A multi-user cognitive (secondary) radio system is considered, where the spatial multiplexing mode of operation is implemented amongst the nodes, under the presence of multiple primary transmissions. The secondary receiver carries out minimum mean-squared error (MMSE) detection to effectively decode the secondary data streams, while it performs spectrum sensing at the remaining signal to capture the presence of primary activity or not. New analytical closed-form expressions regarding some important system measures are obtained, namely, the outage and detection probabilities; the transmission power of the secondary nodes; the probability of unexpected interference at the primary nodes; blue and the detection efficiency with the aid of the area under the receive operating characteristics curve . The realistic scenarios of channel fading time variation and channel estimation errors are encountered for the derived results. Finally, the enclosed numerical results verify the accuracy of the proposed framework, while some useful engineering insights are also revealed, such as the key role of the detection accuracy to the overall performance and the impact of transmission power from the secondary nodes to the primary system.
In addition, the concept of simultaneous data reception and spectrum sensing for single-antenna nodes was studied in @cite_25 @cite_14 , while for multiple-antenna nodes in @cite_3 . However, these works used the central limit theorem to approximate the total received signal as a Gaussian input (invoking the constraint of sufficiently large amount of received samples), whereas they provided only semi-analytical and or simulation results with respect to the system performance.
@cite_14 @cite_25 @cite_3
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The cognitive radio (CR) systems usually arrange for the quiet period to detect the primary user (PU) effectively. Since all CR users do not transmit any data during quiet period, the interference caused by other CR users can be prevented in the channel sensing for PU detection. Even though the quiet period improves the PU detection performance, it degrades the channel utilization of CR system. To cope with this problem, we propose a channel sensing scheme without quiet period, which is based on the pilot cancellation, and analyze its performance. The numerical results show that the proposed scheme highly outperforms the existing PU detection schemes. We consider the problem of sensing in the presence of a desired signal in the context of future 3GPP LTE-A based cognitive cellular systems employing multiple-input multiple-output (MIMO) transmission. Energy detection (ED) based on equal gain combining and beamforming are investigated. Receive beamformers for energy detection (ED) are designed according to the Neyman-Pearson criterion to maximize the probability of detection for a given probability of false alarm. Suitable suboptimum solutions to the maximization problem with a good tradeoff between performance and complexity are identified. Furthermore, we also formulate the likelihood ratio test (LRT) for this scenario. Performance simulations indicate that a significant performance gain is achieved in ED if the receive beamformer is chosen properly.