Christoph Spiegel

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

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.

On the physical layer performance with rank indicator selection in LTE/LTE-Advanced system

The 3GPP (Third Generation Partnership Project) LTE (Long Term Evolution) and LTE-Advanced activities work toward the evolved UMTS (Universal Mobile Telecommunications System) Terrestrial Radio Access (E-UTRA), and the solution of IMT-Advanced (International Mobile Telecommunications) and systems beyond. The combination of OFDM (orthogonal frequency division multiplexing) and MIMO (multiple-input multiple-output) has been introduced into LTE and LTE-Advanced systems for achieving high system capacity. Furthermore, the closed-loop concept with codebook based precoding MIMO and transmission layers selection, termed as RI (rank indicator) selection have also been included to provide robust transmission in mobile wireless communication scenarios and increase the cell coverage. This manuscript focuses on the RI selection study and implementation in LTE and LTE-Advanced systems and illustrates the downlink performance evaluation and comparison with different RI selection schemes. According to the analytical and numerical results from an LTE and LTE-Advanced compliant simulator, the mutual information based scheme is chosen as the best candidate for RI selection.

On MIMO with successive interference cancellation applied to UTRA LTE

The long term evolution of UMTS (Universal Mobile Telecommunications System) Terrestrial Radio Access, abbreviated as UTRA LTE, makes use of OFDM (orthogonal frequency division multiplexing) combined with MIMO (multiple-input multiple-output), termed MIMO-OFDM. The potential maximization of transmitted data rates has been considered a most beneficial feature of MIMO schemes. This maximization shall be strived for by spatial multiplexing. In particular, high data rates in the downlink have been considered desirable. Also, in view of an efficient implementation, the downlink requires a thorough assessment. Therefore, the authors will discuss the deployment of spatial multiplexing in the UTRA LTE downlink and will show that the performance of successive interference cancellation (SIC) based data detection techniques for MIMO-OFDM is beneficial.

MIMO Schemes in UTRA LTE, A Comparison

The long term evolution of UMTS (Universal Mobile Telecommunications System) Terrestrial Radio Access, abbreviated as UTRA LTE, will be based on OFDM (orthogonal frequency division multiplexing). Furthermore, MIMO (multiple-input multiple-output) techniques have been considered as a means for the improvement of wireless connectivity. In wireless systems, high data rates in the downlink are desirable: Furthermore, with respect to an efficient implementation, the downlink requires a thorough assessment. In particular, the Alamouti and the V-BLAST (Vertical Bell Labs Layered Space Time) schemes are seen as interesting concepts. In this communication, the authors will compare these two MIMO schemes w.r.t. the achievable performance in the UTRA LTE downlink using up to two transmit and two receive antennas. Furthermore, the authors will discuss the deployment of spatial multiplexing in the UTRA LTE downlink and will show that the performance of successive interference cancellation (SIC) based data detection techniques for MIMO-OFDM is beneficial.

A DVB-T2 receiver realization based on a software-defined radio concept

When DVB-T (Digital Video Broadcasting - Terrestrial) was introduced in the 1990s, it was impossible to foresee the upcoming demand for HDTV devices. Thus, a revision of this broadcasting standard, namely DVB-T2, was necessary. Recently finalized, this standard is targeting to high-definition television (HDTV). To pave the way to commercialization, an appropriate implementation concept and its corresponding validation are of utmost importance. Without a doubt, the most challenging requirements introduced by the DVB-T2 specification are an FFT (Fast Fourier Transform) size of up to 32k samples, 256-QAM (Quadrature Amplitude Modulation) and LDPC (Low-Density Parity-Check) coding with a block size of 64800 bits. Within this manuscript, the authors present a software-defined radio based realization of a demonstrator platform. This platform employs a combined DSP (Digital Signal Processor) and FPGA (Field-Programmable Gate Array) solution being capable of meeting these requirements.

Dynamic transmission mode selection in LTE/LTE-Advanced system

Recently, the LTE (Long Term Evolution) and LTE-Advanced systems, developed by the 3GPP (Third Generation Partnership Project), has been proposed as the candidate for the 4G systems (forth mobile communication systems). The combination of OFDM (orthogonal frequency division multiplexing) and MIMO (multiple-input multiple-output) transmission technologies has been introduced into LTE systems for achieving high system performance required by 4G systems. Furthermore, the closed-loop concept with codebook based precoding MIMO and dynamic transmission mode selection, termed as RI (rank indicator) selection, have also been deployed in LTE systems to provide robust link connection and large cell coverage. In this manuscript, the authors focused on the study of dynamic transmission mode selection and its implementation in LTE systems. Different RI selection schemes were proposed in this manuscript with the corresponding downlink performance evaluation. According to the analytical and numerical results, the authors conclude that the mutual information based scheme is the best candidate for RI selection in LTE/LTE-Advanced compliant systems.

