Simulation Software Radio Mobile Communications 19 !FULL!

Sebastian Koslowski, Friedrich K. Jondral:Short Paper: SIC-MMSE Detection for Filter Bank Multicarrier Systems2015 IEEE 82nd Vehicular Technology Conference, Boston, USA, Sep 6-9, 2015Abstract:Filter bank multicarrier is one of the candidates for next generation mobile radio systems. Using filtered sub-channels reduces side-lopes as well as interference among sub-channels. Symbols overlap in time and are not separated by a cyclic prefix resulting in inter-symbol inference as well as interference from adjacent sub-channels under multi-path propagation. Equalization methods known from OFDM can not be directly applied. However, a linear per-subchannel equalizer with minimum meansquared error has been proposed. This has also been used for iterative decoding and equalization by remodulating decoded symbols to cancel-out interference. In this short paper, we extend this concept and derive a MMSE equalizer using soft interference cancellation. Using soft-information increases performance and enables turbo equalization for filter bank multicarrier systems.[ back to overview ]

Michael Schwall, Tamal Bose, Friedrich K. Jondral:On the Performance of SC-MMSE-FD Equalization for Fixed-Point Implementations 8th International Symposium on Turbo Codes and Iterative Decoding (ISTC), Bremen, Germany, August 18 - 22, 2014Abstract:A fixed-point implementation of a minimum mean square error (MMSE) based frequency domain (FD) equalizer with soft interference cancellation (SC) is studied. The equalizer additionally processes \apriori information about the transmitted symbols and is used for turbo equalization. In this paper, we analyze the quantization and the clipping for different fixed-point representations and modulation schemes. The analysis allows to derive efficient representations for all symbols within the equalizer. This procedure is demonstrated for a generic system configuration featuring a 16-QAM. Finally, a fixed-point implementation in an integrated design environment for FPGAs verifies the theoretical studies and shows the device utilizations for different FPGAs that are embedded in current software defined radios. The results show, that on average 10 bits per symbol are required for a near-optimum equalization performance utilizing less than 8% area of state of the art FPGAs.[ back to overview]

Ralph Tanbourgi, Holger Jäkel, Friedrich K. Jondral:Cooperative Interference Cancellation using Device-to-Device CommunicationsIEEE Communications Magazine: Special Issue on Smart Device-to-Smart Device Communications, June 2014Abstract:The ongoing densification in cellular networks has turned interference into a serious problem in future cellular networks. Since the interference experienced by close-by users in a cellular network is usually correlated, it can be cooperatively suppressed to improve user experience. In this paper, we introduce the idea of cooperative interference cancellation (CIC) between close-by users using device-to-device (D2D) communications for the example of the upcoming 3rd Generation Partnership Program (3GPP) Long Term Evolution (LTE) Rel-12 D2D technology. We understand CIC as a new network interference management tool, capable of exploiting interference correlation to improve downlink throughput. We discuss possible deployment scenarios as well as theoretical and practical challenges. To each challenge we provide some possible solutions. Finally, a first feasibility analysis using numerical simulations is presented which demonstrates the potential gains of CIC.[ back to overview]

Noha El Gemayel, Holger Jäkel, Friedrich K. Jondral:Error Analysis of a Low Cost TDoA Sensor NetworkIEEE/ION Position, Location and Navigation Symposium 2014, Monterey, CA, USA, May 5-8, 2014Abstract:Geolocation methods are recently gaining a lot of interest due to their new range of applicability. Location based mobile services as well as frequency regulators aiming at efficient spectrum usage are interested in flexible, low cost geolocation systems with high accuracy. One method that meets those requirements is Time Difference of Arrival (TDoA). It has been subject to research for many years now. The main focus of research published about TDoA is presenting new algorithms or calculating estimation bounds in different scenarios. Due to new low cost available hardware solutions, a simple TDoA system can be built and used as a testbed for different algorithms in different real scenarios. This contribution presents an error analysis of a TDoA sensor network using low cost, off-the-shelf software defined radio platforms. The system relies on GPS time stamps provided by the platforms. Five important TDoA error types caused by hardware as well as different channel effects are analyzed. Each error is analyzed in its influence on the position estimate and a possible solution is given. Finally, a general structure of how a smart TDoA system should work is described.[ back to overview]

