T. Fujiwara, S. Nakayama, N. Iida, and T. Watanabe (Japan)
Wireless network, Ad hoc network, Cellular network, Multihop access, MAC protocol, Emergency communications.
Several institutes for the fourth generation wireless networks have been discussing about multihopping to improve performances, area coverage and energy consumption. This paper proposes a hybrid wireless network scheme for emergency communications, which combines ad hoc networks with a centralized network to maintain connections. In a natural disaster or an emergency, some links of the centralized network are not maintained due to damage to facilities or an interruption on wireless channels. To make matters worse, communication congestions may occur and interrupt network access. Whereby, emergency communication services cannot work normally, even though they should be given priority over others. In the proposed scheme, a terminal operating in cellular mode under normal circumstances, switches to ad hoc mode to access a base station (BS) by way of multihopping when a link between BS and the terminal is disconnected. The route discovery manner of the scheme is capable of building a route by monitoring communications without route request used by other ad hoc routing protocols. The simulation results show that 90% of terminals in a cell can access BS within three hops with the proposed hybrid network in the circumstances where only 20% of terminals are able to reach the BS directly.
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