Reliable Real-time Measurement and Characterization of Wireless Communications Systems

Network latency and reliability become critical performance indicators for future mission critical services based on wireless connectivity. In this paper we present a measuring system for quantifying end-to-end (E2E) latency and reliability of communication systems based on single or multiple links. The approach is tailored for characterization of access diversity mechanisms critical to ultra-reliable wireless communications in 4G and 5G networks, e.g. multi-connectivity or hybrid access methods. An active-probe measuring approach is adopted, consisting of a client that transmits time-stamped packets to a server, and vice versa, via one or multiple communication links being tested. The setup allows us to measure the one-way latency performance in uplink and downlink separately, and allows fully synchronized measurements of multiple links in parallel. The traffic generation is highly flexible in terms of packet size, transport protocol (TCP or UDP), and inter-arrival time interval of the generated packets, hence being a powerful tool for benchmarking the performance for different application-specific message flows. Special emphasis is put on the tail of the latency distribution, i.e. the latency that can be achieved with a certain probability constraint, e.g. 99.9%. Given the challenge of measuring such rare events, we measure and validate the stability of the measuring equipment, i.e. making sure that the observed performance is not compromised by undesired behavior or malfunction of the equipment. The system including interfacing with the modem accessing the communication link under test, shows a latency jitter 1ms at the 99.9 percentile and 3ms at the 99.999% percentile. The capability and applicability of the measuring system is illustrated by mounting it on a drone and conducting a measuring test using two simultaneous LTE connections.