We consider an unreliable queueing system which can be used for modeling a broadband hybrid communication channel consisting FSO (Free Space Optics) channel and radio wave channel. The radio channel is backup and is connected when the optical channel is not available. In order to save energy, a hysteresis strategy for connecting a backup channel is used. This strategy is given by two thresholds: j1 and j2,j1 ≤ j2. If the main channel fails, the backup channel connects to information transmission if the number i of customers in the system is such that i>j 2. If during backup channel operation the number of customers in the system becomes such that i ≤ j1, then the backup channel is disabled and the current customer continues to be serviced at the main server. If at some point in time the number i of customers in the system becomes such that j1

The paper provides a brief overview of the state-of-the-art of development of tethered high-altitude unmanned telecommunication platforms. It is described an architecture, scientific and technical issues and the designing principles of such platforms which can be used to expand the capabilities of ground-based electronic warfare. The experience of Institute of Control Sciences (ICS RAS) on the development and implementing the tethered platform is also presented.

The paper describes a formal model of social network users who have definite sets of interests in different subjects. The users are represented by heterogeneous agents with multiple inputs of different types and multiple outputs of different types (MIMO-agents). Each type corresponds to one of the interests of users. Agents have a cumulative activation function, depending on current external influence from their neighbors and previous network states. If the value of this function at a certain time step is above a specified threshold, the agent becomes active according to one of the types. The choice of this type depends both on his internal structure (personal preferences specified by a vector) and on the proportion of active neighbors of every type. A network of such agents is capable of generating various kinds of complex activity patterns. We consider several examples of activity propagation and show the dependence of stable activity patterns on the parameters of agents. Networks of MIMO-agents with similar properties can be used not only to describe the interaction of users of social networks, but also in modeling the transfer of heterogeneous information in telecommunications networks.

Methods of queueing theory are often used for telecommunication systems performance evaluation. According to this approach, all MAC and PHY layer protocols details are modelled with a given service time distribution, and the precision of the estimated properties depends on this distribution function selection. While for Ethernet and wireless relay networks the service time is roughly equal to the sum of packet and headers sizes divided by the channel bitrate, it is not so easy to estimate the service time for wireless networks channels based on CSMA/CA including IEEE 802.11 (WiFi) and IEEE 802.15.4 (ZigBee) due to random exponential backoff and collisions. In this paper we use a simple model of the saturated channel described as a semi-Markov random absorbing process, which is based on Bianchi model [2]. We use this process to find a service time phase-type (PH) distribution matching the first two moments of the semi-Markov process. We also use channel simulation model to sample transmission delays in unsaturated mode and find another PH-distribution using G-FIT [12] algorithm. Then we use these PH-distributions to estimate end-to-end delays, queue sizes and nodes utilization in a multi-hop wireless network with linear topology using M/PH/1/N→∙/PH/1/N∙⋯∙/PH/1/N queueing network. All results are compared to wireless network simulation model, and demonstrate the cases in which the queueing network tends to provide results close to real network performance.

We present a new covering theorem for a nonlinear mapping on a convex cone, under the assumptions weaker than the classical Robinson’s regularity condition. When the latter is violated, one cannot expect to cover the entire neighborhood of zero in the image space. Nevertheless, our covering theorem gives rise to natural conditions guaranteeing stability of a solution of a cone-constrained equation subject to wide classes of perturbations, and allowing for nonisolated solutions, and for systems with the same number of equations and variables. These features make these results applicable to various classes of variational problems, like nonlinear complementarity problems. We also consider the related stability issues for generalized Nash equilibrium problems.