Utility-Based Scheduling Algorithm Supporting Heterogeneous Services In OFDM System

Due to the scarcity of spectrum resources, the rapid development of wireless services and applications is severely limited, which exerts a great influence on major increases in achievable spectral efficiency. Orthogonal Frequency Division Multiplexing (OFDM) technology is an effective method to alleviate the frequency selective fading and inter-symbol interference and is widely used in advanced wireless telecommunications. Due to the flexibility to assign subcarriers between different users, OFDM access method has been suggested as a candidate for wireless communication systems. The problem of resource allocation for homogeneous services in OFDM-based spectrum sharing systems has been widely studied.OFDM based cognitive radio (CR) has been viewed as a promising technique to solve spectrum scarcity problem of the future wireless communication system. While long term evolution advanced(LTE-A) wireless system will be widely used in the future. As one of the key technology, coordinated multi-point (CoMP) transmission/reception strategy was proposed to mitigate inter-cell interference (ICI) by applying the signals transmitted from other cells to assist the transmission instead of acting as interference.Firstly, in CR networks, the Lagrangian dual method is proposed according to convex optimization theory,, in which the joint subcarrier assignment and power allocation are performed to achieve the optimal solution. To simplify the computation complexity, a low complexity dynamic subcarrier allocation algorithm, named Max Utility for Multiple Services on Cognitive Radio (CR-MUMS), is formulated to extend the non-linear integer optimization to a continuous convex optimization. Then based on these good performance of attribution algorithm, I further introduce the CoMP mode for single-user multi-input multi-output (CoMP-SU-MIMO) scenario in Long Term Evolution Advanced (LTE-A) system. With the CoMP mechanism the resource block (RB) competition of different users is transformed into transmission rate competition. Service model is introduced in LTE-A system-level simulation platform instead of full-buffer model. To better the solution, the quality of service (QoS) property is added into the judgment of CoMP mode to achieve the optimal performance of sector throughput and cell-edge users (UEs) rates.Final simulation results illustrate that the proposed algorithm with low computational complexity provides better optimal performance than Modified Largest Weighted Delay First (M-LWDF) and Proportional Fair (PF) algorithms. After introducing CoMP mechanism in LTE-A system, both the average sector throughput and cell-edge users’transmission rate have been greatly improved.