| 1. |
- 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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| 2. |
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| 3. |
- Alvarado, Alex, 1982, et al.
(författare)
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High-SNR Asymptotics of Mutual Information for Discrete Constellations
- 2013
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Ingår i: IEEE International Symposium on Information Theory - Proceedings. - 2157-8095. - 9781479904464 ; , s. 2274-2278
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Konferensbidrag (refereegranskat)abstract
- The high-signal-to-noise ratio (SNR) asymptotic behavior of the mutual information (MI) for discrete constellations over the scalar additive white Gaussian noise channel is studied. Exact asymptotic expressions for the MI for arbitrary one-dimensional constellations and input distributions are presented in the limit as the SNR tends to infinity. Using the relationship between the MI and the minimum mean-square error (MMSE), asymptotics of the MMSE are also developed. It is shown that for any input distribution, the MI and the MMSE have an asymptotic behavior proportional to a Gaussian Q-function, whose argument depends only on the minimum Euclidean distance of the constellation and the SNR. Closed-form expressions for the coefficients of these Q-functions are calculated.
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| 4. |
- Alvarado, A., et al.
(författare)
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High-SNR Asymptotics of Mutual Information for Discrete Constellations With Applications to BICM
- 2014
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Ingår i: IEEE Transactions on Information Theory. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9448 .- 1557-9654. ; 60:2, s. 1061-1076
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Tidskriftsartikel (refereegranskat)abstract
- Asymptotic expressions of the mutual information between any discrete input and the corresponding output of the scalar additive white Gaussian noise channel are presented in the limit as the signal-to-noise ratio (SNR) tends to infinity. Asymptotic expressions of the symbol-error probability (SEP) and the minimum mean-square error (MMSE) achieved by estimating the channel input given the channel output are also developed. It is shown that for any input distribution, the conditional entropy of the channel input given the output, MMSE, and SEP have an asymptotic behavior proportional to the Gaussian Q-function. The argument of the Q-function depends only on the minimum Euclidean distance (MED) of the constellation and the SNR, and the proportionality constants are functions of the MED and the probabilities of the pairs of constellation points at MED. The developed expressions are then generalized to study the high-SNR behavior of the generalized mutual information (GMI) for bit-interleaved coded modulation (BICM). By means of these asymptotic expressions, the long-standing conjecture that Gray codes are the binary labelings that maximize the BICM-GMI at high SNR is proven. It is further shown that for any equally spaced constellation whose size is a power of two, there always exists an anti-Gray code giving the lowest BICM-GMI at high SNR.
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| 5. |
- Alvarado, Alex, 1982, et al.
(författare)
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High SNR Bounds for the BICM Capacity
- 2011
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Ingår i: IEEE Information Theory Workshop ITW 2011, Paraty, Brazil. ; , s. 360-364
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Konferensbidrag (refereegranskat)abstract
- In this paper, different aspects of the bit-interleaved coded modulation (BICM) capacity for the Gaussian channel are analyzed. Analytical bounds for the BICM capacity are developed. These bounds suggest that the BICM capacity at high signal-to-noise ration (SNR) is determined by the multiplicity of the minimum Euclidean distance over all the subconstellations generated by the mapper. Based on this observation, we conjecture that for any constellation, the highest BICM capacity at high SNR is always obtained by a Gray code, if one exists. Ready-to-use expressions based on Gauss--Hermite quadratures to compute the coded modulation and BICM capacities for any SNR are also presented. Using these expressions, it is shown that the BICM capacity is in general a nonconvex, nonconcave function of the input bit distribution. For 8PAM and 8PSK, there exist 12 and 7 classes of mappings, respectively, with equivalent high-SNR behavior, of which the best class comprises all Gray codes.
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| 6. |
- Alvarado, Alex, 1982, et al.
(författare)
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On Optimal TCM Encoders
- 2013
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Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 61:6, s. 2178 - 2189
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Tidskriftsartikel (refereegranskat)abstract
- An asymptotically optimal trellis-coded modulation (TCM) encoder requires the joint design of the encoder and the binary labeling of the constellation. Since analytical approaches are unknown, the only available solution is to perform an exhaustive search over the encoder and the labeling. For large constellation sizes and/or many encoder states, however, an exhaustive search is unfeasible. Traditional TCM designs overcome this problem by using a labeling that follows the set-partitioning principle and by performing an exhaustive search over the encoders. In this paper we study binary labelings for TCM and show how they can be grouped into classes, which considerably reduces the search space in a joint design. For $8$-ary constellations, the number of different binary labelings that must be tested is reduced from $8!=40320$ to $240$. For the particular case of an $8$-ary pulse amplitude modulation constellation, this number is further reduced to $120$ and for $8$-ary phase shift keying to only $30$. An algorithm to generate one labeling in each class is also introduced. Asymptotically optimal TCM encoders are tabulated which are up to $0.3$~dB better than the previously best known encoders.
