The Head-of-Line Blocking Problem on Exposed Terminals in MANETs

In Mobile Ad hoc NETworks (MANETs), the hidden and the exposed terminal problems affect the throughput of the Medium Access Control (MAC) protocols. Several MAC schemes have been proposed to solve these problems by allowing the exposed terminals to send their packets concurrent with the on-going transmission. Due to their locations, the exposed terminals are likely to have data packets for neighbors that are temporarily unavailable to receive. This leads to the so called Head-Of-Line (HOL) blocking problem. In this paper, the authors propose the Exposed Terminal Scheduling (ETS) technique to solve the problem. In the ETS scheme, all nodes collect the local topology and transmission information to make sure that they will not send to those temporarily unavailable nodes.