Cross-Layer Design for Exposed Node Reduction in Ad Hoc WLANs

Eun-Chan PARK
Moo Wan KIM

IEICE TRANSACTIONS on Communications   Vol.E101-B    No.7    pp.1575-1588
Publication Date: 2018/07/01
Publicized: 2018/01/22
Online ISSN: 1745-1345
DOI: 10.1587/transcom.2017CQP0015
Type of Manuscript: Special Section PAPER (Special Section on Communication Quality in Wireless Networks)
RTS/CTS,  cross-layer,  exposed node,  AODV,  NS-2,  

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Interference in ad hoc WLANs is a common occurrence as there is no centralized access point controlling device access to the wireless channel. IEEE 802.11 WLANs use carrier sense multiple access with collision avoidance (CSMA/CA) which initiates the Request to Send/Clear to Send (RTS/CTS) handshaking mechanism to solve the hidden node problem. While it solves the hidden node problem, RTS/CTS triggers the exposed node problem. In this paper, we present an evaluation of a method for reducing exposed nodes in 802.11 ad hoc WLANs. Using asymmetric transmission ranges for RTS and CTS frames, a cross-layer design is implemented between Layer 2 and 3 of the OSI model. Information obtained by the AODV routing protocol is utilized in adjusting the RTS transmission range at the MAC Layer. The proposed method is evaluated with the NS-2 simulator and we observe significant throughput improvement, and confirm the effectiveness of the proposed method. Especially when the mobile nodes are randomly distributed, the throughput gain of the Asymmetric RTS/CTS method is up to 30% over the Standard RTS/CTS method.