The Open Radio Access Network (O-RAN) Alliance proposes an open architecture that disaggregates the RAN and supports executing custom control logic in near-real time from third-party applications, the xApps. Despite O-RAN's efforts, the creation of xApps remains a complex and time-consuming endeavor, aggravated by the fragmented, outdated, or deprecated documentation from the O-RAN Software Community (OSC). These challenges hinder academia and industry from developing and validating solutions and algorithms on O-RAN networks. This tutorial addresses this gap by providing the first comprehensive guide for developing xApps to manage the O-RAN ecosystem, from theory to practice. We provide a thorough theoretical foundation of the O-RAN architecture and detail the functionality offered by Near Real-Time RAN Intelligent Controller (Near-RT RIC) components. We examine the xApp design and detail its configuration. We explore the xApp lifecycle and demonstrate how to deploy and manage xApps on a Near-RT RIC. We dive deep into the xApps' interfaces and capabilities, accompanied by practical examples. We also provide comprehensive details on how xApps can control the RAN. We discuss debugging strategies and good practices to aid the xApp developers in testing their xApps. Finally, we review the current landscape and open challenges for creating xApps.

翻译：开放无线接入网络（O-RAN）联盟提出了一种开放架构，该架构解耦了无线接入网（RAN）并支持通过第三方应用程序（即xApp）以近实时方式执行定制控制逻辑。尽管O-RAN联盟已付出诸多努力，xApp的开发仍是一项复杂且耗时的工作，而O-RAN软件社区（OSC）文档的碎片化、过时或废弃状态进一步加剧了此问题。这些挑战阻碍了学术界与工业界在O-RAN网络上开发和验证解决方案与算法。本教程通过提供首个涵盖从理论到实践的O-RAN生态系统管理xApp开发综合指南，以弥补这一空白。我们系统阐述了O-RAN架构的理论基础，并详述了近实时无线接入网智能控制器（Near-RT RIC）组件提供的功能。我们剖析了xApp的设计框架并详解其配置方法，探究了xApp的生命周期，演示了如何在Near-RT RIC上部署与管理xApp。通过结合实践案例，我们深入解析了xApp的接口与功能特性，并完整阐述了xApp控制无线接入网的具体实现机制。此外，我们讨论了调试策略与最佳实践，以协助xApp开发者测试其应用程序。最后，我们对当前xApp开发领域的现状与开放挑战进行了全面评述。