Communication method and apparatus
AssigneeOki Electric Industry Co., Ltd.
InventorsYutaka Kaneko, Masaharu Hamaguchi
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Abstract
In a wireless communication system, the communicating stations reduce their transmitting power level when they detect interference exceeding a certain level. Interference is detected by down-shifting the received signal to place the desired signal in the baseband, then sampling the down-shifted signal, first at a sampling frequency high enough to catch the interference, then at a lower sampling frequency that excludes the interference. This system is useful for vehicle-to-vehicle communication in an environment in which vehicle-to-roadside communication may also be present at various nearby frequencies, because it does not require exact knowledge of the interfering frequencies and allows communication to continue even when interference is present.
Claims19
A method of communicating among a plurality of stations in a wireless environment in which a first signal having a first center frequency is present in a first frequency band, the plurality of stations communicating in a second frequency band having a second center frequency, the first center frequency and the second center frequency being mutually spaced apart by a separation frequency, the method comprising a transmitting method and a receiving method,
- the transmitting method including:
- generating a transmit packet signal according to transmit data and a control signal;
- modulating the transmit packet signal onto a carrier signal having the second center frequency to generate a modulated signal;
- controlling a transmitting power level of the modulated signal;
- and
- transmitting the modulated signal at the controlled transmitting power level;
- and
- the receiving method including:
- receiving an incoming signal including the first signal and a second signal having the second center frequency, thereby obtaining a received signal;
- generating a third signal by frequency down-conversion of the received signal so that the second signal is converted to a baseband signal;
- sampling the third signal at a first sampling frequency, thereby converting the third signal to a discrete received signal;
- and
- detecting a level of the first signal as interference in the discrete received signal.
A communication apparatus for communicating among a plurality of stations in a wireless environment in which a first signal having a first center frequency is present in a first frequency band, the plurality of stations communicating in a second frequency band having a second center frequency, the first center frequency and the second center frequency being mutually spaced apart by a separation frequency, the communication apparatus comprising:
- a transmit packet generator for generating a transmit packet signal according to transmit data and a control signal;
- a transmitting circuit for modulating the transmit packet signal onto a carrier signal having the second center frequency to generate a modulated signal and transmitting the modulated signal at a controlled transmitting power level;
- a high-frequency receiving circuit for receiving an incoming signal including the first signal and a second signal having the second center frequency, thereby obtaining a received signal, and generating a third signal by frequency down-conversion of the received signal so that the second signal is converted to a baseband signal;
- a sampling unit for determining a sampling frequency from the separation frequency, and sampling the third signal at the sampling frequency, thereby converting the third signal to a discrete received signal;
- an interference level detector for detecting an interference level of the first signal in the discrete received signal;
- and
- a transmit level controller for controlling the transmitting power level of the modulated signal according to the detected interference level.
Dependencies are inferred from the claim text.