Abstract
At present, in robot technology, remote control of robot is realized by wireless communication technology, and data anti-interference in wireless channel becomes a very important part. Any wireless communication system has an inherent multi-path propagation problem, which leads to the expansion of generated symbols on a time scale, resulting in symbol overlap and Inter-symbol Interference (ISI). ISI in the signal must be removed and the signal restores to its original state at the time of transmission or becomes as close to it as possible. Blind equalization is a popular equalization method for recovering transmitted symbols of superimposed noise without any pilot signal. In this work, we propose a concurrent modified constant modulus algorithm (MCMA) and the decision-directed scheme (DDS) with the Barzilai-Borwein (BB) method for the purpose of blind equalization of wireless communications systems (WCS). The BB method, which is two-step gradient method, has been widely employed to solve multidimensional unconstrained optimization problems. Considering the similarity of equalization process and optimization process, the proposed algorithm combines existing blind equalization algorithm and Barzilai-Borwein method, and concurrently operates a MCMA equalizer and a DD equalizer. After that, it modifies the DD equalizer's step size (SS) by the BB method. Theoretical investigation was involved and it demonstrated rapid convergence and improved equalization performance of the proposed algorithm compared with the original one. Additionally, the simulation results were consistent with the proposed technique.
Highlights
As is known, inter-symbol interference (ISI) is a major impairment for improvement in capacity or data transmission rate in wireless communication systems (WCS), especially in the field of robot wireless control (Lewis et al, 2020; Ye et al, 2020)
We focus on the joint modified constant modulus algorithm (MCMA)-DD equalization algorithm (Ashmawy et al, 2009) and propose a concurrent MCMA and DD with the Barzilai-Borwein (BB) method (Barzilai and Borwein, 1988) blind equalization algorithm for the wireless communications systems (WCS) using quadrature amplitude modulation (QAM) signals
We considered applying Equation (17) to update the value of μDD in concurrent MCMA and DD algorithm, which could improve the convergence speed (CS)
Summary
Inter-symbol interference (ISI) is a major impairment for improvement in capacity or data transmission rate in wireless communication systems (WCS), especially in the field of robot wireless control (Lewis et al, 2020; Ye et al, 2020). Liyi et al (2009) proposed a variable step size (VSS) technique and applied it to CMA for 16 quadrature amplitude modulation (QAM) signals It improves the performance of the equalizer to some extent. It fails to take the higher-order QAM signals into account, which is another problem of this approach On this basis, the modified constant modulus algorithm (MCMA) (Liyi et al, 2009) was proposed, which could improve the CMA performance by achieving low steady-state (SS) MSE. CMA may not be able to achieve MSE as expected, at such a low level Another possible method is to combine the existing blind equalization algorithm with the optimization algorithm to obtain improved equalization performance.
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