An Improved Constant Modulus Algorithm for Blind Signal Adaptation in Wireless Communications

Emmanuel Adotse Otsapa, Abdoulie Momodou Sunkary Tekanyi, Kabir Ahmed Abubilal,Mahmud Tukur Kabir,Muntari Bello,Emmanuel Kasai Akut, Oluwatobiloba Alade Ayofe, Haruna Ibrahim

Keywords: Blind beamforming, Improved CMA, Equalization (or Adaptation), Convergence, Side lobe level

While the Constant Modulus Algorithm (CMA) is the most often used blind signal equalization or adaptation technique, it converges slowly and produces excessive Side Lobe Level (SLL) radiation, which wastes energy and interferes with other equipment. Additionally, interfering signals may be picked up by side lobes, increasing the noise level in the receiver. A normalized constant-modulus method with adjustable step size was devised, which considerably increased its convergence rate. The Blackman window was also applied to the CMA to lower the SLL. The designed beam former improved convergence rate by 40%, as observed by lower Mean Square Error (MSE) to Signal to Interference plus Noise Ratio (SINR) values. As a result, the beam former is a viable alternative in an environment where channel conditions are constantly changing. Furthermore, the use of the Blackman window had the ability to minimize the Peak Side Lobe Level (PSLL) and resulted in a 5 dB improvement over CMA for the SLL rejection gain. As compared to the conventional CMA, the Improved CMA displayed the highest reduction in PSLL with quick convergence capabilities and saved a lot of energy wastage due to side lobes minimization. These characteristics make the ICMA a potential choice for advanced wireless applications.