Changes between Version 2 and Version 3 of MobiCom2008

Jul 24, 2008, 1:06:17 PM (16 years ago)



  • MobiCom2008

    v2 v3  
    33Authors: J. Camp, E. Knightly
    5 Submitted to MobiCom 2008
     5To Appear in MobiCom 2008
    77== Abstract ==
    88Accurately selecting modulation rates for time-varying channel conditions is critical for avoiding performance degradations due to rate over-selection when channel conditions degrade or under-selection when channel conditions improve.  In this paper, we design a custom cross-layer framework that enables (i) implementation of multiple and previously unimplemented rate adaptation mechanisms, (ii) experimental evaluation and comparison of rate adaption protocols on controlled, repeatable channels as well as residential urban and downtown vehicular and no-mobile environments in which we accurately measure channel conditions with 100-µs granularity, and (iii) comparison of performance on a per-packet basis with the ideal modulation rate obtained via exhaustive experimental search.  Our evaluation reveals that SNR-triggered protocols are susceptible to over-selection from the ideal rate when the coherence time is low (a scenario that we show occurs in practice even in a non-mobile topology), and that "in-situ" training can produce large gains to overcome this sensitivity.  Another key finding is that a mechanism effective in differentiating between collision and fading losses for hidden terminals has severely imbalanced throughput sharing when competing links are even based protocols outperform loss-based protocols in terms of the ability to track vehicular clients, accuracy within outdoor environments, and balanced sharing with heterogeneous links (even with physical layer capture).
    10         {Camp:2008,
    11         Author = {J. Camp, E. Knightly},
    12         Journal = {MobiCom 2008,
    13         Title = {Modulation Rate Adaptation in Urban and Vehicular Environments:  Cross-layer Implementation and Experimental Evaluation},
    14         Year = {2008}}
     11 author = {Joseph Camp and Edward Knightly},
     12 title = {Modulation Rate Adaptation in Urban and Vehicular Environments: Cross-layer Implementation and Experimental Evaluation},
     13 booktitle = {{ACM MobiCom}},
     14 month = sep,
     15 year = {2008},
     16 address = {San Francisco, CA},