Christian Drewes

Bio: Christian Drewes is an academic researcher from Intel. The author has contributed to research in topics: MIMO & Orthogonal frequency-division multiplexing. The author has an hindex of 14, co-authored 99 publications receiving 898 citations. Previous affiliations of Christian Drewes include Apple Inc. & Intel Mobile Communications.

A Closed Concept for Synchronization and Cell Search in 3GPP LTE Systems

Abstract: In this paper we investigate the time and frequency synchronization as well as the sector and cell search for the 3GPP Long Term Evolution (LTE) downlink. The proposed algorithms rely on the synchronization and cell-specific reference signals and are hence compliant to most recent 3GPP specifications. Time and (fractional) frequency offset coarse synchronization are performed in the time domain with the cyclic prefix based autocorrelation, while the sector and cell as well as the integer frequency offset are estimated in the frequency domain by using the primary and secondary synchronization signals. To improve the cell detection reliability, the estimated cell is afterwards confirmed through the cell-specific reference signal. All algorithms are evaluated under multipath channel conditions and an initial carrier frequency mismatch. Compromising high performance with reasonable implementation complexity, we draw a practical solution for an LTE receiver.

Methods and devices for radio communications

Abstract: A circuit arrangement includes a preprocessing circuit configured to obtain context information related to a user location, a learning circuit configured to determine a predicted user movement based on context information related to a user location to obtain a predicted route and to determine predicted radio conditions along the predicted route, and a decision circuit configured to, based on the predicted radio conditions, identify one or more first areas expected to have a first type of radio conditions and one or more second areas expected to have a second type of radio conditions different from the first type of radio conditions and to control radio activity while traveling on the predicted route according to the one or more first areas and the one or more second areas.

On 3G LTE Terminal Implementation - Standard, Algorithms, Complexities and Challenges

Abstract: Currently, 3GPP standardizes an evolved UTRAN (E-UTRAN) within the Release 8 Long Term Evolution (LTE) project. Targets include higher spectral efficiency, lower latency, higher peak data rate when compared to previous 3GPP air interfaces. The air interface of E-UTRAN is based on OFDMA and MIMO in downlink and on SCFDMA in uplink Main challenges for a terminal implementation include efficient realization of the inner receiver, especially for channel estimation and equalisation, and the outer receiver including a turbo decoder which needs to handle data rates of up to 75 Mbps per spatial MIMO stream. We show that the inner receiver can nicely and straightforwardly be parallelized due to frequency domain processing. In addition to the computational complexity of even a simple linear equaliser, one of the challenges is an efficient implementation considering necessary flexibility for different MIMO modes, power consumption and silicon area. This paper will briefly overview the current LTE standard, highlight a functional data flow through the single entities of an LTE terminal and elaborate more on possible first implementation details, including sample algorithms and first complexity estimates.

System and method for optimizing network wireless communication resources

Abstract: Embodiments are described that provide methods and radio networks that communicate data between a mobile communication device and a core network. The methods include using network coding to encode data, and communicating a subset of the encoded data between the mobile communication device and the core network through a dynamic relay station.

Closed loop transmission with precoding selection in LTE/LTE-Advanced system

Abstract: Closed-loop transmission combined with MIMO (multiple-input multiple-output) and OFDM (orthogonal frequency division multiplexing) technologies have drawn most attentions during development of the 4G systems (fourth generation of mobile communication systems). In LTE (Long Term Evolution) and LTE-Advanced systems, which are proposed by 3GPP (Third Generation Partnership Project) to be the most competitive candidate for the 4G systems, the codebook based precoding scheme is deployed for realizing the closed-loop transmission concept. This scheme introduces the precoding matrix selection at the receiver and precoding operation at the transmitter and achieves a good tradeoff between the system complexity and the performance gain given by the closed-loop transmission. In this manuscript, the authors give a brief overview of the LTE/LTE-Advanced system downlink transmission. Furthermore, different precoding matrix selection criteria are discussed at the aim of optimal receiver design. Following the analytical and numerical results, the authors conclude that the minimum post mean squared error based criterion is the optimal candidate for precoding matrix selection at the receiver in LTE compliant systems.

