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Opportunistic secondary spectrum usage has the potential to dramatically increase spectral efficiency and rates of a network of secondary cognitive users. In this work we consider a cognitive network: n pairs of cognitive transmitter and receiver wish to communicate simultaneously in the presence of a single primary transmitter-receiver link. We assume each cognitive transmitter-receiver pair communicates...
In this paper, we study the Transport Capacity (TC) of a Mobile Ad hoc NETwork (MANET) of secondary nodes without a predefined bandwidth assignment. These secondary users' access of the spectrum is governed by Opportunistic Spectrum Access (OSA) rules, i.e., they can use portions of the spectrum as long as their transmissions do not interfere with the spectrum's primary (protected) users. We present...
We consider a multiple access, doubly-selective block Rayleigh fading channel in which the users coordinate spectrum sharing through a limited feedback scheme. Each user probes a random set of sub-channels, known to the receiver, by sending a pilot sequence at the beginning of each coherence block. Multiple users may probe the same sub-channel, causing interference. The receiver assigns each sub-channel...
We consider opportunistic spectrum access under design constraints imposed at both node and link levels. First, hardware and energy limitations at node level may prevent a secondary user from sensing all the channels in the spectrum simultaneously. A channel selection strategy is thus necessary to track the time-varying spectrum opportunities. Second, sensing errors are inevitable. A secondary user...
Cognitive radios sense the radio spectrum in order to find unused frequency bands and use them in an agile manner. Transmission by the primary user must be detected reliably even in the low signal-to-noise ratio (SNR) regime and in the face of shadowing and fading. Communication signals are typically cyclostationary, and have many periodic statistical properties related to the symbol rate, the coding...
The IEEE 802.22 wireless regional area network (WRAN) is the first worldwide commercial application of cognitive radio (CR) networks in unlicensed television broadcast bands. With the intent of efficiently occupying under-utilized spectrum, the network must be cognizant of spectrum available for secondary use and vacate channels as primary users are present. According to FCC's recent public notice,...
Efficient use of radio spectrum is a necessity for future wireless systems. This can, for example, be accomplished by cognitive radios. An important point for designing future systems is to gain knowledge about the occupation of the frequency bands which may be used by the cognitive radio. This includes the general characterization of the traffic density at the frequency bands as well as a detailed...
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