| 1. |
- Agrell, Erik, 1965, et al.
(författare)
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Roadmap on optical communications
- 2024
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Ingår i: Journal of Optics. - 2040-8978 .- 2040-8986. ; 26:9
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Forskningsöversikt (refereegranskat)abstract
- The Covid-19 pandemic showed forcefully the fundamental importance broadband data communication and the internet has in our society. Optical communications forms the undisputable backbone of this critical infrastructure, and it is supported by an interdisciplinary research community striving to improve and develop it further. Since the first ‘Roadmap of optical communications’ was published in 2016, the field has seen significant progress in all areas, and time is ripe for an update of the research status. The optical communications area has become increasingly diverse, covering research in fundamental physics and materials science, high-speed electronics and photonics, signal processing and coding, and communication systems and networks. This roadmap describes state-of-the-art and future outlooks in the optical communications field. The article is divided into 20 sections on selected areas, each written by a leading expert in that area. The sections are thematically grouped into four parts with 4-6 sections each, covering, respectively, hardware, algorithms, networks and systems. Each section describes the current status, the future challenges, and development needed to meet said challenges in their area. As a whole, this roadmap provides a comprehensive and unprecedented overview of the contemporary optical communications research, and should be essential reading for researchers at any level active in this field.
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| 2. |
- Chen, Hui, 1992, et al.
(författare)
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A Tutorial on Terahertz-Band Localization for 6G Communication Systems
- 2022
-
Ingår i: IEEE Communications Surveys and Tutorials. - 1553-877X. ; 24:3, s. 1780-1815
-
Tidskriftsartikel (refereegranskat)abstract
- Terahertz (THz) communications are celebrated as key enablers for converged localization and sensing in future sixth-generation (6G) wireless communication systems and beyond. Instead of being a byproduct of the communication system, localization in 6G is indispensable for location-aware communications. Towards this end, we aim to identify the prospects, challenges, and requirements of THz localization techniques. We first review the history and trends of localization methods and discuss their objectives, constraints, and applications in contemporary communication systems. We then detail the latest advances in THz communications and introduce THz-specific channel and system models. Afterward, we formulate THz-band localization as a 3D position/orientation estimation problem, detailing geometry-based localization techniques and describing potential THz localization and sensing extensions. We further formulate the offline design and online optimization of THz localization systems, provide numerical simulation results, and conclude by providing lessons learned and future research directions. Preliminary results illustrate that under the same transmission power and array footprint, THz-based localization outperforms millimeter wave-based localization. In other words, the same level of localization performance can be achieved at THz-band with less transmission power or a smaller footprint.
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| 3. |
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| 4. |
- Guo, Hao, 1992, et al.
(författare)
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A Semi-Linear Approximation of the First-Order Marcum Q-function with Application to Predictor Antenna Systems
- 2021
-
Ingår i: IEEE Open Journal of the Communications Society. - 2644-125X. ; 2, s. 273-286
-
Tidskriftsartikel (refereegranskat)abstract
- First-order Marcum Q-function is observed in various problem formulations. However, it is not an easy-to-handle function. For this reason, in this paper, we first present a semi-linear approximation of the Marcum Q-function. Our proposed approximation is useful because it simplifies, e.g., various integral calculations including Marcum Q-function as well as different operations such as parameter optimization. Then, as an example of interest, we apply our proposed approximation approach to the performance analysis of predictor antenna (PA) systems. Here, the PA system is referred to as a system with two sets of antennas on the roof of a vehicle. Then, the PA positioned in the front of the vehicle can be used to improve the channel state estimation for data transmission of the receive antenna that is aligned behind the PA. Considering spatial mismatch due to the mobility, we derive closed-form expressions for the instantaneous and average throughput as well as the throughput-optimized rate allocation. As we show, our proposed approximation scheme enables us to analyze PA systems with high accuracy. Moreover, our results show that rate adaptation can improve the performance of PA systems with different levels of spatial mismatch.
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| 5. |
- Guo, Hao, 1992, et al.
