The Study On Two Adaptive Beam-forming Algorithm In Smart Antenna Technology

With the rapid development of mobile communication, its capacity and service quality is badly needed. To improve the frequency utilization becomes no time to delay. The technology of smart antenna brings great energy to the total wireless communication field. The core of smart antenna research is algorithm of beaming, whose rapid converging and excellent performance is very importance to implement the adaptive beaming. And the least mean squares (LMS) algorithm is often emphasized due to its simple structure and the convenience of realization. But its inherent contradiction between convergence rate and maladjustment of steady condition, confines its applications. In the paper, LMS algorithm is studied and the main work is as follows:1. The advantage and disadvantage of linear array and circular array are discussed respectively. Author analyze some classic beam-former algorithms and make comparison of them. Thereof, basic theory support of LMS algorithm is provided.2. A robust variable step size adaptive algorithm is proposed, who can effectively adjust the step size by utilizing the correlation characteristic of output signal with previous iteration error signal. The algorithm allows more flexible control of maladjustment and convergence time without the compromise one for the other and it can maintain the immunity against noise disturbance. The result of simulations also shows that the algorithm is robust to an abrupt change.3. Author analyze the variable step size LMS algorithm, and focus on the problem of reduction of performance of the modified variable step size LMS algorithm (MVSSLMS), due to the descent of its convergence speed, when the input signals heavy correlated. By the virtue of the principle of correlation, weight coefficients are updated by the orthogonal component of the input signal and normalized.As a result, an uncorrelated variable step size normalized LMS algorithm (UVSSNLMS) is proposed, which can achieve better performance. The theoretical analysis and result of simulations supports that the modified algorithm is immunized from noise and the process of norm extends the dynamic input of step size.4. The two newly proposed algorithms, RVSSLMS and UVSSNLMS,are analyzed and simulated in some aspects, such as disturbance resistance, tracking capability and complexity. In conclusion, the RVSSLMS is more suitable for wireless...