Ultra-Dense Networks for 5G and Beyond

7Massive MIMO for High‐performance Ultra‐dense Networks in the Unlicensed Spectrum

Adrian Garcia‐Rodriguez¹, Giovanni Geraci², Lorenzo Galati‐Giordano¹ and David López‐Pérez¹

¹Nokia Bell Labs, Dublin, Ireland

²Department of Information and Communication Technologies, Universitat Pompeu Fabra, Spain

7.1 Introduction

As a result of the ever‐increasing wireless data demand, the wireless industry has started to embrace unlicensed spectrum bands to enhance the performance of cellular networks 1–4. For instance, mobile operators can improve their offered peak data rates via the aggregation of licensed and unlicensed bands, extend the coverage for their users, and/or offload best‐effort traffic from the scarce and costly licensed bands below 6 GHz.

Access points (APs) operating in the unlicensed spectrum can complement existing small cell base stations operating in the licensed bands. A variety of technologies have been developed with the purpose of enabling such inter‐working in recent years:

1. Long‐term evolution (LTE) wireless local area network (WLAN) aggregation (LWA)‐like technologies realize licensed unlicensed spectrum aggregation through Wi‐Fi APs. Fundamentally, LWA splits protocol data units (PDUs) of a bearer at the packet data convergence protocol (PDCP) layer, transmitting them either through one of the LTE or Wi‐Fi radio links by fast switching or through both radio links to enhance capacity. This is achieved by leveraging the dual connectivity framework developed by the ...