(författare)
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High-Rate Uninterrupted Internet of Vehicle Communications in Highways: Dynamic Blockage Avoidance and CSIT Acquisition
- 2022
-
Ingår i: IEEE Communications Magazine. - 0163-6804 .- 1558-1896. ; 60:7, s. 44-50
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Tidskriftsartikel (refereegranskat)abstract
- In future wireless networks, one of the use cases of interest is the Internet of Vehicles (IoV). Here, IoV refers to two different functionalities, namely, serving the in-vehicle users and supporting the connected-vehicle functionalities, where both can be well provided by the transceivers installed on top of vehicles. Such dual functionality of on-vehicle transceivers implies strict rate and reliability requirements, for which one may need to communicate at millimeter-wave (mmWave) frequencies. However, IoV communication at mmWave requires up-to-date channel state information (CSI) and blockage avoidance. In this article, we incorporate the recently proposed concept of predictor antennas (PAs) into a large-scale cooperative PA (LSCPA) setup where both temporal blockages and CSI out-dating are avoided via base stations (BSs)/vehicles cooperation. Summarizing the ongoing standardization progress enabling IoV communications, we present the potential and challenges of the LSCPA setup, and compare the effect of cooperative and non-cooperative schemes on the performance of IoV links. As we show, BS cooperation and blockage/CSI prediction can boost the performance of IoV links remarkably.
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| 6. |
- Guo, Hao, 1992, et al.
(författare)
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On Delay-limited Average Rate of HARQ-based Predictor Antenna Systems
- 2021
-
Ingår i: IEEE Wireless Communications Letters. - 2162-2345 .- 2162-2337. ; 10:8, s. 1628-1632
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Tidskriftsartikel (refereegranskat)abstract
- Predictor antenna (PA) system is referred to as a system with two sets of antennas on the roof of a vehicle, where the PAs positioned in the front of the vehicle are used to predict the channel state observed by the receive antennas (RAs) that are aligned behind the PAs. In this work, we study the effect of spatial mismatch on the accuracy of channel state information estimation, and analyze the delay-constrained average rate of hybrid automatic repeat request (HARQ)-based PA systems. We consider variable-length incremental redundancy (INR) HARQ protocol, and derive a closed-form expression for the maximum average rate subject to a maximum delay constraint. Moreover, we study the effect of different parameters such as the vehicle speed, the antenna distance and the rate allocation on the system performance. The results indicate that, compared to the open-loop case, the delay-limited average rate is considerably improved with our proposed PA-HARQ scheme.
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| 7. |
- Guo, Hao, 1992, et al.
(författare)
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Power Allocation in HARQ-based Predictor Antenna Systems
- 2020
-
Ingår i: IEEE Wireless Communications Letters. - 2162-2345 .- 2162-2337. ; 9:12, s. 2025-2029
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we study the performance of predictor antenna (PA) systems using hybrid automatic repeat request (HARQ). Here, the PA system is referred to as a system with two sets of antennas on the roof of a vehicle. In this setup, the PA positioned in the front of the vehicle can be used to predict the channel state information at the transmitter (CSIT) for the receive antenna (RA) that is aligned behind the PA. Considering spatial mismatch due to mobility, we derive closed-form expressions for the optimal power allocation and the minimum average power of PA systems under different outage probability constraints. The results are presented for different types of HARQ protocols and we study the effect of different parameters on the performance of PA systems. As we show, our proposed approximation scheme enables us to analyze PA systems with high accuracy. Moreover, for different vehicle speeds, we show that HARQ-based feedback can reduce the outage-limited power consumption of PA systems by orders of magnitude.
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| 8. |
- Guo, Hao, 1992, et al.
