In this work, we present a simple (in that it uses few primitive system parameters), approximate analytical model for the performance analysis of context-aware applications that use floating content. From a system design perspective, our analysis can be used to tune key system parameters so as to achieve the desired application performance. In particular, we apply our analysis to estimate the "success probability" for two representative categories of context-aware applications, and show how the system can be configured to achieve the application’s target. In order to complement our analytical study, we validate our model using extensive simulations under different settings and mobility patterns. Our simulation results show that our model-based predictions are indeed highly accurate under a wide range of conditions.

1. A Simple Approximate Analysis
of Floating Content
for Context-Aware Applications
Shahzad Ali, Gianluca Rizzo, Marco Ajmone
Marsan, Balaji Rengarajan
Institute Imdea Networks, Madrid, Spain
HES–SO Valais, Sierre, Switzerland

2. The Floating Content service
Objective: ensuring the availability of some data
to mobile users
– within a certain geographic area
– for a given duration in time
– without infrastructure support
Applications: Emergency services,
road traffic information,
social networks…

3. I - A node generates content
The basic FC mechanism

4. II - Content is replicated opportunistically
The basic FC mechanism

5. III: Content starts to float
The basic
FC mechanism
III - Content “floats” within the Anchor Zone

6. We considered the performance of FC
from an application perspective
What is the performance of applications using FC?
• What applications can be supported with acceptable
performance?
• How to engineer the application to achieve a given
QoS?
State of the art:
• Analysis: sufficient conditions for the content to float

7. Our results
• We developed an simple analytical model for
performance analysis of applications relying
on FC
– Our model is accurate on a variety of
configurations
– Simulations: our result are accurate even outside
of the model
• FC is a viable communication service for a
large class of context aware applications

8. We built a simple model for
application performance
• Random direction mobility model
• Users distributed according to a Poisson PP
P(s)=P(a user gets the content before leaving the AZ)
P(at least 1 successful contact over K)P( having K contacts)

9. The formula is accurate,
even outside the model

10. Future work
–Extension to more realistic mobility
models
–Evaluation on real mobility traces