# 3 GPP Evolution from 5G to 6G: A 10-Year Retrospective
## 1 Introduction  
The journey of mobile communication technologies has always been a story of relentless innovation, ambition, and collaboration. Over the past decades, the 3 rd Generation Partnership Project (3 GPP) has been at the forefront of shaping the telecommunications landscape, transforming the possibilities of wireless communication [1]. From the advent of the fifth generation (5G) to the initial steps toward the sixth generation (6G), 3 GPP's development timeline as illustrated in Figure 1, spanning Releases 15 to 20, offers a rich roadmap of the latest mobile technology breakthroughs in the last decade. This 10-year retrospective examines how 3 GPP has evolved the foundation of mobile networks, enabling a seamless transition from the 5G era to the dawn of 6G. 3 GPP started its 5G work by hosting a workshop in September 2015. At the workshop, there was an emerging consensus that there would be new, non-backward compatible radio access technology (RAT) for 5G. After 5G studies in the Release-14 timeframe, 3 GPP completed Release 15 in June 2018, marking the birth of 5G [2]. This milestone introduced the New Radio (NR) air interface, laying the groundwork for a new generation of connectivity defined by improved speed, reliability, and flexibility [3]. Designed to address three International Mobile Telecommunications-2020 (IMT-2020) key usage scenarios (enhanced mobile broadband (eMBB), ultra-reliable low-latency communications (URLLC), and massive machine-type communications (mMTC)) [4], Release 15 established a flexible framework for 5G's diverse applications. It introduced both standalone (SA) and non-standalone (NSA) architectures, enabling a gradual migration from existing Long-TermBuilding on the success of Release 15, 3 GPP Release 16, finalized in mid-2020, took 5G a step further by qualifying it as an IMT-2020 technology approved by the International Telecommunication Union (ITU) [6]. Release 16 introduced significant enhancements, including support for the industrial Internet of Things (IoT), vehicle-to-everything (V2X) communication, integrated access and backhaul (IAB), operation in an unlicensed spectrum, and positioning, among others [7; 8]. By broadening 5G's application scope, Release 16 enhanced the network's ability to support emerging use cases, such as smart manufacturing and autonomous vehicles. Release 17, finalized in 2022, represented the expansion of 5G into new domains, pushing the boundaries of what the technology could achieve [9]. It introduced support for non-terrestrial networks (NTNs), allowing connectivity through satellites to extend the reach of 5G to remote and underserved areas. This release also defined reduced capability (RedCap) devices, enabling cost-effective solutions for IoT applications. By continuing to enhance multiple-input multiple-output (MIMO) capabilities, coverage, and power-saving features, Release 17 continued to improve 5G's performance to meet a diverse range of global needs. A significant inflection point arrived with Release 18, finalized in 2024, marking the beginning of the 5G-Advanced era [10; 11]. This phase brought a sharper focus on integrating artificial intelligence (AI)/machine learning (ML) into 5G to optimize use cases such as load balancing and mobility at the 5G architecture level. Release 18 also introduced network energy-saving techniques and enhancements for extended reality (XR) applications, reflecting the growing emphasis on sustainability and immersive experiences. Additionally, Release 18 addressed new deployment needs, such as deployments in a spectrum with less than 5 MHz bandwidth for the future railway mobile communication system (FRMCS). The momentum of 5G-Advanced continues with Release 19, set for completion in late 2025 [12]. Release 19 integrates AI/ML into the NR air interface, enabling smarter beam management and positioning.