LDRP: Device-Centric Latency Diagnostic and Reduction for Cellular Networks Without Root.

We design and implement LDRP, a device-based, standard-compliant solution to latency diagnosis and reduction in mobile networks without root privilege. LDRP takes a data-driven approach and works with a variety of latency-sensitive applications. After identifying elements in LTE uplink latency, we design LDRP that can infer the critical parameter used in data transmission and infer them for diagnosis. In addition, LDRP designates small dummy messages, which precede uplink data transmissions, thus eliminating latency elements due to power-saving, scheduling, etc. It imposes proper timing control among dummy messages and data packets to handle various conflicts. We achieve the latency diagnosis and reduction without requiring root privilege and ensure the latency is no worse than the legacy LTE design. The design of LDRP is also applicable for 5G. The evaluation shows that, LDRP infers the latency with at most 4% error and reduces the median LTE uplink latency by a factor up to 7.4× (from 42 to 5 ms) for four apps over 4 mobile carriers.