In recent years, a communication terminal including a plurality of wireless interfaces has been attracting attention. This communication terminal executes communication by selecting a channel and a communication method to be used from among various frequencies (channels) and communication methods. In addition, a multi-channel/multi-interface (MCH/IF) environment has also been attracting attention as a network including such communication terminal.
In an MCH/IF environment, a communication terminal determines a channel used by each of the wireless interfaces provided with the communication terminal from among many available channels. In this operation, a network topology in which a plurality of channels are multiplexed is established.
There are possible ways to multiplex wireless interfaces and channels. For example, when a single wireless interface executes communication, by quickly switching to a suitable channel, it is possible to make it look as if the communication terminal is simultaneously using a plurality of channels. In another possible way, by allocating one type of channel to a single wireless interface and by providing a plurality of such wireless interfaces, different channels are simultaneously used.
In either way, the same network topology is generated as a result. The following description will be made based on an environment where one type of channel is allocated to a single wireless interface as an example. In addition, selection of a wireless interface executing re-forwarding and selection of a forwarding channel will be deemed as being identical.
Communication links constituting a topology in an MCH/IF environment have different characteristics, depending on the frequency levels used by the wireless interfaces. For example, in the low-frequency VHF (Very High Frequency) or UHF (Ultra High Frequency) bandwidth, while long-distance communication is possible, the communication bandwidth (capacity) is limited to several hundred kbps. In contrast, in the high-frequency SHF (Super High Frequency) bandwidth of 3 GHz or more, while a bandwidth of a few M to several hundred Mbps can be obtained, the communication distance is limited to approximately several hundred meters to several dozen meters.
A communication terminal uses a plurality of wireless interfaces, and a different channel is allocated to each of the wireless interfaces. Thus, the communication terminal recognizes a different number of neighboring terminals and has a different capacity per wireless interface/channel. In addition, a plurality of communication links including different communication characteristics (capacities, communication ranges) with respect to each communication terminal can exist.
In a network topology in such MCH/IF environment, in order to execute path control and to control an application in the same way as before, a broadcast distribution technique for enabling data transmission to all the communication terminals on a network or to communication terminals within a certain range is needed.
For example, Non Patent Literatures NPL1 and NPL2 disclose a method for selecting an optimum forwarding channel from among the channels that can currently be used by wireless interfaces provided with a communication terminal when a network topology in an MCH/IF environment is previously given.
[NPL1]
    Li Li, Bin Qin, Chunyuan Zhang and Haiyan Li, “Efficient Broadcasting in Multi-radio Multi-channel and Multi-hop Wireless Networks Based on Self-pruning,” High Performance Computing and Communications Lecture Notes in Computer Science, 2007, Vol. 4782/2007, p. 484-495.[NPL2]    Kai Han and Yang Liu, “Reducing Multicast Redundancy and Latency in Multi-Interface Multi-Channel Wireless Mesh Networks,” I.J. Information Engineering and Electronic Business, 2009, 1, p. 42-50 Published Online October 2009 in MECS.
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