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| 7. |
- Alvarado, Alex, 1982, et al.
(författare)
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On the Equivalence of TCM Encoders
- 2012
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Ingår i: 2012 IEEE International Symposium on Information Theory, ISIT 2012. Cambridge, MA, 1 - 6 July 2012. - 9781467325790 ; , s. 2401-2405
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Konferensbidrag (refereegranskat)abstract
- Optimal trellis-coded modulation (TCM) schemes are obtained by jointly designing the convolutional encoder and the binary labeling of the constellation. Unfortunately this approach is infeasible for large encoder memories or constellation sizes. Traditional TCM designs circumvent this problem by using a labeling that follows the set-partitioning principle and by performing an exhaustive search over the encoders. Therefore, traditional TCM schemes are not necessarily optimal. In this paper, we study binary labelings for TCM and show how they can be grouped into classes, which considerably reduces the search space in a joint design. For the particular case of 8-ary modulation the search space is reduced from 40320 to 240. Using this classification, we formally prove that for any channel it is always possible to design a TCM system based on the binary-reflected Gray code with identical performance to the one proposed by Ungerboeck in 1982. Moreover, the classification is used to tabulate asymptotically optimal TCM schemes.
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| 8. |
- Andersson, Fredrik W., 1974, et al.
(författare)
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Sick listing-Partly a family phenomenon?
- 2011
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Ingår i: Journal of Socio-Economics. - : Elsevier BV. - 1053-5357. ; 40:5, s. 496-502
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Tidskriftsartikel (refereegranskat)abstract
- Being sick listed is not always identical to being ill; it is rather a behaviour associated with illness. In this paper we have analysed whether there is a higher risk of becoming sick listed if a family member has been sick listed earlier-partly a family phenomenon. This aspect of sick listing has never been investigated before. Our results indicate that an individual's risk of being sick listed in 2007 was higher if he/she had family members who had been sick listed in 2006. This may be a sign for an existing " sick listing culture" -social norms within families. © 2010 Elsevier Inc.
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| 9. |
- Bencheikh Lehocine, Chouaib, 1993, et al.
(författare)
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Antenna Combiner for Periodic Broadcast V2V Communication Under Relaxed Worst-Case Propagation
- 2023
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Ingår i: IEEE Transactions on Intelligent Transportation Systems. - 1524-9050 .- 1558-0016. ; 24:9, s. 9817-9834
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Tidskriftsartikel (refereegranskat)abstract
- The performance of a previously developed analog combining network (ACN) of phase shifters for periodic broadcast vehicle-to-vehicle (V2V) communication is investigated. The original ACN was designed to maximize the sum of signal-to-noise ratios (SNRs) for $K$ consecutive cooperative awareness messages (CAMs). The design was based on the assumption of a dominant propagation path with an angle of arrival (AOA) that is constant for $K$ messages. In this work, we relax this assumption by allowing the AOA and path-loss (PL) of the dominant path to be time-variant. Assuming a highway scenario with a line of sight (LOS) propagation between vehicles, we use affine approximations to model the time variation of different path quantities, including the PL, the relative distance-dependent phase shift between antennas, and the AOA-dependent far-field function of the antennas. By leveraging these approximations, we analytically derive the ACN sum-SNR as each one of these quantities varies over $K$ CAMs. Moreover, we suggest a design rule for a phase slope that is robust against time variation of the dominant path and optimal under time-invariant conditions. Finally, we validate this design rule using numerical computations and an example of vehicular communication antenna elements.
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| 10. |
- Bencheikh Lehocine, Chouaib, 1993, et al.
(författare)
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Hybrid Combining of Directional Antennas for Periodic Broadcast V2V Communication
- 2022
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Ingår i: IEEE Transactions on Intelligent Transportation Systems. - 1524-9050 .- 1558-0016. ; 23:4, s. 3226-3243
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Tidskriftsartikel (refereegranskat)abstract
- A hybrid analog-digital combiner for broadcast vehicular communication is proposed. It has an analog part that does not require any channel state information or feedback from the receiver, and a digital part that uses maximal ratio combining (MRC). We focus on designing the analog part of the combiner to optimize the received signal strength along all azimuth angles for robust periodic vehicle-to-vehicle (V2V) communication, in a scenario of one dominant component between the communicating vehicles (e.g., highway scenario). We show that the parameters of a previously suggested fully analog combiner solves the optimization problem of the analog part of the proposed hybrid combiner. Assuming L directional antennas with uniform angular separation together with the special case of a two-port receiver, we show that it is optimal to combine groups of ⌈L/2⌉ and ⌊L/2⌋ antennas in analog domain and feed the output of each group to one digital port. This is shown to be optimal under a sufficient condition on the sidelobes level of the directional antennas. Moreover, we derive a performance bound for the hybrid combiner to guide the choice of antennas needed to meet the reliability requirements of the V2V communication links.
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