Introduction: queueing systems special issue on queueing systems with abandonments

The investigation of queueing systems with impatient customers has a long history in queueing theory, with the now standard Erlang-A model going back at least to Palm’s classic 1957 paper. Despite this long record of work, focus on systems with abandonments has been rekindled due to recent interest in analyzing complex service systems, most notably large call centers. Interestingly, this new surge of work has been motivated both by applied and theoretical advances. In the applied realm, very large call centers are now an important component in many industrial sectors and advanced call management software enables the use of sophisticated algorithms in operating these centers. On the more theoretical side, there have been great advances in approximating large queueing systems with abandonments via many-server asymptotics and related diffusion approximations. Furthermore, there have been numerous advances in the understanding of flexible server models with abandonments, which serve as models for systems with “cross-trained” agents. Techniques from revenue management, game theory, and stochastic optimization have also been applied to the operation of such systems. In addition, queueing systems with impatient customers also have a rich connection with perishable inventory and organ transplantation systems. Thus the requirements of practitioners, and the myriad new tools of theoreticians, have motivated this focused issue on stochastic systems with abandonments. This special issue actually consists of nine papers, eight of which appear together here. Due to a publishing error, one of the papers, by Baris Ata and Mustafa H.