Joint Optimization Strategy for Video Transmission over Distributed Cognitive Radio Networks

A novel joint optimization strategy for the secondary user( SU) was proposed to consider the short-term and long-term video transmissions over distributed cognitive radio networks( DCRNs).Since the long-term video transmission consisted of a series of shortterm transmissions, the optimization problem in the video transmission was a composite optimization process. Firstly,considering some factors like primary user's( PU's) collision limitations,non-synchronization between SU and PU,and SU's limited buffer size, the short-term optimization problem was formulated as a mixed integer non-linear program( MINLP) to minimize the block probability of video packets. Secondly,combining the minimum packet block probability obtained in shortterm optimization and SU's constraint on hardware complexity,the partially observable Markov decision process( POMDP) framework was proposed to learn PU's statistic information over DCRNs.Moreover,based on the proposed framework,joint optimization strategy was designed to obtain the minimum packet loss rate in long-term video transmission. Numerical simulation results were provided to demonstrate validity of our strategies.

A CHANNEL ASSIGNMENT ALGORITHM VIA CONFLICT SHIFTING FOR DISTRIBUTED COGNITIVE NETWORKS

Channel assignment is a challenge for distributed cognitive networks due to spectrum mobility and lack of centralized entity.We present a dynamic and efficient algorithm via conflict shifting,referred as Shifting-based Channel Assignment(SCA).In this algorithm,the system was modeled with a conflict graph,and users cannot assign the channels that primary users(legacy users) and neighbors already occupied.In order to eliminate the conflicts between neighbors efficiently,secondary users(unlicensed users) try to transfer them through a straight path to the boundary,where conflicts are easier to solve as there are less neighbors for boundary users.Actions in one shift are executed in slots,and users act in a synchronous and separated manner.As a result,some of the conflicting channels are avoid from directly abandoned,and for this,utility of the entire network can be improved.Simulation results show that the proposed algorithm can provide similar utility performance while obviously reducing the communication cost than bargaining-base algorithms.In small scale networks with low user mobility(under 20%),it reduces 50% of the communication overhead than the later.

The Stabilizing Role of Material Structure in Scientific Practice

Knowledge of the environment is essential for the survival of organisms; but those organisms have to have the capacity to stabilize such knowledge. The aim of this article is to analyze the various strategies for stabilizing human knowledge, with a special focus on its material anchors and their interactions with other stabilization means. In particular, I consider how such stabilization is reflected in scientific activity and practice, and what its repercussions are for the models of science that have dominated the philosophical landscape of the 20th century. My starting hypothesis will be that the role of material anchors in stabilizing conceptual blends is analogous to that of technology in grounding scientific knowledge. The framework I adopt with regard to conceptualization is that of Fauconnier and Turner （2002） on conceptual blends. Just as technology intervenes in scientific practice in conjunction with conceptual elements, so do material anchors, which conjoin other non-material strategies of knowledge stabilization. Endowing knowledge with a material basis may be understood firstly as an element （sometimes a key element） for representing knowledge and offering an explanation, and secondly as a way of providing a scientific hypothesis with empirical grounding. It is this second sense that connects with scientific experimentation and the use of instruments and technology.