A Programmable Receiver for Communication Systems and Its Application to Impulse Radio

The design of a programmable receiver for an ultra wideband (UWB) communication is presented. The receiver is using a fast analog to digital converter (ADC) and a field programmable gate array (FPGA) allowing a rapid performance evaluation for various system architectures and signal processing algorithms. To demonstrate the performance and the versatility of the receiver, a simple communication system and a localization system are implemented. The accuracy of the latter is presented for an indoor environment.

Chip-Level HARQ Chase Combining for HSUPA

Hybrid automatic repeat request (HARQ) is used in high-speed uplink packet access (HSUPA) to increase the data rate. Chase combining is the simplest of HARQ algorithms. It provides a time diversity and requires a small memory. In this paper, we propose a technique to increase the chase combining efficiency. In this method, HARQ transmissions are seen as additional receive antennas which are jointly combined at chip-level using a space-time linear minimum square error (LMMSE). We demonstrate that the chase combining diversity gain is considerably increased especially for high-order modulation.

The Measurement Paradox in Valiant Network Design

Valiant network design was proposed, at least in part, to counter the difficulties in measuring network traffic matrices. However, in this paper we show that in a Valiant network design, the traffic matrix is in fact easy to measure, leading to a subtle paradox in the design strategy.

A Reduced-Complexity Mixer Linearization Scheme

Measurement results of the signals emanating from both IF and LO ports of a double balanced mixer are presented, and, thus, it is shown that the linearization of the output in a down-converting mixer by the summation of the IF signal and the signal emanating from the LO or RF port is feasible. Feedforward-based architectures for the linearization of down-conversion mixers are introduced that exploit this phenomenon, and linearity performance results of the frequency translation of both two-tone and TETRA-modulated signals are presented. This technique employs only a single mixer and hence overcomes the complexity of other mixer linearization schemes. The overall processing gain of the system is limited by the level of wanted signal present in the error signal.

Decoding the Ternary (23, 11, 9) Quadratic Residue Code

The algebraic decoding of binary quadratic residue codes can be performed using the Peterson or the Berlekamp-Massey algorithm once certain unknown syndromes are determined or eliminated. The technique of determining unknown syndromes is applied to the nonbinary case to decode the expurgated ternary quadratic residue code of length 23.

Energy Detection of Multilevel PAM Signals with Systematic Threshold Mismatch

We address a symbol decision problem with spectrally efficient energy detected multilevel pulse amplitude modulated (PAM) signals. First, we analytically quantify the relationship between a systematic threshold mismatch and the required increase of the average signal-to-noise ratio to preserve a desired symbol error rate. For the case in which such an increase is not tolerable, we present a novel near-optimal multilevel threshold selection scheme, which is accurate for a wide range of system parameters.

Modeling Distance and Bandwidth Dependency of TOA-Based UWB Ranging Error for Positioning

A statistical model for the range error provided by TOA estimation using UWB signals is given, based on UWB channel measurements between 3.1 and 10.6 GHz. The range error has been modeled as a Gaussian random variable for LOS and as a combination of a Gaussian and an exponential random variable for NLOS. The distance and bandwidth dependency of both the mean and the standard deviation of the range error has been analyzed, and insight is given in the different phenomena which affect the estimation accuracy. A possible application of the model to weighted least squares positioning is finally investigated. Noticeable improvements compared to the traditional least squares method have been obtained.

Throughput of Type II HARQ-OFDM/TDM Using MMSE-FDE in a Multipath Channel

In type II hybrid ARQ (HARQ) schemes, the uncoded information bits are transmitted first, while the error correction parity bits are sent upon request. Consequently, frequency diversity cannot be exploited during the first transmission. In this paper, we present the use of OFDM/TDM with MMSE-FDE and type II HARQ to increase throughput of OFDM due to frequency diversity gain.

PacketTwins: A Novel Method for Capacity Estimation of a Heavy-Loaded Path

We propose a method called PacketTwins for estimating the capacity of heavy-loaded paths. Unlike popular packet pair methods, which probe a path with a series of two equal-sized packets, PacketTwins uses a series of twin probe packets that are slightly different in size. By sending twin probe packets alternately, we can obtain new information about selecting valid samples for capacity estimation when a network path is heavy loaded.

Optimal Filtering in Pilot-Aided Carrier Recovery

The paper deals with carrier recovery based on pilot symbols in single-carrier systems. Wiener's method is used to determine the optimal unconstrained filter in estimation of phase noise assuming that a sequence of equally spaced pilot symbols is available. Our analysis allows to capture two effects that are not considered in the existing literature: the impact of aliasing due to sampling of the phase noise sequence at the pilot rate and the cyclostationary nature of the estimate hence of its performance. Experimental results are derived also for the case, where the filter is constrained to the cascade of two moving averages. These results show that, in the considered example, the mean-square phase error of the constrained filter is within 0.35 dB from the MSE of the optimal filter.