Frame Length Control for Wireless LANs in Fast Mobile Environments

Ryoichi SHINKUMA  Takayuki YAMADA  Tatsuro TAKAHASHI  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E91-A    No.7    pp.1580-1588
Publication Date: 2008/07/01
Online ISSN: 1745-1337
DOI: 10.1093/ietfec/e91-a.7.1580
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Multi-dimensional Mobile Information Networks)
fast-mobile environment,  road-vehicle communication,  wireless local area network,  relative speed,  frame length,  

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In this paper, we propose a novel solution to improving wireless channel quality of wireless local area networks (WLANs) in fast-mobile environments, which uses a media-access-control (MAC) layer approach: adaptive frame-length control and block acknowledgement (ACK). In fast-mobile environments, using short frame lengths can suppress channel estimation error and decrease frame errors. However, it increases the MAC overhead, resulting in decreased throughput. To solve this tradeoff, we combined block ACK, which is specified in IEEE802.11e as an optional function, with adaptive frame-length control. Although adaptive frame-length control considering this tradeoff has previously been investigated, the targets were different from WLANs using orthogonal frequency division multiplexing (OFDM) in fast-mobile environments. The MAC-overhead reduction using block ACK is suitable for our frame-length control because it does not change the frame format in the physical layer. Also, it is a new idea to use block ACK as a solution to improving channel quality in fast-mobile environments. In this paper, we evaluate our method through computer simulations and verify the effectiveness of adaptive frame-length control that can accommodate relative speeds.