(författare)
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Predictor Antenna: A Technique to Boost the Performance of Moving Relays
- 2021
-
Ingår i: IEEE Communications Magazine. - 0163-6804 .- 1558-1896. ; 59:7, s. 80-86
-
Tidskriftsartikel (refereegranskat)abstract
- In future wireless systems, a large number of users may access the networks via moving relays (MRs) installed on top of vehicles. One of the main challenges of MRs is rapid channel variation which may make channel estimation, and its following procedures, difficult. To address these issues, various schemes are designed, among which predictor antenna (PA) is a candidate. The PA setup refers to a system with two (sets of) antennas on top of a vehicle, where the PA(s) positioned in front of the vehicle is(are) utilized to predict the channel state information required for data transmission to the receive antennas (RAs) aligned behind the PA. In this paper, we introduce the concept and the potentials of PA systems. Moreover, summarizing the field trials for PAs and the 3GPP attempts on (moving) relays, we compare the performance of different PA and non-PA methods for vehicle communications in both urban and rural areas with the PA setup backhauled through terrestrial or satellite technology, respectively. As we show, with typical parameter settings and vehicle speeds, a single-antenna PA-assisted setup can boost the backhaul throughput of MRs, compared to state-of-the-art open-loop schemes, by up to 50%.
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| 9. |
- Madapathage Don, Charitha Madapatha, 1992, et al.
(författare)
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On Integrated Access and Backhaul Networks: Current Status and Potentials
- 2020
-
Ingår i: IEEE Open Journal of the Communications Society. - 2644-125X. ; 1, s. 1374-1389
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Tidskriftsartikel (refereegranskat)abstract
- In this article, we introduce and study the potentials and challenges of integrated access and backhaul (IAB) as one of the promising techniques for evolving 5G networks. We study IAB networks from different perspectives. We summarize the recent Rel-16 as well as the upcoming Rel-17 3GPP discussions on IAB, and highlight the main IAB-specific agreements on different protocol layers. Also, concentrating on millimeter wave-based communications, we evaluate the performance of IAB networks in both dense and suburban areas. Using a finite stochastic geometry model, with random distributions of IAB nodes as well as user equipments (UEs) in a finite region, we study the service coverage rate defined as the probability of the event that the UEs' minimum rate requirements are satisfied. We present comparisons between IAB and hybrid IAB/fiber-backhauled networks where a part or all of the small base stations are fiber-connected. Finally, we study the robustness of IAB networks to weather and various deployment conditions and verify their effects, such as blockage, tree foliage, rain as well as antenna height/gain on the coverage rate of IAB setups, as the key differences between the fiber-connected and IAB networks. As we show, IAB is an attractive approach to enable the network densification required by 5G and beyond.
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| 10. |
- Madapathage Don, Charitha Madapatha, 1992, et al.
(författare)
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On Topology Optimization and Routing in Integrated Access and Backhaul Networks: A Genetic Algorithm-Based Approach
- 2021
-
Ingår i: IEEE Open Journal of the Communications Society. - 2644-125X. ; 2, s. 2273-2291
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we study the problem of topology optimization and routing in integrated access and backhaul (IAB) networks, as one of the promising techniques for evolving 5G networks. We study the problem from different perspectives. We develop efficient genetic algorithm-based schemes for both IAB node placement and non-IAB backhaul link distribution, and evaluate the effect of routing on bypassing temporal blockages. Here, concentrating on millimeter wave-based communications, we study the service coverage probability, defined as the probability of the event that the user equipments' (UEs) minimum rate requirements are satisfied. Moreover, we study the effect of different parameters such as the antenna gain, blockage, and tree foliage on the system performance. Finally, we summarize the recent Rel-16 as well as the upcoming Rel-17 3GPP discussions on routing in IAB networks, and discuss the main challenges for enabling mesh-based IAB networks. As we show, with a proper network topology, IAB is an attractive approach to enable the network densification required by 5G and beyond.
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| 11. |
- Makki, Behrooz, 1980, et al.
