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Low-cost, resource-constrained, maintenance-free, and energy-harvesting (EH) Internet of Things (IoT) devices, referred to as zero-energy devices (ZEDs), are rapidly attracting attention from industry and academia due to their myriad of applications. To date, such devices remain primarily unsupported by modern IoT connectivity solutions due to their intrinsic fabrication, hardware, deployment, and operation limitations, while lacking clarity on their key technical enablers and prospects. Herein, we address this by discussing the main characteristics and enabling technologies of ZEDs within the next generation of mobile networks, specifically focusing on unconventional EH sources, multi-source EH, power management, energy storage solutions, manufacturing material and practices, backscattering, and low-complexity receivers. Moreover, we highlight the need for lightweight and energy-aware computing, communication, and scheduling protocols, while discussing potential approaches related to TinyML, duty cycling, and infrastructure enablers like radio frequency wireless power transfer and wake-up protocols. Challenging aspects and open research directions are identified and discussed in all the cases. Finally, we showcase an experimental ZED proof-of-concept related to ambient cellular backscattering., Comment: 8 pages, 4 Figures

Uplink configured Grant allocation has been introduced in 3rd Generation Partnership Project New Radio Release 15. This is beneficial in supporting Ultra-Reliable and Low Latency Communication for industrial communication, a key Fifth Generation mobile communication usage scenario. This scheduling mechanism enables a user with periodic traffic to transmits its data readily and bypasses the control signaling entailed to scheduling requests and scheduling grants and provides low latency access. To facilitate ultra-reliable communication, the scheduling mechanism can allow users to transmit consecutive redundant transmissions in a pre-defined period. However, if the traffic is semi-deterministic, the current standardized configured grant allocation is not equipped to emulate the traffic as the configured grant's period is pre-configured and fixed. This article describes the recent advancements in the standardization process in Release 15 and 16 for configured grant allocation and the prospective solutions to accommodate semi-deterministic traffic behavior for configured grant allocations., Comment: Accepted in IEEE Communications Standard Magazine 2021, 5 figures

Configured Grant-based allocation has been adopted in New Radio 3rd Generation Partnership Project Release 16. This scheme is beneficial in supporting Ultra-Reliable and Low Latency Communication for industrial communication, a key Fifth Generation mobile communication usage scenario. This scheduling mechanism enables a user with a periodic traffic to transmit its data readily and bypasses the signaling entailed to scheduling requests and scheduling grants; and provides low latency access. To facilitate ultra-reliable communication, the scheduling mechanism can allow the user to transmit redundant transmissions at consecutive repetition occasions in a pre-defined period. However, for the user with semi-deterministic traffic, the reliability and latency performance with Configured Grant-based allocation deteriorates. This can be due to, e.g., late data arrival in the buffer, and the user unable to transmit its repetitions, which leads to reliability degradation. To improve the Configured Grant reliability performance with semi-deterministic traffic, we consider various allocation designs utilizing, e.g., additional unlicensed spectrum, or flexible transmission in a Configured Grant period, or allowing time-gaps between the repetitions, etc. These enhancements could be a stepping-stone for Sixth Generation Configured Grant models., Comment: 6G Wireless Summit 2020, poster paper, 2 pages

As wireless communication becomes an ever-more evolving and pervasive part of the existing world, system capacity and Quality of Service (QoS) provisioning are becoming more critically evident. In order to improve system capacity and QoS, it is mandatory that we pay closer attention to operational bandwidth efficiency issues. We address this issue for two operators' spectrum sharing in the same geographical area. We model and analyze interactions between the competitive operators coexisting in the same frequency band as a strategic noncooperative game, where the operators simultaneously share the spectrum dynamically as per their relative requirement. If resources are allocated in a conventional way (static orthogonal allocation), spectrum utilization becomes inefficient when there is load asymmetry between the operators and low inter-operator interference. Theoretically, operators can share resources in a cooperative manner, but pragmatically they are reluctant to reveal their network information to competitors. By using game theory, we design a distributed implementation, in which self-interested operators play strategies and contend for the spectrum resources in a noncooperative manner. We have proposed two game theoretic approaches in the thesis, one using a virtual carrier price; and the other based on a mutual history of favors. The former approach takes into account a penalty proportional to spectrum usage in its utility function, whereas in the latter, operators play strategies based on their history of interactions, i.e., how well the other behaved in the past. Finally, based on the simulations, we assess the performance of the proposed game theoretic approaches in comparison to existing conventional allocations., Comment: Master Thesis, Published on 25/8/2014, Aalto University (https://aaltodoc.aalto.fi/handle/123456789/13922)

Currently, mobile network operators are allocated spectrum bands on an exclusive basis. While this approach facilitates interference control, it may also result in low spectrum utilization efficiency. Inter-operator spectrum sharing is a potential method to enhance spectrum utilization. In order to realize it, a protocol to coordinate the actions of operators is needed. We propose a spectrum sharing protocol which is distributed in nature, it does not require operator-specific information exchange and it incurs minimal communication overhead between the operators. Operators are still free to decide whether they share spectrum or not as the protocol is based on the book keeping of spectrum usage favors, asked and received by the operators. We show that operators can enhance their QoS in comparison with traditional orthogonal spectrum allocation while also maintaining reciprocity i.e. no operator benefits over the other in the long run. We demonstrate the usability of the proposed protocol in an indoor deployment scenario with frequent network load variations as expected to have in small cell deployments., Comment: Published in proceedings of 23rd edition of European Conference on Networks and Communications (EuCNC), Bologna, Jun. 2014

We consider spectrum sharing between a limited set of operators having similar rights for accessing spectrum. A coordination protocol acting on the level of the Radio Access Network (RAN) is designed. The protocol is non-cooperative, but assumes an agreement to a set of negotiation rules. The signaling overhead is low, and knowledge of competitor's channel state information is not assumed. No monetary transactions are involved; instead, spectrum sharing is based on a RAN-internal virtual currency. The protocol is applicable in a scenario of mutual renting and when the operators form a spectrum pool. The protocol is reactive to variations in interference and load of the operators, and shows gains in a simulated small cell scenario compared to not using any coordination protocol., Comment: To be published in IEEE Communications Magazine, Jul. 2015

We consider two small cell operators deployed in the same geographical area, sharing spectrum resources from a common pool. A method is investigated to coordinate the utilization of the spectrum pool without monetary transactions and without revealing operator-specific information to other parties. For this, we construct a protocol based on asking and receiving spectrum usage favors by the operators, and keeping a book of the favors. A spectrum usage favor is exchanged between the operators if one is asking for a permission to use some of the resources from the pool on an exclusive basis, and the other is willing to accept that. As a result, the proposed method does not force an operator to take action. An operator with a high load may take spectrum usage favors from an operator that has few users to serve, and it is likely to return these favors in the future to show a cooperative spirit and maintain reciprocity. We formulate the interactions between the operators as a repeated game and determine rules to decide whether to ask or grant a favor at each stage game. We illustrate that under frequent network load variations, which are expected to be prominent in small cell deployments, both operators can attain higher user rates as compared to the case of no coordination of the resource utilization., Comment: To be published in proceedings of IEEE International Conference on Communications (ICC) at London, Jun. 2015