Priority Based Scheduling to Provide Differentiated QoS for Delay Sensitive Services in HSDPA

In wireless cellular networks, normally synchronous dedicated channels are used for real time services due to their delay sensitivity. However the increasing demand for high data-rate multimedia real time services has led to the use of asynchronous time shared channels in the forward link for realtime services in 3G wireless networks, such as HSDPA, EV-DO and EV-DV. Strict and different QoS requirements for realtime services, along with time varying channel conditions and constraints on the total forward link transmit power imposes a great deal of challenge on the user scheduler. In this paper we consider the problem of scheduling users on the forward link in a multiuser system where multiple users can be scheduled during each interval. We introduce a delay aware priority based scheduling algorithm SPS-Delay (Strict Policy Scheduling for Delay) to support differentiated QoS requirements in the form of tolerable latency specified by the user applications. We developed an HSDPA system in OPNET, and implemented our scheduling algorithm along with other well-known algorithms. Our simulations show that SPS-Delay provides improved performance over other schedulers in meeting the delay constraints if allowed by radio conditions and cell capacity.