The initial specifications enabled non-standalone 5G radio systems integrated with previous generation i.e LTE networks. This scope of Release-15 expands to cover standalone 5G with the development of a new radio system i.e 5G NR(New Radio). Rel-15 and Rel-16 constitute the basis of 5G technology. The ultra-lean design of NR enhances the network energy performance and reduces interference. The most important enhancements of NR in Rel-16 are in the areas of multiple-input-multiple-output (MIMO) and beamforming enhancements, dynamic spectrum sharing (DSS), dual connectivity (DC), carrier aggregation (CA), and user equipment (UE) power savings.
Multiple-input Multiple-output (MIMO) and beamforming enhancements
Rel-16 introduces enhanced beam handling and channel state information (CSI) feedback, as well as support for transmission to a single UE from multiple transmission points (multi-TRP) and full-power transmission from multiple UE antennas in the uplink (UL). These enhancements increase throughput, reduce overhead, and provide additional robustness.
Dynamic Spectrum Sharing
DSS provides a very cost-effective and cost-efficient solution for enabling a smooth transition from 4G to 5G by allowing LTE(Long term Evolution) and NR (New Radio) to share the same carrier. The number of rate matching patterns that are available in NR has been increased to allow spectrum sharing when the CA (carrier aggregation) is used for the LTE technology.
Dual connectivity and Carrier Aggregation
3GPP Rel-16 reduces latency for setup and activation of Carrier Aggregation(CA)/Dual Connectivity(DC), which leads to improved system capacity and the ability to achieve higher data rates. Rel-16 introduces aperiodic triggering of CSI reference signal transmissions in case of the aggregation of carriers with different numerology.
User equipment power savings
To reduce UE power consumption which includes a wake-up signal along with enhancements to control signaling and scheduling mechanisms.
New verticals and deployment scenarios addressed in the Rel-16 are in the areas of:
- Integrated Access and Backhaul
- NR in unlicensed spectrum
- Features related to the industrial internet of things and URLLC (Ultra-reliable low latency communications)
- Intelligent transport system and vehicle to anything communications
5G NR Frequency bands
New Radio supports a spectrum that has a varied frequency range and the spectrum is categorized as a low band (below 1 GHz), mid-band ( 1-6 GHz), and high band (Above 24 GHz). The high band is also named as mmWave band. It uses two frequency ranges FR1 and FR2. FR1 includes 6 GHz frequency bands and below. FR2 supports bands in the mm-wave range which includes 24.25 – 52.6 GHz. The mmWave bands are helpful to enable 5G UWB (Ultra-wideband).5G NR supports five types of sub-carrier spacing of 15 kHz, 30 kHz, 60 kHz, 120 kHz, and 240 kHz in the FR 1 (Frequency range 1) and FR2 (Frequency range 2).
5G NR supported technologies
Different technologies that make it possible to have NR are Scalable OFDM numerology, which has a flexible slot-based framework, advanced channel coding techniques, multi-edge LDPC and CRC aided polar, massive MIMO Reciprocity based MU-MIMO ( Multi-user multiple inputs multiple outputs), beamforming and beam tracking techniques. The scalable OFDM-based 5G NR air interface has scalable numerology, frequency localization, lower power consumption, and asynchronous multiple access.
- Optimized OFDM: The specific version of OFDM used in the 5G NR downlink is cyclic prefix OFDM and DFT-S OFDM. CP-OFDM is used as the access technology for 5G NR, it is similar to the access technology used in LTE however CP-OFDM features variable subcarrier spacing termed numerology. It can utilize 15 kHz, 30 kHz, 60 kHz, and 120 kHz, etc subcarrier separation. When the SC spacing is changed, the cyclic prefix duration per symbol also changes. DFT-S OFDM is a discrete Fourier transform spread OFDM is a single carrier-like transmission scheme that is combined with OFDM. It is commonly known as SC-OFDM ( Single carrier OFDM). The transmission scheme of SC-FDMA is very similar to OFDMA. For each user, the sequence of bits transmitted is mapped to a complex constellation of symbols. Then different transmitters are assigned different Fourier coefficients.
- 5G MU-MIMO: MU-MIMO is a multi-user multiple inputs multiple outputs. In MU-MIMO, the base station sends multiple data streams, one per UE, using the same time-frequency resources. Hence, it increases the total cell throughput i.e the cell capacity. It enables the UEs to operate without the need for knowledge of the channel or additional processing to obtain the data streams. MU-MIMO in the downlink significantly improves the capacity of the gNB antennas. It can scale with the minimum of the gNB antennas which can achieve higher capacity gains.
- Spectrum sharing techniques: 5G spectrum sharing is a critical benefit for 5G technology. It is valuable for a wide range of deployments like licensed spectrum aggregation, enhanced local broadband, and 5G private networks.
- Small cells: A Small cell network is a group of low-power transmitting base stations that use mmWaves to increase the overall network capacity. The 5G small cell network operates by coordinating a group of different small cells to share the load and increase the capacity of the system.
5G NR deployment
Deployment modes of 5G NR are of two types: NSA (Non-Standalone) and SA (standalone). Initial 5G NR launches depend on the existing 4G infrastructure and this mode is called NSA where the new network has to depend upon the existing infrastructure. SA is a fully deployed mode with no dependence on the previous generation, it has its core network as 5GC. In the Non-Standalone mode of 5G NR that refers to an option of 5G NR deployment that depends on the control plane of an existing LTE network for all the control plane functions, while the 5G NR is completely focused on the data plane. The deployment’s standalone mode refers to using 5G cells for both the signaling and the data transfer. It includes the new 5G core instead of relying on the LTE infrastructure. DSS (Dynamic spectrum sharing) is a technique where carriers may dynamically share between 4G LTE and 5G NR. The terminals need to be compatible with DSS.