In multihop wireless networks, end-to-end throughput is often hard to predict and is even harder to optimize due to the effect of interference. To date there is no precise result other than asymptotic bounds for this question: if there is no routing information given, what is the maximum throughput of a network using uncoordinated transmission such as IEEE 802.11 MAC? This paper attempts to address this question for a given network with specific traffic demand. In this paper we use a cross-layer design scheme to optimize network performance. The paper includes a basic linear programming model, from which the routing paths and link data rates are derived, and then an extended model to consider links with different loss rates. Using ns2 simulation, we show that our joint routing and rate control scheme indeed can predict the maximum throughput and improve network throughput.