This paper investigates the impact of using directional antennas and beamforming schemes on the connectivity of cognitive radio ad hoc networks (CRAHNs). Specifically, considering that secondary users use two kinds of directional antennas, i.e., uniform linear array (ULA) and uniform circular array (UCA) antennas, and two different beamforming schemes, i.e., randomized beamforming and center-di...

For the random binary search tree with n nodes inserted the number of ancestors of the elements with ranks k and `, 1 ≤ k < ` ≤ n, as well as the path distance between these elements in the tree are considered. For both quantities central limit theorems for appropriately rescaled versions are derived. For the path distance the condition ` − k → ∞ as n → ∞ is required. We obtain tail bounds and ...

For several real-time applications it is critical that the failure of a network component does not lead to unexpected termination or long disruption of service. In this paper, we propose a scheme called RAFT (Resource Aggregation for Fault Tolerance) that guarantees recovery in a timely and resource-eecient manner. RAFT is presented in the framework of the Reliable Backbone (RBone), a virtual n...

Some features of SCTP provide opportunities for creating redundancies for signalling over IP networks. This paper presents the behaviour of SCTP in failover scenarios, based on literature review and simulations. Simulations were carried out using NS2 in a multi-homing environment. It was found, as expected, that when failover took place, the undelivered chunks were retransmitted to the secondar...

In this paper a modified version of the Akthar’s method for online secondary path modeling in active noise control systems is proposed. The proposed method defines two variable step sizes for control filter and modeling filter. The control filter step size μm is adapted by using the variable threshold value Tj and the modeling filter step size μm is adapted by using a new modified variable step...

Reasonable welding path has a significant impact on welding efficiency, and a collision-free path should be considered first in the process of welding robot path planning. The shortest path length is considered as an optimization objective, and obstacle avoidance is considered as the constraint condition in this paper. First, a grid method is used as a modeling method after the optimization obj...