Ad-hoc wireless networks with multi-rate radios (such as 802.11a, b, g) require a new class of MAC/PHY aware metrics that take into account factors such as physical-layer link speed and MAC-layer channel congestion. Conventional “layer 3” ad-hoc routing algorithms typically make routing decisions based on the minimum hop-count (MH). Use of the MH metric leads to selection of paths with few hops but one or more of these hops may turn out to be low-speed radio links due to adaptive rate selection at the physical layer. In this paper, we investigate a new crosslayer routing metric that takes into account both physical layer link speed as well as estimated channel congestion, thus aiming to minimize end-to-end delay that includes both transmission and access times. The proposed “PARMA” routing metric will thus help spread the traffic across the “good links and nodes” in the network, increasing network capacity and reducing packet loss and delay. This paper presents the design...