# 3 GPP Evolution from 5G to 6G: A 10-Year Retrospective
## 2 3 GPP Release 15: Birth of 5G  
3 GPP Release 15 marked the inception of the 5G NR system. As the first release dedicated to 5G, it laid the foundational framework for a new era in mobile communication, establishing the technical specifications for both the SA and NSA modes of 5G operation. This section provides an overview of 5G design in Release 15. Interested readers may find more detailed information in [15; 16; 17; 18]. \begin{table}
\begin{tabular}{|c|c|l|l|} \hline
**3 GPP Release** & \multicolumn{2}{c|}{**Enhancements to Existing Features**} & \multicolumn{2}{c|}{**New Features**} \\ \hline
**Release 19:** & \(\bullet\) & MIMO & \(\bullet\) & Artificial intelligence/machine learning \\
**5G-Advanced Growth** & \(\bullet\) & Mobility enhancements & for NR air interface \\  & \(\bullet\) & Non-terrestrial networks & \(\bullet\) & Subband non-overlapping full duplex \\  & \(\bullet\) & Extended reality support & \(\bullet\) & Low-power wake-up signal/receiver \\  & \(\bullet\) & Artificial intelligence/machine learning & \(\bullet\) & Ambient IoT \\  & & for next-generation radio & \(\bullet\) & Wireless access backhaul \\  & & access network & \(\bullet\) & Femtocell \\  & \(\bullet\) & Others: sidelink communication, & \(\bullet\) & _Toward 6G_: Channel modeling for \\  & & network energy savings, & & integrated sensing and communication \\  & & multi-carrier enhancements & & and 7-24 GHz spectrum \\ \hline
**Release 20 Evolution to 6G** & \(\bullet\) & MIMO & \(\bullet\) & Artificial intelligence/machine learning \\ (Outlook) & \(\bullet\) & Artificial intelligence/machine learning & for mobility \\  & & for next-generation radio & \(\bullet\) & _Toward 6G_: 6G studies \\  & & access network & & \\  & \(\bullet\) & Artificial intelligence/machine learning & \\  & & for NR air interface & \\  & \(\bullet\) & Ambient IoT & \\  & \(\bullet\) & Non-terrestrial networks & \\  & \(\bullet\) & Integrated sensing and communication & & \\ \hline \end{tabular}
\end{table} 
Table 1: _Cont._The next-generation radio access network (NG-RAN) for 5G NR systems comprises base stations known as 5G node B (gNB) for NR and next-generation evolved node B (ng-eNB) for LTE connectivity [19]. These components interact via the NG interface for core network communications and the Xn interface for inter-RAN operations. This architecture supports dual connectivity (DC) and network slicing, which allow operators to allocate network resources dynamically, ensuring efficient performance across various applications. Functional splits within the architecture facilitate optimized resource management, seamless session handling, and robust security. The NG-C and NG-U interfaces are designed to enable control plane and user plane communications between RAN and the core network, respectively, while the Xn interface ensures smooth inter-node operations. Figure 2 provides an illustration of the 5G NR protocol architecture [20; 21]. The physical layer plays a critical role in interfacing the user equipment (UE) with the network. At its core, the NR physical layer adopts orthogonal frequency division multiplexing (OFDM) with a cyclic prefix (CP) as its waveform. This scheme is used for both uplink and downlink transmissions, with an additional option of discrete Fourier transform-spread OFDM (DFT-s-OFDM) for the uplink to improve power efficiency in certain applications. The physical layer is designed to operate across a wide range of spectrum allocations in frequency range 1 (FR1) of 410-7.125 GHz and frequency range 2 (FR2) of 24.25-52.6 GHz, making it adaptable for global deployments. Resource blocks, each spanning 12 subcarriers, form the building blocks for frequency allocation, and these are managed within a frame structure accompanied by flexible subcarrier spacing to support diverse use cases. In NR, there are several physical channels for both uplink and downlink communication [22].