miniTP: A protocol for the minimization of the transmit power in wireless networks

The environmental conditions under which a wireless communication system needs to work not always can be accurately modeled a priori. As a consequence, in many cases the Radio Frequency (RF) output power should be adjusted on the field at run-time in order to guarantee the functionalities and the performances of the network. It is especially true for networks with nonstationary channel, in particular for mobile networks. Today many RF devices allow to set at run-time the RF transmit power to different levels by the help of embedded micro-controllers. In this work I present a protocol for the minimization of the transmit power (miniTP) in wireless networks on the basis of the specifications and the requirements of the considered network system, that is on the basis of its network topology, of its communication protocol and of its expected performances, e.g. in terms of Link Quality (LQ), energy consumption, interference, etc. miniTP has been designed to work with a large spectrum of wireless communication protocols. Without loss of generality, to provide a more detailed treatment, in the paper I formally describe miniTP for cluster-tree Wireless Sensor Networks (WSNs) that must satisfy given requirements of LQ within each cluster and I analyze its benefits considering the case study of a cluster-tree WSN for the monitoring of servers in large data centers. To simulate and to test miniTP for the considered case study by the use of the TOSSIM 2 simulator, miniTP has been implemented in NesC under TinyOS for the WSN module MicaZ from Crossbow Technology, Inc., which includes the IEEE 802.15.4 RF device CC2420 from Texas Instruments, Inc. that is embedded also in several other WSN nodes. During the test miniTP has set at run-time the minimum transmit power among the ones allowed by the CC2420 transceiver to satisfy the requirements of the case study and in particular to maintain the PARR of the star links within each cluster greater than or equal to a fixed minimum thres- - hold, where the PARR has been defined as the packet reception rate (PRR) for ACK-based transmissions. The results obtained have shown that miniTP has worked as expected under nonstationary conditions, also with mobile nodes.