Patent ID: 8855077

Claim:
A first communication apparatus configured to transmit OFDM signals, each of the OFDM signals comprising a first period and a second period, the first communication apparatus comprising: a transmitting circuit configured for transmitting the OFDM signals to a second communication apparatus by using a plurality of subcarriers allocated among a number M of contiguous frequency channels that can be used simultaneously by the second communication apparatus, wherein the number M is an even number greater than or equal to two and does not exceed the number of frequency channels that can be simultaneously used by the first communication apparatus; and a processing circuit configured for: allocating data for transmission during the first period to a first subset of subcarriers of the plurality of subcarriers without allocating data to each of respective subcarriers positioned in respective centers of the number M of the contiguous frequency channels, allocating data for transmission during the second period to a second subset of subcarriers of the plurality of subcarriers without allocating data to at least a subcarrier positioned in a center of a frequency band of the number M of the contiguous frequency channels for the second period, the second subset of carriers comprising the respective subcarriers positioned in respective centers of the number M of the contiguous frequency channels.