| 1. |
- Ahani, Ghafour, et al.
(författare)
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Age-Optimal UAV Scheduling for Data Collection With Battery Recharging
- 2021
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Ingår i: IEEE Communications Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1089-7798 .- 1558-2558. ; 25:4, s. 1254-1258
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Tidskriftsartikel (refereegranskat)abstract
- We study route scheduling of a UAV for data collection from sensor nodes (SNs) with battery recharging. The freshness of the collected information is captured by the metric of age of information (AoI). The objective is to minimize the average AoI cost of all SNs over a scheduling time horizon. We prove that the problem in its general form is NP-hard. Then, for a special case of the problem, we prove that optimum can be computed in polynomial time. Next, we develop an algorithm based on graph labeling. Finally, we show the effectiveness of our algorithm in comparison to greedy scheduling.
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| 2. |
- Al-Salihi, Hayder, et al.
(författare)
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A Successive Optimization Approach to Pilot Design for Multi-Cell Massive MIMO Systems
- 2018
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Ingår i: IEEE Communications Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1089-7798 .- 1558-2558. ; 22:5, s. 1086-1089
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Tidskriftsartikel (refereegranskat)abstract
- In this letter, we introduce a novel pilot designapproach that minimizes the total mean square errors of theminimum mean square error estimators of all base stations (BSs)subject to the transmit power constraints of individual users inthe network, while tackling the pilot contamination in multicellmassive MIMO systems. First, we decompose the originalnon-convex problem into distributed optimization sub-problemsat individual BSs, where each BS can optimize its own pilotsignals given the knowledge of pilot signals from the remainingBSs. We then introduce a successive optimization approach totransform each optimization sub-problem into a linear matrixinequality form, which is convex and can be solved by availableoptimization packages. Simulation results confirm the fast convergenceof the proposed approach and prevails a benchmarkscheme in terms of providing higher accuracy.
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| 3. |
- Alinia, Bahram, et al.
(författare)
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Maximizing Quality of Aggregation in Delay-Constrained Wireless Sensor Networks
- 2013
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Ingår i: IEEE Communications Letters. - : IEEE Press. - 1089-7798 .- 1558-2558. ; 17:11, s. 2084-2087
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Tidskriftsartikel (refereegranskat)abstract
- In this letter, both the number of participating nodes and spatial dispersion are incorporated to establish a bi-objective optimization problem for maximizing the quality of aggregation under interference and delay constraints in tree-based wireless sensor networks (WSNs). The formulated problem is proved to be NP-hard with respect to Weighted-sum scalarization and a distributed heuristic aggregation scheduling algorithm, named SDMAX, is proposed. Simulation results show that SDMAX not only gives a close approximation of the Pareto-optimal solution, but also outperforms the best, to our knowledge, existing alternative proposed so far in the literature.
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| 4. |
- Alvarado, A., et al.
(författare)
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A Simple Approximation for the Bit-Interleaved Coded Modulation Capacity
- 2014
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Ingår i: IEEE Communications Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-2558 .- 1089-7798. ; 18:3, s. 495-498
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Tidskriftsartikel (refereegranskat)abstract
- The generalized mutual information (GMI) is an achievable rate for bit-interleaved coded modulation (BICM) and is highly dependent on the binary labeling of the constellation. The BICM-GMI, sometimes called the BICM capacity, can be evaluated numerically. This approach, however, becomes impractical when the number of constellation points and/or the constellation dimensionality grows, or when many different labelings are considered. A simple approximation for the BICM-GMI based on the area theorem of the demapper's extrinsic information transfer (EXIT) function is proposed. Numerical results show the proposed approximation gives good estimates of the BICM-GMI for labelings with close to linear EXIT functions, which includes labelings of common interest, such as the natural binary code, binary reflected Gray code, etc. This approximation is used to optimize the binary labeling of the 32-APSK constellation defined in the DVB-S2 standard. Gains of approximately 0.15 dB are obtained.
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| 5. |
- Alvarado, Alex, 1982, et al.
(författare)
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On BICM-ID with Multiple Interleavers
- 2010
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Ingår i: IEEE Communications Letters. - 1558-2558 .- 1089-7798. ; 14:9, s. 785-787
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Tidskriftsartikel (refereegranskat)abstract
- In this letter, we study the performance of BICM-ID with multiple interleavers (BICM-ID-M) in terms of bit-error rate (BER), and show that BICM-ID-M is well-suited to exploit the unequal error protection (UEP) caused by the binary labeling. We show that BICM-ID-M should always be the preferred alternative for BICM-ID and that the gains obtained appear even for the simplest configuration (0.5-0.75 dB for a BER of 10-7). It is found that conventional design paradigms such as maximizing the free distance of the code should be modified.
