This paper proposes an optimal cooperative spectrum sensing scheme, based on the criterion of deflection coefficient maximization of the global decision statistic. Multiple cooperative secondary users serve in the cognitive radio network to provide space diversity for spectrum sensing. After the fusion center acquires the optimal fusion weights, an optimal global threshold setting strategy is u...

In cognitive radio system, the secondary users can use the frequency bands when the primary users are not present. Therefore, the secondary users need to sense the channel periodically. When the primary users are detected, the secondary users have to stop using that channel. This makes the probability of detection important to the cognitive radio system. However, detection is compromised when a...

Many pervasive protocols which continue to be used in distributed/decentralized communication networking today fundamentally rely on “cooperative behavior” of the participating end-hosts/users. In particular, TCP in layer 4 and MAC in layer 2 of the OSI protocol hierarchy prescribe distributed transmission back-off rules in response to detected congestion and, in the case of some MAC protocols,...

Collaboration based on GIS provides a spatially referenced negotiation environment for decision makers. Among the collaboration process, the operations of the system users may conflict. The existing solutions to operation conflict are essentially based on the time the operations occur. It doesn’t consider the characteristics of the operations and the collaborative relationships between the syst...

In cognitive radio networks, cognitive users can be coordinated to perform cooperative spectrum sensing so as to detect the primary user more accurately. In this paper, a hybrid cooperative spectrum sensing method is investigated to improve the sensing performance by exploiting double-fusion approach. In special, data fusion and decision fusion are both studied. For the first stage, cognitive u...

In this paper, we propose network coding, as an efficient and low cost option for the implementation of blockMarkov coding for cooperative communications. Cooperative communications is a strategy where users, besides transmitting their own encoded information, also relay re-encoded versions of other users’ information to a common destination. Our work is motivated by the recent information-theo...

Cooperative ubiquitous environments support user interaction and cooperative work by adapting to the prevalent situation of the present users. They are typically complex and have many environment components—interconnected devices and software modules—that realise new interaction techniques and facilitate collaboration. Despite this complexity, users need to be able to easily adapt their environ...

This paper studies cooperative techniques that rely on femtocell user diversity to improve the downlink communication quality of macrocell users. We analytically analyze and evaluate the achievable performance of these techniques in the downlink of Rayleigh fading channels. We provide an approximation of both the bit-error rate (BER) and the data throughput that macrocell users receive with and...

In this paper we present the COMODIN (COoperative Media On-Demand on the InterNet) system, a media on-demand platform for synchronous cooperative work, which is aimed at securely supporting an explicitly-formed cooperative group of distributed users for (i) requesting an archived multimedia session, (ii) sharing the playback, and (iii) collaborating with each other through questioning and, opti...

Non-cooperative behaviors in communication networks can significantly adversely affect the entire network. Recently, researchers have begun to study such non-cooperative communication systems within a game theory framework and strive to engineer the system to prevent performance degradation under non-cooperative behaviors. The WWAN/WLAN two-hop-relay system described in [1] integrates two types...