The project M4 focus on the indoor scenario with limited mobility, where low-cost low-complexity miniature consumer electronic devices like tablets and smartphones are deployed. An ultra-wideband system design is presented which supports wireless Internet access and similar short-range applications with data rates of the order of 100Gbps. Unlike concurrent work exploring the 60GHz regime and beyond for this purpose, our focus is on the 6.0–8.5GHz frequency band. Hence, a bandwidth efficiency of about 50bps/Hz is necessary. This sophisticated goal is targeted by employing two key enabling techniques: massive MIMO communications in conjunction with multi-mode antennas. This concept is suitable both for small-scale terminals like smartphones, as well as for powerful access points. Compared to mm-wave and THz band communications, the 6.0–8.5GHz frequency band offers more robustness in NLOS scenarios and is more mature with respect to system components. Besides ultra-fast wireless Internet access, massive IoT deployments are investigated.