Patent ID: 8175983

Claim:
A communication system that receives vehicle information asynchronously transmitted from a plurality of sensors provided in a vehicle, comprising: a portable communication device; and an in-vehicle communication device that communicates with the portable communication device through synchronous communication, wherein the potable communication device transmits dummy signals simulating the vehicle information to the in-vehicle communication device in a first period, and the in-vehicle communication device learns and records a first filter coefficient to filter signals including the vehicle information, noise and the dummy signals, that are received in the first period, to zero signal levels of signals received in the first period, learns and records a second filter coefficient to filter signals including the vehicle information and noise, that are received from the sensors in a second period in which the portable communication device does not transmit the dummy signals, to zero signal levels of signals received in the second period, and calculates a third filter coefficient based on the first and second filter coefficients to filter signals including the vehicle information and noise, received from the sensors in a third period, using the third filter coefficient to remove the noise in the signals received from the sensors, the vehicle information being output without the noise.