The proliferation of smart hand-held devices (smartphones and tablets) with their powerful computing strength has created a new class of applications which relies on the mobility. In this article, a robust Wifi-based localization technique is introduced as the basis of a home appliance control application. This application is a ubiquitous computing extension to existing classical smart-home systems with electrical equipment controllable via a central server, and is designed to address the fact that every appliance requires specific remote control which is not always with the user when he needs.

System Architechture The proposed system is a house of a number of rooms and corridors which can be commonly referred as zones. The zones can be disposed in multiple floors. Electrical appliances, including bulbs, lamps, fans, air conditions, televisions, security cameras…, in the house are connected to a central server so that they can be controlled and their states can be managed from this server.

Robust Wifi-based User Localization
	A hybrid approach is introduced to address the Wifi-based localization in 3D space. Like geometrical approach, by measuring RSSI, distances to the neighbor access points (APs) are estimated. However, probabilistic characteristics are included to take advantage of the RSSI uncertainty. An optimization process is also applied to tune system parameters for best fitting with the devices in use.

Experiment results

For experiments, the devices and appliances are disposed in three floors (8^th, 9^th and 10^th) of an eleven-floor building, as shown in the figure below. In 23 zones of the 8^th floor with total area of 1656m², 6 APs are disposed. For the 9^th floor, there are 22 zones (1512m²) and 4 APs; and for the 10^th floor, there are 19 zones (1368m²) and 5 APs. All floors are of 4m height with 0.2m-thick concrete walls and floors. All APs are of Linksys™ WRT120N model which is compliant with 802.11 b/g/n standards, and are fixed just under the ceilings.

The appliances in experiment including a television, a projector, three air conditioners, three bulbs, and a security camera are disposed in the Showroom and the Smart-room areas in the 8^th floor.

The remote control app installed on the user’s smart device (smartphone or tablet) has two modes: manual and automatic. In manual mode, the user can choose to navigate to the control panel corresponding to the appliance of interest, then presses the function buttons. In automatic mode, the user only needs to head the smart device toward the appliance of interest, and the corresponding control panel will be shown automatically.