Introduction to Packet Scheduling Algorithms for Communication Networks

As implied by the word “packet scheduling”, the shared transmission resource should be intentionally assigned to some users at a given time. The process of assigning users’ packets to appropriate shared resource to achieve some performance guarantee is so-called packet scheduling. It is anticipated that packetized transmissions over links via proper packet scheduling algorithms will possibly make higher resource utilization through statistical multiplexing of packets compared to conventional circuit-based communications. A packet-switched and integrated service environment is therefore prevalent in most practical systems nowadays. However, it will possibly lead to crucial problems when multiple packets associated to different kinds of Quality of Service (QoS) (e.g. required throughput, tolerated delay, jitter, etc) or packet lengths competing for the finite common transmission resource. That is, when the traffic load is relatively heavy, the first-come-first-serve discipline may no longer be an efficient way to utilize the available transmission resource to satisfy the QoS requirements of each user. In such case, appropriate packet-level scheduling algorithms, which are designed to schedule the order of packet transmission under the consideration of different QoS requirements of individual users or other criteria, such as fairness, can alter the service performance and increase the system capacity . As a result, packet scheduling algorithms have been one of the most crucial functions in many practical wired and wireless communication network systems. In this chapter, we will focus on such topic direction for complete investigation. Till now, many packet scheduling algorithms for wired and wireless communication network systems have been successfully presented. Generally speaking, in the most parts of researches, the main goal of packet scheduling algorithms is to maximize the system capacity while satisfying the QoS of users and achieving certain level of fairness. To be more specific, most of packet scheduling algorithm proposed are intended to achieve the following desired properties: 1. Efficiency: The basic function of packet scheduling algorithms is scheduling the transmission order of packets queued in the system based on the available shared resource in a way that satisfies the set of QoS requirements of each user. A packet scheduling algorithm is generally said to