Hendrik Lieske

Increasing Transmission Reliability for Telemetry Systems Using Telegram Splitting

This paper analyzes the reliability and throughput of the telegram-splitting concept in the presence of inter-system and intra-system interference. Using telegram splitting, the data of one telegram is split into multiple sub-packets, which are then transmitted with temporal spacing. As a result, collisions with other telegrams destroy only some sub-packets that can be recovered using forward error correction. Consequently, the reliability of the data transmission in case of inter- and intra-system interference - a significant problem in license-exempt bands - is highly improved. In this paper, probabilities for the resulting telegram error rate of random media access systems using telegram splitting are derived. Furthermore, the achievable throughput is analyzed. The theoretical considerations in addition to simulation results prove the significant gain of the telegram-splitting concept for telemetry systems.

A stochastic geometry approach to model the shadow fading for mobile ad-hoc networks

This paper deals with the problem of modeling shadow fading for wireless links in mobile ad-hoc networks (MANET). In contrast to broadcasting or cellular applications, the links in a MANET generally cannot be analyzed indepen-dently. Thus the evaluation of routing techniques and network protocols for future systems requires a realistic modeling of the correlation of the links. In the following a novel modeling approach based on stochastic geometry will be presented. This computationally inexpensive model allows for dual mobility, the simultaneous movement of the transmitter and the receiver, and can be easily adapted for various environments. The model can be integrated in network simulators and therefore enables the analysis of the influence of shadow fading on the performance of MANET routing algorithms and protocols.

Decoding Performance in Low-Power Wide Area Networks With Packet Collisions

This paper proposes an analytical framework for the prediction of decoding error probabilities in heterogeneous wireless environments, where transmissions from various radio nodes with distinct Poisson-arrival rates and packet lengths populate the channel. Random channel access without feedback is assumed, where partial packet collisions can lead to the loss of packets. The analysis is based on the modeling of the collision length distribution between competing nodes. With recent results from information theory in the finite block length regime, we provide bounds on achievable decoding error probabilities for a given interference scenario. The new framework enables jointly considering inter- and intra-system interference, which is an important aspect in unlicensed radio bands. The frameworks applicability to optimize system designs is demonstrated for a typical low-power wide area network scenario. We study the tradeoff between reliability and code rate for a point-to-point link and present achievable throughput regions. The analysis reveals the superior performance of coded time-hopping spread spectrum systems. They reach very low error probability even under strong interference for wide ranges of practically relevant load regions.

On the Importance of Realistic Correlated Shadow Fading Modeling for Mobile Ad-Hoc Networks

The simulation of typical network scenarios is essential for the evaluation of design proposals for future mobile adhoc network (MANET) systems. In this paper, we demonstrate the importance of realistic correlated shadow fading modeling for this application. This is done by simulating a basic mobile network scenario and comparing the estimated outage probability values for an uncorrelated link model and a more realistic correlated link model to the results of real world measurements. The simulations show that the use of a shadow fading model, which does not consider the correlation between the links in a network, results in significant estimation errors. The stochastic geometry shadowing model, which incorporates the link correlation, is able to provide a much more realistic estimate. Using this correlated model rather than the models currently in use will help to avoid flawed design decisions which would affect future systems.

Numerical Evaluation of Information Outage for BPSK FHSS Link Performance Analysis

The information outage probability serves as a practical benchmark for the performance evaluation of channel codes in the finite block length region. The metric is derived from the distribution of the mutual information between a channels in- and output and is readily available for the Gaussian AWGN channel. To review its applicability for modulation constraint channel inputs, we propose a numerical method for the evaluation of the mutual information random variable for BPSK modulated code words. We apply the model to a block fading channel to study the link performance of a frequency hopping spread spectrum (FHSS) system in a slow-fading two-path propagation environment, which is a typical scenario for low power wide area (LPWA) applications. The information outage probability closely reproduces the behavior of a practical rate 1/3 Turbo decoder.

Outage probability and base station coverage in low power wide area networks

This paper presents an analytical model for the uplink performance analysis of low power wide area (LPWA) networks. Such networks typically serve for data aggregation in machine-to-machine (M2M) communication scenarios. Our model predicts the outage probability of desired radio nodes and is based on the inversion of the moment-generating function of a suitable defined random variable. Due to the peculiarities of LPWA networks, namely low access probabilities and static channel conditions, the numerical inversion is not a trivial task, and we propose the use of a special inversion algorithm to address this problem. The applicability of the proposed model is demonstrated for an exemplary network topology with a latency constraint. We obtain optimum medium access probabilities for either maximized network coverage area or a trade-off between coverage and power consumption.

Improving Medium Access in Single-Destination Networks with Heterogeneous Propagation Channels

This paper studies coverage probabilities of randomly deployed radio nodes in single-destination networks. Such networks are typically operated for data aggregation in machine-to-machine (M2M) communication scenarios. In large-scale deployments, diverse environments usually result in heterogeneous propagation channels. We address the question to which extent an increased medium access can compensate for impaired propagation conditions. Based on superimposed Poisson Point Processes and a strongest interferer approximation, we propose a closed-form solution for the probability of a successful packet transmission under heterogeneous channel conditions. The applicability of the framework is demonstrated for an exemplary network configuration with a given latency constraint. Jointly optimising the medium access probabilities can either increase the network coverage area (e.g. by factor two) or reduce the overall networks power consumption by up to more than 30% in sufficiently dense deployments.

Spectrum aware interference modelling in large-scale smart metering networks

An approach for a more realistic simulation of wireless smart metering networks in smart grid applications is presented in this work. Conventional network simulations usually ignore spectral properties of transmission signals. Thus, adjacent channel interference is ignored, which may lead to unreliable packet loss rate estimations. To overcome this drawback, we introduce a general method to model modulation schemes in a network simulation. The proposed solution is examined in an OMNeT++ simulation with two exemplary spectrum models, which differ in their levels of detail. The simulations were conducted for varying channel spacings and load situations for a smart metering network with up to 12,000 radio units. The results show that the use of a detailed spectrum model should be favoured. Since our approach improves adjacent channel interference modelling, it is an important component for more reliable results when evaluating communication protocols in network simulations.