Browsing by Author "Robinson, Daniel"
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- ItemNB-IoT (LTE Cat-NB1 / narrow-band IoT) performance evaluation of variability in multiple LTE vendors, UE devices and MNOs(Stellenbosch : Stellenbosch University, 2020-04) Robinson, Daniel; Booysen, M. J.; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.ENGLISH ABSTRACT: Cellular 2G/GPRS is a sun-setting technology worldwide leaving behind a void for wireless low-power widearea-networks (LPWANs) such as LoRaWAN, SigFox and NB-IoT to fill. With NB-IoT on the roadmap towards 5G New Radio (NR), it is a promising contender due to its bidirectionality, power-saving mechanisms and ease of integration with existing equipment, yet there still exists a general uncertainty with regard to adoption. Research shows that most literature on NB-IoT is based on precise mathematical models, analysis or simulations, except for a few empirical performance evaluations which find variability in devices connected to a single network. The study theorizes that networks are responsible for the variation found in metrics and estimations, due to the high underlying complexity of Long-Term Evolution (LTE) architecture on which NB-IoT is based. Thus, the study proposes an empirical investigation using mobile-network operators (MNOs) in South Africa by comparing multiple top LTE vendors including Ericsson and ZTE on MTN’s network, and on Vodacom’s network Huawei and Nokia. Furthermore, similar user equipment (UE) devices such as Ublox and Quectel are used as a control to observe network changes via RF attenuation. A set of telemetry tests are developed to capture various metrics and estimations into datasets for comparison, which include differently sized UDP packet datagrams, cellular operator selection (COPS), extended discontinuous reception (eDRX) and periodic tracking-area-updates (PTAU). Data is measured using an external energy capture device or reported by the UE device for post-processing and analysis in plots, mean distribution tables and boxplots. Metrics such as latency, power efficiency, signal strength, enhanced coverage level (ECL) classes, throughput and data overhead are included, as well as estimates for telemetry interval periodicity and battery longevity. K-means clustering is applied to the datasets to reduce the skewness induced by the increased number of low-latency values during captures to normalize the number of unique features for comparison. Most clearly visible in the tests is how MTN leads Vodacom in NB-IoT performance due to Nokia’s subpar results. Power efficiency and latency metrics show that when connected to Vodacom-Nokia, results can factor up 20 and 10 times worse, respectively. Otherwise, ZTE, Ericsson and Huawei show satisfactory latency under the 10 second 3GPP standard. Although LTE vendors meet the 164 dBm MCL requirement, Vodacom-Nokia has 10 dB less receive sensitivity, with the rest at -130 dBm. Transmit power increases at 10 dBm per RSRP decade until its maximum at 23 dBm, except for Nokia which remains at full power. ECL classes overlap with respect to RSRP, yet partially correlate, which suggests an unknown network factor or hysteresis of a few seconds in the test captures. Nevertheless, Nokia is mostly in ECL class 1, while others are a mix of ECL class 0 and 1. This has an impact on the number of dynamic repetitions of messages between UE devices and cell-tower eNodeBs. Throughput is under 10 kbps, which is half or less than UE device claims by manufacturers. A quarter of datagrams in the telemetry test set show protocol overhead extending over 512 bytes in uplink and 200 bytes in downlink, except for Nokia extending up to 10,000 bytes. Telemetry interval and battery longevity estimates on a 9.36 Wh AA battery suggest that ZTE, Ericsson and Huawei can transmit 16-512 bytes between every 5 to 30 minutes to last at least a year, or hourly to last up to 10 years, however, a device that transmits hourly on the Vodacom-Nokia network will only last 2 months. The study provides recommendations based on these results. Finally, South Africa is ready for mobile network operators to deploy national NB-IoT coverage using ZTE, Ericsson and Huawei, but not using Nokia. With a satisfactory inter-cell tower distance, UE devices avoid having to use dynamic repetitions in higher ECL classes, thus keeping the variability that affects many of the metrics and estimates in the study to a minimum.