Enhanced slotted aloha protocols for underwater sensor networks with large propagation delay

Yi Zhou, Kai Chen, Jianhua He, Haibing Guan

Research output: Chapter in Book/Published conference outputConference publication


Recently underwater sensor networks (UWSN) attracted large research interests. Medium access control (MAC) is one of the major challenges faced by UWSN due to the large propagation delay and narrow channel bandwidth of acoustic communications used for UWSN. Widely used slotted aloha (S-Aloha) protocol suffers large performance loss in UWSNs, which can only achieve performance close to pure aloha (P-Aloha). In this paper we theoretically model the performances of S-Aloha and P-Aloha protocols and analyze the adverse impact of propagation delay. According to the observation on the performances of S-Aloha protocol we propose two enhanced S-Aloha protocols in order to minimize the adverse impact of propagation delay on S-Aloha protocol. The first enhancement is a synchronized arrival S-Aloha (SA-Aloha) protocol, in which frames are transmitted at carefully calculated time to align the frame arrival time with the start of time slots. Propagation delay is taken into consideration in the calculation of transmit time. As estimation error on propagation delay may exist and can affect network performance, an improved SA-Aloha (denoted by ISA-Aloha) is proposed, which adjusts the slot size according to the range of delay estimation errors. Simulation results show that both SA-Aloha and ISA-Aloha perform remarkably better than S-Aloha and P-Aloha for UWSN, and ISA-Aloha is more robust even when the propagation delay estimation error is large.
Original languageEnglish
Title of host publication2011 IEEE 73rd Vehicular Technology Conference
Number of pages5
ISBN (Print)978-1-4244-8332-7
Publication statusPublished - 2011
EventIEEE 73rd Vehicular Technology Conference - Yokohama, Japan
Duration: 15 May 201118 May 2011

Publication series

NameProceedings of IEEEVTS Vehicular Technology Conference
ISSN (Print)1550-2252


ConferenceIEEE 73rd Vehicular Technology Conference
Abbreviated titleVTC Spring


  • underwater sensor network
  • slotted aloha
  • medium access control


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