Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
2000-08-08
2004-08-31
Maung, Nay (Department: 2684)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
65
Reexamination Certificate
active
06785545
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a digital-mobile-wireless-communications apparatus and the system using the same.
BACKGROUND OF THE INVENTION
In a zone-configured digital-mobile-wireless-phone system, a radio-wave-transmission environment changes every moment caused by a multipath fading. To deal with this problem, a transmission quality has been maintained by changing a zone or a transmission channel as needed while a telephone call is in progress. As the changes of the radio-wave-transmission environment of transmission paths highly depend on the velocity of a mobile phone, the velocity is calculated prior to a changeover, then the changeover is done based on the calculated velocity. For example, in Laid-open Japanese patent H998465, signals transmitted from a plurality of Global Positioning System (GPS) satellites are received by GPS-receiving antenna
901
of mobile phone
900
shown in FIG.
9
. The received signal is led into radio-frequency-receiving circuit
902
to demodulate, then fed into GPS-signal-processing circuit
903
. Circuit
903
decodes information on GPS-satellite's orbital position and time information from the demodulated signal to output them to data-processing circuit
904
. Circuit
904
calculates the current position of mobile phone
900
accurately, and the result is entered to velocity-detecting circuit
905
. Circuit
905
calculates the velocity of mobile phone
900
based on the current-position information obtained at intervals over time, and outputs the calculated velocity to control circuit
909
. Control circuit
909
sends a control signal, which is determined according to the magnitude of the velocity, to transmitting and receiving circuit
907
, and changes a time period that monitors a transmission channel adjacent to the in-use channel (this time period is hereafter referred to as a monitoring period). If a channel whose radio-wave-transmission environment is better than that of the in-use channel is detected, control circuit
909
changes the transmission channel into the detected channel.
In such a conventional way, however, the accurately calculated velocity of a mobile phone has not been exploited fully. This velocity has been previously used for the purpose of changing the monitoring period of the adjacent channel. Specifically, because the detected velocity is not directly related to a physical measure representing a radio-wave-transmission environment of transmission paths, evaluating information on the radio-wave-transmission environment could not be obtained accurately. For example, the calculated velocity of a mobile phone is not related to a degradation of a bit-error-rate (BER), which is caused by a Doppler shift (Doppler frequency) of carrier frequencies for the mobile phone moving at a high speed. Although the way mentioned above is effective at finding a transmission channel having a good-conditioned transmission environment, another problem to be improved lies in the conventional way: the calculated velocity of a mobile phone is not related to a receiving-electric-field intensity of the mobile phone. That is, even if the mobile phone is moving at a high speed under the condition with a sufficient receiving-electric-field intensity, in other words, the condition with a favorable radio-wave-transmission environment, a changeover of the monitoring period is unnecessarily performed as is the case that the radio-wave-transmission environment is in a poor condition. Consequently, the transmission is often subjected to a momentary interruption.
SUMMARY OF THE INVENTION
By making efficient use of information on the velocity and the receiving-electric-field intensity of a mobile phone, it is possible to evaluate the radio-wave-transmission environment with much accuracy. The present invention thus enables to provide a digital-mobile-wireless-communications apparatus with a capability of getting a higher transmission quality.
The communications apparatus of the present invention operates at a receiver as follows:
1) Receiving velocity information for the communications apparatus, a velocity-signal generator converts the velocity information into an electric signal (hereafter referred to as a velocity signal.)
2) Receiving the velocity signal, a Doppler-frequency calculator calculates a Doppler frequency of a radio-wave corresponding to the velocity signal, then converts the Doppler frequency into an electric signal (hereafter referred to as a Doppler-frequency signal.)
3) Detecting a receiving-electric-field intensity at the input section of the communications apparatus, a receiving-electric-field-intensity-signal generator outputs the receiving-electric-field intensity as an electric signal (hereafter referred to as a receiving-electric-field-intensity signal.)
4) Receiving the two signals described above, i.e., the Doppler-frequency signal and the receiving-electric-field-intensity signal as input signals, transmission-environment-inference means evaluates the radio-wave-transmission environment of the communications apparatus based on the entered two signals, then outputs the result as an electric signal (hereafter referred to as a transmission-environment-inference signal.)
For a mobile-wireless-communications apparatus used in a digital communications system, it is generally known that the higher the velocity, the greater the Doppler shift affecting carrier frequencies. This degrades a bit-error-rate (BER), that is, it degrades the transmission quality. The relation between a shift of the carrier frequencies and the influence on the BER by the shift depends on which digital-modulation scheme is used, and the relation is often explained theoretically or experimentally under a radio-wave-transmission environment chosen as a model. Therefore, if the Doppler frequency under a modulation scheme can be calculated, the “most probable” BER corresponding to the Doppler frequency can be also determined by applying data obtained from a radio-wave-transmission environment modeled after a real-world situation. In a like manner, the relation between the receiving-electric-field intensity and its influence on the BER also depends on which digital-modulation scheme is used, and the relation is often explained theoretically or experimentally under a radio-wave-transmission environment chosen as a model. Therefore, if the receiving-electric-field intensity under a modulation scheme can be calculated, the “most probable” BER corresponding to the receiving-electric-field intensity can be also determined by applying data obtained from a radio-wave-transmission environment modeled after a real-world situation. Here, the “most probable” has an implication that the modeled-radio-wave-transmission environment from which the data is obtained is not always fit to the actual radio-wave-transmission environment, in the both cases of the evaluations of the Doppler frequency and the receiving-electric-field intensity.
Therefore, calculating two physical measures, i.e., the Doppler frequency and the receiving-electric-field intensity, the communications apparatus of the present invention can estimate the radio-wave-transmission environment for transmission paths more accurate than before.
Some possible applications for the present invention are described below.
a) The velocity information fed into the velocity-signal generator may include information on a velocity itself of a vehicle or an airplane, or on the satellite position and time information transmitted from GPS satellites.
b) The receiving-electric-field-intensity-signal generator can generate a receiving-electric-field-intensity signal based on an output signal from a Received Signal Strength Indicator (RSSI). The RSSI is arranged to acquire d. c. voltage being proportional to a receiving-electric-field intensity of a received radio wave.
c) Transmission-environment-inference means can be arranged so as to output a transmission-environment-inference signal according to data obtained from a radio-wave-transmission environment model similar to the actual situation unde
Matsuoka Akihiko
Murakami Yutaka
Orihashi Masayuki
Takabayashi Shinichiro
Maung Nay
Nguyen Tu
RatnerPrestia
LandOfFree
Digital mobile wireless communications apparatus and the... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Digital mobile wireless communications apparatus and the..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Digital mobile wireless communications apparatus and the... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3319606