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The poor performance of TCP in wireless networks is further diminished in IEEE 802.11-based ad hoc networks networks due to the unnecessary actions of on-demand routing protocols when interference-induced packet drops happen at the medium access control (MAC) layer. In this paper, we present a cross-layer hop-by-hop congestion control scheme designed to improve TCP performance in multihop wireless networks. The proposed scheme, which we will refer to as CHCC, attempts to determine the actual cause of a MAC-layer packet loss and then coordinates the congestion-control response among the MAC, network, and transport protocols. The congestion control efforts are invoked at all intermediate and source nodes along the upstream paths directed from the wireless link experiencing the congestion-induced packet drop. Simulation results show that the proposed scheme achieves up to 70% higher throughput than TCP-Reno. The CHCC approach is interoperable with standard TCP and can be used transparently when using transport protocols (e.g., UDP) that do not implement congestion control.