152 research outputs found
Random Access based Reliable Uplink Communication and Power Transfer using Dynamic Power Splitting
Large communication networks, e.g. Internet of Things (IoT), are known to be vulnerable to co-channel interference. One possibility to address this issue is the use of orthogonal multiple access (OMA) techniques. However, due to a potentially very long duty cycle, OMA is not well suited for such schemes. Instead, random medium access (RMA) appears more promising. An RMA scheme is based on transmission of short data packets with random scheduling, which is typically unknown to the receiver. The received signal, which consists of the overlapping packets, can be used for energy harvesting and powering of a relay device. Such an energy harvesting relay may utilize the energy for further information processing and uplink transmission. In this paper, we address the design of a simultaneous information and power transfer scheme based on randomly scheduled packet transmissions and reliable symbol detection. We formulate a prediction problem with the goal to maximize the harvested power for an RMA scenario. In order to solve this problem, we propose a new prediction method, which shows a significant performance improvement compared to the straightforward baseline scheme. Furthermore, we investigate the complexity of the proposed method and its vulnerability to imperfect channel state information
Receive Beamforming for Ultrareliable Random Access based SWIPT
Ultrareliable uplink communication based on random access poses novel research challenges for the receiver design. Here, the uncertainty imposed by the random access and a large amount of interfering transmissions is the limiting factor for the system performance. Recently, this type of communication has been addressed in context of simultaneous wireless information and power transfer (SWIPT). The need to adapt the power splitting to the signal states according to the underlying random access has been tackled by introducing a predictor, which determines the valid states of the received signal based on the long-term observation. Hence, the power splitting factor is scaled accordingly in order to guarantee ultrareliable communication and maximized harvested energy.In this work, we extend the considered SWIPT scenario by introducing multiple antennas at the receiver side. Through this, the received energy can be substantially increased, if the energy harvesting parameters and the spatial filter coefficients are jointly optimized. Hence, we propose an optimization procedure, which aims at maximizing the harvested energy under the ultrareliability constraint. The mentioned prediction method is then combined with the optimization solution and the resulting system performance is numerically evaluated
Ultra reliable low latency communication in MTC network
Abstract. Internet of things is in progress to build the smart society, and wireless networks are critical enablers for many of its use cases. In this thesis, we present some of the vital concept of diversity and multi-connectivity to achieve ultra-reliability and low latency for machine type wireless communication networks. Diversity is one of the critical factors to deal with fading channel impairments, which in term is a crucial factor to achieve targeted outage probabilities and try to reach out such requirement of five 9’s as defined by some standardization bodies. We evaluate an interference-limited network composed of multiple remote radio heads connected to the user equipment. Some of those links are allowed to cooperate, thus reducing interference, or to perform more elaborated strategies such as selection combining or maximal ratio combining. Therefore, we derive their respective closed-form analytical solutions for respective outage probabilities. We provide extensive numerical analysis and discuss the gains of cooperation and multi-connectivity enabled to be a centralized radio access network
Statistical Tools and Methodologies for Ultrareliable Low-Latency Communications -- A Tutorial
Ultra-reliable low-latency communication (URLLC) constitutes a key service
class of the fifth generation and beyond cellular networks. Notably, designing
and supporting URLLC poses a herculean task due to the fundamental need to
identify and accurately characterize the underlying statistical models in which
the system operates, e.g., interference statistics, channel conditions, and the
behavior of protocols. In general, multi-layer end-to-end approaches
considering all the potential delay and error sources and proper statistical
tools and methodologies are inevitably required for providing strong
reliability and latency guarantees. This paper contributes to the body of
knowledge in the latter aspect by providing a tutorial on several statistical
tools and methodologies that are useful for designing and analyzing URLLC
systems. Specifically, we overview the frameworks related to i) reliability
theory, ii) short packet communications, iii) inequalities, distribution
bounds, and tail approximations, iv) rare events simulation, vi) queuing theory
and information freshness, and v) large-scale tools such as stochastic
geometry, clustering, compressed sensing, and mean-field games. Moreover, we
often refer to prominent data-driven algorithms within the scope of the
discussed tools/methodologies. Throughout the paper, we briefly review the
state-of-the-art works using the addressed tools and methodologies, and their
link to URLLC systems. Moreover, we discuss novel application examples focused
on physical and medium access control layers. Finally, key research challenges
and directions are highlighted to elucidate how URLLC analysis/design research
may evolve in the coming years.Comment: Accepted in IEEE Proceedings of the IEEE. 40 pages, 20 figures, 11
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Joint Power and Blocklength Optimization for URLLC in a Factory Automation Scenario
Ultra-reliable and low-latency communication (URLLC) is one of three pillar applications defined in the fifth generation new radio (5G NR), and its research is still in its infancy due to the difficulties in guaranteeing extremely high reliability (say 10 -9 packet loss probability) and low latency (say 1 ms) simultaneously. In URLLC, short packet transmission is adopted to reduce latency, such that conventional Shannon's capacity formula is no longer applicable, and the achievable data rate in finite blocklength becomes a complex expression with respect to the decoding error probability and the blocklength. To provide URLLC service in a factory automation scenario, we consider that the central controller transmits different packets to a robot and an actuator, where the actuator is located far from the controller, and the robot can move between the controller and the actuator. In this scenario, we consider four fundamental downlink transmission schemes, including orthogonal multiple access (OMA), non-orthogonal multiple access (NOMA), relay-assisted, and cooperative NOMA (C-NOMA) schemes. For all these transmission schemes, we aim for jointly optimizing the blocklength and power allocation to minimize the decoding error probability of the actuator subject to the reliability requirement of the robot, the total energy constraints, as well as the latency constraints. We further develop low-complexity algorithms to address the optimization problems for each transmission scheme. For the general case with more than two devices, we also develop a low-complexity efficient algorithm for the OMA scheme. Our results show that the relay-assisted transmission significantly outperforms the OMA scheme, while the NOMA scheme performs well when the blocklength is very limited. We further show that the relay-assisted transmission has superior performance over the C-NOMA scheme due to larger feasible region of the former scheme
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