Wirelesssensornetworksareanemergingtechnologyforlow-cost,unattendedmonitoringofawiderangeofenvironments.TheirimportancehasbeenenforcedbytherecentdeliveryoftheIEEE802.15.4standardforthephysicalandMAClayersandtheforthcomingZigbeestandardforthenetworkandapplicationlayers.Thefastprogress