In this paper a novel active queue management technique for ad hoc networks is proposed, where the dropping probability depends on the number of wireless hops traversed by the enqueued packets in the node. The advantages accruing of protecting flows with routes that span over a large number of wireless hops by the proposed Hop Based Queueing (HBQ) algorithm are mainly twofold. Firstly, it decreases the mean excess delay on the MANET (and as a side effect preserves the scare power resources of nodes), by assigning higher dropping probability for packets that have traversed less number of intermediate nodes. Secondly, because the vulnerability of the TCP state machine increases with the number of wireless hops, by protecting these TCP flows from buffer overflow due to queueing, the number of timeouts events which have a deleterious effects on performance due to lengthly recovery through retransmission timeouts, are reduced.
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