Fading channels: information-theoretic and communications aspects

Abstract: In this paper we review the most peculiar and interesting information-theoretic and communications features of fading channels. We first describe the statistical models of fading channels which are frequently used in the analysis and design of communication systems. Next, we focus on the information theory of fading channels, by emphasizing capacity as the most important performance measure. Both single-user and multiuser transmission are examined. Further, we describe how the structure of fading channels impacts code design, and finally overview equalization of fading multipath channels.

Autonomous inspection and maintenance

Abstract: The different advantageous embodiments may provide an apparatus that may comprise a number of mobile robotic machines, a wireless communications system and a computer system. The number of mobile robotic machines may be capable of moving to a number of locations in a maintenance area and may be capable of performing a number of maintenance operations on a structure in the maintenance area. The wireless communications system may be capable of providing communication with the number of mobile robotic machines within the maintenance area. The computer system may be capable of exchanging information with the number of mobile robotic machines using the wireless communications system.

Methods and apparatus to perform measurements

Abstract: Methods and apparatus to perform measurements are disclosed. An example method disclosed herein for a user equipment (UE) to perform measurements comprises receiving configuration information from a network, the configuration information to configure the UE to perform logging of measurements in an idle mode, logging measurements in the idle mode, and sending an indication that logged measurements are available.

Compensation of IQ imbalance and phase noise in OFDM systems

Abstract: Nowadays, a lot of effort is spent on developing inexpensive orthogonal frequency-division multiplexing (OFDM) receivers. Especially, zero intermediate frequency (zero-IF) receivers are very appealing, because they avoid costly IF filters. However, zero-IF front-ends also introduce significant additional front-end distortion, such as IQ imbalance. Moreover, zero-IF does not solve the phase noise problem. Unfortunately, OFDM is very sensitive to the receiver nonidealities IQ imbalance and phase noise. Therefore, we developed a new estimation/compensation scheme to jointly combat the IQ imbalance and phase noise at baseband. In this letter, we describe the algorithms and present the performance results. Our compensation scheme eliminates the IQ imbalance based on one OFDM symbol and performs well in the presence of phase noise. The compensation scheme has a fast convergence and a small residual degradation: even for large IQ imbalance, the overall system performance for an OFDM-wireless local area network (WLAN) case study is within 0.6 dB of the optimal case. As such, our approach greatly relaxes the mismatch specifications and thus enables low-cost zero-IF receivers.

FPGA-based Implementation of Signal Processing Systems

Abstract: Field programmable gate arrays (FPGAs) are an increasingly popular technology for implementing digital signal processing (DSP) systems. By allowing designers to create circuit architectures developed for the specific applications, high levels of performance can be achieved for many DSP applications providing considerable improvements over conventional microprocessor and dedicated DSP processor solutions. The book addresses the key issue in this process specifically, the methods and tools needed for the design, optimization and implementation of DSP systems in programmable FPGA hardware. It presents a review of the leading-edge techniques in this field, analyzing advanced DSP-based design flows for both signal flow graph- (SFG-) based and dataflow-based implementation, system on chip (SoC) aspects, and future trends and challenges for FPGAs. The automation of the techniques for component architectural synthesis, computational models, and the reduction of energy consumption to help improve FPGA performance, are given in detail. Written from a system level design perspective and with a DSP focus, the authors present many practical application examples of complex DSP implementation, involving: high-performance computing e.g. matrix operations such as matrix multiplication; high-speed filtering including finite impulse response (FIR) filters and wave digital filters (WDFs); adaptive filtering e.g. recursive least squares (RLS) filtering; transforms such as the fast Fourier transform (FFT). FPGA-based Implementation of Signal Processing Systems is an important reference for practising engineers and researchers working on the design and development of DSP systems for radio, telecommunication, information, audio-visual and security applications. Senior level electrical and computer engineering graduates taking courses in signal processing or digital signal processing shall also find this volume of interest.