| 1. |
- Azari, Amin, et al.
(författare)
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Energy-Efficient and Reliable IoT Access Without Radio Resource Reservation
- 2021
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Ingår i: IEEE TRANSACTIONS ON GREEN COMMUNICATIONS AND NETWORKING. - : Institute of Electrical and Electronics Engineers (IEEE). - 2473-2400. ; 5:2, s. 908-920
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Tidskriftsartikel (refereegranskat)abstract
- One of the major challenges for Internet-of-Things applications is that the existing cellular technologies do not support the uplink IoT traffic in an energy-efficient manner. There are two principal ways for serving the uplink IoT traffic: grant-based (i.e., scheduled) and grant-free (i.e., random access). Grant-based access provides fine-grained control of reliability and latency at the cost of energy consumption required for signaling. Grant-free access removes the signaling overhead at the cost of looser control of performance in terms of reliability and latency. However, a precise analysis of reliability, latency and energy performance of grant-free access (GFA) is largely missing. This article focuses on a GFA-type protocol, in which a device transmits several packet replicas, asynchronously with respect to the other devices. Using stochastic geometry, we derive closed-form expressions for reliability, delay, and energy consumption, which can be used to identify the tradeoffs among these performance parameters. In order to improve the performance of the protocol, we develop a receiver that leverages the random timing and frequency offsets among the devices in order to facilitate resolution of collisions. This is complemented by a per-device adaptive scheme that controls the number of transmitted replicas. The evaluation confirms the validity of the analysis and the potential of the proposed solution, identifying operating regions in which GFA outperforms the grant-based access.
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| 2. |
- Azari, Amin, 1988-
(författare)
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Energy Efficient Machine-Type Communications over Cellular Networks : A Battery Lifetime-Aware Cellular Network Design Framework
- 2016
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Internet of Things (IoT) refers to the interconnection of uniquely identifiable smart devices which enables them to participate more actively in everyday life. Among large-scale applications, machine-type communications (MTC) supported by cellular networks will be one of the most important enablers for the success of IoT. The existing cellular infrastructure has been optimized for serving a small number of long-lived human-oriented communications (HoC) sessions, originated from smartphones whose batteries are charged in a daily basis. As a consequence, serving a massive number of non-rechargeable machine-type devices demanding a long battery lifetime is a big challenge for cellular networks.The present work is devoted to energy consumption modeling, battery lifetime analysis, and lifetime-aware network design for massive MTC services over cellular networks. At first, we present a realistic model for energy consumption of machine devices in cellular connectivity, which is employed subsequently in deriving the key performance indicator, i.e. network battery lifetime. Then, we develop an efficient mathematical foundation and algorithmic framework for lifetime-aware clustering design for serving a massive number of machine devices. Also, by extending the developed framework to non-clustered MTC, lifetime-aware uplink scheduling and power control solutions are derived. Finally, by investigating the delay, energy consumption, spectral efficiency, and battery lifetime tradeoffs in serving coexistence of HoC and MTC traffic, we explore the ways in which energy saving for the access network and quality of service for HoC traffic can be traded to prolong battery lifetime for machine devices.The numerical and simulation results show that the proposed solutions can provide substantial network lifetime improvement and network maintenance cost reduction in comparison with the existing approaches.
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| 3. |
- Azari, Amin, 1988-, et al.
(författare)
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Grant-Free Radio Access for Cellular IoT
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Radio resource management (RRM) is a major factor affecting the delay, reliability, and energy consumption of Internet of Things (IoT) communications. This article is focused on grant-free access, a class of techniques suited to support massive IoT connectivity. Within the proposed scheme, the IoT devices transmit multiple replicas of the same packet. In addition to that, the receiver makes use of the random timing and frequency offsets in order to carry out Successive Interference Cancellation (SIC). The system performance is investigated by using a model based on stochastic geometry, leading to closed-form expressions for the key performance indicators, such as reliability and battery lifetime. The framework allows optimization of the number of replicas per device. This results in overall improvement of the energy consumption, delay and reliability, at the expense of more complex processing at the Base Station. The evaluation results indicate that the proposed data transmission and reception schemes can significantly prolong battery lifetime of IoT devices by removing the need for connection establishment and reducing the number of retransmissions. The obtained results also indicate existence of traffic-load regions, where grant-free radio access outperforms the grant-based one, which is used in LTE and NB-IoT systems. These results pave the way for enabling intelligent grant-based/free operation mode switching in 5G networks.
