Design and performance evaluation of contention-based transmission schemes for URLLC services

Abstract

We investigate in this paper uplink multiple transmission schemes for 5G Ultra-Reliable Low Latency Communications (URLLC) traffic. The URLLC class of services has been defined for applications requiring extremely stringent latency and reliability. We show that, in systems with episodic traffic and many users compared with the number of transmission resources, randomly transmitting multiple copies of a packet allows to meet the URLLC requirements. We develop analytical models for the packet loss rate for two contention based multiple transmission schemes and show that one outperforms the other in the parameter range for which the URLLC requirements are met. We then propose an advanced replication scheme where positions for the different replicas are pre-allocated to users so that users have pairwise-distinct positions. We show that this advanced scheme achieves very high reliability with low resource consumption.

Improved Exact Evaluation of Equal-Gain Diversity Receivers in Rayleigh Fading Channels

“…Monte-Carlo simulations validate our analysis. 2 For the analysis, we employed the mathematical software Wolfram Mathematica running over a 1.4 GHz Quad-Core Intel i5 processor.…”

“…To evaluate the efficiency of ( 17), we take as an example 10 test scenarios which are presented in Table 1. In this table, f † Z (z) denotes the PDF of Z obtained by numerically evaluating the multi-fold Brennan's integral [19], 3 and (1) and (2) respectively denote the absolute errors for (17) and [22, eq. ( 4)], computed by…”

“…One of the fifth-generation (5G) mobile systems use cases is associated with ultra-reliable-low-latency communications (URLLC) [1], [2], that among some technical aspects, imply a very high reliability, or equivalently, a very low outage probability (OP) [3]. To guarantee the values set for these key-performance indicators (KPIs), future wireless systems are expected to employ different techniques, among which we can highlight spatial diversity obtained with a large number of receiving antennas [4].…”

Optimal random packet replication policies for IIoT in 5G and Beyond considering different feedback regimes

“…There have been several propositions in this direction. Authors in [10] proposed to send these replicas in a contention-based manner on different frequency resources on consecutive TTI, while in [4] the authors considered a more flexible scheme where replicas can be sent on any of the available time-frequency resources before the delay budget expires. Other sets of works consider the presence of ACKs that cause early stopping before all the replicas are transmitted.…”

“…• We develop mathematical models for the loss probability for each of the policies. While the model for the blind one-shot case is derived from [4], the models for the other schemes are novel. In addition, these models consider sporadic and asynchronous traffic patterns, dislike other works that consider synchronous and cyclic traffic ( [6], [7]) and explicitly integrate the interaction between interfering users in an industrial setting where all devices are configured for following the same transmission policy.…”