Patent ID: 6937558
Filing Date: 2005-08-30
Classification: H04B,H04L

Abstract:
1. A transmitter apparatus making use of an orthogonal frequency division multiplexing modulation and a spectrum spreading modulation in combination comprising: an orthogonal frequency division multiplexing circuit which selectively modulates information signals to be transmitted by orthogonal frequency division multiplexing; a spectrum spreading circuit which selectively performs a spectrum spreading modulation of said information signals to be transmitted; and a transmission signal processing circuit which transfers said information signals which have been modulated by either said orthogonal frequency division multiplexing modulation or said spectrum spreading modulation to a receiver apparatus as a transmission signal, wherein, when said receiver apparatus and said transmitter apparatus are located so close to each other that the received signal level of said receiver apparatus is sufficient to maintain the communication between said receiver apparatus and said transmitter apparatus with signals which are modulated on the basis of said orthogonal frequency division multiplexing modulation but not modulated on the basis of said spectrum spreading modulation, said orthogonal frequency division multiplexing circuit performs the modulation of said information signals to be transmitted while said spectrum spreading circuit does not perform said spectrum spreading modulation of said information signals to be transmitted, and wherein, when said receiver apparatus and said transmitter apparatus are located so remote from each other that the received signal level of said receiver apparatus is not sufficient to maintain the communication between said receiver apparatus and said transmitter apparatus with signals which are modulated on the basis of said orthogonal frequency division multiplexing modulation but not modulated on the basis of said spectrum spreading modulation, said orthogonal frequency division multiplexing circuit does not perform said orthogonal frequency division multiplexing modulation of said information signals to be transmitted while said spectrum spreading circuit performs said spectrum spreading modulation of said information signals to be transmitted.