Introduction:
The development of cellular technology is changing society. 5G networks are completely changing society from 2020 and beyond. 5G technology is expected to provide a diverse range of use cases: eMBB (enhanced Mobile broadband), URLLC (ultra-reliable low latency communications), and mMTC (massive Machine type communications). For the enhanced Mobile Broadband services, user experienced data rate of about 100 Mbps is expected. It has an area capacity of 10mbps/ sq. meter., it can support large bandwidth. Mobility is also an important factor and it should be improved to support devices moving at a speed of 500 kmph. For URLLC (Ultra-Reliable Low-latency Communications) usage scenarios, the latency is 1 msec with 99.999% reliability.
Radio interface technology components:
- Physical layer structure
- Initial Access and Mobility
- Channel coding and Modulation
- Scheduling and Hybrid ARQ
- MIMO
RF Requirements and spectrum bands:
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). m
5G Interfaces
NG1: A reference point between the UE and the Access and Mobility Management Function (AMF).
NG2: A reference point between the gNB and the Access and Mobility Management Function (AMF).
NG3: A reference point between the gNB and the User Plane Function (UPF).
NG4: A reference point between the Session management function (SMF) and the User plane function (UPF).
NG5: A reference point between the Policy control function (PCF) and an application function (AF).
NG6: A reference point between the User Plane Function (UPF) and a Data Network (DN).
NG7: A reference point between the Session Management Function (SMF) and the Policy control function (PCF).
NG8: A reference point between the Unified Data Management (UDM) and Access and Mobility management function (AMF).
NG9: A reference point between two Core User Plane Functions (UPFs).
NG10: A reference point between the Unified Data Management (UDM) and Session management function (SMF).
NG11: A reference point between the Access and Mobility Management Function (AMF) and Session management function (SMF).
NG12: A reference point between the Access and Mobility Management Function (AMF) and Authentication Server Function (AUSF).
NG13: A reference point between the UDM (Unified Data Management) and Authentication Server Function (AUSF).
NG14: A reference point between two Access and Mobility Management functions.
NG15: A reference point between the PCF (Policy control function) and the AMF (Access and Mobility Management Function ) in case of non-roaming scenario, V-PCF, and AMF in case of roaming scenario.
The Reference point representation of Architecture is the good old way of representing Architecture and it is known from the previous generations.
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.
The new Synchronization signals for initial access and mobility are designed in 5G NR to provide more flexibility. 5G NR supports both SA (StandAlone) and NSA (Non-StandAlone) including the LTE-NR DC. 5G supports multiple numerologies, the wider channel bandwidths, the more flexible UL-DL slot configurations, etc.
