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—Cognitive radio is an enabling technology for efficient utilization of radio spectrum. A key function of cognitive radios is spectrum sensing, which enables secondary users to identify vacant spectrum not used by primary users (a.k.a. spectrum " white spaces "). Although spectrum sensing is one of the essential functionalities of cognitive radios, its(More)
Establishing a control channel for medium access control is a challenging problem in multi-channel and dynamic spectrum access (DSA) networks. In the design of multi-channel MAC protocols, the use of channel (or frequency) hopping techniques (a.k.a. parallel rendezvous) have been proposed to avoid the bottleneck of a single control channel. In DSA networks,(More)
—In decentralized cognitive radio (CR) networks, establishing a link between a pair of communicating nodes requires that the radios " rendezvous " in a common channel—such a channel is called a rendezvous channel—to exchange control information. When unlicensed (secondary) users opportunistically share spectrum with licensed (primary or incumbent) users, a(More)
—In decentralized cognitive radio (CR) networks, enabling the radios to establish a control channel (i.e., " rendezvous " to establish a link) is a challenging problem. The use of a dedicated common control channel simplifies the rendezvous process but may not be feasible in many opportunistic spectrum sharing scenarios due to the dynamically changing(More)
Existing code designs for display-camera based visual communication all have an all-or-nothing behavior, i.e., they assume the entire code must be decoded. However, diverse operational conditions due to device hardware diversity (in camera resolution and frame rate) and distance range motivate more scalable designs. In this paper, we borrow the notion of(More)
—Neighbor discovery plays a crucial role in the formation of wireless sensor networks and mobile networks where the power of sensors (or mobile devices) is constrained. Due to the difficulty of clock synchronization, many asynchronous protocols based on wake-up scheduling have been developed over the years in order to enable timely neighbor discovery(More)
As children increasingly use the Internet, there have been mounting concerns about their privacy online. As a result, the U.S. Congress enacted the Children's Online Privacy Protection Act (COPPA) to prohibit websites from collecting information from children under 13 years of age without verifiable parental consent. Unfortunately, few technologies are(More)
In cognitive radio (CR) networks, a pair of CR nodes have to ``rendezvous'' on a common channel for link establishment. Channel hopping (CH) protocols have been proposed for creating rendezvous over multiple channels to reduce the possibility of rendezvous failures caused by the detection of primary user signals. Rendezvous within a minimal bounded time(More)
—In Cognitive Radio (CR) networks, establishing a link between a pair of communicating nodes requires that their radios are able to " rendezvous " on a common channel (a.k.a. a rendezvous channel). When unlicensed (secondary) users opportunistically share spectrum with licensed (primary or incumbent) users, a given rendezvous channel may become unavailable(More)