Pulse or digital communications – Pulse position – frequency – or spacing modulation
Reexamination Certificate
1998-07-14
2001-07-10
Chin, Stephen (Department: 2634)
Pulse or digital communications
Pulse position, frequency, or spacing modulation
C375S302000, C332S119000, C370S529000
Reexamination Certificate
active
06259731
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to a system and method for radio-communication, and in particular, to a system and method for raido-communication using frequency modulated signals.
BACKGROUND OF THE INVENTION
Over the last several years, radio-communication technology, and in particular cellular phone technology, has become a fixture in the everyday lives of many Americans. No longer tied to the fixed public switched telephone network, people have grown accustomed to the great flexibility and freedom that this “wireless” technology allows.
However, there still remains the annoying necessity of holding the cellular phone unit in place during use. As a consequence, the user either has to keep at least one hand holding the unit or has to crook his or her neck in an attempt to support the unit between the ear and the shoulder. As cellular phones become smaller and smaller, the later option becomes less and less viable.
To eliminate this problem, it has been suggested that cellular phones be equipped with circuitry to allow the phone to be used in combination with a headset which the cellular phone user can wear. Having one or more headphones and a microphone, as well as a series of control switches to turn the headset on and off, these headset/phone systems offer a tantalizing “hands free” alternative to those cellular phone users who seem to have their cellular phones “glued” to their ears.
To offer such an alternative, the headset/phone system must be able to establish a communications link between the headset and the phone. The link must support full duplex transmission of control information and audio information, with the control information preferably in digital form and the audio information presently preferably in analog form.
At the present time, at least one headset/phone system has been developed which provides duplex transmission of control and audio information. The system employs bursts or pulses of an RF carrier to convey control and audio information. Specifically, the time between pulses is used to convey both the control and audio information.
This system has a number of drawbacks. The signal to noise ratio may be poor, because of a narrow range of timing values employed between pulses. Moreover, all headset/phone pairs of this system operate on the same frequency, the manufacturer having attempted to use time shifting to separate the pulse streams of different headset/phone pairs. As a consequence, if two or more headset/mobile phone pairs of this system are used in close proximity over a prolonged period of time, problems may eventually occur as the time bases of different units “drift” into an interference condition.
SUMMARY OF THE INVENTION
According to an aspect of the present invention, a method of communicating control and audio information between at least two radio-communication devices is provided. The method has the steps of generating a first control message having a plurality of message symbols to be transmitted from a first radio-communications device to a second radio-communications device, and generating a first audio message to be transmitted from the first radio-communications device to the second radio-communications device. The first audio message is sampled to obtain a first plurality of audio samples, each with an instantaneous signal value, and a first radio frequency signal which varies in frequency from a first predetermined radio frequency dependent on the instantaneous signal values of the first plurality of samples is generated. The first radio frequency signal is formatted into a first pulsed radio frequency signal, each pulse having a time duration representative of one of the plurality of message symbols of the first control message, which is transmitted from the first radio-communication device to the second radio-communication device.
The step of generating a first audio message may include the step of receiving the first audio message from a cellular base station.
The first pulsed radio frequency signal may be received at the second radio-communication device, and the time duration of each pulse of the first pulsed radio frequency signal and the variation in frequency of each pulse of the first pulsed radio-frequency signal from the first predetermined radio frequency may be determined. The first control message may then be regenerated from the determined time durations, and the first audio message may be regenerated from the determined frequency variations.
The method may also include the step of transmitting the regenerated first audio message from the second radio-communications device to a cellular base station.
The method may also include the step of driving a speaker using the regenerated first audio signal.
Where the first pulsed radio frequency signal has a predetermined time between pulses, the method may include the steps of generating a second control message including a plurality of message symbols to be transmitted from the second radio-communications device to the first radio-communications device, and generating a second audio message to be transmitted from the second radio-communications device to the first radio-communications device. The second audio message is sampled to obtain a second plurality of audio samples, each with an instantaneous signal value. A second radio frequency signal is generated which varies in frequency from the first predetermined radio frequency dependent on the instantaneous signal values of the second plurality of audio samples. The second radio frequency signal is formatted into a second pulsed radio frequency signal, each pulse having a time duration representative of one of the plurality of message symbols of the second control message. The pulses of the second pulsed radio frequency signal from the second radio-communication device to the first communications device are transmitted during the predetermined time between the pulses of the first pulsed radio frequency signal.
The method may also include the steps of generating a second control message having a plurality of message symbols to be transmitted from a third radio-communications device to a fourth radio-communications device. A second audio message may also be generated to be transmitted from the third radio-communications device to the fourth radio-communications device. The second audio message may be sampled to obtain a second plurality of audio samples, each with an instantaneous signal value. A second radio frequency signal may be generated which varies in frequency from a second predetermined radio frequency dependent on the instantaneous signal values of the second plurality of samples, the second predetermined radio frequency being different from the first predetermined radio frequency. The second radio frequency signal is formatted into a second pulsed radio frequency signal, each pulse having a time duration representative of one of the plurality of message symbols of the second control message, which is transmitted from the third radio-communication device to the fourth communication device.
Also, the method may include tuning in a first radio frequency from a plurality of radio frequencies, and determining the level of noise or interference associated with the first radio frequency. The first radio frequency may be designated as the first predetermined radio frequency if the determined level is below a predetermined threshold level.
Another radio frequency may be tuned in from the plurality of radio frequencies other than the first radio frequency if the level of noise associated with the first radio frequency is above the predetermined threshold level, and the level of noise or interference associated with the other radio frequency may be determined. The other radio frequency may be designated as the first predetermined radio frequency if the determined level associated with the other radio frequency is below the predetermined threshold level.
A second radio frequency may be tuned in from the plurality of radio frequencies other than the first radio frequency, and the level of noise or
Dent Paul W.
Hayes, Jr. John J.
Chin Stephen
Ericsson Inc.
Fan Chieh M.
Wood Phillips VanSanten Clark & Mortimer
LandOfFree
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