טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentXie Yueming
SubjectAn Invitation Control Policy for Proactive Service Systems:
Balancing Efficiency, Value and Service Level
DepartmentDepartment of Industrial Engineering and Management
Supervisors Dr. Galit Yom-Tov
Dr. Liron Yedidsion


Abstract

Proactive service systems permit a controllable arrival rate managed by the service provider, which is different from classic service systems. Conceptually, some (or all) of the customers are invited to the system, so as to allow for a better control over operational indicators and profitability. Such a proactive service system is used, for example, to model an online chat service system, or for planning preventive care strategies for health care service providers.

Through an empirical study of a proactive chat service system, the validity of customer ranking information is elaborated for optimizing invitation control. It is also shown that service level measures can be formulated in terms of penalty for abandonment and cost of waiting. Hence, an infinite-time-horizon multiclass multiserver queueing system has been developed with impatient customers. We find an asymptotically optimal policy using a fluid approximation, by solving a linear programming problem that maximizes revenues. The asymptotic optimal invitation policy we developed invites customers by their rµ ranking in decreasing order until there are no idle servers. Then, an equivalent threshold policy is proposed that is easy to implement in practice. Numerical simulations were performed to demonstrate the performance of the policy and identify its limitations. We show that the fluid policy has a good performance but is also crude.

In order to refine the fluid policy, we analyzed a fluid approximation of the system under a more flexible threshold policy. The equilibrium is found to strongly depend on system parameters. In particular, it depends on the threshold value. It is also shown that the equilibrium is globally asymptotically stable via trajectory and Lyapunov analysis. Furthermore, in order to propose an invitation policy for proactive service systems that balances revenues and service level, the probability of implementing admission control is approximated, and several approximations of performance metrics are calculated. Simulations are performed to examine the performance of these approximations. All of them perform well especially in large-size systems.