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dependent on the number of samples taken and average distance between them.
In general, the fewer the number of samples (tuples) recorded the greater the
improvement that is obtained using the k-nearest neighbor method.
Accuracy of the Empirical Model.
The empirical model requires substan-
tial time and effort to collect, organize, and employ the appropriate algorithms.
The time of day that measurements are taken is of critical importance as the
propagation of radio waves in an indoor environment varies greatly depending
on changing obstacles in the building, most notably people. A solution to this
problem is to create various maps and employ them at different times of the day.
However, this further illustrates the inflexibility of the empirical model. The up-
keep for this method must remain consistent, and evolve with architectural and
usage changes. This being said, the empirical model is more accurate than the
propagation model and is the most accurate model that exists to date, yielding
an accuracy of under 2m [1]. The reason for this is because empirical measure-
ments inherently take into account the obstacles and nuances of a building, such
as doors, walls and building geometry [3] that the propagation model cannot
account for.
3 Privacy Issues
Wireless LAN positioning introduces serious privacy issues. As mapping a wire-
less LAN involves associating connected users to real geographic locations it is
possible to track the movement and location of a wireless device. This being the
case, there is a responsibility among software developers and system adminis-
trators to keep users informed and their location data private. The good news
is that the right tools, namely encryption and rule-based control systems, used
appropriately, could eliminate many of the risks.
On a computer network users are identified by a hardware code called a
Media Access Control (MAC) address. A MAC address is a code that identifies
a particular network interface card, in this case a wireless card. MAC addresses
are unique and never change. As such it is entirely possible to match a user
to his or her MAC address. This makes determining a user's location possible
whenever he or she is connected to the network and, depending on the nature
of the positioning system, makes it possible to determine where the user has
been throughout the course of his or her day. For this reason, strong encryption
should be used in the handling of MAC addresses. MAC addresses should not
be directly linked to identifying information about users and MAC address data
should never be permanently stored or even kept lingering after it is no longer
needed.
3.1
Rule-Based Control
Context-aware programs need to request information on users in order to op-
erate properly. In order for users to maintain control over the distribution of
their location information, there must be some control in place for approving or
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