NEC teams for mmwave 256 MIMO transceiver for the IoT
Researchers in Japan have built a 28GHz mmwave phased-array transceiver that supports low latency switching for more reliable 5G communications in the Internet of Things (IoT)
The joint team at Tokyo Institute of Technology (Tokyo Tech) and NEC developed the transceiver on a 65nm process with fast beam switching between 256 beams leakage cancellation mechanisms to reduce the noise and power consumption.
Millimetre wave designs at 28GHz and above for 5G can offer data rates over 10 Gbit/s with multiple-in-multiple-out (MIMO) technology, and this needs large scale phased-array transceivers. While MIMO systems boost spectral performance, large-scale phased-array systems face several challenges such as increased power dissipation and implementation costs.
One such critical challenge is latency caused by beam switching time. Beam switching is an important feature that enables the selection of the most optimal beam for each terminal.
The design highlighted at the 2021 VLSI Symposium uses dual-polarized operation with data transmitted simultaneously through horizontal and vertical-polarized waves. However, one issue with these systems is cross-polarization leakage, which results in signal degradation.
“Fortunately, we were able to devise a cross-polarization detection and cancellation methodology, using which we could suppress the leakages in both transmit and receive mode,” said Prof Kenichi Okada who led the team.
One critical feature of the proposed mechanism is the ability to achieve low-latency beam switching and high-accuracy beam control. Static elements control the building blocks of the mechanism, while on-chip SRAM is used to store the settings for different beams. This mechanism leads to fast beam switching with ultra-low latency being achieved. It also enables fast switching in transmit and receive modes due to the use of separate registers for each mode.
Another aspect of the proposed transceiver is its low cost and small size. The transceiver has a bi-directional architecture, which allows for a smaller chip size of 5 × 4.5 mm2 and with 256-pattern beam settings stored on chip can switch beams in 4ns. The accuracy, or error vector magnitude (EVM), was 5.5 percent in 64QAM and 3.5 percent in 256QAM.
“The technology we developed for the 5G NR network supports high-volume data streaming with low latency. Thanks to its rapid beam switching capabilities, it can be used in scenarios where enhanced multi-user perception is required. This device sets the stage for a myriad of applications, including machine connectivity and the construction of smart cities and factories,” said Okada.
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