Head of Line Blocking in Wireless Ad Hoc Networks using Directional Antennas

Abstract

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. In this paper we propose a method to address the Head of Line blocking problem that can be used for Medium Access Control protocol for wireless Ad Hoc networks using Directional Antennas. The present proposal is about processing the data packets in the queue ready for transmission in other directions when the data packet on top of the queue finds the channel busy in its intended direction. This method is independent of mechanisms used for sensing and transmission by a MAC protocol for directional antennas thus can be part of any MAC protocol using directional antennas with out much change to the protocol. We propose Individual queues for each beam direction and also propose to transmit all the packets waiting at a time once the medium is idle in the intended direction. Our results indicate that the method outperforms other methods proposed for avoiding head of line blocking while increasing throughput and reducing the end-to-end delay.