An Optimal Eigenvalue Based Spectrum Sensing Algorithm for Cognitive Radio

Spectrum is a scarce resource, and licensed spectrum is intended to be used only by the spectrum owners. Various measurements of spectrum utilization have shown unused resources in frequency, time and space. Cognitive radio is a new concept of reusing licensed spectrum in an unlicensed manner. The unused resources are often referred to as spectrum holes or white spaces. These spectrum holes could be reused by cognitive radios, sometimes called secondary users. All man-made signals have some structure that can be potentially exploited to improve their detection performance. This structure is intentionally introduced for example by the channel coding, the modulation and by the use of space-time codes. This structure, or correlation, is inherent in the sample covariance matrix of the received signal. In particular the eigenvalues of the sample covariance matrix have some spread, or in some cases some known features that can be exploited for detection. This work aims to implement, evaluate, and eventually improve on algorithms for efficient computation of eigenvalue-based spectrum sensing methods. The computations will be based on power methods for computation of the dominant eigenvalue of the covariance matrix of signals received at the secondary users. The proposed method endeavors to overcome the noise uncertainty problem, and perform better than the ideal energy detection method. The method should be used for various signal detection applications without requiring the knowledge of the signal, channel and noise power

Generalized antenna sequence spatial modulation (GASSM): a novel framework for enhanced PHY layer security and energy efficiency

Abstract In antenna sequence spatial modulation (ASSM), the spatial and symbol domains are both used to encode information. The sequencing of the antennas’ transmissions within given time slots and the symbol carried in those time slots represent information in the spatial and symbol domains, respectively. The receiver’s task is to decode this sequence of transmission and to detect the symbol carried in the time slots, equal to the number of antennas. For better energy efficiency and greater security, we propose a generalized ASSM, GASSM. In the GASSM, while the information is contained in both the sequence and the symbols transmitted, different symbols can be transmitted within the time slots forming the frame. This expands the code domain since the symbol and the spatial information represent a longer code in the mapper table. As a special case, we present the case of three transmit antennas, transmitting within three time slots. A combination of the antennas’ sequence and the symbol carried in the time slots is used as a code for a bit sequence. Results obtained from simulation and analysis of the bit error rate performance and secrecy capacity are contrasted and presented. Comparing the GASSM to the standard spatial modulation (SM) and the ASSM, we deduce that the GASSM has a higher secrecy capacity and higher energy efficiency per bit and unlike conventional SM allows utilization of odd number of antennas