Estimating Rate of Queue Usage to Differentiate Cause of Packet Loss in Multi-hop Wireless Networks

When TCP operates in multi-hop wireless networks, it suffers from severe performance degradation. This is because TCP considers all packet losses as congestion signals, and reacts even to wireless packet losses by decreasing unnecessarily its sending rate. Although several loss differentiation schemes are proposed to avoid such performance degradation, these schemes are designed for the last-hop wireless networks, and their accuracies in wireless loss discrimination are not high as much as we expect. In this paper, we suggest a new end-to-end loss differentiation which works entirely at the TCP sender. To improve its accuracy, we estimate the rate of queue usage using information available to TCP. If the estimated queue usage is larger than a certain threshold when a packet is lost, our scheme diagnoses the packet loss as congestion losses. Otherwise it assumes the packet loss as wireless losses. Through the extensive simulations, we compare and evaluate our scheme with previous schemes in terms of accuracy and stability. And the results show that our scheme has the highest accuracy among the previous schemes, and its accuracy is reliable under various multi-hop wireless network conditions.