314 research outputs found
A Robust Low-Complexity MIMO Detector for Rank 4 LTE/LTE-A Systems
This paper deals with MIMO detection for rank 4 LTE systems. The paper
revolves around a previously known detector [1, by Inkyu Lee, TCOM'2010] which
we shall refer to as RCSMLD
(Reduced-Constellation-Size-Maximum-Likelihood-Detector). However, a direct
application of the scheme in [1, by Inkyu Lee, TCOM'2010] to LTE/LTE-A rank 4
test cases results in unsatisfactory performance. The first contribution of the
paper is to introduce several modifications that can jointly be applied to the
basic RCSMLD scheme which, taken together, result in excellent performance. Our
second contribution is the development of a highly efficient hardware structure
for RCSMLD that allows for an implementation with very few multiplications.Comment: Accepted for publication in PIMRC-2014, Washington DC, US
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
Probabilistically Bounded Soft Sphere Detection for MIMO-OFDM Receivers: Algorithm and System Architecture
Iterative soft detection and channel decoding for MIMO OFDM downlink receivers is studied in this work. Proposed inner soft sphere detection employs a variable upper bound for number of candidates per transmit antenna and utilizes the breath-first candidate-search algorithm. Upper bounds are based on probability distribution of the number of candidates found inside the spherical region formed around the received symbol-vector. Detection accuracy of unbounded breadth-first candidate search is preserved while significant reduction of the search latency and area cost is achieved. This probabilistically bounded candidate-search algorithm improves error-rate performance of non-probabilistically bounded soft sphere detection algorithms,
while providing smaller detection latency with same hardware resources. Prototype architecture of soft sphere detector is synthesized on Xilinx FPGA and for an ASIC design. Using area-cost of a single soft sphere detector, a level of processing parallelism required to achieve targeted high data rates for future wireless systems (for example, 1 Gbps data rate) is determined.NokiaNational Science Foundatio
Performance - Complexity Comparison of Receivers for a LTE MIMO–OFDM System
Implementation of receivers for spatial multiplexing multiple-input multiple-output (MIMO) orthogonal-frequency-division-multiplexing (OFDM) systems is considered. The linear minimum mean-square error (LMMSE) and the K-best list
sphere detector (LSD) are compared to the iterative successive interference cancellation (SIC) detector and the iterative K-best LSD. The performance of the algorithms is evaluated in 3G long-term evolution (LTE) system. The SIC algorithm is found to perform worse than the K-best LSD when the MIMO channels
are highly correlated, while the performance difference diminishes when the correlation decreases. The receivers are designed for 2X2 and 4X4 antenna systems and three different modulation schemes. Complexity results for FPGA and ASIC implementations are found. A modification to the K-best LSD which increases
its detection rate is introduced. The ASIC receivers are designed to meet the decoding throughput requirements in LTE and the K-best LSD is found to be the most complex receiver although it gives the best reliable data transmission throughput. The SIC receiver has the best performance–complexity tradeoff in the 2X2 system but in the 4X4 case, the K-best LSD is the most efficient. A receiver architecture which could be reconfigured to using a simple or a more complex detector as the channel conditions change would achieve the best performance while consuming the least amount of power in the receiver
Transmission Experiment of Bandwidth Compressed Carrier Aggregation in a Realistic Fading Channel
In this paper, an experimental testbed is designed to evaluate the performance of a bandwidth compressed multicarrier technique termed spectrally efficient frequency division multiplexing (SEFDM) in a carrier aggregation (CA) scenario1. Unlike orthogonal frequency division multiplexing (OFDM), SEFDM is a non-orthogonal waveform which, relative to OFDM, packs more sub-carriers in a given bandwidth, thereby improving spectral efficiency. CA is a long term evolution-advanced (LTE-Advanced) featured technique that offers a higher throughput by aggregating multiple legacy radio bands. Considering the scarcity of radio spectrum, SEFDM signals can be utilized to enhance CA performance. The combination of the two techniques results in a larger number of aggregated component carriers (CCs) and therefore increased data rate in a given bandwidth with no additional spectral allocation. It is experimentally shown that CA-SEFDM can aggregate up to 7 CCs in a limited bandwidth while CA-OFDM can only put 5 CCs in the same bandwidth. In this work, LTE-like framed CA-SEFDM signals are generated and delivered through a realistic LTE channel. A complete experimental setup is described together with error performance and effective spectral efficiency comparisons. Experimental results show that the measured BER performance for CA-SEFDM is very close to CA-OFDM and the effective spectral efficiency of CA-SEFDM can be substantially higher than that of CA-OFDM
A High Throughput Configurable SDR Detector for Multi-user MIMO Wireless Systems
Spatial division multiplexing (SDM) in
MIMO technology significantly increases the spectral
efficiency, and hence capacity, of a wireless communication
system: it is a core component of the next generation
wireless systems, e.g. WiMAX, 3GPP LTE and
other OFDM-based communication schemes. Moreover,
spatial division multiple access (SDMA) is one
of the widely used techniques for sharing the wireless
medium between different mobile devices. Sphere detection
is a prominent method of simplifying the detection
complexity in both SDM and SDMA systems
while maintaining BER performance comparable with
the optimum maximum-likelihood (ML) detection. On
the other hand, with different standards supporting
different system parameters, it is crucial for both base
station and handset devices to be configurable and
seamlessly switch between different modes without the
need for separate dedicated hardware units. This challenge
emphasizes the need for SDR designs that target
the handset devices. In this paper, we propose the
architecture and FPGA realization of a configurable
sort-free sphere detector, Flex-Sphere, that supports
4, 16, 64-QAM modulations as well as a combination of 2, 3 and 4 antenna/user configuration for handsets.
The detector provides a data rate of up to 857.1 Mbps
that fits well within the requirements of any of the next
generation wireless standards. The algorithmic optimizations
employed to produce an FPGA friendly realization
are discussed.Xilinx Inc.National Science Foundatio
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