Mobility and Predictability of Ultra Mobile Users Jeeyoung Kim and Ahmed Helmy.
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Transcript of Mobility and Predictability of Ultra Mobile Users Jeeyoung Kim and Ahmed Helmy.
Mobility Models?
Mobility models: based on WLAN usage traces How realistic are these mobility models? How much mobility do these WLAN
traces capture?
Why VoIP?
VoIP Characteristics Devices are on most of the time Devices are light enough to carry around
while in use
Ultra mobile?
Are VoIP users good enough? Based on different mobility metrics, we
sampled users who are assumed to be ultra mobile (not including VoIP device users)
In order to determine the validity of our findings
VoIP vs. WLAN : Mobility
Prevalence for VoIP Device Users Prevalence for General WLAN Users
Prevalence
VoIP vs. WLAN : Mobility
# of APs visited for VoIP Device Users # of APs visited for General WLAN Users
Number of APs visited
VoIP vs. WLAN : Mobility
Activity Range for VoIP Device Users Activity Range for General WLAN Users
Activity Range
Predictors: Order-k Markov
Assumes location can be predicted from the current context which is the sequence of the k most recent symbols in the location history
Markov model represents each state as a context, and transitions represent the possible locations that follow that context.
We use Order 1, 2 and 3 predictors for our prediction
Predictors: Lempel-Ziv (LZ)
Predicts in the case when the next symbol in the produced sequence is dependent on only its current state (but does not have to correspond to a string of fixed length)
Similar to O(k) Markov but k is a variable allowed to grow to infinity
Predictors
Each predictor is run for the WLAN movement trace and for each of the ultra mobile test sets including the VoIP trace set
The prediction accuracy is measured as the percentage of correct predictions of the next AP to visit
Ultra Mobile vs. WLAN : Predictability
Prediction Accuracy Using Markov O(1) for 2001-2004 Trace
Prediction Accuracy Using Markov O(1) for 2005-2006 Trace
Markov O(1)
Ultra Mobile vs. WLAN : Predictability
Prediction Accuracy Using Markov O(2) for 2001-2004 Trace
Prediction Accuracy Using Markov O(2) for 2005-2006 Trace
Markov O(2)
Ultra Mobile vs. WLAN : Predictability
Prediction Accuracy Using Markov O(3) for 2001-2004 Trace
Prediction Accuracy Using Markov O(3) for 2005-2006 Trace
Markov O(3)
Change in Trend
VoIP Device Users highly predictable What happened? VoIP users becoming more stationary?
General WLAN Users less predictable More and more light-weight devices are
being introduced everyday No longer need to have a VoIP device to
use the service
Future Work Better predictor for “ultra mobile”
users 60% is better than 25% but it still is not
accurate enough Different flavors of Markov Chain, LZ
Family, Prediction using regression methods, etc.
Better mobility models That will incorporate “ultra mobile” users
better