Browsing by Author "Lysko, Albert"

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    Open Access
    Performance analysis of hybrid WiFi and TV white space links
    (2020) Lamola, Mokwape Magdeline; Johnson, David Lloyd; Densmore, Melissa; Lysko, Albert
    Internet access has the potential to improve economic growth in developing countries, yet in developing countries with emerging economies, such as South Africa, Internet access opportunities are not evenly distributed. This digital divide exists between urban and rural areas and even within urban areas in many developing countries. Urban areas are densely populated - simplifying telecommunication infrastructure roll-out, whereas rural areas are sparsely populated - making the roll-out of telecommunication infrastructure considerably more complex and expensive. This digital divide poses a significant challenge since a large portion of the developing country's population is based in rural areas. Cellular, satellite and some pockets of WiFi technologies are mostly used to provide access in rural areas. Although these technologies help mitigate connectivity challenges in rural areas, they are often costly and provide limited broadband access. The high cost of access in rural areas is due to the lack of fibre for backhaul that provides cost effective bulk wholesale capacity and the use of costly satellite links or cellular links for Internet access. Cost-effective technology alternatives such as WiFi and/or Television White Space (TVWS) can provide an effective approach to provide affordable last mile and middle mile connectivity for Internet access in many of these poorly connected areas. TVWS provides excellent coverage and penetration through vegetation, buildings since it utilizes spectrum in the UHF bands currently used for Television broadcasting to offer broadband wireless connectivity. Although TVWS has good propagation characteristics in some non-line-ofsight (NLOS) scenarios and can offer better coverage than WiFi, thanks to the mass production and massive industry and development support behind it, WiFi provides low-cost connectivity with better throughput speeds in line-of-sight (LOS) scenarios. Previous research has focused on the characteristics and performance of TVWS and WiFi in isolation. This study aims to describe how their individual characteristics can then be used to compliment each other for improvement in the last-mile access. This work looked at the performance of WiFi and TVWS technology in different settings, including line-of-sight, non-line-of-sight environments and using different combinations of these technologies. Experiments focused on the performance of WiFi (IEEE 802.11a) and TVWS (IEEE 802.11g cards downconverted to UHF) with an objective to help improve connectivity in areas with poor coverage, due to environmental factors, such as vegetation and distance. The study utilized the Council of Scientific and Industrial Research's (CSIR's) Meraka Institute custom built White Space Mesh Node (WSMN) equipped with WiFi and TVWS radio interface cards to carry out the experiments. The study particularly focuses on the 5 GHz Wi-Fi and Ultra High Frequency (UHF) 530 to 600 MHz frequency bands. The study presents an analysis of data collected over the dual-radio wireless network in indoor and outdoor environments. Presentation of this data follows measurements of single radio and aggregate radio link traffic collected in various line-of-sight and non-line-of-sight environments. These measurements deduce the effects of environment on 5 GHz and TVWS frequency band, effects of modifying performance parameters, improvement or degradation of aggregated TVWS WiFi links, and the usage of the measured performance data for network planning. Each experiment tests different combinations of radio settings, such as channel, transmit power and channel width to measure throughput, signal strength, packet loss, and Signal to Noise Ratio. These tests were done in both indoor and outdoor environments. The results collected and presented in this work show that although TVWS has superior propagation characteristics compared to WiFi, its performance is often poorer than WiFi when there is clear line-of-site and at shorter distances. The study, in addition, presents data that shows that the overall radio performance in a network is affected by more than just spectrum availability in space or time, but also by radio settings and the environment. The study also goes on to show that aggregated links, that combine both TVWS and WiFi, do not always lead to better network performance. The study lastly presents tailored scenarios of single and aggregated radio links that lead to better performance with the hope that these will help network designers and researchers make better-informed decisions on how to use available radio resources effectively.
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    Open Access
    Time Sensitive Networking for Wi-Fi Based Wireless Industrial Environments
    (2021) Kinabo, Arnold Baraka Doste; Mwangama, Joyce; Lysko, Albert
    In production industries, mission-critical assignments require networks characterised by deterministic low latency, dedicated bandwidth resources, and, chiefly, reliability. Several fieldbus technologies are specially placed for this. Their commonality is that they run on standard Ethernet. The relatively new Time Sensitive Networking (TSN) is among these technologies. It is a set of Ethernet standards that guarantees determinism for real-time usecases. TSN sets itself apart in that it is vendor-agnostic. And so, it promotes interoperability among standard-conformant devices. Being based on Ethernet, even TSN is plagued by downsides associated with cabled networks, most importantly, the limited range and mobility. In this regard, wireless networks are an attractive option – it would be an opportunistic venture to operate TSN in the wireless medium. Previous works have tried to address how this can be done, but as yet, it is an open problem. The issue is that most wireless networks are not optimised for determinism. Most lack the scheduling, synchronisation and other capabilities that timing-stringent applications require. Wi-Fi, for instance, suffers from many issues stemming from randomised medium access and interference, which remove the predictability from its communications. Critical TSN traffic needs special consideration when run with other services in current Wi-Fi. That being said, the key research question is: can one contend with the problem of transmitting TSN and non-TSN traffic together in the same wireless network? To answer this, the work develops a TSN simulation model that operates in Wi-Fi, whose test results can be studied to aid in analysing wireless TSN. The prototype model runs in a simulation environment, and was developed using methods that involved reusing and modifying the present wireless architecture to support the TSN traffic. Through the course of several iterative experiments, it was revealed that although the current generation of Wi-Fi can support TSN traffic, it does so inefficiently. Even with no interference, the TSN traffic experiences low losses only when the network capacity utilisation is very low, below a small percentage value. Considering the typically low demands on bandwidth in many TSN applications, this inefficient operation may still be sufficient for operating TSN over existing Wi-Fi networks. For more robust and general applications, Wi-Fi requires further enhancements to its mode of operation in order to support prioritisation of TSN traffic and more accurately cope with higher loads.