Performance analysis of a novel decentralised MAC protocol for cognitive radio networks

Due to the demand of emerging Cognitive Radio (CR) technology to permits using the unused licensed spectrum parts by cognitive users (CUs) to provide opportunistic and efficient utilisation of the white spaces. This requires deploying a CR MAC with the required characteristics to coordinate the spectrum access among CUs. Therefore, this paper presents the design and implementation of a novel Medium Access Control (MAC) protocol for decentralised CRNs (MCRN). The protocol provides efficient utilisations of the unused licensed channels and enables CUs to exchange data successfully over licensed channels. This is based on the observation procedure of sensing the status of the Licensed Users (LUs) are ON or OFF over the licensed channels. The protocol is validated with the comparison procedure against two different benchmark protocols in terms of the network performance; communication time and throughput. Therefore, performance analysis demonstrated that the proposed MCRN perform better and achieve higher throughput and time benefits than the benchmarks protocols

Spectrum sharing security and attacks in CRNs: a review

Cognitive Radio plays a major part in communication technology by resolving the shortage of the spectrum through usage of dynamic spectrum access and artificial intelligence characteristics. The element of spectrum sharing in cognitive radio is a fundament al approach in utilising free channels. Cooperatively communicating cognitive radio devices use the common control channel of the cognitive radio medium access control to achieve spectrum sharing. Thus, the common control channel and consequently spectrum sharing security are vital to ensuring security in the subsequent data communication among cognitive radio nodes. In addition to well known security problems in wireless networks, cognitive radio networks introduce new classes of security threats and challenges, such as licensed user emulation attacks in spectrum sensing and misbehaviours in the common control channel transactions, which degrade the overall network operation and performance. This review paper briefly presents the known threats and attacks in wireless networks before it looks into the concept of cognitive radio and its main functionality. The paper then mainly focuses on spectrum sharing security and its related challenges. Since spectrum sharing is enabled through usage of the common control channel, more attention is paid to the security of the common control channel by looking into its security threats as well as protection and detection mechanisms. Finally, the pros and cons as well as the comparisons of different CR - specific security mechanisms are presented with some open research issues and challenges

Minimum energy wireless sensor networks

PhD programme overviewHere, on-off keying modulation is used as a means of reducing the transmit energy requirements whilst exploiting inherent channel coding, which sets the scene of this PhD study

DDH-MAC: a novel dynamic de-centralized hybrid MAC protocol for cognitive radio networks

The radio spectrum (3kHz - 300GHz) has become saturated and proven to be insufficient to address the proliferation of new wireless applications. Cognitive Radio Technology which is an opportunistic network and is equipped with fully programmable wireless devices that empowers the network by OODA cycle and then make intelligent decisions by adapting their MAC and physical layer characteristics such as waveform, has appeared to be the only solution for current low spectrum availability and under utilization problem. In this paper a novel Dynamic De-Centralized Hybrid “DDH-MAC” protocol for Cognitive Radio Networks has been presented which lies between Global Common Control Channel (GCCC) and non-GCCC categories of cognitive radio MAC protocols. DDH-MAC is equipped with the best features of GCCC MAC protocols but also overcomes the saturation and security issues in GCCC. To the best of authors' knowledge, DDH-MAC is the first protocol which is hybrid between GCCC and non-GCCC family of protocols. DDH-MAC provides multiple levels of security and partially use GCCC to transmit beacon which sets and announces local control channel for exchange of free channel list (FCL) sensed by the co-operatively communicating cognitive radio nodes, subsequently providing secure transactions among participating nodes over the decided local control channel. This paper describes the framework of the DDH-MAC protocol in addition to its pseudo code for implementation; it is shown that the pre-transmission time for DDH-MAC is on average 20% better while compared to other cognitive radio MAC protocols

Some hydrologic aspects of snowmelt runoff under summer conditions, in the Barpu glacier basin, Central Karakoram, Himalaya, northern Pakistan

