R-3 Repository :: Browsing by Author "Dick, Chris"

Browsing by Author "Dick, Chris"

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Design and Architecture of Spatial Multiplexing MIMO Decoders for FPGAs
(IEEE, 2008-10-01) Dick, Chris; Amiri, Kiarash; Cavallaro, Joseph R.; Rao, Raghu; Center for Multimedia Communication
Spatial multiplexing multiple-input-multiple-output (MIMO) communication systems have recently drawn significant attention as a means to achieve tremendous gains in wireless system capacity and link reliability. The optimal hard decision detection for MIMO wireless systems is the maximum likelihood (ML) detector. ML detection is attractive due to its superior performance (in terms of BER). However, direct implementation grows exponentially with the number of antennas and the modulation scheme, making its ASIC or FPGA implementation infeasible for all but low-density modulation schemes using a small number of antennas. Sphere decoding (SD) solves the ML detection problem in a computationally efficient manner. However, even with this complexity reduction, real-time implementation on a DSP processor is generally not feasible and high-performance parallel computing platforms such as FPGAs are increasingly being employed for this class of applications. The sphere detection problem affords many opportunities for algorithm and micro-architecture optimizations and tradeoffs. This paper provides an overview of techniques to simplify and minimize FPGA resource utilization of sphere detectors for high performance low-latency systems.
Flex-Sphere: An FPGA Configurable Sort-Free Sphere Detector For Multi-user MIMO Wireless Systems
(SDR Forum, 2008-10-01) Amiri, Kiarash; Dick, Chris; Rao, Raghu; Cavallaro, Joseph R.; Center for Multimedia Communication
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. There are several approaches for realizing sphere detectors, and the algorithmic landscape is rich with methods that enable the designer to make various tradeoffs between performance, e.g. throughput of the wireless channel, BER, and implementation complexity, e.g. silicon area for an ASIC implementation or FPGA resource envelope for an FPGA implementation. This paper describes the FPGA realization of a configurable and flexible 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 uplink transmission. The detector provides a data rate of up to 849:9 Mbps. The algorithmic optimizations employed to produce an FPGA friendly realization are discussed.
An FPGA Implementation Of Alamouti's Transmit Diversity Technique
(2003-10-01) Murphy, Patrick; Frantz, Patrick; Dick, Chris; Center for Multimedia Communications (http://cmc.rice.edu/)
This paper presents the FPGA implementation of a multiple antenna wireless communications system based on Alamouti's transmit diversity scheme. Alamouti's transmit diversty scheme is a space-time block code with support for two transmit antennas and an arbitrary number of receive antennas. Our implementaiton demonstrates this space-time code in a system with two transmit and just one antenna at the receiver. In addition to implementing the encoding and decoding algorithms described in Alamouti's paper, we have designed and implemented additional subsystems necessary to establish an end-to- end link over real wireless channels. These systems, described in detail below, address the challenges of timing synchronization, carrier offset recovery and channel estimation. When combined with an implementaiton of Alamouti's code, these designs form a complete multiple antenna wireless communications sytem.
FPGA Implementation of Matrix Inversion Using QRD-RLS Algorithm
(2005-11-01) Karkooti, Marjan; Cavallaro, Joseph R.; Dick, Chris; Center for Multimedia Communications (http://cmc.rice.edu/)
This paper presents a novel architecture for matrix inversion by generalizing the QR decomposition-based recursive least square (RLS) algorithm. The use of Squared Givens rotations and a folded systolic array makes this architecture very suitable for FPGA implementation. Input is a 4 by 4 matrix of complex, floating point values. The matrix inversion design can achieve throughput of 0.13 M updates per second on a state of the art Xilinx Virtex4 FPGA running at 115 MHz. Due to the modular partitioning and interfacing between multiple Boundary and Internal processing units, this architecture is easily extendable for other matrix sizes.
FPGA Implementation of Matrix Inversion Using QRD-RLS Algorithm
(2005-10-01) Karkooti, Marjan; Cavallaro, Joseph R.; Dick, Chris; Center for Multimedia Communications (http://cmc.rice.edu/)
This paper presents a novel architecture for matrix inversion by generalizing the QR decomposition-based recursive least square (RLS) algorithm. The use of Squared Givens rotations and a folded systolic array makes this architecture very suitable for FPGA implementation. Input is a 4 Ã 4 matrix of complex, floating point values. The matrix inversion design can achieve throughput of 0.13M updates per second on a state of the art Xilinx Virtex4 FPGA running at 115 MHz. Due to the modular partitioning and interfacing between multiple Boundary and Internal processing units, this architecture is easily extendable for other matrix sizes.
