A Downlink Puncturing Scheme for Simultaneous Transmission of URLLC and eMBB Traffic by Exploiting Data Similarity

Abstract

Ultra Reliable and Low Latency Communications (URLLC) is deemed to be an essential service in 5G systems and beyond (also called 6G) to accommodate a wide range of emerging applications with stringent latency and reliability requirements. Coexistence of URLLC alongside other service categories calls for developing spectrally efficient multiplexing techniques. Specifically, coupling URLLC and conventional enhanced Mobile BroadBand (eMBB) through superposition/puncturing naturally arises as a promising option due to the tolerance of the latter in terms of latency and reliability. The idea here is to transmit URLLC packets (typically sporadic and of short size) over resources occupied by ongoing eMBB transmissions while minimizing the impact on the eMBB transmissions. In this paper, we propose a novel downlink URLLC-eMBB multiplexing technique that exploits possible similarities among URLLC and eMBB symbols, with the objective of reducing the size of the punctured eMBB symbols. We propose that the base station (BS) scans the eMBB traffic' symbol sequences and punctures those that have the highest symbol similarity with that of the URLLC users to be served. As the eMBB and URLLC may use different constellation sizes, we introduce the concept of symbol region similarity to accommodate the different constellations. We assess the performance of the proposed scheme analytically, where we derive closed-form expressions for the symbol error rate (SER) of the eMBB and URLLC services. We also derive an expression for the eMBB loss function due to puncturing in terms of the eMBB SER. We demonstrate through numerical and simulation results the efficacy of the proposed scheme where we show that 1) the eMBB spectral efficiency is improved by puncturing fewer symbols, 2) the SER and reliability performance of eMBB are improved, and 3) the URLLC data is accommodated within the specified delay constraint while maintaining its reliability, 4) and the proposed strategy has polynomial time complexity making it an efficient solution to be used in practice.

Resource Allocation for Co-Existence of eMBB and URLLC Services in 6G Wireless Networks: A Survey

“…Thus, an adjustment in rate splitting factor results URLLC sum-rate improvement based on average SNR rather than instantaneous channel state information (CSI). A eMBB-URLLC multiplexing technique for a downlink transmission scenario is proposed in [50] with an objective of reducing the size of punctured eMBB symbols by exploiting possible similarities between two types of symbols. For this, BS only scans the eMBB traffic symbols which are punctured by URLLC users that have maximum symbol similarity.…”

“…For the eMBB and URLLC coexistence models, three main network slicing techniques have been utilized in various works in the literature: OMA, NOMA and RSMA. Works in [27], [47] and [48] demonstrated use of OMA and NOMA by adopting both puncturing and superposition schemes whereas [49], [50] and [52] used the RSMA as a superior network slicing technique than OMA and NOMA. Orthogonalization and decoding interference are the traditional techniques to mitigate the interference in OMA and NOMA respectively.…”

Scheduling of Heterogeneous Services by Resolving Conflicts

“…We focus, in this work, on downlink scheduling, similarly to the majority of the existing related works in the literature, e.g., [13]- [23]. The system model and the scheduling framework follow the structure of [1], [8].…”

“…The above operation is described in Lines 1-3. Afterwards, in Line 4, we remove the overlapping blocks with the higher aggregated throughput loss (within each category), using (13).…”

“…Moreover, at present, URLLC services are expected to have lower traffic volumes than eMBB services [12], but this will not hold in the future for applications such as virtual reality and haptics. In this framework, the design of radio resource allocation strategies for URLLC traffic, when coexisting with eMBB, has been a focal point of recent research efforts [13]- [16].…”