New beamforming and DOA estimation techniques in wireless communications

The development and performance evaluation of new techniques for direction of arrival (DOA) estimation, single-user beamforming (SUB), and multiuser beamforming (MUB) to be used in wireless communications are investigated.; Two of the most commonly used beamformer configurations in direct-sequence code-division multiple access (DS-CDMA) systems, the chip-based (CB) and the symbol-based (SB) configurations for the base station (BS) receiver, are studied and their performance is evaluated. It is shown that using the CB configuration, different interfering components are rejected based on the spatial distribution of their power. In the SB configuration, spatial diversity is exploited after despreading and different interfering components are rejected based on their interfering strength which depends on both their power and code correlation with the signal of interest. For the SB configuration, more effort is applied to rejecting the interfering components with higher interfering strength and thus a more selective and efficient system is achieved. Detailed performance analysis and simulations show that in the presence of multiple-access interference, the SB configuration can lead to a significant improvement in the signal-to-interference-plus-noise ratio relative to that achieved with the CB configuration for both asynchronous and synchronous DS-CDMA systems.; A new technique for DOA estimation is proposed. The new technique, called sub-array beamforming-based DOA (SBDOA) estimation, uses two virtual sub-arrays to form a signal whose phase relative to the reference signal is a function of the DOA. The DOA is then estimated based on the computation of the phase shift between the reference signal and the phase-shifted target signal. Since the phase-shifted target signal is obtained after interference rejection through beamforming, the effect of co-channel interference on the estimation is significantly reduced. The proposed technique is computationally simple and the number of signal sources detectable is not bounded by the number of antenna elements used. Performance analysis and extensive simulations show that the proposed technique offers significantly improved estimation resolution, capacity, accuracy, and tracking capability relative to existing techniques. (Abstract shortened by UMI.)...