1. New Radio (NR) Is the Name of the Air Interface
The wording New Radio or 5G NR might not be the most original, but it’s what the 3rd Generation Partnership Project (3GPP) is calling the output of Release 15. NR is equivalent to how the mobile communications industry has used LTE to describe 4G technology or UMTS to describe 3G technology. The draft specifications for Release 15 were approved in December 2017 and are expected to be finalized in mid-2019. Release 15 is just the start, as it establishes only phase one of a 5G mobile communication standard. Release 16 provides specifications for a second phase and is expected to be finalized in 2019.
2. 5G Uses New Spectrum
The question of which spectrum 5G networks will use has been considerable, and the answer is slowly becoming clearer. When research on 5G began, many were excited about the possibility of using the mmWave spectrum for 5G. And it will be a big part of the solution. However, in the shorter term, the sub-6 GHz spectrum and mmWave bands are significant parts of the equation. Release 15 outlines several groups of new spectrum specifically for NR deployments ranging from 2.5 GHz to 44 GHz. Two bands being targeted for more immediate deployment for mobile use cases are the 3.3 GHz to 3.8 GHz and 4.4 GHz to 5.0 GHz bands, with early demonstrations at the Winter Olympics in February 2018. Regulatory bodies in the United States, Europe, and various Asian countries have already opened this spectrum for 5G usage. And the wide bandwidths available in this band are appealing for carriers. But spectrum below 50 GHz is only the beginning. Future 3GPP releases could allow for use of spectrum up to 86 GHz.
3. Beamforming Is Going to Be a Big Deal
To optimize signal strength at the mobile device, NR uses a combination of analog and digital beamforming. The idea of beamforming is not new to mobile communications, as LTE networks extensively use digital beamforming today. With 5G, however, the challenges of signal propagation and smaller antenna sizes motivate the use of extensive analog beamforming techniques. Above 24 GHz, analog beamforming of narrower beam widths gives 5G base stations the ability to steer downlink signals more efficiently. The process first involves beam scanning, so the base station can identify the most effective beam location for a specific mobile device. Using this approach, the recipient of the downlink transmission benefits from higher signal strength—particularly by using higher order modulation schemes. However, beamforming ultimately introduces significant test challenges. Not only does each beam need to be characterized and tested but over-the-air measurements are also critical to validate radio performance.
4. The First 5G Devices Will Still Rely on LTE
5G NR phase one will eventually feature both standalone and non-standalone modes of operation. In non-standalone mode, the mobile device uses 4G and 5G networks simultaneously, maintaining a connection with both an LTE eNB and a 5G gNB. The specification for non-standalone mode completed in December 2017, and standalone mode is scheduled to wrap up when Release 15 is finalized. In the meantime, radios will use both LTE and NR transceivers simultaneously, placing considerable attention on improving power efficiency and reducing interference.
5. Phase One Is Still Based on an OFDM Waveform
Although many candidate waveforms have been proposed for 5G, the first phase of NR uses a version of orthogonal frequency division multiplexing (OFDM). The specific version of OFDM used in 5G NR downlink is cyclic prefix—OFDM is the same waveform LTE has adopted for the downlink signal. However, unlike LTE, 5G NR also uses CP-OFDM- and DFT-S-OFDM-based waveforms in the uplink. Also unlike LTE, 5G NR allows for significant variation in subcarrier spacing. Whereas LTE subcarriers were almost always spaced at 15 kHz, 5G NR allows a flexible scheme where subcarriers are spaced at 15 kHz x 2n. In 5G NR, the maximum subcarrier spacing allowed is 240 kHz, and it is reserved for the scenario where 400 MHz carrier bandwidth is used.
Technical White Paper
5G New Radio: Introduction to the Physical Layer
Learn how the recently specified 5G New Radio physical layer will help make the leap into the future of 5G a reality, including:
The choice of key OFDM waveforms
The benefits of a flexible, scalable numerology
Support for mmWave operation and multi-user MIMO
Bandwidth parts for efficient spectrum utilization