FPGA in Wireless Communications Applications
(Elsevier, Waltham, MA, 2012-07-12) Amiri, Kiarash; Duarte, Melissa; Cavallaro, Joseph R.; Dick, Chris; Rao, Raghu; Sabharwal, Ashutosh; Center for Multimedia Communication
In the past decade we have witnessed explosive growth in the wireless communications industry with over 4 billion subscribers worldwide. While first and second generation systems focused on voice communications, third generation networks (3GPP and 3GPP2) embraced code division multiple access (CDMA) and had a strong focus on enabling wireless data services. As we reflect on the rollout of 3G services, the reality is that first generation 3G systems did not entirely fulfill the promise of high-speed transmission, and the rates supported in practice were much lower than those claimed in the standards. Enhanced 3G systems were subsequently deployed to address the deficiencies. However, the data rate capabilities and network architecture of these systems were insufficient to address the insatiable consumer and business sector demand for the nomadic delivery of media and datacentric services to an increasingly rich set of mobile platforms.
A High Throughput Configurable SDR Detector for Multi-user MIMO Wireless Systems
(Springer, 2011-02-01) Amiri, Kiarash; Cavallaro, Joseph R.; Dick, Chris; Rao, Raghu Mysore; Center for Multimedia Communication
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.
A High Throughput Configurable SDR Detector for Multi-user MIMO Wireless Systems
(Springer, 2009-04-08) Amiri, Kiarash; Cavallaro, Joseph R.; Dick, Chris; Rao, Raghu Mysore; CMC
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.
High-Throughput Data Detection for Massive MU-MIMO-OFDM Using Coordinate Descent
(IEEE, 2016) Wu, Michael; Dick, Chris; Cavallaro, Joseph R.; Studer, Christoph
Data detection in massive multi-user (MU) multiple-input multiple-output (MIMO) wireless systems is among the most critical tasks due to the excessively high implementation complexity. In this paper, we propose a novel, equalization-based soft-output data-detection algorithm and corresponding reference FPGA designs for wideband massive MU-MIMO systems that use orthogonal frequency-division multiplexing (OFDM). Our data-detection algorithm performs approximate minimum mean-square error (MMSE) or box-constrained equalization using coordinate descent. We deploy a variety of algorithm-level optimizations that enable near-optimal error-rate performance at low implementation complexity, even for systems with hundreds of base-station (BS) antennas and thousands of subcarriers. We design a parallel VLSI architecture that uses pipeline interleaving and can be parametrized at design time to support various antenna configurations. We develop reference FPGA designs for massive MU-MIMO-OFDM systems and provide an extensive comparison to existing designs in terms of implementation complexity, throughput, and error-rate performance. For a 128 BS antenna, 8-user massive MU-MIMO-OFDM system, our FPGA design outperforms the next-best implementation by more than 2.6× in terms of throughput per FPGA look-up tables.
Implementation Trade-Offs For Linear Detection In Large-Scale MIMO Systems
(IEEE, 2013-06) Yin, Bei; Wu, Michael; Studer, Christoph; Cavallaro, Joseph R.; Dick, Chris
In this paper, we analyze the VLSI implementation tradeoffs for linear data detection in the uplink of large-scale multiple-input multiple-output (MIMO) wireless systems. Specifically, we analyze the error incurred by using the suboptimal, low-complexity matrix inverse proposed in Wu et al., 2013, ISCAS, and compare its performance and complexity to an exact matrix inversion algorithm. We propose a Cholesky-based reference architecture for exact matrix inversion and show corresponding implementation results on an Virtex-7 FPGA. Using this reference design, we perform a performance/complexity trade-off comparison with an FPGA implementation for the proposed approximate matrix inversion, which reveals that the inversion circuit of choice is determined by the antenna configuration (base-station antennas vs. number of users) of large-scale MIMO systems.
