Study of local alternative ad hoc routing protocol for the exposed terminal problem

Ad-hoc network is an autonomous network that consists of only mobile terminals without an infrastructure such as base stations. The wireless LAN system with IEEE 802.11 standard is one of the candidate schemes to realize ad-hoc network. In IEEE 802.11, CSMA/CA (carrier sense multiple access with collision avoidance) is used as access control method. Moreover RTS/CTS (request to send/clear to send) mechanism is implemented to solve the hidden terminal problem. However it is well known that RTS/CTS mechanism causes the exposed terminal problem in which the communication route between terminals would be suppressed. In this paper, we clarify the effect of the exposed terminal problem to the ad-hoc networks. Moreover we propose a local alternative routing protocol method that prepares back up routes to avoid the temporary suppression of transmissions. Simulation results show that the proposed method can prevent the route reconstruction and improve the packet delivery ratio