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Low Power Wide Area Networks (LPWAN) technologies in the 2.4 GHz band offer the opportunity to employ multiple antennas at the sensor, which can be used to create antenna diversity. In this paper, we present our software-defined, interference-robust, and highly mobile channel sounder architecture and experimentally evaluate the long-range outdoor-to- outdoor MIMO channel in a typical Smart City environment. Analyzing the measurements we have obtained over a wide area, we estimate path loss, coherence bandwidth, and antenna correlations. Link budget calculations show that, despite the higher frequency compared to popular LPWAN technologies such as LoRa or SigFox, multi-kilometer links are feasible. Furthermore, the comparison of an IEEE 802.15.4 PHY designed for LPWANs with a recently proposed multi-antenna scheme indicates that considerable performance gains are possible through antenna diversity schemes, even with rather high antenna correlation.

We present the design of a low-complexity air interface for the uplink in Low Power Wide Area Networks (LPWANs) based on a recently published Differential Spatial Modulation scheme for two transmit antennas achieving full transmit diversity (FD-DSM). Extending the authors' work, we derive an optimized assignment from bits to space-time matrices comparable to Gray coding, which improves the bit error rate by up to 1 dB. Furthermore, FD-DSM's superiority over single-antenna differential PSK schemes as used in current LPWAN technologies is evaluated in extensive simulations and confirmed in uncoded and coded scenarios, where a convolutional code with soft-input Viterbi decoding is employed. It is shown that existing systems are outperformed by at least 5 dB for packet error rates below 1%. Our system utilizes the DSSS technique to achieve the enormous processing gains required to enable links over many kilometers. We propose the insertion of time gaps between chip sequences to allow for the rise and fall time of conventional, spectrally-efficient pulse shaping filters and to thus facilitate antenna switching without spectral broadening, a challenging issue in Spatial Modulation (SM) systems. The resulting rate loss is negligible but allows the realization of practical SM systems with the theoretical minimum of a single RF chain.

In this proposal, we provide details on our approach for the design of a cognitive overlay system which is implemented on a heterogeneous Software Defined Radio (SDR) platform consisting of an off-the-shelf consumer laptop and a USRP X310. To ensure high flexibility, spectral efficiency and low out-of-band radiation, we chose Filter Bank Multicarrier (FBMC) as physical layer waveform. For the cognitive aspect we propose a hybrid solution based on learning of Primary User (PU) transmission parameters and behavioral patterns as well as continuous, low-delay channel monitoring. To achieve a low delay and to improve performance, we implement critical signal processing components on an FPGA. Detection thresholds are optimized by using feedback information on the PU error rate.

Understanding the performance of a spectrum sharing system by means of a hardware deployment is a challenging task. Motivated by this fact, we propose a prototype of a secondary system that co-exists with a primary system and simultaneously sustains the constraints defined by the regulatory. In this paper, we propose several key-techniques for the secondary system, which will be deployed on a hardware.

Industrial environments often exhibit harsh propagation conditions for wireless transmissions. This paper investigates the influence of different interference characteristics on the performance of IEEE 802.15.4 using the OQPSK and Chirp Spread Spectrum (CSS) PHY. Bit error rates are determined for AWGN, Rayleigh fading and self-interference scenarios. GNU Radio, a Software Defined Radio framework, serves as simulation environment. In addition to the implementation of the CSS transmitter and receiver, a low-complexity synchronization algorithm, which only consists of a correlator and a second order Phase Locked Loop (PLL), and its limitations are presented. Furthermore, MAC layer simulations are performed for beacon-enabled (slotted) as well as nonbeacon- enabled (unslotted) mode to make a statement about achievable throughput and latency in the presence of interference. It shows that the CSS PHY clearly surpasses the OQPSK PHY in throughput. Moreover, the simulation results are confirmed by the derivation of the theoretical maximum throughput for the investigated PHY layers.

In this paper, we describe the original problem statement and the two winning solutions to the IEEE DySPAN Challenge, organized in Baltimore in 2017. The idea of the challenge was to invite teams to propose as diverse as possible solutions to a well defined problem, and evaluate the performance of the proposed solutions in a realistic environment. The challenge is defined to enable benchmarking and comparison of multiple teams, possibly working on different parts of the system, in a real environment. The winning solutions represented a complete and working system, working robustly and adapting to both anticipated scenario changes, as well as random effects caused by the conference setting. The code for running the challenge along with the winning solutions is publicly available, so that interested teams can start from the code when designing or benchmarking solutions, as well as when setting up own challenges and competitions. As a result, the challenge can serve as a milestone toward the creation of a benchmarking series. This paper contains all the necessary details about the software repositories so that it becomes possible to rerun the challenge and start building novel solutions based on the winners in IEEE DySPAN 2017.