A rectangular radio pulse propagation in a selectively absorbing medium

A pulse with rectangular envelope propagation, in which carrier frequency is close to the medium spectral absorption line’s one frequency, is considered. It is shown that when the signal carrier frequency is shifted relative to the spectral line centre, the primary interference and the response signal can lead to the total signal significant oscillations over time.

Bit Error Rate Analysis of Cognitive Radio Network in the Presence of Primary Interference

In this paper, Bit Error Rate (BER) of Orthogonal Frequency Division Multiplexing (OFDM) based cognitive radio network is analyzed in the presence of Primary User Interference (PUI). Since, the PUI signal affects only few subcarriers of the OFDM signal, it can be modeled as a sparsity vector. In this network model, half duplex Amplify and Forward (AF) relaying is considered in the absence of direct link. Further, it is assumed that the network is operating in the overlay mode, thus the primary user transmitted signal act as interference at secondary user relay and destination nodes. In this paper, the PUI is mitigated using convex optimization. Bit Error Rate (BER) is analyzed using Quadrature Phase Shift Keying (QPSK) Modulation and Quadrature Amplitude Modulation (16-QAM). Simulation results conclude that after primary interference suppression, the performance of the proposed system is significantly improved.

On some sufficient conditions for distributed QoS support in wireless networks

Given a wireless network where some pairs of communication links interfere with each other, we study sufficient conditions for determining whether a given set of minimum bandwidth Quality of Service (QoS) requirements can be satisfied. We are especially interested in distributed implementations which have low communication overhead and low processing complexity. Row constraints are known to be sufficient, and we introduce the notion of the induced star number of a graph and show that this quantity determines the performance of this condition. We further investigate this problem for some special classes of networks and interference models such as unit disk networks and primary interference constraints. We determine the exact worst-case performance of some distributed algorithms for admission control and thereby show that they can be arbitrarily far away from optimal; we then show that these algorithms are within a bounded factor away from optimal for some well known classes of networks and interference models.