Abstract
This paper proposes the establishment of a simultaneous cognitive radio communication based on a subdistribution of power made over unselected subchannels which were discarded by the primary user through an initial optimal power allotment. The aim of this work is to show the possibility of introducing an opportunistic communication into a licensed transmission where the total power constraint is shared. The analysis of the proposed transmission scheme was performed by considering 128 and 2048 independent subchannels affected byRayleighfading, over 10,000 channel realizations, and three different signal-to-noise ratios (8 , 16 , and 24 ). From the system evaluation it was possible to find the optimal power allotment for the primary user, the subdistribution of power for the secondary user, as well as the attenuation and the capacity per subchannel for every channel realization. Moreover, thePDFandCDFof the total obtained capacities, as well as the generation of empirical capacity regions, were estimated as complementary results.
Highlights
The radio signals propagating through the environment are associated to a specific operation frequency belonging to one of the many wireless communications systems (i.e., LTE, WiMAX, etc.) existing today, which are strictly allocated by government agencies (i.e., FCC) or international organizations (i.e., ITU) [1, 2]
This paper proposes the establishment of a simultaneous cognitive radio communication based on a subdistribution of power made over unselected subchannels which were discarded by the primary user through an initial optimal power allotment
On the basis of a scenario where the operation band belonging to the primary user is divided in several (128 & 2048) subbands, and once an optimal power distribution is applied by using the algorithm known as waterfilling, the proposed methodology consists in making use of those subchannels that were not used or discarded by the PU for applying a subdistribution of power leading to the establishment of a low-priority communication in parallel
Summary
The radio signals propagating through the environment are associated to a specific operation frequency belonging to one of the many wireless communications systems (i.e., LTE, WiMAX, etc.) existing today, which are strictly allocated by government agencies (i.e., FCC) or international organizations (i.e., ITU) [1, 2]. An emerging technology that is able to reliable sense the spectral environment over a wide band, detect the presence/absence of licensed users (primary users), and use the spectrum only if the communication does not interfere with primary users is defined by the term cognitive radio (CR) [8, 9]. The spectrum utilization can be improved by making a secondary user access into the spectrum holes or spectrum portions that in a particular location and time are not being used by a primary user In this regard, according to the current proposals of the CR protocol, the device is constantly aware of its wireless environment in order to determine (at least in space and time) which part of the spectrum is not being occupied by making use of spectrum sensing techniques [10, 11] to later on adapt its signal to fill those spectrum gaps. Between the main differences it is possible to highlight that the channel characteristics on that research work are considered to be nearly the same for both the primary and the secondary users, while the idea behind the establishment of a simultaneous cognitive radio transmission is based on the assumption that the primary user in any case will not International Journal of Digital Multimedia Broadcasting h1
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