Snow and ice in high mountains represent and important water resource in many parts of the world, especially the dry continental interior of Central Asia. In the Northern Areas of Pakistan, mountain ranges are the primary sources of annually renewed water supplies. They give rise to rivers which are the only significant, sustainable source of fresh water. The Indus basin is drained by the river Indus and its major tributaries, the Kabul, Jhelum, Chanab, Ravi and Sutlej. Snowmelt contributes about 70 percent to the annual flow of these rivers, but is not timed to meet the requirements for crop production, hydroelectric power generation, and other multi-purpose objectives. This situation has led to the development of an irrigation economy that requires effective management of the water resources in these drainage basins. A basic understanding of snow distribution and its contribution to streamflow is needed for effective prediction of flow events. Snowfields between elevation of 2,500 m and 5,500 m constitute a small percentage of the area contributing to runoff in the Central Karakoram, Northern Pakistan. However, they are considered to have a higher water content, and to produce runoff for longer periods than snowpacks at lower elevations. The melt regime of a basin may be better understood by examining snowpack recession and runoff hydrograph. Identifying the time of daily peak flow, snow cover/runoff relation and its variation through the season may prove helpful to flow modelling. This study involved taking hydrological and meteorological observations in two small snow-fed basins having different aspects in the basin of Barpu Glacier in the Central Karakoram range of the Himalaya in Pakistan. The conservational network was designed to cover a range of elevations within the experimental basins. This type of network is essential to account for the effects of typography and microclimate on snow hydrology. Patterns of snowmelt runoff examined in two contrasting environments within the Barpu Glacier Basin suggest that topography influences the rate of spring snowmelt in several ways. Aspect and degree of slope modify the winter and spring snowpack by causing unequal rates of ablation. Relief creates an unequal distribution of snow which in turn causes areal variation in the volume of spring melt. Normal linear and curvilinear multiple regression anaylsis is an appropriate method for studying of hydrologic relationships. Snow cover area and subsequent snowmelt runoff can be correlated to estimate streamflow. For a particular catchment, the relationship between area of snow-cover and snowmelt runoff appears to depend on morphometrical factors such as elevation, aspect, slope, and drainage density. However, for each basin a different empirical relation exists between snow cover and snow-melt runoff. The logarithmic relationships between snow-cover and snowmelt runoff indicates a substantial increase in snowdepth with increasing elevation. The results also suggest that mean temperature is the best single indicator of runoff variation. Meteorological observations over a range of elevations provide valuable information concerning the altitudinal gradient. The concluding chapter reviews some of the practical and technical implications of the work for hydrological investigations in the Upper Indus Basin. It suggests what can (and cannot) be learned from this type of study in relation to macroscale water resource assessment and forecasting

Template-based reverse engineering of parametric CAD models from point clouds

openEven if many Reverse Engineering techniques exist to reconstruct real objects in 3D, very few are able to deal directly and efficiently with the reconstruction of editable CAD models of assemblies of mechanical parts that can be used in the stages of Product Development Processes (PDP). In the absence of suitable segmentation tools, these approaches struggle to identify and reconstruct model the different parts that make up the assembly. The thesis aims to develop a new Reverse Engineering technique for the reconstruction of editable CAD models of mechanical parts’ assemblies. The originality lies in the use of a Simulated Annealing-based fitting technique optimization process that leverages a two-level filtering able to capture and manage the boundaries of the parts’ geometries inside the overall point cloud to allow for interface detection and local fitting of a part template to the point cloud. The proposed method uses various types of data (e.g. clouds of points, CAD models possibly stored in database together with the associated best parameter configurations for the fitting process). The approach is modular and integrates a sensitivity analysis to characterize the impact of the variations of the parameters of a CAD model on the evolution of the deviation between the CAD model itself and the point cloud to be fitted. The evaluation of the proposed approach is performed using both real scanned point clouds and as-scanned virtually generated point clouds which incorporate several artifacts that could appear with a real scanner. Results cover several Industry 4.0 related application scenarios, ranging from the global fitting of a single part to the update of a complete Digital Mock-Up embedding assembly constraints. The proposed approach presents good capacities to help maintaining the coherence between a product/system and its digital twin.openXXXIII CICLO - INGEGNERIA MECCANICA, ENERGETICA E GESTIONALE - Meccanica, misure e robotica01/A3 - ANALISI MATEMATICA, PROBABILITA' E STATISTICA MATEMATICA01/B1 - INFORMATICA09/B2 - IMPIANTI INDUSTRIALI MECCANICIShah, GHAZANFAR AL