(författare)
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A Genetic Algorithm-based Antenna Selection Approach for Large-but-Finite MIMO Networks
- 2017
-
Ingår i: IEEE Transactions on Vehicular Technology. - 0018-9545 .- 1939-9359. ; 66:7, s. 6591-6595
-
Tidskriftsartikel (refereegranskat)abstract
- We study the performance of antenna selection-based multiple-input-multiple-output networks with large-but-finite number of transmit antennas and receivers. Considering the continuous and bursty communication scenarios with different users' data request probabilities, we develop an efficient antenna selection scheme using genetic algorithms (GAs).As demonstrated, the proposed algorithm is generic in the sense that it can be used in the cases with different objective functions, precoding methods, levels of available channel state information, and channel models. Our results show that the proposed GA-based algorithm reaches (almost) the same throughput as the exhaustive search-based optimal approach, with substantially less implementation complexity.
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| 12. |
- Makki, Behrooz, 1980, et al.
(författare)
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Adaptive Space-Time Coding using ARQ
- 2015
-
Ingår i: IEEE Transactions on Vehicular Technology. - 0018-9545 .- 1939-9359. ; 64:9, s. 4331-4337
-
Tidskriftsartikel (refereegranskat)abstract
- We study the energy-limited outage probability of the block space-time coding (STC)-based systems utilizing automatic repeat request (ARQ) feedback and adaptive power allocation. Taking the ARQ feedback costs into account, we derive closed-form solutions for the energy-limited optimal power allocation and investigate the diversity gain of different STCARQ schemes. Also, sufficient conditions are derived for the usefulness of ARQ, in terms of energy-limited outage probability. The results show that, for a large range of feedback costs, the energy efficiency is substantially improved by the combination of ARQ and STC techniques, if optimal power allocation is utilized.
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| 13. |
- Makki, Behrooz, 1980, et al.
(författare)
-
Coordinated Hybrid Automatic Repeat Request
- 2014
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Ingår i: IEEE Communications Letters. - 1558-2558 .- 1089-7798. ; 18:11, s. 1975-1978
-
Tidskriftsartikel (refereegranskat)abstract
- We develop a coordinated hybrid automatic repeat request (HARQ) approach. With the proposed scheme, if a usermessage is correctly decoded in the first HARQ rounds, its spectrum is allocated to other users, to improve the network outage probability and the users’ fairness. The results, which are obtained for single- and multiple-antenna setups, demonstrate the efficiency of theproposed approach in different conditions. For instance, with a maximum of M retransmissions and single transmit/receive antennas, the diversity gain of a user increases from M to (J+1)(M−1)+1 where J is the number of users helping that user.
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| 14. |
- Makki, Behrooz, 1980, et al.
(författare)
-
Finite Block-length Analysis of Large-but-finite MIMO Systems
- 2019
-
Ingår i: IEEE Wireless Communications Letters. - 2162-2345 .- 2162-2337. ; 8:1, s. 113-116
-
Tidskriftsartikel (refereegranskat)abstract
- This letter studies the performance of point-to-point multiple-input-multiple-output (MIMO) systems in the presence of large but finite numbers of transmit and receive antennas. We use some recent results on the achievable rates of finite-length codes to analyze the system performance in the cases with short packets. The results are presented for different fading models. With codewords of finite length, we derive closed-form expressions for the error probability/throughput and determine the minimum number of antennas which are required to satisfy different error probability/throughput requirements. As we show, while the error-constrained required number of antennas is sensitive to the length of short codewords, its effect is negligible for codewords of moderate/long length.
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| 15. |
- Makki, Behrooz, 1980, et al.
(författare)
-
On the Performance of HARQ-Based RF-FSO Links
- 2015
-
Ingår i: Proceedings - IEEE Global Communications Conference, GLOBECOM. - 2334-0983 .- 2576-6813. - 9781479959525
-
Konferensbidrag (refereegranskat)abstract
- This paper studies the performance of the hybridradio-frequency (RF) and free-space optical (FSO) links assuming perfect channel state information (CSI) at the receiver. Considering the cases with and without hybrid automatic repeat request (HARQ), we derive closed-form expressions for the message decoding probabilities as well as the throughput and the outage probability of the RF-FSO setups. We also evaluate the effect of different channel conditions on the throughput and the outageprobability. The results show the efficiency of the RF-FSO links in different conditions.
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| 16. |
- Makki, Behrooz, 1980, et al.
