A survey on MAC protocols for complex self-organizing cognitive radio networks

Complex self-organizing cognitive radio (CR) networks serve as a framework for accessing the spectrum allocation dynamically where the vacant channels can be used by CR nodes opportunistically. CR devices must be capable of exploiting spectrum opportunities and exchanging control information over a control channel. Moreover, CR nodes should intelligently coordinate their access between different cognitive radios to avoid collisions on the available spectrum channels and to vacate the channel for the licensed user in timely manner. Since inception of CR technology, several MAC protocols have been designed and developed. This paper surveys the state of the art on tools, technologies and taxonomy of complex self-organizing CR networks. A detailed analysis on CR MAC protocols form part of this paper. We group existing approaches for development of CR MAC protocols and classify them into different categories and provide performance analysis and comparison of different protocols. With our categorization, an easy and concise view of underlying models for development of a CR MAC protocol is provided

Remaining idle time aware intelligent channel bonding schemes for cognitive radio sensor networks

Channel bonding (CB) is a technique used to provide larger bandwidth to users. It has been applied to various networks such as wireless local area networks, wireless sensor networks, cognitive radio networks, and cognitive radio sensor networks (CRSNs). The implementation of CB in CRSNs needs special attention as primary radio (PR) nodes traffic must be protected from any harmful interference by cognitive radio (CR) sensor nodes. On the other hand, CR sensor nodes need to communicate without interruption to meet their data rate requirements and conserve energy. If CR nodes perform frequent channel switching due to PR traffic then it will be difficult to meet their quality of service and data rate requirements. So, CR nodes need to select those channels which are stable. By stable, we mean those channels which having less PR activity or long remaining idle time and cause less harmful interference to PR nodes. In this paper, we propose two approaches remaining idle time aware intelligent channel bonding (RITCB) and remaining idle time aware intelligent channel bonding with interference prevention (RITCB-IP) for cognitive radio sensor networks which select stable channels for CB which have longest remaining idle time. We compare our approaches with four schemes such as primary radio user activity aware channel bonding scheme, sample width algorithm, cognitive radio network over white spaces and AGILE. Simulation results show that our proposed approaches RITCB and RITCB-IP decrease harmful interference and increases the life time of cognitive radio sensor nodes

Technological and chemical properties of heat-treated Anatolian black pine wood

In this study the effect of heat treatment on air-dry density (Dm), oven-dry density (D0), shrinkage (), swelling (), fiber saturation point (FSP), compression strength parallel to grain (c//), bending strength (b), modulus of elasticity (MOE) in bending, Brinell-hardness (HB), equilibrium moisture content (EMC), chemical content and cellulose crystallinity of Anatolian black pine [Pinus nigra J.F. Arnold subsp. nigra var. caramenica (Loudon) Rehder] was evaluated. Specimens were subjected to heat under atmospheric pressure at 3 different temperature (130, 180 and 230°C) and 2 different time levels (2 and 8 h). The value of Dm, D0, , , FSP, EMC, c//, b, MOE, holocellulose, 1% NaOH and alcohol solubility decreased, whereas, lignin content increased depending on the heating temperature and the time. Cellulose crystallinity of the specimens was not changed significantly. 130°C showed minimum effect, on the other hand, 230°C showed maximum effect on all properties of treated wood. Accordingly, for heat treatment process, 130°C for 2 h should be applied in place where mechanical properties are important. However, 230°C for 2 h should be used in place where a physical property is preferred.Consequently, heat treated Anatolian black pine woods could be utilized in applications for several purposes such as kitchen furniture, outdoor furniture and windows frames

High temperature treatment allows the detection of episesamin in paulownia wood extractives

The composition and the relative variation of secondary metabolites of Paulownia tomentosa S. wood under thermal effect is a little explored area. Wood material was previously thermo-treated at 210 °C for 3 hours using a press vacuum technology. Extractives of untreated and thermo-treated wood material achieved with Soxhlet extraction techniques were obtained. Then the extracts were chromatographed by using thin layer chromatography. Component groups in extracts were determined by gas chromatography in combination with mass spectrometry. In terms of wood change the thermo-treatment of wood induces a darkening of wood color surface (ΔL* = 28.3), an increase of mass loss (3.5%) and an increase of the amount of extractives and lignin content as well as an increase of the chloroform soluble fraction. This work mainly describes the chemical exploration of the extract from paulownia wood, leading to the isolation and identification of episesamin