Abstract

In this paper, we present an analytical framework for the performance evaluation of a pre-emptive priority scheduler in multi-resource networks, like those using Orthogonal Frequency Division Multiple Access (OFDMA). We focus on Quality of Service (QoS)-guaranteed traffic for which QoS is guaranteed to individual users by restricting the number of admitted users. For this, the QoS-constrained capacity, in terms of the number of supported users, needs to be ascertained a priori. The QoS-constrained capacity is a function of users’ QoS requirements, channel conditions, and radio resource allocation algorithms, which in this work is the pre-emptive priority scheduler. It is, thus, a variable quantity and mostly obtained using time-consuming offline computer simulations. Mathematical models, on the other hand, are timely and accurate, allowing the capacity to be derived in real-time as a function of the current network configuration. Existing works on mathematical modelling of pre-emptive priority schedulers have mostly focussed on single servers or multiple servers where a single server is assigned to each user. In contrast, OFDMA networks have multiple radio resources, i.e., multiple servers and each user may need more than one radio resource for a single packet transmission, i.e. it is a multi-resource system, which has been accounted for in this paper. We classify the users based on their resource requirements and model the pre-emptive priority scheduler as a multi-class, multi-server, multi-resource, non-work conserving queueing system. We derive its QoS metrics like average delay, packet drop probability, throughput, etc., from its continuous-time Markov Chain. We then use the derived QoS metrics to obtain the QoS-constrained capacity and design a threshold based predictive call admission control unit. We have validated the results using extensive discrete event simulations.

中文翻译：

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多资源OFDMA网络中具有抢占式优先级调度程序的多个QoS设置

摘要

在本文中，我们提出了一个分析框架，用于评估多资源网络中的抢占式优先级调度程序的性能，例如使用正交频分多址（OFDMA）的网络。我们专注于通过服务质量（QoS）保证的流量，通过限制允许用户的数量来保证单个用户的QoS。为此，需要根据支持的用户数量事先确定QoS约束的容量。受QoS约束的容量取决于用户的QoS要求，信道条件和无线电资源分配算法，在这项工作中，它们是抢先优先级调度程序。因此，它是一个可变的量，主要是通过耗时的脱机计算机模拟获得的。另一方面，数学模型是及时而准确的，允许根据当前网络配置实时导出容量。抢先优先级调度程序的数学建模的现有工作主要集中于单个服务器或多个服务器，其中单个服务器分配给每个用户。相反，OFDMA网络具有多个无线电资源，即多个服务器，每个用户可能需要不止一个无线电资源来进行单个数据包传输，即，它是一种多资源系统，本文已对此进行了说明。我们根据用户的资源需求对其进行分类，并将抢占式优先级调度程序建模为多类，多服务器，多资源，非工作保存队列系统。我们从其连续时间马尔可夫链得出其QoS度量，例如平均延迟，丢包概率，吞吐量等。然后，我们使用导出的QoS度量来获取QoS约束的容量，并设计基于阈值的预测呼叫允许控制单元。我们已经使用广泛的离散事件模拟验证了结果。