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Author: Brzozowski, Marcin ×

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    Support for a long lifetime and short end-to-end delays with TDMA protocols in sensor networks
    (London : Hindawi, 2012) Brzozowski, Marcin; Salomon, Hendrik; Langendoerfer, Peter
    This work addresses a tough challenge of achieving two opposing goals: ensuring long lifetimes and supporting short end-to-end delays in sensor networks. Obviously, sensor nodes must wake up often to support short delays in multi-hop networks. As event occurs seldom in common applications, most wake-up are useless: nodes waste energy due to idle listening. We introduce a set of solutions, referred to as LETED (limiting end-to-end delays), which shorten the wake-up periods, reduce idle listening, and save energy. We exploit hardware features of available transceivers that allow early detection of idle wake-up periods. This feature is introduced on top of our approach to reduce idle listening stemming from clock drift owing to the estimation of run-time drift. To evaluate LETED and other MAC protocols that support short end-to-end delays we present an analytical model, which considers almost 30 hardware and software parameters. Our evaluation revealed that LETED reduces idle listening by 15x and more against similar solutions. Also, LETED outperforms other protocols and provides significant longer lifetimes. For example, nodes with LETED work 8x longer than those with a common TDMA and 2x-3x longer than with protocols based on preamble sampling, like B-MAC.
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    European H2020 Project WORTECS Wireless Mixed Reality Prototyping
    (Oulu : Academy Publisher, 2020) Bouchet, Olivier; O'Brien, Dominic; Singh, Ravinder; Faulkner, Grahame; Ghoraishi, Mir; Garcia-Marquez, Jorge; Vercasson, Guillaume; Brzozowski, Marcin; Sark, Vladica
    This paper presents European collaborative project WORTECS objectives and reports on the development of several radio and optical wireless prototypes and a demonstrator targeting mixed reality (MR) application. The aim is to achieve a net throughput of up to Tbps in an indoor heterogeneous network for the MR use case, which seems to be a high throughput "killer application" beyond 5G. A special routing device is associated with the demonstrator to select the most suitable wireless access technology. Post introduction to the project, an overview of the demonstrator is presented with details of the current progress of the prototypes.
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    Data link layer considerations for future 100 Gbps terahertz band transceivers
    (London : Hindawi, 2017) Lopacinski, Lukasz; Brzozowski, Marcin; Kraemer, Rolf
    This paper presents a hardware processor for 100Gbps wireless data link layer. A serial Reed-Solomon decoder requires a clock of 12.5GHz to fulfill timings constraints of the transmission. Receiving a single Ethernet frame on a 100 Gbps physical layer may be faster than accessing DDR3 memory. Processing so fast streams on a state-of-the-art FPGA (field programmable gate arrays) requires a dedicated approach. Thus, the paper presents lightweight RS FEC engine, frames fragmentation, aggregation, and a protocol with selective fragment retransmission. The implemented FPGA demonstrator achieves nearly 120 Gbps and accepts bit error rate (BER) up to 2e - 3. Moreover, redundancy added to the frames is adopted according to the channel BER by a dedicated link adaptation algorithm. At the end, ASIC synthesis results are presented including detailed statistics of consumed energy per bit.
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    Disruptive events in high-density cellular networks
    (Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2018) Keeler, Paul; Jahnel, Benedikt; Maye, Oliver; Aschenbach, Daniel; Brzozowski, Marcin
    Stochastic geometry models are used to study wireless networks, particularly cellular phone networks, but most of the research focuses on the typical user, often ignoring atypical events, which can be highly disruptive and of interest to network operators. We examine atypical events when a unexpected large proportion of users are disconnected or connected by proposing a hybrid approach based on ray launching simulation and point process theory. This work is motivated by recent results [12] using large deviations theory applied to the signal-to-interference ratio. This theory provides a tool for the stochastic analysis of atypical but disruptive events, particularly when the density of transmitters is high. For a section of a European city, we introduce a new stochastic model of a single network cell that uses ray launching data generated with the open source RaLaNS package, giving deterministic path loss values. We collect statistics on the fraction of (dis)connected users in the uplink, and observe that the probability of an unexpected large proportion of disconnected users decreases exponentially when the transmitter density increases. This observation implies that denser networks become more stable in the sense that the probability of the fraction of (dis)connected users deviating from its mean, is exponentially small. We also empirically obtain and illustrate the density of users for network configurations in the disruptive event, which highlights the fact that such bottleneck behaviour not only stems from too many users at the cell boundary, but also from the near-far effect of many users in the immediate vicinity of the base station. We discuss the implications of these findings and outline possible future research directions.