| 1. |
- Fountoulakis, Emmanouil, et al.
(författare)
-
Information Freshness and Packet Drop Rate Interplay in a Two-User Multi-Access Channel
- 2021
-
Ingår i: 2020 IEEE INFORMATION THEORY WORKSHOP (ITW). - : IEEE. - 9781728159621
-
Konferensbidrag (refereegranskat)abstract
- In this work, we combine the two notions of timely delivery of information to study their interplay; namely, deadline-constrained packet delivery due to latency constraints and freshness of information. More specifically, we consider a two-user multiple access setup with random-access, in which user 1 is a wireless device with a queue and has external bursty traffic which is deadline-constrained, while user 2 monitors a sensor and transmits status updates to the destination. We provide analytical expressions for the throughput and drop probability of user 1, and an analytical expression for the average Age of Information (AoI) of user 2 monitoring the sensor. The relations reveal that there is a trade-off between the average AoI of user 2 and the drop rate of user 1: the lower the average AoI, the higher the drop rate, and vice versa. Simulations corroborate the validity of our theoretical results.
|
|
| 2. |
- Fountoulakis, Emmanouil, et al.
(författare)
-
Information Freshness and Packet Drop Rate Interplay in a Two-User Multi-Access Channel
- 2022
-
Ingår i: Journal of Communications and Networks. - : Korean Institute of Communication Sciences. - 1229-2370 .- 1976-5541. ; 24:3, s. 357-364
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, we combine the two notions of timely delivery of information to study their interplay; namely, deadline -constrained packet delivery due to latency constraints and freshness of information. More specifically, we consider a two -user multiple access setup with random access, in which user 1 is a wireless device with a buffer and has external bursty traffic which is deadline-constrained, while user 2 monitors a sensor and transmits status updates to the destination. We provide analytical expressions for the throughput and drop probability of user 1. For user 2, we derive in closed form the age of information distribution, the average age of information (AoI), and the probability the AoI to be larger than a certain value for each time slot. The relations reveal a trade-off between the average AoI of user 2 and the drop rate of user 1: the lower the average AoI, the higher the drop rate, and vice versa. Simulations corroborate the validity of our theoretical results.
|
|
| 3. |
- Nomikos, Nikolaos, et al.
(författare)
-
Deadline-constrained Bursty Traffic in Random Access Wireless Networks
- 2018
-
Ingår i: 2018 IEEE 19th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC). - : IEEE. - 9781538635124
-
Konferensbidrag (refereegranskat)abstract
- We consider a network of buffer-aided wireless devices having to transmit deadline-constrained data packets on a slotted-ALOHA random-access channel. While retransmission- based communication enhances reliability, the transmission of packets in the queue is delayed and as a result, they might get dropped before they are transmitted successfully. In this work, we study the performance of deadline-constrained bursty traffic with retransmissions providing a Markov chain-based analysis. The aim is to reveal the trade-off between the packet deadline and the number of retransmissions as a function of the arrival rate, and pave the way towards finding the optimal number of retransmissions, given the packet deadline and packet arrival rate. Furthermore, performance evaluation is conducted for a user with varying transmit probability and different number of retransmissions. The results reveal the effect of these parameters on the drop probability and average throughput showing the values under which, improved performance can be obtained.
|
|
| 4. |
- Nomikos, Nikolaos, et al.
(författare)
-
LoLa4SOR : Leveraging Successive Transmissions for Low-Latency Buffer-Aided Opportunistic Relay Networks
- 2021
-
Ingår i: IEEE Open Journal of the Communications Society. - : IEEE. - 2644-125X. ; 2, s. 1041-1054
-
Tidskriftsartikel (refereegranskat)abstract
- Buffer-aided (BA) relaying improves the diversity of cooperative networks often at the cost of increasing end-to-end packet delays. This characteristic renders BA relaying unsuitable for delay-sensitive applications. However, the increased diversity makes BA relaying appealing for ultra-reliable communications. Towards enabling ultra-reliable low-latency communication (URLLC), we aim at enhancing BA relaying for supporting delay-sensitive applications. In this paper, reliable full-duplex (FD) network operation is targeted and for this purpose, hybrid relay selection algorithms are formulated, combining BA successive relaying (SuR) and delay- and diversity-aware (DDA) half-duplex (HD) algorithms. In this context, a hybrid FD DDA algorithm is presented, namely LoLa4SOR, switching between SuR and HD operation. Additionally, a low-complexity distributed version is given, namely d-LoLa4SOR, providing a trade-off among channel state information requirements and performance. The theoretical analysis shows that the diversity of LoLa4SOR equals to two times the number of available relays K, i.e., 2K, when the buffer size L is greater than or equal to 3. Comparisons with other HD, SuR and hybrid algorithms reveal that LoLa4SOR offers superior outage and throughput performance while, the average delay is reduced due to SuR-based FD operation and the consideration of buffer state information for relay-pair selection. d-LoLa4SOR, as one of the few distributed algorithms in the literature, has a reasonable performance that makes it a more practical approach.
|
|
| 5. |
- Stamatakis, George, et al.
