f the concept is addressed. In Section 10.3, characteristics of VoIP traffic are given by describing the proper- ties and functionality of the used voice codec in HSPA/LTE and by presenting the requirements and the used quality criteria for VoIP traffic. The most important mechanisms to optimize air interface for VoIP traffic in (E-) UTRAN are presented in Section 10.4. Section 10.5 provides a description for the most important practi- cal limitations in radio interface optimization, and existing solutions (if any) to avoid these limitations are covered in Section 10.6. The chapter concludes with a system simulation-based performance analysis of VoIP service, including a compar- ison between HSPA and LTE. Thus, some optimized solutions addressing the VoIP bottlenecks in the leading cellular systems such as HSPA and LTE were proposed and studied. The control channel overhead reduction solutions adopted by 3GPP are especially attractive because they provide very good performance. Chapter 11 ("Early Real-Time Experiments and Field Trial Measurements with 3GPP-LTE Air Interface Implemented on Reconfigurable Hardware Platform") verifies that the 3GPP LTE air interface can be operated indoors as well as outdoors, achieving very high data rates. Robustness to channel conditions has also been shown for coverage areas of up to 800 m with mobility. Furthermore, the chapter demonstrates the benefits of the new 3GPP-LTE air interface with a new cross-layer MAC architecture of link adaptation, transmit MIMO mode selection, and modu- lation and coding scheme (MCS) level selection, all of which are frequency depen- dent. The main focus of this chapter is on discussion of multiple antenna gains in the downlink for a single-user case and single-cell scenario. Measurement results with the authors' MIMO configuration test-bed have shown throughput exceeding 100 Mb/s, a significant increase over the existing single-antenna system. The reverberation chamber has for about three decades been used for electro- magnetic compatibility (EM