Wireless communication technology has progressed dramatically over the past 25 years, in terms of societal adoption as well as technical sophistication. In 1998, mobile phones were still in the process of becoming compact and affordable devices that could be widely utilized in both developed and developing countries. There were "only" 300 million mobile subscribers in the world [1]. Cellular networks were among the first privatized telecommunication markets, and competition turned the devices into fashion accessories with attractive designs that could be individualized. The service was circumscribed to telephony and text messaging, but it was groundbreaking in that, for the first time, telecommunication was between people rather than locations. Wireless networks have changed dramatically over the past few decades, enabling this revolution in service provisioning and making it possible to accommodate the ensuing dramatic growth in traffic. There are many contributing components, including new air interfaces for faster transmission, channel coding for enhanced reliability, improved source compression to remove redundancies, and leaner protocols to reduce overheads. Signal processing is at the core of these improvements, but nowhere has it played a bigger role than in the development of multiantenna communication. This article tells the story of how major signal processing advances have transformed the early multiantenna concepts into mainstream technology over the past 25 years. The story therefore begins somewhat arbitrarily in 1998. A broad account of the state-of-the-art signal processing techniques for wireless systems by 1998 can be found in [2], and its contrast with recent textbooks such as [3]-[5] reveals the dramatic leap forward that has taken place in the interim.

翻译：无线通信技术在过去25年间取得了巨大进步，无论是从社会普及程度还是技术复杂性来看皆是如此。1998年，移动电话仍处于向紧凑便携设备转型的阶段，这类设备有望在发达国家和发展中国家广泛普及。当时全球仅有3亿移动用户[1]。蜂窝网络是最早实现私有化的电信市场之一，市场竞争促使手机成为兼具时尚设计和个性化功能的配件。服务范围限于语音通话和短信，但这一突破性意义在于：电信首次实现了人与人之间的通信，而非地点之间的通信。过去几十年间，无线网络发生了翻天覆地的变化，推动了服务提供方式的革命，并使得随之而来的流量爆炸式增长成为可能。这得益于多项技术的共同进步，包括提升传输速率的新空中接口、增强可靠性的信道编码、消除冗余的改进信源压缩，以及降低开销的精简协议。信号处理正是这些改进的核心，而它在多天线通信技术发展中的作用尤为突出。本文讲述了在过去25年间，重大信号处理进步如何将早期多天线概念转化为主流技术的故事。这一故事大致始于1998年。关于1998年无线系统信号处理技术最新进展的全面综述可参见文献[2]，将其与近期教科书[3]-[5]对比，即可发现这一时期技术实现的跨越式发展。