(författare)
-
Semantics-Aware Active Fault Detection in Status Updating Systems
- 2024
-
Ingår i: IEEE Open Journal of the Communications Society. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 2644-125X. ; 5, s. 1182-1196
-
Tidskriftsartikel (refereegranskat)abstract
- With its growing number of deployed devices and applications, the Internet of Things (IoT) raises significant challenges for network maintenance procedures. In this work, we address a problem of active fault detection in an IoT scenario, whereby a monitor can probe a remote device to acquire fresh information and facilitate fault detection. However, probing could significantly impact the system's energy and communication resources. To this end, we utilize the Age of Information to measure the freshness of information at the monitor and adopt a semantics-aware communication approach between the monitor and the remote device. In semantics-aware communications, the processes of generating and transmitting information are treated jointly to consider the importance of information and the purpose of communication. We formulate the problem as a Partially Observable Markov Decision Process and show analytically that the optimal policy is of a threshold type. Finally, we use a computationally efficient stochastic approximation algorithm to approximate the optimal policy and present numerical results that exhibit the advantage of our approach compared to a conventional delay-based probing policy.
|
|
| 6. |
- Tepelenis, Kostas, et al.
(författare)
-
Laparoscopic versus open approach to neurolytic celiac plexus block in inoperable pancreatic cancer
- 2018
-
Ingår i: ANZ journal of surgery. - : WILEY. - 1445-1433 .- 1445-2197. ; 88:11, s. E767-E771
-
Tidskriftsartikel (refereegranskat)abstract
- Background Methods Neurolytic celiac plexus block (NCPB) is an effective method of palliative pain control. The purpose of this study was to evaluate the feasibility and effectiveness of the laparoscopic NCPB versus open approach. Eight patients (Group A) underwent diagnostic laparoscopy which revealed an inoperable pancreatic cancer. Forty millilitres of solution (20 mL of 95% ethanol mixed with 20 mL of xylocaine) was injected into either side of para-aortic soft tissue. The same solution was injected in 10 patients (Group B), with inoperable pancreatic body cancer diagnosed during laparotomy. Results Conclusions There were no intraoperative or post-operative, NCPB related, complications. Patients in both groups, reported significant pain relief in the early post-operative period. Using the visual analogue scale preoperatively, in second post-operative day, first and third post-operative month, no significant different was observed between the two groups. The mean hospital stay in both groups was 2.1 versus 5.2 (P = 0.0005) and the mean survival 8.1 versus 7.9 months (ns). The NCPB is feasible method for palliation in inoperable pancreatic cancer. Laparoscopic NCPB gives excellent results and could still be considered in selected cases, as an effective alternative during staging laparoscopy.
|
|
| 7. |
- Abd-Elmagid, Mohamed A., et al.
(författare)
-
A Reinforcement Learning Framework for Optimizing Age of Information in RF-Powered Communication Systems
- 2020
-
Ingår i: IEEE Transactions on Communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 0090-6778 .- 1558-0857. ; 68:8, s. 4747-4760
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we study a real-time monitoring system in which multiple source nodes are responsible for sending update packets to a common destination node in order to maintain the freshness of information at the destination. Since it may not always be feasible to replace or recharge batteries in all source nodes, we consider that the nodes are powered through wireless energy transfer (WET) by the destination. For this system setup, we investigate the optimal online sampling policy (referred to as the age-optimal policy) that jointly optimizes WET and scheduling of update packet transmissions with the objective of minimizing the long-term average weighted sum of Age of Information (AoI) values for different physical processes (observed by the source nodes) at the destination node, referred to as the sum-AoI. To solve this optimization problem, we first model this setup as an average cost Markov decision process (MDP) with finite state and action spaces. Due to the extreme curse of dimensionality in the state space of the formulated MDP, classical reinforcement learning algorithms are no longer applicable to our problem even for reasonable-scale settings. Motivated by this, we propose a deep reinforcement learning (DRL) algorithm that can learn the age-optimal policy in a computationally-efficient manner. We further characterize the structural properties of the age-optimal policy analytically, and demonstrate that it has a threshold-based structure with respect to the AoI values for different processes. We extend our analysis to characterize the structural properties of the policy that maximizes average throughput for our system setup, referred to as the throughput-optimal policy. Afterwards, we analytically demonstrate that the structures of the age-optimal and throughput-optimal policies are different. We also numerically demonstrate these structures as well as the impact of system design parameters on the optimal achievable average weighted sum-AoI.
|
|
| 8. |
- Abd-Elmagid, Mohamed A., et al.
