Various transmission control protocol (TCP) enhancement schemes have been proposed to improve TCP performance over mixed wired/wireless networks. A general principle of these end-to-end TCP enhancement schemes is to distinguish wireless loss from congestion loss, and to take the cause of the loss into consideration when performing TCP congestion control. However, they do not consider the ratio of congestion losses to wireless losses which significantly affects their performance, mainly in terms of their throughputs. In this paper, a new approach has been developed to address this issue. To apply the approach into an end-to-end TCP enhancement scheme, the ratio of congestion losses to wireless losses are estimated and the parameters used in the scheme are adjusted to further improve its performance. The simulation experiments showed that Veno, a popular end-to-end TCP enhancement scheme, with the new approach always outperformed the original Veno in terms of throughput and fairness, and their differences could be more than two times better.