“…In such a system, an idle server does not start serving customers unless there are 1 N customers waiting for service in which N is a fixed value. Extensive literatures exist on the N-policy continuous-time queues with different circumstances, and the readers may refer to Bell (1971), Kimura (1981), Takagi (1993a), Bisdikian (1994), Gakis et al (1995), Wang and Huang (1995), Wang and Ke (2000), Ke and Wang (2002), Ke (2006), Zhang and Xu (2008), Wang and Huang (2009), Choudhury et al (2009), Wang et al (2010), Choudhury et al (2011), Chang and Pearn (2011), and Yang et al (2011), Chen (2012). On the other hand, the N-policy discrete-time queues has just received little attention in the literatures.…”