In recent years, various MAC (Medium Access Control) protocols using directional antennas have been proposed for ad hoc networks including our proposed MAC protocol called SWAMP (Smart antennas based Wider-range Access MAC Protocol). These are typically referred to as directional MAC protocols. This paper first summarizes the proposed directional MAC protocols and points out these common issues...

Underwater sensor networks (UWSNs) are characterized by large energy consumption, limited power supply, low bit rate, and long propagation delay, as well spatial-temporal uncertainty, which present both challenges opportunities for media access control (MAC) protocol design. The time-division transmissions can effectively avoid collisions since different nodes transmit packets at period of time...