Energy-conserving access protocols for transmitting data in unicast and broadcast mode

In the recent years many applications have emerged, where the demand for communicating with a very large number of small-size and low-cost nodes becomes a necessity. Such applications involve for example, radio frequency identification (RFID) and smart card networks, or even mobile computing devices, in general. A critical energy constraint is imposed on the communication (access) protocols used in these systems, so that the total time a node needs to be active for transmitting or receiving information should be minimized. Another area with great interest is that of broadcast-based information systems which, compared to traditional unicast data transfer, can be much more efficient for disseminating information to a large number of nodes in applications where there is a high degree of commonality among node interests. Unlike previous work on energy-conserving protocols with unicast data transfer, we propose and evaluate broadcast-based communication protocols with energy constraint, in which the number of time slots during which nodes need to be in the active state is minimized, while the access delays are kept low