Using Mobile Elements as Dynamic Bridges in Sparse Wireless Sensor Networks

Abstract

Sparse  Wireless  Sensor  Networks  using several  mobile  nodes  and  a  small  number  of  static sensor  nodes  have  been  widely  used  for  many applications,  especially  for  traffic-generated  pollution monitoring.  This  paper  proposes  a  method  for  data collection and forwarding using Mobile Elements (MEs), which are moving on predefined trajectories in contrast to previous works that use a mixture of MEsand static nodes. In our method, MEscan be used as data collector as well as dynamic bridges for data transfer. We design the  trajectories  in  such  a  way,  that  they  completely cover  the  deployed  area  and  data  will  be  gradually forwarded  from  outermost  trajectories  to  the  center whenever  a  pair  of MEs contacts  each  other  on  an overlapping road distance of respective trajectories. The method  is based  on  direction-oriented  level  and  weight assignment.  We  analyze  the  contact  opportunity  for data  exchange  while MEs move.  The  method  has  been successfully tested for traffic pollution monitoring in an urban area.