Implicit vs. Explicit Approximate Matrix Inversion for Wideband Massive MU-MIMO Data Detection
(Springer, 2017) Wu, Michael; Yin, Bei; Li, Kaipeng; Dick, Chris; Cavallaro, Joseph R.; Studer, Christoph
Massive multi-user (MU) MIMO wireless technology promises improved spectral efficiency compared to that of traditional cellular systems. While data-detection algorithms that rely on linear equalization achieve near-optimal error-rate performance for massive MU-MIMO systems, they require the solution to large linear systems at high throughput and low latency, which results in excessively high receiver complexity. In this paper, we investigate a variety of exact and approximate equalization schemes that solve the system of linear equations either explicitly (requiring the computation of a matrix inverse) or implicitly (by directly computing the solution vector). We analyze the associated performance/complexity trade-offs, and we show that for small base-station (BS)-to-user-antenna ratios, exact and implicit data detection using the Cholesky decomposition achieves near-optimal performance at low complexity. In contrast, implicit data detection using approximate equalization methods results in the best trade-off for large BS-to-user-antenna ratios. By combining the advantages of exact, approximate, implicit, and explicit matrix inversion, we develop a new frequency-adaptive e qualizer (FADE), which outperforms existing data-detection methods in terms of performance and complexity for wideband massive MU-MIMO systems.
Improving MIMO Sphere Detection Through Antenna Detection Order Scheduling
(Wireless Innovation Forum, 2011-12-01) Wu, Michael; Dick, Chris; Cavallaro, Joseph R.; Center for Multimedia Communication
This paper proposes a novel scalable Multiple-Input Multiple-Output (MIMO) detector that does not require preprocessing to achieve good bit error rate (BER) performance. MIMO processing is a key technology in broadband wireless technologies such as 3G LTE, WiMAX, and 802.11n. Existing detectors such as Flexsphere use preprocessing before MIMO detection to improve performance. Instead of costly preprocessing, the proposed detector schedules multiple search passes, where each search pass detects the transmit stream with a different permuted detection order. By changing the number of parallel search passes, we show that this scalable detector can achieve comparable performance to Flexsphere with reduced resource requirement, or can eliminate LLR clipping and achieve BER performance within 0.25 dB of exhaustive search with increased resource requirement.
Low complexity scalable MIMO sphere detection through antenna detection reordering
(Springer, 2012-07-01) Wu, Michael; Dick, Chris; Sun, Yang; Cavallaro, Joseph R.; Center for Multimedia Communication
This paper describes a novel low complexity scalable multiple-input multiple-output (MIMO) detector that does not require preprocessing and the optimal squared l2-norm computations to achieve good bit error (BER) performance. Unlike existing detectors such as Flexsphere that use preprocessing before MIMO detection to improve performance, the proposed detector instead performs multiple search passes, where each search pass detects the transmit stream with a different permuted detection order. In addition, to reduce the number of multipliers required in the design, we use l1-norm in place of the optimal squared l2-norm. To ameliorate the BER performance loss due to l1- norm, we propose squaring then scaling the l1-norm. By changing the number of parallel search passes and using norm scaling, we show that this design achieves comparable performance to Flexsphere with reduced resource requirement or achieves BER performance close to exhaustive search with increased resource requirement.
Novel Sort-Free Detector with Modified Real-Valued Decomposition (M-RVD) Ordering in MIMO Systems
(IEEE, 2008-11-01) Amiri, Kiarash; Dick, Chris; Rao, Raghu; Cavallaro, Joseph R.; Center for Multimedia Communication
K-best MIMO detection technique is the prominent method of simplifying the detection complexity in MIMO systems while maintaining BER performance comparable with the optimum maximum-likelihood (ML) detection technique. However, sorting the candidate nodes in the tree search of the conventional K-best detection can take a significant number of cycles which would reduce the achievable data rate of the detector. In order to reduce this delay, and keep high performance at the same time, we propose using a novel sort-free based MIMO detector which avoids the demanding sorting step. Moreover, this detector utilizes a novel modified real-valued decomposition (M-RVD) ordering that, when compared to the conventional real valued decomposition scheme, can improve the BER performance at no extra computational cost. We show that our proposed detector can outperform the conventional K-best detector with a smaller combination of computation and latency requirements.
Reduced Complexity Soft MMSE MIMO Detector Architecture
(Wireless Innovation Forum, Inc., 2010-12-01) Amiri, Kiarash; Dick, Chris; Rao, Raghu; Cavallaro, Joseph R.; Center for Multimedia Communication
Computing the soft LLR values in MMSE receivers of MIMO systems requires a very large complexity. In this paper, we propose a reduced complexity soft MMSE detector for MIMO systems. We use different complexity reductions techniques and propose an architecture based on the new reduced-complexity method. We also compare the complexity and show more than 2x complexity reduction using this method. We present complexity/performance tradeoffs to demonstrate the efficacy of our techniques. More importantly, these techniques give the receivers the flexibility to choose how accurately they perform the detection based on the available resources.

Browsing by Author "Dick, Chris"

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