The ERA Foundation is currently funding exciting new research which will significantly increase the capacity of overloaded wireless communications networks. The research, which is being undertaken by ERA Technology, is assessing whether new low cost SMART antenna systems can provide this capacity enhancement with little or no increase in system cost.

The key potential advantages of SMART antennas include:

	increased range and coverage
	fewer outages, dropped calls and blocking
	higher throughput
	lower latency
	higher densities of access points and terminals
	longer equipment battery life

A SMART antenna system can alter its radiation pattern in a way that is favourable to the propagation environment that the system is being used in, thereby reducing co-channel interference. This interference is caused when unwanted transmitters radiate towards a given receiver using the same channel as the desired source, as illustrated in the diagram below.

t The omni-directional antenna (left) inherently receives signals from all directions; a smart antenna (right) discriminates between the interferer and the desired source using beamforming lobes and nulls.

The concept of using an antenna array to control the radiation pattern is not new, but the ability to accomplish this at low cost with acceptable performance is novel. Most SMART antenna arrays use many elements, each with active control of phase and amplitude; hence, they are expensive and complex. The antenna concept requires only a single driven element surrounded by a set of parasitically excited radiators.

A Wireless Local Area Network (WLAN) application has been chosen as a means to demonstrate the potential for the new technology. Initial simulations have been carried out aimed at quantifying the benefits that the low cost SMART antenna can bring to the performance of an 802.11g network and identifying the antenna characteristics required to maximise these benefits.

To date, results have been produced for a variety of theoretical patterns representative of the low cost technology, including some with sharply defined peaks and others with deep nulls. The results of the simulations show that the new SMART antenna provides simultaneous access to the same 802.11g channel in the same environment (i.e. by providing spatial filtering) and, in particular, can improve capacity in dense Access Point (AP) deployments, such as offices and shopping centres.

Work is currently underway to manufacture a number of SMART antenna prototypes for use in a demonstration system. The antennas will be used in a typical WLAN environment and the system will be configured to demonstrate that SMART antennas can offer significant improvements in performance when compared to a "non-SMART" antenna system.

For more information please contact: info@erafoundation.org