Michael Mühlhaus, Friedrich Jondral:A Fully Blind Receiver for Automatic Modulation Classification of MIMO SignalsProceedings of the 8th Karlsruhe Workshop on Software Radios, Karlsruhe, Germany, March 2014, pp. 148-152Abstract:Automatic modulation classification (AMC) finds its applications in spectrum surveillance, in signals intelligence, and nowadays in cognitive radios. Many articles examine the problem of AMC in single input single output (SISO) systems. Modern communications standards often use multiple input multiple outputs (MIMO) transmission that causes a rising interest in the AMC of MIMO signals. Usually in the literature a perfectly synchronized system is assumed. In this contribution, we extend these ideas to a fully blind receiver that does not require any a-priori knowledge of the transmitted signal. We propose methods for blind frequency, symbol rate, timing, channel, and phase estimation, as well as a low complexity AMC algorithm. Furthermore, the entire receiver is verified by the test bed using universal software Radio Platforms (USRP).[ back to overview]

Michael Schwall, Friedrich K. Jondral:High-Speed Turbo Equalization for GPP-based Software Defined RadiosThe 2013 Military Communications Conference, San Diego, USA, Nov 18-20, 2013Abstract:High data rate waveforms for software defined radios (SDR) have to cope with frequency selective fading due to the mobile use in different harsh transmission environments. The received signal needs to be equalized in order to restore the transmitted information. Turbo equalization is a promising approach to deal with the inter-symbol interference occurring at the receiver. The iterative exchange of soft information between the equalizer and the decoder improves the decision reliability and hence reduces the bit error probability compared to conventional receivers. However, the necessary resource-demanding soft-input soft-output algorithms require a high processing performance to ensure real-time capability. In this paper, we will present a highspeed implementation of a turbo equalizer for SDRs with digital signal processing being performed on general purpose processors (GPP). The implementation will utilize linear MMSE filtering and suboptimal algorithms like overlapping sub-trellis MAXLog- MAP decoding, approximations of mathematical operations, parallelization methods such as threading-based pipelining, and processor specific optimizations like single instruction multiple data (SIMD) commands. We will present the processing gains for each optimization level, highlight the performance loss for the suboptimal modifications and analyze the latency introduced by the pipelined processing. So far, transmissions with data rates up to 5.4 Mbit/s can be decoded in real-time with negligible performance loss and tolerable delay.[ back to overview]

Ankit Kaushik, Marcus Mueller, Friedrich K. Jondral:Cognitive Relay: Detecting Spectrum Holes in a Dynamic ScenarioProceedings of IEEE International Symposium on Wireless Communication Systems ISWCS 2013, IlmenauAbstract:Cognitive radio has been in discussion for more than a decade. Dynamic access to the spectrum is considered its major application to solve the bandwidth demands of the mobile network operator. Literature in the form of paper and books exists. Through Cognitive Relaying, the authors make an attempt to abridge the gap between the theoretical concepts and a practical implementation.[ back to overview]

Martin Braun, Nico Otterbach, Jens Elsner, Friedrich K. Jondral:Rapid Prototyping of a Frequency Hopping Ad Hoc Network SystemProceedings of 23rd Virginia Tech Symposium on Wireless Communications, Blacksburg, May 2013Abstract:Wireless networks in-the-loop is a method to develop software radio systems which operate in networks. It eliminates the gap between simulations and live testing by allowing the developer to use the same code for both types of testing. This allows the parallel development of signal processing and protocols in a network context without having to use intermediary tools. We demonstrate this concept using the example of frequency hopping ad hoc networks, which are both challenging on the signal processing side as well as on the network side.[ back to overview]

Noha El Gemayel, Sebastian Koslowski, Friedrich K. Jondral:A low cost TDOA Localization System: Setup, Challenges and Results10th Workshop on Positioning, Navigation and Communication 2013 (WPNC'13), Dresden, Germany, March 20-21, 2013Abstract:In this paper we present a prototype location estimation system which uses Time Difference of Arrival. The system consists of five low cost sensors that are synchronized using GPS time stamps. The sensors were installed on the rooftops of the university campus. The system is based on software defined radios which enable receiving signals with different carrier frequencies and sampling rates with the aim of applying it as a frequency monitoring and regulating system. The paper presents the expected challenges we face from the system and compares them to the measured results.[ back to overview] 2b1af7f3a8