| 1. |
- Alvarado, Alex, 1982, et al.
(author)
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On the performance of BICM with trivial interleavers in nonfading channels
- 2011
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In: IEEE International Conference on Communications ICC 2011. - : IEEE. - 1550-3607. - 9781612842332
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Conference paper (peer-reviewed)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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| 2. |
- Chatzidiamantis, N. D., et al.
(author)
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Diversity combining in hybrid RF/FSO systems with PSK modulation
- 2011
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In: IEEE International Conference on Communications. - : IEEE. - 1550-3607. - 9781612842332 ; , s. Art. no. 5962684-
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Conference paper (peer-reviewed)abstract
- We present a novel architecture for hybrid radio frequency (RF)/ free space optical (FSO) wireless systems without feedback or channel state information (CSI) at the transmitter. Under the assumption that 60 GHz RF and FSO systems support the same data rates, the proposed implementation transmits the same data over both links, using phase shift keying (PSK) as a common modulation scheme, and combines the signals from each individual link at the receiver on a symbol-by-symbol basis. Two popular diversity combining schemes are considered, namely, selection combining (SC) and maximal ratio combining (MRC), while tractable analytical approximations for the bit error rate (BER) are obtained. Investigations over various weather conditions and link distances revealed that the proposed implementation fully exploits the complementary nature of RF and FSO channels, even when one of the two available links fails. Furthermore, the comparison of the combining schemes demonstrates MRC as the optimum combining scheme, offering link distance gains compared to SC.
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| 3. |
- Gholami, Mohammad Reza, 1976, et al.
(author)
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Hybrid TW-TOA/TDOA Positioning Algorithms for Cooperative Wireless Networks
- 2011
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In: IEEE International Conference on Communications. - : IEEE. - 1550-3607. - 9781612842332
-
Conference paper (peer-reviewed)abstract
- The problem of positioning an unknown target is studied for a cooperative wireless sensor network using hybrid two-way time-of-arrival and time-difference-of-arrival measurements. A maximum likelihood estimator (MLE) can be employed to solve the problem. Due to the non-linear nature of the cost function in the MLE, a numerical method, e.g., an iterative search algorithm with a good initial point, should be taken to accurately estimate the target. To avoid drawbacks in a numerical method, we insteadlinearize the measurements and obtain a new two-step estimator that has a closed-form solution in each step.Simulation results confirm that the proposed linear estimator can attain Cram\'er-Rao lower bound for sufficiently high SNR.
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| 4. |
- Tan, Ahmet Serdar, 1982, et al.
(author)
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An ML-based Detector for Optical Communication in the Presence of Nonlinear Phase Noise
- 2011
-
In: IEEE International Conference on Communications. - : IEEE. - 1550-3607. - 9781612842332 ; , s. Art. no. 5962741-
-
Conference paper (peer-reviewed)abstract
- We present a closed-form maximum likelihood-based data detection algorithm for long-haul optical channels with dominant nonlinear phase noise induced by self-phase modulation. The closed-form detector is evaluated in terms of symbol error rate as a function of input power, and compared with other sub-optimal detectors as well as a non-parametric detector. We show that the performance of the detector deteriorates for high input power levels, resulting in an optimal operation region. We also provide insights into the behavior of the detector in the highly nonlinear regime.
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| 5. |
- Abu-Shaban, Z., et al.
(author)
-
Near-field Localization with a Reconfigurable Intelligent Surface Acting as Lens
- 2021
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In: IEEE International Conference on Communications. - 1550-3607. ; June 2021
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Conference paper (peer-reviewed)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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| 6. |
- Ahmad, Suhail, 1992, et al.
(author)
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Predictive Resource Allocation Evaluation with Real Channel Measurements
- 2017
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In: IEEE International Conference on Communications. - 1550-3607.
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Conference paper (peer-reviewed)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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| 7. |
- Alegria, Juan Vidal, et al.
(author)
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Enabling Decentralized Computation of the WAX Decomposition
- 2022
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In: ICC 2022 - IEEE International Conference on Communications. - 1550-3607. ; 2022
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Conference paper (peer-reviewed)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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| 8. |
- Alvarado, Alex, 1982, et al.
(author)
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Correcting Suboptimal Metrics in Iterative Decoders
- 2009
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In: IEEE International Conference on Communications. - 1550-3607. - 9781424434350
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Conference paper (peer-reviewed)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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| 9. |
- Alvarado, Alex, 1982, et al.
(author)
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Unequal Error Protection in BICM with QAM Constellations: Interleaver and Code Design
- 2009
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In: IEEE International Conference on Communications. - 1550-3607. - 9781424434350
-
Conference paper (peer-reviewed)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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| 10. |
- Aulin, Jocelyn, 1964, et al.
(author)
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Compressive Sensing Aided Determination of WCDMA Constrained Capacity
- 2012
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In: IEEE International Conference on Communications. - 1550-3607. - 9781457720536 ; , s. 4072-4077
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Conference paper (peer-reviewed)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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