Applying Zero-Crossing Demodulation to the Bluetooth Enhanced Data Rate Mode

Short range communication systems such as Bluetooth and DECT (digital enhanced cordless telecommunications) require low-cost transceiver structures. Hence, the development of appropriate receiver techniques has been a major research topic. Particularly, analog limiter-discriminator with integrate and dump filtering (LDI) techniques have received considerable attention. With the availability of digital signal processing (DSP), the digital implementation of LDI techniques has become increasingly attractive. In order to make LDI receivers more accessible, zero-crossing detection was proposed. In this communication, the authors shall focus on a novel, yet promising, approach to digital zero-crossing detection in the intermediate frequency domain. Zero-crossing demodulation is an irregular sampling technique, which replaces the commonly employed regular, i.e. temporally equidistant sampling technique in the mentioned low-cost receivers. In this manuscript, the authors will present the theoretical aspects of zero-crossing demodulation with special focus on Bluetooth enhanced data rate (EDR). Next, the obtained performance results in terms of the bit error ratio (BER). Comparisons with theoretical bounds show the advantageous performance. Furthermore, a demonstrator concept termed HAWK shall be discussed and first measurement results will be presented

Platform Based Design of Termninals and Infrastructure Components for Cognitive Wireless Networks

Cooperation in wireless networks will facilitate a new dimension in the evolution of multimedia communications, sCtting out from the todays situation with a multitude of communication standards and radio interfaces both in the licensed and thC unlicensed domain. In order to pave the way towards cooperative networks, the deployment of cognitive wireless solutions, which will form the communication platforms, will be a key asset. In the future, we expect to see an increasingly flexible, ad-hoc utilization of the available spectrum in the unlicensed domain and a co-existence of communication standards in the licensed bands. In this communication, the authors will illustrate a platform based approach towards cognitive wireless communications. Also, the authors will present three software defined radio concepts designed by the members of the Lehrstuhl für KommunikationsTechnik, namely the HAWK (Highly Adaptable Wireless Kit), the FALCON (Flxible Access Logic for COmmunication Networks), and the MUSTANG (MUlti-STAndard single chip transceiver for the Next Generation), finally, giving an outlook on their wireless optical communication device, termed ARGOS. HAWK, FALCON, MUSTANG and ARGOS form the basis of the cognitive wireless platform, developed by the authors, termed PROMETHEUS. The setup of PROMETHEUS and its functionality shall be illustrated together with selected measurement results.

Petri Net Based Controller Concept For Cognitive Radios in Wireless Access Networks

This paper will give a detailed discussion about the authors view on Software Defined and Cognitive Radio. After an introduction on different aspects of software radio and a novel approach on cognitive radio is presented. As proof of concept a software defined cognitive radio demonstrator termed Falcon was built up which is described afterwards. The Falcon is entirely based on a modular signal processing concept. In particular, the receiver deploys modules which process and generate log-likelihood ratio (LLR) signals, hence, providing the capability of a plug-and-play-type reconfigurability. To the best knowledge of the authors, such a reconfigurability approach has not yet been pursued as consequently before.

Cognitive Radio Prototyping

Future wireless systems have been evolving toward a broadband and open architecture for efficient multi-service operation, which will have a great impact on the terminal and infrastructure component design methodology for supporting multiple radio schemes. Cooperation in wireless networks, requiring cognitive radio implementations, will facilitate a new dimension in the evolution of multimedia communications. The growing price pressure requires ever increasing high levels of integration efficiency, of flexibility and of future proofness at the same time, setting out in the digital baseband domain. In this communication, the authors will illustrate a platform based prototyping process, setting out from the paradigm developed in the IST-27960 STREP URANUS (UNIVERSAL RADIO-LINK PLATFORM FOR EFFICIENT USER-CENTRIC ACCESS). URANUS investigates the design of a universal radio link platform able to be incorporated in any existing proprietary and standardized wireless system in a seamless way, to ease the introduction of future personalized communications and reconfigurable air interfaces.