Search

We consider a fully-loaded ground wireless network supporting unmanned aerial vehicle (UAV) transmission services. To enable the overload transmissions to a ground user (GU) and a UAV, two transmission schemes are employed, namely non-orthogonal multiple access (NOMA) and relaying, depending on whether or not the GU and UAV are served simultaneously. Under the assumption of the system operating with infinite blocklength (IBL) codes, the IBL throughputs of both the GU and the UAV are derived under the two schemes. More importantly, we also consider the scenario in which data packets are transmitted via finite blocklength (FBL) codes, i.e., data transmission to both the UAV and the GU is performed under low-latency and high reliability constraints. In this setting, the FBL throughputs are characterized again considering the two schemes of NOMA and relaying. Following the IBL and FBL throughput characterizations, optimal resource allocation designs are subsequently proposed to maximize the UAV throughput while guaranteeing the throughput of the cellular user. Moreover, we prove that the relaying scheme is able to provide transmission service to the UAV while improving the GU's performance, and that the relaying scheme potentially offers a higher throughput to the UAV in the FBL regime than in the IBL regime. On the other hand, the NOMA scheme provides a higher UAV throughput (than relaying) by slightly sacrificing the GU's performance. [ABSTRACT FROM AUTHOR]

We study a multi-node Internet of Things system supporting low-latency high-reliability communication to a destination node. The rest of the nodes are potential relays in which the best single relay (BSR) is selected to assist the transmission to the destination. The system operates with finite blocklength (FBL) codes to satisfy the low-latency requirement. The scope of this work is to derive and improve the FBL performance of the considered BSR system. On the one hand, we extend Polyanskiy's FBL model of a single-hop scenario to the considered relaying system and derive the corresponding achievable reliability. On the other hand, by employing a practical FBL coding scheme, namely polar codes (PCs), an FBL performance bound attainable by a low-complexity coding scheme is presented. In particular, we provide a reliability bound of a dynamic-length PC scheme. Addressing a source-driven BSR strategy, as well as a relay-driven BSR strategy, we investigate two viable strategies for relay selection in the FBL regime, while the corresponding performance under an infinite blocklength (IBL) assumption serves as a reference. We prove that the two BSR strategies have the same performance in the IBL regime, while the relay-driven strategy is significantly more reliable than the source-driven one when considering the FBL regime. Furthermore, following the derived FBL performance model, we provide an optimal design to minimize the overall error probability via blocklength allocation. Through simulation and numerical investigations, we show the appropriateness of the proposed analytical model. Moreover, we evaluate both the achievable performance with FBLs and the performance of PCs in the considered scenarios while comparing the source-driven and relay-driven strategies. [ABSTRACT FROM AUTHOR]

This paper considers simultaneous wireless information and power transfer (SWIPT) mechanisms in a relaying-assisted ultra-reliable low latency communication network operating with finite blocklength codes. The reliability of the network is maximized by the optimal selection of SWIPT parameters under both a power splitting (PS) protocol and a time switching (TS) protocol. In addition, we propose a protocol to improve the reliability performance by introducing a tradeoff between the PS and TS protocols. To further improve the reliability, a joint design is provided, which aligns the optimal selection of SWIPT parameters together with a blocklength allocation between two relaying hops. Via simulations, we validate our analytical model and show that the proposed algorithm achieves the same performance as that obtained with exhaustive search. In addition, we evaluate the considered network, and characterize the impact of blocklength, transmit power, and packet size on the reliability of the considered SWIPT-enabled relaying network. Finally, the performance advantages of the proposed protocol (in comparison with the PS and TS protocols) and the proposed joint designs are investigated. [ABSTRACT FROM AUTHOR]

Under the assumption of outdated channel state information at the source, we maximize the finite blocklength throughput of a two-hop relaying system while guaranteeing a reliability constraint. We investigate the tradeoff between the choice of so-called scheduling weights to avoid transmission errors and the resulting coding rate. We show that the corresponding maximization of the throughput can be solved efficiently by iterative algorithms that require a recomputation of the scheduling weights prior to each transmission. Thus, we also study heuristics relying on choosing the scheduling weights only once. Through numerical analysis, we first provide insights to the structure of the throughput under different scheduling weights and channel correlation coefficients. We then turn to the comparison of the optimal scheduling with the heuristic and show that the performance gap between them is only significant for relaying systems with high average signal-to-noise ratios on the backhaul and relaying link. In particular, the optimal scheduling scheme provides most value in case that the data transmission is subject to strict reliability constraints, justifying the significant additional computational burden. [ABSTRACT FROM AUTHOR]

In this paper, the blocklength-limited performance of a relaying system is studied, where channels are assumed to experience quasi-static Rayleigh fading while at the same time only the average channel state information (CSI) is available at the source. Both the physical-layer performance (blocklength-limited throughput) and the link-layer performance (effective capacity) of the relaying system are investigated. We propose a simple system operation by introducing a factor based on which we weight the average CSI and let the source determine the coding rate accordingly. We show that both the blocklength-limited throughput and the effective capacity are quasi-concave in the weight factor. Through numerical analysis, we investigate the relaying performance with average CSI while considering perfect CSI scenario and direct transmission as comparison schemes. We observe that relaying is more efficient than direct transmission in the finite blocklength regime. Moreover, this performance advantage of relaying under the average CSI scenario is more significant than under the perfect CSI scenario. Finally, the speed of convergence (between the blocklength-limited performance and the performance with infinite blocklengths) in relaying system is faster in comparison to the direct transmission under both the average CSI scenario and the perfect CSI scenario. [ABSTRACT FROM PUBLISHER]

In this paper, relaying performance is studied under the finite-blocklength regime. The overall error probability of relaying is derived. Moreover, we investigate the blocklength-limited capacity (BL-capacity) of relaying. We prove that the BL-capacity of relaying is quasiconcave in the overall error probability. Therefore, the BL-capacity has a global maximum value, which can be achieved by choosing an appropriate error probability. Through numerical investigations, we validate our analytical model and compare the performance of relaying under the finite-blocklength regime versus the Shannon capacity regime. [ABSTRACT FROM AUTHOR]

We consider a two-phase relaying system with finite blocklengths. We study the performance difference of relaying under the finite blocklength regime as well as under the Shannon capacity regime. Most importantly, we are interested in the conditions that lead to a higher performance of relaying under the finite blocklength regime. We find that these situations are characterized by error probabilities of relaying, e.g., the overall error probability of relaying and the error probability of the bottleneck link of relaying. We identify scenarios where relaying outperforms direct transmission under the finite blocklength regime even if their performances are similar under the Shannon capacity regime. Moreover, we prove that under these scenarios the performance advantage of relaying is more significant with short blocklengths. Finally, numerical results are provided and discussed. [ABSTRACT FROM PUBLISHER]