As part of its ongoing and ambitious 5G work, NTT DoCoMo, in collaboration with MediaTek, successfully developed a chipset to increase the spectral efficiency of mobile devices by up to 2.3 times compared to existing LTE technology.
DoCoMo contributed the non-orthogonal multiple access (NOMA) radio access technology and MediaTek supplied the multi-user interference cancellation (MUIC) technology required to achieve NOMA.
According to DoCoMo, NOMA multiplexes signals at a base-station transmitter to leverage the increased signal processing capacity of user devices and cancel interference among multiplexed user signals. MUIC removes interference from other users when a base station transmits a signal to a number of users simultaneously.
The pair used three smartphone-sized devices embedded with the chipsets, with each placed in a different location, and they received data that was transmitted simultaneously from a base station using the same frequency, while the transmission power of the signal transmitted to each device was adjusted. Using the new chipset, each device successfully eliminated interfering signals intended for the other devices and received only the intended data, resulting in up to 2.3 times greater spectral efficiency than that of single-user Multi Input Multi Output (MIMO).
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These are busy times for DoCoMo. The company also has agreed with Sony to conduct a joint trial involving the real-time transmission of high-definition video via a 5G system to a 4K digital signage system fitted to the outside of the New Concept Cart, an experimental high-tech vehicle developed by Sony.
The trial will be conducted at the 5G Trial Site in Tokyo, which DoCoMo built to evaluate 5G technologies and potential commercial services. The test will evaluate the speed and quality of high-definition video transmitted via a 5G system to the vehicle's high-definition 4K digital sign.
DoCoMo also said it was able to complete the world’s first successful outdoor trial of 5G for ultra-reliable low-latency communications (URLLC) using a 4.5 GHz system developed in collaboration with Huawei.
During the trial, which used a stationary mobile terminal, DoCoMo achieved an over-the-air latency of less than 1 millisecond together with a packet transmission success rate of more than 99.999%, which are required for URLLC as defined by 3GPP and ITU. Similarly, ultra-reliable low-latency communications also were achieved at distances of approximately 0.3 km to 0.6 km from the base station, when the mobile terminal was moving at approximately 25 km/h.
A combination of several key technologies led to the successful trial, according to a press release, including technology to always retransmit radio signals irrespective of the terminal's radio conditions, ensuring high reliability. Antenna diversity technology was also implemented, as well as a new radio frame structure incorporating extremely short transmission time slots to reduce over-the-air latency.
DoCoMo expects to launch 5G devices and services in 2020.