(författare)
-
AoI-Optimal Joint Sampling and Updating for Wireless Powered Communication Systems
- 2020
-
Ingår i: IEEE Transactions on Vehicular Technology. - : IEEE. - 0018-9545 .- 1939-9359. ; 69:11, s. 14110-14115
-
Tidskriftsartikel (refereegranskat)abstract
- This paper characterizes the structure of the Age of Information (AoI)-optimal policy in wireless powered communication systems while accounting for the time and energy costs of generating status updates at the source nodes. In particular, for a single source-destination pair in which a radio frequency (RF)-powered source sends status updates about some physical process to a destination node, we minimize the long-term average AoI at the destination node. The problem is modeled as an average cost Markov Decision Process (MDP) in which, the generation times of status updates at the source, the transmissions of status updates from the source to the destination, and the wireless energy transfer (WET) are jointly optimized. After proving the monotonicity property of the value function associated with the MDP, we analytically demonstrate that the AoI-optimal policy has a threshold-based structure w.r.t. the state variables. Our numerical results verify the analytical findings and reveal the impact of state variables on the structure of the AoI-optimal policy. Our results also demonstrate the impact of system design parameters on the optimal achievable average AoI as well as the superiority of our proposed joint sampling and updating policy w.r.t. the generate-at-will policy.
|
|
| 9. |
- Abd-Elmagid, Mohamed A., et al.
(författare)
-
On the Role of Age of Information in the Internet of Things
- 2019
-
Ingår i: IEEE Communications Magazine. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0163-6804 .- 1558-1896. ; 57:12, s. 72-77
-
Tidskriftsartikel (refereegranskat)abstract
- In this article, we provide an accessible introduction to the emerging idea of Age of Information (AoI) that quantifies freshness of information and explore its possible role in the efficient design of freshness-aware Internet of Things (IoT). We start by summarizing the concept of AoI and its variants with emphasis on the differences between AoI and other well-known performance metrics in the literature, such as throughput and delay. Building on this, we explore freshness-aware IoT design for a network in which IoT devices sense potentially different physical processes and are supposed to frequently update the status of these processes at a destination node (e.g., a cellular base station). Inspired by recent interest, we also assume that these IoT devices are powered by wireless energy transfer by the destination node. For this setting, we investigate the optimal sampling policy that jointly optimizes wireless energy transfer and scheduling of update packet transmissions from IoT devices with the goal of minimizing long-term weighted sum-AoI. Using this, we characterize the achievable AoI region. We also compare this AoI-optimal policy with the one that maximizes average throughput (throughput-optimal policy), and demonstrate the impact of system state on their structures. Several promising directions for future research are also presented.
|
|
| 10. |
- Abd-Elmagid, Mohamed A., et al.
(författare)
-
Online Age-minimal Sampling Policy for RF-powered IoT Networks
- 2019
-
Ingår i: 2019 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM). - : IEEE. - 9781728109626
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we study a real-time Internet of Things (IoT)-enabled monitoring system in which a source node (e.g., IoT device or an aggregator located near a group of IoT devices) is responsible for maintaining the freshness of information status at a destination node by sending update packets. Since it may not always be feasible to replace or recharge batteries in all IoT devices, we consider that the source node is powered by wireless energy transfer (WET) by the destination. For this system setup, we investigate the optimal online sampling policy that minimizes the long-term average Age-of-Information (AoI), referred to as the age-optimal policy. The age-optimal policy determines whether each slot should be allocated for WET or update packet transmission while considering the dynamics of battery level, AoI, and channel state information (CSI). To solve this optimization problem, we model this setup as an average cost Markov Decision Process (MDP). After analytically establishing the monotonicity property of the value function associated with the MDP, the age-optimal policy is proven to be a threshold based policy with respect to each of the system state variables. We extend our analysis to characterize the structural properties of the policy that maximizes average throughput for our system setup, referred to as the throughput-optimal policy. Afterwards, we analytically demonstrate that the structures of the age optimal and throughput-optimal policies are different. We also numerically demonstrate these structures as well as the impact of system design parameters on the optimal achievable average AoI.
|
|