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| 4. |
- Azari, Amin, et al.
(författare)
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Grant-Free Radio Access for Short-Packet Communications over 5G Networks
- 2017
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Ingår i: 2017 IEEE Global Communications Conference, GLOBECOM 2017 - Proceedings. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781509050192
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Konferensbidrag (refereegranskat)abstract
- Radio access management plays a vital role in delay and energy consumption of connected devices. The radio access in existing cellular networks is unable to efficiently support massive connectivity, due to its signaling overhead. In this paper, we investigate an asynchronous grant-free narrowband data transmission protocol that aims to provide low energy consumption and delay, by relaxing the synchronization/reservation requirement at the cost of sending several packet copies at the transmitter side and more complex signal processing at the receiver side. Specifically, the timing and frequency offsets, as well as sending of multiple replicas of the same packet, are exploited as form of diversities at the receiver-side to trigger successive interference cancellation. The proposed scheme is investigated by deriving closed-form expressions for key performance indicators, including reliability and battery-lifetime. The performance evaluation indicates that the scheme can be tuned to realize long battery lifetime radio access for low-complexity devices. The obtained results indicate existence of traffic load regions, where synchronous access outperforms asynchronous access and vice versa.
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| 5. |
- Azari, Amin, 1988-, et al.
(författare)
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Latency-Energy Tradeoff based on Channel Scheduling and Repetitions in NB-IoT Systems
- 2018
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Ingår i: 2018 IEEE Global Communications Conference, GLOBECOM 2018 - Proceedings. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538647271
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Konferensbidrag (refereegranskat)abstract
- Narrowband Internet of Things (NB-IoT) is the latest IoT connectivity solution presented by the 3rd generation partnership project (3GPP). NB-IoT introduces coverage classes and offers a significant link budget improvement by allowing repeated transmissions by nodes that experience high path loss. However, those repetitions necessarily increase the energy consumption and the latency in the whole NB-IoT system. The extent to which the whole system is affected depends on the scheduling of the uplink and downlink channels. We address this question, not treated previously, by developing a tractable model of NB-IoT access protocol operation, comprising message exchanges in random-access, control, and data channels, both in the uplink and downlink The model is then used to analyze the impact of channel scheduling as well as the interaction of coexisting coverage classes, through derivation of the expected latency and battery lifetime for each coverage class. These results are subsequently employed in investigation of latency-energy tradeoff in NB-IoT channel scheduling as well as determining the optimized operation points. Simulations results show validity of the analysis and confirm that channel scheduling and coexistence of coverage classes significantly affect latency and battery lifetime performance of NB-IoT devices.
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| 6. |
- Azari, Amin, 1988-, et al.
(författare)
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Reliable and Energy-Efficient IoT Systems : Design Considerations in Coexistence Deployments
- 2023
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Ingår i: IEEE Transactions on Network and Service Management. - : Institute of Electrical and Electronics Engineers (IEEE). - 1932-4537. ; 20:3, s. 2412-2427
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Tidskriftsartikel (refereegranskat)abstract
- Currently, there is a plethora of low-power wide-area IoT networking solutions available, each targeting a specific niche of use-cases and deployment scenarios. Existing studies on reliability evaluations of IoT solutions rely on the assumption that a single technology is deployed in the service area, or different IoT technologies operate over dedicated spectrum bands. Here, we investigate the reliability performance of IoT communications in coexisting scenarios, where multiple competing radio-access technologies share spectrum resources. Our focus is on solutions exploiting grant-free communications, which are gaining traction due to their potential to lower the energy consumption, and have been adopted in recent IoT technologies like SigFox and LoRa. We first derive an analytical model of the interference, comprising both inter- and intra-technology interference sources. We then leverage the Poisson Cluster Process for modeling distribution of devices in the service area, and derive expressions for the communication reliability, energy consumption, and battery lifetime of IoT devices. Exploiting these expressions, we study the energy-reliability trade-offs and investigate strategies to maintain or improve communication reliability, while minimizing energy consumption in coexisting scenarios by proper adjustment of communications parameters at the device side and provisioning resources at the network side. We verify the analytical results via numerical evaluations, confirming their accuracy and performing optimization in some example networking setups.
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| 7. |
- Farag, Hossam, et al.