(författare)
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On the Performance of Millimeter Wave-based RF-FSO Links with HARQ Feedback
- 2016
-
Ingår i: 2016 Ieee 27th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (Pimrc). ; , s. 937-942
-
Konferensbidrag (refereegranskat)abstract
- This paper studies the performance of hybrid radio-frequency (RF) and free-space optical (FSO) links in the cases with and without hybrid automatic repeat request (HARQ). Considering millimeter wave (mmwave) characteristics in the RF link and pointing errors in the FSO link, we derive closed-form expressions for the message decoding probabilities as well as the throughput and the outage probability of the RF-FSO setups. We also evaluate the effect of various parameters such as power amplifiers efficiency, different transmission techniques in the FSO link, pointing errors in the FSO link as well as different coherence times/symbol rates of the RF and the FSO links on the throughput and outage probability. The results show the efficiency of the RF-FSO links in different conditions. Moreover, the HARQ can effectively improve the outage probability/energy efficiency, and compensate the effect of hardware impairments in RF-FSO links.
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| 17. |
- Makki, Behrooz, 1980, et al.
(författare)
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On the Performance of Millimeter Wave-based RF-FSO Multi-hop and Mesh Networks
- 2017
-
Ingår i: IEEE Transactions on Wireless Communications. - 1558-2248 .- 1536-1276. ; 16:12, s. 7746-7759
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Tidskriftsartikel (refereegranskat)abstract
- This paper studies the performance of multi-hop and mesh networks composed of millimeter wave-based radio frequency (RF) and free-space optical (FSO) links. The results are obtained in cases with and without hybrid automatic repeat request (HARQ). Using the central limit theorem as well as other state-of-the-art approximation schemes, we derive closed-form expressions for the networks’ outage probability and ergodic achievable rates. We also evaluate the effect of various parameters such as power amplifiers efficiency, number of antennas as well as different coherence times of the RF and the FSO links on the system performance. Finally, we determine the minimum number of the transmit antennas in the RF link such that the same rate is supported in the RF- and the FSO-based hops. The results show the efficiency of the RF-FSO setups in different conditions. Moreover, HARQ can effectively improve the outage probability/energy efficiency, and compensate for the effect of hardware impairments in RF-FSO networks. For common parameter settings of the RF-FSO dual-hop networks, outage probability of 10−4 and code rate of 3 nats-per-channel-use, the implementation of HARQ with a maximum of 2 and 3 retransmissions reduces the required power, compared to cases with open-loop communication, by 13 and 17 dB, respectively.
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| 18. |
- Makki, Behrooz, 1980, et al.
(författare)
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On the Performance of RF-FSO Links with and without Hybrid ARQ
- 2016
-
Ingår i: IEEE Transactions on Wireless Communications. - 1558-2248 .- 1536-1276. ; 15:7, s. 4928-4943
-
Tidskriftsartikel (refereegranskat)abstract
- This paper studies the performance of hybrid radio frequency (RF) and free-space optical (FSO) links assuming perfect channel state information (CSI) at the receiver. Considering the cases with and without hybrid automatic repeat request (HARQ), we derive closed-form expressions for the message decoding probabilities as well as the throughput and the outage probability of the RF-FSO setups. We also evaluate the effect of adaptive power allocation and different channel conditions onthe throughput and the outage probability. The results show the efficiency of the RF-FSO links in different conditions.
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| 19. |
- Makki, Behrooz, 1980, et al.
(författare)
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On the Required Number of Antennas in a Point-to-Point Large-but-Finite MIMO System
- 2015
-
Ingår i: IEEE International Conference on Ubiquitous Wireless Broadband, ICUWB 2015, Montreal, Canada, 4-7 October. - 9781467365550 ; , s. Art. no. 7324486-
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Konferensbidrag (refereegranskat)abstract
- In this paper, we investigate the performance of thepoint-to-point multiple-input-multiple-output (MIMO) systems in the presence of a large but finite numbers of antennas at the transmitters and/or receivers. Considering the cases with and without hybrid automatic repeat request (HARQ) feedback, we determine the minimum numbers of the transmit/receive antennas which are required to satisfy different outage probabilityconstraints. We study the effect of the spatial correlation between the antennas on the system performance. Also, the required number of antennas are obtained for different fading conditions. Our results show that different outage requirements can be satisfied with relatively few transmit/receive antennas.
