{'fraction_non_alphanumeric': 0.04186046511627907, 'fraction_numerical': 0.008637873754152824, 'mean_word_length': 5.301255230125523, '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}}
A Power Efficient Baseband Engine for Multiuser Mobile MIMO-OFDMA Communications

In this paper, the authors present a configurable and power efficient multiuser MIMO-OFDMA baseband processor for uplink mobile communications. To solve the carrier frequency offset (CFO) problem in multiuser transmission, an inter-carrier interference-based (ICI-cancellation-based) CFO estimator is implemented based on an iterative search criterion of minimum signal-to-interference-noise (SINR) ratio. Compared to the state-of-the-art methods, the proposed CFO estimator is more robust to transmission configurations (MIMO and multiuser) and CFO variations. Moreover, the authors propose an efficient architecture that saves 78% of the hardware complexity compared to the direct implemented architecture by employing Taylor series expansion for ICI/multiple-access interference (MAI) cancellation. Meanwhile, a 2-D linear channel estimator is also proposed to assist the CFO estimator and track the time-variant multipath channel. Two kinds of MIMO detector, vertical Bell Laboratory layered space-time (V-BLAST) and V-BLAST with maximum likelihood (V-ML), are adopted to minimize output latency and achieve the best ML bit-error-rate (BER) performance. An ASIC fabricated by 0.13 μm 1P8M CMOS technology is measured with 2.31 Mbps/mW power efficiency and less than 1.5 dB implementation loss. In addition, the whole transceiver is integrated and verified by a system-on-chip (SoC) platform to demonstrate its efficacy.