Large-Scale MIMO Detection for 3GPP LTE: Algorithms and FPGA Implementations

Large-scale (or massive) multiple-input multiple-output (MIMO) is expected to be one of the key technologies in next-generation multi-user cellular systems, based on the upcoming 3GPP LTE Release 12 standard, for example. In this work, we propose - to the best of our knowledge - the first VLSI design enabling high-throughput data detection in single-carrier frequency-division multiple access (SC-FDMA)-based large-scale MIMO systems. We propose a new approximate matrix inversion algorithm relying on a Neumann series expansion, which substantially reduces the complexity of linear data detection. We analyze the associated error, and we compare its performance and complexity to those of an exact linear detector. We present corresponding VLSI architectures, which perform exact and approximate soft-output detection for large-scale MIMO systems with various antenna/user configurations. Reference implementation results for a Xilinx Virtex-7 XC7VX980T FPGA show that our designs are able to achieve more than 600 Mb/s for a 128 antenna, 8 user 3GPP LTE-based large-scale MIMO system. We finally provide a performance/complexity trade-off comparison using the presented FPGA designs, which reveals that the detector circuit of choice is determined by the ratio between BS antennas and users, as well as the desired error-rate performance.Comment: To appear in the IEEE Journal of Selected Topics in Signal Processin

Flexible N-Way MIMO Detector on GPU

This paper proposes a flexible Multiple-Input Multiple-Output (MIMO) detector on graphics processing units (GPU). MIMO detection is a key technology in broadband wireless system such as LTE,WiMAX, and 802.11n. Existing detectors either use costly sorting for better performance or sacrifice sorting for higher throughput. To achieve good performance with high thoughput, our detector runs multiple search passes in parallel, where each search pass detects the transmit stream with a different permuted detection order. We show that this flexible detector, including QR decomposition preprocessing, outperforms existing GPU MIMO detectors while maintaining good bit error rate (BER) performance. In addition, this detector can achieve different tradeoffs between throughput and accuracy by changing the number of parallel search passes.National Science Foundation (NSF

Low Complexity Opportunistic Decoder for Network Coding

In this paper, we propose a novel opportunistic decoding scheme for network coding decoder which significantly reduces the decoder complexity and increases the throughput. Network coding was proposed to improve the network throughput and reliability, especially for multicast transmissions. Although network coding increases the network performance, the complexity of the network coding decoder algorithm is still high, especially for higher dimensional finite fields or larger network codes. Different software and hardware approaches were proposed to accelerate the decoding algorithm, but the decoder remains to be the bottleneck for high speed data transmission. We propose a novel decoding scheme which exploits the structure of the network coding matrix to reduce the network decoder complexity and improve throughput. We also implemented the proposed scheme on Virtex 7 FPGA and compared our implementation to the widely used Gaussian elimination.Renesas MobileNational Science Foundation (NSF

Ultrastable embedded surface plasmon confocal interferometry

As disease diagnosis becomes more sophisticated, there is a requirement to measure small numbers of molecules attached to, for instance, an antibody. This requires a sensor capable not only of high sensitivity but also the ability to make measurements over a highly localized region. In previous publications, we have shown how a modified confocal microscope allows one to make localized surface plasmon (SP) measurements on a scale far smaller than the surface plasmon propagation distance. The present implementation presents a new ultrastable interferometer system, which greatly improves the noise performance. Hitherto, we have used the central part of the back focal plane to form a reference beam with the reradiated surface plasmons. In the current system, we block the central part and use the spatial light modulator to deflect s-polarized light into the pinhole to form an interference signal with the surface plasmons, thus creating an ultrastable interferometer formed with two beams incident at very similar angles. We demonstrate the superior noise performance of the system in hostile environments and examine further adaptations of the system to further enhance noise performance