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This paper investigates spectrum occupancy trends of voice services in the band of 450 MHz. An occupancy model of channel occupancy in the frequency and time domain was developed. A robust algorithm is proposed to allocate white spaces within a channel group with by primary users. The algorithm statistically identifies which channels can be used with a higher probability of having a white space, so...
Currently the spectrum occupancy has been the major concern for regulatory bodies because there are repressed demands of telecommunications users, especially in large cities due to lack of free frequencies. The cognitive radio technology appears on the scene as a solution to improve the spectrum efficiency by increasing the density of users on radio frequencies. However, there are still open issues...
A new Markovian model for burst-error processes is herein presented. Our basic idea consists of imposing a convenient structure on this model, with the double purpose of reproducing the generation of some typical patterns of burst error sequences and facilitating the maximum-likelihood estimation of the model's parameters. A simple procedure for calculating the maximum-likelihood metric of those parameters...
Text clustering is a theme that is receiving considerable attention nowadays in areas such as text mining and information retrieval. A starting point for clustering methods applied on unstructured document collection is the creation of a vector-space model usually known as bag-ofwords model [1J. Documents are then usually described by a matrix which happens to be huge and extremely sparse which is...
In packet networks very often variable length packets must be padded with extra bits to match a given frame size. At the UMTS transport framework for transmitting IP packets, the proper design of the padding operation leads to the following optimization problem: given a certain number of different frames, determine the respective frame sizes so that the waste caused by padding of variable length packets...
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