LTE下行鏈路中具調適服務品質及公平性考量之排程研究

Abstract

隨著全球通訊技術的發展，第四代行動通訊系統(4G)已進入我們的生活之中。其中又以長期演進技術（Long Term Evolution, LTE）為代表。LTE使用了正交分頻多工(Orthogonal Frequency-Division Multiplexing, OFDM)以及多輸入多輸出(Multi-Input Multi-Output, MIMO)技術，使得第四代行動網路在上傳以及下載時，能擁有更大的傳輸量，及更遠的傳輸距離。\n 當下載時，因為每位使用者所在的環境不同，造成傳輸量、延遲時間因而不同，所以基地台分配資源時，尚有許多改善的空間。目前，許多文獻在探討如何公平且有效地分配資源塊(Resource Block, RB)給使用者裝置(User Equipment, UE)，如Proportional Fair (PF)與Modified Largest Weighted Delay First (MLWDF)兩種排程機制。前者考量了優先權的公平性，但沒有考量服務品質(Quality of Service, QoS)；後者對於較即時的封包有較高的優先權，卻導致資源分配不均，將大量的資源給部份使用者。本篇論文著重於公平性以及服務品質的考量，使用不同方式的佇列存放各種不同的資源型態(resource type)，依照資源型態佔整體資源數量的比例，以及計算出Adaptive Modified Largest Weighted Delay First (AMLWDF)的優先權值，針對各個UE與各個通道(channel)做全面性地配置，來提昇公平性及降低延遲以符合QoS要求。

Owing to the development of global communication technology, the Long Term Evolution (LTE) is the latest technology for the fourth generation mobile communication systems (4G) that has entered into our lives. LTE uses Orthogonal Frequency Division Multiplexing (OFDM) and Multiple-Input Multiple-Output (MIMO) technology to provide high data rate transmission and long distance transmission when users doing download and upload.\nWhen doing download, users may have different throughput, delay time, and jitter due to they are in different locations. To improve these performance indexes, the E-UTRAN Node B (eNodeB) has to allocate resource blocks efficiently.\nIn the literature, many works explore how to fairly allocate resource blocks (RB) to users. Proportional Fair (PF) and Modified Largest Weighted Delay First (MLWDF) are two example scheduling mechanisms. PF considers service priority and fairness, but doesn`t consider the Quality of Service (QoS). MLWDF considers QoS but not service priority and fairness, and allows eNodeB giving more resources to particular users. \nIn this thesis, we focus on resource allocation problem of downlink scheduling in LTE. Considering fairness and QoS, we store various resource types into particular queues and calculate the priorities using Adaptive Modified Largest Weighted Delay First (AMLWDF). The relationships between users and channels are coordinated according to the priorities for the sake of enhancing the fairness and reducing the delay time and jitter.