at step S 504 ). 
   When the interrupt signal IS L  is generated (YES at step S 504 ), the CPU  13  controls the transmission system  30  such that a message indicating that the mobile telephone does not move at high speeds is transmitted to the network (step S 505 ). Such a message may be displayed on the LCD  22  to make the driver aware of resetting the drive mode Thereafter, control goes back to the step S 501 . 
   In the case where an incoming call to the mobile telephone occurs after receiving the high-speed-movement notification from the mobile telephone, the network starts a voice mail system to send the caller a preset voice message indicating that the destination terminal is moving at high speeds. When receiving the not-movement notification from the mobile telephone, the network resets the voice mail system and returns to the normal call processing operation. Since the automatic answering function is provided in the network side In the second embodiment, the amount of hardware in the mobile telephone is further reduced. 
   In this manner, the drive mode is automatically set and canceled depending on an interrupt signal generated by the high-speed-movement decision section  16  without driver&#39;s attention to the mobile telephone. The high-speed-movement decision section  16  is allowed to be turn on and off depending on a user&#39;s instruction through a keypad (not shown). 
   In the above-described case as shown in  FIG. 4 , it is assumed that the base transceiver station  303  is selected as a main branch and the AFC operation is performed by weighting the main branch at a rate of approximately 100%. In this case, the branch frequency offset ΔBf 3  for the base transceiver station  303  is almost 0 Hz and the branch frequency offset ΔBf 1  for the base transceiver station  301  is almost −370 Hz. Therefore, in the case of the predetermined reference set value f REF2  being set to 300 Hz, |ΔBf 1 &gt;f REF2  (YES at step S 403 ) and |ΔBf 3 |&lt;L AFC  (YES at step S 404 ) Since both conditions are satisfied, the high-speed-movement decision section  16  generates an interrupt signal IS H  to the CPU  13  to indicate that the mobile telephone is on the move (step S 405 ). 
   When the high-speed-movement interrupt signal IS H  is generated, the CPU  13  set the mobile telephone to the drive mode and the notification indicating that the mobile telephone is moving at high speeds is transmitted to the network. In this status, when an incoming call occurs, the network sends a voice message having the same contents to the caller. 
   On the other hand, when the velocity of the mobile telephone is reduced to some extent without changing in direction, |ΔBf 1 | become smaller than f REF2 =300 and therefore the interrupt signal IS L  is generated, resulting in the drive mode being automatically canceled. 
   As described above, when the user is driving a car and moving at high speeds, the mobile telephone is automatically set to the drive mode. When the user stops the car or reduces speed to below a predetermined velocity, the mobile telephone is automatically reset to the normal operation mode. Since a preset message is displayed on the LCD, the user is aware of setting the mobile telephone to the drive mode. Further, when an incoming call occurs on driving, a preset voice message is automatically sent from the network to the caller. Therefore, the caller is aware of the destination telephone moving at high speeds. 
   The high-speed-movement decision method as shown in  FIG. 2  may be combined with the operation of the CPU  13  as shown in  FIG. 7 . Contrarily, the high-speed-movement decision method as shown in  FIG. 6  may be combined with the operation of the CPU  13  as shown in  FIG. 3 .