Juergen Becker

Error Vector Magnitude as a Performance Measure for Advanced Modulation Formats

We examine the relation between optical signal-to-noise ratio (OSNR), error vector magnitude (EVM), and bit-error ratio (BER). Theoretical results and numerical simulations are compared to measured values of OSNR, EVM, and BER. We conclude that the EVM is an appropriate metric for optical channels limited by additive white Gaussian noise. Results are supported by experiments with six modulation formats at symbol rates of 20 and 25 GBd generated by a software-defined transmitter.

Real-time LUT-based network topologies for dynamic and partial FPGA self-reconfiguration

Xilinx Virtex FPGAs offer the possibility of dynamic and partial run-time reconfiguration. If a system uses this feature the designer has to take care, that no signal lines cross the border to other reconfigurable regions. Traditional solutions connecting modules on a dynamic and partial reconfigurable system use TBUF elements for connection and separation of the functional blocks. While automatically placing and routing the design, the routing-tool sometimes uses signal lines which cross the module border. The constraints given by the designer are ignored. To solve this problem, we use slices instead of TBUF elements which leads to a benefit by using an automatic modular design flow. This paper gives an overview of the used techniques and the complete system on a Xilinx XC2V3000 FPGA.

Single-laser 32.5 Tbit/s Nyquist WDM transmission

Single-laser 32.5 Tbit/s 16QAM Nyquist-WDM transmission with 325 carriers over 227 km at a net spectral efficiency of 6.4 bit/s/Hz is reported.

Power estimation and power measurement of Xilinx Virtex FPGAs: trade-offs and limitations

The power consumption of reconfigurable systems has become a fundamental aspect in designing applications. Especially for mobile systems with a limited power supply, it is necessary to identify and optimize the power loss. Moreover, it is essential to evaluate during application development time exact power trade-offs, especially including the consideration of the dynamic reconfiguration phases of corresponding devices, e.g. the Virtex-series from Xilinx. This paper discusses the exact power consumption trade-offs between the measured runtime consumption of a mapped application and the measured reconfiguration-time consumption of different dynamically (partially and completely) reconfigured applications. Moreover, the possibilities and limitations of todays available power estimation tools are discussed and compared to the exact measurements.

KAHRISMA: a novel hypermorphic reconfigurable-instruction-set multi-grained-array architecture

Facing the requirements of next generation applications, current approaches of embedded systems design will soon hit the limit where they may no longer perform efficiently. The unpredictable nature and diverse processing behavior of future applications requires to transgress the barrier of tailor-made, application-/domain-specific embedded system designs. As a consequence, next generation architectures for embedded systems have to react much more flexible to unforeseeable run-time scenarios. In this paper we present our innovative processor architecture concept KAHRISMA (KArlsruhes Hypermorphic Reconfigurable-Instruction-Set Multi-grained-Array). It tightly integrates coarse- and fine-grained run-time reconfigurable fabrics that can incorporate to realize hardware acceleration for computationally complex algorithms. Furthermore, the fabrics can be combined to realize different Instruction Set Architectures that may execute in parallel. With the help of an encrypted H.264 en-/decoding case study we demonstrate that our novel KAHRISMA architecture will deliver the required flexibility to design future-proof embedded systems that are not limited to a certain computational domain.

Quality metrics for optical signals: Eye diagram, Q-factor, OSNR, EVM and BER

Measuring the quality of optical signals is one of the most important tasks in optical communications. A variety of metrics are available, namely the general shape of the eye diagram, the optical signal-to-noise power ratio (OSNR), the Q-factor as a measure of the eye opening, the error vector magnitude (EVM) that is especially suited for quadrature amplitude modulation (QAM) formats, and the bit error ratio (BER). While the BER is the most conclusive quality determinant, it is sometimes difficult to quantify, especially for simulations and off-line processing. We compare various metrics analytically, by simulation, and through experiments. We further discuss BER estimates derived from OSNR, Q-factor and EVM data and compare them to measurements employing six modulation formats at symbol rates of 20 GBd and 25 GBd, which were generated by a software-defined transmitter. We conclude that for optical channels with additive Gaussian noise the EVM metric is a reliable quality measure. For nondata-aided reception, BER below 0.01 can be estimated from measured EVM.

101.5 Gbit/s real-time OFDM transmitter with 16QAM modulated subcarriers

We demonstrate for the first time a 101.5 Gbit/s single-polarization OFDM transmitter based on real-time FPGA processing. We modulate 58 subcarriers with 16QAM.

Towards future adaptive multiprocessor systems-on-chip: An innovative approach for flexible architectures

This paper introduces adaptive techniques targeted for heterogeneous manycore architectures and introduces the FlexTiles platform, which consists of general purpose processors with some dedicated accelerators. The different components are based on low power DSP cores and an eFPGA on which dedicated IPs can be dynamically configured at run-time. These features enable a breakthrough in term of computing performance while improving the on-line adaptive capabilities brought from smart heuristics. Thus, we propose a virtualisation layer which provides a higher abstraction level to mask the underlying heterogeneity present in such architectures. Given the large variety of possible use cases that these platforms must support and the resulting workload variability, offline approaches are no longer sufficient because they do not allow coping with time changing workloads. The upcoming generation of applications include smart cameras, drones, and cognitive radio. In order to facilitate the architecture adaptation under different scenarios, we propose a programming model that considers both static and dynamic behaviors. This is associated with self adaptive strategies endowed by an operating system kernel that provides a set of functions that guarantee quality of service (QoS) by implementing runtime adaptive policies. Dynamic adaptation will be mainly used to reduce both overall power consumption and temperature and to ease the problem of decreasing yield and reliability that results from submicron CMOS scales.

Fine grain fault tolerance — A key to high reliability for FPGAs in space

Nowadays using SRAM-based FPGAs in space missions due to their flexibility and reprogrammability is on focus. In contrary, they are effective against radiation effects and need new trends in reliability issues. This paper concerns fine grain views to mitigation problem in FPGAs. For new FPGA generations simply replicating complete systems in Triple Modular Redundancy (TMR) technique may not be sufficient anymore. This especially applies to the environments like space, as higher failure rates may disrupt a second instance before the first one recovers. We focus on SEU mitigation challenges in SRAM-based FPGAs, which can result in crucial situations. The approach is a fine grain fault tolerance with using fine grain TMR also Quadruple Force Decide Redundancy (QFDR). We transform the classical concept of TMR and Quadded Redundancy on Logic Gates to a technological approach based on FPGA structure primitives like LUTs. We integrate common CAD tools to apply the techniques for different, complex designs simply. We simulate the faulty circuit and count the number of LUTs, which can be corrupted while the system still functions. Result shows the reliability increase of about 50 percent for QFDR.

Corrections to “Error Vector Magnitude as a Performance Measure for Advanced Modulation Formats” [Jan 1, 2012 61-63]

In the above titled paper (ibid., vol. 24, no. 1, pp. 61-63, Jan. 1, 2012), equation (4) contains an error. The corrected equation is presented here. Additionally, the paper should include an Appendix, which is presented here.