{'fraction_non_alphanumeric': 0.032, 'fraction_numerical': 0.0, 'mean_word_length': 5.186813186813187, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Impact and Mitigation of Multiantenna Analog Front-End Mismatch in Transmit Maximum Ratio Combining

Transmit maximum ratio combining (MRC) allows to extend the range of wireless local area networks (WLANs) by exploiting spatial diversity and array gains. These gains, however, depend on the availability of the channel state information (CSI). In this perspective, an open-loop approach in time-division-duplex (TDD) systems relies on channel reciprocity between up- and downlink to acquire the CSI. Although the propagation channel can be assumed to be reciprocal, the radio-frequency (RF) transceivers may exhibit amplitude and phase mismatches between the up- and downlink. In this contribution, we present a statistical analysis to assess the impact of these mismatches on the performance of transmit-MRC. Furthermore, we propose a novel mixed-signal calibration scheme to mitigate these mismatches, which allows to reduce the implementation loss to as little as a few tenths of a dB. Finally, we also demonstrate the feasibility of the proposed calibration scheme in a real-time wireless MIMO-OFDM prototyping platform.