Various communication specifications are used for wireless communication, but in recent years, wireless communication apparatuses that comply with Bluetooth® low energy (BLE) specifications have come into widespread use. In the BLE specifications, when a slave apparatus intends to establish a connection with a master apparatus, the slave apparatus first transmits a signal that is referred to as an advertisement signal, which is a type of communication control signal, and the master apparatus recognizes the slave apparatus is present by receiving the advertisement signal. Thereafter, the master apparatus, now aware of the presence of the slave apparatus, transmits a connection request signal to the slave apparatus that makes it possible to establish a connection and perform data transmission and reception between the master apparatus and the slave apparatus.
In the BLE specifications, an ISM band of 2.4 GHz is used. There are 40 wireless channels in this 2.4 GHz ISM band, and, from among the 40 channels, three channels are used for the transmission of the advertisement signal.
Because the advertisement signal is intermittently transmitted by the slave apparatus until a connection with a master apparatus is established, a reduction in power consumption for the transmission of this advertisement signal makes it possible for a slave-side battery, to operate for a longer time.
To cope with this power consumption problem in some devices, measures may be taken to perform advertisement signal transmission using only a channel through which a connection can be established and thus to reduce power consumption by not transmitting advertisement signals over the other two channels.
However, the 2.4 GHz ISM band is also used by various apparatuses, such as a wireless LAN, a microwave oven, and, more generally, other industrial, scientific, and medical apparatuses. Depending on a situation of the occupation of the advertisement channel by any of these other apparatuses, the fact that a connection was once previously established in the past without interference does not guarantee that another connection can be established over the same channel at some later point in time since interference(s) may come and go. Furthermore, the time required for the connection to be established using only one specific channel may be lengthened considerably, and this also results in excessive power consumption.