Jetmir Haxhibeqiri

LoRa scalability : a simulation model based on interference measurements

LoRa is a long-range, low power, low bit rate and single-hop wireless communication technology. It is intended to be used in Internet of Things (IoT) applications involving battery-powered devices with low throughput requirements. A LoRaWAN network consists of multiple end nodes that communicate with one or more gateways. These gateways act like a transparent bridge towards a common network server. The amount of end devices and their throughput requirements will have an impact on the performance of the LoRaWAN network. This study investigates the scalability in terms of the number of end devices per gateway of single-gateway LoRaWAN deployments. First, we determine the intra-technology interference behavior with two physical end nodes, by checking the impact of an interfering node on a transmitting node. Measurements show that even under concurrent transmission, one of the packets can be received under certain conditions. Based on these measurements, we create a simulation model for assessing the scalability of a single gateway LoRaWAN network. We show that when the number of nodes increases up to 1000 per gateway, the losses will be up to 32%. In such a case, pure Aloha will have around 90% losses. However, when the duty cycle of the application layer becomes lower than the allowed radio duty cycle of 1%, losses will be even lower. We also show network scalability simulation results for some IoT use cases based on real data.

Scalability Analysis of Large-Scale LoRaWAN Networks in ns-3

As LoRaWAN networks are actively being deployed in the field, it is important to comprehend the limitations of this low power wide area network technology. Previous work has raised questions in terms of the scalability and capacity of LoRaWAN networks as the number of end devices grows to hundreds or thousands per gateway. Some works have modeled LoRaWAN networks as pure ALOHA networks, which fails to capture important characteristics such as the capture effect and the effects of interference. Other works provide a more comprehensive model by relying on empirical and stochastic techniques. This paper uses a different approach where a LoRa error model is constructed from extensive complex baseband bit error rate simulations and used as an interference model. The error model is combined with the LoRaWAN MAC protocol in an ns-3 module that enables to study multichannel, multispreading factor, multigateway, bi-directional LoRaWAN networks with thousands of end devices. Using the LoRaWAN ns-3 module, a scalability analysis of LoRaWAN shows the detrimental impact downstream traffic has on the delivery ratio of confirmed upstream traffic. The analysis shows that increasing gateway density can ameliorate but not eliminate this effect, as stringent duty cycle requirements for gateways continue to limit downstream opportunities.

To Mesh or not to Mesh: Flexible Wireless Indoor Communication Among Mobile Robots in Industrial Environments

Mobile robots such as automated guided vehicles become increasingly important in industry as they can greatly increase efficiency. For their operation such robots must rely on wireless communication, typically realized by connecting them to an existing enterprise network. In this paper we motivate that such an approach is not always economically viable or might result in performance issues. Therefore we propose a flexible and configurable mixed architecture that leverages on mesh capabilities whenever appropriate. Through experiments on a wireless testbed for a variety of scenarios, we analyse the impact of roaming, mobility and traffic separation and demonstrate the potential of our approach.

Wireless industrial communication for connected shuttle systems in warehouses

In the last decade, we have seen the uptake of connected solutions to support and improve manufacturing, warehousing and distribution operations in industry. However, deterministic and reliable wireless communication in large-scale, dynamic and mobile applications still remains one of the greatest challenges for the realization of the Digital Factory of the Future. In this paper, we investigate more open, flexible and reliable wireless network structures that can be used in connected warehouses, focusing on connected shuttle systems for transporting goods.

Flexible Wi-Fi Communication among Mobile Robots in Indoor Industrial Environments

In order to speed up industrial processes and to improve logistics, mobile robots are getting important in industry. In this paper, we propose a flexible and configurable architecture for the mobile node that is able to operate in different network topology scenarios. The proposed solution is able to operate in presence of network infrastructure, in ad hoc mode only, or to use both possibilities. In case of mixed architecture, mesh capabilities will enable coverage problem detection and overcoming. The solution is based on real requirements from an automated guided vehicle producer. First, we evaluate the overhead introduced by our solution. Since the mobile robot communication relies in broadcast traffic, the broadcast scalability in mesh network is evaluated too. Finally, through experiments on a wireless testbed for a variety of scenarios, we analyze the impact of roaming, mobility and traffic separation, and demonstrate the advantage of our approach in handling coverage problems.

Wireless handover performance in industrial environments: A case study

Wireless communication is an enabling technology for industrial automation. For mobile industrial devices operating in large areas, the performance of the wireless handover process is crucial. For the welfare of industrial processes short time communication outage must be ensured, especially for time-critical traffic. This paper assesses the handover performance for three industrial real-life use cases with different requirements. It covers handover performance under heavy interference, its impact on time-critical traffic and on broadcast traffic latency, followed by lessons learned and opportunities for further research.

New method to design multiplier-less pulse shaping filters with minimal number of operations

Software-Defined Radio (SDR) technology is evolving rapidly, offering higher flexibility for wireless communication networks. For the sake of performance, and power consumption, filtering is commonly implemented in hardware using FPGAs. Pulse shaping in the transmitter and the corresponding matched filtering in the receiver, which together satisfy the Nyquist inter symbol interference (ISI) criterion, are no exception to this. To decrease the FPGA resources used by filters, to increase speed and to decrease power consumption the filter coefficients can be optimized by expressing them in canonical signed digit (CSD) form, using as few arithmetic operations per filter as possible, while maintaining acceptable filter characteristics. In this paper a new method to decrease the number of nonzero signed digits is presented. With this method a reduction of up to 65% of the nonzero signed digits per filter is realized, while decreasing the ISI ratio too.