This book is part of the IEEE Standards Wireless Networks Series. This book describes Wireless Local Area Networks Quality of Service enhancements. Those enhancements enable the support of real-time applications such as voice and video. The scope of the book includes: - Overview of QoS mechanisms and architectures. - WLAN QoS mechanisms and relationship to QoS general architectures. - Performance analysis and case studies. WLAN QoS planning and engineering are challenging tasks to both network operators and end users. This book is an attempt to satisfy the need for better understanding of WLAN QoS features as well as the related engineering challenges. The reader will be able to understand WLAN QoS mechanisms and features in a simple and clear way beyond that obtained by just reading standard documents. The reader of the book should be able to understand: - WLAN QoS basic operation. How WLAN QoS is related to other QoS architectures especially IP QoS, and the related interworking issues. - How to tackle WLAN QoS main issues including admission control, scheduling, and buffer management. How to engineer a WLAN-based network to support QoS-based applications.