Abstract
In this paper it is envisaged that cognitive radios (CRs) consult a supporting network infrastructure for per-mission to transmit. The network server either grants or rejects these requests by estimating, from the CR’s geo-location and antenna features, the likely impact its transmission would have on incumbents and other CR devices. This decision would be based on a real-time radio environment map [1] which would be kept up to date with readings from CRs, sensors and dynamic radio propagation prediction. By this means coexistence with incumbents and other CRs can be satisfied. It is maintained here that integral-equation (IE) - based al-gorithms are suitable candidates for the propagation engine given their ‘automatic’ nature and that they can be implemented to give results arbitrarily close to the exact numerical solution. IE methods based on the Fast Multipole Method are examined as a likely route to achieve the accuracy and speed necessary for real-time propagation mapping. It is concluded that the results obtained using one of the most recent of these, the Field Extrapolation Method (FEXM) [2], are promising for rural/suburban profiles and could serve to enable co-existence, for example, in IEEE802.22 networks. It is also explained how dynamic propagation prediction can address some fundamental security threats to CR networks.
Highlights
Cognitive Radio (CR) is a radio technology that refers to the ability of a radio device to sense/learn the communication parameters of its environment and adapt its transmissions
This decision would be based on a real-time radio environment map [1] which would be kept up to date with readings from CRs, sensors and dynamic radio propagation prediction
‘The Radio Environment Map (REM) itself is an abstraction of realworld radio scenarios; it characterizes the radio environment of CRs in multiple domains, such as geographical features, regulation, policy, radio equipment capability profile and radio frequency emissions’ [1]—in short it is a multidimensional map of what is happening in the radio environment in multiple domains
Summary
Cognitive Radio (CR) is a radio technology that refers to the ability of a radio device to sense/learn the communication parameters of its environment and adapt its transmissions . CR presents the radio community with brand new challenges Chief among these is the ability of these devices to co-exist with the incumbent operators and other CRs without causing harmful interference. On the basis of whether or not this transmission would adversely affect incumbents or other CRs a decision would be made by the server whether or not to grant permission to transmit and what the appropriate power limitations should be. This is an explicit solution to the Hidden Node Problem. To this end a highly accurate and robust propagation predictor capable of operating in a dynamic environment is needed
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