| 1. |
- Sheikhi, Ashkan, et al.
(författare)
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Massive MIMO with Per-Antenna Digital Predistortion Size Optimization : Does it Help?
- 2021
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Ingår i: ICC 2021 - IEEE International Conference on Communications, Proceedings. - 1550-3607. - 9781728171227
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Konferensbidrag (refereegranskat)abstract
- In this paper, we study the effect of optimizing the per-antenna digital predistortion (DPD) sizes on the performance of the downlink massive MIMO system with residual hardware impairment. In particular, we first quantify the capacity after applying some per-antenna DPD with different numbers of coefficients at each antenna and then maximize the capacity by finding optimum values of the per-antenna DPD sizes under a constraint on the total number of DPD coefficients in the system. Two closed-form sub-optimal solutions are derived and numerical examples illustrate that their performance is very close to the optimal solution. It is shown that when the channel large-scale gains have high variation over the transmitter array, which is the case in practical scenarios, using our proposed optimized DPD sizes can improve the system capacity significantly. This allows us to scale down the massive MIMO system but still maintain performance. We also study the asymptotic behavior of the derived capacity and show that by using the optimized DPD sizes, the system performance can approach the asymptotic bound with a significantly smaller number of antennas.
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| 2. |
- Abu-Shaban, Z., et al.
(författare)
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Near-field Localization with a Reconfigurable Intelligent Surface Acting as Lens
- 2021
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Ingår i: IEEE International Conference on Communications. - 1550-3607. ; June 2021
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Konferensbidrag (refereegranskat)abstract
- Exploiting wavefront curvature enables localization with limited infrastructure and hardware complexity. With the introduction of reconfigurable intelligent surfaces (RISs), new opportunities arise, in particular when the RIS is functioning as a lens receiver. We investigate the localization of a transmitter using a RIS-based lens in close proximity to a single receive antenna element attached to reception radio frequency chain. We perform a Fisher information analysis, evaluate the impact of different lens configurations, and propose a two-stage localization algorithm. Our results indicate that positional beamforming can lead to better performance when a priori location information is available, while random beamforming is preferred when a priori information is lacking. Our simulation results for a moderate size lens operating at 28 GHz showcased that decimeter-level accuracy can be attained within 3 meters to the lens.
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| 3. |
- Ahmad, Suhail, 1992, et al.
(författare)
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Predictive Resource Allocation Evaluation with Real Channel Measurements
- 2017
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Ingår i: IEEE International Conference on Communications. - 1550-3607.
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Konferensbidrag (refereegranskat)abstract
- Mobile services, especially video streaming, has seen a rapid usage increase in recent years. Base stations (BSs) need to employ smarter and efficient resource allocation strategies to maintain high quality of service (QoS) to users at all the times. Predictive resource allocation (PRA), is one such novel scheme, in which BSs seek to anticipate the user demands and offer service to users in advance. As a result, the QoS can be improved, network load can be distributed over time, while at the same time offering efficient utilization of BS power. In location-aware PRA, the BS exploits location information of the users to predict the channel expected variations and adapt the BS resources accordingly. We evaluate PRA strategies based on an empirical study of the radio channel variation from measured location-aided channel radio maps using a smart phone. We observed that gains offered by the PRA scheme are highly dependent on user mobility patterns.
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| 4. |
- Alegria, Juan Vidal, et al.
(författare)
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Enabling Decentralized Computation of the WAX Decomposition
- 2022
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Ingår i: ICC 2022 - IEEE International Conference on Communications. - 1550-3607. ; 2022
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Konferensbidrag (refereegranskat)abstract
- As the number of antennas scales up, research efforts have been directed towards finding decentralized receiver solutions for multi-antenna architectures. In a recent paper, a novel matrix decomposition - the WAX decomposition - was proposed, which has direct bearing on characterizing the level of decentralization that is possible if the complexity of the decentralized processing is limited. However, the available work on WAX decomposition has left some gaps in determining how one of its basis matrices has to be defined. In this paper we present a number of constructions for effectively defining said basis matrix, and we show how they facilitate decentralized calculation of the WAX decomposition itself for applying information-lossless processing in architectures with an arbitrary level of decentralization. Thereby, taking a major step towards realizing decentralized receiver solution for large scale antenna systems.
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| 5. |
- Alvarado, Alex, 1982, et al.
(författare)
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Correcting Suboptimal Metrics in Iterative Decoders
- 2009
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Ingår i: IEEE International Conference on Communications. - 1550-3607. - 9781424434350
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Konferensbidrag (refereegranskat)abstract
- In this paper the issue of improving the performance of iterative decoders based on sub-optimal calculation of the messages exchanged during iterations (L-values) is addressed. It is well known in the literature that a simple---yet very effective---way to improve the performance of suboptimal iterative decoders is based on applying a scaling factor to the L-values. In this paper, starting with a theoretical model based on the so-called consistency condition of a random variable, we propose a methodology for correcting the L-values that relies only on the distribution of the soft information exchanged in the iterative process. This methodology gives a clear explanation of why the well-known linear scaling factor provides a very good performance. Additionally, the proposed methodology allows us to avoid the exhaustive search required otherwise. Numerical simulations show that for turbo codes the scaling factors found closely follow the optimum values, which translates to a close-to-optimal BER performance. Moreover, for LDPC codes, the proposed methodology produces a better BER performance compared with the known method in the literature.
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| 6. |
- Alvarado, Alex, 1982, et al.
