| Budget Amount *help |
¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 2000: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1999: ¥2,400,000 (Direct Cost: ¥2,400,000)
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| Research Abstract |
It is necessary to reduce the effects of fading and interference in the DS/CDMA used for the next generation mobile communication systems. On the other hand, there arises the similar problem in the ITS (Intelligent Transport Systems) which has the same radio environments as the mobile communications. Therefore, this research project deals with high-function smart antennas based on the digital beamformer to suppress the effects of the fading and interference.
1. In 1999, we focused on the CMA (Constant Modulus Algorithm) adaptive array suitable for the mobile communications, and tried to improve the performance. When the CMA system is optimized by using the steepest descent method, it happens that the convergence rate is extremely low and also the output signal-to-interference-plus-noise ratio degrades depending on the initial weights. To improve the characteristics, we proposed the CMA adaptive array with phase-only control of the input signals. Some computer simulation results showed the effectiveness of the proposed algorithm in the DS/CDMA systems.
2. In 2000, we studied the DOA (direction of arrival) estimation using ESPRIT (one of the high-resolution spectrum analysis techniques), which would be an elementary technology of smart antennas. First, we considered application of 2D-ESPRIT to several planar arrays, and proposed the estimation method with less computational load and no reliability test. Computer simulation results in 2D-DOA estimation using the triangular array showed the effectiveness of the proposed algorithm. Next, the fast recursive 2D Unitary ESPRIT was proposed to realize the high computation efficiency. Computer simulation of 2D-DOA estimation of coherent waves was carried out together with complexization pairing of the estimates. As a result, the practical effectiveness of the proposed algorithm was shown in terms of estimation accuracy, computation time and DOA tracking ability in mobile communications and ITS.
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