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| 20. |
- Makki, Behrooz, 1980, et al.
(författare)
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On the Required Number of Antennas in a Point-to-Point Large-but-Finite MIMO System: Outage-Limited Scenario
- 2016
-
Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 64:5, s. 1968-1983
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the performance of the pointto-point multiple-input-multiple-output (MIMO) systems in the presence of a large but finite numbers of antennas at the transmitters and/or receivers. Considering the cases with and without hybrid automatic repeat request (HARQ) feedback, we determine the minimum numbers of the transmit/receive antennas which are required to satisfy different outage probability constraints. Our results are obtained for different fading conditions and the effectof the power amplifiers efficiency/feedback error probability on the performance of the MIMO-HARQ systems is analyzed. Then, we use some recent results on the achievable rates of finite blocklength codes, to analyze the effect of the codewords lengths on the system performance. Moreover, we derive closed-form expressions for the asymptotic performance of the MIMO-HARQ systems when the number of antennas increases. Our analyticaland numerical results show that different outage requirements can be satisfied with relatively few transmit/receive antennas.
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| 21. |
- Makki, Behrooz, 1980, et al.
(författare)
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On the Throughput of Large-but-Finite MIMO Networks Using Schedulers
- 2019
-
Ingår i: IEEE Transactions on Wireless Communications. - 1558-2248 .- 1536-1276. ; 18:1, s. 152-166
-
Tidskriftsartikel (refereegranskat)abstract
- This paper studies the sum throughput of the multi-user multiple-input-single-output networks in the cases with a large-but-finite number of transmit antennas and users. Considering continuous and bursty communication scenarios with different users' data request probabilities, we derive quasi-closed-form expressions for the maximum achievable throughput of the networks using optimal schedulers. The results are obtained in various cases with different levels of interference cancellation. Also, we develop an efficient scheduling scheme using genetic algorithms (GAs) and evaluate the effect of different parameters, such as channel/precoding models, number of antennas/users, scheduling costs, and power amplifiers' efficiency, on the system performance. Finally, we use the recent results on the achievable rates of finite block-length codes to analyze the system performance in the cases with short packets. As demonstrated, the proposed GA-based scheduler reaches (almost) the same throughput as in the exhaustive search-based optimal scheduler, with substantially less implementation complexity. Moreover, the power amplifiers' inefficiency and the scheduling delay affect the performance of the scheduling-based systems significantly.
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| 22. |
- Makki, Behrooz, 1980, et al.
(författare)
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Performance Analysis of ARQ-based RF-FSO Links
- 2017
-
Ingår i: IEEE Communications Letters. - 1558-2558 .- 1089-7798. ; 21:6, s. 1253-1256
-
Tidskriftsartikel (refereegranskat)abstract
- In this letter, we study the performance of hybrid radio-frequency (RF) and free-space optical (FSO) links using automatic repeat request (ARQ). We derive closed-form expressions for the message decoding probabilities, throughput, and outage probability with different relative coherence times of the RF and FSO links. We also evaluate the effect of adaptive power allocation between the ARQ retransmissions on the system performance. The results show that joint implementation of the RF and FSO links leads to substantial performance improvement, compared to the cases with only the RF or the FSO link.
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| 23. |
- Makki, Behrooz, 1980, et al.
