Wireless Access for Ultra-Reliable Low-Latency Communication: Principles and Building Blocks

URLLC is an important new feature brought by 5G, with a potential to support a vast set of applications that rely on mission-critical links. In this article, we first discuss the principles for supporting URLLC from the perspective of the traditional assumptions and models applied in communication/information theory. We then discuss how these principles are applied in various elements of system design, such as use of various diversity sources, design of packets, and access protocols. The important message is that there is a need to optimize the transmission of signaling information, as well as a need for lean use of various sources of diversity.

Introduction

The big difference between the fifth generation (5G) and the previous generations of mobile wireless systems is that 5G is natively addressing two generic modes of machine-type communications (MTC): ultra-reliable low-latency communications (URLLC) and massive MTC (mMTC). URLLC is arguably the most innovative feature brought in 5G, as it will be used for mission critical communications, like reliable remote action with robots or coordination among vehicles. Ultra-reliable communication [1] is potentially an enabler of a vast set of applications, some of which are yet unknown. To put this in perspective, wireless connectivity and embedded processing have significantly transformed many products by expanding functionality and transcending the traditional product boundaries [2]; for example, a product stays connected to its manufacturer through its lifetime for maintenance and update. Ultra-reliable connectivity brings this transformation to the next level: Once a system designer can safely assume that wireless connectivity is “truly anywhere and anytime,” for example, guaranteed > 99.999 percent of the time, the approach to system design and operation changes fundamentally. An example is Industrie 4.0, where different parts of an object or a machine need not be physically attached as long as they can use mission-critical ultra-reliable links to work in concert toward accomplishing a production task.