Slope based discard: a buffer management scheme for 3G links supporting TCP traffic

This paper introduces Slope Based Discard (SBD), a novel Active Queue Management (AQM) scheme that improves TCP performance over 3G wireless links. Its main objective is to prevent buffer overflow at the downlink buffer in the Radio Network Controller, where the flows of a single user are multiplexed. In contrast to Random Early Detection (RED), SBD is a deterministic algorithm, and its discarding policy is based on the observation of the filling rate of the buffer. By means of extensive simulation experiments, we disclose the influence of each SBD parameter on TCP goodput and latency. Compared to RED, which parameter configuration is also addresed, SBD shows similar goodput figures but lower delays. We describe other characteristics that make SBD a better choice than RED for 3G links, like its greater capability to prevent buffer overflow, and its easier implementation.

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