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In cognitive radio networks (CRNs), spectrum sensing is the key functionality for unlicensed users to detect the unused spectrum. Currently, almost all the spectrum sensing schemes for CRNs are implemented at the physical layer. However, one serious problem with current physical layer spectrum sensing is that it can only detect the presence of licensed user signals but it cannot distinguish between...
Global time synchronization is an important function that enables all devices in a network to have a unified time. In traditional wireless ad hoc networks, since the spectrum is always available, the global time synchronization process usually can be performed without any interruption. However, in cognitive radio (CR) ad hoc networks, the global time synchronization process among secondary users may...
End-to-end congestion control, aiming to find out how much traffic load offered by the source can be handled by a network, is an essential function of a transport layer protocol. In traditional wireless ad hoc networks, numerous solutions have been proposed to solve this issue. However, in cognitive radio (CR) ad hoc networks, the end-to-end congestion control issue still remains unexplored. More...
Broadcast is an important operation in wireless networks where control information is usually propagated as broadcasts for the realization of most networking protocols. In traditional ad hoc networks, broadcasts are conducted on a common channel which is shared by all nodes in the network. However, in cognitive radio (CR) networks, unlicensed users may observe heterogeneous spectrum availability which...
Ridership forecast is one of the important bases for urban rail transport network planning, design, construction and operation. For the shortcomings of traditional ridership forecast in the stiff human-computer interaction forms, the signal forecast model, the low computational efficiency and the intensive labor, multi-agent-based urban rail transport ridership forecast system was designed. The Man-Machine-Agent...
Cognitive radio (CR) is a promising solution to improve the spectrum utilization by enabling unlicensed users to exploit the spectrum in an opportunistic manner. However, because unlicensed users are considered as temporary visitors to the licensed spectrum, they are required to vacate the spectrum when a licensed user reuses the current spectrum. Due to the randomness of the reappearance of licensed...
In a cognitive radio (CR) network, CR users intend to operate over the same spectrum band licensed to legacy networks. A tradeoff exists between protecting the communications in legacy networks and maximizing the throughput of CR transmissions, especially when CR links are unstable due to the mobility of CR users. Because of the non-zero probability of false detection and implementation complexity...
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