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| 6. |
- Amani, Navid, 1985, et al.
(författare)
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Per-Antenna Power Distribution of a Zero-Forcing Beamformed ULA in pure LOS MU-MIMO
- 2018
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Ingår i: IEEE Communications Letters. - 1558-2558 .- 1089-7798. ; 22:12, s. 2515-2518
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Tidskriftsartikel (refereegranskat)abstract
- An analytical model is presented to determine the per-antenna power distribution of a beamformed M-element uniform linear array (ULA) as a base station antenna (BSA). The analysis assumes a single sector cell serving two user equipments (UEs) in a downlink multiuser multiple-input multiple-output (MU-MIMO) system employing zeroforcing (ZF) transmission. Determinative design parameters of the BSA configuration are identified. Afterwards, their effects on the power spread across the array are investigated when the positions of the users are random and they are uniformly distributed over the cell. It is shown that the power distribution across the ULA antenna aperture is a periodic function whose characteristics mainly depend on the angular separation of two UEs and the number of BSA elements. A significant variation between ULA input powers is seen to occur if the number of elements in the ULA is smaller than one period of this power distribution function. In order to mitigate the dynamic range of the power variation across the array, an upper bound for the inter-element spacing, depending on the field-of-view (FoV) of the BSA, is defined. It is shown that, in a 20-element ULA, increasing the inter-element spacing from 0.5-wavelength to 1.4-wavelength reduces the power variation from 19 dB to 10 dB for differentiating two close-by UEs with 1 degree angular separation.
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| 7. |
- Anderlind, Erik, et al.
(författare)
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A Traffic Model for Non-Real-Time Data Users in Wireless Radio Networks
- 1997
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Ingår i: IEEE Communications Letters. - : IEEE. - 1089-7798 .- 1558-2558. ; 1:2, s. 37-39
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Tidskriftsartikel (refereegranskat)abstract
- Based on an analysis of Internet protocols for data communication, we propose a simple model for future data traffic in wireless radio networks. Model parameters are selected so as to resemble traffic from the Worldwide Web (WWW) access and from distributed file systems. By changing a single parameter, the model can be switched between resembling up- or down-link traffic. The model is intended for design and performance analysis of radio resource allocation algorithms in future wireless systems.
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| 8. |
- Andersson, Mattias, et al.
(författare)
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Nested Polar Codes for Wiretap and Relay Channels
- 2010
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Ingår i: IEEE Communications Letters. - : IEEE. - 1089-7798 .- 1558-2558. ; 14:8, s. 752-754
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Tidskriftsartikel (refereegranskat)abstract
- We show that polar codes asymptotically achieve the whole capacity-equivocation region for the wiretap channel when the wiretapper's channel is degraded with respect to the main channel, and the weak secrecy notion is used. Our coding scheme also achieves the capacity of the physically degraded receiver-orthogonal relay channel. We show simulation results for moderate block length for the binary erasure wiretap channel, comparing polar codes and two edge type LDPC codes.
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| 9. |
- Angelakis, Vangelis, et al.
(författare)
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Optimal and Collaborative Rate Selection for Interference Cancellation in Wireless Networks
- 2011
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Ingår i: IEEE Communications Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1089-7798 .- 1558-2558. ; 15:8, s. 819-821
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Tidskriftsartikel (refereegranskat)abstract
- Analysis of wireless systems commonly assumes single-user detection at the receivers. Interference is typically treated as noise. On the other hand, multiuser detection has long been taking advantage of interference cancellation (IC) to increase capacity. We exploit IC by optimal rate selection. Transmission rates are collaboratively optimized to maximize the benefit of IC. A link reduces its rate, if that enables IC to significantly boost the SINR on other links. We provide a complexity analysis and an integer programming model to find the optimal IC pattern. Simulation results indicate that throughput improvement is over 30% in low SINR regimes.
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| 10. |
- Athanasiou, Georgios, et al.
(författare)
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Auction-Based Resource Allocation in MillimeterWave Wireless Access Networks
- 2013
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Ingår i: IEEE Communications Letters. - IEEE. - 1089-7798 .- 1558-2558. ; 17:11, s. 2108-2111
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Tidskriftsartikel (refereegranskat)abstract
- The resource allocation problem of optimal assignment of the stations to the available access points in 60 GHz millimeterWave wireless access networks is investigated. The problem is posed as a multi-assignment optimization problem. The proposed solution method converts the initial problem to a minimum cost flow problem and allows to design an efficient algorithm by a combination of auction algorithms. The solution algorithm exploits the network optimization structure of the problem, and thus is much more powerful than computationally intensive general-purpose solvers. Theoretical and numerical results evince numerous properties, such as optimality, convergence, and scalability in comparison to existing approaches.
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