ding 100 Mb/s, a significant increase over the existing single- antenna system. These MIMO-OFDM measurement results were performed in an office and in a suburban outdoor scenario. We argue that frequency-dependent link adaptation in combination with transmit mode selection is a vital feature in our system design. In principle, we show that this parallelized link adaptation provides robust gains in a cellular broadband system. The robustness is seen in both indoor and outdoor measurement results. The key feature of our work is implementation of multiple-antenna concepts in a broadband wireless system. 11.2.1 Channel-Aware Link Adaptation A complete schematic of frequency-dependent link adaptation is shown in Figure 11.9. Two key features of this link adaptation are described next. 11.2.1.1 Adaptive Modulation One important advantage of OFDM compared to CDMA (code division mul- tiple access) techniques is that it exploits frequency-dependent resource allocation. Resources are used independently, with specific modulation and coding schemes (MCSs) for a specific user. The broadband system is decomposed into parallel channels. The effective SINR after MIMO detection at receiver is calculated. This value acts as input for © 2009 by Taylor & Francis Group, LLC Long Term Evolution: 3GPP LTE Radio and Cellular Technology User Equipment 0 Selectable equalizer: Adaptive MRC- or user 0 MMSE-based demapper Base Station stream separation Multi-user Adaptive Queueing Channel estimation system mapper and SINR calculation User Equipment 1 Scheduling algorithm: Selectable Frequency-selective assignment equalizer: of spatial mode, Adaptive MRC- or user 1 i.e., either diversity or multiplexing MMSE-based and modulation + coding scheme demapper stream separation SINR feedback from UEO Channel estimation and SINR calculation SINR feedback from UE1 Figure 11.9 Principle of frequency-dependent link adaptation. an adaptive bit-loading algorithm. The calculation of the effective SINR includes the estimated channel coefficients, the automa