  Jamming attacks can significantly impact the performance of wireless
communication systems. In addition to reducing the capacity, such attacks may
lead to insurmountable overhead in terms of re-transmissions and increased
power consumption. In this paper, we consider the multiple-input single-output
(MISO) broadcast channel (BC) in the presence of a jamming attack in which a
subset of the receivers can be jammed at any given time. Further,
countermeasures for mitigating the effects of such jamming attacks are
presented. The effectiveness of these anti-jamming countermeasures is
quantified in terms of the degrees-of-freedom (DoF) of the MISO BC under
various assumptions regarding the availability of the channel state information
(CSIT) and the jammer state information at the transmitter (JSIT). The main
contribution of this paper is the characterization of the DoF region of the two
user MISO BC under various assumptions on the availability of CSIT and JSIT.
Partial extensions to the multi-user broadcast channels are also presented.
