GENERALIZING THE INFRASTRUCTURE

The prototype location infrastructure can be configured in several ways that facilitate different forms of interaction between the users and the environment. By controlling the placement of transmitters and which devices record beacon IDs, various levels of privacy can be achieved.

1. No state: Sounds are determined by user location and neither the wearable nor the environment records any information.
2. State only on wearable: The wearable records the presence of other transmitter's IDs and the order they were received. By mounting transmitters on players as well as in the environment, multiple players can interact in the same augmented reality.
3. State in the environment and on the wearable: The environment records the IDs of transmitters that pass nearby and the beacons can therefore respond differently to individual users. This configuration allows the users to share one virtual world if all of the environmental beacons are networked together permitting more complex and rich interactions.

In the first system the audio is directly triggered by the current location. The system used for Guided By Voices is of the second type but has no transmitters on the wearable. Each user can share the same physical space, but the augmented realities are completely separate. Placing transmitters on the wearables would allow the users to interact in the virtual world linking the personal augmented realities together. An example using this additional infrastructure would by to extend Guided by Voices such that there is a location that requires two players to cooperate to get a particular item. Likewise, by using the third type of infrastructure and having the environment track the users, Guided by Voices could be extended to allow locations to have a memory of who visited over time and across users. If one player's actions in a location destroyed a monster, when another player visited they would encounter the remnants of the battle. This infrastructure would further link the augment realities of the users and extend the abilities to cooperate and compete with other users.

The location information provided by the positioning infrastructure poses some privacy concerns for users of the augmented reality. With the current Guided by Voices configuration only the environment transmits IDs and all location information is local to each wearable. By mounting transmitters on other wearable systems (the second configuration) the users of the augmented reality can track their proximity to other users. Although the location of a wearable is no longer private to each person, only the other people physically present at the same time and place receive the other user's location. In the third configuration the environment tracks the users position and records that information. This poses the greatest privacy concerns because other people could potentially query the environment about a user's location and a great deal of effort would be needed to make sure that the environment is secure and trusted. For the last two configurations that have a transmitter on the wearable the user could, in theory, selectively reveal himself/herself to the environmental infrastructure if such exposure would add desired functionality. Selecting the correct type of infrastructure to support augmented realities must weigh the concerns about the privacy of user's location against the added functionality achieved.