Exploiting and Defending Opportunistic Scheduling in Cellular Data Networks

Radmilo Racic, Denys Ma, Hao Chen, and Xin Liu

Third Generation (3G) cellular networks take advantage of time-varying
and location-dependent channel conditions of mobile users
to provide broadband services. Under fairness and QoS constraints, they use
opportunistic scheduling to efficiently utilize the available spectrum.
Opportunistic scheduling algorithms rely on the collaboration among
all mobile users to achieve their design objectives.  However, we
demonstrate that rogue cellular devices can exploit vulnerabilities in
popular opportunistic scheduling algorithms, such as Proportional Fair
(PF) and Temporal Fair (TF), to usurp the majority of time slots in 3G
networks.  Our simulations show that, under realistic conditions, only five
rogue device per 50-user cell can capture up to 95% of the time slots, and can
cause two-second end-to-end inter-packet transmission delay on VoIP
applications for every user in the same cell, rendering VoIP
applications useless.  To defend against this attack, we propose
strengthening the PF and TF schedulers and a robust handoff
scheme.