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5G NR Introduction
5G is the fifth generation of wireless communications and NR is the new radio interface which is designed for the fifth generation. It is a new radio interface that has new radio access technologies for faster data transmission and meets all the requirements of the new generation. 5G NR (New Radio) is a unified and more capable air interface with several diversified services, different spectrum, and deployment methods. This new Air interface is designed in such a way that it would be able to meet all the requirements of 5G technology which demands 10 times decrease in end-to-end latency, ten times increase in experienced throughput, three times increase in spectral efficiency, hundred times increase in traffic capacity and network efficiency and 10-time increase in connection density of the networks. The Air interface of 4G technology is not able to comply with the above-stated requirements, so for 5G there is a requirement to design a new air interface and it is named New Radio (NR). NR is unified in nature and it is more capable than the previous generations. Diversified services supported by NR include eMBB (enhanced Mobile Broadband), URLLC (ultra-reliable low latency communications ), and mMTC (massive Machine type 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.