Cognitive network

About: Cognitive network is a research topic. Over the lifetime, 4213 publications have been published within this topic receiving 107093 citations.

Energy-efficient user association in cognitive heterogeneous networks

Abstract: Due to the ever increasing data traffic demands, which are directly connected to increased energy consumption, it becomes challenging for operators to achieve capacity enhancement while limiting their electric bill. To that end, exploiting the context awareness of future cognitive networks is expected to play a key role. Next generation cellular networks are about to include a plethora of small cells, with users being able to communicate via multiple bands. Given that small cells are expected to be eventually as close as 50 m apart, not all of them will have a direct connection to the core network; thus, multihop communication through neighboring small cells may be required. In such architectures, the user association problem becomes challenging, with backhaul energy consumption being a definitive parameter. Thus, in this article, we study the user association problem in cognitive heterogeneous networks. We evaluate the existing approaches in terms of energy efficiency and show the potential of exploiting the available context-aware information (i.e., users' measurements and requirements, knowledge of the network architecture, and the available spectrum resources of each base station) to associate the users in an energy-efficient way, while maintaining high spectrum efficiency. Our study considers both the access network and backhaul energy consumption, while the performance of the association algorithms is evaluated under two different case study scenarios.

Uplink Scheduling with QoS Provisioning for Cognitive Radio Systems

Abstract: Scheduling schemes have been extensively studied in the framework of cellular networks, but the emergence of new system concepts, such as cognitive radio, brings this topic into the focus of research again. In this paper, we investigate multiuser uplink scheduling with quality-of-service (QoS) provisioning for multiple cognitive users working at the same area with a primary user. In this work, the proposed scheduling schemes attempt to provide a satisfactory tradeoff between maximizing the system capacity, achieving fairness among cognitive users, minimizing the interference to the primary user, and satisfying delay constraints to individual cognitive user. Simulation results are presented to evaluate the performance of the proposed scheduling schemes.

Queueing analysis of opportunistic access in cognitive radios

Abstract: This paper presents queueing analysis of opportunistic access in cognitive radios. The primary (licensed user) has priority over the secondary user and it does not need to care about the secondary user transmissions. A time slotted system is assumed, so that the secondary user can perform spectrum sensing at the beginning of the slot to know if it is occupied by primary or not. If the slot is free, it can be utilized for secondary transmissions. This leads to no interference with primary user communication, assuming perfect sensing. Finding waiting time and queue length of this type of system has not, according to our best knowledge, been performed before. We perform theoretical analysis by applying M/D/1 priority queueing scheme. The results were used to evaluate the performance of the cognitive network. Simulation are used to validate the results, and simulation results demonstrate a high degree of accuracy for the derived expressions. Results indicate that the performance of the secondary user depends on the data traffic characteristics of the primary user, and under high arrival rate for the primary, the average waiting and average queueing length of the secondary user grow especially when the combined arrival rate approach the queue utilization factor.

Docitive networks: an emerging paradigm for dynamic spectrum management [Dynamic Spectrum Management]

Abstract: Prime design goals for next-generation wireless networks to support emerging applications are spectral efficiency and low operational cost. Among a gamut of technical solutions, cognitive approaches have long been perceived as a catalyst for the above goals by facilitating the coexistence of primary and secondary users by means of efficient dynamic spectrum management. While most available techniques today are essentially opportunistic in nature, a truly cognitive device needs to exhibit a certain degree of intelligence to draw optimum decisions based on prior observations and anticipated actions. Said intelligence however, comes along with high complexity and poor convergence, which currently prevents any viable deployment of cognitive networks. We thus introduce an emerging and largely unexplored concept of docitive networks, where nodes effectively teach other nodes with the prime aims of reducing cognitive complexity, speeding up the learning process, and drawing better and more reliable decisions. To this end, we review some important concepts borrowed from the machine learning community for both centralized and decentralized systems, in order to position the emerging docitive with known cognitive approaches. Finally, we validate introduced concepts in the context of a primary digital television system dynamically coexisting with IEEE 802.22 secondary networks. For this scenario, we demonstrate the superiority of various unprecedented docitive over known opportunistic/cognitive algorithms.

Cognitive Radio Networks: The Spectrum Supply Chain Paradigm

Abstract: Cognitive radio provides a basis for addressing the practical issue of spectrum scarcity. This issue has been raised due to the continuing advances in wireless technology, which has led to ever-increasing demand for larger bandwidth. The issue of spectrum scarcity has been exacerbated due to inefficient use of the electromagnetic spectrum. Adopting the novel idea of cognitive radio for secondary usage of underutilized spectrum results in the existence of two worlds of wireless communications going on side by side: the legacy wireless world and the cognitive wireless world. Spectrum holes (i.e., the unused spectrum subbands) are the medium, through which these two worlds dynamically interact. Releasing subbands by primary users allows the cognitive radio users to sustain communication and perform their normal tasks. Combination of the two wireless worlds can be viewed as a spectrum-supply chain network, in which the legacy owners and their customers (primary users) play the role of the suppliers and cognitive radios (secondary users) play the role of consumers. This paper discusses two classes of spectrum-supply chain networks based on two regimes, one allows open-access to the spectrum, and the other is a market-driven regime. Each one of them has its own merits and suitability for a different environment; therefore, they have complementary roles. Analytic models are developed for these two classes of networks, which allow for analysis of both equilibrium and transient behaviors.