Link quality-based transmission power adaptation for energy saving in IEEE 802.11

Today, many wireless devices are mobile and battery powered, which means that the service duration is highly dependent on energy consumptions and battery capacities. Based on the fact that battery capacity is still limited, energy saving is an important issue in wireless communication. Many methods have been proposed to save energy in wireless communication, such as power-aware routing and sleep mode. However, another important approach, transmission power adaptation, is not yet well discussed. In this paper, we propose a mechanism that selects the appropriate transmission power level to transmit packets instead of using a fixed default power level for all packets, which is common in IEEE 802.11. Lower transmission power levels may result in more retransmissions, but still consumes less energy. In total, energy can be saved and interference can be reduced by selecting a good transmission power level. We propose a two phase power saving mechanism and implemented it in a real test-bed. To evaluate the performance of our mechanism, we used an indoor environment to carry out measurements. The measurement results indicate that a significant amount of energy can be saved for the transmitter in most scenarios compared to using a fixed transmission power level for all packets.