| In recent years, the quantity of subscribers is increasing rapidly with the fast development of mobile communications and the business of communications is changed from voice communications in narrow band into the data transmission of multimedia in wide band. The limited frequency spectra are getting crowded and the co-channel interference is more serious. To increase the channel capacity and to improve the performance of communications is the most important aim of mobile communications. Wireless communication systems are limited in performance and capacity by three major impairments: co-channel interference, multipath fading and delay spread. Smart antenna can overcome the impairments by the different space features of the received signals: DoA (Directions of Arrival). Smart antenna can improve coverage and system capacity with the same performance of communication. It is the expanded multiple accessing technology of SDMA (Space Division Multiple Access) after the traditional multiple access technology such as FDMA, TDMA and CDMA. In the coming the 3rd generation of mobile communication, smart antenna is adopted as the important spare technology.Smart antenna technology is the combinations of array antenna and spacial-temporal signal processing. The adaptive array technology in array antenna is mature after development of 40 years and is mainly used in military communication. There are very big differences between military communication and civil communication. In former case, there are few strong interferences which azimuth angles are fixed, but the characteristics of the interferences are unknown before detecting; in the latter, all the subscribers are interferences between each other, and when the signal of a subscriber is picked up by the base station, other subscribers are treated as interferences which quantity is large and their positions change randomly, but the base station can use the unique known characteristic to pick up each signal separately. As known, the numbers of interferences can be larger than the numbers of array elements. In military communication, strong interferences can be suppressed byinadaptive nulling beamforming because the interferences are very few. Because the subscribers are much more than the numbers of array elements in civil communication, it is impossible to adopt adaptive nulling beamforming to suppress all the interferences. So adaptive array must combinate with spacial-temporal signal processing to realize the MIMO(Multiple Inputs and Multiple Outputs). The speed and accuracy of the spatial filtering algorithms must be rather fast and high in order to track the subscribers in real time for the base station. So the speed is the key for smart antenna to be practical. This paper present a novel adaptive beamforming algorithm in a CDMA mobile communication environment, namely, LBA(Lagrange Based Algorithm), which the proposed smart antenna system can be viewed as a time-space filter. It is noteworthy that, in our procedure of the time-space filtering, the spatial filtering part exploits the merits of the present RAKE receiver with a minimal computational load.This paper investigates the effects of mutual coupling between the elements of an array on beamforming algorithms. Mutual coupling severely undermines the interference suppression capabilities of beamforming algorithms. The method of moments (MoM) is used to evaluate the mutual coupling between the elements of a given array. The MoM admittance matrix is then used to eliminate the effects of mutual coupling.The main contents of this paper:1 .The numerical simulation experiments of traditional adaptive algorithms such as LMS, RLS and CMA;2.Researching on the novel fast adaptive beamforming algorithm, namely, LBA and developing the Matlab?code;3.Evaluating the mutual coupling between the elements of a given array by MoM andproviding a method to compensate the effects of mutual coupling;4.Developing C code on DSP board TMS320C6711 DSK and passing the real timesimulation. |
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