Abstract
Cognitive radio (CR) technology has the potential to detect and share the unutilized spectrum by enabling dynamic spectrum access. To detect the primary users’ (PUs) activity, energy detection (ED) is widely exploited due to its applicability when it comes to sensing a large range of PU signals, low computation complexity, and implementation costs. As orthogonal frequency-division multiplexing (OFDM) transmission has been proven to have a high resistance to interference, the ED of OFDM signals has become an important local spectrum-sensing (SS) concept in cognitive radio networks (CRNs). In combination with multiple-input multiple-output (MIMO) transmissions, MIMO-OFDM-based transmissions have started to become a widely accepted air interface, which ensures a significant improvement in spectral efficiency. Taking into account the future massive implementation of MIMO-OFDM systems in the fifth and sixth generation of mobile networks, this work introduces a mathematical formulation of expressions that enable the analysis of ED performance based on the square-law combining (SLC) method in MIMO-OFDM systems. The analysis of the ED performance was done through simulations performed using the developed algorithms that enable the performance analysis of the ED process based on the SLC in the MIMO-OFDM systems having a different number of transmit (Tx) and receive (Rx) communication branches. The impact of the distinct factors including the PU Tx power, the false alarm probability, the number of Tx and Rx MIMO branches, the number of samples in the ED process, and the different modulation techniques on the ED performance in environments with different levels of signal-to-noise ratios are presented. A comprehensive analysis of the obtained results indicated how the appropriate selection of the analyzed factors can be used to enhance the ED performance of MIMO-OFDM-based CRNs.
Highlights
Due to the huge enlargement in the number of new applications and the constant demand for faster data rates in modern wireless communication systems, the radio frequency (RF) spectrum has become crowded
The investigation of the impact of different parameters such as Tx powers, modulation types, the number of samples used for energy detection (ED), the level of false alarm probability, and the number of multiple-input multiple-output (MIMO) Tx-Rx branches on the detection probability of the signals detected using the square-law combining (SLC) ED method in MIMO-orthogonal frequency-division multiplexing (OFDM) systems
The modeling of the SS based on the SLC ED method in MIMO-OFDM cognitive radio networks (CRNs) and generating the MIMO-OFDM signal according to Algorithm 1 was performed using Matlab software
Summary
Due to the huge enlargement in the number of new applications and the constant demand for faster data rates in modern wireless communication systems, the radio frequency (RF) spectrum has become crowded. Besides the usage of the OFDM technique, the implementation of systems based on a combination of OFDM and Multiple-Input Multiple-Output (MIMO) transmissions have gained popularity in the last few years. This is because MIMO improves the spectral efficiency, reliability, quality of service (QoS), capacity, and data throughput of wireless communication networks. Since non-coherent combining schemes can exploit the diversity gain in the absence of CSI, they represent a simpler solution for practical implementation of the ED method Such simplicity in the practical implementation of the SLC technique was additional motivation to develop and present in this paper a simulation study that enables the evaluation of SS performance based on the ED of signals in MIMO-OFDM systems.
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