Blind Adaptive Beamforming Algorithm Using Software Radio

摘要

The recent rapid growth in wireless network technology has greatly expanded the capabilities of mobile computing devices. However, the multitude of wireless network standards hinders seamless interoperability by requiring different physical devices to inter-operate with different networks. A new challenge to the mobile communication industry is the integration of multiple systems and applications on a single device. Although third generation wireless communication concepts (e.g. UMTS, IMT-2000) address the goal of global standardization, a more realistic approach in the intermediate term is to develop transceivers that will work with several standards and in several frequency bands on a common hardware platform. Such a platform would allow flexible and programmable transceiver operations. This type of software radio is expected to be a key technology in several applications of wireless communications. The technology of smart or adaptive antenna systems is proposed to open up another resource, i.e. space, for mitigating key problems in wireless communications systems. Smart antennas are a new technology for wireless systems that use a fixed set of antenna elements in an array. The signals from these antenna elements are combined to form a movable beam pattern that can be steered, using either digital signal processing, or RF hardware, to a desired direction that tracks mobile units as they move. A smart antenna combines antenna array with digital signal processing unit that optimizes reception and radiation patterns dynamically in response to the signal environment, i.e. mobile moving about the coverage area. The software radio basestations are a promising approach to further enhance the spectral efficiency with minimum impact on actual hardware and existing infrastructure. This paper describes the design of a blind adaptive beamforming algorithm for a beamforming system based on software radio. The beamforming system has the analog to digital conversion as close as possible to the antenna. Furthermore, the in -phase and quadrature components of each antenna signal are generated in the digital domain using a programmable down -converter. The use of blind adaptive beamforming without the need for array calibration will provide economical base stations with tremendous operational flexibility.