Due to MAC collisions and mobility, quality of service (QoS) provisioning in mobile ad hoc networks is very challenging. In this paper, we propose an innovative scheme to grant high priority to communications between some important nodes in TDMA based ad hoc networks. In addition to bandwidth reservation in previous QoS routing approaches, our scheme adopts a new approach: bandwidth pre-reservation. Some bandwidth is pre-reserved at intermediate nodes in a quadrangleshaped area formed between

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... portant nodes. The key idea is to utilize each node's geographic location information and minimize potential scheduling conflicts for transmissions. In this way, time slot collisions in adjacent wireless links along a path can be reduced so that more high priority connections can be accepted into the network. Extensive simulations show that our scheme can successfully provide better communication quality at a relatively low price. I.