(författare)
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On the performance of BICM with trivial interleavers in nonfading channels
- 2011
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Ingår i: IEEE International Conference on Communications ICC 2011. - : IEEE. - 1550-3607. - 9781612842332
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Konferensbidrag (refereegranskat)abstract
- Recent results have shown that the performance of bit-interleaved coded modulation (BICM) using convolutional codes in nonfading channels can be greatly improved if the bit-level interleaver takes a trivial form (BICM-T), i.e., if it does not interleave the bits at all. The reported gains reach a few decibels and are obtained using a less complex BICM system. In this paper, we give a formal explanation for these results and show that BICM-T is in fact the combination of a TCM transmitter and a BICM receiver. Analytical bounds that predict the performance of BICM-T are developed and a new type of distance spectrum for the convolutional code is introduced.
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| 7. |
- Alvarado, Alex, 1982, et al.
(författare)
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Unequal Error Protection in BICM with QAM Constellations: Interleaver and Code Design
- 2009
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Ingår i: IEEE International Conference on Communications. - 1550-3607. - 9781424434350
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Konferensbidrag (refereegranskat)abstract
- In this paper we present a general methodology for the interleaver and code design for QAM-based BICM transmissions. We develop analytical bounds on the bit error rate and we use them to predict the performance of BICM when unequal error protection (UEP) is introduced by the constellation labeling. Based on these bounds, the optimum design of interleaver and code is presented. The improvements obtained reached 2~dB for the analyzed cases, and are obtained without complexity increase. Although previous works noted the influence of the interleaver design and the UEP, to the best of our knowledge, this paper is the first to analyze formally this problem for BICM transmissions.
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| 8. |
- Aulin, Jocelyn, 1964, et al.
(författare)
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Compressive Sensing Aided Determination of WCDMA Constrained Capacity
- 2012
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Ingår i: IEEE International Conference on Communications. - 1550-3607. - 9781457720536 ; , s. 4072-4077
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Konferensbidrag (refereegranskat)abstract
- The continual challenge for Wideband Code Division Multiple Access (WCDMA) communication networks is to provide increasingly higher data rates for more and more users for mobile broadband. Hence, WCDMA single-user and multiple-user capacity results are important references for practical WCDMA networks since they provide limits of performance to which practical systems strive to approach. Analysis and determination of the single and multiple-user WCDMA capacity for dispersive fading channels which include the effects of inter-symbol interference (ISI), inter-channel interference (ICI) and multi-user interference (MUI) (without over-simplifying assumptions to not restrict the applicability of the results) has been a difficult and computationally costly problem. In this paper, we study the WCDMA constrained capacity of a doubly-dispersive wide sense stationary uncorrelated scattering (WSSUS) fading channel, using an equivalent vector channel model of the system with inter-symbol, inter-channel and the multi-user interference due to multipath. To reduce the computational cost of determining the capacity numerically, due to interference, we propose a novel method based on compressive sensing (CS).
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| 9. |
- Aulin, Jocelyn, 1964, et al.
(författare)
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Compressive Sensing for the Capacity of a Rayleigh Fading Channel
- 2011
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Ingår i: 2011 IEEE International Conference on Communications, ICC 2011; Kyoto; Japan; 5 June 2011 through 9 June 2011. - : IEEE. - 1550-3607. - 9781612842325 ; , s. Art. no. 5962506-
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Konferensbidrag (refereegranskat)abstract
- A given objective function, $I(p_X(x))$, is to be maximized over the argument $p_X(x)$, where $p_X(x)$ is a continuous function of $x in R^1$. Rather than optimizing $I(p_X(x))$ over the domain of functions, where the optimal solution $p_X^*(x)$ is non-zero only at a few but unknown discrete points $x in {x_1 , x_2 , ldots , x_S } $, is it possible to solve the optimization problem by optimizing the objective function over S discrete components only? This is the main problem addressed and is solved using compressive sensing (CS) with application to the determination of the capacity of a discrete memoryless Rayleigh-fading channel with peak and average input power constraints. A novel optimization algorithm is developed and applied to a known example. Simulation results, using this novel optimization algorithm, are generated which provides an accurate estimate of the optimizing distribution and the resultant capacity. The significance of this approach is that it can be applied to optimization problems in general and specifically, to communication systems where the domain can be compressed.
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| 10. |
- Banugondi Rajashekara, Manoj, et al.
(författare)
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Adversarial Attacks on Deep Learning Based Power Allocation in a Massive MIMO Network
- 2021
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Ingår i: IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC 2021). - : IEEE. - 9781728171227
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Konferensbidrag (refereegranskat)abstract
- Deep learning (DL) is becoming popular as a new tool for many applications in wireless communication systems. However, for many classification tasks (e.g., modulation classification) it has been shown that DL-based wireless systems are susceptible to adversarial examples; adversarial examples are well-crafted malicious inputs to the neural network (NN) with the objective to cause erroneous outputs. In this paper, we extend this to regression problems and show that adversarial attacks can break DL-based power allocation in the downlink of a massive multiple-input-multiple-output (maMIMO) network. Specifically, we extend the fast gradient sign method (FGSM), momentum iterative FGSM, and projected gradient descent adversarial attacks in the context of power allocation in a maMIMO system. We benchmark the performance of these attacks and show that with a small perturbation in the input of the NN, the white-box attacks can result in infeasible solutions up to 86%. Furthermore, we investigate the performance of black-box attacks. All the evaluations conducted in this work are based on an open dataset and NN models, which are publicly available.
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