Survey on Protocols Addressing Head of Line Blocking Problem in Wireless Ad Hoc Networks Using Directional Antennas

Head of Line blocking phenomenon is common in First In First Out (FIFO) nature queues. Head of line blocking problem becomes significant in wireless ad hoc networks using directional antennas as it uses FIFO queue which consists of packets intended for different directions. A packet on the top of the queue may block the remaining packets if it finds the medium busy in its intended direction, where as the packets in the queue intended for other directions may find the medium to be idle. Very few of the MAC protocols for ad hoc networks using directional antennas have addressed this problem.