On Secrecy Rates and Outage in Multi-User Multi-Eavesdroppers MISO   Systems
  In this paper, we study the secrecy rate and outage probability in Multiple-Input-Single-Output (MISO) Gaussian wiretap channels at the limit of a large number of legitimate users and eavesdroppers. In particular, we analyze the asymptotic achievable secrecy rates and outage, when only statistical knowledge on the wiretap channels is available to the transmitter.   The analysis provides exact expressions for the reduction in the secrecy rate as the number of eavesdroppers grows, compared to the boost in the secrecy rate as the number of legitimate users grows. 
Joseph Kampeas, Asaf Cohen and Omer Gurewitz
cs.IT math.IT