(författare)
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Performance analysis of RF-FSO multi-hop networks
- 2017
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Ingår i: IEEE Wireless Communications and Networking Conference, WCNC. - 1525-3511. ; , s. Article no 7925522-
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Konferensbidrag (refereegranskat)abstract
- © 2017 IEEE. We study the performance of multi-hop networks composed of millimeter wave (MMW)-based radio frequency (RF) and free-space optical (FSO) links. The results are obtained in the cases with and without hybrid automatic repeat request (HARQ). Taking the MMW characteristics of the RF links into account, we derive closed-form expressions for the network outage probability. We also evaluate the effect of various parameters such as power amplifiers efficiency, number of antennas as well as different coherence times of the RF and the FSO links on the system performance. Finally, we present mappings between the performance of RF- FSO multi-hop networks and the ones using only the RF- or the FSO-based communication, in the sense that with appropriate parameter settings the same outage probability is achieved in these setups. The results show the efficiency of the RF-FSO setups in different conditions. Moreover, the HARQ can effectively improve the outage probability/energy efficiency, and compensate the effect of hardware impairments in RF-FSO networks. For common parameter settings of the RF-FSO dual- hop networks, outage probability 10^{-4} and code rate 3 nats-per-channel-use, the implementation of HARQ with a maximum of 2 and 3 retransmissions reduces the required power, compared to the cases with no HARQ, by 13 and 17 dB, respectively.
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| 24. |
- Makki, Behrooz, 1980, et al.
(författare)
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Wireless Energy and Information Transmission in FSO and RF-FSO Links
- 2018
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Ingår i: IEEE Wireless Communications Letters. - 2162-2345 .- 2162-2337. ; 7:1, s. 90-93
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Tidskriftsartikel (refereegranskat)abstract
- We propose and analyze a wireless energy and information transmission scheme in free-space optical (FSO) links. The results are presented for both quasi-static and fast-fading conditions. We derive closed-form expressions for throughput, outage probability and optimal power allocation optimizing the system throughput/outage probability. Finally, we complement the FSO link with an additional radio frequency (RF) link to create a hybrid RF-FSO system and reduce the system outage probability. The results show that joint implementation of the RF and FSO links leads to considerable performance improvement, compared to the cases with only FSO-based communication.
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| 25. |
- Rahman, Aniq Ur, et al.
(författare)
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Network Graph Generation through Adaptive Clustering and Infection Dynamics: A Step Towards Global Connectivity
- 2022
-
Ingår i: IEEE Communications Letters. - 1558-2558 .- 1089-7798. ; 26:4, s. 783-787
-
Tidskriftsartikel (refereegranskat)abstract
- More than 40% of the world’s population is not connected to the internet, majorly due to the lack of adequate infrastructure. Our work aims to bridge this digital divide by proposing solutions for network deployment in remote areas. Specifically, a number of access points (APs) are deployed as an interface between the users and backhaul nodes (BNs). The main challenges include designing the number and location of the APs, and connecting them to the BNs. In order to address these challenges, we first propose a metric called connectivity ratio to assess the quality of the deployment. Next, we propose an agile search algorithm to determine the number of APs that maximizes this metric and perform clustering to find the optimal locations of the APs. Furthermore, we propose a novel algorithm inspired by infection dynamics to connect all the deployed APs to the existing BNs economically. To support the existing terrestrial BNs, we investigate the deployment of non-terrestrial BNs, which further improves the network performance in terms of average hop count, traffic distribution, and backhaul length. Finally, we use real datasets from a remote village to test our solution.
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| 26. |
- Shekhar, Shashank, et al.
(författare)
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Outage Probability Analysis of Uplink Cell-Free Massive MIMO Network With and Without Pilot Contamination
- 2024
-
Ingår i: IEEE Open Journal of the Communications Society. - 2644-125X. ; 5, s. 168-184
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Tidskriftsartikel (refereegranskat)abstract
- This paper derives approximate outage probability (OP) expressions for uplink cell-free massive multiple-input-multiple-output (CF-mMIMO) systems with and without pilot contamination. The system’s access points (APs) are considered to have imperfect channel state information (CSI). The signal-to-interference-plus-noise ratio (SINR) of the CF-mMIMO system is approximated via a Log-normal distribution using a two-step moment matching method. OP and ergodic rate expressions are derived with the help of the approximated Log-normal distribution. For the no-pilot contamination scenario, an exact expression is first derived using conditional expectations in terms of a multi-fold integral. Then, a novel dimension reduction method is used to approximate it by the sum of single-variable integrations. Both the approximations derived for the CF-mMIMO systems are also useful for single-cell collocated massive MIMO (mMIMO) systems and lead to closed-form expression. The derived expressions closely match the simulated numerical values for OP and ergodic rate.
