The ultimate goal of next generation multiple access (NGMA) is to support massive terminals and facilitate multiple functionalities over the limited radio resources of wireless networks in the most efficient manner possible. However, the random and uncontrollable wireless radio environment is a major obstacle to realizing this NGMA vision. Given the prominent feature of achieving 360{\deg} smart radio environment, simultaneously transmitting and reflecting surfaces (STARS) are emerging as one key enabling technology among the family of reconfigurable intelligent surfaces for NGMA. This paper provides a comprehensive overview of the recent research progress of STARS, focusing on fundamentals, performance analysis, and full-space beamforming design, as well as promising employments of STARS in NGMA. In particular, we first introduce the basics of STARS by elaborating on the foundational principles and operating protocols as well as discussing different STARS categories and prototypes. Moreover, we systematically survey the existing performance analysis and beamforming design for STARS-aided wireless communications in terms of diverse objectives and different mathematical approaches. Given the superiority of STARS, we further discuss advanced STARS applications as well as the attractive interplay between STARS and other emerging techniques to motivate future works for realizing efficient NGMA.

翻译：下一代多址接入（NGMA）的最终目标是以最高效的方式，在无线网络有限的无线电资源上支持海量终端并实现多功能通信。然而，随机且不可控的无线电磁环境是实现这一NGMA愿景的主要障碍。同步传输与反射超表面（STARS）凭借其实现360度智能无线电环境的突出特性，正逐渐成为可重构智能超表面家族中支撑NGMA的关键使能技术之一。本文全面综述了STARS的最新研究进展，重点关注其基本原理、性能分析、全空间波束赋形设计，以及STARS在NGMA中的潜在应用。具体而言，我们首先通过阐述STARS的基本原理与操作协议，并讨论不同的STARS类别与原型，介绍其基础概念。此外，我们系统性地梳理了现有STARS辅助无线通信的性能分析与波束赋形设计研究，涵盖不同优化目标与数学方法。基于STARS的优越性，我们进一步探讨了其先进应用场景，以及STARS与其他新兴技术之间富有前景的协同融合，以推动未来实现高效NGMA的研究工作。