On the exact distribution of mutual information of two-user mimo mac based on quotient distribution of wishart matrices

We propose an exact calculation of the probability density function (PDF) and cumulative distribution function (CDF) of mutual information (MI) for a two-user multiple-input multiple-output (MIMO) multiple access channel (MAC) network over block Rayleigh fading channels. This scenario can be found in the uplink channel of MIMO non-orthogonal multiple access (NOMA) system, a promising multiple access technique for 5G networks. So far, the PDF and CDF have been numerically evaluated since MI depends on the quotient of two Wishart matrices, and no closed form for this quotient was available. We derive exact results for the PDF and CDF of extreme (the Smallest/the largest) eigenvalues. Based on the results of quotient ensemble, the exact calculation for PDF and CDF of mutual information is presented via Laplace transform approach and by direct integration of joint PDF of quotient ensemble's eigenvalues. Furthermore, our derivations also provide the parameters to apply the Gaussian approximation method, which is comparatively easier to implement. We show that approximation matches the exact results remarkably well for outage probability, i.e., CDF, above 10%. However, the approximation could also be used for 1% outage probability with a relatively Small error. We apply the derived expressions to investigate the effects of adding antennas in the receiver and its ability to decode the weak user signal. By supposing no channel knowledge at transmitters and successive decoding at receiver, the capacity of the weak user increases and its outage probability decreases with the increment of extra antennas at the receiver end2017CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESnão temBEX10714/14-

On the distribution of an effective channel estimator for multi-cell massive MIMO

Accurate channel estimation is of utmost importance for massive MIMO systems to provide significant improvements in spectral and energy efficiency. In this work, we present a study on the distribution of a simple but yet effective and practical channel estimator for multi-cell massive MIMO systems suffering from pilot-contamination. The proposed channel estimator performs well under moderate to aggressive pilot contamination scenarios without previous knowledge of the inter-cell large-scale channel coefficients and noise power, asymptotically approximating the performance of the linear MMSE estimator as the number of antennas increases. We prove that the distribution of the proposed channel estimator can be accurately approximated by the circularly-symmetric complex normal distribution, when the number of antennas, M, deployed at the base station is greater than 10

Accurate log-normal approximation to the signal-to-interference ratio in massive multiple-input multiple-output systems

In this paper, a very tight approximation is derived for the signal-to-interference ratio of a multicell massive multiple-input multiple-output system with a finite number of base station (BS) antennas. The approximation is derived considering that each term in the SIR is log-normal distributed. To this end, the first and second moments of the logarithm of each variable are used. In addition, an exact expression is derived for the cumulative distribution function for the net capacity. In order to corroborate our derivations, simulations using the Monte Carlo method were carried out, and it was observed that the proposed analytical results tightly match the numerical simulations. The asymptotic result is also obtained for the case in which the number of BS antennas tends to infinity (M -> infinity), considering both uniform and nonuniform spatial user distributions14FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP2016/16181-

Comments on “Cutset bounds on the capacity of MIMO relay channels”

We comment on the paper “Cutset Bounds on the Capacity of MIMO Relay Channels”by Jeong et al. and point out that, unlike what appears from a remark and some other contents by these authors, the matrix distribution for the sum of two complex random Wishart matrices has already been derived by Kumar for the general case of arbitrary covariance matrices and not only for the special case when one of them is assumed proportional to the identity matrix. The latter assumption has been made only for deriving the corresponding eigenvalue distribution. Furthermore, we draw attention to the result that when all covariance matrices are chosen proportional to the identity matrix, then it is possible to obtain exact and closed form expressions for the sum of an arbitrary number of Wishart matrices and not only for two as considered by Jeong et al6351293513

Activation of Fgf4 Gene Expression in the Myotomes Is Regulated by Myogenic bHLH Factors and by Sonic Hedgehog

