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We synthesize a maximum-likely algorithm for detecting an arbitrary-shaped signal with unknown duration and amplitude, which
is observed against the background of additive Gaussian white noise. The synthesized algorithm is analyzed on the assumption
of sufficiently large signal-to-noise ratios. Asymptotically accurate expressions for the detection-error probabilities are
found. The efficiency of the synthesized algorithm is estimated by numerical simulation and the applicability limits of the
asymptotic expressions are determined.

Content Type Journal ArticlePages 1-10DOI 10.1007/s11141-011-9296-2Authors
A. P. Trifonov, Voronezh State University, Voronezh, RussiaYu. É. Korchagin, Voronezh State University, Voronezh, RussiaP. A. Kondratovich, Voronezh State University, Voronezh, Russia

Journal Radiophysics and Quantum ElectronicsOnline ISSN 1573-9120Print ISSN 0033-8443

We perform theoretical analysis of the method of field focusing in a randomly inhomogeneous waveguide using reradiation of
the received signal with time reversal. The simplest case where point sources and receivers are used for emission and reception
is considered. As an example, the waveguide is chosen which simulates an underwater sound channel with refractive-index fluctuations
caused by random internal waves. In underwater acoustics, the considered method of field focusing is usually applied at relatively
short distances that are shorter than or about 10

We analyzed features of the influence of perturbations in an anisotropic medium on the propagation of quasioptical wave beams.
The solutions of the quasioptical equation in the nonaberrational approximation are found, which describe the evolution of
the wave-beam width. It is shown that the influence of perturbations in an anisotropic medium differs qualitatively from the
influence of the perturbations in an isotropic medium. Examples are presented of numerical calculations of the wave beam profiles
in model media corresponding to the cases of density and magnetic field perturbations in the magnetoplasma confined in toroidal
devices (tokamaks and stellarators).

Content Type Journal ArticlePages 1-9DOI 10.1007/s11141-011-9291-7Authors
A. A. Balakin, Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novrogod, RussiaE. D. Gospodchikov, Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novrogod, Russia

Journal Radiophysics and Quantum ElectronicsOnline ISSN 1573-9120Print ISSN 0033-8443

We study the conditions and features of the polariton mode lasing in traps for the Bose condensation of dipolar excitons.
We discuss the spectral linewidth of lasing modes and the effects of spatial and spectral inhomogeneity of the exciton distribution.
We study in detail the possibility of the polariton mode lasing in the vicinity of the Bose condensation threshold. We analyze
the impact of the inhomogeneous broadening of the exciton line on the stability of stationary lasing. We also propose additional
experiments aimed at obtaining more information on the polariton mode lasing in semiconductor structures for the Bose condensation
of excitons.

Content Type Journal ArticlePages 1-18DOI 10.1007/s11141-011-9293-5Authors
P. A. Kalinin, Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novgorod, RussiaV. V. Kocharovsky, Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novgorod, RussiaVl. V. Kocharovsky, Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novgorod, Russia

Journal Radiophysics and Quantum ElectronicsOnline ISSN 1573-9120Print ISSN 0033-8443

We consider the problem of parallel data transmission via several spatial channels in modern high-throughput cellular systems
employing the OFDM (Orthogonal Frequency Division Multiplexing) and antenna arrays at both ends of the communication system.
Parallel data transmission in such MIMO (Multiple Input Multiple Output) systems is achieved by using the beamforming schemes
in the transmitter and the special methods of the spatial-channel division in the receiver. Interference immunity of the scheme
of the spatial-channel division by the maximum-likelihood criterion using the method of successive interference cancellation
is analyzed. Probability of implementation of the stage of successive interference cancellation for the case of two spatial
channels and various combinations of the coding schemes and modulations is obtained. We analyze the efficiency of a cellular
communication system using horizontal coding and successive interference cancellation. Practical recommendations on choosing
modulation and the code speed for each spatial channel, which ensure maximum interference immunity of a receiver with successive
interference cancellation, are made.

Content Type Journal ArticlePages 1-8DOI 10.1007/s11141-011-9295-3Authors
A. V. Davydov, N. I. Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod, RussiaA. A. Mal’tsev, N. I. Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod, Russia

Journal Radiophysics and Quantum ElectronicsOnline ISSN 1573-9120Print ISSN 0033-8443