Abstract
A multistage fuzzy minimum output energy (MOE) detector is proposed for multiple input multiple output (MIMO) multi-carrier code-division-multiple access (MC-CDMA) uplink systems with carrier frequency offset (CFO) over multipath fading channels. The first stage of the receiver uses a novel MIMO receiver model with offset symbols to achieve a fuzzy CFO-constrained MOE detector that suppresses multiple access interference (MAI) and minimizes cancellation of the desired signal. To suppress noise and to enhance signal reception after the fuzzy MOE detector, a signal subspace projection and minimum mean square error weight combiner is proposed to enhance signal-to-interference-plus-noise ratio and bit error rate performances. Simulation results show that the proposed MIMO detector outperforms conventional MOE detectors and achieves the ideal receiver performance against MAI and CFO effects.
Highlights
Multi-carrier code-division-multiple access (MCCDMA) systems [1,2,3,4] are currently under consideration for application in WiMAX and WiFi systems in future broadband wireless communication systems
Its performance is limited by multiple access interference (MAI) and carrier frequency offset (CFO) [5]
To acquire spatial diversity, this study develops a robust multiple input multiple output (MIMO) fuzzy minimum output energy (MOE) detector to suppress MAI, to prevent signal cancellation caused by the CFO effect, and to acquire the multipath and spatial diversity gains
Summary
Multi-carrier code-division-multiple access (MCCDMA) systems [1,2,3,4] are currently under consideration for application in WiMAX and WiFi systems in future broadband wireless communication systems. Since the conventional space–time block decoding scheme in [18] cannot be used for the MAI, ICI, and multipath interference scenarios, the proposed MIMO STBC receiver with fuzzy constrained MOE detector suppresses interference and effectively detects desired signals. The conventional receiver design detects the signal in (3) by first compensating for the frequency offset effect and using linear weight combiner to suppress the MAI interference. A robust fuzzy CFO-constrained MIMO MOE method with coarse CFO estimation and signal subspace projection is designed to suppress MAI. A fuzzy frequency offset-constrained MIMO MOE receiver is proposed for effective suppression of strong MAI. After the coarse CFO estimation, the fine residual CFO parameter can be considered for use in the MOE detector of Section 3.3 to span the effective signal subspace, to acquire the desired signal reception, and to suppress MAI interference. Let V be the D × 2 weight matrix for the combining procedure, i.e., xðiÞ 1⁄4 VH zðiÞ ð20Þ where the projected MIMO MOE detector output data vector z(i) is a D × 1 vector zðiÞ 1⁄4 1⁄2 z1;1 ⋯ z1;D T 1⁄4 WHs _yðiÞ ð21Þ
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