On the Suitability of LTE Air Interface for Reliable Low-Latency Applications

In this paper we study the potential of commercial Long Term Evolution (LTE) networks for supporting reliable low-latency applications. To this end, we use one-way end-to-end latency measurements of a commercial LTE network deployed in Vodafone R&D's Innovation Lab where we control the over-the-air traffic and air interface configuration. The experimental results show that the achievable latency and reliability is mainly limited by two features of the LTE radio system: the configured Discontinuous Reception (DRX) pattern and the Scheduling Request (SR) periodicity of the UE. The one-way latencies vary between 40 and 95 ms at the 99.9% percentile, depending on the inter-arrival time of the generated traffic. By disabling or applying less-restrictive DRX and SR patterns and using an aggressive uplink allocation technique, we show how the one-way latency performance improves significantly, e.g. as low as 7 ms with 99.9% probability regardless of the traffic characteristics. For cases where configuring the radio interface is not feasible, we show different options available at the application layer for improving the latency performance of the application. For instance, the application may frequently transmit small packets to reduce the probability of the UE going to DRX mode, or coordinate the message generation interval with the SR opportunities and DRX patterns of the underlying radio system.