One of the main challenges already faced by communication networks is the efficient management of increasing complexity. Cognitive networks are put forwarded in the framework of evolution of network architectures as novel paradigms to provide autonomous in network reasoning to support end to end goals. This paper aims at proposing a new method for modifying spectral efficiency of topology control using new vertex coloring algorithm in Thomas cognitive networks.

One of the most important designing problems in cellular communication is the Channel Assignment Problem (CAP). The goal of Channel Assignment is to assign the required number of Channels to each cell, such that frequency spectrum utilization is maximized and frequency interference effect is minimized. Due to the limitation of the usable frequency spectrum, the optimal Channel Assignment can improve capacity, quality, and performance of the system. Since in its simplest form this problem is known to be equivalent to a graph-coloring problem, belonging to the class of NP-complete optimization problems, different techniques such as heuristic techniques, neural networks, simulated annealing, and evolutionary algorithms have been used to solve it. In this paper, a modified Hopfield neural network has been proposed. The modifications, include structure of the network, initialization method, and the updating procedure. In the network structure, contrary to usual structures, there is also a connection from each neuron’s output to its input with negative weight and instead convergence is obtainable with the procedure of updating. Simulation results show better performance than the previous presented networks.

Spectrum shortage in Vehicular Communications has become an area of concern due to the diverse nature of applications served. Though the allocated 5.9GHz Dedicated Short Range Communication (DSRC) spectrum for vehicular communication is inefficiently utilized, the problem of congestion creates an impression that there is always a scarcity in the spectrum. The criticality of the issue becomes high when a safety message is unable to access the Channel or is dropped due to congestion. This paper proposes an approach to prioritize Channel access to safety messages through dynamic spectrum sharing. In case, when a safety message finds all the DSRC sub-Channels occupied, then any one of the ongoing non-safety messages is switched over to the adjacent 5.8GHz ISM/UNII-3 band allowing the former to access the DSRC band. The proposed approach shows an increased QoS and reduced Channel access delay for safety messages compared to the previous works.

In this paper, we study relay-assisted underlay Device-to-Device (D2D) communication operating at millimeter-wave (mmWave) band in which halfduplex/ full-duplex (HD/FD) relays may assist D2D users to improve transmission quality and coverage range. We aim to jointly select D2D transmission mode, assign one or more cellular resource blocks (RBs) to each D2D user and control the powers of users to maximize the aggregate data rate of the network. We focus on the main features of mmWave communication including larger bandwidth, directive antenna arrays utilization, and severe path loss and shadowing. As the optimization problem is mixed-integer-non-linear programming, two heuristic algorithms are proposed, assuming full Channel Side Information (CSI) and limited CSI at Base Station, respectively. Simulation results show the superiority of utilizing FD relays, especially for non-line-of-sight links, which is the dominant propagation mechanism in mmWave band. Furthermore, mode selection may imropves the performance in the case of large residual-selfinterference. The limited CSI algorithm has considerably lower complexity. Moreover, when the number of RBs far exceeds the number of D2D users, the gap between two algorithms vanishes.

In this paper, dual-hops and multi-hops cognitive radio Ad Hoc networks has been considered. It is vital mentioning that the primary user interference effect on the secondary user has also been considered. The design of the problem is to achieve an optimal solution for Channel allocation and power in dual and multi hop in Cognitive Radio Ad Hoc Networks (CRNs). The main goal is to minimize the outage probability and increasing the length of your network life time, while simultaneously observing the transmission power constraints and the threshold of interference with the primary user. This problem was solved using the standard technique of solving convex optimization problem and weighted bipartite matching. All of the analysis is for both DF, and amplifying and transmission AF protocols. Comparison and measurement of the systems performance is outage probability. Simulation results have shown that the proposed scheme not only minimizes the outage probability compared to existing ones, but also reduces PU interference and saves overall transmission efficiency by Secondary Users.

An important problem for the WiMAX networks is how to provide a guaranteed quality of service for applications. A key aspect of this problem is how BSs should share bandwidth capacity between different classes of traffic. This decision needs to be made for each incoming packet, and is known as the packet scheduling problem.A major challenge in packet scheduling is that the behavior of each traffic class may not be known in advance, and can vary dynamically.In this paper, we describe how we have modeled the packet scheduling problem as an application for reinforcement learning (RL). We demonstrate how our RL approach can learn scheduling policies that satisfy the quality of service requirements of multiple traffic classes under a variety of conditions. The proposed solution has been designed to have an ability to accommodate integrated traffic in the networks with effective scheduling schemes. A series of simulation experiments have been carried out to evaluate the performance of the proposed scheduling algorithm. The results reveal that the proposed solution performs effectively to the integrated traffic composed of messages with or without time constraints and achieves proportional fairness among different types of traffic.

In this paper, we propose smart step closed-loop power control (SSPC) algorithm and base station Assignment based on minimizing the transmitter power (BSAMTP)technique in a direct sequence-code division multiple access (DS-CDMA) receiver in  the presence of frequency-selective Rayleigh fading. This receiver consists of three stages. In the first stage, with conjugate gradient (CG) adaptive beam forming algorithm, the desired users’ signal in an arbitrary path is passed and the inter-path interference is canceled in other paths in each RAKE finger. Also in this stage, the multiple access interference (MAI) from other users is reduced. Thus, the matched filter (MF) can be used for the MAI reduction in each RAKE finger in the second stage. Also in the third stage, the output signals from the matched filters are combined according to the conventional maximal ratio combining (MRC) principle and then are fed into the decision circuit of the desired user. The simulation results indicate that the SSPC algorithm and the BSA-MTP technique can significantly improve the network bit error rate (BER) in comparison with other algorithms. Also, we observe that significant savings in total transmit power (TTP) are possible with our proposed methods.