A UL-NOMA system providing low E2E latency

The 5G (5th generation mobile communications systems) will not only realize high speed and high capacity communication but also support the Internet of Things (IoT). To support IoT, it is important that a base station (BS) of 5G is able to deal with massive uplink signals transmitted from IoT devices. In addition, some IoT devices used for automatic operation require low latency communication. Therefore, low latency communication is also important to support IoT. We have developed techniques based on non-orthogonal multiple access in uplink (UL-NOMA) in order to realize both massive device connectivity and low latency. Although we could not measure the delay time between an UE transmitting uplink data and receiving downlink data (E2E latency) because of no downlink signal in our previous system, we developed a downlink system and an application to measure E2E latency, and measured E2E latency at this time. We conducted the experiment using hardware to evaluate the E2E latency. Under the condition of Rician and Nakagami fading with K factor = 20 dB, we confirm that the probability that our system can achieve an E2E latency of 20 ms or less is about 90% when two UEs send the uplink signals. In the case of three UEs, the probability is about 50%.