<FONT face=Verdana>This paper theoretically analyzes the performance of the sleep mode for the mobile station with multi-services

and finds that the energy-saving efficiency is very poor due to the asynchrony of the listening windows of different power saving classes. Then it proposes a COoperative Power Saving Mechanism (COPS) which tries to synchronize the listening windows of different power saving classes cooperatively to improve the energy-saving efficiency. Both theoretical results and simulation results show that COPS not only improves the energy efficiency but also reduces the average MAC frame response time.