A single beam smart antenna for wireless communication in a highly reflective and narrow environment

Multipath reflections are prevalent in underground mine wireless communication systems and are less constructive when an omnidirectional antenna is used. This phenomenon can be significantly controlled by eliminating the source of all multipaths with a single beam. The single beam must be rotatable towards the desired user to be of any use. The single directed beam will avoid generating multipath reflections and efficiently consume the valuable stored energy. In this paper we present an analysis of an array antenna using dipoles that forms a single beam without the need for reflectors or any complex arrangement of the array elements. It can be shown that dipole elements placed in a straight line are not effective in minimizing energy consumption and a minimum of three elements are sufficient for forming a single directed beam that is electronically rotatable to all directions. We have compared three, four and six elements for the accuracy. It is also shown that the elements of the array antenna should b placed on the circumference of a circle to avoid re-computation of weights to rotate the beam on to any desired direction, thus significantly reducing the computational burden of the single beam, steerable smart antenna

Channel modeling of reconfigurable antennas for undeground communications

The wireless communication channel in underground mines is often modelled as a waveguide, with multiple propagation zones and multipath interference. We show through simulation that a directional reconfigurable antenna defines a single propagation zone and improves the quality of a communication link by reducing multipath and increasing the gain in the direction of the receiver, making it ideal for an underground mine communication system. Our results show that depending on the beam-width produced by the antenna and the distance of the communication link, multipath interference can be mitigated or completely removed. For longer distance links (> 50 m), a beam-width of 20 is capable of mitigating multipath with satisfactory improvements in gain, extending coverage range and ultimately system's reliability

Improved communications in underground mines using reconfigurable antennas

Fixed performing antennas are ineffective in providing optimum performance in a changing multi-path environment, such as underground mines where channel conditions quickly change as the antenna is moved. Hence, we investigated the performance of a pattern reconfigurable antenna in improving the wireless communications link in a hard rock underground mine. A reconfigurable antenna and a dipole were characterized and compared in line-of-sight (LOS) and non-line-of-sight (NLOS) propagation scenarios. As a proof of concept, experiments were performed at the University of Queensland Experimental Mine using a 1 GHz frequency band centered at 2.45 GHz. Analysis of complex channel impulses captured through frequency domain channel sounding is presented. Also, the results show that reconfigurability in the rich multipath environment achieves a 20% and 34% improvement in path loss and delay spread, respectively, compared to a fixed-beam antenna in NLOS propagation. Furthermore, more than 34% improvement in coherence bandwidth is observed in LOS and NLOS. Therefore, reliable high-data rate communication is achievable in underground mines by the effective management of multipath effects using the reconfigurable antenna