A survey of QoS-aware web service composition techniques

Web service composition can be briefly described as the process of aggregating services with disparate functionalities into a new composite service in order to meet increasingly complex needs of users. Service composition process has been accurate on dealing with services having disparate functionalities, however, over the years the number of web services in particular that exhibit similar functionalities and varying Quality of Service (QoS) has significantly increased. As such, the problem becomes how to select appropriate web services such that the QoS of the resulting composite service is maximized or, in some cases, minimized. This constitutes an NP-hard problem as it is complicated and difficult to solve. In this paper, a discussion of concepts of web service composition and a holistic review of current service composition techniques proposed in literature is presented. Our review spans several publications in the field that can serve as a road map for future research

Wireless quality-of-service for 60GHz streaming media

PhD programmeThe primary aim of this PhD is firstly to understand Ultra-wideband technology (WiMedia), its applications, QoS requirements and then feed this knowledge into development of some novel secure QoS policies and architecture for the said technology before deploying them after analysis performed through modelling and simulations

The mediating effect of affective commitment between organizational justice, job crafting, appreciative leadership and workplace belongingness

Enterprises globally are facing the issue of work place belongingness whereby, dearth of research exists on how it could be addressed particularly in an emerging private higher education sector in Pakistan. Due to the emerging concept of workplace belongingness, numerous researchers suggest more focus on workplace belongingness in the higher education sector. This study examines the effect of organizational justice, job crafting and appreciative leadership on workplace belongingness. The study also examined the mediating effect of affective commitment between organization justice, job crafting, appreciative leadership and workplace belongingness. The research framework is developed under the norms of belongingness theory. Self-administered questionnaires are distributed to the faculty members in private universities of Punjab and Sindh provinces in Pakistan. A total of 390 questionnaires were used to analyze the data. This study utilizes the partial least squares structural equation modeling (PLS-SEM) to analyze the data. The findings of this study show that the direct effect of appreciative leadership on workplace belongingness is not significant. However, the direct effect of distributional justice on workplace belongingness is significant. Further, the direct effect of interactional justice, procedural justice and job crafting on workplace belongingness is not significant. However, the direct effect of appreciative leadership, distributional, interactional, procedural justice and job crafting on affective commitment is significant. Similarly, the direct effect of affective commitment on workplace belongingness is significant. Further, the mediating effect of affective commitment between appreciative leadership, interactional, procedural justice and job crafting, and workplace belongingness are significant and these are full mediation. The mediating effect of affective commitment between distributional justice and workplace belongingness is not significant. The results show that the mediating effect of affective commitment is significant between organization justice, job crafting and appreciative leadership and workplace belongingness

Accessing on-chip temperature health monitors using the IEEE 1687 standard

The IEEE 1687 (IJTAG) is a newly IEEE approved standard to access embedded instruments. The usage of these embedded instruments (health monitors) is increasing in order to perform different online measurements for testing purposes as dependability is becoming a key concern in today’s electronics. Aging and intermittent resistive faults (IRF) are two threats to a highly dependable system, and temperature can accelerate these two phenomena. In this paper, the work carried out for enabling online IJTAG control, observation and reconfiguration of the health monitors will be discussed. Three temperature monitors along with an IJTAG controller are used to demonstrate online temperature measurements using an IJTAG network interface. The simulation results show that the proposed (on-chip)methodology can reduce the dependency on the PC while observing the (static) embedded instruments in the field