The cooperative communication is one of technologies which can explore the space diversity to resist fading channel. The spatial diversity is achieved by allowing various terminals behaving or a virtual antenna array and forwarding signal for a source terminal in cooperative manner. Under the existence of multiple sources, resource allocation to each source user is even more crucial to enhance the system performance and achieve higher diversity gain. In this work, we proposed a multiuser relaying strategy for a cooperative network with multiple sources sharing the radio resource provided by the cooperative relays simultaneously. Different from the existing work, the set of relays forwards signals of all source users over a common channel to raise spectral efficiency. With full channel information available at relays, the set of sub-optimal precoders and decoders was proposed in terms of maximal the average SNR over all users, subject to eliminating the multiple access interference (MAI) at each destination and satisfying total power constraint among all relays. It shows from the simulation results that, compared with the conventional cooperative strategy and direct transmission, the proposed scheme provides pronounced improvement on the outage capacity. Keywords: user cooperation, multiple access, resource allocation

In our thesis, we investigate the detection of malicious behavior in cooperative networks. Our model contain one source, one destination and two relays where relays adopt Orthogonal Space Time Block Code (OSTBC) to achieve spatial diversity. Cooperative communication takes two phases to forward signal to the destination. During first phase, source broadcasts data symbols to relay and destination, and a few tracing symbols are inserted randomly in data symbols. The values and positions of tracing symbols are known at source and destination. The random placement of tracing symbols is to prevent relays evade the detection of malicious behavior. In second phase, relays adopt orthogonal space time block code to forward the received signals after decoding source message successfully. We consider two scenarios based on the decoding capability at relays. The first scenario assumes perfect source¡Vrelay links. So, relays can always decode symbols correctly. Second scenario considers decoding failures at relays. In both scenarios, relays have a certain probability to perform maliciously. After receiving symbols at destination, the destination extracts and detect the tracing symbols. The malicious behavior of relay is detected depending on the value of the correlation between detected and exact tracing symbols. Moreover, depending on the average received energy, we can distinguish whether relays behaves as in outage. Through computer simulation, we can verify that our proposed tracing algorithm and decoding strategy reduce bit error rate.

This study uses a quasi-experimental, nonequivalent control group design and aims to investigate the effects of the application of cooperative learning to visual arts curriculum on the creativity and drawing performance of the the lower graders. Subjects are students from two second grade classes in an elementary school in Tainan City. One class represents the experimental group, while the other one is the control group. Each of the classes is given instruction for twenty sessions of classes in ten weeks. The experimental group receives cooperative learning based on STAD. The control group receives seperate learning. This study incorporates quantitative and qualitative approaches. Two assessment tools are conducted, which include ¡§New Creativity Test for Use with Students in Taiwan¡¨ developed by Dr. Ching-Chi Wu, and the ¡§Rating Scale for the drawing performance of the the lower graders ¡¨ designed by the author. Quantitative data are analyzed by ANCOVA and MANCOVA. Qualitative data processed by content analysis are gathered from teacher's classroom anecdotes, student works of curriculum, student feedback about the instruction , and vedio records of teaching process. The results of this study indicate that in the aspect of creativity, application of cooperative learning to visual arts curriculum increases the lower grader¡¦s verbal creativity in terms of flexibility as well as the figural creativity regarding fluency, flexibility and elaboration. In the aspect of drawing performance, application of cooperative learning to visual arts curriculum significantly improved the lower grader¡¦s drawing performance on ¡§content¡¨, ¡§illustrate¡¨, ¡§image ¡¨and ¡¨ color¡¨. The possibility of applying cooperative learning to the visual arts curriculum for the lower grade in the elementary school is recognized.students in the experimental group show positive acknowledgement and feedbacks to the whole instruction. Conclusions for practical application and suggestions for further research are discussed.

Thesis (doctoral)--Universität Basel, 1935. / Includes bibliographical references.

Thesis--Uppsala. / Includes bibliographical references (p. 172-177).

Thesis (M.A.)-University of KwaZulu-Natal, Durban, 2009. / Full text also available online. Scroll down for electronic link.

Cooperative services--a term which includes any system that relies on the resources and participation of its clients to function--have proven to be a popular, naturally scalable means to disseminate content, distribute computational workloads, or provide network connectivity. However, because these services critically depend on participants that are not controlled by a single administrative domain, these services must be designed to function in environments where no participant--because of failure or selfishness--will necessarily follow the specified protocol. This thesis addresses the challenge of establishing and maintaining cooperation in cooperative services by (1) advancing our understanding of the limits to what our services can guarantee in the presence of failure, (2) demonstrating the critical role that correct participants can play in the incentives provided by the service, and (3) proposing a new notion of equilibrium that, unlike traditional notions, provides both rigorous yet practical guarantees in the presence of collusion. Furthermore, we demonstrate that our ideas can be applied to practice by designing and implementing Seer, a system that provides a scalable, reliable, and robust method for disseminating content even if participants may fail arbitrarily or deviate selfishly as a coalition. / text

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Time-sensitive applications that are also CPU intensive like video games, video playback, eye-candy desktops etc. are increasingly common. These applications run on commodity operating systems that are targeted at diverse hardware, and hence they cannot assume that sufficient CPU is always available. Increasingly, these applications are designed to be adaptive. When executing multiple such applications, the operating system must not only provide good timeliness but also (optionally) allow co-ordinating their adaptations so that applications can deliver uniform fidelity. In this work, we present a starvation-free, fair, process scheduling algorithm that provides predictable and low latency execution without the use of reservations and assists adaptive time sensitive tasks with achieving consistent quality through cooperation. We combine an event-driven application model called cooperative polling with a fair-share scheduler. Cooperative polling allows sharing of timing or priority information across applications via the kernel thus providing good timeliness, and the fair-share scheduler provides fairness and full utilization. Our experiments show that cooperative polling leverages the inherent efficiency advantages of voluntary context switching versus involuntary pre-emption. In CPU saturated conditions, we show that the scheduling responsiveness of cooperative polling is five times better than a well-tuned fair-share scheduler, and orders of magnitude better than the best-effort scheduler used in the mainstream Linux kernel.

Wireless Sensor Networks (WSNs) are networks of small devices, called motes, designed to monitor resources and report to a server. Motes are battery-powered and have very little memory to store data. To conserve power, the motes usually form clusters to coordinate their activities. In heterogeneous WSNs, the motes have different resources available to them. For example, some motes might have more powerful radios, or larger power supplies. By exploiting heterogeneity within a WSN can allow the network to stay active for longer periods of time. In WSNs, the communications between motes draw the most power. By choosing better clusterheads in the clusters to control and route messages, all motes in the network will have longer lifespans. By leveraging heterogeneity to select better clusterheads, I have developed Heterogeneous Clustering Control Protocol (HCCP). HCCP is designed to be highly robust to change and to fully utilize the resources that are currently available.