(författare)
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A Deep Reinforcement Learning Approach for Improving Age of Information in Mission-Critical IoT
- 2021
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Ingår i: The 2021 IEEE Global Conference on Artificial Intelligence and Internet of Things (GCAIoT) - 2021 IEEE GCAIoT. - : IEEE. ; , s. 14-18
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Konferensbidrag (refereegranskat)abstract
- The emerging mission-critical Internet of Things (IoT) play a vital role in remote healthcare, haptic interaction, and industrial automation, where timely delivery of status updates is crucial. The Age of Information (AoI) metric is introduced as an effective criterion for evaluating the freshness of information received at the destination. A system design based solely on the optimization of the average AoI might not be adequate to capture the requirements of mission-critical applications, since averaging eliminates the effects of extreme events. In this paper, we introduce a Deep Reinforcement Learning (DRL)-based algorithm to improve AoI in mission-critical IoT applications. The objective is to minimize an AoI-based metric consisting of the weighted sum of the average AoI and the probability of exceeding an AoI threshold. We utilize the actor-critic method to train the algorithm to achieve optimized scheduling policy to solve the formulated problem. The performance of our proposed method is evaluated in a simulated setup and the results show a significant improvement in terms of the average AoI and the AoI violation probability compared to the related-work.
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| 8. |
- Farag, Hossam, et al.
(författare)
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Distributed Backlog-Aware Protocol for Heterogeneous D2D Communication-Assisted Wireless Sensor Networks
- 2024
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Ingår i: IEEE Transactions on Mobile Computing. - : IEEE. - 1536-1233 .- 1558-0660. ; 23:5, s. 3981-3992
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Tidskriftsartikel (refereegranskat)abstract
- Age of Information (AoI) and delay are crucial performance metrics for Industrial Internet of Things (IIoT) applications not only to perform seamless actuation and control actions but also to enable self-organized and re-configurable manufacturing systems. A challenging task in heterogeneous IIoT networks is to minimize the AoI while maintaining a predefined delay constraint. In this work, we consider a Device-to-Device (D2D)-based heterogeneous IIoT network that supports two types of traffic flows, namely AoI-sensitive flow and delay-sensitive flow. First, we introduce a distributed backlog-aware random access protocol that allows the AoI-sensitive nodes to opportunistically access the channel based on the queue occupancy of the delay-sensitive node. Then, we develop an analytical framework to evaluate the average delay and the average AoI, and formulate an optimization problem to minimize the AoI under a given delay constraint. Finally, we provide numerical results to demonstrate the impact of different network parameters on the performance in terms of the average delay and the average AoI. We also give numerical solutions of the optimal parameters that minimize the AoI subject to a defined delay constraint.
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| 9. |
- Graell I Amat, Alexandre, 1976, et al.
(författare)
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Coded Slotted Aloha with Stopping Set Resolution: A Group Testing Approach
- 2022
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Ingår i: Conference Record - Asilomar Conference on Signals, Systems and Computers. - 1058-6393. ; 2022-October, s. 677-681
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Konferensbidrag (refereegranskat)abstract
- In this work, we explore the use of group testing techniques to steer a collision resolution phase in the context of coded slotted Aloha protocols. The problem can be defined as the discovery of stopping sets based on the residual collision pattern after successive interference cancellation decoding. We show how the application of the simple combinatorial orthogonal matching pursuit algorithm is sufficient to resolve a large number of the collisions that hinder the success of the iterative interference cancellation process. We highlight the design choices that have to be addressed to benefit from the proposed approach. Finally, we outline a few interesting directions for future developments.
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| 10. |
- Ivanov, Mikhail, 1986, et al.
(författare)
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Probabilistic Handshake in All-to-all Broadcast Coded Slotted ALOHA
- 2015
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Ingår i: Proc. IEEE Int. Workshop Signal Proc. Advances Wireless Commun., Stockholm, Sweden, June 2015. - 9781479919307 ; , s. 690-694
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Konferensbidrag (refereegranskat)abstract
- We propose a probabilistic handshake mechanism for all-to-all broadcast coded slotted ALOHA. We consider a fully connected network where each user acts as both transmitter and receiver in a half-duplex mode. Users attempt to exchange messages with each other and to establish one-to-one handshakes, in the sense that each user decides whether its packet was success-fully received by the other users: After performing decoding, each user estimates in which slots the resolved users transmitted their packets and, based on that, decides if these users successfully received its packet. The simulation results show that the proposed handshake algorithm allows the users to reliably perform the handshake. The paper also provides some analytical bounds on the performance of the proposed algorithm which are in good agreement with the simulation results.
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