Patent ID: 8761704

Claim:
An interference suppression method for a receiver in a packet radio communication system using the carrier sense multiple access method, comprising the sequential steps of: filtering a received signal by narrowband filtering; at a received signal strength indicator, detecting an electric field strength of the received signal; at a carrier sense judgment device, receiving an output from the received signal strength indicator indicating the electric field strength of the received signal; at the carrier sense judgment device, determining, based on the output from the received signal strength indicator, whether the received signal is a carrier; and upon a determination at the carrier sense judgment device that the received signal is a carrier, changing the filtering of the received signal from narrowband filtering to wideband filtering without being subjected to the narrowband filtering, and causing a demodulator to begin demodulating the received signal filtered by wideband filtering; and wherein the filtering, in a first mode having the narrowband characteristic, is configured with a passband that is narrower than a one-channel modulation occupied bandwidth and the filtering, in a second mode having the wideband characteristic, is configured with a passband equal to or wider than the one-channel modulation occupied bandwidth.