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| 27. |
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| 28. |
- Zahnstecher, Brian, et al.
(författare)
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Energy Efficiency
- 2022
-
Ingår i: Proceedings. - : Institute of Electrical and Electronics Engineers (IEEE).
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Konferensbidrag (refereegranskat)abstract
- This 2021 Edition of the IEEE International Network Generations Roadmap (INGR) contains a new Chapter dedicated to Energy Efficiency, which builds upon the initial white paper released in April 2020 [1]. For this purpose, the Energy Efficiency Working Group developed an analysis of the energy efficiency constraints across the whole ecosystem of the Fifth Generation '5G' and following network infrastructure, which can be leveraged by all stakeholders to prioritize resources allocation and technology development to ensure that both technical and economic forecasts can be met. The complexity of the ecosystem and the traditionally siloed approach within the Industry has often prevented the adoption of a holistic approach to addressing the fundamental problem of energy, which is the ultimate constraint to any complex deployment. The proposed framework facilitates an assessment of bottlenecks and their implication on the network: it may be used by both academic and industry stakeholders to develop solutions that address the real issues and enable a healthy ecosystem. After a comprehensive survey of the ecosystem and its challenges, the following key areas were selected for a more in-depth analysis:Network EfficiencySmall Cell MigrationBase Station PowerEconomic FactorsGrid/UtilityThis Chapter also identifies the need for a comprehensive 'Systems-of-Systems' (SoS) analysis to address the complex inter-relations among the multiple layers, which the infrastructure leverages. An initial proposal describes how a model can be built to enable a comprehensive assessment of energy requirements across such a diverse ecosystem. A future step in the process will consolidate a proposal for standardization of this model, which can be utilized by all stakeholders for both analysis and forecasting of capabilities and return on investment.
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| 29. |
- Zahnstecher, Brian, et al.
(författare)
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Energy Efficiency
- 2023
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Ingår i: Proceedings - 2023 IEEE Future Networks World Forum: Future Networks: Imagining the Network of the Future, FNWF 2023. - : Institute of Electrical and Electronics Engineers (IEEE).
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Konferensbidrag (refereegranskat)abstract
- This 2023 Edition of the IEEE International Network Generations Roadmap (INGR) updates the already very comprehensive chapter dedicated to Energy Efficiency, which builds upon the initial white paper released in April 2020[1] with subsequent annual updates to the roadmap (available from IEEE). For this purpose, the Energy Efficiency Working Group developed an analysis of the energy efficiency constraints across the whole ecosystem of the Fifth Generation '5G' and following network infrastructure, which can be leveraged by all stakeholders to prioritize resource allocation and technology development to ensure that both technical and economic forecasts can be met. The complexity of the ecosystem and the traditionally siloed approach within the industry has often prevented the adoption of a holistic approach to addressing the fundamental problem of energy, which is the ultimate constraint to any complex deployment. The proposed framework facilitates an assessment of bottlenecks and their implication on the network. It may be used by both academic and industry stakeholders to develop solutions that address the real issues and enable a healthy ecosystem. After a comprehensive survey of the ecosystem and its challenges, the following key areas were selected for a more in-depth analysis: ▪Network Efficiency ▪Small Cell Migration ▪Base Station Power ▪Economic Factors ▪Grid / Utility This chapter also identifies the need for a comprehensive 'Systems-of-Systems' (SoS) analysis to address the complex inter-relationships among the multiple layers, which the infrastructure leverages. An initial proposal describes how a model can be built to enable a comprehensive assessment of energy requirements across such a diverse ecosystem. A future step in the process will consolidate a proposal for standardization of this model, which can be utilized by all stakeholders for both analysis and forecasting of capabilities and return on investment. Being green is also green ($$$)!
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