1. Field of the Invention
The present invention relates to a communication apparatus and method of controlling same in which handover of a control station in a network is performed in accordance with the state of the power supply of the communication apparatus.
2. Description of the Related Art
In conventional communication systems compliant with IEEE 802.15.3, a single wireless terminal serves as a control station (master) and controls a plurality of other wireless terminals (slaves), thereby constructing a piconet. A single piconet uses the same channel, and communication is assigned to respective time slots obtained by time division. Each wireless terminal is notified by a beacon signal transmitted by the control station, and the piconet operates in such a manner that the wireless terminals communicate with one another. The wireless terminals therefore communicate with one another directly based upon the beacon signal received.
A wireless terminal may function as both a control station and a wireless terminal. In ordinary operation, therefore, the wireless terminal to which power is introduced first searches for and acquires an available channel and then transmits the beacon signal to thereby start the construction of the network. The other wireless terminals receive the beacon signal from the control station and attempt to associate, as a result of which a piconet is formed.
In order to minimize consumption of a battery in the case of a wireless terminal (slave) powered by a battery, the wireless terminal transitions to a power-saving mode in which it receives the beacon signal at a rate of once every several number of transmissions and operates intermittently only at the timing of a time slot that has been allocated to it for the purpose of communication.
The IEEE 802.15.3 standard is such that if a new wireless terminal has become associated with the network, this wireless terminal undergoes a functional comparison and the control operation can be handed over to this new wireless terminal. However, after one control station and multiple 1 to N wireless terminals constructing a piconet have completed association, the capabilities of these wireless terminals are not compared and handover of the control station is not carried out.
Since the wireless terminal operating as the control station constantly transmits a beacon, receives various requests and information from each of the other wireless terminals and monitors status such as interference, power consumption by this terminal is severe. Hence there is the likelihood that communication will be interrupted owing to consumption of the battery. A further problem is that in response to shutdown of the wireless terminal serving as the control station, the beacon from the control station ceases being transmitted, communication among all of the wireless terminals that are communicating over the piconet of the control station is interrupted and continuation of communication becomes impossible.