AbstractThe Fgf4 gene encodes an important signaling molecule which is expressed in specific developmental stages, including the inner cell mass of the blastocyst, the myotomes, and the limb bud apical ectodermal ridge (AER). Using a transgenic approach, we previously identified overlapping but distinct enhancer elements in the Fgf4 3′ untranslated region necessary and sufficient for myotome and AER expression. Here we have investigated the hypothesis that Fgf4 is a target of myogenic bHLH factors. We show by mutational analysis that a conserved E box located in the Fgf4 myotome enhancer is required for Fgf4-lacZ expression in the myotomes. A DNA probe containing the E box binds MYF5, MYOD, and bHLH-like activities from nuclear extracts of differentiating C2-7 myoblast cells, and both MYF5 and MYOD can activate gene expression of reporter plasmids containing the E-box element. Analyses of Myf5 and MyoD knockout mice harboring Fgf4-lacZ transgenes show that Myf5 is required for Fgf4 expression in the myotomes, while MyoD is not, but MyoD can sustain Fgf4 expression in the ventral myotomes in the absence of Myf5. Sonic hedgehog (Shh) signaling has been shown to have an essential inductive function in the expression of Myf5 and MyoD in the epaxial myotomes, but not in the hypaxial myotomes. We show here that expression of an Fgf4-lacZ transgene in Shh−/− embryos is suppressed not only in the epaxial but also in the hypaxial myotomes, while it is maintained in the AER. This suggests that Shh mediates Fgf4 activation in the myotomes through mechanisms independent of its role in the activation of myogenic factors. Thus, a cascade of events, involving Shh and bHLH factors, is responsible for activating Fgf4 expression in the myotomes in a spatial- and temporal-specific manner

Bit error rate closed-form expressions for lora systems under nakagami and rice fading channels

We derive exact closed-form expressions for Long Range (LoRa) bit error probability and diversity order for channels subject to Nakagami-m, Rayleigh and Rician fading. Analytical expressions are compared with numerical results, showing the accuracy of our proposed exact expressions. In the limiting case of the Nakagami and Rice parameters, our bit error probability expressions specialize into the non-fading case1920CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ313239/2017-7; 304946/2016-

Performance analysis of a multijunction solar cell operating under natural conditions and various concentration rates

El desempeño de una celda fotovoltaica multiunión con 1,0 cm2 es evaluado para varias tasas de concentración. Parámetros que caracterizan la celda son extraídos de curvas características obtenidas experimentalmente con base en el modelo de un diodo. Especial atención es dedicada a resistencia serie de la celda. Resultados demuestran que el procedimiento es consistente, permitiendo obtener una visión general del comportamiento de las celdas multiunión, a pesar de grandes variaciones experimentales de temperatura y radiación. Se observa una alta resistencia serie (3,8 Ω) para baja concentración. Esta resistencia disminuye, alcanzando un valor estable para altas concentraciones (0,024 Ω). Se han medido eficiencias promedio de conversión del 35% cuando se convierte la temperatura de referencia. La resistencia serie obtenida para altas concentraciones limita el índice de concentración que corresponde a máxima eficiencia entre 243 y 278. Mayores índices de concentración y probablemente eficiencias superiores requieren mayor reducción de la resistencia serie.The performance of a CPV multijunction (MJ) cell of 1.0 cm2 was evaluated for various concentration ratios. Parameters which characterize the cell were extracted from experimental characteristic curves using the one diode model. Special attention was given to series resistance which effects can change significantly the cell performance. Results obtained show that the procedure adopted is considerably consistent, enabling to obtain a general picture of solar cell behavior in spite of large temperature and irradiance experimental variations. A large series resistance (3.8 Ω) is observed for low concentration values. This resistance decays rapidly, attaining a stable value for high concentrations (0.024 Ω). Average conversion efficiency of 35% have been measured when converted to temperatures of 47 ºC. Series resistance obtained for high concentrations limits concentration ratio corresponding to maximum efficiency to values between 243 and 278. Higher concentration ratios and probably higher efficiencies require further reduction of series resistance.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES

Capacity bounds for dense massive MIMO in a line-of-sight propagation environment

The use of large-scale antenna arrays grants considerable benefits in energy and spectral efficiency to wireless systems due to spatial resolution and array gain techniques. By assuming a dominant line-of-sight environment in a massive multiple-input multiple-output scenario, we derive analytical expressions for the sum-capacity. Then, we show that convenient simplifications on the sum-capacity expressions are possible when working at low and high signal-to-noise ratio regimes. Furthermore, in the case of low and high signal-to-noise ratio regimes, it is demonstrated that the Gamma probability density function can approximate the probability density function of the instantaneous channel sum-capacity as the number of served devices and base station antennas grows, respectively. A second important demonstration presented in this work is that a Gamma probability density function can also be used to approximate the probability density function of the summation of the channel's singular values as the number of devices increases. Finally, it is important to highlight that the presented framework is useful for a massive number of Internet of Things devices as we show that the transmit power of each device can be made inversely proportional to the number of base station antennas.20