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In Cognitive Radio systems, the performance of spectrum sensing will directly affect spectrum reallocation. Energy detection (ED) method is one of the most commonly used signal sensing methods in spectrum sensing, due to its low implementation complexity. ED can achieve a good detection performance when the noise variance is known. However in most cases, the noise variance is estimated. To reduce...
Reducing interference to primary users while achieving high throughput for secondary user transmissions is a critical issue in an underlay cognitive radio network. In this paper, we explore the use of beamforming at secondary user transmitters. Two power allocation schemes, fixed transmit power allocation (FTPA) and adaptive transmit power allocation (ATPA) are investigated considering scenarios with/without...
In the Long Term Evolution (LTE) system, there is limited on uplink average data rate the cell edge users for the power limitation and the inherent short Transmission Time Interval (TTI) length of the cell edge users. TTI bundling scheme was presented for the VoIP service in the LTE Release 8 specifications to solve the cell coverage problem. But the R8 TTI bundling is restricted to bundles of 4 TTIs,...
We resort to a Bayesian framework and design knowledge-aided (KA) Rao and Wald tests for radar adaptive detection based on the partially homogeneous model, which outperform their conventional counterparts in heterogeneous environment. Meanwhile, the coincidence of the proposed detectors is proved.
This paper deals with the adaptive detection of a signal of interest in the presence of Gaussian noise with unknown covariance matrix (CM). To this end, we resort to a Bayesian approach based on a suitable model for the probability density function (PDF) of unknown CM. Under this assumption, the maximum a-posteriori (MAP) estimation of CM is derived. The MAP estimate is in turn used to yield Bayesian...
The orthogonal frequency division multiple access (OFDMA) is widely used for its characteristics of high data transmission rate and the flexibility of bandwidth allocation. In this paper, an equivalent SISO model for the MIMO STBC system was presented, and a Multi-user multirate adaptive sub-carrier allocation scheme was proposed also. We apply the algorithm to the OFDMA. The simulations results show...
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