Study Of HSDPA Scheduling Algorithm Based On TD-SCDMA

TD-SCDMA of 3G mobile systems is first Chinese domestic telecom standard, had been approved by International Telecom Union., but it has not been commercial .In order to accelerate TD development, High Speed Downlink Packet Access (HSDPA), labeled a 3.5G wireless system, has been introduced in it. HSDPA based on TD-SCDMA is expected to achieve higher performance with a peak data rate of about 10 Mb/s. The high transmission rate of HSDPA will also allow TD-SCDMA to support new high data rate services and improve the QoS of already existing ones.HSDPA relies on new technologies that make it possible to achieve such a high data rate. These new technologies include adaptive modulation and coding, hybrid automatic repeat request,, and fast packet scheduling. Packet scheduling is one of the key design features of HSDPA, included Round Robin algorithm(RR), Max C/I algorithm and Proportional Fairness (PF) algorithm.RR algorithm is fair in terms of the distribution of user throughput since each user gets the same amount of throughput regardless of its channel condition, it suffers from lower system throughout than other fast scheduling algorithms. Max C/I algorithm tends to maximize the system throughput by serving, in every TTI, the user with the best channel quality, but it has an obvious drawback in that it ignores those users with bad channel conditions, which may lead to starvation. The PF algorithm tries to increase the degree of fairness among users by selecting those with the largest relative channel quality.In this paper we provide breadth and depth analyzed performance of related three algorithm of packet scheduling, and provided some modified suggests for PF algorithm. Finally simulation, the simulation results showed performance of the three algorithm, and effectiveness of modified PF algorithm.