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

Abstract

Ultra-reliable low latency communication (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 the system design, such as use of various diversity sources, design of packets and access protocols. The important messages are that there is a need to optimize the transmission of signaling information, as well as a need for a lean use of various sources of diversity.

Joint Power Control and Rate Allocation Enabling Ultra-Reliability and Energy Efficiency in SIMO Wireless Networks

“…The principles for supporting URLLC are discussed in [3] by considering, for instance, the design of packets and access protocols. In [6], [7] authors outline the key technical requirements and architectural approaches pertaining to wireless access protocols, radio resource management aspects, next generation core networking capabilities, edge-cloud, and edge artificial intelligence capabilities, and propose first avenues for specific solutions to enable the Tactile Internet revolution.…”

“…However, a dedicated receiver on each branch may be needed for systems that transmit continuously in order to simultaneously and continuously monitor SIR on each branch. In this work 3 T 0 may send some pilot symbols as overhead when transmitting to R 0 for the latter be able to estimate the CSI. be able to estimate the CSI.…”

“…Notice that this overhead can be accounted as part of the constraint r min (check Section III); while although we assume perfect CSI, the imperfectness may be modeled as a loss in the SIR as in [12], [26]. 4 Diversity is an important building block for supporting URLLC [3], and herein we focus simply on spatial diversity taking advantage of the multiple receive antennas. Notice that other diversity sources such as frequency, time and/or polarization could also be available [28], and our results and methodology can be easily re-utilized/extended to cover such scenario.…”

“…As p 0 increases T 0 is capable of transmitting with a larger bit rate for the same reliability target, thus, the curve r 0 vs p 0 with P[O(r 0 , p 0 )] = ε is increasing on p 0 as shown in the figure. Let us focus the attention on the red point on the curve P[O(r 0 , p 0 )] = ε, and notice that for any positive α 1 and α 2 , P[O(r 0 − α 1 , p 0 + α 2 )] < ε holds, but according to (3) and based on the fact that ε ≪ 1 we have that EE(r 0 − α 1 , p 0 + α 2 , β) < EE(r 0 , p 0 , β), thus, the solution of P1 lies on the curve P[O(r 0 , p 0 )] = ε. Additionally, P1 has a non-empty solution when P[O(r min , p max )] ≤ ε. Notice that the solutions of P1, named p * 0 and r * 0 , must depend on information easy to obtain for T 0 .…”

Achieving Ultra-Reliable Communication via CRAN-Enabled Diversity Schemes

“…Multi-connectivity with signal-to-noise ratio (SNR) gain at receiver side using schemes like joint decoding, selection combining and maximal ratio combining (MRC) are discussed in [5]. Use of various diversity sources, packet design and access protocols as key component supporting URLLC in wireless communication system are discussed in [6]. Authors in [7] discussed the way to offer URLLC without intervention in physical layer design by using interface diversity and integrating multiple com-munication interfaces, where each interface is based on different technology.…”